Current balance control method, device, equipment and storage medium under unbalanced power grid

Abstract

The present invention provides a current balance control method and device, equipment, and storage medium under an unbalanced power grid, which belongs to the field of power electronics technology. The method includes: coordinate transformation of the three-phase voltage of a three-phase energy storage converter to obtain a d-axis voltage component and a q-axis voltage component; filtering the d-axis voltage component and the q-axis voltage component respectively to obtain a d-axis voltage positive sequence component and a q-axis voltage positive sequence component; obtaining a d-axis voltage negative sequence component based on the d-axis voltage component and the d-axis voltage positive sequence component, and obtaining a q-axis voltage negative sequence component based on the q-axis voltage component and the q-axis voltage positive sequence component; inputting the d-axis voltage positive sequence component, the d-axis voltage negative sequence component, the q-axis voltage positive sequence component, and the q-axis voltage negative sequence component as feedforward components into the output end of the current regulator to obtain a converter drive signal to control the current of the three-phase energy storage converter. The present invention can realize the balanced control and harmonic suppression of the grid-connected current of the three-phase energy storage converter under an unbalanced power grid.

Description

Technical Field

[0001] The present disclosure belongs to the field of power electronics technology, and more specifically, relates to a current balance control method and device, equipment, and storage medium under an unbalanced power grid. Background Art

[0002] The three-phase energy storage converter can convert the AC power of the power grid into DC power to charge the energy storage equipment (such as battery packs, etc.). During the low load period of the power grid, the excess electric energy can be stored to play the role of peak load reduction and valley filling, thus improving the stability and efficiency of the power grid operation.

[0003] Conventional current control methods for three-phase energy storage converters are as follows: Figure 1 As shown in the figure, it consists of two parts: voltage coordinate transformation and phase locking, and current coordinate transformation and grid connection control. In the voltage coordinate transformation and phase locking part, the sampled three-phase line voltage is first converted to and The stationary coordinate system (hereinafter referred to as coordinate system) and , and then the synchronous rotating coordinate system (hereinafter referred to as coordinate system) and , and finally get the phase information through the phase-locked loop and In the current coordinate transformation and grid-connected control part, the battery voltage is first Perform closed-loop control to obtain the grid-connected current active reference value , at the same time, the three-phase current , and The same coordinate transformation steps as the grid voltage are used to obtain Coordinate system components and Furthermore, and Closed-loop control is performed separately and feedforward is performed at the output of each closed-loop regulator. and ,get Modulation signal in coordinate system and Furthermore, The modulation signal of the coordinate system is transformed into the inverse coordinate system to obtain the modulation signal in the abc coordinate system , and , the converter drive signal is obtained through discontinuous pulse width modulation (DPWM). However, when the grid voltage is unbalanced, Grid voltage components in the coordinate system and will no longer have the same magnitude, resulting in Grid voltage components on the coordinate system and There is double frequency pulsation, which ultimately affects the performance of the phase-locked loop and the quality of the grid-connected current. Summary of the invention

[0004] The purpose of the present disclosure is to provide a current balancing control method and device, equipment, and storage medium under an unbalanced power grid, so as to achieve balanced control and harmonic suppression of the grid-connected current of a three-phase energy storage converter under an unbalanced harmonic power grid.

[0005] According to a first aspect of an embodiment of the present disclosure, a current balancing control method in an unbalanced power grid is provided, comprising:

[0006] Performing coordinate transformation on the three-phase voltage of the three-phase energy storage converter to obtain a d-axis voltage component and a q-axis voltage component;

[0007] The d-axis voltage component and the q-axis voltage component are filtered respectively to obtain the d-axis voltage positive sequence component and the q-axis voltage positive sequence component;

[0008] The d-axis voltage negative sequence component is obtained based on the d-axis voltage component and the d-axis voltage positive sequence component, and the q-axis voltage negative sequence component is obtained based on the q-axis voltage component and the q-axis voltage positive sequence component;

[0009] The d-axis voltage positive sequence component, the d-axis voltage negative sequence component, the q-axis voltage positive sequence component, and the q-axis voltage negative sequence component are input as feedforward components to the output end of the current regulator to obtain a converter drive signal to perform current control on the three-phase energy storage converter.

[0010] A second aspect of the embodiments of the present disclosure provides a current balancing control device in an unbalanced power grid, comprising:

[0011] A coordinate transformation module is used to perform coordinate transformation on the three-phase voltage of the three-phase energy storage converter to obtain a d-axis voltage component and a q-axis voltage component;

[0012] A voltage positive sequence component determination module is used to filter the d-axis voltage component and the q-axis voltage component respectively to obtain the d-axis voltage positive sequence component and the q-axis voltage positive sequence component;

[0013] A voltage negative sequence component determination module, used to obtain a d-axis voltage negative sequence component based on a d-axis voltage component and a d-axis voltage positive sequence component, and to obtain a q-axis voltage negative sequence component based on a q-axis voltage component and a q-axis voltage positive sequence component;

[0014] The current control module is used to input the d-axis voltage positive sequence component, the d-axis voltage negative sequence component, the q-axis voltage positive sequence component, and the q-axis voltage negative sequence component as feedforward components into the output end of the current regulator to obtain a converter drive signal to perform current control on the three-phase energy storage converter.

[0015] According to a third aspect of an embodiment of the present disclosure, an electronic device is provided, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, wherein the processor implements the steps of the above-mentioned current balancing control method under an unbalanced power grid when executing the computer program.

[0016] According to a fourth aspect of an embodiment of the present disclosure, a computer-readable storage medium is provided, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the current balancing control method under an unbalanced power grid are implemented.

[0017] The beneficial effects of the current balance control method, device, equipment, and storage medium under an unbalanced power grid provided by the embodiments of the present disclosure are:

[0018] The embodiment of the present disclosure takes into account that the negative sequence current generated by the unbalanced grid voltage will increase the output current amplitude of the energy storage converter, thereby affecting the operation safety of the energy storage converter. Therefore, by calculating the positive sequence component and the negative sequence component of the three-phase voltage, and adding the positive sequence component and the negative sequence component of the three-phase voltage to the output end of the current regulator, the control signal of the current regulator is corrected so that it can better adapt to the situation of unbalanced grid voltage.

[0019] Among them, the coordinate transformation technology effectively decomposes the three-phase voltage into d-axis and q-axis components, simplifying the complex three-phase system analysis; secondly, the present disclosure obtains the positive sequence component of the voltage through filtering processing, which not only removes the harmonic interference, but also improves the purity of the signal; furthermore, the negative sequence component is calculated based on the positive sequence component, which realizes the accurate identification and compensation of the voltage imbalance, and enhances the stable operation ability of the device under unbalanced conditions; finally, the present disclosure can effectively improve the adaptability and reliability of the three-phase energy storage converter under unbalanced power grid through the current control method based on the feedforward component, ensure that the device can operate continuously and stably, and provide high-quality electric energy to the power grid. Therefore, the present disclosure realizes the balanced control and harmonic suppression of the grid-connected current of the three-phase energy storage converter under the unbalanced harmonic power grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 A conventional current control block diagram of a three-phase energy storage converter provided in an embodiment of the present disclosure;

[0022] Figure 2 A flow chart of a current balancing control method in an unbalanced power grid provided by an embodiment of the present disclosure;

[0023] Figure 3 A flowchart of a digital filter according to an embodiment of the present invention;

[0024] Figure 4 An equivalent Bode diagram of a digital filter provided by an embodiment of the present disclosure;

[0025] Figure 5 A control block diagram of a current balancing control method under an unbalanced power grid provided by an embodiment of the present disclosure;

[0026] Figure 6 A structural block diagram of a current balancing control device in an unbalanced power grid provided by an embodiment of the present disclosure;

[0027] Figure 7 A schematic block diagram of an electronic device provided by an embodiment of the present disclosure. DETAILED DESCRIPTION

[0028] In the following description, specific details such as specific system structures and technologies are provided for the purpose of illustration rather than limitation, so as to provide a thorough understanding of the embodiments of the present disclosure. However, it should be clear to those skilled in the art that the present disclosure may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid obstructing the description of the present disclosure with unnecessary details.

[0029] In order to make the purpose, technical solutions and advantages of the present disclosure more clear, specific embodiments will be described below in conjunction with the accompanying drawings.

[0030] Please refer to Figure 2 , Figure 2 A flow chart of a current balancing control method under an unbalanced power grid provided in an embodiment of the present disclosure, the method comprising:

[0031] S101: performing coordinate transformation on the three-phase voltage of the three-phase energy storage converter to obtain a d-axis voltage component and a q-axis voltage component.

[0032] In this embodiment, the commonly used coordinate transformations in the three-phase power system are Clark transformation and Park transformation. Clark transformation is to transform the three-phase stationary coordinate system (abc coordinate system) into a two-phase stationary coordinate system ( Coordinate system), while Park transformation is based on Clark transformation, which transforms the two-phase stationary coordinate system ( coordinate system) is further transformed into a two-phase rotating coordinate system ( coordinate system).

[0033] For example, firstly, the sampled three-phase line voltage and The stationary coordinate system (hereinafter referred to as coordinate system) and , and then the synchronous rotating coordinate system (hereinafter referred to as coordinate system) and ,Right now represents the d-axis voltage component, represents the q-axis voltage component.

[0034] For the three-phase voltage of the three-phase energy storage converter, through coordinate transformation (i.e. Clark transformation and Park transformation), the three-phase voltage of the three-phase energy storage converter can be obtained. The d-axis voltage component and the q-axis voltage component in the coordinate system.

[0035] In the control of three-phase energy storage converter, the adjustment of d-axis voltage can control the size of active power, and the adjustment of q-axis voltage component can control the size of reactive power. By reasonably controlling the d-axis voltage component and the q-axis voltage component, better current balance control of the three-phase energy storage converter can be achieved under unbalanced power grid.

[0036] S102: filtering the d-axis voltage component and the q-axis voltage component respectively to obtain a d-axis voltage positive-sequence component and a q-axis voltage positive-sequence component.

[0037] In an unbalanced power grid, the three-phase voltage contains positive-sequence, negative-sequence and zero-sequence components, and the d-axis voltage component and the q-axis voltage component obtained after coordinate transformation also contain the above-mentioned phase sequence components.

[0038] The main purpose of the filtering operation is to extract the positive sequence component from the d-axis voltage component and the q-axis voltage component containing multiple phase sequence components, thereby obtaining the d-axis voltage positive sequence component and the q-axis voltage positive sequence component. Therefore, the above steps can reduce the interference of the negative sequence and zero sequence components on the subsequent control process, so that the energy storage converter can work better under an unbalanced power grid.

[0039] Specifically, this embodiment can use a digital filter to perform filtering operations, that is, according to the digital filter and Processing to obtain positive sequence component and ,in, represents the positive sequence component of the d-axis voltage, Represents the positive sequence component of the q-axis voltage.

[0040] In a three-phase system, positive-sequence voltage and positive-sequence current are the main factors that generate active power and reactive power. For the case where a three-phase energy storage converter transmits power to the grid, only accurate control based on the positive-sequence component can ensure stable transmission and reasonable distribution of power. For example, in the control of a grid-connected inverter, adjusting the output of the inverter according to the positive-sequence component can achieve precise control of active power and reactive power, thereby meeting the needs of the grid and the functional requirements of the energy storage system.

[0041] The stability of the positive sequence component is of great significance to the stability of the entire power system. In an unbalanced power grid, if the positive sequence component cannot be effectively extracted and utilized, the three-phase energy storage converter is easily disturbed by the negative sequence and zero sequence components, resulting in problems such as output current imbalance and voltage fluctuation, which will further affect the stability of the power grid, such as causing grid voltage drop and harmonic increase. This embodiment can provide a stable reference signal for subsequent current balance control by obtaining the positive sequence component of the d-axis voltage and the positive sequence component of the q-axis voltage, which helps to maintain the stable operation of the system.

[0042] S103: obtaining a d-axis voltage negative-sequence component based on the d-axis voltage component and the d-axis voltage positive-sequence component, and obtaining a q-axis voltage negative-sequence component based on the q-axis voltage component and the q-axis voltage positive-sequence component.

[0043] In this embodiment, the voltage (or current) can be decomposed into positive sequence, negative sequence and zero sequence components. The positive sequence component is a symmetrical component with equal amplitude, 120° phase difference and phase sequence ABC in three phases. The positive sequence component is the main component of the normal operation of the three-phase balanced system; the negative sequence component is a symmetrical component with equal amplitude, 120° phase difference and phase sequence ACB in three phases. The existence of the negative sequence component is usually caused by three-phase imbalance (such as asymmetric three-phase load, power grid fault, etc.); the zero sequence component is a component with equal magnitude and the same phase in three phases.

[0044] For the obtained d-axis voltage component and q-axis voltage component (including positive-sequence, negative-sequence and other components) and the extracted d-axis voltage positive-sequence component and q-axis voltage positive-sequence component, the negative-sequence component can be separated through certain calculations.

[0045] For example, the negative sequence component of the d-axis voltage can be calculated by the third formula:

[0046]

[0047] in, represents the d-axis voltage component, represents the positive sequence component of the d-axis voltage, Represents the negative sequence component of the d-axis voltage.

[0048] Similarly, the negative sequence component of the q-axis voltage can be calculated using the fourth formula:

[0049]

[0050] in, represents the q-axis voltage component, represents the positive sequence component of q voltage, Represents the negative sequence component of the q-axis voltage.

[0051] The principle of the above calculation method is based on the superposition of phase sequence components. Because the d-axis (or q-axis) voltage component is the superposition of the positive-sequence component and the negative-sequence component (and the possible zero-sequence component, the influence of the zero-sequence component on the d-axis and q-axis is not considered in this calculation, because in some cases, such as in a three-phase three-wire system, there is no zero-sequence path), when the total voltage component and the positive-sequence voltage component are known, the negative-sequence voltage component can be obtained by subtraction.

[0052] After obtaining the d-axis voltage negative sequence component and the q-axis voltage negative sequence component in this embodiment, an important basis can be provided for the subsequent current balance control strategy. For example, a corresponding compensation device can be designed or the control parameters of the converter can be adjusted according to the magnitude and phase of the negative sequence component to reduce the impact of the negative sequence component on the system and achieve current balance. Specifically, the negative sequence current in the power grid can be offset by controlling the converter to generate a current opposite to the negative sequence current caused by the negative sequence voltage component, thereby achieving the purpose of current balance.

[0053] S104: inputting the d-axis voltage positive sequence component, d-axis voltage negative sequence component, q-axis voltage positive sequence component, and q-axis voltage negative sequence component as feedforward components to the output end of the current regulator to obtain a converter drive signal to perform current control on the three-phase energy storage converter.

[0054] In this embodiment, feedforward control is a control method based on disturbance compensation. Figure 3In the current balance control method, the d-axis voltage positive sequence component, the d-axis voltage negative sequence component, the q-axis voltage positive sequence component, and the q-axis voltage negative sequence component are input as feedforward components to the output end of the current regulator. The purpose is to compensate in advance for disturbances that may affect the output of the device, thereby improving the response speed and control accuracy of the present invention.

[0055] When a three-phase energy storage converter is operated under an unbalanced power grid, the unbalanced power grid voltage will lead to the unbalanced output current of the converter. This embodiment extracts the positive sequence component of the d-axis voltage, the negative sequence component of the d-axis voltage, the positive sequence component of the q-axis voltage, and the negative sequence component of the q-axis voltage, and uses the positive and negative components and the negative sequence component as the feedforward signal of the current regulator, so that the current regulator can estimate and compensate for the voltage disturbance that may cause the current imbalance before receiving the output current feedback signal, so that it can better adapt to the situation of unbalanced power grid voltage.

[0056] For example, the current regulator usually adopts a proportional regulator or a proportional integral differential regulator, and its working principle is to generate a control signal to adjust the working state of the converter based on the difference between the set current reference value and the actual output current through the regulator's calculation, so that the output current is as close to the reference value as possible.

[0057] When the above feedforward component is added, the current regulator will take into account the feedforward signal and the current feedback signal when calculating the control signal. For example, in a proportional regulator, the proportional link can respond quickly to the current error, and the integral link can eliminate the steady-state error. The addition of the feedforward component can adjust the effect of the proportional and integral parameters to a certain extent, so that the regulator can generate control signals more quickly and accurately.

[0058] After a series of processing (such as pulse width modulation, etc.), the output of the current regulator obtains the drive signal of the converter. The drive signal is used to control the on and off time of the power switching device (such as insulated gate bipolar transistor IGBT) in the converter, thereby adjusting the output voltage and current of the converter.

[0059] Under unbalanced power grid, the three-phase energy storage converter can output balanced current by properly adjusting the drive signal. Specifically, the drive signal will be adjusted in real time according to the changes of the feedforward component and the current feedback signal, so that the converter can respond quickly to the imbalance of the grid voltage, suppress the generation of negative sequence current, and achieve the goal of current balance control.

[0060] From the above, it can be concluded that, firstly, the coordinate transformation technology effectively decomposes the three-phase voltage into d-axis and q-axis components, simplifying the complex three-phase system analysis; secondly, the present embodiment obtains the positive sequence component of the voltage through filtering processing, which not only removes the harmonic interference, but also improves the purity of the signal; furthermore, the negative sequence component is calculated based on the positive sequence component, which realizes the accurate identification and compensation of the voltage imbalance, and enhances the stable operation ability of the device under unbalanced conditions; finally, the present embodiment can effectively improve the adaptability and reliability of the three-phase energy storage converter under unbalanced power grid through the current control method based on the feedforward component, ensure that the device can operate continuously and stably, and provide high-quality electric energy to the power grid. Therefore, the present embodiment realizes the balanced control and harmonic suppression of the grid-connected current of the three-phase energy storage converter under the unbalanced harmonic power grid.

[0061] In one embodiment of the present disclosure, filtering the d-axis voltage component and the q-axis voltage component respectively to obtain the d-axis voltage positive sequence component and the q-axis voltage positive sequence component includes:

[0062] Determining a first delay time based on a power grid cycle;

[0063] Delay processing is performed on the d-axis voltage component and the q-axis voltage component based on the first delay time to obtain a d-axis delayed voltage component and a q-axis delayed voltage component;

[0064] Filtering the d-axis voltage component based on the d-axis delayed voltage component to obtain the d-axis voltage positive sequence component;

[0065] The q-axis voltage component is filtered based on the q-axis delayed voltage component to obtain the q-axis voltage positive sequence component.

[0066] In this embodiment, for signals of specific frequencies in the d-axis voltage component, by delaying the d-axis voltage component, a signal component (i.e., a d-axis delayed voltage component) having a phase opposite or nearly opposite to that of the original d-axis voltage component can be obtained. Therefore, by subtracting the d-axis voltage component from the d-axis delayed voltage component, the signal amplitudes of these frequencies can be reduced or even offset, thereby filtering out some unnecessary frequency components and obtaining a d-axis voltage positive-sequence component that does not contain harmonics.

[0067] Similarly, the same method can be used to filter the q-axis voltage component to obtain the q-axis voltage positive sequence component.

[0068] The delay processing time (i.e., the first delay time) can be determined by calculating a certain proportion of the power grid cycle. The selection of this proportion depends on the specific control algorithm and system requirements. For example, a power grid cycle can be selected as the first delay time, which can ensure the accuracy and timeliness of the positive sequence component extraction to a certain extent.

[0069] It can be concluded from the above that this embodiment can effectively extract the positive sequence component from the d-axis voltage component and the q-axis voltage component containing unbalanced components by determining the first delay time, performing delay processing and filtering operations. This is crucial for the current balance control of the three-phase energy storage converter under an unbalanced power grid. The positive sequence voltage component is a key factor in achieving stable power transmission and control. Only by accurately extracting the positive sequence component and using it in subsequent control links such as the current regulator can the converter output a balanced current.

[0070] In one embodiment of the present disclosure, delay processing is performed on the d-axis voltage component and the q-axis voltage component based on the first delay time to obtain the d-axis delayed voltage component and the q-axis delayed voltage component, including:

[0071] Determine the number of cycles based on the grid cycle and the interruption cycle of the controller in the three-phase energy storage converter ; Number of cycles Used to indicate the number of controller interruption cycles contained in one power grid cycle;

[0072] In each power grid cycle, the execution Data access operation;

[0073] Data access operations include:

[0074] Store the d-axis voltage component in the first array The q-axis voltage component is stored in the first position of the second array. positions; the number of elements in the first array and the second array are both , ;

[0075] The first array The data of the position of the second array is determined as the d-axis delayed voltage component; The data of each position is determined as the q-axis delayed voltage component; among them, ;

[0076] The counter and counter Add 1 to each;

[0077] In the After the data access operation, the counter Initialize to 0 and set the counter Initialize to .

[0078] In this embodiment, the number of cycles It is determined based on the grid cycle and the interruption cycle of the controller in the three-phase energy storage converter, and represents the number of controller interruption cycles contained in one grid cycle.

[0079] The controller usually runs with a fixed interruption cycle. By calculating the ratio between the grid cycle and the interruption cycle, the number of interruptions required to be performed within a grid cycle, i.e. the number of cycles, can be determined. For example, if the grid cycle is 20ms, the controller interrupt cycle is ms, then N = 480. This ensures that enough data access operations can be performed within a power grid cycle to achieve accurate delay processing.

[0080] In each power grid cycle, the execution Each data access operation includes storing the current d-axis voltage component and q-axis voltage component in specific locations of the first array and the second array (i.e., the first locations).

[0081] The number of elements in the first and second arrays is , this is to be able to store enough data to achieve delayed processing. The calculation formula for the storage location is , that is, in each interruption cycle, the latest d-axis voltage component is stored in the first array, and the latest q-axis voltage component is stored in the second value. is a counter that increments after each data access operation. This formula ensures that the data is stored in the array in a circular manner.

[0082] At the same time, data is read from the array to determine the d-axis delay voltage component and the q-axis delay voltage component. The calculation formula for the read position is ,in It is also a counter that increments after each data access operation. Position and The data at the positions differ by N data, that is, Position and The time difference between the data at each location is one grid cycle.

[0083] Therefore, "the first array The data of the position of the second array is determined as the d-axis delayed voltage component. The data at each position is determined as the q-axis delayed voltage component” can be understood as: in each interruption cycle, the oldest data is taken from the first array as the d-axis delayed voltage component, and the oldest data is taken from the second array as the q-axis delayed voltage component.

[0084] After each data access operation, the counter and counter Accumulate 1 to record the number of operations and the index position of the array.

[0085] In the After the data access operation, the counter Initialize to 0, the counter Initialize to This is to restart the data access operation at the beginning of the next power grid cycle and ensure that the index position of the array is correct.

[0086] It can be concluded from the above that the present embodiment can continuously update the data in the array in each power grid cycle, and accurately obtain the delayed voltage component according to the value of the counter, so as to provide accurate input data for subsequent filtering operations and current balance control; by utilizing array storage and counter control, the delayed processing of the d-axis voltage component and the q-axis voltage component is realized, which lays the foundation for extracting the positive sequence component and realizing the current balance control.

[0087] In one embodiment of the present disclosure, filtering the d-axis voltage component based on the d-axis delayed voltage component to obtain the d-axis voltage positive sequence component includes:

[0088] The d-axis voltage component is filtered based on the first formula, which is:

[0089]

[0090] in, It represents the intermediate variable used to calculate the positive sequence component of the d-axis voltage obtained during the current controller interruption cycle. represents the intermediate variable used to calculate the positive sequence component of the d-axis voltage obtained in the previous controller interrupt cycle, represents the d-axis voltage component, represents the delayed voltage component corresponding to the d-axis voltage component; represents the positive sequence component of the d-axis voltage, Indicates the interrupt frequency of the controller, Indicates the grid frequency.

[0091] In one embodiment of the present disclosure, filtering the q-axis voltage component based on the q-axis delayed voltage component to obtain the q-axis voltage positive sequence component includes:

[0092] The q-axis voltage component is filtered based on the second formula, which is:

[0093]

[0094] in, It represents the intermediate variable used to calculate the positive sequence component of the q-axis voltage obtained during the current controller interruption cycle. represents the intermediate variable used to calculate the positive sequence component of the q-axis voltage obtained in the previous controller interrupt cycle, represents the q-axis voltage component, represents the delayed voltage component corresponding to the q-axis voltage component; represents the positive sequence component of the q-axis voltage, Indicates the interrupt frequency of the controller, Indicates the grid frequency.

[0095] Specifically, this embodiment filters the d-axis voltage component and the q-axis voltage component based on a digital filter. Figure 3 This is the implementation flow chart of the digital filter. The steps are as follows:

[0096] (1) Define counter and counter And initialize it, the counter The initial value of the counter is 0. The initial value is ;in, ;

[0097] (2) Definitions contain The first array of variables and the second array (in Indicates the main interrupt operation frequency of the digital controller, Represents the grid frequency) and initializes it. The initial values ​​of all variables in the array are 0;

[0098] (3) Transform the grid voltage coordinates ( Transformation) and Store in first array and the second array In the array, store the position number and The remainders are equal;

[0099] (4) The first array and the second array The position number and Take out the variables with the same remainder and assign them to variables and variables ;

[0100] (5) Set the counter and counter Add 1 to each;

[0101] (6) Determine the counter Is it equal to If not, repeat steps (3)-(6) in the next interrupt cycle; if yes, first set the counter Initialize to 0, the counter Initialize to , and then repeat steps (3)-(6) in the next interrupt cycle.

[0102] In addition, in each interrupt cycle, the variables in step (4) are further processed and the variables and variables Assign the values ​​to variables and variables ; and press Figure 3 The first and second formulas shown calculate the variables and variables , and finally let the variable and variables Multiply each by Get the required feedforward component and . Figure 4 It is the equivalent Bode diagram of the digital filter.

[0103] It can be concluded from the above that this embodiment proposes a digital filter to achieve the feedforward component and The fast extraction of and It is fed forward to the output of the dq axis current closed-loop regulator to achieve current balance control of the three-phase grid-connected converter under unbalanced harmonic power grid.

[0104] In one embodiment of the present disclosure, the d-axis voltage positive sequence component, the d-axis voltage negative sequence component, the q-axis voltage positive sequence component, and the q-axis voltage negative sequence component are input as feedforward components to the output end of the current regulator to obtain a converter drive signal, including:

[0105] The d-axis voltage positive sequence component and the d-axis voltage negative sequence component are input as feedforward components to the output end of the d-axis current component regulator to obtain a d-axis modulation signal; the q-axis voltage positive sequence component and the q-axis voltage negative sequence component are input as feedforward components to the output end of the q-axis current component regulator to obtain a q-axis modulation signal; the d-axis current component and the q-axis current component are obtained by performing coordinate transformation on the three-phase current of the three-phase energy storage converter;

[0106] A converter drive signal is obtained based on the d-axis modulation signal and the q-axis modulation signal.

[0107] Figure 5 The control block diagram of the current balance control method under unbalanced power grid includes: voltage coordinate transformation, feedforward component extraction, phase locking part, current coordinate transformation and grid connection control part.

[0108] Voltage coordinate transformation, feedforward component extraction and phase locking, including:

[0109] Sampling three-phase line voltage and Obtaining the static component of three-phase voltage based on Clarke transformation and ;

[0110] For stationary components and Perform Park transformation to obtain On the coordinate system and ;

[0111] According to the digital filter and Processing to obtain the feedforward component and ;

[0112] right Perform phase-locked control to obtain phase information and .

[0113] Current coordinate transformation and grid-connected control part, including:

[0114] Battery voltage Perform closed-loop control to obtain the grid-connected current active reference value ;

[0115] Three-phase current , and Perform Clarke transform and Park transform to obtain Coordinate components and ;

[0116] right and Closed-loop control is performed separately and feedforward is performed at the output of each closed-loop regulator. , , and ,get Modulation signal in coordinate system and ;

[0117] Based on d-axis modulation signal and q-axis modulation signal , the converter drive signal can be obtained through further processing. For example, the two modulation signals can be synthesized to obtain a two-dimensional modulation signal space. Then, according to a specific modulation strategy (such as space vector modulation, etc.), this two-dimensional modulation signal is converted into a drive signal for each power switch device in the converter to adjust the output voltage and current of the converter. For example, in pulse width modulation technology, the modulation signal can be compared with a fixed frequency triangle wave to generate a series of pulse signals to control the switching state of the converter.

[0118] In this embodiment, the d-axis voltage positive sequence component and negative sequence component are input as feedforward components to the output end of the d-axis current component regulator, and the q-axis voltage positive sequence component and negative sequence component are input to the output end of the q-axis current component regulator. The purpose is to allow the current regulator to take into account the voltage imbalance in advance, so as to adjust the output more quickly to achieve current control of the three-phase energy storage converter. For example, when the power grid is unbalanced, the negative sequence component of the voltage will cause current imbalance. By inputting the negative sequence component of the voltage as a feedforward signal into the current regulator, the regulator can take measures to compensate before the current is obviously unbalanced.

[0119] In one embodiment of the present disclosure, obtaining a converter drive signal based on a d-axis modulation signal and a q-axis modulation signal includes:

[0120] Performing inverse coordinate transformation on the d-axis modulation signal and the q-axis modulation signal to obtain a three-phase modulation signal;

[0121] The inverter driving signal is obtained by performing pulse width modulation based on the three-phase modulation signal.

[0122] In this embodiment, if Figure 5 As shown, Modulation signal of the coordinate system and Perform inverse coordinate transformation and get Modulation signal in coordinate system , and ;

[0123] right Modulation signal in coordinate system , and Perform intermittent pulse width modulation to obtain the converter drive signal.

[0124] The reverse coordinate transformation is to convert the modulated signals on the d-axis and q-axis back to the three-phase stationary The process in the coordinate system corresponds to the coordinate transformation from the three-phase stationary coordinate system to the coordinate system. ) and Park transformation (from the two-phase stationary coordinate system The transformation to the three-phase stationary coordinate system abc) is applied sequentially in order to obtain a three-phase modulation signal for control in a three-phase system.

[0125] Pulse Width Modulation (PWM) based on three-phase modulation signals is a key step in generating converter drive signals. PWM technology controls the on and off time of power switching devices in the converter by converting continuous analog signals into a series of discrete pulse signals.

[0126] In each control cycle, the action time of each basic voltage vector is calculated according to the size and phase of the three-phase modulation signal, and the corresponding pulse signal is generated as the converter drive signal. These drive signals control the on and off of the power switch devices in the converter, thereby adjusting the output voltage and current of the converter to track the given three-phase modulation signal.

[0127] It can be concluded from the above that this embodiment can achieve accurate control of the converter output, improve the efficiency and dynamic performance of the present disclosure. At the same time, by reasonably adjusting the PWM strategy, the harmonic content can be reduced and balanced current control can be achieved.

[0128] In an unbalanced power grid without harmonics, the method based on positive and negative sequence decomposition and feedforward can generate orthogonal positive sequence components with equal amplitudes, in which case the grid-connected current of the energy storage converter is balanced. However, when the unbalanced power grid contains a large number of harmonics, the method based on positive and negative sequence decomposition and feedforward can no longer obtain orthogonal positive sequence components with equal amplitudes, in which case the grid-connected current will be seriously unbalanced and have waveform distortion. However, after adopting the technical solution of the present disclosure, regardless of whether the unbalanced power grid contains harmonics, the positive sequence components used for closed-loop regulation of the grid-connected current are always orthogonal and have equal amplitudes, which can ensure that the grid-connected current of the energy storage converter is always balanced. At the same time, all harmonic components are extracted to the negative sequence components, and by subtracting the negative sequence components from the output signal of the current regulator, the harmonic suppression of the grid-connected current in the unbalanced harmonic power grid can be further achieved. Therefore, the present disclosure realizes the balanced control and harmonic suppression of the grid-connected current of the three-phase energy storage converter in the unbalanced harmonic power grid.

[0129] From the above, it can be concluded that the three-phase current is converted from the three-phase stationary coordinate system to the two-phase synchronous rotating coordinate system ( coordinate system), current control can be performed more conveniently. In the coordinate system, the d-axis current is mainly related to the active power, and the q-axis current is mainly related to the reactive power. By controlling the d-axis and q-axis currents respectively, the active power and reactive power output by the converter can be independently adjusted. The above-mentioned drive signal determines the magnitude and phase of the output voltage and current of the converter, thereby realizing precise control of the three-phase energy storage converter. By reasonably adjusting the modulation signal, the converter can output a balanced current under an unbalanced power grid, thereby improving the stability and reliability of the present disclosure.

[0130] Corresponding to the current balancing control method under the unbalanced power grid in the above embodiment, Figure 6 This is a structural block diagram of a current balancing control device for an unbalanced power grid provided by an embodiment of the present disclosure. For ease of explanation, only the parts related to the embodiment of the present disclosure are shown. Figure 6 The current balance control device 20 under unbalanced power grid includes: a coordinate transformation module 21, a voltage positive sequence component determination module 22, a voltage negative sequence component determination module 23 and a current control module 24.

[0131] The coordinate transformation module 21 is used to perform coordinate transformation on the three-phase voltage of the three-phase energy storage converter to obtain a d-axis voltage component and a q-axis voltage component;

[0132] A voltage positive sequence component determination module 22 is used to filter the d-axis voltage component and the q-axis voltage component respectively to obtain a d-axis voltage positive sequence component and a q-axis voltage positive sequence component;

[0133] A voltage negative sequence component determination module 23, configured to obtain a d-axis voltage negative sequence component based on a d-axis voltage component and a d-axis voltage positive sequence component, and to obtain a q-axis voltage negative sequence component based on a q-axis voltage component and a q-axis voltage positive sequence component;

[0134] The current control module 24 is used to input the d-axis voltage positive sequence component, d-axis voltage negative sequence component, q-axis voltage positive sequence component, and q-axis voltage negative sequence component as feedforward components into the output end of the current regulator to obtain a converter drive signal to perform current control on the three-phase energy storage converter.

[0135] In one embodiment of the present disclosure, the voltage negative sequence component determination module 23 is further configured to:

[0136] Determining a first delay time based on a power grid cycle;

[0137] Delay processing is performed on the d-axis voltage component and the q-axis voltage component based on the first delay time to obtain a d-axis delayed voltage component and a q-axis delayed voltage component;

[0138] Filtering the d-axis voltage component based on the d-axis delayed voltage component to obtain the d-axis voltage positive sequence component;

[0139] The q-axis voltage component is filtered based on the q-axis delayed voltage component to obtain the q-axis voltage positive sequence component.

[0140] In one embodiment of the present disclosure, the voltage negative sequence component determination module 23 is further configured to:

[0141] Determine the number of cycles based on the grid cycle and the interruption cycle of the controller in the three-phase energy storage converter ; Number of cycles Used to indicate the number of controller interruption cycles contained in one power grid cycle;

[0142] In each power grid cycle, the execution Data access operation;

[0143] Data access operations include:

[0144] Store the d-axis voltage component in the first array The q-axis voltage component is stored in the first position of the second array. positions; the number of elements in the first array and the second array are both , ;

[0145] The first array The data of the position of the second array is determined as the d-axis delayed voltage component; The data of each position is determined as the q-axis delayed voltage component; among them, ;

[0146] The counter and counter Add 1 to each;

[0147] In the After the data access operation, the counter Initialize to 0 and set the counter Initialize to .

[0148] In one embodiment of the present disclosure, the voltage negative sequence component determination module 23 is further configured to:

[0149] The d-axis voltage component is filtered based on the first formula, which is:

[0150]

[0151]

[0152]

[0153] in, and are all intermediate variables. represents the d-axis voltage component, represents the delayed voltage component corresponding to the d-axis voltage component; represents the positive sequence component of the d-axis voltage, Indicates the interrupt frequency of the controller, Indicates the grid frequency.

[0154] In one embodiment of the present disclosure, the voltage negative sequence component determination module 23 is further configured to:

[0155] The q-axis voltage component is filtered based on the second formula, which is:

[0156]

[0157]

[0158]

[0159] in, and are all intermediate variables. represents the q-axis voltage component, represents the delayed voltage component corresponding to the q-axis voltage component; represents the positive sequence component of the q-axis voltage, Indicates the interrupt frequency of the controller, Indicates the grid frequency.

[0160] In one embodiment of the present disclosure, the current control module 24 is further configured to:

[0161] The d-axis voltage positive sequence component and the d-axis voltage negative sequence component are input as feedforward components to the output end of the d-axis current component regulator to obtain a d-axis modulation signal; the q-axis voltage positive sequence component and the q-axis voltage negative sequence component are input as feedforward components to the output end of the q-axis current component regulator to obtain a q-axis modulation signal; the d-axis current component and the q-axis current component are obtained by performing coordinate transformation on the three-phase current of the three-phase energy storage converter;

[0162] A converter drive signal is obtained based on the d-axis modulation signal and the q-axis modulation signal.

[0163] In one embodiment of the present disclosure, the current control module 24 is further configured to:

[0164] Performing inverse coordinate transformation on the d-axis modulation signal and the q-axis modulation signal to obtain a three-phase modulation signal;

[0165] The inverter driving signal is obtained by performing pulse width modulation based on the three-phase modulation signal.

[0166] See also Figure 7 , Figure 7 A schematic block diagram of an electronic device provided by an embodiment of the present disclosure. Figure 7 The electronic device 300 in the embodiment shown may include: one or more processors 301, one or more input devices 302, one or more output devices 303 and one or more memories 304. The processors 301, input devices 302, output devices 303 and memories 304 communicate with each other via a communication bus 305. The memory 304 is used to store computer programs, which include program instructions. The processor 301 is used to execute the program instructions stored in the memory 304. The processor 301 is configured to call the program instructions to execute the functions of each module / unit in the above-mentioned device embodiments, such as Figure 6 The functions of modules 21 to 24 are shown.

[0167] It should be understood that in the embodiment of the present disclosure, the processor 301 may be a central processing unit (CPU), and the processor may also be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc.

[0168] The input device 302 may include a touch panel, a fingerprint collection sensor (for collecting the user's fingerprint information and fingerprint direction information), a microphone, etc., and the output device 303 may include a display (LCD, etc.), a speaker, etc.

[0169] The memory 304 may include a read-only memory and a random access memory, and provide instructions and data to the processor 301. A portion of the memory 304 may also include a non-volatile random access memory. For example, the memory 304 may also store information about the device type.

[0170] In a specific implementation, the processor 301, input device 302, and output device 303 described in the embodiments of the present disclosure can execute the implementation methods described in the first and second embodiments of the current balancing control method under an unbalanced power grid provided in the embodiments of the present disclosure, and can also execute the implementation methods of the electronic device described in the embodiments of the present disclosure, which will not be repeated here.

[0171] In another embodiment of the present disclosure, a computer-readable storage medium is provided, wherein the computer-readable storage medium stores a computer program, wherein the computer program includes program instructions, and when the program instructions are executed by the processor, all or part of the processes in the above-mentioned embodiment method are implemented, and the computer program can also be completed by instructing the relevant hardware through the computer program. The computer program can be stored in a computer-readable storage medium, and when the computer program is executed by the processor, the steps of each of the above-mentioned method embodiments can be implemented. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form, etc. The computer-readable medium can include: any entity or device capable of carrying computer program code, recording medium, U disk, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), electric carrier signal, telecommunication signal and software distribution medium, etc.

[0172] The computer-readable storage medium may be an internal storage unit of the electronic device of any of the aforementioned embodiments, such as a hard disk or memory of the electronic device. The computer-readable storage medium may also be an external storage device of the electronic device, such as a plug-in hard disk, a smart memory card (Smart Media Card, SMC), a secure digital (SecureDigital, SD) card, a flash card (Flash Card), etc. equipped on the electronic device. Furthermore, the computer-readable storage medium may also include both an internal storage unit of the electronic device and an external storage device. The computer-readable storage medium is used to store computer programs and other programs and data required by the electronic device. The computer-readable storage medium may also be used to temporarily store data that has been output or is to be output.

[0173] Those of ordinary skill in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in terms of function in the above description. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this disclosure.

[0174] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the electronic devices and units described above can refer to the corresponding processes in the aforementioned method embodiments, and will not be repeated here.

[0175] In the several embodiments provided in the present application, it should be understood that the disclosed electronic devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interfaces or units, or it can be an electrical, mechanical or other form of connection.

[0176] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the embodiments of the present disclosure.

[0177] In addition, each functional unit in each embodiment of the present disclosure may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0178] The above are only specific embodiments of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed in the present disclosure, and these modifications or replacements should be included in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be based on the protection scope of the claims.

Claims

1. A current balance control method under an unbalanced power grid, characterized in that: include: Performing coordinate transformation on the three-phase voltage of the three-phase energy storage converter to obtain a d-axis voltage component and a q-axis voltage component; The d-axis voltage component and the q-axis voltage component are filtered respectively to obtain the d-axis voltage positive sequence component and the q-axis voltage positive sequence component; The filtering of the d-axis voltage component and the q-axis voltage component to obtain the d-axis voltage positive sequence component and the q-axis voltage positive sequence component respectively includes: Determining a first delay time based on a power grid cycle; Based on the first delay time, the d-axis voltage component and the q-axis voltage component are respectively delayed to obtain the d-axis delayed voltage component and the q-axis delayed voltage component; wherein the delay is one power grid cycle; Filtering the d-axis voltage component based on the d-axis delayed voltage component to obtain the d-axis voltage positive sequence component; The q-axis voltage component is filtered based on the q-axis delayed voltage component to obtain the q-axis voltage positive sequence component; The filtering of the d-axis voltage component based on the d-axis delayed voltage component to obtain the d-axis voltage positive sequence component includes: The d-axis voltage component is filtered based on a first formula, wherein the first formula is: in, and are all intermediate variables. represents the d-axis voltage component, represents the delayed voltage component corresponding to the d-axis voltage component; represents the positive sequence component of the d-axis voltage, Indicates the interrupt frequency of the controller, Indicates the grid frequency; The d-axis voltage negative sequence component is obtained based on the d-axis voltage component and the d-axis voltage positive sequence component, and the q-axis voltage negative sequence component is obtained based on the q-axis voltage component and the q-axis voltage positive sequence component; The d-axis voltage positive sequence component, the d-axis voltage negative sequence component, the q-axis voltage positive sequence component, and the q-axis voltage negative sequence component are input as feedforward components to the output end of the current regulator to obtain a converter drive signal to perform current control on the three-phase energy storage converter; the converter is controlled to generate a current opposite to the negative sequence current caused by the negative sequence voltage component.

2. The current balance control method under unbalanced power grid according to claim 1, characterized in that: The method of performing delay processing on the d-axis voltage component and the q-axis voltage component based on the first delay time to obtain the d-axis delayed voltage component and the q-axis delayed voltage component includes: Determine the number of cycles based on the grid cycle and the interruption cycle of the controller in the three-phase energy storage converter ; The number of cycles Used to indicate the number of controller interruption cycles contained in one power grid cycle; In each power grid cycle, the execution Data access operation; The data access operation includes: Store the d-axis voltage component in the first array The q-axis voltage component is stored in the first position of the second array. positions; the number of elements in the first array and the second array are both , ; The first array The data of the position of the second array is determined as the d-axis delayed voltage component; The data of each position is determined as the q-axis delayed voltage component; among them, ; The counter and counter Add 1 to each; In the After the data access operation, the counter Initialize to 0, the counter Initialize to .

3. The current balance control method under unbalanced power grid according to claim 1, characterized in that: The filtering of the q-axis voltage component based on the q-axis delayed voltage component to obtain the q-axis voltage positive sequence component includes: The q-axis voltage component is filtered based on a second formula, wherein the second formula is: in, and are all intermediate variables. represents the q-axis voltage component, represents the delayed voltage component corresponding to the q-axis voltage component; represents the positive sequence component of the q-axis voltage, Indicates the interrupt frequency of the controller, Indicates the grid frequency.

4. The current balance control method under unbalanced power grid according to claim 1, characterized in that: The method of inputting the d-axis voltage positive sequence component, the d-axis voltage negative sequence component, the q-axis voltage positive sequence component, and the q-axis voltage negative sequence component as feedforward components into the output end of the current regulator to obtain a converter drive signal includes: Inputting the d-axis voltage positive sequence component and the d-axis voltage negative sequence component as feedforward components into the output end of the d-axis current component regulator to obtain a d-axis modulation signal; inputting the q-axis voltage positive sequence component and the q-axis voltage negative sequence component as feedforward components into the output end of the q-axis current component regulator to obtain a q-axis modulation signal; the d-axis current component and the q-axis current component are obtained by performing coordinate transformation on the three-phase current of the three-phase energy storage converter; A converter drive signal is obtained based on the d-axis modulation signal and the q-axis modulation signal.

5. The current balance control method under unbalanced power grid according to claim 4, characterized in that: The step of obtaining a converter drive signal based on the d-axis modulation signal and the q-axis modulation signal comprises: Performing inverse coordinate transformation on the d-axis modulation signal and the q-axis modulation signal to obtain a three-phase modulation signal; The inverter driving signal is obtained by performing pulse width modulation based on the three-phase modulation signal.

6. A current balance control device under unbalanced power grid, characterized in that: A method for controlling current balance in an unbalanced power grid according to any one of claims 1 to 5, comprising: A coordinate transformation module is used to perform coordinate transformation on the three-phase voltage of the three-phase energy storage converter to obtain a d-axis voltage component and a q-axis voltage component; A voltage positive sequence component determination module is used to filter the d-axis voltage component and the q-axis voltage component respectively to obtain the d-axis voltage positive sequence component and the q-axis voltage positive sequence component; A voltage negative sequence component determination module, used to obtain a d-axis voltage negative sequence component based on a d-axis voltage component and a d-axis voltage positive sequence component, and to obtain a q-axis voltage negative sequence component based on a q-axis voltage component and a q-axis voltage positive sequence component; The current control module is used to input the d-axis voltage positive sequence component, the d-axis voltage negative sequence component, the q-axis voltage positive sequence component, and the q-axis voltage negative sequence component as feedforward components into the output end of the current regulator to obtain a converter drive signal to perform current control on the three-phase energy storage converter.

7. An electronic device comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 5 are implemented.

8. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 5 are implemented.

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