Photovoltaic inverter and control method thereof

Abstract

The invention discloses a photovoltaic inverter and a control method thereof, relates to the technical field of energy, and is used for effectively reducing the working loss of the photovoltaic inverter. The input end of the photovoltaic inverter is used for being connected with a photovoltaic array, and the photovoltaic inverter comprises a first HERIC circuit, a second HERIC circuit, a first coupling inductor and a second coupling inductor. The direct current input of the first HERIC circuit and the direct current input of the second HERIC circuit are connected in parallel and are used for being connected with a direct current bus; the first coupling inductor comprises a first winding and a second winding, the second coupling inductor comprises a third winding and a fourth winding, the alternating current output of the first HERIC circuit is respectively connected with the dotted terminal of the first winding and the dotted terminal of the third winding, and the alternating current output of the second HERIC circuit is respectively connected with the synonym terminal of the second winding and the synonym terminal of the fourth winding; the synonym terminal of the first winding is in short circuit with the dotted terminal of the second winding, and the synonym terminal of the third winding is in short circuit with the dotted terminal of the fourth winding, so as to output alternating current.

Description

Technical Field

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

[0002] With the continuous development of new energy technology, photovoltaic inverters have received more and more attention, and photovoltaic inverters with natural heat dissipation tend to develop in the direction of high efficiency, high density and miniaturization. However, after miniaturization, photovoltaic inverters under natural cooling conditions have heat dissipation problems.

[0003] Taking the traditional highly efficient and reliable inverter concept (Heric) topology and H6 topology as examples, in the Heric topology and H6 topology, semiconductor devices (such as switching tubes) and magnetic components (such as inductors) are relatively concentrated. The heat generated by the working losses of semiconductors and magnetic components will further aggravate the heat dissipation risk of photovoltaic inverters.

[0004] Therefore, how to effectively reduce the working loss of photovoltaic inverters has become an urgent problem to be solved. Summary of the invention

[0005] The present application provides a photovoltaic inverter and a control method thereof, which are used to effectively reduce the working loss of the photovoltaic inverter.

[0006] To achieve the above objectives, the embodiments of the present application adopt the following technical solutions:

[0007] In a first aspect, a photovoltaic inverter is provided, wherein the input end of the photovoltaic inverter is used to connect a photovoltaic array, and the photovoltaic inverter comprises a first HERIC circuit and a second HERIC circuit, a first coupled inductor and a second coupled inductor; the DC input of the first HERIC circuit and the DC input of the second HERIC circuit are connected in parallel and are used to connect a DC bus; the first coupled inductor comprises a first winding and a second winding, the second coupled inductor comprises a third winding and a fourth winding, the AC output of the first HERIC circuit is respectively connected to the same-name end of the first winding and the same-name end of the third winding, and the AC output of the second HERIC circuit is respectively connected to the opposite-name end of the second winding and the opposite-name end of the fourth winding; the opposite-name end of the first winding and the same-name end of the second winding are short-circuited, and the opposite-name end of the third winding and the same-name end of the fourth winding are short-circuited for outputting AC power.

[0008] In the above technical solution, the first HERIC circuit and the second HERIC circuit are staggered in parallel by using the first coupled inductor and the second coupled inductor. Compared with the related art of connecting a switch tube in parallel next to each switch tube, the synchronization requirements for driving the switch tubes at the same position in the two HERIC circuits are reduced, and the problem of uneven loss distribution due to asynchronous driving of the switch tubes is avoided, which can improve the reliability and stability of the photovoltaic inverter. Based on the current-sharing characteristics of the coupled inductor, the current of the first HERIC circuit and the second HERIC circuit is balanced, while reducing the conduction loss of each switch tube in the first HERIC circuit and the second HERIC circuit, the heat dissipation of each switch tube is more uniform, reducing the working loss of the photovoltaic inverter and improving the overload capacity of the photovoltaic inverter.

[0009] In addition, according to the conduction conditions of multiple switching tubes in the first HERIC circuit and the second HERIC circuit, multiple levels of voltage difference can be achieved at the output ends of the first coupled inductor and the second coupled inductor, thereby increasing the current change frequency of the inverter inductor in the photovoltaic inverter, reducing the inductance requirement of the inverter inductor, and thereby reducing the device size, device cost and device loss of the inverter inductor (i.e., magnetic component), further reducing the operating loss of the photovoltaic inverter.

[0010] In any possible implementation of the first aspect, any HERIC circuit in the first HERIC circuit or the second HERIC circuit includes a first bridge arm, a second bridge arm and a third bridge arm; the first bridge arm and the second bridge arm are connected in parallel between the positive DC bus and the negative DC bus, and the third bridge arm is connected between the midpoint of the first bridge arm and the midpoint of the second bridge arm; the first bridge arm includes two switch tubes with the same freewheeling direction connected in series, and the second bridge arm includes two switch tubes with the same freewheeling direction connected in series; the third bridge arm includes two switch tubes with opposite freewheeling directions. In the above possible technical solutions, a possible topological structure of a HERIC circuit is provided, and through the cooperation of 6 switch tubes, smoother voltage output and current output can be achieved, thereby improving the reliability and stability of the photovoltaic inverter.

[0011] In any possible implementation of the first aspect, any HERIC circuit further includes a diode, the anode of the diode is connected to the midpoint of the third bridge arm, and the cathode of the diode is used to connect to the positive DC bus. In the above possible technical solution, another possible topological structure of the HERIC circuit is provided, by arranging a diode between the midpoint of the third bridge arm and the positive DC bus, the diode can be a clamping diode, that is, the clamping function is realized, and the reliability and stability of the photovoltaic inverter are further improved.

[0012] In any possible implementation of the first aspect, any HERIC circuit further includes a first diode, a second diode and a fourth bridge arm; the fourth bridge arm is connected between the midpoint of the first bridge arm and the midpoint of the second bridge arm; the fourth bridge arm includes two switch tubes with opposite freewheeling directions; wherein the connection mode of the switch tubes in the fourth bridge arm is opposite to the connection mode of the switch tubes in the third bridge arm; the anode of the first diode is used to connect the midpoints of the positive and negative DC bus capacitors, the cathode of the first diode is connected to the midpoint of the third bridge arm, the anode of the second diode is connected to the midpoint of the fourth bridge arm, and the cathode of the second diode is used to connect the midpoints of the positive and negative DC bus capacitors. In the above possible technical solutions, by setting the first diode, the second diode and the fourth bridge arm, the clamping function can also be realized, further improving the reliability and stability of the photovoltaic inverter.

[0013] In any possible implementation of the first aspect, in the positive half-cycle of the modulation wave of the photovoltaic inverter, the upper bridge arm switch tube of the first bridge arm and the lower bridge arm switch tube of the second bridge arm are synchronously turned on, the switch tube in the third bridge arm is complementary to the upper bridge arm switch tube of the first bridge arm, and the lower bridge arm switch tube of the first bridge arm and the upper bridge arm switch tube of the second bridge arm are turned off; in the negative half-cycle of the modulation wave of the photovoltaic inverter, the upper bridge arm switch tube of the first bridge arm and the lower bridge arm switch tube of the second bridge arm are turned off, the lower bridge arm switch tube of the first bridge arm and the upper bridge arm of the second bridge arm are synchronously turned on, and the switch tube in the third bridge arm is complementary to the lower bridge arm switch tube of the first bridge arm. In the above possible technical solutions, the photovoltaic inverter can be controlled to convert the received direct current into alternating current through different control signals in the positive half-cycle and the negative half-cycle.

[0014] In any possible implementation of the first aspect, the photovoltaic inverter further includes a filter inductor, one end of the filter inductor is connected to the opposite-name end of the first winding and the same-name end of the second winding, and the other end of the filter inductor is connected to the opposite-name end of the third winding and the same-name end of the fourth winding. In the above possible technical solutions, the filter inductor can filter the alternating current output by the photovoltaic inverter, thereby improving the stability of the output voltage of the photovoltaic inverter.

[0015] In any possible implementation of the first aspect, the phase of the driving signal of the switch tube in the first HERIC circuit and the phase of the driving signal of the switch tube in the second HERIC circuit are different. In the above possible technical solutions, the phases of the driving signals of the switch tubes in the first HERIC circuit and the second HERIC circuit may differ by 90°, 120°, 150°, 170° or 180°. For example, when the upper bridge arm switch tube of the first bridge arm in the first HERIC circuit is turned on by the driving signal, the upper bridge arm switch tube of the first bridge arm of the second HERIC circuit may be turned on or off, which greatly reduces the synchronization requirements for each switch tube in the photovoltaic inverter.

[0016] In any possible implementation of the first aspect, the phase difference between the driving signal of the switch tube in the first HERIC circuit and the driving signal of the switch tube in the second HERIC circuit is 180°. In the above possible technical scheme, when the phase difference between the driving signals of the switch tubes in the two HERIC circuits is 180°, the bus voltage can be converted into an alternating current of a preset voltage. For example, when the bus voltage is 400V, the first HERIC circuit and the second HERIC circuit can convert the bus voltage of 400V into an alternating current with a maximum voltage of 311V, that is, after converting the bus voltage of 400V into an alternating current with an effective value of 220V, power is directly supplied to the grid or the load.

[0017] In a second aspect, a photovoltaic inverter is provided, wherein an input end of the photovoltaic inverter is used to connect a photovoltaic array, and the photovoltaic inverter comprises a first H6 circuit and a second H6 circuit, a first coupled inductor and a second coupled inductor; a DC input of the first H6 circuit and a DC input of the second H6 circuit are connected in parallel and are used to connect a DC bus; the first coupled inductor comprises a first winding and a second winding, the second coupled inductor comprises a third winding and a fourth winding, an AC output of the first H6 circuit is respectively connected to the same-name end of the first winding and the same-name end of the third winding, and an AC output of the second H6 circuit is respectively connected to the opposite-name end of the second winding and the opposite-name end of the fourth winding; the opposite-name end of the first winding and the same-name end of the second winding are short-circuited, and the opposite-name end of the third winding and the same-name end of the fourth winding are short-circuited for outputting AC power.

[0018] In the above technical solution, the first H6 circuit and the second H6 circuit are staggered in parallel by using the first coupled inductor and the second coupled inductor. Compared with the prior art of connecting a switch tube in parallel next to each switch tube, the synchronization requirements for driving the switch tubes at the same position in the two H6 circuits are reduced, and the problem of uneven loss distribution due to asynchronous driving of the switch tubes is avoided, which can improve the reliability and stability of the photovoltaic inverter. Based on the current-sharing characteristics of the coupled inductor, the current of the first H6 circuit and the second H6 circuit is balanced, which reduces the conduction loss of each switch tube in the first H6 circuit and the second H6 circuit, and makes the heat dissipation of each switch tube more uniform, reduces the working loss of the photovoltaic inverter, and improves the overload capacity of the photovoltaic inverter.

[0019] In addition, according to the conduction conditions of multiple switching tubes in the first H6 circuit and the second H6 circuit, multiple levels of voltage difference can be achieved at the output ends of the first coupled inductor and the second coupled inductor, thereby improving the current change frequency of the inverter inductor in the photovoltaic inverter, reducing the inductance requirement of the inverter inductor, and thereby reducing the device size, device cost and device loss of the inverter inductor (i.e., magnetic component), further reducing the operating loss of the photovoltaic inverter.

[0020] In any possible implementation of the second aspect, any H6 circuit in the first H6 circuit or the second H6 circuit includes a first bridge arm, a second bridge arm, and a first switch tube and a second switch tube; one end of the first bridge arm and one end of the second bridge arm are connected to one end of the first switch tube, and the other end of the first switch tube is used to connect to the positive DC bus; the other end of the first bridge arm and the other end of the second bridge arm are connected to one end of the second switch tube, and the other end of the second switch tube is used to connect to the negative DC bus; the first bridge arm includes two switch tubes with the same freewheeling direction connected in series, and the second bridge arm includes two switch tubes with the same freewheeling direction connected in series. In the above possible technical solutions, a possible topological structure of an H6 circuit is provided, and through the cooperation of 6 switch tubes, smoother voltage output and current output can be achieved, thereby improving the reliability and stability of the photovoltaic inverter.

[0021] In any possible implementation of the second aspect, in the positive half-cycle of the modulation wave of the photovoltaic inverter, the first switch tube, the second switch tube and the lower bridge arm switch tube of the second bridge arm are synchronously turned on, the upper bridge arm switch tube of the second bridge arm is complementary to the first switch tube, the upper bridge arm switch tube of the first bridge arm is turned on, and the lower bridge arm switch tube of the first bridge arm is turned off; in the negative half-cycle of the modulation wave of the photovoltaic inverter, the first switch tube, the second switch tube and the lower bridge arm switch tube of the first bridge arm are synchronously turned on, the upper bridge arm switch tube of the first bridge arm is complementary to the first switch tube, the upper bridge arm switch tube of the second bridge arm is turned on, and the lower bridge arm switch tube of the second bridge arm is turned off. In the above possible technical solutions, the photovoltaic inverter can be controlled to convert the received direct current into alternating current through different control signals in the positive half-cycle and the negative half-cycle.

[0022] In any possible implementation of the second aspect, the photovoltaic inverter further includes a filter inductor, one end of the filter inductor is connected to the opposite-name end of the first winding and the same-name end of the second winding, and the other end of the filter inductor is connected to the opposite-name end of the third winding and the same-name end of the fourth winding. In the above possible technical solutions, the filter inductor can filter the alternating current output by the photovoltaic inverter, thereby improving the stability of the output voltage of the photovoltaic inverter.

[0023] In any possible implementation of the second aspect, the phase of the driving signal of the switch tube in the first H6 circuit is different from that of the driving signal of the switch tube in the second H6 circuit. In the above possible technical solutions, the carrier phases of the first H6 circuit and the second H6 circuit may differ by 90°, 120°, 150°, 170° or 180°. For example, when the first switch tube in the first H6 circuit is turned on by the control signal, the first switch tube in the second H6 circuit may be turned on or off, which greatly reduces the synchronization requirements for each switch tube in the photovoltaic inverter.

[0024] In any possible implementation of the second aspect, the phase difference between the driving signal of the switch tube in the first H6 circuit and the driving signal of the switch tube in the second H6 circuit is 180°. In the above possible technical solution, when the phase difference between the driving signals of the switch tubes in the two H6 circuits is 180°, the bus voltage can be converted into an alternating current of a preset voltage. For example, when the bus voltage is 400V, the first H6 circuit and the second H6 circuit can convert the 400V bus voltage into an alternating current with a maximum voltage of 311V, that is, after converting the 400V bus voltage into an alternating current with an effective value of 220V, it directly supplies power to the grid or the load.

[0025] In a third aspect, a control method for a photovoltaic inverter is provided, and the control method for the photovoltaic inverter is applied to the photovoltaic inverter, the input end of the photovoltaic inverter is used to connect the photovoltaic array, the input end of the photovoltaic inverter is used to connect the photovoltaic array, the photovoltaic inverter includes a first HERIC circuit and a second HERIC circuit, a first coupled inductor and a second coupled inductor; the DC input of the first HERIC circuit and the DC input of the second HERIC circuit are connected in parallel and are used to connect the DC bus; the first coupled inductor includes a first winding and a second winding, the second coupled inductor includes a third winding and a fourth winding, the AC input of the first HERIC circuit is connected to the DC input of the second HERIC circuit, and the DC input of the first HERIC circuit is connected to the DC bus; the first coupled inductor includes a first winding and a second winding, the second coupled inductor includes a third winding and a fourth winding, and the AC input of the first HERIC circuit is connected to the DC input of the second HERIC circuit. The current output is respectively connected to the same-name end of the first winding and the same-name end of the third winding, and the AC output of the second HERIC circuit is respectively connected to the opposite-name end of the second winding and the opposite-name end of the fourth winding; the opposite-name end of the first winding and the same-name end of the second winding are short-circuited, and the opposite-name end of the third winding and the same-name end of the fourth winding are short-circuited to output alternating current; the control method includes: controlling the switch tube in the first HERIC circuit to be turned on or off, and controlling the switch tube in the second HERIC circuit to be turned on or off; wherein the driving signal of the switch tube in the first HERIC circuit and the driving signal of the switch tube in the second HERIC circuit are different in phase.

[0026] In any possible implementation of the third aspect, any HERIC circuit in the first HERIC circuit or the second HERIC circuit includes a first bridge arm, a second bridge arm and a third bridge arm; the first bridge arm and the second bridge arm are connected in parallel between the positive DC bus and the negative DC bus, and the third bridge arm is connected between the midpoint of the first bridge arm and the midpoint of the second bridge arm; controlling the switch tube in the first HERIC circuit or the second HERIC circuit to be turned on or off includes: in the positive half cycle of the modulation wave of the photovoltaic inverter, the first bridge arm The upper bridge arm switch tube and the lower bridge arm switch tube of the second bridge arm are turned on synchronously, the switch tube in the third bridge arm is turned on complementarily with the upper bridge arm switch tube of the first bridge arm, and the lower bridge arm switch tube of the first bridge arm and the upper bridge arm switch tube of the second bridge arm are turned off; in the negative half cycle of the modulation wave of the photovoltaic inverter, the upper bridge arm switch tube of the first bridge arm and the lower bridge arm switch tube of the second bridge arm are turned off, the lower bridge arm switch tube of the first bridge arm and the upper bridge arm switch tube of the second bridge arm are turned on synchronously, and the switch tube in the third bridge arm is turned on complementarily with the lower bridge arm switch tube of the first bridge arm.

[0027] In a fourth aspect, a control method for a photovoltaic inverter is provided. The control method for the photovoltaic inverter is applied to a photovoltaic inverter. The input end of the photovoltaic inverter is used to connect a photovoltaic array. The photovoltaic inverter includes a first H6 circuit and a second H6 circuit, a first coupled inductor and a second coupled inductor. The DC input of the first H6 circuit and the DC input of the second H6 circuit are connected in parallel and are used to connect a DC bus. The first coupled inductor includes a first winding and a second winding, the second coupled inductor includes a third winding and a fourth winding, and the AC output of the first H6 circuit is connected to the first winding and the AC output of the second H6 circuit. The same-name end of the group is connected to the same-name end of the third winding, and the AC output of the second H6 circuit is respectively connected to the opposite-name end of the second winding and the opposite-name end of the fourth winding; the opposite-name end of the first winding and the same-name end of the second winding are short-circuited, and the opposite-name end of the third winding and the same-name end of the fourth winding are short-circuited, for outputting AC power. The control method includes: controlling the switch tube in the first H6 circuit to be turned on or off, and controlling the switch tube in the second H6 circuit to be turned on or off; wherein the driving signal of the switch tube in the first H6 circuit is different from the phase of the driving signal of the switch tube in the second H6 circuit.

[0028] In any possible implementation of the fourth aspect, any H6 circuit in the first H6 circuit or the second H6 circuit includes a first bridge arm, a second bridge arm, and a first switch tube and a second switch tube; one end of the first bridge arm and one end of the second bridge arm are connected to one end of the first switch tube, and the other end of the first switch tube is used to connect to the positive DC bus; the other end of the first bridge arm and the other end of the second bridge arm are connected to one end of the second switch tube, and the other end of the second switch tube is used to connect to the negative DC bus; controlling the switch tube in the first H6 circuit or the second H6 circuit to be turned on or off includes: in the photovoltaic inverter In the positive half cycle of the modulation wave of the photovoltaic inverter, the first switch tube, the second switch tube and the lower bridge arm switch tube of the second bridge arm are controlled to be turned on synchronously, the upper bridge arm switch tube of the second bridge arm is controlled to be complementary to the first switch tube, and the upper bridge arm switch tube of the first bridge arm is controlled to be turned on, and the lower bridge arm switch tube of the first bridge arm is turned off; in the negative half cycle of the modulation wave of the photovoltaic inverter, the first switch tube, the second switch tube and the lower bridge arm switch tube of the first bridge arm are controlled to be turned on synchronously, the upper bridge arm switch tube of the first bridge arm and the first switch tube are controlled to be complementary, and the upper bridge arm switch tube of the second bridge arm is controlled to be turned on, and the lower bridge arm switch tube of the second bridge arm is turned off.

[0029] It can be understood that the beneficial effects that can be achieved by the photovoltaic inverter provided by the second aspect or any possible implementation of the second aspect, the control method of the photovoltaic inverter provided by the third aspect or any possible implementation of the third aspect, and the control method of the photovoltaic inverter provided by the fourth aspect or any possible implementation of the fourth aspect can correspond to the beneficial effects in the photovoltaic inverter provided by the first aspect or any possible implementation of the first aspect, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic diagram of a circuit topology of a photovoltaic inverter;

[0031] Figure 2 A schematic diagram of an application scenario of a photovoltaic inverter provided in an embodiment of the present application;

[0032] Figure 3 A schematic diagram of another application scenario of the photovoltaic inverter provided in an embodiment of the present application;

[0033] Figure 4 A schematic diagram of a circuit topology of a photovoltaic inverter provided in an embodiment of the present application;

[0034] Figure 5 Schematic diagram of input and output waveforms of a photovoltaic inverter provided in an embodiment of the present application Figure 1 ;

[0035] Figure 6 Schematic diagram of input and output waveforms of a photovoltaic inverter provided in an embodiment of the present application Figure 2 ;

[0036] Figure 7 Schematic diagram of input and output waveforms of a photovoltaic inverter provided in an embodiment of the present application Figure 3 ;

[0037] Figure 8 A schematic diagram of another circuit topology of a photovoltaic inverter provided in an embodiment of the present application;

[0038] Fig. 9 A schematic diagram of a circuit topology of another photovoltaic inverter provided in an embodiment of the present application;

[0039] Fig.10 A schematic diagram of a circuit topology of another photovoltaic inverter provided in an embodiment of the present application;

[0040] Fig.11 A schematic diagram of a circuit topology of another photovoltaic inverter provided in an embodiment of the present application;

[0041] Fig.12 A schematic diagram of input and output waveforms of another photovoltaic inverter provided in an embodiment of the present application. DETAILED DESCRIPTION

[0042] The following will discuss the making and use of each embodiment in detail. However, it should be understood that many applicable inventive concepts provided by this application can be implemented in a variety of specific environments. The specific embodiments discussed are only illustrative of the specific ways to implement and use this application and this technology, and do not limit the scope of this application.

[0043] Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art.

[0044] Each circuit or other component may be described or referred to as "used to" perform one or more tasks. In this case, "used to" is used to imply a structure by indicating that the circuit / component includes a structure (e.g., a circuit system) that performs one or more tasks during operation. Therefore, even when a specified circuit / component is currently inoperable (e.g., not turned on), the circuit / component can be referred to as being used to perform the task. Circuits / components used with the wording "used to" include hardware, such as circuits that perform operations, etc. In addition, in embodiments of the present application, words such as "first", "second", etc. do not limit quantity and order.

[0045] In this application, the words "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in this application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of the words "exemplary" or "for example" is intended to present the related concepts in a concrete way.

[0046] Before introducing the embodiments of the present application, the background technology involved in the present application is first introduced.

[0047] High efficiency, high density and miniaturization are the development trends of photovoltaic inverters with natural heat dissipation. However, after miniaturization, photovoltaic inverters under natural cooling conditions have heat dissipation problems. In the Heric topology and H6 topology of photovoltaic inverters, semiconductor devices (such as switching tubes) and magnetic components (such as inductors) are relatively concentrated. The heat generated by the working loss of semiconductors and magnetic components will further increase the heat dissipation risk of photovoltaic inverters.

[0048] In order to reduce the working loss of photovoltaic inverters and improve the heat dissipation problem of photovoltaic inverters, the related technology usually adopts the method of connecting semiconductor devices in parallel to reduce the conduction loss of semiconductor devices. Figure 1 As shown, the photovoltaic inverter 100 includes 12 switch tubes (Q1 to Q6, and Q1' to Q6'). The switch tube Q1' is connected in parallel with the switch tube Q1, the switch tube Q2' is connected in parallel with the switch tube Q2, the switch tube Q3' is connected in parallel with the switch tube Q3, the switch tube Q4' is connected in parallel with the switch tube Q4, the switch tube Q5' is connected in parallel with the switch tube Q5, and the switch tube Q6' is connected in parallel with the switch tube Q6. Taking the bridge arm where the switch tubes Q1 and Q2 are located as an example, due to the existence of the switch tube Q1', the current passing through the switch tube Q1 is reduced, thereby reducing the conduction loss of the switch tube.

[0049] However, due to the difference in threshold values ​​between the switches, the above technical solution may cause the two parallel switches to be out of sync. For example, the switch Q1 and the switch Q1' may be turned on and off asynchronously, which may lead to uneven distribution of switch losses and reduce the reliability and stability of the photovoltaic inverter.

[0050] In order to solve the above technical problems, the embodiments of the present application provide a photovoltaic inverter and a control method of the photovoltaic inverter, which are used to effectively reduce the working loss of the photovoltaic inverter. The photovoltaic inverter provided in the embodiments of the present application includes multiple HERCI topology circuits or multiple H6 topology circuits, and the multiple HERIC topology circuits or multiple H6 topology circuits are staggered in parallel through two coupled inductors, which can reduce the conduction current and conduction loss of each switch tube while reducing the requirements for the synchronization of the switch tube, so that the heat dissipation of the switch tube is more uniform, thereby avoiding the problem of uneven loss.

[0051] The photovoltaic inverter provided in the embodiment of the present application can be applied to Figure 2 and Figure 3 In the application scenario shown. The input end of the photovoltaic inverter 100 is used to connect to the photovoltaic array 200, and the output end of the photovoltaic inverter 100 is used to connect to the power grid 400 or the load 500. The load 500 includes but is not limited to a charging pile, a socket, an air conditioner or a refrigerator, etc., and this embodiment of the application does not specifically limit this.

[0052] The photovoltaic array 200 is used to convert solar energy into direct current, and the photovoltaic inverter 100 is used to convert the direct current into alternating current and then supply power to the grid 400 or the load 500. For example, the photovoltaic inverter 100 may be Figure 2 The single-stage photovoltaic inverter shown in Figure 3 The two-stage photovoltaic inverter shown in FIG. Compared with the single-stage photovoltaic inverter including a direct current (DC) / alternating current (AC) conversion circuit, the two-stage photovoltaic inverter also includes a DC / DC conversion circuit, which is used to convert the direct current output by the photovoltaic array 200 into a voltage, for example, boosting the direct current voltage output by the photovoltaic array 200 to a direct current voltage of 400V.

[0053] The photovoltaic inverter 100 provided in the embodiment of the present application can be applied to household scenarios or small industrial and commercial scenarios. The circuit topology structure of the photovoltaic inverter 100 can also be applied to an uninterruptible power supply (UPS), a station power supply or an emergency power supply, etc. The embodiment of the present application does not make any specific limitations on this.

[0054] In one possible embodiment, referring to Figure 2 and Figure 3 The photovoltaic inverter 100 provided in the embodiment of the present application can be applied to a photovoltaic power generation system 300 .

[0055] The application scenarios of the embodiments of the present application are described above. The circuit topology of the photovoltaic inverter 100 provided in the embodiments of the present application is described below in conjunction with the accompanying drawings. As an example but not a limitation, the embodiments of the present application are described by taking the photovoltaic inverter 100 as an example including two topology circuits, for example, the two topology circuits are respectively a first HERIC circuit 110 and a second HERIC circuit 120.

[0056] like Figure 4As shown, the input end of the photovoltaic inverter 100 provided in the embodiment of the present application is used to connect the photovoltaic array 200, and the photovoltaic inverter 100 includes a first HERIC circuit 110 and a second HERIC circuit 120, a first coupled inductor T1 and a second coupled inductor T2; the DC input of the first HERIC circuit 110 and the DC input of the second HERIC circuit 120 are connected in parallel and are used to connect the DC bus.

[0057] Specifically, the two DC input terminals of the first HERIC circuit 110 are respectively used to connect the positive DC bus BUS+ and the negative DC bus BUS-, and the two DC input terminals of the second HERIC circuit 120 are respectively used to connect the positive DC bus BUS+ and the negative DC bus BUS-. The voltage between the positive DC bus BUS+ and the negative DC bus BUS- is the bus voltage Vbus. Optionally, the bus voltage Vbus can be the voltage directly output by the photovoltaic array 200, or it can be the voltage after the DC / DC voltage conversion circuit boosts the voltage, and the embodiment of the present application does not specifically limit this.

[0058] In a possible embodiment, the photovoltaic inverter 100 further includes positive and negative bus capacitors Cbus disposed between the positive DC bus BUS+ and the negative DC bus BUS-, for stabilizing and filtering the bus voltage Vbus input to the photovoltaic array 200, so as to improve the stability of the input voltage of the photovoltaic inverter 100.

[0059] Reference Figure 4 The first coupled inductor T1 includes a first winding and a second winding, the second coupled inductor T2 includes a third winding and a fourth winding, the AC output of the first HERIC circuit 110 is respectively connected to the same-name end of the first winding and the same-name end of the third winding, and the AC output of the second HERIC circuit 120 is respectively connected to the opposite-name end of the second winding and the opposite-name end of the fourth winding; the opposite-name end of the first winding and the same-name end of the second winding are short-circuited, and the opposite-name end of the third winding and the same-name end of the fourth winding are short-circuited for outputting AC power. Figure 4 The “*” in the table indicates the same-named ends of the windings.

[0060] The number of windings in the first coupled inductor T1 and the second coupled inductor T2 is related to the number of topological circuits in the photovoltaic inverter 100. For example, when the photovoltaic inverter 100 includes two HERIC circuits, any coupled inductor in the first coupled inductor T1 or the second coupled inductor T2 includes two windings and a magnetic core; when the photovoltaic inverter 100 includes three HERIC circuits, any coupled inductor in the first coupled inductor T1 or the second coupled inductor T2 includes three windings and a magnetic core. The embodiment of the present application does not specifically limit the connection method of the windings and the magnetic core.

[0061] In the embodiment of the present application, the first HERIC circuit 110 and the second HERIC circuit 120 are staggered in parallel by using the first coupling inductor T1 and the second coupling inductor T2. Compared with the prior art in which a switch tube is connected in parallel next to each switch tube, the synchronization requirements for driving the switch tubes (for example, the first switch tube V1 and the first switch tube T1) at the same position in the two HERIC circuits are reduced, and the problem of uneven loss distribution due to asynchronous driving of the switch tubes is avoided, which can improve the reliability and stability of the photovoltaic inverter 100. Based on the current-sharing characteristics of the coupling inductor, the current of the first HERIC circuit 110 and the second HERIC circuit 120 is current-sharing, which reduces the conduction loss of each switch tube in the first HERIC circuit 110 and the second HERIC circuit 120, and makes the heat dissipation of each switch tube more uniform, thereby reducing the working loss of the photovoltaic inverter 100 and improving the overload capacity of the photovoltaic inverter 100.

[0062] In addition, the conduction conditions of multiple switching tubes in the first HERIC circuit 110 and the second HERIC circuit 120 can achieve multiple levels of voltage difference at the output ends of the first coupled inductor T1 and the second coupled inductor T2, thereby increasing the current change frequency of the inverter inductor in the photovoltaic inverter 100, reducing the inductance requirement for the inverter inductor, and thereby reducing the device size, device cost and device loss of the inverter inductor (i.e., magnetic component), further reducing the operating loss of the photovoltaic inverter 100.

[0063] In one embodiment, if Figure 4 As shown, any HERIC circuit in the first HERIC circuit 110 or the second HERIC circuit 120 includes a first bridge arm, a second bridge arm and a third bridge arm. The first bridge arm and the second bridge arm are connected in parallel between the positive DC bus BUS+ and the negative DC bus BUS-, and the third bridge arm is connected between the midpoint of the first bridge arm and the midpoint of the second bridge arm.

[0064] Specifically, the midpoint of the first bridge arm of the first HERIC circuit 110 is an AC output terminal of the first HERIC circuit 110, connected to the same-name terminal of the first winding; the midpoint of the second bridge arm of the first HERIC circuit 110 is another AC output terminal of the first HERIC circuit 110, connected to the same-name terminal of the third winding. The midpoint of the first bridge arm of the second HERIC circuit 120 is an AC output terminal of the second HERIC circuit 120, connected to the opposite-name terminal of the second winding; the midpoint of the second bridge arm of the second HERIC circuit 120 is another AC output terminal of the second HERIC circuit 120, connected to the opposite-name terminal of the fourth winding.

[0065] Reference Figure 4In the above-mentioned first HERIC circuit 110, the above-mentioned first bridge arm includes two switch tubes with the same freewheeling direction connected in series, such as a first switch tube V1 and a second switch tube V2; the second bridge arm includes two switch tubes with the same freewheeling direction connected in series, such as a third switch tube V3 and a fourth switch tube V4; one end of the first switch tube V1 and one end of the third switch tube V3 are both used to connect to the positive DC bus BUS+, and one end of the second switch tube V2 and one end of the fourth switch tube V4 are both used to connect to the negative DC bus BUS-.

[0066] Among them, according to the position of the switch tube in the bridge arm, the above-mentioned first switch tube V1 can also be called the upper bridge arm switch tube of the first bridge arm, the second switch tube V2 can also be called the lower bridge arm switch tube of the first bridge arm, the third switch tube V3 can also be called the upper bridge arm switch tube of the second bridge arm, and the fourth switch tube V4 can also be called the lower bridge arm switch tube of the second bridge arm.

[0067] The third bridge arm includes two switch tubes with opposite freewheeling directions, such as a fifth switch tube V5 and a sixth switch tube V6. The opposite freewheeling directions mean that the drain or collector of the fifth switch tube V5 is connected to the drain or collector of the sixth switch tube V6, or the source or emitter of the fifth switch tube V5 is connected to the source or emitter of the sixth switch tube V6.

[0068] Similarly, in the above-mentioned second HERIC circuit 120, the first bridge arm includes a first switch tube T1 and a second switch tube T2 connected in series, and the second bridge arm includes a third switch tube T3 and a fourth switch tube T4 connected in series; one end of the first switch tube T1 and one end of the third switch tube T3 are both used to connect the positive DC bus BUS+, and one end of the second switch tube T2 and one end of the fourth switch tube T4 are both used to connect the negative DC bus BUS-; the third bridge arm includes a fifth switch tube T5 and a sixth switch tube T6, and the drain or collector of the fifth switch tube T5 is connected to the drain or collector of the sixth switch tube T6, or the source or emitter of the fifth switch tube T5 is connected to the source or emitter of the sixth switch tube T6.

[0069] Optionally, the first switch tube V1 to the sixth switch tube V6, and each switch tube in the following embodiments may include a metal-oxide-semiconductor field-effect transistor (MOSFET), which may also be referred to as a MOS tube, each MOS tube including a reverse-biased body diode. Alternatively, each switch tube may include an insulated-gate bipolar transistor (IGBT) and a diode D, the collector of the IGBT being connected to the cathode of the diode D, and the emitter of the IGBT being connected to the anode of the diode D. As an example and not a limitation, the embodiments of the present application are described by taking each switch tube including an IGBT and a diode D as an example.

[0070] Furthermore, the photovoltaic inverter 100 further includes a controller ( Figure 4 The controller is used to control the conduction or disconnection of each switch tube in the first HERIC circuit 110 and the second HERIC circuit 120. Optionally, the controller can be a digital signal processing (digital signal process, DSP) chip or a microcontroller unit (microcontroller unit, MCU), etc. The microcontroller unit can also be called a single chip microcomputer, which is not specifically limited in the embodiment of the present application.

[0071] Continue reading Figure 4 The photovoltaic inverter 100 provided in the embodiment of the present application also includes a filter inductor, one end of which is connected to the opposite end of the first winding and the same end of the second winding, and the other end of which is connected to the opposite end of the third winding and the same end of the fourth winding.

[0072] In a possible embodiment, Figure 4 As shown, the above-mentioned filter inductor includes a first inductor L1 and a second inductor L2. One end of the first inductor L1 is connected to the opposite-name end of the first winding and the same-name end of the second winding, and the other end of the first inductor L1 is used to output alternating current, one end of the second inductor L2 is connected to the opposite-name end of the third winding and the same-name end of the fourth winding, and the other end of the second inductor L2 is used to output alternating current.

[0073] Optionally, the photovoltaic inverter 100 further includes a capacitor C1, which is disposed between the first inductor L1 and the second inductor L2. The capacitor C1, the first inductor L1 and the second inductor L2 together constitute an LC filter circuit for filtering the alternating current output by the photovoltaic inverter 100 to improve the stability of the output voltage of the photovoltaic inverter 100.

[0074] The above describes a circuit topology of a photovoltaic inverter 100 provided in an embodiment of the present application. Figure 4 The circuit topology of the photovoltaic inverter 100 shown in FIG. Figures 5 to 7 , the wave generation method of the photovoltaic inverter 100 is introduced in detail.

[0075] like Figure 5 As shown, in the embodiment of the present application, the modulation wave of the photovoltaic inverter 100 is a sine wave m, and the carrier of the photovoltaic inverter 100 is a triangular wave. The controller can use a unipolar wave generation method to compare the modulation wave with the triangular carrier to generate a pulse width modulation (PWM) signal. Figure 5 (a) and (b) in FIG. 1 respectively show the wave generation mode of the first HERIC circuit 110 and the wave generation mode of the second HERIC circuit 120. Figure 5 In the waveform diagram shown, the vertical axis represents voltage or level, the horizontal axis represents time, and Figure 5 The signal waveform shown is the signal waveform within 20 milliseconds.

[0076] The following first takes the first HERIC circuit 110 as an example to introduce the wave generation method of the HERIC circuit in detail.

[0077] In a possible embodiment, in the positive half cycle of the modulation wave of the photovoltaic inverter 100, the upper bridge arm switch tube of the first bridge arm and the lower bridge arm switch tube of the second bridge arm are synchronously turned on, that is, the first switch tube V1 and the fourth switch tube V4 are synchronously turned on, the switch tube in the third bridge arm and the upper bridge arm switch tube of the first bridge arm are complementarily turned on, that is, the fifth switch tube V5 and the first switch tube V1 are complementarily turned on, the lower bridge arm switch tube of the first bridge arm and the upper bridge arm switch tube of the second bridge arm are turned off, that is, the second switch tube V2 and the third switch tube V3 are turned off, and the sixth switch tube V6 in the third bridge arm is always on; in the negative half cycle of the modulation wave of the photovoltaic inverter 100, the first switch tube V1 and the fourth switch tube V4 are turned off, the fifth switch tube V5 is turned on, the second switch tube V2 and the third switch tube V3 are synchronously turned on, and the sixth switch tube V6 is synchronously turned off.

[0078] See also Figure 5In (a), in the positive half cycle of the sine wave m, the triangular wave tri1-1 and the sine wave m generate the first PWM signal, and the PWM signal is the driving signal of the switch tube. Specifically, when the amplitude of the triangular wave tri1-1 is greater than the sine wave m, a low-level signal is generated, and when the amplitude of the triangular wave tri1-1 is less than the sine wave m, a high-level signal is generated. The first PWM signal is used to drive the first switch tube V1 and the fourth switch tube V4 to turn on synchronously, and drive the fifth switch tube V5 and the first switch tube V1 to turn on complementary, that is, when the amplitude of the triangular wave tri1-1 is greater than the sine wave m, the first switch tube V1 and the fourth switch tube V4 are turned off at the same time, and the fifth switch tube V5 is turned on at the same time, and when the amplitude of the triangular wave tri1-1 is less than the sine wave m, the first switch tube V1 and the fourth switch tube V4 are turned on at the same time, and the fifth switch tube V5 is turned off at the same time. The second switch tube V2 and the third switch tube V3 remain turned off in the positive half cycle of the sine wave m, and the sixth switch tube V6 remains turned on in the positive half cycle of the sine wave m.

[0079] In the negative half cycle of sine wave m, triangular wave tri1-2 and sine wave m generate a second PWM signal. When the amplitude of triangular wave tri1-2 is greater than sine wave m, a high level signal is generated, and when the amplitude of triangular wave tri1-2 is less than sine wave m, a low level signal is generated. The second PWM signal is used to drive the second switch tube V2 and the third switch tube V3 to conduct synchronously, and drive the sixth switch tube V6 to complement the second switch tube V2 to conduct, that is, when the amplitude of triangular wave tri1-2 is greater than sine wave m, the second switch tube V2 and the third switch tube V3 are turned on at the same time, and the sixth switch tube V6 is turned off at the same time. When the amplitude of triangular wave tri1-2 is less than sine wave m, the second switch tube V2 and the third switch tube V3 are turned off at the same time, and the sixth switch tube V6 is turned on at the same time. The first switch tube V1 and the fourth switch tube V4 remain turned off in the negative half cycle of sine wave m, and the fifth switch tube V5 remains turned on in the negative half cycle of sine wave m.

[0080] In a possible implementation, the phases of the driving signal of the switch tube in the first HERIC circuit 110 and the driving signal of the switch tube in the second HERIC circuit 120 are different.

[0081] Optionally, the phase difference between the driving signal of the switch tube in the first HERIC circuit 110 and the driving signal of the switch tube in the second HERIC circuit 120 is 90°, 120°, 150°, 170° or 180°. Since the phase of the PWM signal is related to the phase of the carrier, the controller of the photovoltaic inverter 100 generates carrier signals with different phases, thereby providing carrier signals with different phases to the switch tubes in different HERIC circuits, so that the switch tubes in different HERIC circuits have driving signals (i.e., PWM signals) with different phases. For example, in the first HERIC circuit 110, when the first switch tube V1 and the fourth switch tube V4 are turned on under the action of the first PWM signal, in the second HERIC circuit 120, the driving signal may drive the first switch tube M1 and the fourth switch tube M4 to turn on, or may drive the first switch tube M1 and the fourth switch tube M4 to turn off, which greatly reduces the synchronization requirements for each switch tube in the two HERIC circuits.

[0082] Furthermore, the phase difference between the driving signal of the switch tube in the first HERIC circuit 110 and the driving signal of the switch tube in the second HERIC circuit 120 is 180°. Exemplarily, under the action of the driving signals with a phase difference of 180°, the first HERIC circuit 110 and the second HERIC circuit 120 can convert the 400V bus voltage Vbus into an AC power with a maximum voltage of 311V, that is, after converting the 400V bus voltage Vbus into an AC power with an effective value of 220V, directly supply power to the grid 400 or the load 500.

[0083] like Figure 5 As shown in (b), in the positive half cycle of the sine wave m, the triangular wave tri2-1 and the sine wave m generate a third PWM signal. Specifically, when the amplitude of the triangular wave tri2-1 is greater than the sine wave m, a low level signal is generated, and when the amplitude of the triangular wave tri2-1 is less than the sine wave m, a high level signal is generated. The third PWM signal is used to drive the first switch tube M1 and the fourth switch tube M4 to be synchronously turned on, and drive the fifth switch tube M5 to be complementary turned on, that is, when the amplitude of the triangular wave tri2-1 is greater than the sine wave m, the first switch tube M1 and the fourth switch tube M4 are turned off at the same time, and the fifth switch tube M5 is turned on at the same time. When the amplitude of the triangular wave tri2-1 is less than the sine wave m, the first switch tube M1 and the fourth switch tube M4 are turned on at the same time, and the fifth switch tube M5 is turned off at the same time. The second switch tube M2 and the third switch tube M3 remain turned off in the positive half cycle of the sine wave m, and the sixth switch tube M6 remains turned on in the positive half cycle of the sine wave m.

[0084] In the negative half cycle of the sine wave m, the triangular wave tri2-2 and the sine wave m generate a fourth PWM signal. When the amplitude of the triangular wave tri2-2 is greater than the sine wave m, a high level signal is generated, and when the amplitude of the triangular wave tri2-2 is less than the sine wave m, a low level signal is generated. The fourth PWM signal is used to drive the second switch tube M2 and the third switch tube M3 to be synchronously turned on, and drive the sixth switch tube M6 to be complementary turned on, that is, when the amplitude of the triangular wave tri2-2 is greater than the sine wave m, the second switch tube M2 and the third switch tube M3 are turned on at the same time, and the sixth switch tube M6 is turned off at the same time, and when the amplitude of the triangular wave tri2-2 is less than the sine wave m, the second switch tube M2 and the third switch tube M3 are turned off at the same time, and the sixth switch tube M6 is turned on at the same time. The first switch tube M1 and the fourth switch tube M4 remain turned off in the negative half cycle of the sine wave m, and the fifth switch tube M5 remains turned on in the negative half cycle of the sine wave m.

[0085] The wave generation modes of the first HERIC circuit 110 and the second HERIC circuit 120 are respectively introduced above. The following describes in detail the changes in the inductor current of the photovoltaic inverter and the changes in the output voltage of the photovoltaic inverter when the phase difference between the driving signal of the switch tube in the first HERIC circuit 110 and the driving signal of the switch tube in the second HERIC circuit 120 is 180° in combination with the accompanying drawings.

[0086] like Figure 5 As shown in (a) and (b) in the figure, in the positive half cycle of the sine wave m, there are the following three situations:

[0087] The first case: the first switch tube V1 and the second switch tube V4 in the first HERCI circuit 110 are turned on under the action of the first PWM signal, the fifth switch tube V5 is turned off under the action of the first PWM signal, and the sixth switch tube V6 is turned on; the first switch tube M1 and the second switch tube M4 in the second HERIC circuit 120 are turned off under the action of the third PWM signal, the fifth switch tube M5 is turned off under the action of the third PWM signal, and the sixth switch tube M6 is turned on. At this time, the output voltage VL of the first coupling inductor T1 is 3 / 4Vbus, the output voltage VN of the second coupling inductor T2 is 1 / 4Vbus, and the voltage difference VLN between the two output ends of the photovoltaic inverter 100 is VL-VN=1 / 2Vbus.

[0088] The second case: the first switch tube V1 and the second switch tube V4 in the first HERCI circuit 110 are turned off under the action of the first PWM signal, the fifth switch tube V5 is turned on under the action of the first PWM signal, and the sixth switch tube V6 is turned on; the first switch tube T1 and the second switch tube T4 in the second HERIC circuit 120 are turned off under the action of the third PWM signal, the fifth switch tube M5 is turned on under the action of the third PWM signal, and the sixth switch tube M6 is turned on. At this time, the output voltage VL of the first coupling inductor T1 is 0, the output voltage VN of the second coupling inductor T2 is 0, and the voltage difference VLN between the two output ends of the photovoltaic inverter 100 is VL-VN=0.

[0089] The third case: the first switch tube V1 and the second switch tube V4 in the first HERCI circuit 110 are turned on under the action of the first PWM signal, the fifth switch tube V5 is turned off under the action of the first PWM signal, and the sixth switch tube V6 is turned on; the first switch tube M1 and the second switch tube M4 in the second HERIC circuit 120 are turned on under the action of the third PWM signal, the fifth switch tube M5 is turned off under the action of the third PWM signal, and the sixth switch tube M6 is turned on. At this time, the output voltage VL of the first coupling inductor T1 is Vbus, the output voltage VN of the second coupling inductor T2 is 0, and the voltage difference VLN between the two output ends of the photovoltaic inverter 100 is VL-VN=Vbus.

[0090] In the negative half cycle of the sine wave m, there are also the following three situations:

[0091] The first case: the second switch tube V2 and the third switch tube V3 in the first HERCI circuit 110 are turned on under the action of the second PWM signal, the sixth switch tube V6 is turned off under the action of the second PWM signal, and the fifth switch tube V5 is turned on; the second switch tube M2 and the third switch tube M3 in the second HERIC circuit 120 are turned off under the action of the fourth PWM signal, the sixth switch tube M6 is turned off under the action of the fourth PWM signal, and the fifth switch tube M5 is turned on. At this time, the output voltage VL of the first coupling inductor T1 is 1 / 4Vbus, the output voltage VN of the second coupling inductor T2 is 3 / 4Vbus, and the voltage difference VLN between the two output ends of the photovoltaic inverter 100 is VL-VN=-1 / 2Vbus.

[0092] The second case: the second switch tube V2 and the third switch tube V3 in the first HERCI circuit 110 are turned off under the action of the second PWM signal, the sixth switch tube V6 is turned on under the action of the second PWM signal, and the fifth switch tube V5 is turned on; the second switch tube M2 and the third switch tube M3 in the second HERIC circuit 120 are turned off under the action of the fourth PWM signal, the sixth switch tube M6 is turned off under the action of the fourth PWM signal, and the fifth switch tube M5 is turned on. At this time, the output voltage VL of the first coupling inductor T1 is 00, the output voltage VN of the second coupling inductor T2 is 0, and the voltage difference VLN between the two output ends of the photovoltaic inverter 100 is 0.

[0093] The third case: the second switch tube V2 and the third switch tube V3 in the first HERCI circuit 110 are turned on under the action of the second PWM signal, the sixth switch tube V6 is turned off under the action of the second PWM signal, and the fifth switch tube V5 is turned on; the second switch tube M2 and the third switch tube M3 in the second HERIC circuit 120 are turned on under the action of the fourth PWM signal, the sixth switch tube M6 is turned on under the action of the fourth PWM signal, and the fifth switch tube M5 is turned on. At this time, the output voltage VL of the first coupling inductor T1 is 0, the output voltage VN of the second coupling inductor T2 is Vbus, and the voltage difference VLN between the two output ends of the photovoltaic inverter 100 is VL-VN=-Vbus.

[0094] Thus, the voltage difference between the two output terminals of the photovoltaic inverter 100 can be five levels, namely -Vbus, -1 / 2Vbus, 0, 1 / 2Vbus and Vbus. In the embodiment of the present application, the number of levels of the voltage difference between the two output terminals of the photovoltaic inverter 100 is related to the number of topological structures, and the embodiment of the present application does not specifically limit this.

[0095] See also Figure 6 ,and Figure 5 compared to, Figure 6 In the waveform diagram shown, the vertical axis represents the level, current or voltage, and the horizontal axis represents time. Figure 6 The signal waveform shown is the signal waveform within 2 milliseconds. Figure 6As shown, the PWM signal of the first switch tube V1 and the PWM signal of M1 have the same frequency and a phase difference of 180°. In one switching cycle (for example, between two rising edges of the waveform shown by the first switch tube V1 or M1, or between two falling edges), the voltage difference VLN between the two output terminals of the photovoltaic inverter 100 changes twice, so that the frequency of the inductor current iL of the first inductor L1 or the second inductor L2 changes twice, that is, the inductor current iL of the first inductor L1 and the second inductor L2 is doubled, which further reduces the inductance requirement of the photovoltaic inverter 100, which is conducive to reducing the device volume, device cost and device power consumption of the inductor in the photovoltaic inverter 100.

[0096] For further information, see Figure 7 , Figure 7 The signal waveform shown in is the signal waveform within 0.02 seconds. Figure 7 As shown, iL1 and iL2 represent the inductor current on the first winding and the inductor current on the second winding of the first coupled inductor T1 respectively; VT is used to represent the voltage difference across the first winding or the voltage difference across the second winding, that is, VT=VL_1-VL=VL-VL_2; similarly, VT can also be used to represent the voltage difference across the third winding or the voltage difference across the fourth winding, that is, VT=VN_1-VN=VN-VN_2. Figure 7 It can be seen that the photovoltaic inverter 100 provided in the embodiment of the present application can achieve five levels of voltage output, namely 0V, 200V, 400V, -200V and -400V, at the output end of the first coupled inductor T1 and the second coupled inductor T2 through two HERIC circuits that are staggered in parallel and emit waves in staggered phases, and the voltage variation amplitude is within 200V, which is equivalent to reducing the voltage variation amplitude, indirectly increasing the voltage variation frequency, and reducing the inductance requirement under the same current ripple.

[0097] It can be understood that the above is only one circuit topology of the HERIC circuit. The HERIC circuit can also include but is not limited to various methods such as splitting the bus, adding diodes or connecting power tubes in series / parallel, etc. to achieve other functions such as clamping and multi-level output. As an example but not a limitation, the circuit topology of the photovoltaic inverter 100 provided in the embodiment of the present application can also be as follows Figure 8 , Fig. 9 or Fig.10 The topology shown.

[0098] like Figure 8 As shown, taking the first HERIC circuit 110 as an example, Figure 4 Compared to the first HERIC circuit 110 shown, Figure 8The first HERIC circuit 110 shown further includes a diode D1 , an anode of the diode D1 is connected to a connection point between the fifth switch tube V5 and the sixth switch tube V6 , and a cathode of the diode D1 is used to connect to a positive DC bus BUS+.

[0099] Correspondingly, the second HERIC circuit 120 includes a diode VD1, an anode of the diode VD1 is connected to the connection point of the fifth switch tube M5 and the sixth switch tube M6, and a cathode of the diode VD1 is used to connect to the positive DC bus BUS+.

[0100] like Fig. 9 As shown, taking the first HERIC circuit 110 as an example, Figure 4 Compared to the first HERIC circuit 110 shown, Fig. 9 The first HERIC circuit 110 shown also includes a first diode D1, a second diode D2 and a fourth bridge arm; the fourth bridge arm is connected between the midpoint of the first bridge arm and the midpoint of the second bridge arm; the fourth bridge arm includes two switch tubes with opposite freewheeling directions, such as a seventh switch tube V7 and an eighth switch tube V8, the source or emitter of the seventh switch tube V7 is connected to the source or emitter of the eighth switch tube V8, or the drain or collector of the seventh switch tube V7 is connected to the drain or collector of the eighth switch tube V8; wherein the connection mode of the switch tubes in the fourth bridge arm is opposite to the connection mode of the switch tubes in the third bridge arm; the anode of the first diode D1 is used to connect the midpoint N of the positive and negative DC bus capacitors, the cathode of the first diode D1 is connected to the midpoint of the third bridge arm, the anode of the second diode D2 is connected to the midpoint of the fourth bridge arm, and the cathode of the second diode D2 is used to connect the midpoint N of the positive and negative DC bus capacitors.

[0101] The positive and negative DC bus capacitors include a first bus capacitor Cbus1 and a second bus capacitor Cbus2 connected in series, and a connection point between the first bus capacitor Cbus1 and the second bus capacitor Cbus2 is a midpoint N.

[0102] Correspondingly, the second HERIC circuit 120 also includes a first diode VD1, a second diode VD2 and a fourth bridge arm; the fourth bridge arm is connected between the midpoint of the first bridge arm and the midpoint of the second bridge arm; the fourth bridge arm includes a seventh switch tube M7 and an eighth switch tube M8, the source or emitter of the seventh switch tube M7 is connected to the source or emitter of the eighth switch tube M8, or the drain or collector of the seventh switch tube M7 is connected to the drain or collector of the eighth switch tube M8; wherein the connection mode of the switch tubes in the fourth bridge arm is opposite to the connection mode of the switch tubes in the third bridge arm; the anode of the first diode VD1 is used to connect the midpoint N of the positive and negative DC bus capacitors, the cathode of the first diode VD1 is connected to the midpoint of the third bridge arm, the anode of the second diode VD2 is connected to the midpoint of the fourth bridge arm, and the cathode of the second diode VD2 is used to connect the midpoint N of the positive and negative DC bus capacitors.

[0103] like Fig.10 As shown, taking the first HERIC circuit 110 as an example, Figure 4 Compared to the first HERIC circuit 110 shown, Fig.10 The third bridge arm in the first HERIC circuit 110 shown includes a first diode D1 and a fifth switch tube V5, and the first HERIC circuit 110 also includes a fourth bridge arm, the fourth bridge arm includes a second diode D2 and a sixth switch tube V6, and the third bridge arm and the fourth bridge arm are connected between the bridge arm midpoint of the first bridge arm and the bridge arm midpoint of the second bridge arm. The cathode of the first diode D1 is connected to the drain or collector of the fifth switch tube V5, and the cathode of the second diode D2 is connected to the drain or collector of the sixth switch tube V6; or the anode of the first diode D1 is connected to the source or emitter of the fifth switch tube V5, and the anode of the second diode D2 is connected to the source or emitter of the sixth switch tube V6.

[0104] Correspondingly, the third bridge arm in the second HERIC circuit 120 includes a first diode VD1 and a fifth switch tube M5, and the second HERIC circuit 120 also includes a fourth bridge arm, which includes a second diode VD2 and a sixth switch tube M6. The third bridge arm and the fourth bridge arm are connected between the midpoint of the bridge arm of the first bridge arm and the midpoint of the bridge arm of the second bridge arm. The cathode of the first diode VD1 is connected to the drain or collector of the fifth switch tube M5, and the cathode of the second diode VD2 is connected to the drain or collector of the sixth switch tube M6; or the anode of the first diode VD1 is connected to the source or emitter of the fifth switch tube M5, and the anode of the second diode VD2 is connected to the source or emitter of the sixth switch tube M6.

[0105] The present application also provides a photovoltaic inverter. Figure 4 Compared with the photovoltaic inverter shown in FIG. 1 , in the embodiment of the present application, the topology structure of the inverter circuit in the photovoltaic inverter 100 may also be an H6 topology.

[0106] like Fig.11 As shown, the input end of the photovoltaic inverter 100 is used to connect the photovoltaic array 200. The photovoltaic inverter 100 includes a first H6 circuit 130 and a second H6 circuit 140, a first coupling inductor T1 and a second coupling inductor T2; the DC input of the first H6 circuit 130 is connected in parallel with the DC input of the second H6 circuit 140, and is used to connect the DC bus. The first coupling inductor T1 includes a first winding and a second winding, and the second coupling inductor T2 includes a third winding and a fourth winding. The AC output of the first H6 circuit 130 is connected to the same-name end of the first winding and the same-name end of the third winding respectively, and the AC output of the second H6 circuit 140 is connected to the opposite-name end of the second winding and the opposite-name end of the fourth winding respectively; the opposite-name end of the first winding and the same-name end of the second winding are short-circuited, and the opposite-name end of the third winding and the same-name end of the fourth winding are short-circuited for outputting AC power.

[0107] In the embodiment of the present application, the first H6 circuit 130 and the second H6 circuit 140 are staggered in parallel by using the first coupled inductor T1 and the second coupled inductor T2. Compared with the prior art in which a switch tube is connected in parallel next to each switch tube, the synchronization requirement for driving the switch tubes (for example, the first switch tube V1 and the first switch tube T1) at the same position in the two HERIC circuits is reduced, and the problem of uneven loss distribution caused by asynchronous driving of the switch tubes is avoided, which can improve the reliability and stability of the photovoltaic inverter 100. Based on the current-sharing characteristics of the coupled inductor, the current of the first H6 circuit 130 and the second H6 circuit 140 is balanced, and while reducing the conduction loss of each switch tube in the first H6 circuit 130 and the second H6 circuit 140, the heat dissipation of each switch tube is more uniform, which reduces the working loss of the photovoltaic inverter 100 and improves the overload capacity of the photovoltaic inverter 100.

[0108] In addition, the conduction condition of each switch tube of the first H6 circuit 130 and the second H6 circuit 140 can achieve multiple levels of voltage difference at the output ends of the first coupled inductor T1 and the second coupled inductor T2, thereby improving the current change frequency of the inverter inductor in the photovoltaic inverter 100, reducing the inductance requirement of the inverter inductor, and thereby reducing the device size, device cost and device loss of the inverter inductor (i.e., magnetic component), further reducing the working loss of the photovoltaic inverter 100.

[0109] In one embodiment, if Fig.11 As shown, any H6 circuit in the first H6 circuit 130 or the second H6 circuit 140 includes a first bridge arm, a second bridge arm, and a first switch tube and a second switch tube.

[0110] Reference Fig.11In the above-mentioned first H6 circuit 130, one end of the first bridge arm and one end of the second bridge arm are both connected to one end of the first switch tube V1, and the other end of the first switch tube V1 is used to connect the positive DC bus BUS+; the other end of the first bridge arm and the other end of the second bridge arm are both connected to one end of the second switch tube V2, and the other end of the second switch tube V2 is used to connect the negative DC bus; the first bridge arm includes two switch tubes with the same freewheeling direction connected in series, such as the third switch tube V3 and the fourth switch tube V4, and the second bridge arm includes two switch tubes with the same freewheeling direction connected in series, such as the fifth switch tube V5 and the sixth switch tube V6; one end of the third switch tube V3 and one end of the fifth switch tube V5 are both connected to one end of the first switch tube V1, and one end of the fourth switch tube V4 and one end of the sixth switch tube V6 are both connected to the other end of the second switch tube V2.

[0111] Among them, the third switch tube V3 can also be called the upper bridge arm switch tube of the first bridge arm, the fourth switch tube can also be called the lower bridge arm switch tube of the first bridge arm, the fifth switch tube V5 can also be the upper bridge arm switch tube of the second bridge arm, and the sixth switch tube can also be called the lower bridge arm switch tube of the second bridge arm.

[0112] Similarly, in the above-mentioned second H6 circuit 140, one end of the first bridge arm and one end of the second bridge arm are both connected to one end of the first switch tube M1, and the other end of the first switch tube M1 is used to connect the positive DC bus BUS+; the other end of the first bridge arm and the other end of the second bridge arm are both connected to one end of the second switch tube M2, and the other end of the second switch tube M2 is used to connect the negative DC bus; the first bridge arm includes a third switch tube V3 and a fourth switch tube M4 connected in series, and the second bridge arm includes a fifth switch tube M5 and a sixth switch tube M6 connected in series; one end of the third switch tube M3 and one end of the fifth switch tube M5 are both connected to one end of the first switch tube M1, and one end of the fourth switch tube V4 and one end of the sixth switch tube M6 are both connected to the other end of the second switch tube M2.

[0113] Furthermore, the photovoltaic inverter 100 further includes a controller ( Fig.11 The controller is used to control the conduction or shutoff of each switch tube in the first H6 circuit 130 and the second H6 circuit 140. The controller may be a digital signal processing DSP chip or an MCU, and the MCU may also be called a single-chip microcomputer, which is not specifically limited in the present embodiment of the application.

[0114] The photovoltaic inverter 100 provided in the embodiment of the present application further includes a filter inductor, one end of which is connected to the opposite-name end of the first winding and the same-name end of the second winding, and the other end of which is connected to the opposite-name end of the third winding and the same-name end of the fourth winding.

[0115] In a possible embodiment, Fig.11As shown, the above-mentioned filter inductor includes a first inductor L1 and a second inductor L2. One end of the first inductor L1 is connected to the opposite-name end of the first winding and the same-name end of the second winding, and the other end of the first inductor L1 is used to output alternating current, one end of the second inductor L2 is connected to the opposite-name end of the third winding and the same-name end of the fourth winding, and the other end of the second inductor L2 is used to output alternating current.

[0116] Optionally, the photovoltaic inverter 100 further includes a capacitor C1, which is disposed between the first inductor L1 and the second inductor L2. The capacitor C1, the first inductor L1 and the second inductor L2 together constitute an LC filter circuit for filtering the alternating current output by the photovoltaic inverter 100 to improve the stability of the output voltage of the photovoltaic inverter 100.

[0117] The above describes another circuit topology of a photovoltaic inverter 100 provided in an embodiment of the present application. Fig.11 The circuit topology of the photovoltaic inverter 100 shown in FIG. Fig.12 , the wave generation method of the photovoltaic inverter 100 is introduced in detail.

[0118] like Fig.12 As shown, in the embodiment of the present application, the modulation wave of the photovoltaic inverter 100 is a sine wave m, and the carrier wave of the photovoltaic inverter 100 is a triangular wave. The controller can use a unipolar wave generation method to compare the modulation wave with the triangular carrier wave to generate a PWM signal. Fig.12 (a) and (b) in FIG. 1 respectively show the wave generation mode of the first H6 circuit 130 and the wave generation mode of the second H6 circuit 140. Fig.12 In the waveform diagram shown, the vertical axis represents voltage or level, the horizontal axis represents time, and Fig.12 The signal waveform shown is the signal waveform within 20 milliseconds.

[0119] The following first takes the first H6 circuit 130 as an example to introduce the wave generation method of the H6 circuit in detail.

[0120] In a possible implementation, in the positive half cycle of the modulation wave m of the photovoltaic inverter 100, the first switch tube V1, the second switch tube V2 and the lower bridge arm switch tube of the second bridge arm, i.e., the sixth switch tube V6, are turned on synchronously, the upper bridge arm switch tube of the second bridge arm, i.e., the fifth switch tube V5, is turned on complementarily with the first switch tube V1, the upper bridge arm switch tube of the first bridge arm, i.e., the third switch tube V3, is turned on, and the lower bridge arm switch tube of the first bridge arm, i.e., the fourth switch tube V4, is turned off; in the negative half cycle of the modulation wave m of the photovoltaic inverter 100, the first switch tube V1, the second switch tube V2 and the fourth switch tube V4 are turned on synchronously, the third switch tube V3 is turned on complementarily with the first switch tube V1, the fifth switch tube V5 is turned on, and the sixth switch tube V6 is turned off.

[0121] See also Fig.12 (a) in which, in the positive half cycle of the sine wave m, the triangular wave tri1-1 and the sine wave m generate the fifth PWM signal. Specifically, when the amplitude of the triangular wave tri1-1 is greater than the sine wave m, a low level signal is generated, and when the amplitude of the triangular wave tri1-1 is less than the sine wave m, a high level signal is generated. The fifth PWM signal is used to drive the first switch tube V1, the second switch tube V2 and the sixth switch tube V6 to be turned on synchronously, and to drive the fifth switch tube V5 and the first switch tube V1 to be turned on complementary, that is, when the amplitude of the triangular wave tri1-1 is greater than the sine wave m, the first switch tube V1, the second switch tube V2 and the sixth switch tube V6 are turned off at the same time, and the fifth switch tube V5 is turned on at the same time, and when the amplitude of the triangular wave tri1-1 is less than the sine wave m, the first switch tube V1, the second switch tube V2 and the sixth switch tube V6 are turned on at the same time, and the fifth switch tube V5 is turned off at the same time. The third switch tube V3 remains turned on during the positive half cycle of the sine wave m, and the fourth switch tube V4 remains turned off during the positive half cycle of the sine wave m.

[0122] In the negative half cycle of the sine wave m, the triangular wave tri1-2 and the sine wave m generate the sixth PWM signal. When the amplitude of the triangular wave tri1-2 is greater than the sine wave m, a high level signal is generated, and when the amplitude of the triangular wave tri1-2 is less than the sine wave m, a low level signal is generated. The sixth PWM signal is used to drive the first switch tube V1, the second switch tube V2 and the fourth switch tube V4 to be synchronously turned on, and drive the third switch tube V3 and the first switch tube V1 to be complementary turned on, that is, when the amplitude of the triangular wave tri1-2 is greater than the sine wave m, the first switch tube V1, the second switch tube V2 and the fourth switch tube V4 are turned on at the same time, and the third switch tube V3 is turned off at the same time. When the amplitude of the triangular wave tri1-2 is less than the sine wave m, the first switch tube V1, the second switch tube V2 and the sixth switch tube V6 are turned off at the same time, and the fifth switch tube V5 is turned on at the same time. The fifth switch tube V5 remains turned on during the negative half cycle of the sine wave m, and the sixth switch tube V6 remains turned off during the negative half cycle of the sine wave m.

[0123] In a possible implementation, the phases of the driving signal of the switch tube in the first H6 circuit 130 and the driving signal of the switch tube in the second H6 circuit 140 are different.

[0124] Optionally, the carrier phases of the first H6 circuit 130 and the second H6 circuit 140 differ by 90°, 120°, 150°, 170° or 180°. Since the phase of the PWM signal is related to the phase of the carrier, different carrier signals are provided to different HERIC circuits, so that different HERIC circuits can have control signals (i.e., PWM signals) with different phases. For example, when the first H6 circuit 130 drives the first switch tube V1 to turn on under the action of the fifth PWM signal, the PWM signal of the second H6 circuit 140 may drive the first switch tube M1 to turn on, or may drive the first switch tube M1 to turn off, which greatly reduces the synchronization requirements for each switch tube in the two H6 circuits.

[0125] Further, the phase difference between the driving signal of the switch tube in the first H6 circuit 130 and the driving signal of the switch tube in the second H6 circuit 140 is 180°. Exemplarily, the carrier phases of the first H6 circuit 130 and the second H6 circuit 140 are set to differ by 180°, so that the control signals of the first H6 circuit 130 and the second H6 circuit 140 differ by 180° in phase. In this way, under the action of the control signals with a phase difference of 180°, the first H6 circuit 130 and the second H6 circuit 140 can convert the 400V bus voltage Vbus into an AC with a maximum voltage of 311V, that is, after converting the 400V bus voltage Vbus into an AC with an effective value of 220V, it directly supplies power to the power grid 400 or the load 500.

[0126] like Fig.12 As shown in (b), in the positive half cycle of the sine wave m, the triangular wave tri2-1 and the sine wave m generate the seventh PWM signal. Specifically, when the amplitude of the triangular wave tri2-1 is greater than the sine wave m, a low level signal is generated, and when the amplitude of the triangular wave tri2-1 is less than the sine wave m, a high level signal is generated. The seventh PWM signal is used to drive the first switch tube M1, the second switch tube M2 and the sixth switch tube M6 to be synchronously turned on, and drive the fifth switch tube M5 and the first switch tube M1 to be complementary turned on, that is, when the amplitude of the triangular wave tri2-1 is greater than the sine wave m, the first switch tube M1, the second switch tube M2 and the sixth switch tube M6 are turned off at the same time, and the fifth switch tube M5 is turned on at the same time. When the amplitude of the triangular wave tri2-1 is less than the sine wave m, the first switch tube M1, the second switch tube M2 and the sixth switch tube M6 are turned on at the same time, and the fifth switch tube M5 is turned off at the same time. The third switch tube M3 remains turned on in the positive half cycle of the sine wave m, and the fourth switch tube V4 remains turned off in the positive half cycle of the sine wave m.

[0127] In the negative half cycle of the sine wave m, the triangular wave tri2-2 and the sine wave m generate an eighth PWM signal. When the amplitude of the triangular wave tri2-2 is greater than the sine wave m, a high level signal is generated, and when the amplitude of the triangular wave tri2-2 is less than the sine wave m, a low level signal is generated. The eighth PWM signal is used to drive the first switch tube M1, the second switch tube M2 and the fourth switch tube M4 to be synchronously turned on, and to drive the third switch tube M3 and the first switch tube M1 to be complementary turned on, that is, when the amplitude of the triangular wave tri2-2 is greater than the sine wave m, the first switch tube M1, the second switch tube M2 and the fourth switch tube M4 are turned on at the same time, and the third switch tube M3 is turned off at the same time. When the amplitude of the triangular wave tri2-2 is less than the sine wave m, the first switch tube M1, the second switch tube M2 and the fourth switch tube M4 are turned off at the same time, and the third switch tube M3 is turned on at the same time. The fifth switch tube M5 remains turned on in the negative half cycle of the sine wave m, and the sixth switch tube M6 remains turned off in the negative half cycle of the sine wave m.

[0128] When the phase difference between the driving signal of the switch tube in the first H6 circuit 130 and the driving signal of the switch tube in the second H6 circuit 140 is 180°, the change of the output voltage of the photovoltaic inverter 100 is similar to the change when the phase difference between the driving signal of the switch tube in the first HERCI circuit 110 and the second HERIC circuit 120 in the previous embodiment is 180°, which is not elaborated in the embodiment of the present application.

[0129] The present application also provides a control method for a photovoltaic inverter, which is applied to Figure 4 , Figure 8 , Fig. 9 or Fig.10 In the photovoltaic inverter 100 shown in . The input end of the photovoltaic inverter 100 is used to connect the photovoltaic array including the first HERIC circuit 110 and the second HERIC circuit 120. The input end of the photovoltaic inverter 100 is used to connect the photovoltaic array 200. The photovoltaic inverter 100 includes the first HERIC circuit and the second HERIC circuit, the first coupling inductor T1 and the second coupling inductor T2; the DC input of the first HERIC circuit 110 and the DC input of the second HERIC circuit 120 are connected in parallel and used to connect the DC bus; the first coupling inductor T1 includes a first winding and a second winding, the second coupling inductor T2 includes a third winding and a fourth winding, the AC output of the first HERIC circuit 110 is respectively connected to the same-name end of the first winding and the same-name end of the third winding, and the AC output of the second HERIC circuit 120 is respectively connected to the opposite-name end of the second winding and the opposite-name end of the fourth winding; the opposite-name end of the first winding and the same-name end of the second winding are short-circuited, and the opposite-name end of the third winding and the same-name end of the fourth winding are short-circuited for outputting AC power.

[0130] The control method includes: controlling the switch tube in the first HERIC circuit 110 to be turned on or off, and controlling the switch tube in the second HERIC circuit 120 to be turned on or off; wherein the driving signal of the switch tube in the first HERIC circuit 110 and the driving signal of the switch tube in the second HERIC circuit 120 have different phases.

[0131] Further, any HERIC circuit in the first HERIC circuit 110 or the second HERIC circuit 120 includes a first bridge arm, a second bridge arm and a third bridge arm. The first bridge arm and the second bridge arm are connected in parallel between the positive DC bus BUS+ and the negative DC bus BUS-, and the third bridge arm is connected between the midpoint of the first bridge arm and the midpoint of the second bridge arm.

[0132] Controlling the switch tube in the first HERIC circuit or the second HERIC circuit to turn on or off includes:

[0133] In the positive half cycle of the modulation wave of the photovoltaic inverter 100, the upper bridge arm switch tube of the first bridge arm and the lower bridge arm switch tube of the second bridge arm are synchronously turned on, the switch tube in the third bridge arm is complementary to the upper bridge arm switch tube of the first bridge arm, and the lower bridge arm switch tube of the first bridge arm and the upper bridge arm switch tube of the second bridge arm are turned off;

[0134] In the negative half cycle of the modulation wave of the photovoltaic inverter 100, the upper bridge arm switch tube of the first bridge arm and the lower bridge arm switch tube of the second bridge arm are turned off, the lower bridge arm switch tube of the first bridge arm and the upper bridge arm switch tube of the second bridge arm are turned on synchronously, and the switch tube in the third bridge arm is turned on complementarily with the lower bridge arm switch tube of the first bridge arm.

[0135] The present application also provides a control method for a photovoltaic inverter, which is applied to Fig.11 In the photovoltaic inverter 100 shown. The input end of the photovoltaic inverter 100 is used to connect the photovoltaic array 200, and the photovoltaic inverter 100 includes a first H6 circuit 130 and a second H6 circuit 140, a first coupling inductor T1 and a second coupling inductor T2; the DC input of the first H6 circuit 130 is connected in parallel with the DC input of the second H6 circuit 140, and is used to connect the DC bus. The first coupling inductor T1 includes a first winding and a second winding, and the second coupling inductor T2 includes a third winding and a fourth winding. The AC output of the first H6 circuit 130 is respectively connected to the same-name end of the first winding and the same-name end of the third winding, and the AC output of the second H6 circuit 140 is respectively connected to the opposite-name end of the second winding and the opposite-name end of the fourth winding; the opposite-name end of the first winding and the same-name end of the second winding are short-circuited, and the opposite-name end of the third winding and the same-name end of the fourth winding are short-circuited for outputting AC power.

[0136] The control method includes: controlling the switch tube in the first H6 circuit 130 to be turned on or off, and controlling the switch tube in the second H6 circuit 140 to be turned on or off; wherein the driving signal of the switch tube in the first H6 circuit 130 and the driving signal of the switch tube in the second H6 circuit 140 have different phases.

[0137] Furthermore, any H6 circuit in the first H6 circuit 130 or the second H6 circuit 140 includes a first bridge arm, a second bridge arm, and a first switch tube and a second switch tube; one end of the first bridge arm and one end of the second bridge arm are both connected to one end of the first switch tube, and the other end of the first switch tube is used to connect to the positive DC bus; the other end of the first bridge arm and the other end of the second bridge arm are both connected to one end of the second switch tube, and the other end of the second switch tube is used to connect to the negative DC bus.

[0138] Controlling the switch tube in the first H6 circuit 130 or the second H6 circuit 140 to be turned on or off includes:

[0139] In the positive half cycle of the modulation wave of the photovoltaic inverter 100, the first switch tube, the second switch tube and the lower bridge arm switch tube of the second bridge arm are controlled to be turned on synchronously, the upper bridge arm switch tube of the second bridge arm is controlled to be turned on complementary to the first switch tube, and the upper bridge arm switch tube of the first bridge arm is controlled to be turned on, and the lower bridge arm switch tube of the first bridge arm is turned off;

[0140] In the negative half cycle of the modulation wave of the photovoltaic inverter 100, the first switch tube, the second switch tube and the lower bridge arm switch tube of the first bridge arm are controlled to be turned on synchronously, the upper bridge arm switch tube of the first bridge arm and the first switch tube are controlled to be turned on complementarily, and the upper bridge arm switch tube of the second bridge arm is controlled to be turned on, and the lower bridge arm switch tube of the second bridge arm is turned off.

[0141] The above detailed description of the photovoltaic inverter and the analysis of the beneficial effects can be correspondingly referred to the control method of the photovoltaic inverter, and the embodiments of the present application will not be repeated here.

[0142] Finally, it should be noted that the above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A photovoltaic inverter, characterized in that: The input end of the photovoltaic inverter is used to connect to the photovoltaic array, and the photovoltaic inverter includes a first HERIC circuit and a second HERIC circuit, a first coupled inductor and a second coupled inductor; The DC input of the first HERIC circuit and the DC input of the second HERIC circuit are connected in parallel and are used to connect a DC bus; The first coupled inductor includes a first winding and a second winding, the second coupled inductor includes a third winding and a fourth winding, the AC output of the first HERIC circuit is respectively connected to the same-name end of the first winding and the same-name end of the third winding, and the AC output of the second HERIC circuit is respectively connected to the opposite-name end of the second winding and the opposite-name end of the fourth winding; The opposite-name end of the first winding and the same-name end of the second winding are short-circuited, and the opposite-name end of the third winding and the same-name end of the fourth winding are short-circuited for outputting alternating current.

2. The photovoltaic inverter according to claim 1, characterized in that: Any HERIC circuit of the first HERIC circuit or the second HERIC circuit comprises a first bridge arm, a second bridge arm and a third bridge arm; The first bridge arm and the second bridge arm are connected in parallel between the positive DC bus and the negative DC bus, and the third bridge arm is connected between the midpoint of the first bridge arm and the midpoint of the second bridge arm; The first bridge arm includes two switch tubes connected in series with the same freewheeling direction, the second bridge arm includes two switch tubes connected in series with the same freewheeling direction, and the third bridge arm includes two switch tubes with opposite freewheeling directions.

3. The photovoltaic inverter according to claim 2, characterized in that: Any of the HERIC circuits further includes a diode, an anode of the diode is connected to the midpoint of the third bridge arm, and a cathode of the diode is used to connect to the positive DC bus.

4. The photovoltaic inverter according to claim 2, characterized in that: Any of the HERIC circuits further comprises a first diode, a second diode and a fourth bridge arm; the fourth bridge arm is connected between the midpoint of the first bridge arm and the midpoint of the second bridge arm; The fourth bridge arm includes two switch tubes with opposite freewheeling directions, wherein the connection mode of the switch tubes in the fourth bridge arm is opposite to the connection mode of the switch tubes in the third bridge arm; The anode of the first diode is used to connect the midpoint of the positive and negative DC bus capacitors, the cathode of the first diode is connected to the midpoint of the third bridge arm, the anode of the second diode is connected to the midpoint of the fourth bridge arm, and the cathode of the second diode is used to connect the midpoint of the positive and negative DC bus capacitors.

5. The photovoltaic inverter according to any one of claims 2 to 4, characterized in that: In the positive half cycle of the modulation wave of the photovoltaic inverter, the upper bridge arm switch tube of the first bridge arm and the lower bridge arm switch tube of the second bridge arm are synchronously turned on, the switch tube in the third bridge arm is complementary to the upper bridge arm switch tube of the first bridge arm, and the lower bridge arm switch tube of the first bridge arm and the upper bridge arm switch tube of the second bridge arm are turned off; In the negative half cycle of the modulation wave of the photovoltaic inverter, the upper bridge arm switch tube of the first bridge arm and the lower bridge arm switch tube of the second bridge arm are turned off, the lower bridge arm switch tube of the first bridge arm and the upper bridge arm switch tube of the second bridge arm are turned on synchronously, and the switch tube in the third bridge arm is turned on complementarily with the lower bridge arm switch tube of the first bridge arm.

6. The photovoltaic inverter according to any one of claims 2 to 5, characterized in that: The photovoltaic inverter further includes a filter inductor, one end of which is connected to the opposite-name end of the first winding and the same-name end of the second winding, and the other end of which is connected to the opposite-name end of the third winding and the same-name end of the fourth winding.

7. The photovoltaic inverter according to any one of claims 2 to 6, characterized in that: The phases of the driving signal of the switch tube in the first HERIC circuit and the driving signal of the switch tube in the second HERIC circuit are different.

8. The photovoltaic inverter according to any one of claims 2 to 7, characterized in that: The phase difference between the driving signal of the switch tube in the first HERIC circuit and the driving signal of the switch tube in the second HERIC circuit is 180°.

9. A photovoltaic inverter, characterized in that: The input end of the photovoltaic inverter is used to connect to the photovoltaic array, and the photovoltaic inverter includes a first H6 circuit and a second H6 circuit, a first coupled inductor and a second coupled inductor; The DC input of the first H6 circuit and the DC input of the second H6 circuit are connected in parallel and are used to connect a DC bus; The first coupled inductor includes a first winding and a second winding, the second coupled inductor includes a third winding and a fourth winding, the AC output of the first H6 circuit is respectively connected to the same-name end of the first winding and the same-name end of the third winding, and the AC output of the second H6 circuit is respectively connected to the opposite-name end of the second winding and the opposite-name end of the fourth winding; The opposite-name end of the first winding and the same-name end of the second winding are short-circuited, and the opposite-name end of the third winding and the same-name end of the fourth winding are short-circuited for outputting alternating current.

10. The photovoltaic inverter according to claim 9, characterized in that: Any H6 circuit of the first H6 circuit or the second H6 circuit includes a first bridge arm, a second bridge arm, and a first switch tube and a second switch tube; one end of the first bridge arm and one end of the second bridge arm are both connected to one end of the first switch tube, and the other end of the first switch tube is used to connect to a positive DC bus; the other end of the first bridge arm and the other end of the second bridge arm are both connected to one end of the second switch tube, and the other end of the second switch tube is used to connect to a negative DC bus; The first bridge arm includes two switch tubes connected in series with the same freewheeling direction, and the second bridge arm includes two switch tubes connected in series with the same freewheeling direction.

11. The photovoltaic inverter according to claim 10, characterized in that: In the positive half cycle of the modulation wave of the photovoltaic inverter, the first switch tube, the second switch tube and the lower bridge arm switch tube of the second bridge arm are synchronously turned on, the upper bridge arm switch tube of the second bridge arm is complementary to the first switch tube, the upper bridge arm switch tube of the first bridge arm is turned on, and the lower bridge arm switch tube of the first bridge arm is turned off; In the negative half cycle of the modulation wave of the photovoltaic inverter, the first switch tube, the second switch tube and the lower bridge arm switch tube of the first bridge arm are synchronously turned on, the upper bridge arm switch tube of the first bridge arm is complementarily turned on with the first switch tube, the upper bridge arm switch tube of the second bridge arm is turned on, and the lower bridge arm switch tube of the second bridge arm is turned off.

12. The photovoltaic inverter according to claim 10 or 11, characterized in that: The photovoltaic inverter further includes a filter inductor, one end of which is connected to the opposite-name end of the first winding and the same-name end of the second winding, and the other end of which is connected to the opposite-name end of the third winding and the same-name end of the fourth winding.

13. A control method for a photovoltaic inverter, characterized in that: Applied to a photovoltaic inverter, the input end of the photovoltaic inverter is used to connect to a photovoltaic array, and the photovoltaic inverter includes a first HERIC circuit and a second HERIC circuit, a first coupled inductor and a second coupled inductor; The DC input of the first HERIC circuit and the DC input of the second HERIC circuit are connected in parallel and are used to connect a DC bus; The first coupled inductor includes a first winding and a second winding, the second coupled inductor includes a third winding and a fourth winding, the AC output of the first HERIC circuit is respectively connected to the same-name end of the first winding and the same-name end of the third winding, and the AC output of the second HERIC circuit is respectively connected to the opposite-name end of the second winding and the opposite-name end of the fourth winding; The opposite-name end of the first winding and the same-name end of the second winding are short-circuited, and the opposite-name end of the third winding and the same-name end of the fourth winding are short-circuited, for outputting alternating current; The method comprises: Control the switch tube in the first HERIC circuit to be turned on or off, and control the switch tube in the second HERIC circuit to be turned on or off; wherein the driving signal of the switch tube in the first HERIC circuit and the driving signal of the switch tube in the second HERIC circuit have different phases.

14. The method according to claim 13, characterized in that Either the first HERIC circuit or the second HERIC circuit comprises a first bridge arm, a second bridge arm and a third bridge arm; the first bridge arm and the second bridge arm are connected in parallel between a positive DC bus and a negative DC bus, and the third bridge arm is connected between a midpoint of the first bridge arm and a midpoint of the second bridge arm; Controlling the switch tube in the first HERIC circuit or the second HERIC circuit to be turned on or off includes: In the positive half cycle of the modulation wave of the photovoltaic inverter, the upper bridge arm switch tube of the first bridge arm and the lower bridge arm switch tube of the second bridge arm are controlled to be synchronously turned on, the switch tube in the third bridge arm is controlled to be complementary to the upper bridge arm switch tube of the first bridge arm, and the lower bridge arm switch tube of the first bridge arm and the upper bridge arm switch tube of the second bridge arm are controlled to be turned off; In the negative half cycle of the modulation wave of the photovoltaic inverter, the upper bridge arm switch tube of the first bridge arm and the lower bridge arm switch tube of the second bridge arm are controlled to be turned off, the lower bridge arm switch tube of the first bridge arm and the upper bridge arm switch tube of the second bridge arm are controlled to be turned on synchronously, and the switch tube in the third bridge arm and the lower bridge arm switch tube of the first bridge arm are controlled to be turned on complementarily.

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