Control method of off-grid micro inverter and related equipment

Abstract

The invention relates to a control method of an off-grid micro inverter and related equipment, and relates to the technical field of micro inverters. A specific embodiment of the method comprises the steps of obtaining an output voltage given value and an output voltage value corresponding to an output end of a voltage doubling rectifying circuit, and determining a voltage difference value between the output voltage given value and the output voltage value; determining an output current given value according to the voltage difference value, obtaining an induced current value in the voltage doubling rectifying circuit, and determining a current difference value between the output current given value and the induced current value; and determining target switching frequencies of a plurality of switching tubes in the micro-inverter according to the current difference value, and controlling the micro-inverter to transmit an output voltage meeting an output voltage given value to the load through the target switching frequencies. According to the embodiment, the off-grid function of the micro inverter based on the primary power conversion topology is realized, the economical efficiency of load power utilization is improved, and the application scene of the micro inverter is expanded.

Description

Technical Field

[0001] The present application relates to the technical field of micro inverters, and in particular to a control method and related equipment for an off-grid micro inverter. Background Art

[0002] Micro inverters generally refer to inverters with a power of less than or equal to 1000 watts and component-level MPPT (Maximum Power Point Tracking) in photovoltaic power generation systems. The full name is micro photovoltaic inverter. "Micro inverter" is relative to traditional centralized inverters. The traditional photovoltaic inverter method is to connect all the DC power generated by photovoltaic cells under sunlight in series and parallel, and then use an inverter to invert the DC power into AC power and connect it to the power grid; micro inverters invert each component. Its advantage is that each component can be independently controlled by MPPT, which can greatly improve the overall efficiency.

[0003] Current micro-inverters are usually connected to photovoltaic modules and AC power grids respectively to convert the DC power in photovoltaic modules into AC power for grid connection. In order to meet the needs of high-power photovoltaic modules, the relevant technology mainly adopts a two-stage power conversion topology to improve the power and efficiency of micro-inverters, but it is still difficult to meet the needs of high-power photovoltaic modules. At the same time, grid-connected micro-inverters need to use the mains power in the grid, which has the problems of poor economic efficiency and narrow application scenarios of micro-inverters. Summary of the invention

[0004] The embodiments of the present invention provide a control method and related equipment for an off-grid micro-inverter, which at least solve the problem that there is no control solution for realizing off-grid function for a micro-inverter with a primary power conversion topology in the related art, and that the grid-connected micro-inverter has poor economy and narrow application scenarios.

[0005] In order to solve the above problems, one aspect of an embodiment of the present invention provides a control method for an off-grid micro-inverter, wherein the micro-inverter is used to transmit sinusoidal AC power to a load based on a circuit topology of primary power conversion, and the circuit topology of the micro-inverter includes: a resonant circuit, a winding transformer and a voltage doubler rectifier circuit, wherein the resonant circuit is connected to a primary winding of the winding transformer, and the voltage doubler rectifier circuit is connected to a secondary winding of the winding transformer; the method includes:

[0006] Obtaining an output voltage given value and an output voltage value corresponding to an output end of the voltage doubler rectifier circuit, and determining a voltage difference between the output voltage given value and the output voltage value;

[0007] Determine the output current given value according to the voltage difference, obtain the induced current value in the voltage doubler rectifier circuit, and determine the current difference between the output current given value and the induced current value;

[0008] The target switching frequency of multiple switch tubes in the micro inverter is determined according to the current difference, and the micro inverter is controlled by the target switching frequency to transmit an output voltage that meets a given output voltage value to the load.

[0009] In some embodiments, the step of determining a given output current value according to the voltage difference includes:

[0010] The voltage difference is processed by a controller through proportional-integral control or proportional-resonance control to determine the output current given value corresponding to the micro-inverter; wherein, when the output current of the micro-inverter satisfies the output current given value, the output voltage of the micro-inverter satisfies the output voltage given value.

[0011] In some embodiments, the step of determining the target switching frequency of a plurality of switch tubes in the micro inverter according to the current difference includes:

[0012] The controller performs proportional-integral control or proportional-resonance control on the current difference to determine a control signal;

[0013] The control signal is subjected to voltage-frequency conversion processing via a voltage-frequency converter to generate a drive signal; wherein the drive signal is used to drive the conduction and shutdown 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.

[0014] In some of the embodiments, the method further comprises an output gain control step, comprising:

[0015] Determine whether the target switching frequency is less than or equal to a preset switching frequency threshold, and if so, determine the switching frequency adjustment strategy as the target adjustment strategy; if not, determine the phase shift angle adjustment strategy as the target adjustment strategy; wherein the switching frequency adjustment strategy is to adjust the switching frequency of multiple switching tubes in the micro-inverter, and the phase shift angle adjustment strategy is to adjust the phase shift angle between multiple switching tubes in the micro-inverter;

[0016] According to the target regulation strategy, multiple switch tubes are regulated to control the output gain of the micro inverter.

[0017] In some of these embodiments, the method further comprises:

[0018] Detect the maximum power value of the photovoltaic module corresponding to the micro inverter and receive the current input by the photovoltaic module.

[0019] In some of the embodiments, the working state of the multiple switch tubes is a soft switching working state.

[0020] In order to solve the above problems, one aspect of an embodiment of the present invention provides a micro inverter, including: a processor, and a memory for storing a program, characterized in that the program includes instructions, and when the instructions are executed by the processor, the processor executes a control method according to any of the above-mentioned off-grid micro inverters.

[0021] In order to solve the above problems, one aspect of an embodiment of the present invention provides a non-transitory machine-readable medium storing computer instructions, wherein the computer instructions are used to enable a computer to execute any of the above-mentioned control methods for off-grid micro-inverters.

[0022] Beneficial effects of the embodiments of the present invention: A micro-inverter that transmits sinusoidal AC power to a load based on a circuit topology of a primary power conversion determines the voltage difference between the output voltage given value and the output voltage value by obtaining the output voltage given value and the output voltage value corresponding to the output end of the voltage doubler rectifier circuit; determines the output current given value according to the voltage difference, obtains the induced current value in the voltage doubler rectifier circuit, and determines the current difference between the output current given value and the induced current value; determines the target switching frequency of multiple switch tubes in the micro-inverter according to the current difference, and controls the micro-inverter to transmit an output voltage that meets the output voltage given value to the load through the target switching frequency. The technical means overcomes the problem that there is no control scheme for realizing the off-grid function for a micro-inverter with a primary power conversion topology in the related art, and the micro-inverter connected to the grid has poor economy and narrow application scenarios; realizes the off-grid function control of a micro-inverter based on a primary power conversion topology, improves the economy of load power consumption, improves the efficiency and power of the micro-inverter, and expands the application scenarios of the micro-inverter.

[0023] The details of one or more embodiments of the invention are set forth in the following drawings and description so that other features, objects, and advantages of the invention are more readily apparent. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order 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 prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other embodiments can be obtained based on these drawings without creative work.

[0025] Figure 1 It is a flowchart of a control method for an off-grid micro-inverter according to an embodiment of the present invention.

[0026] Figure 2 It is a schematic diagram of the electrical topology of a micro inverter of a primary power conversion topology according to an embodiment of the present invention.

[0027] Figure 3 Schematic diagram of the structure of the electronic device of this embodiment. DETAILED DESCRIPTION

[0028] Embodiments of the present embodiment will be described in more detail below with reference to the accompanying drawings. Although certain embodiments of the present embodiment are shown in the accompanying drawings, it should be understood that the present embodiment can be implemented in various forms and should not be construed as being limited to the embodiments set forth herein, which are instead provided for a more thorough and complete understanding of the present embodiment. It should be understood that the drawings and embodiments of the present embodiment are only for exemplary purposes and are not intended to limit the scope of protection of the present embodiment.

[0029] The current micro-inverter is connected to the photovoltaic module and the AC power grid respectively. Its circuit topology is mainly based on the flyback circuit topology. The secondary side of the transformer converts the output current into AC through the folding circuit, so as to realize the conversion of DC in the photovoltaic module into AC and connect it to the power grid. This circuit topology is limited by the volume of the transformer core and the switching frequency, and the power is difficult to increase, and the efficiency of the inverter is low. As the power of photovoltaic modules increases, the power and efficiency of micro-inverters are required to increase. Most micro-inverters in related technologies use two-stage power conversion technology, but the total efficiency of the micro-inverter during two-stage power conversion is equal to the product of the two conversion efficiencies, which makes it difficult for the efficiency of the micro-inverter to exceed 96%. That is, although the power and efficiency of the micro-inverter are improved by adopting a two-stage power conversion topology in the related technology, it is still difficult to meet the needs of high-power photovoltaic modules, and there are problems such as complex control flow and high cost of the micro-inverter. At the same time, there is currently no control solution for realizing the off-grid function of micro-inverters with a one-stage power conversion topology, and the grid-connected micro-inverters have the problems of poor economy and narrow application scenarios.

[0030] In order to solve the above problems, an embodiment of the present invention provides a control method for an off-grid micro-inverter. The control method for an off-grid micro-inverter is applied to a micro-inverter based on a primary power conversion topology, such as Figure 1 As shown, the control method of the micro inverter includes:

[0031] Step S101, obtaining an output voltage given value and an output voltage value corresponding to an output end of a voltage doubler rectifier circuit, and determining a voltage difference between the output voltage given value and the output voltage value.

[0032] Step S102, determining an output current given value according to the voltage difference, acquiring an induced current value in the voltage doubler rectifier circuit, and determining a current difference between the output current given value and the induced current value.

[0033] Step S103, determining the target switching frequency of multiple switch tubes in the micro inverter according to the current difference, and controlling the micro inverter to transmit an output voltage that meets a given output voltage value to the load through the target switching frequency.

[0034] Among them, the micro inverter provided by the embodiment of the present invention is used to transmit sinusoidal AC power to the load based on the circuit topology of primary power conversion. The circuit topology 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.

[0035] Through the above settings, the embodiment of the present invention calculates the voltage difference between the output voltage value and the output voltage given value through the controller, and then determines the output current given value; then the target switching frequency of multiple switching tubes in the micro-inverter is determined by the current difference between the output current given value and the induced current value, thereby controlling the micro-inverter to deliver an output voltage that meets the output voltage given value to the load, thereby realizing the off-grid function of the micro-inverter based on the first-level power conversion topology, improving the economy of load electricity consumption, and expanding the applicable scenarios of the micro-inverter.

[0036] Among them, the output voltage value provided in the embodiment of the present invention refers to the actual voltage value output by the output terminal of the micro inverter; the output voltage set value refers to the voltage value required when the load is operating normally, that is, the rated voltage value. Since the rated voltage value corresponding to the load operation has a certain floating interval, the above-mentioned output voltage set value can be a range value, such as 220V, 230V, 240V. The output current set value provided in the present invention refers to the current value when the load is operating normally, that is, the rated current value. Since the rated current value corresponding to the normal operation of the load also has a certain floating interval, the above-mentioned output current set value can be a range value.

[0037] In some of the embodiments, the step of determining the output current set value based on the voltage difference includes: performing proportional-integral control or proportional resonance control on the voltage difference through a controller to determine the output current set value corresponding to the micro-inverter; wherein, when the output current of the micro-inverter satisfies the output current set value, the output voltage of the micro-inverter satisfies the output voltage set value.

[0038] Among them, the controller provided by the embodiment of the present invention includes a PI controller (proportional integral (PI) controller, a controller for proportional regulation and integral regulation) and a PR controller (proportional resonant (PR) controller, a proportional resonant controller). Specifically, the PI controller is a linear controller, which forms a control deviation based on a given value and an actual output value, and forms a control quantity by linearly combining the proportion (P) and integral (I) of the deviation to control the controlled object. The PR controller is mainly used in power electronic control, and can track a specific frequency signal without static error, and is used to increase the gain amplitude of the loop at a specific frequency point.

[0039] According to a specific implementation of an embodiment of the present invention, the output voltage set value corresponding to the drive controller is obtained as the target voltage set signal, and then the actual output voltage value corresponding to the output end of the voltage doubler rectifier circuit is obtained, and the actual output voltage value is used as the voltage sampling feedback signal, and the voltage sampling feedback signal is compared with the target voltage set signal to determine the voltage signal difference, and the voltage signal difference is PI controlled and adjusted by a PI controller, or PR controlled and adjusted by a PR controller to form a voltage loop control signal, and the voltage loop control signal indicates the output current set value, that is, when the output current in the circuit topology of the micro inverter needs to be adjusted to the output current set value, the corresponding output voltage can be adjusted to the output voltage set value. Through the above setting, the voltage difference is used as the data input, and the voltage loop control signal formed determines the output current set value, so that the current difference is determined by the output current set value and the induced current in the subsequent process, and then the current loop control signal is formed, forming a voltage-current dual-loop control signal in a nested relationship, thereby controlling the micro inverter to deliver an output voltage to the load while meeting the output voltage set value.

[0040] In some of the embodiments, the step of determining the target switching frequency of multiple switching tubes in the micro-inverter based on the current difference includes: performing proportional-integral control or proportional-resonance control on the current difference by a controller to determine a control signal; performing voltage-frequency conversion on the control signal by 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.

[0041] According to a specific implementation of an embodiment of the present invention, after the output current given value is determined according to the voltage loop control signal determined by the voltage difference, the output current given value is used as the target current given signal of the drive controller, and then the induced current value in the secondary winding of the voltage doubler rectifier circuit is obtained, and the induced current value is used as the current sampling feedback signal for output current sampling, and the current sampling feedback signal is compared with the target current given signal of the drive controller to determine the current signal difference, and the current signal difference is subjected to PI control adjustment by a PI controller or PR control adjustment by a PR controller to form a current loop control signal, and then the current loop control signal is processed by a voltage-frequency converter to output a drive signal with adjustable frequency (the adjustment frequency of the drive signal is consistent with the target switching frequency corresponding to the switch tube), and the drive signal is used to drive multiple switch tubes in the micro inverter to be turned on and off according to the target switching frequency, thereby realizing the delivery of an output voltage that meets the output voltage given value to the load.

[0042] Through the above settings, the output current set value is determined according to the voltage difference, and the current difference is determined according to the output current set value and the induced current value. The controller is adjusted according to the current difference, and the target switching frequency corresponding to the switching tube is determined by voltage-frequency conversion processing. The micro inverter is controlled to transmit an output voltage that meets the output voltage set value and an output current that meets the output current set value to the load, which further improves the control effect and control rate of the off-grid control of the micro inverter and improves the safety and stability of load power consumption.

[0043] The target switching frequency provided in the embodiment of the present invention corresponds to the frequency of turning on and off multiple switch tubes in the micro inverter of the primary power conversion topology, and the specific value of the frequency changes dynamically. Specifically, the target switching frequency changes dynamically in response to the voltage difference and the current difference.

[0044] In some embodiments, the method further includes an output gain control step, including: determining whether the target switching frequency is less than or equal to a preset switching frequency threshold, and if so, determining the switching frequency adjustment strategy as the target adjustment strategy; if not, determining the phase shift angle adjustment strategy as the target adjustment strategy; wherein the switching frequency adjustment strategy is to adjust the switching frequency of multiple switching tubes in the micro-inverter, and the phase shift angle adjustment strategy is to adjust the phase shift angle between multiple switching tubes in the micro-inverter; according to the target adjustment strategy, multiple switching tubes are adjusted to control the output gain of the micro-inverter.

[0045] The target switching frequency mentioned in the above judgment step is the switching frequency corresponding to the multiple switching tubes in the micro inverter determined according to the current difference. The preset switching frequency threshold refers to the upper limit of the switching frequency of the switching tube obtained by combining the switching tube model and operating conditions while ensuring the stability of the switching tube performance.

[0046] The above steps specifically disclose the steps of determining the target adjustment strategy based on the switching frequency and controlling the output gain of the micro-inverter. When the target switching frequency is less than or equal to the preset threshold value of the switching frequency, the switching frequency of the switch 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 switch tubes in the micro-inverter. When the target switching frequency is large, that is, the target switching frequency is greater than the preset threshold value of the switching frequency, since the actual switching frequency of the switch tube has been adjusted to the maximum (adjusted to the preset threshold value of the switching frequency), the output gain can no longer be reduced by increasing the switching frequency. At this time, the target adjustment strategy can be determined to be the phase shift angle adjustment strategy, that is, the output gain is controlled by adjusting the phase shift angles corresponding to multiple switch tubes in the micro-inverter. The embodiment of the present invention thus realizes the output gain control of a wide voltage range for a micro-inverter with a primary power conversion topology, and expands the applicable scenarios of the micro-inverter with a primary power conversion topology.

[0047] According to a specific implementation of an embodiment of the present invention, when the above-mentioned target adjustment strategy is a switching frequency adjustment strategy (i.e., output gain control is achieved by adjusting the switching frequencies of multiple switching tubes in the micro-inverter), the load current value is obtained, and the load current value is used as the output current given value. The output current given value is processed by taking the absolute value as the target given signal of the drive controller. At the same time, the induced current value in the secondary winding of the voltage doubler rectifier circuit is obtained, and the absolute value and filtering processing are also performed as the feedback signal of the output current sampling. The feedback signal of the output current sampling is compared with the target given signal of the drive controller to determine the signal difference, and the signal difference is PI-regulated by a PI regulator 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 to adjust the switching frequencies of multiple switching tubes in the micro-inverter, thereby controlling the output gain of the micro-inverter and improving the power and efficiency of the micro-inverter. Among them, after the above-mentioned difference is adjusted by the PI regulator, the switching frequency corresponding to the switching tube is finally output. Among them, when the target given signal corresponding to the output current given value is greater than the feedback signal corresponding to the induced current value, that is, the signal difference is positive, the output switching frequency decreases; when the target non-set signal corresponding to the output current given value is less than the feedback signal corresponding to the induced current value, that is, when the signal difference is negative, the output switching frequency increases.

[0048] In some of the embodiments, if the sinusoidal wave period of the output current is the positive half period of the sinusoidal 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, 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; 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 switch tube and the fourth switch tube in the resonant circuit are turned off, the resonant cavity current in the resonant circuit feeds the first capacitor on the DC side bus, controls the third switch tube and the second switch tube to be turned on to form a second conduction current loop, and forms an induced current in the voltage doubler rectifier circuit, controls the seventh switch tube and the eighth switch tube 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 switch tube, the first capacitor, the parasitic diode of the second switch 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 switch tube, and the parasitic diode of the seventh switch tube in sequence. When the resonant cavity current is zero, the photovoltaic component inputs current to 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 switch tube and the second switch tube in the resonant circuit are turned off, the resonant cavity current in the resonant circuit feeds the first capacitor on the DC side bus, controls the first switch tube and the fourth switch tube to be turned on to form a fourth conduction current loop, generates an induced current in the voltage doubler rectifier circuit, 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 fourth induced current loop; wherein, the current in the fourth conduction current loop passes through the parasitic diode of the fourth switch tube, the LLC circuit, the parasitic diode of the first switch 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 switch tube, the parasitic diode of the fifth switch tube, and the second capacitor in sequence.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 switch tube and the fourth switch tube in the resonant circuit are turned on, the current input by the photovoltaic component forms a fifth conduction current loop in the resonant circuit, and generates an induced current in the voltage doubler rectifier circuit, and controls the seventh switch tube and the eighth switch tube 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 component in the fifth 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 fifth induced current loop passes through the MOS tube of the seventh switch tube, the parasitic diode of the eighth switch tube, and the third capacitor in sequence. When the first switch tube and the fourth switch tube in the resonant circuit are turned off, the resonant cavity current in the resonant circuit feeds the first capacitor on the DC side bus, controls the third switch tube and the second switch tube to be turned on to form a sixth conduction current loop, and forms an induced current in the voltage doubler rectifier circuit, 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 sixth induced current loop; wherein, the resonant cavity current in the sixth conduction current loop passes through the parasitic diode of the second switch tube, the LLC circuit, the parasitic diode of the third switch tube, and the first capacitor in sequence; and the induced current in the sixth 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 resonant cavity current is zero, the current input by the photovoltaic component forms a seventh conduction current loop in the resonant circuit, and generates an induced current in the voltage doubler rectifier circuit, and the induced current flows through the second capacitor of the capacitor bridge arm to form a seventh induced current loop; wherein, the current input by the photovoltaic component in the seventh 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 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 switch tube and the second switch tube in the resonant circuit are turned off, the resonant cavity current in the resonant circuit feeds the first capacitor on the DC side bus, controls the first switch tube and the fourth switch tube to be turned on to form an eighth conduction current loop, generates an induced current in the voltage doubler rectifier circuit, controls the seventh switch tube and the eighth switch tube 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 switch tube, the LLC circuit, the parasitic diode of the first switch 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 switch tube, the parasitic diode of the eighth switch tube, and the third capacitor in sequence.

[0049] According to a specific implementation of an embodiment of the present invention, when the above-mentioned target adjustment strategy is a phase shift angle adjustment strategy (i.e., output gain control is achieved by adjusting the phase shift angles of multiple switch tubes in the micro-inverter), the output current corresponding to the output end of the voltage doubler rectifier circuit is obtained, and the output current is used as the output current given value; and the sine wave period corresponding to the output current at the output end of the voltage doubler rectifier circuit and the switching frequency of multiple switch tubes in the micro-inverter within the sine wave period are determined; the mapping relationship between the output voltage gain and the phase shift angle is obtained, and according to the mapping relationship, the sine wave period and the switching frequency, the phase shift angle between the switch tube of the first bridge arm and the switch tube of the second bridge arm in the resonant circuit is adjusted to adjust the duty cycle of the multiple switch tubes in the voltage doubler rectifier circuit, and to achieve the control of the output gain of the micro-inverter. Among them, the phase shift angle adjustment strategy provided by the embodiment of the present invention is: output gain control is performed by adjusting the phase shift angles corresponding to the multiple switch tubes in the micro-inverter.

[0050] When the target switching frequency is large, that is, the target switching frequency of multiple switch tubes determined based on the current difference is greater than the preset threshold of the switching frequency, since the target switching frequency has been adjusted to the maximum, the output gain can no longer be reduced by increasing the switching frequency. At this time, the target adjustment strategy can be determined to adjust the phase shift angle corresponding to multiple switch tubes in the micro-inverter to further reduce the output gain. Based on this, the output gain control of the micro-inverter with a one-stage power conversion topology over a wide voltage range is realized, expanding the applicable scenarios of the micro-inverter with a one-stage power conversion topology.

[0051] In some of the embodiments, the method further includes: detecting a maximum power value of a photovoltaic component corresponding to the micro-inverter, and receiving a current input by the photovoltaic component.

[0052] According to an embodiment of the present invention, an MPPT (Maximum Power Point Tracking) controller may be used to detect the maximum power value of a photovoltaic module, and then receive the current input by the photovoltaic module when the photovoltaic module meets the maximum power value.

[0053] In some of the embodiments, the smaller one between the output current set value determined based on MPPT and the current set value generated based on the actual output voltage value corresponding to the voltage doubler rectifier current output terminal can be taken as the actual load current loop set value, which can ensure that in off-grid mode, the device will not be unable to carry the load due to overpower operation and the photovoltaic components will not be unable to carry the load.

[0054] In some of the embodiments, the working state of the above-mentioned multiple switch tubes is a soft switching working state.

[0055] In the micro-inverter with a one-stage power conversion topology provided in the embodiment of the present invention, multiple switch tubes can operate in a soft switching state, thereby reducing switching losses and thereby improving the power generation of the micro-inverter.

[0056] In some of the embodiments, the turns ratio between the primary winding and the secondary winding in the winding transformer is determined by actual operating conditions such as the power and quantity of the photovoltaic modules and the grid voltage.

[0057] The micro inverter provided by the embodiment of the present invention is used to transmit sinusoidal AC power to the load based on the circuit topology of primary power conversion. Figure 2 A schematic diagram of a circuit topology of a micro inverter in an embodiment of the present invention is shown. Figure 2 As shown, the circuit topology of the above-mentioned 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.

[0058] 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 doubler rectifier circuit includes a switch bridge arm and a capacitor bridge arm connected in parallel, and the voltage doubler rectifier circuit is connected to the secondary winding of the winding transformer, and is used to generate 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 realize a multiple voltage boost; wherein, the output end of the voltage doubler rectifier circuit is used to deliver a sinusoidal output current to the load.

[0059] In some of the embodiments, Figure 2 As shown, when the resonant circuit is a full-bridge resonant circuit, it includes: 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 Q1 and a second switch tube Q2 connected in series, and the second bridge arm includes a third switch tube Q3 and a fourth switch tube Q4 connected in series; the LLC circuit includes a leakage inductance Lr, an excitation inductance Lm and a resonant capacitor Cr connected in series, wherein the excitation inductance Lm is also 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.

[0060] In some of the embodiments, Figure 2As shown, the switch bridge arm in the voltage doubler rectifier circuit includes an upper switch bridge arm and a lower switch bridge arm, wherein the upper switch bridge arm includes a fifth switch tube Q5 and a sixth switch tube Q6 connected in series and arranged in a mirror image, and the lower switch bridge arm includes a seventh switch tube Q7 and an eighth switch tube Q8 connected in series and arranged in a mirror image. The capacitor bridge arm in the 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 voltage doubler rectifier circuit. The filter inductor Lg can be provided on one side of the output end of the voltage doubler rectifier circuit, or on both sides of the output end of the voltage doubler rectifier circuit. 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.

[0061] The micro-inverter applied based on the embodiment of the present invention realizes that a circuit topology based on primary power conversion can transmit sinusoidal AC power to the AC power grid, thereby effectively improving the efficiency and power of the micro-inverter.

[0062] The control method of the above-mentioned off-grid micro-inverter provided in the embodiment of the present invention is a micro-inverter that transmits sinusoidal AC power to the load based on the circuit topology of the first-level power conversion, and determines the voltage difference between the output voltage given value and the output voltage value by obtaining the output voltage given value and the output voltage value corresponding to the output end of the voltage doubler rectifier circuit; determines the output current given value according to the voltage difference, and obtains the induced current value in the voltage doubler rectifier circuit to determine the current difference between the output current given value and the induced current value; determines the target switching frequency of multiple switch tubes in the micro-inverter according to the current difference, and controls the micro-inverter to transmit the output voltage that meets the output voltage given value to the load through the target switching frequency. The technical means overcomes the problem that there is no control scheme for realizing the off-grid function for the micro-inverter with the first-level power conversion topology in the related art, and the micro-inverter connected to the grid has poor economy and narrow application scenarios; realizes the off-grid function control of the micro-inverter based on the first-level power conversion topology, improves the economy of load power consumption, improves the efficiency and power of the micro-inverter, and expands the application scenarios of the micro-inverter.

[0063] The embodiment of the present invention further provides a micro inverter, comprising: at least one processor; and a memory connected to the at least one processor in communication. The memory stores a computer program executable by the at least one processor, and the computer program is used to enable an electronic device to perform the method of the embodiment of the present invention when executed by the at least one processor.

[0064] 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 execute the method of the embodiment of the present invention.

[0065] 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 execute the method of the embodiment of the present invention.

[0066] refer to Figure 3 , a block diagram of an electronic device that can be used as a 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. Electronic devices are intended to represent various forms of digital electronic computer devices, such as laptop computers, desktop computers, workbenches, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. Electronic devices 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.

[0067] like Figure 3 As shown, the electronic device includes a computing unit 301, which can perform various appropriate actions and processes according to a computer program stored in a read-only memory (ROM) 302 or a computer program loaded from a storage unit 308 into a random access memory (RAM) 303. In the RAM 303, various programs and data required for the operation of the electronic device can also be stored. The computing unit 301, the ROM 302, and the RAM 303 are connected to each other via a bus 304. An input / output (I / O) interface 305 is also connected to the bus 304.

[0068] Multiple components in the electronic device are connected to the I / O interface 305, including: an input unit 306, an output unit 307, a storage unit 308, and a communication unit 309. The input unit 306 can be any type of device that can input information to the electronic device, and the input unit 306 can receive input digital or character information, and generate key signal input related to user settings and / or function control of the electronic device. The output unit 307 can be any type of device that can present information, and can include but is not limited to a display, a speaker, a video / audio output terminal, a vibrator, and / or a printer. The storage unit 308 can include but is not limited to a disk, an optical disk. The communication unit 309 allows the electronic device to exchange information / data with other devices through a computer network such as the Internet and / or various telecommunication networks, and can 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.

[0069] The computing unit 301 may be a variety of general and / or special processing components with processing and computing capabilities. Some examples of the computing unit 301 include, but are not limited to, a CPU, a graphics processing unit (GPU), various dedicated artificial intelligence (AI) computing chips, various computing units running machine learning model algorithms, digital signal processors (DSPs), and any appropriate processors, controllers, microcontrollers, etc. The computing unit 301 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 308. In some embodiments, part or all of the computer program may be loaded and / or installed on an electronic device via ROM 302 and / or a communication unit 309. In some embodiments, the computing unit 301 may be configured to perform the above-described method in any other appropriate manner (e.g., by means of firmware).

[0070] 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 flow chart and / or block diagram are implemented. The computer programs may be executed entirely on the machine, partially on the machine, partially on the machine as a stand-alone software package and partially on a remote machine, or entirely on a remote machine or server.

[0071] In the context of an embodiment of the present invention, a machine-readable medium may be a tangible medium that may contain or store a program for use by or in conjunction with an instruction execution system, device, or equipment. A machine-readable medium may be a machine-readable signal medium or a machine-readable storage medium. A machine-readable signal medium may 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 may include an electrical connection based on one or more lines, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0072] It should be noted that the term "including" and its variations used in the embodiments of the present invention are open inclusions, that is, "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"; the term "some embodiments" means "at least some embodiments". The modifications of "one" and "multiple" mentioned in the embodiments of the present invention are illustrative rather than restrictive. Those skilled in the art should understand that unless the context clearly indicates otherwise, it should be understood as "one or more".

[0073] The various steps described in the method implementation methods provided in the embodiments of the present invention may be performed in different orders and / or in parallel. In addition, the method implementation methods may include additional steps and / or omit the steps shown. The scope of protection of the present invention is not limited in this respect.

[0074] 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 refer to each other. In particular, for the device, equipment, and system embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and the relevant parts refer to the partial description of the method embodiment.

[0075] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of patent protection. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the attached claims.

Claims

1. A control method for an off-grid micro-inverter, characterized in that: The micro-inverter is used to deliver sinusoidal AC power to a load based on a circuit topology of primary power conversion. The circuit topology of the micro-inverter includes: a resonant circuit, a winding transformer and a voltage doubler rectifier circuit. The resonant circuit is connected to a primary winding of the winding transformer, and the voltage doubler rectifier circuit is connected to a secondary winding of the winding transformer. The method includes: Obtaining an output voltage given value and an output voltage value corresponding to an output end of the voltage doubler rectifier circuit, and determining a voltage difference between the output voltage given value and the output voltage value; Determine an output current given value according to the voltage difference, obtain an induced current value in the voltage doubler rectifier circuit, and determine a current difference between the output current given value and the induced current value; The target switching frequency of multiple switch tubes in the micro inverter is determined according to the current difference, and the micro inverter is controlled by the target switching frequency to transmit an output voltage that meets the given output voltage value to the load.

2. The control method according to claim 1, characterized in that: The step of determining the output current given value according to the voltage difference comprises: The voltage difference is subjected to proportional-integral control processing or proportional-resonance control processing by a controller to determine an output current given value corresponding to the micro-inverter; wherein, when the output current of the micro-inverter satisfies the output current given value, the output voltage of the micro-inverter satisfies the output voltage given value.

3. The control method according to claim 1, characterized in that: The step of determining the target switching frequency of a plurality of switch tubes in the micro inverter according to the current difference comprises: Performing proportional-integral control or proportional-resonance control on the current difference by a controller to determine a control signal; The control signal is subjected to voltage-frequency conversion processing via a voltage-frequency converter to generate a drive signal; wherein the drive signal is used to drive the conduction and shutdown 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.

4. The control method according to claim 1, characterized in that: The method further comprises an output gain control step, comprising: Determine whether the target switching frequency is less than or equal to a preset switching frequency threshold, and if so, determine that the switching frequency adjustment strategy is the target adjustment strategy; if not, determine that the phase shift angle adjustment strategy is the target adjustment strategy; wherein the switching frequency adjustment strategy is to adjust the switching frequencies of multiple switching tubes in the micro-inverter, and the phase shift angle adjustment strategy is to adjust the phase shift angles between multiple switching tubes in the micro-inverter; According to the target adjustment strategy, the multiple switch tubes are adjusted to control the output gain of the micro inverter.

5. The control method according to claim 1, characterized in that: The method further comprises: The maximum power value of the photovoltaic component corresponding to the micro-inverter is detected, and the current input by the photovoltaic component is received.

6. The control method according to claim 1, characterized in that: The working state of the multiple switch tubes is a soft switching working state.

7. 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 6.

8. 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 1-6.

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