Low-voltage fault tolerance control method and related device for network construction type energy storage converter

Abstract

The invention belongs to the technical field of network construction type energy storage control, and discloses a network construction type energy storage converter low-voltage fault tolerance control method and a related device. The low-voltage fault tolerance control method for the network construction type energy storage converter comprises the following steps: based on a selected network construction type energy storage converter, obtaining three-phase voltage data of a grid-connected point and carrying out two-phase rotating coordinate system transformation to obtain a direct-axis voltage component and a quadrature-axis voltage component; performing fault judgment based on the quadrature-axis voltage component to obtain a fault judgment result; and based on the fault discrimination result, control strategy adaptive switching is carried out. According to the technical scheme disclosed by the invention, the transient process of the grid-forming type energy storage converter in the low-voltage fault occurrence and recovery stage can be improved, the active supporting capability of grid-forming type energy storage on the power system under the fault can be ensured, and the safe and stable operation level of the power system can be further improved.

Description

Technical Field

[0001] This invention belongs to the field of grid-type energy storage control technology, and specifically relates to a low-voltage fault tolerance control method and related devices for grid-type energy storage converters. Background Technology

[0002] The large-scale grid connection of high proportions of renewable energy and the large-scale application of power electronic equipment have significantly reduced the security and stability of traditional power systems. Against this backdrop, grid-based energy storage is expected to become an active support resource for the stable operation of new power systems. Explained, grid-based energy storage has stable energy support capabilities, can autonomously respond to changes in the power system through instantaneous power response mechanisms, and exhibits voltage source characteristics externally. It can participate in frequency and voltage control throughout the entire process before and after disturbances of varying magnitudes to support the stable operation of the power system.

[0003] As the interface between energy storage and the power grid, energy storage converters can provide active support to the power system and effectively mitigate fault impacts by simulating the physical external characteristics of synchronous generators. However, the actual power grid operating environment is complex and faults such as short circuits can occur, which may lead to cascading generator trips and other accidents in severe cases, endangering the operational stability of the power grid.

[0004] Under low-voltage faults in the power grid, existing traditional grid-connected energy storage converters do not need to undertake voltage and frequency support tasks; they only need to smoothly overcome the fault. However, grid-connected energy storage converters, due to their synchronous generator characteristics, not only need to ensure smooth passage but also need to provide sufficient voltage and frequency support to maintain grid stability as much as possible. Existing traditional control methods have shortcomings in dealing with low-voltage faults, including: the introduction of positive and negative sequence separation during symmetrical faults and recovery phases introduces unnecessary delays, reducing control stability; and during asymmetrical faults, the lack of a rapid fault type identification mechanism prevents adaptive switching of control strategies, resulting in poor transient processes during fault occurrence and recovery, affecting the active support effect of grid-connected energy storage systems on the power grid. Therefore, it is necessary to study low-voltage tolerance control strategies for grid-connected energy storage converters under low-voltage faults to ensure the active support capability of grid-connected energy storage for the power system under fault conditions and to guarantee the safe and stable operation of the power system. Summary of the Invention

[0005] The purpose of this invention is to provide a low-voltage fault tolerance control method and related apparatus for grid-type energy storage converters to solve one or more of the aforementioned technical problems. The technical solution disclosed in this invention can improve the transient process of grid-type energy storage converters during the occurrence and recovery phases of low-voltage faults, ensuring the active support capability of grid-type energy storage for the power system under fault conditions, thereby enhancing the safe and stable operation level of the power system.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a low-voltage fault tolerance control method for a grid-type energy storage converter, comprising the following steps: Based on the selected grid-connected energy storage converter, the three-phase voltage data at the grid connection point are acquired and a two-phase rotating coordinate system transformation is performed to obtain the direct-axis voltage component and the quadrature-axis voltage component. Fault identification is performed based on the quadrature-axis voltage component to obtain a fault identification result; wherein, during the fault identification process, if the quadrature-axis voltage component is less than a preset action threshold, the fault identification result is that no fault has occurred or a symmetrical voltage drop fault has occurred; if the quadrature-axis voltage component is greater than or equal to the preset action threshold, the fault identification result is that an asymmetrical voltage drop fault has occurred. Based on the fault identification result, the control strategy is adaptively switched. If the fault identification result is that no fault has occurred or a symmetrical voltage drop fault has occurred, a current vector control strategy is adopted. If the fault identification result is that an asymmetrical voltage drop fault has occurred, a positive-negative sequence separation control strategy is adopted. In the positive-negative sequence separation control strategy, the positive-sequence component and the negative-sequence component in the control quantity are separated. The positive-sequence component is sent to the active support control loop, the power / current conversion loop and the positive-sequence current loop, and the negative-sequence component is sent to the negative-sequence current loop for control.

[0007] A further improvement to the technical solution of this invention lies in the process of acquiring three-phase voltage data at the grid connection point and performing a two-phase rotating coordinate system transformation based on a selected grid-connected energy storage converter to obtain the direct-axis voltage component and the quadrature-axis voltage component. The three-phase voltage at the grid connection point consists of positive-sequence and negative-sequence components, expressed as: ; In the formula, , , This refers to the three-phase power grid voltage. This represents the positive sequence voltage amplitude of the power grid. This represents the negative sequence voltage amplitude of the power grid. The angular frequency of the grid voltage; This represents the phase difference between the positive-sequence voltage and the negative-sequence voltage of the power grid. For time; The direct-axis voltage component and the quadrature-axis voltage component are expressed as follows: ; In the formula, , These are the direct-axis voltage component and the quadrature-axis voltage component, respectively.

[0008] A further improvement of the technical solution of the present invention is that the preset action threshold is 0.02. U n ,U n This is the rated voltage of the grid-type energy storage converter.

[0009] A further improvement of the technical solution of the present invention is that, in the current vector control strategy and the positive and negative sequence separation control strategy, the positive sequence current command is solved for the initial value using the power-current relationship.

[0010] A further improvement of the technical solution of the present invention is that, in the positive and negative sequence separation control strategy, the calculation expression of the negative sequence current command is: ; In the formula, This is the direct-axis reference value for the negative-sequence current command; The quadrature axis reference value for the negative sequence current command; The proportional coefficient of the dynamic negative sequence reactive current of the grid-type energy storage converter, with a value greater than or equal to 1; This represents the per-unit value of the negative sequence component of the output voltage of the grid-connected energy storage converter. This is the rated current of the grid-type energy storage converter.

[0011] A further improvement of the technical solution of the present invention is that, in the current vector control strategy and the positive and negative sequence separation control strategy, the output current amplitude of the grid-type energy storage converter is composed of positive sequence DC and negative sequence double frequency AC; wherein, the maximum output current amplitude is the sum of the positive sequence current and the negative sequence current amplitude, and the maximum output current amplitude is less than or equal to the maximum current amplitude that the grid-type energy storage converter is allowed to pass for a short time.

[0012] A further improvement of the technical solution of the present invention is that the output current amplitude of the grid-type energy storage converter is greater than or equal to the lower limit constraint value of the output current; wherein, the lower limit constraint value of the output current can meet the requirement of the grid-type energy storage converter to provide active voltage support under low voltage fault conditions.

[0013] A second aspect of the present invention provides a low-voltage fault tolerance control system for a grid-type energy storage converter, comprising: The data acquisition unit is used to acquire three-phase voltage data at the grid connection point based on the selected grid-connected energy storage converter and perform two-phase rotating coordinate system transformation to obtain the direct-axis voltage component and the quadrature-axis voltage component. The fault determination unit is used to determine faults based on the quadrature-axis voltage component and obtain a fault determination result. During the fault determination process, if the quadrature-axis voltage component is less than a preset action threshold, the fault determination result is that no fault has occurred or a symmetrical voltage drop fault has occurred. If the quadrature-axis voltage component is greater than or equal to the preset action threshold, the fault determination result is that an asymmetrical voltage drop fault has occurred. The strategy switching unit is used to adaptively switch control strategies based on the fault identification result. If the fault identification result is that no fault has occurred or a symmetrical voltage drop fault has occurred, a current vector control strategy is adopted. If the fault identification result is that an asymmetrical voltage drop fault has occurred, a positive-negative sequence separation control strategy is adopted. In the positive-negative sequence separation control strategy, after separating the positive-sequence component and the negative-sequence component in the control quantity, the positive-sequence component is sent to the active support control loop, the power / current conversion loop and the positive-sequence current loop, and the negative-sequence component is sent to the negative-sequence current loop for control.

[0014] In a third aspect, the present invention provides an electronic device including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the program, implements the low-voltage fault tolerance control method for a grid-type energy storage converter as described in any one of the first aspects of the present invention.

[0015] In a fourth aspect, the present invention provides a non-transitory computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the low-voltage fault tolerance control method for a grid-type energy storage converter as described in any one of the first aspects of the present invention.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a low-voltage fault tolerance control method for grid-connected energy storage converters. Under normal operating conditions, it does not affect the normal operation of the grid-connected energy storage converter, always possessing inertia and damping simulation capabilities, and can participate in frequency and voltage regulation of the power grid to ensure the safe and stable operation of the power system. During symmetrical faults and fault recovery, the control strategy proposed in this invention does not involve positive and negative sequence separation and control loops, but instead adopts a current vector control strategy, reducing the impact of delay loops compared to existing traditional control methods. During asymmetrical faults, based on the fault type identification results, this invention freezes the positive and negative sequence separation and negative sequence current control loops in the control loop (interpretatively, locking and maintaining the working state of the positive and negative sequence separation and negative sequence current control loops, without dynamic adjustment), thereby improving the transient process of the grid-connected energy storage converter during the fault occurrence and recovery phases of low-voltage faults and enhancing the safe and stable operation level of the power system. To further explain, the technical solution of this invention mainly proposes a rapid fault type identification method for power grids by analyzing the differentiated characteristics of power grids under symmetrical and asymmetrical faults. Based on the identification results, it adaptively selects whether to perform positive and negative sequence component separation and control, thereby improving the transient process during the fault occurrence and recovery stages.

[0017] In a preferred embodiment of the present invention, the calculation expression of the negative sequence current command in the positive and negative sequence separation control strategy is specifically disclosed, which mitigates the negative sequence voltage at the grid connection point by absorbing negative sequence reactive power. Among them, mitigating the negative sequence voltage at the grid connection point by absorbing negative sequence reactive power is one of the core control logics. Essentially, it utilizes the correlation between negative sequence reactive power and negative sequence voltage to actively adjust the negative sequence current through the converter, thereby offsetting the disturbance of the negative sequence voltage of the grid and suppressing the degree of voltage asymmetry. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 This is a flowchart illustrating a low-voltage fault tolerance control method for a grid-type energy storage converter, as described in an embodiment of the present invention.

[0020] Figure 2 This is a schematic diagram of a low-voltage fault tolerance control system for a grid-type energy storage converter in an embodiment of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention; obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0022] Based on the technical solutions disclosed in the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products, or devices.

[0023] Please see Figure 1 The present invention discloses a low-voltage fault tolerance control method for a grid-type energy storage converter, comprising the following steps: Step 1: Based on the selected grid-connected energy storage converter, acquire the three-phase voltage data at the grid connection point and perform a two-phase rotating coordinate system transformation to obtain the direct-axis voltage component and the quadrature-axis voltage component; Explain, the above two-phase rotating coordinate system transformation is... dqCoordinate transformation, where the coordinate system has two mutually perpendicular coordinate axes: d The shaft is defined as the direct shaft of the motor rotor (coinciding with the axis of the rotor magnetic poles). q The shaft is the quadrature axis of the motor rotor; dq The coordinate system rotates synchronously with the rotor, and the rotational angular velocity is equal to the rotor's electrical angular velocity; Step 2: Based on the quadrature-axis voltage component, perform fault identification to obtain a fault identification result; wherein, when performing fault identification, if the quadrature-axis voltage component is less than a preset action threshold, the fault identification result is that no fault has occurred or a symmetrical voltage drop fault has occurred; if the quadrature-axis voltage component is greater than or equal to the preset action threshold, the fault identification result is that an asymmetrical voltage drop fault has occurred. Step 3: Based on the fault identification results obtained in Step 2, adaptive switching of control strategy is performed. If the fault identification result is that no fault has occurred or a symmetrical voltage drop fault has occurred, current vector control is adopted. If the fault identification result is that an asymmetrical voltage drop fault has occurred, positive and negative sequence separation control is adopted. In positive and negative sequence separation control, the positive sequence component and the negative sequence component in the control quantity are separated. The positive sequence component is sent to the active support control loop, the power / current conversion loop and the positive sequence current loop, and the negative sequence component is sent to the negative sequence current loop for control.

[0024] In the technical solution disclosed in this invention embodiment, low-voltage fault tolerance control of grid-type energy storage converters is achieved through fault type discrimination and adaptive switching process of control strategy. Specifically, in the technical solution of this invention embodiment, the grid fault type is first quickly discerned, and then the discrimination signal is set to drive the switching of the control loop based on the fault discrimination result. Among them, in the case of symmetrical voltage drop faults and no faults, the positive and negative sequence separation loop is not switched, and current vector control is directly adopted, avoiding unnecessary delay loops in traditional methods, improving control stability, and retaining the inertia and damping simulation capability of the converter, which can ensure normal frequency and voltage regulation functions. In the case of asymmetrical voltage drop faults, the positive and negative sequence separation control loop is precisely switched, and the positive and negative sequence components are targeted for regulation, effectively improving the transient process in the fault occurrence and recovery stages, enhancing the voltage support capability of grid-type energy storage converters, and improving the safe and stable operation level of the power system.

[0025] In the exemplary optional technical solution of this invention, the specific process of obtaining the three-phase voltage data of the grid connection point and performing a two-phase rotating coordinate system transformation based on the selected grid-connected energy storage converter to obtain the direct-axis voltage component and quadrature-axis voltage component is as follows: The obtained three-phase voltage data at the grid connection point, assuming it consists of positive-sequence and negative-sequence components, is expressed as follows: (1) In the formula, , , This refers to the three-phase power grid voltage. This represents the positive sequence voltage amplitude of the power grid. This represents the negative sequence voltage amplitude of the power grid. The angular frequency of the grid voltage; This represents the phase difference between the positive-sequence voltage and the negative-sequence voltage of the power grid. For time; Perform a test on the grid voltage in equation (1). dq Coordinate transformation, the result of which is expressed as: (2) In the formula, , These are the direct-axis voltage component and the quadrature-axis voltage component, respectively. Explained, from equation (2), it can be seen that when a symmetrical voltage drop fault occurs in the power grid, =0; When an asymmetrical voltage dip fault occurs in the power grid It manifests as a second harmonic fluctuation with an amplitude of ; based on this, the sampled three-phase grid voltage is analyzed and the differential characteristics of symmetrical voltage drop faults and asymmetrical voltage drop faults are extracted, which can realize the rapid identification of grid fault types.

[0026] In an exemplary optional technical solution of this invention, in step 2, during the process of fault discrimination based on the quadrature-axis voltage component to obtain the fault discrimination result, the influence of noise and accuracy error in actual sampling is taken into consideration. When the grid voltage is not faulty or experiences a symmetrical voltage drop fault, it cannot be strictly zero. To avoid frequent switching of control actions, a certain action threshold needs to be preset for fault category judgment. In this step, based on actual operating experience, the action threshold is set to 0.02. U n , U n The rated voltage of the grid-type energy storage converter; for specific examples, illustratively, when | |<0.02U n When the voltage is symmetrical, it indicates that the grid voltage is symmetrical; conversely, it indicates that the grid voltage is asymmetrical and that positive and negative sequence component separation and control are required.

[0027] In the technical solution of this invention embodiment, an action threshold of 0.02 is set based on experience. U n When | |<0.02 U n When the fault is determined to be a symmetrical voltage drop fault or no fault; when | |≥0.02 U nThe fault was identified as an asymmetrical voltage drop. Setting the action threshold too high can lead to missed fault detection, while setting it too low can cause frequent switching of the control loop. This invention has been verified by combining a large amount of actual operating data, and has balanced the accuracy of the detection with the stability of the control.

[0028] In a further exemplary optional technical solution, when the fault is determined to be a symmetrical voltage dip or no fault, the discrimination signal can be set to a low level, and the positive / negative sequence separation and control loop is not activated. Ordinary current vector control is used to reduce the delay. When the fault is determined to be an asymmetrical voltage dip, the discrimination signal can be set to a high level, and positive / negative sequence separation control is activated. The positive sequence component of the control quantity is sent to the active support control loop, the power / current conversion loop, and the positive sequence current loop, while the negative sequence component is sent to the negative sequence current loop for control. The transient process of power grid fault occurrence and recovery is extremely short, requiring fault discrimination and control strategy switching to be completed in a short time (e.g., milliseconds). The fault discrimination and adaptive switching logic of the present invention is simple and can adapt to real-time requirements. The control quantity does not contain a negative sequence component during current vector control. Compared with traditional positive / negative sequence separation control, this reduces unnecessary delay loops and increases control stability.

[0029] In the exemplary optional technical solutions of this invention, the positive sequence current command for both symmetrical and asymmetrical voltage dip faults is calculated using the conventional power-current relationship to obtain the initial value. Additionally, during an asymmetrical voltage dip fault, the negative sequence current command is calculated using the following formula to mitigate the negative sequence voltage at the grid connection point by absorbing negative sequence reactive power.

[0030] Based on the positive and negative sequence current vector sum, the output current amplitude is calculated to ensure that the maximum output current amplitude does not exceed the maximum current amplitude that the converter is allowed to pass for a short time. At the same time, the minimum requirement for positive sequence reactive current is defined to ensure the active voltage support capability under fault conditions.

[0031] In an exemplary optional technical solution of this invention, when a grid fault occurs, in order to ensure that the output current of the grid-connected energy storage converter does not exceed the limit, it is necessary to solve for the current command; wherein, The current command solution for a symmetrical voltage dip fault in the power grid is the same as the positive sequence current command solution for an asymmetrical voltage dip fault. Further explanation: for positive sequence current, the initial values ​​of the positive sequence active current command and reactive current command output by the grid-type energy storage converter are mainly determined using the power-current relationship, which is the same as the current calculation method for conventional current in grid-type energy storage converters. For negative sequence current, when an asymmetrical voltage dip fault occurs in the power grid, the grid-type energy storage converter mitigates the negative sequence voltage at the grid connection point by absorbing negative sequence reactive power, and calculates the negative sequence current command according to equation (3): (3) In the formula, The proportional coefficient of the dynamic negative sequence reactive current of the grid-type energy storage converter is not less than 1. This represents the per-unit value of the negative sequence component of the output voltage of the grid-connected energy storage converter. This refers to the rated current of the grid-type energy storage converter; The direct axis of the negative sequence current command ( d (Axis) reference value; The cross axis of the negative sequence current command ( q (Axis) reference value.

[0032] After initially determining the solution process for the positive and negative sequence current commands, in order to achieve withstand under low voltage faults, it is also necessary to consider the current limiting problem of the grid-type energy storage converter under fault conditions, so as to ensure that the voltage active support capability of the grid-type energy storage converter to the power grid is enhanced while meeting the current limiting requirements. Therefore, the output current of the grid-type energy storage converter is generally the vector sum of the positive and negative sequence currents, as shown in equation (4): (4) In the formula, This represents the positive sequence current amplitude. This represents the negative sequence current amplitude. The phase difference between the positive and negative sequence components of the output current of the grid-type energy storage converter; This is the lower limit constraint value for the output current.

[0033] The output current amplitude is composed of a positive-sequence DC current and a negative-sequence double-frequency AC current. The maximum amplitude of the output current is the sum of the positive-sequence and negative-sequence current amplitudes. To ensure that the fault current does not exceed the limit, the maximum amplitude of the output current should not exceed the maximum current amplitude that the grid-type energy storage converter is allowed to pass for a short time. To ensure that grid-connected energy storage converters provide active voltage support during grid faults, a minimum requirement for the positive-sequence reactive current output of these converters needs to be determined. For example, this can be quantified using a "voltage drop-reactive power support correlation model," which combines the degree of grid voltage drop with the voltage support requirement. Specifically, under low-voltage grid faults, the voltage amplitude at the grid connection point must recover to a certain percentage (e.g., 90%) of the rated voltage, serving as the target threshold for voltage support. Based on the voltage-reactive power sensitivity of the power system (reactive power is positively correlated with voltage amplitude), the minimum reactive power output is determined. Combined with the converter's rated voltage, the minimum reactive power is converted into a positive-sequence reactive current, which must be less than the converter's maximum allowable current amplitude during short periods (to avoid equipment overload). For different degrees of voltage drop (e.g., 20% or 50%), simulations or experiments are used to verify whether this minimum current can achieve the voltage support target, ultimately determining a unified minimum requirement.

[0034] The following are embodiments of the apparatus of the present invention, which can be used to execute embodiments of the method of the present invention. For details not disclosed in the apparatus embodiments, please refer to the embodiments of the method of the present invention.

[0035] Please see Figure 2 In this embodiment of the invention, a low-voltage fault tolerance control system for a grid-type energy storage converter is provided, comprising: The data acquisition unit is used to acquire three-phase voltage data at the grid connection point based on the selected grid-connected energy storage converter and perform two-phase rotating coordinate system transformation to obtain the direct-axis voltage component and the quadrature-axis voltage component. The fault determination unit is used to determine faults based on the quadrature-axis voltage component and obtain a fault determination result. During the fault determination process, if the quadrature-axis voltage component is less than a preset action threshold, the fault determination result is that no fault has occurred or a symmetrical voltage drop fault has occurred. If the quadrature-axis voltage component is greater than or equal to the preset action threshold, the fault determination result is that an asymmetrical voltage drop fault has occurred. The strategy switching unit is used to adaptively switch control strategies based on the fault identification result. If the fault identification result is that no fault has occurred or a symmetrical voltage drop fault has occurred, a current vector control strategy is adopted. If the fault identification result is that an asymmetrical voltage drop fault has occurred, a positive-negative sequence separation control strategy is adopted. In the positive-negative sequence separation control strategy, after separating the positive-sequence component and the negative-sequence component in the control quantity, the positive-sequence component is sent to the active support control loop, the power / current conversion loop and the positive-sequence current loop, and the negative-sequence component is sent to the negative-sequence current loop for control.

[0036] In one embodiment of the present invention, a computer device is provided, comprising a processor and a memory. The memory stores a computer program, which includes program instructions. The processor executes the program instructions stored in the computer storage medium. The processor may be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. It is the computing and control core of the terminal, suitable for implementing one or more instructions, specifically suitable for loading and executing one or more instructions in the computer storage medium to achieve a corresponding method flow or corresponding function. The processor described in this embodiment of the present invention can be used to execute the operation of a low-voltage fault tolerance control method for a grid-type energy storage converter.

[0037] In one embodiment of the present invention, a storage medium is provided, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device used to store programs and data. It is understood that the computer-readable storage medium here can include both the built-in storage medium in the computer device and extended storage media supported by the computer device. The computer-readable storage medium provides storage space that stores the operating system of the terminal. Furthermore, the storage space also stores one or more instructions suitable for loading and execution by a processor. These instructions can be one or more computer programs (including program code). It should be noted that the computer-readable storage medium here can be high-speed RAM (Random Access Memory) or non-volatile memory, such as at least one disk storage device. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the corresponding steps of the low-voltage fault tolerance control method for grid-type energy storage converters in the above embodiments.

[0038] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, optical storage, etc.) containing computer-usable program code.

[0039] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0040] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0041] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0042] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A low-voltage fault tolerance control method for a grid-type energy storage converter, characterized in that, Includes the following steps: Based on the selected grid-connected energy storage converter, the three-phase voltage data at the grid connection point are acquired and a two-phase rotating coordinate system transformation is performed to obtain the direct-axis voltage component and the quadrature-axis voltage component. Fault identification is performed based on the quadrature-axis voltage component to obtain a fault identification result; wherein, during the fault identification process, if the quadrature-axis voltage component is less than a preset action threshold, the fault identification result is that no fault has occurred or a symmetrical voltage drop fault has occurred; if the quadrature-axis voltage component is greater than or equal to the preset action threshold, the fault identification result is that an asymmetrical voltage drop fault has occurred. Based on the fault identification result, the control strategy is adaptively switched. If the fault identification result is that no fault has occurred or a symmetrical voltage drop fault has occurred, a current vector control strategy is adopted. If the fault identification result is that an asymmetrical voltage drop fault has occurred, a positive-negative sequence separation control strategy is adopted. In the positive-negative sequence separation control strategy, the positive-sequence component and the negative-sequence component in the control quantity are separated. The positive-sequence component is sent to the active support control loop, the power / current conversion loop and the positive-sequence current loop, and the negative-sequence component is sent to the negative-sequence current loop for control.

2. The low-voltage fault tolerance control method for a grid-type energy storage converter according to claim 1, characterized in that, Based on the selected grid-connected energy storage converter, the three-phase voltage data at the grid connection point is acquired and a two-phase rotating coordinate system transformation is performed to obtain the direct-axis voltage component and the quadrature-axis voltage component. The three-phase voltage at the grid connection point consists of positive-sequence and negative-sequence components, expressed as: ； In the formula, , , This refers to the three-phase power grid voltage. This represents the positive sequence voltage amplitude of the power grid. This represents the negative sequence voltage amplitude of the power grid. The angular frequency of the grid voltage; This represents the phase difference between the positive-sequence voltage and the negative-sequence voltage of the power grid. For time; The direct-axis voltage component and the quadrature-axis voltage component are expressed as follows: ； In the formula, , These are the direct-axis voltage component and the quadrature-axis voltage component, respectively.

3. The low-voltage fault tolerance control method for a grid-type energy storage converter according to claim 1, characterized in that, The preset action threshold is 0.

02. U n , U n This is the rated voltage of the grid-type energy storage converter.

4. The low-voltage fault tolerance control method for a grid-type energy storage converter according to claim 1, characterized in that, In both the current vector control strategy and the positive-negative sequence separation control strategy, the positive sequence current command is solved for its initial value using the power-current relationship.

5. The low-voltage fault tolerance control method for a grid-type energy storage converter according to claim 1, characterized in that, In the positive and negative sequence separation control strategy, the calculation expression for the negative sequence current command is: ； In the formula, This is the direct-axis reference value for the negative-sequence current command; The quadrature axis reference value for the negative sequence current command; The proportional coefficient of the dynamic negative sequence reactive current of the grid-type energy storage converter, with a value greater than or equal to 1; This represents the per-unit value of the negative sequence component of the output voltage of the grid-connected energy storage converter. This is the rated current of the grid-type energy storage converter.

6. The low-voltage fault tolerance control method for a grid-type energy storage converter according to claim 1, characterized in that, In the current vector control strategy and the positive and negative sequence separation control strategy, the output current amplitude of the grid-type energy storage converter consists of positive sequence DC current and negative sequence double frequency AC current; wherein, the maximum output current amplitude is the sum of the positive sequence current amplitude and the negative sequence current amplitude, and the maximum output current amplitude is less than or equal to the maximum current amplitude that the grid-type energy storage converter is allowed to pass for a short time.

7. The low-voltage fault tolerance control method for a grid-type energy storage converter according to claim 6, characterized in that, The output current amplitude of the grid-type energy storage converter is greater than or equal to the lower limit constraint value of the output current; wherein, the lower limit constraint value of the output current can meet the requirement of the grid-type energy storage converter to provide active voltage support under low voltage fault conditions.

8. A low-voltage fault tolerance control system for a grid-type energy storage converter, characterized in that, include: The data acquisition unit is used to acquire three-phase voltage data at the grid connection point based on the selected grid-connected energy storage converter and perform two-phase rotating coordinate system transformation to obtain the direct-axis voltage component and the quadrature-axis voltage component. The fault determination unit is used to determine faults based on the quadrature-axis voltage component and obtain a fault determination result. During the fault determination process, if the quadrature-axis voltage component is less than a preset action threshold, the fault determination result is that no fault has occurred or a symmetrical voltage drop fault has occurred. If the quadrature-axis voltage component is greater than or equal to the preset action threshold, the fault determination result is that an asymmetrical voltage drop fault has occurred. The strategy switching unit is used to adaptively switch control strategies based on the fault identification result. If the fault identification result is that no fault has occurred or a symmetrical voltage drop fault has occurred, a current vector control strategy is adopted. If the fault identification result is that an asymmetrical voltage drop fault has occurred, a positive-negative sequence separation control strategy is adopted. In the positive-negative sequence separation control strategy, after separating the positive-sequence component and the negative-sequence component in the control quantity, the positive-sequence component is sent to the active support control loop, the power / current conversion loop and the positive-sequence current loop, and the negative-sequence component is sent to the negative-sequence current loop for control.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the low-voltage fault tolerance control method for a grid-type energy storage converter as described in any one of claims 1 to 7.

10. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the low-voltage fault tolerance control method for grid-type energy storage converters as described in any one of claims 1 to 7.

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