Micro-inverter and control method therefor

Abstract

Provided in the present application are a micro-inverter and a control method therefor. The micro-inverter comprises a primary circuit, a transformer, and a secondary circuit. A power extraction circuit of the secondary circuit is used for extracting power from the secondary circuit and supply the power to a driving circuit, which is used for controlling the turning-on or turning-off of bridge arm switching transistors. When a high-level input voltage of the driving circuit is below a preset high-level voltage threshold, a primary switching transistor is controlled to switch between on and off states, and both an upper bridge arm switching transistor and a lower bridge arm switching transistor are controlled to be in an off state, such that the power extraction circuit can continuously extract power from the primary circuit and stores the power. When the high-level input voltage of the driving circuit is above or equal to the preset high-level voltage threshold, the primary switching transistor, the upper bridge arm switching transistor, and the lower bridge arm switching transistor are controlled to switch between on and off states, such that a voltage is normally output. In this way, by means of controlling a micro-inverter to switch working states, it is ensured that the micro-inverter can operate normally when needed.

Description

Micro inverter and control method thereof

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office of the People's Republic of China on March 8, 2024, with application number 202410282649.0 and invention name "A micro inverter and its control method", the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application relates to the field of power electronics technology, and in particular to a micro inverter and a control method thereof. Background Art

[0004] Microinverters are widely used in photovoltaic power generation systems. They can directly convert the direct current (DC) power of photovoltaic panels into alternating current (AC) and output this AC power to the grid or load. Typically, the drive circuit of a microinverter is equipped with a power supply circuit. This power supply circuit primarily utilizes the charge and discharge characteristics of energy storage elements to power the drive circuit. In some microinverters, the power supply circuit is equipped with a voltage limiting circuit. This voltage limiting circuit can ensure the stability of the power supply circuit without the need for additional active circuits. However, in some special scenarios, such as low voltage ride-through or burst conditions, controlling the power supply circuit to ensure the proper operation of the microinverter remains a technical challenge. Summary of the Invention

[0005] The present application provides a micro inverter and a control method thereof, which controls the micro inverter to switch its working state when the input high-level voltage of the driving circuit of the secondary circuit is low, thereby ensuring that the micro inverter can work normally when needed.

[0006] In a first aspect, the present application provides a micro-inverter. Specifically, the micro-inverter includes a primary circuit, a transformer, a secondary circuit, and a controller. The input side of the primary circuit is connected to a photovoltaic module, and the output side of the primary circuit is connected to the primary winding of the transformer. The input side of the secondary circuit is connected to the secondary winding of the transformer, and the output side of the secondary circuit is connected to the power grid or a load. The primary circuit includes a primary switching tube. The secondary circuit includes a self-driving circuit, a first capacitor, and a second capacitor. The first capacitor and the second capacitor are connected in series and in parallel with the self-driving circuit. The self-driving circuit includes a secondary upper bridge arm and a secondary lower bridge arm. The connection point between the secondary upper bridge arm and the secondary lower bridge arm is connected to one end of the secondary winding of the transformer, and the connection point between the first capacitor and the second capacitor is connected to the other end of the secondary winding of the transformer. In the self-driving circuit, the secondary upper bridge arm includes an upper bridge arm switching tube, an upper bridge arm power supply circuit, and an upper bridge arm driving circuit. The upper arm power supply circuit is used to draw power from the secondary circuit and supply power to the upper arm drive circuit. The upper arm drive circuit is used to control the conduction or shutdown of the upper arm switch tube. The secondary lower arm includes the lower arm switch tube, the lower arm power supply circuit, and the lower arm drive circuit. The lower arm power supply circuit is used to draw power from the secondary circuit and supply power to the lower arm drive circuit. The lower arm drive circuit is used to control the conduction or shutdown of the lower arm switch tube. The primary circuit and the secondary circuit are respectively electrically connected to the controller. The controller is used to:

[0007] When the high-level voltage input to the upper-arm drive circuit is lower than a set high-level voltage threshold, and the high-level voltage input to the lower-arm drive circuit is lower than the set high-level voltage threshold, the primary-side switch is controlled to switch between on and off, and both the upper-arm switch and the lower-arm switch are controlled to be in the off state. At this point, the micro-inverter is in the first operating mode.

[0008] When the input high-level voltage of the upper-arm drive circuit is higher than or equal to the set high-level voltage threshold, and the input high-level voltage of the lower-arm drive circuit is higher than or equal to the set high-level voltage threshold, the primary-side switch, the upper-arm switch, and the lower-arm switch are controlled to switch between on and off. At this time, the micro-inverter is in the second operating mode.

[0009] In the micro-inverter of the present application, the power-taking circuit draws power from the secondary circuit and supplies power to the drive circuit. When the input high-level voltage of the upper-bridge arm drive circuit and the lower-bridge arm drive circuit is lower than the set high-level voltage threshold, the amount of power taken by the power-taking circuit is lower than the amount of power provided to the drive circuit, so the power-taking circuit is in a power-consuming state. At this time, the primary-side switch tube of the micro-inverter switches between on and off, so that the power-taking circuit can continue to draw power from the secondary circuit; the upper-bridge arm switch tube and the lower-bridge arm switch tube of the secondary circuit are controlled to be in the off state, so that the electric energy obtained by the power-taking circuit from the secondary circuit is stored in the power-taking circuit for the drive circuit to control the upper-bridge arm switch tube and the lower-bridge arm switch tube, thereby ensuring that the micro-inverter can operate normally when needed.

[0010] The microinverter of the present application is applicable to various scenarios. In one possible implementation, the microinverter can be used in a low voltage ride-through scenario. In this scenario, when the amplitude of the output voltage of the secondary circuit is lower than a set voltage threshold, during a first time period, the input high-level voltage of the upper-bridge arm drive circuit is lower than the set high-level voltage threshold, and the input high-level voltage of the lower-bridge arm drive circuit is lower than the set high-level voltage threshold; and during a second time period, the input high-level voltage of the upper-bridge arm drive circuit is higher than or equal to the set high-level voltage threshold, and the input high-level voltage of the lower-bridge arm drive circuit is higher than or equal to the set high-level voltage threshold. The first time period and the second time period do not overlap. That is, during the first time period, the power supply circuit is in a charging state; during the second time period, the power supply circuit can supply power to the drive circuit. Therefore, by designing alternating first and second time periods, the microinverter switches between the first and second operating modes during the low voltage ride-through period, allowing the microinverter to continue to output voltage.

[0011] The alternating arrangement of the first time period and the second time period may refer to the continuous alternation of the first time period and the second time period. Alternatively, the first time period and the second time period may also be arranged at intervals set at a set time. For example, in one possible implementation, the controller is further configured to control the primary switch tube, the upper bridge arm switch tube, and the lower bridge arm switch tube to be in an off state at the end of the first time period and before the start of the second time period. That is, the microinverter charges during the first time period, then stops working, and then operates normally during the second time period. Alternatively, the controller is further configured to control the primary switch tube, the upper bridge arm switch tube, and the lower bridge arm switch tube to be in an off state at the end of the second time period and before the start of the first time period. That is, the microinverter operates normally during the second time period, then stops working, and then charges during the first time period.

[0012] In another possible implementation, the microinverter can be used in a burst scenario. In this scenario, when the input power of the primary circuit is lower than a power threshold, during a third time period, the input high-level voltage of the upper-bridge-arm drive circuit is lower than a set high-level voltage threshold, and the input high-level voltage of the lower-bridge-arm drive circuit is lower than the set high-level voltage threshold; and during a fourth time period, the input high-level voltage of the upper-bridge-arm drive circuit is higher than or equal to the set high-level voltage threshold, and the input high-level voltage of the lower-bridge-arm drive circuit is higher than or equal to the set high-level voltage threshold. The third time period and the fourth time period do not overlap. That is, during the third time period, the power extraction circuit is in a charging state; during the fourth time period, the power extraction circuit can supply power to the drive circuit. Therefore, by assigning the third and fourth time periods to the burst-off and burst-on states, the microinverter switches to the first operating mode for charging in the burst-off state and switches to the second operating mode for normal output voltage in the burst-on state.

[0013] The alternating arrangement of the third and fourth time periods may refer to the continuous alternation of the third and fourth time periods. Alternatively, the third and fourth time periods may be arranged at intervals set. For example, in one possible implementation, at the end of the third time period and before the beginning of the fourth time period, the primary switch, the upper arm switch, and the lower arm switch are controlled to be in an off state. In other words, the microinverter charges during the third time period, then stops operating, and then operates normally during the fourth time period. Alternatively, at the end of the fourth time period and before the beginning of the third time period, the primary switch, the upper arm switch, and the lower arm switch are controlled to be in an off state. In other words, the microinverter operates normally during the fourth time period, then stops operating, and then charges during the third time period.

[0014] In the above-mentioned micro-inverter, the high-level voltage threshold is set to be greater than or equal to the minimum operating voltage value of the upper-arm switching tube and the lower-arm switching tube, and the high-level voltage threshold is set to be less than the maximum operating voltage value of the upper-arm switching tube and the lower-arm switching tube, so as to avoid the input high-level voltage of the driving circuit being too low and failing to turn on the corresponding switching tube.

[0015] When the secondary circuit is specifically set up, the power-taking circuit can store energy through the energy storage element. In one possible implementation, the upper arm power-taking circuit includes a first energy storage capacitor, and the lower arm power-taking circuit includes a second energy storage capacitor. The above-mentioned controller is also used to: when the primary switch tube switches between on and off, and the upper arm switch tube and the lower arm switch tube are in the off state, charge the first energy storage capacitor and the second energy storage capacitor respectively. When the primary switch tube, the upper arm switch tube and the lower arm switch tube switch between on and off, control the first energy storage capacitor to supply power to the upper arm drive circuit, and control the second energy storage capacitor to supply power to the lower arm drive circuit.

[0016] In the above-mentioned micro-inverter, the upper arm power supply circuit may further include a third capacitor, a first diode, a second diode, and a first zener diode. The third capacitor is used to divide the source-drain voltage of the upper arm switch tube during the off period of the upper arm switch tube, and the first zener diode is used to stabilize the voltage of the first energy storage capacitor. The positive electrode of the third capacitor is connected to one end of the upper arm switch tube, the negative electrode of the first diode is connected to the negative electrode of the third capacitor, and the positive electrode of the first diode is connected to the other end of the upper arm switch tube. The second diode is connected in series with the first energy storage capacitor and then in parallel with the first diode. The positive electrode of the second diode is connected to the negative electrode of the first diode, and the negative electrode of the first energy storage capacitor is connected to the positive electrode of the first diode. The first zener diode is connected in parallel with the first energy storage capacitor. The upper arm drive circuit is connected in parallel with the first energy storage capacitor. The lower arm power supply circuit may further include a fourth capacitor, a third diode, a fourth diode, and a second zener diode. The fourth capacitor is used to divide the source-drain voltage of the lower arm switch tube during the off period of the lower arm switch tube, and the second zener diode is used to stabilize the voltage of the second energy storage capacitor. The positive electrode of the fourth capacitor is connected to one end of the lower bridge arm switching tube, the negative electrode of the third diode is connected to the negative electrode of the fourth capacitor, and the positive electrode of the third diode is connected to the other end of the lower bridge arm switching tube. The fourth diode is connected in series with the second energy storage capacitor and then in parallel with the third diode. The positive electrode of the fourth diode is connected to the negative electrode of the third diode, and the negative electrode of the second energy storage capacitor is connected to the positive electrode of the third diode. The second voltage stabilizing diode is connected in parallel with the second energy storage capacitor. The lower bridge arm drive circuit is connected in parallel with the second energy storage capacitor.

[0017] In one possible implementation, when one of the input high-level voltage of the upper-arm drive circuit and the input high-level voltage of the lower-arm drive circuit is lower than a set high-level voltage threshold, and the other is higher than or equal to the set high-level voltage threshold, the controller is further configured to control the primary-side switch tube to switch between on and off, and to control the upper-arm switch tube and the lower-arm switch tube to be in the off state. Therefore, when either the upper-arm drive circuit or the lower-arm drive circuit is in a power-consuming state, the controller can control the micro-inverter to switch to a first operating state, so that the electrical energy obtained by the power extraction circuit from the secondary circuit is stored in the power extraction circuit for the drive circuit to control the upper-arm switch tube and the lower-arm switch tube, thereby ensuring that the micro-inverter can operate normally when needed.

[0018] In a second aspect, the present application further provides a control method. The control method is used to control a micro inverter, and may specifically include:

[0019] When the input high-level voltage of the upper bridge arm drive circuit is lower than the set high-level voltage threshold, and the input high-level voltage of the lower bridge arm drive circuit is lower than the set high-level voltage threshold, the primary side switch tube is controlled to switch between on and off, and the upper bridge arm switch tube and the lower bridge arm switch tube are controlled to be in the off state;

[0020] When the input high-level voltage of the upper-arm drive circuit is higher than or equal to the set high-level voltage threshold, and the input high-level voltage of the lower-arm drive circuit is higher than or equal to the set high-level voltage threshold, the primary side switch tube, the upper-arm switch tube and the lower-arm switch tube are controlled to switch between on and off.

[0021] The microinverter includes a primary circuit, a transformer, and a secondary circuit. The output side of the primary circuit is connected to the primary winding of the transformer, and the input side of the secondary circuit is connected to the secondary winding of the transformer. The primary circuit includes a primary switching tube. The secondary circuit includes a secondary upper bridge arm and a secondary lower bridge arm. The connection point of the secondary upper bridge arm and the secondary lower bridge arm is connected to one end of the secondary winding of the transformer. The secondary upper bridge arm includes an upper bridge arm switching tube and an upper bridge arm drive circuit. The upper bridge arm drive circuit is used to control the conduction or shutdown of the upper bridge arm switching tube. The secondary lower bridge arm includes a lower bridge arm switching tube and a lower bridge arm drive circuit. The lower bridge arm drive circuit is used to control the conduction or shutdown of the lower bridge arm switching tube.

[0022] In the control method of the present application, when the input high-level voltage of the upper-bridge-arm drive circuit and the lower-bridge-arm drive circuit is lower than the set high-level voltage threshold, the secondary circuit is in a power-consuming state. At this time, controlling the primary-side switch tube to switch between on and off, and controlling the upper-bridge-arm switch tube and the lower-bridge-arm switch tube to be in the off state, can put the secondary circuit in a charging state, thereby ensuring that the drive circuit can control the upper-bridge-arm switch tube and the lower-bridge-arm switch tube to switch between on and off when needed, thereby enabling the normal operation of the microinverter.

[0023] The control method of the present application can be used to control microinverters in various scenarios. In one possible implementation, the microinverter can be used in a low voltage ride-through scenario. In this scenario, when the output voltage amplitude of the secondary circuit is lower than a set voltage threshold, during a first time period, the input high-level voltage of the upper-arm drive circuit is lower than the set high-level voltage threshold, and the input high-level voltage of the lower-arm drive circuit is lower than the set high-level voltage threshold; and during a second time period, the input high-level voltage of the upper-arm drive circuit is higher than or equal to the set high-level voltage threshold, and the input high-level voltage of the lower-arm drive circuit is higher than or equal to the set high-level voltage threshold. The first time period and the second time period do not overlap. That is, during the first time period, the power supply circuit is in a charging state; during the second time period, the power supply circuit can supply power to the drive circuit. Therefore, by designing alternating first and second time periods, the microinverter switches between the first and second operating modes during the low voltage ride-through period, allowing the microinverter to continue to output voltage.

[0024] The alternating arrangement of the first time period and the second time period may refer to the continuous alternation of the first time period and the second time period. Alternatively, the first time period and the second time period may also be arranged at a set time interval. For example, in one possible implementation, the control method may further include controlling the primary switch tube, the upper bridge arm switch tube, and the lower bridge arm switch tube to be in an off state at the end of the first time period and before the start of the second time period. That is, the microinverter charges during the first time period, then stops working, and then operates normally during the second time period. Alternatively, the control method may further include controlling the primary switch tube, the upper bridge arm switch tube, and the lower bridge arm switch tube to be in an off state at the end of the second time period and before the start of the first time period. That is, the microinverter operates normally during the second time period, then stops working, and then charges during the first time period.

[0025] In another possible implementation, the microinverter can be used in a burst scenario. In this scenario, when the input power of the primary circuit is lower than a power threshold, during a third time period, the input high-level voltage of the upper-bridge-arm drive circuit is lower than a set high-level voltage threshold, and the input high-level voltage of the lower-bridge-arm drive circuit is lower than the set high-level voltage threshold; and during a fourth time period, the input high-level voltage of the upper-bridge-arm drive circuit is higher than or equal to the set high-level voltage threshold, and the input high-level voltage of the lower-bridge-arm drive circuit is higher than or equal to the set high-level voltage threshold. The third time period and the fourth time period do not overlap. That is, during the third time period, the power extraction circuit is in a charging state; during the fourth time period, the power extraction circuit can supply power to the drive circuit. Therefore, by assigning the third and fourth time periods to the burst-off and burst-on states, the microinverter switches to the first operating mode for charging in the burst-off state and switches to the second operating mode for normal output voltage in the burst-on state.

[0026] The alternating arrangement of the third and fourth time periods may refer to the continuous alternation of the third and fourth time periods. Alternatively, the third and fourth time periods may be arranged at intervals set at set times. For example, in one possible implementation, the control method may further include controlling the primary switch tube, the upper bridge arm switch tube, and the lower bridge arm switch tube to be in an off state at the end of the third time period and before the beginning of the fourth time period. That is, the microinverter charges during the third time period, then stops operating, and then operates normally during the fourth time period. Alternatively, the control method may further include controlling the primary switch tube, the upper bridge arm switch tube, and the lower bridge arm switch tube to be in an off state at the end of the fourth time period and before the beginning of the third time period. That is, the microinverter operates normally during the fourth time period, then stops operating, and then charges during the third time period.

[0027] In one possible implementation, the secondary upper bridge arm further includes an upper bridge arm power-taking circuit, which is used to take power from the secondary circuit and supply power to the upper bridge arm drive circuit. The secondary lower bridge arm further includes a lower bridge arm power-taking circuit, which is used to take power from the secondary circuit and supply power to the lower bridge arm drive circuit. The power-taking circuit can store energy through an energy storage element. Specifically, the upper bridge arm power-taking circuit includes a first energy storage capacitor, and the lower bridge arm power-taking circuit includes a second energy storage capacitor. The control method may further include:

[0028] When the primary switch tube switches between on and off, and the upper arm switch tube and the lower arm switch tube are in the off state, the first energy storage capacitor and the second energy storage capacitor are charged respectively;

[0029] When the primary switch tube, the upper bridge arm switch tube and the lower bridge arm switch tube switch between on and off, the first energy storage capacitor is controlled to supply power to the upper bridge arm drive circuit, and the second energy storage capacitor is controlled to supply power to the lower bridge arm drive circuit.

[0030] In one possible implementation, the control method further includes:

[0031] When one of the input high-level voltage of the upper-arm drive circuit and the input high-level voltage of the lower-arm drive circuit is lower than the set high-level voltage threshold, and the other is higher than or equal to the set high-level voltage threshold, the primary-side switch tube is controlled to switch between on and off, and the upper-arm switch tube and the lower-arm switch tube are controlled to be in the off state. Therefore, when either the upper-arm drive circuit or the lower-arm drive circuit is in the power consumption state, the micro-inverter can be controlled to switch to the first operating state, so that the power obtained by the power extraction circuit from the secondary circuit is stored in the power extraction circuit for the drive circuit to control the upper-arm switch tube and the lower-arm switch tube, thereby ensuring that the micro-inverter can be in the normal operating state when needed. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG1 is a schematic diagram of a micro-inverter provided in an embodiment of the present application;

[0033] FIG2 is a schematic diagram of a primary circuit provided in an embodiment of the present application;

[0034] FIG3 is a schematic diagram of a secondary circuit provided in an embodiment of the present application;

[0035] FIG4 is a schematic diagram of a bridge arm on a secondary side provided in an embodiment of the present application;

[0036] FIG5 is a waveform diagram of a primary circuit and a secondary circuit provided in an embodiment of the present application in a first working mode;

[0037] FIG6 is a waveform diagram of the primary circuit and the secondary circuit provided in an embodiment of the present application in a second working mode;

[0038] FIG7 is a flow chart of a control method provided in an embodiment of the present application. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical solutions and advantages of this application clearer, this application will be further described in detail below with reference to the accompanying drawings.

[0040] It should be noted that the terms used in the following embodiments are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in the specification and claims of this application, the singular expressions "a," "an," "said," "above," "the," and "this" are intended to include expressions such as "one or more," unless the context clearly indicates otherwise.

[0041] References to "one embodiment" or "some embodiments" in this specification mean that a particular feature, structure, or characteristic described in conjunction with that embodiment is included in one or more embodiments of the present application. Thus, phrases such as "in one embodiment," "in some embodiments," "in other embodiments," and "in yet other embodiments" appearing in various places in this specification do not necessarily refer to the same embodiment, but rather mean "one or more but not all embodiments," unless otherwise specifically emphasized. The terms "including," "comprising," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0042] The present application provides a micro inverter and a control method thereof, which controls the micro inverter to switch its working state when the input high-level voltage of the driving circuit of the secondary circuit is low, thereby ensuring that the micro inverter can work normally when needed.

[0043] The following describes a micro-inverter provided by an exemplary embodiment of the present application, in conjunction with the application scenarios of the present application, with reference to the accompanying drawings. It should be noted that the application scenarios are provided solely to facilitate understanding of the principles of the present application, and the embodiments of the present application are not limited in this respect. For example, the technical solutions of the present application may be modified and applied to products such as inverters, chargers, server power supplies, and specialty power supplies. As long as they do not depart from the design principles of the present application, the present application also intends to include such modifications and variations.

[0044] Figure 1 is a schematic diagram of a microinverter provided in an embodiment of the present application. As shown in Figure 1, the microinverter provided in an embodiment of the present application includes a transformer, a primary circuit, a secondary circuit, and a controller. This microinverter can be used in a photovoltaic power generation system, wherein the input side of the primary circuit is connected to the photovoltaic module, and the output side of the secondary circuit is connected to the power grid / load. In this microinverter, the output side of the primary circuit is connected to the primary winding of the transformer, and the input side of the secondary circuit is connected to the secondary winding of the transformer. The primary circuit includes a primary switching transistor. The secondary circuit includes a self-driving circuit, a first capacitor C1, and a second capacitor C2, wherein the first capacitor C1 and the second capacitor C2 are connected in series and then in parallel with the self-driving circuit. The self-driving circuit includes a secondary upper bridge arm and a secondary lower bridge arm. The connection point of the secondary upper bridge arm and the secondary lower bridge arm is connected to one end of the secondary winding of the transformer, and the connection point of the first capacitor C1 and the second capacitor C2 is connected to the other end of the secondary winding of the transformer. The primary circuit and the secondary circuit are each electrically connected to the controller.

[0045] FIG2 is a schematic diagram of a primary circuit provided by an embodiment of the present application. As shown in FIG2 , the primary circuit is a full-bridge circuit. Specifically, the full-bridge circuit includes four primary switch tubes, namely a first switch tube Q1, a second switch tube Q2, a third switch tube Q3, and a fourth switch tube Q4. The first switch tube Q1 and the second switch tube Q2 are connected in series, and the third switch tube Q3 and the fourth switch tube Q4 are connected in series and in parallel with the first switch tube Q1 and the second switch tube Q2. The connection point of the first switch tube Q1 and the second switch tube Q2 is connected to one end of the primary winding of the transformer, and the connection point of the third switch tube Q3 and the fourth switch tube Q4 is connected to the other end of the primary winding of the transformer.

[0046] FIG3 is a schematic diagram of a secondary side circuit provided in an embodiment of the present application. As shown in FIG3 , the secondary side upper bridge arm includes an upper bridge arm switching tube, an upper bridge arm power supply circuit and an upper bridge arm drive circuit. The upper bridge arm power supply circuit and the upper bridge arm drive circuit are respectively connected to the upper bridge arm switching tube, and the upper bridge arm power supply circuit is connected to the upper bridge arm drive circuit. The upper bridge arm power supply circuit is used to draw power from the secondary side circuit and supply power to the upper bridge arm drive circuit, and the upper bridge arm drive circuit is used to control the conduction or shutdown of the upper bridge arm switching tube. The secondary side lower bridge arm includes a lower bridge arm switching tube, a lower bridge arm power supply circuit and a lower bridge arm drive circuit. The lower bridge arm power supply circuit and the lower bridge arm drive circuit are respectively connected to the lower bridge arm switching tube, and the lower bridge arm power supply circuit is connected to the lower bridge arm drive circuit. The lower bridge arm power supply circuit is used to draw power from the secondary side circuit and supply power to the lower bridge arm drive circuit, and the lower bridge arm drive circuit is used to control the conduction or shutdown of the lower bridge arm switching tube.

[0047] As shown in Figure 3, the upper bridge arm switch tube may include a fifth switch tube Q5 and a sixth switch tube Q6, and the freewheeling direction of the fifth switch tube Q5 is opposite to the freewheeling direction of the sixth switch tube Q6. Similarly, the lower bridge arm switch tube may include a seventh switch tube Q7 and an eighth switch tube Q8, and the freewheeling direction of the seventh switch tube Q7 is opposite to the freewheeling direction of the eighth switch tube Q8. It should be noted that the switch tubes in this application include but are not limited to metal-oxide-semiconductor field-effect transistors (MOSFETs), insulated-gate bipolar transistors (IGBTs), thyristors and other power electronic devices. The MOSFET tube with an anti-parallel diode is shown as an example in the drawings of this application.

[0048] As shown in Figure 3, in one embodiment, the upper bridge arm power supply circuit specifically includes a first power supply circuit and a second power supply circuit. The first power supply circuit includes a third capacitor C3, a fourth capacitor C4, a first diode D1, a second diode D2, and a first energy storage capacitor Cx1. The third capacitor C3 and the fourth capacitor C4 are connected in series and then connected in parallel with the fifth switch tube Q5, the first diode D1 is connected in parallel with the fourth capacitor C4, the second diode D2 is connected in series with the first energy storage capacitor Cx1 and then connected in parallel with the first diode D1, and the first energy storage capacitor Cx1 is connected in parallel to the power supply end of the upper bridge arm drive circuit. Correspondingly, the second power supply circuit includes a fifth capacitor C5, a sixth capacitor C6, a third diode D3, a fourth diode D4, and a first energy storage capacitor Cx1, and the first power supply circuit and the second power supply circuit share the first energy storage capacitor Cx1. The fifth capacitor C5 and the sixth capacitor C6 are connected in series and in parallel with the sixth switch Q6. The third diode D3 is connected in parallel with the sixth capacitor C6. The fourth diode D4 is connected in series with the first energy storage capacitor Cx1 and in parallel with the sixth capacitor C6. The first energy storage capacitor Cx1 is connected in parallel to the power supply terminal of the upper bridge arm drive circuit. Similarly, the structure of the lower bridge arm power supply circuit is the same as that of the upper bridge arm power supply circuit and will not be repeated here.

[0049] In the above embodiment, taking the secondary upper bridge arm as an example, the third capacitor C3 serves as a voltage divider component, the fourth capacitor C4 and the first diode D1 serve as a voltage divider and shunt component. The voltage divider component and the shunt component are connected in series and then connected in parallel with the source and drain of the corresponding fifth switch tube Q5. The voltage divider and shunt component is connected in parallel with the first energy storage capacitor Cx1. The third capacitor C3 is used to divide the source-drain voltage of the fifth switch tube Q5 during the period when the corresponding fifth switch tube Q5 is turned off. The drain-source voltage of the fifth switch tube Q5 is generated by the voltage of the primary circuit sensed by the secondary circuit. The fourth capacitor C4 and the first diode D1 are used to divide the source-drain voltage of the fifth switch tube Q5 during the period when the corresponding fifth switch tube Q5 is turned off, and to shunt the current flowing into the voltage divider and shunt component. Similarly, the fifth capacitor C5 serves as a voltage divider component, the sixth capacitor C6 and the third diode D3 serve as a voltage divider shunt component, the voltage divider component and the shunt component are connected in series and then connected in parallel with the source and drain of the corresponding sixth switch tube Q6, and the voltage divider shunt component is connected in parallel with the first energy storage capacitor Cx1. The fifth capacitor C5 is used to divide the source-drain voltage of the sixth switch tube Q6 during the period when the corresponding sixth switch tube Q6 is turned off. The drain-source voltage of the sixth switch tube Q6 is generated by the voltage of the primary circuit sensed by the secondary circuit. The sixth capacitor C6 and the third diode D3 are used to divide the source-drain voltage of the sixth switch tube Q6 during the period when the corresponding sixth switch tube Q6 is turned off, and to shunt the current flowing into the voltage divider shunt component. The voltage divided by the voltage divider component is greater than the voltage divided by the voltage divider shunt component. Therefore, the voltage divider component clamps the voltage of the voltage divider shunt component and the first energy storage capacitor Cx1 at a lower level by series voltage division, so as to avoid the voltage of the first energy storage capacitor Cx1 being too large. The voltage divider shunt component is connected in parallel with the first energy storage capacitor Cx1 to avoid excessive current flowing into the first energy storage capacitor Cx1. Therefore, the first energy storage capacitor Cx1 can draw power and store it at both ends of the corresponding fifth switch tube Q5 and the sixth switch tube Q6 to supply power to the power supply end of the upper bridge arm drive circuit. The circuit structure of this embodiment does not require an additional active circuit for voltage limiting, the topology is simple, and the energy storage component has no risk of overcurrent and overvoltage, which makes the power supply circuit more stable.

[0050] FIG4 is a schematic diagram of the secondary upper bridge arm provided in an embodiment of the present application. As shown in FIG4 , in another embodiment, the first power supply circuit of the upper bridge arm power supply circuit specifically includes a third capacitor C3, a first diode D1, a second diode D2, a first energy storage capacitor Cx1, and a first voltage regulator diode Z1. The third capacitor C3 is connected in series with the first diode D1, the second diode D2 is connected in series with the first energy storage capacitor Cx1 and then connected in parallel with the first diode D1, and the first voltage regulator diode Z1 is connected in parallel with the first energy storage capacitor Cx1. The first energy storage capacitor Cx1 is connected in parallel to the power supply end of the upper bridge arm drive circuit. In this embodiment, the first voltage regulator diode Z1 is used to stabilize the voltage of the first energy storage capacitor Cx1 to avoid the risk of overcurrent and overvoltage of the first energy storage capacitor Cx1. Accordingly, the second power supply circuit includes a fifth circuit C5, a third diode D3, and a fourth diode D4. The fifth circuit C5 is connected in series with the third diode D3, and the fourth diode D4 is connected in series with the first energy storage capacitor Cx1 and then connected in parallel with the third diode D3.

[0051] It should be noted that, in the micro inverter of the present application, the circuit structures of the upper arm power taking circuit and the lower arm power taking circuit in the above embodiments are only for illustration and do not limit the structures of the upper arm power taking circuit and the lower arm power taking circuit.

[0052] In the micro-inverter of the present application, the controller can be used to control the operating states of the primary circuit and the secondary circuit. Specifically, when the input high-level voltage of the upper bridge arm drive circuit is lower than the set high-level voltage threshold, and the input high-level voltage of the lower bridge arm drive circuit is lower than the set high-level voltage threshold, the controller can control the primary switch tubes (the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, and the fourth switch tube Q4) to switch between on and off, and control the upper bridge arm switch tubes (the fifth switch tube Q5 and the sixth switch tube Q6) and the lower bridge arm switch tubes (the seventh switch tube Q7 and the eighth switch tube Q8) to be in the off state. When the input high-level voltage of the upper-arm drive circuit is greater than or equal to a set high-level voltage threshold, and the input high-level voltage of the lower-arm drive circuit is greater than or equal to a set high-level voltage threshold, the controller can control the primary-side switches (first switch Q1, second switch Q2, third switch Q3, and fourth switch Q4), the upper-arm switches (fifth switch Q5 and sixth switch Q6), and the lower-arm switches (seventh switch Q7 and eighth switch Q8) to switch between on and off. In this way, when the input high-level voltage of the secondary-side drive circuit is low, the micro-inverter is controlled to switch its operating state, thereby ensuring that the micro-inverter can operate normally when needed.

[0053] In practical applications, the fifth switch Q5, the sixth switch Q6, the seventh switch Q7, and the eighth switch Q8 can be switches of the same model and with the same parameters. Taking the fifth switch Q5, the sixth switch Q6, the seventh switch Q7, and the eighth switch Q8 as MOSFETs as an example, in one embodiment, during the on-period, the fifth switch Q5, the sixth switch Q6, the seventh switch Q7, and the eighth switch Q8 have an input high-level voltage range of 9V to 15V during normal operation. To prevent the driver circuit from failing to turn on the switches due to the input high-level voltage being too low, a high-level voltage threshold can be set based on the fifth switch Q5, the sixth switch Q6, the seventh switch Q7, and the eighth switch Q8, and satisfy the following requirements: the high-level voltage threshold is greater than or equal to the minimum operating voltage of the upper-arm switch and the lower-arm switch, and the high-level voltage threshold is less than the maximum operating voltage of the upper-arm switch and the lower-arm switch. Specifically, after the upper-arm drive circuit is activated, the input voltage of the upper-arm drive circuit increases from 0 volts and remains at the operating voltage. The upper-arm drive circuit outputs a square-wave alternating current to control the upper-arm switch tube to switch between on and off, wherein the output high-level voltage of the upper-arm drive circuit is equal to the input high-level voltage. After the lower-arm drive circuit is activated, the input voltage of the lower-arm drive circuit increases from 0 volts and remains at the operating voltage. The lower-arm drive circuit outputs a square-wave alternating current to control the lower-arm switch tube to switch between on and off, wherein the output high-level voltage of the lower-arm drive circuit is equal to the input high-level voltage. In other words, when the input high-level voltage of the upper arm drive circuit is lower than the set high-level voltage threshold, the output high-level voltage of the upper arm drive circuit is lower than the minimum operating voltage value of the upper arm switch tube (the fifth switch tube Q5 and the sixth switch tube Q6); when the input high-level voltage of the upper arm drive circuit is higher than or equal to the set high-level voltage threshold, the output high-level voltage of the upper arm drive circuit is higher than or equal to the minimum operating voltage value of the upper arm switch tube (the fifth switch tube Q5 and the sixth switch tube Q6); when the input high-level voltage of the lower arm drive circuit is lower than the set high-level voltage threshold, the output high-level voltage of the lower arm drive circuit is lower than the minimum operating voltage value of the lower arm switch tube (the seventh switch tube Q7 and the eighth switch tube Q8); when the input high-level voltage of the lower arm drive circuit is higher than or equal to the set high-level voltage threshold, the output high-level voltage of the lower arm drive circuit is higher than or equal to the minimum operating voltage value of the lower arm switch tube (the seventh switch tube Q7 and the eighth switch tube Q8). For example, in the above embodiment, the high-level voltage threshold may be set to be greater than or equal to 9V and less than 15V, such as 9V, 9.2V, 9.6V, 10V or 10.3V, etc., which are not listed here one by one.

[0054] Specifically, when the controller controls the primary-side switches (the first switch Q1, the second switch Q2, the third switch Q3, and the fourth switch Q4) to switch between on and off, and controls the upper-arm switches (the fifth switch Q5 and the sixth switch Q6) and the lower-arm switches (the seventh switch Q7 and the eighth switch Q8) to be in the off state, this state can be the first operating mode of the microinverter. In the first operating mode, on the primary circuit side, the primary switches (the first switch Q1, the second switch Q2, the third switch Q3, and the fourth switch Q4) switch between on and off states; on the secondary circuit side, all the secondary switches are in the off state. Figure 5 is a waveform diagram of the primary and secondary circuits in the first operating mode provided by an embodiment of the present application. As shown in Figure 5, in the first operating mode, the switching states of the first switch Q1 and the second switch Q2 are different. That is, when the first switch Q1 is on, the second switch Q2 is off, and when the first switch Q1 is off, the second switch Q2 is on. Similarly, the switching states of the third switch Q3 and the fourth switch Q4 are different. That is, when the third switch Q3 is on, the fourth switch Q4 is off, and when the third switch Q3 is off, the fourth switch Q4 is on. The first switch Q1 and the third switch Q3 can be on and off at least at the same time, and the second switch Q2 and the fourth switch Q4 can be on and off at least at the same time. Therefore, in the present application, when the micro-inverter is in the first operating mode, the upper-arm power circuit and the lower-arm power circuit draw power from the secondary circuit and charge the first energy storage capacitor Cx1 of the upper-arm power circuit and the second energy storage capacitor Cx2 of the lower-arm power circuit.

[0055] When the controller controls the primary side switches (first switch Q1, second switch Q2, third switch Q3, and fourth switch Q4), the upper bridge arm switches (fifth switch Q5 and sixth switch Q6), and the lower bridge arm switches (seventh switch Q7 and eighth switch Q8) to switch between on and off, this state can be the second operating mode of the microinverter. In the second operating mode, the primary side switches (first switch Q1, second switch Q2, third switch Q3, and fourth switch Q4) of the primary circuit, as well as the upper bridge arm switches (fifth switch Q5 and sixth switch Q6) and lower bridge arm switches (seventh switch Q7 and eighth switch Q8) of the secondary circuit side switch between on and off states. Figure 6 is a waveform diagram of the primary circuit and secondary circuit in the second operating mode provided by an embodiment of the present application. As shown in Figure 6, in the second operating mode, on the primary circuit side, the first switch Q1 and the second switch Q2 have different switching states. That is, when the first switch Q1 is on, the second switch Q2 is off, and when the first switch Q1 is off, the second switch Q2 is on. Similarly, the third switch Q3 and the fourth switch Q4 have different switching states. That is, when the third switch Q3 is on, the fourth switch Q4 is off, and when the third switch Q3 is off, the fourth switch Q4 is on. The first switch Q1 and the third switch Q3 can be simultaneously on or off, and the second switch Q2 and the fourth switch Q4 can be simultaneously on or off. On the secondary circuit side, when the output voltage of the secondary circuit is positive, the fifth switch tube Q5 and the seventh switch tube Q7 switch between the on state and the off state, and the sixth switch tube Q6 and the eighth switch tube Q8 are in the long-on state; when the secondary output voltage of the secondary circuit is negative, the sixth switch tube Q6 and the eighth switch tube Q8 switch between the on state and the off state, and the fifth switch tube Q5 and the seventh switch tube Q7 are in the long-on state; when the output voltage of the secondary circuit passes through zero, the fifth switch tube Q5 and the seventh switch tube Q7 are turned on or turned off at the same time, and the sixth switch tube Q6 and the eighth switch tube Q8 are turned on or turned off at the same time. Therefore, in this application, when the micro-inverter is in the second working mode, the upper bridge arm power supply circuit draws power from the upper bridge arm switch tube (the fifth switch tube Q5 and the sixth switch tube Q6) and charges the first energy storage capacitor Cx1. The first energy storage capacitor Cx1 supplies power to the upper bridge arm drive circuit to drive the fifth switch tube Q5 and the sixth switch tube Q6 to be turned on and off. The lower-arm power circuit draws power from the lower-arm switches (seventh and eighth switches Q7 and Q8) and charges the second energy storage capacitor Cx2. The second energy storage capacitor Cx2 supplies power to the lower-arm drive circuit to turn on and off the seventh and eighth switches Q7 and Q8.

[0056] In actual applications, the first and second operating modes of the microinverter can be operated alternately. The first and second operating modes can be operated continuously. Alternatively, after the first operating mode ends, the microinverter can be temporarily inactive, with the first, second, third, fourth, fourth, fifth, sixth, sixth, seventh, and eighth switches Q1, Q2, Q3, Q4, Q5, Q6, Q7, and Q8 all turned off. The microinverter then enters the second operating mode.

[0057] The micro inverter of the present application adopts a hybrid working mode of the first working mode and the second working mode, and can be applied to different application scenarios.

[0058] In one embodiment, the microinverter of the present application can be used in low voltage ride-through (LVRT) scenarios. Taking the output side of the microinverter as an example, LVRT refers to a period of time when the grid voltage is lower than the original grid voltage, while the photovoltaic power generation system remains operational. In this scenario, the grid voltage can be lower than 20%, 40%, 60%, or 80% of the original grid voltage, without limitation. In other words, the amplitude of the output voltage of the secondary circuit is lower than a set voltage threshold. At this time, because the charge level of the first and second energy storage capacitors Cx1 and Cx2 is lower than the discharge level, the first and second energy storage capacitors Cx1 and Cx2 are in a continuous power consumption state. When the first and second energy storage capacitors Cx1 and Cx2 remain in a continuous power consumption state for an extended period of time, power cannot be supplied to the drive circuit, and thus the switching transistors of the secondary circuit cannot be controlled. Therefore, to ensure that the microinverter can still output voltage, during a first time period, the input high-level voltage of the upper bridge arm drive circuit is lower than the set high-level voltage threshold, and the input high-level voltage of the lower bridge arm drive circuit is lower than the set high-level voltage threshold. At this time, the controller can control the micro-inverter to enter the first working mode. And in the second time period, the input high-level voltage of the upper bridge arm drive circuit is higher than or equal to the set high-level voltage threshold, and the input high-level voltage of the lower bridge arm drive circuit is higher than or equal to the set high-level voltage threshold. At this time, the controller can control the micro-inverter to enter the second working mode, and the first time period and the second time period do not overlap. That is, in the first time period, the first energy storage capacitor Cx1 and the second energy storage capacitor Cx2 can be continuously charged to supply power to the drive circuit in the second time period. In actual application, the voltage output by the micro-inverter in the low voltage ride-through scenario may be 10% to 80% lower than the voltage output during normal operation.

[0059] Furthermore, in another embodiment, the microinverter of the present application can be used in a burst scenario. In this scenario, the microinverter's input power may be insufficient for a period of time, resulting in a low input power supply to the microinverter. For example, in one embodiment, the microinverter can be used in a photovoltaic power generation system, with the input side of the microinverter connected to photovoltaic modules. During the early morning or evening hours, due to insufficient sunlight, the input power of the primary circuit falls below a power threshold. In this situation, the microinverter switches between a burst-off state and a burst-on state. In the burst-off state, the power circuit cannot obtain sufficient power to supply the first and second energy storage capacitors Cx1 and Cx2. In the burst-on state, the microinverter operates normally. Therefore, since the first and second energy storage capacitors Cx1 and Cx2 are in a continuous power consumption state for an extended period of time, the first and second energy storage capacitors Cx1 and Cx2 cannot supply power to the driver circuit, and thus cannot control the switching transistors of the secondary circuit. Therefore, in order to enable the micro-inverter to still output voltage normally, during the third time period of burst off, the input high-level voltage of the upper bridge arm drive circuit is lower than the set high-level voltage threshold, and the input high-level voltage of the lower bridge arm drive circuit is lower than the set high-level voltage threshold. At this time, the controller can control the micro-inverter to enter the first operating mode. And during the fourth time period of burst on, the input high-level voltage of the upper bridge arm drive circuit is higher than or equal to the set high-level voltage threshold, and the input high-level voltage of the lower bridge arm drive circuit is higher than or equal to the set high-level voltage threshold. At this time, the controller can control the micro-inverter to enter the second operating mode, and the third time period and the fourth time period do not overlap.

[0060] Of course, in some embodiments, it may happen that one of the input high-level voltage of the upper bridge arm drive circuit and the input high-level voltage of the lower bridge arm drive circuit is lower than the set high-level voltage threshold, and the other is higher than or equal to the set high-level voltage threshold. In this case, the controller can control the primary switch tube to switch between on and off, and control the upper bridge arm switch tube and the lower bridge arm switch tube to be in the off state. Therefore, when either the upper bridge arm drive circuit or the lower bridge arm drive circuit is in the power consumption state, the controller can control the micro-inverter to switch to the first working state, so that the power obtained by the power taking circuit from the secondary circuit is stored in the power taking circuit for the drive circuit to control the upper bridge arm switch tube and the lower bridge arm switch tube, thereby ensuring that the micro-inverter can be in the normal working state when needed.

[0061] Based on the same technical concept, the present application also provides a control method for a micro-inverter. FIG7 is a flow chart of the control method provided in an embodiment of the present application. As shown in FIG7 , the control method can be used to control the micro-inverter of the above embodiment. Specifically, the control method may include:

[0062] When the input high-level voltage of the upper-arm drive circuit is lower than the set high-level voltage threshold, and the output-input high-level voltage of the lower-arm drive circuit is lower than the set high-level voltage threshold, the primary-side switches (the first switch Q1, the second switch Q2, the third switch Q3, and the fourth switch Q4) are controlled to switch between on and off, and the upper-arm switches (the fifth switch Q5 and the sixth switch Q6) and the lower-arm switches (the seventh switch Q7 and the eighth switch Q8) are controlled to be in the off state;

[0063] When the input high-level voltage of the upper-arm drive circuit is higher than or equal to the set high-level voltage threshold, and the input high-level voltage of the lower-arm drive circuit is higher than or equal to the set high-level voltage threshold, the primary-side switch tubes (the first switch tube Q1, the second switch tube Q2, the third switch tube Q3, and the fourth switch tube Q4), the upper-arm switch tubes (the fifth switch tube Q5 and the sixth switch tube Q6), and the lower-arm switch tubes (the seventh switch tube Q7 and the eighth switch tube Q8) are controlled to switch between on and off.

[0064] In the micro-inverter of the present application, the power-taking circuit draws power from the secondary circuit and supplies power to the drive circuit. When the input high-level voltage of the upper-bridge-arm drive circuit and the lower-bridge-arm drive circuit is lower than the set high-level voltage threshold, the power taken by the power-taking circuit is lower than the power supplied to the drive circuit, and the power-taking circuit is in a power-consuming state. At this time, the control method of the present application can control the primary side switch tube (the first switch tube Q1, the second switch tube Q2, the third switch tube Q3 and the fourth switch tube Q4) to switch between on and off, so that the power-taking circuit can continue to draw power from the secondary side circuit; control the upper bridge arm switch tube (the fifth switch tube Q5 and the sixth switch tube Q6) and the lower bridge arm switch tube (the seventh switch tube Q7 and the eighth switch tube Q8) of the secondary side circuit to be in the off state, so that the electric energy obtained by the power-taking circuit from the primary circuit is stored in the power-taking circuit, for the drive circuit to control the upper bridge arm switch tube (the fifth switch tube Q5 and the sixth switch tube Q6) and the lower bridge arm switch tube (the seventh switch tube Q7 and the eighth switch tube Q8), thereby ensuring that the micro inverter can work normally when needed.

[0065] In one embodiment, when the micro-inverter is applied to a low voltage ride-through scenario, when the amplitude of the output voltage of the secondary circuit is lower than the set voltage threshold, in the first time period, the input high-level voltage of the upper bridge arm drive circuit is lower than the set high-level voltage threshold, and the input high-level voltage of the lower bridge arm drive circuit is lower than the set high-level voltage threshold. At this time, the control method can control the primary side switch tube (the first switch tube Q1, the second switch tube Q2, the third switch tube Q3 and the fourth switch tube Q4) to switch between on and off, and control the upper bridge arm switch tube (the fifth switch tube Q5 and the sixth switch tube Q6) and the lower bridge arm switch tube (the seventh switch tube Q7 and the eighth switch tube Q8) to be in the off state. In the second time period, the input high-level voltage of the upper bridge arm drive circuit is higher than or equal to the set high-level voltage threshold, and the input high-level voltage of the lower bridge arm drive circuit is higher than or equal to the set high-level voltage threshold. At this time, the control method can control the primary-side switches (first switch Q1, second switch Q2, third switch Q3, and fourth switch Q4), the upper-arm switches (fifth switch Q5 and sixth switch Q6), and the lower-arm switches (seventh switch Q7 and eighth switch Q8) to switch between on and off. The first time period does not overlap with the second time period.

[0066] That is, during the first time period, the power extraction circuit is in a charging state; during the second time period, the power extraction circuit can supply power to the drive circuit. Therefore, by designing alternating first and second time periods, the microinverter switches between the first and second operating modes during the low voltage ride-through period, allowing the microinverter to continue to output voltage.

[0067] The alternating arrangement of the first and second time periods may refer to the continuous alternation of the first and second time periods. Alternatively, the first and second time periods may be arranged with a set time interval. For example, in one possible implementation, at the end of the first time period and before the start of the second time period, the primary switches (the first switch Q1, the second switch Q2, the third switch Q3, and the fourth switch Q4), the upper arm switches (the fifth switch Q5 and the sixth switch Q6), and the lower arm switches (the seventh switch Q7 and the eighth switch Q8) are controlled to be in the off state. In other words, the microinverter charges during the first time period, then stops operating, and then operates normally during the second time period. Alternatively, at the end of the second time period and before the start of the first time period, the primary switches (the first switch Q1, the second switch Q2, the third switch Q3, and the fourth switch Q4), the upper arm switches (the fifth switch Q5 and the sixth switch Q6), and the lower arm switches (the seventh switch Q7 and the eighth switch Q8) are controlled to be in the off state. In other words, the microinverter operates normally during the second time period, then stops operating, and then charges during the first time period.

[0068] In another embodiment, when the microinverter is applied to a burst scenario, the control method includes:

[0069] When the input power of the primary circuit is lower than the power threshold, in the third time period, the input high level voltage of the upper bridge arm drive circuit is lower than the set high level voltage threshold, and the input high level voltage of the lower bridge arm drive circuit is lower than the set high level voltage threshold. At this time, the control method can control the primary switch tube (the first switch tube Q1, the second switch tube Q2, the third switch tube Q3 and the fourth switch tube Q4) to switch between on and off, and control the upper bridge arm switch tube (the fifth switch tube Q5 and the sixth switch tube Q6) and the lower bridge arm switch tube (the seventh switch tube Q7 and the eighth switch tube Q8) to be in the off state. In the fourth time period, the input high level voltage of the upper bridge arm drive circuit is higher than or equal to the set high level voltage threshold, and the input high level voltage of the lower bridge arm drive circuit is higher than or equal to the set high level voltage threshold. At this time, the control method can control the primary-side switches (first switch Q1, second switch Q2, third switch Q3, and fourth switch Q4), the upper-arm switches (fifth switch Q5 and sixth switch Q6), and the lower-arm switches (seventh switch Q7 and eighth switch Q8) to switch between on and off. The third time period does not overlap with the fourth time period.

[0070] That is, during the third time period, the power extraction circuit is in a charging state; during the fourth time period, the power extraction circuit can supply power to the drive circuit. Therefore, by assigning the third and fourth time periods to the burst-off and burst-on states, the microinverter switches to the first operating mode for charging in the burst-off state and switches to the second operating mode for normal voltage output in the burst-on state.

[0071] The alternating arrangement of the third and fourth time periods may refer to the continuous alternation of the third and fourth time periods. Alternatively, the third and fourth time periods may be arranged with a set time interval. For example, in one possible implementation, at the end of the third time period and before the start of the fourth time period, the primary switches (the first switch Q1, the second switch Q2, the third switch Q3, and the fourth switch Q4), the upper arm switches (the fifth switch Q5 and the sixth switch Q6), and the lower arm switches (the seventh switch Q7 and the eighth switch Q8) are controlled to be in the off state. In other words, the microinverter charges during the third time period, then stops operating, and then operates normally during the fourth time period. Alternatively, at the end of the fourth time period and before the start of the third time period, the primary switches (the first switch Q1, the second switch Q2, the third switch Q3, and the fourth switch Q4), the upper arm switches (the fifth switch Q5 and the sixth switch Q6), and the lower arm switches (the seventh switch Q7 and the eighth switch Q8) are controlled to be in the off state. That is, the micro inverter is charged in the fourth time period, then stops working, and then works normally in the third time period.

[0072] In the embodiment shown in FIG3 , the power taking circuit stores energy through the energy storage element. The above control method also includes:

[0073] When the primary switching tubes (the first switching tube Q1, the second switching tube Q2, the third switching tube Q3, and the fourth switching tube Q4) are switched between on and off, and the upper-arm switching tubes (the fifth switching tube Q5 and the sixth switching tube Q6) and the lower-arm switching tubes (the seventh switching tube Q7 and the eighth switching tube Q8) are in the off state, the first energy storage capacitor Cx1 and the second energy storage capacitor Cx2 are charged respectively. When the primary switching tubes (the first switching tube Q1, the second switching tube Q2, the third switching tube Q3, and the fourth switching tube Q4), the upper-arm switching tubes (the fifth switching tube Q5 and the sixth switching tube Q6), and the lower-arm switching tubes (the seventh switching tube Q7 and the eighth switching tube Q8) are switched between on and off, the first energy storage capacitor Cx1 is controlled to supply power to the upper-arm driving circuit, and the second energy storage capacitor Cx2 is controlled to supply power to the lower-arm driving circuit.

[0074] Of course, in some embodiments, it may happen that one of the input high-level voltage of the upper bridge arm drive circuit and the input high-level voltage of the lower bridge arm drive circuit is lower than the set high-level voltage threshold, and the other is higher than or equal to the set high-level voltage threshold. In this case, the control method can control the primary switch tube to switch between on and off, and control the upper bridge arm switch tube and the lower bridge arm switch tube to be in the off state. Therefore, when either the upper bridge arm drive circuit or the lower bridge arm drive circuit is in the power consumption state, the micro-inverter can be controlled to switch to the first working state, so that the power obtained by the power taking circuit from the secondary circuit is stored in the power taking circuit for the drive circuit to control the upper bridge arm switch tube and the lower bridge arm switch tube, thereby ensuring that the micro-inverter can be in the normal working state when needed.

[0075] The above are only specific embodiments of the present application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A micro inverter, characterized in that: It includes a primary circuit, a transformer, a secondary circuit and a controller, wherein: The input side of the primary circuit is connected to the photovoltaic module, the output side of the primary circuit is connected to the primary winding of the transformer, the input side of the secondary circuit is connected to the secondary winding of the transformer, and the output side of the secondary circuit is connected to the power grid or the load; the primary circuit includes a primary switching tube; the secondary circuit includes a self-driving circuit, a first capacitor and a second capacitor, the first capacitor and the second capacitor are connected in series and then connected in parallel with the self-driving circuit; the self-driving circuit includes a secondary upper bridge arm and a secondary lower bridge arm, the connection point of the secondary upper bridge arm and the secondary lower bridge arm is connected to one end of the secondary winding of the transformer, and the connection point of the first capacitor and the second capacitor is connected to the other end of the secondary winding of the transformer; The secondary side upper bridge arm includes an upper bridge arm switching tube, an upper bridge arm power taking circuit and an upper bridge arm driving circuit, wherein the upper bridge arm power taking circuit is used to take power from the secondary side circuit and supply power to the upper bridge arm driving circuit, and the upper bridge arm driving circuit is used to control the conduction or shutdown of the upper bridge arm switching tube; the secondary side lower bridge arm includes a lower bridge arm switching tube, a lower bridge arm power taking circuit and a lower bridge arm driving circuit, wherein the lower bridge arm power taking circuit is used to take power from the secondary side circuit and supply power to the lower bridge arm driving circuit, and the lower bridge arm driving circuit is used to control the conduction or shutdown of the lower bridge arm switching tube; The primary circuit and the secondary circuit are electrically connected to the controller respectively. The controller is used to: When the input high-level voltage of the upper bridge arm driving circuit is lower than the set high-level voltage threshold, and the input high-level voltage of the lower bridge arm driving circuit is lower than the set high-level voltage threshold, controlling the primary side switch tube to switch between on and off, and controlling the upper bridge arm switch tube and the lower bridge arm switch tube to be in the off state; When the input high-level voltage of the upper bridge arm drive circuit is higher than or equal to the set high-level voltage threshold, and the input high-level voltage of the lower bridge arm drive circuit is higher than or equal to the set high-level voltage threshold, the primary side switch tube, the upper bridge arm switch tube and the lower bridge arm switch tube are controlled to switch between on and off.

2. The micro-inverter according to claim 1, wherein: When the amplitude of the output voltage of the secondary circuit is lower than the set voltage threshold, within a first time period, the input high-level voltage of the upper bridge arm drive circuit is lower than the set high-level voltage threshold, and the input level voltage of the lower bridge arm drive circuit is lower than the set high-level voltage threshold; and within a second time period, the input high-level voltage of the upper bridge arm drive circuit is higher than or equal to the set high-level voltage threshold, and the input high-level voltage of the lower bridge arm drive circuit is higher than or equal to the set high-level voltage threshold; the first time period and the second time period do not overlap.

3. The micro-inverter according to claim 2, wherein: The controller is also used for: At the end of the first time period and before the start of the second time period, or at the end of the second time period and before the start of the first time period, the primary switch tube, the upper bridge arm switch tube and the lower bridge arm switch tube are controlled to be in an off state.

4. The micro-inverter according to claim 1, wherein: When the input power of the primary circuit is lower than the power threshold, within a third time period, the input high-level voltage of the upper bridge arm drive circuit is lower than the set high-level voltage threshold, and the input high-level voltage of the lower bridge arm drive circuit is lower than the set high-level voltage threshold; and within a fourth time period, the input high-level voltage of the upper bridge arm drive circuit is higher than or equal to the set high-level voltage threshold, and the input high-level voltage of the lower bridge arm drive circuit is higher than or equal to the set high-level voltage threshold; the third time period does not overlap with the fourth time period.

5. The micro-inverter according to claim 4, wherein: The controller is also used for: At the end of the third time period and before the start of the fourth time period, or at the end of the fourth time period and before the start of the third time period, the primary side switch tube, the upper bridge arm switch tube and the lower bridge arm switch tube are controlled to be in an off state.

6. The micro-inverter according to any one of claims 1 to 5, characterized in that: The set high-level voltage threshold is greater than or equal to the minimum operating voltage value of the upper arm switch tube and the lower arm switch tube, and the set high-level voltage threshold is less than the maximum operating voltage value of the upper arm switch tube and the lower arm switch tube.

7. The micro-inverter according to any one of claims 1 to 6, characterized in that: The upper bridge arm power taking circuit includes a first energy storage capacitor, and the lower bridge arm power taking circuit includes a second energy storage capacitor; The controller is also used for: When the primary switch tube switches between on and off, and the upper arm switch tube and the lower arm switch tube are in the off state, the first energy storage capacitor and the second energy storage capacitor are charged respectively; When the primary switch tube, the upper bridge arm switch tube and the lower bridge arm switch tube are switched between on and off, the first energy storage capacitor is controlled to supply power to the upper bridge arm drive circuit, and the second energy storage capacitor is controlled to supply power to the lower bridge arm drive circuit.

8. The micro-inverter according to claim 7, wherein: The upper arm power-taking circuit also includes a third capacitor, a first diode, a second diode and a first voltage-stabilizing diode. The third capacitor is used to divide the source-drain voltage of the upper arm switch tube during the off period of the upper arm switch tube, and the first voltage-stabilizing diode is used to stabilize the voltage of the first energy storage capacitor; wherein, the positive electrode of the third capacitor is connected to one end of the upper arm switch tube, the negative electrode of the first diode is connected to the negative electrode of the third capacitor, and the positive electrode of the first diode is connected to the other end of the upper arm switch tube; the second diode is connected in series with the first energy storage capacitor and then connected in parallel with the first diode, the positive electrode of the second diode is connected to the negative electrode of the first diode, and the negative electrode of the first energy storage capacitor is connected to the positive electrode of the first diode; the first voltage-stabilizing diode is connected in parallel with the first energy storage capacitor; the upper arm drive circuit is connected in parallel with the first energy storage capacitor; The lower bridge arm power supply circuit also includes a fourth capacitor, a third diode, a fourth diode and a second voltage-stabilizing diode. The fourth capacitor is used to divide the source-drain voltage of the lower bridge arm switch tube during the period when the lower bridge arm switch tube is turned off, and the second voltage-stabilizing diode is used to stabilize the second energy storage capacitor; wherein, the positive electrode of the fourth capacitor is connected to one end of the lower bridge arm switch tube, the negative electrode of the third diode is connected to the negative electrode of the fourth capacitor, and the positive electrode of the third diode is connected to the other end of the lower bridge arm switch tube; the fourth diode is connected in series with the second energy storage capacitor and then connected in parallel with the third diode, the positive electrode of the fourth diode is connected to the negative electrode of the third diode, and the negative electrode of the second energy storage capacitor is connected to the positive electrode of the third diode; the second voltage-stabilizing diode is connected in parallel with the second energy storage capacitor; the lower bridge arm drive circuit is connected in parallel with the second energy storage capacitor.

9. The micro-inverter according to any one of claims 1 to 8, characterized in that: The controller is also used to control the primary side switch tube to switch between on and off, and control the upper arm switch tube and the lower arm switch tube to be in the off state when one of the input high level voltage of the upper arm drive circuit and the input high level voltage of the lower arm drive circuit is lower than the set high level voltage threshold and the other is higher than or equal to the set high level voltage threshold.

10. A control method for a micro inverter, characterized in that: The control method includes: When the input high-level voltage of the upper bridge arm drive circuit is lower than the set high-level voltage threshold, and the input high-level voltage of the lower bridge arm drive circuit is lower than the set high-level voltage threshold, the primary side switch tube is controlled to switch between on and off, and the upper bridge arm switch tube and the lower bridge arm switch tube are controlled to be in the off state; When the input high-level voltage of the upper bridge arm driving circuit is higher than or equal to the set high-level voltage threshold, and the input high-level voltage of the lower bridge arm driving circuit is higher than or equal to the set high-level voltage threshold, controlling the primary side switch tube, the upper bridge arm switch tube and the lower bridge arm switch tube to switch between on and off; The micro-inverter includes a primary circuit, a transformer and a secondary circuit, wherein the output side of the primary circuit is connected to the primary winding of the transformer, and the input side of the secondary circuit is connected to the secondary winding of the transformer; the primary circuit includes the primary switching tube; the secondary circuit includes a secondary upper bridge arm and a secondary lower bridge arm, and the connection point of the secondary upper bridge arm and the secondary lower bridge arm is connected to one end of the secondary winding of the transformer; the secondary upper bridge arm includes the upper bridge arm switching tube and the upper bridge arm driving circuit, and the upper bridge arm driving circuit is used to control the conduction or shutdown of the upper bridge arm switching tube; the secondary lower bridge arm includes the lower bridge arm switching tube and the lower bridge arm driving circuit, and the lower bridge arm driving circuit is used to control the conduction or shutdown of the lower bridge arm switching tube.

11. The control method according to claim 10, wherein: When the amplitude of the output voltage of the secondary circuit is lower than the set voltage threshold, within a first time period, the input high-level voltage of the upper bridge arm drive circuit is lower than the set high-level voltage threshold, and the input level voltage of the lower bridge arm drive circuit is lower than the set high-level voltage threshold; and within a second time period, the input high-level voltage of the upper bridge arm drive circuit is higher than or equal to the set high-level voltage threshold, and the input high-level voltage of the lower bridge arm drive circuit is higher than or equal to the set high-level voltage threshold; the first time period and the second time period do not overlap.

12. The control method according to claim 11, wherein: The control method further includes: At the end of the first time period and before the start of the second time period, or at the end of the second time period and before the start of the first time period, the primary switch tube, the upper bridge arm switch tube and the lower bridge arm switch tube are controlled to be in an off state.

13. The control method according to claim 10, wherein: When the input power of the primary circuit is lower than the power threshold, within a third time period, the input high-level voltage of the upper bridge arm drive circuit is lower than the set high-level voltage threshold, and the input high-level voltage of the lower bridge arm drive circuit is lower than the set high-level voltage threshold; and within a fourth time period, the input high-level voltage of the upper bridge arm drive circuit is higher than or equal to the set high-level voltage threshold, and the input high-level voltage of the lower bridge arm drive circuit is higher than or equal to the set high-level voltage threshold; the third time period does not overlap with the fourth time period.

14. The control method according to claim 13, wherein: The control method further includes: At the end of the third time period and before the start of the fourth time period, or at the end of the fourth time period and before the start of the third time period, the primary side switch tube, the upper bridge arm switch tube and the lower bridge arm switch tube are controlled to be in an off state.

15. The control method according to any one of claims 10 to 14, characterized in that: The secondary upper bridge arm further includes an upper bridge arm power taking circuit, the upper bridge arm power taking circuit is used to take power from the secondary circuit and supply power to the upper bridge arm drive circuit, and the upper bridge arm power taking circuit includes a first energy storage capacitor; the secondary lower bridge arm further includes a lower bridge arm power taking circuit, the lower bridge arm power taking circuit is used to take power from the secondary circuit and supply power to the lower bridge arm drive circuit, and the lower bridge arm power taking circuit includes a second energy storage capacitor; The control method further includes: When the primary switch tube switches between on and off, and the upper arm switch tube and the lower arm switch tube are in the off state, the first energy storage capacitor and the second energy storage capacitor are charged respectively; When the primary switch tube, the upper bridge arm switch tube and the lower bridge arm switch tube are switched between on and off, the first energy storage capacitor is controlled to supply power to the upper bridge arm drive circuit, and the second energy storage capacitor is controlled to supply power to the lower bridge arm drive circuit.

16. The control method according to any one of claims 10 to 15, characterized in that: The control method further includes: When one of the input high-level voltage of the upper bridge arm drive circuit and the input high-level voltage of the lower bridge arm drive circuit is lower than the set high-level voltage threshold, and the other is higher than or equal to the set high-level voltage threshold, the primary side switch tube is controlled to switch between on and off, and the upper bridge arm switch tube and the lower bridge arm switch tube are controlled to be in the off state.

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