Fault ride-through control method, energy storage system and storage medium

Abstract

The invention discloses a fault ride-through control method, an energy storage system and a storage medium, and relates to the technical field of energy storage system control, and the method comprises the steps: sequentially carrying out the single-proportion control, current vector amplitude limiting and current proportional integral PI control of a received voltage reference signal when a system fault is detected, and obtaining an energy storage input voltage; performing energy storage conversion on the energy storage input voltage to obtain system output; the system output comprises system output current; virtual power is obtained according to the product of the system output current and the voltage reference signal; controlling and adjusting a virtual synchronous generator (VSG) according to the received instruction power and the virtual power to obtain a virtual internal potential; determining the virtual internal potential as a voltage reference signal, and returning to execute the steps of performing single-proportion control, current vector amplitude limiting and current proportional-integral PI control on the voltage reference signal in sequence so as to enable the system to maintain output and realize system fault ride-through; the effect of enhancing the transient synchronization stability of the system is achieved.

Description

Technical Field

[0001] The present application relates to the technical field of energy storage system control, and particularly to a fault ride-through control method, an energy storage system, and a storage medium. Background Technique

[0002] In a high-voltage direct-connected energy storage system, battery cells are connected in series and then connected to an inverter, and the inverter is directly connected to the high-voltage power grid for operation to achieve efficient energy storage and rapid release. The traditional high-voltage direct-connected energy storage system adopts a grid-following (GFL) control method to achieve synchronization with the power grid. This control method has poor stability in application scenarios with low grid strength and insufficient voltage support ability.

[0003] In related technologies, for the grid-forming control method adopted by the high-voltage direct-connected energy storage system, when faults such as short circuits, voltage dips, or phase angle jumps occur in the power grid, there are problems of poor transient synchronization stability. And due to the need to limit the fault current during the fault process, a current vector limiting link is introduced in the grid-forming high-voltage direct-connected energy storage system. The introduction of the current vector limiting link deteriorates the problem of poor transient synchronization stability existing in the grid-forming high-voltage direct-connected energy storage system during faults. Summary of the Invention

[0004] The main purpose of the present application is to provide a fault ride-through control method, an energy storage system, and a storage medium, aiming to solve the technical problem of poor transient synchronization stability of the high-voltage direct-connected energy storage system under faults in related technologies.

[0005] To achieve the above object, the present application proposes a fault ride-through control method, which is applied to a grid-forming high-voltage direct-connected energy storage system, and the method includes: When a system fault is detected, the received voltage reference signal is sequentially subjected to single proportional control, current vector limiting, and current proportional integral (PI) control to obtain the energy storage input voltage; Perform energy storage current conversion on the energy storage input voltage to obtain a system output; the system output includes a system output current; Obtain virtual power according to the product of the system output current and the voltage reference signal; Perform virtual synchronous generator (VSG) control and regulation according to the received command power and the virtual power to obtain a virtual internal potential; Determine the virtual internal potential as the voltage reference signal, and return to execute the step of sequentially performing single proportional control, current vector limiting, and current proportional integral (PI) control on the received voltage reference signal to obtain the energy storage input voltage, so that the system maintains the output and realizes system fault ride-through.

[0006] In one embodiment, the steps of successively performing single proportional control, current vector limiting, and current proportional integral PI control on the received voltage reference signal to obtain the energy storage input voltage include: Perform single proportional control on the voltage reference signal to obtain a first reference current; Perform current vector limiting on the first reference current to obtain a second reference current; wherein, current vector limiting means adaptively adjusting the resistance value of the equivalent virtual resistance so that the amplitude of the second reference current remains within the preset maximum output current; Perform current PI control on the second reference current to obtain the energy storage input voltage.

[0007] In one embodiment, the steps of performing current vector limiting on the first reference current to obtain a second reference current include: Compare the amplitude of the first reference current with the maximum output current; When the amplitude of the first reference current is less than or equal to the maximum output current, determine the amplitude of the first reference current as the amplitude of the second reference current and obtain the second reference current; When the amplitude of the first reference current is greater than the maximum output current, determine the resistance value of the equivalent virtual resistance according to the amplitude of the first reference current, and determine a proportionality coefficient according to the resistance value, so as to determine the amplitude of the second reference current according to the product of the maximum output current and the proportionality coefficient and obtain the second reference current.

[0008] In one embodiment, in the steps of performing current vector limiting on the first reference current to obtain a second reference current, the calculation formula involved in current vector limiting is: ; Wherein, I refdq represents the second reference current i ref the dq-axis current of I * refdq represents the first reference current i * ref the dq-axis current of I * refd is I * refdq the corresponding d-axis current component, I * refq is I * refdq the corresponding q-axis current component, I maxRepresents the maximum output current.

[0009] In one embodiment, the commanded power includes the commanded active power and the commanded reactive power, and the virtual power includes the virtual active power and the virtual reactive power; The steps of performing virtual synchronous generator (VSG) control and regulation based on the received commanded power and virtual power to obtain the virtual internal electromotive force include: Performing VSG control based on the commanded active power, virtual active power, and the received commanded voltage angular velocity to obtain the virtual internal electromotive force angular velocity; Performing voltage magnitude regulation based on the commanded reactive power, virtual reactive power, and the received commanded voltage magnitude to obtain the voltage magnitude; Generating a voltage vector based on the virtual internal electromotive force angular velocity and voltage magnitude to obtain the virtual internal electromotive force.

[0010] In one embodiment, in the steps of performing VSG control and regulation based on the received commanded power and virtual power to obtain the virtual internal electromotive force, the calculation formulas involved in performing VSG control and regulation are: ; Wherein, P * Represents the commanded power p * The commanded active power in Q * Represents the commanded power p * The commanded reactive power in P vir Represents the virtual power p vir The virtual active power in Q vir Represents the virtual power p vir The virtual reactive power in ω * Represents the commanded voltage angular velocity, ω Represents the virtual internal electromotive force angular velocity, V * Represents the commanded voltage magnitude, V Represents the voltage magnitude, J Represents the virtual inertia constant, D m Represents the damping coefficient, n Represents the reactive droop coefficient.

[0011] In one embodiment, after determining the virtual internal electromotive force as the voltage reference signal and returning to perform the steps of successively performing single proportional control, current vector limiting, and current proportional integral PI control on the received voltage reference signal to obtain the energy storage input voltage, the method further includes: Multiplying the d-axis current component corresponding to the system output current by the amplitude of the virtual internal electromotive force to obtain the virtual active power; wherein, the amplitude of the virtual internal electromotive force is equal to the voltage amplitude; Multiplying the q-axis current component corresponding to the system output current by the amplitude of the virtual internal electromotive force and taking the negative value to obtain the virtual reactive power.

[0012] In addition, to achieve the above object, the present application also proposes an energy storage system, which is a network-forming high-voltage direct-connected energy storage system. The system includes a feedback control module, a PI control module, an energy storage converter module connected in sequence, and a virtual power calculation module. The virtual power calculation module is respectively connected to the energy storage converter module and the feedback control module; Wherein, the PI control module is used to successively perform single proportional control, current vector limiting, and current proportional integral PI control on the received voltage reference signal when detecting a system fault to obtain the energy storage input voltage; The energy storage converter module is used to perform energy storage conversion on the energy storage input voltage to obtain the system output; the system output includes the system output current; The virtual power calculation module is used to obtain the virtual power according to the product of the system output current and the voltage reference signal; The feedback control module is used to perform virtual synchronous generator VSG control and regulation according to the received command power and the virtual power to obtain the virtual internal electromotive force; The PI control module is further used to continue performing single proportional control, current vector limiting, and current proportional integral PI control after determining the virtual internal electromotive force as the voltage reference signal, so as to maintain the system output through the energy storage converter module and achieve system fault ride-through.

[0013] In one embodiment, the PI control module includes a voltage PI inner loop unit, a current vector limiting unit, and a current PI inner loop unit connected in sequence. The voltage PI inner loop unit is connected to the feedback control module, and the current PI inner loop unit is connected to the energy storage converter module; Wherein, the voltage PI inner loop unit is used to perform single proportional control on the voltage reference signal to obtain the first reference current; The current vector limiting unit is used to perform current vector limiting on the first reference current to obtain the second reference current; wherein, current vector limiting means that the amplitude of the second reference current is kept within the preset maximum output current value by adaptively adjusting the resistance value of the equivalent virtual resistor; The current PI inner loop unit is used to perform current PI control on the second reference current to obtain the energy storage input voltage.

[0014] In addition, to achieve the above object, the present application also provides a storage medium, which is a computer-readable storage medium. A computer program is stored on the storage medium, and when the computer program is executed by a processor, the steps of the fault ride-through control method as described above are implemented.

[0015] One or more technical solutions provided by the present application have at least the following technical effects: A fault ride-through control method is provided, which is applied to a network-forming high-voltage direct-connected energy storage system. When a system fault is detected, the received voltage reference signal is sequentially subjected to single proportional control, current vector limiting, and current proportional integral (PI) control to obtain the energy storage input voltage, and then the energy storage input voltage is subjected to energy storage current conversion to obtain the system output; the system output includes the system output current. The virtual power can be obtained according to the product of the system output current and the voltage reference signal, and then the virtual synchronous generator (VSG) control and regulation are performed according to the received command power and the virtual power to obtain the virtual internal potential. After the virtual internal potential is determined as the voltage reference signal, it can continue to be sequentially subjected to single proportional control, current vector limiting, current proportional integral PI control, and energy storage current conversion to maintain the system output, realizing the fault ride-through of the high-voltage direct-connected energy storage system under the fault current limiting condition; in this method, the current vector limiting is triggered during the system fault, which can limit the fault current, ensure that the system outputs a current of a constant magnitude, enable the electric energy output by the system to be normally transmitted to the power grid, and maintain the normal operation of the system; compared with the method of using the real power of the system as the power feedback in the related art, the virtual power is used as the power feedback in this method. In the system fault state, the virtual power will be greater than the real power output by the system, which can effectively reduce the accelerating area and increase the decelerating area, thereby effectively enhancing the transient synchronous stability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings herein are incorporated into the specification and form a part of the specification, showing embodiments consistent with the present application, and are used together with the specification to explain the principles of the present application.

[0017] To more clearly illustrate the technical solutions in the embodiments of the present application or the related art, the following will briefly introduce the drawings required for use in the description of the embodiments or the related art. Obviously, for those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0018] Figure 1 It is a schematic flowchart of an embodiment of the fault ride-through control method provided by the present application; Figure 2 It is a schematic connection diagram of the network-forming high-voltage direct-connected energy storage system involved in the embodiments of the present application; Figure 3 is Figure 2 an example of an energy storage converter module in a grid-forming high-voltage direct-connected energy storage system; Figure 4 is Figure 2 a schematic diagram of the equivalent circuit of a grid-forming high-voltage direct-connected energy storage system; Figure 5 is a schematic diagram of the power angle curve of a comparative example provided by an embodiment of the present application; Figure 6 is a schematic diagram of the power angle curve of an application example provided by an embodiment of the present application; Figure 7 is a simulation experiment result graph of a comparative example provided by an embodiment of the present application under different fault clearing times; Figure 8 is a simulation experiment result graph of an application example provided by an embodiment of the present application under different fault clearing times.

[0019] The realization, functional characteristics, and advantages of the objectives of the present application will be further described in conjunction with the embodiments and with reference to the accompanying drawings. Specific Embodiments

[0020] It should be understood that the specific embodiments described herein are only used to explain the technical solutions of the present application and are not used to limit the present application. For a better understanding of the technical solutions of the present application, the following will be described in detail in conjunction with the accompanying drawings of the specification and specific embodiments.

[0021] The high-voltage direct-connected energy storage system is a new type of energy storage system that realizes efficient energy storage and rapid release. Different from low-voltage or medium-voltage energy storage systems, the high-voltage direct-connected energy storage system, with its higher efficiency, more compact design, and more flexible application scenarios, will become an important part of the "dual-high" power system and has broad application prospects in the fields of power grid peak shaving, frequency regulation, voltage support, renewable energy, and grid connection optimization.

[0022] Traditional high-voltage direct-connected energy storage systems use a grid-following (GFL) control method to synchronize with the power grid. This control method highly depends on a phase-locked loop (PLL), and there are problems with poor stability in application scenarios with low grid strength and insufficient voltage support capabilities. For this reason, a grid-forming control method for high-voltage direct-connected energy storage systems has emerged.

[0023] Common grid-forming control methods include droop control, virtual synchronous generator (VSG: Virtual Synchronous Generator) control, and virtual oscillator control. When faults such as short circuits, voltage dips, or phase angle jumps occur in the power grid, the grid-forming high-voltage direct-connected energy storage system has problems with poor transient synchronization stability, and due to the poor over-current capacity of power electronic devices, it is generally necessary to limit the fault current during the fault process. For this reason, a current limiting link is introduced in the grid-forming high-voltage direct-connected energy storage system, and the common current limiting method is current vector limiting. When the current vector limiting link is triggered, the grid-forming high-voltage direct-connected energy storage system can be regarded as a voltage source in series with an adaptive resistor to output a constant current. Although current vector limiting solves the over-current problem of the high-voltage direct-connected energy storage system during faults, the introduction of the current vector limiting link deteriorates the problem of poor transient synchronization stability existing in the grid-forming high-voltage direct-connected energy storage system during faults.

[0024] In view of the above problems, the embodiments of the present application provide a fault ride-through control method, an energy storage system, and a storage medium.

[0025] The embodiments of the present application provide a fault ride-through control method.

[0026] In one embodiment, referring to Figure 1 , Figure 1 is a schematic flowchart of an embodiment of the fault ride-through control method of the present application. This fault ride-through control method can be applied to a grid-forming high-voltage direct-connected energy storage system. The method may include steps S10 to S50: Step S10, when a system fault is detected, the received voltage reference signal is sequentially subjected to single proportional control, current vector limiting, and current proportional integral PI control to obtain the energy storage input voltage v abc_ref .

[0027] It should be noted that the execution subject of this method can be a virtual control device in the system, or the main controller in the system, or an external control device interacting with the system, such as a computing service device with data processing, network communication, and program running functions. No specific limitation is made here. When the execution subject is a virtual control device, each step can be implemented by different functional modules. Through the connection and communication of each functional module, the steps of this method can be realized; when the execution subject is the main controller or an external control device, it may include a memory, a processor, and a computer program stored on the memory and running on the processor. The computer program is configured to implement the steps of this method.

[0028] It should also be noted that the system fault can be a fault caused by a short circuit, voltage dip or phase angle jump in the power grid, or other fault conditions detected by the fault detection device within the system. Specifically, it can be a fault condition where the current increases during a fault and the current needs to be limited, or it can be a fault condition where the system can continue to maintain output without causing safety impacts on the internal components of the system or the subsequent power grid through current limiting. In practical applications, it can be set according to needs and is not specifically limited here. Fault ride-through means that in the case of a power grid fault, the system can continue to operate without disconnecting from the power grid until the fault is removed and the system returns to a normal and stable operating state.

[0029] The voltage reference signal can be a reference voltage obtained by parsing or controlling and processing the received system control instruction, or a reference voltage generated by controlling and regulating based on the feedback signal, which is not specifically limited here; among them, the system control instruction can be an instruction sent by the upper computer or an external device to this system. The single proportional control can be implemented by the voltage PI (Proportional-Integral) inner loop in the system. Specifically, the integral coefficient in the voltage PI inner loop is set to zero to ensure that the voltage loop does not lock up (wind-up), and the function of this voltage PI inner loop changes from voltage PI control to single proportional control. The current vector limiting can be triggered only when a system fault is detected. When the system is operating normally, the current vector limiting is not triggered, and the received voltage reference signal can be subjected to voltage PI control and current PI control in sequence. Therefore, a voltage-current inner loop double closed-loop PI control can be set in the system, and a current vector limiting link is introduced into this double closed-loop.

[0030] Exemplarily, referring to Figure 2 , Figure 2 is a connection schematic diagram of the grid-forming high-voltage direct-connected energy storage system provided in this embodiment. The system can include multiple functional modules, specifically including a feedback control module, a PI control module, and an energy storage converter module connected in sequence, as well as a virtual power calculation module. The virtual power calculation module is respectively connected to the energy storage converter module and the feedback control module; among them, this step S10 can be implemented through the PI control module to output the energy storage input voltage v abc_ref to the subsequent energy storage converter module.

[0031] Step S20, perform energy storage conversion on the energy storage input voltage to obtain the system output; the system output can include the system output current.

[0032] It should be noted that the electric energy output by the system can be transmitted to the power grid through the transmission line, and the energy storage input voltage v abc_refIt can be three-phase alternating current. The transmission line can be a high-voltage transmission cable and can be a three-phase system, which is not specifically limited here.

[0033] Exemplarily, as Figure 2 shown, this step S20 can be implemented by an energy storage inverter module. The input of the energy storage inverter module is the energy storage input voltage v abc_ref , and its output is the system output. The system output can include the system output voltage v pcc and the system output current i pcc . The real power of the system output can be calculated from the two. Figure 2 In X g , it represents the equivalent impedance of the transmission line, v g and

[0034] is the grid connection point voltage.

[0035] It should be noted that when the system is in the fault current limiting condition, in the related art, the real power of the system output is used as the power feedback for subsequent control and adjustment. In this embodiment, however, a virtual power is calculated based on the system output current and the reference voltage in the voltage reference signal received by the PI control module, and this virtual power is used as the power feedback.

[0036] It should also be noted that the calculation of the virtual power can directly calculate the product of the current value and the voltage value as the virtual power, or separately calculate the active power and the reactive power to obtain a virtual power including the virtual active power and the virtual reactive power.

[0037] Exemplarily, as Figure 2 shown, this step S30 can be implemented by a virtual power calculation module. The virtual power calculation module is connected to the energy storage inverter module and can obtain the system output current from the energy storage inverter module i pcc . The virtual power calculation module can be connected in parallel with the input of the PI control module to receive the voltage reference signal simultaneously and calculate the virtual power p vir and then give it to the feedback control module.

[0038] Step S40, perform virtual synchronous generator (VSG) control and adjustment based on the received command power and virtual power to obtain a virtual internal potential.

[0039] It should be noted that the command power can be a reference power obtained by parsing or controlling and processing based on the received system control command. When a system fault occurs, the grid-forming control method of the virtual synchronous generator (VSG) is used for subsequent control and regulation. Here, the virtual power replaces the system real power in the related technology, and the virtual power is used as the power feedback of the VSG to obtain the virtual internal potential.

[0040] Exemplarily, such as Figure 2 shown, this step S40 can be implemented by a feedback control module. The feedback control module is connected to the virtual power calculation module and receives the virtual power p vir . At the same time, the feedback control module can also be connected to the upper computer or external device to receive the system control command to parse and obtain the command power p * . Then, the VSG is used to perform control and regulation according to the command power p * and the virtual power p vir to obtain the virtual internal potential v ref . This virtual internal potential v ref can be given to the PI control module and the virtual power calculation module.

[0041] Step S50, determine the virtual internal potential as the voltage reference signal, and return to execute the step of sequentially performing single proportional control, current vector limiting, and current proportional integral PI control on the received voltage reference signal to obtain the energy storage input voltage, so as to maintain the system output and achieve system fault ride-through.

[0042] It should be noted that the initial voltage reference signal can be the command voltage. However, during a system fault, after triggering the current vector limiting, the calculated virtual power can be used as the power feedback to obtain the corresponding new voltage reference signal, that is, the virtual internal potential. At this time, single proportional control, current vector limiting, and current proportional integral PI control, as well as energy storage variable current, can be performed on this virtual internal potential to maintain the system output, and the system output current will not exceed the limit, ensuring that the system outputs a current of a constant magnitude, enabling the electric energy output by the system to be normally transmitted to the power grid, maintaining the normal operation of the system, that is, achieving system fault ride-through, so that this grid-forming high-voltage direct-connected energy storage system has a fault crossing loss function.

[0043] Exemplarily, such as Figure 2 shown, after the virtual internal potential v ref is given to the PI control module, the PI control module can determine it as the voltage reference signal and perform operations on the virtual internal potential v refPerform single proportional control, current vector limiting, and current proportional-integral (PI) control in sequence to obtain the energy storage input voltage v abc_ref ; The subsequent energy storage converter module continues to perform energy storage conversion on the energy storage input voltage v abc_ref to obtain the subsequent system output, so as to maintain the stable output of the system and the continuous reception of voltage by the power grid v ref .

[0044] Different from the method of using the real power at the point of common coupling (PCC) between the energy storage system and the transmission line as power feedback in the related art, the method of this embodiment and the grid-forming high-voltage direct-connected energy storage system involved therein have two working states: under normal operating conditions, using voltage-current inner-loop double-closed-loop PI control, the system output voltage v pcc tracks the virtual internal potential generated by the VSG control v ref , and the virtual power at this time is the real power output by the system; under the fault current limiting condition, since the calculated virtual power p vir will be greater than the real power output by the system, using this virtual power p vir as power feedback can effectively reduce the accelerating area, increase the decelerating area, improve the transient synchronous stability of the grid-forming high-voltage direct-connected energy storage system under faults, enhance the fault crossing ability of the grid-forming high-voltage direct-connected energy storage system, and ensure the safe and stable operation of the system under faults.[[ID=,25]]

[0045] This embodiment provides a fault ride-through control method, which is applied to a network-forming high-voltage direct-connected energy storage system. When a system fault is detected, the received voltage reference signal is sequentially subjected to single proportional control, current vector limiting, and current proportional-integral (PI) control to obtain the energy storage input voltage, and then the energy storage input voltage is subjected to energy storage current conversion to obtain the system output. The system output includes the system output current. The virtual power can be obtained according to the product of the system output current and the voltage reference signal, and then the virtual synchronous generator (VSG) control and regulation are performed according to the received command power and the virtual power to obtain the virtual internal potential. After determining the virtual internal potential as the voltage reference signal, it can continue to be sequentially subjected to single proportional control, current vector limiting, current proportional-integral PI control, and energy storage current conversion to maintain the system output, realizing the fault ride-through of the high-voltage direct-connected energy storage system under the fault current limiting condition. In this method, the current vector limiting is triggered during a system fault, which can limit the fault current, ensure that the system outputs a current of a constant magnitude, enable the electric energy output by the system to be normally transmitted to the power grid, and maintain the normal operation of the system. Compared with the method of using the real power of the system as the power feedback in the related technology, the virtual power is used as the power feedback in this method. In the system fault state, the virtual power will be greater than the real power output by the system, which can effectively reduce the accelerating area and increase the decelerating area, thereby effectively enhancing the transient synchronous stability of the system.

[0046] In a feasible implementation manner, step S10 may include steps S11 to S13: Step S11, perform single proportional control on the voltage reference signal to obtain the first reference current; Step S12, perform current vector limiting on the first reference current to obtain the second reference current. Wherein, the current vector limiting means that the magnitude of the second reference current is kept within the preset maximum output current value by adaptively adjusting the resistance value of the equivalent virtual resistance Req; Step S13, perform current PI control on the second reference current to obtain the energy storage input voltage.

[0047] It should be noted that the single proportional control refers to the control performed when the integral coefficient of the PI control is set to zero. The current vector limiting can be equivalent to an equivalent virtual resistance Req whose resistance value can be adaptively adjusted. Under normal operating conditions, the current vector limiting may not be triggered and does not work. At this time, the resistance value of the equivalent virtual resistance Req R eq = 0; Under the fault current limiting condition, the current vector limiting is triggered, and the resistance value can be adaptively adjusted according to the fault degree R eq to control the current output by itself, that is, the second reference current i ref to be kept within the current allowable range, and the allowable range may specifically be such that the second reference currenti ref The amplitude of I max is maintained within a preset maximum output current, that is, below the maximum output current. I max Specifically, it can also be to make the amplitude of the second reference current i ref not exceed the maximum output current. I max .

[0048] Exemplarily, as Figure 2 shown, the PI control module may include a voltage PI inner loop unit, a current vector limiting unit, and a current PI inner loop unit connected in sequence; among them, the current PI inner loop unit is connected to the energy storage converter module and outputs the energy storage input voltage v abc_ref ; the voltage PI inner loop unit may be connected to the feedback control module to determine the virtual internal potential v ref as the voltage reference signal for subsequent processing; the voltage PI inner loop unit may also be connected to the host computer or external device to obtain the initial voltage reference signal.

[0049] When a system fault is detected, the current vector limiting is triggered, and the integral coefficient in the voltage PI inner loop is set to zero to ensure that the voltage PI inner loop does not lock up (wind-up). At this time, the voltage PI inner loop unit performs single proportional control on the voltage reference signal (or virtual internal potential v ref ) to obtain the first reference current i * ref and outputs it; the current vector limiting unit performs current vector limiting on the first reference current i * ref to obtain the second reference current i ref and outputs it, specifically by adaptively adjusting the resistance value of the equivalent virtual resistance Req R eq to make the amplitude of the second reference current i ref maintained within a preset maximum output current I max ; the current PI inner loop unit performs current PI control on the second reference current i ref to obtain the energy storage input voltage v abc_ref .

[0050] In this embodiment, a simple improvement can be made to the existing voltage-current inner-loop double closed-loop PI control of the energy storage system to achieve the fault ride-through of the system. The introduced current vector limiting not only solves the overcurrent problem of the high-voltage direct-connected energy storage system during the fault, but also does not deteriorate the transient synchronization stability of the system, overcoming the technical loopholes existing in the related technologies.

[0051] In a specific embodiment, step S12 may include steps S121 to S123: Step S121, compare the amplitude of the first reference current i * ref with the maximum value of the output current I max ; Step S122, when the amplitude of the first reference current i * ref is less than or equal to the maximum value of the output current I max , determine the amplitude of the first reference current i * ref as the amplitude of the second reference current i ref , and obtain the second reference current i ref ; Step S123, when the amplitude of the first reference current i * ref is greater than the maximum value of the output current I max , determine the resistance value i * ref of the equivalent virtual resistance Req according to the amplitude of the first reference current R eq , and determine a proportionality coefficient according to the resistance value R eq to determine the amplitude of the second reference current I max by multiplying the maximum value of the output current i ref with this proportionality coefficient, and obtain the second reference current i ref .

[0052] It should be noted that, referring to Figure 2 , the first reference current i * refThe second reference current is the command current output by the voltage PI inner loop without passing through the current vector limiting link; i ref The maximum output current is the command current of the input current PI inner loop after passing through the current vector limiting link. I max The maximum output current allowed by the system can be determined by the user according to the system parameters and is not specifically limited here. i * ref The amplitude of determines the resistance of the equivalent virtual resistance Req R eq When the resistance value is R eq When determining the proportional coefficient, it can be determined by conventional methods such as automatic table lookup, manual input, etc., or it can be determined based on the first reference current i * ref It can be determined by calculation or the like, and is not specifically limited here.

[0053] In this embodiment, the second reference current is determined by a simple calculation method. i ref The amplitude is small, the operation is simple, and the system occupies less resources.

[0054] In another specific implementation, step S12 may also perform current vector amplitude limiting according to the following calculation formula: ; in, I refdq Indicates the second reference current i ref The dq axis current, I * refdq Indicates the first reference current i * ref The dq axis current, I * refd for I * refdq The corresponding d-axis current component, I * refq for I * refdq The corresponding q-axis current component, I max Indicates the maximum output current.

[0055] In this embodiment, the second reference current is determined by an accurate calculation method i ref to make the amplitude more accurate for fault condition determination and the calculation result more accurate.

[0056] It can be understood that the first implementation manner of step S12 provided above is simpler in the operation of current vector limiting than the second implementation manner. Therefore, the first implementation manner has a higher determination efficiency for the second reference current i ref . And because the second implementation manner calculates the second reference current i ref more accurately than the first implementation manner, the second implementation manner has a higher determination accuracy for the second reference current i ref .

[0057] The above are only two feasible implementation manners of step S12 provided in this embodiment, and the specific implementation manner of step S12 in this embodiment is not specifically limited.

[0058] In an optional implementation manner, step S20 may include steps S21 to S22: Step S21: Perform energy storage current conversion processing on the energy storage input voltage v abc_ref to output a converted current i f ; Step S22: Perform filtering processing on the converted current i f to obtain the system output.

[0059] It should be noted that the energy storage current conversion processing can be directly implemented by an energy storage current converter (PCS: Power Conversion System) or an energy storage current conversion system, and the filtering processing can use LC filtering or other filters, which is not specifically limited here.

[0060] In an example, referring to Figure 3 , Figure 3 is an example of an energy storage current conversion module in a grid-connected high-voltage direct-connected energy storage system. The energy storage current conversion module can directly adopt a high-voltage cascaded energy storage system with three-phase input terminals in parallel. The high-voltage cascaded energy storage system includes a three-phase energy storage circuit, and the energy storage circuit is composed of multiple energy storage units connected in cascade. Each energy storage unit may include an energy storage battery, a current converter, and a filter connected in sequence; the three-phase output terminals of the high-voltage cascaded energy storage system are respectively connected to the three-phase input terminals of the high-voltage power grid through a transmission line, Figure 3 in which, X ga represents the equivalent impedance of the a-phase transmission line,X gb represents the equivalent impedance of the b-phase transmission line, X gc represents the equivalent impedance of the c-phase transmission line, v ga represents the voltage at the a-phase connection point of the high-voltage power grid, v gb represents the voltage at the b-phase connection point of the high-voltage power grid, v gc represents the voltage at the c-phase connection point of the high-voltage power grid.

[0061] In another example, as Figure 2 shown, the energy storage converter module may include a directly-connected high-voltage energy storage unit and a filtering unit connected in sequence. The directly-connected high-voltage energy storage unit is connected to the PI control module, and the filtering unit is connected to the power grid through a transmission line. Specifically, the filtering unit may include an inductor Lf and a capacitor Cf. One end of the inductor Lf is connected to the directly-connected high-voltage energy storage unit, the other end is connected to one end of the capacitor Cf, and is connected to the power grid through a transmission line. The other end of the capacitor Cf is grounded, and the output of this filtering unit is the final output of the system.

[0062] Optionally, the filtering unit is also connected to the voltage PI inner loop unit to feed back the system output voltage v pcc to the voltage PI inner loop, enabling it to perform voltage PI inner loop control on the voltage reference signal (or virtual internal electromotive force v pcc ), to achieve voltage loop PI regulation; the directly-connected high-voltage energy storage unit is also connected to the current PI inner loop unit to feed back the converter current v ref to the current PI inner loop, enabling it to perform current PI inner loop control on the second reference current i f according to the converter current i f to achieve current loop PI regulation, so as to output a more accurate energy storage input voltage i ref v abc_ref abc_ref .

[0063] In this embodiment, two different energy storage converter configuration methods are provided. Specifically, after performing energy storage conversion processing and filtering processing on the energy storage input voltage, the system output is obtained, which can effectively remove the interference factors in the system, ensure that the electric energy output to the power grid meets the application requirements while having a stable voltage and frequency, so as to improve the power quality of the distribution network.

[0064] In an optional embodiment, the virtual power p vir includes virtual active powerP vir and the virtual reactive power Q vir ; Step S30 may include steps S31 to S32: Step S31, multiplying the d-axis current component corresponding to the system output current i pcc by the amplitude of the reference voltage in the voltage reference signal to obtain the virtual active power P vir ; Step S32, multiplying the q-axis current component corresponding to the system output current i pcc by the amplitude of the reference voltage in the voltage reference signal and taking the negative value to obtain the virtual reactive power Q vir .

[0065] It should be noted that the system output current i pcc is the actual output true current of this network-forming high-voltage direct-connected energy storage system, that is, the initial virtual power can be calculated from the reference voltage and the system output current i pcc . Correspondingly, in the subsequent cyclic process after determining the virtual internal potential as the voltage reference signal, step S31 may be multiplying the d-axis current component corresponding to the system output current i pcc by the amplitude of the virtual internal potential v ref to obtain the virtual active power P vir ; Step S32 may be multiplying the q-axis current component corresponding to the system output current i pcc by the amplitude of the virtual internal potential v ref and taking the negative value to obtain the virtual reactive power Q vir .

[0066] In this embodiment, a specific calculation method for virtual power is provided. Specifically, the system output current and the reference voltage before PI control are used to calculate the virtual power, and the characteristics that power includes active power and reactive power are fully considered, so that more accurate and more practical virtual power can be obtained for the system operation.

[0067] Based on an embodiment of the above fault ride-through control method, in another embodiment of the fault ride-through control method of the present application, for the same or similar content as the above embodiment, reference may be made to the above introduction and will not be elaborated hereinafter. On this basis, the commanded power includes commanded active power and commanded reactive power, and the virtual power includes virtual active power and virtual reactive power.

[0068] In a feasible implementation, step S40 may include steps S41 to S43: Step S41, perform VSG control according to the commanded active power, virtual active power, and the received commanded voltage angular velocity to obtain the virtual internal potential angular velocity; Step S42, adjust the voltage magnitude according to the commanded reactive power, virtual reactive power, and the received commanded voltage amplitude to obtain the voltage amplitude; Step S43, generate a voltage vector based on the virtual internal potential angular velocity and the voltage amplitude to obtain the virtual internal potential.

[0069] It should be noted that the commanded voltage angular velocity may be a reference angular velocity obtained by parsing or control processing based on the received system control command, and the commanded voltage amplitude may be the reference voltage in the reference voltage of the voltage reference signal, that is, the amplitude of the reference voltage obtained by parsing or control processing based on the received system control command.

[0070] Exemplarily, as Figure 2 shown, steps S41 and S42 can be implemented by a virtual power feedback control unit to obtain the virtual internal potential angular velocity ω and the voltage amplitude V , and the virtual power feedback control unit is connected to the virtual power calculation module and correspondingly receives the virtual active power pvir in the virtual power Pvir and the virtual reactive power Qvir ; the virtual power feedback control unit is also connected to the upper computer or external device to obtain the commanded active power p* in the commanded power P* and the commanded reactive power Q* , as well as the commanded voltage angular velocity ω * and the commanded voltage amplitude V* .

[0071] The virtual power feedback control unit may include an active power control loop and a reactive power control loop. The active power control loop can be directly implemented by a VSG as Figure 2 shown, perform VSG control according to the commanded active power P* , the virtual active power Pvir and the commanded voltage angular velocity ω * and output the virtual internal potential angular velocity ω ; the reactive power control loop adjusts the voltage magnitude according to the commanded reactive power Q* , the virtual reactive power Qvir and the commanded voltage amplitude V* and outputs the voltage amplitude V .

[0072] Optionally, step S43 may include steps S431 to S432: Step S431, integrating the virtual internal potential angular velocity ω to obtain the voltage phase; Step S432, performing voltage synthesis based on the voltage phase and the voltage amplitude V to obtain the virtual internal potential v ref .

[0073] Exemplarily, as Figure 2 shown, step S43 can be implemented by a virtual voltage generation unit (such as the Figure 2 connected to each other in and voltage synthesis) to obtain the virtual internal potential v ref , and this virtual voltage generation unit is connected to the virtual power feedback control unit, correspondingly receiving the virtual internal potential angular velocity ω and the voltage amplitude V , and is connected to the PI control module, so that after the PI control module determines the virtual internal potential v ref as the voltage reference signal, continue with PI control and energy storage current conversion to generate a continuous system output.

[0074] In this embodiment, a method is provided for respectively using virtual active power and virtual reactive power to perform active power control and reactive power control correspondingly, so as to generate an accurate voltage vector that better meets the actual application requirements, thereby facilitating the grid-connected high-voltage direct-connected energy storage system to maintain a stable output.

[0075] In another feasible embodiment, step S40 can also perform virtual synchronous generator VSG control and regulation according to the following calculation formula: ; where P * represents the commanded active power in the commanded power p * , Q * represents the commanded reactive power in the commanded power p * , P vir represents the virtual active power in the virtual power p vir , Q vir represents the virtual reactive power in the virtual power <{ p vir , ω *Represents the angular velocity of the command voltage ω Represents the angular velocity of the virtual internal potential V * Represents the amplitude of the command voltage V Represents the voltage amplitude J Represents the virtual inertia constant D m Represents the damping coefficient n Represents the reactive power droop coefficient

[0076] It should be noted that the angular velocity of the virtual internal potential can be obtained through the above calculation formula ω and the voltage amplitude V , and then according to the angular velocity of the virtual internal potential ω and the voltage amplitude V to generate a voltage vector and obtain the virtual internal potential v ref . For details, please refer to the aforementioned steps S431~S432 and will not be elaborated here

[0077] In this embodiment, two specific power feedback control methods for generating the virtual internal potential are provided. The first implementation method is simpler to operate for VSG control and regulation than the second implementation method. Therefore, the first implementation method has a higher calculation efficiency for the virtual internal potential v ref . And because the second implementation method is more accurate in calculation when performing VSG control and regulation than the first implementation method, the second implementation method has a higher determination accuracy for the virtual internal potential v ref . The above are only two feasible implementation methods of step S40 provided in this embodiment, and the specific implementation method of step S40 in this embodiment is not specifically limited

[0078] In an alternative implementation, the virtual power p ]> vir includes the virtual active power P vir and the virtual reactive power Q vir ; after step S50, the method may further include repeatedly executing step S30, and the repeatedly executed step S30 may include steps S31’~S32’: Step S31’: Multiply the d-axis current component i pcc corresponding to the system output current I pccd by the amplitude v ref of the virtual internal potential V ref to obtain the virtual active powerP vir ; among them, the virtual internal electromotive force v ref has an amplitude V ref equal to the voltage amplitude V . ; Step S32': Multiply the q-axis current component i pcc corresponding to the system output current I pccq by the amplitude v ref of the virtual internal electromotive force and take the negative value to obtain the virtual reactive power V ref . Q vir .

[0079] It should be noted that after determining the virtual internal electromotive force v ref as the voltage reference signal, the subsequent return to execute steps S10 - S20 will continue to generate the system output and continue to execute step S30. At this time, step S30 can specifically execute the above steps S31' - S32', and the corresponding specific calculation formula is: .

[0080] Among them, the d-axis current component i pcc corresponding to the system output current and the q-axis current component I pccd can be the d-axis component and the q-axis component of the system PCC point output current obtained with the voltage phase generated by VSG control as the reference. I pccq

[0081] In this embodiment, a specific calculation method for virtual power is provided. Specifically, the system output current and the virtual internal electromotive force are used to calculate the virtual power, and the characteristics that power includes active power and reactive power are fully considered, so that a more accurate and practical virtual power can be obtained.

[0082] Based on the above embodiments of the fault ride-through control method, in an optional embodiment, the same or similar content as the above embodiments can be referred to the above introduction and will not be repeated hereinafter. On this basis, the fault ride-through control method may further include steps S60 - S80: Step S60, when the system is operating normally or the detected fault is removed, for the voltage reference signal (or the virtual internal electromotive force v refPerform voltage PI control and current PI control in sequence to obtain the energy storage input voltage v abc_ref ; Step S70, perform energy storage current conversion on the energy storage input voltage v abc_ref to obtain the system output; the system output includes the system output current i pcc , the system output voltage v pcc , the real power of the system output p out . The system output voltage v pcc is equal to the voltage reference signal (or virtual internal electromotive force v ref ), , and the real power p out includes the real active power P out and the real reactive power Q out ; Step S80, obtain the virtual power i pcc according to the product of the system output current v ref and the voltage reference signal (or virtual internal electromotive force p vir ); the virtual active power p vir in the virtual power P vir is equal to the real active power p out in the real power P out , and the virtual reactive power p vir in the virtual power Q vir is equal to the real reactive power p out in the real power Q out ; , .

[0083] Exemplarily, for the grid-forming high-voltage direct-connected energy storage system shown in Figure 2 , when the method of this embodiment is executed, the following states and effects are presented: Under normal operating conditions, the current vector limiting is not triggered, and the voltage PI inner-loop control system outputs the voltage v pccTracking the virtual internal electromotive force generated by VSG control v ref , at this time, ; the virtual power is the real power output by the system, so, , .

[0084] Referring to Figure 4 , Figure 4 is the schematic diagram of the equivalent circuit of the grid-forming high-voltage direct-connected energy storage system. Under the fault current limiting condition, the current vector amplitude limiting is triggered, and the voltage PI inner loop becomes a single proportional control loop. At this time, the current vector amplitude limiting unit is equivalent to an equivalent virtual resistor Req with an adaptive adjustable resistance value. In this case, the calculated virtual active power P vir and the real active power in the real power output by the system P out are different, and the expression for their comparison is: , and, the feedback control module based on the virtual power for feedback control is equivalent to a voltage source, and the output of the voltage source is v ref .

[0085] In order to more clearly understand the technical effects that this method can achieve, according to the calculation formula of the real active power P out and the calculation formula of the virtual active power P vir for specific comparative analysis. Among them, the calculation formula of the real active power P out is: , The calculation formula of the virtual active power P vir is: , where, δ represents the power angle, X g represents the equivalent impedance of the line during the process of transmitting the system output to the power grid through the transmission line; V g represents the voltage X g on the line equivalent impedance v g (which is also the amplitude of the voltage at the grid connection point). It can be seen from this that under the fault current limiting condition, P vir is greater than P out .

[0086] Taking the grid-forming HVDC energy storage system adopting the traditional grid-forming control method as a comparative example, and taking the grid-forming HVDC energy storage system adopting the fault ride-through control method provided in the above embodiment as an application example, the power angle curves of the normal operating state before the fault and the fault current limiting state during the fault are respectively plotted, and the schematic diagrams of the power angle curves of a pair of comparative examples as shown in Figure 5 and the schematic diagrams of the power angle curves of an application example as shown in Figure 6 are obtained. Among them, the horizontal axis represents the power angle and the vertical axis represents the power. Figure 5 In P , A1 represents the acceleration area when the feedback virtual active power in the comparative example is vir , D1 represents the deceleration area when the feedback virtual active power in the comparative example is P vir , and CCA1 is the critical fault clearing angle in the comparative example; Figure 6 In P , A2 represents the acceleration area when the feedback virtual active power in the application example is vir , D2 represents the deceleration area when the feedback virtual active power in the application example is P vir , and CCA2 is the critical fault clearing angle in the application example.

[0087] From Figure 5 and Figure 6 , it can be seen that under the fault current limiting state, the virtual active power P vir is greater than the real active power P out . Compared with the traditional grid-forming control method of feedback real power in the comparative example, the method of the present application is based on virtual power feedback, has a smaller acceleration area and a larger deceleration area margin, and thus has a larger critical fault clearing angle (CCA: Critical Clearance Angle), greatly enhancing the transient synchronous stability of the grid-forming HVDC directly-connected energy storage system.

[0088] To verify the effectiveness of this method, simulation experiments are respectively carried out on the above comparative example and application example, and it is assumed that there is a grid fault, specifically, the grid voltage drops by 0.8 p.u. (per unit: per-unit value), and the fault current is limited to 1.4 times the rated current. In this case, the grid voltage drops to 0.2 p.u., and after the fault is cleared, the grid voltage recovers to the normal 1 p.u., and the simulation experiment results diagram of the comparative example at different fault clearing times as shown in Figure 7 and the as shown in Figure 8 ​​​​​​​​The figure shows the simulation experiment results of the application example shown at different fault clearing times. Among them, the simulation experiment results include the voltage value at the connection point of phase a of the high-voltage power grid V ga , the current value output by the system to the phase a transmission line I pcca , the true active power output by the system P out and the waveforms of the power angle δ.

[0089] In Figure 7 , Figure 7 (a) shows the V ga , I pcca , P out and δ waveforms obtained by simulation when the fault clearing time is 0.68 for the comparative example, Figure 7 (b) shows the V ga , I pcca , P out and δ waveforms obtained by simulation when the fault clearing time is 0.69 for the comparative example. It can be seen that the critical fault clearing time of the grid-forming HVDC energy storage system using the traditional grid-forming control method is 0.68 s; in Figure 8 , Figure 8 (a) shows the V ga , I pcca , P out and δ waveforms obtained by simulation when the fault clearing time is 2.06 for the application example, Figure 8 (b) shows the V ga , I pcca , P out and δ waveforms obtained by simulation when the fault clearing time is 2.07 for the application example. It can be seen that the critical fault clearing time of the grid-forming HVDC energy storage system using the fault ride-through control method provided in the above embodiment is 2.06 s. Thus, it can be known that the critical fault clearing time of the system of the above application example is more than 3 times longer than that of the system of the comparative example, showing a significant increase; it can be proved that the transient synchronization stability of the system of the above application example is effectively enhanced compared with the system of the comparative example.

[0090] It should be noted that the above examples are only for understanding the present application and do not constitute a limitation on the fault ride-through control method of the present application. Based on this technical concept, more forms of simple transformations are within the protection scope of the present application.

[0091] The present application also provides an energy storage system. Referring to Figure 2 , this energy storage system is a network-forming high-voltage direct-connected energy storage system. The system includes a feedback control module, a PI control module, and an energy storage converter module connected in sequence, as well as a virtual power calculation module. The virtual power calculation module is respectively connected to the energy storage converter module and the feedback control module; Among them, the PI control module is used to perform single proportional control, current vector limiting, and current proportional integral (PI) control on the received voltage reference signal in sequence when a system fault is detected, to obtain the energy storage input voltage v abc_ref ; The energy storage converter module is used to perform energy storage conversion on the energy storage input voltage v abc_ref to obtain the system output; the system output includes the system output current i pcc ; The virtual power calculation module is used to obtain the virtual power according to the product of the system output current i pcc and the voltage reference signal p vir ; The feedback control module is used to perform virtual synchronous generator (VSG) control and regulation according to the received command power p * and the virtual power p vir to obtain the virtual internal potential v ref ; The PI control module is also used to determine the virtual internal potential v ref as the voltage reference signal, and then continue to perform single proportional control, current vector limiting, and current proportional integral (PI) control, so as to maintain the system output through the energy storage converter module and achieve system fault ride-through.

[0092] In one embodiment, the PI control module includes a voltage PI inner loop unit, a current vector limiting unit, and a current PI inner loop unit connected in sequence. The voltage PI inner loop unit is connected to the feedback control module, and the current PI inner loop unit is connected to the energy storage converter module; Among them, the voltage PI inner loop unit is used to perform single proportional control on the voltage reference signal to obtain the first reference current i * ref ; The current vector limiting unit is used to perform current vector limiting on the first reference current i * ref to obtain a second reference current i ref ; where the current vector limiting means that by adaptively adjusting the resistance value of the equivalent virtual resistance Req R eq the magnitude of the second reference current i ref is maintained within the preset maximum output current I ref ; I max The current PI inner loop unit is used to perform current PI control on the second reference current to obtain the energy storage input voltage i ref ; v abc_ref .

[0093] It can be understood that the voltage PI inner loop unit is also used to perform voltage PI control on the received voltage reference signal to obtain the first reference current when the system is operating normally, that is, when no system fault is detected i * ref ; the current PI inner loop unit is also used to directly perform current PI control on the first reference current i * ref to obtain the energy storage input voltage v abc_ref when the pre-stage current vector limiting unit is not triggered, so as to realize the normal operation of the system

[0094] It should be noted that the functions that can be realized by each module, unit, loop, etc. as shown Figure 2 correspond to the steps of the specific implementations in the various embodiments of the above-mentioned fault ride-through control method or refer to the descriptions of the specific examples, and the achieved effects are also correspondingly consistent, so they will not be repeated here

[0095] In particular, according to the embodiments disclosed in the present application, the process described in the above connection schematic diagram of the grid-connected high-voltage direct-connected energy storage system can be implemented as a computer software program. For example, the embodiments disclosed in the present application include a computer program product, which includes a computer program carried on a computer-readable storage medium, and the computer program contains program codes for executing the method shown in the above process schematic diagram. In such an embodiment, when the computer program is executed, it executes the above-mentioned functions defined in the fault ride-through control method disclosed in the embodiments of the present application

[0096] The energy storage system provided by this application, which adopts the fault ride-through control method in the above-mentioned embodiment, can solve the technical problem of poor transient synchronization stability of the high-voltage direct-connected energy storage system under faults in the related art. Compared with the related art, the beneficial effects of the energy storage system provided by this application are the same as those of the fault ride-through control method provided by the above-mentioned embodiment, and other technical features in this energy storage system are the same as those disclosed in the fault ride-through control method of the above-mentioned embodiment, which will not be elaborated here.

[0097] It should be understood that each part disclosed in this application can be implemented by hardware, software, firmware or a combination thereof. In the description of the above embodiments, specific features, structures, materials or characteristics can be combined in a suitable manner in any one or more embodiments or examples.

[0098] The above are only specific embodiments of this application, but the protection scope of this application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in this application should be covered by the protection scope of this application. Therefore, the protection scope of this application should be subject to the protection scope of the claims.

[0099] This application also provides a computer-readable storage medium with computer-readable program instructions (i.e., computer programs) stored thereon, and the computer-readable program instructions are used to execute the fault ride-through control method in the above-mentioned embodiment.

[0100] The computer-readable storage medium provided by this application can be, for example, a USB flash drive, but is not limited to electrical, magnetic, optical, electromagnetic, infrared or semiconductor systems or devices, or any combination of the above. More specific examples of computer-readable storage media can include, but are not limited to: portable computer disks with electrical connections having one or more wires, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM) or flash memory, optical fibers, portable compact disk read-only memory (CD-ROM), optical storage devices, magnetic storage devices, etc., or any suitable combination of the above. In this embodiment, the computer-readable storage medium can be any tangible medium that contains or stores a program, and this program can be used by an instruction execution system or device, or used in combination with both. The program code contained on the computer-readable storage medium can be transmitted by any appropriate medium, including but not limited to: wires, optical cables, RF (Radio Frequency), etc., or any suitable combination of the above.

[0101] The above computer-readable storage medium may be included in an energy storage system; or it may exist independently without being assembled into an energy storage system.

[0102] The above computer-readable storage medium carries one or more programs. When the above one or more programs are executed by an energy storage system, the energy storage system can implement the above functions defined in the fault ride-through control method disclosed in the embodiments of the present application.

[0103] Computer program code for performing the operations of the present application can be written in one or more programming languages or combinations thereof. The above programming languages include object-oriented programming languages such as Java, Smalltalk, C++, and also include conventional procedural programming languages such as the "C" language or similar programming languages. The program code can be executed entirely on the user's computer, partially on the user's computer, executed as an independent software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the case of a remote computer, the remote computer can be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or connected to an external computer, for example, using the Internet connection provided by an Internet service provider.

[0104] The flowcharts and block diagrams in the accompanying drawings illustrate the possible architectures, functions, and operations of methods, devices, systems, and computer program products according to various embodiments of the present application. In this regard, each block in the flowchart or block diagram may represent a module, a program segment, or a part of code that contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the blocks may occur in a different order than marked in the accompanying drawings. For example, two consecutive blocks shown may actually be executed substantially in parallel, and they may sometimes be executed in the reverse order, depending on the functions involved. It should also be noted that each block in the block diagram and / or flowchart, and combinations of blocks in the block diagram and / or flowchart, can be implemented by a dedicated hardware-based system for performing the specified functions or operations, or can be implemented by a combination of dedicated hardware and computer instructions.

[0105] The modules described in the embodiments of the present application can be implemented in software or in hardware. In some cases, the name of the module does not constitute a limitation on the unit itself.

[0106] The storage medium provided by this application is a computer-readable storage medium, on which computer-readable program instructions (i.e., computer programs) for executing the above-mentioned fault ride-through control method are stored, which can solve the technical problem of poor transient synchronization stability of the high-voltage direct-connected energy storage system under faults in the related art. Compared with the related art, the beneficial effects of the computer-readable storage medium provided by this application are the same as those of the fault ride-through control method provided in the above embodiments, and will not be elaborated here.

[0107] The above are only partial embodiments of this application, and do not limit the patent scope of this application accordingly. Any equivalent structural transformation made under the technical concept of this application by using the content of the specification and drawings of this application, or direct / indirect application in other related technical fields, is included in the patent protection scope of this application.

Claims

1. A fault ride-through control method, characterized in that, Applied to a network-forming high-voltage direct-connected energy storage system, the method includes: When a system fault is detected, the received voltage reference signal is sequentially subjected to single proportional control, current vector limiting, and current proportional-integral (PI) control to obtain the energy storage input voltage; Perform energy storage current conversion on the energy storage input voltage to obtain the system output; the system output includes the system output current; Obtain the virtual power according to the product of the system output current and the voltage reference signal; Perform virtual synchronous generator (VSG) control and regulation according to the received command power and the virtual power to obtain the virtual internal potential; Determine the virtual internal potential as the voltage reference signal, and return to execute the step of sequentially performing single proportional control, current vector limiting, and current proportional-integral (PI) control on the received voltage reference signal to obtain the energy storage input voltage, so as to maintain the output of the system and achieve system fault ride-through.

2. The fault ride-through control method according to claim 1, characterized in that The step of sequentially performing single proportional control, current vector limiting, and current proportional-integral (PI) control on the received voltage reference signal to obtain the energy storage input voltage includes: Perform single proportional control on the voltage reference signal to obtain the first reference current; Perform current vector limiting on the first reference current to obtain the second reference current; wherein, the current vector limiting means that the amplitude of the second reference current is maintained within the preset maximum output current value by adaptively adjusting the resistance value of the equivalent virtual resistance; Perform current PI control on the second reference current to obtain the energy storage input voltage.

3. The fault ride-through control method according to claim 2, wherein The step of performing current vector limiting on the first reference current to obtain the second reference current includes: Compare the amplitude of the first reference current with the maximum output current value; When the amplitude of the first reference current is less than or equal to the maximum output current value, determine the amplitude of the first reference current as the amplitude of the second reference current, and obtain the second reference current; When the amplitude of the first reference current is greater than the maximum output current value, determine the resistance value of the equivalent virtual resistance according to the amplitude of the first reference current, and determine a proportionality coefficient according to the resistance value, so as to determine the amplitude of the second reference current according to the product of the maximum output current value and the proportionality coefficient, and obtain the second reference current.

4. The fault ride-through control method according to claim 2, characterized in that, In the step of performing current vector limiting on the first reference current to obtain the second reference current, the calculation formula involved in current vector limiting is: ； Among them, I refdq represents the second reference current i ref of the dq-axis current, I * refdq represents the first reference current i * ref of the dq-axis current, I * refd is I * refdq the corresponding d-axis current component, I * refq is I * refdq the corresponding q-axis current component, I max represents the maximum value of the output current.

5. The fault ride-through control method according to claim 1, characterized in that The command power includes command active power and command reactive power, and the virtual power includes virtual active power and virtual reactive power; The step of performing virtual synchronous generator (VSG) control and regulation according to the received command power and the virtual power to obtain the virtual internal potential includes: Perform VSG control according to the command active power, the virtual active power, and the received command voltage angular velocity to obtain the virtual internal potential angular velocity; Perform voltage magnitude regulation according to the command reactive power, the virtual reactive power, and the received command voltage magnitude to obtain the voltage magnitude; Generate a voltage vector based on the virtual internal potential angular velocity and the voltage amplitude to obtain the virtual internal potential.

6. The fault ride-through control method according to claim 1, wherein In the step of performing virtual synchronous generator (VSG) control and regulation based on the received command power and the virtual power to obtain the virtual internal potential, the calculation formulas involved in the VSG control and regulation are as follows: ； Among them, P * represents the command power p * in the command active power, Q * represents the command power p * in the command reactive power, P vir represents the virtual power p vir in the virtual active power, Q vir represents the virtual power p vir in the virtual reactive power, ω * represents the command voltage angular velocity, ω represents the virtual internal potential angular velocity, V * represents the command voltage amplitude, V represents the voltage amplitude, J represents the virtual inertia constant, D m represents the damping coefficient, n represents the reactive power droop coefficient.

7. The fault ride-through control method according to claim 5 or 6, characterized in that, After determining the virtual internal potential as the voltage reference signal and returning to execute the step of sequentially performing single proportional control, current vector limiting, and current proportional-integral (PI) control on the received voltage reference signal to obtain the energy storage input voltage, the method further includes: Multiply the d-axis current component corresponding to the system output current by the amplitude of the virtual internal potential to obtain the virtual active power; wherein, the amplitude of the virtual internal potential is equal to the voltage amplitude. Multiply the q-axis current component corresponding to the system output current by the amplitude of the virtual internal potential and take the negative value to obtain the virtual reactive power.

8. A energy storage system, characterized in that, The system is a grid-forming high-voltage direct-connected energy storage system, which includes a feedback control module, a PI control module, an energy storage converter module connected in sequence, and a virtual power calculation module. The virtual power calculation module is respectively connected to the energy storage converter module and the feedback control module. Among them, the PI control module is used to sequentially perform single proportional control, current vector limiting, and current proportional-integral PI control on the received voltage reference signal when detecting a system fault to obtain the energy storage input voltage. The energy storage converter module is used to perform energy storage conversion on the energy storage input voltage to obtain the system output; the system output includes the system output current. The virtual power calculation module is used to obtain the virtual power according to the product of the system output current and the voltage reference signal. The feedback control module is used to perform virtual synchronous generator (VSG) control and regulation based on the received command power and the virtual power to obtain the virtual internal potential. The PI control module is further used to continue performing single proportional control, current vector limiting, and current proportional-integral PI control after determining the virtual internal potential as the voltage reference signal, so as to maintain the system output through the energy storage converter module and achieve system fault ride-through.

9. The energy storage system according to claim 8, wherein, The PI control module includes a voltage PI inner loop unit, a current vector limiting unit, and a current PI inner loop unit connected in sequence. The voltage PI inner loop unit is connected to the feedback control module, and the current PI inner loop unit is connected to the energy storage converter module. Among them, the voltage PI inner loop unit is used to perform single proportional control on the voltage reference signal to obtain the first reference current. The current vector limiting unit is used to perform current vector limiting on the first reference current to obtain the second reference current; wherein, the current vector limiting means that the amplitude of the second reference current is maintained within the preset maximum output current value by adaptively adjusting the resistance value of the equivalent virtual resistance. The current PI inner loop unit is used to perform current PI control on the second reference current to obtain the energy storage input voltage.

10. A storage medium, characterized in that, The storage medium is a computer-readable storage medium, and a computer program is stored on the storage medium. When the computer program is executed by a processor, the steps of the fault ride-through control method according to any one of claims 1 to 7 are implemented.

Images