Energy storage converter control method and device, storage medium and electronic device

Abstract

The application provides a control method and device of an energy storage converter, a storage medium and an electronic device, and the method comprises: in the case of detecting that a grid voltage value is greater than a first threshold value, suppressing grid-connected negative sequence current and power double-frequency fluctuation by: obtaining a power model of an alternating current (AC) / direct current (DC) converter, setting negative sequence parameters and double-frequency parameters of the power model of the AC / DC converter to be less than a second threshold value, so as to determine an active power instruction of the energy storage converter; in the case of detecting that the grid voltage value is less than the first threshold value, suppressing grid-connected negative sequence current and power double-frequency fluctuation by: obtaining a power model of an AC / DC converter, setting negative sequence parameters and double-frequency parameters of the power model of the AC / DC converter to be less than a second threshold value, and on the DC / DC converter side, determining a current instruction according to a derating correction coefficient, and determining an output of the energy storage converter according to the current instruction.

Description

Technical Field

[0001] This invention relates to the field of communications, and more specifically, to a control method and apparatus for an energy storage converter, a storage medium, and an electronic device. Background Technology

[0002] As distributed power sources become increasingly prevalent in microgrids, the intermittent and uncertain nature of their output power has led to increasingly prominent negative impacts, necessitating the introduction of energy storage systems to regulate power fluctuations within the microgrid. Energy storage converters, as key components in energy storage systems, play a crucial role in ensuring the stability of the entire energy storage system and even the entire power grid under grid-connected conditions.

[0003] There are many common control strategies for energy storage converters, among which dual-loop control is the most typical. The outer loop includes PQ control, V / f control, droop control, etc., while the inner loop is often a current loop. The inner loop control is directly related to the steady-state and dynamic performance of the energy storage converter in grid-connected operation. Common technologies include vector control and direct power control. Vector control directly controls the current through the current loop, and has the characteristics of high control accuracy, good harmonic characteristics, and easy current limiting. It mainly includes proportional-integral (PI) control, proportional-resonant (PR) control, deadbeat (DB) control, sliding mode control, etc. These control technologies are all based on the research of control strategies for energy storage converters under ideal grid conditions. In actual grids, there are often non-ideal conditions such as harmonic distortion, voltage asymmetry, and even voltage drops. If these non-ideal conditions of the grid during actual operation are ignored, and the energy storage converter still operates according to the control strategy of an ideal grid when the grid is in a non-ideal state, its performance will degrade. In severe cases, it will cause the fault protection device to activate, or even burn out related equipment, and will also pollute the grid and disrupt its stability. At the same time, under non-ideal grid conditions, the DC bus voltage will generate second harmonic fluctuations, and the lifespan of the DC bus capacitors will also be affected.

[0004] Related technologies have proposed control strategies for predicting the current of energy storage converters under grid asymmetry conditions based on the α-β coordinate system. However, these strategies only achieve low-voltage ride-through capability under non-ideal grid conditions and do not suppress the negative-sequence current injected into the grid by the energy storage converter when the grid voltage is unbalanced. Related technologies have also proposed a coordinated control strategy between grid-connected current imbalance and active power fluctuations for photovoltaic inverters when the grid voltage is distorted and unbalanced. While this strategy improves power quality to some extent, a small amount of negative-sequence current still enters the grid, and it does not provide low-voltage ride-through capability. Related technologies have also proposed a composite control strategy combining proportional-integral and repetitive control in parallel for small grid disturbances. While this strategy effectively suppresses grid-connected current harmonics, it still cannot achieve low-voltage ride-through capability during voltage dips.

[0005] Regarding the issues in related technologies, such as how to effectively suppress the second-harmonic oscillation of grid-connected negative sequence current and power of energy storage converters under non-ideal conditions (e.g., grid voltage imbalance or even voltage drop), and how to enable energy storage converters to have a certain low-voltage ride-through capability, no effective technical solutions have yet been proposed. Summary of the Invention

[0006] This invention provides a control method and apparatus for an energy storage converter, a storage medium, and an electronic device, to at least solve the problems in related technologies such as how to effectively suppress the second harmonic oscillation of the grid-connected negative sequence current and power of the energy storage converter under non-ideal conditions (e.g., grid voltage imbalance or even voltage drop), and how to enable the energy storage converter to have a certain low voltage ride-through capability.

[0007] According to an embodiment of the present invention, a control method for an energy storage converter is provided, comprising: when the grid voltage value is detected to be greater than a first threshold, suppressing grid-connected negative-sequence current and power second harmonic fluctuations by: acquiring the power model of an AC / DC converter, setting the negative-sequence parameter and second harmonic parameter of the power model of the AC / DC converter to be less than a second threshold, thereby determining the active power command of the energy storage converter; when the grid voltage value is detected to be less than the first threshold, suppressing grid-connected negative-sequence current and power second harmonic fluctuations by: acquiring the power model of the AC / DC converter, setting the negative-sequence parameter and second harmonic parameter of the power model of the AC / DC converter to be less than the second threshold, and on the DC / DC converter side, determining the current command according to the derating correction coefficient, and determining the output of the energy storage converter according to the current command.

[0008] According to another embodiment of the present invention, a control device for an energy storage converter is also provided, comprising: a suppression module, configured to suppress grid-connected negative-sequence current and power second-harmonic frequency fluctuations by means of: acquiring a power model of an AC / DC converter, setting the negative-sequence parameter and second-harmonic frequency parameter of the power model of the AC / DC converter to be less than a second threshold, thereby determining an active power command for the energy storage converter; and a processing module, configured to suppress grid-connected negative-sequence current and power second-harmonic frequency fluctuations by means of: acquiring a power model of an AC / DC converter, setting the negative-sequence parameter and second-harmonic frequency parameter of the power model of the AC / DC converter to be less than a second threshold, and on the DC / DC converter side, determining a current command based on a derating correction coefficient, and determining the output of the energy storage converter based on the current command.

[0009] According to another embodiment of the present invention, a storage medium is also provided, wherein the storage medium stores a computer program, wherein the computer program is configured to execute the control method of the energy storage converter described in any of the above embodiments when running.

[0010] According to another embodiment of the present invention, an electronic device is also provided, including a memory and a processor, wherein the memory stores a computer program and the processor is configured to run the computer program to perform the control method of the energy storage converter described in any of the above embodiments.

[0011] According to this invention, when the grid voltage value is detected to be greater than a first threshold, the grid-connected negative sequence current and power second harmonic fluctuation are suppressed by means of the following: obtaining the power model of the AC / DC converter, and setting the negative sequence parameter and second harmonic parameter of the power model of the AC / DC converter to be less than the second threshold, so as to determine the active power command of the energy storage converter.

[0012] When the grid voltage is detected to be less than the first threshold, the grid-connected negative sequence current and power second harmonic fluctuations are suppressed by the following method: The power model of the AC / DC converter is obtained, and the negative sequence parameter and second harmonic parameter of the AC / DC converter power model are both set to be less than the second threshold. On the DC / DC converter side, a current command is determined based on the derating correction coefficient, and the output of the energy storage converter is determined based on the current command. This technical solution solves the problems in related technologies, such as how to effectively suppress the grid-connected negative sequence current and power second harmonic oscillations of the energy storage converter under non-ideal conditions (e.g., grid voltage imbalance or even voltage drop), and how to enable the energy storage converter to have a certain low-voltage ride-through capability. Therefore, it can effectively suppress the grid-connected negative sequence current and power second harmonic oscillations of the energy storage converter, and also enable the energy storage converter to have a certain low-voltage ride-through capability. Attached Figure Description

[0013] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings:

[0014] Figure 1 A flowchart of a control method for an energy storage converter according to an embodiment of the present invention;

[0015] Figure 2 This is a structural block diagram of the control device for an energy storage converter according to an embodiment of the present invention;

[0016] Figure 3 This is a control block diagram for suppressing grid-connected negative sequence current components and power second harmonic fluctuations according to an embodiment of the present invention;

[0017] Figure 4 This is a block diagram of a derating low voltage ride-through control strategy based on a dual rotating coordinate system according to an embodiment of the present invention. Detailed Implementation

[0018] The present invention will be described in detail below with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in the present application can be combined with each other.

[0019] It should be noted that the terms "first," "second," etc., in the specification, claims, and drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0020] Example 1

[0021] This invention provides a solution. Figure 1 A flowchart of a control method for an energy storage converter according to an embodiment of the present invention is shown below. Figure 1 As shown, it includes the following steps:

[0022] Step S102: When the grid voltage value is detected to be greater than the first threshold, the grid-connected negative sequence current and power second harmonic fluctuation are suppressed by the following method: the power model of the AC / DC converter is obtained, and the negative sequence parameter and second harmonic parameter of the power model of the AC / DC converter are set to be less than the second threshold, so as to determine the active power command of the energy storage converter.

[0023] It should be noted that the second threshold can be a value that is infinitely close to 0, for example, such that the negative sequence parameter and the second harmonic parameter of the power model of the AC / DC converter are both equal to 0.

[0024] Step S104: When the grid voltage value is detected to be less than the first threshold, the grid-connected negative sequence current and power second harmonic fluctuation are suppressed by the following method: the power model of the AC / DC converter is obtained, the negative sequence parameter and second harmonic parameter of the power model of the AC / DC converter are set to be less than the second threshold, and on the DC / DC converter side, the current command is determined according to the derating correction coefficient, and the output of the energy storage converter is determined according to the current command.

[0025] According to this invention, when the grid voltage value is detected to be greater than a first threshold, the grid-connected negative sequence current and power second harmonic fluctuation are suppressed by means of the following: obtaining the power model of the AC / DC converter, and setting the negative sequence parameter and second harmonic parameter of the power model of the AC / DC converter to be less than the second threshold, so as to determine the active power command of the energy storage converter.

[0026] When the grid voltage is detected to be less than the first threshold, the grid-connected negative sequence current and power second harmonic fluctuations are suppressed by the following method: The power model of the AC / DC converter is obtained, and the negative sequence parameter and second harmonic parameter of the AC / DC converter power model are both set to be less than the second threshold. On the DC / DC converter side, a current command is determined based on the derating correction coefficient, and the output of the energy storage converter is determined based on the current command. This technical solution solves the problems in related technologies, such as how to effectively suppress the grid-connected negative sequence current and power second harmonic oscillations of the energy storage converter under non-ideal conditions (e.g., grid voltage imbalance or even voltage drop), and how to enable the energy storage converter to have a certain low-voltage ride-through capability. Therefore, it can effectively suppress the grid-connected negative sequence current and power second harmonic oscillations of the energy storage converter, and also enable the energy storage converter to have a certain low-voltage ride-through capability.

[0027] It should be noted that the above steps S102 and S104 do not represent the execution order. In actual technical solutions, step S104 may be executed first, followed by step S102. This embodiment of the invention does not limit this.

[0028] Optionally, the power model of the AC / DC converter includes:

[0029] Wherein, P0 and Q0 represent the active DC component and reactive DC component output by the energy storage converter, respectively; P c2 P s2 Q c2 Q s2 These represent the active second harmonic component and the reactive second harmonic component of the energy storage converter output, respectively. This represents the negative sequence component of the converter output current along the d-axis. This represents the negative sequence q-axis component of the converter output current. This represents the positive sequence component of the converter output current along the d-axis. This represents the positive-sequence q-axis component of the converter output current. This represents the negative sequence component of the grid voltage along the d-axis. This represents the negative sequence component of the grid voltage along the q-axis. Represents the positive sequence component of the grid voltage along the d-axis. The negative sequence parameter represents the positive q-axis component of the grid voltage, and includes: and The second harmonic parameter includes: P c2 P s2 Q c2 Q s2 .

[0030] In an optional embodiment of the present invention, the negative sequence parameter and second harmonic parameter of the power model of the AC / DC converter are both set to 0 to determine the active power command of the energy storage converter, including: determining the active power command using the following formula. : .

[0031] Specifically, on the DC / DC converter side, the current command is determined based on the derating correction factor, which can be achieved through the following technical solutions:

[0032] The current command is determined according to the following formula. :

[0033] ,in, The reduction correction coefficient is mentioned above. This represents the minimum effective value of the three-phase grid voltage after per-unit marking. The command current for the energy storage converter is the current before the grid voltage value is lower than the first threshold.

[0034] The above technical solution provides a control method to address the adverse effects of energy storage converters on microgrid systems and large power grids when grid voltage is unbalanced or even drops. This control method can not only effectively suppress the second-harmonic oscillation of grid-connected negative sequence current and power of the energy storage converter, but also enable the energy storage converter to have a certain low-voltage ride-through capability. In addition, this control method can realize automatic switching between ideal grid conditions and non-ideal grid conditions.

[0035] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods according to the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) and includes several instructions to cause a terminal device (which may be a mobile phone, computer, server, or network device, etc.) to execute the methods of the various embodiments of the present invention.

[0036] Example 2

[0037] This embodiment also provides a control device for an energy storage converter, which is used to implement the above embodiments and preferred embodiments; details already described will not be repeated. As used below, the term "module" can refer to a combination of software and / or hardware that implements a predetermined function. Although the device described in the following embodiments is preferably implemented in software, hardware implementation, or a combination of software and hardware, is also possible and contemplated.

[0038] Figure 2 This is a structural block diagram of the control device for an energy storage converter according to an embodiment of the present invention, such as... Figure 2 As shown, the device includes:

[0039] The suppression module 20 is used to suppress grid-connected negative sequence current and power second harmonic fluctuations when the grid voltage value is detected to be greater than the first threshold by: obtaining the power model of the AC / DC converter, setting the negative sequence parameter and second harmonic parameter of the power model of the AC / DC converter to be less than the second threshold, so as to determine the active power command of the energy storage converter.

[0040] Processing module 22 is used to suppress grid-connected negative sequence current and power second harmonic fluctuations when the grid voltage value is detected to be less than the first threshold by: obtaining the power model of the AC / DC converter, setting the negative sequence parameter and second harmonic parameter of the power model of the AC / DC converter to be less than the second threshold, and on the DC / DC converter side, determining the current command according to the derating correction coefficient, and determining the output of the energy storage converter according to the current command.

[0041] It should be noted that the second threshold can be a value that is infinitely close to 0, for example, such that the negative sequence parameter and the second harmonic parameter of the power model of the AC / DC converter are both equal to 0.

[0042] According to this invention, when the grid voltage value is detected to be greater than a first threshold, the grid-connected negative sequence current and power second harmonic fluctuation are suppressed by means of the following: obtaining the power model of the AC / DC converter, and setting the negative sequence parameter and second harmonic parameter of the power model of the AC / DC converter to be less than the second threshold, so as to determine the active power command of the energy storage converter.

[0043] When the grid voltage is detected to be less than the first threshold, the grid-connected negative sequence current and power second harmonic fluctuations are suppressed by the following method: The power model of the AC / DC converter is obtained, and the negative sequence parameter and second harmonic parameter of the AC / DC converter power model are both set to be less than the second threshold. On the DC / DC converter side, a current command is determined based on the derating correction coefficient, and the output of the energy storage converter is determined based on the current command. This technical solution solves the problems in related technologies, such as how to effectively suppress the grid-connected negative sequence current and power second harmonic oscillations of the energy storage converter under non-ideal conditions (e.g., grid voltage imbalance or even voltage drop), and how to enable the energy storage converter to have a certain low-voltage ride-through capability. Therefore, it can effectively suppress the grid-connected negative sequence current and power second harmonic oscillations of the energy storage converter, and also enable the energy storage converter to have a certain low-voltage ride-through capability.

[0044] Optionally, the power model of the AC / DC converter includes:

[0045] Wherein, P0 and Q0 represent the active DC component and reactive DC component output by the energy storage converter, respectively; P c2 P s2 Q c2 Q s2 These represent the active second harmonic component and the reactive second harmonic component of the energy storage converter output, respectively. This represents the negative sequence component of the converter output current along the d-axis. This represents the negative sequence q-axis component of the converter output current. This represents the positive sequence component of the converter output current along the d-axis. This represents the positive-sequence q-axis component of the converter output current. This represents the negative sequence component of the grid voltage along the d-axis. This represents the negative sequence component of the grid voltage along the q-axis. Represents the positive sequence component of the grid voltage along the d-axis. The negative sequence parameter represents the positive q-axis component of the grid voltage, and includes: and The second harmonic parameter includes: P c2 P s2 Q c2 Q s2 .

[0046] In this embodiment of the invention, the processing module 22 is further configured to determine the current command according to the following formula. :

[0047] ,in, The reduction correction coefficient is mentioned above. This represents the minimum effective value of the three-phase grid voltage after per-unit marking. The command current for the energy storage converter is the current before the grid voltage value is lower than the first threshold.

[0048] Suppression module 20 is also used to determine the active power command using the following formula. : .

[0049] Specifically, on the DC / DC converter side, the processing module is also used to determine the current command according to the following formula. : ,in, The reduction correction coefficient is mentioned above. This represents the minimum effective value of the three-phase grid voltage after per-unit marking. The command current for the energy storage converter is the current before the grid voltage value is lower than the first threshold.

[0050] It should be noted that the above modules can be implemented by software or hardware. For the latter, they can be implemented in the following ways, but are not limited to: all the above modules are located in the same processor; or, the above modules are located in different processors in any combination.

[0051] The above technical solutions are described below with reference to preferred embodiments of the present invention, but are not intended to limit the technical solutions of the embodiments of the present invention.

[0052] The technical solution adopted in this invention is: to provide a control method for energy storage converters under non-ideal power grids, including a control strategy for suppressing grid-connected negative sequence current and power frequency double-frequency fluctuations based on dual second-order generalized integral phase-locked loop (DSOGI-PLL) technology, and a derating low-voltage ride-through control strategy based on a dual rotating coordinate system.

[0053] The DSOGI-PLL technology described above can quickly and accurately track the positive and negative sequence voltage phases when the grid voltage is unbalanced, laying the foundation for achieving unity power factor operation of a two-stage energy storage converter.

[0054] The aforementioned strategy for suppressing grid-connected negative sequence current and power double-frequency fluctuations aims to balance the grid-connected current output of the two-stage energy storage converter and prevent double-frequency fluctuations in the output power when the grid voltage experiences a small-amplitude imbalance, thereby ensuring the power quality of the grid and the safe operation of related equipment.

[0055] The derating low-voltage ride-through strategy based on a dual rotating coordinate system is designed to ensure that, in the event of a grid dip fault, the two-stage energy storage converter can remain connected to the grid for a certain period of time without disconnecting, and can quickly return to the operating state before the fault after the grid voltage returns to normal.

[0056] This invention relates to a control strategy for energy storage converters under non-ideal power grids. The method is based on a control strategy for suppressing negative sequence current and power second-harmonic frequency fluctuations in a dual rotating coordinate system, as well as a derating low-voltage ride-through control strategy.

[0057] When grid voltage fluctuates between 85% and 110% of its rated value, causing grid imbalance, a control strategy to suppress negative sequence current and power second-harmonic fluctuations on the AC side can be adopted to achieve the control objective of symmetrical three-phase grid-connected current and smooth power second-harmonic fluctuations. This strategy is based on the mathematical model of the DC / AC side of the energy storage converter under a non-ideal grid.

[0058] (1);

[0059] Combined with the power calculation formula

[0060] (2);

[0061] The active and reactive power equations in the dq coordinate system can be derived as follows:

[0062] (3);

[0063] Where P0 and Q0 represent the active DC component and reactive DC component of the energy storage converter output, respectively; P c2 P s2 Q c2 Q s2 These represent the active and reactive second harmonic components output by the energy storage converter, respectively.

[0064] To suppress grid-connected negative sequence current and power second harmonic fluctuations, let equation (3) contain...

[0065] (4);

[0066] The output power command can then be obtained as follows:

[0067] (5);

[0068] Solving equation (5), we can obtain the control command for the inner current loop at this time as follows:

[0069] (6);

[0070] In practical control, to achieve unity power factor operation of the energy storage converter, it is generally possible to set... Since changes in active power will cause corresponding changes in DC bus voltage, the active power command can be given by the outer loop of the DC bus voltage.

[0071] (7);

[0072] K p K i These represent the proportional and integral coefficients of the voltage outer loop PI regulator, respectively. The DC bus voltage is given.

[0073] (8);

[0074] In summary, the active power command is generated by using the output of the AC side voltage outer loop PI controller as the d-axis current command of the AC side current inner loop, and then calculating it according to the power calculation formula (8) in the dq coordinate system. To simplify control, the preferred embodiment of the present invention adopts a voltage and current dual closed-loop control strategy. On the basis of effectively controlling the positive sequence component, the control suppresses the grid-connected negative sequence current component and the power double frequency fluctuation through the feedback of the grid voltage negative sequence component. The control block diagram is as follows. Figure 3 As shown.

[0075] When a grid voltage dip occurs, the DC-side power of the two-stage energy storage converter cannot change abruptly, while the AC-side voltage decreases. If the AC output current is not suppressed, the two-stage energy storage converter may experience an AC overcurrent fault, leading to shutdown. If the AC output current is limited, the DC bus voltage will rise, causing a DC bus overvoltage fault and shutdown. To address this, this invention proposes a derating low-voltage ride-through control strategy based on a dual rotating coordinate system. Furthermore, considering that grid voltage imbalance dips can cause grid-connected current imbalances, a strategy to suppress negative-sequence grid-connected current is incorporated into the low-voltage ride-through control strategy. This strategy is also applicable to symmetrical grid voltage dips.

[0076] (9);

[0077] Equation (9) is the current command derating formula, where, A new current command following a voltage drop in the power grid; This represents the minimum effective value of the three-phase grid voltage after per-unit marking. This is the command current for the energy storage power converter before the grid voltage drop; This is the reduction correction factor.

[0078] like Figure 4 As shown in the diagram, based on the derating low-voltage ride-through control strategy in a dual rotating coordinate system, when a grid voltage dip occurs, the DC / AC side still employs control to suppress the grid-connected negative-sequence current. However, for the DC / DC side, the minimum effective grid voltage value is selected based on the effective value after the grid voltage dip. This value is then multiplied by the current command value of the energy storage converter after per-unit scaling and further multiplied by the derating correction factor, thereby reducing the active power output of the energy storage converter. This reduces the AC output current of the energy storage converter under grid voltage dip conditions, preventing AC overcurrent faults. Simultaneously, after the DC-side power decreases, the DC bus voltage is controlled by the voltage outer loop, preventing excess energy accumulation on the bus. This achieves low-voltage ride-through for the energy storage power converter. For asymmetrical grid voltage dips, the suppression of negative-sequence current control strategy also ensures that the grid-connected current does not have a negative-sequence component.

[0079] The technical solution of this invention detects whether the grid voltage is normal. If an imbalance occurs between 85% and 110% of the rated voltage, the energy storage converter can operate continuously by suppressing grid-connected negative sequence current and power frequency double-frequency fluctuation control strategies. When the grid voltage is detected to be below 85% of the rated voltage, the control system immediately switches to derating low-voltage ride-through control and completes the low-voltage ride-through within a certain time as required. The switching between these two control states can be accomplished using a flag bit.

[0080] In summary, the preferred embodiment of the present invention provides a generalized second-order integral phase-locked loop, which can be used for phase-locking under both ideal power grid conditions and non-ideal power grid conditions, while realizing the separation of positive and negative sequences of voltage and current.

[0081] The strategy to suppress grid-connected negative sequence current and power double frequency fluctuations is based on the AC / DC side power model under non-ideal grid conditions. The negative sequence parameter and the double frequency parameter in the model are both set to 0, and the positive sequence current is given by the power outer loop output of the DC / DC side.

[0082] The derating low-voltage ride-through control strategy involves suppressing grid-connected negative sequence current and power frequency double-frequency fluctuation control on the AC / DC side, and introducing a derating correction coefficient on the DC / DC side to achieve low-voltage ride-through when the grid voltage drops. In the technical solutions of the embodiments and preferred embodiments of the present invention, the parameters in the control algorithm are all calculated using per-unit values.

[0083] For three-phase phase-locked loop (PLL) technology, this invention provides a dual second-order generalized integral PLL technology. Of course, dual synchronous coordinate decoupling PLL technology can also be used. In comparison, the dual second-order generalized integral PLL technology is simple to implement and requires fewer coordinate transformations, which greatly saves CPU computing resources. As for the current loop control algorithm, this invention provides a proportional-integral (PI) controller. It can also be implemented using a proportional-resonant (PR) controller. However, the PR control algorithm is more complex, and parameter tuning is more difficult, resulting in poor robustness.

[0084] It should be noted that the technical solutions of Embodiments 1 and 2 above can be used in combination or individually, and the embodiments of the present invention do not limit this.

[0085] In summary, the embodiments of this invention address both small-amplitude grid voltage imbalances and large-amplitude voltage drops in the control of the energy storage converter. By suppressing the second harmonic fluctuations of grid-connected negative-sequence current and power, the power quality of the grid is guaranteed, resolving the DC bus fluctuation problem of the energy storage converter caused by the second harmonic fluctuation of power. Through a derating low-voltage ride-through control strategy, the problems of DC bus overvoltage and output overcurrent of the energy storage converter during grid voltage drops are resolved, achieving fault ride-through capability of the energy storage converter. Compared with existing technologies, the control method of this invention has advantages such as fast dynamic response speed, stable control, easy algorithm implementation, and saving hardware resources.

[0086] Example 3

[0087] Embodiments of the present invention also provide a storage medium comprising a stored program, wherein the program, when executed, performs any of the methods described above.

[0088] Optionally, in this embodiment, the storage medium may be configured to store program code for performing the following steps:

[0089] S1, when the grid voltage value is detected to be greater than the first threshold, the grid-connected negative sequence current and power second harmonic fluctuation are suppressed by the following method: the power model of the AC / DC converter is obtained, and the negative sequence parameter and second harmonic parameter of the power model of the AC / DC converter are set to be less than the second threshold, so as to determine the active power command of the energy storage converter.

[0090] S2, when the grid voltage value is detected to be less than the first threshold, the grid-connected negative sequence current and power second harmonic fluctuation are suppressed by the following method: the power model of the AC / DC converter is obtained, the negative sequence parameter and second harmonic parameter of the power model of the AC / DC converter are set to be less than the second threshold, and on the DC / DC converter side, the current command is determined according to the derating correction coefficient, and the output of the energy storage converter is determined according to the current command.

[0091] Optionally, in this embodiment, the storage medium may include, but is not limited to, various media capable of storing program code, such as USB flash drives, read-only memory (ROM), random access memory (RAM), portable hard drives, magnetic disks, or optical disks.

[0092] Optionally, specific examples in this embodiment can refer to the examples described in the above embodiments and optional implementations, and will not be repeated here.

[0093] It is obvious to those skilled in the art that the modules or steps of the present invention described above can be implemented using general-purpose computing devices. They can be centralized on a single computing device or distributed across a network of multiple computing devices. Optionally, they can be implemented using computer-executable program code, thereby storing them in a storage device for execution by a computing device. In some cases, the steps shown or described can be performed in a different order than those presented herein, or they can be fabricated as separate integrated circuit modules, or multiple modules or steps can be fabricated as a single integrated circuit module. Thus, the present invention is not limited to any particular combination of hardware and software.

[0094] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A control method for an energy storage converter, characterized in that, include: When the grid voltage value is detected to be greater than the first threshold, the grid-connected negative sequence current and power second harmonic fluctuation are suppressed by the following method: the power model of the AC / DC converter is obtained, and the negative sequence parameter and second harmonic parameter of the power model of the AC / DC converter are set to be less than the second threshold, so as to determine the active power command of the energy storage converter. When the grid voltage value is detected to be less than the first threshold, the grid-connected negative sequence current and power second harmonic fluctuations are suppressed by the following method: the power model of the AC / DC converter is obtained, the negative sequence parameter and second harmonic parameter of the power model of the AC / DC converter are set to be less than the second threshold, and on the DC / DC converter side, the current command is determined according to the derating correction coefficient, and the output of the energy storage converter is determined according to the current command.

2. The method according to claim 1, characterized in that, The power model of the AC / DC converter includes: Wherein, P0 and Q0 represent the active DC component and reactive DC component output by the energy storage converter, respectively; P c2 P s2 Q c2 Q s2 These represent the active second harmonic component and the reactive second harmonic component of the energy storage converter output, respectively. This represents the negative sequence component of the converter output current along the d-axis. This represents the negative sequence q-axis component of the converter output current. This represents the positive sequence component of the converter output current along the d-axis. This represents the positive-sequence q-axis component of the converter output current. This represents the negative sequence component of the grid voltage along the d-axis. This represents the negative sequence component of the grid voltage along the q-axis. This represents the positive sequence component of the grid voltage along the d-axis. The negative sequence parameter represents the positive q-axis component of the grid voltage, and includes: and The second harmonic parameter includes: P c2 P s2 Q c2 Q s2 .

3. The method according to claim 2, characterized in that, Setting the negative sequence parameter and second harmonic parameter of the power model of the AC / DC converter to be less than the second threshold includes: setting the negative sequence parameter and second harmonic parameter of the power model of the AC / DC converter to be equal to 0.

4. The method according to claim 3, characterized in that, The negative sequence parameter and second harmonic parameter of the power model of the AC / DC converter are set to be equal to 0 to determine the active power command of the energy storage converter, including: The active power command is determined using the following formula. : 。 5. The method according to claim 1, characterized in that, On the DC / DC converter side, the current command is determined based on the derating correction factor, including: The current command is determined according to the following formula. : ,in, The reduction correction coefficient is mentioned above. This represents the minimum effective value of the three-phase grid voltage after per-unit marking. The command current for the energy storage converter is the current before the grid voltage value is lower than the first threshold.

6. A control device for an energy storage converter, characterized in that, include: The suppression module is used to suppress grid-connected negative sequence current and power second harmonic fluctuations when the grid voltage value is detected to be greater than a first threshold by: obtaining the power model of the AC / DC converter, setting the negative sequence parameter and second harmonic parameter of the power model of the AC / DC converter to be less than a second threshold, so as to determine the active power command of the energy storage converter. The processing module is configured to suppress grid-connected negative sequence current and power second harmonic fluctuations when the grid voltage value is detected to be less than the first threshold by: acquiring the power model of the AC / DC converter, setting the negative sequence parameter and second harmonic parameter of the power model of the AC / DC converter to be less than the second threshold, and on the DC / DC converter side, determining the current command according to the derating correction coefficient, and determining the output of the energy storage converter according to the current command.

7. The apparatus according to claim 6, characterized in that, The power model of the AC / DC converter includes: Wherein, P0 and Q0 represent the active DC component and reactive DC component output by the energy storage converter, respectively; P c2 P s2 Q c2 Q s2 These represent the active second harmonic component and the reactive second harmonic component of the energy storage converter output, respectively. This represents the negative sequence component of the converter output current along the d-axis. This represents the negative sequence q-axis component of the converter output current. This represents the positive sequence component of the converter output current along the d-axis. This represents the positive-sequence q-axis component of the converter output current. This represents the negative sequence component of the grid voltage along the d-axis. This represents the negative sequence component of the grid voltage along the q-axis. This represents the positive sequence component of the grid voltage along the d-axis. The negative sequence parameter represents the positive q-axis component of the grid voltage, and includes: and The second harmonic parameter includes: P c2 P s2 Q c2 Q s2 .

8. The apparatus according to claim 6, characterized in that, The processing module is further configured to determine the current command according to the following formula. : ,in, The reduction correction coefficient is mentioned above. This represents the minimum effective value of the three-phase grid voltage after per-unit marking. The command current for the energy storage converter is the current before the grid voltage value is lower than the first threshold.

9. A storage medium, characterized in that, The storage medium stores a computer program, wherein the computer program is configured to execute the method described in any one of claims 1 to 5 when it is run.

10. An electronic device comprising a memory and a processor, characterized in that, The memory stores a computer program, and the processor is configured to run the computer program to perform the method described in any one of claims 1 to 5.

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