Power compensation method and device based on parallel energy storage converter

Abstract

The invention discloses a power compensation method and device based on a parallel energy storage converter, and relates to the field of power systems, and the method comprises the steps: obtaining the maximum transmission power of a first energy storage converter; obtaining the maximum output apparent power accessed to the second energy storage converter based on the direct voltage compensation control strategy; according to the maximum transmission power of the first energy storage converter, the load apparent power of the power system, the power factor angle and the maximum output apparent power of the second energy storage converter, an objective function is constructed, and the objective function is used for representing the incidence relation between the output power factor of the first energy storage converter and the voltage compensation capability value of the energy storage system; and determining a target reactive compensation amount for the first energy storage converter according to the target function. The problem that reactive power output is difficult to automatically adjust to improve the overall voltage compensation capability of the system when the parallel energy storage converter in the power system responds to the power instruction, especially under the condition of voltage drop is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power systems, in particular, to a power compensation method and device based on a parallel type energy storage converter. BACKGROUND

[0002] With the wide application of distributed energy and renewable energy, the stability of the power grid and the power quality in the power system are facing new challenges. As an important part of the power system, the main function of the parallel type energy storage converter is to respond to the power instruction and realize the storage and release of electric energy. However, when the grid voltage drops, because the traditional energy storage converter control strategy mainly focuses on the transmission and control of active power, and the dynamic adjustment capability of reactive power is insufficient, the reactive power compensation capability is limited, and the parallel type energy storage converter usually cannot automatically and quickly adjust the reactive power output, in this case, the parallel type energy storage converter cannot effectively improve the overall voltage compensation capability of the system, resulting in slow recovery of the grid voltage and affecting the stability of the power system and the power quality.

[0003] At present, there is no effective solution to the above problems. SUMMARY

[0004] The embodiments of the present application provide a power compensation method and device based on a parallel type energy storage converter, to at least solve the technical problem that the parallel type energy storage converter in the power system is difficult to automatically adjust the reactive power output to improve the overall voltage compensation capability of the system when responding to the power instruction, especially in the case of voltage drop.

[0005] According to an aspect of an embodiment of the present application, a power compensation method based on a parallel type energy storage converter is provided, comprising: obtaining the maximum transmission power of a first energy storage converter, wherein the first energy storage converter is a parallel type energy storage converter considering power instruction response and harmonic current compensation access, wherein the first energy storage converter obtains a power instruction value according to the improved allocation result of the power instruction; obtaining the maximum output apparent power of a second energy storage converter based on a direct voltage compensation control strategy accessing the power system, wherein the apparent power value output by the second energy storage converter is related to the compensation voltage amplitude output by the second energy storage converter, and the second energy storage converter is a series type energy storage converter; constructing a target function according to the maximum transmission power of the first energy storage converter, the load apparent power of the power system, the power factor angle and the maximum output apparent power of the second energy storage converter, wherein the target function is used to represent the correlation between the output power factor of the first energy storage converter and the voltage compensation capability value of the energy storage system, the output power factor is the ratio of the output active power and the apparent power of the first energy storage converter, and the voltage compensation capability value is used to quantitatively represent the degree of voltage drop or fluctuation compensation of the energy storage converter; determining the target reactive compensation amount for the first energy storage converter according to the target function.

[0006] Optionally, the target function is constructed according to the maximum transmission power of the first energy storage converter, the load apparent power of the power system, the power factor angle, and the maximum output apparent power of the second energy storage converter, including: obtaining the inductive reactance value and the impedance value in the line impedance; constructing the target function according to the inductive reactance value, the impedance value, the maximum transmission power of the first energy storage converter, the load apparent power of the power system, the power factor angle, and the maximum output apparent power of the second energy storage converter.

[0007] Optionally, the target function is constructed according to the inductive reactance value, the impedance value, the maximum transmission power of the first energy storage converter, the load apparent power of the power system, the power factor angle, and the maximum output apparent power of the second energy storage converter, including: constructing the cosine function and the sine function about the output power factor of the first energy storage converter; constructing the cosine function and the sine function about the power factor angle; constructing the target function according to the cosine function and the sine function of the output power factor, the cosine function and the sine function of the power factor angle, the inductive reactance value, the impedance value, the maximum transmission power of the first energy storage converter, the load apparent power of the power system, and the maximum output apparent power of the second energy storage converter.

[0008] Optionally, the target function is constructed according to the cosine function and the sine function of the output power factor, the cosine function and the sine function of the power factor angle, the inductive reactance value, the impedance value, the maximum transmission power of the first energy storage converter, the load apparent power of the power system, and the maximum output apparent power of the second energy storage converter, including: calculating the product of the sine function of the output power factor and the inductive reactance value to obtain a first sub-function; calculating the product of the cosine function of the output power factor and the impedance value to obtain a second sub-function; summing the first sub-function and the second sub-function to obtain a third sub-function; calculating the product of the third sub-function and the maximum transmission power of the first energy storage converter to obtain a fourth sub-function; constructing the target function according to the fourth sub-function, the cosine function and the sine function of the power factor angle, the load apparent power of the power system, and the maximum output apparent power of the second energy storage converter.

[0009] Optionally, the target function is constructed according to the fourth sub-function, the cosine function and the sine function of the power factor angle, the load apparent power of the power system and the maximum output apparent power of the second energy storage converter, including: calculating the product of the sine function of the power factor angle and the load apparent power of the power system to obtain a fifth sub-function; calculating the product of the sine function of the output power factor and the maximum transmission power of the first energy storage converter to obtain a sixth sub-function; performing a complete square difference operation on the fifth sub-function and the sixth sub-function to obtain a seventh sub-function; calculating the product of the cosine function of the power factor angle and the load apparent power of the power system to obtain an eighth sub-function; calculating the product of the cosine function of the output power factor and the maximum transmission power of the first energy storage converter to obtain a ninth sub-function; performing a complete square difference operation on the eighth sub-function and the ninth sub-function to obtain a tenth sub-function; summing the seventh sub-function and the tenth sub-function, and calculating an arithmetic square root of the sum to obtain an eleventh sub-function; calculating the ratio of the maximum output apparent power of the second energy storage converter and the eleventh sub-function to obtain a twelfth sub-function; summing the fourth sub-function and the twelfth sub-function to obtain the target function.

[0010] Optionally, the target reactive compensation quantity for the first energy storage converter is determined according to the target function, including: constructing a partial derivative function of the target function; calculating a target solution about the output power factor when the partial derivative function is equal to 0; calculating a target sine value corresponding to the target solution; calculating the product of the target sine value and the maximum output apparent power of the second energy storage converter to obtain the target reactive compensation quantity of the first energy storage converter.

[0011] Optionally, after the target reactive compensation quantity for the first energy storage converter is determined according to the target function, the power compensation method based on the parallel type energy storage converter further includes: when it is detected that the grid voltage drops, performing reactive power compensation on the first energy storage converter according to the target reactive compensation quantity.

[0012] Optionally, after the maximum output apparent power of the second energy storage converter accessing the power system based on the direct voltage compensation control strategy is obtained, the power compensation method based on the parallel type energy storage converter further includes: calculating the product of the current flowing through the transformer line and the compensation voltage output by the second energy storage converter to obtain the apparent power currently output by the second energy storage converter; calculating the ratio of the maximum output apparent power of the second energy storage converter and the current flowing through the transformer line, and selecting the minimum value between the ratio and the maximum compensation voltage that can be output by the second energy storage converter limited by the withstand voltage of the switching device as the maximum output compensation voltage of the second energy storage converter.

[0013] According to a further aspect of the embodiments of the present application, a power compensation device based on a parallel energy storage converter is also provided, comprising: a transmission power acquisition unit configured to acquire maximum transmission power of a first energy storage converter, wherein the first energy storage converter is a parallel energy storage converter considering power instruction response cooperative harmonic current compensation access, and wherein the first energy storage converter obtains a power instruction value according to an improved allocation result of the power instruction; a reactive power acquisition unit configured to acquire maximum output reactive power of a second energy storage converter based on direct voltage compensation control strategy access to a power system, wherein a reactive power value output by the second energy storage converter is related to a compensation voltage amplitude value output by the second energy storage converter, and the second energy storage converter is a series energy storage converter; a target function construction unit configured to construct a target function according to the maximum transmission power of the first energy storage converter, load reactive power of the power system, a power factor angle, and the maximum output reactive power of the second energy storage converter, wherein the target function is used to represent a correlation between an output power factor of the first energy storage converter and a voltage compensation capability value of the energy storage system, the output power factor is a ratio of output active power and reactive power of the first energy storage converter, and the voltage compensation capability value is used to quantitatively represent a degree of voltage drop or fluctuation compensated by the energy storage converter; and a reactive power compensation determination unit configured to determine a target reactive power compensation amount for the first energy storage converter according to the target function.

[0014] According to a further aspect of the embodiments of the present application, a computer readable storage medium is also provided, and the computer readable storage medium stores a computer program, wherein when the computer program is executed, the computer readable storage medium causes a device where the computer readable storage medium is located to perform the power compensation method based on the parallel energy storage converter.

[0015] According to a further aspect of the embodiments of the present application, an electronic device is also provided, comprising one or more processors and a memory, and the memory is configured to store one or more programs, wherein when the one or more programs are executed by the one or more processors, the one or more processors perform the power compensation method based on the parallel energy storage converter.

[0016] According to a further aspect of the embodiments of the present application, a computer program product is also provided, comprising a computer program or instructions, and the computer program or instructions, when executed by a processor, implement the power compensation method based on the parallel energy storage converter.

[0017] In the embodiment of the present application, the power control system can first acquire the maximum transmission power of the first energy storage converter, wherein the first energy storage converter is a parallel energy storage converter considering power instruction response and harmonic current compensation access, and the first energy storage converter obtains a power instruction value according to an improved allocation result of the power instruction; and acquire the maximum output apparent power of the second energy storage converter based on the direct voltage compensation control strategy access to the power system, wherein the apparent power value output by the second energy storage converter is related to the compensation voltage amplitude output by the second energy storage converter, and the second energy storage converter is a series energy storage converter. Then, according to the maximum transmission power of the first energy storage converter, the load apparent power of the power system, the power factor angle and the maximum output apparent power of the second energy storage converter, a target function is constructed, wherein the target function is used to represent the correlation between the output power factor of the first energy storage converter and the voltage compensation capability value of the energy storage system, the output power factor is the ratio of the output active power and the apparent power of the first energy storage converter, and the voltage compensation capability value is used to quantitatively represent the degree of voltage drop or fluctuation compensated by the energy storage converter. Finally, the target reactive compensation amount for the first energy storage converter is determined according to the target function.

[0018] From the above, the embodiment of the present application provides accurate power parameters for the power control system by acquiring the maximum transmission power of the first energy storage converter and the maximum output apparent power of the second energy storage converter. The first energy storage converter, as a parallel device, can dynamically adjust the power instruction value according to the improved power allocation result in combination with harmonic current compensation. The maximum output apparent power of the second energy storage converter, as a series device, is related to the compensation voltage amplitude and can directly affect the voltage level of the power grid. By constructing the target function, the power control system can quantify the relationship between the output power factor of the first energy storage converter and the voltage compensation capability of the energy storage system, thereby optimizing the allocation of reactive power.

[0019] In the case of voltage drop, the present application uses the target function to determine the target reactive compensation amount of the first energy storage converter, so as to automatically adjust the reactive power output. Through automatic adjustment, the parallel energy storage converter can quickly respond when the voltage drops and provide necessary reactive power support, thereby improving the overall voltage compensation capability of the system. The power control system of the present application can more effectively manage voltage fluctuations, enhance the stability and power quality of the power grid, and thus solve the technical problem that it is difficult for the parallel energy storage converter in the power system to automatically adjust the reactive power output to improve the overall voltage compensation capability of the system when the power instruction responds, especially in the case of voltage drop. BRIEF DESCRIPTION OF DRAWINGS

[0020] The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and together with the description serve to explain the application. In the drawings:

[0021] Figure 1 is a schematic diagram of an optional power compensation method based on a parallel type energy storage converter according to an embodiment of the application;

[0022] Figure 2 is a schematic diagram of a harmonic current elimination and improved power control circuit of an energy storage converter considering power instruction response and harmonic current compensation access according to an embodiment of the application;

[0023] Figure 3 is a three-dimensional surface diagram of system voltage compensation capability of an energy storage converter considering power instruction response and harmonic current compensation access according to an embodiment of the application;

[0024] Figure 4 is a schematic diagram of an optional power compensation device based on a parallel type energy storage converter according to an embodiment of the application. DETAILED DESCRIPTION

[0025] In order to enable persons skilled in the art to better understand the scheme of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by persons skilled in the art without creative labor should fall within the scope of protection of the present application.

[0026] It should be noted that the terms "first", "second", and the like in the specification and claims of the present application and the above-described drawings are used to distinguish similar objects, and do not necessarily have to be used to describe a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to only those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to the process, method, product or device.

[0027] According to the power compensation method based on the parallel energy storage converter provided in the embodiments of the present application, it should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0028] According to the power compensation method based on the parallel energy storage converter provided in the embodiments of the present application, it should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0029] Figure 1 The power compensation method based on the parallel energy storage converter according to the embodiments of the present application is shown in FIG. 1, which includes the following steps: Figure 1

[0030] In step S101, the maximum transmission power of the first energy storage converter is obtained, wherein the first energy storage converter is a parallel energy storage converter connected for power instruction response and harmonic current compensation, and the power instruction value of the first energy storage converter is obtained according to the improved allocation result of the power instruction.

[0031] Optionally, the first energy storage converter can adopt a parallel energy storage converter, which can not only respond to the power instruction, but also cooperatively compensate the harmonic current. The first energy storage converter determines its power instruction value through an improved power allocation strategy. Specifically, the purpose of obtaining the maximum transmission power of the first energy storage converter is to understand the maximum capability range of the first energy storage converter in the power system. The maximum transmission power of the first energy storage converter is used to represent the sum of the maximum active power and reactive power that the first energy storage converter can transmit under normal working conditions. By considering the power instruction response and the cooperative harmonic current compensation, the first energy storage converter can more effectively participate in the voltage regulation and power quality improvement of the power grid. The improved allocation result of the power instruction is used to represent the optimized allocation of the power output of the first energy storage converter after considering the actual demand of the power grid, the performance limitation of the converter and the harmonic compensation requirement, so as to obtain the power instruction value that can meet the power response and voltage compensation requirements at the same time.

[0032] ​In step S102, the maximum output apparent power of the second energy storage converter based on the direct voltage compensation control strategy accessing the power system is obtained, wherein the apparent power value output by the second energy storage converter to the power grid is related to the amplitude of the output compensation voltage, and the second energy storage converter is a series type energy storage converter.

[0033] Optionally, the second energy storage converter can be a series type energy storage converter, and the second energy storage converter accesses the power grid through the direct voltage compensation control strategy. The main function of the second energy storage converter is to output a compensation voltage to the power grid to improve the voltage level of the power grid. The maximum output apparent power of the second energy storage converter is used to represent the sum of the maximum active power and reactive power that the second energy storage converter can output under given power grid conditions. The apparent power value output by the second energy storage converter to the power grid is closely related to the amplitude of the output compensation voltage, i.e. the greater the amplitude of the compensation voltage, the greater the apparent power output. By obtaining the maximum output apparent power of the second energy storage converter, the ability of the second energy storage converter in power grid voltage compensation can be better evaluated, thereby optimizing the voltage regulation strategy of the entire power system. Through the direct voltage compensation control strategy, the second energy storage converter can effectively respond to changes in the power grid voltage, provide necessary voltage support, and enhance the stability and power quality of the power system.

[0034] In step S103, a target function is constructed according to the maximum transmission power of the first energy storage converter, the load apparent power of the power system, the power factor angle, and the maximum output apparent power of the second energy storage converter, wherein the target function is used to represent the correlation between the output power factor of the first energy storage converter and the voltage compensation capability value of the energy storage system, the output power factor is the ratio of the output active power and the apparent power of the first energy storage converter, and the voltage compensation capability value is used to quantify the degree of compensation of the energy storage converter for voltage drop or fluctuation.

[0035] Optionally, the load apparent power of the power system is used to represent the total apparent power of all loads in the current power grid, including active power and reactive power, reflecting the actual load demand of the power grid.

[0036] Optionally, the power factor angle is used to represent the phase angle that measures the power factor in the power grid, which can directly affect the active and reactive power distribution of the power grid, and the size of the power factor angle determines the size and direction of the reactive power in the power grid. The maximum output apparent power of the second energy storage converter is used to represent the maximum apparent power that the second energy storage converter can output under the direct voltage compensation control strategy, which is related to the output compensation voltage amplitude and reflects the maximum capability of the second energy storage converter in voltage compensation. The output power factor is used to represent the ratio of the output active power to the apparent power of the first energy storage converter, which reflects the efficiency and power distribution of the first energy storage converter when transmitting power. The voltage compensation capability value is used to quantify the actual effect of the energy storage converter when compensating voltage drop or fluctuation, which is a quantitative index for measuring the voltage compensation capability of the energy storage converter.

[0037] By constructing the objective function, the correlation between the output power factor of the first energy storage converter and the voltage compensation capability value of the energy storage system can be represented. The construction of the objective function enables the power control system to consider multiple key parameters comprehensively, thereby optimizing the power distribution strategy of the energy storage converter. For example, by optimizing the output power factor, the power transmission efficiency of the first energy storage converter can be improved, and the waste of reactive power can be reduced, while ensuring that the power control system can quickly and effectively compensate for reactive power in the case of voltage drop or other grid abnormalities. The quantification of the voltage compensation capability value enables the power control system to accurately evaluate the effect of the energy storage converter when compensating voltage drop or fluctuation, thereby achieving more accurate voltage control. Through optimization, not only the stability and power quality of the power grid are improved, but also the adaptability and reliability of the energy storage converter under complex grid conditions are enhanced.

[0038] Step S104, determining the target reactive compensation amount for the first energy storage converter according to the objective function.

[0039] Optionally, in order to optimize the reactive power output of the parallel energy storage converter and improve the overall voltage compensation capability of the system, the target reactive compensation amount of the first energy storage converter needs to be determined according to the constructed objective function. The objective function comprehensively considers multiple key parameters such as the maximum transmission power of the first energy storage converter, the load apparent power of the power system, the power factor angle, and the maximum output apparent power of the second energy storage converter, so as to comprehensively evaluate the voltage compensation demand of the power system. By solving the objective function, the optimal reactive compensation amount that makes the voltage compensation capability of the power system optimal, i.e., the target reactive compensation amount, can be found. For example, partial derivatives can be calculated and the point at which the objective function reaches an extreme value can be found, so as to determine the optimal reactive power value that the first energy storage converter should output under a specific operating condition. The target reactive compensation amount is used to guide the energy storage converter to adjust its reactive power output under voltage sag or other grid abnormal conditions, so as to achieve rapid and effective voltage recovery and enhance the stability and power quality of the power system.

[0040] It should be noted that both the vector control and the virtual synchronous machine control of the energy storage converter considering power instruction response and harmonic current compensation access can achieve reactive power output compensation for grid voltage fluctuation and voltage sag. Therefore, in addition to harmonic current control, the energy storage converter considering power instruction response and harmonic current compensation access can also achieve voltage coordinated control through power compensation, and together with the energy storage converter based on direct voltage compensation control strategy access system to compensate and control the grid voltage. When the energy storage converter considering power instruction response and harmonic current compensation access control adopts virtual synchronous generator control, it cannot take into account the high-frequency harmonic current control link. Therefore, the voltage coordinated control of the energy storage converter considering power instruction response and harmonic current compensation access based on vector control is needed, which obtains the coordinated voltage compensation control of the energy storage converter considering power instruction response and harmonic current compensation access by taking the load end voltage as the control target.

[0041] Referring to Figure 2 , the harmonic current elimination and improved power control circuit of the energy storage converter considering power instruction response and harmonic current compensation access can mainly include harmonic current detection and elimination and improved power control. In the harmonic current detection and elimination part, the power control system can first filter out the high-frequency harmonic component in the input current through a low-pass filter (LPF) to obtain the fundamental current , representing the three-phase alternating current on the grid side. Then, through Clarke-Park transformation (Park), the current in the three-phase stationary coordinate system is converted to the two-phase rotating coordinate system to obtain , the Clarke-Park transform is used to represent a mathematical transform that converts three-phase alternating current into two orthogonal coordinate systems. Then, proportional resonant (PR) controllers are used to detect and eliminate harmonic currents, generating compensation voltages , for canceling harmonic currents, and then through the inverse Park transform (iPark), the compensation voltages are converted from the two-phase rotating coordinate system back to the three-phase stationary coordinate system, obtaining compensation currents in the three-phase coordinate system , for harmonic current compensation in actual power electronic devices. Among them, the proportional resonant controller is a controller that can amplify signals of a specific frequency, i.e. the resonant frequency, and suppress signals of other frequencies. Two proportional resonant controllers can be provided, one proportional resonant controller can be used to process 6th harmonic currents , and the other proportional resonant controller can be used to process 12th harmonic currents , so as to generate corresponding compensation voltages, thereby effectively eliminating grid harmonic currents.

[0042] In the improved power control part, the power control system adjusts the input reference active power and the reference reactive power through proportional-integral (PI) controllers, for example, the initial input signal of the active power control loop can be zero or the reference value of the DC side current , the first proportional-integral controller in the active loop can receive the input signal and the DC side current reference value , for adjusting the difference between the active power and the actual power , the first proportional-integral controller reduces the error through proportional and integral action to improve the response speed and stability of the system. The second proportional-integral controller is used to further adjust the error signal to generate an active current reference value . The active current reference value can be used to control the output of the inverter or rectifier to achieve the desired active power.

[0043] The initial input signal of the reactive power control loop can be the reference value of the load voltage , the first proportional-integral controller in the reactive loop can receive the error signal between the load voltage reference value and the actual voltage, for adjusting the reference reactive power , and the comparator can be used to compare the reference reactive power with the actual reactive power The error signal is outputted by comparing the active current reference value with the actual active current . The error signal is further adjusted by the second proportional-integral controller in the reactive power loop to generate a reactive current reference value . This current reference value will be used to control the output of the inverter or rectifier to achieve the desired reactive power. The active current reference value is compared with the actual current in the corresponding direct-axis direction , and the voltage command in the corresponding direction is obtained by adjusting the error signal through a proportional-integral controller . The voltage command in the corresponding direction is finally converted from the two-phase rotating coordinate system to the three-phase stationary coordinate system through an inverse Park transform (iPark) to obtain the improved power control signal and , which are used to control the power output of the power system.

[0044] The harmonic current detection and elimination part can effectively reduce harmonic pollution in the power grid and improve power quality. The improved power control part optimizes the power factor of the power system and enhances the voltage support capability of the power system by accurately controlling active and reactive power, which not only improves the stability of the power system, but also reduces energy loss caused by harmonics and poor power factor, thereby improving the operating efficiency of the entire power system. In addition, by dynamically adjusting the power output, the power system can better adapt to changes in the load of the power grid, achieve more flexible and efficient energy management, and improve the power quality and stability of the power electronic system.

[0045] The power instruction value of the energy storage converter considering power instruction response and harmonic current compensation access is obtained according to the improved distribution result of the power instruction. Among them, the active outer loop detects its output in the steady state and obtains the active instruction value by tracking control. When voltage sag occurs, the reactive outer loop detects the effective value of the load voltage, determines the reactive instruction value according to proportional control, and sets the reactive instruction amplitude value according to the calculation of the optimal reactive compensation amount. In order to realize the zero-error regulation of the load voltage, an integral element needs to be added, and the voltage deviation is taken as the feedback signal. The reactive outer loop in the basic reactive control is changed into a proportional-integral control link. After obtaining the power instruction value of the energy storage converter considering power instruction response and harmonic current compensation access, power-current double closed loop control is adopted. The obtained power instruction is first input into the power loop for proportional-integral adjustment to obtain the active and reactive current instruction values, and then input into the current loop for proportional-integral control and modulation to obtain the output reference voltage.

[0046] In an optional embodiment, a target function is constructed according to the maximum transmission power of the first energy storage converter, the load apparent power of the power system, the power factor angle, and the maximum output apparent power of the second energy storage converter, including: the power control system can obtain the inductive reactance value and the impedance value in the line impedance; and then the target function is constructed according to the inductive reactance value, the impedance value, the maximum transmission power of the first energy storage converter, the load apparent power of the power system, the power factor angle, and the maximum output apparent power of the second energy storage converter.

[0047] Optionally, the line impedance is used to represent the hindering effect of the power line on the current flow, and can include the inductive reactance and the impedance. The inductive reactance is caused by the line inductance, and is mainly related to the inductance of the line and the working frequency, and affects the phase and amplitude of the current. The impedance is the total impedance of the line, including the resistance and the inductive reactance, and determines the size of the line current. By obtaining the inductive reactance value and the impedance value in the line impedance, the power transmission and voltage drop in the power system can be understood. The load apparent power of the power system is used to represent the total power consumed by the load, and reflects the power demand of the load on the power system. The power factor angle is used to represent the phase difference between the active power and the apparent power, and the cosine value of the power factor angle is the power factor, which is used to reflect the efficiency of power transmission in the power system. The maximum output apparent power of the second energy storage converter is used to represent the maximum apparent power that the second energy storage converter can output when compensating the voltage, and is directly related to the amplitude of the compensation voltage, and is used to measure the compensation ability.

[0048] By obtaining the inductive reactance value and the impedance value in the line impedance, and combining the maximum transmission power of the first energy storage converter, the load apparent power of the power system, the power factor angle, and the maximum output apparent power of the second energy storage converter, a target function can be constructed. The target function is used to represent the correlation between the output power factor of the first energy storage converter and the voltage compensation ability of the energy storage system. Specifically, the inductive reactance value and the impedance value affect the size and phase of the current, thereby affecting the drop of the voltage. The maximum transmission power of the first energy storage converter and the load apparent power of the power system determine the power distribution and flow in the system. The power factor angle reflects the efficiency of power transmission, and the maximum output apparent power of the second energy storage converter directly affects the effect of voltage compensation. By constructing the target function with the above parameters, the reactive power output of the first energy storage converter can be optimized, so that the reactive power output is automatically adjusted when the voltage drops, the overall voltage compensation ability of the system is improved, and the stability and power quality of the power system are enhanced.

[0049] For example, considering that the power instruction response cooperative harmonic current compensation access energy storage converter can automatically adjust the output voltage phase angle The power transmission of the power grid is controlled bidirectionally, and the output power variation of the load and the connected energy storage converter is considered to be equivalent to the same size power variation on the load side. The line voltage drop can be represented by formula (1):

[0050] Formula (1)

[0051] Wherein, is used to represent the inductive part of the line impedance, is used to represent the resistive part of the line impedance, which can be obtained by an active disturbance injection impedance measurement method; is used to represent the active power variation on the load side; is used to represent the reactive power variation on the load side; is used to represent the voltage variation in the line, is used to represent the rated load voltage. When the active power and the reactive power of the load change, the voltage will change. The change of the reactive power affects the voltage through the inductance , and the change of the active power affects the voltage through the resistance .

[0052] In an alternative embodiment, a target function is constructed according to the inductance value, the impedance value, the maximum transmission power of the first energy storage converter, the apparent power of the load of the power system, the power factor angle, and the maximum output apparent power of the second energy storage converter, including: the power control system can construct the cosine function and the sine function of the output power factor of the first energy storage converter, and construct the cosine function and the sine function of the power factor angle, and then construct the target function according to the cosine function and the sine function of the output power factor, the cosine function and the sine function of the power factor angle, the inductance value, the impedance value, the maximum transmission power of the first energy storage converter, the apparent power of the load of the power system, and the maximum output apparent power of the second energy storage converter.

[0053] Alternatively, the output power factor is used to represent the ratio of the active power to the apparent power output by the first energy storage converter, reflecting the quality of the converter output power. The cosine function of the output power factor is used to represent the proportion of the active power in the apparent power, and the sine function of the output power factor is used to represent the proportion of the reactive power in the apparent power. The power factor angle is used to represent the phase difference between the active power and the apparent power, and the cosine function and the sine function of the power factor angle are also used to describe the active and reactive parts of the power. The cosine function and the sine function of both the output power factor and the power factor angle can be used to help accurately describe and control the flow and distribution of power.

[0054] By constructing the cosine function and the sine function of the output power factor of the first energy storage converter, and the cosine function and the sine function of the power factor angle, the power control system can more accurately describe and control the power output of the converter. The cosine function and the sine function of the output power factor, the cosine function and the sine function of the power factor angle, the reactance value, the impedance value, the maximum transmission power of the first energy storage converter, the load apparent power of the power system, and the maximum output apparent power of the second energy storage converter can be combined to construct a target function. The target function can quantitatively represent the relationship between the output power factor of the first energy storage converter and the voltage compensation capability of the energy storage system. Specifically, the cosine function and the sine function of the output power factor reflect the active and reactive parts of the output power of the first energy storage converter, and the cosine function and the sine function of the power factor angle further refine the relationship between the active and reactive parts. The target function in the embodiments of the present application can comprehensively consider various factors to optimize the reactive power output of the energy storage converter, thereby automatically adjusting the reactive power output during voltage drop, improving the overall voltage compensation capability of the power system, and enhancing the stability and power quality of the power system.

[0055] For example, considering that the change of the output power of the energy storage converter accessed in response to the power instruction and the harmonic current compensation will have an impact on the load voltage due to the existence of the line impedance, thereby directly affecting the voltage compensation. In addition, considering that the change of the output power of the energy storage converter accessed in response to the power instruction and the harmonic current compensation will also change the current flowing through the transformer line, thereby indirectly affecting the voltage compensation of the energy storage converter accessed in the system based on the direct voltage compensation control strategy, and the load power factor angle is , the current flowing through the transformer line can be expressed as formula (2):

[0056] Formula (2)

[0057] wherein, is used to represent the current flowing through the transformer line; is used to represent the load apparent power of the power system, which can include the active power part and the reactive power part. is used to represent the power factor angle, which is the phase difference between the active power and the apparent power of the power system, is used to represent the cosine function of the power factor angle; is used to represent the sine function of the power factor angle. is used to represent the reactive power provided by the first energy storage converter; is used to represent the active power provided by the first energy storage converter; is used to represent the line voltage.

[0058] ​It can be seen from formula (2) that when the active power exchange between the energy storage converter considering power instruction response and the harmonic current compensation access and the power grid is considered, in the case that the transmission capacity of the energy storage converter based on the direct voltage compensation control strategy is limited, the maximum voltage amplitude that can be output by the energy storage converter is changed by affecting the value of the line current , so as to affect the coordinated voltage compensation capability of the multi-mode access energy storage converter system. According to the above analysis, the voltage compensation capability of the energy storage converter system considering the output power coupling influence of the energy storage converter considering power instruction response and harmonic current compensation access is derived as formula (3):

[0059] Formula (3)

[0060] , wherein, is used to represent the voltage compensation capability value of the energy storage system; is used to represent the inductive reactance value in the line impedance; is used to represent the impedance value in the line impedance; is used to represent the active power provided by the first energy storage converter; is used to represent the reactive power provided by the first energy storage converter; is used to represent the rated load voltage; is used to represent the maximum output apparent power of the second energy storage converter; is used to represent the line voltage; is used to represent the load apparent power of the power system, which can include an active power part and a reactive power part; is used to represent the power factor angle.

[0061] According to formula (3), when the load power is 20 MW, the power factor is 0.98, and the rated output power of the energy storage converter considering power instruction response and harmonic current compensation access is 5 MW. At this time, the influence of the change of the output active power and reactive power of the energy storage converter within the rated power range on the voltage compensation capability of the energy storage converter system is as shown in Figure 3 .

[0062] Referring to Figure 3 , Figure 3 a three-dimensional surface diagram of the system voltage compensation capability considering the power coupling influence of the energy storage converter considering power instruction response and harmonic current compensation access is shown, for example, the X axis can be used to represent the active power provided by the output of the first energy storage converter on the parallel side , and the Y axis can be used to represent the reactive power provided by the output of the first energy storage converter on the parallel side ​; the Z-axis can be used to represent the voltage compensation capability influence, reflecting the degree of change in the voltage compensation capability. The color bar of the surface plot is used to represent the size of the voltage compensation capability influence, with the color changing from blue (negative influence) to red (positive influence) and the numerical range from -0.1 to 0.1. When the surface plot displays a blue area, it indicates that the voltage compensation capability is reduced at the active power and reactive power output combination. When the surface plot displays a red area, it indicates that the voltage compensation capability is enhanced at the active power and reactive power output combination. Figure 3 The power output of the parallel type energy storage converter is analyzed and optimized to automatically adjust the reactive power output in the case of voltage sag, thereby improving the overall voltage compensation capability of the system. By adjusting the values of and , the optimal power output combination is found, so that the voltage compensation capability is maximized, thereby improving the stability and power quality of the power system.

[0063] When considering that the energy storage converter with power instruction response and harmonic current compensation access absorbs active power and reactive power from the power grid, the overall voltage compensation capability of the power system is reduced. Because it is equivalent to adding a power path to the load power, increasing the line current of the series transformer, thereby reducing the upper limit of the output compensation voltage amplitude, thereby limiting the overall voltage compensation capability of the power system. When considering that the energy storage converter with power instruction response and harmonic current compensation access outputs active and reactive power to the power grid for compensation, the voltage can be directly lifted by means of line impedance, and the line current can be reduced. At this time, assuming that the output compensation voltage of the energy storage converter based on the direct voltage compensation control strategy is unchanged, the apparent power output by the energy storage converter with power instruction response and harmonic current compensation access is reduced, and the spare capacity can further increase the amplitude of the compensation voltage .

[0064] In an alternative embodiment, a target function is constructed according to the cosine function and the sine function of the output power factor, the cosine function and the sine function of the power factor angle, the inductive reactance value, the impedance value, the maximum transmission power of the first energy storage converter, the load apparent power of the power system, and the maximum output apparent power of the second energy storage converter, including: the power control system calculates the product of the sine function of the output power factor and the inductive reactance value to obtain a first sub-function, and calculates the product of the cosine function of the output power factor and the impedance value to obtain a second sub-function. Then the first sub-function and the second sub-function are summed to obtain a third sub-function, and then the product of the third sub-function and the maximum transmission power of the first energy storage converter is calculated to obtain a fourth sub-function. Finally, the target function is constructed according to the fourth sub-function, the cosine function and the sine function of the power factor angle, the load apparent power of the power system, and the maximum output apparent power of the second energy storage converter.

[0065] Optionally, a first sub-function reflecting the influence of reactive power on voltage compensation can be obtained by calculating the product of the sine function of the output power factor and the reactance value. Meanwhile, a second sub-function reflecting the influence of active power on voltage compensation can be obtained by calculating the product of the cosine function of the output power factor and the impedance value. The first sub-function and the second sub-function can be used to represent the role of reactive power and active power in voltage compensation, respectively. The third sub-function obtained by adding the first sub-function and the second sub-function comprehensively reflects the influence of reactive power and active power, and further reflects the total effect of the power factor in voltage compensation. Then, the fourth sub-function obtained by multiplying the third sub-function and the maximum transmission power of the first energy storage converter is used to quantify the comprehensive influence of the power factor of the energy storage converter on voltage compensation under the maximum transmission power limit.

[0066] The objective function can be constructed by combining the fourth sub-function, the cosine function and the sine function of the power factor angle, the apparent power of the power system and the maximum output apparent power of the second energy storage converter. The objective function of the embodiments of the present application can comprehensively represent the relationship between the output power factor of the first energy storage converter and the voltage compensation capability of the energy storage system. Specifically, the fourth sub-function reflects the comprehensive influence of the power factor of the energy storage converter on voltage compensation under the maximum transmission power limit; the cosine and sine functions of the power factor angle further refine the influence; and the apparent power of the load and the maximum output apparent power of the second energy storage converter provide the overall power demand and compensation capability of the power system. Through the objective function, the power control system can optimize the reactive power output of the first energy storage converter, automatically adjust the reactive power output during voltage drop, improve the overall voltage compensation capability of the power system, and thus enhance the stability and power quality of the power system.

[0067] In an alternative embodiment, the objective function is constructed according to the fourth sub-function, the cosine and sine functions of the power factor angle, the load apparent power of the power system, and the maximum output apparent power of the second energy storage converter, including: calculating the product of the sine function of the power factor angle and the load apparent power of the power system to obtain a fifth sub-function; calculating the product of the sine function of the output power factor and the maximum transmission power of the first energy storage converter to obtain a sixth sub-function; performing a complete square difference operation on the fifth sub-function and the sixth sub-function to obtain a seventh sub-function. And calculating the product of the cosine function of the power factor angle and the load apparent power of the power system to obtain an eighth sub-function; calculating the product of the cosine function of the output power factor and the maximum transmission power of the first energy storage converter to obtain a ninth sub-function; performing a complete square difference operation on the eighth sub-function and the ninth sub-function to obtain a tenth sub-function. Then summing the seventh sub-function and the tenth sub-function, and calculating the arithmetic square root of the sum to obtain an eleventh sub-function. Then calculating the ratio of the maximum output apparent power of the second energy storage converter to the eleventh sub-function to obtain a twelfth sub-function. Finally, summing the fourth sub-function and the twelfth sub-function to obtain the objective function.

[0068] Alternatively, the product of the sine function of the power factor angle and the load apparent power of the power system is calculated to obtain a fifth sub-function, which reflects the influence of reactive power demand on voltage compensation. The product of the sine function of the output power factor and the maximum transmission power of the first energy storage converter is calculated to obtain a sixth sub-function, which is used to represent the reactive power output capability of the energy storage converter. The fifth sub-function and the sixth sub-function are subjected to a complete square difference operation to obtain a seventh sub-function, which is used to quantify the difference between reactive power demand and output capability. Similarly, the product of the cosine function of the power factor angle and the load apparent power is calculated to obtain an eighth sub-function, and the product of the cosine function of the output power factor and the maximum transmission power is calculated to obtain a ninth sub-function, which are used to reflect active power demand and output capability, respectively. The eighth and ninth sub-functions are subjected to a complete square difference operation to obtain a tenth sub-function, which is used to quantify the difference between active power demand and output capability. The seventh sub-function and the tenth sub-function are summed and the arithmetic square root is calculated to obtain an eleventh sub-function, which is used to integrate the differences in reactive power and active power. Finally, the ratio of the maximum output apparent power of the second energy storage converter to the eleventh sub-function is calculated to obtain a twelfth sub-function, which is used to reflect the compensation capability of the energy storage converter connected to the system based on the direct voltage compensation control strategy.

[0069] The objective function of the embodiment of the present application comprehensively considers the reactive and active power output capability of the first energy storage converter, the load demand of the power system, and the compensation capability of the second energy storage converter. The construction of the objective function enables the system to accurately evaluate and optimize the reactive power output of the energy storage converter, so as to achieve the best voltage compensation effect. In the case of voltage drop, the objective function can help the power system automatically adjust the reactive power output of the energy storage converter, ensure the stability of the grid voltage, and improve the stability and power quality of the power system. The optimization method of the embodiment of the present application considers the influence of various factors on voltage compensation, so that the power system can maintain efficient and stable operation under complex working conditions.

[0070] It should be noted that the energy storage converter considering power instruction response and harmonic current compensation access has the ability to compensate active power to the power grid when the voltage drops, so that the active power of the load at the access point of the energy storage converter considering power instruction response and harmonic current compensation access is reduced, , thereby reducing the line current , which has a similar compensation effect to reactive power compensation for reducing line current. In addition, the active power change of the energy storage converter considering power instruction response and harmonic current compensation access at the load access point can also affect the voltage, but the voltage drop caused by the line impedance << The energy storage converter considering power instruction response and harmonic current compensation access has the same active power output as the reactive power output, and the voltage compensation effect of the voltage drop of the transmission line impedance can be ignored. Therefore, when the energy storage converter considering power instruction response and harmonic current compensation access participates in voltage coordinated control, the priority target should be to output reactive power compensation.

[0071] In operation, there may be a working condition in which the load power factor is high or the load is lightly loaded. If the energy storage converter considering power instruction response and harmonic current compensation access uses all the remaining capacity for reactive power compensation, the compensated reactive power may exceed the reactive part of the load power , and the excess part will increase the reactive current in the line, thereby reducing the voltage compensation capability of the energy storage converter based on the direct voltage compensation control strategy access to the power system. When the reactive output overcompensation causes the current flowing through the series transformer line to increase, thereby weakening the voltage compensation capability of the energy storage converter based on the direct voltage compensation control strategy access to the power system, when the effect of the voltage compensation capability of the line impedance caused by the reactive output in formula (1) is exceeded, further increasing the reactive output will weaken the overall voltage compensation capability of the power system. Therefore, there is a maximum value for the coordinated voltage compensation capability, and the compensation power factor of the energy storage converter considering power instruction response and harmonic current compensation access is , and the maximum transmission power is operated, and formula (3) can be obtained about the voltage compensation capability The function expression of the target function can refer to formula (4):

[0072]

[0073] Formula (4)

[0074] wherein, is used to represent the voltage compensation capability value of the energy storage system; is used to represent the maximum transmission power of the first energy storage converter; is used to represent the output power factor of the first energy storage converter; is used to represent the inductive reactance value in the line impedance; is used to represent the impedance value in the line impedance; is used to represent the maximum output apparent power of the second energy storage converter; is used to represent the load apparent power of the power system, which can include an active power part and a reactive power part; is used to represent the power factor angle.

[0075] In an optional embodiment, the target reactive compensation amount for the first energy storage converter is determined according to the target function, which includes that the power control system can construct the partial derivative function of the target function, then calculate the target solution about the output power factor when the partial derivative function is equal to 0, then calculate the target sine value corresponding to the target solution, and finally calculate the product result of the target sine value and the maximum output apparent power of the second energy storage converter to obtain the target reactive compensation amount of the first energy storage converter.

[0076] Optionally, the partial derivative function of the target function can be used to find the extreme point of the target function, that is, the optimal reactive compensation amount under the given condition. By calculating the solution when the partial derivative function is equal to 0, the target solution value about the output power factor can be obtained, which represents the optimal power factor under the current power system condition. Then, because the reactive power is directly related to the sine value of the power factor, the target sine value corresponding to the target solution value can be calculated. Finally, the target sine value is multiplied by the maximum output apparent power of the second energy storage converter to obtain the target reactive compensation amount of the first energy storage converter, which utilizes the calculus and optimization theory to facilitate accurate calculation of the optimal reactive compensation amount.

[0077] By constructing the partial derivative function of the objective function and solving, the power control system can accurately determine the optimal reactive power compensation amount of the first energy storage converter. The embodiments of the present application consider the load demand of the power system, the transmission capacity of the energy storage converter, and the effect of voltage compensation, thereby ensuring that the power system can automatically adjust the reactive power output to achieve the best voltage compensation effect under voltage drop and other conditions, not only improving the stability and power quality of the power system, but also reducing unnecessary energy loss through accurate mathematical calculation, improving the overall efficiency of the power system. The power system of the embodiments of the present application can maintain efficient and stable operation under complex working conditions, while maximizing the compensation capacity of the energy storage converter.

[0078] For example, in formula (4), take the partial derivative of x and let Solving the independent variable x, the optimal reactive power compensation amount of the energy storage converter considering the power command response harmonic current compensation access that takes the maximum value of the coordinated voltage compensation capacity can be solved, that is, the target reactive power compensation amount of the first energy storage converter , referring to formulas (5) to (7):

[0079] Formula (5)

[0080] Formula (6)

[0081] Formula (7)

[0082] Wherein, is used to represent the voltage compensation capacity value of the energy storage system; is used to represent the maximum transmission power of the first energy storage converter; is used to represent the output power factor of the first energy storage converter; is used to represent the inductive reactance value in the line impedance; is used to represent the impedance value in the line impedance; is used to represent the maximum output apparent power of the second energy storage converter; is used to represent the load apparent power of the power system, which can include active power and reactive power parts; is used to represent the power factor angle; is used to represent the output power factor of the first energy storage converter when is solved; is used to represent the target reactive power compensation amount of the first energy storage converter.

[0083] Based on the above analysis, when the grid voltage drop depth exceeds the compensation capability of the energy storage converter connected to the power system based on the direct voltage compensation control strategy, the reactive power outer loop control of the energy storage converter connected considering the power instruction response and harmonic current compensation is adjusted to play a regulating function. At this time, the optimal reactive compensation amount is calculated The power instruction is improved and distributed: the capacity of the energy storage converter connected considering the power instruction response and harmonic current compensation is compared with the calculated optimal reactive compensation amount. If , it means that within the capacity limit of the energy storage converter connected considering the power instruction response and harmonic current compensation, the reactive power compensation is better than the active power compensation in improving the voltage compensation capability. At this time, the active outer loop is disabled, and the energy storage converter connected considering the power instruction response and harmonic current compensation only performs reactive power compensation; if , the upper limit of the reactive power output instruction value is set to , and if the reactive power compensation of the energy storage converter connected considering the power instruction response and harmonic current compensation reaches , the remaining capacity further outputs active power to compensate for the active part of the load, thereby obtaining higher coordinated voltage compensation capability under the same conditions.

[0084] In an optional embodiment, after determining the target reactive compensation amount for the first energy storage converter according to the target function, the power compensation method of the parallel energy storage converter further includes: when detecting that the grid voltage drops, performing reactive power compensation on the first energy storage converter according to the target reactive compensation amount.

[0085] Optionally, when the grid voltage drops, the power control system performs reactive power compensation on the first energy storage converter according to the pre-calculated target reactive compensation amount. The compensation operation is based on real-time monitoring and analysis of the grid voltage fluctuation, and by adjusting the reactive power output of the energy storage converter, the influence of voltage drop is offset, so as to quickly restore the grid voltage to normal level. Through automatic reactive power compensation, the stability of the power system in the face of voltage disturbance can be effectively enhanced, the power quality can be improved, and the reliable operation of the power system can be ensured, which is convenient for protecting the safety and stability of the grid.

[0086] In an alternative embodiment, after obtaining the maximum output apparent power of the second energy storage converter accessing the power system based on the direct voltage compensation control strategy, the power compensation method based on the parallel energy storage converter further comprises: the power control system can calculate the product of the current flowing through the transformer line and the compensation voltage output by the second energy storage converter, to obtain the apparent power currently output by the second energy storage converter. Then, the ratio of the maximum output apparent power of the second energy storage converter to the current flowing through the transformer line is calculated, and the minimum value of the ratio and the maximum compensation voltage that the second energy storage converter can output under the withstand voltage limitation of the switching device is selected as the maximum output compensation voltage of the second energy storage converter.

[0087] Alternatively, the power control system can monitor the actual output power of the second energy storage converter in real time by calculating the product of the current flowing through the transformer line and the compensation voltage output by the second energy storage converter to obtain the apparent power currently output by the second energy storage converter. Next, the power control system calculates the ratio of the maximum output apparent power of the second energy storage converter to the current flowing through the transformer line, which reflects the maximum compensation voltage that the second energy storage converter can output under the current current condition. At the same time, the power control system also needs to consider the maximum compensation voltage that the second energy storage converter can output under the withstand voltage limitation of the switching device. Finally, the power control system selects the minimum value of the ratio and the maximum compensation voltage that the second energy storage converter can output under the withstand voltage limitation of the switching device as the maximum output compensation voltage of the second energy storage converter, to ensure that the second energy storage converter operates within a safe range while maximizing its compensation capability.

[0088] The power control system of the embodiment of the present application can accurately control the output compensation voltage of the second energy storage converter, ensuring that it operates within a safe and efficient operating range, not only considering the actual output capability of the second energy storage converter, but also considering the withstand voltage limitation of the switching device, avoiding equipment damage caused by excessively high voltage output. By selecting the minimum value as the maximum output compensation voltage, the power control system can maximize the compensation capability while ensuring the safety of the equipment, thereby effectively improving the voltage stability and power quality of the power grid, and through dynamic adjustment, the power system can flexibly respond under different working conditions, ensuring the reliable operation of the power grid.

[0089] For example, in combination with the control method of the energy storage converter accessing in response to the power instruction and harmonic current compensation, the analysis of voltage compensation coordinated by the energy storage converter accessing in multiple modes is carried out. First, the following assumptions are made for the power system:

[0090] (1) When the switching device in the energy storage converter is in normal operation, the element output limitation is mainly limited by the maximum transmission power;

[0091] (2) The power transmission limit of the DC side energy storage unit meets the maximum transmission power requirement of the double-sided converter;

[0092] (3) The energy storage converter based on the direct voltage compensation control strategy accessing the system is matched with the transformer capacity, and the two can be considered together when considering the transmission power limit.

[0093] The apparent power value output by the energy storage converter based on the direct voltage compensation control strategy accessing the system is related to the compensation voltage amplitude output. Since the output current is the same as the main line current of the power grid, the compensation voltage The phase is also the same as the phase of the grid voltage, and the output power and the upper limit of the output compensation voltage capacity can be represented as formula (8):

[0094] Formula (8)

[0095] wherein, apparent power output by the energy storage converter based on the direct voltage compensation control strategy accessing the system, capacity of the energy storage unit; compensation voltage output; the upper limit of the output compensation voltage, i.e. the maximum value of the output compensation voltage; current flowing through the transformer line; the maximum compensation voltage that can be output by the energy storage converter based on the direct voltage compensation control strategy accessing the system under the withstand voltage limit of the switching device; the maximum apparent power output by the second energy storage converter.

[0096] Referring to Figure 4 , according to another aspect of the embodiments of the present application, a power compensation device based on a parallel energy storage converter is also provided, which comprises a transmission power acquisition unit 401, an apparent power acquisition unit 402, a target function construction unit 403 and a reactive power compensation determination unit 404.

[0097] The transmission power acquisition unit 401 is configured to acquire the maximum transmission power of the first energy storage converter, wherein the first energy storage converter is a parallel energy storage converter considering power instruction response cooperative harmonic current compensation access, and the first energy storage converter obtains a power instruction value according to an improved allocation result of the power instruction; the apparent power acquisition unit 402 is configured to acquire the maximum output apparent power of a second energy storage converter accessing the power system based on a direct voltage compensation control strategy, wherein the apparent power value output by the second energy storage converter is related to the compensation voltage amplitude output by the second energy storage converter, and the second energy storage converter is a series energy storage converter; the objective function construction unit 403 is configured to construct an objective function according to the maximum transmission power of the first energy storage converter, the load apparent power of the power system, the power factor angle, and the maximum output apparent power of the second energy storage converter, wherein the objective function is used to represent the correlation between the output power factor of the first energy storage converter and the voltage compensation capability value of the energy storage system, the output power factor is the ratio of the output active power of the first energy storage converter to the apparent power, and the voltage compensation capability value is used to quantitatively represent the degree of voltage drop or fluctuation compensated by the energy storage converter; and the reactive power compensation determination unit 404 is configured to determine the target reactive power compensation amount for the first energy storage converter according to the objective function.

[0098] Optionally, the objective function construction unit 403 comprises: a line parameter acquisition subunit, configured to acquire the inductive reactance value and the impedance value in the line impedance; and an objective function construction subunit, configured to construct the objective function according to the inductive reactance value, the impedance value, the maximum transmission power of the first energy storage converter, the load apparent power of the power system, the power factor angle, and the maximum output apparent power of the second energy storage converter.

[0099] Optionally, the objective function construction subunit comprises: an output power factor function construction module, configured to construct the cosine function and the sine function about the output power factor of the first energy storage converter; a power factor angle function construction module, configured to construct the cosine function and the sine function about the power factor angle; and an objective function construction module, configured to construct the objective function according to the cosine function and the sine function of the output power factor, the cosine function and the sine function of the power factor angle, the inductive reactance value, the impedance value, the maximum transmission power of the first energy storage converter, the load apparent power of the power system, and the maximum output apparent power of the second energy storage converter.

[0100] Optionally, the objective function construction module comprises: a first sub-function determination submodule configured to calculate a product of a sine function of the output power factor and the reactance value to obtain a first sub-function; a second sub-function determination submodule configured to calculate a product of a cosine function of the output power factor and the impedance value to obtain a second sub-function; a third sub-function determination submodule configured to sum the first sub-function and the second sub-function to obtain a third sub-function; a fourth sub-function determination submodule configured to calculate a product of the third sub-function and the maximum transmission power of the first energy storage converter to obtain a fourth sub-function; and an objective function construction submodule configured to construct the objective function according to the fourth sub-function, the cosine function and the sine function of the power factor angle, the load apparent power of the power system, and the maximum output apparent power of the second energy storage converter.

[0101] Optionally, the objective function construction submodule comprises: a fifth sub-function determination submodule configured to calculate a product of a sine function of the power factor angle and the load apparent power of the power system to obtain a fifth sub-function; a sixth sub-function determination submodule configured to calculate a product of a sine function of the output power factor and the maximum transmission power of the first energy storage converter to obtain a sixth sub-function; a seventh sub-function determination submodule configured to perform a complete square difference operation on the fifth sub-function and the sixth sub-function to obtain a seventh sub-function; an eighth sub-function determination submodule configured to calculate a product of a cosine function of the power factor angle and the load apparent power of the power system to obtain an eighth sub-function; a ninth sub-function determination submodule configured to calculate a product of a cosine function of the output power factor and the maximum transmission power of the first energy storage converter to obtain a ninth sub-function; a tenth sub-function determination submodule configured to perform a complete square difference operation on the eighth sub-function and the ninth sub-function to obtain a tenth sub-function; an eleventh sub-function determination submodule configured to sum the seventh sub-function and the tenth sub-function, and calculate an arithmetic square root of the sum to obtain an eleventh sub-function; a twelfth sub-function determination submodule configured to calculate a ratio of the maximum output apparent power of the second energy storage converter to the eleventh sub-function to obtain a twelfth sub-function; and an objective function determination submodule configured to sum the fourth sub-function and the twelfth sub-function to obtain the objective function.

[0102] Optionally, the reactive power compensation determination unit 404 comprises: a partial derivative function construction submodule configured to construct a partial derivative function of the objective function; an objective solution submodule configured to calculate an objective solution with respect to the output power factor when the partial derivative function is equal to 0; an objective sine determination submodule configured to calculate an objective sine value corresponding to the objective solution; and an objective reactive power compensation determination submodule configured to calculate a product of the objective sine value and the maximum output apparent power of the second energy storage converter to obtain the target reactive power compensation amount of the first energy storage converter.

[0103] Optionally, the power compensation device based on the parallel-type energy storage converter further comprises a reactive power compensation processing unit configured to perform reactive power compensation on the first energy storage converter according to a target reactive power compensation amount when it is detected that the grid voltage drops.

[0104] Optionally, the power compensation device based on the parallel-type energy storage converter further comprises a current apparent power determination unit configured to calculate a product of the current flowing through the transformer line and the compensation voltage output by the second energy storage converter to obtain the current apparent power output by the second energy storage converter; and a maximum compensation voltage determination unit configured to calculate a ratio of the maximum output apparent power of the second energy storage converter to the current flowing through the transformer line, and select a minimum value between the ratio and the maximum compensation voltage that can be output by the second energy storage converter under the withstand voltage limitation of the switching device as the maximum output compensation voltage of the second energy storage converter.

[0105] According to another aspect of the embodiments of the present application, a computer readable storage medium is provided, and the computer readable storage medium stores a computer program. When the computer program is run, the computer readable storage medium enables a device where the computer readable storage medium is located to perform the power compensation method based on the parallel-type energy storage converter.

[0106] According to another aspect of the embodiments of the present application, an electronic device is provided, and the electronic device comprises one or more processors and a memory. The memory is configured to store one or more programs. When the one or more programs are executed by the one or more processors, the one or more processors perform the power compensation method based on the parallel-type energy storage converter.

[0107] According to another aspect of the embodiments of the present application, a computer program product is provided, and the computer program product comprises a computer program or instructions. When the computer program or instructions are executed by a processor, the computer program or instructions implement the power compensation method based on the parallel-type energy storage converter.

[0108] The serial numbers of the above embodiments of the present application are only for description, and do not represent the advantages or disadvantages of the embodiments.

[0109] In the above embodiments of the present application, the description of each embodiment has its own focus, and the parts not described in detail in a certain embodiment can be referred to the relevant description of other embodiments.

[0110] In several embodiments provided in the present application, it should be understood that the disclosed technology can be implemented by other ways. Among them, the above-described device embodiments are only schematic, for example, the division of the units can be a logical function division, and actual implementation can have another division manner, for example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the displayed or discussed units can be indirect coupling or communication connection through some interfaces, units or modules, and can be electrical or other forms.

[0111] The units described as separate components can or can not be physically separate, and the components shown as units can or can not be physical units, that is, they can be located in one place, or they can be distributed to multiple units. Part or all of the units can be selected according to actual needs to achieve the purpose of the embodiment.

[0112] In addition, the functional units in each embodiment of the present application can be integrated in one processing unit, or each unit can be physically present separately, or two or more units can be integrated in one unit. The integrated unit can be realized in the form of hardware or in the form of a software functional unit.

[0113] The integrated unit, if realized in the form of a software functional unit and sold or used as an independent product, can be stored in a computer readable storage medium. Based on this understanding, the technical solutions of the present application essentially or the part that contributes to the prior art or the whole or part of the technical solutions can be embodied in the form of a software product. The computer software product is stored in a storage medium, including a plurality of instructions for causing a computer device (which can be a personal computer, a server or a network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application. The foregoing storage medium includes: a U disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), a mobile hard disk, a magnetic disk or an optical disk, and various media that can store program codes.

[0114] The above is only the preferred embodiment of the present application, and it should be pointed out that for ordinary skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should be considered as the protection scope of the present application.

Claims

1. A power compensation method based on a parallel energy storage converter, characterized in that, include: Obtain the maximum transmission power of the first energy storage converter, wherein the first energy storage converter is a parallel energy storage converter connected with consideration of power command response and coordinated harmonic current compensation, wherein the first energy storage converter obtains the power command value according to the improved allocation result of the power command. The maximum apparent output power of the second energy storage converter connected to the power system based on the direct voltage compensation control strategy is obtained, wherein the apparent power value output by the second energy storage converter to the grid is related to the amplitude of the compensation voltage output, and the second energy storage converter is a series energy storage converter. Based on the maximum transmission power of the first energy storage converter, the apparent load power of the power system, the power factor angle, and the maximum output apparent power of the second energy storage converter, an objective function is constructed. The objective function is used to characterize the correlation between the output power factor of the first energy storage converter and the voltage compensation capability value of the energy storage system. The output power factor is the ratio of the output active power to the apparent power of the first energy storage converter. The voltage compensation capability value is used to quantitatively characterize the degree to which the energy storage converter compensates for voltage drops or fluctuations. The target reactive power compensation amount for the first energy storage converter is determined based on the objective function.

2. The power compensation method based on a parallel energy storage converter according to claim 1, characterized in that, Based on the maximum transmission power of the first energy storage converter, the apparent load power of the power system, the power factor angle, and the maximum apparent output power of the second energy storage converter, an objective function is constructed, including: Obtain the inductive reactance and impedance values ​​in the line impedance; The objective function is constructed based on the inductive reactance value, the impedance value, the maximum transmission power of the first energy storage converter, the apparent load power of the power system, the power factor angle, and the maximum apparent output power of the second energy storage converter.

3. The power compensation method based on a parallel energy storage converter according to claim 2, characterized in that, Based on the inductive reactance value, the impedance value, the maximum transmission power of the first energy storage converter, the apparent load power of the power system, the power factor angle, and the maximum apparent output power of the second energy storage converter, the objective function is constructed, including: Construct the cosine and sine functions of the output power factor of the first energy storage converter; Construct cosine and sine functions for the power factor angle; The objective function is constructed based on the cosine and sine functions of the output power factor, the cosine and sine functions of the power factor angle, the inductive reactance, the impedance, the maximum transmission power of the first energy storage converter, the apparent load power of the power system, and the maximum apparent output power of the second energy storage converter.

4. The power compensation method based on a parallel energy storage converter according to claim 3, characterized in that, The objective function is constructed based on the cosine and sine functions of the output power factor, the cosine and sine functions of the power factor angle, the inductive reactance, the impedance, the maximum transmission power of the first energy storage converter, the apparent load power of the power system, and the maximum apparent output power of the second energy storage converter. The objective function includes: The first sub-function is obtained by multiplying the sinusoidal function of the output power factor with the inductive reactance value. The second sub-function is obtained by multiplying the cosine function of the output power factor with the impedance value. Summing the first sub-function and the second sub-function yields the third sub-function; The fourth sub-function is obtained by multiplying the third sub-function and the maximum transmission power of the first energy storage converter. The objective function is constructed based on the fourth sub-function, the cosine and sine functions of the power factor angle, the apparent load power of the power system, and the maximum apparent output power of the second energy storage converter.

5. The power compensation method based on a parallel energy storage converter according to claim 4, characterized in that, Based on the fourth sub-function, the cosine and sine functions of the power factor angle, the apparent load power of the power system, and the maximum apparent output power of the second energy storage converter, the objective function is constructed, including: The fifth sub-function is obtained by multiplying the sine function of the power factor angle with the apparent load power of the power system; the sixth sub-function is obtained by multiplying the sine function of the output power factor with the maximum transmission power of the first energy storage converter; and the seventh sub-function is obtained by performing a perfect square difference operation on the fifth and sixth sub-functions. The product of the cosine function of the power factor angle and the apparent load power of the power system is calculated to obtain the eighth sub-function; the product of the cosine function of the output power factor and the maximum transmission power of the first energy storage converter is calculated to obtain the ninth sub-function; the perfect square difference operation is performed on the eighth sub-function and the ninth sub-function to obtain the tenth sub-function. Summing the seventh and tenth sub-functions and calculating the arithmetic square root of the summation result yields the eleventh sub-function; The twelfth sub-function is obtained by calculating the ratio of the maximum apparent output power of the second energy storage converter to the eleventh sub-function. The target function is obtained by summing the fourth sub-function and the twelfth sub-function.

6. The power compensation method based on a parallel energy storage converter according to claim 1, characterized in that, Determining the target reactive power compensation amount for the first energy storage converter based on the objective function includes: Construct the partial derivatives of the objective function; The objective solution for the output power factor is to calculate the partial derivative function when it equals 0. Calculate the target sine value corresponding to the solution of the target; The target reactive power compensation of the first energy storage converter is obtained by multiplying the target sine value with the maximum apparent output power of the second energy storage converter.

7. The power compensation method based on a parallel energy storage converter according to claim 1, characterized in that, After determining the target reactive power compensation amount for the first energy storage converter according to the objective function, the power compensation method based on the parallel energy storage converter further includes: When a voltage drop in the grid is detected, reactive power compensation is performed on the first energy storage converter according to the target reactive power compensation amount.

8. The power compensation method based on a parallel energy storage converter according to claim 1, characterized in that, After obtaining the maximum apparent output power of the second energy storage converter connected to the power system based on the direct voltage compensation control strategy, the power compensation method based on the parallel energy storage converter further includes: The apparent power currently output by the second energy storage converter is obtained by multiplying the current flowing through the transformer line and the compensation voltage output by the second energy storage converter. Calculate the ratio of the maximum apparent output power of the second energy storage converter to the current flowing through the transformer line, and select the minimum value between this ratio and the maximum compensation voltage that the second energy storage converter can output due to the voltage withstand limitation of the switching devices as the maximum output compensation voltage of the second energy storage converter.

9. A power compensation device based on a parallel energy storage converter, characterized in that, include: A power transmission acquisition unit is used to acquire the maximum transmission power of the first energy storage converter, wherein the first energy storage converter is a parallel energy storage converter connected with consideration of power command response and coordinated harmonic current compensation, wherein the first energy storage converter obtains the power command value according to the improved allocation result of the power command. Apparent power acquisition unit is used to acquire the maximum output apparent power of the second energy storage converter connected to the power system based on the direct voltage compensation control strategy. The apparent power value output by the second energy storage converter to the grid is related to the output compensation voltage amplitude. The second energy storage converter is a series energy storage converter. The objective function construction unit is used to construct an objective function based on the maximum transmission power of the first energy storage converter, the apparent load power of the power system, the power factor angle, and the maximum output apparent power of the second energy storage converter. The objective function is used to characterize the correlation between the output power factor of the first energy storage converter and the voltage compensation capability value of the energy storage system. The output power factor is the ratio of the output active power to the apparent power of the first energy storage converter, and the voltage compensation capability value is used to quantitatively characterize the degree to which the energy storage converter compensates for voltage drops or fluctuations. The reactive power compensation determination unit is used to determine the target reactive power compensation amount for the first energy storage converter based on the objective function.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, wherein when the computer program is executed, the device containing the computer-readable storage medium performs the power compensation method based on a parallel energy storage converter as described in any one of claims 1 to 8.

11. An electronic device, characterized in that, It includes one or more processors and a memory, the memory being used to store one or more programs, wherein when the one or more programs are executed by the one or more processors, the one or more processors cause the one or more processors to perform the power compensation method based on a parallel energy storage converter as described in any one of claims 1 to 8.

12. A computer program product, characterized in that, It includes a computer program or instructions that, when executed by a processor, implement the power compensation method based on a parallel energy storage converter according to any one of claims 1 to 8.

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