Energy storage converter low voltage ride through control method and energy storage converter

Abstract

The invention provides an energy storage converter low-voltage ride-through control method and an energy storage converter, and relates to the field of low-voltage ride-through control, and the method comprises the steps: obtaining a three-phase line voltage of a power grid; based on the three-phase line voltage, calculating a coordinate transformation angle by using a phase-locked loop method of a second-order generalized integrator to obtain a first coordinate transformation angle; based on the three-phase line voltage, calculating a coordinate transformation angle by using a phase-locked loop method of BC phase line voltage zero crossing point detection to obtain a second coordinate transformation angle; calculating an absolute value of a difference value between the first coordinate transformation angle and the second coordinate transformation angle to obtain a transformation angle difference value; integrating the first coordinate transformation angle and the second coordinate transformation angle into 0-2pi; and determining a target coordinate transformation angle according to the power grid voltage drop condition and the transformation angle difference value. According to the method provided by the invention, the low-voltage ride-through requirements under different power grid voltage drop conditions can be met, and the low-voltage ride-through capability and the system stability of the energy storage converter are improved.

Description

[0001] This application is a divisional application. The application number of the original application is 202510376699.X, and the original application date is March 27, 2025. The entire content of the original application is incorporated into this application by reference. Technical Field

[0002] The present application relates to the field of low voltage ride-through control, and in particular to a low voltage ride-through control method for an energy storage converter and an energy storage converter. Background Art

[0003] The phase-locked loop used in the energy storage converter in the related technology will experience sudden changes in output frequency and phase when the grid voltage drops severely. In particular, when the grid voltage drops to zero, the phase-locked loop can no longer lock the phase normally, causing the system to experience overcurrent and inaccurate reactive power output during low voltage ride-through, especially during zero voltage ride-through, affecting the reliability of low voltage ride-through. Summary of the Invention

[0004] The present application provides a low voltage ride-through control method for an energy storage converter and an energy storage converter, which can meet the low voltage ride-through requirements under different grid voltage drop conditions and improve the low voltage ride-through capability and system stability of the energy storage converter.

[0005] In a first aspect, the present application provides a low voltage ride-through control method for an energy storage converter, comprising:

[0006] Obtain the three-phase line voltage of the power grid;

[0007] Based on the three-phase line voltage, the coordinate transformation angle is calculated using a phase-locked loop method of a second-order generalized integrator to obtain a first coordinate transformation angle;

[0008] Based on the three-phase line voltage, the coordinate transformation angle is calculated using a phase-locked loop method for detecting the zero-crossing point of the BC phase line voltage to obtain a second coordinate transformation angle; the coordinate transformation angle is the transformation angle from the three-phase stationary coordinate system to the two-phase rotating coordinate system or from the two-phase rotating coordinate system to the three-phase stationary coordinate system;

[0009] Calculating the absolute value of the difference between the first coordinate transformation angle and the second coordinate transformation angle to obtain the transformation angle difference;

[0010] Determine the grid voltage drop;

[0011] The target coordinate transformation angle and the target reactive current positive sequence and negative sequence component given values ​​are determined according to the grid voltage drop and the transformation angle difference. The target coordinate transformation angle is the first coordinate transformation angle or the second coordinate transformation angle.

[0012] In a second aspect, the present application provides an energy storage converter, comprising: a processor and a memory, the memory being used to store a computer program; the processor being used to run the computer program to implement the low voltage ride-through control method of the energy storage converter as described in the first aspect.

[0013] The beneficial effects of this application are:

[0014] The present application provides a low voltage ride-through control method for an energy storage converter, which obtains the three-phase line voltage of the power grid; based on the three-phase line voltage, calculates the coordinate transformation angle using a second-order generalized integrator phase-locked loop method to obtain a first coordinate transformation angle; based on the three-phase line voltage, calculates the coordinate transformation angle using a BC phase line voltage zero-crossing detection phase-locked loop method to obtain a second coordinate transformation angle; calculates the absolute value of the difference between the first coordinate transformation angle and the second coordinate transformation angle to obtain a transformation angle difference; judges the power grid voltage drop; determines the target coordinate transformation angle and the target reactive current positive and negative sequence component given values ​​based on the power grid voltage drop and the transformation angle difference. The method provided in the present application comprehensively utilizes the advantages of the two phase-locked loops based on the second-order generalized integrator phase-locked loop and the phase-locked loop based on the BC phase line voltage zero-crossing detection. In the low voltage ride-through interval, a single current loop control is adopted, and the target coordinate transformation angle, the reactive current positive and negative sequence component given values ​​are determined based on the angle difference between the two phase-locked loops and the voltage drop, so as to perform reactive current control. This method can meet the low voltage ride-through requirements under different grid voltage drop conditions. Even if the grid voltage drops completely to zero, it can successfully achieve the low voltage ride-through function and output the required reactive current, thereby improving the low voltage ride-through capability of the energy storage converter and the system stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A schematic flow chart of a low voltage ride-through control method for an energy storage converter provided in an embodiment of the present application;

[0016] Figure 2 A schematic diagram of the structure of the BC phase line voltage zero-crossing point detection provided in an embodiment of the present application;

[0017] Figure 3 A schematic diagram of the structure of the low voltage ride-through control algorithm provided in an embodiment of the present application;

[0018] Figure 4 A schematic diagram of the structure of the energy storage converter provided in an embodiment of the present application. DETAILED DESCRIPTION

[0019] In the embodiments of this application, unless otherwise specified, the character " / " indicates that the associated objects are in an "or" relationship. For example, A / B can represent A or B. "And / or" describes the relationship between the associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exists simultaneously, or B exists alone.

[0020] It should be pointed out that the words "first", "second", etc. involved in the embodiments of this application are only used for distinguishing description purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated, nor can they be understood as indicating or implying order.

[0021] In the embodiments of the present application, "at least one" refers to one or more, and "plurality" refers to two or more. In addition, "at least one of the following" or similar expressions refers to any combination of these items, which may include any combination of single items or plural items. For example, at least one of A, B, or C can represent: A, B, C, A and B, A and C, B and C, or A, B and C. Among them, each of A, B, and C can be an element itself, or a set containing one or more elements.

[0022] In the embodiments of this application, the terms "exemplary," "in some embodiments," and "in another embodiment" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" in this application should not be construed as preferred or advantageous over other embodiments or designs. Rather, the use of the word "exemplary" is intended to present concepts in a concrete manner.

[0023] In the embodiments of this application, the terms "of," "corresponding," and "relevant" may sometimes be used interchangeably. It should be noted that, when the distinction between them is not emphasized, the meanings they convey are the same. In the embodiments of this application, the terms "communication" and "transmission" may sometimes be used interchangeably. It should be noted that, when the distinction between them is not emphasized, the meanings they convey are the same. For example, "transmission" may include "sending" and / or "receiving," and may be either a noun or a verb.

[0024] In the embodiments of this application, "equal to" can be used in conjunction with "greater than" and is applicable to the technical solution adopted when "greater than" is used, and can also be used in conjunction with "less than" and is applicable to the technical solution adopted when "less than" is used. It should be noted that when "equal to" is used in conjunction with "greater than", it cannot be used in conjunction with "less than"; and when "equal to" is used in conjunction with "less than", it cannot be used in conjunction with "greater than".

[0025] First, the terms mentioned in this application are explained.

[0026] Low Voltage Ride Through (LVRT): When a grid fault or disturbance causes a voltage drop, the power generation equipment can maintain its connection with the grid and operate without disconnecting from the grid for a certain period of time, while providing a certain amount of reactive power to the grid to support grid voltage recovery.

[0027] Zero Voltage Ride Through (ZVT): is a special case of low voltage ride through, which means that when the grid voltage drops to zero, the power generation equipment can still maintain grid-connected operation and quickly resume normal operation after the voltage recovers.

[0028] Up / down counting method: It is a working mode of a counter. The value of the counter increases within a cycle, then starts to decrease after reaching the maximum value, and then repeats the process after returning to the minimum value.

[0029] Triangular carrier: It is a periodic waveform. In each cycle, it first rises linearly, reaches a peak, and then drops linearly.

[0030] Clark transform (also known as Clarke transform): is a mathematical transformation method that converts the current or voltage in a three-phase stationary coordinate system (ABC coordinate system) into a two-phase stationary coordinate system (αβ coordinate system).

[0031] Symmetrical drop: When the grid voltage drops, the amplitudes of the three-phase voltages drop simultaneously, and the phases remain symmetrical.

[0032] Asymmetric sag: When the grid voltage sags, the amplitude and phase of the three-phase voltage are asymmetric.

[0033] PWM (Pulse-Width Modulation) is a technology that controls the average level of the output signal by changing the width of the pulse signal.

[0034] The phase-locked loop (PLL) used in the energy storage converter in the related technology (such as the traditional PLL based on the second-order generalized integrator) will suddenly change the output frequency and phase when the grid voltage drops severely. In particular, when the grid voltage drops to zero, the PLL can no longer lock the phase normally, causing the system to have overcurrent and inaccurate reactive power output during low voltage crossing, especially during zero voltage crossing, affecting the reliability of low voltage crossing.

[0035] Based on the above problems, the embodiment of the present application proposes a low voltage ride-through control method for an energy storage converter, which can meet the low voltage ride-through requirements under different grid voltage drop conditions and improve the low voltage ride-through capability and system stability of the energy storage converter.

[0036] Now combined Figure 1-Figure 3The low voltage ride-through control method of the energy storage converter provided in the embodiment of the present application is described.

[0037] Figure 1 The flowchart of the low voltage ride-through control method for the energy storage converter provided in the embodiment of the present application specifically includes the following steps:

[0038] Step S11, obtaining the three-phase line voltage of the power grid.

[0039] Specifically, the triangular carrier is generated by increasing and decreasing counting method, and the three-phase line voltages of the power grid AB, BC, and CA are sampled at each triangular carrier zero point to obtain the three-phase line voltages Uab, Ubc, and Uca of the power grid, and further obtain the system carrier frequency f carry , the system control period is 1 / f carry .

[0040] Step S12: Based on the three-phase line voltage, a coordinate transformation angle is calculated using a phase-locked loop method of a second-order generalized integrator to obtain a first coordinate transformation angle.

[0041] Specifically, Clark transformation is performed on the three-phase line voltages Uab, Ubc, and Uca to obtain the voltages Uα and Uβ in a two-phase stationary coordinate system; the positive-sequence and negative-sequence components of the voltages Uα and Uβ in the two-phase stationary coordinate system are extracted using a second-order generalized integrator to obtain the positive-sequence components Uα+ and Uβ+ and the negative-sequence components Uα- and Uβ-; two-phase rotation transformation is performed on the positive-sequence components Uα+ and Uβ+ and the negative-sequence components Uα- and Uβ- to obtain the positive-sequence components Ud+ and Uq+ and the negative-sequence components Ud- and Uq- in a rotating coordinate system; PI regulation and integration operation are performed on the positive-sequence component Uq+ to obtain the first coordinate transformation angle.

[0042] In some optional embodiments, performing PI regulation and integral operation on the positive-sequence component Uq+ to obtain a first coordinate transformation angle includes: regulating the positive-sequence component Uq+ to zero through a PI regulator to obtain an angular frequency of the positive-sequence component of the grid voltage; performing an integral operation on the angular frequency of the positive-sequence component of the grid voltage to obtain a two-phase positive-sequence voltage rotation transformation angle; subtracting π / 6 from the two-phase positive-sequence voltage rotation transformation angle, and integrating the calculation result into the range of 0 to 2π to obtain a first coordinate transformation angle θ1.

[0043] Among them, the role of the PI regulator is to make Uq+ approach zero, thereby ensuring the phase alignment of the d-axis of the rotating coordinate system and the positive sequence component of the grid voltage. Through the two-phase rotation transformation and the PI regulator, the positive sequence component of the grid voltage is converted to the rotating coordinate system, and phase locking is achieved by adjusting Uq+ to zero, and the final rotation angle θ1 is obtained.

[0044] Subtracting π / 6 from the two-phase positive-sequence voltage rotation transformation angle is done to convert the line voltage into phase voltage (the phase voltage lags 30° relative to the line voltage) and to facilitate comparison with the second coordinate transformation angle calculated in step S13. The calculation results are also consolidated into a fixed range (e.g., 0 to 2π) to facilitate comparison and simplify subsequent control logic.

[0045] In other embodiments, the method provided in this application may further include: obtaining the grid rated voltage E n Based on the positive sequence components Ud+ and Uq+, the grid rated voltage E n Calculate the percentage d of the voltage positive sequence component; when d is less than 90% and the duration is greater than 2ms, enter the low voltage ride-through control mode; or when d is greater than 92% and the duration is greater than 2ms, exit the low voltage ride-through control mode; calculate the effective value U of the negative sequence component of the grid voltage based on the negative sequence components Ud- and Uq- 负 .

[0046] Among them, when d is less than 90% and the duration is greater than 2ms, it means that the d value is less than 90% within a time period of more than 2ms (such as 3ms, 4ms). Similarly, when d is greater than 92% and the duration is greater than 2ms, it means that the d value is greater than 92% within a time period of more than 2ms (such as 3ms, 4ms).

[0047] Specifically, the voltage positive sequence component percentage d is calculated by the following formula:

[0048]

[0049] Effective value of negative sequence component of grid voltage U 负 Calculated by the following formula:

[0050]

[0051] By judging the size and duration of the percentage d value of the voltage positive sequence component, it can be determined whether the system enters the low voltage ride-through control mode or exits the low voltage ride-through control mode. Setting the duration is to prevent the rapid change of the size of the d value caused by short-term fluctuations in the power grid, which leads to misjudgment, and plays a role in preventing jitter and misjudgment. If the duration is set too short, it cannot play a role in preventing misjudgment. If the duration is set too long, the response speed of the system is slow, and it cannot quickly enter the low voltage ride-through control mode or exit the low voltage ride-through control mode, which is not conducive to ensuring the stability of the power grid voltage. Therefore, this application sets the duration to 2ms, which can prevent misjudgment and take into account speed.

[0052] Step S13 , based on the three-phase line voltage, a coordinate transformation angle is calculated using a phase-locked loop method for detecting the zero-crossing point of the BC phase line voltage to obtain a second coordinate transformation angle.

[0053] The coordinate transformation angle (including the first coordinate transformation angle θ1 and the second coordinate transformation angle θ2 ) is a transformation angle from a three-phase stationary coordinate system to a two-phase rotating coordinate system or from a two-phase rotating coordinate system to a three-phase stationary coordinate system.

[0054] Specifically, the counter is started to count, and increases by 1 in each control cycle; the signal of the BC phase line voltage crossing the zero point from negative to positive is converted into a rising edge signal; when the low voltage ride-through control mode is not entered, the controller software interrupt is triggered in response to the rising edge signal, and the grid frequency is updated and the counter is cleared; when the low voltage ride-through control mode is entered, the grid frequency update is stopped, and the counter counts continuously until the low voltage ride-through control mode is exited, and the response to the rising edge signal is resumed, and the grid frequency is updated and the counter is cleared; the last grid frequency updated before entering the low voltage ride-through control mode, the count value of the counter during the process of entering the low voltage ride-through control mode, and the carrier frequency are obtained; the second coordinate transformation angle θ2 is calculated based on the last updated grid frequency, the count value of the counter, and the carrier frequency.

[0055] Converting the signal indicating the BC phase line voltage's transition from negative to positive zero-crossing point to a rising edge signal can involve utilizing a hardware circuit (e.g., a zero-crossing detection circuit) to detect the BC phase line voltage's transition from negative to positive zero-crossing point and converting it into a digital signal (e.g., a rising edge signal from 0 to 1). The present application converts the zero-crossing signal to a rising edge signal to enable the controller to better capture the zero-crossing signal, thereby triggering a controller software interrupt in response to the rising edge signal when the controller has not entered the low voltage ride-through control mode.

[0056] When the low voltage ride-through control mode is not entered, the controller software interrupt is triggered in response to the rising edge signal, the current grid frequency value is read, and the grid frequency at the time of the last controller software interrupt is recorded. At the same time, the counter is cleared. That is, when the low voltage ride-through control mode is not entered, the grid frequency is continuously updated and the counter is cleared.

[0057] When entering the low voltage ride through control mode, the grid frequency update is stopped, and the last grid frequency f updated before entering the low voltage ride through control mode is obtained. grid-pre1 The counter counts continuously until it exits the low voltage ride-through control mode, and then resumes responding to the rising edge signal to update the grid frequency and clear the counter, and obtains the count value N of the counter during the process of entering the low voltage ride-through control mode.

[0058] According to the last updated grid frequency f grid-pre1 , the counter value N, the carrier frequency f carry Calculate the second coordinate transformation angle θ2, which can be obtained according to the following formula:

[0059]

[0060] Furthermore, the second coordinate transformation angle θ2 is integrated into a fixed range (such as 0 to 2π). If θ2 exceeds the range of 0 to 2π, it can be adjusted by adding or subtracting multiples of 2π. Integrating the second coordinate transformation angle θ2 into a fixed range facilitates comparison with the first coordinate transformation angle θ1 and simplifies the control logic.

[0061] Figure 2 The schematic diagram of the structure of the BC phase line voltage zero-crossing detection provided in the embodiment of the present application is as follows: Figure 2 As shown, the system enters the low voltage ride-through control mode at time T1 and exits the low voltage ride-through control mode at time T2. During the time period from 0 to T1, the BC phase line voltage changes from negative to positive at two zero-crossing points, namely S1 and S2. The zero-crossing point signal is converted into a rising edge signal. During the time period from T1 to T2, the BC phase line voltage changes from negative to positive at multiple zero-crossing points, including Figure 2 S3, S4, S5 shown in , and convert the zero-crossing signal into a rising edge signal.

[0062] Step S14: Calculate the absolute value of the difference between the first coordinate transformation angle and the second coordinate transformation angle to obtain the transformation angle difference.

[0063] Specifically, according to the first coordinate transformation angle θ1 calculated in step S12 and the second coordinate transformation angle θ2 calculated in step S13, the absolute value of the difference between the two is calculated to obtain the transformation angle difference Δθ, that is, Δθ=|θ1-θ2|.

[0064] Step S15: determining whether the grid voltage has dropped.

[0065] Specifically, the grid voltage drop includes symmetrical drop and asymmetrical drop. When entering the low voltage ride-through control mode, the timing is started. After 5ms, the percentage of the voltage positive sequence component d and the effective value of the grid voltage negative sequence component U are calculated respectively. 负 The sliding average within 1ms is used to obtain d ave and U 负ave ; when U 负ave When it is less than 10% of the rated voltage of the grid, it is determined that the grid voltage has a symmetrical drop; or when U 负ave When the voltage drops by 10% or more, the grid voltage is considered to have experienced an asymmetric drop. The sliding average method uses a sliding window to calculate the average value, which is faster and more accurate than conventional average calculations and is less prone to sudden changes.

[0066] The system enters the low voltage ride through control mode for a period of time (such as 5ms), and the grid voltage amplitude drops are unstable. Therefore, the grid voltage drop is judged 5ms after entering the low voltage ride through control mode to reduce the impact of grid fluctuations and make the judgment result more accurate. In addition, the present application uses the percentage d of the voltage positive sequence component and the effective value U of the grid voltage negative sequence component to determine the voltage drop. 负 The sliding average value within 1ms is used to judge the grid voltage drop, which can more accurately evaluate the grid voltage drop.

[0067] In other embodiments, the method provided in the present application also includes: when entering the low voltage ride-through control mode, recording the initial reactive current positive sequence and negative sequence component given values; within 6ms of entering the low voltage ride-through control mode, setting the reactive current positive sequence and negative sequence component given values ​​to 0.

[0068] Specifically, when entering the low voltage ride-through control mode, the variable I 0+ Record the given value of the reactive current positive sequence component I at the time of voltage drop 0+ =iq+*, using variable I 0- Record the given value of the negative sequence component of reactive current I at the time of voltage drop 0- =iq-*. Where, I 0+ , I 0- These are the initial values ​​of the reactive current positive and negative sequence components. When entering the LVRT control mode, the LVRT timer begins counting. Within 6 ms, the reactive current positive and negative sequence components are reset to 0, i.e., id+* = 0, iq+* = 0, id-* = 0, and iq-* = 0.

[0069] Since the voltage drop amplitude is unstable within a period of time (such as 6ms) after the system enters the low voltage ride-through control mode, the calculated reactive current positive-sequence and negative-sequence component given values ​​are inaccurate. Therefore, the reactive current positive-sequence and negative-sequence component given values ​​are set to 0 within 6ms, and the system will stop controlling the positive-sequence and negative-sequence reactive currents to avoid further impact on the power grid.

[0070] This application ensures stable operation of the system under low voltage conditions by recording the reactive current set value (including positive and negative sequence component set values) at the time of grid drop, starting a timer, and setting the reactive current set value to zero within a certain period of time.

[0071] Step S16, determining the target coordinate transformation angle and the target reactive current positive sequence and negative sequence component given values ​​according to the grid voltage drop and the transformation angle difference.

[0072] The target coordinate transformation angle θ is the first coordinate transformation angle θ1 or the second coordinate transformation angle θ2.

[0073] Specifically, 6ms after entering the low voltage ride-through control mode, when the grid voltage drops symmetrically, the initial reactive current positive sequence given value is compensated to obtain the target reactive current positive sequence given value, and the target reactive current negative sequence given value is the initial reactive current negative sequence given value; if 10% ≤ d ave <90%, then the target coordinate transformation angle is determined by comparing the transformation angle difference with the preset value; or if d ave <10%, the target coordinate transformation angle is the second coordinate transformation angle;

[0074] 6ms after entering the low voltage ride-through control mode, when the grid voltage drops asymmetrically, the initial reactive current positive sequence given value is compensated to obtain the target reactive current positive sequence given value; the initial reactive current negative sequence given value is compensated to obtain the target reactive current negative sequence given value; the target coordinate transformation angle is determined by comparing the transformation angle difference with the preset value.

[0075] In this application, during symmetrical sags, reactive power output is adjusted by the positive-sequence current setpoint to support the grid voltage. During asymmetrical sags, in addition to adjusting the positive-sequence current, negative-sequence current control is also required to suppress unbalanced currents and ensure three-phase current balance.

[0076] This application evaluates different grid voltage drop conditions, determines the target coordinate transformation angle, and the target reactive current positive and negative sequence component given values, thereby achieving precise control of the grid voltage and current and ensuring stable operation of the system under low voltage conditions.

[0077] In one possible embodiment, the target coordinate transformation angle is determined based on a comparison between the transformation angle difference and a preset value, including: if the transformation angle difference is greater than or equal to the preset value, the target coordinate transformation angle is the second coordinate transformation angle; or if the transformation angle difference is less than the preset value, the target transformation angle is the first coordinate transformation angle.

[0078] For example, if Δθ≥0.25, then θ=θ2; if Δθ<0.25, then θ=θ1.

[0079] During low-voltage ride-through (LVRT), the appropriate coordinate transformation angle is selected by determining the value of Δθ to ensure stable system operation during voltage dips. The selection of the coordinate transformation angle plays a key role in LVRT control, directly affecting the accuracy of extracting the positive and negative sequence components of the grid voltage and the implementation of the LVRT control strategy. During LVRT control, a suitable coordinate transformation angle minimizes overcurrent and overvoltage. Proper selection and dynamic adjustment of the coordinate transformation angle are key to ensuring stable system operation.

[0080] The target coordinate transformation angle and the selection of the target reactive current positive sequence and negative sequence component given values ​​are shown in Table 1.

[0081] Table 1. Selection table of target coordinate transformation angle and target reactive current positive sequence and negative sequence component given values

[0082]

[0083] Among them, I in Table 1 0+ , I 0- is the initial value of the given value of the positive and negative sequence components of reactive current, I N , K1, K2 + 、K2 - is the calibration value. ave <10%, U 负ave <10%*E n When , it means that the grid voltage drops seriously at this time, and the coordinate transformation angle (i.e., the second coordinate transformation angle) calculated by the phase-locked loop method based on the BC phase line voltage zero-crossing point detection should be used to perform reactive compensation on the grid voltage.

[0084] Figure 3 A schematic diagram of the structure of the low voltage ride-through control algorithm provided in the embodiment of the present application is shown as follows: Figure 3 As shown, according to the grid voltage u abc The coordinate transformation angles are calculated using a second-order generalized integrator phase-locked loop method and a BC phase line voltage zero-crossing point detection phase-locked loop method, respectively, to obtain a first coordinate transformation angle θ1 and a second coordinate transformation angle θ2. According to the method shown in the above embodiment, the transformation angle difference is calculated and the grid voltage drop is determined. The target coordinate transformation angle (θ1 or θ2) is determined based on the grid voltage drop and the transformation angle difference. The voltage and current positive and negative sequence separation is performed based on the target coordinate transformation angle (θ1 or θ2), and the target reactive current positive and negative sequence component set values ​​are determined. The grid voltage is then adjusted through a PI controller, a coordinate transformation module dq / abc, and a PWM wave generation module to meet the low voltage ride-through requirements under different grid voltage drop conditions, thereby improving the low voltage ride-through capability and system stability of the energy storage converter.

[0085] Optionally, during low voltage ride-through (LVRT), the system dynamically adjusts reactive power output through current loop control to maintain grid voltage stability. Once the voltage recovers, the system exits LVRT mode and switches back to dual-loop control: the outer power loop regulates active power, while the inner current loop regulates current, ensuring high efficiency and stability during normal operation.

[0086] The method provided in this application comprehensively utilizes the advantages of two phase-locked loops: a phase-locked loop based on a second-order generalized integrator and a phase-locked loop based on BC phase line voltage zero-crossing point detection. In the low voltage ride-through interval, a single current loop control is adopted, and the target coordinate transformation angle, the given values ​​of the positive and negative sequence components of the reactive current are determined according to the angle difference of the two phase-locked loops and the voltage drop, and reactive current control is performed. This method can meet the low voltage ride-through requirements under different grid voltage drop conditions. Even if the grid voltage drops completely to zero, it can successfully achieve the low voltage ride-through function and output the required reactive current, thereby improving the low voltage ride-through capability and system stability of the energy storage converter. At the same time, it can also reduce the impact current during the grid voltage mutation process and improve the reactive power control accuracy during the low voltage ride-through period.

[0087] The following combination Figure 4 The exemplary energy storage converter provided in the embodiments of the present application is further introduced. Figure 4 FIG. 4 shows a structural diagram of an energy storage converter 4000 .

[0088] The energy storage converter 4000 may include: at least one processor; and at least one memory in communication with the processor, wherein: the memory stores program instructions that can be executed by the processor, and the processor calls the program instructions to execute the low voltage ride-through control method for the energy storage converter provided in the embodiment shown in this application. The memory is used to store the programs and data required for the operation of the processor; the processor is one of the core components of the energy storage converter, used to perform various control and management tasks, such as charge and discharge control, power regulation, grid synchronization and other functions; it can also process data from sensors (such as voltage, current, temperature sensors) to perform rapid calculations and decisions; interact with external devices (such as battery management systems, grid monitoring systems, energy management systems) for data; monitor system status, detect and handle faults in a timely manner, and ensure safe operation of the equipment. In this application, the processor in the energy storage converter is mainly used to execute the low voltage ride-through control method for the energy storage converter in the above embodiment.

[0089] Figure 4 A block diagram of an exemplary energy storage converter 4000 suitable for implementing the embodiments of the present application is shown. Figure 4 The energy storage converter 4000 shown is merely an example and should not limit the functions and scope of use of the embodiments of the present application.

[0090] like Figure 4 As shown, the energy storage converter 4000 is implemented as a general-purpose computing device. Components of the energy storage converter 4000 may include, but are not limited to, one or more processors 4010, a memory 4020, a communication bus 4040 connecting various system components (including the memory 4020 and the processor 4010), and a communication interface 4030.

[0091] Communication bus 4040 represents one or more of several types of bus structures, including a memory bus or memory controller, a peripheral bus, an accelerated graphics port, a processor, or a local bus using any of a variety of bus architectures. Examples of these architectures include, but are not limited to, the Industry Standard Architecture (ISA) bus, the Micro Channel Architecture (MAC) bus, the Enhanced ISA bus, the Video Electronics Standards Association (VESA) local bus, and the Peripheral Component Interconnection (PCI) bus.

[0092] The memory 4020 may include computer system readable media in the form of volatile memory, such as random access memory (RAM) and / or cache memory. The energy storage converter may further include other removable / non-removable, volatile / non-volatile computer system storage media. Figure 4 Not shown, a disk drive for reading and writing to a removable non-volatile disk (e.g., a "floppy disk"), and an optical disk drive for reading and writing to a removable non-volatile optical disk (e.g., a Compact Disc Read Only Memory (hereinafter referred to as: CD-ROM), a Digital Video Disc Read Only Memory (hereinafter referred to as: DVD-ROM), or other optical media) may be provided. In these cases, each drive can be connected to the communication bus 4040 via one or more data medium interfaces. The memory 4020 may include at least one program product having a set (e.g., at least one) of program modules that are configured to perform the functions of the various embodiments of the present application.

[0093] A program / utility having a set (at least one) of program modules may be stored in memory 4020. Such program modules include, but are not limited to, an operating system, one or more application programs, other program modules, and program data, each of which, or some combination thereof, may include an implementation of a network environment. The program modules generally implement the functions and / or methods of the embodiments described herein.

[0094] The energy storage converter 4000 may also communicate with one or more external devices (e.g., a battery management system (BMS), an energy management system (EMS), etc.), one or more devices that allow a user to interact with the energy storage converter, and / or any device that allows the energy storage converter to communicate with one or more other computing devices (e.g., a network card, a modem, etc.). Such communication may be performed via the communication interface 4030. In addition, the energy storage converter 4000 may also communicate via a network adapter ( Figure 4 The network adapter can communicate with one or more networks (e.g., a local area network (LAN), a wide area network (WAN), and / or a public network, such as the Internet) via the communication bus 4040. Figure 4 Not shown, other hardware and / or software modules may be used in conjunction with the energy storage converter 4000, including but not limited to: microcode, device drivers, redundant processing units, external disk drive arrays, disk arrays (Redundant Arrays of Independent Drives; hereinafter referred to as: RAID) systems, tape drives, and data backup storage systems.

[0095] The processor 4010 executes various functional applications and data processing by running the programs stored in the memory 4020, such as implementing the method provided in the embodiment of the present application.

[0096] It is understood that the interface connection relationship between the modules illustrated in the embodiments of the present application is merely illustrative and does not constitute a structural limitation on the energy storage converter 4000. In other embodiments of the present application, the energy storage converter 4000 may also adopt a different interface connection method from the above embodiments, or a combination of multiple interface connection methods.

[0097] In each of the above embodiments, the processor involved may include, for example, a CPU (Central Processing Unit), a DSP (Digital Signal Processor), a microcontroller, and may also include a GPU (Graphics Processing Unit), an embedded neural network processor (Neural-network Process Units; hereinafter referred to as: NPU) and an image signal processor (Image Signal Processing; hereinafter referred to as: ISP). The processor may also include necessary hardware accelerators or logic processing hardware circuits, such as ASICs (Application-Specific Integrated Circuits, application-specific integrated circuits), or one or more integrated circuits for controlling the execution of the program of the technical solution of this application. In addition, the processor may have the function of operating one or more software programs, and the software programs may be stored in a storage medium.

[0098] Those skilled in the art will appreciate that the various units and algorithm steps described in the embodiments disclosed herein can be implemented using a combination of electronic hardware, computer software, and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0099] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0100] In the several embodiments provided in this application, if any function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of each embodiment of this application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (Read-Only Memory; hereinafter referred to as: ROM), random access memory (Random Access Memory; hereinafter referred to as: RAM), disk or optical disk, and other media that can store program codes.

[0101] The above are only specific embodiments of the present application. Any person skilled in the art can easily conceive of changes or substitutions within the technical scope disclosed in this application, and all such changes or substitutions should be included in the scope of protection of this application. The scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A low voltage ride-through control method for an energy storage converter, characterized in that: The method comprises: Obtain the three-phase line voltage of the power grid; Based on the three-phase line voltage, a coordinate transformation angle is calculated using a phase-locked loop method of a second-order generalized integrator to obtain a first coordinate transformation angle; Based on the three-phase line voltage, a coordinate transformation angle is calculated using a phase-locked loop method for detecting the zero crossing point of the BC phase line voltage to obtain a second coordinate transformation angle; the coordinate transformation angle is a transformation angle from a three-phase stationary coordinate system to a two-phase rotating coordinate system or from a two-phase rotating coordinate system to a three-phase stationary coordinate system; the first coordinate transformation angle and the second coordinate transformation angle are integrated within a range of 0 to 2π; Calculating an absolute value of a difference between the first coordinate transformation angle and the second coordinate transformation angle to obtain a transformation angle difference; A target coordinate transformation angle is determined according to a grid voltage drop condition and the transformation angle difference, and the target coordinate transformation angle is the first coordinate transformation angle or the second coordinate transformation angle.

2. The low voltage ride-through control method for an energy storage converter according to claim 1, characterized in that: The method further comprises: Performing Clark transformation on the three-phase line voltage to obtain voltages Uα and Uβ in a two-phase stationary coordinate system; Extracting positive sequence components of the voltages Uα and Uβ using a second-order generalized integrator to obtain positive sequence components Uα+ and Uβ+; Performing a two-phase rotation transformation on the positive sequence components Uα+ and Uβ+ to obtain positive sequence components Ud+ and Uq+ in a rotating coordinate system; Get the rated voltage of the power grid; Calculate the voltage positive sequence component percentage d based on the positive sequence components Ud+ and Uq+ and the rated voltage of the power grid; Entering or exiting the low voltage ride through control mode is determined according to the voltage positive sequence component percentage d.

3. The low voltage ride-through control method for an energy storage converter according to claim 2, characterized in that: The method further comprises: When entering the low voltage ride-through control mode, current loop control is performed; When exiting the low voltage ride-through control mode, dual-loop control of the power outer loop and the current inner loop is performed.

4. The low voltage ride-through control method for an energy storage converter according to claim 2, characterized in that: Determining whether to enter or exit the low voltage ride-through control mode according to the voltage positive sequence component percentage d includes: When d is less than 90% and lasts longer than 2ms, it enters the low voltage ride-through control mode; or When d is greater than 92% and lasts longer than 2ms, the low voltage ride-through control mode is exited.

5. The low voltage ride-through control method for an energy storage converter according to claim 1, characterized in that: Integrating the first coordinate transformation angle and the second coordinate transformation angle into a range from 0 to 2π includes: If the first coordinate transformation angle or the second coordinate transformation angle exceeds the range of 0 to 2π, the first coordinate transformation angle or the second coordinate transformation angle is adjusted by adding or subtracting multiples of 2π.

6. The low voltage ride-through control method for an energy storage converter according to claim 2, characterized in that: Based on the three-phase line voltage, a coordinate transformation angle is calculated using a phase-locked loop method of a second-order generalized integrator to obtain a first coordinate transformation angle, including: PI regulation and integration operation are performed on the positive sequence component Uq+ to obtain the first coordinate transformation angle.

7. The low voltage ride-through control method for an energy storage converter according to claim 2, characterized in that: Based on the three-phase line voltage, a coordinate transformation angle is calculated using a phase-locked loop method for detecting the zero-crossing point of the BC phase line voltage to obtain a second coordinate transformation angle, including: The start counter starts counting and increases by 1 in each control cycle; Convert the BC phase line voltage zero-crossing point signal from negative to positive into a rising edge signal; When the low voltage ride-through control mode is not entered, triggering a controller software interrupt in response to the rising edge signal, and performing grid frequency update and counter clearing; When entering the low voltage ride-through control mode, the grid frequency update is stopped, and the counter continues counting until the low voltage ride-through control mode is exited, and then the response to the rising edge signal is resumed to update the grid frequency and clear the counter; Obtain the last updated grid frequency before entering the low voltage ride-through control mode, the counter value during the process of entering the low voltage ride-through control mode, and the carrier frequency; The second coordinate transformation angle is calculated according to the last updated grid frequency, the count value of the counter, and the carrier frequency.

8. The low voltage ride-through control method for an energy storage converter according to claim 2, characterized in that: The grid voltage drop condition includes a symmetrical drop and an asymmetrical drop, and determining the target coordinate transformation angle according to the grid voltage drop condition and the transformation angle difference includes: When entering the low voltage ride-through control mode, start timing, and after 5ms, calculate the sliding average value of the voltage positive sequence component percentage d within 1ms to obtain d ave ; After 6ms, when the grid voltage drops symmetrically, if 10%≤d ave <90%, then the target coordinate transformation angle is determined based on the comparison between the transformation angle difference and the preset value; if d ave <10%, the target coordinate transformation angle is the second coordinate transformation angle; or After 6 ms, when the grid voltage drops asymmetrically, the target coordinate transformation angle is determined based on a comparison between the transformation angle difference and a preset value.

9. The low voltage ride-through control method for an energy storage converter according to claim 8, characterized in that: Determining the target coordinate transformation angle according to the comparison between the transformation angle difference and a preset value includes: If the transformation angle difference is greater than or equal to the preset value, the target coordinate transformation angle is the second coordinate transformation angle; or If the transformation angle difference is less than the preset value, the target transformation angle is the first coordinate transformation angle.

10. An energy storage converter, characterized in that: include: A processor and a memory, the memory being used to store a computer program; the processor being used to run the computer program to implement the low voltage ride-through control method for an energy storage converter as described in any one of claims 1 to 9.

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