Power control method and device of grid-connected inverter and medium

Abstract

The invention relates to a power control method and device for a grid-connected inverter and a medium. The method comprises the following steps: establishing a DQ-axis coordinate system model of a grid-connected power transmission system formed by sequentially connecting a direct-current power supply, an inverter, an LCR filter, an equivalent line simulation device and a power grid; calculating a reference current value of a grid-connected point in the DQ-axis coordinate system model, and obtaining a phase angle of the reference current through zero crossing point detection in a zero power state to obtain a real-time DQ value of the current of the grid-connected point; a DQ voltage value of an inverter side is obtained through current closed-loop control under a DQ-axis coordinate system, and a phase angle value and a voltage amplitude are obtained through arc tangent calculation of the DQ voltage value, so that a control voltage value of the inverter is obtained, and power control of the grid-connected inverter is realized. Compared with the prior art, the method has the advantages of high stability, high accuracy and the like.

Description

Technical Field

[0001] The present invention relates to the field of power grid control, and in particular to a power control method, device and medium of a grid-connected inverter. Background Art

[0002] Power transmission equipment, mainly grid-connected inverters, are susceptible to changes in the grid architecture, such as line changes, power fluctuations, and the disconnection and connection of equipment units. Changes in the equivalent transmission impedance and inductance-to-resistance ratio between the grid connection point and the stable voltage point will affect the stability, accuracy, and responsiveness of power transmission. Therefore, grid-connected inverters require control strategy design.

[0003] In the existing mainstream methods, when the grid structure changes, there are usually the following deficiencies: 1. Current control method based on the grid connection point voltage phase-locked loop: This control method usually relies on the phase-locked loop technology. When the grid structure changes, especially when the grid impedance changes significantly or the short-circuit ratio decreases, the performance of the phase-locked loop may be affected. Specifically, the dynamic response of the phase-locked loop slows down, and even the lock may be lost. 2. Voltage control method based on generator characteristic simulation: This control method mainly includes droop control and virtual synchronous machine technology, which realizes power control by adjusting the relationship between the inverter output power and the grid frequency and voltage. However, when the grid structure changes, especially when the grid impedance changes or in a strong grid environment, the performance of traditional droop control and VSG may drop significantly. However, in a low-impedance grid, the simulated inertia characteristics of the VSG may cause the grid to over-respond to frequency changes. When the grid parameters change greatly, the inertia and damping characteristics of the system may be too large or too small. Too large damping will result in slow response and excessive stability, while too small damping will result in oscillation and instability. Faced with these problems, many controller designs are improved by adding control links or enhancing adaptability through judgment combinations, but this form increases complexity during implementation.

[0004] In summary, the current method has the disadvantages of low stability adaptability and limited response time when facing large-scale changes in the power grid structure, as well as the problems of missing reactive power transmission and complex controllers. Therefore, it is necessary to design a simple control strategy that can adapt to large-scale changes in power grid structure parameters. Summary of the invention

[0005] The purpose of the present invention is to provide a power control method, device and medium for a grid-connected inverter in order to overcome the defects of the above-mentioned prior art.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A power control method for a grid-connected inverter comprises the following steps:

[0008] S1: Establish a DQ axis coordinate system model of a grid-connected power transmission system consisting of a DC power supply, an inverter, an LCR filter, an equivalent circuit simulation device and a power grid connected in sequence;

[0009] S2: Calculate the reference current value of the grid-connected point in the DQ axis coordinate system model, obtain the phase angle of the reference current through zero-crossing point detection in the zero power state, and obtain the real-time DQ value of the grid-connected point current;

[0010] S3: The DQ voltage value on the inverter side is obtained through the current closed-loop control in the DQ axis coordinate system, and the phase angle value and voltage amplitude are obtained through the inverse tangent calculation of the DQ voltage value, thereby obtaining the control voltage value of the inverter to realize the power control of the grid-connected inverter.

[0011] Furthermore, the mathematical expression of the grid-connected power transmission system is:

[0012]

[0013] Where K = A, B, C, R g is the resistance in the equivalent transmission line, L g is the inductance of the equivalent transmission line, for each κ phase, i gk is the current connected to the grid, u sκ and u gκ is the voltage at the grid connection point and the grid stability point, and t is the time.

[0014] Furthermore, the calculation expression of the DQ axis coordinate system model is:

[0015]

[0016] In the formula, u sd and u sq is the inverter grid-connected point control voltage in the DQ axis coordinate system, i gd and i gq is the grid-connected current in the DQ axis coordinate system, R g is the resistance in the equivalent transmission line, L gd and L gq is the inductance of the equivalent transmission line in the DQ axis coordinate system, i gd and i gq is the grid-connected current in the DQ axis coordinate system, and ω is the phase.

[0017] Furthermore, the calculation expression of the reference current value is:

[0018]

[0019] In the formula, i gd and i gq is the grid-connected current in the DQ axis coordinate system, igd and i gq is the grid-connected current in the DQ axis coordinate system, and is the expected power at the grid stability point, and Control current in the DQ axis coordinate system.

[0020] Furthermore, taking the stable grid point as the reference voltage point, the calculation expression of the reference current value is:

[0021] u gd =V g

[0022] u gq =0

[0023]

[0024] In the formula, and is the control current in the DQ axis coordinate system, and is the expected power at the grid stability point, V g It is the amplitude corresponding to the stable grid voltage level.

[0025] Furthermore, the calculation expression of the DQ voltage value on the inverter side is:

[0026]

[0027] In the formula, and is the DQ control voltage value, and is the control current in the DQ axis coordinate system, i gd and i gq is the grid-connected current in the DQ axis coordinate system, V g It is the amplitude corresponding to the stable grid voltage level.

[0028] Further, step S4 is specifically as follows: obtaining the phase value by calculating the inverse tangent of the DQ voltage value, obtaining the control phase angle of the inverter reference voltage, and then obtaining the control voltage value of the inverter by inverse Pike transformation in combination with the DQ control voltage value on the inverter side.

[0029] Furthermore, the inverter is a three-phase two-level three-leg inverter.

[0030] According to a second aspect of the present invention, a power control device for a grid-connected inverter includes a memory, a processor, and a program stored in the memory, and when the processor executes the program, it implements any of the above methods for controlling the power of a grid-connected inverter.

[0031] A third aspect of the present invention is a storage medium having a program stored thereon, which implements any of the above methods for controlling power of a grid-connected inverter when the program is executed.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1) The present invention uses the DQ axis coordinate system model to calculate the current formed by the constant power load and the coupling term on the DQ axis, thereby getting rid of the real-time phase lock of the grid connection point voltage and avoiding the voltage disturbance and phase lock inaccuracy caused by line changes. The impact of line changes only exists in the tracking scope of the control system and no longer belongs to a large-scale robustness problem, thereby achieving a high degree of stability.

[0034] 2) The present invention responds through a current closed loop, has a fast calculation speed, and has higher accuracy than droop control through current tracking.

[0035] 3) Since the real purpose of the present invention is to transmit power to the stable voltage point of the power grid, the power transmission at the grid connection point is not the goal, which can play the role of effective transmission and has higher effectiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a system structure diagram of the present invention.

[0037] Figure 2 This is a block diagram of the overall system of the present invention.

[0038] Figure 3 This is a current closed-loop block diagram used in the simulation of the present invention.

[0039] Figure 4 This is the current control block diagram of the grid-connected point voltage phase-locked loop.

[0040] Figure 5 A block diagram of droop control.

[0041] Figure 6 A block diagram of a virtual synchronous machine control.

[0042] Figure 7 These are the active and reactive response curves of the grid point under the weak grid startup condition of the proposed control.

[0043] Figure 8 The active and reactive response curves of the grid point under weak grid startup based on phase-locked control.

[0044] Fig. 9 The active and reactive response curves of the grid point under the droop control when the weak grid is started.

[0045] Fig.10It is the active and reactive response curves of the grid point under the condition of virtual synchronous generator control starting in weak grid.

[0046] Fig.11 These are the active and reactive response curves of the grid point under the strong grid startup condition for the proposed control.

[0047] Fig.12 It is the active and reactive response curves of the grid point under strong grid startup based on phase-locked control.

[0048] Fig.13 Active and reactive response curves of the grid point under strong grid startup for droop control.

[0049] Fig.14 It is the active and reactive response curves of the grid point under the condition of strong grid startup for virtual synchronous generator control. DETAILED DESCRIPTION

[0050] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0051] Example 1

[0052] The present invention proposes a novel composite nonlinear control strategy for the constant power load fed by the isolated AC microgrid. The current formed by the constant power load and the coupling term on the DQ axis are estimated by designing a disturbance observer; a simple homogeneous feedback control form is used to construct a feedback control framework. The experimental results show that the proposed invention can use a simple control form to achieve large signal stability and rapid performance recovery of the voltage of the isolated AC microgrid when the constant power load changes over a large range.

[0053] The present invention is a power control method, device and medium for a grid-connected inverter, the method comprising the following steps:

[0054] S1: Establish a DQ axis coordinate system model of a grid-connected power transmission system consisting of a DC power supply, an inverter, an LCR filter, an equivalent circuit simulation device and a power grid connected in sequence;

[0055] According to the actual operating parameters of the grid-connected inverter and the access grid, the full system mathematical model of grid-connected power transmission is established:

[0056]

[0057] Where κ = a, b, c, R g is the resistance in the equivalent transmission line, L g is the inductance of the equivalent transmission line, for each k phase, i gkis the current connected to the grid, u sκ and u gκ is the voltage between the grid connection point and the grid stability point, and t is the time. For each k phase, i gκ is the current connected to the grid, u sk and u gk is the voltage between the grid connection point and the grid stability point. Space vector PWM is achieved through u sk Calculate 6 pulse signals to give to the three-phase two-level converter to form a switching voltage.

[0058] According to Park transformation, the three-phase stationary abc reference system (1) can be transformed into the following rotating DQ reference system:

[0059]

[0060] In the formula, u sd and u sq is the inverter grid-connected point control voltage in the DQ axis coordinate system, i gd and i gq is the grid-connected current in the DQ axis coordinate system, R g is the resistance in the equivalent transmission line, L gd and L gg is the inductance of the equivalent transmission line in the DQ axis coordinate system, i gd and i gq is the grid-connected current in the DQ axis coordinate system, and ω is the phase.

[0061] S2: Calculate the reference current value of the grid-connected point in the DQ axis coordinate system model, obtain the phase angle of the reference current through zero-crossing point detection in the zero power state, and obtain the real-time DQ value of the grid-connected point current;

[0062] In the zero transmission power state, since there is no voltage drop and angle deviation caused by the current passing through the line, the grid connection point voltage at this time is recorded as That is u gκ At this time, the initial phase of the phase angle can be detected by connecting the positive zero-crossing point of the output voltage of the voltage sensor connected to phase A and the neutral point, that is, triggering at the positive zero-crossing point. At this triggering point, the integrator constructs the rotation angle θ at the frequency level of the grid (such as 50Hz or 60Hz). g By measuring The maximum value or through θ g Combined with Parker transformation to obtain the amplitude V corresponding to the stable grid voltage level g .

[0063] At this time, in order to achieve the desired power of the grid stability point and The effective transmission of the equivalent transmission line can be achieved by tracking the reference value of the grid-connected point current, regardless of whether the information and changes of the equivalent transmission line are known. First, the current status information of the grid-connected point needs to be obtained through the three-phase current sensor combined with θ g To perform a Pike change to obtain i gd and i gq This processing method avoids the real-time phase locking of the grid connection point voltage and avoids reactive power loss. Second, according to the power calculation formula:

[0064]

[0065] The reference current value is:

[0066]

[0067] In the formula, i gd and i gq is the grid-connected current in the DQ axis coordinate system, i gd and i gq is the grid-connected current in the DQ axis coordinate system, and is the expected power at the grid stability point, and Control current in the DQ axis coordinate system.

[0068] Considering the stable grid point as the reference voltage point, then u gd =V g ,u gq =0. Then the reference current value can be rewritten as:

[0069]

[0070] In the formula, and is the control current in the DQ axis coordinate system, and is the expected power at the grid stability point, V g It is the amplitude corresponding to the stable grid voltage level.

[0071] S3: The DQ voltage value on the inverter side is obtained through the current closed-loop control in the DQ axis coordinate system, and the phase angle value and voltage amplitude are obtained through the inverse tangent calculation of the DQ voltage value, thereby obtaining the control voltage value of the inverter to realize the power control of the grid-connected inverter.

[0072] The DQ voltage value on the inverter side is obtained through the current closed-loop control in the DQ axis coordinate system:

[0073]

[0074] In the formula, and is the DQ control voltage value, and is the control current in the DQ axis coordinate system, i gd and i gq is the grid-connected current in the DQ axis coordinate system, V g It is the amplitude corresponding to the stable grid voltage level.

[0075] The phase value is obtained by calculating the inverse tangent of the DQ voltage value. So as to obtain the control phase angle of the inverter reference voltage Combined with the DQ control voltage value on the inverter side and The control voltage value of the inverter is obtained through the reverse Pike transformation to realize the power transmission control of the grid-connected inverter.

[0076] The present invention proposes a new control strategy for the power transmission problem of the grid-connected inverter facing the large-scale changes of the power grid, which greatly improves the stability and rapidity, and realizes accurate and effective transmission. Specifically, 1) in terms of stability, since the real-time phase locking of the grid-connected point voltage is eliminated, the voltage disturbance and phase locking inaccuracy caused by the line change are avoided. The impact of the line change only exists in the tracking scope of the control system, and no longer belongs to the large-scale robustness problem, and a high degree of stability is achieved. 2) in terms of rapidity, the control method that simulates the characteristics of the generator has a long response time, while this method can respond quickly by using the current closed loop method, and can ensure stability at the same time. 3) in terms of transmission accuracy, droop control cannot achieve precise control, while the current tracking method can achieve accuracy. 4) in terms of transmission effectiveness, since the real purpose is to transmit power to the stable voltage point of the power grid, not taking the transmission power of the grid-connected point as the goal can play the role of effective transmission, and the power measured at the grid-connected point minus the target power under precise control is the line loss.

[0077] The effectiveness and superiority of the present invention are illustrated by simulation experiments. The control parameter settings of the present invention and the traditional ones are shown in Table 1:

[0078] Table 1 Control parameters

[0079]

[0080] Among them, the current control method based on the grid-connected point voltage phase-locked loop is as follows Figure 4 As shown, the droop control method is as follows Figure 5 As shown, the virtual synchronous machine control method is as follows Figure 6 shown.

[0081] The three control methods in this part belong to the prior art and will not be described in detail here, but are only used as a comparison with the actual effects produced by the present invention.

[0082] The present invention sets up the following two groups of experiments, wherein Experiments 1 to 4 are the first group of experiments, and Experiments 5 to 8 are the second group of experiments. The main difference between the two groups of experiments is that the order of switching operating conditions is different, which corresponds to two different operating conditions during startup and switching.

[0083] Experiment 1: Simulation of the invention: voltage level is 220V, frequency level is 50Hz, equivalent line impedance is 0.2488 ohms and 6.6mH, no-load start, active transmission target is set to 2kW at 0.02 seconds, reactive transmission target is set to 500var, equivalent line impedance becomes 0.0995 ohms and 2.6mH at 1 second, simulation is stopped at 0.6 seconds, and curves of active power and reactive power on the grid side are obtained by simulation.

[0084] Experiment 2: A comparative simulation is conducted on the current control method based on the grid-connected point voltage phase-locked loop under the conditions of Experiment 1.

[0085] Experiment 3: A comparative simulation is conducted based on droop control under the conditions of Experiment 1.

[0086] Experiment 4: A comparative simulation is conducted based on the virtual synchronous machine control method under the conditions of Experiment 1.

[0087] Experiment 5: Simulation of the invention: the grid voltage level is set to 100Vrms, the frequency level is 50Hz, the equivalent line impedance is 0.0995 ohms and 2.6mH, and it is started at no-load. The active transmission target is set to 2kW and the reactive transmission target is set to 500var at 0.02 seconds. The equivalent line impedance becomes 0.2488 ohms and 6.6mH at 1 second. The simulation is stopped at 0.6 seconds, and the curves of active power and reactive power on the grid side are obtained by simulation.

[0088] Experiment 6: A comparative simulation is conducted on the current control method based on the grid-connected point voltage phase-locked loop under the conditions of Experiment 1.

[0089] Experiment 7: A comparative simulation is conducted based on droop control under the conditions of Experiment 1.

[0090] Experiment 8: A comparative simulation is conducted based on the virtual synchronous machine control method under the conditions of Experiment 1.

[0091] like Figure 1 As shown, a system block diagram of the present invention is shown, which illustrates that in a grid-connected inverter power transmission system, a grid-connected inverter connected to a DC power source is connected to a grid-connected point via a current sensor and a voltage sensor, and the grid-connected point is connected to a stable grid point via an equivalent line, and the current sensor and the voltage sensor respectively output i La ,i Lb ,i Lc and u sa,u sb ,u sc , output to the system of the present invention, and the PWM signal output by the present invention is input to the grid-connected inverter.

[0092] like Figure 2 As shown in the figure, the overall block diagram of the present invention illustrates that the three-phase current of the grid connection point is transformed into the corresponding component i of the DQ axis after the Parker coordinate transformation. gd and i gg , the angle value θ used for Parker transformation g The A-phase voltage sensor in the zero power transmission state is obtained through positive zero-crossing detection and 50Hz integrator, and V is obtained by measuring the maximum value of the voltage at this time. g . Obtain the grid current reference value based on the grid power demand and The DQ voltage value on the inverter side is obtained by current closed-loop control in the DQ axis coordinate system, and then the phase value is obtained by the inverse tangent calculation of the DQ voltage value. So as to obtain the control phase angle of the inverter reference voltage Combined with the DQ control voltage value on the inverter side and The control voltage value of the inverter is obtained through the reverse Pike transformation to realize the power transmission control of the grid-connected inverter.

[0093] like Figure 3 As shown, the current closed loop block diagram used in the simulation of the present invention, in which k pd , k id , k pq and k iq They represent the proportional and integral coefficients of the d-axis current loop and the q-axis current loop, respectively, and R g0 and L g0 The information is considered unknown and is taken as 0 in the simulation.

[0094] like Figure 4 As shown in the current control block diagram of the grid-connected voltage phase-locked loop, it can be seen that its input is u sd ,u sq ,i gd ,i gq , P ref and Q ref , the output is u sd,r and u sq,r .

[0095] like Figure 5 As shown in the figure, a droop control block diagram is shown. Its input is u sd ,u sq ,i gd ,i gq, P ref and Q rrf , the output is u sd,r and u sq,r .

[0096] like Figure 6 As shown in the figure, a virtual synchronous machine control block diagram, it can be seen that its input is u sd ,u sq ,i gd ,i gq and P ref , Q ref , the output is u sd,r and u sq,r .

[0097] like Figure 7 , Figure 8 , Fig. 9 and Fig.10 As shown in Figure 2, the active response and reactive response curves are based on Experiments 1 to 4. Figure 7 and Figure 8 , Fig. 9 , Fig.10 It can be found that: 1) the present invention exhibits the characteristics of low overshoot and smooth transition during the power response process of weak grid startup and when the grid strength increases, reflecting good stability; 2) the present invention responds faster to the target power and recovers faster after the grid strength changes, showing good rapidity; 3) the present invention targets the grid end, and the power tracking is more accurate; 4) after the grid strength changes, the present invention can automatically adjust the reactive power of the grid connection point to maintain the target tracking of the reactive power at the grid end.

[0098] like Fig.11 , Fig.12 , Fig.13 and Fig.14 As shown in Figure 2, the active response and reactive response curves are based on Experiments 5 to 8. Fig.11 and Fig.12 , Fig.13 , Fig.14 It can be found that: 1) the present invention shows the characteristics of low overshoot and smooth transition in the power response process of strong power grid startup and when the power grid strength decreases, reflecting good stability; 2) the present invention responds faster to the target power and recovers faster after the power grid strength changes, showing good rapidity; 3) the present invention takes the power grid end as the target, and the power tracking is more accurate; 4) after the power grid strength changes, the present invention can automatically adjust the reactive power of the grid connection point to maintain the target tracking of the reactive power at the power grid end.

[0099] The program code for implementing the method of the present invention can be written in any combination of one or more programming languages. These program codes can be provided to a processor or controller of a general-purpose computer, a special-purpose computer or other programmable data processing device, so that the program code, when executed by the processor or controller, enables the functions / operations specified in the flow chart and / or block diagram to be implemented. The program code can be executed entirely on the machine, partially on the machine, partially on the machine as a stand-alone software package and partially on a remote machine, or entirely on a remote machine or server.

[0100] In the context of the present invention, a machine-readable medium may be a tangible medium that may contain or store a program for use by or in conjunction with an instruction execution system, device, or equipment. A machine-readable medium may be a machine-readable signal medium or a machine-readable storage medium. A machine-readable medium may include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices, or equipment, or any suitable combination of the foregoing. A more specific example of a machine-readable storage medium may include an electrical connection based on one or more lines, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0101] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A power control method for a grid-connected inverter, characterized in that: The following steps are involved: S1: Establish a DQ axis coordinate system model of a grid-connected power transmission system consisting of a DC power supply, an inverter, an LCR filter, an equivalent circuit simulation device and a power grid connected in sequence; S2: Calculate the reference current value of the grid-connected point in the DQ axis coordinate system model, obtain the phase angle of the reference current through zero-crossing point detection in the zero power state, and obtain the real-time DQ value of the grid-connected point current; S3: The DQ voltage value on the inverter side is obtained through the current closed-loop control in the DQ axis coordinate system, and the phase angle value and voltage amplitude are obtained through the inverse tangent calculation of the DQ voltage value, thereby obtaining the control voltage value of the inverter to realize the power control of the grid-connected inverter.

2. The power control method of a grid-connected inverter according to claim 1, characterized in that: The mathematical expression of the grid-connected power transmission system is: Where κ = a, b, c, R g is the resistance in the equivalent transmission line, L g is the inductance of the equivalent transmission line, for each κ phase, i gκ is the current connected to the grid, u sκ and u gκ is the voltage at the grid connection point and the grid stability point, and t is the time.

3. The power control method of a grid-connected inverter according to claim 1, characterized in that: The calculation expression of the DQ axis coordinate system model is: In the formula, u sd and u sq is the inverter grid-connected point control voltage in the DQ axis coordinate system, i gd and i gq is the grid-connected current in the DQ axis coordinate system, R g is the resistance in the equivalent transmission line, L gd and L gq is the inductance of the equivalent transmission line in the DQ axis coordinate system, i gd and i gq is the grid-connected current in the DQ axis coordinate system, and ω is the phase.

4. The power control method of a grid-connected inverter according to claim 1, characterized in that: The calculation expression of the reference current value is: In the formula, i gd and i gq is the grid-connected current in the DQ axis coordinate system, i gd and i gq is the grid-connected current in the DQ axis coordinate system, and is the expected power at the grid stability point, and Control current in the DQ axis coordinate system.

5. The power control method of a grid-connected inverter according to claim 4, characterized in that: Taking the stable grid point as the reference voltage point, the calculation expression of the reference current value is: in gd =P g u gq ＝0 In the formula, and is the control current in the DQ axis coordinate system, and is the expected power at the grid stability point, V g It is the amplitude corresponding to the stable grid voltage level.

6. The power control method of a grid-connected inverter according to claim 1, characterized in that: The calculation expression of the DQ voltage value on the inverter side is: In the formula, and is the DQ control voltage value, and is the control current in the DQ axis coordinate system, i gd and i gq is the grid-connected current in the DQ axis coordinate system, V g It is the amplitude corresponding to the stable grid voltage level.

7. The power control method of a grid-connected inverter according to claim 1, characterized in that: Step S4 is specifically as follows: obtaining the phase value by calculating the inverse tangent of the DQ voltage value, obtaining the control phase angle of the inverter reference voltage, and then obtaining the control voltage value of the inverter by inverse Pike transformation in combination with the DQ control voltage value on the inverter side.

8. The power control method of a grid-connected inverter according to claim 1, characterized in that: The inverter is a three-phase two-level three-bridge-arm inverter.

9. A power control device for a grid-connected inverter, comprising a memory, a processor, and a program stored in the memory, characterized in that: When the processor executes the program, a power control method for a grid-connected inverter as described in any one of claims 1-8 is implemented.

10. A storage medium having a program stored thereon, characterized in that: When the program is executed, a power control method for a grid-connected inverter as described in any one of claims 1-8 is implemented.

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