Power grid unbalance suppression method and system of grid-forming inverter

Abstract

The invention belongs to the technical field of network-forming type inverters. The method comprises the following steps: separating positive sequence components and negative sequence components of a power grid voltage and a power grid current by adopting a second-order generalized integrator, and according to weight distribution coefficients of the current, active power and reactive power, calculating the imbalance of the power grid according to the weight distribution coefficients of the current, the active power and the reactive power; respectively obtaining a first fluctuation function of the current relative to the comprehensive adjustment coefficient, a second fluctuation function of the active power relative to the comprehensive adjustment coefficient and a third fluctuation function of the reactive power relative to the comprehensive adjustment coefficient; and selecting the fluctuation function with the maximum result in the first fluctuation function, the second fluctuation function and the third fluctuation function as a comprehensive fluctuation function, searching an optimal comprehensive adjustment coefficient to enable the comprehensive fluctuation function to take a minimum value, obtaining an optimal negative sequence current reference value, and performing multi-target coordination control on current and power. Through the design of the negative sequence current control loop, the balance control of the power grid current and the suppression of the instantaneous power fluctuation are realized.

Description

Technical Field

[0001] The present invention relates to the technical field of grid-type inverters, and in particular to a method and system for suppressing grid imbalance of a grid-type inverter. Background Art

[0002] The statements in this section merely provide background art related to the present invention and do not necessarily constitute prior art.

[0003] With the increasing number of new energy grid connections and distributed power generation systems, grid-connected inverters are gradually changing from grid-following to grid-forming, and grid unbalance conditions are frequent. If the three-phase PWM converter control strategy under the balanced grid is continued, it is easy to cause grid-connected current distortion and DC voltage secondary ripple, further deteriorating the power quality of the grid and threatening the safety of the grid; and the traditional unbalance suppression strategy has certain limitations, and it is urgent to develop a more effective and reliable control method for grid-forming inverters.

[0004] Researchers have proposed some solutions to unbalanced power grids. For example, the control method based on dual synchronous coordinate systems realizes the decoupling control of current under asymmetric conditions by independently controlling the positive and negative sequence currents in the positive and negative sequence synchronous coordinate systems, but the control target of this method is relatively single and it is difficult to meet more complex performance requirements; the control method based on virtual voltage introduces virtual grid voltage as the reference output voltage, and suppresses the overcurrent problem caused by the voltage asymmetry drop by adjusting the virtual reference, but the dynamic response accuracy and tracking ability of this method are limited; the direct power control method based on model prediction control no longer relies on the traditional current control loop, which improves the dynamic performance of the system. However, the model prediction method requires real-time complex calculations, which increases the calculation burden and implementation difficulty of the system. Summary of the invention

[0005] In order to solve the control problem of a grid-connected inverter under unbalanced grid conditions, the present invention provides a grid imbalance suppression method and system for a grid-connected inverter, which realizes balanced control of grid current and suppression of instantaneous power fluctuations through the design of a negative-sequence current control loop.

[0006] In order to achieve the above object, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for suppressing grid imbalance of a grid-connected inverter.

[0008] A method for suppressing grid imbalance of a grid-connected inverter includes the following steps:

[0009] A second-order generalized integrator is used to separate the positive-sequence component and the negative-sequence component of the grid voltage and grid current, and according to the weight distribution coefficients of the current, active power and reactive power, a first fluctuation function of the current relative to the comprehensive regulation coefficient, a second fluctuation function of the active power relative to the comprehensive regulation coefficient and a third fluctuation function of the reactive power relative to the comprehensive regulation coefficient are obtained respectively;

[0010] The fluctuation function with the largest result among the first fluctuation function, the second fluctuation function and the third fluctuation function is selected as the comprehensive fluctuation function, and the optimal comprehensive adjustment coefficient is found to make the comprehensive fluctuation function take the minimum value, so as to obtain the most ideal negative sequence current reference value and perform multi-objective coordinated control of current and power.

[0011] In a second aspect, the present invention provides a grid imbalance suppression system for a grid-connected inverter.

[0012] A grid unbalance suppression system for a grid-forming inverter, comprising:

[0013] The fluctuation function calculation unit is configured to: use a second-order generalized integrator to separate the positive sequence component and the negative sequence component of the grid voltage and the grid current, and obtain a first fluctuation function of the current relative to the comprehensive regulation coefficient, a second fluctuation function of the active power relative to the comprehensive regulation coefficient, and a third fluctuation function of the reactive power relative to the comprehensive regulation coefficient according to the weight distribution coefficients of the current, the active power, and the reactive power;

[0014] The multi-objective coordination control unit is configured to: select the fluctuation function with the largest result among the first fluctuation function, the second fluctuation function and the third fluctuation function as the comprehensive fluctuation function, find the optimal comprehensive adjustment coefficient so that the comprehensive fluctuation function takes the minimum value, obtain the most ideal negative sequence current reference value, and perform multi-objective coordinated control of current and power.

[0015] In a third aspect, the present invention provides a computer device, comprising: a processor and a computer-readable storage medium;

[0016] a processor adapted to execute a computer program;

[0017] A computer-readable storage medium, wherein a computer program is stored in the computer-readable storage medium, and when the computer program is executed by the processor, the method for suppressing grid imbalance of a grid-connected inverter as described in the first aspect of the present invention is implemented.

[0018] In a fourth aspect, the present invention provides a computer-readable storage medium storing a computer program, wherein the computer program is suitable for being loaded by a processor and executing the grid imbalance suppression method of a grid-connected inverter as described in the first aspect of the present invention.

[0019] In a fifth aspect, the present invention provides a computer program product, which includes a computer program. When the computer program is executed by a processor, it implements the grid imbalance suppression method of the grid-connected inverter as described in the first aspect of the present invention.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The present invention innovatively proposes a negative-sequence current suppression strategy with integrated multiple control objectives, selects the fluctuation function with the largest result among the first fluctuation function, the second fluctuation function and the third fluctuation function as the integrated fluctuation function, finds the optimal comprehensive adjustment coefficient so that the integrated fluctuation function takes the minimum value, obtains the most ideal negative-sequence current reference value, performs multi-objective coordinated control of current and power, realizes current balance and power fluctuation suppression, and ensures the stable operation of the grid-connected inverter under unbalanced power grid conditions.

[0022] 2. The present invention utilizes a second-order generalized integrator (SOGI) to separate positive and negative sequence voltage / current components at a specific frequency, providing an accurate benchmark for the unbalanced suppression strategy, and has strong practicality.

[0023] 3. Under the condition of unbalanced power grid, the present invention establishes a mathematical model of a grid-connected inverter based on virtual oscillator control, analyzes the power transmission performance, designs a comprehensive negative-sequence current controller, and realizes current balance and power fluctuation suppression.

[0024] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0026] Figure 1 A structural diagram of a grid-type inverter system based on a virtual oscillator provided in Embodiment 1 of the present invention;

[0027] Figure 2 A block diagram of the unbalanced current comprehensive control strategy provided in Example 1 of the present invention;

[0028] Figure 3 The grid voltage and grid current waveforms provided in Example 1 of the present invention;

[0029] Figure 4 The active power and reactive power waveforms provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0030] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0031] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0032] In the absence of conflict, the embodiments of the present invention and the features of the embodiments may be combined with each other.

[0033] Embodiment 1:

[0034] The grid-connected inverter based on virtual oscillator control achieves synchronization and global stability of the grid phase angle by simulating the dynamics of weak nonlinear limit cycle oscillators, and is particularly suitable for the grid-connected control of distributed power generation units. However, there are few studies on grid imbalance suppression for such grid-connected inverters. It is of great significance to design an imbalance suppression strategy with diverse control objectives and good dynamic and static tracking performance. In view of this, the present invention proposes a negative-sequence current suppression method with integrated multiple control objectives. Through the design of a negative-sequence current control loop, balanced control of grid current and suppression of instantaneous power fluctuations are achieved. Figure 1 As shown, it is a structure diagram of a grid-type inverter system based on a virtual oscillator, wherein the control structure design of the virtual oscillator includes:

[0035] Measure the three-phase grid current and three-phase grid voltage of the converter a ,i b ,i c and e ga , e gb , e gc According to Clark transformation, the current in the two-phase stationary coordinate system is i α ,i β And the voltage v in the two-phase stationary coordinate system α and v β As a nonlinear controller, the dynamic mathematical model of the virtual oscillator is expressed in polar coordinates as follows:

[0036]

[0037] Among them, V n is a given voltage reference value, ω n is the natural resonant frequency, V is the output voltage of the virtual oscillator, C is the resonant capacitor, P * and Q * are the reference power of active and reactive power respectively, ξ is the convergence coefficient, k v , k iis the gain coefficient, is the line impedance angle.

[0038] Generally, the power grid and converter are approximated as inductive networks, that is, When , the dynamic mathematical model of the virtual oscillator can be simplified as:

[0039]

[0040] in, θ is the phase angle of the inverter output, P and Q They are the active power and reactive power output by the inverter respectively.

[0041] According to the detected three-phase grid current and voltage, the active and reactive power of the inverter are calculated. Combined with the established virtual oscillator dynamic model (i.e., formula (3)), the virtual oscillator network control of the three-phase converter can be realized.

[0042] Measure the three-phase grid current and three-phase grid voltage of the converter a ,i b ,i c and e ga , e gb , e gc According to the Park coordinate transformation, the grid current i in the two-phase rotating coordinate system is obtained d ,i q and grid voltage e gd , e gq , in an unbalanced power grid, the grid voltage / current in the two-phase rotating coordinate system consists of positive and negative sequence components, that is:

[0043]

[0044] in, and Represents e gdq The positive and negative sequence components of and Represents i dq The positive and negative sequence components.

[0045] According to the instantaneous power theory, the instantaneous complex power of the power grid is expressed as:

[0046]

[0047] When the grid voltage is unbalanced, negative sequence components will appear in the grid voltage, which causes the current output by the grid-connected inverter to be unbalanced as well. The positive and negative sequence components in the output voltage and current interact with each other, causing the oscillation of the system power, namely:

[0048]

[0049] According to the definitions of active power and reactive power, the specific expression of instantaneous power under unbalanced conditions is:

[0050]

[0051] Among them, P 0 , Q 0 is the average active and reactive power, P c2 , P s2 is the double frequency component of active power, Q c2 , Q s2 It is the double frequency component of reactive power.

[0052] Under unbalanced grid conditions, the control objectives of the three-phase grid-connected inverter are: to obtain balanced three-phase grid current, suppress fluctuations in active power and reactive power, and ensure that the average power follows the power reference. The above control objectives can be converted into:

[0053]

[0054] Among them, the double frequency fluctuations of active power and reactive power are both related to the negative sequence current. Therefore, the control problem of the three-phase PWM converter under unbalanced power grid is transformed into the control problem of negative sequence current.

[0055] The present invention designs a grid unbalance suppression method for a grid-connected inverter based on a virtual oscillator. Specifically, the control method includes a positive and negative sequence component separation module based on a second-order generalized integrator and an unbalanced current control module. A second-order generalized integrator is introduced to obtain accurate positive and negative sequence components to avoid control instability problems caused by noise, and an unbalanced current comprehensive control module is designed to ensure that under unbalanced grid conditions, the system can achieve the control goals of current balance and power fluctuation suppression.

[0056] In order to achieve more accurate positive and negative sequence control, it is necessary to separate the positive and negative sequence of voltage and current. According to the three-phase three-wire system, taking voltage as an example, the voltage can be decomposed into:

[0057]

[0058] in, is the amplitude of the positive and negative sequence voltage, are the phase angles of the positive and negative sequence voltages respectively. By transforming the above equation, we can get the voltage in the two-phase rotating dq coordinate system:

[0059]

[0060] It can be seen that in the dq coordinate system, the positive sequence component and negative sequence component of the unbalanced voltage appear as a DC component and an AC component with a frequency twice the fundamental frequency, respectively.

[0061] The following is the transfer function of the Second Order Generalized Integral (SOGI) module:

[0062]

[0063] Among them, k c ,ω c They are the closed-loop resonance coefficient and resonant frequency respectively. The positive and negative sequence voltage or current components at a specific frequency can be accurately extracted through reasonable parameter design.

[0064] In order to obtain a three-phase sinusoidal and balanced grid current, according to the instantaneous complex power analysis, it is necessary to set the reference input of the negative sequence current to zero, that is, the grid current balance control strategy:

[0065]

[0066] To ensure that the system outputs constant active power, P c2 , P s2 =0, that is, active power balance control strategy:

[0067]

[0068] According to the power analysis of formula (7), the negative sequence reference current at this time can be obtained as:

[0069]

[0070] Similarly, in order to suppress the fluctuation of reactive power, Q c2 , Q s2 Needs to be controlled to zero, and the reactive power balance control strategy is obtained:

[0071]

[0072] According to the power analysis of formula (7), the negative sequence reference current at this time can be obtained as:

[0073]

[0074] It can be seen from formulas (12), (14), and (16) that it is necessary to integrate these three control objectives in a unified manner to achieve comprehensive control of current and power, thereby improving the overall performance of the system and the quality of power. Therefore, a comprehensive adjustment coefficient K is introduced to establish a unified negative sequence current reference output expression:

[0075]

[0076] According to the grid voltage vector orientation principle, the positive sequence and negative sequence vectors of the grid voltage are positioned at the synchronous rotating coordinate system. Axis and axis, so Substituting the negative sequence current obtained by formula (17) into formula (7), the double frequency fluctuation components of active power and reactive power can be obtained as follows:

[0077]

[0078] In order to more intuitively describe the fluctuation of active and reactive power, the fluctuation value is compared with the reference value to obtain the relative fluctuation, that is:

[0079]

[0080] The current imbalance is expressed by the ratio of the negative sequence component to the positive sequence component, that is,

[0081]

[0082] Then, use It represents the relative unbalance of current, the relative fluctuation of active power and the relative fluctuation of reactive power. From this, the fluctuation function expressions of current, active power and reactive power can be obtained respectively as follows:

[0083]

[0084] Among them, m i , m P , m Q They are the weight distribution coefficients of current, active power and reactive power, respectively. Their sizes are set according to actual needs. In order to minimize the current and power fluctuations, the comprehensive fluctuation function is constructed as follows:

[0085] f(K)=max(f i (K), f P (K), f Q (k)) (25);

[0086] By optimizing the comprehensive fluctuation function (25), a K value can be found to minimize f(K), thereby obtaining the most ideal negative sequence current reference value, realizing multi-objective coordinated control of current and power, and providing an effective means for the flexible adjustment of the system under multiple operating conditions under unbalanced conditions.

[0087] like Figure 2 As shown in the figure, the implementation block diagram of the suppression method proposed in this implementation method mainly consists of four parts: virtual oscillator, second-order generalized integrator, positive and negative sequence voltage and current loop, and comprehensive current control. The positive and negative sequence voltages generated by the positive and negative sequence voltage and current loop are superimposed and transformed into v abcThe modulation wave is generated through PWM modulation to realize the control of the grid-type inverter. Figure 3 is the control effect of grid current and grid voltage under unbalanced grid, Figure 4 The control effect of active power and reactive power is shown in Figure 2. At 0.3s, the single-phase voltage drop occurs in the power grid, and only the current balance control strategy is used at 0.4s-0.5s. At this time, m i =1, m P =m Q =0; only active power balance control strategy is adopted during 0.5s-0.6s, at this time m P =1, m i =m Q =0 waveform; only the unbalanced current comprehensive control strategy is used at 0.6s-0.7s, at this time m i =0.5, m P =0.3, m Q =0.2. It can be seen from the figure that when the unbalanced current comprehensive control strategy is adopted, the THD of the grid-connected current is significantly reduced compared with the active power balance control strategy, and the power fluctuation is significantly smaller than that of the current balance control strategy alone.

[0088] Embodiment 2:

[0089] This implementation provides a grid unbalance suppression system for a grid-connected inverter, including:

[0090] The fluctuation function calculation unit is configured to: use a second-order generalized integrator to separate the positive sequence component and the negative sequence component of the grid voltage and the grid current, and obtain a first fluctuation function of the current relative to the comprehensive regulation coefficient, a second fluctuation function of the active power relative to the comprehensive regulation coefficient, and a third fluctuation function of the reactive power relative to the comprehensive regulation coefficient according to the weight distribution coefficients of the current, the active power, and the reactive power;

[0091] The multi-objective coordination control unit is configured to: select the fluctuation function with the largest result among the first fluctuation function, the second fluctuation function and the third fluctuation function as the comprehensive fluctuation function, find the optimal comprehensive adjustment coefficient so that the comprehensive fluctuation function takes the minimum value, obtain the most ideal negative sequence current reference value, and perform multi-objective coordinated control of current and power.

[0092] The specific working process of each of the above units is described in Example 1 and will not be repeated here.

[0093] It is understandable that the above-mentioned various units can be separately or all combined into one or several other units to constitute, or some (some) units therein can also be split into multiple smaller units in function to constitute, which can achieve the same operation without affecting the realization of the technical effects of the embodiments of the present application. The above-mentioned units are divided based on logical functions. In practical applications, the function of a unit can also be realized by multiple units, or the function of multiple units can be realized by one unit. In other embodiments of the present application, the system can also include other units. In practical applications, these functions can also be implemented with the assistance of other units, and can be implemented by the collaboration of multiple units.

[0094] According to another embodiment of the present application, the system described in this embodiment can be constructed, and the method of Example 1 of the present application can be implemented by running a computer program (including program code) capable of executing the steps involved in the corresponding method described in Example 1 on a general computing device such as a computer including processing elements and storage elements such as a central processing unit (CPU), random access memory (RAM), and read-only memory (ROM). The computer program can be recorded on, for example, a computer-readable recording medium, and loaded into the above-mentioned computing device through the computer-readable recording medium and run therein.

[0095] Embodiment 3:

[0096] This implementation provides an electronic device, which includes a processor, a communication interface, and a computer-readable storage medium, wherein the processor, the communication interface, and the computer-readable storage medium may be connected via a bus or other means.

[0097] Among them, the communication interface is used to receive and send data, the computer-readable storage medium can be stored in the memory of the electronic device, the computer-readable storage medium is used to store a computer program, the computer program includes program instructions, and the processor is used to execute the program instructions stored in the computer-readable storage medium.

[0098] A processor (or CPU (Central Processing Unit)) is the computing core and control core of an electronic device, which is suitable for implementing one or more instructions, and specifically suitable for loading and executing one or more instructions to implement corresponding method flows or corresponding functions.

[0099] The processor is configured to perform the following process:

[0100] According to the weight distribution coefficients of current, active power and reactive power, a first fluctuation function of current relative to the comprehensive regulation coefficient, a second fluctuation function of active power relative to the comprehensive regulation coefficient and a third fluctuation function of reactive power relative to the comprehensive regulation coefficient are obtained respectively;

[0101] The fluctuation function with the largest result among the first fluctuation function, the second fluctuation function and the third fluctuation function is selected as the comprehensive fluctuation function, and the optimal comprehensive adjustment coefficient is found to make the comprehensive fluctuation function take the minimum value, so as to obtain the most ideal negative sequence current reference value and perform multi-objective coordinated control of current and power.

[0102] The specific working process is described in Example 1 and will not be repeated here.

[0103] Embodiment 4:

[0104] This implementation provides a computer-readable storage medium (Memory), which is a memory device in an electronic device for storing programs and data. It is understandable that the computer-readable storage medium here can include both built-in storage media in the electronic device and, of course, extended storage media supported by the electronic device. The computer-readable storage medium provides a storage space that stores the processing system of the electronic device.

[0105] In addition, the storage space also stores one or more instructions suitable for being loaded and executed by the processor, and these instructions may be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here may be a high-speed RAM memory, or a non-volatile memory, such as at least one disk memory; optionally, it may also be at least one computer-readable storage medium located away from the aforementioned processor.

[0106] In one embodiment, the computer-readable storage medium stores one or more instructions; the processor loads and executes the one or more instructions stored in the computer-readable storage medium to implement the following process:

[0107] According to the weight distribution coefficients of current, active power and reactive power, a first fluctuation function of current relative to the comprehensive regulation coefficient, a second fluctuation function of active power relative to the comprehensive regulation coefficient and a third fluctuation function of reactive power relative to the comprehensive regulation coefficient are obtained respectively;

[0108] The fluctuation function with the largest result among the first fluctuation function, the second fluctuation function and the third fluctuation function is selected as the comprehensive fluctuation function, and the optimal comprehensive adjustment coefficient is found to make the comprehensive fluctuation function take the minimum value, so as to obtain the most ideal negative sequence current reference value and perform multi-objective coordinated control of current and power.

[0109] The specific working process is described in Example 1 and will not be repeated here.

[0110] Embodiment 5:

[0111] The present implementation provides a computer program product or a computer program, which includes computer instructions stored in a computer-readable storage medium. A processor of an electronic device reads the computer instructions from the computer-readable storage medium, and the processor executes the computer instructions, so that the electronic device performs the following process:

[0112] According to the weight distribution coefficients of current, active power and reactive power, a first fluctuation function of current relative to the comprehensive regulation coefficient, a second fluctuation function of active power relative to the comprehensive regulation coefficient and a third fluctuation function of reactive power relative to the comprehensive regulation coefficient are obtained respectively;

[0113] The fluctuation function with the largest result among the first fluctuation function, the second fluctuation function and the third fluctuation function is selected as the comprehensive fluctuation function, and the optimal comprehensive adjustment coefficient is found to make the comprehensive fluctuation function take the minimum value, so as to obtain the most ideal negative sequence current reference value and perform multi-objective coordinated control of current and power.

[0114] The specific working process is described in Example 1 and will not be repeated here.

[0115] A person skilled in the art can appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed in this application can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. A person skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0116] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When implemented using software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When loading and executing computer program instructions on a computer, the process or function according to the embodiment of the present application is generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network or other programmable device. The computer instruction can be stored in a computer-readable storage medium or transmitted by a computer-readable storage medium. The computer instruction can be transmitted from a website site, a computer, a server or a data center to another website site, a computer, a server or a data center by wired (for example, coaxial cable, optical fiber, digital line (DSL)) or wireless (for example, infrared, wireless, microwave, etc.) mode. The computer-readable storage medium can be any available medium that a computer can access or a data processing device such as a server, a data center, etc. that contains one or more available media integration. Available media can be magnetic media (for example, floppy disk, hard disk, tape), optical media (for example, DVD), or semiconductor media (for example, solid-state drive (Solid State Disk, SSD)) and the like.

[0117] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for suppressing grid imbalance of a grid-connected inverter, characterized in that: The process includes: A second-order generalized integrator is used to separate the positive-sequence component and the negative-sequence component of the grid voltage and grid current, and according to the weight distribution coefficients of the current, active power and reactive power, a first fluctuation function of the current relative to the comprehensive regulation coefficient, a second fluctuation function of the active power relative to the comprehensive regulation coefficient and a third fluctuation function of the reactive power relative to the comprehensive regulation coefficient are obtained respectively; The fluctuation function with the largest result among the first fluctuation function, the second fluctuation function and the third fluctuation function is selected as the comprehensive fluctuation function, and the optimal comprehensive adjustment coefficient is found to make the comprehensive fluctuation function take the minimum value, so as to obtain the most ideal negative sequence current reference value and perform multi-objective coordinated control of current and power.

2. The method for suppressing grid imbalance of a grid-connected inverter according to claim 1, characterized in that: The first wave function is: The second wave function is: The third wave function is: Among them, m i , m P , m Q are the weight distribution coefficients of current, active power and reactive power respectively, It indicates the relative unbalance of current, the relative fluctuation of active power and the relative fluctuation of reactive power. K is the comprehensive adjustment coefficient. is the positive sequence component of the d-axis voltage in the rotating coordinate system, is the negative sequence component of the d-axis voltage, is the positive sequence component of the d-axis current in the rotating coordinate system, is the positive sequence component of the q-axis current in the rotating coordinate system, P * is the reference power of active power, Q * is the reference power of reactive power.

3. The method for suppressing grid imbalance of a grid-connected inverter according to claim 2, characterized in that: Relative current imbalance, including: in, It is the negative sequence component of the q-axis current in the rotating coordinate system.

4. The method for suppressing grid imbalance of a grid-connected inverter according to claim 2, characterized in that: Relative fluctuations in active power, including: Among them, P c2 , P s2 It is the double frequency component of active power.

5. The method for suppressing grid imbalance of a grid-connected inverter according to claim 2, characterized in that: and relative fluctuations in reactive power, including: Among them, Q c2 , Q s2 It is the double frequency component of reactive power.

6. The method for suppressing grid imbalance of a grid-connected inverter according to any one of claims 2 to 5, characterized in that: A second-order generalized integrator is used to separate the positive and negative sequences of voltage and current. The transfer function of the second-order generalized integrator is: Among them, k c ,ω c are the closed-loop resonance coefficient and resonant frequency respectively.

7. A grid unbalance suppression system for a grid-type inverter, characterized in that: include: The fluctuation function calculation unit is configured to: use a second-order generalized integrator to separate the positive sequence component and the negative sequence component of the grid voltage and the grid current, and obtain a first fluctuation function of the current relative to the comprehensive regulation coefficient, a second fluctuation function of the active power relative to the comprehensive regulation coefficient, and a third fluctuation function of the reactive power relative to the comprehensive regulation coefficient according to the weight distribution coefficients of the current, the active power, and the reactive power; The multi-objective coordination control unit is configured to: select the fluctuation function with the largest result among the first fluctuation function, the second fluctuation function and the third fluctuation function as the comprehensive fluctuation function, find the optimal comprehensive adjustment coefficient so that the comprehensive fluctuation function takes the minimum value, obtain the most ideal negative sequence current reference value, and perform multi-objective coordinated control of current and power.

8. A computer device, characterized in that: include: a processor and a computer readable storage medium; a processor adapted to execute a computer program; A computer-readable storage medium, wherein a computer program is stored in the computer-readable storage medium, and when the computer program is executed by the processor, the method for suppressing grid imbalance of a grid-connected inverter according to any one of claims 1 to 6 is implemented.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and the computer program is suitable for being loaded by a processor and executing the grid imbalance suppression method of a grid-connected inverter according to any one of claims 1 to 6.

10. A computer program product, characterized in that The computer program product includes a computer program, and when the computer program is executed by a processor, the method for suppressing grid imbalance of a grid-connected inverter according to any one of claims 1 to 6 is implemented.

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