Micro inverter of solar cell and control method

Abstract

The invention discloses a micro inverter of a solar cell and a control method. The inverter comprises a photovoltaic input assembly, a regulation and control module, a direct current side rectification module, an alternating current side rectification module, a transformer and a load. The photovoltaic input assembly is used for providing voltage, and the voltage provided by the photovoltaic input assembly changes along with the change of the environment; the regulation and control module is used for acquiring voltage provided by the photovoltaic input assembly and increasing the voltage to a preset voltage threshold value; the direct-current side rectification module is used for converting the voltage of the regulation and control module into alternating-current voltage and transmitting the alternating-current voltage through the transformer; and the alternating current side rectification module is used for converting the alternating current voltage of the transformer into alternating current voltage with lower frequency and outputting the alternating current voltage to a load. According to the technology, through cooperative work of the photovoltaic input assembly and the regulation and control module, the hardware design pressure of a subsequent circuit is reduced, and the complexity of a subsequent circuit regulation and control strategy is reduced.

Description

Technical Field

[0001] The present application relates to the field of solar energy, and in particular to a micro inverter for solar cells and a control method thereof. Background Art

[0002] The voltage output by solar cells is low-voltage DC voltage, which cannot be used directly by ordinary households. Therefore, solar cells must be converted into AC power through an inverter and connected to the grid before they can be used.

[0003] In the prior art, voltage inverters usually have complex structures and complicated control strategies, which increases the complexity and cost of the system.

[0004] Accordingly, the art needs a new micro inverter for solar cells to solve the above problems. Summary of the invention

[0005] In order to overcome the above-mentioned defects, the present invention is proposed to provide a solution or at least partially solve the technical problem that the solar cell control system in the prior art is too complicated and costly.

[0006] In a first aspect, the present invention provides a micro-inverter for solar cells, the inverter comprising: a photovoltaic input component, a control module, a DC side rectifier module, an AC side rectifier module, a transformer and a load; the photovoltaic input component is used to provide a voltage, wherein the voltage provided by the photovoltaic input component varies with changes in the environment; the control module is used to obtain the voltage provided by the photovoltaic input component and increase the voltage to a preset voltage threshold; the DC side rectifier module is used to convert the voltage of the control module into an AC voltage and transmit it through the transformer; the AC side rectifier module is used to convert the AC voltage of the transformer into an AC voltage with a lower frequency and output it to the load

[0007] As an alternative or supplement to the above solution, in a method according to an embodiment of the present invention, the photovoltaic input component includes at least two photovoltaic power supply units, each photovoltaic power supply unit is regulated by a corresponding regulation module, and the regulation modules are connected in parallel.

[0008] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, the control module includes a control capacitor, a control inductor, a first control electronic switch, and a second control electronic switch; wherein the control capacitor is connected in parallel with the first photovoltaic power supply unit, and one end of the control capacitor is connected to the same node as one end of the first photovoltaic power supply unit and the first end of the control inductor. The second end of the control inductor is connected to the same node as the first control electronic switch and the second control electronic switch, and the ends of the first control electronic switch and the second control electronic switch that are not connected to the control inductor serve as the output end of the control module.

[0009] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, a DC side rectifier module includes: a first DC side bridge arm and a second DC side bridge arm, wherein the first DC side bridge arm and the second DC side bridge arm are connected in parallel, and the first DC side bridge arm and the second DC side bridge arm each have two electronic switches arranged opposite to each other, the first end of the first DC side bridge arm and the first end of the second DC side bridge arm are connected to the first end of the primary side of the transformer as the output end of the DC side rectifier module, the second end of the first DC side bridge arm and the second end of the second DC side bridge arm are connected to the second end of the primary side of the transformer as another output end of the DC side rectifier module, and the midpoint of the first DC side bridge arm and the midpoint of the second DC side bridge arm are connected to the control module as the output end of the DC side rectifier module.

[0010] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, the DC side rectifier module includes: a DC side capacitor, a first electronic switch, a second electronic switch, a third electronic switch and a fourth electronic switch, the drain of the first electronic switch and the first end of the output end of the modulation module, the first end of the DC side capacitor, and the drain of the second electronic switch are connected to the same node; the source of the first electronic switch and the drain of the third electronic switch and the first end of the primary side of the transformer are connected to the same node. The source of the third electronic switch and the second end of the output end of the modulation module, the second end of the DC side capacitor, and the source of the fourth electronic switch are connected to the same node; the drain of the fourth electronic switch and the second end of the primary side of the source transformer of the second electronic switch are connected to the same node.

[0011] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, the AC side rectifier module includes: a first bridge arm on the AC side and a second bridge arm on the AC side, the first bridge arm on the AC side and the second bridge arm on the AC side each include two electronic switches arranged opposite to each other, the first bridge arm on the AC side and the second bridge arm on the AC side are respectively provided with parallel capacitors, the first end of the first bridge arm on the AC side and the first end of the second bridge arm on the AC side are connected to the first end of the secondary side of the transformer through inductance as the input end of the AC side rectifier module, wherein the two parallel capacitors are connected, and the connection point between the two parallel capacitors is connected to the second end of the secondary side of the transformer as another input end of the AC side rectifier module, and the connection point between the parallel capacitors and the corresponding bridge arms is used as the output end of the AC side rectifier module.

[0012] As an alternative or supplement to the above scheme, in a method according to an embodiment of the present invention, an AC side rectifier module includes: an AC side inductor, a first capacitor, a second capacitor, a fifth electronic switch, a sixth electronic switch, a seventh electronic switch and an eighth electronic switch; the drain of the fifth electronic switch is connected to the first end of the first capacitor, and the node where the drain of the fifth electronic switch is connected to the first end of the first capacitor serves as one of the output ends of the AC side rectifier module; the source of the fifth electronic switch is connected to the source of the sixth electronic switch; the source of the sixth electronic switch is connected to the source of the seventh electronic switch and the first end of the AC side inductor at the same node; the second end of the AC side inductor is connected to the first end of the secondary side of the transformer; the source of the seventh electronic switch is connected to the source of the eighth electronic switch; the drain of the eighth electronic switch is connected to the second end of the second capacitor; the node where the drain of the eighth electronic switch is connected to the second end of the second capacitor serves as another node of the output end of the AC side rectifier module; the second end of the first capacitor is connected to the first end of the second capacitor and the second end of the secondary side of the transformer.

[0013] In a second aspect, a method for controlling a micro-inverter of a solar cell is provided, wherein the micro-inverter of the solar cell is obtained based on the micro-inverter of the solar cell described in any one of the first aspects, and is characterized in that the AC side rectifier module includes an LLC circuit, wherein the AC side rectifier module uses an LLC open-loop control strategy.

[0014] In the above one or more technical solutions of the present invention, at least one or more of the following beneficial effects are achieved:

[0015] In the technical solution of the present invention, the photovoltaic input component and the control module work together to stabilize and increase the voltage output by the solar cell to reach the preset threshold, thereby reducing the hardware design pressure of the subsequent circuit and reducing the complexity of the subsequent circuit control strategy. At the same time, the reliability and cost-effectiveness of the system are improved, and finally the high efficiency of voltage regulation and system optimization are achieved, and the adaptability and stability of solar cell grid connection are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0017] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0018] Figure 1 is a schematic diagram of the connection relationship of a micro inverter according to an embodiment of the present invention;

[0019] Figure 2 is a schematic diagram of module classification of micro inverters according to an embodiment of the present invention;

[0020] Figure 3 1 is a schematic diagram of a micro-inverter topology with two photovoltaic power supply units according to an embodiment of the present invention. DETAILED DESCRIPTION

[0021] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0022] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0023] like Figure 1 As shown, Figure 1 This is a schematic diagram of the connection relationship of the micro inverter.

[0024] The present technology provides a micro inverter topology, which specifically includes: a photovoltaic input component, a control module, a DC side rectifier module, an AC side rectifier module, a transformer and a load.

[0025] Among them, the photovoltaic input component is the power source, and the output end of the photovoltaic component is connected to the control module. The photovoltaic input component can be a photovoltaic power supply unit, or it can be obtained by connecting multiple photovoltaic power supply units in parallel. The photovoltaic power supply unit is a power generation mechanism composed of solar panels as the smallest unit. The control component is used to adjust the output of the photovoltaic input component. The control component will increase the fluctuating voltage of the photovoltaic input component to a preset value for output. The DC side rectifier module is used to convert the DC power output by the control module into AC power, so that the voltage can be changed through a transformer. The output of the transformer is high-frequency AC power, which can be converted into relatively low-frequency AC power through the AC side rectifier module, and finally the converted low-frequency AC power is provided to the load.

[0026] like Figure 1 As shown, the power provided by the photovoltaic input component will first be controlled by the control module, and then the voltage passing through the control module will pass through the DC side rectifier module, the transformer and the AC side rectifier module in sequence, and finally reach the load to supply power to the load.

[0027] like Figure 2 As shown, Figure 2 This is a schematic diagram of the module classification of micro inverters. Figure 2 The various modules in are described in detail as follows:

[0028] 1) Control module:

[0029] In the prior art, the load can only accept a stable voltage. The photovoltaic input component is affected by different lighting conditions, and its output voltage fluctuates. This fluctuation will increase the burden on subsequent devices (DC side rectifier module, AC side rectifier module, transformer), and puts higher requirements on the stability and regulation strategy of subsequent devices. Specifically, the DC side rectifier module has one control degree of freedom, and the AC side rectifier module includes LLC current, so the AC side rectifier module has two control degrees of freedom. Therefore, when the output voltage of the photovoltaic input component changes over time, the subsequent three control degrees of freedom need to cooperate with each other, which makes the control strategy complicated. At the same time, due to the complexity of the control strategy, the quality requirements for subsequent devices are also improved, increasing the overall cost. In addition, when there are multiple photovoltaic power supply units in the photovoltaic input component, there are multiple photovoltaic power supply units at this time, which will amplify the instability of the output voltage of the above photovoltaic power supply units, and put higher requirements on the subsequent control strategy and the quality of the devices. Therefore, a regulation module is designed.

[0030] The control module is used to stabilize the voltage provided by the photovoltaic input component and provide a stable DC power supply for the subsequent rectification and conversion process. The control module will increase the output voltage of the photovoltaic input component to a preset voltage threshold by controlling its internal duty cycle. The preset voltage threshold is a pre-set voltage threshold.

[0031] The control module may include a power control element and a filter circuit. The power control element may use a field effect transistor (MOSFET) or an insulated gate bipolar transistor (IGBT) or similar electronic switch to achieve precise voltage and current control. The filter circuit usually contains an inductor and a capacitor to smooth the fluctuations of voltage and current to ensure that the output DC power is stable and reliable.

[0032] Depend on Figure 2 It can be seen that the control module includes a control capacitor CPV1, a control inductor LPV1, a first control electronic switch S11, and a second control electronic switch S12.

[0033] The control capacitor CPV1 is connected in parallel with the first photovoltaic power supply unit PV1. One end of the control capacitor CPV1 is connected to one end of the first photovoltaic power supply unit PV1 to form a node, which is also connected to the first end of the control inductor LPV1. The second end of the control inductor LPV1 is also connected to the first control electronic switch S11 and the second control electronic switch S12.

[0034] In some embodiments, the two control electronic switches are composed of three ports, namely, a first port, a second port and a control port. The control port is used to control the opening and closing of the two control electronic switches. One of the two control electronic switches is connected to the second port of the control inductor LPV1, and the other port of the two control electronic switches is used as the output port of the control module.

[0035] In one embodiment, the second end of the first regulating electronic switch S11 and the first end of the second regulating electronic switch S12 are connected to the second end of the regulating inductor LPV1. The first end of the first regulating electronic switch S11 and the second end of the second regulating electronic switch S12 serve as output ends of the regulating module. Further, the first regulating electronic switch S11 and the second regulating electronic switch S12 are both N-type MOSFET tube electronic switches. The electronic switch contains a body diode, the positive electrode of the body diode is connected to the source of the electronic switch, and the negative electrode of the body diode is connected to the drain of the electronic switch. When the electronic switch is turned off, the body diode allows current to flow from the source to the drain.

[0036] In some embodiments, the first regulating electronic switch S11 may also be a unidirectional diode. However, compared to a unidirectional diode, the first regulating electronic switch will reduce losses when using an N-type MOSFET. This is because MOSFET has a lower on-resistance than a unidirectional diode, and a traditional diode will produce a fixed forward voltage drop when it is turned on, usually between 0.7V (silicon diode) and above 1V (power diode), which will result in a large conduction loss. In contrast, the conduction loss of MOSFET mainly depends on its on-resistance. When its on-resistance is low enough, it can effectively reduce the loss when current passes through. In other embodiments, the regulating inductor LPV1 can exchange positions with the second regulating electronic switch S12. That is, at this time, the regulating inductor LPV1 is connected in parallel with the first photovoltaic power supply unit PV1, and at this time, one end of the first photovoltaic power supply unit PV1, one end of the regulating capacitor CPV1 and one end of the second regulating electronic switch S12 form a node.

[0037] exist Figure 2 In the control module shown, the control capacitor CPV1 is used for filtering and voltage stabilization. The control capacitor CPV1 and the control inductor LPV1 together form an LC filter, which can filter the ripples in the input current provided by the first photovoltaic power supply unit PV1 to obtain a relatively smooth DC voltage.

[0038] In addition, the first regulating electronic switch S11 and the second regulating electronic switch S12 are electronic switches in the regulating module, and the voltage value of the first photovoltaic power supply unit PV1 outputted in the regulating module can be changed by regulating the opening and closing strategies of the above two electronic switches. Specifically, the voltage amplitude outputted by the regulating module can be controlled by control means such as PWM (pulse width modulation), and the voltage can be outputted stably.

[0039] The working principle of the control module is as follows: when the output voltage of the first photovoltaic power supply unit PV1 is input to the control module, different electronic switch control strategies will be adopted according to the size of the output voltage of the first photovoltaic power supply unit PV1. If it is detected that the output voltage from the photovoltaic cell input component is lower than the preset voltage threshold at this time, the first control electronic switch S11 is closed and the second control electronic switch S12 is opened, so that the first photovoltaic power supply unit PV1, the control inductor LPV1 and the second control electronic switch S12 form a loop. The current of the first photovoltaic power supply unit PV1 flows through the control inductor LPV1. In this process, the current in the control inductor LPV1 gradually increases. The self-inductance of the control inductor LPV1 will hinder the increase of the circuit, and in this process, the electrical energy will be converted into magnetic energy and stored by the control inductor LPV1. After that, the first control electronic switch S11 is turned on and the second control electronic switch S12 is turned off. At this time, the stored voltage is released together with the voltage of the first photovoltaic power supply unit PV1, thereby raising the output voltage of the control module.

[0040] The control module converts the output voltage of the first photovoltaic power supply unit PV1 into a suitable stable value (preset voltage value) for output by boosting the input voltage. Because the output of the modulated voltage is a preset voltage value, the requirements for subsequent electronic devices during processing will be reduced, and at the same time, the control strategy of the subsequent electronic devices will be easier to set accordingly.

[0041] 2) DC side rectifier module, AC side rectifier module and transformer

[0042] like Figure 2 As shown, the DC side rectifier module obtains the voltage from the control module, and converts the output current of the control module from DC current to AC current, and outputs the AC current. The transformer then receives the AC current output by the DC side rectifier module and transmits it from the primary side of the transformer to the secondary side. The AC current output from the secondary side of the transformer will be received by the AC side rectifier module, and the AC current will be converted back into DC current in the AC side rectifier module, and finally supplied to the load.

[0043] DC side rectifier module:

[0044] like Figure 2As shown, the DC side rectifier module includes: a first DC side bridge arm and a second DC side bridge arm, wherein the first DC side bridge arm and the second DC side bridge arm are connected in parallel, and the first DC side bridge arm and the second DC side bridge arm each have two electronic switches arranged opposite to each other, the first end of the first DC side bridge arm and the first end of the second DC side bridge arm are connected to the first end of the primary side of the transformer as the output end of the DC side rectifier module, the second end of the first DC side bridge arm and the second end of the second DC side bridge arm are connected to the second end of the primary side of the transformer as another output end of the DC side rectifier module, and the midpoint of the first DC side bridge arm and the midpoint of the second DC side bridge arm are connected to the control module as the output end of the DC side rectifier module. The midpoint is the connection point between the two electronic switches.

[0045] By controlling the opening and closing of the electronic switch in the DC side rectifier module, DC power can be converted into AC power.

[0046] exist Figure 2 In the embodiment, the DC side rectifier module includes: a DC side capacitor, a first electronic switch S1, a second electronic switch S2, a third electronic switch S3 and a fourth electronic switch S4. The electronic switches S1-S4 are described by taking N-type MOSFET as an example. The details are as follows:

[0047] The drain of the first electronic switch S1 is connected to the same node with the first end of the output end of the modulation module, the first end of the DC side capacitor, and the drain of the second electronic switch S2. The source of the first electronic switch S1 is connected to the same node with the drain of the third electronic switch S3 and the first end of the primary side of the transformer T. The source of the third electronic switch S1 is connected to the same node with the second end of the output end of the modulation module, the second end of the DC side capacitor, and the source of the fourth electronic switch S4. The drain of the fourth electronic switch S4 is connected to the same node with the source of the second electronic switch S2 and the second end of the primary side of the transformer T. The gates of the above four electronic switches (S1-S4) are all connected to the control end, and the control end is used to control the opening and closing of the electronic switches.

[0048] The DC side capacitor filters the output of the control module, and the above four electronic switches are used to convert the DC power output by the control module into AC power.

[0049] The DC side rectifier module inputs the converted AC power into the primary side of the transformer T. The transformer T scales the voltage on the primary side according to the turns ratio inside the transformer T and outputs it from the secondary side to the AC side rectifier module.

[0050] AC side rectifier module:

[0051] The AC side rectifier module includes: a first bridge arm on the AC side and a second bridge arm on the AC side, the first bridge arm on the AC side and the second bridge arm on the AC side each include two electronic switches arranged opposite to each other, the first bridge arm on the AC side and the second bridge arm on the AC side are respectively provided with parallel capacitors, the first end of the first bridge arm on the AC side and the first end of the second bridge arm on the AC side are connected to the first end of the secondary side of the transformer through an inductor as the input end of the AC side rectifier module, wherein the two parallel capacitors are connected, and the connection point between the two parallel capacitors is connected to the second end of the secondary side of the transformer as another input end of the AC side rectifier module, and the connection point between the parallel capacitors and the corresponding bridge arms is used as the output end of the AC side rectifier module.

[0052] like Figure 2 As shown, the AC side rectifier module includes two capacitors and two half-bridge structures connected in parallel with the capacitors. Specifically, the AC side rectifier module includes: an AC side inductor L1K, a first capacitor C1, a second capacitor C2, a fifth electronic switch S5, a sixth electronic switch S6, a seventh electronic switch S7, and an eighth electronic switch S8. The sixth electronic switch S6 and the seventh electronic switch S7 are connected back to back. The back-to-back connection refers to two electronic switches (such as MOSFET or IGBT) being connected in reverse parallel with the body diodes facing in opposite directions.

[0053] Specifically, the drain of the fifth electronic switch S5 is connected to the first end of the first capacitor C1, and the node where the drain of the fifth electronic switch S5 is connected to the first end of the first capacitor C1 serves as one of the output ends of the AC side rectifier module. The source of the fifth electronic switch S5 is connected to the source of the sixth electronic switch S6. The source of the sixth electronic switch D6 is connected to the same node as the source of the seventh electronic switch S7 and the first end of the AC side inductor L1K. The second end of the AC side inductor L1K is connected to the first end of the secondary side of the transformer T. The source of the seventh electronic switch S7 is connected to the source of the eighth electronic switch S8. The drain of the eighth electronic switch S8 is connected to the second end of the second capacitor C2, and the node where the drain of the eighth electronic switch S8 is connected to the second end of the second capacitor C2 serves as another node of the output end of the AC side rectifier module. The second end of the first capacitor C1 is connected to the first end of the second capacitor C2 and the second end of the secondary side of the transformer T.

[0054] The AC side inductor L1K, the excitation inductor in the transformer T and the resonant capacitor (the first capacitor C1 and the second capacitor C2) together constitute an LLC circuit. The LLC circuit uses the resonant frequency to adjust the voltage and current to achieve the effect of maximizing efficiency and regulating power.

[0055] In order to better understand the LLC circuit in the present invention, the control strategy used by the LLC circuit without a control module is briefly described. In the absence of a control module, the LLC circuit used to control the input current of the photovoltaic input component is a closed-loop control. The closed-loop control includes a feedback circuit ( Figure 2 The feedback circuit can adjust the input frequency and duty cycle of the subsequent devices (electronic switches S5-S8) to maintain the stability of the subsequent output voltage. In addition to the feedback circuit, a relatively complex controller is usually required in closed-loop control, which increases the cost and complexity of the control circuit.

[0056] In this embodiment, the voltage of the unstable photovoltaic input component is regulated to a preset voltage value by using a control module, thereby providing a stable input voltage (for the AC side rectifier module). The stable input voltage allows the LLC circuit to use an open-loop control method. Open-loop control does not require a feedback loop and a complex controller, reducing the cost and complexity of the control circuit.

[0057] Furthermore, when there are multiple photovoltaic power supply units, each photovoltaic power supply unit is regulated by a corresponding regulation module. Figure 3 As shown, Figure 3 This is a schematic diagram of a micro-inverter topology with two photovoltaic power supply units. Figure 3 In addition to the original first photovoltaic power supply unit PV1, there is also a new photovoltaic power supply unit - PV2. Figure 3 It can be seen that the second photovoltaic power supply unit PV2 has the same control module as the first photovoltaic power supply unit PV1 for increasing the voltage of the second photovoltaic power supply unit PV2. The structure of the control module corresponding to the second photovoltaic power supply unit PV2 is not repeated here.

[0058] The two control modules corresponding to the first photovoltaic power supply unit PV1 and the second photovoltaic power supply unit PV2 are connected in parallel. In other words, the control module corresponding to the first photovoltaic power supply unit PV1 and the control module corresponding to the second photovoltaic power supply unit PV2 share the same output. Figure 3 In other words, the drain of the third regulating electronic switch S21 is connected to the same node as the drain of the first regulating electronic switch S11, and the source of the fourth regulating electronic switch S22 is connected to the same node as the source of the second regulating electronic switch S12. The above two nodes serve as the output ends of the regulating module.

[0059] By providing a control module for each photovoltaic power supply unit, each photovoltaic power supply unit can be independently controlled by the control module, which helps to maximize the efficiency of each photovoltaic power supply unit.

[0060] It should be pointed out that although the various steps in the above embodiments are described in a specific order, those skilled in the art can understand that in order to achieve the effects of the present invention, different steps do not have to be performed in such an order. They can be performed simultaneously (in parallel) or in other orders. These changes are within the scope of protection of the present invention.

[0061] Further, it should be understood that since the setting of each module is only for illustrating the functional units of the device of the present invention, the physical devices corresponding to these modules may be the processor itself, or a part of the software in the processor, a part of the hardware, or a part of the combination of software and hardware. Therefore, the number of each module in the figure is only schematic.

[0062] Those skilled in the art will appreciate that the modules in the device can be adaptively split or merged. Such splitting or merging of specific modules will not cause the technical solution to deviate from the principle of the present invention, and therefore, the technical solutions after splitting or merging will fall within the protection scope of the present invention.

[0063] It should be noted that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of this application, and these improvements and modifications should also be regarded as the scope of protection of this application.

Claims

1. A micro inverter for solar cells, characterized in that: include: Photovoltaic input components, control modules, DC side rectifier modules, AC side rectifier modules, transformers and loads; The photovoltaic input component is used to provide voltage, wherein the voltage provided by the photovoltaic input component changes with changes in the environment; The control module is used to obtain the voltage provided by the photovoltaic input component and increase the voltage to a preset voltage threshold; The DC side rectifier module is used to convert the voltage of the control module into an AC voltage and transmit it through the transformer; The AC side rectifier module is used to convert the AC voltage of the transformer into an AC voltage with a lower frequency for output to a load.

2. The micro inverter for solar cells according to claim 1, characterized in that: The photovoltaic input component includes at least two photovoltaic power supply units, each photovoltaic power supply unit is regulated by a corresponding regulation module, and the regulation modules are connected in parallel.

3. The micro inverter for solar cells according to claim 2, characterized in that: The control module includes a control capacitor, a control inductor, a first control electronic switch, and a second control electronic switch; The control capacitor is connected in parallel with the first photovoltaic power supply unit, one end of the control capacitor is connected to the same node as one end of the first photovoltaic power supply unit and the first end of the control inductor, the second end of the control inductor is connected to the same node as the first control electronic switch and the second control electronic switch, and the ends of the first control electronic switch and the second control electronic switch that are not connected to the control inductor serve as the output end of the control module.

4. The micro inverter for solar cells according to claim 1, characterized in that: The DC side rectifier module includes: a first DC side bridge arm and a second DC side bridge arm, wherein the first DC side bridge arm and the second DC side bridge arm are connected in parallel, and the first DC side bridge arm and the second DC side bridge arm each have two electronic switches arranged opposite to each other, the first end of the first DC side bridge arm and the first end of the second DC side bridge arm are connected to the first end of the primary side of the transformer as the output end of the DC side rectifier module, the second end of the first DC side bridge arm and the second end of the second DC side bridge arm are connected to the second end of the primary side of the transformer as another output end of the DC side rectifier module, and the midpoint of the first DC side bridge arm and the midpoint of the second DC side bridge arm are connected to the control module as the output end of the DC side rectifier module.

5. The micro inverter for solar cells according to claim 4, characterized in that: The DC side rectifier module includes: a DC side capacitor, a first electronic switch, a second electronic switch, a third electronic switch and a fourth electronic switch. The drain of the first electronic switch, the first end of the output end of the regulation module, the first end of the DC link capacitor, and the drain of the second electronic switch are connected to the same node; the source of the first electronic switch, the drain of the third electronic switch, and the first end of the primary side of the transformer are connected to the same node; the source of the third electronic switch, the second end of the output end of the regulation module, the second end of the DC link capacitor, and the source of the fourth electronic switch are connected to the same node; the drain of the fourth electronic switch, the source of the second electronic switch, and the second end of the primary side of the transformer are connected to the same node.

6. The micro inverter for solar cells according to any one of claims 1 to 5, characterized in that: The AC side rectifier module includes: a first bridge arm on the AC side and a second bridge arm on the AC side, the first bridge arm on the AC side and the second bridge arm on the AC side each include two electronic switches arranged opposite to each other, the first bridge arm on the AC side and the second bridge arm on the AC side are respectively provided with parallel capacitors, the first end of the first bridge arm on the AC side and the first end of the second bridge arm on the AC side are connected to the first end of the secondary side of the transformer through an inductor as the input end of the AC side rectifier module, wherein the two parallel capacitors are connected, and the connection point between the two parallel capacitors is connected to the second end of the secondary side of the transformer as another input end of the AC side rectifier module, and the connection point between the parallel capacitors and the corresponding bridge arms is used as the output end of the AC side rectifier module.

7. The micro inverter for solar cells according to claim 6, characterized in that: The AC side rectifier module includes: an AC side inductor, a first capacitor, a second capacitor, a fifth electronic switch, a sixth electronic switch, a seventh electronic switch and an eighth electronic switch; The drain of the fifth electronic switch is connected to the first end of the first capacitor, and the node where the drain of the fifth electronic switch is connected to the first end of the first capacitor serves as one of the output ends of the AC side rectifier module; the source of the fifth electronic switch is connected to the source of the sixth electronic switch; the source of the sixth electronic switch is connected to the same node as the source of the seventh electronic switch and the first end of the AC side inductor; the second end of the AC side inductor is connected to the first end of the secondary side of the transformer; the source of the seventh electronic switch is connected to the source of the eighth electronic switch; the drain of the eighth electronic switch is connected to the second end of the second capacitor; the node where the drain of the eighth electronic switch is connected to the second end of the second capacitor serves as another node of the output end of the AC side rectifier module; the second end of the first capacitor is connected to the first end of the second capacitor and the second end of the secondary side of the transformer.

8. A method for controlling a micro-inverter of a solar cell, wherein the micro-inverter of the solar cell is obtained based on the micro-inverter of the solar cell according to any one of claims 1 to 7, characterized in that: The AC side rectifier module includes an LLC circuit, wherein the AC side rectifier module uses an LLC open-loop control strategy.

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