Control method for microinverter and related device therefor

Abstract

The present application relates to the technical field of inverter control, and relates to a control method for a microinverter and a related device therefor. A specific embodiment of the method comprises: acquiring a maximum power value of a photovoltaic module and a phase angle corresponding to a power grid current in an alternating current power grid, and, on the basis of the maximum power value and the phase angle, determining a target output current; and acquiring a mains frequency current corresponding to an output end of the microinverter, determining a current difference value between the target output current and the mains frequency current, on the basis of the current difference value, determining a target switching frequency corresponding to a plurality of switch tubes in the microinverter, and, by means of the target switching frequency, controlling the turning on and turning off of the plurality of switch tubes in the microinverter, so as to implement the transmission of a current to the alternating current power grid. According to the embodiment, the wave driving control of a microinverter based on a one-stage power conversion topology is achieved, which increases the efficiency and power of the microinverter, reduces the costs of the microinverter, and improves the control effect of the microinverter.

Description

Micro inverter control method and related equipment

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on October 20, 2023, with application number 202311370539.1 and application name “Control method of micro inverter and related equipment”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of inverter control technology, and in particular to a control method for a micro inverter and related equipment. Background Art

[0003] A microinverter generally refers to an inverter in a photovoltaic power generation system with a power of less than or equal to 1000 watts and component-level MPPT (Maximum Power Point Tracking). The full name is micro photovoltaic inverter. "Microinverter" is relative to traditional centralized inverters. The traditional photovoltaic inversion method is to connect all the direct current generated by photovoltaic cells under sunlight in series and parallel, and then use an inverter to convert the direct current into alternating current for connection to the grid; microinverters perform inversion for each component. The advantage of microinverters is that they can perform independent MPPT control on each component, which can greatly improve overall efficiency.

[0004] Related technologies primarily use a two-stage power conversion topology to improve the power and efficiency of microinverters. However, this still fails to meet the demands of high-power photovoltaic modules and increases microinverter costs. Currently, no effective solution has been proposed to address the low efficiency and power, high cost, and poor control performance of microinverters resulting from the control strategies of microinverters using a two-stage power conversion topology.

[0005] Summary of the Invention

[0006] The micro-inverter control method and related devices provided by the embodiments of the present invention at least solve the problems of low efficiency and power, high cost, and poor control effect of micro-inverters in related technologies.

[0007] To solve the above problem, one aspect of an embodiment of the present invention provides a control method for a micro-inverter, wherein the micro-inverter has a circuit topology based on a one-stage power conversion, and the method includes:

[0008] Obtain the maximum power value of the photovoltaic module and the phase angle corresponding to the grid current in the AC grid, and determine the target output current based on the maximum power value and the phase angle;

[0009] Obtain the industrial frequency current corresponding to the output end of the micro-inverter, determine the current difference between the target output current and the industrial frequency current, determine the target switching frequency corresponding to multiple switch tubes in the micro-inverter based on the current difference, and control the conduction and shutdown of multiple switch tubes in the micro-inverter through the target switching frequency to realize current transmission to the AC power grid.

[0010] In some embodiments, the steps of obtaining a maximum power value of a photovoltaic module and a phase angle corresponding to a grid current in an AC grid, and determining a target output current according to the maximum power value and the phase angle include:

[0011] Obtain the maximum power value of the photovoltaic module, determine the output voltage amplitude corresponding to the maximum power value, and determine the output current amplitude corresponding to the microinverter based on the output voltage amplitude;

[0012] The phase angle is obtained, and the target output current corresponding to the micro-inverter is determined according to the phase angle and the output current amplitude.

[0013] In some embodiments, after the step of obtaining the maximum power value of the photovoltaic module and the phase angle corresponding to the grid current in the AC grid, the method further includes:

[0014] The phase adjustment angle of the sine wave corresponding to the output current is obtained, and the target output current corresponding to the micro-inverter is determined according to the phase adjustment angle, the phase angle and the output current amplitude.

[0015] In some embodiments, the steps of obtaining the power frequency current corresponding to the output terminal of the micro-inverter and determining the current difference between the target output current and the power frequency current include:

[0016] Obtaining a sampling current corresponding to the output end of the micro-inverter, and performing power frequency extraction processing on the sampling current to obtain a power frequency current;

[0017] The target output current is rectified to determine a current difference between the power frequency current and the rectified target output current.

[0018] In some embodiments, the step of performing power frequency extraction processing on the sampled current to obtain the power frequency current includes:

[0019] The sampled current is rectified and filtered to obtain the power frequency current.

[0020] In some embodiments, the steps of determining target switching frequencies corresponding to multiple switches in the microinverter based on the current difference, and controlling the on and off of the multiple switches in the microinverter based on the target switching frequencies to achieve current delivery to the AC grid include:

[0021] Performing proportional-integral control or proportional-resonance control on the current difference to determine a control signal;

[0022] The control signal is subjected to voltage-frequency conversion to generate a drive signal, which is used to control the on and off of multiple switching tubes in the microinverter to achieve current transmission to the AC power grid; wherein the drive signal is used to drive the on and off of multiple switching tubes in the microinverter, and the adjustment frequency of the drive signal is consistent with the target switching frequency of the multiple switching tubes in the microinverter.

[0023] In some embodiments, the method further comprises:

[0024] Determining whether the target switching frequency is less than or equal to a preset switching frequency threshold;

[0025] If so, multiple switching tubes in the micro-inverter are driven to be turned on and off according to the target switching frequency to control the output gain of the micro-inverter.

[0026] In some embodiments, if the target switching frequency is greater than a preset switching frequency threshold, the method further includes:

[0027] The switching frequency corresponding to the preset switching frequency threshold is used to drive the conduction and shutdown of multiple switching tubes in the micro inverter, and the phase shift angle between the multiple switching tubes in the micro inverter is adjusted to control the output gain of the micro inverter.

[0028] In some embodiments, if the target switching frequency is greater than a preset switching frequency threshold, the method further includes:

[0029] The switching frequency corresponding to the preset switching frequency threshold is used to drive the conduction and shutdown of multiple switching tubes in the micro inverter, and the conduction time corresponding to the multiple switching tubes in the micro inverter is adjusted to control the output gain of the micro inverter.

[0030] In some embodiments, the circuit topology of the primary power conversion of the micro-inverter includes: a resonant circuit, a winding transformer and a voltage doubler rectifier circuit, the resonant circuit is connected to the primary winding of the winding transformer, and the voltage doubler rectifier circuit is connected to the secondary winding of the winding transformer; wherein, when the resonant circuit in the primary circuit topology of the micro-inverter is a full-bridge resonant circuit, it includes: a first capacitor on the DC side bus, a first bridge arm, a second bridge arm and an LLC circuit; wherein the first bridge arm and the second bridge arm are connected in parallel, the first bridge arm includes a first switch tube and a second switch tube connected in series, and the second bridge arm includes a third switch tube and a fourth switch tube connected in series; the LLC circuit The C circuit includes a leakage inductor, an excitation inductor, and a resonant capacitor connected in series. One end of the LLC circuit is connected to the midpoint of the first bridge arm, and the other end of the LLC circuit is connected to the midpoint of the second bridge arm. The voltage doubler rectifier circuit in the secondary circuit topology of the microinverter includes: a switch bridge arm and a capacitor bridge arm connected in parallel. The switch bridge arm includes an upper switch bridge arm and a lower switch bridge arm. The upper switch bridge arm includes a fifth switch transistor and a sixth switch transistor connected in series and arranged in a mirror image. The lower switch bridge arm includes a seventh switch transistor and an eighth switch transistor connected in series and arranged in a mirror image. The capacitor bridge arm includes a second capacitor and a third capacitor connected in series. The method further includes:

[0031] The DC power is received from the photovoltaic panels, converted into sinusoidal AC power through the first-stage power conversion circuit topology of the micro-inverter, and then the sinusoidal AC power is transmitted to the AC grid.

[0032] In some embodiments, the method further comprises:

[0033] respectively determining a first current value zero point corresponding to the power frequency current and a second current value zero point corresponding to the target output current;

[0034] According to the first current value zero point and the second current value zero point, the conduction and closing of multiple switch tubes in the secondary circuit topology are controlled to realize current transmission to the AC power grid through the secondary circuit topology.

[0035] In some embodiments, the step of controlling the on and off of multiple switches in the secondary circuit topology includes:

[0036] When the target output current is positive, if the power frequency current is positive, the fifth and sixth switches are controlled to be turned on, and the seventh and eighth switches are controlled to be turned off; if the power frequency current is negative, the seventh and eighth switches are controlled to be turned on, and the fifth and sixth switches are controlled to be turned off;

[0037] When the target output current is negative, if the power frequency current is positive, the seventh and eighth switch tubes are controlled to be turned on, and the fifth and sixth switch tubes are controlled to be turned off; if the power frequency current is negative, the fifth and sixth switch tubes are controlled to be turned on, and the seventh and eighth switch tubes are controlled to be turned off.

[0038] In some embodiments, the method further comprises:

[0039] Multiple switch tubes in the primary circuit topology are used as primary switch tubes, and multiple switch tubes in the secondary circuit topology are used as secondary switch tubes. The phase shift angle between the primary switch tube and the secondary switch tube is controlled to meet the phase shift angle threshold, so that: when the target output current is positive, the average value of the current flowing through the fifth switch tube and the sixth switch tube is positive, and when the target output current is negative, the average value of the current flowing through the seventh switch tube and the eighth switch tube is negative, so as to realize current transmission to the AC power grid through the secondary circuit topology.

[0040] In some embodiments, the method further comprises:

[0041] respectively determining a first current value zero point corresponding to the power frequency current and a second current value zero point corresponding to the target output current;

[0042] Multiple switching tubes in the primary circuit topology are used as primary switching tubes, and multiple switching tubes in the secondary circuit topology are used as secondary switching tubes. An initial phase shift angle between the secondary switching tubes and the primary switching tubes is obtained. With the average value of the current flowing through the fifth switching tube and the sixth switching tube being positive and the average value of the current flowing through the seventh switching tube and the eighth switching tube being negative as constraints, a target phase shift angle between the secondary switching tube and the primary switching tube is determined. The secondary switching tubes are adjusted according to the target phase shift angle to achieve current transmission to the AC power grid through the secondary circuit topology.

[0043] In some embodiments, the method further comprises:

[0044] Determine the sine wave period corresponding to the power frequency current according to the target output current;

[0045] When the power frequency current is in the positive half cycle of the sine wave, the sixth switch tube and the eighth switch tube are controlled to remain in the on state; when the power frequency current is in the negative half cycle of the sine wave, the fifth switch tube and the seventh switch tube are controlled to remain in the on state.

[0046] In some embodiments, the method further comprises:

[0047] Determine a preset time interval corresponding to the power frequency current, including the current value zero time;

[0048] The first switching frequency corresponding to the multiple switch tubes in the secondary circuit topology within the preset time interval is controlled to be higher than the second switching frequency corresponding to the multiple switch tubes in the secondary circuit topology within the non-preset time interval.

[0049] To solve the above problems, one aspect of an embodiment of the present invention provides a micro inverter, including: a processor, and a memory storing a program, wherein the program includes instructions, and when the instructions are executed by the processor, the processor executes any of the above micro inverter control methods.

[0050] In order to solve the above problem, one aspect of an embodiment of the present invention provides a non-transitory machine-readable medium storing computer instructions, where the computer instructions are used to enable a computer to execute any of the above micro-inverter control methods.

[0051] Beneficial effects of the embodiments of the present invention: A micro-inverter based on a circuit topology of a first-stage power conversion obtains the maximum power value of a photovoltaic module and the phase angle corresponding to the grid current in an AC power grid, and determines a target output current according to the maximum power value and the phase angle; obtains the industrial frequency current corresponding to the output end of the micro-inverter, determines the current difference between the target output current and the industrial frequency current, determines the target switching frequency corresponding to multiple switch tubes in the micro-inverter according to the current difference, and controls the conduction and shutdown of multiple switch tubes in the micro-inverter by the target switching frequency to realize a technical means of transmitting current to the AC power grid, overcoming the problems of low efficiency and power, high cost, and poor control effect of the micro-inverter caused by the control strategy of the micro-inverter based on the second-stage power conversion topology in the related art, and realizes wave driving control of the micro-inverter based on the first-stage power conversion topology, thereby improving the efficiency and power of the micro-inverter, reducing the cost of the micro-inverter, and improving the control effect of the micro-inverter.

[0052] The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below so that other features, objects, and advantages of the invention are more readily apparent. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be derived from these drawings without inventive effort.

[0054] FIG1 is a flow chart of a method for controlling a micro-inverter according to an embodiment of the present invention.

[0055] FIG2 is a flow chart of a control method for a micro-inverter according to another embodiment of the present invention.

[0056] FIG3a is a schematic diagram of the method shown in FIG2 , in which the sampling current is rectified and filtered in sequence to obtain the power frequency current;

[0057] FIG3 b is a schematic diagram of determining a wave generation strategy based on a target output current and a sampled current in the method shown in FIG2 ;

[0058] FIG3 c is a schematic diagram of another method of determining a wave generation strategy based on a target output current and a sampled current in the method shown in FIG2 .

[0059] FIG4 is a schematic diagram of a circuit topology of a micro-inverter based on one-stage power conversion in the method shown in FIG2 .

[0060] FIG5 a is a schematic diagram of the electrical levels flowing through multiple switching tubes in the primary circuit topology when the switching frequency adjustment strategy is adopted in the method shown in FIG2 ;

[0061] FIG5 b is a schematic diagram of the electrical levels flowing through multiple switching tubes in the primary circuit topology when the phase shift angle adjustment strategy is adopted in the method shown in FIG2 ;

[0062] FIG5 c is a schematic diagram of the electrical levels flowing through multiple switching tubes in the primary circuit topology when the on-time adjustment strategy is adopted in the method shown in FIG2 .

[0063] FIG6 a shows a schematic diagram of the current flowing through the primary resonant cavity, the secondary resonant cavity and the secondary switch tube based on a secondary switch tube regulation strategy;

[0064] FIG6 b shows a schematic diagram of current flowing through the primary resonant cavity, the secondary resonant cavity and the secondary switch tube based on another secondary switch tube regulation strategy.

[0065] FIG7 a shows a schematic diagram of the current flowing through the secondary-side switch tube based on the supplementary regulation strategy of a secondary-side switch tube;

[0066] FIG7 b shows a schematic diagram of the current flowing through the secondary-side switch tube based on the supplementary regulation strategy of another secondary-side switch tube.

[0067] FIG8 is a schematic structural diagram of an electronic device according to this embodiment. DETAILED DESCRIPTION

[0068] The following describes embodiments of the present invention in more detail with reference to the accompanying drawings. Although certain embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be construed as being limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the present invention. It should be understood that the accompanying drawings and embodiments of the present invention are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0069] Current microinverters are connected to photovoltaic panels and the AC grid separately, primarily using a flyback circuit topology. The secondary side of the transformer converts the output current to AC through a folded circuit, thereby converting the DC power from the photovoltaic panel to AC and transmitting it to the AC grid. This circuit topology is limited by the transformer core volume and switching frequency, making it difficult to increase power output and resulting in low inverter efficiency. As photovoltaic panel power increases, microinverters are required to increase power and improve efficiency. Most microinverters in the related art use two-stage power conversion technology. However, the total efficiency of the microinverter in two-stage power conversion is equal to the product of the two conversion efficiencies, making it difficult to exceed 96% efficiency. While the related art uses a two-stage power conversion topology to improve the power and efficiency of microinverters, it still fails to meet the requirements of high-power photovoltaic panels. The device layout required for the multi-stage power conversion topology increases the cost of the microinverter, and the control process is complex and the control effect is poor.

[0070] To solve the above problems, an embodiment of the present invention provides a control method for a micro-inverter. As shown in FIG1 , the control method for the micro-inverter mainly includes:

[0071] Step S101 : obtaining a maximum power value of a photovoltaic module and a phase angle corresponding to a grid current in an AC grid, and determining a target output current according to the maximum power value and the phase angle.

[0072] The microinverter provided in this embodiment of the present invention uses a single-stage power conversion circuit topology to convert DC power input from photovoltaic modules into sinusoidal AC power for output to the AC grid. By adopting a single-stage power conversion topology, the microinverter avoids the increased cost of microinverters caused by the device layout required by multi-stage power conversion topologies. It also effectively improves the power and efficiency of the microinverter, enabling it to meet the needs of high-power photovoltaic modules and expanding the application scenarios of microinverters.

[0073] In some embodiments, the steps of obtaining the maximum power value of the photovoltaic module and the phase angle corresponding to the grid current in the AC power grid, and determining the target output current based on the maximum power value and the phase angle include: obtaining the maximum power value of the photovoltaic module, determining the output voltage amplitude corresponding to the maximum power value, and determining the output current amplitude corresponding to the microinverter based on the output voltage amplitude; obtaining the phase angle corresponding to the grid current in the AC power grid, and determining the target output current corresponding to the microinverter based on the phase angle and the output current amplitude.

[0074] According to an embodiment of the present invention, the maximum power value of the photovoltaic module is obtained based on the MPPT (Maximum Power Point Tracking) strategy, and the output voltage amplitude that the photovoltaic module can provide based on the maximum power value is determined. Then, combined with the working conditions of the micro-inverter, the output current amplitude required to meet the output voltage amplitude can be determined. Combined with the phase angle (ωt) corresponding to the grid current in the AC power grid, the phase angle indicates the frequency and phase of the grid current, and the target output current corresponding to the micro-inverter is determined by the output current amplitude and the phase angle corresponding to the grid current. Through the above settings, the target output current corresponding to the micro-inverter is determined by combining the MPPT strategy with the phase angle of the grid current in the AC power grid, which improves the accuracy of the determined target output current, helps to improve the accuracy of the subsequent determined current difference and target switching frequency, and provides data support for improving the control effect of the micro-inverter.

[0075] According to a specific implementation of the embodiment of the present invention, the symbol A is used to represent the output current amplitude, ωt is used to represent the phase angle corresponding to the grid current, and I O _set represents the target output current, then the target output current I O _set = A*sin(ωt), where ω is the angular frequency of the sine wave corresponding to the grid current, indicating how quickly the sine wave signal changes, t is the current time, and ωt is the phase angle of the grid current. Based on the above expression for the target output current, the frequency and phase of the sine wave corresponding to the target output current are consistent with those of the sine wave corresponding to the grid current. Therefore, while delivering sinusoidal AC power to the AC grid, active power is also output.

[0076] In some embodiments, after the step of obtaining the maximum power value of the photovoltaic component and the sinusoidal wave signal corresponding to the grid current in the AC power grid, the above method also includes: obtaining the phase adjustment angle of the sinusoidal wave corresponding to the output current, and determining the target output current corresponding to the microinverter based on the phase adjustment angle, the phase angle and the output current amplitude.

[0077] Through the above settings, the control method of the micro-inverter provided by the embodiment of the present invention also provides a solution for outputting reactive power, that is, when determining the given amplitude of the output current, a preset phase adjustment angle is set according to the proportion of reactive power required to be output in the output power. but Due to the phase difference between the sine wave of the output current and the sine wave corresponding to the grid current When reactive power is output, the frequency of the sine wave corresponding to the output current is consistent with the frequency of the sine wave of the grid current in the AC grid, while the phase of the sine wave corresponding to the output current is inconsistent with the phase of the sine wave of the grid current in the AC grid.

[0078] In some embodiments, the steps of obtaining the power frequency current corresponding to the output end of the micro-inverter and determining the current difference between the target output current and the power frequency current include: obtaining the output current corresponding to the output end of the micro-inverter, performing power frequency extraction processing on the output current to obtain the power frequency current; rectifying the target output current, and determining the current difference between the power frequency current and the target output current after rectification.

[0079] Among them, the output current provided according to the embodiment of the present invention can be sampled by using high-bandwidth, high-slew rate sensors and operational amplifier devices (which can sample high-frequency signals up to tens of kilohertz or even higher to avoid waveform distortion). For example, CT sensors, Hall elements, etc. are used to sample the current in the secondary circuit of the micro-inverter, and then the output current value corresponding to the output end is obtained, thereby improving the accuracy of the sampling value.

[0080] According to a specific implementation of the embodiment of the present invention, the step of performing power frequency extraction processing on the output current to obtain the power frequency current includes: performing rectification processing and filtering processing on the output current to obtain the power frequency current.

[0081] Since the secondary output current (i.e., the sampling current) of the micro-inverter includes high-frequency harmonic current, if the harmonic current enters the power grid, it will interfere with sensitive equipment in the power grid. Therefore, the secondary current needs to be subjected to high-frequency filtering to filter out the high-frequency current (high-frequency current is relative to the power frequency current, and the frequency corresponding to the high-frequency current is higher than the frequency corresponding to the power frequency current) and obtain low-frequency current (i.e., power frequency current, industrial power / mains frequency, power frequency is a very low frequency, and power frequency current in my country refers to 50HZ AC) to be transmitted to the AC power grid. Therefore, when determining the target switching frequency corresponding to the multiple switches in the micro-inverter based on the current difference, after obtaining the induced current value (Is_smp, i.e., the sampling current) corresponding to the output end of the micro-inverter based on the sampling strategy, the embodiment of the present invention provides a solution for extracting the power frequency current value from the sampling current, that is, the sampling current is sequentially rectified and high-frequency filtered to obtain the power frequency current value; it should be noted that other power frequency extraction methods in the related art can also be used to obtain the power frequency current corresponding to the output end of the micro-inverter. At the same time, since the target output current The current value fluctuates around the current zero point. Therefore, it is necessary to rectify the target output current and then calculate the current difference between the rectified target output current and the power frequency current.

[0082] The current difference calculation method provided by the above steps uses the maximum power point of the photovoltaic module and the phase angle of the AC grid current as reference data, improving the accuracy of the determined current difference. This helps to improve the accuracy of the target switching frequency subsequently determined based on the current difference, thereby improving the control effect of the microinverter. Furthermore, by taking into account the preset phase adjustment angle, it also achieves the regulation and control of the output reactive power and useful power, which not only improves the control effect of the microinverter but also helps expand the application scenarios of microinverters.

[0083] Step S102: Obtain the power frequency current corresponding to the output end of the micro-inverter, determine the current difference between the target output current and the power frequency current, determine the target switching frequency corresponding to the multiple switches in the micro-inverter based on the current difference, and control the conduction and shutdown of the multiple switches in the micro-inverter according to the target switching frequency to realize current transmission to the AC power grid.

[0084] Among them, the circuit topology of the micro inverter provided by the embodiment of the present invention includes: a resonant circuit, a winding transformer and a voltage doubler rectifier circuit, the resonant circuit is connected to the primary winding of the winding transformer, and the voltage doubler rectifier circuit is connected to the secondary winding of the winding transformer.

[0085] In some embodiments, when the resonant circuit in the primary circuit topology of the above-mentioned micro-inverter is a full-bridge resonant circuit, it includes: a first capacitor on the DC side bus, a first bridge arm, a second bridge arm, and an LLC circuit; wherein the first bridge arm and the second bridge arm are connected in parallel, the first bridge arm includes a first switch tube and a second switch tube connected in series, and the second bridge arm includes a third switch tube and a fourth switch tube connected in series; the LLC circuit includes a leakage inductance, an excitation inductance, and a resonant capacitor connected in series, one end of the LLC circuit is connected to the midpoint of the first bridge arm, and the other end of the LLC circuit is connected to the midpoint of the second bridge arm; the voltage doubler rectifier circuit in the secondary circuit topology of the micro-inverter includes: a switch bridge arm and a capacitor bridge arm connected in parallel; wherein the switch bridge arm includes an upper half switch bridge arm and a lower half switch bridge arm, the upper half switch bridge arm includes a fifth switch tube and a sixth switch tube connected in series and arranged in a mirror image, the lower half switch bridge arm includes a seventh switch tube and an eighth switch tube connected in series and arranged in a mirror image, and the capacitor bridge arm includes a second capacitor and a third capacitor connected in series.

[0086] The micro-inverter applied based on the embodiment of the present invention realizes a circuit topology based on primary power conversion to transmit sinusoidal AC power to the AC grid, thereby effectively improving the efficiency and power of the micro-inverter.

[0087] In some embodiments, the above-mentioned step of determining the target switching frequency corresponding to multiple switching tubes in the microinverter based on the current difference, and controlling the conduction and shutdown of the multiple switching tubes in the microinverter by the target switching frequency to achieve current delivery to the AC power grid includes: performing proportional-integral control processing or proportional-resonance control processing on the current difference by a controller to determine a control signal; performing voltage-frequency conversion processing on the control signal by a voltage-frequency converter to generate a drive signal, and controlling the conduction and shutdown of the multiple switching tubes in the microinverter by the drive signal to achieve current delivery to the AC power grid; wherein the drive signal is used to drive the conduction and shutdown of the multiple switching tubes in the microinverter, and the adjustment frequency of the drive signal is consistent with the target switching frequency of the multiple switching tubes in the microinverter.

[0088] The controllers provided by the embodiments of the present invention include a PI controller (proportional integral (PI) controller, a controller that combines proportional and integral regulation) and a PR controller (proportional resonant (PR) controller). Specifically, a PI controller is a linear controller that forms a control deviation based on a given value and an actual output value, and linearly combines the proportional (P) and integral (I) of the deviation to form a control variable to control the controlled object. PR controllers are primarily used in power electronic control and can track specific frequency signals without static error, thereby increasing the gain amplitude of the loop at a specific frequency point.

[0089] According to a specific implementation of an embodiment of the present invention, after determining the target output current and the power frequency current corresponding to the output end of the micro-inverter, the target output current is used as the target current given signal corresponding to the driver, and the power frequency current corresponding to the output end of the micro-inverter is used as the current sampling feedback signal. The current sampling feedback signal is compared with the target current given signal of the drive controller to determine a current signal difference. The current signal difference is PI-controlled and adjusted by a PI controller or PR-controlled and adjusted by a PR controller to form a current loop control signal. The current loop control signal is then processed by a voltage-frequency converter to output a frequency-adjustable drive signal (the adjustment frequency of the drive signal is consistent with the target switching frequency corresponding to multiple switch tubes in the micro-inverter). The drive signal is used to drive the multiple switch tubes in the micro-inverter to turn on and off according to the target switching frequency, thereby achieving current transmission to the AC power grid, and the output current also meets the target value given by the target output current.

[0090] In some embodiments, the method further includes: determining whether the target switching frequency is less than or equal to a preset switching frequency threshold; if so, driving multiple switching tubes in the micro-inverter to be turned on and off according to the target switching frequency to control the output gain of the micro-inverter.

[0091] The target switching frequency mentioned in the determination step is the switching frequency corresponding to the multiple switches in the microinverter, determined based on the current difference. The preset switching frequency threshold is the upper limit of the switching frequency of the switch, determined based on the switch model and operating conditions, while ensuring stable performance of the switch.

[0092] When the target switching frequency is less than or equal to the preset switching frequency threshold, the switching frequency of the switching tube is negatively correlated with the output gain. Increasing the switching frequency can reduce the output gain. Therefore, the target adjustment strategy is determined to be the switching frequency adjustment strategy, that is, the output gain is controlled by adjusting the switching frequencies corresponding to multiple switching tubes in the micro-inverter.

[0093] In some embodiments, if the target switching frequency is greater than a preset switching frequency threshold, the method further includes: using the preset switching frequency threshold as the switching frequency corresponding to multiple switching tubes in the microinverter, and controlling the output gain of the microinverter by adjusting the phase shift angle between the multiple switching tubes in the microinverter.

[0094] When the target switching frequency is high, that is, the target switching frequency is greater than the preset switching frequency threshold, the actual switching frequency of the switch tube has been adjusted to the maximum (adjusted to the preset switching frequency threshold), and the output gain can no longer be reduced by increasing the switching frequency. In this case, a phase shift angle adjustment strategy can be used, that is, a strategy for controlling the output gain by adjusting the phase shift angle between the multiple switches in the microinverter. Accordingly, embodiments of the present invention implement output gain control over a wide voltage range for microinverters with a one-stage power conversion topology, expanding the applicable scenarios of microinverters with a one-stage power conversion topology.

[0095] In some embodiments, if the target switching frequency is greater than a preset switching frequency threshold, the method further includes: using the preset switching frequency threshold as the switching frequency corresponding to multiple switching tubes in the microinverter, and controlling the output gain of the microinverter by adjusting the conduction time corresponding to the multiple switching tubes in the microinverter.

[0096] When the target switching frequency is relatively high, in addition to the phase shift angle adjustment strategy, an embodiment of the present invention provides another adjustment strategy, namely, a conduction time adjustment strategy. That is, based on the preset switching frequency threshold as the switching frequency corresponding to the multiple switching tubes in the micro-inverter, the output gain of the micro-inverter is controlled by adjusting the conduction time of the multiple switching tubes in the micro-inverter.

[0097] When the target switching frequency is low, that is, the target switching frequency is less than or equal to the preset switching frequency threshold, the present invention provides a switching frequency adjustment strategy for the primary circuit topology, also known as frequency modulation, which reduces the output gain by increasing the switching frequency within the preset switching frequency threshold. When the target switching frequency is high, that is, the target switching frequency is greater than the preset switching frequency threshold, the present invention provides two control strategies for adjusting the output gain of the micro-inverter for the primary circuit topology. The phase shift angle adjustment strategy, also known as phase shift modulation, reduces the output gain by adjusting the phase shift angle between multiple switching tubes in the micro-inverter by fixing the switching frequency and using the preset switching frequency threshold as the switching frequency in actual operation; and the on-time adjustment strategy, also known as width modulation, controls the on-time of multiple switching tubes by fixing the switching frequency, reducing the duty cycle and reducing the output gain.

[0098] In some embodiments, the method further includes: respectively determining a first current value zero point corresponding to the power frequency current and a second current value zero point corresponding to the target output current; and controlling the on and off of multiple switch tubes in the secondary circuit topology according to the first current value zero point and the second current value zero point, so as to achieve the transmission of a sinusoidal output current to the AC power grid through the secondary circuit topology; wherein the step of controlling the on and off of multiple switch tubes in the secondary circuit topology includes: when the target output current is positive, if the power frequency current is positive, controlling the fifth switch tube and the sixth switch tube to be turned on, and controlling the seventh switch tube and the eighth switch tube to be turned off; if the power frequency current is negative, controlling the seventh switch tube and the eighth switch tube to be turned on, and controlling the fifth switch tube and the sixth switch tube to be turned off; when the target output current is negative, if the power frequency current is positive, controlling the seventh switch tube and the eighth switch tube to be turned on, and controlling the fifth switch tube and the sixth switch tube to be turned off; if the power frequency current is negative, controlling the fifth switch tube and the sixth switch tube to be turned on, and controlling the seventh switch tube and the eighth switch tube to be turned off.

[0099] Through the above settings, an embodiment of the present invention provides a regulation strategy for multiple switch tubes in a secondary circuit topology. Specifically, by determining the zero crossing point of the target output current and the zero crossing point of the power frequency current in the secondary sampling current (i.e., the sampling current), the conduction and shutdown of multiple switch tubes in the secondary circuit topology are switched on and off when the power frequency current crosses zero, which can achieve low current or zero current opening and closing, thereby reducing the switching loss of the switch tube. According to a specific implementation of the embodiment of the present invention, when the target output current is positive, if the power frequency current is positive, the fifth switch tube and the sixth switch tube are controlled to be turned on, and the seventh switch tube and the eighth switch tube are controlled to be turned off; if the power frequency current is negative, the seventh switch tube and the eighth switch tube are controlled to be turned on, and the fifth switch tube and the sixth switch tube are controlled to be turned off. When the target output current is negative, if the power frequency current is positive, the seventh switch tube and the eighth switch tube are controlled to be turned on, and the fifth switch tube and the sixth switch tube are controlled to be turned off; if the power frequency current is negative, the fifth switch tube and the sixth switch tube are controlled to be turned on, and the seventh switch tube and the eighth switch tube are controlled to be turned off.

[0100] In some embodiments, the above method also includes: using multiple switch tubes in the primary circuit topology as primary switch tubes, and using multiple switch tubes in the secondary circuit topology as secondary switch tubes, controlling the phase shift angle between the primary switch tube and the secondary switch tube to meet the phase shift angle threshold, so that: when the target output current is positive, the average value of the current flowing through the fifth switch tube and the sixth switch tube is positive, and when the target output current is negative, the average value of the current flowing through the seventh switch tube and the eighth switch tube is negative, so as to realize current transmission to the AC power grid through the secondary circuit topology.

[0101] Through the above-mentioned settings, an embodiment of the present invention provides another regulation strategy for multiple switch tubes in a secondary circuit topology. Specifically, the on and off drives of the multiple switch tubes in the secondary circuit topology are delayed compared to the on and off drives of the multiple switch tubes in the primary circuit topology. Furthermore, the above-mentioned delay processing can be achieved by adjusting the phase shift angle to ensure that when the target output current is a positive current, the average current flowing through the fifth switch tube and the sixth switch tube is positive, that is, the current waveform flowing through the fifth switch tube and the sixth switch tube at this stage is mostly positive current; when the target output current is a negative current, the average current flowing through the seventh switch tube and the eighth switch tube is negative, that is, the current waveform flowing through the seventh switch tube and the eighth switch tube at this stage is mostly negative current. According to a specific implementation of an embodiment of the present invention, the phase shift angle can also be adjusted so that: the positive current flows completely through the fifth switch tube and the sixth switch tube, and the negative current flows completely through the seventh switch tube and the eighth switch tube.

[0102] In some embodiments, the above method also includes: respectively determining a first current value zero point corresponding to the power frequency current and a second current value zero point corresponding to the target output current; using multiple switch tubes in the primary circuit topology as primary switch tubes and multiple switch tubes in the secondary circuit topology as secondary switch tubes, obtaining an initial phase shift angle between the secondary switch tube and the primary switch tube, and using the average value of the current flowing through the fifth switch tube and the sixth switch tube to be positive and the average value of the current flowing through the seventh switch tube and the eighth switch tube to be negative as constraints, determining a target phase shift angle between the secondary switch tube and the primary switch tube, and adjusting the secondary switch tube according to the target phase shift angle to achieve the transmission of sinusoidal AC power to the AC power grid through the secondary circuit topology.

[0103] In some embodiments, multiple switching tubes in the above-mentioned two secondary circuit topologies can also be combined. According to the target output current zero-crossing point judgment result and the power frequency current zero-crossing point judgment result in the sampled current, the current values ​​flowing through the fifth switching tube, the sixth switching tube, the seventh switching tube, and the eighth switching tube are determined. With the average current flowing through the fifth switching tube and the sixth switching tube being positive and the average current flowing through the seventh switching tube and the eighth switching tube being negative as constraints, the target phase shift angle between the secondary switching tube and the primary switching tube is determined, and then the multiple switching tubes in the secondary circuit topology are adjusted according to the target phase shift angle to realize the transmission of sinusoidal AC power to the AC power grid through the secondary circuit topology.

[0104] In some embodiments, the above method also includes: determining the sinusoidal wave period corresponding to the power frequency current based on the target output current; when the power frequency current is in the positive half period of the sinusoidal wave, controlling the sixth switch tube and the eighth switch tube to remain in the on state; when the power frequency current is in the negative half period of the sinusoidal wave, controlling the fifth switch tube and the seventh switch tube to remain in the on state.

[0105] An embodiment of the present invention provides a supplementary solution corresponding to the regulation strategy of multiple switches in a secondary circuit topology. Specifically, because the fifth and sixth switches are connected in series and mirror-imaged in the upper switching arm of the secondary circuit topology, and the seventh and eighth switches are connected in series and mirror-imaged in the lower switching arm of the secondary circuit topology, the sixth and eighth switches can be kept normally open during the positive half-cycle of the power-frequency current; and the fifth and seventh switches can be kept normally open during the negative half-cycle of the power-frequency current, thereby avoiding switch losses caused by high-frequency switching.

[0106] In some embodiments, the above method also includes: determining a preset time interval corresponding to the industrial frequency current, including the current value zero moment; controlling the first switching frequency corresponding to multiple switching tubes in the secondary circuit topology within the preset time interval to be higher than the second switching frequency corresponding to multiple switching tubes in the secondary circuit topology within the non-preset time interval.

[0107] An embodiment of the present invention provides another supplementary solution corresponding to the regulation strategy of multiple switch tubes in the secondary circuit topology. Specifically, when the power frequency current is near the zero point (i.e., within the above-mentioned preset time interval, the corresponding current in this time interval is a small current), the conduction and shutdown of the secondary switch tube is controlled at a higher switching frequency. When the power frequency current is near the non-zero point (i.e., within the above-mentioned non-preset time interval, the corresponding current is a large current), the conduction and shutdown of the secondary switch tube is controlled at a lower switching frequency. The first switching frequency corresponding to the multiple switch tubes in the secondary circuit topology within the preset time interval is controlled to be higher than the second switching frequency corresponding to the multiple switch tubes in the secondary circuit topology within the non-preset time interval. Through the above-mentioned setting, low current or zero current can be turned on and off, reducing the switching loss of the switch tube.

[0108] Among them, the control method of the micro-inverter provided in the embodiment of the present invention is based on a micro-inverter with a circuit topology of a first-stage power conversion. By obtaining the maximum power value of the photovoltaic module and the phase angle corresponding to the grid current in the AC power grid, the target output current is determined according to the maximum power value and the phase angle; the power frequency current corresponding to the output terminal of the micro-inverter is obtained, the current difference between the target output current and the power frequency current is determined, and the target switching frequency corresponding to multiple switches in the micro-inverter is determined according to the current difference. The target switching frequency is used to control the conduction and shutdown of the multiple switches in the micro-inverter to achieve the technical means of transmitting current to the AC power grid. This method overcomes the problems of low efficiency and power, high cost, and poor control effect of the micro-inverter caused by the control strategy of the micro-inverter based on the second-stage power conversion topology in the related art. It realizes wave driving control of the micro-inverter based on the first-stage power conversion topology, improves the efficiency and power of the micro-inverter, reduces the cost of the micro-inverter, and improves the control effect of the micro-inverter.

[0109] An embodiment of the present invention also provides a micro-inverter control method, which is applied to a micro-inverter based on a first-stage power conversion topology. The micro-inverter receives DC power input from a photovoltaic module and converts it into sinusoidal AC power via the first-stage power conversion topology for transmission to the AC power grid. As shown in Figure 2, the micro-inverter control method provided by the embodiment of the present invention mainly includes:

[0110] Step S201 : obtaining the maximum power value of the photovoltaic module, determining the output voltage amplitude corresponding to the maximum power value, and determining the output current amplitude corresponding to the micro inverter according to the output voltage amplitude.

[0111] Among them, the maximum power value of the photovoltaic module provided in the embodiment of the present invention is detected and obtained through the MPPT controller, and then based on the output voltage amplitude that can be provided by the maximum power value, combined with the working conditions of the micro inverter, the output current amplitude A required to meet the output voltage amplitude can be determined.

[0112] Step S202 , obtaining a preset phase adjustment angle and a phase angle corresponding to the grid current in the AC grid, and determining a target output current corresponding to the micro-inverter according to the phase angle, the output current amplitude and the preset phase adjustment angle.

[0113] The phase angle ωt corresponding to the grid current provided in the embodiment of the present invention indicates the frequency and initial phase of the grid current, wherein ω is the angular frequency of the sine wave corresponding to the grid current, indicating the speed of the change of the sine wave signal, t is the current moment, and the initial phase is 0. The preset phase adjustment angle provided in the embodiment of the present invention refers to the phase difference between the sine wave corresponding to the output current and the sine wave corresponding to the grid power value, which is a preset value and is represented by the symbol Characterization. Target output current Due to the phase difference between the sine wave of the output current and the sine wave corresponding to the grid current When reactive power is output, the frequency of the sine wave corresponding to the output current is consistent with the frequency of the sine wave of the grid current in the AC grid, and the phase of the sine wave corresponding to the output current is inconsistent with the phase of the sine wave of the grid current in the AC grid.

[0114] The above settings combine the MPPT strategy with the phase angle of the AC grid current to determine the target output current for the microinverter. This improves the accuracy of the target output current, helps improve the accuracy of the subsequent current difference and target switching frequency, and provides data support for improving the control effect of the microinverter. Furthermore, by adding a preset phase adjustment angle, the output active power and reactive power can be adjusted.

[0115] Step S203 , obtaining a sampled current corresponding to the output end of the micro-inverter, performing power frequency extraction processing on the sampled current to obtain a power frequency current value; rectifying the target output current, and determining a current difference between the power frequency current and the target output current after rectification.

[0116] According to an embodiment of the present invention, the step of performing power frequency extraction processing on the sampled current to obtain the power frequency current value may include: performing rectification processing and filtering processing on the output current to obtain the power frequency current.

[0117] Figure 3a is a schematic diagram of the method shown in Figure 2 in which the sampled current is sequentially rectified and filtered to obtain the power frequency current. As shown in Figure 3a, since the sampled current includes high-frequency current and low-frequency current (i.e., power frequency current), its corresponding signal is a sampled sinusoidal envelope signal (i.e., two sinusoidal waves with different amplitudes and frequencies are superimposed to form a sinusoidal wave with an envelope). The sampled sinusoidal envelope signal is then rectified to flip the waveform of the negative half-cycle of the sine wave to the positive half-cycle to obtain a rectified signal. Finally, the rectified signal is subjected to high-frequency filtering to obtain the power frequency current.

[0118] In order to improve the accuracy of the determined current difference through the above setting, it is necessary not only to determine the target output current by combining the maximum power value of the photovoltaic module and the phase angle of the grid current, but also to extract the low-frequency current, i.e., the power frequency current, from the sampled current at the output of the micro-inverter. According to a specific implementation of an embodiment of the present invention, two schemes for extracting the power frequency current are provided. As shown in FIG3b, the target output current is rectified (i.e., the absolute value is taken), and the secondary current sample value I is rectified. S _smp (i.e., sampling current) is rectified and high-frequency filtered to obtain the power frequency current. The current difference between the target output current and the power frequency current after absolute value processing is calculated. After processing by the controller, a wave strategy is output, that is, a drive signal with adjustable output frequency. The drive signal is used to drive the conduction and shutdown of multiple switches in the micro-inverter. The driving frequency of the drive signal is consistent with the target switching frequency of the multiple switches in the micro-inverter. As shown in Figure 3c, other power frequency extraction methods can be used to extract the secondary current sampling value I S _smp performs power frequency extraction processing to obtain power frequency current, calculates the current difference, and determines the wave generation strategy based on the current difference (the steps of determining the wave generation strategy based on the current difference are consistent with those in Figure 3b).

[0119] In step S204, the controller performs proportional-integral control or proportional-resonance control on the current difference to determine a control signal; the control signal is subjected to voltage-frequency conversion via a voltage-frequency converter to generate a drive signal; wherein the drive signal is used to drive the conduction and shutdown of multiple switching tubes in the micro-inverter, and the adjustment frequency of the drive signal is consistent with the target switching frequency of the multiple switching tubes in the micro-inverter.

[0120] According to a specific implementation of an embodiment of the present invention, after determining a target output current and an industrial frequency current corresponding to an output terminal of a micro-inverter, the target output current is used as a target current given signal corresponding to the driver, and the industrial frequency current corresponding to the output terminal of the micro-inverter is used as a current sampling feedback signal. The current sampling feedback signal is compared with the target current given signal of the drive controller to determine a current signal difference. The current signal difference is PI-controlled and adjusted by a PI controller or PR-controlled and adjusted by a PR controller to form a current loop control signal. The current loop control signal is then processed by a voltage-frequency converter to output a frequency-adjustable drive signal (the adjustment frequency of the drive signal is consistent with the target switching frequency corresponding to multiple switch tubes in the micro-inverter). The drive signal is used to drive the multiple switch tubes in the micro-inverter to turn on and off according to the target switching frequency, thereby achieving a sinusoidal output current to be delivered to the AC power grid, and the output current also meets the target value given by the target output current. Among them, after the above-mentioned current difference is adjusted by the PI regulator, the target switching frequency corresponding to the output switching tube is finally output. Among them, when the target given signal corresponding to the target output current is greater than the feedback signal corresponding to the power frequency current, that is, the signal difference is positive, the output target switching frequency decreases; when the target given signal corresponding to the target output current is less than the feedback signal corresponding to the power frequency current, that is, the signal difference is negative, the output target switching frequency increases.

[0121] In some embodiments, the circuit topology of the micro-inverter provided by the embodiments of the present invention includes: a resonant circuit, a winding transformer, and a voltage-doubling rectifier circuit, wherein the resonant circuit is connected to the primary winding of the winding transformer, and the voltage-doubling rectifier circuit is connected to the secondary winding of the winding transformer. Specifically, the resonant circuit is connected to the primary winding of the winding transformer, and the input end of the resonant circuit is connected to the photovoltaic module for receiving the current input by the photovoltaic module; the voltage-doubling rectifier circuit includes a switch bridge arm and a capacitor bridge arm connected in parallel, and the voltage-doubling rectifier circuit is connected to the secondary winding of the winding transformer for generating an induced current through the secondary winding, and the induced current flows through the capacitor in the capacitor bridge arm to form an induced current loop and achieve a multiple voltage boost; wherein the output end of the voltage-doubling rectifier circuit is used to deliver a sinusoidal output current to the load.

[0122] In some embodiments, as shown in FIG4 , when the resonant circuit is a full-bridge resonant circuit, it includes: a first capacitor C1 on the DC bus, a first bridge arm, a second bridge arm, and an LLC circuit. The first bridge arm and the second bridge arm are connected in parallel, the first bridge arm includes a first switching transistor Q1 and a second switching transistor Q2 connected in series, and the second bridge arm includes a third switching transistor Q3 and a fourth switching transistor Q4 connected in series. The LLC circuit includes a leakage inductor Lr, an excitation inductor Lm, and a resonant capacitor Cr connected in series, wherein the excitation inductor Lm also represents the primary winding of the winding transformer. One end of the LLC circuit is connected to the midpoint of the first bridge arm, and the other end of the LLC circuit is connected to the midpoint of the second bridge arm. The switching bridge arms in the voltage doubler rectifier circuit include an upper switching bridge arm and a lower switching bridge arm. The upper switching bridge arm includes a fifth switching transistor Q5 and a sixth switching transistor Q6 connected in series and arranged in a mirrored manner, and the lower switching bridge arm includes a seventh switching transistor Q7 and an eighth switching transistor Q8 connected in series and arranged in a mirrored manner. The capacitor bridge arm in the above-mentioned voltage doubler rectifier circuit includes a second capacitor C2 and a third capacitor C3 connected in series; wherein, one end of the secondary winding is connected to the midpoint of the switch bridge arm, and the other end of the secondary winding is connected to the midpoint of the capacitor bridge arm. A filter inductor Lg is provided at the output end of the above-mentioned voltage doubler rectifier circuit. wherein, the filter inductor Lg can be provided on one side of the output end of the voltage doubler rectifier circuit, or the filter inductor can be provided on both sides of the output end of the voltage doubler rectifier circuit, and at the same time, the filter inductor can also be provided at the output end of the voltage doubler rectifier circuit in the form of a common-mode inductor. The embodiment of the present invention forms an LC high-frequency filter circuit by using the capacitor in the capacitor bridge arm provided in the voltage doubler rectifier circuit and the filter inductor provided at the output end of the voltage doubler rectifier circuit, thereby achieving a filtering processing effect on the output current.

[0123] The micro-inverter applied based on the embodiment of the present invention realizes a circuit topology based on primary power conversion to transmit sinusoidal AC power to the AC grid, thereby effectively improving the efficiency and power of the micro-inverter.

[0124] Step S205: Determine whether the target switching frequency is less than or equal to a preset switching frequency threshold. If so, that is, the target switching frequency is less than or equal to the preset switching frequency threshold, and execute step S206; if not, that is, the target switching frequency is greater than the preset switching frequency threshold, and execute step S207.

[0125] The preset switching frequency threshold provided in the embodiment of the present invention refers to the upper limit of the switching frequency of the switching tube obtained by combining the model and operating conditions of the switching tube while ensuring the stable performance of the switching tube.

[0126] Because the switching frequencies of multiple switches in a microinverter are limited by a preset switching frequency threshold, if the target switching frequency exceeds the preset switching frequency threshold, continuing to adjust the multiple switches according to the target switching frequency threshold will not only fail to ensure the operational stability of the switches, but also fail to reduce the output gain even if the switching frequency is increased. Therefore, embodiments of the present invention provide a switching frequency determination step to determine different microinverter adjustment strategies based on actual conditions, thereby improving the control performance of the microinverter and expanding its applicable scenarios.

[0127] Step S206 , adjusting the multiple switching tubes in the micro-inverter according to the switching frequency adjustment strategy to control the output gain of the micro-inverter; wherein the switching frequency adjustment strategy is to adjust the switching frequencies of the multiple switching tubes in the micro-inverter.

[0128] When the target switching frequency is less than or equal to the preset switching frequency threshold, the switching frequency of the switching tube is negatively correlated with the output gain. Increasing the switching frequency can reduce the output gain. Therefore, the target adjustment strategy is determined to be the switching frequency adjustment strategy, that is, the output gain is controlled by adjusting the switching frequencies corresponding to multiple switching tubes in the micro-inverter.

[0129] According to a specific implementation of an embodiment of the present invention, when multiple switching tubes in a micro-inverter are adjusted according to a switching frequency adjustment strategy:

[0130] If the sine wave period of the output current is the positive half period of the sine wave, then in the process of adjusting the switching frequency to control the output gain: when the first switch tube and the fourth switch tube in the resonant circuit are turned on, the current input by the photovoltaic component forms a first conduction current loop in the resonant circuit, and generates an induced current in the voltage doubler rectifier circuit, which controls the fifth switch tube and the sixth switch tube to be turned on, and the induced current flows through the second capacitor in the capacitor bridge arm to form a first induced current loop; wherein, the current input by the photovoltaic component in the first conduction current loop passes through the MOS tube of the first switch tube, the LLC circuit, the MOS tube of the fourth switch tube, and the first capacitor in sequence; and the induced current in the first induced current loop passes through the MOS tube of the sixth switch tube, the parasitic diode of the fifth switch tube, and the second capacitor in sequence. When the first and fourth switching tubes in the resonant circuit are turned off, the resonant cavity current in the resonant circuit feeds the first capacitor on the DC side bus, controlling the third and second switching tubes to be turned on to form a second conduction current loop, and forming an induced current in the voltage doubler rectifier circuit. The seventh and eighth switching tubes are controlled to be turned on, and the induced current flows through the third capacitor in the capacitor bridge arm to form a second induced current loop; wherein, the resonant cavity current in the second conduction current loop passes through the parasitic diode of the third switching tube, the first capacitor, the parasitic diode of the second switching tube, and the LLC circuit in sequence; and the induced current in the second induced current loop passes through the third capacitor, the MOS tube of the eighth switching tube, and the parasitic diode of the seventh switching tube in sequence. When the resonant cavity current is zero, the photovoltaic component inputs current into the resonant circuit through the first capacitor on the DC side bus to form a third conduction current loop, and generates an induced current in the voltage doubler rectifier circuit. The induced current flows through the third capacitor in the capacitor bridge arm to form a third induced current loop; wherein, the current input by the photovoltaic component in the third conduction current loop passes through the MOS tube of the third switch tube, the LLC circuit, the MOS tube of the second switch tube, and the first capacitor in sequence, and the induced current in the third induced current loop passes through the third capacitor, the MOS tube of the eighth switch tube, and the parasitic diode of the seventh switch tube in sequence. When the third and second switching tubes in the resonant circuit are turned off, the resonant cavity current in the resonant circuit feeds the first capacitor on the DC side bus, controlling the first and fourth switching tubes to be turned on to form a fourth conduction current loop, and generating an induced current in the voltage doubler rectifier circuit. The fifth and sixth switching tubes are controlled to be turned on, and the induced current flows through the second capacitor in the capacitor bridge arm to form a fourth induced current loop; wherein, the current in the fourth conduction current loop passes through the parasitic diode of the fourth switching tube, the LLC circuit, the parasitic diode of the first switching tube, and the first capacitor in sequence, and the induced current in the fourth induced current loop passes through the MOS tube of the sixth switching tube, the parasitic diode of the fifth switching tube, and the second capacitor in sequence.

[0131] If the sine wave period of the output current is the negative half-period of the sine wave, then in the process of adjusting the switching frequency to control the output gain: when the first and fourth switching tubes in the resonant circuit are turned on, the current input by the photovoltaic module forms a fifth conduction current loop in the resonant circuit, and generates an induced current in the voltage doubler rectifier circuit, which controls the seventh and eighth switching tubes to be turned on, and the induced current flows through the third capacitor in the capacitor bridge arm to form a fifth induced current loop; wherein, the current input by the photovoltaic module in the fifth conduction current loop passes through the MOS tube of the first switching tube, the LLC circuit, the MOS tube of the fourth switching tube, and the first capacitor in sequence; and the induced current in the fifth induced current loop passes through the MOS tube of the seventh switching tube, the parasitic diode of the eighth switching tube, and the third capacitor in sequence. When the first and fourth switching tubes in the resonant circuit are turned off, the resonant cavity current in the resonant circuit feeds the first capacitor on the DC bus, controlling the third and second switching tubes to be turned on to form a sixth conduction current loop, and generating an induced current in the voltage doubler rectifier circuit. The fifth and sixth switching tubes are controlled to be turned on, and the induced current flows through the second capacitor in the capacitor bridge arm to form a sixth induced current loop. The resonant cavity current in the sixth conduction current loop sequentially passes through the parasitic diode of the second switching tube, the LLC circuit, the parasitic diode of the third switching tube, and the first capacitor. The induced current in the sixth induced current loop sequentially passes through the second capacitor, the MOS tube of the fifth switching tube, and the parasitic diode of the sixth switching tube. When the resonant cavity current is zero, the current input by the photovoltaic module forms a seventh conduction current loop in the resonant circuit and generates an induced current in the voltage-doubling rectifier circuit. The induced current flows through the second capacitor of the capacitor bridge arm to form a seventh induced current loop. In the seventh conduction current loop, the current input by the photovoltaic module passes through the MOS tube of the third switch tube, the LLC circuit, the MOS tube of the second switch tube, and the first capacitor in sequence. The induced current in the seventh induced current loop passes through the second capacitor, the MOS tube of the fifth switch tube, and the parasitic diode of the sixth switch tube in sequence. When the third and second switching tubes in the resonant circuit are turned off, the resonant cavity current in the resonant circuit feeds the first capacitor on the DC side bus, controlling the first and fourth switching tubes to be turned on to form an eighth conduction current loop, and generating an induced current in the voltage doubler rectifier circuit. The seventh and eighth switching tubes are controlled to be turned on, and the induced current flows through the third capacitor of the capacitor bridge arm to form an eighth induced current loop; wherein, the current in the eighth conduction current loop passes through the parasitic diode of the fourth switching tube, the LLC circuit, the parasitic diode of the first switching tube, and the first capacitor in sequence, and the induced current in the eighth induced current loop passes through the MOS tube of the seventh switching tube, the parasitic diode of the eighth switching tube, and the third capacitor in sequence.

[0132] In step S207, the preset switching frequency threshold is used as the switching frequency corresponding to the multiple switching tubes in the microinverter, and the multiple switching tubes in the microinverter are adjusted according to the phase shift angle adjustment strategy to control the output gain of the microinverter; wherein the phase shift angle adjustment strategy is to adjust the phase shift angle between the multiple switching tubes in the microinverter; or the preset switching frequency threshold is used as the switching frequency corresponding to the multiple switching tubes in the microinverter, and the multiple switching tubes in the microinverter are adjusted according to the on-time adjustment strategy to control the output gain of the microinverter; wherein the on-time adjustment strategy is to adjust the on-time of the multiple switching tubes in the microinverter.

[0133] When the target switching frequency is large, that is, the target switching frequency is greater than the preset switching frequency threshold, since the actual switching frequency of the switch tube has been adjusted to the maximum (adjusted to the preset switching frequency threshold), the output gain can no longer be reduced by increasing the switching frequency. In this case, the embodiment of the present invention provides two adjustment strategies, one is through the phase shift angle adjustment strategy, that is, the output gain is controlled by adjusting the phase shift angle corresponding to the multiple switch tubes in the micro-inverter; the other is through the conduction time adjustment strategy, based on the switching frequency preset threshold as the switching frequency corresponding to the multiple switch tubes in the micro-inverter, by adjusting the conduction time of the multiple switch tubes in the micro-inverter, the output gain of the micro-inverter is controlled. The embodiment of the present invention thus realizes output gain control over a wide voltage range for the micro-inverter with a one-stage power conversion topology, and expands the applicable scenarios of the micro-inverter with a one-stage power conversion topology.

[0134] In some embodiments, the method further includes: determining a first current value zero point corresponding to the power frequency current and a second current value zero point corresponding to the target output current; and controlling the conduction and shutdown of multiple switches in the secondary circuit topology based on the first current value zero point and the second current value zero point to achieve transmission of a sinusoidal output current to the AC power grid through the secondary circuit topology; wherein the step of controlling the conduction and shutdown of the multiple switches in the secondary circuit topology includes: when the target output current is positive, if the power frequency current is positive, controlling the fifth and sixth switches to be turned on, and controlling the seventh and eighth switches to be turned off; if the power frequency current is negative, controlling the seventh and eighth switches to be turned on, and controlling the fifth and sixth switches to be turned off. When the target output current is negative, if the power frequency current is positive, controlling the seventh and eighth switches to be turned on, and controlling the fifth and sixth switches to be turned off; and if the power frequency current is negative, controlling the fifth and sixth switches to be turned on, and controlling the seventh and eighth switches to be turned off.

[0135] Through the above-mentioned setting, an embodiment of the present invention provides a regulation strategy for multiple switch tubes in a secondary circuit topology. Specifically, by determining the zero-crossing point of the target output current and the zero-crossing point of the power frequency current in the secondary sampling current (i.e., the sampling current), it is used as a node to determine whether the target output current switches from zero to a positive or negative value, and whether the power frequency current switches from zero to a positive or negative value. Thus, when the power frequency current crosses zero, the multiple switch tubes in the secondary circuit topology are switched on and off, which can achieve low current or zero current opening and closing, and reduce the switching loss of the switch tube. According to a specific implementation of an embodiment of the present invention, when the target output current is positive, if the power frequency current is positive, the fifth switch tube and the sixth switch tube are controlled to be turned on, and the seventh switch tube and the eighth switch tube are controlled to be turned off; if the power frequency current is negative, the seventh switch tube and the eighth switch tube are controlled to be turned on, and the fifth switch tube and the sixth switch tube are controlled to be turned off. When the target output current is negative, if the power frequency current is positive, the seventh and eighth switch tubes are controlled to be turned on, and the fifth and sixth switch tubes are controlled to be turned off; if the power frequency current is negative, the fifth and sixth switch tubes are controlled to be turned on, and the seventh and eighth switch tubes are controlled to be turned off.

[0136] Figure 6a shows a schematic diagram of the current flowing through the primary resonant cavity, the secondary resonant cavity, and the secondary switch tube based on a secondary switch tube regulation strategy; as shown in Figure 6a, the current flowing through the fifth switch tube and the sixth switch tube in the secondary switch tube is a positive current, and the current flowing through the seventh switch tube and the eighth switch tube in the secondary switch tube is a negative current.

[0137] In some embodiments, the above method also includes: using multiple switch tubes in the primary circuit topology as primary switch tubes, and using multiple switch tubes in the secondary circuit topology as secondary switch tubes, controlling the phase shift angle between the primary switch tube and the secondary switch tube to meet the phase shift angle threshold, so that: when the target output current is positive, the average value of the current flowing through the fifth switch tube and the sixth switch tube is positive, and when the target output current is negative, the average value of the current flowing through the seventh switch tube and the eighth switch tube is negative, so as to achieve the transmission of a sinusoidal output current to the AC power grid through the secondary circuit topology.

[0138] Figure 6b shows a schematic diagram of the current flowing through the primary resonant cavity, the secondary resonant cavity and the secondary switch tube based on another secondary switch tube regulation strategy; as shown in Figure 6b, the average current flowing through the fifth switch tube and the sixth switch tube in the secondary switch tube is positive, that is, most of the positive current flows through the fifth switch tube and the sixth switch tube; the average current flowing through the seventh switch tube and the eighth switch tube in the secondary switch tube is negative, that is, most of the negative current flows through the seventh switch tube and the eighth switch tube.

[0139] Through the above-mentioned settings, an embodiment of the present invention provides another regulation strategy for multiple switch tubes in a secondary circuit topology. Specifically, the on and off drives of the multiple switch tubes in the secondary circuit topology are delayed compared to the on and off drives of the multiple switch tubes in the primary circuit topology. Furthermore, the above-mentioned delay processing can be achieved by adjusting the phase shift angle to ensure that when the target output current is positive, the average current flowing through the fifth switch tube and the sixth switch tube is positive, that is, the current waveform flowing through the fifth switch tube and the sixth switch tube at this stage is mostly positive current; when the target output current is negative, the average current flowing through the seventh switch tube and the eighth switch tube is negative, that is, the current waveform flowing through the seventh switch tube and the eighth switch tube at this stage is mostly negative current. According to a specific implementation of an embodiment of the present invention, the phase shift angle can also be adjusted so that: the positive current flows completely through the fifth switch tube and the sixth switch tube, and the negative current flows completely through the seventh switch tube and the eighth switch tube.

[0140] In some embodiments, the above method also includes: respectively determining a first current value zero point corresponding to the power frequency current and a second current value zero point corresponding to the target output current; using multiple switch tubes in the primary circuit topology as primary switch tubes and multiple switch tubes in the secondary circuit topology as secondary switch tubes, obtaining an initial phase shift angle between the secondary switch tube and the primary switch tube, and using the average value of the current flowing through the fifth switch tube and the sixth switch tube to be positive and the average value of the current flowing through the seventh switch tube and the eighth switch tube to be negative as constraints, determining a target phase shift angle between the secondary switch tube and the primary switch tube, and adjusting the secondary switch tube according to the target phase shift angle to achieve the transmission of sinusoidal AC power to the AC power grid through the secondary circuit topology.

[0141] In some embodiments, multiple switching tubes in the above-mentioned two secondary circuit topologies can also be combined. According to the target output current zero-crossing point judgment result and the power frequency current zero-crossing point judgment result in the sampled current, the current values ​​flowing through the fifth switching tube, the sixth switching tube, the seventh switching tube, and the eighth switching tube are determined. With the average current flowing through the fifth switching tube and the sixth switching tube being positive and the average current flowing through the seventh switching tube and the eighth switching tube being negative as constraints, the target phase shift angle between the secondary switching tube and the primary switching tube is determined, and then the multiple switching tubes in the secondary circuit topology are adjusted according to the target phase shift angle to realize the transmission of sinusoidal AC power to the AC power grid through the secondary circuit topology.

[0142] In some embodiments, the above method also includes: determining the sinusoidal wave period corresponding to the power frequency current based on the target output current; when the power frequency current is in the positive half period of the sinusoidal wave, controlling the sixth switch tube and the eighth switch tube to remain in the on state; when the power frequency current is in the negative half period of the sinusoidal wave, controlling the fifth switch tube and the seventh switch tube to remain in the on state.

[0143] An embodiment of the present invention provides a supplementary solution corresponding to a plurality of switch regulation strategies in a secondary circuit topology. Specifically, since the fifth and sixth switch tubes are connected in series and mirror-imaged in the upper half of the switch bridge arm in the secondary circuit topology, and the seventh and eighth switch tubes are connected in series and mirror-imaged in the lower half of the switch bridge arm in the secondary circuit topology, when the power frequency current is in the positive half-cycle of the sine wave, the sixth and eighth switch tubes can be kept normally open; when the power frequency current is in the negative half-cycle of the sine wave, the fifth and seventh switch tubes can be kept normally open. FIG7a shows a schematic diagram of the current flowing through the secondary switch tube based on the supplementary regulation strategy of a secondary switch tube. As can be seen from FIG7a, keeping Q6 and Q8 normally open during the positive half-cycle and keeping Q5 and Q7 normally open during the negative half-cycle can avoid switch tube losses caused by high-frequency switching.

[0144] In some embodiments, the above method also includes: determining a preset time interval corresponding to the industrial frequency current, including the current value zero moment; controlling the first switching frequency corresponding to multiple switching tubes in the secondary circuit topology within the preset time interval to be higher than the second switching frequency corresponding to multiple switching tubes in the secondary circuit topology within the non-preset time interval.

[0145] An embodiment of the present invention provides another supplementary solution corresponding to the regulation strategy for multiple switches in a secondary circuit topology. Specifically, the secondary switch is controlled to be on and off at a higher switching frequency near the zero-crossing point of the power frequency current, and is controlled to be on and off at a lower switching frequency during high current (non-power frequency current). The first switching frequency corresponding to the multiple switches in the secondary circuit topology within the zero-current value interval is controlled to be higher than the second switching frequency corresponding to the multiple switches in the secondary circuit topology within the non-zero-current value interval. Figure 7b shows a schematic diagram of the current flowing through the secondary switch based on another supplementary regulation strategy for the secondary switch. Through the above arrangement, the switch can be controlled to be on and off at a higher switching frequency during low current or zero current, thereby reducing the switching loss of the switch.

[0146] The control method for the micro-inverter provided in an embodiment of the present invention is based on a micro-inverter with a circuit topology of a first-stage power conversion. The method obtains the maximum power value of the photovoltaic module and the phase angle corresponding to the grid current in the AC power grid, and determines the target output current based on the maximum power value and the phase angle. The method also obtains the power frequency current corresponding to the output terminal of the micro-inverter, determines the current difference between the target output current and the power frequency current, and determines the target switching frequency corresponding to multiple switches in the micro-inverter based on the current difference. The method controls the conduction and shutdown of the multiple switches in the micro-inverter using the target switching frequency to achieve a technical means of delivering a sinusoidal output current to the AC power grid. The method overcomes the problems of low efficiency and power, high cost, and poor control effect of the micro-inverter caused by the control strategy of the micro-inverter based on the second-stage power conversion topology in the related art. The method implements wave driving control for the micro-inverter based on the first-stage power conversion topology, thereby improving the efficiency and power of the micro-inverter, reducing the cost of the micro-inverter, and enhancing the control effect of the micro-inverter.

[0147] An embodiment of the present invention further provides a micro-inverter, comprising: at least one processor; and a memory communicatively connected to the at least one processor. The memory stores a computer program executable by the at least one processor, wherein the computer program, when executed by the at least one processor, causes an electronic device to perform the method of an embodiment of the present invention.

[0148] An embodiment of the present invention further provides a non-transitory machine-readable medium storing a computer program, wherein the computer program, when executed by a processor of a computer, is used to cause the computer to perform the method of the embodiment of the present invention.

[0149] An embodiment of the present invention further provides a computer program product, including a computer program, wherein when the computer program is executed by a processor of a computer, it is used to enable the computer to perform the method of the embodiment of the present invention.

[0150] With reference to Figure 8, the structural block diagram of the electronic device that can be used as the server or client of an embodiment of the present invention will now be described, which is an example of a hardware device that can be applied to various aspects of the present invention. The electronic device is intended to represent various forms of digital electronic computer equipment, such as laptop computers, desktop computers, workstations, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. The electronic device can also represent various forms of mobile devices, such as personal digital processing, cellular phones, smart phones, wearable devices and other similar computing devices. The components shown herein, their connections and relationships, and their functions are merely examples and are not intended to limit the implementation of the present invention described and / or required herein.

[0151] As shown in Figure 8, the electronic device includes a computing unit 801, which can perform various appropriate actions and processes according to a computer program stored in a read-only memory (ROM) 802 or a computer program loaded from a storage unit 808 into a random access memory (RAM) 803. In the RAM 803, various programs and data required for the operation of the electronic device can also be stored. The computing unit 801, ROM 802, and RAM 803 are connected to each other via a bus 804. An input / output (I / O) interface 805 is also connected to the bus 804.

[0152] Multiple components within the electronic device are connected to the I / O interface 805, including an input unit 806, an output unit 807, a storage unit 808, and a communication unit 809. The input unit 806 can be any type of device capable of inputting information into the electronic device. The input unit 806 can receive input digital or character information and generate key signal inputs related to user settings and / or function control of the electronic device. The output unit 807 can be any type of device capable of presenting information and may include, but is not limited to, a display, a speaker, a video / audio output terminal, a vibrator, and / or a printer. The storage unit 808 may include, but is not limited to, a magnetic disk or an optical disk. The communication unit 809 allows the electronic device to exchange information / data with other devices via a computer network such as the Internet and / or various telecommunication networks and may include, but is not limited to, a modem, a network card, an infrared communication device, a wireless communication transceiver, and / or a chipset, such as a Bluetooth device, a WiFi device, a WiMax device, a cellular communication device, and / or the like.

[0153] The computing unit 801 may be a variety of general and / or special processing components with processing and computing capabilities. Some examples of the computing unit 801 include, but are not limited to, a CPU, a graphics processing unit (GPU), various dedicated artificial intelligence (AI) computing chips, various computing units that run machine learning model algorithms, digital signal processors (DSPs), and any appropriate processors, controllers, microcontrollers, etc. The computing unit 801 performs the various methods and processes described above. For example, in some embodiments, the method embodiments of the present invention may be implemented as a computer program, which is tangibly contained in a machine-readable medium, such as a storage unit 808. In some embodiments, part or all of the computer program may be loaded and / or installed on an electronic device via ROM 802 and / or communication unit 809. In some embodiments, the computing unit 801 may be configured to perform the above-described method in any other appropriate manner (e.g., by means of firmware).

[0154] The computer programs for implementing the methods of the embodiments of the present invention may be written in any combination of one or more programming languages. These computer programs may be provided to a processor or controller of a general-purpose computer, a special-purpose computer, or other programmable data processing device, so that when the computer programs are executed by the processor or controller, the functions / operations specified in the flowcharts and / or block diagrams are implemented. The computer programs may be executed entirely on the machine, partially on the machine, as a stand-alone software package, partially on the machine and partially on a remote machine, or entirely on a remote machine or server.

[0155] In the context of an embodiment of the present invention, a machine-readable medium can be a tangible medium that can contain or store a program for use by an instruction execution system, device or equipment or used in combination with an instruction execution system, device or equipment. A machine-readable medium can be a machine-readable signal medium or a machine-readable storage medium. A machine-readable signal medium can include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared or semiconductor system, device or equipment, or any suitable combination of the foregoing. A more specific example of a machine-readable storage medium can 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.

[0156] It should be noted that the term "including" and its variations used in the embodiments of the present invention are open-ended, i.e., "including but not limited to." The term "based on" means "based at least in part on." The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one other embodiment"; and the term "some embodiments" means "at least some embodiments." The modifications of "one" and "a plurality of" mentioned in the embodiments of the present invention are illustrative and non-restrictive. Those skilled in the art should understand that, unless the context clearly indicates otherwise, they should be understood as "one or more."

[0157] The various steps described in the method implementation scheme provided in the embodiments of the present invention may be performed in different orders and / or in parallel. In addition, the method implementation scheme may include additional steps and / or omit the steps shown. The scope of protection of the present invention is not limited in this respect.

[0158] The term "embodiment" in this specification refers to specific features, structures, or characteristics described in conjunction with the embodiment that can be included in at least one embodiment of the present invention. The appearance of this phrase in various places in the specification does not necessarily mean the same embodiment, nor does it mean that it is mutually exclusive with other embodiments and is independent or optional. The various embodiments in this specification are described in a related manner, and the same or similar parts between the various embodiments are referenced to each other. In particular, for the embodiments of the device, equipment, and system, since they are basically similar to the method embodiments, the description is relatively simple, and the relevant parts are referred to the partial description of the method embodiment.

[0159] The above-described embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of the present invention. Therefore, the scope of the present invention shall be determined by the appended claims.

Claims

1. A control method for a micro inverter, characterized in that: The micro inverter has a circuit topology based on primary power conversion, and the method includes: Obtaining a maximum power value of the photovoltaic module and a phase angle corresponding to a grid current in an AC grid, and determining a target output current according to the maximum power value and the phase angle; Obtain the industrial frequency current corresponding to the output end of the micro-inverter, determine the current difference between the target output current and the industrial frequency current, determine the target switching frequency corresponding to the multiple switch tubes in the micro-inverter according to the current difference, and control the conduction and closing of the multiple switch tubes in the micro-inverter by the target switching frequency to realize current transmission to the AC power grid.

2. The method according to claim 1, characterized in that The step of obtaining the maximum power value of the photovoltaic module and the phase angle corresponding to the grid current in the AC grid, and determining the target output current according to the maximum power value and the phase angle comprises: Acquire the maximum power value of the photovoltaic module, determine the output voltage amplitude corresponding to the maximum power value, and determine the output current amplitude corresponding to the micro inverter according to the output voltage amplitude; The phase angle is obtained, and a target output current corresponding to the micro inverter is determined according to the phase angle and the output current amplitude.

3. The method according to claim 2, characterized in that After the step of obtaining the maximum power value of the photovoltaic module and the phase angle corresponding to the grid current in the AC grid, the method further includes: A phase adjustment angle of a sine wave corresponding to the output current is obtained, and a target output current corresponding to the micro inverter is determined according to the phase adjustment angle, the phase angle, and the output current amplitude.

4. The method according to claim 1, characterized in that: The step of obtaining the power frequency current corresponding to the output end of the micro inverter and determining the current difference between the target output current and the power frequency current comprises: Acquire a sampling current corresponding to the output end of the micro-inverter, and perform power frequency extraction processing on the sampling current to obtain the power frequency current; The target output current is rectified to determine a current difference between the power frequency current and the rectified target output current.

5. The method according to claim 4, characterized in that The step of performing power frequency extraction processing on the sampled current to obtain the power frequency current comprises: The sampling current is rectified and filtered to obtain the power frequency current.

6. The method according to claim 1, characterized in that The step of determining the target switching frequency corresponding to the multiple switch tubes in the micro inverter according to the current difference, and controlling the on and off of the multiple switch tubes in the micro inverter by the target switching frequency to realize the current transmission to the AC power grid includes: Performing proportional-integral control processing or proportional-resonance control processing on the current difference to determine a control signal; The control signal is subjected to voltage-frequency conversion processing to generate a drive signal, and the conduction and closing of multiple switch tubes in the micro-inverter are controlled by the drive signal to realize current transmission to the AC power grid; wherein the drive signal is used to drive the conduction and closing of multiple switch tubes in the micro-inverter, and the adjustment frequency of the drive signal is consistent with the target switching frequency of the multiple switch tubes in the micro-inverter.

7. The method according to claim 1, characterized in that The method further comprises: Determining whether the target switching frequency is less than or equal to a preset switching frequency threshold; If so, multiple switch tubes in the micro inverter are driven to be turned on and off according to the target switching frequency to control the output gain of the micro inverter.

8. The method according to claim 7, characterized in that If the target switching frequency is greater than the preset switching frequency threshold, the method further includes: The switching frequency corresponding to the preset switching frequency threshold is used to drive the conduction and closing of multiple switching tubes in the micro inverter, and the phase shift angle between the multiple switching tubes in the micro inverter is adjusted to control the output gain of the micro inverter.

9. The method according to claim 7, characterized in that: If the target switching frequency is greater than the preset switching frequency threshold, the method further includes: The switching frequency corresponding to the preset switching frequency threshold is used to drive the conduction and shutdown of multiple switch tubes in the micro inverter, and the conduction time corresponding to the multiple switch tubes in the micro inverter is adjusted to control the output gain of the micro inverter.

10. The method according to claim 1, characterized in that The circuit topology of the primary power conversion of the micro-inverter includes: a resonant circuit, a winding transformer and a voltage doubling rectifier circuit, wherein the resonant circuit is connected to the primary winding of the winding transformer, and the voltage doubling rectifier circuit is connected to the secondary winding of the winding transformer; wherein, when the resonant circuit in the primary circuit topology of the micro-inverter is a full-bridge resonant circuit, it includes: a first capacitor, a first bridge arm, a second bridge arm and an LLC circuit on the DC side bus; wherein, the first bridge arm and the second bridge arm are connected in parallel, the first bridge arm includes a first switch tube and a second switch tube connected in series, and the second bridge arm includes a third switch tube and a fourth switch tube connected in series; the LLC circuit includes The LLC circuit comprises a leakage inductance, an excitation inductance and a resonant capacitor connected in series, one end of the LLC circuit is connected to the midpoint of the first bridge arm, and the other end of the LLC circuit is connected to the midpoint of the second bridge arm; the voltage doubling rectifier circuit in the secondary circuit topology of the micro-inverter comprises: a switch bridge arm and a capacitor bridge arm connected in parallel; wherein the switch bridge arm comprises an upper half switch bridge arm and a lower half switch bridge arm, the upper half switch bridge arm comprises a fifth switch tube and a sixth switch tube connected in series and arranged in a mirror image, the lower half switch bridge arm comprises a seventh switch tube and an eighth switch tube connected in series and arranged in a mirror image, and the capacitor bridge arm comprises a second capacitor and a third capacitor connected in series; the method further comprises: The direct current is received from the photovoltaic assembly, the direct current is converted into a sinusoidal alternating current through the circuit topology of the primary power conversion of the micro inverter, and the sinusoidal alternating current is transmitted to the alternating current grid.

11. The method according to claim 10, characterized in that The method further comprises: respectively determining a first current value zero point corresponding to the power frequency current and a second current value zero point corresponding to the target output current; According to the first current value zero point and the second current value zero point, the on and off of multiple switch tubes in the secondary circuit topology are controlled to realize current transmission to the AC power grid through the secondary circuit topology.

12. The method according to claim 11, characterized in that The step of controlling the on and off of multiple switch tubes in the secondary circuit topology includes: When the target output current is positive, if the power frequency current is positive, the fifth switch tube and the sixth switch tube are controlled to be turned on, and the seventh switch tube and the eighth switch tube are controlled to be turned off; if the power frequency current is negative, the seventh switch tube and the eighth switch tube are controlled to be turned on, and the fifth switch tube and the sixth switch tube are controlled to be turned off; When the target output current is negative, if the power frequency current is positive, the seventh switch tube and the eighth switch tube are controlled to be turned on, and the fifth switch tube and the sixth switch tube are controlled to be turned off; if the power frequency current is negative, the fifth switch tube and the sixth switch tube are controlled to be turned on, and the seventh switch tube and the eighth switch tube are controlled to be turned off.

13. The method according to claim 10, characterized in that The method further comprises: Using multiple switch tubes in the primary circuit topology as primary switch tubes, and multiple switch tubes in the secondary circuit topology as secondary switch tubes, the phase shift angle between the primary switch tube and the secondary switch tube is controlled to meet the phase shift angle threshold, so that: when the target output current is positive, the average current flowing through the fifth switch tube and the sixth switch tube is positive, and when the target output current is negative, the average current flowing through the seventh switch tube and the eighth switch tube is negative, so as to realize current transmission to the AC power grid through the secondary circuit topology.

14. The method according to claim 10, characterized in that The method further comprises: respectively determining a first current value zero point corresponding to the power frequency current and a second current value zero point corresponding to the target output current; Taking multiple switch tubes in the primary circuit topology as primary switch tubes, and taking multiple switch tubes in the secondary circuit topology as secondary switch tubes, an initial phase shift angle between the secondary switch tube and the primary switch tube is obtained, and taking the average current flowing through the fifth switch tube and the sixth switch tube as positive and the average current flowing through the seventh switch tube and the eighth switch tube as negative as constraints, a target phase shift angle between the secondary switch tube and the primary switch tube is determined, and the secondary switch tube is adjusted according to the target phase shift angle to realize current transmission to the AC power grid through the secondary circuit topology.

15. The method according to any one of claims 11 to 14, characterized in that The method further comprises: Determining the sinusoidal wave period corresponding to the power frequency current according to the target output current; When the power frequency current is in the positive half cycle of the sine wave, the sixth switch tube and the eighth switch tube are controlled to remain in the on state; when the power frequency current is in the negative half cycle of the sine wave, the fifth switch tube and the seventh switch tube are controlled to remain in the on state.

16. The method according to claims 11-14, characterized in that The method further comprises: Determine a preset time interval corresponding to the power frequency current, including a current value zero time; A first switching frequency corresponding to the plurality of switch tubes in the secondary circuit topology within the preset time interval is controlled to be higher than a second switching frequency corresponding to the plurality of switch tubes in the secondary circuit topology within the non-preset time interval.

17. A micro inverter, comprising: A processor, and a memory storing a program, wherein the program comprises instructions, which, when executed by the processor, cause the processor to perform the method according to any one of claims 1 to 16.

18. A non-transitory machine-readable medium storing computer instructions, characterized in that: The computer instructions are used to cause the computer to execute the method according to any one of claims 1-16.

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