Control method and system of energy storage converter, electronic equipment and storage medium

Abstract

The invention relates to the technical field of energy storage converters, and provides a control method and system of an energy storage converter, electronic equipment and a storage medium. The control method of the energy storage converter comprises the following steps: acquiring a first voltage signal and a first current signal of the energy storage converter and a second voltage signal of a power grid; determining active power and reactive power of the energy storage converter according to the first voltage signal and the first current signal; determining a phase compensation value and an amplitude compensation value according to the first voltage signal and the second voltage signal; inputting the active power, the reactive power, the phase compensation value and the amplitude compensation value into a virtual synchronous generator control algorithm model to obtain a third voltage signal; and controlling the energy storage converter to perform grid-connected operation according to the third voltage signal and the second voltage signal. According to the invention, the phase synchronization time is shortened, and rapid switching of the energy storage converter between the off-grid working mode and the grid-connected working mode is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage converters, and in particular to a control method and system, electronic equipment and storage medium for an energy storage converter. Background Art

[0002] In recent years, the increase in the number of energy storage converters has caused the problem of missing inertia in the power system. Therefore, the concept of virtual synchronous generator (VSG) has gradually gained attention. VSG control is used to simulate the inertia and damping characteristics of synchronous generators. According to the changes in the active power and frequency output by the virtual synchronous generator, the damping and rotational inertia are adjusted, which can make the distributed inverter power supply have similar operating characteristics to the synchronous generator, and play an important supporting role in improving the stability of the power system. At present, some research results have been achieved on the VSG control of energy storage converters, which mainly focus on the problem of grid-connected pre-synchronization, and there is less research on the seamless switching of grid-connected and off-grid. In addition, the traditional energy storage converter VSG control often has asynchronism when connected to the grid, and the control is complex and the pre-synchronization time is long. Summary of the invention

[0003] The present invention aims to solve the technical problem of too long synchronization time existing in the prior art or related art.

[0004] To this end, a first aspect of the present invention proposes a control method for an energy storage converter.

[0005] A second aspect of the present invention provides a control system for an energy storage converter.

[0006] A third aspect of the present invention provides an electronic device.

[0007] A fourth aspect of the present invention provides a storage medium.

[0008] In view of this, according to the first aspect of the present invention, a control method for an energy storage inverter is proposed, including: collecting a first voltage signal and a first current signal of the energy storage inverter and a second voltage signal of the power grid; determining the active power and reactive power of the energy storage inverter according to the first voltage signal and the first current signal; determining a phase compensation value and an amplitude compensation value according to the first voltage signal and the second voltage signal; inputting the active power, reactive power, phase compensation value and amplitude compensation value into a virtual synchronous generator control algorithm model to obtain a third voltage signal; and controlling the energy storage inverter to perform grid-connected operation according to the third voltage signal and the second voltage signal.

[0009] The control method of the energy storage converter provided by the present invention mainly comprises: firstly collecting the first voltage signal and the first current signal output by the energy storage converter, and also collecting the second voltage signal of the power grid. Then, the active power and reactive power of the energy storage converter are determined according to the first voltage signal and the first current signal, wherein the first voltage signal may be a three-phase voltage, and the first current signal may be a three-phase current. Therefore, when determining the active power and reactive power of the energy storage converter according to the first voltage signal and the first current signal, it is necessary to perform coordinate transformation processing on the first voltage signal and the first current signal, that is, converting the current and voltage in the three-phase stationary coordinate system (abc coordinate system) into the current and voltage in the rotating coordinate system (dq coordinate system), and then using the current and voltage in the converted rotating coordinate system to calculate the active power and reactive power of the energy storage converter. Then, a phase compensation value and an amplitude compensation value are determined according to the first voltage signal and the second voltage signal, wherein the process of determining the phase compensation value according to the first voltage signal and the second voltage signal is the process of pre-synchronizing the voltage phase, and the phase compensation value that needs to be compensated when the energy storage inverter is connected to the grid is determined by comparing the two voltage signals, and the process of determining the amplitude compensation value according to the first voltage signal and the second voltage signal is the process of pre-synchronizing the amplitude, and the amplitude compensation value that needs to be compensated when the energy storage inverter is connected to the grid is determined by comparing the two voltage signals. After the amplitude compensation value and the phase compensation value are determined, the amplitude compensation value, the phase compensation value, the active power and the reactive power are input into the virtual synchronous generator control algorithm model to obtain a third voltage signal, wherein the virtual synchronous generator control algorithm model is obtained through the virtual synchronous generator (VSG, Virtual Synchronous Generator) technology, and the virtual synchronous generator can imitate the dynamic characteristics of the synchronous generator, provide rotational inertia and damping for the power system, and contribute to the stable operation of the power system. Therefore, after the amplitude compensation value, the phase compensation value, the active power and the reactive power are input into the virtual synchronous generator control algorithm model, the virtual synchronous generator control algorithm model will determine the voltage signal emitted by the energy storage inverter when it is in the grid-connected working mode, that is, the third voltage signal, according to the amplitude compensation value, the phase compensation value, the active power and the reactive power and the rotational inertia and damping in the virtual synchronous generator control algorithm model. Finally, the third voltage signal is compared with the second voltage signal. If the comparison result meets the preset conditions, the energy storage inverter is controlled to perform grid-connected operation. If the comparison result does not meet the preset conditions, the above process is repeated until the comparison result meets the preset conditions, wherein the preset conditions refer to that the voltage difference and frequency difference between the third voltage signal and the second voltage signal are both less than the preset threshold.The present invention determines the active power and reactive power of the energy storage converter according to the first voltage signal and the first current signal, then determines the phase compensation value and the amplitude compensation value according to the output voltage of the energy storage converter, i.e., the first voltage signal and the second voltage signal of the power grid, then determines the final third voltage signal according to the active power, reactive power, phase compensation value, amplitude compensation value and the virtual synchronous generator control algorithm model, and finally controls the energy storage converter to switch between the off-grid working mode and the grid-connected working mode according to the third voltage signal and the second voltage signal. The present invention simplifies the control structure by avoiding the use of a phase-locked loop in the on-grid and off-grid switching process, making the control structure simpler, the algorithm performance better, and improving the synchronization stability of the system; at the same time, by improving the pre-synchronization phase control and adopting fast phase tracking adjustment, the phase synchronization time is shortened, and fast switching between the on-grid and off-grid working modes is achieved.

[0010] The control method of the energy storage converter according to the present invention may also have the following technical features: In some technical schemes, optionally, before the step of inputting active power, reactive power, phase compensation value and amplitude compensation value into the virtual synchronous generator control algorithm model to obtain the third voltage signal, it includes: determining the frequency change and frequency change of the virtual synchronous generator; determining the moment of inertia based on the frequency change and the frequency change; determining the damping coefficient based on the frequency change and the frequency change; constructing a first mathematical equation based on the moment of inertia and the damping coefficient, wherein the first mathematical equation is an equation with power and speed as variables; and determining the virtual synchronous generator control algorithm model based on the first mathematical equation and the stator electrical equation.

[0011] In the technical solution, before the step of inputting active power, reactive power, phase compensation value and amplitude compensation value into the virtual synchronous generator control algorithm model to obtain the third voltage signal, it includes: first determining the frequency change amount and frequency change amount of the virtual synchronous generator, and then determining the moment of inertia according to the frequency change amount and the frequency change amount, wherein the moment of inertia is an adaptively adjustable moment of inertia, which is related to the frequency converter and the frequency change amount, and therefore it is necessary to determine the moment of inertia according to the frequency change amount and the frequency change amount. Then, the damping coefficient is determined according to the frequency change amount and the frequency change amount, wherein the damping coefficient is also an adaptively adjustable damping coefficient. After obtaining the damping coefficient and the moment of inertia, a first mathematical equation is constructed according to the moment of inertia and the damping coefficient, wherein the first mathematical equation is an equation with power and speed as variables, that is, a rotor mechanical equation with power and speed as variables is constructed by the moment of inertia and the damping coefficient. Then, the virtual synchronous generator control algorithm model is determined according to the stator electrical equation and the first mathematical equation. In the present invention, the moment of inertia and the damping coefficient are determined according to the frequency variation and the frequency change, and then the rotor mechanical equation is constructed according to the moment of inertia and the damping coefficient. Finally, the virtual synchronous generator control algorithm model is obtained according to the rotor mechanical equation and the stator electrical equation, thereby realizing adaptive regulation, fast tracking speed, suppressing system power oscillation, maintaining stable system operation, and also suppressing transient overcurrent occurring during the switching process between on-grid and off-grid, thereby realizing seamless switching between on-grid and off-grid.

[0012] In some technical solutions, optionally, the step of determining the moment of inertia based on the frequency change amount and the frequency change amount includes: determining the change relationship between the frequency change amount, the frequency change amount and the moment of inertia; and determining the moment of inertia based on the change relationship and the time constant.

[0013] In the technical scheme, the step of determining the moment of inertia according to the frequency variation and the frequency change comprises: first determining the variation relationship among the frequency variation, the frequency change and the moment of inertia, wherein the variation relationship comprises: when the frequency variation is greater than zero and the frequency variation is greater than zero, the moment of inertia gradually increases. When the frequency variation is greater than zero and the frequency variation is less than zero, the moment of inertia gradually decreases. When the frequency variation is less than zero and the frequency variation is less than zero, the moment of inertia gradually increases. When the frequency variation is less than zero and the frequency variation is greater than zero, the moment of inertia gradually decreases. It can be seen that the moment of inertia is an adaptive and adjustable moment of inertia, so in order to facilitate the determination of the moment of inertia, a mathematical formula can be established according to the variation relationship and the time constant, and then the current frequency variation and the frequency variation are input into the mathematical formula to obtain the required moment of inertia.

[0014] In some technical solutions, optionally, the step of determining the damping coefficient based on the frequency variation and the frequency change includes: determining an extreme learning machine neural network model; inputting the frequency variation and the frequency change into the extreme learning machine neural network model to obtain the damping coefficient.

[0015] In the technical solution, the step of determining the damping coefficient according to the frequency variation and the frequency change includes: first determining an extreme learning machine (ELM) neural network model, wherein the ELM neural network model mainly includes: an input layer, a hidden layer, and an output layer. Then, the frequency variation and the frequency change are input into the ELM neural network model to obtain the damping coefficient. The damping coefficient is determined by using the ELM neural network model, thereby ensuring the accuracy of the damping coefficient on the one hand, and improving work efficiency on the other hand.

[0016] In some technical schemes, optionally, the step of determining the phase compensation value and the amplitude compensation value based on the first voltage signal and the second voltage signal includes: performing coordinate transformation processing on the first voltage signal to obtain a fourth voltage signal and a fifth voltage signal, wherein the fourth voltage signal is a voltage signal on the direct axis and the fifth voltage signal is a voltage signal on the quadrature axis; performing coordinate transformation processing on the second voltage signal to obtain a sixth voltage signal and a seventh voltage signal, wherein the sixth voltage signal is a voltage signal on the direct axis and the seventh voltage signal is a voltage signal on the quadrature axis; determining a first difference between the fourth voltage signal and the sixth voltage signal; determining a second difference between the fifth voltage signal and the seventh voltage signal; and determining the phase compensation value and the amplitude compensation value based on the first difference and the second difference.

[0017] In the technical solution, the step of determining the phase compensation value and the amplitude compensation value according to the first voltage signal and the second voltage signal includes: firstly, coordinate transformation processing is performed on the first voltage signal to obtain the fourth voltage signal and the fifth voltage signal, wherein the coordinate transformation processing refers to converting the voltage in the three-phase stationary coordinate system (abc coordinate system) into the voltage in the rotating coordinate system (dq coordinate system), so that the fourth voltage signal obtained is the voltage signal on the direct axis (d axis), and the fifth voltage signal is the voltage signal on the quadrature axis (q axis). Similarly, coordinate transformation processing is performed on the second voltage signal to obtain the sixth voltage signal and the seventh voltage signal, wherein the sixth voltage signal is the voltage signal on the direct axis (d axis), and the seventh voltage signal is the voltage signal on the quadrature axis (q axis). Then, the first difference between the fourth voltage signal and the sixth voltage signal is calculated, and the second difference between the fifth voltage signal and the sixth voltage signal is calculated, and finally, the phase compensation value and the amplitude compensation value are determined according to the first difference and the second difference. The first voltage signal and the second voltage signal are respectively transformed into coordinates to obtain the corresponding direct-axis voltage and quadrature-axis voltage, and then the direct-axis voltage difference and the quadrature-axis voltage difference of the two voltages are respectively calculated, and finally the phase compensation value and the amplitude compensation value are determined according to the two differences, thereby improving the pre-synchronization phase control, adopting fast phase tracking adjustment, and shortening the phase synchronization time.

[0018] In some technical schemes, optionally, the step of determining the phase compensation value and the amplitude compensation value based on the first difference and the second difference includes: performing a first processing operation on the first difference to obtain an amplitude compensation value, wherein the first processing operation includes: a proportional integral control operation and a low-pass filtering processing operation; performing a square operation on the first difference to obtain a third difference; performing a square operation on the second difference to obtain a fourth difference; calculating the sum of the third difference and the fourth difference to obtain a first numerical value; performing a first processing operation on the first numerical value to obtain a phase compensation value.

[0019] In the technical solution, the step of determining the phase compensation value and the amplitude compensation value according to the first difference and the second difference includes: firstly, performing a first processing operation on the first difference to obtain an amplitude compensation value, wherein the first processing operation includes a proportional integral control operation and a low-pass filter processing operation. That is, the first difference is input into a proportional integral (PI) controller and a low-pass filter for processing, thereby obtaining an amplitude compensation value. Then, the first difference is squared to obtain a third difference, the second difference is squared to obtain a fourth difference, and then the sum of the third difference and the fourth difference is calculated to obtain a first value, and finally, the first value is processed by the first processing operation to obtain a phase compensation value. That is, after obtaining the first value, the first value is input into a PI controller and a low-pass filter to obtain a phase compensation value.

[0020] In some technical schemes, optionally, the step of controlling the energy storage inverter to perform grid-connected operation according to the third voltage signal and the second voltage signal includes: respectively calculating the voltage difference, phase difference and frequency difference between the third voltage signal and the second voltage signal; based on the voltage difference being less than or equal to the first threshold, the phase difference being less than or equal to the second threshold, and the frequency difference being less than or equal to the third threshold, controlling the energy storage inverter to perform grid-connected operation.

[0021] In the technical solution, the step of controlling the energy storage converter to perform grid-connected operation according to the third voltage signal and the second voltage signal includes: first, respectively calculating the voltage difference, phase difference and frequency difference between the third voltage signal and the second voltage signal. Then, the voltage difference, phase difference and frequency difference are respectively compared with the first threshold, the second threshold and the third threshold. When the voltage difference is less than or equal to the first threshold, and the phase difference is less than or equal to the second threshold, and the frequency difference is less than or equal to the third threshold, the energy storage converter is controlled to perform grid-connected operation. If the above conditions are not met, the third voltage signal is re-determined until the above conditions are met.

[0022] According to a second aspect of the present invention, a control system for an energy storage inverter is proposed, wherein the control system of the energy storage inverter includes: a first acquisition module, the first acquisition module is used to acquire a first voltage signal and a first current signal of the energy storage inverter and a second voltage signal of the power grid; a first determination module, the first determination module is used to determine the active power and reactive power of the energy storage inverter according to the first voltage signal and the first current signal; a first calculation module, the first calculation module is used to determine a phase compensation value and an amplitude compensation value according to the first voltage signal and the second voltage signal; a first processing module, the first processing module is used to input the active power, reactive power, phase compensation value and amplitude compensation value into a virtual synchronous generator control algorithm model to obtain a third voltage signal; and a second processing module, the second processing module is used to control the energy storage inverter to perform grid-connected operation according to the third voltage signal and the second voltage signal.

[0023] The control system of the energy storage converter provided by the present invention mainly includes: a first acquisition module, a first determination module, a first calculation module, a first processing module and a second processing module. Among them, the first acquisition module can collect the first voltage signal and the first current signal output by the energy storage converter, and also collect the second voltage signal of the power grid. Then the first determination module determines the active power and reactive power of the energy storage converter according to the first voltage signal and the first current signal, wherein the first voltage signal can be a three-phase voltage, and the first current signal can be a three-phase current. Therefore, when determining the active power and reactive power of the energy storage converter according to the first voltage signal and the first current signal, it is necessary to perform coordinate transformation processing on the first voltage signal and the first current signal, that is, convert the current and voltage in the three-phase stationary coordinate system (abc coordinate system) into the current and voltage in the rotating coordinate system (dq coordinate system), and then use the current and voltage in the converted rotating coordinate system to calculate the active power and reactive power of the energy storage converter. Then the first calculation module determines the phase compensation value and the amplitude compensation value according to the first voltage signal and the second voltage signal, wherein the process of determining the phase compensation value according to the first voltage signal and the second voltage signal is the process of pre-synchronization voltage phase, and the two voltage signals are compared to determine the phase compensation value that needs to be compensated when the energy storage inverter is connected to the grid, and the process of determining the amplitude compensation value according to the first voltage signal and the second voltage signal is the process of pre-synchronization amplitude, and the two voltage signals are compared to determine the amplitude compensation value that needs to be compensated when the energy storage inverter is connected to the grid. After determining the amplitude compensation value and the phase compensation value, the first processing module inputs the amplitude compensation value, the phase compensation value, the active power and the reactive power into the virtual synchronous generator control algorithm model to obtain a third voltage signal, wherein the virtual synchronous generator control algorithm model is obtained through the virtual synchronous generator (VSG, VirtualSynchronous Generator) technology. The virtual synchronous generator can imitate the dynamic characteristics of the synchronous generator, provide rotational inertia and damping for the power system, and contribute to the stable operation of the power system. Therefore, after the amplitude compensation value, the phase compensation value, the active power and the reactive power are input into the virtual synchronous generator control algorithm model, the virtual synchronous generator control algorithm model will determine the voltage signal emitted by the energy storage inverter when it is in the grid-connected working mode, that is, the third voltage signal, according to the amplitude compensation value, the phase compensation value, the active power and the reactive power and the rotational inertia and damping in the virtual synchronous generator control algorithm model. Finally, the second processing module compares the third voltage signal with the second voltage signal. If the comparison result meets the preset conditions, the energy storage inverter is controlled to perform grid-connected operation. If the comparison result does not meet the preset conditions, the above process is repeated until the comparison result meets the preset conditions, wherein the preset conditions refer to that the voltage difference and frequency difference between the third voltage signal and the second voltage signal are both less than the preset threshold.The present invention determines the active power and reactive power of the energy storage converter according to the first voltage signal and the first current signal, then determines the phase compensation value and the amplitude compensation value according to the output voltage of the energy storage converter, i.e., the first voltage signal and the second voltage signal of the power grid, then determines the final third voltage signal according to the active power, reactive power, phase compensation value, amplitude compensation value and the virtual synchronous generator control algorithm model, and finally controls the energy storage converter to switch between the off-grid working mode and the grid-connected working mode according to the third voltage signal and the second voltage signal. The present invention simplifies the control structure by avoiding the use of a phase-locked loop in the on-grid and off-grid switching process, making the control structure simpler, the algorithm performance better, and improving the synchronization stability of the system; at the same time, by improving the pre-synchronization phase control and adopting fast phase tracking adjustment, the phase synchronization time is shortened, and fast switching between the on-grid and off-grid working modes is achieved.

[0024] According to a third aspect of the present invention, an electronic device is proposed, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the steps of the control method of the energy storage converter as described in any one of the above items are implemented.

[0025] The electronic device provided by the present invention, in which the processor implements the steps of the control method of the above-mentioned energy storage converter when executing the computer program, can achieve the technical effect of any of the above-mentioned technical solutions, which will not be repeated here.

[0026] According to a fourth aspect of the present invention, a storage medium is provided, on which a computer program is stored, and when the computer program is executed by a processor, the steps of the control method of the energy storage converter as described in any one of the above items are implemented.

[0027] The storage medium provided by the present invention implements the steps of the control method of the above-mentioned energy storage converter when the computer program is executed by the processor, and can achieve the technical effects of any of the above-mentioned technical solutions, which will not be repeated here.

[0028] Additional aspects and advantages of the present invention will become apparent from the following description or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which: Figure 1 One of the flow charts of a control method of an energy storage converter according to an embodiment of the present invention is shown; Figure 2A flow chart showing a control method for an energy storage converter according to an embodiment of the present invention before the step of inputting active power, reactive power, phase compensation value and amplitude compensation value into a virtual synchronous generator control algorithm model to obtain a third voltage signal is shown; Figure 3 A schematic flow chart showing the step of determining the moment of inertia according to the frequency variation and the frequency change amount in a control method for an energy storage converter according to an embodiment of the present invention; Figure 4 A schematic flow chart showing a step of determining a damping coefficient according to a frequency variation and a frequency change amount in a control method for an energy storage converter according to an embodiment of the present invention is shown; Figure 5 A schematic flow chart showing the steps of determining a phase compensation value and an amplitude compensation value according to a first voltage signal and a second voltage signal in a control method for an energy storage converter according to an embodiment of the present invention is shown; Figure 6 A schematic flow chart showing a step of determining a phase compensation value and an amplitude compensation value according to a first difference and a second difference in a control method for an energy storage converter according to an embodiment of the present invention is shown; Figure 7 A schematic flow chart showing the steps of controlling the energy storage converter to perform grid-connected operation according to a third voltage signal and a second voltage signal in a control method of the energy storage converter according to an embodiment of the present invention; Figure 8 A second flow chart of a method for controlling an energy storage converter according to an embodiment of the present invention is shown; Fig. 9 A topological structure block diagram of an energy storage converter according to an embodiment of the present invention is shown; Fig.10 The overall structure block diagram of the VSG control strategy of an embodiment of the present invention is shown; Fig.11 A block diagram of a pre-synchronization control structure of an embodiment of the present invention is shown; Figure 12-A One of the graphs showing the relationship between power variation and angular velocity according to one embodiment of the present invention; Figure 12-B A second graph showing the relationship between power variation and angular velocity according to an embodiment of the present invention; Fig.13 A schematic diagram of a neural network structure of an embodiment of the present invention is shown; Fig.14 A schematic block diagram of a control system of an energy storage converter according to an embodiment of the present invention is shown; Fig.15 A schematic block diagram of an electronic device according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0030] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0031] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0032] Figure 1 A flow chart of a control method for an energy storage converter according to an embodiment of the present invention is shown. The method comprises: Step 102: collecting a first voltage signal and a first current signal of the energy storage converter and a second voltage signal of the power grid; Step 104: determining the active power and reactive power of the energy storage converter according to the first voltage signal and the first current signal; Step 106: determining a phase compensation value and an amplitude compensation value according to the first voltage signal and the second voltage signal; Step 108: inputting the active power, reactive power, phase compensation value and amplitude compensation value into the virtual synchronous generator control algorithm model to obtain a third voltage signal; Step 110: Control the energy storage converter to perform grid-connected operation according to the third voltage signal and the second voltage signal.

[0033] The control method of the energy storage converter provided by the present invention mainly comprises: firstly collecting the first voltage signal and the first current signal output by the energy storage converter, and also collecting the second voltage signal of the power grid. Then, the active power and reactive power of the energy storage converter are determined according to the first voltage signal and the first current signal, wherein the first voltage signal may be a three-phase voltage, and the first current signal may be a three-phase current. Therefore, when determining the active power and reactive power of the energy storage converter according to the first voltage signal and the first current signal, it is necessary to perform coordinate transformation processing on the first voltage signal and the first current signal, that is, converting the current and voltage in the three-phase stationary coordinate system (abc coordinate system) into the current and voltage in the rotating coordinate system (dq coordinate system), and then using the current and voltage in the converted rotating coordinate system to calculate the active power and reactive power of the energy storage converter. Then, a phase compensation value and an amplitude compensation value are determined according to the first voltage signal and the second voltage signal, wherein the process of determining the phase compensation value according to the first voltage signal and the second voltage signal is the process of pre-synchronizing the voltage phase, and the phase compensation value that needs to be compensated when the energy storage inverter is connected to the grid is determined by comparing the two voltage signals, and the process of determining the amplitude compensation value according to the first voltage signal and the second voltage signal is the process of pre-synchronizing the amplitude, and the amplitude compensation value that needs to be compensated when the energy storage inverter is connected to the grid is determined by comparing the two voltage signals. After the amplitude compensation value and the phase compensation value are determined, the amplitude compensation value, the phase compensation value, the active power and the reactive power are input into the virtual synchronous generator control algorithm model to obtain a third voltage signal, wherein the virtual synchronous generator control algorithm model is obtained through the virtual synchronous generator (VSG, Virtual Synchronous Generator) technology, and the virtual synchronous generator can imitate the dynamic characteristics of the synchronous generator, provide rotational inertia and damping for the power system, and contribute to the stable operation of the power system. Therefore, after the amplitude compensation value, the phase compensation value, the active power and the reactive power are input into the virtual synchronous generator control algorithm model, the virtual synchronous generator control algorithm model will determine the voltage signal emitted by the energy storage inverter when it is in the grid-connected working mode, that is, the third voltage signal, according to the amplitude compensation value, the phase compensation value, the active power and the reactive power and the rotational inertia and damping in the virtual synchronous generator control algorithm model. Finally, the third voltage signal is compared with the second voltage signal. If the comparison result meets the preset conditions, the energy storage inverter is controlled to perform grid-connected operation. If the comparison result does not meet the preset conditions, the above process is repeated until the comparison result meets the preset conditions, wherein the preset conditions refer to that the voltage difference and frequency difference between the third voltage signal and the second voltage signal are both less than the preset threshold.The present invention determines the active power and reactive power of the energy storage converter according to the first voltage signal and the first current signal, then determines the phase compensation value and the amplitude compensation value according to the output voltage of the energy storage converter, i.e., the first voltage signal and the second voltage signal of the power grid, then determines the final third voltage signal according to the active power, reactive power, phase compensation value, amplitude compensation value and the virtual synchronous generator control algorithm model, and finally controls the energy storage converter to switch between the off-grid working mode and the grid-connected working mode according to the third voltage signal and the second voltage signal. The present invention simplifies the control structure by avoiding the use of a phase-locked loop in the on-grid and off-grid switching process, making the control structure simpler, the algorithm performance better, and improving the synchronization stability of the system; at the same time, by improving the pre-synchronization phase control and adopting fast phase tracking adjustment, the phase synchronization time is shortened, and fast switching between the on-grid and off-grid working modes is achieved.

[0034] Figure 2 The present invention shows a flow chart of a control method for an energy storage converter according to an embodiment of the present invention before the step of inputting active power, reactive power, phase compensation value and amplitude compensation value into a virtual synchronous generator control algorithm model to obtain a third voltage signal; wherein, before the step of inputting active power, reactive power, phase compensation value and amplitude compensation value into a virtual synchronous generator control algorithm model to obtain a third voltage signal, the method includes: Step 202: Determine the frequency variation and frequency change of the virtual synchronous generator; Step 204: Determine the moment of inertia according to the frequency variation and the frequency change; Step 206: Determine the damping coefficient according to the frequency variation and the frequency change; Step 208: constructing a first mathematical equation according to the moment of inertia and the damping coefficient, wherein the first mathematical equation is an equation with power and rotation speed as variables; Step 210: Determine a virtual synchronous generator control algorithm model according to the first mathematical equation and the stator electrical equation.

[0035] In this embodiment, before the step of inputting active power, reactive power, phase compensation value and amplitude compensation value into the virtual synchronous generator control algorithm model to obtain the third voltage signal, it includes: first determining the frequency change amount and frequency change amount of the virtual synchronous generator, and then determining the moment of inertia according to the frequency change amount and frequency change amount, wherein the moment of inertia is an adaptively adjustable moment of inertia, which is related to the frequency converter and the frequency change amount, and therefore the moment of inertia needs to be determined according to the frequency change amount and frequency change amount. Then, the damping coefficient is determined according to the frequency change amount and frequency change amount, wherein the damping coefficient is also an adaptively adjustable damping coefficient. After obtaining the damping coefficient and the moment of inertia, a first mathematical equation is constructed according to the moment of inertia and the damping coefficient, wherein the first mathematical equation is an equation with power and speed as variables, that is, a rotor mechanical equation with power and speed as variables is constructed by the moment of inertia and the damping coefficient. Then, the virtual synchronous generator control algorithm model is determined according to the stator electrical equation and the first mathematical equation. In the present invention, the moment of inertia and the damping coefficient are determined according to the frequency variation and the frequency change, and then the rotor mechanical equation is constructed according to the moment of inertia and the damping coefficient. Finally, the virtual synchronous generator control algorithm model is obtained according to the rotor mechanical equation and the stator electrical equation, thereby realizing adaptive regulation, fast tracking speed, suppressing system power oscillation, maintaining stable system operation, and also suppressing transient overcurrent occurring during the switching process between on-grid and off-grid, thereby realizing seamless switching between on-grid and off-grid.

[0036] Figure 3 A schematic flow chart of a step of determining the moment of inertia according to the frequency variation and the frequency change amount in a control method of an energy storage converter according to an embodiment of the present invention is shown; wherein the step of determining the moment of inertia according to the frequency variation and the frequency change amount includes: Step 302: Determine the frequency change amount, and the change relationship between the frequency change amount and the moment of inertia; Step 304: Determine the moment of inertia according to the frequency variation, the frequency change, the variation relationship and the time constant.

[0037] In this embodiment, the step of determining the moment of inertia according to the frequency variation and the frequency change comprises: first determining the variation relationship among the frequency variation, the frequency change and the moment of inertia, wherein the variation relationship comprises: when the frequency variation is greater than zero and the frequency variation is greater than zero, the moment of inertia gradually increases. When the frequency variation is greater than zero and the frequency variation is less than zero, the moment of inertia gradually decreases. When the frequency variation is less than zero and the frequency variation is less than zero, the moment of inertia gradually increases. When the frequency variation is less than zero and the frequency variation is greater than zero, the moment of inertia gradually decreases. It can be seen that the moment of inertia is an adaptive and adjustable moment of inertia, so in order to facilitate the determination of the moment of inertia, a mathematical formula can be established according to the variation relationship and the time constant, and then the current frequency variation and the frequency variation are input into the mathematical formula to obtain the required moment of inertia.

[0038] Figure 4 A schematic flow chart of a step of determining a damping coefficient according to a frequency variation and a frequency change amount in a control method for an energy storage converter according to an embodiment of the present invention is shown; wherein the step of determining the damping coefficient according to the frequency variation and the frequency change amount includes: Step 402: Determine an extreme learning machine neural network model; Step 404: Input the frequency variation and the frequency change into the extreme learning machine neural network model to obtain the damping coefficient.

[0039] In this embodiment, the step of determining the damping coefficient according to the frequency variation and the frequency change comprises: first determining an extreme learning machine (ELM) neural network model, wherein the ELM neural network model mainly comprises: an input layer, a hidden layer, and an output layer. Then the frequency variation and the frequency change are input into the ELM neural network model to obtain the damping coefficient. The damping coefficient is determined by using the ELM neural network model, thereby ensuring the accuracy of the damping coefficient on the one hand, and improving the work efficiency on the other hand.

[0040] Figure 5 A flow chart showing a step of determining a phase compensation value and an amplitude compensation value according to a first voltage signal and a second voltage signal in a control method for an energy storage converter according to an embodiment of the present invention is shown; wherein the step of determining a phase compensation value and an amplitude compensation value according to the first voltage signal and the second voltage signal comprises: Step 502: performing coordinate transformation processing on the first voltage signal to obtain a fourth voltage signal and a fifth voltage signal, wherein the fourth voltage signal is a voltage signal on a direct axis and the fifth voltage signal is a voltage signal on a quadrature axis; Step 504: performing coordinate transformation processing on the second voltage signal to obtain a sixth voltage signal and a seventh voltage signal, wherein the sixth voltage signal is a voltage signal on the direct axis and the seventh voltage signal is a voltage signal on the quadrature axis; Step 506: Determine a first difference between the fourth voltage signal and the sixth voltage signal; Step 508: Determine a second difference between the fifth voltage signal and the seventh voltage signal; Step 510: Determine a phase compensation value and an amplitude compensation value according to the first difference and the second difference.

[0041] In this embodiment, the step of determining the phase compensation value and the amplitude compensation value according to the first voltage signal and the second voltage signal includes: firstly, coordinate transformation processing is performed on the first voltage signal to obtain the fourth voltage signal and the fifth voltage signal, wherein the coordinate transformation processing refers to converting the voltage in the three-phase stationary coordinate system (abc coordinate system) into the voltage in the rotating coordinate system (dq coordinate system), so that the fourth voltage signal obtained is the voltage signal on the direct axis (d axis), and the fifth voltage signal is the voltage signal on the quadrature axis (q axis). Similarly, coordinate transformation processing is performed on the second voltage signal to obtain the sixth voltage signal and the seventh voltage signal, wherein the sixth voltage signal is the voltage signal on the direct axis (d axis), and the seventh voltage signal is the voltage signal on the quadrature axis (q axis). Then, the first difference between the fourth voltage signal and the sixth voltage signal is calculated, and the second difference between the fifth voltage signal and the sixth voltage signal is calculated, and finally, the phase compensation value and the amplitude compensation value are determined according to the first difference and the second difference. The first voltage signal and the second voltage signal are respectively transformed into coordinates to obtain the corresponding direct-axis voltage and quadrature-axis voltage, and then the direct-axis voltage difference and the quadrature-axis voltage difference of the two voltages are respectively calculated, and finally the phase compensation value and the amplitude compensation value are determined according to the two differences, thereby improving the pre-synchronization phase control, adopting fast phase tracking adjustment, and shortening the phase synchronization time.

[0042] Figure 6 A flow chart of a step of determining a phase compensation value and an amplitude compensation value according to a first difference and a second difference in a control method of an energy storage converter according to an embodiment of the present invention is shown; wherein the step of determining a phase compensation value and an amplitude compensation value according to the first difference and the second difference includes: Step 602: performing a first processing operation on the first difference to obtain an amplitude compensation value, wherein the first processing operation includes: a proportional integral control operation and a low-pass filtering operation; Step 604: performing a square operation on the first difference to obtain a third difference; Step 606: performing a square operation on the second difference to obtain a fourth difference; Step 608: Calculate the sum of the third difference and the fourth difference to obtain a first value; Step 610: Perform a first processing operation on the first value to obtain a phase compensation value.

[0043] In this embodiment, the step of determining the phase compensation value and the amplitude compensation value according to the first difference and the second difference includes: firstly, performing a first processing operation on the first difference to obtain an amplitude compensation value, wherein the first processing operation includes a proportional integral control operation and a low-pass filter processing operation. That is, the first difference is input into a proportional integral (PI) controller and a low-pass filter for processing, thereby obtaining an amplitude compensation value. Then, a square operation is performed on the first difference to obtain a third difference, a square operation is performed on the second difference to obtain a fourth difference, and then the sum of the third difference and the fourth difference is calculated to obtain a first value, and finally, a first processing operation is performed on the first value to obtain a phase compensation value. That is, after obtaining the first value, the first value is input into a PI controller and a low-pass filter to obtain a phase compensation value.

[0044] Figure 7 A schematic flow chart of the steps of controlling the energy storage converter to perform grid-connected operation according to a third voltage signal and a second voltage signal in a control method of an energy storage converter according to an embodiment of the present invention is shown; wherein the steps of controlling the energy storage converter to perform grid-connected operation according to the third voltage signal and the second voltage signal include: Step 702: Calculate the voltage difference, phase difference and frequency difference between the third voltage signal and the second voltage signal respectively; Step 704: Based on the voltage difference being less than or equal to the first threshold, the phase difference being less than or equal to the second threshold, and the frequency difference being less than or equal to the third threshold, control the energy storage converter to perform grid-connected operation.

[0045] In this embodiment, the step of controlling the energy storage converter to perform grid-connected operation according to the third voltage signal and the second voltage signal includes: first, respectively calculating the voltage difference, phase difference and frequency difference between the third voltage signal and the second voltage signal. Then, the voltage difference, phase difference and frequency difference are respectively compared with the first threshold, the second threshold and the third threshold. When the voltage difference is less than or equal to the first threshold, and the phase difference is less than or equal to the second threshold, and the frequency difference is less than or equal to the third threshold, the energy storage converter is controlled to perform grid-connected operation. If the above conditions are not met, the third voltage signal is re-determined until the above conditions are met.

[0046] Figure 8 A second flow chart of a control method for an energy storage converter according to an embodiment of the present invention is shown; wherein the method comprises: Step 802: sampling the output voltage and current of the energy storage converter and the voltage and current of the grid; Step 804: adopt VSG control to simulate the synchronous generator rotor motion characteristic equation; Step 806: introducing adaptive moment of inertia and damping coefficient, and adjusting according to the change of frequency; Step 808: Perform Park transformation on the voltage and current signals to calculate the output active power and reactive power; Step 810: Calculate the square sum of the dq axis difference between the output voltage and the grid-side voltage, and add the active power-frequency link as compensation through the PI controller; Step 812: The voltage difference between the output voltage and the grid-side voltage is added to the reactive-voltage link as compensation through a PI controller; Step 814: Determination ; If the result is yes, execute step 816, if the result is no, re-execute step 810 and step 812; Step 816: Disconnect the pre-synchronization switch to achieve smooth grid connection.

[0047] The control method of the energy storage converter provided by the present invention is mainly a virtual synchronous machine (VSG) improved pre-synchronization off-grid switching method applicable to the energy storage converter, such as Fig. 9 As shown, it mainly includes: a three-phase full-bridge inverter circuit, in which a plurality of switch tubes are included, namely S1, S2, S3, S4, S5 and S6, and a plurality of capacitors C, and a power supply U dc The current flows from points A, B and D through the inductor L1 into the power conditioning center (PCC), where it is processed and finally gets e a 、e b and e c The present invention includes a voltage and current analog signal sampling module, an AD (Analog-to-Digital) conversion module, an instantaneous power calculation module, an active power control loop, a reactive power control loop and a modulation wave synthesis module. Fig.10As shown in FIG. 1 , the control part adopts virtual synchronous machine control and voltage-current dual closed-loop control. First, the three-phase voltage and current of the power grid are collected through the measuring circuit. After the coordinate change, the active power and reactive power actually output by the virtual synchronous machine are calculated. Then, after the virtual synchronous machine control algorithm, and after the rotor motion equation and the stator voltage equation, the system has inertial damping and electromagnetic transient characteristics. Finally, the command value of the voltage signal is obtained. After the coordinate inverse transformation, the three-phase voltage command signal is obtained. The PWM (Pulse Width Modulation) pulse generation module generates pulses to control the grid-connected inverter to realize the control of the converter switch tube. That is, first, the output voltage and output current of the energy storage converter, i.e., i0 and v0, are obtained. Then, the active power P and reactive power Q are obtained through Power Calculate, respectively. Then, the active power reference value P is used. ref and reactive power reference value Q ref The active power P and reactive power Q are compensated respectively, and the detected angular velocity ω is compared with the angular velocity reference value ω ref Calculate and get the angular velocity. Input the compensated active power, compensated reactive power and angular velocity into the algorithm model of the virtual synchronous generator based on the stator electrical equation and the rotor mechanical equation, that is, perform I / ω, I / J, I / s and damping coefficient D processing in sequence, and then get the voltage value and angular velocity. Then get the reference voltage v according to the voltage value and angular velocity ref , while v ref Perform coordinate transformation (abc / dq), and convert the reference voltage v after coordinate transformation ref Entering the voltage and current double closed-loop control, the three-phase current i Labc And the output voltage v0 is transformed into coordinates, and then according to the transformed v 0d and v 0q 、v ref and Labc The current after coordinate transformation is input into multiple PIs (proportional-integral regulators) to obtain a voltage signal, and finally the voltage signal is input into a PWM generator to generate pulses. The PWM generator can send pulses to the inverter through its own ports S1, S2, S3, S4, S5 and S6 to control the converter switch tube.

[0048] The specific process is to first sample the output voltage signal, output current signal, grid voltage signal and grid current signal of the energy storage converter, and then adopt the algorithm model of the virtual synchronous generator based on the stator electrical equation and rotor mechanical equation, and introduce the adaptive adjustable moment of inertia J, and collect the change of system frequency through the ELM neural network algorithm. The change in frequency Δω tracks the damping parameter D in the predictive active-frequency control. Fig.10 As shown in FIG. 1 , it is the overall structure block diagram of the VSG control strategy of the present invention, that is, the process of the algorithm model of the virtual synchronous generator based on the stator electrical equation and the rotor mechanical equation. It can be understood that the mechanical part of the synchronous generator can be expressed as T j =T m -T e -T D , where T j is the inertia torque of the rotor; T m is the mechanical torque; T e is the electromagnetic torque; T D is the damping torque in the system. This equation can be rewritten as an equation with power-speed as a variable: ; Where J is the moment of inertia; ω is the actual angular velocity, Δω is the velocity difference between the two; P m is the input mechanical power; P e is the output electromagnetic power; D is the damping coefficient, ω0 is the initial angular velocity, T m is the mechanical torque, T e is the electromagnetic torque, and θ is the synchronous angular velocity.

[0049] At the same time, the VSG control adaptive adjustable moment of inertia specifically refers to: Δω maximum frequency deviation, Frequency changes, As a judgment condition, such as Figure 12-A and Figure 12-B As shown, Figure 12-A is the curve between power fluctuation and angular velocity, Figure 12-B is the curve between angular velocity and time, where Figure 12-A and Figure 12-B In , , as well as Corresponding to intervals 1, 2, 3 and 4 in Table 1, a, b and c represent the angular velocity δ s The corresponding power P e , angular velocity δ max The corresponding power P e and the angular velocity δ min The corresponding power P e .exist Figure 12-B In the figure, t1, t2, t3, t4 and t5 represent time, ω0 is the initial angular velocity, ω min is the minimum angular velocity and ω max is the maximum angular velocity. It can be seen from the figure that the moment of inertia is related to Δω, as well as The relationship between Figure 12-A and Figure 12-B In , , as well as Corresponding to intervals 1, 2, 3 and 4 in Table 1. As shown in Table 1: Table 1

[0050] Then, in order to simplify the algorithm, the VSG control inertia time constant is set to the maximum and minimum values, and the threshold and are set to prevent the judgment from failing when the frequency oscillates near the zero point. Therefore, the variable inertia controlled by the VSG can be given by the following formula: ; Wherein, J represents the adaptively adjusted moment of inertia; J0 represents the steady-state moment of inertia constant; M represents the system angular velocity change rate threshold; N represents the system angular velocity deviation threshold; and k is the moment of inertia adjustment coefficient.

[0051] Furthermore, the damping coefficient is calculated by the ELM neural network algorithm specifically means that the input variable of the ELM neural network is the frequency change and frequency variable Δω, the output variable is the damping coefficient D, where Fig.13 As shown, the ELM neural network includes an input layer, a hidden layer and an output layer. The hidden layer includes k neurons, and the weight from the input layer to the hidden layer is W ij , the threshold of the hidden layer node is b1~b t , the weight from the hidden layer to the output layer is β ij ; The weights and thresholds of the ELM neural network are obtained through processing; X1, X2 and X n Represents input, Y1, Y2 and Y m Indicates output. The real-time frequency change of the system The frequency change Δω is input into the optimized neural network to obtain the damping coefficient D, where the activation function of the ELM neural network is: ; Among them, y j represents the jth output variable, ω i represents the i-th weight, b j represents the jth weight, x j represents the jth input variable, β i and g i Represents a constant.

[0052] After obtaining the VSG control algorithm model, the voltage and current signals output by the energy storage converter are transformed from abc to dq to calculate the output active power and reactive power, which are respectively sent to the active-frequency link and reactive-voltage link of the VSG control; then Fig.11 As shown, in the pre-synchronization voltage phase, the d-axis component u of the output voltage of the energy storage converter is o_d The d-axis component u of the grid voltage g_d Square the difference and convert the q-axis component u of the output voltage of the energy storage converter o_q The q-axis component u of the grid voltage g_q The difference is squared, and the sum of the two squares is compensated to the energy storage converter output active power through PI (proportional-integral regulator) control and LowPass Filter. In the pre-synchronization voltage amplitude, the energy storage converter output voltage u o With grid voltage u g The difference is made and compensated to the output voltage of the energy storage converter through PI (proportional-integral regulator) control and Low Pass Filter. In the pre-synchronization voltage amplitude, the output voltage u of the energy storage converter is o It can be the d-axis component u of the output voltage of the energy storage converter o_d , grid voltage u g It can be the d-axis component u of the grid voltage g_q Specifically, first determine that Park transformation transforms the variables in the two-phase stationary coordinate system into the DC quantities in the dq two-phase rotating coordinate system. Based on the relationship between the two, the inverter variable formula in the two-phase rotating coordinate system can be obtained: ; Among them, u d represents the voltage component on the d-axis, u q represents the voltage component on the q axis, u α It represents the component of voltage on the axis, u β It represents the voltage component on the β axis.

[0053] Then, according to the above formula, the components of the energy storage converter output voltage on the dq axis and the components of the grid voltage on the dq axis are calculated respectively. o_d 、u o_q They represent the components of the output voltage of the energy storage converter on the dq axis, u g_d 、u g_q Represent the components of the grid voltage on the d and q axes respectively. o_d with u g_d The error Δu is obtained by subtracting d , will u o_q with ug_q The error Δu is obtained by subtracting q , then square the two errors and sum them to get Δu 2 The PI regulator then performs error-free regulation to obtain the phase compensation value Δθ. The formula is as follows: ; Among them, u o_d 、u o_q They represent the components of the output voltage of the energy storage converter on the dq axis, u g_d 、u g_q They represent the components of the grid voltage on the d and q axes, Δu d is u o_d with u g_d The error between q is u o_q with u g_q The error between 2 represents the sum of the squares of the two error quantities.

[0054] Finally, the phase difference and amplitude difference between the output voltage of the energy storage converter and the grid voltage are used to determine whether the system meets the grid connection conditions. When the difference is less than the predetermined threshold, the system meets the grid connection conditions, and the grid connection command is issued and the grid connection closing operation is completed. Among them, the VSG output voltage and the grid voltage are: ; The instantaneous voltage difference between the two is: ; It can be seen that the error value Δu is a sinusoidal quantity. When the phases of the two input voltages are equal, that is, θ1 is equal to θ2, the error Δu is equal to zero, that is, the phase synchronization is completed. θ1 represents the phase of the VSG output voltage, θ2 represents the phase of the grid voltage, and U represents the voltage.

[0055] When the voltage difference and frequency difference between the VSG control output voltage and the grid-side voltage meet the following conditions, the pre-synchronization switch is disconnected to achieve smooth grid connection of the system: ; Among them, Δω, Δθ, and ΔU are the frequency difference, phase difference, and voltage difference between the microgrid and the three-phase grid, respectively; A, B, and C are the thresholds of the frequency difference, phase difference, and voltage difference, respectively.

[0056] Fig.14 A schematic block diagram of a control system of an energy storage converter according to an embodiment of the present invention is shown; wherein the control system 140 of the energy storage converter includes: A first acquisition module 1402, used to acquire a first voltage signal and a first current signal of the energy storage converter and a second voltage signal of the power grid; A first determination module 1404, configured to determine the active power and reactive power of the energy storage converter according to the first voltage signal and the first current signal; A first calculation module 1406, configured to determine a phase compensation value and an amplitude compensation value according to the first voltage signal and the second voltage signal; The first processing module 1408 is used to input the active power, reactive power, phase compensation value and amplitude compensation value into the virtual synchronous generator control algorithm model to obtain a third voltage signal; The second processing module 1410 is used to control the energy storage converter to perform grid-connected operation according to the third voltage signal and the second voltage signal.

[0057] The control system 140 of the energy storage converter provided by the present invention mainly includes: a first acquisition module 1402, a first determination module 1404, a first calculation module 1406, a first processing module 1408 and a second processing module 1410. Among them, the first acquisition module 1402 can collect the first voltage signal and the first current signal output by the energy storage converter, and also collect the second voltage signal of the power grid. Then the first determination module 1404 determines the active power and reactive power of the energy storage converter according to the first voltage signal and the first current signal, wherein the first voltage signal can be a three-phase voltage, and the first current signal can be a three-phase current. Therefore, when determining the active power and reactive power of the energy storage converter according to the first voltage signal and the first current signal, it is necessary to perform coordinate transformation processing on the first voltage signal and the first current signal, that is, convert the current and voltage in the three-phase stationary coordinate system (abc coordinate system) into the current and voltage in the rotating coordinate system (dq coordinate system), and then use the current and voltage in the converted rotating coordinate system to calculate the active power and reactive power of the energy storage converter. Then the first calculation module 1406 determines the phase compensation value and the amplitude compensation value according to the first voltage signal and the second voltage signal, wherein the process of determining the phase compensation value according to the first voltage signal and the second voltage signal is the process of pre-synchronizing the voltage phase, and by comparing the two voltage signals, the phase compensation value that needs to be compensated when the energy storage inverter is connected to the grid is determined, and the process of determining the amplitude compensation value according to the first voltage signal and the second voltage signal is the process of pre-synchronizing the amplitude, and by comparing the two voltage signals, the amplitude compensation value that needs to be compensated when the energy storage inverter is connected to the grid is determined. After determining the amplitude compensation value and the phase compensation value, the first processing module 1408 inputs the amplitude compensation value, the phase compensation value, the active power and the reactive power into the virtual synchronous generator control algorithm model to obtain a third voltage signal, wherein the virtual synchronous generator control algorithm model is obtained through the virtual synchronous generator (VSG, Virtual Synchronous Generator) technology. The virtual synchronous generator can imitate the dynamic characteristics of the synchronous generator, provide rotational inertia and damping for the power system, and contribute to the stable operation of the power system. Therefore, after the amplitude compensation value, the phase compensation value, the active power and the reactive power are input into the virtual synchronous generator control algorithm model, the virtual synchronous generator control algorithm model will determine the voltage signal emitted by the energy storage converter when it is in the grid-connected working mode, that is, the third voltage signal, according to the amplitude compensation value, the phase compensation value, the active power and the reactive power and the rotational inertia and damping in the virtual synchronous generator control algorithm model.Finally, the second processing module 1410 compares the third voltage signal with the second voltage signal. If the comparison result meets the preset conditions, the energy storage converter is controlled to perform grid-connected operation. If the comparison result does not meet the preset conditions, the above process is repeated until the comparison result meets the preset conditions, wherein the preset conditions refer to that the voltage difference and frequency difference between the third voltage signal and the second voltage signal are both less than the preset threshold. The present invention determines the active power and reactive power of the energy storage converter according to the first voltage signal and the first current signal, and then determines the phase compensation value and the amplitude compensation value according to the output voltage of the energy storage converter, i.e., the first voltage signal and the second voltage signal of the power grid, and then determines the final third voltage signal according to the active power, reactive power, phase compensation value, amplitude compensation value and virtual synchronous generator control algorithm model, and finally controls the energy storage converter to switch between off-grid working mode and grid-connected working mode according to the third voltage signal and the second voltage signal. The present invention simplifies the control structure by avoiding the use of a phase-locked loop during the on-grid and off-grid switching process, making the control structure simpler, the algorithm performance better, and the synchronization stability of the system improved; at the same time, by improving the pre-synchronization phase control and adopting fast phase tracking adjustment, the phase synchronization time is shortened, and fast switching between on-grid and off-grid working modes is achieved.

[0058] In some embodiments, optionally, the control system 140 of the energy storage inverter is also used to determine the frequency change and frequency change of the virtual synchronous generator; determine the moment of inertia based on the frequency change and the frequency change; determine the damping coefficient based on the frequency change and the frequency change; construct a first mathematical equation based on the moment of inertia and the damping coefficient, wherein the first mathematical equation is an equation with power and speed as variables; determine the virtual synchronous generator control algorithm model based on the first mathematical equation and the stator electrical equation.

[0059] In this embodiment, the control system 140 of the energy storage converter is also used to first determine the frequency change amount and the frequency change amount of the virtual synchronous generator, and then determine the moment of inertia based on the frequency change amount and the frequency change amount, wherein the moment of inertia is an adaptively adjustable moment of inertia, which is related to the frequency converter and the frequency change amount, and therefore the moment of inertia needs to be determined based on the frequency change amount and the frequency change amount. Then the damping coefficient is determined based on the frequency change amount and the frequency change amount, wherein the damping coefficient is also an adaptively adjustable damping coefficient. After obtaining the damping coefficient and the moment of inertia, a first mathematical equation is constructed based on the moment of inertia and the damping coefficient, wherein the first mathematical equation is an equation with power and speed as variables, that is, a rotor mechanical equation with power and speed as variables is constructed through the moment of inertia and the damping coefficient. Then the virtual synchronous generator control algorithm model is determined based on the stator electrical equation and the first mathematical equation. In the present invention, the moment of inertia and the damping coefficient are determined according to the frequency variation and the frequency change, and then the rotor mechanical equation is constructed according to the moment of inertia and the damping coefficient. Finally, the virtual synchronous generator control algorithm model is obtained according to the rotor mechanical equation and the stator electrical equation, thereby realizing adaptive regulation, fast tracking speed, suppressing system power oscillation, maintaining stable system operation, and also suppressing transient overcurrent occurring during the switching process between on-grid and off-grid, thereby realizing seamless switching between on-grid and off-grid.

[0060] In some embodiments, optionally, the control system 140 of the energy storage converter is also used to determine the frequency change amount, the change relationship between the frequency change amount and the moment of inertia; and determine the moment of inertia according to the change relationship and the time constant.

[0061] In this embodiment, the step of determining the moment of inertia according to the frequency variation and the frequency change comprises: first determining the variation relationship among the frequency variation, the frequency change and the moment of inertia, wherein the variation relationship comprises: when the frequency variation is greater than zero and the frequency variation is greater than zero, the moment of inertia gradually increases. When the frequency variation is greater than zero and the frequency variation is less than zero, the moment of inertia gradually decreases. When the frequency variation is less than zero and the frequency variation is less than zero, the moment of inertia gradually increases. When the frequency variation is less than zero and the frequency variation is greater than zero, the moment of inertia gradually decreases. It can be seen that the moment of inertia is an adaptive and adjustable moment of inertia, so in order to facilitate the determination of the moment of inertia, a mathematical formula can be established according to the variation relationship and the time constant, and then the current frequency variation and the frequency variation are input into the mathematical formula to obtain the required moment of inertia.

[0062] In some embodiments, optionally, the control system 140 of the energy storage converter is also used to determine an extreme learning machine neural network model; the frequency variation and the frequency change are input into the extreme learning machine neural network model to obtain a damping coefficient.

[0063] In this embodiment, the step of determining the damping coefficient according to the frequency variation and the frequency change comprises: first determining an extreme learning machine (ELM) neural network model, wherein the ELM neural network model mainly comprises: an input layer, a hidden layer, and an output layer. Then the frequency variation and the frequency change are input into the ELM neural network model to obtain the damping coefficient. The damping coefficient is determined by using the ELM neural network model, thereby ensuring the accuracy of the damping coefficient on the one hand, and improving the work efficiency on the other hand.

[0064] In some embodiments, optionally, the first calculation module 1406 is specifically used to perform coordinate transformation processing on the first voltage signal to obtain a fourth voltage signal and a fifth voltage signal, wherein the fourth voltage signal is a voltage signal on the direct axis and the fifth voltage signal is a voltage signal on the quadrature axis; perform coordinate transformation processing on the second voltage signal to obtain a sixth voltage signal and a seventh voltage signal, wherein the sixth voltage signal is a voltage signal on the direct axis and the seventh voltage signal is a voltage signal on the quadrature axis; determine a first difference between the fourth voltage signal and the sixth voltage signal; determine a second difference between the fifth voltage signal and the seventh voltage signal; and determine a phase compensation value and an amplitude compensation value based on the first difference and the second difference.

[0065] In this embodiment, the first calculation module 1406 is specifically used to perform coordinate transformation processing on the first voltage signal to obtain a fourth voltage signal and a fifth voltage signal, wherein the coordinate transformation processing refers to converting the voltage in the three-phase stationary coordinate system (abc coordinate system) into the voltage in the rotating coordinate system (dq coordinate system), so that the fourth voltage signal obtained is a voltage signal on the direct axis (d axis), and the fifth voltage signal is a voltage signal on the quadrature axis (q axis). Similarly, the second voltage signal is subjected to coordinate transformation processing to obtain a sixth voltage signal and a seventh voltage signal, wherein the sixth voltage signal is a voltage signal on the direct axis (d axis), and the seventh voltage signal is a voltage signal on the quadrature axis (q axis). Then, the first difference between the fourth voltage signal and the sixth voltage signal is calculated, and the second difference between the fifth voltage signal and the sixth voltage signal is calculated, and finally, the phase compensation value and the amplitude compensation value are determined according to the first difference and the second difference. The first voltage signal and the second voltage signal are respectively transformed into coordinates to obtain the corresponding direct-axis voltage and quadrature-axis voltage, and then the direct-axis voltage difference and the quadrature-axis voltage difference of the two voltages are respectively calculated, and finally the phase compensation value and the amplitude compensation value are determined according to the two differences, thereby improving the pre-synchronization phase control, adopting fast phase tracking adjustment, and shortening the phase synchronization time.

[0066] In some embodiments, optionally, the first calculation module 1406 is also specifically used to perform a first processing operation on the first difference to obtain an amplitude compensation value, wherein the first processing operation includes: a proportional integral control operation and a low-pass filtering processing operation; performing a square operation on the first difference to obtain a third difference; performing a square operation on the second difference to obtain a fourth difference; calculating the sum of the third difference and the fourth difference to obtain a first numerical value; performing a first processing operation on the first numerical value to obtain a phase compensation value.

[0067] In this embodiment, the first calculation module 1406 is also specifically used to perform a first processing operation on the first difference to obtain an amplitude compensation value, wherein the first processing operation includes a proportional integral control operation and a low-pass filter processing operation. That is, the first difference is input into a proportional integral (PI) controller and a low-pass filter for processing, thereby obtaining an amplitude compensation value. Then, a square operation is performed on the first difference to obtain a third difference, and a square operation is performed on the second difference to obtain a fourth difference, and then the sum of the third difference and the fourth difference is calculated to obtain a first value, and finally, the first value is subjected to a first processing operation to obtain a phase compensation value. That is, after obtaining the first value, the first value is input into a PI controller and a low-pass filter to obtain a phase compensation value.

[0068] In some embodiments, optionally, the second processing module 1410 is specifically used to respectively calculate the voltage difference, phase difference and frequency difference between the third voltage signal and the second voltage signal; based on the voltage difference being less than or equal to the first threshold, the phase difference being less than or equal to the second threshold, and the frequency difference being less than or equal to the third threshold, the energy storage inverter is controlled to perform grid-connected operation.

[0069] In this embodiment, the second processing module 1410 is specifically used to calculate the voltage difference, phase difference and frequency difference between the third voltage signal and the second voltage signal, respectively. Then the voltage difference, phase difference and frequency difference are compared with the first threshold, the second threshold and the third threshold, respectively. When the voltage difference is less than or equal to the first threshold, and the phase difference is less than or equal to the second threshold, and the frequency difference is less than or equal to the third threshold, the energy storage converter is controlled to perform grid-connected operation. If the above conditions are not met, the third voltage signal is re-determined until the above conditions are met.

[0070] Fig.15 A schematic block diagram of an electronic device of an embodiment of the present invention is shown; wherein the electronic device 150 includes a memory 1502, a processor 1504, and a computer program stored in the memory 1502 and executable on the processor 1504, and when the processor 1504 executes the computer program, the steps of the control method of the energy storage converter as described above are implemented.

[0071] The electronic device 150 provided by the present invention implements the steps of the control method of the energy storage converter when the processor 1504 executes the computer program, which can achieve the technical effect of any of the above embodiments and will not be repeated.

[0072] An embodiment of the present invention provides a storage medium on which a computer program is stored. When the computer program is executed by a processor, the steps of the control method of the energy storage converter as described above are implemented.

[0073] The storage medium provided by the present invention implements the steps of the control method of the above-mentioned energy storage converter when the computer program is executed by the processor, which can achieve the technical effect of any of the above-mentioned embodiments and will not be repeated here.

[0074] In the description of this specification, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance unless otherwise clearly specified and limited; the terms "connection", "installation", "fixation" and the like should be understood in a broad sense, for example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0075] In the description of this specification, the description of the terms "one embodiment", "some embodiments", "specific embodiments", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0076] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A control method for an energy storage converter, characterized in that: include: Collecting a first voltage signal and a first current signal of the energy storage converter and a second voltage signal of the power grid; Determine the active power and reactive power of the energy storage converter according to the first voltage signal and the first current signal; determining a phase compensation value and an amplitude compensation value according to the first voltage signal and the second voltage signal; Inputting the active power, the reactive power, the phase compensation value and the amplitude compensation value into a virtual synchronous generator control algorithm model to obtain a third voltage signal; The energy storage converter is controlled to perform grid-connected operation according to the third voltage signal and the second voltage signal.

2. The control method of the energy storage converter according to claim 1, characterized in that: Before the step of inputting the active power, the reactive power, the phase compensation value and the amplitude compensation value into the virtual synchronous generator control algorithm model to obtain the third voltage signal, the step includes: determining a frequency variation and a frequency change of a virtual synchronous generator; determining the moment of inertia according to the frequency variation and the frequency change; determining a damping coefficient according to the frequency variation and the frequency change; constructing a first mathematical equation according to the moment of inertia and the damping coefficient, wherein the first mathematical equation is an equation with power and rotation speed as variables; The virtual synchronous generator control algorithm model is determined according to the first mathematical equation and the stator electrical equation.

3. The control method of the energy storage converter according to claim 2, characterized in that: The step of determining the moment of inertia according to the frequency variation and the frequency change comprises: Determining the frequency variation, and a variation relationship between the frequency variation and the moment of inertia; The moment of inertia is determined based on the frequency variation, the frequency change, the variation relationship, and a time constant.

4. The control method of the energy storage converter according to claim 2, characterized in that: The step of determining the damping coefficient according to the frequency variation and the frequency change comprises: Determine the extreme learning machine neural network model; The frequency variation and the frequency change are input into the extreme learning machine neural network model to obtain the damping coefficient.

5. The control method of the energy storage converter according to any one of claims 1 to 4, characterized in that: The step of determining a phase compensation value and an amplitude compensation value according to the first voltage signal and the second voltage signal comprises: Performing coordinate transformation processing on the first voltage signal to obtain a fourth voltage signal and a fifth voltage signal, wherein the fourth voltage signal is a voltage signal on a direct axis, and the fifth voltage signal is a voltage signal on a quadrature axis; Performing coordinate transformation processing on the second voltage signal to obtain a sixth voltage signal and a seventh voltage signal, wherein the sixth voltage signal is a voltage signal on a direct axis, and the seventh voltage signal is a voltage signal on a quadrature axis; determining a first difference between the fourth voltage signal and the sixth voltage signal; determining a second difference between the fifth voltage signal and the seventh voltage signal; The phase compensation value and the amplitude compensation value are determined according to the first difference and the second difference.

6. The control method of the energy storage converter according to claim 5, characterized in that: The step of determining the phase compensation value and the amplitude compensation value according to the first difference and the second difference comprises: Performing a first processing operation on the first difference to obtain the amplitude compensation value, wherein the first processing operation includes: a proportional integral control operation and a low-pass filtering operation; Performing a square operation on the first difference to obtain a third difference; Performing a square operation on the second difference to obtain a fourth difference; Calculating the sum of the third difference and the fourth difference to obtain a first value; The first processing operation is performed on the first value to obtain the phase compensation value.

7. The control method of the energy storage converter according to claim 1, characterized in that: The step of controlling the energy storage converter to perform grid-connected operation according to the third voltage signal and the second voltage signal comprises: respectively calculating a voltage difference, a phase difference and a frequency difference between the third voltage signal and the second voltage signal; Based on the fact that the voltage difference is less than or equal to a first threshold, the phase difference is less than or equal to a second threshold, and the frequency difference is less than or equal to a third threshold, the energy storage converter is controlled to perform grid-connected operation.

8. A control system for an energy storage converter, characterized in that: include: A first acquisition module, the first acquisition module is used to acquire a first voltage signal and a first current signal of the energy storage converter and a second voltage signal of the power grid; A first determination module, the first determination module is used to determine the active power and reactive power of the energy storage converter according to the first voltage signal and the first current signal; a first calculation module, the first calculation module being used to determine a phase compensation value and an amplitude compensation value according to the first voltage signal and the second voltage signal; A first processing module, wherein the first processing module is used to input the active power, the reactive power, the phase compensation value and the amplitude compensation value into a virtual synchronous generator control algorithm model to obtain a third voltage signal; A second processing module, wherein the second processing module is used to control the energy storage converter to perform grid-connected operation according to the third voltage signal and the second voltage signal.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the computer program, the steps of the method for controlling the energy storage converter according to any one of claims 1 to 7 are implemented.

10. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method for controlling the energy storage converter according to any one of claims 1 to 7 are implemented.

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