Inverter control method and inversion system

Abstract

The invention discloses a control method of an inverter, which comprises the following steps: power grid voltage is acquired, constant-amplitude Clarke transformation and Park transformation are carried out, and a reference phase of the Park transformation meets the following conditions: q-axis voltage uq of the power grid voltage is enabled to be 0; taking the reference phase as a phase instruction theta set of the power grid voltage, and taking a d-axis voltage component ud of the power grid voltage when a q-axis voltage component uq is 0 as a voltage amplitude instruction Uset; taking the phase instruction theta set as the reference angular frequency of the output voltage of the inverter to realize phase synchronization of the inverter, and taking the voltage amplitude instruction Uset as the reference amplitude of the output voltage of the inverter to realize amplitude synchronization of the inverter; and controlling the inverter to be switched from the island mode to the grid-connected mode in response to the fact that the phase and the amplitude of the output voltage of the inverter are both synchronous with the power grid voltage. According to the control method of the inverter, zero-static-error control of the output voltage of the inverter can be realized.

Description

Technical Field

[0001] The present application relates to the field of electric power supply regulation, and in particular to a control method and an inverter system of an inverter. Background Art

[0002] When the inverter switches from off-grid operation to grid-connected operation, its phase, frequency, and amplitude usually deviate from those of the grid. If the grid-connected switch is closed directly, a large impact current will inevitably occur, endangering the safety of the equipment. Therefore, the grid-connected pre-synchronization control strategy is the research focus of the grid-connected inverter.

[0003] In the prior art, there are two mainstream schemes for grid-connected pre-synchronization: First, based on the principle of synchronization between the inverter and the grid when the grid-connected power is zero, synchronization is achieved by controlling the virtual grid-connected power to zero; Second, the voltage amplitude, phase and other information of the inverter and the grid are collected separately through two phase-locked loops, and the inverter output is compensated by the amplitude synchronizer and the phase synchronizer to achieve synchronization.

[0004] In the related art, the control structure of grid-connected pre-synchronization is complex. The mainstream solution one needs to construct a virtual grid-connected power based on droop control or virtual synchronous generator control (power calculation is required as described in patent CN102723741A). Compared with normal operation, the mainstream solution two needs to add a phase-locked loop, a phase synchronizer, and an amplitude synchronizer, and needs to design closed-loop parameters, which increases the difficulty and time of debugging. Summary of the invention

[0005] In order to solve the deficiencies of the prior art, this application adopts the following technical solutions:

[0006] The present application provides a control method for an inverter, the control method is applied to the inverter, the inverter includes an island mode and a grid-connected mode, the control method includes a pre-synchronization step before the inverter switches from the island mode to the grid-connected mode, the pre-synchronization step includes the following steps:

[0007] Obtain the grid voltage, perform equal-amplitude Clarke transformation and Park transformation on the grid voltage, wherein the reference phase of the Park transformation satisfies the following conditions: make the q-axis voltage u of the grid voltage q is 0;

[0008] The reference phase is used as the phase command θ of the grid voltage set , and the grid voltage is in the q-axis voltage component u q The d-axis voltage component u is 0 d As the voltage amplitude command U set ;

[0009] The phase command θ set As the reference angular frequency of the inverter output voltage, it can realize the phase synchronization of the inverter and set the voltage amplitude command Uset As the reference amplitude of the inverter output voltage, to achieve the amplitude synchronization of the inverter;

[0010] In response to the phase and amplitude of the output voltage of the inverter being synchronized with the grid voltage, the inverter is controlled to switch from the island mode to the grid-connected mode.

[0011] Furthermore, the method also includes:

[0012] Collect the three-phase output voltage and three-phase output current of the inverter, and based on the phase command θ set and voltage amplitude command U set , the output voltage of the inverter is controlled by a voltage-current dual-loop regulator to achieve phase synchronization and amplitude synchronization of the inverter.

[0013] Furthermore, the voltage-current dual-loop regulator includes a voltage-loop regulator and a current-loop regulator, and controlling the output voltage of the inverter using the voltage-current dual-loop regulator includes:

[0014] Obtain the three-phase output voltage and three-phase output current of the inverter, perform equal-amplitude Clarke transformation and Park transformation on the three-phase output voltage and three-phase output current to obtain the voltage feedback value u inv-dq and the current feedback value i inv-dq , where the reference phase of the Park transformation is equal to the phase command θ set ;

[0015] Voltage amplitude command U set , and voltage feedback value u inv-dq After passing through the voltage loop regulator, a reference current for the current loop is generated;

[0016] Reference current and current feedback value i inv-dq After passing through the current loop regulator, a PWM drive signal is generated to drive the inverter bridge arm switch tube on and off.

[0017] Furthermore, a phase-locked loop is used to generate a phase command θ set .

[0018] Furthermore, a phase-locked loop is used to generate a phase command θ set The following steps are involved:

[0019] With phase command θ set The reference phase of the Park transform is the q-axis component u obtained by the Park transform. q The PI regulation is performed with zero reference. The output angular frequency of the PI regulator is added to the natural angular frequency to obtain the output angular frequency. The output angular frequency is then output as the phase command θ after passing through the integral link. set .

[0020] Furthermore, the method also includes:

[0021] In response to the inverter being kept in the island mode, a second voltage amplitude command U is generated using the rated voltage and rated frequency of the inverter. set1 With the second phase command θ set1 ;

[0022] The three-phase output voltage and the three-phase output current of the inverter are collected, and based on the second phase instruction and the second voltage amplitude instruction, the output voltage of the inverter is controlled by using a voltage-current dual-loop regulator.

[0023] The present application also provides an inverter system, which applies the inverter control method as described above.

[0024] Furthermore, the inverter system includes:

[0025] A voltage acquisition module, the voltage acquisition module is at least used to collect the grid voltage;

[0026] Phase-locked module, used to generate voltage amplitude command U set and phase command θ set ;

[0027] The voltage and current dual-loop regulator is electrically connected to the phase-locked module and receives the voltage amplitude command U sent by the phase-locked module. set and phase command θ set , and based on the voltage amplitude command U set and phase command θ set Adjust the output voltage of the inverter.

[0028] Furthermore, the inverter system includes:

[0029] Grid-connected relay, which is arranged between the inverter and the grid;

[0030] In response to the stable operation of the phase-locked module, the grid-connected relay is controlled to close, and the inverter is connected to the grid for operation.

[0031] Further, in response to the phase locking module maintaining the output phase and the phase command θ set equal, judging that the phase-locked module is running stably.

[0032] According to the above description, in the control method of the inverter of the present application, the output result of the phase-locked loop (i.e., the voltage amplitude command U set and phase command θ set ) is used as a control instruction to adjust the output voltage of the inverter and realize zero-static-error control of the inverter output voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the droop control principle in the related art;

[0034] Figure 2 It is a schematic diagram of the medium-amplitude Clarke transformation in the related art;

[0035] Figure 3 It is a schematic diagram of Park transformation in the related art;

[0036] Figure 4 A small signal control block diagram provided for an embodiment of the present application;

[0037] Figure 5 A phase-locked loop control block diagram provided in an embodiment of the present application;

[0038] Figure 6 A control block diagram of a voltage-current dual-loop regulator provided in an embodiment of the present application;

[0039] Figure 7 A schematic diagram of an inverter system provided in an embodiment of the present application. DETAILED DESCRIPTION

[0040] The present application will be described in detail below in conjunction with the specific implementation modes shown in the accompanying drawings, but these implementation modes do not limit the present application. Structural, methodological, or functional changes made by ordinary technicians in the field based on these implementation modes are included in the protection scope of the present application.

[0041] The present application provides a control strategy for an inverter, which is applied to an inverter having the capability of operating in both island and grid-connected dual modes. According to the control strategy provided by the present application, the inverter can smoothly switch between the two operating modes of grid-connected and island.

[0042] The island mode refers to the isolation of the microgrid from the large grid, and the grid-connected mode refers to the connection of the microgrid to the large grid. The so-called smooth switching requires that the voltage phase, amplitude and frequency of the microgrid will not change suddenly before and after the mode switching, and the load in the microgrid can obtain uninterrupted high-quality electricity without causing excessive current impact on the large grid.

[0043] When the inverter switches from island mode to grid-connected mode, in order to avoid causing huge impact current and causing equipment damage, certain pre-synchronization control measures need to be taken to ensure that the microgrid voltage is synchronized with the large grid voltage.

[0044] Based on the above objectives, the inverter control strategy provided by the present application includes the following steps:

[0045] Step S1: In island mode, use the rated voltage and rated frequency of the inverter to generate a voltage amplitude command U set1 With phase command θ set1 ;

[0046] For example, Figure 1 As shown, it shows the droop control principle. According to the droop control principle, the active power output by the inverter power supply is linearly related to the frequency, and the reactive power is linearly related to the voltage amplitude.

[0047] For example, when the inverter outputs active power P 0 and reactive power is Q 0 When the inverter output voltage frequency is f 0 , the amplitude is V 0 , that is, running at the rated operating point A of the droop characteristic curve. In island mode, the voltage amplitude command U is generated according to the rated voltage and rated frequency of the inverter. set1 With phase command θ set1 The following steps are controlled with the two command values ​​to realize the control in the island mode, so that the inverter outputs the rated voltage required by the load based on the rated voltage and rated frequency. It should be noted that the rated voltage and rated frequency are determined by the power grid company.

[0048] Step S2: Using the phase command θ obtained in step S1 set1 Calculate the voltage feedback value u in the rotating coordinate system inv-dq and the current feedback value i inv-dq .

[0049] Specifically, step S2 includes the following steps:

[0050] Step S21, collecting the three-phase output voltage and output current (also referred to as the proximal three-phase voltage and three-phase current) of the inverter;

[0051] Step S22, performing equal-amplitude Clarke transformation on the three-phase output voltage;

[0052] Specifically, in step S22, the abc three-phase stationary coordinate system is transformed into the α-β two-phase stationary coordinate system. The principle is as follows: Figure 2 shown. Figure 2 The α axis of the α-β two-phase stationary coordinate system is defined to coincide with the A-phase coordinate axis of the abc three-phase stationary coordinate system. According to the principle of equal-amplitude transformation, its transformation matrix can be expressed by formula 1.

[0053]

[0054] The state equation of the inverter in the abc three-phase stationary coordinate system can be obtained by multiplying the state equation of the inverter in the α-β two-phase stationary coordinate system by the transformation matrix shown in formula (1).

[0055] Step S23, perform Park transformation on the result of the equal-amplitude Clarke transformation, thereby converting the α-β two-phase stationary coordinate system into the dq two-phase rotating coordinate system, wherein the reference phase used in the Park transformation is equal to the phase instruction θ obtained in step S1 set1 .

[0056] Specifically, the principle of converting to the dq two-phase rotating coordinate system is as follows Figure 3 The dq two-phase rotating coordinate system rotates synchronously counterclockwise at an angular velocity ω relative to the α-β two-phase stationary coordinate system, where ω is the angular frequency of the alternating current in the stationary coordinate system, and θ is the phase angle difference between the d-axis and the α-axis (i.e., the reference phase used by the Park transformation).

[0057] According to the principle of equal-amplitude transformation, the Park transformation matrix from the α-β two-phase stationary coordinate system to the dq two-phase rotating coordinate system can be expressed by formula (2).

[0058]

[0059] The state equation of the inverter in the α-β two-phase stationary coordinate system is multiplied by the Park transformation matrix shown in formula (2), and the state equation of the inverter in the dq two-phase rotating coordinate system can be obtained. According to the state equation in the dq two-phase rotating coordinate system, the voltage feedback value u in the rotating coordinate system can be obtained. inv-dq It should be noted that the voltage feedback value u inv-dq The voltage feedback value u of the d-axis component of the dq two-phase rotating coordinate system inv-d And the voltage feedback value u of the q-axis component inv-q .

[0060] Step S24: Perform equal-amplitude Clarke transformation and Park transformation on the three-phase output current to obtain the current feedback value i inv-dq , where the reference phase used by the Park transformation is equal to the phase command θ obtained in step S1 set1 . Current feedback value i inv-dq The current feedback value i of the d-axis component of the dq two-phase rotating coordinate system inv-d and the current feedback value i of the q-axis component inv-q .

[0061] The process of the equal-amplitude Clarke transformation and Park transformation of the three-phase output current refers to the process of the equal-amplitude Clarke transformation and Park transformation of the three-phase output voltage in step S22 and step S23, and will not be repeated here.

[0062] Step S3: Using the voltage amplitude command U obtained in step S1 set1 And the voltage feedback value u obtained in step S2 inv-dq and the current feedback value iinv-dq , the output voltage is closed-loop controlled (voltage and current dual-loop control).

[0063] Specifically, the voltage amplitude command U set1 And voltage feedback value u inv-dq After the voltage loop regulator, the reference current of the current loop is generated. This reference current and the current feedback value i inv-dq After passing through the current loop regulator, a PWM drive signal is generated to drive the inverter bridge arm switch tube on and off.

[0064] According to the automatic control principle, the control strategy provided in the present application uses a proportional-integral controller in a rotating coordinate system, thereby achieving zero-static-error control of the output voltage of the inverter in the island mode.

[0065] Furthermore, when the voltage of the large power grid is restored, pre-synchronization control is required before switching the inverter from the island mode to the grid-connected mode. To this end, the control strategy provided by the present application also includes the following steps:

[0066] Step S4, obtaining the grid voltage, and performing equal-amplitude Clarke transformation and Park transformation on the grid voltage, wherein the reference phase of the Park transformation satisfies the following conditions: the q-axis voltage u of the remote three-phase voltage q =0; take this reference phase as the phase command θ of the grid voltage set , and the q-axis voltage u of the remote three-phase voltage q The d-axis component u is 0 d As the voltage amplitude command U set .

[0067] Specifically, the remote three-phase voltage (i.e., the grid voltage) is first collected, and the remote three-phase voltage is subjected to equal-amplitude Clarke transformation and Park transformation to obtain the d-axis voltage u d and q-axis voltage u q .

[0068] Assume that the three-phase AC voltage of the power grid is:

[0069]

[0070] Where U represents the three-phase AC voltage amplitude of the power grid.

[0071] After the equal-amplitude Clarke transformation, the state equation of the grid voltage in the α-β two-phase stationary coordinate system can be obtained, as shown in formula (4).

[0072]

[0073] The equal-amplitude Clarke transformation result of the grid voltage is further subjected to Park transformation, and the state equation of the grid voltage in the dq two-phase rotating coordinate system is specifically shown in formula (5).

[0074]

[0075] According to the principle of small signal analysis, the following relationship exists near the steady-state operating point of the phase-locked loop:

[0076] θ≈ωt(6);

[0077] According to Taylor expansion, formula (6) can be obtained:

[0078] sin(ωt-θ)≈ωt-θ (7);

[0079] Combining formula (5) and formula (7), we can know that

[0080] u q =U(ωt-θ) (8);

[0081] cos(ωt-θ)≈1 (9);

[0082] Arranging formula (5), formula (8) and formula (9), we can know that:

[0083]

[0084] According to formula (10), the q-axis voltage u of the remote three-phase voltage can be obtained: q The d-axis component u is 0 d .

[0085] The phase in formula (6) is used as the phase command θ of the grid voltage set , and the q-axis voltage u of the remote three-phase voltage q The d-axis component u is 0 d As the voltage amplitude command U set .

[0086] In one embodiment, using Figure 4 The control diagram shown implements the control of formula (10) to obtain the phase command θ set and voltage amplitude command U set The specific principles are as follows:

[0087] Figure 4 In the diagram, U includes the above-mentioned Clarke transform and Park transform processes, where θ is used as the reference phase of the Park transform and the q-axis component u obtained by the Park transform is q With zero reference for PI regulation, the output angular frequency of the PI regulator is equal to the natural angular frequency ω n(generally taken as the rated angular frequency of the grid voltage 100π) is added to obtain the output angular frequency, and then the output angular frequency is passed through the integration link to obtain the final output phase θ.

[0088] Since θ≈ωt, we can Figure 4 The block diagram shown simplifies to Figure 5 As shown in the block diagram. Figure 5 As shown, the three-phase grid voltage u abc After Clarke transformation and Park transformation, the voltage u in the two-phase rotating coordinate system is obtained. d and u q , the q-axis component u obtained by Park transformation q With zero reference for PI regulation, the output angular frequency of the PI regulator is equal to the natural angular frequency ω n (generally taken as the rated angular frequency of the grid voltage 100π) is added to obtain the output angular frequency, and then the output angular frequency is passed through the integration link to obtain the final output phase θ.

[0089] Step S5: Change the phase command of the inverter output voltage from the rated phase command (θ set1 ) is switched to the phase-locked loop output phase θ set , after waiting for the loop to stabilize, the inverter completes phase synchronization;

[0090] Step S6: Change the amplitude command from the rated voltage amplitude command U set1 Switch to phase-locked loop output d-axis component u d , after waiting for the loop to stabilize, the inverter completes amplitude synchronization.

[0091] As an optional implementation, in step S5 and step S6, the voltage and current dual-loop control scheme can be used to control the voltage and current in the dq coordinate system to achieve phase synchronization and amplitude synchronization of the inverter. Step S5 and step S6 are similar to step S3 in the island state, except that step S3 is based on the rated phase command (θ set1 ) as the phase command, and in step S5 the phase locked loop output phase θ set As a phase command.

[0092] Specifically, Figure 6 As shown, it shows the voltage and current dual-loop control block diagram. Figure 6 In the figure, the outer loop is the voltage loop and the inner loop is the current loop. cd-ref Equivalent to voltage amplitude command U set .

[0093] The input end of the voltage loop receives the voltage feedback value u in the rotating coordinate system inv-dq and voltage amplitude command U set (The figure shows u cd-ref), after subtracting the two, the voltage regulator H cv (It can be realized by PI regulator) output current command value; the current command value and the current feedback value i in the rotating coordinate system inv-dq After subtraction, it passes through the current regulator H ci (It can be realized by PI regulator) to obtain the target value U after voltage and current dual loop control rd , and the target value U rd The target value is input to the SVPWM unit, and the SVPWM controls the inverter unit according to the target value: a PWM drive signal is generated to drive the inverter bridge arm switch tube on and off.

[0094] Voltage loop control enables the inverter output voltage to quickly and accurately track the voltage amplitude command U set Given, current loop control further improves the dynamic response characteristics of the system.

[0095] Step S7: After the inverter completes the amplitude and phase synchronization, the drive pulse is blocked, the inverter unit does not work, and the control in the island mode is disconnected. At the same time, the grid-connected switch STS is closed to connect to the grid and prepare for the control in the grid-connected mode.

[0096] Step S8: After waiting for the grid-connected switch STS to be completely closed, the inverter starts the grid-connected control algorithm and releases the driving pulse to enter the grid-connected control strategy.

[0097] According to the above description, in the inverter control method provided in the embodiment of the present application,

[0098] After the power grid is restored, the phase-locked loop (PLL) g-abc Phase-locked control is performed, and the grid voltage phase output by the phase-locked loop is used as the phase command of the off-grid voltage command (θ set ), the grid voltage amplitude output by the phase-locked loop (u d ) as the amplitude command of the off-grid voltage command (U set ), adjust the output voltage of the inverter to achieve zero-static-error control of the inverter output voltage. inv-abc ), current (i inv-abc ) after sampling and coordinate transformation (T abc-dq ) to obtain the feedback value (u inv-dq 、i inv-dq ). The off-grid controller is designed in a rotating coordinate system, and the proportional-integral control can be used to achieve voltage zero static error control. When the controller enters the steady state, it can immediately track the amplitude and phase of the grid voltage.

[0099] like Figure 7 As shown, the present application also provides an inverter system, which applies the inverter control method provided in the embodiment of the present application.

[0100] As an optional implementation, the inverter system includes:

[0101] A voltage acquisition module, wherein the voltage acquisition module is at least used to acquire grid voltage;

[0102] Phase lock module, used to generate the voltage amplitude instruction U set and the phase command θ set ;

[0103] A voltage and current dual-loop regulator, the voltage and current dual-loop regulator is electrically connected to the phase-locked module, and receives the voltage amplitude instruction U sent by the phase-locked module. set and the phase command θ set , and based on the voltage amplitude command U set and the phase command θ set The output voltage of the inverter is adjusted.

[0104] As an optional implementation method, the inverter system also includes:

[0105] A grid-connected relay, the grid-connected relay being arranged between the inverter and the power grid;

[0106] In response to the stable operation of the phase-locking module, the grid-connected relay is controlled to be closed, and the inverter is connected to the grid for operation.

[0107] In response to the phase lock module maintaining the output phase with the phase command θ set are equal, it is determined that the phase-locked module operates stably.

[0108] According to the above description, in the inverter system provided by the embodiment of the present application, the voltage and current dual-loop regulator uses the output result of the phase-locked loop (i.e., the voltage amplitude command U set and phase command θ set ) is used as a control instruction to adjust the output voltage of the inverter and realize zero-static-error control of the inverter output voltage.

[0109] It will be appreciated that the word "exemplary" as used herein means "serving as an example, instance, or illustration". Any embodiment described as "exemplary" is not necessarily preferred or superior to other embodiments and / or does not exclude the combination of features of other embodiments. It will be appreciated that certain features of the present application described in the context of separate embodiments for the sake of clarity may also be provided in a single embodiment by combination. Conversely, various features of the present application described in the context of a single embodiment for the sake of clarity may also be provided individually or in any suitable combination or as any other described embodiment of the present application.

[0110] The above disclosure is only the preferred embodiment of the present application, but it is not intended to limit the scope of rights of the present application. A person of ordinary skill in the art can understand that without departing from the spirit and scope of the present application and the appended claims, changes, modifications, substitutions, combinations, and simplifications should all be equivalent replacement methods and still fall within the scope of the invention.

[0111] The application fields of the technology of the present invention include but are not limited to pipeline safety. As long as the essence of the technical solution does not deviate from the scope of the technical solution of each embodiment of the present invention, it falls within the protection scope of the present invention.

Claims

1. A control method for an inverter, wherein the control method is applied to an inverter, wherein the inverter includes an island mode and a grid-connected mode, and wherein: The control method includes a pre-synchronization step before the inverter switches from the island mode to the grid-connected mode, and the pre-synchronization step includes the following steps: Obtain the grid voltage, perform a Clarke transformation and a Park transformation on the grid voltage, wherein the reference phase of the Park transformation satisfies the following conditions: q is 0; The reference phase is used as the phase command θ of the grid voltage set The grid voltage is in the q-axis voltage component u q The d-axis voltage component u is 0 d As the voltage amplitude command U set ; The phase command θ set As the reference angular frequency of the inverter output voltage, to achieve the phase synchronization of the inverter, and to set the voltage amplitude command U set As a reference amplitude of the inverter output voltage, so as to achieve amplitude synchronization of the inverter; In response to the phase and amplitude of the output voltage of the inverter being synchronized with the grid voltage, the inverter is controlled to switch from the island mode to the grid-connected mode.

2. The inverter control method according to claim 1, characterized in that: The method further comprises: Collect the three-phase output voltage and three-phase output current of the inverter, and based on the phase command θ set and the voltage amplitude command U set , using a voltage-current dual-loop regulator to control the output voltage of the inverter to achieve phase synchronization and amplitude synchronization of the inverter.

3. The control method of the inverter according to claim 2, characterized in that: The voltage-current dual-loop regulator includes a voltage-loop regulator and a current-loop regulator, and the method of controlling the output voltage of the inverter by using the voltage-current dual-loop regulator includes: Obtain the three-phase output voltage and the three-phase output current of the inverter, and perform equal-amplitude Clarke transformation and Park transformation on the three-phase output voltage and the three-phase output current to obtain a voltage feedback value u inv-dq and the current feedback value i inv-dq , where the reference phase of the Park transformation is equal to the phase command θ set ; The voltage amplitude command U set , and voltage feedback value u inv-dq Generate a reference current of the current loop through the voltage loop regulator; The reference current and the current feedback value i inv-dq The current loop regulator generates a PWM drive signal to drive the inverter bridge arm switch tube to turn on and off.

4. The control method of the inverter according to claim 1, characterized in that: The phase command θ is generated by a phase-locked loop set .

5. The control method of the inverter according to claim 4, characterized in that: The phase command θ is generated by using a phase-locked loop set The following steps are involved: With phase command θ set The reference phase of the Park transform is the q-axis component u obtained by the Park transform. q The output angular frequency of the PI regulator is added to the natural angular frequency to obtain the output angular frequency, and then the output angular frequency is output as the phase command θ after passing through the integral link. set .

6. The control method of the inverter according to claim 1, characterized in that: The method further comprises: In response to the inverter being maintained in the island mode, a second voltage amplitude command U is generated using the rated voltage and rated frequency of the inverter. set1 With the second phase command θ set1 ; The three-phase output voltage and the three-phase output current of the inverter are collected, and based on the second phase instruction and the second voltage amplitude instruction, the output voltage of the inverter is controlled by using a voltage-current dual-loop regulator.

7. An inverter system, the inverter system applying the inverter control method according to any one of claims 1 to 6.

8. The inverter system according to claim 7, characterized in that: The inverter system comprises: A voltage acquisition module, wherein the voltage acquisition module is at least used to acquire grid voltage; Phase lock module, used to generate the voltage amplitude instruction U set and the phase command θ set ; A voltage and current dual-loop regulator, the voltage and current dual-loop regulator is electrically connected to the phase-locked module, and receives the voltage amplitude instruction U sent by the phase-locked module. set and the phase command θ set , and based on the voltage amplitude command U set and the phase command θ set The output voltage of the inverter is adjusted.

9. The inverter system according to claim 8, characterized in that: The inverter system comprises: A grid-connected relay, the grid-connected relay being arranged between the inverter and the power grid; In response to the stable operation of the phase-locking module, the grid-connected relay is controlled to be closed, and the inverter is connected to the grid for operation.

10. The inverter system according to claim 9, characterized in that: In response to the phase lock module maintaining the output phase with the phase command θ set are equal, it is determined that the phase-locked module operates stably.

Images