Circuit topology of inverter, inverter and control method therefor, and photovoltaic power generation system

Abstract

A circuit topology of an inverter, an inverter and a control method therefor, and a photovoltaic power generation system. The circuit topology comprises: at least one DC-DC conversion circuit, which converts an input voltage thereof into a direct-current low voltage and outputs the direct-current low voltage to a low-voltage direct-current bus; and a DC-AC conversion circuit, a direct-current side of which is connected to the at least one DC-DC conversion circuit by means of the low-voltage direct-current bus, wherein the DC-AC conversion circuit is used for inverting the voltage of the low-voltage direct-current bus into an alternating-current output voltage.

Description

Inverter circuit topology, inverter and control method thereof, photovoltaic power generation system

[0001] Related applications

[0002] This application claims priority to Chinese patent application number 202311708290.0, filed on December 12, 2023, entitled “Circuit topology of inverter, inverter and control method thereof, photovoltaic power generation system,” the entire text of which is hereby incorporated by reference. Technical Field

[0003] The present application relates to the field of photovoltaic power generation, and in particular to a circuit topology of an inverter, an inverter and a control method thereof, and a photovoltaic power generation system. Background Art

[0004] Single-stage micro-PV inverters typically use a high-step-up ratio DC-AC converter circuit. However, due to the wide range of PV module output voltage variations, single-stage high-step-up ratio DC-AC converter circuits struggle to maintain high efficiency across this wide voltage range. Typically, when the PV module output voltage is low, the circuit gain is high, leading to a significant drop in system efficiency. A two-stage micro-PV inverter utilizes the voltage regulation function of the front-stage DC-DC converter circuit to enable the rear-stage DC-AC converter circuit to operate within a narrower input voltage range, thereby improving the overall efficiency of the DC-AC converter circuit.

[0005] Traditional two-stage micro-PV inverters typically utilize a high-step-up ratio DC-DC converter circuit in series with a PWM bridge-type step-down DC-AC converter circuit. The DC-DC converter circuit first converts the low-voltage DC power from the individual PV modules connected to its input to a high-voltage DC bus. This step-up voltage is significant. For single-phase micro-PV inverters, the voltage of this high-voltage DC bus is typically above 350V, exceeding the 220V single-phase grid voltage. The subsequent circuitry utilizes a PWM bridge-type step-down DC-AC inverter circuit for grid connection. This high-voltage DC bus solution requires high-voltage power switching devices in both the DC / DC converter and the DC-AC converter circuit, increasing device costs. Furthermore, the PWM bridge inverter circuit exhibits high switching losses under hard-switching conditions, and the switching frequency is generally designed to be low, which hinders system power density. Summary of the Invention

[0006] According to various embodiments of the present application, a circuit topology of an inverter, an inverter and a control method thereof, and a photovoltaic power generation system are provided.

[0007] In a first aspect, an embodiment of the present application provides a circuit topology of an inverter, the circuit topology comprising:

[0008] At least one DC-DC conversion circuit, which converts its input voltage into a DC low voltage and outputs it to a low-voltage DC bus;

[0009] The DC-AC conversion circuit has a DC side connected to the at least one DC-DC conversion circuit through the low-voltage DC bus, and is used to invert the voltage of the low-voltage DC bus into an AC output voltage.

[0010] In some embodiments, the DC-AC conversion circuit is a buck-boost conversion circuit, and the voltage of the low-voltage DC bus is less than the peak value of the AC output voltage.

[0011] In some embodiments, the DC-DC conversion circuit is a Boost circuit or a Buck-Boost circuit.

[0012] In some embodiments, the DC-AC conversion circuit includes:

[0013] an inverter unit, configured to invert the voltage of the low-voltage DC bus into a high-frequency AC voltage;

[0014] a transformer, connected to the inverter unit, for boosting the high-frequency AC voltage;

[0015] a resonant unit, connected to the transformer, for implementing soft switching of the DC-AC conversion circuit;

[0016] The frequency conversion unit is connected to the resonance unit and is used to perform AC-AC conversion on the boosted high-frequency AC voltage to obtain the low-frequency AC output voltage.

[0017] In some embodiments, the DC-AC conversion circuit further includes:

[0018] The filtering unit is connected to the cyclic conversion unit and is used to filter the output current of the cyclic conversion unit.

[0019] In some embodiments, the cycloconversion unit is a three-phase cycloconversion topology or a single-phase cycloconversion topology.

[0020] In some embodiments, the cyclotron conversion unit is a half-bridge cyclotron conversion topology or a full-bridge cyclotron conversion topology.

[0021] In some embodiments, the DC-AC conversion circuit includes:

[0022] a flyback conversion unit, configured to boost the voltage of the low-voltage DC bus and convert it into a pulsating DC high voltage;

[0023] The flip unit is used to shape the pulsating DC high voltage half-wave into the AC output voltage.

[0024] In some embodiments, the circuit topology includes a plurality of DC-DC conversion circuits, and output ends of the plurality of DC-DC conversion circuits are connected in parallel to the low-voltage DC bus.

[0025] In a second aspect, an embodiment of the present application proposes an inverter, comprising a circuit topology and a controller as described in the first aspect, wherein the controller is used to control a DC-DC conversion circuit to convert its input voltage into a DC low voltage and output it to a low-voltage DC bus, and to control a DC-AC conversion circuit to invert the voltage of the low-voltage DC bus into an AC output voltage.

[0026] In some embodiments, the DC-AC conversion circuit is a buck-boost conversion circuit, and the controller is used to control the voltage of the low-voltage DC bus to be less than the peak value of the AC output voltage.

[0027] In some embodiments, the inverter further includes:

[0028] The energy storage port is connected to the low-voltage DC bus and is used to access the energy storage battery.

[0029] In a third aspect, an embodiment of the present application provides a method for controlling an inverter, which is used for the inverter according to the second aspect. The method includes:

[0030] Control the DC-DC conversion circuit to convert its input voltage into a DC low voltage and output it to the low voltage DC bus;

[0031] The DC-AC conversion circuit is controlled to invert the voltage of the low-voltage DC bus into an AC output voltage.

[0032] In a fourth aspect, an embodiment of the present application proposes a photovoltaic power generation system, comprising at least one photovoltaic DC power supply and at least one inverter as described in the second aspect, wherein the inverter is correspondingly connected to the at least one photovoltaic DC power supply.

[0033] The details of one or more embodiments of the present application are set forth in the following drawings and description to make other features, objects, and advantages of the present application more readily apparent. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the following briefly introduces the drawings required for use in the embodiments or related technical descriptions. Obviously, the drawings described below are merely embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the disclosed drawings without any creative work.

[0035] FIG1 is a schematic structural diagram of a circuit topology of an inverter in some embodiments provided in this application.

[0036] FIG2 is a schematic structural diagram of a DC-AC conversion circuit in some embodiments provided in this application.

[0037] FIG3 is a schematic diagram of a circuit topology of an inverter in a first exemplary embodiment provided by the present application.

[0038] FIG4 is a schematic diagram of a circuit topology of an inverter in a second exemplary embodiment provided by the present application.

[0039] FIG5 is a schematic diagram of a circuit topology of an inverter in a third exemplary embodiment provided by the present application.

[0040] FIG6 is a schematic diagram of a circuit topology of an inverter in a fourth exemplary embodiment provided by the present application.

[0041] FIG7 is a schematic structural diagram of a DC-AC conversion circuit in some other embodiments provided by the present application.

[0042] FIG8 is a schematic diagram of a circuit topology of an inverter in a fifth exemplary embodiment provided by the present application.

[0043] FIG9 is a schematic diagram of a circuit topology of an inverter in a sixth exemplary embodiment provided by the present application.

[0044] FIG10 is a schematic diagram of a DC-DC conversion circuit in some embodiments provided in the present application.

[0045] FIG11 is a schematic structural diagram of an inverter in some embodiments provided in this application.

[0046] FIG12 is a flow chart of a method for controlling an inverter in some embodiments provided in this application.

[0047] FIG13 is a schematic structural diagram of a photovoltaic power generation system in some embodiments provided in this application. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solutions and advantages of the present application clearer, the present application is described and illustrated below in conjunction with the accompanying drawings and examples. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. Based on the embodiments provided in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application. In addition, it can also be understood that although the efforts made in this development process may be complex and lengthy, for ordinary technicians in the field related to the contents disclosed in the present application, some changes in design, manufacturing or production based on the technical contents disclosed in the present application are only conventional technical means and should not be understood as the contents disclosed in the present application are insufficient.

[0049] References to "embodiments" in this application mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it refer to independent or alternative embodiments that are mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described in this application may be combined with other embodiments unless there is a conflict.

[0050] Unless otherwise defined, the technical or scientific terms used in this application should have the ordinary meaning understood by a person of ordinary skill in the technical field to which this application belongs. The words "one", "a", "the" and the like used in this application do not indicate a limit on quantity and may indicate the singular or plural. The terms "include", "comprise", "have" and any variations thereof used in this application are intended to cover non-exclusive inclusions; for example, a process, method, system, product or device that includes a series of steps or modules (units) is not limited to the listed steps or units, but may also include steps or units that are not listed, or may also include other steps or units that are inherent to these processes, methods, products or devices. The words "connect", "connected", "coupled" and the like used in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The word "multiple" used in this application means greater than or equal to two. "And / or" describes the association relationship of associated objects, indicating that three relationships can exist. For example, "A and / or B" can mean: A exists alone, A and B exist at the same time, and B exists alone. The terms "first", "second", "third" and the like involved in this application are merely used to distinguish similar objects and do not represent a specific ordering of the objects.

[0051] As shown in FIG1 , the embodiment of the present application proposes a circuit topology of an inverter, the circuit topology comprising: at least one DC-DC conversion circuit 100, the DC-DC conversion circuit 100 is used to convert its input voltage V in Converts the voltage V of the low voltage DC bus to a DC-AC converter circuit 200, which is connected to the at least one DC-DC converter circuit 100 via the low voltage DC bus. bus Inverted into AC output voltage V g .

[0052] Low voltage DC bus voltage V bus It is equal to the DC low voltage output by the DC-DC conversion circuit 100 .

[0053] In this embodiment, since the voltage V busBecause the voltage is low, all power switching devices in the front-stage DC-DC converter circuit 100 and the power switching devices on the DC side of the rear-stage DC-AC converter circuit 200 can use low-voltage power switching devices, which has better switching performance. At the same time, the input voltage fluctuation range of the high-gain rear-stage DC-AC converter circuit 200 is smaller, which is conducive to the optimized design of the circuit and allows the DC-AC converter circuit 200 to operate at a more efficient operating condition. At the same time, compared with the single-stage topology, the operating range of the low-voltage DC bus voltage in the two-stage topology is smaller, which can also reduce the capacity of the bus capacitor on the low-voltage DC bus.

[0054] In some embodiments, the DC-AC conversion circuit 200 is a buck-boost conversion circuit, and the voltage V bus Less than the AC output voltage V g peak value.

[0055] Specifically, when the DC-AC conversion circuit 200 outputs three-phase power, the AC output voltage V g The peak value refers to the peak value of the line voltage between any two phases;

[0056] When the DC-AC conversion circuit 200 outputs single-phase power, the AC output voltage V g The peak value refers to the peak value of the phase voltage.

[0057] In some embodiments, the DC-DC converter circuit 100 is a Boost circuit or a Buck-Boost circuit.

[0058] In one embodiment, the circuit topology of the inverter can operate bidirectionally, operating in an inversion or rectification state.

[0059] In some specific embodiments, as shown in FIG2 , the DC-AC conversion circuit 200 includes: an inverter unit 201 for converting the voltage V of the low-voltage DC bus to bus The inverter 201 is connected to the inverter unit 201 and is used to boost the high-frequency AC voltage. The resonant unit 203 is connected to the transformer 202 and is used to implement the soft switching of the DC-AC conversion circuit 200. The frequency conversion unit 204 is connected to the resonant unit 203 and is used to perform AC-AC conversion on the boosted high-frequency AC voltage to obtain a low-frequency AC output voltage V g .

[0060] The low frequency here is generally the grid frequency or the industrial frequency. The inverter unit 201 can be implemented by an inverter circuit, the resonant unit 203 can be implemented by a resonant circuit composed of a resonant inductor, etc., and the frequency conversion unit 204 can be implemented by a frequency conversion circuit composed of reversely connected switching tubes, etc.

[0061] In a further embodiment, the DC-AC conversion circuit 200 further includes: a filtering unit 205 connected to the frequency conversion unit 204 and configured to filter the output current of the frequency conversion unit 204 .

[0062] The cycloconversion unit 204 may be a three-phase cycloconversion topology or a single-phase cycloconversion topology, a half-bridge cycloconversion topology or a full-bridge cycloconversion topology.

[0063] The input end of the DC-DC conversion circuit 100 can be connected to a photovoltaic DC power supply, but is not limited thereto, wherein the photovoltaic DC power supply is, for example, a single photovoltaic module, a single photovoltaic cell substring, multiple photovoltaic modules connected in series and / or parallel, and multiple photovoltaic cell substrings connected in series and / or parallel.

[0064] During normal operation, the front-stage DC-DC conversion circuit 100 can be used to implement the maximum power point tracking (MPPT) of the photovoltaic DC power supply, and the rear-stage DC-AC conversion circuit 200 can be used to adjust the voltage V bus control.

[0065] To ensure the safety of the power devices of the DC-DC converter circuit 100 , the DC low voltage output by the DC-DC converter circuit 100 must be lower than the withstand voltage of the power devices of the DC-DC converter circuit 100 and maintain a certain margin.

[0066] FIG3 is a schematic diagram of the circuit topology of the inverter in the first exemplary embodiment. The circuit topology of the inverter is a single-phase topology, providing a single-phase AC output voltage V g The circuit topology includes a DC-DC conversion circuit 100 using a synchronous Boost circuit and a DC-AC conversion circuit 200 using a boostable resonant cycloconversion circuit.

[0067] The DC-DC converter circuit 100 is a synchronous Boost circuit, including a switch tube Q b1 , Q b2 , input capacitor C in1 and inductor L b1 .

[0068] The DC-AC conversion circuit 200 includes an inverter unit 201, a transformer 202, a resonant unit 203, a frequency conversion unit 204 and a filter unit 205. The inverter unit 201 includes a switch tube Q 1H , Q 1L , Q 2H , Q 2L The H bridge and DC bus capacitor C busThe primary side of the transformer 202 is connected to the midpoint of the two bridge arms of the inverter unit 201, and the secondary side is connected to the resonance unit 203 and the frequency conversion unit 204. The resonance unit 203 includes an inductor L connected in series. r and capacitor C r The frequency conversion unit 204 includes a single-phase half-bridge frequency conversion circuit composed of switch tubes Q3, Q4, Q5, and Q6. The filter unit 205 is connected to the output end of the frequency conversion unit 204 and includes an inductor L f and capacitor C f The filter circuit is composed of a filter unit 205, which outputs an AC output voltage V g to the grid or load.

[0069] In some embodiments, the resonant unit 203 may be in the form of a single inductor, a single capacitor, a CLLC structure, etc. The resonant unit 203 may also be disposed on the primary side of the transformer 202 .

[0070] In some embodiments, the DC-DC converter circuit 100 may also use a non-synchronous Boost, that is, the switch tube Q b1 Replace with a diode.

[0071] In some embodiments, the inverter unit 201 may also adopt a half-bridge circuit.

[0072] In this embodiment, on the one hand, the DC-DC conversion circuit 100 adopts a synchronous Boost circuit to reduce the diode conduction loss and improve efficiency. On the other hand, since the DC-AC conversion circuit 200 adopts a boostable resonant cycloconversion circuit, the voltage V bus The control range is more flexible. The output voltage of a single photovoltaic DC power supply is usually within 60V. For example, the voltage of the low-voltage DC bus V bus Controlled within 60V, both the front-stage DC-DC converter circuit 100 and the rear-stage DC-AC converter circuit 200 can utilize 60V withstand voltage components, resulting in improved switching performance. Furthermore, the rear-stage DC-AC converter circuit 200 operates within a narrower input voltage range, eliminating the need to consider the significant increase in operating current when the input voltage is low. This facilitates the optimized design of the DC-AC converter circuit, improving its operating efficiency and supporting a wider input voltage range provided by the photovoltaic DC power supply (and allowing for a lower lower limit of the input voltage during normal operation).

[0073] FIG4 is a schematic diagram of the inverter circuit topology in the second exemplary embodiment. This circuit topology includes a DC-DC converter circuit 100 employing a synchronous boost circuit and a DC-AC converter circuit 200 employing a boostable resonant cycloconverter circuit. The difference from the first exemplary embodiment is that the cycloconverter unit 204 in the second exemplary embodiment adopts a full-bridge cycloconverter topology, including a single-phase full-bridge cycloconverter circuit composed of switches Q3, Q4, Q5, Q6, Q7, Q8, Q9, and Q10.

[0074] In some other embodiments, the switch tubes Q5 and Q6 can be replaced by a capacitor respectively, and the switch tubes Q9 and Q10 can also be replaced by a capacitor respectively. In this case, the capacitor C in the resonant unit 203 r Can be omitted.

[0075] FIG5 is a schematic diagram of the circuit topology of the inverter in the third exemplary embodiment. The circuit topology includes a DC-DC conversion circuit 100 using a synchronous boost circuit and a DC-AC conversion circuit 200 using a boostable resonant cycloconverter circuit. The difference from the first exemplary embodiment is that the circuit topology of the inverter in the third exemplary embodiment is a three-phase circuit topology, providing a three-phase AC output voltage V ga 、V gb 、V gc The cycloconversion unit 204 is a three-phase cycloconversion topology, including a three-phase half-bridge cycloconversion circuit composed of switch tubes Q3, Q4, Q5, Q6, Q7, Q8, capacitors C17, C18, and C19. Correspondingly, the filtering unit 205 includes three filtering circuits, which output AC output voltage V ga 、V gb 、V gc The first corresponding filter circuit consists of capacitor C fa and inductor L fa The second corresponding filter circuit is composed of capacitor C fb and inductor L fb The third corresponding filter circuit is composed of capacitor C fc and inductor L fc constitute.

[0076] FIG6 is a schematic diagram of the inverter circuit topology in a fourth exemplary embodiment. This circuit topology includes multiple DC-DC converter circuits 100 using synchronous boost circuits and a DC-AC converter circuit 200 using a boostable resonant cycloconverter circuit. The fourth exemplary embodiment differs from the first exemplary embodiment in that the circuit topology includes multiple DC-DC converter circuits 100, the output ends of which are connected in parallel to a DC bus, and the input ends of each DC-DC converter circuit 100 can be connected to a corresponding photovoltaic DC power source.

[0077] In this embodiment, by adopting multiple DC-DC conversion circuits 100, power capacity can be expanded to adapt to application scenarios with multiple DC inputs.

[0078] In other embodiments, specifically, as shown in FIG7 , the DC-AC conversion circuit 200 includes: a flyback conversion unit 206 for converting the voltage V bus The voltage is boosted and converted into a pulsating DC high voltage; the flip unit 207 is used to half-wave shape the pulsating DC high voltage into the AC output voltage Vg.

[0079] In a further embodiment, the DC-AC conversion circuit 200 further includes a filtering unit 205 connected to the output end of the flipping unit 207 .

[0080] In this embodiment, the subsequent stage adopts a buck-boost DC-AC conversion circuit 200 comprising a flyback conversion unit 206 and a flip unit 207 , which has a simple circuit structure and fewer power devices.

[0081] FIG8 is a schematic diagram of the circuit topology of the inverter in the fifth exemplary embodiment. The circuit topology includes a DC-DC converter circuit 100 using a synchronous Boost circuit and a buck-boost DC-AC converter circuit 200 using a flyback converter unit 206 and a flip-flop unit 207. The difference from the first exemplary embodiment is that the DC-AC converter circuit 200 in the fifth exemplary embodiment includes a flyback converter unit 206, a flip-flop unit 207, and a filter unit 205. The flyback converter unit 206 includes a switch tube Q11, a transformer T1, a diode D1, a DC bus capacitor C bus The flip unit 207 includes an H-bridge flip circuit composed of switch tubes Q12, Q13, Q14, and Q15.

[0082] Figure 9 is a circuit topology diagram of the inverter in the sixth exemplary embodiment. This circuit topology includes multiple DC-DC converter circuits 100 using synchronous boost circuits and a buck-boost DC-AC converter circuit 200 using a flyback converter unit 206 and a flip-flop unit 207. The difference from the fifth exemplary embodiment is that the circuit topology of the sixth exemplary embodiment includes multiple DC-DC converter circuits 100, the output terminals of which are connected in parallel to the DC bus, and the input terminals of each DC-DC converter circuit 100 can be connected to a corresponding photovoltaic DC power source.

[0083] In some embodiments, the DC-DC converter circuit 100 may also use a Buck-Boost circuit. As shown in FIG10 , the Buck-Boost circuit includes an input capacitor C in1 , switch tube Qb3 , Q b4 , Q b5 , Q b6 and inductor L b1 The DC-DC conversion circuit 100 can operate in both a boost mode and a buck mode. When the output voltage of the DC-DC conversion circuit 100 is greater than the input voltage, it operates in the boost mode. When the input voltage of the DC-DC conversion circuit 100 is greater than the output voltage, it operates in the buck mode.

[0084] It should be noted that the DC-DC conversion circuit 100 may also adopt other forms of Buck-Boost circuits.

[0085] It should be noted that the Boost circuits in the above exemplary embodiments can be replaced by Buck-Boost circuits.

[0086] In the second aspect, the embodiment of the present application proposes an inverter, as shown in FIG11, including the circuit topology and the controller 300 as described in the above embodiment, wherein the controller 300 is used to control the DC-DC conversion circuit 100 to input the voltage V in Converts it into a DC low voltage and outputs it to the low voltage DC bus, and controls the DC-AC conversion circuit 200 to convert the voltage V bus Inverted into AC output voltage V g .

[0087] The inverter may be a micro inverter that takes a single photovoltaic DC power source as input.

[0088] In addition, due to the presence of the DC bus, the inverter is also suitable for multi-input application scenarios, such as a micro-inverter with multiple photovoltaic DC power sources as inputs, or a hybrid inverter that includes a photovoltaic DC power source and an energy storage battery as inputs.

[0089] Specifically, when the inverter is a micro-inverter with multiple input ports and multiple photovoltaic DC power supplies as inputs, the inverter includes multiple DC-DC conversion circuits whose output ends are connected in parallel to the DC bus, and the input ends of each DC-DC conversion circuit are respectively connected to the corresponding photovoltaic DC power supply.

[0090] The controller 300 can be any one of a microcontroller unit (MCU), a central processing unit (CPU), a field programmable gate array (FPGA), and a digital signal processor (DSP). Of course, the specific form of the controller is not limited to the above examples.

[0091] In some embodiments, the DC-AC conversion circuit is a buck-boost conversion circuit, and the controller controls the voltage of the low-voltage DC bus to be less than the peak value of the AC output voltage.

[0092] In some embodiments, the inverter further includes: an energy storage port connected to the low-voltage DC bus for accessing an energy storage battery.

[0093] The energy storage battery can be charged and discharged. Furthermore, the energy storage battery can be a low-voltage battery, and its operating voltage is, for example, less than 60V.

[0094] When the input voltage of the DC-DC conversion circuit 100 is greater than the operating voltage of the energy storage battery, the DC-DC conversion circuit 100 operates in a step-down mode; when the input voltage of the DC-DC conversion circuit 100 is less than the operating voltage of the energy storage battery, the DC-DC conversion circuit 100 operates in a step-up mode.

[0095] Since the processing and functions implemented by the inverter in the above embodiment correspond to the embodiments, principles and examples of the above circuit topology, for any details not fully described in this embodiment, reference can be made to the relevant descriptions in the above embodiment and no further elaboration will be given here.

[0096] Based on the above inverter, an embodiment of the present application further proposes a method for controlling the inverter, as shown in FIG12 . The method includes:

[0097] S102: Control the DC-DC conversion circuit to convert its input voltage into a DC low voltage and output it to the low-voltage DC bus;

[0098] S104: Control the DC-AC conversion circuit to invert the voltage of the low-voltage DC bus into an AC output voltage.

[0099] In some embodiments, the voltage of the low-voltage DC bus is controlled to be less than the peak value of the AC output voltage.

[0100] Since the processing and functions implemented by the control method of the above embodiment correspond to the embodiments, principles and examples of the above circuit topology, for any details not fully described in the description of this embodiment, please refer to the relevant descriptions in the above embodiment and will not be repeated here.

[0101] Based on the above-mentioned inverter, an embodiment of the present application further proposes a photovoltaic power generation system, as shown in FIG13 , comprising at least one photovoltaic DC power source PV and at least one inverter, wherein the inverter is correspondingly connected to at least one photovoltaic DC power source PV.

[0102] The photovoltaic DC power supply is a single photovoltaic module, a single photovoltaic cell substring, multiple photovoltaic modules connected in series and / or in parallel, or multiple photovoltaic cell substrings connected in series and / or in parallel.

[0103] In some embodiments, the photovoltaic power generation system further includes a junction device connected to at least one of the inverters. The junction device is, for example, a junction box or other device having a junction function.

[0104] Since the processing and functions implemented by the photovoltaic power generation system in the above embodiment correspond to the embodiments, principles and examples of the above circuit topology, for any details not fully described in this embodiment, please refer to the relevant descriptions in the above embodiment and will not be repeated here.

[0105] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0106] The above embodiments merely illustrate several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A circuit topology of an inverter, characterized in that: The circuit topology includes: At least one DC-DC conversion circuit, which converts its input voltage into a DC low voltage and outputs it to a low voltage DC bus; The DC-AC conversion circuit has a DC side connected to the at least one DC-DC conversion circuit through the low-voltage DC bus, and is used to invert the voltage of the low-voltage DC bus into an AC output voltage.

2. The circuit topology of the inverter according to claim 1, wherein: The DC-AC conversion circuit is a buck-boost conversion circuit, and the voltage of the low-voltage DC bus is less than the peak value of the AC output voltage.

3. The circuit topology of the inverter according to claim 1, wherein: The DC-DC conversion circuit is a Boost circuit or a Buck-Boost circuit.

4. The circuit topology of the inverter according to claim 1, wherein: The DC-AC conversion circuit comprises: An inverter unit, used for inverting the voltage of the low-voltage DC bus into a high-frequency AC voltage; A transformer, connected to the inverter unit, for boosting the high-frequency AC voltage; A resonance unit, connected to the transformer, for realizing soft switching of the DC-AC conversion circuit; The frequency conversion unit is connected to the resonance unit and is used for performing AC-AC conversion on the boosted high-frequency AC voltage to obtain the low-frequency AC output voltage.

5. The circuit topology of the inverter according to claim 4, wherein: The DC-AC conversion circuit also includes: The filter unit is connected to the frequency conversion unit and is used to filter the output current of the frequency conversion unit.

6. The circuit topology of the inverter according to claim 4, wherein: The cycloconversion unit is a three-phase cycloconversion topology or a single-phase cycloconversion topology.

7. The circuit topology of the inverter according to claim 4, wherein: The cyclotron conversion unit is a half-bridge cyclotron conversion topology or a full-bridge cyclotron conversion topology.

8. The circuit topology of the inverter according to claim 1, wherein: The DC-AC conversion circuit comprises: A flyback conversion unit, used for boosting the voltage of the low-voltage DC bus and converting it into a pulsating DC high voltage; The flip unit is connected to the flyback conversion unit and is used for half-wave shaping the pulsating DC high voltage into the AC output voltage.

9. The circuit topology of the inverter according to any one of claims 1 to 8, wherein: The circuit topology includes a plurality of DC-DC conversion circuits, and output ends of the plurality of DC-DC conversion circuits are connected in parallel to the low-voltage DC bus.

10. An inverter, characterized in that: It includes a circuit topology and a controller as described in any one of claims 1 to 9, wherein the controller is used to control a DC-DC conversion circuit to convert its input voltage into a DC low voltage and output it to a low-voltage DC bus, and to control a DC-AC conversion circuit to invert the voltage of the low-voltage DC bus into an AC output voltage.

11. The inverter according to claim 10, wherein: The DC-AC conversion circuit is a buck-boost conversion circuit, and the controller controls the voltage of the low-voltage DC bus to be less than the peak value of the AC output voltage.

12. The inverter according to claim 10, wherein: The inverter further comprises: The energy storage port is connected to the low-voltage DC bus and is used to access the energy storage battery.

13. A control method for an inverter, used for the inverter according to any one of claims 10 to 12, characterized in that: The method comprises: Control the DC-DC conversion circuit to convert its input voltage into a DC low voltage and output it to a low voltage DC bus; The DC-AC conversion circuit is controlled to invert the voltage of the low-voltage DC bus into an AC output voltage.

14. A photovoltaic power generation system, characterized in that: It comprises at least one photovoltaic DC power source and at least one inverter according to any one of claims 10 to 12, wherein the inverter is correspondingly connected to the at least one photovoltaic DC power source.

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