Virtual synchronization control method and device of energy storage system, equipment and storage medium

Abstract

The invention relates to a virtual synchronous control method, device and equipment for an energy storage system and a storage medium, and the method comprises the steps: controlling the output voltage of a DC energy storage valve according to an output electric signal measurement value of the DC side of a voltage source converter valve and an output voltage reference value of the DC energy storage valve. Furthermore, according to the grid-connected point electric signal measurement value and the grid-connected point electric signal reference value of the voltage source converter valve, an output signal of the alternating current side of the voltage source converter valve is controlled. Therefore, the virtual synchronous control method for independently controlling the voltage source converter valve and the direct-current energy storage valve in the energy storage system is realized, so that the virtual synchronous control method can be suitable for virtual synchronous control of the high-voltage direct-current direct-hanging energy storage system. Besides, the voltage source converter valve and the direct-current energy storage valve in the energy storage system are independently controlled, so that the voltage source converter valve does not need to consider both direct-current side control and alternating-current side control, and the complexity of a control loop of the voltage source converter valve can be simplified.

Description

Technical Field

[0001] The present application relates to the technical field of energy storage, and in particular, to a virtual synchronous control method, device, equipment, and storage medium for an energy storage system. Background Art

[0002] With the rapid development of a new power system mainly based on new energy, an energy storage system with high voltage, large capacity, and friendly grid connection will become a new development requirement and trend. Among them, a high-voltage DC directly-connected energy storage system has become an important development direction.

[0003] In the related art, a high-voltage DC directly-connected energy storage system integrates a voltage source converter (VSC) and a DC energy storage valve, and has advantages such as high modularity. However, compared with a traditional energy storage system, the high-voltage DC directly-connected energy storage system is different from the traditional energy storage system in terms of topology and function. Therefore, how to perform virtual synchronous control on the high-voltage DC directly-connected energy storage system is an urgent problem to be solved. Summary of the Invention

[0004] In view of the above problems, the present application provides a virtual synchronous control method, device, equipment, and storage medium for an energy storage system, which can solve the problem of virtual synchronous control of a high-voltage DC directly-connected energy storage system in the related art.

[0005] In a first aspect, the present application provides a virtual synchronous control method for an energy storage system. The energy storage system includes a voltage source converter and a DC energy storage valve. The method includes:

[0006] Controlling the output voltage of the DC energy storage valve according to the measured value of the output electrical signal on the DC side of the voltage source converter and the reference value of the output voltage of the DC energy storage valve;

[0007] Controlling the output signal on the AC side of the voltage source converter according to the measured value of the grid connection point electrical signal of the voltage source converter and the reference value of the grid connection point electrical signal.

[0008] In the technical solution of the embodiment of the present application, by measuring the output electrical signal value on the DC side of the voltage source converter valve and the output voltage reference value of the DC energy storage valve, independent control of the output voltage of the DC energy storage valve can be achieved, and by measuring the grid connection point electrical signal value of the voltage source converter valve and the grid connection point electrical signal reference value, independent control of the output signal on the AC side of the voltage source converter valve can be achieved. It can be seen that the embodiment of the present application realizes a virtual synchronous control method for independently controlling the voltage source converter valve and the DC energy storage valve in the energy storage system, so that it can be applied to the virtual synchronous control of the high-voltage DC directly-connected energy storage system, facilitating the grid-forming control of the high-voltage DC directly-connected energy storage system and being beneficial to improving the low-voltage fault ride-through ability of the energy storage system. In addition, by independently controlling the voltage source converter valve and the DC energy storage valve in the energy storage system, the voltage source converter valve does not need to consider both DC side control and AC side control, thus simplifying the complexity of the control loop of the voltage source converter valve.

[0009] In some embodiments, the grid connection point electrical signal measurement value includes: the grid connection point active power measurement value, the grid connection point reactive power measurement value, and the grid connection point voltage measurement value, and the grid connection point electrical signal reference value includes: the grid connection point active power reference value, the grid connection point reactive power reference value, and the grid connection point voltage reference value. Controlling the output signal on the AC side of the voltage source converter valve according to the grid connection point electrical signal measurement value and the grid connection point electrical signal reference value of the voltage source converter valve includes:

[0010] Controlling the output frequency on the AC side of the voltage source converter valve according to the grid connection point active power measurement value and the grid connection point active power reference value;

[0011] Controlling the output voltage amplitude on the AC side of the voltage source converter valve according to the grid connection point reactive power measurement value, the grid connection point voltage measurement value, the grid connection point reactive power reference value, and the grid connection point voltage reference value.

[0012] In the technical solution of the embodiment of the present application, by according to the grid connection point active power measurement value and the grid connection point active power reference value, the active power-frequency control of the voltage source converter valve is realized, and by according to the grid connection point reactive power measurement value, the grid connection point voltage measurement value, the grid connection point reactive power reference value, and the grid connection point voltage reference value, the reactive power-voltage control of the voltage source converter valve is realized, thus realizing the virtual synchronous control of the active power and reactive power decoupling of the voltage source converter valve, which is beneficial to the transient support of the grid connection point frequency and the grid connection point voltage, and thus can further improve the low-voltage fault ride-through ability of the energy storage system.

[0013] In some embodiments, controlling the output frequency on the AC side of the voltage source converter valve according to the grid connection point active power measurement value and the grid connection point active power reference value includes:

[0014] Determine the active power deviation at the grid connection point according to the measured value of the active power at the grid connection point and the reference value of the active power at the grid connection point;

[0015] Perform first closed-loop control processing on the active power deviation at the grid connection point to obtain a closed-loop result;

[0016] Control the output frequency according to the closed-loop result and the rated angular frequency of the power grid.

[0017] In the technical solution of the embodiment of the present application, by converting the active power deviation at the grid connection point into the output frequency of the AC side of the voltage source converter valve, it is beneficial to adjust the active power at the grid connection point to the reference value of the active power at the grid connection point.

[0018] In some embodiments, determining the active power deviation at the grid connection point according to the measured value of the active power at the grid connection point and the reference value of the active power at the grid connection point includes:

[0019] Perform clipping processing on the reference value of the active power at the grid connection point according to the maximum limit value of the active power and the minimum limit value of the active power to obtain the clipped reference value of the active power at the grid connection point;

[0020] Subtract the measured value of the active power at the grid connection point from the clipped reference value of the active power at the grid connection point to obtain the active power deviation at the grid connection point.

[0021] In the technical solution of the embodiment of the present application, by performing clipping processing on the reference value of the active power at the grid connection point, the clipped reference value of the active power at the grid connection point can conform to the actual capacity of the energy storage system, so that a more accurate active power deviation at the grid connection point can be obtained according to the clipped reference value of the active power at the grid connection point and the measured value of the active power at the grid connection point, which is beneficial to more accurately controlling the output frequency of the AC side of the voltage source converter valve according to the active power deviation at the grid connection point.

[0022] In some embodiments, performing first closed-loop control processing on the active power deviation at the grid connection point to obtain a closed-loop result includes:

[0023] Determine the first feedback signal according to the historical closed-loop result and the damping coefficient;

[0024] Perform first integration processing on the difference signal between the active power deviation at the grid connection point and the first feedback signal to obtain a closed-loop result.

[0025] In some embodiments, performing first integration processing on the difference signal between the active power deviation at the grid connection point and the first feedback signal to obtain a closed-loop result includes:

[0026] Perform first integration processing on the difference signal according to the inertia time constant and the latch coefficient to obtain a closed-loop result.

[0027] In some embodiments, the method further includes:

[0028] Adjust the maximum limit value and minimum limit value of the active power according to the grid connection point fault detection signal, so that the reference value of the active power of the energy storage system does not exceed the actual capacity of the system during the fault, thereby improving the transient stability of the energy storage system during the fault.

[0029] In some embodiments, adjusting the maximum limit value and minimum limit value of the active power according to the grid connection point fault detection signal includes:

[0030] When it is detected that the grid connection point fault detection signal is used to indicate that a fault occurs in the energy storage system, adjust the maximum limit value of the active power to the target maximum limit value of the power, and adjust the minimum limit value of the active power to the target minimum limit value of the power; or,

[0031] When it is detected that the grid connection point fault detection signal is used to indicate that the fault is cleared within the first preset time period, adjust the maximum limit value of the active power from the target maximum limit value of the power to the preset maximum limit value of the power, and adjust the minimum limit value of the active power from the target minimum limit value of the power to the preset minimum limit value of the power.

[0032] In some embodiments, both the target maximum limit value of the power and the target minimum limit value of the power are related to the measured value of the reactive power at the grid connection point, the measured value of the grid connection point voltage, and the drop amplitude of the measured value of the grid connection point voltage during the fault.

[0033] In the technical solution of the embodiment of the present application, by adjusting the target maximum limit value and the target minimum limit value of the power according to the measured value of the reactive power at the grid connection point, the measured value of the grid connection point voltage, and the drop amplitude of the measured value of the grid connection point voltage during the fault, it can be ensured that the reference value of the active power of the energy storage system does not exceed the actual capacity of the system during the fault, thereby alleviating the problem that the input of the active power is always greater than zero, resulting in the continuous increase of the power angle, and finally causing the periodic change of the grid connection point voltage and the large swing of the active power, thereby improving the transient stability of the energy storage system during the fault.

[0034] In some embodiments, the method further includes:

[0035] Adjust the damping coefficient and the latching coefficient according to the grid connection point fault detection signal, so that the reference value of the active power of the energy storage system does not exceed the actual capacity of the system during the fault, thereby improving the transient stability of the energy storage system during the fault.

[0036] In some embodiments, adjusting the damping coefficient and the latching coefficient according to the grid connection point fault detection signal includes:

[0037] When a grid connection point fault detection signal indicating a fault in the energy storage system is detected, adjust the damping coefficient to a target damping coefficient and adjust the latching coefficient to a target latching coefficient; or,

[0038] When a grid connection point fault detection signal indicating that the fault is cleared within a second preset duration is detected, adjust the damping coefficient from the target damping coefficient to a preset damping coefficient and adjust the latching coefficient from the target latching coefficient to a preset latching coefficient.

[0039] In the technical solution of the embodiment of the present application, by adaptively adjusting the damping coefficient and adaptively adjusting the latching coefficient to adjust the integral link of the active power frequency, the swing of the power angle during the fault can be further reduced, so that the absolute value of the active power deviation is as small as possible, to alleviate the large power angle swing and the continuous periodic fluctuation of the grid connection point voltage after the fault recovery, thereby improving the transient stability of the energy storage system during the fault recovery process.

[0040] In some embodiments, the target latching coefficient is zero, and the target damping coefficient is related to the offset of the grid connection point active power during the fault and the allowable frequency offset during the fault.

[0041] In some embodiments, the method further includes:

[0042] Determine the grid connection point fault detection signal according to the grid connection point voltage measurement value, the preset fault detection threshold and the preset fault clearing threshold.

[0043] In the technical solution of the embodiment of the present application, by determining the grid connection point fault detection signal according to the grid connection point voltage measurement value, the preset fault detection threshold and the preset fault clearing threshold, it is convenient to adjust the active power limit value, the damping coefficient and the latching coefficient according to the grid connection point fault detection signal, so that the active power reference value of the energy storage system does not exceed the actual system capacity during the fault, thereby improving the transient stability of the energy storage system during the fault.

[0044] In some embodiments, determining the grid connection point fault detection signal according to the grid connection point voltage measurement value, the preset fault detection threshold and the preset fault clearing threshold includes:

[0045] When it is detected that the change value of the grid connection point voltage measurement value is less than 0 and the grid connection point voltage measurement value is less than or equal to the preset fault detection threshold within a third preset duration, determine that the grid connection point fault detection signal indicates that a fault has occurred in the energy storage system, and record the drop amplitude of the grid connection point voltage measurement value during the fault;

[0046] When it is detected that the change value of the grid-connected point voltage measurement value is greater than 0, and the grid-connected point voltage measurement value is greater than or equal to the preset fault clearing threshold, it is determined that the grid-connected point fault detection signal is used to indicate that the energy storage system clears the fault within the fourth preset duration, and the voltage drop amplitude of the grid-connected point voltage measurement value during the fault period is adjusted to the preset voltage drop amplitude.

[0047] In some embodiments, according to the grid-connected point reactive power measurement value, the grid-connected point voltage measurement value, the grid-connected point reactive power reference value, and the grid-connected point voltage reference value, controlling the output voltage amplitude of the AC side of the voltage source converter valve includes:

[0048] Determine the first internal potential amplitude of the voltage source converter valve according to the grid-connected point reactive power measurement value, the grid-connected point voltage measurement value, the grid-connected point reactive power reference value, and the grid-connected point voltage reference value;

[0049] Control the output voltage amplitude of the AC side of the voltage source converter valve according to the first internal potential amplitude of the voltage source converter valve.

[0050] In the technical solution of the embodiment of the present application, by determining the first internal potential amplitude of the voltage source converter valve and controlling the output voltage amplitude of the AC side of the voltage source converter valve according to the first internal potential amplitude, the reactive power-voltage control of the voltage source converter valve is realized, which is beneficial to adjusting the grid-connected point voltage to the grid-connected point voltage reference value.

[0051] In some embodiments, determining the first internal potential amplitude of the voltage source converter valve according to the grid-connected point reactive power measurement value, the grid-connected point voltage measurement value, the grid-connected point reactive power reference value, and the grid-connected point voltage reference value includes:

[0052] Determine the grid-connected point reactive power deviation according to the grid-connected point reactive power measurement value and the grid-connected point reactive power reference value;

[0053] Determine the grid-connected point voltage deviation according to the grid-connected point voltage measurement value and the grid-connected point voltage reference value;

[0054] Perform a second integration process according to the grid-connected point reactive power deviation and / or the grid-connected point voltage deviation to obtain the first internal potential amplitude.

[0055] In some embodiments, controlling the output voltage amplitude of the AC side of the voltage source converter valve according to the first internal potential amplitude of the voltage source converter valve includes:

[0056] Perform a voltage outer loop control process according to the first internal potential amplitude of the voltage source converter valve and the grid-connected point voltage measurement value to obtain the current command value of the current inner loop;

[0057] Perform a current limiting inner loop process according to the current command value to obtain the output voltage signal of the AC side of the voltage source converter valve;

[0058] Control the output voltage amplitude of the AC side of the voltage source converter valve according to the output voltage signal of the AC side of the voltage source converter valve.

[0059] In some embodiments, perform voltage outer loop control processing based on the amplitude of the first internal electromotive force of the voltage source converter valve and the measured value of the grid connection point voltage to obtain the current command value of the current inner loop, including:

[0060] Perform first PI regulation processing, dynamic virtual impedance processing, or static virtual impedance processing on the amplitude of the first internal electromotive force of the voltage source converter valve and the measured value of the grid connection point voltage to obtain the current command value of the current inner loop.

[0061] In some embodiments, the method further includes:

[0062] When it is detected that the energy storage system is in the initial grid connection stage, perform pre-synchronization processing on the output signal of the AC side of the voltage source converter valve according to the measured value of the grid connection point voltage, so that the amplitude of the internal electromotive force and the output phase angle (or called vector angle) of the voltage source converter valve can be the same as the amplitude and vector angle of the grid connection point voltage respectively, so as to minimize the current impact at the grid connection moment, which is beneficial to smooth switching.

[0063] In some embodiments, the measured value of the grid connection point voltage includes a first-axis voltage measurement component and a second-axis voltage measurement component. Performing pre-synchronization processing on the output signal of the AC side of the voltage source converter valve according to the measured value of the grid connection point voltage includes:

[0064] Perform second PI regulation processing on the first-axis voltage measurement component to obtain the adjusted first-axis voltage measurement component;

[0065] Perform second integration processing on the adjusted first-axis voltage measurement component and the rated grid angular frequency to obtain the output voltage phase angle of the AC side of the voltage source converter valve; wherein, the output voltage phase angle is the same as the grid connection point voltage phase angle;

[0066] Perform second closed-loop processing on the second-axis voltage measurement component to obtain the amplitude of the second internal electromotive force of the voltage source converter valve; wherein, the amplitude of the second internal electromotive force is the same as the amplitude of the grid connection point voltage.

[0067] In the technical solution of the embodiment of the present application, by performing PI regulation processing and integration processing on the first-axis voltage measurement component, and performing second closed-loop processing on the second-axis voltage measurement component, the amplitude of the internal electromotive force and the output voltage phase angle of the voltage source converter valve synchronized with the grid connection point voltage can be generated, so as to minimize the current impact at the grid connection moment, which is beneficial to smooth switching.

[0068] In some embodiments, performing second closed-loop processing on the second-axis voltage measurement component to obtain the amplitude of the second internal electromotive force of the voltage source converter valve includes:

[0069] Determine the second feedback signal according to the historical internal potential amplitude;

[0070] Perform third PI regulation processing and third integration processing on the difference signal between the second shaft voltage measurement component and the second feedback signal in sequence to obtain the second internal potential amplitude.

[0071] In some embodiments, the output electrical signal measurement value includes: the output voltage measurement value of the DC side of the voltage source converter valve and the output current measurement value of the DC side of the voltage source converter valve. According to the output electrical signal measurement value of the DC side of the voltage source converter valve and the output voltage reference value of the DC energy storage valve, controlling the output voltage of the DC energy storage valve includes:

[0072] Perform fourth PI regulation processing on the DC voltage difference between the output voltage measurement value of the DC side of the voltage source converter valve and the output voltage reference value of the DC energy storage valve to obtain the DC current command value;

[0073] Perform fifth PI regulation processing on the DC current difference between the output current measurement value of the DC side of the voltage source converter valve and the DC current command value to obtain the output voltage command value of the DC energy storage valve;

[0074] Control the output voltage of the DC energy storage valve according to the output voltage command value of the DC energy storage valve.

[0075] In the technical solution of the embodiment of the present application, by according to the output voltage measurement value, output current measurement value of the DC side of the voltage source converter valve and the output voltage reference value of the DC energy storage valve, the independent control of the output voltage of the DC energy storage valve is realized, which can enable the voltage source converter valve to not need to take into account the DC side control and AC side control. On the one hand, it can simplify the complexity of the control loop of the voltage source converter valve, and on the other hand, it is also beneficial to improve the dynamic control performance of the output voltage of the DC energy storage valve, so as to realize the grid-forming control of the energy storage system, so as to provide effective inertia support and voltage support for the power grid.

[0076] In a second aspect, the present application provides a virtual synchronous control device for an energy storage system. The energy storage system includes a voltage source converter valve and a DC energy storage valve. The device includes:

[0077] The first control module is used to control the output voltage of the DC energy storage valve according to the output electrical signal measurement value of the DC side of the voltage source converter valve and the output voltage reference value of the DC energy storage valve;

[0078] The second control module is used to control the output signal of the AC side of the voltage source converter valve according to the grid connection point electrical signal measurement value and the grid connection point electrical signal reference value of the voltage source converter valve.

[0079] In a third aspect, the present application provides a control device for an energy storage system, including a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, the steps in the embodiment of the virtual synchronous control method for the energy storage system described above are implemented.

[0080] In a fourth aspect, the present application provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps in the embodiment of the virtual synchronous control method for the energy storage system described above are implemented.

[0081] In a fifth aspect, the present application provides a computer program product, including a computer program. When the computer program is executed by a processor, the steps in the embodiment of the virtual synchronous control method for the energy storage system described above are implemented.

[0082] The above description is only an overview of the technical solution of the present application. In order to be able to understand the technical means of the present application more clearly, it can be implemented according to the content of the description. And in order to make the above and other purposes, features and advantages of the present application more obvious and understandable, the specific embodiments of the present application are specifically given below. BRIEF DESCRIPTION OF THE DRAWINGS

[0083] By reading the detailed description of the preferred embodiments below, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present application. And in all the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0084] Figure 1 is a schematic structural diagram of an energy storage system provided by some embodiments of the present application;

[0085] Figure 2 is a schematic diagram of the virtual synchronous control framework of an energy storage system provided by some embodiments of the present application;

[0086] Figure 3 is a schematic flowchart of the virtual synchronous control method for an energy storage system provided by some embodiments of the present application;

[0087] Figure 4 is a schematic flowchart of the virtual synchronous control method for an energy storage system provided by other embodiments of the present application;

[0088] Figure 5 is a schematic flowchart of the output frequency control method for the AC side of a voltage source converter valve provided by some embodiments of the present application;

[0089] Figure 6A is a schematic flowchart of the first closed-loop control processing method provided by some embodiments of the present application;

[0090] Figure 6B Flow diagram of the first integral processing method provided by some embodiments of the present application;

[0091] Figure 6C Flow diagram of the output frequency control method provided by some embodiments of the present application;

[0092] Figure 6D Flow diagram of the active power - frequency control method provided by some embodiments of the present application;

[0093] Figure 7 Flow diagram of the output voltage amplitude control method for the AC side of the voltage source converter valve provided by some embodiments of the present application;

[0094] Figure 8A Flow diagram of the first internal potential amplitude determination method for the voltage source converter valve provided by some embodiments of the present application;

[0095] Figure 8B Flow diagram of the reactive power - voltage control method provided by some embodiments of the present application;

[0096] Figure 9A Flow diagram of the output voltage amplitude control method for the AC side of the voltage source converter valve provided by some embodiments of the present application;

[0097] Figure 9B Flow diagram of the first PI regulation processing method provided by some embodiments of the present application;

[0098] Figure 9C Flow diagram of the dynamic virtual impedance processing method provided by some embodiments of the present application;

[0099] Figure 9D Flow diagram of the static virtual impedance processing method provided by some embodiments of the present application;

[0100] Figure 10 Flow diagram of the active power limit value adjustment method provided by some embodiments of the present application;

[0101] Figure 11 Flow diagram of the damping coefficient and latching coefficient adjustment method provided by some embodiments of the present application;

[0102] Figure 12 Flow diagram of the grid connection point fault detection signal determination method provided by some embodiments of the present application;

[0103] Figure 13A Flow diagram of the pre - synchronization processing method for the output signal of the AC side of the voltage source converter valve provided by some embodiments of the present application;

[0104] Figure 13B Schematic flowchart of the method for determining the output voltage phase angle on the AC side of the voltage source converter valve provided by some embodiments of this application;

[0105] Figure 13C Schematic flowchart of the second closed-loop processing method provided by some embodiments of this application;

[0106] Figure 13D Schematic flowchart of the second closed-loop processing method provided by some embodiments of this application;

[0107] Figure 14A Schematic flowchart of the virtual synchronous control method of the energy storage system provided by some other embodiments of this application;

[0108] Figure 14B Schematic flowchart of the fourth PI regulation processing method provided by some embodiments of this application;

[0109] Figure 14C Schematic flowchart of the fifth PI regulation processing method provided by some embodiments of this application;

[0110] Figure 14D Schematic flowchart of the output voltage control method of the DC energy storage valve provided by some embodiments of this application;

[0111] Figure 15 Schematic diagram of the virtual synchronous control framework of the energy storage system provided by some embodiments of this application;

[0112] Figure 16A Schematic diagram of the simulation results of the active power P at the grid connection point, the reactive power Q at the grid connection point, and the AC grid voltage amplitude U provided by the embodiments of this application s ;

[0113] Figure 16B Schematic diagram of the simulation results of the output voltage u of the DC energy storage valve, the output current i on the DC side of the voltage source converter valve dc and the output frequency ω on the AC side of the voltage source converter valve provided by the embodiments of this application; dc ;

[0114] Figure 17 Schematic diagram of the structure of the virtual synchronous control device of the energy storage system provided by some embodiments of this application;

[0115] Figure 18 Schematic diagram of the structure of the control device of the energy storage system in some embodiments of this application. Detailed implementation manners

[0116] The embodiments of the technical solution of the present application will be described in detail below with reference to the accompanying drawings. The following embodiments are only used to illustrate the technical solution of the present application more clearly, so they are only examples and cannot be used to limit the protection scope of the present application.

[0117] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the term "including" and any variation thereof in the specification and claims of this application and the above description of the drawings are intended to cover non-exclusive inclusion.

[0118] In the description of the embodiments of this application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity, specific order or primary-secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "a plurality" is two or more (including two), unless otherwise specifically defined.

[0119] The virtual synchronous control method, device, equipment and storage medium provided by the embodiments of this application can be applied to the virtual synchronous control application scenario of a high-voltage DC directly-connected energy storage system; of course, it can also be applied to other application scenarios.

[0120] With the rapid development of a new power system with new energy as the main body, the proportion of new energy in the new power system is continuously increasing, resulting in the lack of inertia and damping in the power system and making it relatively fragile. Therefore, a high-voltage and large-capacity energy storage system that can be friendly connected to the power grid will become a new development demand and trend. Among them, whether it has virtual inertia and damping support capabilities and whether it has the ability to form a grid will become the key indicators for the stable operation of the new power system.

[0121] Generally, the grid-forming control strategy of the energy storage system is mainly realized through the virtual synchronous generator (VSG) technology, which can enable the energy storage system to transform from the current-source type grid-following control mode to the voltage-source type grid-forming control mode. Among them, through the VSG technology, the energy storage system is controlled to imitate the characteristics of a traditional synchronous generator, so that the energy storage system becomes an independent voltage source, can independently supply power to the load, and can also provide necessary inertia and damping support for the power grid, which has important research significance for the stable operation of the new power system.

[0122] With the development of energy storage technology, the high-voltage DC directly-connected energy storage system has become an important development direction. The high-voltage DC directly-connected energy storage system integrates the voltage source converter (VSC) and the DC energy storage valve in terms of topology and function, and has the advantages of high modularity, good economic benefits, and high operation stability. Compared with the traditional energy storage system, the high-voltage DC directly-connected energy storage system is different from the traditional energy storage system in terms of topology and function. The DC side of the high-voltage DC directly-connected energy storage system also needs to be controlled, and the virtual synchronous control method of the traditional energy storage system cannot be applied to the high-voltage DC directly-connected energy storage system. Therefore, how to perform virtual synchronous control on the high-voltage DC directly-connected energy storage system is an urgent problem to be solved.

[0123] In addition, the grid-connected inverter or VSC of the VSG technology in the related art can simulate the characteristics of a synchronous generator and has effective inertia and damping support capabilities in the face of fluctuations in the grid frequency and voltage amplitude. However, once a severe grid fault occurs (for example, a deep grid voltage dip, etc.), the VSG technology in the related art lacks current or power limiting, resulting in an inability to suppress the fault current impact in the VSC valve, making the system fault ride-through performance poor. Another part of the related research introduces virtual impedance / resistance to suppress the impact current, but the current limiting effect of the virtual impedance / resistance under a severe short-circuit fault is relatively insufficient, and the response speed is slow, unable to meet the stability requirements of the new power system.

[0124] In order to solve the problem of how to perform virtual synchronous control on the high-voltage DC directly-connected energy storage system in the related art, the embodiments of the present application propose a virtual synchronous control method that independently controls the voltage source converter valve and the DC energy storage valve in the energy storage system, which can be applied to the virtual synchronous control of the high-voltage DC directly-connected energy storage system, so as to facilitate the implementation of the grid-forming control of the high-voltage DC directly-connected energy storage system and is beneficial to improving the low-voltage fault ride-through ability of the energy storage system.

[0125] For the convenience of understanding, the structure of the energy storage system in the embodiments of the present application is first introduced and illustrated exemplarily. Exemplarily, the energy storage system in the embodiments of the present application may include, but is not limited to, a high-voltage DC directly-connected energy storage system. Among them, compared with the traditional energy storage system, the high-voltage DC directly-connected energy storage system can directly support the voltage source converter valve to operate in a virtual synchronous control manner, has a higher voltage level, a larger capacity, and stronger grid regulation ability and grid support effect.

[0126] In some embodiments, Figure 1 is a schematic structural diagram of an energy storage system provided in some embodiments of the present application, as Figure 1As shown in the figure, the energy storage system according to the embodiment of the present application may include, but is not limited to, a voltage source converter valve 101, a DC energy storage valve 102, and a control device 103 of the energy storage system. Among them, the AC side of the voltage source converter valve 101 is connected to the AC power grid 104, and the DC side of the voltage source converter valve 101 is connected to the DC energy storage valve 102. The control device 103 in the embodiment of the present application can be used to control the voltage source converter valve 101 and the DC energy storage valve 102 by using the virtual synchronous control method of the energy storage system provided by the embodiment of the present application.

[0127] It should be understood that in the case where the voltage source converter valve 101 and the DC energy storage valve 102 are controlled by different control devices, the control device 103 may include a first sub-control device corresponding to the voltage source converter valve 101 and a second sub-control device corresponding to the DC energy storage valve 102. Correspondingly, the first sub-control device can control the voltage source converter valve 101 by using the control method related to the voltage source converter valve 101 in the virtual synchronous control method of the energy storage system provided by the embodiment of the present application, and the second sub-control device can control the DC energy storage valve 102 by using the control method related to the DC energy storage valve 102 in the virtual synchronous control method of the energy storage system provided by the embodiment of the present application.

[0128] It should be noted that Figure 1 is shown by taking the control device 103 of the energy storage system in the embodiment of the present application as independent of the voltage source converter valve 101 and the DC energy storage valve 102 as an example; of course, the control device 103 of the energy storage system can also be integrated in the voltage source converter valve 101 and / or the DC energy storage valve 102.

[0129] In some embodiments, Figure 2 is a schematic diagram of the virtual synchronous control framework of the energy storage system provided by some embodiments of the present application. As Figure 2 shown, the energy storage system according to the embodiment of the present application may include, but is not limited to: a voltage source converter valve 101, a DC energy storage valve 102, and a control device 103 of the energy storage system. Among them, the voltage source converter valve 101 can be connected to the AC power grid 104 through a transformer 105; Figure 2 The parameters in can refer to those shown in Table 1.

[0130] Table 1 is Figure 2 a schematic table of the parameters in

[0131]

[0132]

[0133] It should be noted that the voltage source converter valve 101 can be directly connected to the AC power grid 104 without passing through the transformer 105, that is, can be deleted Figure 2The transformer 105 therein. Correspondingly, it is not necessary to distinguish between the AC side of the voltage source converter valve for the AC network side or the AC valve side of the voltage source converter valve, or rather, the AC network side of the voltage source converter valve is the same as the AC valve side of the voltage source converter valve.

[0134] Exemplarily, the control device 103 in the embodiments of the present application may include but is not limited to: a voltage source converter valve control unit 1031 for controlling the voltage source converter valve 101 and a DC energy storage valve control unit 1032 for controlling the DC energy storage valve 102. Among them, the voltage source converter valve control unit 1031 may include but is not limited to: a fault detection unit 1031A for detecting whether a fault occurs in the energy storage system, a VSG control unit 1031B, and a voltage and current control unit 1031C.

[0135] Among them, the VSG control unit 1031B may be used to implement pre-synchronization processing of the voltage source converter valve, active power - frequency control, and / or reactive power - voltage control. The voltage and current control unit 1031C may be used for voltage outer loop control processing and / or current limit inner loop processing.

[0136] Among them, the DC energy storage valve control unit 1032 may include but is not limited to: a DC voltage outer loop control unit 1032A for DC voltage outer loop processing and a DC current inner loop control unit 1032B for DC current inner loop processing.

[0137] It should be noted that the relevant content of the above different processes will be introduced and illustrated exemplarily in the following embodiments of the present application.

[0138] Any measured value involved in the embodiments of the present application may include but is not limited to the per-unit value of the measured value, and / or the nominal value of the measured value (or referred to as non-per-unit value).

[0139] It should be understood that the per-unit value is a relative unit system and belongs to a commonly used numerical marking method in power system analysis and engineering calculations, representing the relative value of each physical quantity (nominal value) relative to a certain reference value, with the unit of pu (it can also be considered dimensionless).

[0140] Any reference value involved in the embodiments of the present application may include but is not limited to the per-unit value of the reference value, and / or the nominal value of the reference value.

[0141] In some embodiments, Figure 3 is a schematic flowchart of the virtual synchronous control method for the energy storage system provided in some embodiments of the present application. In the embodiments of the present application, this method is described by taking its application to the virtual synchronous control device of the above energy storage system as an example. Exemplarily, the energy storage system in the embodiments of the present application may include but is not limited to a voltage source converter valve and a DC energy storage valve. As Figure 3As shown, the method of the embodiment of the present application may include the following steps:

[0142] Step S301: Control the output voltage of the DC energy storage valve according to the measured value of the output electrical signal on the DC side of the voltage source converter valve and the reference value of the output voltage of the DC energy storage valve.

[0143] Exemplarily, the measured value of the output electrical signal on the DC side of the voltage source converter valve in the embodiment of the present application may include, but is not limited to, the measured value of the output voltage on the DC side of the voltage source converter valve, and / or the measured value of the output current on the DC side of the voltage source converter valve.

[0144] In this step, the virtual synchronous control device may control the output voltage of the DC energy storage valve according to the measured value of the output electrical signal on the DC side of the voltage source converter valve and the reference value of the output voltage of the DC energy storage valve.

[0145] Exemplarily, the virtual synchronous control device may perform DC voltage outer loop processing and / or DC current inner loop processing according to the measured value of the output electrical signal on the DC side of the voltage source converter valve and the reference value of the output voltage of the DC energy storage valve to obtain the output voltage command value of the DC energy storage valve, so as to control the output voltage of the DC energy storage valve according to the output voltage command value.

[0146] The DC voltage outer loop processing in the embodiment of the present application may include, but is not limited to, proportional-integral (PI) regulation processing based on the DC voltage difference between the measured value of the output voltage on the DC side of the voltage source converter valve and the reference value of the output voltage of the DC energy storage valve.

[0147] The DC current inner loop processing in the embodiment of the present application may include, but is not limited to, PI regulation processing based on the DC current difference between the measured value of the output current on the DC side of the voltage source converter valve and the reference value of the output current of the DC energy storage valve.

[0148] It can be seen that in this step, by according to the measured value of the output electrical signal on the DC side of the voltage source converter valve and the reference value of the output voltage of the DC energy storage valve, independent control of the output voltage of the DC energy storage valve can be achieved.

[0149] Step S302: Control the output signal on the AC side of the voltage source converter valve according to the measured value of the grid connection point electrical signal of the voltage source converter valve and the reference value of the grid connection point electrical signal.

[0150] Exemplarily, the measured value of the grid connection point electrical signal in the embodiment of the present application may include, but is not limited to, at least one of the following: the measured value of the grid connection point active power, the measured value of the grid connection point reactive power, and the measured value of the grid connection point voltage.

[0151] Exemplarily, the reference value of the grid connection point electrical signal in the embodiments of the present application may include, but is not limited to, at least one of the following: the reference value of the active power at the grid connection point, the reference value of the reactive power at the grid connection point, and the reference value of the voltage at the grid connection point.

[0152] In this step, the virtual synchronous control device can control the output signal of the AC side of the voltage source converter valve by controlling the output frequency and / or the output voltage amplitude of the AC side of the voltage source converter valve according to the measured value of the grid connection point electrical signal of the voltage source converter valve and the reference value of the grid connection point electrical signal.

[0153] Exemplarily, when the voltage source converter valve 101 is connected to the AC grid 104 through the transformer 105, the AC side of the voltage source converter valve in the embodiments of the present application may include: the AC grid side of the voltage source converter valve, and / or, the AC valve side of the voltage source converter valve.

[0154] Another exemplarily, when the voltage source converter valve 101 is directly connected to the AC grid 104, it is not necessary to distinguish between the AC grid side and the AC valve side of the voltage source converter valve in the embodiments of the present application, or rather, the AC grid side of the voltage source converter valve is the same as the AC valve side of the voltage source converter valve.

[0155] It can be seen that in this step, by according to the measured value of the grid connection point electrical signal of the voltage source converter valve and the reference value of the grid connection point electrical signal, the independent control of the output signal of the AC side of the voltage source converter valve can be achieved.

[0156] The virtual synchronous control method of the above energy storage system controls the output voltage of the DC energy storage valve by according to the measured value of the output electrical signal of the DC side of the voltage source converter valve and the reference value of the output voltage of the DC energy storage valve. Further, by according to the measured value of the grid connection point electrical signal of the voltage source converter valve and the reference value of the grid connection point electrical signal, the output signal of the AC side of the voltage source converter valve is controlled. In the embodiments of the present application, by according to the measured value of the output electrical signal of the DC side of the voltage source converter valve and the reference value of the output voltage of the DC energy storage valve, the independent control of the output voltage of the DC energy storage valve can be achieved, and by according to the measured value of the grid connection point electrical signal of the voltage source converter valve and the reference value of the grid connection point electrical signal, the independent control of the output signal of the AC side of the voltage source converter valve can be achieved. It can be seen that the embodiments of the present application implement a virtual synchronous control method for independently controlling the voltage source converter valve and the DC energy storage valve in the energy storage system, so as to be applicable to the virtual synchronous control of the high-voltage DC directly-connected energy storage system, facilitate the implementation of the grid-forming control of the high-voltage DC directly-connected energy storage system, and be beneficial to improving the low-voltage fault ride-through ability of the energy storage system. In addition, by the way of independently controlling the voltage source converter valve and the DC energy storage valve in the energy storage system, the voltage source converter valve does not need to take into account the control of the DC side and the AC side, so as to simplify the complexity of the control loop of the voltage source converter valve.

[0157] In some embodiments, Figure 4 FIG. is a schematic flowchart of a virtual synchronous control method for an energy storage system provided in some other embodiments of the present application. On the basis of the above embodiments, the embodiments of the present application introduce the relevant content of "controlling the output signal of the AC side of the voltage source converter valve according to the measured value of the grid connection point electrical signal and the reference value of the grid connection point electrical signal" in step S302 above. Exemplarily, the measured value of the grid connection point electrical signal in the embodiments of the present application may include but is not limited to: the measured value of the active power at the grid connection point, the measured value of the reactive power at the grid connection point, and the measured value of the voltage at the grid connection point; the reference value of the grid connection point electrical signal may include but is not limited to: the reference value of the active power at the grid connection point, the reference value of the reactive power at the grid connection point, and the reference value of the voltage at the grid connection point. As Figure 4 shown, the above step S302 may include the following steps:

[0158] Step S3021: Control the output frequency of the AC side of the voltage source converter valve according to the measured value of the active power at the grid connection point and the reference value of the active power at the grid connection point.

[0159] In this step, the virtual synchronous control device may control the output frequency of the AC side of the voltage source converter valve according to the measured value of the active power at the grid connection point and the reference value of the active power at the grid connection point, realizing the active power-frequency control of the voltage source converter valve, so that the active power at the grid connection point can be adjusted to the reference value of the active power at the grid connection point.

[0160] Exemplarily, the virtual synchronous control device controls the output frequency of the AC side of the voltage source converter valve according to the active power deviation at the grid connection point between the measured value of the active power at the grid connection point and the reference value of the active power at the grid connection point, so that the active power at the grid connection point can be adjusted to the reference value of the active power at the grid connection point.

[0161] Step S3022: Control the output voltage amplitude of the AC side of the voltage source converter valve according to the measured value of the reactive power at the grid connection point, the measured value of the voltage at the grid connection point, the reference value of the reactive power at the grid connection point, and the reference value of the voltage at the grid connection point.

[0162] In this step, the virtual synchronous control device may control the output voltage amplitude of the AC side of the voltage source converter valve according to the measured value of the reactive power at the grid connection point, the measured value of the voltage at the grid connection point, the reference value of the reactive power at the grid connection point, and the reference value of the voltage at the grid connection point, realizing the reactive power-voltage control of the voltage source converter valve, so that the voltage at the grid connection point can be adjusted to the reference value of the voltage at the grid connection point.

[0163] Exemplarily, the virtual synchronous control device controls the output voltage amplitude of the AC side of the voltage source converter valve according to the grid connection point reactive power deviation between the grid connection point reactive power measurement value and the grid connection point reactive power reference value, and / or the grid connection point voltage deviation between the grid connection point voltage measurement value and the grid connection point voltage reference value, so that the grid connection point voltage can be adjusted to the grid connection point voltage reference value.

[0164] In summary, in the embodiments of the present application, the output frequency of the AC side of the voltage source converter valve is controlled according to the grid connection point active power measurement value and the grid connection point active power reference value. Further, the output voltage amplitude of the AC side of the voltage source converter valve is controlled according to the grid connection point reactive power measurement value, the grid connection point voltage measurement value, the grid connection point reactive power reference value, and the grid connection point voltage reference value. It can be seen that in the embodiments of the present application, the active power-frequency control of the voltage source converter valve is realized by according to the grid connection point active power measurement value and the grid connection point active power reference value, and the reactive power-voltage control of the voltage source converter valve is realized according to the grid connection point reactive power measurement value, the grid connection point voltage measurement value, the grid connection point reactive power reference value, and the grid connection point voltage reference value, thereby realizing the virtual synchronous control of decoupling the active power and reactive power of the voltage source converter valve, which is beneficial to the transient support of the grid connection point frequency and the grid connection point voltage, and thus can further improve the low voltage ride-through ability of the energy storage system.

[0165] In some embodiments, Figure 5 FIG. is a schematic flowchart of the output frequency control method for the AC side of the voltage source converter valve provided in some embodiments of the present application. On the basis of the above embodiments, the relevant content of "controlling the output frequency of the AC side of the voltage source converter valve according to the grid connection point active power measurement value and the grid connection point active power reference value" in step S3021 is introduced and explained exemplarily in the embodiments of the present application. As Figure 5 shown, the above step S3021 may include the following steps:

[0166] Step S501: Determine the grid connection point active power deviation according to the grid connection point active power measurement value and the grid connection point active power reference value.

[0167] In this step, the virtual synchronous control device can determine the grid connection point active power deviation according to the grid connection point active power measurement value and the grid connection point active power reference value, so as to control the output frequency of the AC side of the voltage source converter valve according to the grid connection point active power deviation, thereby realizing the active power-frequency control of the voltage source converter valve.

[0168] It should be noted that the active power-frequency control of the voltage source converter valve involved in the embodiments of the present application can convert the grid connection point active power deviation into the output frequency of the AC side of the voltage source converter valve by simulating the rotor inertia and governor droop characteristics of the synchronous machine.

[0169] In a possible implementation, the virtual synchronous control device can subtract the active power reference value at the grid connection point from the measured active power value at the grid connection point to obtain the active power deviation at the grid connection point.

[0170] In another possible implementation, the virtual synchronous control device can limit the active power reference value at the grid connection point according to the maximum limit value of active power and the minimum limit value of active power to obtain the limited active power reference value at the grid connection point, and subtract the measured active power value at the grid connection point from the limited active power reference value at the grid connection point to obtain the active power deviation at the grid connection point.

[0171] In this implementation, the virtual synchronous control device can limit the active power reference value at the grid connection point according to the maximum limit value of active power and the minimum limit value of active power, so that the limited active power reference value at the grid connection point can conform to the actual capacity of the energy storage system. Among them, the maximum limit value of active power refers to the maximum limit value of active power at the grid connection point, and the minimum limit value of active power refers to the minimum limit value of active power at the grid connection point.

[0172] It should be noted that the maximum limit value of active power and the minimum limit value of active power in the embodiments of the present application can be preset values, or can be values adjusted in real time according to the grid connection point fault detection signal. Among them, the grid connection point fault detection signal can be used to indicate whether a fault occurs in the energy storage system.

[0173] Exemplarily, if the active power reference value at the grid connection point is greater than the maximum limit value of active power, the virtual synchronous control device can use the maximum limit value of active power as the limited active power reference value at the grid connection point.

[0174] Another exemplarily, if the active power reference value at the grid connection point is less than or equal to the maximum limit value of active power and greater than or equal to the minimum limit value of active power, the virtual synchronous control device can use the active power reference value at the grid connection point as the limited active power reference value at the grid connection point.

[0175] Another exemplarily, if the active power reference value at the grid connection point is less than the minimum limit value of active power, the virtual synchronous control device can use the minimum limit value of active power as the limited active power reference value at the grid connection point.

[0176] Furthermore, the virtual synchronous control device can subtract the measured active power value at the grid connection point from the limited active power reference value at the grid connection point to obtain the active power deviation at the grid connection point, so as to more accurately control the output frequency of the AC side of the voltage source converter valve according to the active power deviation at the grid connection point.

[0177] Step S502: Perform a first closed-loop control process on the active power deviation at the grid connection point to obtain a closed-loop result.

[0178] In this step, the virtual synchronous control device can perform a first closed-loop control process on the active power deviation at the grid connection point, so as to perform control based on the feedback signal, which is conducive to obtaining an accurate closed-loop result. Among them, the first closed-loop control process can include, but is not limited to, a closed-loop control method with the damping coefficient as the feedback coefficient, the product of the inertia time constant and the preset coefficient C as the integral coefficient, and the latch coefficient as the proportional coefficient.

[0179] Exemplarily, Figure 6A is a schematic flowchart of the first closed-loop control process method provided by some embodiments of the present application. As Figure 6A shown, the virtual synchronous control device can determine the first feedback signal according to the historical closed-loop result and the damping coefficient D, and perform a first integration process on the difference signal between the active power deviation at the grid connection point and the first feedback signal to obtain the closed-loop result. Among them, the historical closed-loop result can include, but is not limited to, the result obtained by the virtual synchronous control device performing the previous first closed-loop control process on the historical active power deviation at the grid connection point (or the active power deviation at the grid connection point at the previous moment).

[0180] In the embodiments of the present application, the virtual synchronous control device can multiply the damping coefficient D by the historical closed-loop result to obtain the first feedback signal. Further, the virtual synchronous control device can subtract the first feedback signal from the active power deviation at the grid connection point to obtain the difference signal, and perform a first integration process on the difference signal to obtain the closed-loop result.

[0181] It should be noted that the damping coefficient D in the embodiments of the present application can be a preset value, or can be a value adjusted in real time according to the grid connection point fault detection signal.

[0182] Exemplarily, Figure 6B is a schematic flowchart of the first integration process method provided by some embodiments of the present application. As Figure 6B shown, the virtual synchronous control device can perform a first integration process on the difference signal according to the inertia time constant H and the latch coefficient f SH to obtain the closed-loop result.

[0183] In the embodiments of the present application, the virtual synchronous control device can use the product of the inertia time constant H and the preset coefficient C as the integral coefficient and the latch coefficient f SH as the proportional coefficient to perform a first integration process on the difference signal to obtain the closed-loop result. For example, the preset coefficient C can include, but is not limited to, 2.

[0184] It should be noted that the latch coefficient f in the embodiments of the present application SH can be a preset value, or can be a value adjusted in real time according to the grid connection point fault detection signal.

[0185] Step S503: Control the output frequency according to the closed-loop result and the rated grid angular frequency.

[0186] In this step, the virtual synchronous control device can control the output frequency according to the closed-loop result and the rated grid angular frequency, where the rated grid angular frequency may include, but is not limited to, the per-unit value of the rated grid angular frequency, and / or the nominal value of the rated grid angular frequency (or non-per-unit value).

[0187] Exemplarily, Figure 6C is a schematic flowchart of the control method for the output frequency provided by some embodiments of the present application. As Figure 6C shown, the virtual synchronous control device can add the closed-loop result to the per-unit value ω n，pu of the rated grid angular frequency, and then multiply the sum result by the nominal value ω n of the rated grid angular frequency to obtain the output frequency ω VSG .

[0188] For ease of understanding, in the following embodiments of the present application, the overall process of the active power-frequency control method for the voltage source converter valve is introduced. Figure 6D is a schematic flowchart of the active power-frequency control method provided by some embodiments of the present application. As Figure 6D shown, the virtual synchronous control device can limit the per-unit value P lim,max of the reference active power at the grid connection point according to the maximum limit value P lim,min and the minimum limit value P ref，pu of the active power to obtain the limited reference active power at the grid connection point.

[0189] Further, the virtual synchronous control device can subtract the per-unit value P pu of the measured active power at the grid connection point from the limited reference active power at the grid connection point to obtain the active power deviation at the grid connection point.

[0190] Further, the virtual synchronous control device can perform a first closed-loop control process on the active power deviation at the grid connection point to obtain a closed-loop result. The implementable manner of the first closed-loop control process can refer to the relevant content in the above embodiments and will not be elaborated here.

[0191] Further, the virtual synchronous control device can add the closed-loop result to the per-unit value ω n , pu and then multiply the sum result by the nominal value ω n of the rated grid angular frequency to obtain the output frequency ω VSG , and the reference phase angle θ can be obtained by integrating the output frequency ω VSG .VSG , so that it can be synchronized with the grid frequency and phase autonomously.

[0192] It should be noted that the maximum limit value of the active power P in the embodiments of this application lim,max , the minimum limit value of the active power P lim,min , the damping coefficient D or the latching coefficient f SH can be a value adjusted in real time according to the grid connection point fault detection signal f sig . So that the reference value of the active power of the energy storage system does not exceed the actual capacity of the system during the fault, thereby improving the transient stability of the energy storage system during the fault. Among them, the grid connection point fault detection signal can be used to indicate whether the energy storage system fails.

[0193] In the embodiments of this application, when the reference phase angle θ VSG is larger than the phase angle θ of the grid connection point, or the active power of the grid connection point is greater than the reference value of the active power of the grid connection point, the virtual synchronous control device will reduce the output frequency of the AC side of the voltage source converter valve through the VSG active power-frequency control method, thereby reducing the output phase angle, and finally adjusting the active power of the grid connection point to the per-unit value P of the reference value of the active power of the grid connection point ref，pu , and the grid connection point frequency and the grid connection point phase are synchronized with the grid frequency and the grid phase respectively.

[0194] In summary, in the embodiments of this application, the active power deviation of the grid connection point is determined according to the measured value of the active power of the grid connection point and the reference value of the active power of the grid connection point. Further, the first closed-loop control process is performed on the active power deviation of the grid connection point to obtain a closed-loop result, and the output frequency is controlled according to the closed-loop result and the rated angular frequency of the grid. It can be seen that the active power-frequency control of the voltage source converter valve in the embodiments of this application is beneficial to adjusting the active power of the grid connection point to the reference value of the active power of the grid connection point by converting the active power deviation of the grid connection point into the output frequency of the AC side of the voltage source converter valve.

[0195] In some embodiments, Figure 7 is a schematic flow chart of the output voltage amplitude control method for the AC side of the voltage source converter valve provided in some embodiments of this application. On the basis of the above embodiments, the relevant content of "controlling the output voltage amplitude of the AC side of the voltage source converter valve according to the measured value of the reactive power of the grid connection point, the measured value of the voltage of the grid connection point, the reference value of the reactive power of the grid connection point, and the reference value of the voltage of the grid connection point" in step S3022 above is introduced and explained exemplarily. As Figure 7 shown, the above step S3022 may include the following steps:

[0196] Step S701: Determine the amplitude of the first internal electromotive force of the voltage source converter valve according to the measured value of the reactive power at the grid connection point, the measured value of the voltage at the grid connection point, the reference value of the reactive power at the grid connection point, and the reference value of the voltage at the grid connection point.

[0197] In this step, the virtual synchronous control device can determine the reactive power deviation and voltage deviation at the grid connection point according to the measured value of the reactive power at the grid connection point, the measured value of the voltage at the grid connection point, the reference value of the reactive power at the grid connection point, and the reference value of the voltage at the grid connection point, so as to determine the amplitude of the first internal electromotive force of the voltage source converter valve, that is, the output voltage amplitude on the AC valve side of the voltage source converter valve, according to the reactive power deviation and / or voltage deviation at the grid connection point, thereby realizing the reactive power-voltage control of the voltage source converter valve.

[0198] It should be noted that in the embodiments of the present application, the reactive power-voltage control of the voltage source converter valve can convert the reactive power deviation and voltage deviation at the grid connection point into the amplitude of the first internal electromotive force of the voltage source converter valve by simulating the excitation regulation equation of the synchronous machine.

[0199] Exemplarily, Figure 8A is a schematic flow chart of the method for determining the amplitude of the first internal electromotive force of the voltage source converter valve provided by some embodiments of the present application. On the basis of the above embodiments, the embodiments of the present application provide an exemplary introduction to the relevant content of "determining the amplitude of the first internal electromotive force of the voltage source converter valve according to the measured value of the reactive power at the grid connection point, the measured value of the voltage at the grid connection point, the reference value of the reactive power at the grid connection point, and the reference value of the voltage at the grid connection point" in step S701 above. As Figure 8A shown, the above step S701 may include the following steps:

[0200] Step S7011: Determine the reactive power deviation at the grid connection point according to the measured value of the reactive power at the grid connection point and the reference value of the reactive power at the grid connection point.

[0201] In this step, the virtual synchronous control device can determine the reactive power deviation at the grid connection point according to the measured value of the reactive power at the grid connection point and the reference value of the reactive power at the grid connection point, so as to determine the amplitude of the first internal electromotive force of the voltage source converter valve according to the reactive power deviation at the grid connection point.

[0202] Exemplarily, the virtual synchronous control device can subtract the measured value of the reactive power at the grid connection point from the reference value of the reactive power at the grid connection point to obtain the reactive power deviation at the grid connection point.

[0203] Step S7012: Determine the voltage deviation at the grid connection point according to the measured value of the voltage at the grid connection point and the reference value of the voltage at the grid connection point.

[0204] In this step, the virtual synchronous control device can determine the grid connection point voltage deviation based on the grid connection point voltage measurement value and the grid connection point voltage reference value, so as to determine the amplitude of the first internal potential of the voltage source converter valve according to the grid connection point voltage deviation.

[0205] Exemplarily, the virtual synchronous control device can subtract the grid connection point voltage measurement value from the grid connection point voltage reference value to obtain the grid connection point voltage deviation.

[0206] Step S7013: Perform a second integration process according to the grid connection point reactive power deviation and / or the grid connection point voltage deviation to obtain the amplitude of the first internal potential.

[0207] In this step, the virtual synchronous control device can perform a second integration process according to the grid connection point reactive power deviation and / or the grid connection point voltage deviation to obtain the amplitude of the first internal potential.

[0208] In a possible implementation manner, the virtual synchronous control device can perform a second integration process on the grid connection point reactive power deviation or the adjusted grid connection point reactive power deviation to obtain the amplitude of the first internal potential.

[0209] In another possible implementation manner, the virtual synchronous control device can perform a second integration process on the grid connection point voltage deviation or the adjusted grid connection point voltage deviation to obtain the amplitude of the first internal potential.

[0210] In another possible implementation manner, the virtual synchronous control device can determine the sum of deviations according to the grid connection point reactive power deviation and the grid connection point voltage deviation, and perform a second integration process on the sum of deviations to obtain the amplitude of the first internal potential. The sum of deviations can include but is not limited to the first sum of deviations or the second sum of deviations.

[0211] Exemplarily, the virtual synchronous control device can add the grid connection point reactive power deviation and the grid connection point voltage deviation to obtain the first sum of deviations, and perform a second integration process on the first sum of deviations to obtain the amplitude of the first internal potential.

[0212] In yet another example, the virtual synchronous control device can adjust the grid connection point reactive power deviation and the grid connection point voltage deviation respectively, and add the adjusted grid connection point reactive power deviation and the adjusted grid connection point voltage deviation to obtain the second sum of deviations; further, the virtual synchronous control device can perform a second integration process on the second sum of deviations to obtain the amplitude of the first internal potential.

[0213] Considering that in order to make the first internal potential amplitude more in line with the actual capacity of the energy storage system, the virtual synchronous control device can perform a second integration process based on the reactive power deviation at the grid connection point and / or the voltage deviation at the grid connection point to obtain the first initial internal potential amplitude, and limit the first initial internal potential amplitude according to the maximum internal potential amplitude and the minimum internal potential amplitude to obtain the first internal potential amplitude. Among them, the maximum internal potential amplitude refers to the maximum internal potential amplitude on the AC side of the voltage source converter valve, and the minimum internal potential amplitude refers to the minimum internal potential amplitude on the AC side of the voltage source converter valve.

[0214] It should be noted that the maximum internal potential amplitude and the minimum internal potential amplitude in the embodiments of the present application can be preset values, or can be values obtained by other means.

[0215] Exemplarily, if the first initial internal potential amplitude is greater than the maximum internal potential amplitude, the virtual synchronous control device can use the maximum internal potential amplitude as the first internal potential amplitude.

[0216] Another exemplarily, if the first initial internal potential amplitude is less than or equal to the maximum internal potential amplitude and greater than or equal to the minimum internal potential amplitude, the virtual synchronous control device can use the first initial internal potential amplitude as the first internal potential amplitude.

[0217] Another exemplarily, if the first initial internal potential amplitude is less than the minimum internal potential amplitude, the virtual synchronous control device can use the minimum internal potential amplitude as the first internal potential amplitude.

[0218] It can be seen that in the embodiments of the present application, by limiting the first initial internal potential amplitude according to the maximum internal potential amplitude and the minimum internal potential amplitude, a more accurate first internal potential amplitude can be obtained, so that the output voltage amplitude on the AC side of the voltage source converter valve can be controlled more accurately according to the first internal potential amplitude.

[0219] For the convenience of understanding, in the following embodiments of the present application, the overall process of the reactive power-voltage control method of the voltage source converter valve is introduced. Figure 8B For the flow diagram of the reactive power-voltage control method provided by some embodiments of the present application, as Figure 8B shown, the virtual synchronous control device can subtract the per-unit value Q ref,pu of the reactive power reference value at the grid connection point from the per-unit value Q pu of the measured reactive power value at the grid connection point to obtain the reactive power deviation at the grid connection point.

[0220] Furthermore, the virtual synchronous control device can subtract the per-unit value u s,ref,pu of the voltage reference value at the grid connection point from the per-unit value u s,pu of the measured voltage value at the grid connection point to obtain the voltage deviation at the grid connection point.

[0221] Further, the virtual synchronous control device can adjust the reactive power deviation at the grid connection point according to the reactive droop coefficient K q to obtain the adjusted reactive power deviation at the grid connection point, and adjust the voltage deviation at the grid connection point according to the voltage droop coefficient K v to obtain the adjusted voltage deviation at the grid connection point. Further, the virtual synchronous control device can sum the adjusted reactive power deviation at the grid connection point and the adjusted voltage deviation at the grid connection point to obtain a second deviation sum.

[0222] It should be noted that by changing the reactive droop coefficient K q and / or the voltage droop coefficient K v value, the switching of the reactive power-voltage control mode can be realized. When K q is 1 and K v is 0, it corresponds to constant reactive power control; when K q is 0 and K v is 1, it corresponds to constant voltage control; when K q and K v are both not 0, it corresponds to reactive power-voltage droop control. When K q and K v are respectively selected with appropriate values, the adaptive adjustment of the reactive power at the grid connection point during system faults and the fault recovery process can be realized to support the stability of the voltage at the grid connection point.

[0223] Further, the virtual synchronous control device can perform a second integration process on the second deviation sum according to the first internal potential control integration coefficient K Ei1 to obtain the first initial internal potential amplitude.

[0224] Further, the virtual synchronous control device can limit the first initial internal potential amplitude according to the maximum internal potential amplitude E max and the minimum internal potential amplitude E min to obtain the first internal potential amplitude E.

[0225] It can be seen that the reactive power-voltage control in the embodiment of the present application simulates the excitation regulation equation of a synchronous machine, takes the deviation sum corresponding to the reactive power deviation at the grid connection point and the voltage deviation at the grid connection point as an error signal, and can obtain the first internal potential amplitude through integration processing by an integrator.

[0226] Step S702, control the output voltage amplitude on the AC side of the voltage source converter valve according to the first internal potential amplitude of the voltage source converter valve.

[0227] In this step, the virtual synchronous control device can control the output voltage amplitude on the AC side of the voltage source converter valve according to the first internal potential amplitude of the voltage source converter valve.

[0228] Exemplarily, the virtual synchronous control device may control the output voltage amplitude of the AC side of the voltage source converter valve in a manner of performing voltage outer loop control processing and / or current limiting inner loop processing according to the amplitude of the first internal electromotive force of the voltage source converter valve.

[0229] The voltage outer loop control processing in the embodiments of the present application can be used for, including but not limited to, PI regulation processing, dynamic virtual impedance processing, or static virtual impedance processing based on the amplitude of the first internal electromotive force and the measured value of the grid connection point voltage.

[0230] The current limiting inner loop processing in the embodiments of the present application may include, but not limited to, current limiting processing and / or current inner loop processing.

[0231] Exemplarily, Figure 9A FIG. is a schematic flow chart of a method for controlling the output voltage amplitude of the AC side of a voltage source converter valve provided in some embodiments of the present application. On the basis of the above embodiments, the embodiments of the present application exemplarily introduce and explain the related content of "controlling the output voltage amplitude of the AC side of the voltage source converter valve according to the amplitude of the first internal electromotive force of the voltage source converter valve" in step S702 above. As Figure 9A shown, the above step S702 may include the following steps:

[0232] Step S7021: Perform voltage outer loop control processing according to the amplitude of the first internal electromotive force of the voltage source converter valve and the measured value of the grid connection point voltage to obtain the current command value of the current inner loop.

[0233] In this step, the virtual synchronous control device may perform voltage outer loop control processing according to the amplitude of the first internal electromotive force of the voltage source converter valve and the measured value of the grid connection point voltage to obtain the current command value of the current inner loop.

[0234] Exemplarily, the measured value of the grid connection point voltage in the embodiments of the present application may include, but not limited to, the first axis voltage measurement component, and / or, the second axis voltage measurement component. For example, the first axis voltage measurement component may be the measured value of the q-axis component of the grid connection point voltage in the dq coordinate system (or the measured value of the q-axis component of the output voltage of the AC network side of the voltage source converter valve in the dq coordinate system), and the second axis voltage measurement component may be the measured value of the d-axis component of the grid connection point voltage in the dq coordinate system (or the measured value of the d-axis component of the output voltage of the AC network side of the voltage source converter valve in the dq coordinate system).

[0235] The voltage outer loop control processing in the embodiments of the present application may include, but not limited to, any one of the following: first PI regulation processing, dynamic virtual impedance processing, or static virtual impedance processing.

[0236] The current command value of the current inner loop in the embodiments of the present application may include, but is not limited to, the first-axis current component command value of the current inner loop, and / or the second-axis current component command value of the current inner loop. For example, the first-axis current component command value of the current inner loop may be the q-axis component command value of the current of the current inner loop (or the output current on the AC valve side of the voltage source converter valve) in the dq coordinate system, and the second-axis current component command value may be the d-axis component command value of the current of the current inner loop (or the output current on the AC valve side of the voltage source converter valve) in the dq coordinate system.

[0237] Exemplarily, the virtual synchronous control device may obtain the current command value of the current inner loop by performing a first PI adjustment process, a dynamic virtual impedance process, or a static virtual impedance process on the first internal potential amplitude of the voltage source converter valve and the measured value of the grid connection point voltage.

[0238] Exemplarily, Figure 9B is a schematic flowchart of the first PI adjustment process method provided for some embodiments of the present application. As Figure 9B shown, in the embodiments of the present application, on the one hand, the virtual synchronous control device may subtract the per-unit value u of the d-axis component of the grid connection point voltage in the dq coordinate system from the first internal potential amplitude E, and perform a PI process on the subtraction result, so as to obtain the per-unit value i of the d-axis component command value of the current of the current inner loop in the dq coordinate system. d1,pu On the other hand, the virtual synchronous control device may subtract the per-unit value u of the q-axis component of the grid connection point voltage in the dq coordinate system from zero, and perform a PI process on the subtraction result, so as to obtain the per-unit value i of the q-axis component command value of the current of the current inner loop in the dq coordinate system. d2,cmd,pu q1,pu q2,cmd,pu

[0239] Exemplarily, Figure 9C is a schematic flowchart of the dynamic virtual impedance process method provided for some embodiments of the present application. As Figure 9C shown, in the embodiments of the present application, on the one hand, the virtual synchronous control device may subtract the per-unit value u of the d-axis component of the grid connection point voltage in the dq coordinate system from the first internal potential amplitude E, and add the result to the product of the per-unit value of the q-axis component command value of the current of the historical current inner loop in the dq coordinate system and the virtual reactance X. d1,pu v Further, the virtual synchronous control device may perform the process of the first branch as shown in Figure 9C on the addition result, so as to obtain the per-unit value i of the d-axis component command value of the current of the current inner loop in the dq coordinate system. d2,cmd,pu Among them, R v represents the virtual resistance, and s represents the differential after Laplace transform.

[0240] On the other hand, the virtual synchronous control device can subtract the per-unit value u of the q-axis component of the zero and the grid connection point voltage in the dq coordinate system q1,pu and subtract it from the product of the per-unit value of the d-axis component command value of the current in the historical current inner loop and the virtual reactance X v . Further, the virtual synchronous control device can perform the processing of the fourth branch as shown in Figure 9C to obtain the per-unit value i of the q-axis component command value of the current in the current inner loop in the dq coordinate system q2,cmd,pu .

[0241] Exemplarily, Figure 9D is a schematic flowchart of the static virtual impedance processing method provided by some embodiments of the present application. As shown in Figure 9D , the virtual synchronous control device can subtract the per-unit value u of the d-axis component measurement value of the first internal potential amplitude E and the grid connection point voltage in the dq coordinate system d1,pu to obtain the first subtraction result, and subtract the per-unit value u of the q-axis component measurement value of the zero and the grid connection point voltage in the dq coordinate system q1,pu to obtain the second subtraction result.

[0242] Further, the virtual synchronous control device can perform the processing of the first branch as shown in Figure 9D on the first subtraction result to obtain the first processing result, and perform the processing of the third branch as shown in Figure 9D on the second subtraction result to obtain the third processing result. Further, the virtual synchronous control device can add the first processing result and the third processing result to obtain the per-unit value i of the d-axis component command value of the current in the current inner loop in the dq coordinate system d2,cmd,pu .

[0243] Further, the virtual synchronous control device can perform the processing of the second branch as shown in Figure 9D on the first subtraction result to obtain the second processing result, and perform the processing of the fourth branch as shown in Figure 9D on the second subtraction result to obtain the fourth processing result. Further, the virtual synchronous control device can subtract the fourth processing result from the second processing result to obtain the per-unit value i of the q-axis component command value of the current in the current inner loop in the dq coordinate system q2,cmd,pu .

[0244] Step S7022: Perform current limiting inner loop processing according to the current command value to obtain the output voltage signal of the AC side of the voltage source converter valve.

[0245] Exemplarily, the current limiting inner loop processing in the embodiments of the present application may include, but is not limited to: current limiting processing, and / or, current inner loop processing.

[0246] The output voltage signal on the AC side of the voltage source converter valve in the embodiments of the present application may include, but is not limited to: the first-axis output voltage component on the AC side of the voltage source converter valve, and / or, the second-axis output voltage component on the AC side of the voltage source converter valve. For example, the first-axis output voltage component on the AC side of the voltage source converter valve may be the q-axis component of the output voltage on the AC side of the voltage source converter valve in the dq coordinate system, and the second-axis output voltage component on the AC side of the voltage source converter valve may be the d-axis component of the output voltage on the AC side of the voltage source converter valve in the dq coordinate system.

[0247] In this step, the virtual synchronous control device may perform current limiting processing on the current command value to obtain the current command value after limiting (or referred to as the output current reference value on the AC side of the voltage source converter valve). Further, the virtual synchronous control device may perform current inner loop processing on the current command value after limiting to obtain the output voltage signal on the AC side of the voltage source converter valve.

[0248] Exemplarily, the virtual synchronous control device may perform current inner loop processing on the current command value after limiting according to the measured output current value and the measured output voltage value on the AC side of the voltage source converter valve.

[0249] Step S7023: Control the output voltage amplitude on the AC side of the voltage source converter valve according to the output voltage signal on the AC side of the voltage source converter valve.

[0250] In this step, the virtual synchronous control device may generate a first control signal according to the output voltage signal on the AC side of the voltage source converter valve, where the first control signal is used to control the output voltage amplitude on the AC side of the voltage source converter valve.

[0251] Exemplarily, the virtual synchronous control device may perform coordinate transformation processing on the output voltage signal on the AC side of the voltage source converter valve to obtain the transformed output voltage signal on the AC side of the voltage source converter valve, and generate a first control signal according to the transformed output voltage signal on the AC side of the voltage source converter valve. Among them, the coordinate transformation processing may include, but is not limited to, transformation from the dq coordinate system to the abc coordinate system; the transformed output voltage signal on the AC side of the voltage source converter valve may include, but is not limited to, the output voltage on the AC side of the voltage source converter valve in the abc coordinate system.

[0252] In the embodiments of the present application, by sequentially performing voltage outer-loop control processing and current-limiting inner-loop processing according to the first internal potential amplitude of the voltage-source converter valve and the measured value of the grid connection point voltage, an output voltage signal of the AC side of the voltage-source converter valve is obtained, and according to the output voltage signal of the AC side of the voltage-source converter valve, the output voltage amplitude of the AC side of the voltage-source converter valve is controlled. It can be seen that the embodiments of the present application achieve accurate control of the output voltage amplitude of the AC side of the voltage-source converter valve according to the first internal potential amplitude of the voltage-source converter valve.

[0253] In summary, in the embodiments of the present application, according to the measured value of the reactive power at the grid connection point, the measured value of the grid connection point voltage, the reference value of the reactive power at the grid connection point, and the reference value of the grid connection point voltage, the first internal potential amplitude of the voltage-source converter valve is determined. Further, according to the first internal potential amplitude of the voltage-source converter valve, the output voltage amplitude of the AC side of the voltage-source converter valve is controlled. It can be seen that the reactive power-voltage control of the voltage-source converter valve in the embodiments of the present application converts the reactive power deviation at the grid connection point, and / or, the grid connection point voltage deviation into the first internal potential amplitude of the voltage-source converter valve, and controls the output voltage amplitude of the AC side of the voltage-source converter valve according to the first internal potential amplitude, which is beneficial to adjusting the grid connection point voltage to the reference value of the grid connection point voltage.

[0254] In some embodiments, on the basis of the above embodiments, the adjustment process of the above maximum active power limit value and the minimum active power limit value is introduced and illustrated exemplarily in the embodiments of the present application.

[0255] In order to ensure that the active power reference value does not exceed the actual system capacity during a fault, so as to alleviate the problem of voltage and active power fluctuations at the grid connection point, in the embodiments of the present application, the virtual synchronous control device of the energy storage system can also adjust the maximum active power limit value P lim,max and the minimum active power limit value according to the grid connection point fault detection signal.

[0256] In one possible implementation, when the virtual synchronous control device detects the grid connection point fault detection signal f sig used to indicate that a fault has occurred in the energy storage system, the maximum active power limit value P lim,max can be adjusted to the target maximum power limit value P lim,max,pu , and the minimum active power limit value P lim,min can be adjusted to the target minimum power limit value P lim,min,pu .

[0257] Exemplarily, if the grid connection point fault detection signal f sig is the first preset signal, then the grid connection point fault detection signal f sig can be used to indicate that a fault has occurred in the energy storage system; if the grid connection point fault detection signal f sig is the second preset signal, then the grid connection point fault detection signal fsig It can be used to indicate that there is no fault in the energy storage system. For example, the first preset signal can be 1 and the second preset signal can be 0.

[0258] It should be understood that when there is no fault in the energy storage system, the maximum limit value of active power P lim,max can be the preset maximum limit value of power, and the minimum limit value of active power P lim,min can be the preset minimum limit value of power. For example, the preset maximum limit value of power can be 1 pu, and the preset minimum limit value of power can be -1 pu.

[0259] Exemplarily, the maximum limit value of target power P lim,max,pu and the minimum limit value of target power P lim,min,pu in the embodiments of the present application are both related to the measured value of shunt reactive power, the measured value of shunt voltage, and the drop amplitude of the measured value of shunt voltage during a fault. Among them, the measured value of shunt reactive power and the measured value of shunt voltage can correspond to the shunt voltage feasible region, and the drop amplitude of the measured value of shunt voltage during a fault can correspond to the drop situation of the positive sequence component amplitude of the shunt voltage.

[0260] 1) Shunt voltage feasible region

[0261] The virtual synchronous control device can determine the first candidate maximum limit value of power P lim,max,us,pu and the first candidate minimum limit value of power P lim,min,us,pu .

[0262] Exemplarily, the virtual synchronous control device can determine the first candidate maximum limit value of power P lim,max,us,pu through the following formula (1) according to the measured value of shunt reactive power and the measured value of shunt voltage.

[0263]

[0264] where u s,pu represents the per-unit value of the measured value of shunt voltage, i s,lim,pu represents the preset current limit value, and Q pu represents the per-unit value of the measured value of shunt reactive power.

[0265] Of course, the virtual synchronous control device can also determine the first candidate maximum limit value of power P lim,max,us,pu through other deformations or equivalent formulas of the above formula (1) according to the measured value of shunt reactive power and the measured value of shunt voltage.

[0266] Furthermore, the virtual synchronous control device can determine the first candidate minimum limit value of power P lim,max,us,pu according to the first candidate maximum limit value of power Plim,min,us,pu 。

[0267] Exemplarily, the virtual synchronous control device determines the first candidate power minimum limit amplitude P according to the maximum limit amplitude P of the first candidate power lim,max,us,pu and can determine the first candidate power minimum limit amplitude P through the following formula (2) lim,min,us,pu 。

[0268] P lim,min,us,pu = -P lim,max,us,pu Formula (2)

[0269] Of course, the virtual synchronous control device determines the first candidate power minimum limit amplitude P according to the maximum limit amplitude P of the first candidate power lim,max,us,pu and can also determine the first candidate power minimum limit amplitude P through other deformations or equivalent formulas of the above formula (2) lim,min,us,pu 。

[0270] 2) The falling condition of the positive sequence component amplitude of the grid connection point voltage

[0271] Since the positive sequence component amplitude of the grid connection point voltage is positively correlated with the active power, the virtual synchronous control device can determine the second candidate power maximum limit amplitude P according to the falling amplitude of the grid connection point voltage measurement value during the fault lim,max,ud1,pu and the second candidate power minimum limit amplitude P lim,min,ud1,pu 。

[0272] Exemplarily, the virtual synchronous control device can determine the second candidate power maximum limit amplitude P through the following formula (3) according to the falling amplitude of the grid connection point voltage measurement value during the fault lim,max,ud1,pu 。

[0273] P lim,max,ud1,pu = u record Formula (3)

[0274] where u record represents the falling amplitude of the grid connection point voltage measurement value during the fault

[0275] Of course, the virtual synchronous control device can also determine the second candidate power maximum limit amplitude P through other deformations or equivalent formulas of the above formula (3) according to the falling amplitude of the grid connection point voltage measurement value during the fault lim,max,ud1,pu 。

[0276] Furthermore, the virtual synchronous control device can determine the second candidate power minimum limit amplitude P according to the second candidate power maximum limit amplitude P lim,max,ud1,pu and determine the second candidate power minimum limit amplitude P lim,min,ud1,pu 。

[0277] Exemplarily, the virtual synchronous control device determines the second candidate power minimum limit amplitude P through the following formula (4) according to the second candidate power maximum limit amplitude P lim,max,ud1,pu and can determine the second candidate power minimum limit amplitude P through the following formulalim,min,ud1,pu .

[0278] P lim,min,ud1,pu = -P lim,max,ud1,pu Formula (4)

[0279] Of course, the virtual synchronous control device can also determine the minimum limit amplitude P of the second candidate power through other deformations or equivalent formulas of the above formula (4) according to the maximum limit amplitude P of the second candidate power lim,max,ud1,pu . lim,min,ud1,pu .

[0280] 3) Determine the target power limit amplitude according to the candidate power limit amplitude

[0281] The virtual synchronous control device can take the minimum value of the first candidate power maximum limit amplitude P lim,max,us,pu and the second candidate power maximum limit amplitude P lim,max,ud1,pu as the target power maximum limit amplitude P lim,max,pu , and take the maximum value of the first candidate power minimum limit amplitude P lim,min,us,pu and the second candidate power minimum limit amplitude P lim,min,ud1,pu as the target power minimum limit amplitude P lim,min,pu .

[0282] Of course, the virtual synchronous control device can also determine the target power maximum limit amplitude P lim,max,pu and the target power minimum limit amplitude P lim,min,pu in other ways

[0283] In another possible implementation, when the virtual synchronous control device detects the grid connection point fault detection signal f sig used to indicate that the fault is cleared within the first preset duration, the maximum limit amplitude P of the active power can be adjusted from the target power maximum limit amplitude P lim,max to the preset power maximum limit amplitude, and the minimum limit amplitude P of the active power can be adjusted from the target power minimum limit amplitude P lim,max,pu to the preset power minimum limit amplitude lim,min . lim,min,pu

[0284] Exemplarily, the virtual synchronous control device can adjust the maximum limit amplitude P of the active power from the target power maximum limit amplitude P lim,max to the preset power maximum limit amplitude at the first preset rate, and adjust the minimum limit amplitude P of the active power from the target power minimum limit amplitude P lim,max,pu to the preset power minimum limit amplitude at the second preset rate lim,min . lim,min,pu

[0285] ​​For ease of understanding, the following embodiments of the present application will exemplarily introduce and explain the overall process of the active power limit value adjustment method. Figure 10 The flowchart of the active power limit value adjustment method provided by some embodiments of the present application is shown in Figure 10 As shown, the method of the embodiments of the present application may include the following steps:

[0286] Step S1001. In the initial state, the virtual synchronous control device may set the maximum active power limit value P lim,max to the preset maximum power limit value, and set the minimum active power limit value P lim,min to the preset minimum power limit value.

[0287] Step S1002. The virtual synchronous control device may detect whether the grid connection point fault detection signal f sig is the first preset signal.

[0288] If it is detected that the grid connection point fault detection signal f sig is the first preset signal, that is, it is detected that the energy storage system has a fault according to the grid connection point fault detection signal f sig , then step S1003 is executed; if it is detected that the grid connection point fault detection signal f sig is not the first preset signal, that is, it is detected that the energy storage system has no fault according to the grid connection point fault detection signal f sig , then return to execute step S1002.

[0289] Step S1003. The virtual synchronous control device adjusts the maximum active power limit value P lim,max to the target maximum power limit value P lim,max,pu , and adjusts the minimum active power limit value P lim,min to the target minimum power limit value P lim,min,pu .

[0290] Step S1004. The virtual synchronous control device may detect whether the grid connection point fault detection signal f sig is the second preset signal, and whether the change amount Δf sig of the grid connection point fault detection signal is less than 0.

[0291] If it is detected that the grid connection point fault detection signal f sig is the second preset signal, and the change amount Δf sig of the grid connection point fault detection signal is less than 0, that is, it is detected that the grid connection point fault detection signal f sig is used to indicate that the fault is cleared within the first preset duration, then step S1005 is executed; if it is detected that the grid connection point fault detection signal f sig is not the second preset signal, or the change amount Δf sigNot less than 0, that is, the grid connection point fault detection signal f is detected sig If it is used to indicate that the fault is not cleared within the first preset duration, return to execute step S1004

[0292] Step S1005: The virtual synchronous control device can set the maximum limit value of the active power P lim,max From the target maximum limit value of the power P lim,max,pu Adjust it to the preset maximum limit value of the power, and adjust the minimum limit value of the active power P lim,min From the target minimum limit value of the power P lim,min,pu Adjust it to the preset minimum limit value of the power

[0293] In summary, in the embodiments of the present application, by adjusting the target maximum limit value and the target minimum limit value of the power according to the reactive power measurement value at the grid connection point, the grid connection point voltage measurement value, and the drop amplitude of the grid connection point voltage measurement value during the fault, the active power reference value of the energy storage system during the fault can not exceed the actual system capacity, thereby alleviating the problem that the input of the active power is always greater than zero, resulting in the continuous increase of the power angle, and finally leading to the periodic change of the grid connection point voltage and the large swing of the active power. Therefore, the transient stability of the energy storage system during the fault can be improved

[0294] In some embodiments, on the basis of the above embodiments, the adjustment processes of the damping coefficient and the latching coefficient in the embodiments of the present application are introduced and illustrated exemplarily

[0295] Considering that it is necessary to further prevent the power angle movement during the fault to prevent the periodic fluctuation of the grid connection point voltage and alleviate the problem of the power angle swing after the fault recovery, the core solution idea in the embodiments of the present application is to make the absolute value of ΔP pu =P ref,pu -P pu As small as possible, the following two methods can be adopted: 1. Adaptively increase the damping coefficient D; 2. Adaptively adjust the latching coefficient to adjust the integral link of the active power frequency

[0296] In the embodiments of the present application, the virtual synchronous control device of the energy storage system can also adjust the damping coefficient D and the latching coefficient f according to the grid connection point fault detection signal SH .

[0297] In a possible implementation manner, when the virtual synchronous control device detects the grid connection point fault detection signal f sig Used to indicate that a fault occurs in the energy storage system, the damping coefficient D can be adjusted to the target damping coefficient D f , and the latching coefficient f SH Adjust to the target latching coefficient. For example, the target latching coefficient can be zero

[0298] Correspondingly, as Figure 6C shown, the integral link of the first integral processing can be expressed by the following formula (5).

[0299]

[0300] It should be understood that when there is no fault in the energy storage system, the damping coefficient D can be the preset damping coefficient D 0 , and the latching coefficient f SH can be the preset latching coefficient. For example, the preset latching coefficient can be 1. Correspondingly, as Figure 6C shown, the integral link of the first integral processing can be expressed by the following formula (6).

[0301]

[0302] The target damping coefficient D in the embodiments of the present application f can be related to the offset of the active power at the point of common coupling during the fault and the allowable frequency offset during the fault.

[0303] Exemplarily, according to the offset ΔP of the active power at the point of common coupling during the fault and the allowable frequency offset Δf during the fault, the virtual synchronous control device can determine the target damping coefficient D through the following formula (7) f .

[0304]

[0305] where f b represents the frequency reference value, generally 50Hz; S b represents the AC power reference value; P ref,pu represents the per-unit value of the active power reference value at the point of common coupling.

[0306] Of course, according to the offset ΔP of the active power at the point of common coupling during the fault and the allowable frequency offset Δf during the fault, the virtual synchronous control device can also determine the target damping coefficient D through other deformations or equivalent formulas of the above formula (7) f .

[0307] In another possible implementation, when the virtual synchronous control device detects the fault detection signal f at the point of common coupling sig used to indicate that the fault is cleared within the second preset duration, the damping coefficient D can be adjusted from the target damping coefficient D f to the preset damping coefficient D 0 , and the latching coefficient f SH is adjusted from the target latching coefficient to the preset latching coefficient.

[0308] Exemplarily, the virtual synchronous control device may adjust the damping coefficient D from the target damping coefficient D to the preset damping coefficient D at a third preset rate f so as to solve the problem of power angle swing after fault recovery. 0 To facilitate understanding, the following embodiments of the present application will exemplarily introduce and explain the overall process of the adjustment method of the damping coefficient D and the latching coefficient f.

[0309] FIG. is a schematic flow chart of the adjustment method of the damping coefficient and the latching coefficient provided by some embodiments of the present application. As shown SH in the figure, the method of the embodiment of the present application may include the following steps: Figure 11 Figure 11

[0310]

[0311] Step S1101: In the initial state, the virtual synchronous control device may set the damping coefficient D to the preset damping coefficient D, 0 and set the latching coefficient f SH to the preset latching coefficient.

[0311] Step S1102: The virtual synchronous control device may detect whether the grid connection point fault detection signal f sig is a first preset signal.

[0312] If it is detected that the grid connection point fault detection signal f sig is a first preset signal, that is, it is detected according to the grid connection point fault detection signal f sig that a fault occurs in the energy storage system, then step S1103 is executed; if it is detected that the grid connection point fault detection signal f sig is not a first preset signal, that is, it is detected according to the grid connection point fault detection signal f sig that the energy storage system has no fault, then return to execute step S1102.

[0313] Step S1103: The virtual synchronous control device adjusts the damping coefficient D to the target damping coefficient D, f and adjusts the latching coefficient f SH to the target latching coefficient.

[0314] Step S1104: The virtual synchronous control device may detect whether the grid connection point fault detection signal f sig is a second preset signal, and whether the change amount Δf sig of the grid connection point fault detection signal is less than 0.

[0315] If it is detected that the grid connection point fault detection signal f sig is a second preset signal, and the change amount Δf sig of the grid connection point fault detection signal is less than 0, that is, it is detected that the grid connection point fault detection signal f sigIf it is indicated that the fault is cleared within the second preset duration, then step S1105 is executed; if the grid connection point fault detection signal f sig is not the second preset signal, or the change amount Δf of the grid connection point fault detection signal sig is not less than 0, that is, it is detected that the grid connection point fault detection signal f sig is used to indicate that the fault is not cleared within the second preset duration, then return to execute step S1104.

[0316] In step S1105, the virtual synchronous control device can adjust the damping coefficient D from the target damping coefficient D f to the preset damping coefficient D 0 , and adjust the latching coefficient f SH from the target latching coefficient to the preset latching coefficient.

[0317] In summary, in the embodiments of the present application, by adaptively adjusting the damping coefficient and adaptively adjusting the latching coefficient to adjust the integral link of the active power frequency, the swing of the power angle during the fault can be further reduced, so that the absolute value of the active power deviation is as small as possible, so as to alleviate the large power angle swing and the continuous periodic fluctuation of the grid connection point voltage after the fault recovery, thereby improving the transient stability of the energy storage system during the fault recovery process.

[0318] In some embodiments, on the basis of the above embodiments, the determination process of the above grid connection point fault detection signal in the embodiments of the present application is introduced and illustrated exemplarily.

[0319] In the embodiments of the present application, the virtual synchronous control device of the energy storage system can also determine the grid connection point fault detection signal according to the grid connection point voltage measurement value, the preset fault detection threshold, and the preset fault clearing threshold. Exemplarily, the grid connection point voltage measurement value may include, but is not limited to, the second-axis voltage measurement component. For example, the second-axis voltage measurement component may be the d-axis component measurement value u of the grid connection point voltage in the dq coordinate system d1,pu .

[0320] Exemplarily, in the embodiments of the present application, the virtual synchronous control device determines the grid connection point fault detection signal by comparing the grid connection point voltage measurement value with the preset fault detection threshold and the preset fault clearing threshold.

[0321] In a possible implementation manner, when the virtual synchronous control device detects that the change value of the grid connection point voltage measurement value is less than 0, and the grid connection point voltage measurement value is less than or equal to the preset fault detection threshold fault thd within the third preset duration, it can determine that the grid connection point fault detection signal f sig is used to indicate that a fault occurs in the energy storage system, and record the drop amplitude u of the grid connection point voltage measurement value during the fault record, where the drop amplitude u record can be equal to the measured value of the grid connection point voltage. It should be understood that in the case of no fault in the energy storage system, the drop amplitude u record can be a preset drop amplitude. For example, the preset drop amplitude can include but is not limited to 1 pu.

[0322] In another possible implementation, when the virtual synchronous control device detects that the change value of the measured value of the grid connection point voltage is greater than 0 and the measured value of the grid connection point voltage is greater than or equal to the preset fault clearing threshold clear thd it can determine the grid connection point fault detection signal f sig used to indicate that the energy storage system clears the fault within the fourth preset duration, and adjust the drop amplitude u record of the measured value of the grid connection point voltage during the fault to the preset drop amplitude.

[0323] For ease of understanding, the following embodiments of the present application exemplarily introduce the overall process of the grid connection point fault detection signal determination method. Figure 12 is a schematic flow chart of the grid connection point fault detection signal determination method provided by some embodiments of the present application. As Figure 12 shown, the method of the embodiments of the present application may include the following steps:

[0324] Step S1201: In the initial state, the virtual synchronous control device can set the grid connection point fault detection signal f sig to the second preset signal.

[0325] Step S1202: The virtual synchronous control device can detect whether the change value Δu d1,pu of the measured value of the grid connection point voltage is less than 0 and whether the measured value u d1,pu of the grid connection point voltage is less than or equal to the preset fault detection threshold fault thd .

[0326] If it is detected that the change value Δu d1,pu of the measured value of the grid connection point voltage is less than 0 and the measured value u d1,pu of the grid connection point voltage is less than or equal to the preset fault detection threshold fault thd , then step S1203 is executed; if it is detected that the change value Δu d1,pu of the measured value of the grid connection point voltage is not less than 0, or the measured value u d1,pu of the grid connection point voltage is greater than the preset fault detection threshold fault thd , then step S1204 is executed.

[0327] Step S1203: The virtual synchronous control device can wait for the third preset duration t wait , and detect the measured value u d1,puIs it less than or equal to the preset fault detection threshold fault thd . Among them, the third preset duration t wait can include but is not limited to 5 ms.

[0328] If the measured value u of the grid-connected point voltage is detected d1,pu less than or equal to the preset fault detection threshold fault thd , then step S1205 is executed; if the measured value u of the grid-connected point voltage is detected d1,pu greater than the preset fault detection threshold fault thd , then return to execute step S1202.

[0329] Step S1204, the virtual synchronous control device can continue to set the grid-connected point fault detection signal f sig as the second preset signal, and set the drop amplitude u record as the preset drop amplitude.

[0330] Step S1205, the virtual synchronous control device can adjust the grid-connected point fault detection signal f sig to the first preset signal, and set the drop amplitude u record as the measured value u of the grid-connected point voltage d1,pu .

[0331] Step S1206, the virtual synchronous control device can detect whether the change value Δu of the measured value of the grid-connected point voltage d1,pu is greater than 0, and whether the measured value u of the grid-connected point voltage d1,pu is greater than or equal to the preset fault clearing threshold clear thd .

[0332] If it is detected that the change value Δu of the measured value of the grid-connected point voltage d1,pu is greater than 0, and the measured value u of the grid-connected point voltage d1,pu is greater than or equal to the preset fault clearing threshold clear thd , then step S1207 is executed; if it is detected that the change value Δu of the measured value of the grid-connected point voltage d1,pu is not greater than 0, or the measured value u of the grid-connected point voltage d1,pu is less than the preset fault clearing threshold clear thd , then return to execute step S1206.

[0333] Step S1207, the virtual synchronous control device can adjust the grid-connected point fault detection signal f sig to the second preset signal, and adjust the drop amplitude u of the measured value of the grid-connected point voltage during the fault record to the preset drop amplitude.

[0334] In summary, in the embodiments of the present application, by determining the grid connection point fault detection signal based on the grid connection point voltage measurement value, the preset fault detection threshold, and the preset fault clearing threshold, the active power limit value, the damping coefficient, and the latching coefficient can be adjusted according to the grid connection point fault detection signal, so that the active power reference value of the energy storage system does not exceed the actual system capacity during the fault, thereby improving the transient stability of the energy storage system during the fault.

[0335] In some embodiments, based on the above embodiments, in the embodiments of the present application, the virtual synchronous control device of the energy storage system can also perform pre-synchronization processing on the output signal of the AC side of the voltage source converter valve according to the grid connection point voltage measurement value when it detects that the energy storage system is in the initial stage of grid connection, so that the amplitude of the internal electromotive force and the output phase angle (or vector angle) of the voltage source converter valve can be the same as the amplitude and vector angle of the grid connection point voltage respectively, which is convenient for minimizing the current impact at the grid connection moment and thus conducive to smooth switching.

[0336] It should be noted that after the virtual synchronous control device completes the pre-synchronization processing, it exits the pre-synchronization processing process.

[0337] Figure 13A The flowchart of the pre-synchronization processing method for the output signal of the AC side of the voltage source converter valve provided by some embodiments of the present application is shown in Figure 13A As shown, the pre-synchronization processing method of the embodiments of the present application may include the following steps:

[0338] Step S1301: Perform second PI regulation processing on the first-axis voltage measurement component to obtain the regulated first-axis voltage measurement component.

[0339] Exemplarily, the grid connection point voltage measurement value of the embodiments of the present application may include but is not limited to the first-axis voltage measurement component and the second-axis voltage measurement component. For example, the first-axis voltage measurement component may be the q-axis component measurement value of the grid connection point voltage in the dq coordinate system, and the second-axis voltage measurement component may be the d-axis component measurement value of the grid connection point voltage in the dq coordinate system.

[0340] In this step, the virtual synchronous control device can perform second PI regulation processing on the first-axis voltage measurement component to obtain the regulated first-axis voltage measurement component.

[0341] Step S1302: Perform second integration processing on the regulated first-axis voltage measurement component and the grid rated angular frequency to obtain the output voltage phase angle of the AC side of the voltage source converter valve; wherein, the output voltage phase angle is the same as the grid connection point voltage phase angle.

[0342] Exemplarily, the grid rated angular frequency may include but is not limited to the per-unit value of the grid rated angular frequency, and / or, the nominal value of the grid rated angular frequency (or non-per-unit value).

[0343] In this step, the virtual synchronous control device may perform a second integration process on the adjusted first-axis voltage measurement component and the grid rated angular frequency to obtain the output voltage phase angle on the AC side of the voltage source converter valve, so that the output voltage phase angle is the same as the grid connection point voltage phase angle.

[0344] Exemplarily, Figure 13B is a schematic flowchart of a method for determining the output voltage phase angle on the AC side of a voltage source converter valve provided by some embodiments of this application. As Figure 13B shown, the virtual synchronous control device may perform a second PI adjustment process on the per-unit value u q1,pu of the first-axis voltage measurement component to obtain the adjusted first-axis voltage measurement component. Further, the virtual synchronous control device may multiply the per-unit value ω n，pu of the rated angular frequency by the nominal value ω n of the grid rated angular frequency, and add the multiplication result to the adjusted first-axis voltage measurement component. Further, the virtual synchronous control device may perform a second integration process on the addition result to obtain the output voltage phase angle on the AC side of the voltage source converter valve.

[0345] Step S1303: Perform a second closed-loop process on the second-axis voltage measurement component to obtain the second internal potential amplitude of the voltage source converter valve; where the second internal potential amplitude is the same as the grid connection point voltage amplitude.

[0346] In this step, the virtual synchronous control device may perform a second closed-loop process on the second-axis voltage measurement component to obtain the second internal potential amplitude of the voltage source converter valve, so that the second internal potential amplitude is the same as the grid connection point voltage amplitude. Among them, the second closed-loop process may include but is not limited to a closed-loop control method based on PI adjustment processing and the second internal potential control integration coefficient.

[0347] Exemplarily, Figure 13C is a schematic flowchart of a second closed-loop processing method provided by some embodiments of this application. As Figure 13C shown, the virtual synchronous control device may determine a second feedback signal according to the historical internal potential amplitude, and sequentially perform a third PI adjustment process and a third integration process on the difference signal between the second-axis voltage measurement component and the second feedback signal to obtain the second internal potential amplitude. Among them, the historical internal potential amplitude may include but is not limited to the result obtained by the virtual synchronous control device performing the previous second closed-loop process on the historical second-axis voltage measurement component (or the second-axis voltage measurement component at the previous moment).

[0348] In the embodiments of the present application, the virtual synchronous control device may use the historical internal potential amplitude as the second feedback signal, and subtract the second-axis voltage measurement component from the second feedback signal to obtain a difference signal. Further, the virtual synchronous control device may sequentially perform a third PI regulation process and a third integration process on the difference signal to obtain the second internal potential amplitude.

[0349] Further, considering that in order to make the second internal potential amplitude more consistent with the actual capabilities of the energy storage system, in the embodiments of the present application, the virtual synchronous control device may sequentially perform a third PI regulation process and a third integration process on the difference signal between the second-axis voltage measurement component and the second feedback signal to obtain the second initial internal potential amplitude, and perform a clipping process on the second initial internal potential amplitude according to the maximum internal potential amplitude and the minimum internal potential amplitude to obtain the second internal potential amplitude.

[0350] Exemplarily, Figure 13D is a schematic flow chart of the second closed-loop processing method provided by some embodiments of the present application. As Figure 13D shown, the virtual synchronous control device may use the historical internal potential amplitude as the second feedback signal, and subtract the per-unit value u d1,pu of the second-axis voltage measurement component from the second feedback signal to obtain a difference signal. Further, the virtual synchronous control device may sequentially perform a third PI regulation process and a third integration process according to the second internal potential control integration coefficient K Ei2 on the difference signal to obtain the second initial internal potential amplitude. Further, the virtual synchronous control device may perform a clipping process on the second initial internal potential amplitude according to the maximum internal potential amplitude and the minimum internal potential amplitude to obtain the second internal potential amplitude E.

[0351] It can be seen that in the embodiments of the present application, by performing a clipping process on the second initial internal potential amplitude according to the maximum internal potential amplitude and the minimum internal potential amplitude, a more accurate second internal potential amplitude can be obtained, so that the second internal potential amplitude can be made the same as the grid connection point voltage amplitude according to the second internal potential amplitude, which is beneficial to improving the pre-synchronization processing effect.

[0352] In summary, in the embodiments of the present application, by performing a second PI regulation process on the first-axis voltage measurement component, the adjusted first-axis voltage measurement component is obtained, and the adjusted first-axis voltage measurement component and the grid rated angular frequency are subjected to a second integration process to obtain the output voltage phase angle of the AC side of the voltage source converter valve; wherein, the output voltage phase angle is the same as the grid connection point voltage phase angle. Further, a second closed-loop process is performed on the second-axis voltage measurement component to obtain the second internal potential amplitude of the voltage source converter valve; wherein, the second internal potential amplitude is the same as the grid connection point voltage amplitude. It can be seen that in the embodiments of the present application, by performing a PI regulation process and an integration process on the first-axis voltage measurement component, and performing a second closed-loop process on the second-axis voltage measurement component, the internal potential amplitude and the output voltage phase angle of the voltage source converter valve synchronized with the grid connection point voltage can be generated, so as to minimize the current impact at the grid connection moment, which is conducive to smooth switching.

[0353] In some embodiments, Figure 14A FIG. is a schematic flow chart of the virtual synchronous control method of the energy storage system provided in other embodiments of the present application. On the basis of the above embodiments, the embodiments of the present application introduce the related content of "controlling the output voltage of the DC energy storage valve according to the measured value of the output electrical signal on the DC side of the voltage source converter valve and the output voltage reference value of the DC energy storage valve" in step S301 above. Exemplarily, the measured value of the output electrical signal in the embodiments of the present application may include, but is not limited to: the measured value of the output voltage on the DC side of the voltage source converter valve and the measured value of the output current on the DC side of the voltage source converter valve. As Figure 14A shown, the above step S301 may include the following steps:

[0354] Step S3011: Perform a fourth PI regulation process on the DC voltage difference between the measured value of the output voltage on the DC side of the voltage source converter valve and the output voltage reference value of the DC energy storage valve to obtain a DC current command value.

[0355] In this step, the virtual synchronous control device can subtract the measured value of the output voltage on the DC side of the voltage source converter valve from the output voltage reference value of the DC energy storage valve to obtain a DC voltage difference, and perform a fourth PI regulation process on the DC voltage difference through a PI regulator to obtain a DC current command value, so as to achieve the DC voltage outer loop process.

[0356] Exemplarily, Figure 14B FIG. is a schematic flow chart of the fourth PI regulation process method provided in some embodiments of the present application. As Figure 14B shown, the virtual synchronous control device can make the per-unit value e dc,pu of the measured value of the output voltage on the DC side of the voltage source converter valve and the per-unit value u dc,ref,puPerform subtraction processing to obtain the DC voltage difference. Further, the virtual synchronous control device can use K p,udc as the DC voltage control proportional coefficient and K i,udc as the DC voltage control integral coefficient, and perform fourth PI regulation processing on the DC voltage difference to obtain the per-unit value of the DC current command value i dc,cmd,pu .

[0357] Considering that in order to make the output voltage of the DC energy storage valve more in line with the actual capacity of the energy storage system, the virtual synchronous control device can perform fourth PI regulation processing on the DC voltage difference between the measured value of the output voltage on the DC side of the voltage source converter valve and the reference value of the output voltage of the DC energy storage valve to obtain the initial DC current reference value, and perform limit processing on the initial DC current reference value according to the maximum DC current amplitude and the minimum DC current amplitude to obtain the DC current command value. Among them, the maximum DC current amplitude refers to the maximum amplitude of the output voltage of the DC energy storage valve, and the minimum DC current amplitude refers to the minimum amplitude of the output voltage of the DC energy storage valve.

[0358] Exemplarily, if the initial DC current command value is greater than the maximum DC current amplitude, the virtual synchronous control device can use the maximum DC current amplitude as the DC current command value.

[0359] Another exemplarily, if the initial DC current command value is less than or equal to the maximum DC current amplitude and greater than or equal to the minimum DC current amplitude, the virtual synchronous control device can use the initial DC current command value as the DC current command value.

[0360] Another exemplarily, if the initial DC current command value is less than the minimum DC current amplitude, the virtual synchronous control device can use the minimum DC current amplitude as the DC current command value.

[0361] It can be seen that in the embodiments of the present application, by limiting the initial DC current command value according to the maximum DC current amplitude and the minimum DC current amplitude, a more accurate DC current command value can be obtained, so that a more accurate output voltage command value of the DC energy storage valve can be obtained according to the DC current command value, and thus the output voltage of the DC energy storage valve can be controlled more accurately.

[0362] Step S3012: Perform fifth PI regulation processing on the DC current difference between the measured value of the output current on the DC side of the voltage source converter valve and the DC current command value to obtain the output voltage command value of the DC energy storage valve.

[0363] In this step, the virtual synchronous control device can subtract the measured value of the output current on the DC side of the voltage source converter valve from the DC current command value to obtain the DC current difference, and perform the fifth PI regulation process on the DC current difference through a PI regulator to obtain the output voltage command value of the DC energy storage valve, so as to achieve the DC current inner loop process.

[0364] Exemplarily, Figure 14C is a schematic flow chart of the fifth PI regulation process provided by some embodiments of this application. As Figure 14C shown, the virtual synchronous control device can make the per-unit value i dc,pu of the measured value of the output current on the DC side of the voltage source converter valve and the per-unit value i dc,cmd,pu of the DC current command value be subtracted to obtain the DC current difference. Further, the virtual synchronous control device can use K p,idc as the DC current control proportional coefficient and K i,idc as the DC current control integral coefficient, and perform the fifth PI regulation process on the DC current difference to obtain the per-unit value u dc,cmd,pu of the output voltage command value of the DC energy storage valve.

[0365] Considering that in order to make the output voltage of the DC energy storage valve more in line with the actual capacity of the energy storage system, the virtual synchronous control device can perform the fifth PI regulation process on the DC current difference between the measured value of the output current on the DC side of the voltage source converter valve and the DC current command value to obtain the initial output voltage command value, and perform clipping processing on the initial output voltage command value according to the maximum DC voltage amplitude and the minimum DC voltage amplitude to obtain the output voltage command value. Among them, the maximum DC voltage amplitude refers to the maximum output voltage amplitude of the DC energy storage valve, and the minimum DC voltage amplitude refers to the minimum output voltage amplitude of the DC energy storage valve.

[0366] Exemplarily, if the initial output voltage command value is greater than the maximum DC voltage amplitude, the virtual synchronous control device can use the maximum DC voltage amplitude as the output voltage command value.

[0367] Another exemplarily, if the initial output voltage command value is less than or equal to the maximum DC voltage amplitude and greater than or equal to the minimum DC voltage amplitude, the virtual synchronous control device can use the initial output voltage command value as the output voltage command value.

[0368] Another exemplarily, if the initial output voltage command value is less than the minimum DC voltage amplitude, the virtual synchronous control device can use the minimum DC voltage amplitude as the output voltage command value.

[0369] It can be seen that in the embodiments of the present application, by limiting the initial output voltage command value according to the maximum DC voltage amplitude and the minimum DC voltage amplitude, a more accurate output voltage command value can be obtained, so that the output voltage of the DC energy storage valve can be more accurately controlled according to the output voltage command value.

[0370] For ease of understanding, in the following embodiments of the present application, the overall process of the output voltage control method of the DC energy storage valve will be introduced. Figure 14D It is a schematic flowchart of the output voltage control method of the DC energy storage valve provided by some embodiments of the present application. As Figure 14D shown, the virtual synchronous control device can subtract the per-unit value e of the measured output voltage on the DC side of the voltage source converter valve dc,pu from the per-unit value u of the output voltage reference value of the DC energy storage valve dc,ref,pu to obtain the DC voltage difference. Further, the virtual synchronous control device can use K p,udc as the DC voltage control proportional coefficient and K i,udc as the DC voltage control integral coefficient, perform a fourth PI regulation process on the DC voltage difference to obtain the initial DC current reference value, and perform a DC current limiting process on the initial DC current reference value according to the maximum DC current amplitude and the minimum DC current amplitude to obtain the per-unit value i of the DC current command value dc,cmd,pu .

[0371] Further, the virtual synchronous control device can subtract the per-unit value i of the measured output current on the DC side of the voltage source converter valve dc,pu from the per-unit value i of the DC current command value dc,cmd,pu to obtain the DC current difference. Further, the virtual synchronous control device can use K p,idc as the DC current control proportional coefficient and K i,idc as the DC current control integral coefficient, perform a fifth PI regulation process on the DC current difference to obtain the initial output voltage command value, and perform a DC voltage limiting process on the initial output voltage command value according to the maximum DC voltage amplitude and the minimum DC voltage amplitude to obtain the per-unit value u of the output voltage command value dc,cmd,pu .

[0372] Step S3013: Control the output voltage of the DC energy storage valve according to the output voltage command value of the DC energy storage valve.

[0373] In this step, the virtual synchronous control device can generate a second control signal according to the output voltage command value of the DC energy storage valve, where the second control signal is used to control the output voltage of the DC energy storage valve to achieve independent control of the output voltage of the DC energy storage valve.

[0374] In summary, in the embodiments of the present application, by performing a fourth PI regulation process on the DC voltage difference between the measured output voltage of the DC side of the voltage source converter valve and the reference output voltage of the DC energy storage valve, a DC current command value is obtained. Further, by performing a fifth PI regulation process on the DC current difference between the measured output current of the DC side of the voltage source converter valve and the DC current command value, an output voltage command value of the DC energy storage valve is obtained, and the output voltage of the DC energy storage valve is controlled according to the output voltage command value of the DC energy storage valve. It can be seen that in the embodiments of the present application, by based on the measured output voltage of the DC side of the voltage source converter valve, the measured output current, and the reference output voltage of the DC energy storage valve, independent control of the output voltage of the DC energy storage valve is achieved, which enables the voltage source converter valve to not need to take into account both DC side control and AC side control. On the one hand, the complexity of the control loop of the voltage source converter valve can be simplified, and on the other hand, it is beneficial to improve the dynamic control performance of the output voltage of the DC energy storage valve, so that a grid-forming control of the energy storage system can be realized, in order to provide effective inertia support and voltage support for the power grid.

[0375] In some embodiments, Figure 15 FIG. is a schematic diagram of the virtual synchronous control framework of the energy storage system provided in other embodiments of the present application. On the basis of the above embodiments, an overall block diagram of the virtual synchronous control of the energy storage system in the embodiments of the present application is exemplarily introduced and described.

[0376] As Figure 15 shown, 1) The control link of the DC energy storage valve may include but is not limited to: a DC voltage and current sampling unit, a DC voltage outer loop control unit, a DC current inner loop control unit, and a pulse generation unit. Among them, the DC voltage outer loop control unit and the DC current inner loop control unit are core control units, and their specific implementation methods can refer to the relevant content in the above method embodiments, which will not be elaborated here.

[0377] 2) The control link of the voltage source converter valve may include but is not limited to: an AC voltage and current sampling unit, an AC voltage and current coordinate transformation unit, a grid connection point power and voltage amplitude calculation unit (or simply referred to as a power and amplitude calculation unit), a fault detection unit, a VSG active and reactive decoupling control unit (or simply referred to as a VSG control unit), a voltage outer loop control unit, a current limiting unit, a current inner loop control unit, and a pulse generation unit. Among them, the fault detection unit, the VSG active and reactive decoupling control unit, the voltage outer loop control unit, and the current inner loop control unit are core control units, and their specific implementation methods can refer to the relevant content in the above method embodiments, which will not be elaborated here.

[0378] It should be understood that the AC voltage and current coordinate transformation unit may include but is not limited to a T abc-dq transformation unit (or referred to as a Park transformation unit) and a T dq-abc transformation unit.

[0379] Among them, Figure 15 some of the parameters in can refer to Table 2.

[0380] Table 2 is Figure 15 a schematic table of some parameters in

[0381]

[0382]

[0383] It should be noted that when the voltage source converter valve 101 can be directly connected to the AC power grid 104 without passing through the transformer 105, in the embodiments of the present application, there is no need to distinguish between the AC network side and the AC valve side of the voltage source converter valve on the AC side of the voltage source converter valve, or rather, the AC network side of the voltage source converter valve is the same as the AC valve side of the voltage source converter valve.

[0384] In summary, in the embodiments of the present application, by dividing the high-voltage DC directly-connected energy storage system into two parts, namely a voltage source converter valve and a DC energy storage valve, for independent control. Among them, by adopting a double closed-loop control of DC voltage - DC current for the DC energy storage valve, the voltage on the DC side of the voltage source converter valve is made constant to support the voltage source converter valve to operate in a virtual synchronous control mode, and by adopting a virtual synchronous control with decoupling of active power and reactive power for the voltage source converter valve, transient support for the grid connection point frequency and the grid connection point voltage is achieved. In addition, through the coordinated cooperation of the damping parameter and the power limit value, the problem of large power angle swings and continuous periodic fluctuations of the grid connection point voltage after fault recovery can be solved, which is beneficial to improving the transient stability during system faults and the fault recovery process, and thus reliable low-voltage fault ride-through of the energy storage system can be achieved.

[0385] Figure 16A For the grid connection point active power P, grid connection point reactive power Q and AC power grid voltage amplitude U provided by the embodiments of the present application s is a schematic diagram of the simulation results, Figure 16B For the output voltage u of the DC energy storage valve provided by the embodiments of the present application dc 、the output current i on the DC side of the voltage source converter valve dc and the simulation result schematic diagram of the output frequency ω on the AC side of the voltage source converter valve, as Figure 16A and Figure 16B shown by the simulation results during the single-phase fault on the grid side, it can be seen that: the energy storage system has a full-power step change in active power at the 1s moment; the energy storage system has a fault at the 2.5s moment; the energy storage system has the fault cleared at the 3s moment. Through time-domain simulation verification, the virtual synchronous control method of the energy storage system provided by the embodiments of the present application has the ability of inertia support and grid voltage support, and can meet the requirements of grid connection specifications for the low-voltage fault ride-through ability of the energy storage system.

[0386] It should be understood that although the steps in the flowcharts involved in the above embodiments are sequentially shown according to the indications of the arrows, these steps are not necessarily executed in the order indicated by the arrows. Unless there is a clear description in this article, the execution of these steps has no strict order limit, and these steps can be executed in other orders. Moreover, at least a part of the steps in the flowcharts involved in the above embodiments may include multiple steps or multiple stages. These steps or stages are not necessarily executed at the same moment, but can be executed at different moments. The execution order of these steps or stages is not necessarily sequential, but can be executed alternately or in turn with at least a part of other steps or steps or stages in other steps.

[0387] Based on the same inventive concept, the embodiments of the present application further provide a virtual synchronous control device for implementing the virtual synchronous control method of the energy storage system involved above. The implementation solutions provided by this device to solve problems are similar to the implementation solutions described in the above method. Therefore, the specific limitations in one or more embodiments of the virtual synchronous control device of the energy storage system provided below can refer to the limitations on the virtual synchronous control method of the energy storage system in the above text, and will not be repeated here.

[0388] In some embodiments, Figure 17 is a schematic structural diagram of a virtual synchronous control device of an energy storage system provided for some embodiments of the present application. The virtual synchronous control device of the energy storage system provided by the embodiments of the present application can be applied to the control device of the energy storage system. As Figure 17 shown, the virtual synchronous control device of the energy storage system of the embodiments of the present application may include: a first control module 1701 and a second control module 1702.

[0389] Among them, the first control module 1701 is used to control the output voltage of the DC energy storage valve according to the measured value of the output electrical signal on the DC side of the voltage source converter valve and the reference value of the output voltage of the DC energy storage valve;

[0390] The second control module 1702 is used to control the output signal on the AC side of the voltage source converter valve according to the measured value of the grid connection point electrical signal of the voltage source converter valve and the reference value of the grid connection point electrical signal.

[0391] In some embodiments, the measured value of the grid connection point electrical signal includes: the measured value of the active power at the grid connection point, the measured value of the reactive power at the grid connection point, and the measured value of the voltage at the grid connection point. The reference value of the grid connection point electrical signal includes: the reference value of the active power at the grid connection point, the reference value of the reactive power at the grid connection point, and the reference value of the voltage at the grid connection point. The second control module 1702 includes:

[0392] The first control unit is configured to control the output frequency of the AC side of the voltage source converter valve according to the measured active power value and the reference active power value at the grid connection point;

[0393] The second control unit is configured to control the output voltage amplitude of the AC side of the voltage source converter valve according to the measured reactive power value, the measured grid connection point voltage value, the reference reactive power value and the reference grid connection point voltage value at the grid connection point.

[0394] In some embodiments, the first control unit includes:

[0395] The first determination subunit is configured to determine the active power deviation at the grid connection point according to the measured active power value and the reference active power value at the grid connection point;

[0396] The closed-loop control subunit is configured to perform a first closed-loop control process on the active power deviation at the grid connection point to obtain a closed-loop result;

[0397] The first control subunit is configured to control the output frequency according to the closed-loop result and the rated angular frequency of the power grid.

[0398] In some embodiments, the first determination subunit is specifically configured to:

[0399] Perform amplitude limiting processing on the reference active power value at the grid connection point according to the maximum active power amplitude limit value and the minimum active power amplitude limit value to obtain the amplitude-limited reference active power value at the grid connection point;

[0400] Subtract the measured active power value at the grid connection point from the amplitude-limited reference active power value at the grid connection point to obtain the active power deviation at the grid connection point.

[0401] In some embodiments, the closed-loop control subunit is specifically configured to:

[0402] Determine a first feedback signal according to the historical closed-loop result and the damping coefficient;

[0403] Perform a first integration process on the difference signal between the active power deviation at the grid connection point and the first feedback signal to obtain a closed-loop result.

[0404] In some embodiments, the closed-loop control subunit is specifically configured to:

[0405] Perform a first integration process on the difference signal according to the inertia time constant and the latching coefficient to obtain a closed-loop result.

[0406] In some embodiments, the virtual synchronous control device of the energy storage system further includes:

[0407] The first adjustment module is configured to adjust the maximum active power amplitude limit value and the minimum active power amplitude limit value according to the grid connection point fault detection signal.

[0408] In some embodiments, the first adjustment module is specifically configured to:

[0409] When it is detected that the grid connection point fault detection signal is used to indicate a fault in the energy storage system, adjust the maximum active power limit value to the target maximum power limit value, and adjust the minimum active power limit value to the target minimum power limit value; or,

[0410] When it is detected that the grid connection point fault detection signal is used to indicate that the fault is cleared within the first preset duration, adjust the maximum active power limit value from the target maximum power limit value to the preset maximum power limit value, and adjust the minimum active power limit value from the target minimum power limit value to the preset minimum power limit value.

[0411] In some embodiments, the virtual synchronous control device of the energy storage system further includes:

[0412] A second adjustment module, configured to adjust the damping coefficient and the latching coefficient according to the grid connection point fault detection signal.

[0413] In some embodiments, the second adjustment module is specifically configured to:

[0414] When it is detected that the grid connection point fault detection signal is used to indicate a fault in the energy storage system, adjust the damping coefficient to the target damping coefficient, and adjust the latching coefficient to the target latching coefficient; or,

[0415] When it is detected that the grid connection point fault detection signal is used to indicate that the fault is cleared within the second preset duration, adjust the damping coefficient from the target damping coefficient to the preset damping coefficient, and adjust the latching coefficient from the target latching coefficient to the preset latching coefficient.

[0416] In some embodiments, the virtual synchronous control device of the energy storage system further includes:

[0417] A first determination module, configured to determine the grid connection point fault detection signal according to the grid connection point voltage measurement value, the preset fault detection threshold, and the preset fault clearing threshold.

[0418] In some embodiments, the first determination module is specifically configured to:

[0419] When it is detected that the change value of the grid connection point voltage measurement value is less than 0, and the grid connection point voltage measurement value is less than or equal to the preset fault detection threshold within the third preset duration, determine that the grid connection point fault detection signal is used to indicate a fault in the energy storage system, and record the drop amplitude of the grid connection point voltage measurement value during the fault;

[0420] When the change value of the grid connection point voltage measurement value is detected to be greater than 0 and the grid connection point voltage measurement value is greater than or equal to the preset fault clearing threshold, it is determined that the grid connection point fault detection signal is used to indicate that the energy storage system clears the fault within the fourth preset duration, and the voltage drop amplitude of the grid connection point voltage measurement value during the fault period is adjusted to the preset voltage drop amplitude.

[0421] In some embodiments, the second control unit includes:

[0422] A second determination subunit, configured to determine the amplitude of the first internal electromotive force of the voltage source converter valve according to the grid connection point reactive power measurement value, the grid connection point voltage measurement value, the grid connection point reactive power reference value, and the grid connection point voltage reference value;

[0423] A second control subunit, configured to control the output voltage amplitude of the AC side of the voltage source converter valve according to the amplitude of the first internal electromotive force of the voltage source converter valve.

[0424] In some embodiments, the second determination subunit is specifically configured to:

[0425] Determine the grid connection point reactive power deviation according to the grid connection point reactive power measurement value and the grid connection point reactive power reference value;

[0426] Determine the grid connection point voltage deviation according to the grid connection point voltage measurement value and the grid connection point voltage reference value;

[0427] Perform a second integration process according to the grid connection point reactive power deviation and / or the grid connection point voltage deviation to obtain the amplitude of the first internal electromotive force.

[0428] In some embodiments, the second control subunit is specifically configured to:

[0429] Perform a voltage outer loop control process according to the amplitude of the first internal electromotive force of the voltage source converter valve and the grid connection point voltage measurement value to obtain the current command value of the current inner loop;

[0430] Perform a current limiting inner loop process according to the current command value to obtain the output voltage signal of the AC side of the voltage source converter valve;

[0431] Control the output voltage amplitude of the AC side of the voltage source converter valve according to the output voltage signal of the AC side of the voltage source converter valve.

[0432] In some embodiments, the second control subunit is specifically configured to:

[0433] Perform a first PI regulation process, a dynamic virtual impedance process, or a static virtual impedance process on the amplitude of the first internal electromotive force of the voltage source converter valve and the grid connection point voltage measurement value to obtain the current command value of the current inner loop.

[0434] In some embodiments, the virtual synchronous control device of the energy storage system further includes:

[0435] A pre - synchronization module, configured to perform pre - synchronization processing on the output signal of the AC side of the voltage - source converter valve according to the measured grid - connection point voltage value when it is detected that the energy storage system is in the initial stage of grid connection.

[0436] In some embodiments, the measured grid - connection point voltage value includes a first - axis voltage measurement component and a second - axis voltage measurement component, and the pre - synchronization module includes:

[0437] A first adjustment unit, configured to perform a second PI adjustment process on the first - axis voltage measurement component to obtain an adjusted first - axis voltage measurement component;

[0438] An integration unit, configured to perform a second integration process on the adjusted first - axis voltage measurement component and the rated grid angular frequency to obtain the output voltage phase angle of the AC side of the voltage - source converter valve; wherein, the output voltage phase angle is the same as the grid - connection point voltage phase angle;

[0439] A closed - loop unit, configured to perform a second closed - loop process on the second - axis voltage measurement component to obtain the second internal potential amplitude of the voltage - source converter valve; wherein, the second internal potential amplitude is the same as the grid - connection point voltage amplitude.

[0440] In some embodiments, the closed - loop unit includes:

[0441] A third determination sub - unit, configured to determine a second feedback signal according to the historical internal potential amplitude;

[0442] A fourth determination sub - unit, configured to perform a third PI adjustment process and a third integration process on the difference signal between the second - axis voltage measurement component and the second feedback signal in sequence to obtain the second internal potential amplitude.

[0443] In some embodiments, the measured output electrical signal value includes: the measured output voltage value of the DC side of the voltage - source converter valve and the measured output current value of the DC side of the voltage - source converter valve, and the first control module 1701 includes:

[0444] A second adjustment unit, configured to perform a fourth PI adjustment process on the DC voltage difference between the measured output voltage value of the DC side of the voltage - source converter valve and the output voltage reference value of the DC energy - storage valve to obtain a DC current command value;

[0445] A third adjustment unit, configured to perform a fifth PI adjustment process on the DC current difference between the measured output current value of the DC side of the voltage - source converter valve and the DC current command value to obtain the output voltage command value of the DC energy - storage valve;

[0446] A third control unit, configured to control the output voltage of the DC energy - storage valve according to the output voltage command value of the DC energy - storage valve.

[0447] The virtual synchronous control device of the energy storage system provided by the embodiments of the present application can be used to execute the technical solutions in the embodiments of the virtual synchronous control method of the above-mentioned energy storage system of the present application. The implementation principles and technical effects are similar and will not be elaborated here.

[0448] Each module in the above-mentioned virtual synchronous control device of the energy storage system can be implemented in whole or in part by software, hardware, and their combination. The above-mentioned modules can be embedded in the processor of the control device of the energy storage system in the form of hardware or independent of it, or stored in the memory of the control device of the energy storage system in the form of software, so as to facilitate the processor to call and execute the operations corresponding to the above-mentioned modules.

[0449] In some embodiments, Figure 18 is a schematic structural diagram of the control device of the energy storage system in some embodiments of the present application. As Figure 18 shown, the control device of the energy storage system provided by the embodiments of the present application may include a processor, a memory, a communication interface, and an input device connected through a system bus. Among them, the processor of the control device is used to provide computing and control capabilities. The memory of the control device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The communication interface of the control device is used to communicate with external devices in a wired or wireless manner, and the wireless manner can be implemented through WIFI, a mobile cellular network, NFC (Near Field Communication), or other technologies. When the computer program is executed by the processor, it implements the technical solutions in the embodiments of the virtual synchronous control method of the above-mentioned energy storage system of the present application. The implementation principles and technical effects are similar and will not be elaborated here.

[0450] Exemplarily, the input device of the control device can be a touch layer covering the display screen, or a button, a trackball, or a touchpad provided on the housing of the control device, or an external keyboard, touchpad, or mouse, etc.

[0451] Those skilled in the art can understand that Figure 18 the structure shown in

[0452] is only a block diagram of some structures related to the solution of the present application, and does not constitute a limitation on the control device to which the solution of the present application is applied. The specific control device may include more or fewer components than those shown in the figure, or combine some components, or have different component arrangements.

[0453] In some embodiments, a computer-readable storage medium is further provided, on which a computer program is stored. When the computer program is executed by a processor, the technical solutions in the embodiments of the virtual synchronous control method of the energy storage system of the present application are implemented. The implementation principle and technical effects are similar and will not be elaborated here.

[0454] In some embodiments, a computer program product is further provided, including a computer program. When the computer program is executed by a processor, the technical solutions in the embodiments of the virtual synchronous control method of the energy storage system of the present application are implemented. The implementation principle and technical effects are similar and will not be elaborated here.

[0455] Those of ordinary skill in the art can understand that all or part of the processes in the methods of the above embodiments can be completed by instructing relevant hardware through a computer program. The computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above methods. Among them, any reference to a memory, database, or other medium used in the embodiments provided in the present application can include at least one of non-volatile and volatile memories. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetoresistive random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory can include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc. The processors involved in the embodiments provided in the present application can be general-purpose processors, central processing units, graphics processors, digital signal processors, programmable logic devices, data processing logics based on quantum computing, etc., and are not limited thereto.

[0456] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the various embodiments of the present application, and they should all be covered within the scope of the claims and the specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in each embodiment can be combined in any way. The present application is not limited to the specific embodiments disclosed in the text, but includes all technical solutions falling within the scope of the claims.

Claims

1. A virtual synchronous control method for an energy storage system, characterized in that, the energy storage system includes a voltage source converter valve and a DC energy storage valve, and the method includes: controlling the output voltage of the DC energy storage valve according to the measured value of the output electrical signal on the DC side of the voltage source converter valve and the reference value of the output voltage of the DC energy storage valve; controlling the output signal on the AC side of the voltage source converter valve according to the measured value of the grid connection point electrical signal of the voltage source converter valve and the reference value of the grid connection point electrical signal.

2. The method according to claim 1, characterized in that, the measured value of the grid connection point electrical signal includes: the measured value of the active power at the grid connection point, the measured value of the reactive power at the grid connection point, and the measured value of the voltage at the grid connection point, and the reference value of the grid connection point electrical signal includes: the reference value of the active power at the grid connection point, the reference value of the reactive power at the grid connection point, and the reference value of the voltage at the grid connection point. The controlling the output signal on the AC side of the voltage source converter valve according to the measured value of the grid connection point electrical signal of the voltage source converter valve and the reference value of the grid connection point electrical signal includes: controlling the output frequency on the AC side of the voltage source converter valve according to the measured value of the active power at the grid connection point and the reference value of the active power at the grid connection point; controlling the output voltage amplitude on the AC side of the voltage source converter valve according to the measured value of the reactive power at the grid connection point, the measured value of the voltage at the grid connection point, the reference value of the reactive power at the grid connection point, and the reference value of the voltage at the grid connection point.

3. The method according to claim 2, characterized in that, the controlling the output frequency on the AC side of the voltage source converter valve according to the measured value of the active power at the grid connection point and the reference value of the active power at the grid connection point includes: determining the active power deviation at the grid connection point according to the measured value of the active power at the grid connection point and the reference value of the active power at the grid connection point; performing a first closed-loop control process on the active power deviation at the grid connection point to obtain a closed-loop result; controlling the output frequency according to the closed-loop result and the rated angular frequency of the power grid.

4. The method according to claim 3, characterized in that, the determining the active power deviation at the grid connection point according to the measured value of the active power at the grid connection point and the reference value of the active power at the grid connection point includes: performing a limiting process on the reference value of the active power at the grid connection point according to the maximum limit value of the active power and the minimum limit value of the active power to obtain the limited reference value of the active power at the grid connection point; subtracting the measured value of the active power at the grid connection point from the limited reference value of the active power at the grid connection point to obtain the active power deviation at the grid connection point.

5. The method according to claim 4, characterized in that, the performing a first closed-loop control process on the active power deviation at the grid connection point to obtain a closed-loop result includes: determining a first feedback signal according to the historical closed-loop result and the damping coefficient; performing a first integration process on the difference signal between the active power deviation at the grid connection point and the first feedback signal to obtain the closed-loop result.

6. The method according to claim 5, characterized in that, the performing a first integration process on the difference signal between the active power deviation at the grid connection point and the first feedback signal to obtain the closed-loop result includes: Perform a first integration process on the difference signal according to the inertia time constant and the latching coefficient to obtain the closed-loop result.

7. The method according to any one of claims 4-6, wherein, the method further includes: adjusting the maximum limit value of the active power and the minimum limit value of the active power according to the grid connection point fault detection signal.

8. The method according to claim 7, wherein, the adjusting the maximum limit value of the active power and the minimum limit value of the active power according to the grid connection point fault detection signal includes: when it is detected that the grid connection point fault detection signal is used to indicate that a fault occurs in the energy storage system, adjusting the maximum limit value of the active power to the target maximum limit value of the power, and adjusting the minimum limit value of the active power to the target minimum limit value of the power; or, when it is detected that the grid connection point fault detection signal is used to indicate that the fault is cleared within a first preset time period, adjusting the maximum limit value of the active power from the target maximum limit value of the power to the preset maximum limit value of the power, and adjusting the minimum limit value of the active power from the target minimum limit value of the power to the preset minimum limit value of the power.

9. The method according to claim 6, wherein, the method further includes: adjusting the damping coefficient and the latching coefficient according to the grid connection point fault detection signal.

10. The method according to claim 9, wherein, the adjusting the damping coefficient and the latching coefficient according to the grid connection point fault detection signal includes: when it is detected that the grid connection point fault detection signal is used to indicate that a fault occurs in the energy storage system, adjusting the damping coefficient to the target damping coefficient, and adjusting the latching coefficient to the target latching coefficient; or, when it is detected that the grid connection point fault detection signal is used to indicate that the fault is cleared within a second preset time period, adjusting the damping coefficient from the target damping coefficient to the preset damping coefficient, and adjusting the latching coefficient from the target latching coefficient to the preset latching coefficient.

11. The method according to any one of claims 7-10, wherein, the method further includes: determining the grid connection point fault detection signal according to the grid connection point voltage measurement value, the preset fault detection threshold and the preset fault clearing threshold.

12. The method according to claim 11, wherein, the determining the grid connection point fault detection signal according to the grid connection point voltage measurement value, the preset fault detection threshold and the preset fault clearing threshold includes: when it is detected that the change value of the grid connection point voltage measurement value is less than 0, and the grid connection point voltage measurement value is less than or equal to the preset fault detection threshold within a third preset time period, determining that the grid connection point fault detection signal is used to indicate that a fault occurs in the energy storage system, and recording the drop amplitude of the grid connection point voltage measurement value during the fault. When it is detected that the change value of the grid connection point voltage measurement value is greater than 0 and the grid connection point voltage measurement value is greater than or equal to the preset fault clearing threshold, it is determined that the grid connection point fault detection signal is used to indicate that the energy storage system clears the fault within the fourth preset duration, and the voltage drop amplitude of the grid connection point voltage measurement value during the fault period is adjusted to the preset voltage drop amplitude.

13. The method according to any one of claims 2-12, wherein, controlling the output voltage amplitude of the AC side of the voltage source converter valve according to the grid connection point reactive power measurement value, the grid connection point voltage measurement value, the grid connection point reactive power reference value, and the grid connection point voltage reference value includes: determining the first internal potential amplitude of the voltage source converter valve according to the grid connection point reactive power measurement value, the grid connection point voltage measurement value, the grid connection point reactive power reference value, and the grid connection point voltage reference value; controlling the output voltage amplitude of the AC side of the voltage source converter valve according to the first internal potential amplitude of the voltage source converter valve.

14. The method according to claim 13, wherein, determining the first internal potential amplitude of the voltage source converter valve according to the grid connection point reactive power measurement value, the grid connection point voltage measurement value, the grid connection point reactive power reference value, and the grid connection point voltage reference value includes: determining the grid connection point reactive power deviation according to the grid connection point reactive power measurement value and the grid connection point reactive power reference value; determining the grid connection point voltage deviation according to the grid connection point voltage measurement value and the grid connection point voltage reference value; performing a second integration process on the grid connection point reactive power deviation and / or the grid connection point voltage deviation to obtain the first internal potential amplitude.

15. The method according to claim 13 or 14, wherein, controlling the output voltage amplitude of the AC side of the voltage source converter valve according to the first internal potential amplitude of the voltage source converter valve includes: performing a voltage outer loop control process on the first internal potential amplitude of the voltage source converter valve and the grid connection point voltage measurement value to obtain a current command value of the current inner loop; performing a current limiting inner loop process on the current command value to obtain the output voltage signal of the AC side of the voltage source converter valve; controlling the output voltage amplitude of the AC side of the voltage source converter valve according to the output voltage signal of the AC side of the voltage source converter valve.

16. The method according to claim 15, wherein, performing a voltage outer loop control process on the first internal potential amplitude of the voltage source converter valve and the grid connection point voltage measurement value to obtain a current command value of the current inner loop includes: performing a first PI adjustment process, a dynamic virtual impedance process, or a static virtual impedance process on the first internal potential amplitude of the voltage source converter valve and the grid connection point voltage measurement value to obtain the current command value of the current inner loop.

17. The method according to any one of claims 2-16, wherein, the method further includes: When it is detected that the energy storage system is in the initial stage of grid connection, pre-synchronization processing is performed on the output signal of the AC side of the voltage source converter valve according to the measured value of the grid connection point voltage.

18. The method according to claim 17, wherein, the measured value of the grid connection point voltage includes a first-axis voltage measurement component and a second-axis voltage measurement component, and the pre-synchronization processing of the output signal of the AC side of the voltage source converter valve according to the measured value of the grid connection point voltage includes: performing a second PI adjustment process on the first-axis voltage measurement component to obtain an adjusted first-axis voltage measurement component; performing a second integration process on the adjusted first-axis voltage measurement component and the rated grid angular frequency to obtain the output voltage phase angle of the AC side of the voltage source converter valve; wherein, the output voltage phase angle is the same as the grid connection point voltage phase angle; performing a second closed-loop process on the second-axis voltage measurement component to obtain the second internal potential amplitude of the voltage source converter valve; wherein, the second internal potential amplitude is the same as the grid connection point voltage amplitude.

19. The method according to claim 18, wherein, the performing a second closed-loop process on the second-axis voltage measurement component to obtain the second internal potential amplitude of the voltage source converter valve includes: determining a second feedback signal according to the historical internal potential amplitude; performing a third PI adjustment process and a third integration process on the difference signal between the second-axis voltage measurement component and the second feedback signal in sequence to obtain the second internal potential amplitude.

20. The method according to any one of claims 1-19, wherein, the measured value of the output electrical signal includes: the measured value of the output voltage of the DC side of the voltage source converter valve and the measured value of the output current of the DC side of the voltage source converter valve, and controlling the output voltage of the DC energy storage valve according to the measured value of the output electrical signal of the DC side of the voltage source converter valve and the output voltage reference value of the DC energy storage valve includes: performing a fourth PI adjustment process on the DC voltage difference between the measured value of the output voltage of the DC side of the voltage source converter valve and the output voltage reference value of the DC energy storage valve to obtain a DC current command value; performing a fifth PI adjustment process on the DC current difference between the measured value of the output current of the DC side of the voltage source converter valve and the DC current command value to obtain the output voltage command value of the DC energy storage valve; controlling the output voltage of the DC energy storage valve according to the output voltage command value of the DC energy storage valve.

21. A virtual synchronous control device for an energy storage system, wherein, the energy storage system includes a voltage source converter valve and a DC energy storage valve, and the device includes: a first control module for controlling the output voltage of the DC energy storage valve according to the measured value of the output electrical signal of the DC side of the voltage source converter valve and the output voltage reference value of the DC energy storage valve; a second control module for controlling the output signal of the AC side of the voltage source converter valve according to the measured grid connection point electrical signal value of the voltage source converter valve and the grid connection point electrical signal reference value.

22. A control device for an energy storage system, wherein, It includes a memory and a processor, and the memory stores a computer program. It is characterized in that when the processor executes the computer program, the steps of the method described in any one of claims 1-20 are implemented.

23. A computer-readable storage medium, on which a computer program is stored, It is characterized in that when the computer program is executed by a processor, the steps of the method described in any one of claims 1-20 are implemented.

24. A computer program product, including a computer program, It is characterized in that when the computer program is executed by a processor, the steps of the method described in any one of claims 1-20 are implemented.

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