Power conversion device, control method and power supply system

Abstract

This application provides a power conversion device, a control method, and a power supply system. The power conversion device includes a first set of input terminals, a second set of input terminals, a first DC-DC converter circuit, a second DC-DC converter circuit, a positive DC bus, a negative DC bus, a first bus capacitor, a second bus capacitor, and a first output terminal and a second output terminal. The first bus capacitor and the second bus capacitor are connected in series between the positive DC bus and the negative DC bus, which are respectively connected to the first output terminal and the second output terminal of the power conversion device. The input terminal of the first DC-DC converter circuit is connected to the first set of first input terminals, and its output terminals are respectively connected to the two ends of the first bus capacitor. The input terminal of the second DC-DC converter circuit is connected to the second set of second input terminals, and its output terminals are respectively connected to the two ends of the second bus capacitor. The second set of second input terminals is connected to the negative DC bus, and the first set of first input terminals is connected to the positive DC bus. Using this application can reduce the cost of the power conversion device.

Description

Technical Field

[0001] This application relates to the field of power supply technology, and in particular to a power conversion device, control method and power supply system. Background Technology

[0002] Whether in new energy power generation systems (such as photovoltaic power generation systems) or battery energy storage systems, a large number of power electronic converters (such as inverters) are required for power control to achieve energy interaction and voltage matching between DC and AC, while also enabling flexible control of new energy power generation equipment (such as photovoltaic panels) and energy storage batteries.

[0003] Currently, power supply systems (including new energy power generation systems and battery energy storage systems) all adopt... Figure 1a The inverter shown supplies power to the AC grid. For example... Figure 1a As shown, the inverter includes a DC / DC circuit 1 and a DC / DC circuit 2, and an inverter circuit INV. The input terminal of the DC / DC circuit 1 is connected to the DC power supply DC1, and the two output terminals are connected to the positive DC bus BUS+ and the negative DC bus BUS-, respectively. The input terminal of the DC / DC circuit 2 is connected to the DC power supply DC2, and the two output terminals are connected to the positive DC bus BUS+ and the negative DC bus BUS-, respectively. The positive DC bus BUS+ and the negative DC bus BUS- are connected to the AC power grid through the inverter circuit INV.

[0004] Since the output terminals of DC / DC circuit 1 and DC / DC circuit 2 are directly connected to the positive DC bus BUS+ and the negative DC bus BUS-, DC / DC circuit 1 and DC / DC circuit 2, which have higher circuit costs, are usually used to meet the voltage requirements between the positive DC bus BUS+ and the negative DC bus BUS-.

[0005] For example, to meet the application requirement of a 1500V voltage between the positive DC bus BUS+ and the negative DC bus BUS-, in a photovoltaic power generation system, DC / DC circuit 1 and DC / DC circuit 2 would adopt the following... Figure 1b The diagram shows a flying capacitor three-level boost circuit. The power semiconductors in this circuit are mostly 1000V or 1200V devices, such as 1000V / 1200V Insulated Gate Bipolar Transistors (IGBTs) Q11 and Q12, or 1200V Silicon Carbide-Schottky Barrier Diodes (SiC-SBDs). Clearly, Figure 1bThe DC / DC circuits 1 and 2 shown contain a large number of power semiconductor devices. This results in higher circuit costs for both DC / DC circuits 1 and 2, thus reducing the market competitiveness of the inverters. Therefore, reducing the circuit costs of DC / DC circuits 1 and 2 is of paramount importance. Summary of the Invention

[0006] This application provides a power conversion device, a control method, and a power supply system, which can reduce the circuit cost of the DC-DC conversion circuit in the power conversion device, thereby reducing the cost of the power conversion device.

[0007] In a first aspect, this application provides a power conversion device, which includes a first set of input terminals, a second set of input terminals, a first DC-DC converter circuit, a second DC-DC converter circuit, a positive DC bus, a negative DC bus, a first bus capacitor, a second bus capacitor, and a first output terminal and a second output terminal. The first and second sets of input terminals are respectively connected to a DC power supply, and the first and second output terminals are connected to a load. The first set of input terminals includes a first set of first input terminals and a first set of second input terminals, and the second set of input terminals includes a second set of first input terminals and a second set of second input terminals. The first and second bus capacitors are connected in series between the positive and negative DC buses, which are respectively connected to the first and second output terminals of the power conversion device. The input terminal of the first DC-DC converter circuit is connected to the first set of first input terminals, and the output terminals of the first DC-DC converter circuit are respectively connected to the two ends of the first bus capacitor. The first input terminal of the second DC-DC converter circuit is connected to the second set of second input terminals, and the output terminals of the second DC-DC converter circuit are respectively connected to the two ends of the second bus capacitor. The first group's second input terminal is connected to the negative DC bus, and the second group's first input terminal is connected to the positive DC bus. Furthermore, the power conversion device reduces the voltage drop across each of the two DC conversion circuits by connecting a first bus capacitor and a second bus capacitor in series between the positive and negative DC buses, and by connecting the two output terminals of the first DC conversion circuit to the first bus capacitor and the two output terminals of the second DC conversion circuit to the two ends of the second bus capacitor. This reduces the circuit cost of the two DC conversion circuits, thereby reducing the cost of the power conversion device and further enhancing its market competitiveness.

[0008] In conjunction with the first aspect, in a first possible implementation, the power conversion device further includes a first input capacitor and a second input capacitor. The first DC-DC converter circuit has a first input terminal and a second input terminal. One end of the first input capacitor is connected to the first input terminal and a first group of first input terminals of the first DC-DC converter circuit, and the other end of the first input capacitor is connected to the second input terminal or a first group of second input terminals of the first DC-DC converter circuit. The second DC-DC converter circuit has a first input terminal and a second input terminal. One end of the second input capacitor is connected to the first input terminal and a second group of second input terminals of the second DC-DC converter circuit, and the other end of the second input capacitor is connected to the second input terminal or a second group of first input terminals of the second DC-DC converter circuit. It is understood that the power conversion device can also filter the DC power output from the DC power supply by adding input capacitors, making the DC power input to the DC-DC converter circuit smoother and reducing the impact of the power conversion device on the DC power supply. Furthermore, the input capacitor can be located not only between the two input terminals of the DC-DC converter circuit, but also between a group of input terminals of the power conversion device, offering diverse locations and increasing the versatility and flexibility of the power conversion device structure.

[0009] In conjunction with the first possible implementation of the first aspect, in the second possible implementation, the output terminals of the first DC-DC converter circuit include a first output terminal and a second output terminal. The first DC-DC converter circuit includes a first power inductor, a first switching device, and a second switching device. The first power inductor and the second switching device are connected in series between the first input terminal and the first output terminal of the first DC-DC converter circuit, or the first power inductor and the second switching device are connected in series between the second input terminal and the second output terminal of the first DC-DC converter circuit. One end of the first switching device is connected to the first input terminal or the second input terminal of the first DC-DC converter circuit, and the other end of the first switching device is connected to the connection point between the second switching device and the first power inductor. The second DC-DC converter circuit includes a first output terminal and a second output terminal. The second DC-DC converter circuit includes a third switching device, a fourth switching device, and a second power inductor. The fourth switching device and the second power inductor are connected in series between the first input terminal and the first output terminal of the second DC-DC converter circuit, or the fourth switching device and the second power inductor are connected in series between the second input terminal and the second output terminal of the second DC-DC converter circuit. One end of the third switching device is connected to the first input terminal or the second input terminal of the second DC-DC converter circuit, and the other end of the third switching device is connected to the connection point between the fourth switching device and the second power inductor. Since the first and second bus capacitors are connected in series between the positive and negative DC buses, they typically each bear half of the DC bus voltage. This means the voltage across both the first and second DC-DC converter circuits is halved. Using power semiconductor devices of the same voltage rating, the number of power semiconductor devices used in the DC-DC converter circuit of this embodiment is half that used in a DC-DC converter circuit that bears the entire DC bus voltage. This significantly reduces the circuit cost of the DC-DC converter circuit, and consequently, the cost of the power conversion device. Furthermore, the diverse structures of the first and second DC-DC converter circuits allow for various combinations, resulting in a diverse and flexible power conversion device structure.

[0010] In conjunction with the second possible implementation of the first aspect, in the third possible implementation, both the first and third switching devices are controllable switching transistors, while the second and fourth switching devices are either controllable switching transistors or uncontrollable diodes. Specifically, the controllable switching transistors in this application are bidirectional semiconductor devices, such as insulated-gate bipolar transistors (IGBTs) or metal-oxide-semiconductor field-effect transistors (MOSFETs); the uncontrollable diodes in this application are unidirectional semiconductor devices. In photovoltaic power supply scenarios, since power conversion devices typically have unidirectional power flow, unidirectional semiconductor devices are sufficient for the first and third switching devices. In energy storage power supply scenarios, the power conversion device has bidirectional energy flow, therefore bidirectional semiconductor devices are required for the first and third switching devices. It is understood that the power conversion device is applicable to both photovoltaic power supply scenarios and energy storage power supply scenarios, demonstrating strong applicability.

[0011] In a fourth possible embodiment, combining any of the first to third possible implementations of the first aspect, the power conversion device further includes a bus voltage balancing circuit. The first, second, and third terminals of the bus voltage balancing circuit are respectively connected to the connection point between the first and second bus capacitors, the positive DC bus, and the negative DC bus. This circuit is used to transfer the electrical energy stored in the first bus capacitor to the second bus capacitor, or to transfer the electrical energy stored in the second bus capacitor to the first bus capacitor, thereby reducing the difference between the first bus voltage of the first bus capacitor and the second bus voltage of the second bus capacitor, thus achieving half-bus voltage balancing. The half-bus voltage balancing performed by the bus voltage balancing circuit and the DC power conversion performed by each DC conversion circuit are independent of each other and do not affect each other. Taking a photovoltaic power generation application scenario as an example, controlling the half-bus voltage balancing by controlling the DC conversion circuit usually requires sacrificing its Maximum Power Point Tracking (MPPT) characteristic, i.e., abandoning maximum power operation, which will result in a certain loss of power generation. However, the method of achieving half-bus voltage balance through the bus voltage balancing circuit does not require sacrificing the MPPT characteristics of the DC-DC converter circuit, thereby increasing the power generation of the power conversion device.

[0012] In conjunction with the fourth possible implementation of the first aspect, in the fifth possible implementation, the bus voltage balancing circuit includes an energy storage element. The bus voltage balancing circuit is used to transfer the electrical energy stored in the first bus capacitor to the energy storage element, and to transfer the electrical energy of the energy storage element to the second bus capacitor; or to transfer the electrical energy stored in the second bus capacitor to the energy storage element, and to transfer the electrical energy of the energy storage element to the first bus capacitor, thereby reducing the difference between the first bus voltage and the second bus voltage, and thus achieving half-bus voltage balancing. Since the bus voltage balancing circuit performs half-bus voltage balancing and performs DC power conversion with each DC-DC converter circuit, they are independent of each other and do not affect each other. Therefore, achieving half-bus voltage balancing through the bus voltage balancing circuit allows for decoupling control from each DC-DC converter circuit, ensuring flexible energy control of the DC-DC converter circuit, and without sacrificing the MPPT characteristics of the DC-DC converter circuit, thereby increasing the power generation of the power conversion device.

[0013] In conjunction with the fifth possible implementation of the first aspect, in the sixth possible implementation, the energy storage element is a third power inductor, and the bus voltage balancing circuit further includes a fifth switching device and a sixth switching device. One end of the third power inductor is connected to the first terminal of the bus voltage balancing circuit, and the other end of the third power inductor is connected to the second and third terminals of the bus voltage balancing circuit through the fifth and sixth switching devices, respectively. The bus voltage balancing circuit in this embodiment, namely the BUCK-BOOST circuit, is simple, easy to control, and can improve the stability of the power conversion device.

[0014] In conjunction with the fifth possible implementation of the first aspect, in the seventh possible implementation, the energy storage element is a resonant capacitor, and the bus voltage balancing circuit further includes a seventh switching device, an eighth switching device, a ninth switching device, a tenth switching device, and a resonant inductor. The seventh and eighth switching devices are connected in series to form a first switching bridge arm, with both ends of the first switching bridge arm connected to the second and first ends of the bus voltage balancing circuit, respectively. The first end of the seventh switching device is connected to the second end of the bus voltage balancing circuit. The ninth and tenth switching devices are connected in series to form a second switching bridge arm, with both ends of the second switching bridge arm connected to the first and third ends of the bus voltage balancing circuit, respectively. The first end of the ninth switching device is connected to the first end of the bus voltage balancing circuit. The resonant inductor and resonant capacitor are connected in series between the midpoint of the first and second switching bridge arms. The midpoint of the first switching bridge arm is the connection point between the seventh and eighth switching devices, and the midpoint of the second switching bridge arm is the connection point between the ninth and tenth switching devices. In this embodiment, the bus voltage balancing circuit is a resonant switched capacitor circuit. The diverse structures of the bus voltage balancing circuit improve the diversity and flexibility of the power conversion device structure.

[0015] In conjunction with any of the first to seventh possible embodiments of the first aspect, in the eighth possible embodiment, the DC power source includes a photovoltaic panel, an energy storage battery, or a fuel cell. It is understood that the power conversion device is applicable to photovoltaic power supply scenarios, energy storage power supply scenarios, or fuel cell power supply scenarios, demonstrating strong applicability.

[0016] Secondly, this application provides a control method for controlling a power conversion device provided in any of the second to seventh possible embodiments of the first aspect. The method includes: when there is a deviation between the first bus voltage of the first bus capacitor and the second bus voltage of the second bus capacitor, i.e., when the first bus voltage and the second bus voltage are not equal, the power conversion device adjusts the duty cycle of the first switching device in the first DC-DC converter circuit and / or the duty cycle of the third switching device in the second DC-DC converter circuit to reduce the difference between the first bus voltage and the second bus voltage. This control method does not require additional devices or circuits, effectively reducing the cost of the power conversion device.

[0017] In conjunction with the second aspect, in a first possible implementation, when the first bus voltage is greater than the second bus voltage and the current of the power conversion device flows from the DC power supply to the load, the power conversion device increases the duty cycle of the first switching device and / or decreases the duty cycle of the third switching device, thereby increasing the second bus voltage and / or decreasing the first bus voltage, and thus reducing the difference between the first bus voltage and the second bus voltage to achieve half-bus voltage balance. In this embodiment, the power conversion device can achieve half-bus voltage balance simply by adjusting the duty cycle of the controllable switch in at least one of the first and second DC conversion circuits. The control method is simple and easy to implement. Furthermore, this control method does not require additional components or circuits, effectively reducing the cost of the power conversion device.

[0018] In conjunction with the second aspect, in a second possible implementation, when the first bus voltage is less than the second bus voltage and the current of the power conversion device flows from the DC power supply to the load, the power conversion device increases the duty cycle of the third switching device and / or decreases the duty cycle of the first switching device, thereby increasing the first bus voltage and / or decreasing the second bus voltage, and further reducing the difference between the first bus voltage and the second bus voltage to achieve half-bus voltage balance. In this embodiment, the power conversion device can achieve half-bus voltage balance simply by adjusting the duty cycle of the controllable switch in at least one of the first and second DC conversion circuits. The control method is simple and easy to implement. Furthermore, this control method does not require additional components or circuits, effectively reducing the cost of the power conversion device.

[0019] In conjunction with the second aspect, in a third possible implementation, when the first bus voltage is greater than the second bus voltage and the current of the power conversion device flows from the load to the DC power supply, the power conversion device reduces the duty cycle of the first switching device and / or increases the duty cycle of the third switching device. In this implementation, the power conversion device can achieve half-bus voltage balance simply by adjusting the duty cycle of the controllable switches in at least one of the first and second DC-DC conversion circuits. The control method is simple and easy to implement. Furthermore, this control method does not require additional components or circuits, effectively reducing the cost of the power conversion device.

[0020] In conjunction with the second aspect, in a fourth possible implementation, when the first bus voltage is less than the second bus voltage and the current of the power conversion device flows from the load to the DC power supply, the power conversion device reduces the duty cycle of the third switching device and / or increases the duty cycle of the first switching device. In this implementation, the power conversion device can achieve half-bus voltage balance simply by adjusting the duty cycle of the controllable switch in at least one of the first and second DC conversion circuits. The control method is simple and easy to implement. Furthermore, this control method does not require additional components or circuits, effectively reducing the cost of the power conversion device.

[0021] Thirdly, this application provides a control method for controlling a power conversion device provided in any of the fourth to seventh possible embodiments of the first aspect. The method includes: when there is a deviation between the first bus voltage of the first bus capacitor and the second bus voltage of the second bus capacitor, the power conversion device controls the bus voltage balancing circuit to transfer the electrical energy stored in the bus capacitor corresponding to the larger of the first and second bus voltages to the bus capacitor corresponding to the smaller bus voltage, thereby reducing the difference between the first and second bus voltages to achieve half-bus voltage balancing. Since the half-bus voltage balancing by the bus voltage balancing circuit and the DC power conversion by each DC-DC converter are independent of each other and do not affect each other, achieving half-bus voltage balancing through the bus voltage balancing circuit allows for decoupling control from each DC-DC converter, ensuring flexible energy control of the DC-DC converter without sacrificing the MPPT characteristics of the DC-DC converter, thereby increasing the power generation of the power conversion device.

[0022] In conjunction with the third aspect, in the first possible implementation, when there is a deviation between the first bus voltage and the second bus voltage, the power conversion device controls the bus voltage balancing circuit to transfer the electrical energy stored in the bus capacitor corresponding to the larger of the first and second bus voltages to the energy storage element, and to transfer the electrical energy of the energy storage element to the bus capacitor corresponding to the smaller of the first and second bus voltages. Since the bus voltage balancing circuit performs half-bus voltage balancing and performs DC power conversion with each DC-DC converter circuit, it is independent of and does not affect each other. Therefore, by achieving half-bus voltage balancing through the bus voltage balancing circuit, decoupling control can be achieved with each DC-DC converter circuit, ensuring flexible energy control of the DC-DC converter circuit, and without sacrificing the MPPT characteristics of the DC-DC converter circuit, thereby increasing the power generation of the power conversion device.

[0023] In conjunction with the first possible implementation of the third aspect, in the second possible implementation, the energy storage element is a third power inductor, that is, the bus voltage balancing circuit is the BUCK-BOOST circuit provided in the sixth possible implementation of the first aspect. When the first bus voltage is greater than the second bus voltage, the power conversion device controls the fifth switching device to be turned on for a first preset time and then turned off. During the turn-on process of the fifth switching device, the electrical energy stored in the first bus capacitor is transferred to the third power inductor. After the fifth switching device is turned off, the power conversion device controls the sixth switching device to be turned on for a second preset time and then turned off. During the turn-on process of the sixth switching device, the electrical energy stored in the third power inductor is transferred to the second bus capacitor. It can be understood that the power conversion device, by controlling the fifth and sixth switching devices in the bus voltage balancing circuit (i.e., the BUCK-BOOST circuit), combined with the energy storage capacity of the third power inductor, realizes the transfer of electrical energy between the first bus capacitor, the third power inductor, and the second bus capacitor, thereby achieving half-bus voltage balance. Since the BUCK-BOOST circuit is simple and easy to control, the stability of the power conversion device can be improved.

[0024] In conjunction with the first possible implementation of the third aspect, in the third possible implementation, the energy storage element is a third power inductor, that is, the bus voltage balancing circuit is the BUCK-BOOST circuit provided in the sixth possible implementation of the first aspect. When the first bus voltage is lower than the second bus voltage, the power conversion device controls the sixth switching device to be turned on for a first preset time and then turned off. During the turn-on process of the sixth switching device, the electrical energy stored in the second bus capacitor is transferred to the third power inductor. After the sixth switching device is turned off, the fifth switching device is controlled to be turned on for a second preset time and then turned off. During the turn-on process of the fifth switching device, the electrical energy stored in the third power inductor is transferred to the first bus capacitor. It can be understood that the power conversion device realizes the transfer of electrical energy between the first bus capacitor, the third power inductor, and the second bus capacitor through the bus voltage balancing circuit, that is, the BUCK-BOOST circuit, thereby achieving half-bus voltage balance. Since the BUCK-BOOST circuit is simple and easy to control, it can improve the stability of the power conversion device.

[0025] In conjunction with the first possible implementation of the third aspect, in the fourth possible implementation, the energy storage element is a resonant capacitor, that is, the bus voltage balancing circuit is the resonant switched capacitor circuit provided in the seventh possible implementation of the first aspect. When the first bus voltage is greater than the second bus voltage, the power conversion device controls the seventh and ninth switching devices to be turned on for a third preset time and then turned off. During the conduction of the seventh and ninth switching devices, the electrical energy stored in the first bus capacitor is transferred to the resonant capacitor. After the seventh and ninth switching devices are turned off, the power conversion device controls the eighth and tenth switching devices to be turned on for a fourth preset time and then turned off. During the conduction of the eighth and tenth switching devices, the electrical energy stored in the resonant capacitor is transferred to the second bus capacitor. By controlling the seventh, eighth, ninth, and tenth switching devices in the bus voltage balancing circuit (i.e., the resonant switched capacitor circuit), and combining the energy storage capacity of the resonant capacitor, the power conversion device realizes the transfer of electrical energy among the first bus capacitor, the resonant capacitor, and the second bus capacitor, thereby achieving half-bus voltage balance. The diverse structures of bus voltage balancing circuits lead to diverse bus voltage balancing control methods, thereby increasing the structural diversity and control method diversity of power conversion devices and enhancing their flexibility.

[0026] In conjunction with the first possible implementation of the third aspect, in the fifth possible implementation, the energy storage element is a resonant capacitor, that is, the bus voltage balancing circuit is the resonant switched capacitor circuit provided in the seventh possible implementation of the first aspect. When the first bus voltage is less than the second bus voltage, the power conversion device controls the eighth and tenth switching devices to be turned on for a third preset time and then turned off. During the conduction of the eighth and tenth switching devices, the electrical energy stored in the second bus capacitor is transferred to the resonant capacitor. After the eighth and tenth switching devices are turned off, the seventh and ninth switching devices are controlled to be turned on for a fourth preset time and then turned off. During the conduction of the seventh and ninth switching devices, the electrical energy stored in the resonant capacitor is transferred to the first bus capacitor. It can be understood that the power conversion device realizes the transfer of electrical energy among the first bus capacitor, the resonant capacitor, and the second bus capacitor through the bus voltage balancing circuit, that is, the resonant switched capacitor circuit, thereby achieving half-bus voltage balance. The bus voltage balancing circuit has various structures, which makes the bus voltage balancing control methods diverse, thereby improving the structural diversity and control method diversity of the power conversion device, and increasing its flexibility.

[0027] Fourthly, this application provides a power supply system including an inverter circuit and a power conversion device provided in any of the first to eighth possible embodiments of the first aspect. The first output terminal and the second output terminal of the power conversion device are respectively connected to the first input terminal and the second input terminal of the inverter circuit, and the output terminal of the inverter circuit is connected to the power grid. Furthermore, by employing a power conversion device that reduces circuit costs, the power supply system reduces its cost, thereby enhancing its market competitiveness.

[0028] In conjunction with the fourth aspect, in the first possible implementation, the inverter circuit further includes a third bus capacitor, a fourth bus capacitor, and a third input terminal of the inverter circuit. The third bus capacitor is connected between the first input terminal and the third input terminal of the inverter circuit, and the fourth bus capacitor is connected between the third input terminal and the second input terminal of the inverter circuit. It is understood that the inverter circuit in this embodiment is a multi-level inverter circuit, with diverse structures and high flexibility.

[0029] In conjunction with the fourth aspect, in the second possible implementation, the inverter circuit further includes a third input terminal connected to the connection point between the first bus capacitor and the second bus capacitor. When there is a deviation between the first bus voltage and the second bus voltage, the inverter circuit outputs the electrical energy stored in the first and second bus capacitors to the power grid. Specifically, the bus capacitor corresponding to the larger bus voltage outputs more electrical energy to the power grid than the bus capacitor corresponding to the smaller bus voltage. This reduces the larger bus voltage, thereby reducing the difference between the first and second bus voltages and achieving half-bus voltage balance. It is understood that the power supply system can achieve half-bus voltage balance through the inverter circuit. This control method does not require additional components or circuits, effectively reducing the cost of the power conversion device and the power supply system. Furthermore, since the DC-DC converter circuit and the inverter circuit share the first and second bus capacitors, the number of bus capacitors used in the power supply system can be reduced, further reducing the cost of the power supply system.

[0030] It should be understood that the implementations and beneficial effects of the above-mentioned aspects of this application can be referenced from each other. Attached Figure Description

[0031] Figures 1a to 1b This is a schematic diagram of the structure of an inverter provided by existing technology;

[0032] Figure 2 This is a schematic diagram of the application scenario of the power supply system provided in this application;

[0033] Figure 3 This is a schematic diagram of the power conversion device provided in this application;

[0034] Figure 4a This is another structural schematic diagram of the power conversion device provided in this application;

[0035] Figure 4b This is another structural schematic diagram of the power conversion device provided in this application;

[0036] Figure 5a This is another structural schematic diagram of the power conversion device provided in this application;

[0037] Figure 5b This is another structural schematic diagram of the power conversion device provided in this application;

[0038] Figure 5c This is another structural schematic diagram of the power conversion device provided in this application;

[0039] Figure 5d This is another structural schematic diagram of the power conversion device provided in this application;

[0040] Figure 5e This is another structural schematic diagram of the power conversion device provided in this application;

[0041] Figure 5f This is another structural schematic diagram of the power conversion device provided in this application;

[0042] Figure 6a This is another structural schematic diagram of the power conversion device provided in this application;

[0043] Figure 6b This is another structural schematic diagram of the power conversion device provided in this application;

[0044] Figure 6c This is another structural schematic diagram of the power conversion device provided in this application;

[0045] Figure 6d This is another structural schematic diagram of the power conversion device provided in this application;

[0046] Figure 6e This is another structural schematic diagram of the power conversion device provided in this application;

[0047] Figure 7 This is a structural schematic diagram of the power supply system provided in this application;

[0048] Figure 8 This is another structural schematic diagram of the power supply system provided in this application;

[0049] Figure 9 This is another structural schematic diagram of the power supply system provided in this application;

[0050] Figure 10 This is yet another structural schematic diagram of the power supply system provided in this application;

[0051] Figure 11 This is a schematic flowchart of the bus voltage control method for the power conversion device provided in this application;

[0052] Figure 12 This is another schematic diagram of the bus voltage control method for the power conversion device provided in this application. Detailed Implementation

[0053] The power conversion device and power supply system provided in this application are applicable to various application scenarios, such as photovoltaic power supply scenarios, energy storage power supply scenarios, fuel cell power supply scenarios, and uninterrupted power supply (UPS) power supply scenarios. The following explanation uses the photovoltaic power supply scenario as an example.

[0054] See Figure 2 , Figure 2 This is a schematic diagram illustrating the application scenario of the power supply system provided in this application. For example... Figure 2 As shown, in a photovoltaic power supply scenario, the power supply system provided in this application includes a DC / DC converter and an inverter. The DC / DC converter includes a first set of input terminals, a second set of input terminals, DC / DC circuit 1, DC / DC circuit 2, a positive DC bus BUS+, a negative DC bus BUS-, a positive bus capacitor C1, and a negative bus capacitor C2. The first set of input terminals includes a first set of first input terminals and a first set of second input terminals, and the second set of input terminals includes a second set of first input terminals and a second set of second input terminals. The positive bus capacitor C1 and the negative bus capacitor C2 are connected in series between the positive DC bus BUS+ and the negative DC bus BUS-, and the positive DC bus BUS+ and the negative DC bus BUS- are respectively connected to the positive output terminal and the negative output terminal of the DC / DC converter. The positive input terminal of DC / DC circuit 1 is connected to the positive terminal of photovoltaic panel PV1 through the first set of positive input terminals of the DC / DC converter, and the two output terminals are connected to the two ends of positive bus capacitor C1. The positive input terminal of DC / DC circuit 2 is connected to the negative terminal of photovoltaic panel PV2 through the second set of negative input terminals of the DC / DC converter, and the two output terminals are connected to the two ends of negative bus capacitor C2. The first set of negative input terminals of the DC / DC converter is connected to the negative terminal of photovoltaic panel PV1 and negative DC bus BUS-, and the second set of positive input terminals of the DC / DC converter is connected to the positive terminal of photovoltaic panel PV2 and positive DC bus BUS+. The inverter includes an inverter circuit, whose positive and negative input terminals are connected to the positive and negative output terminals of the DC / DC converter, respectively. The output terminal of the inverter circuit is connected to the AC power grid or household appliances through the output terminal of the inverter.

[0055] After the power supply system starts operating, the DC / DC converter controls DC / DC circuit 1 and DC / DC circuit 2 to convert the DC power generated by photovoltaic panels PV1 and PV2 into DC power that meets the target voltage, and outputs it to the positive DC bus BUS+ and the negative DC bus BUS-. The inverter controls the inverter circuit to convert the DC power obtained from the positive DC bus BUS+ and the negative DC bus BUS- into AC power with the target voltage value, thereby enabling the supply of power to various types of electrical equipment, such as AC loads (e.g., AC power grid or household appliances). Understandably, based on the structure where the positive bus capacitor C1 and the negative bus capacitor C2 are connected in series between the positive DC bus BUS+ and the negative DC bus BUS-, the voltages of both the positive bus capacitor C1 and the negative bus capacitor C2 are less than the DC bus voltage (i.e., the voltage between the positive DC bus BUS+ and the negative DC bus BUS-). Since the two output terminals of DC / DC circuit 1 are connected to the two ends of the positive bus capacitor C1, and the two output terminals of DC / DC circuit 2 are connected to the two ends of the negative bus capacitor C2, the voltage drop across both DC / DC circuit 1 and DC / DC circuit 2 is less than the DC bus voltage. This reduces the circuit cost of DC / DC circuit 1 and DC / DC circuit 2, thereby reducing the cost of the DC / DC converter and further reducing the cost of the power supply system, demonstrating strong applicability. The above is merely an example of the application scenarios of the power supply system provided in this application, and not an exhaustive list. This application does not limit the application scenarios.

[0056] The following is combined with Figures 3 to 10 The working principle of the power conversion device and power supply system provided in this application is illustrated by examples.

[0057] See Figure 3 , Figure 3 This is a schematic diagram of the power conversion device provided in this application. Figure 3 As shown, the power conversion device 11 includes a first set of input terminals, a second set of input terminals, a first DC-DC converter circuit 111, a second DC-DC converter circuit 112, a positive DC bus BUS+, a negative DC bus BUS-, a first bus capacitor C1, a second bus capacitor C2, and a first output terminal out1 and a second output terminal out2. The first set of input terminals in1 is connected to a DC power supply DC1, and the second set of input terminals in2 is connected to a DC power supply DC2. The first output terminal out1 and the second output terminal out2 of the power conversion device 11 are connected to a load. The DC power supplies DC1 and DC2 include photovoltaic panels, energy storage batteries, or fuel cells. The load includes an inverter and a DC power grid. In other words, the output terminals of the power conversion device 11 can be directly connected to the DC power grid, or connected to an AC power grid or other loads via an inverter.

[0058] The first bus capacitor C1 and the second bus capacitor C2 are connected in series between the positive DC bus BUS+ and the negative DC bus BUS-. The positive DC bus BUS+ is connected to the first output terminal out1, and the negative DC bus BUS- is connected to the second output terminal out2. The first set of input terminals in1 of the power conversion device 11 includes the first set of first input terminals in... 11 and the second input terminal of the first group in 12 The first input terminal of the first group in 11 Connect the input terminal in3 of the first DC-DC converter circuit 111, and the first output terminal out of the first DC-DC converter circuit 111. 31 Second output terminal out 32 Connect the two ends of the first bus capacitor C1 respectively, and the first group of second input terminals in 12 Connect to the negative DC bus BUS-. The second set of input terminals in2 includes the second set of first input terminals in... 21 The second input terminal of the second group 22 The first input terminal of the second group is in 21 Connect to the positive DC bus BUS+, the second input terminal of the second group in 22 Connect the input terminal in4 of the second DC-DC converter circuit 112, and the first output terminal out of the second DC-DC converter circuit 112. 41 Second output terminal out 42 Connect the two ends of the second bus capacitor C2 respectively.

[0059] In this embodiment, the power conversion device 11 reduces the voltage drop across each of the two DC conversion circuits by connecting two bus capacitors C1 and C2 in series between the positive DC bus BUS+ and the negative DC bus BUS-, and connecting the two output terminals of the first DC conversion circuit 111 to the first bus capacitor C1 and the two output terminals of the second DC conversion circuit 112 to the two ends of the second bus capacitor C2. This reduces the circuit cost of the two DC conversion circuits, thereby reducing the cost of the power conversion device 11 and further improving its market competitiveness.

[0060] See Figure 4a , Figure 4a This is another structural schematic diagram of the power conversion device provided in this application. For example... Figure 4a As shown, the power conversion device 11 includes a first set of input terminals in1, a second set of input terminals in2, a first DC-DC converter circuit 111, a second DC-DC converter circuit 112, a positive DC bus BUS+, a negative DC bus BUS-, a first bus capacitor C1, a second bus capacitor C2, a first input capacitor C3, a second input capacitor C4, and a first output terminal out1 and a second output terminal out2 of the power conversion device 11.

[0061] The input terminal in3 of the first DC-DC converter circuit 111 includes the first input terminal in 31 Second input terminal in 32 One end of the first input capacitor C3 is connected to the first input terminal in of the first DC-DC converter circuit 111. 31 and the first input terminal of the first group in 11 The other end of the first input capacitor C3 is connected to the second input terminal in of the first DC-DC converter circuit 111. 32 The input terminal in3 of the second DC-DC converter circuit 112 includes the first input terminal in. 41 Second input terminal in 42 One end of the second input capacitor C4 is connected to the first input terminal in of the second DC-DC converter circuit 112. 41 The other end of the second input capacitor C4 is connected to the second input terminal of the second DC-DC converter circuit 112. 42 For a description of the other parts of the power conversion device 11, please refer to [link to relevant documentation]. Figure 3 The description of the corresponding part of the power conversion device 11 shown will not be repeated here.

[0062] Optionally, the first input capacitor C3 can also be located at the first input terminal of the first group. 11 With the second input terminal of the first group in 12 Between, the second input capacitor C4 can also be located at the first input terminal of the second group. 21 With the second input terminal of the second group 22 For details, please refer to [link / reference]. Figure 4b The power conversion device 11 shown.

[0063] In this embodiment, the power conversion device 11 reduces the voltage drop across each of the two DC conversion circuits by connecting two bus capacitors C1 and C2 in series between the positive DC bus BUS+ and the negative DC bus BUS-, and connecting the two output terminals of the first DC conversion circuit 111 to the first bus capacitor C1 and the two output terminals of the second DC conversion circuit 112 to the two ends of the second bus capacitor C2. This reduces the circuit cost of the two DC conversion circuits, thereby reducing the cost of the power conversion device 11 and further improving its market competitiveness.

[0064] Since the operating principle of the power conversion device 11 remains the same regardless of whether the input capacitor is located between the two input terminals of the DC-DC converter circuit or between the two input terminals of each group of the power conversion device 11, for ease of description, the following description will use the example of the input capacitor being located between the two input terminals of the DC-DC converter circuit.

[0065] See Figure 5a , Figure 5a This is another structural schematic diagram of the power conversion device provided in this application. For example... Figure 5a As shown, the power conversion device 11 includes a first group of first input terminals in 11 The first group of second input terminals in 12 The first input terminal of the second group in 21 The second input terminal of the second group 22 The system includes a first DC-DC converter circuit 111, a second DC-DC converter circuit 112, a positive DC bus BUS+, a negative DC bus BUS-, a first bus capacitor C1, a second bus capacitor C2, a first input capacitor C3, a second input capacitor C4, a first output terminal out1 and a second output terminal out2 of the power conversion device 11, and a first controller 113.

[0066] The first DC-DC converter circuit 111 includes a first power inductor L1, a first switching device S11, and a second switching device S12. One end of the first power inductor L1 is connected to the first input terminal in of the first DC-DC converter circuit 111. 31 The other end is connected to the first output terminal out of the first DC-DC converter circuit 111 via the second switching device S12. 31 One end of the first switching device S11 is connected to the second input terminal in of the first DC-DC converter circuit 111. 32 Second output terminal out 32 One end is connected to the connection point of the first power inductor L1 and the second switching device S12. The second DC-DC converter circuit 112 includes a second power inductor L2, a third switching device S21, and a fourth switching device S22. One end of the second power inductor L2 is connected to the first input terminal in of the second DC-DC converter circuit 112. 41 The other end is connected to the first output terminal out of the second DC-DC converter circuit 112 via the fourth switching device S22. 41 One end of the third switching device S21 is connected to the second input terminal in of the second DC-DC converter circuit 112. 42 Second output terminal out 42 The other end is connected to the connection point of the second power inductor L2 and the fourth switching device S22. The second switching device S12 and the fourth switching device S22 are both uncontrollable diodes or controllable switching transistors, while the first switching device S11 and the third switching device S21 are controllable switching transistors. The controllable switching transistors provided in this application are bidirectional semiconductor devices, such as IGBTs or Metal Oxide Semiconductor Field Effect Transistors (MOSFETs). This application does not limit the relationship between the capacitance values ​​of the first bus capacitor C1 and the second bus capacitor C2.

[0067] It should be noted that in scenarios where energy flows in one direction (such as photovoltaic power supply scenarios), Figure 5a The second switching device S12 and the fourth switching device S22 shown are both diodes. The cathode of the second switching device S12 is connected to the first output terminal out of the first DC-DC converter circuit 111. 31 The anode of the fourth switching device S22 is connected to the first output terminal out of the second DC-DC converter circuit 112. 41 In scenarios involving bidirectional energy flow (such as energy storage for power supply), Figure 5a The second switching device S12 and the fourth switching device S22 shown are both controllable switching transistors. The conduction direction of the parasitic diode of the second switching device S12 is the same as the conduction direction of the second switching device S12 when it is a diode in the unidirectional energy flow scenario. The conduction direction of the parasitic diode of the fourth switching device S22 is the same as the conduction direction of the fourth switching device S22 when it is a diode in the unidirectional energy flow scenario.

[0068] Optionally, the first DC-DC converter circuit 111 and the second DC-DC converter circuit 112 may also employ... Figure 5b The circuit structure is shown below. Figure 5b As shown, the circuit structure of the first DC-DC converter circuit 111 is similar to... Figure 5a The circuit structure of the first DC-DC converter circuit 111 shown is the same. The second DC-DC converter circuit 112 includes a second power inductor L2, a third switching device S21, and a fourth switching device S22. One end of the fourth switching device S22 is connected to the second input terminal in of the second DC-DC converter circuit 112. 42 The other end is connected to the second output terminal out of the second DC-DC converter circuit 112 via the second power inductor L2. 42 One end of the third switching device S21 is connected to the first input terminal in of the second DC-DC converter circuit 112. 41 and the first output terminal out 41 The other end is connected to the connection point of the second power inductor L2 and the fourth switching device S22.

[0069] It should be noted that in scenarios where energy flows in one direction (such as photovoltaic power supply scenarios), Figure 5b The second switching device S12 and the fourth switching device S22 shown are both diodes. The cathode of the second switching device S12 is connected to the first output terminal out of the first DC-DC converter circuit 111. 31 The cathode of the fourth switching device S22 is connected to the second input terminal in of the second DC-DC converter circuit 112. 42 In scenarios involving bidirectional energy flow (such as energy storage for power supply), Figure 5bThe second switching device S12 and the fourth switching device S22 shown are both controllable switching transistors. The conduction direction of the parasitic diode of the second switching device S12 is the same as the conduction direction of the second switching device S12 when it is a diode in the unidirectional energy flow scenario. The conduction direction of the parasitic diode of the fourth switching device S22 is the same as the conduction direction of the fourth switching device S22 when it is a diode in the unidirectional energy flow scenario.

[0070] Optionally, the first DC-DC converter circuit 111 and the second DC-DC converter circuit 112 may also employ... Figure 5c The circuit structure is shown below. Figure 5c As shown, the first DC-DC converter circuit 111 includes a first power inductor L1, a first switching device S11, and a second switching device S12. One end of the second switching device S12 is connected to the second input terminal in of the first DC-DC converter circuit 111. 32 The other end is connected to the second output terminal out of the first DC-DC converter circuit 111 via the first power inductor L1. 32 One end of the first switching device S11 is connected to the first input terminal in of the first DC-DC converter circuit 111. 31 and the first output terminal out 31 The other end is connected to the connection point of the first power inductor L1 and the second switching device S12. The circuit structure of the second DC-DC converter circuit 112 is similar to... Figure 5a The circuit structure of the second DC-DC converter circuit 112 shown is the same.

[0071] It should be noted that in scenarios where energy flows in one direction (such as photovoltaic power supply scenarios), Figure 5c The second switching device S12 and the fourth switching device S22 shown are both diodes. The anode of the second switching device S12 is connected to the second input terminal in of the first DC-DC converter circuit 111. 32 The anode of the fourth switching device S22 is connected to the first output terminal out of the second DC-DC converter circuit 112. 41 In scenarios involving bidirectional energy flow (such as energy storage for power supply), Figure 5c The second switching device S12 and the fourth switching device S22 shown are both controllable switching transistors. The conduction direction of the parasitic diode of the second switching device S12 is the same as the conduction direction of the second switching device S12 when it is a diode in the unidirectional energy flow scenario. The conduction direction of the parasitic diode of the fourth switching device S22 is the same as the conduction direction of the fourth switching device S22 when it is a diode in the unidirectional energy flow scenario.

[0072] Optionally, the first DC-DC converter circuit 111 and the second DC-DC converter circuit 112 may also employ... Figure 5d The circuit structure is shown below. Figure 5d As shown, the circuit structure of the first DC-DC converter circuit 111 is similar to... Figure 5cThe circuit structure of the first DC-DC converter circuit 111 shown is the same as that of the second DC-DC converter circuit 112. Figure 5b The circuit structure of the second DC-DC converter circuit 112 shown is the same.

[0073] It should be noted that in scenarios where energy flows in one direction (such as photovoltaic power supply scenarios), Figure 5d The second switching device S12 and the fourth switching device S22 shown are both diodes. The anode of the second switching device S12 is connected to the second input terminal in of the first DC-DC converter circuit 111. 32 The cathode of the fourth switching device S22 is connected to the second input terminal in of the second DC-DC converter circuit 112. 42 In scenarios involving bidirectional energy flow (such as energy storage for power supply), Figure 5d The second switching device S12 and the fourth switching device S22 shown are both controllable switching transistors. The conduction direction of the parasitic diode of the second switching device S12 is the same as the conduction direction of the second switching device S12 when it is a diode in the unidirectional energy flow scenario. The conduction direction of the parasitic diode of the fourth switching device S22 is the same as the conduction direction of the fourth switching device S22 when it is a diode in the unidirectional energy flow scenario.

[0074] exist Figures 5a to 5d In the four power conversion devices 11 with different circuit structures, since the first bus capacitor C1 and the second bus capacitor C2 are connected in series between the positive DC bus BUS+ and the negative DC bus BUS-, under normal circumstances, the first bus capacitor C1 and the second bus capacitor C2 each bear half of the DC bus voltage. That is, the voltage values ​​borne by the first DC conversion circuit 111 and the second DC conversion circuit 112 are both reduced by half. For example, when the DC bus voltage is 1500V, the average voltage of the first bus capacitor C1 and the second bus capacitor C2 is 750V, that is, the voltage values ​​borne by the first DC conversion circuit 111 and the second DC conversion circuit 112 are both reduced by half. Figure 1b Compared to DC / DC circuits 1 and 2, which both require two 1000V IGBTs to withstand a 1500V DC bus voltage, the first DC-DC converter circuit 111 in this application only requires one 1000V IGBT S11, and the second DC-DC converter circuit 112 only requires one 1000V IGBT S21, thus meeting the application requirement of a 1500V DC bus voltage. Clearly, the DC-DC converter circuits and... Figure 1b The DC / DC circuit shown, when using power semiconductor devices of the same voltage level, compared to Figure 1bThe number of power semiconductor devices in the DC / DC circuit shown in this application is reduced by 50%, which can significantly reduce the circuit cost of the DC / DC converter circuit, and thus significantly reduce the cost of the power conversion device 11. In addition, the reduction in the number of power semiconductor devices in the DC / DC converter circuit can also effectively reduce the circuit complexity of the power conversion device 11, thereby reducing the control complexity of the power conversion device 11 and improving the stability of the power conversion device 11.

[0075] Since capacitors cannot conduct direct current, during the operation of the power conversion device 11, it is necessary to ensure that the currents flowing through the midpoint M1 of the DC bus in the first DC conversion circuit 111 and the second DC conversion circuit 112 are exactly canceled out, so as to achieve half-bus voltage balance, that is, the balance between the first bus voltage of the first bus capacitor C1 and the second bus voltage of the second bus capacitor C2. Figures 5a to 5d The power conversion devices 11 shown all achieve half-bus voltage balance in the same way. For ease of description, the following will use the same method. Figure 5a The power conversion device 11 shown is used as an example for introduction.

[0076] In an optional embodiment, after the power conversion device 11 operates, the first controller 113 begins to acquire the first bus voltage of the first bus capacitor C1 and the second bus voltage of the second bus capacitor C2. When the first bus voltage and the second bus voltage are unequal, the first controller 113 adjusts the duty cycle of the first switching device S11 in the first DC-DC converter circuit 111 and / or the duty cycle of the third switching device S21 in the second DC-DC converter circuit 112 to reduce the difference between the first bus voltage and the second bus voltage, thereby achieving half-bus voltage balance. For a detailed explanation of how the power conversion device 11 achieves half-bus voltage balance by adjusting the duty cycle of the first switching device S11 and / or the duty cycle of the third switching device S21, please refer to subsequent explanations. Figure 5e and Figure 5f Corresponding embodiments (i.e., using) Figure 5a The description of the power conversion device 11 shown is based on a detailed embodiment and will not be elaborated here.

[0077] Understandably, the power conversion device 11 can achieve half-bus voltage balance by sampling the first bus voltage of the first bus capacitor C1 and the second bus voltage of the second bus capacitor C2, and then dynamically adjusting the duty cycle of the controllable switch of at least one of the two DC-DC converter circuits through closed-loop control. This control method does not require the addition of additional components or circuits, and can effectively reduce the cost of the power conversion device 11.

[0078] It should be noted that when DC power supplies DC1 and DC2 are photovoltaic panels, the aforementioned DC-DC converter circuits convert the output voltage of the connected photovoltaic panels to the DC bus (i.e., the positive DC bus BUS+ and the negative DC bus BUS-), primarily to achieve maximum power point tracking (MPPT) for the connected photovoltaic panels and ensure efficient power generation. Therefore, in the case of photovoltaic power supply (PV) scenarios, the power conversion device 11 typically operates with unidirectional power flow. When DC power supplies DC1 and DC2 are energy storage batteries, the aforementioned DC-DC converter circuits are used to achieve voltage matching between the connected energy storage batteries and the DC bus, as well as to manage the charging and discharging of the connected energy storage batteries. Therefore, in the case of energy storage power supply (EVS) scenarios, the power conversion device 11 operates with bidirectional energy flow. Based on this, the types of power semiconductor devices (i.e., the second and fourth switching devices) in the DC-DC converter circuits of PV power supply scenarios are not entirely the same as those in the DC-DC converter circuits of EVS power supply scenarios. For details, please refer to the following... Figure 5b and Figure 5c The power conversion device 11 shown.

[0079] For example, see Figure 5e , Figure 5e This is another structural schematic diagram of the power conversion device provided in this application. For example... Figure 5e As shown, DC power supply DC1 and DC power supply DC2 are photovoltaic panels PV1 and PV2, respectively. The second switching device S12 and the fourth switching device S22 can both be SiC-SBDs, and the first switching device S11 and the third switching device S21 can be IGBTs or MOSFETs. This embodiment uses an IGBT as an example to introduce the first switching device S11 and the third switching device S21.

[0080] One end of the first power inductor L1 is connected to the first input terminal of the first DC-DC converter circuit 111. 31 The other end is connected to the anode of SiC-SBDS12 and the drain of IGBT S11, and the cathode of SiC-SBDS12 is connected to the first output terminal out of the first DC-DC converter circuit 111. 31 The source of IGBT S11 is connected to the second input terminal in of the first DC-DC converter circuit 111. 32 Second output terminal out 32 One end of the second power inductor L2 is connected to the first input terminal in of the second DC-DC converter circuit 112. 41 The other end is connected to the cathode of SiC-SBDS22 and the source of IGBT S21, and the anode of SiC-SBDS22 is connected to the first output terminal out of the second DC-DC converter circuit 112.41 The drain of IGBT S21 is connected to the second input terminal in of the second DC-DC converter circuit 112. 42 Second output terminal out 42 .

[0081] In one optional embodiment, after the power conversion device 11 operates, the first controller 113 begins to control the first DC-DC converter 111 to achieve maximum power point tracking (MPPT) of the photovoltaic panel PV1, and controls the second DC-DC converter 112 to achieve MPPT of the photovoltaic panel PV2. Simultaneously, the first controller 113 begins to acquire the first bus voltage of the first bus capacitor C1 and the second bus voltage of the second bus capacitor C2 in real time.

[0082] In an optional embodiment, the first bus voltage is greater than the second bus voltage and the current of the power conversion device 11 flows from the photovoltaic panel to the load (i.e., the current flow direction of the power conversion device 11 is opposite to that of the load). Figure 5e When the reference current direction is the same, the first controller 113 increases the duty cycle of the first switching device IGBT S11 and / or decreases the duty cycle of the third switching device IGBT S21.

[0083] For example, when the first bus voltage is greater than the second bus voltage and the current of the power conversion device 11 flows from the photovoltaic panel to the load, the first controller 113 increases the duty cycle of the first switching device IGBT S11 to increase the second bus voltage, thereby reducing the difference between the first bus voltage and the second bus voltage, and thus achieving half-bus voltage balance.

[0084] For example, when the first bus voltage is greater than the second bus voltage and the current of the power conversion device 11 flows from the photovoltaic panel to the load, the first controller 113 reduces the duty cycle of the third switching device IGBT S21 to reduce the first bus voltage, thereby reducing the difference between the first bus voltage and the second bus voltage, and thus achieving half-bus voltage balance.

[0085] For example, when the first bus voltage is greater than the second bus voltage and the current of the power conversion device 11 flows from the photovoltaic panel to the load, the first controller 113 increases the duty cycle of the first switching device IGBT S11 and decreases the duty cycle of the third switching device IGBT S21, so that the first bus voltage decreases and the second bus voltage increases, thereby reducing the difference between the first bus voltage and the second bus voltage, and thus achieving half-bus voltage balance. It is understandable that simultaneously adjusting the duty cycle of the controllable switching devices in each of the two DC-DC converter circuits can effectively shorten the time required for half-bus voltage balance, thereby improving the operating efficiency of the power conversion device 11.

[0086] Normally, the DC-DC converter circuit operates in MPPT mode to ensure that the photovoltaic panels operate at maximum power. When a deviation occurs in the half-bus voltage, the duty cycle of the first or second DC-DC converter needs to be adjusted to achieve half-bus balance. At this time, the DC power conversion device will exit MPPT mode, resulting in some loss of power generation. However, the advantage is that no additional hardware circuitry is required, thus reducing the cost of the power conversion device.

[0087] In another alternative embodiment, when the first bus voltage is less than the second bus voltage and the current of the power conversion device 11 flows from the photovoltaic panel to the load, the first controller 113 reduces the duty cycle of the first switching device IGBT S11 and / or increases the duty cycle of the third switching device IGBT S21.

[0088] For example, when the second bus voltage is greater than the first bus voltage and the current of the power conversion device 11 flows from the photovoltaic panel to the load, the first controller 113 reduces the duty cycle of the first switching device IGBT S11 to reduce the second bus voltage, thereby reducing the difference between the first bus voltage and the second bus voltage, and thus achieving half-bus voltage balance.

[0089] For example, when the second bus voltage is greater than the first bus voltage and the current of the power conversion device 11 flows from the photovoltaic panel to the load, the first controller 113 increases the duty cycle of the third switching device IGBT S21 to increase the first bus voltage, thereby reducing the difference between the first bus voltage and the second bus voltage, and thus achieving half-bus voltage balance.

[0090] For example, when the second bus voltage is greater than the first bus voltage and the current of the power conversion device 11 flows from the photovoltaic panel to the load, the first controller 113 increases the duty cycle of the third switching device IGBT S21 and decreases the duty cycle of the first switching device IGBT S11, so that the second bus voltage decreases and the first bus voltage increases, thereby reducing the difference between the first bus voltage and the second bus voltage, and thus achieving half-bus voltage balance.

[0091] Understandably, the power conversion device 11 can achieve half-bus voltage balance by sampling the first bus voltage of the first bus capacitor C1 and the second bus voltage of the second bus capacitor C2, and then dynamically adjusting the duty cycle of the controllable switch of at least one of the two DC-DC converter circuits through closed-loop control. This control method does not require the addition of additional components or circuits, and can effectively reduce the cost of the power conversion device 11.

[0092] For example, see Figure 5f , Figure 5fThis is another structural schematic diagram of the power conversion device provided in this application. For example... Figure 5f As shown, DC power supply DC1 and DC power supply DC2 are energy storage batteries Bat1 and Bat2, respectively. The second switching device S12 and the fourth switching device S22 can be IGBTs or MOSFETs, and the first switching device S11 and the third switching device S21 can also be IGBTs or MOSFETs. This embodiment uses IGBTs as an example to introduce the first switching device S11, the second switching device S12, the third switching device S21, and the fourth switching device S22.

[0093] One end of the first power inductor L1 is connected to the first input terminal of the first DC-DC converter circuit 111. 31 The other end is connected to the source of IGBT S12 and the drain of IGBT S11. The drain of IGBT S12 is connected to the first output terminal out of the first DC-DC converter circuit 111. 31 The source of IGBT S11 is connected to the second input terminal in of the first DC-DC converter circuit 111. 32 Second output terminal out 32 One end of the second power inductor L2 is connected to the first input terminal in of the second DC-DC converter circuit 112. 41 The other end is connected to the drain of IGBT S22 and the source of IGBT S21. The source of IGBT S22 is connected to the first output terminal out of the second DC-DC converter circuit 112. 41 The drain of IGBT S21 is connected to the second input terminal in of the second DC-DC converter circuit 112. 42 Second output terminal out 42 .

[0094] Here, when the current of the power conversion device 11 flows from the energy storage battery to the load, that is, the current flow direction of the power conversion device 11 is... Figure 5f When the reference directions of the medium current are the same, the energy storage battery operates in discharge mode. Figure 5f The specific implementation method of the power conversion device 11 shown to achieve half-bus voltage balance is as follows: Figure 5e The descriptions of the corresponding parts in the illustrated embodiments are consistent and will not be repeated here.

[0095] However, when the current of the power conversion device 11 flows from the load to the energy storage battery, that is, when the current flow direction of the power conversion device 11 is... Figure 5f When the reference current direction is opposite, the energy storage battery is operating in charging mode, and the balance control strategy of the half bus voltage is exactly the opposite of the balance control strategy of the half bus voltage when the energy storage battery is operating in discharging mode.

[0096] In an optional embodiment, when the first bus voltage is greater than the second bus voltage and the current of the power conversion device 11 flows from the load to the energy storage battery, the first controller 113 reduces the duty cycle of the first switching device IGBT S11 and / or increases the duty cycle of the third switching device IGBT S21.

[0097] For example, when the first bus voltage is greater than the second bus voltage and the current of the power conversion device 11 flows from the load to the energy storage battery, the first controller 113 reduces the duty cycle of the first switching device IGBT S11 to increase the second bus voltage, thereby reducing the difference between the first bus voltage and the second bus voltage, and thus achieving half bus voltage balance.

[0098] For example, when the first bus voltage is greater than the second bus voltage and the current of the power conversion device 11 flows from the load to the energy storage battery, the first controller 113 increases the duty cycle of the third switching device IGBT S21 to reduce the first bus voltage, thereby reducing the difference between the first bus voltage and the second bus voltage, and thus achieving half bus voltage balance.

[0099] For example, when the first bus voltage is greater than the second bus voltage and the current of the power conversion device 11 flows from the load to the energy storage battery, the first controller 113 reduces the duty cycle of the first switching device IGBT S11 and increases the duty cycle of the third switching device IGBT S21, so that the first bus voltage decreases and the second bus voltage increases, thereby reducing the difference between the first bus voltage and the second bus voltage, and thus achieving half-bus voltage balance. It is understandable that simultaneously adjusting the duty cycle of the controllable switches in each of the two DC-DC converter circuits can effectively shorten the time required for half-bus voltage balance, thereby improving the operating efficiency of the power conversion device 11.

[0100] In another alternative embodiment, when the first bus voltage is less than the second bus voltage and the current of the power conversion device 11 flows from the load to the energy storage battery, the first controller 113 increases the duty cycle of the first switching device IGBT S11 and / or decreases the duty cycle of the third switching device IGBT S21.

[0101] For example, when the second bus voltage is greater than the first bus voltage and the current of the power conversion device 11 flows from the load to the energy storage battery, the first controller 113 increases the duty cycle of the first switching device IGBT S11 to reduce the second bus voltage, thereby reducing the difference between the first bus voltage and the second bus voltage, and thus achieving half bus voltage balance.

[0102] For example, when the second bus voltage is greater than the first bus voltage and the current of the power conversion device 11 flows from the load to the energy storage battery, the first controller 113 reduces the duty cycle of the third switching device IGBT S21 to increase the first bus voltage, thereby reducing the difference between the first bus voltage and the second bus voltage, and thus achieving half bus voltage balance.

[0103] For example, when the second bus voltage is greater than the first bus voltage and the current of the power conversion device 11 flows from the load to the energy storage battery, the first controller 113 reduces the duty cycle of the third switching device IGBT S21 and increases the duty cycle of the first switching device IGBT S11, so that the second bus voltage decreases and the first bus voltage increases, thereby reducing the difference between the first bus voltage and the second bus voltage, and thus achieving half-bus voltage balance.

[0104] In this embodiment, the number of power semiconductor devices in the DC-DC converter circuit is reduced by 50%, which significantly reduces the circuit cost of the DC-DC converter circuit and thus significantly reduces the cost of the power conversion device 11. Furthermore, the reduction in the number of power semiconductor devices in the DC-DC converter circuit also effectively reduces the circuit complexity of the power conversion device 11, thereby reducing the control complexity of the power conversion device 11 and improving its stability. Additionally, the power conversion device 11 can achieve half-bus voltage balance by dynamically adjusting the duty cycle of the controllable switch of at least one of the two DC-DC converter circuits through closed-loop control. This control method does not require additional devices or circuits, effectively reducing the cost of the power conversion device 11. Moreover, the power conversion device 11 provided in this application is applicable to power supply scenarios such as photovoltaic power supply and energy storage power supply, demonstrating strong applicability.

[0105] To achieve half-bus capacitor balance, in addition to adjusting the duty cycle of the controllable switch in at least one of the DC-DC converter circuits 111 and 112, the power conversion device 11 can also achieve this by adding a bus voltage balancing circuit to the power conversion device 11. For details, please refer to [link to relevant documentation]. Figures 6a to 6e The power conversion device 11 shown.

[0106] See Figure 6a , Figure 6a This is another structural schematic diagram of the power conversion device provided in this application. For example... Figure 6a As shown, the power conversion device 11 includes a first group of first input terminals in 11 The first group of second input terminals in 12 The first input terminal of the second group in 21 The second input terminal of the second group 22The system includes a first DC-DC converter circuit 111, a second DC-DC converter circuit 112, a positive DC bus BUS+, a negative DC bus BUS-, a first bus capacitor C1, a second bus capacitor C2, a first input capacitor C3, a second input capacitor C4, a first output terminal out1 and a second output terminal out2 of the power conversion device 11, a first controller 113, and a bus voltage balancing circuit 114.

[0107] The bus voltage balancing circuit 114 has its first, second, and third terminals connected to the bus midpoint M1, the positive DC bus BUS+, and the negative DC bus BUS-, respectively. The bus midpoint M1 is the connection point between the first bus capacitor C1 and the second bus capacitor C2. The bus voltage balancing circuit 114 is used to transfer the electrical energy stored in the first bus capacitor C1 to the second bus capacitor C2, or to transfer the electrical energy stored in the second bus capacitor C2 to the first bus capacitor C1. Specifically, the bus voltage balancing circuit 114 includes an energy storage element. It is used to transfer the electrical energy stored in the first bus capacitor C1 to the energy storage element and then transfer the electrical energy from the energy storage element to the second bus capacitor C2; or to transfer the electrical energy stored in the second bus capacitor C2 to the energy storage element and then transfer the electrical energy from the energy storage element to the first bus capacitor C1. For descriptions of other parts of the power conversion device 11 besides the bus voltage balancing circuit 114, please refer to [link to description]. Figure 4a Description of the corresponding parts in the illustrated embodiment.

[0108] In an optional embodiment, after the power conversion device 11 operates, the first controller 113 begins to acquire the first bus voltage of the first bus capacitor C1 and the second bus voltage of the second bus capacitor C2. If a deviation occurs between the first bus voltage and the second bus voltage, the first controller 113 controls the bus voltage balancing circuit 114 to transfer the electrical energy stored in the bus capacitor corresponding to the larger of the first and second bus voltages to the energy storage element, and to transfer the electrical energy stored in the energy storage element to the bus capacitor corresponding to the smaller bus voltage. This reduces the larger bus voltage, thereby reducing the difference between the first and second bus voltages, and ultimately achieving half-bus voltage balancing.

[0109] In an optional embodiment, when the first bus voltage is greater than the second bus voltage, the first controller 113 controls the bus voltage balancing circuit 114 to transfer a portion of the electrical energy stored in the first bus capacitor C1 to the energy storage element, and to transfer the electrical energy of the energy storage element to the second bus capacitor C2, so as to reduce the difference between the first bus voltage and the second bus voltage, thereby achieving half bus voltage balancing.

[0110] In another optional embodiment, when the first bus voltage is less than the second bus voltage, the first controller 113 controls the bus voltage balancing circuit 114 to transfer a portion of the electrical energy stored in the second bus capacitor C2 to the energy storage element, and to transfer the electrical energy of the energy storage element to the first bus capacitor C1, so as to reduce the difference between the first bus voltage and the second bus voltage, thereby achieving half bus voltage balancing.

[0111] Here, the specific circuit structure of the bus voltage balancing circuit 114, and the specific implementation method of the power conversion device 11 transferring electrical energy among the first bus capacitor C1, the energy storage element, and the second bus capacitor C2 through the bus voltage balancing circuit 114 to achieve half-bus voltage balancing, will be discussed later. Figures 6b to 6e The description of the corresponding embodiments will not be elaborated here.

[0112] See Figure 6b , Figure 6b This is another structural schematic diagram of the power conversion device provided in this application. For example... Figure 6b As shown, the bus voltage balancing circuit 114 includes a third power inductor L3, a fifth switching device S31, and a sixth switching device S32. In this embodiment, the third power inductor L3 is an energy storage element. One end of the third power inductor L3 is connected to the first terminal of the bus voltage balancing circuit 114, and the other end of the third power inductor L3 is connected to the second and third terminals of the bus voltage balancing circuit 114 via the fifth switching device S31 and the sixth switching device S32, respectively. Figure 6b Please refer to the connection relationships of the other parts of the power conversion device 11 shown, except for the bus voltage balancing circuit 114. Figure 5a Description of the corresponding part of the power conversion device 11 shown.

[0113] In an optional embodiment, when the first bus voltage is greater than the second bus voltage, the first controller 113 controls the fifth switching device S31 to be turned on for a first preset time and then turned off. During the turn-on process of the fifth switching device S31, the electrical energy stored in the first bus capacitor C1 charges the third power inductor L3 through the fifth switching device S31, so that part of the energy stored in the first bus capacitor C1 is transferred to the third power inductor L3. After the fifth switching device S31 is turned off, the first controller 113 controls the sixth switching device S32 to be turned on for a second preset time and then turned off. During the turn-on process of the sixth switching device S32, since the current direction of the inductor cannot change abruptly, the electrical energy stored in the third power inductor L3 charges the second bus capacitor C2 through the sixth switching device S32, so that the electrical energy stored in the third power inductor L3 is transferred to the second bus capacitor C2, thereby reducing the difference between the first bus voltage and the second bus voltage, thus achieving half-bus voltage balance. It should be noted that the first preset duration and the second preset duration can be understood as the turn-on time in traditional pulse width modulation (PWM) control. The first controller can flexibly and dynamically adjust the time of the first preset duration and the second preset duration, and achieve half-bus voltage balance control of the power conversion device through multiple control of the switching devices.

[0114] In another optional embodiment, when the first bus voltage is lower than the second bus voltage, the first controller 113 controls the sixth switching device S32 to be turned on for a first preset time and then turned off. During the conduction of the sixth switching device S32, the electrical energy stored in the second bus capacitor C2 charges the third power inductor L3 through the sixth switching device S32, so that part of the electrical energy stored in the second bus capacitor C2 is transferred to the third power inductor L3. After the sixth switching device S32 is turned off, the first controller 113 controls the fifth switching device S31 to be turned on for a second preset time and then turned off. During the conduction of the fifth switching device S31, since the current direction of the inductor cannot change abruptly, the electrical energy stored in the third power inductor L3 charges the first bus capacitor C1 through the fifth switching device S31, so that the electrical energy stored in the third power inductor L3 is transferred to the first bus capacitor C1. This reduces the difference between the first bus voltage and the second bus voltage, thereby achieving half-bus voltage balance.

[0115] Understandably, the power conversion device 11 through Figure 6bThe bus voltage balancing circuit 114 shown, also known as the BUCK-BOOST circuit, realizes the transfer of electrical energy between the first bus capacitor C1, the third power inductor L3, and the second bus capacitor C2, thereby achieving half-bus voltage balancing. By achieving half-bus voltage balancing through the bus voltage balancing circuit 114, decoupling control can be achieved with various DC-DC converter circuits, ensuring flexible energy control of the DC-DC converter circuits. This allows for flexible management of the DC power supply, such as without sacrificing the MPPT of the photovoltaic panels or maximizing the energy utilization of the energy storage batteries.

[0116] The following is combined with Figure 6c and Figure 6d ,right Figure 6b The specific structures of the power conversion device 11 shown are described in both photovoltaic power supply scenarios and energy storage power supply scenarios.

[0117] See Figure 6c , Figure 6c This is another structural schematic diagram of the power conversion device provided in this application. For example... Figure 6c As shown, DC power supply DC1 and DC power supply DC2 are photovoltaic panels PV1 and PV2, respectively. The fifth switching device S31 and the sixth switching device S32 can be IGBTs or MOSFETs. This embodiment uses an IGBT as an example to introduce the fifth switching device S31 and the sixth switching device S32.

[0118] In this circuit, one end of the third power inductor L3 is connected to the first terminal of the bus voltage balancing circuit 114, and the other end is connected to the source of IGBT S31 and the drain of IGBT S32. The drain of IGBT S31 is connected to the second terminal of the bus voltage balancing circuit 114, and the source of IGBT S32 is connected to the third terminal of the bus voltage balancing circuit 114. For the specific structure and connection relationships of the other parts of the power conversion device 11 besides the bus voltage balancing circuit 114, please refer to [link to relevant documentation]. Figure 5b Description of the corresponding part of the power conversion device 11 shown.

[0119] After the power conversion device 11 starts working, the first controller 113 starts controlling the first DC-DC converter 111 to achieve maximum power point tracking (MPPT) of the photovoltaic panel PV1 to ensure high-efficiency power generation of the photovoltaic panel PV1; and controls the second DC-DC converter 112 to achieve MPPT of the photovoltaic panel PV2 to ensure high-efficiency power generation of the photovoltaic panel PV2. Simultaneously, the first controller 113 starts acquiring the first bus voltage of the first bus capacitor C1 and the second bus voltage of the second bus capacitor C2. When a deviation occurs between the first bus voltage and the second bus voltage, the controller controls the operating states of IGBTs S31 and S32 to transfer electrical energy among the first bus capacitor C1, the third power inductor L3, and the second bus capacitor C2, thereby reducing the difference between the first bus voltage and the second bus voltage and achieving half-bus voltage balance.

[0120] Here, for a detailed implementation of the method by which the first controller 113 controls IGBTs S31 and S32 to transfer electrical energy among the first bus capacitor C1, the third power inductor L3, and the second bus capacitor C2, please refer to [link to relevant documentation]. Figure 6b Description of the corresponding parts in the illustrated embodiment.

[0121] See Figure 6d , Figure 6d This is another structural schematic diagram of the power conversion device provided in this application. For example... Figure 6d As shown, DC power supply DC1 and DC power supply DC2 are energy storage batteries Bat1 and Bat2, respectively. The fifth switching device S31 and the sixth switching device S32 can be IGBTs or MOSFETs. This embodiment uses an IGBT as an example to introduce the fifth switching device S31 and the sixth switching device S32.

[0122] In this circuit, one end of the third power inductor L3 is connected to the first terminal of the bus voltage balancing circuit 114, and the other end is connected to the source of IGBT S31 and the drain of IGBT S32. The drain of IGBT S31 is connected to the second terminal of the bus voltage balancing circuit 114, and the source of IGBT S32 is connected to the third terminal of the bus voltage balancing circuit 114. For the specific structure and connection relationships of the other parts of the power conversion device 11 besides the bus voltage balancing circuit 114, please refer to [link to relevant documentation]. Figure 5c Description of the corresponding part of the power conversion device 11 shown.

[0123] After the power conversion device 11 starts working, the first controller 113 begins to acquire the battery voltage (or remaining capacity) of energy storage battery Bat1 and the battery voltage (or remaining capacity) of energy storage battery Bat2. Based on the relationship between the battery voltage (or remaining capacity) of energy storage battery Bat1 and the target battery voltage (or target remaining capacity), the first DC-DC converter 111 controls the charging and discharging of energy storage battery Bat1 to achieve precise management of energy storage battery Bat1. Based on the relationship between the battery voltage (or remaining capacity) of energy storage battery Bat2 and the target battery voltage (or target remaining capacity), the second DC-DC converter 112 controls the charging and discharging of energy storage battery Bat2 to achieve precise management of energy storage battery Bat2. Simultaneously, the first controller 113 begins to acquire the first bus voltage of the first bus capacitor C1 and the second bus voltage of the second bus capacitor C2. When there is a deviation between the first bus voltage and the second bus voltage, it controls the operating state of IGBTs S31 and S32 to realize the transfer of electrical energy among the first bus capacitor C1, the third power inductor L3 and the second bus capacitor C2, so as to reduce the difference between the first bus voltage and the second bus voltage, thereby achieving half-bus voltage balance.

[0124] Here, for a detailed implementation of the method by which the first controller 113 controls IGBTs S31 and S32 to transfer electrical energy among the first bus capacitor C1, the third power inductor L3, and the second bus capacitor C2, please refer to [link to relevant documentation]. Figure 6b Description of the corresponding parts in the illustrated embodiment.

[0125] In this embodiment, the power conversion device 11 can effectively reduce the number of power semiconductor devices in the DC-DC converter circuit, thereby reducing the cost of the power conversion device 11 and improving its market competitiveness. Furthermore, the power conversion device 11 achieves half-bus voltage balance by using a bus voltage balancing circuit 114, i.e., a BUCK-BOOST circuit, to transfer electrical energy among the first bus capacitor C1, the third power inductor L3, and the second bus capacitor C2. Achieving half-bus voltage balance through the bus voltage balancing circuit 114 allows for decoupling control from various DC-DC converter circuits, ensuring flexible energy control of the DC-DC converter circuits and thus enabling flexible management of the DC power supply.

[0126] See Figure 6e , Figure 6e This is another structural schematic diagram of the power conversion device provided in this application. For example... Figure 6eAs shown, the bus voltage balancing circuit 114 includes a resonant capacitor C5, a resonant inductor L4, a seventh switching device S41, an eighth switching device S42, a ninth switching device S43, and a tenth switching device S44. In this embodiment, the resonant capacitor C5 is an energy storage element. The seventh switching device S41 and the eighth switching device S42 are connected in series to form a first switching arm, with both ends of the first switching arm connected to the second and first ends of the bus voltage balancing circuit 114, respectively. The first end of the seventh switching device S41 is connected to the second end of the bus voltage balancing circuit 114. The ninth switching device S43 and the tenth switching device S44 are connected in series to form a second switching arm, with both ends of the second switching arm connected to the first and third ends of the bus voltage balancing circuit 114, respectively. The first end of the ninth switching device S43 is connected to the first end of the bus voltage balancing circuit 114. The resonant inductor L4 and the resonant capacitor C5 are connected in series between the midpoint a of the first switching arm and the midpoint b of the second switching arm. The midpoint a of the first switch bridge arm is the series connection point of the seventh switch device S41 and the eighth switch device S42, and the midpoint b of the second switch bridge arm is the series connection point of the ninth switch device S43 and the tenth switch device S44. Here, Figure 6e Please refer to the connection relationships of the other parts of the power conversion device 11 shown, except for the bus voltage balancing circuit 114. Figure 5a Description of the corresponding part of the power conversion device 11 shown.

[0127] In an optional embodiment, when the first bus voltage is greater than the second bus voltage, the first controller 113 controls the seventh switch device S41 and the ninth switch device S43 to conduct for a third preset time and then turn them off. Since the inductance of the resonant inductor L4 is very small, during the conduction of the seventh switch device S41 and the ninth switch device S43, it can be seen that the electrical energy stored in the first bus capacitor C1 is charged by the seventh switch device S41 and the ninth switch device S43, so that the electrical energy stored in the first bus capacitor C1 is transferred to the resonant capacitor C5. After the seventh switch device S41 and the ninth switch device S43 are turned off, the first controller 113 controls the eighth switch device S42 and the tenth switch device S44 to conduct for a fourth preset time and then turn them off. During the conduction of the eighth switch device S42 and the tenth switch device S44, the electrical energy stored in the resonant capacitor C5 is charged by the eighth switch device S42 and the tenth switch device S44, so that the electrical energy stored in the resonant capacitor C5 is transferred to the second bus capacitor C2. This reduces the difference between the first bus voltage and the second bus voltage, thus achieving half-bus voltage balance. Similarly, the third and fourth preset durations can be understood as the turn-on time in traditional PWM control. The first controller can flexibly and dynamically adjust the durations of the third and fourth preset durations, and achieve half-bus voltage balance control of the power conversion device through multiple controls of the switching devices.

[0128] In another optional embodiment, when the first bus voltage is less than the second bus voltage, the first controller 113 controls the tenth switching device S44 and the eighth switching device S42 to conduct for a third preset time and then turn them off. Since the inductance of the resonant inductor L4 is very small, during the conduction of the tenth switching device S44 and the eighth switching device S42, it can be considered that the electrical energy stored in the second bus capacitor C2 charges the resonant capacitor C5 through the tenth switching device S44 and the eighth switching device S42, so that the electrical energy stored in the second bus capacitor C2 is transferred to the resonant capacitor C5. After the tenth switching device S44 and the eighth switching device S42 are turned off, the first controller 113 controls the ninth switching device S43 and the seventh switching device S41 to conduct for a fourth preset time and then turn them off. During the conduction of the ninth switching device S43 and the seventh switching device S41, the electrical energy stored in the resonant capacitor C5 charges the first bus capacitor C1 through the ninth switching device S43 and the seventh switching device S41, so that the electrical energy stored in the resonant capacitor C5 is transferred to the first bus capacitor C1. This reduces the difference between the first bus voltage and the second bus voltage, thereby achieving half-bus voltage balance.

[0129] Understandably, the power conversion device 11 through Figure 6e The bus voltage balancing circuit 114 shown, also known as a resonant switched capacitor circuit (RSCC), realizes the transfer of electrical energy among the first bus capacitor C1, the resonant capacitor C5, and the second bus capacitor C2, thereby achieving half-bus voltage balancing. Achieving half-bus voltage balancing through the bus voltage balancing circuit allows for decoupling control from various DC-DC converter circuits, ensuring flexible energy control of the DC-DC converter circuits and thus enabling flexible management of the DC power supply. For example, it can achieve maximum energy utilization of the photovoltaic panel without sacrificing the MPPT (Maximum Power Point Test) or the energy storage battery. Furthermore, the bus voltage balancing circuit 114 has diverse structures, thereby increasing the versatility and flexibility of the power conversion device 11's structure.

[0130] See Figure 7 , Figure 7 This is a structural schematic diagram of the power supply system provided in this application. For example... Figure 7 As shown, the power supply system 1 includes an inverter circuit 12 and Figure 4a The power conversion device 11 is shown. The first output terminal out1 and the second output terminal out2 of the power conversion device 11 are respectively connected to the first input terminal in of the inverter circuit 12. 51 Second input terminal in 52 The first output terminal out of inverter circuit 12 51 Second output terminal out 52Connect to the AC power grid. Optionally, the inverter circuit 12 also includes a third bus capacitor C6, a fourth bus capacitor C7, and a third input terminal in of the inverter circuit 12. 53 The third bus capacitor C6 is located at the first input terminal of inverter circuit 12. 51 and the third input terminal in 53 Between, the fourth bus capacitor C7 is located at the third input terminal in of inverter circuit 12. 53 Second input terminal in 52 Between. Among them, inverter circuit 12 is a multi-level inverter circuit. For a description of other parts of the power conversion device 11, please refer to... Figure 4a The descriptions of the corresponding parts of the illustrated embodiments will not be repeated here.

[0131] The power supply system 1 also includes a second controller 13. The second controller 13 can be the same controller as the first controller 113 in the power conversion device 11, or they can be two independent controllers; this application does not impose any restrictions on this. It should be noted that the inverter circuit 12 can be located within the same device as the power conversion device 11 to jointly constitute an inverter. In this case, the second controller 13 and the first controller 113 are the same controller. Alternatively, the inverter circuit 12 can be located separately within the inverter, and the inverter and the power conversion device 11 are independent of each other. In this case, the second controller 13 can be a controller within the inverter, independent of the first controller 113.

[0132] In an optional embodiment, where the inverter circuit 12 and the power conversion device 11 together constitute an inverter: after the power supply system 1 starts working, the second controller 13, in addition to controlling the power conversion device 11 and the inverter circuit 12 to convert the DC power from the DC power supply connected to the input terminal of the power conversion device 11 into AC power that meets the AC requirements of the AC power grid, also acquires the first bus voltage of the first bus capacitor C1 and the second bus voltage of the second bus capacitor C2. If a deviation occurs between the first bus voltage and the second bus voltage, the second controller 13 controls the duty cycle of the controllable switch in the first DC-DC converter circuit 111 or the second DC-DC converter circuit 112 to reduce the difference between the first bus voltage and the second bus voltage, thereby achieving half-bus voltage balance. For a detailed explanation of how the second controller 13 achieves half-bus voltage balance by adjusting the duty cycle of the DC-DC converter circuit, please refer to [link to relevant documentation]. Figures 5a to 5f Description of the corresponding parts in the illustrated embodiment.

[0133] In another alternative embodiment, where the inverter circuit 12 is located solely within the inverter: after the power supply system 1 starts operating, the first controller 113, in addition to controlling the power conversion device 11 to convert the DC power from the DC power source connected to the input terminal of the power conversion device 11 into DC power, also acquires the first bus voltage of the first bus capacitor C1 and the second bus voltage of the second bus capacitor C2. If a deviation occurs between the first bus voltage and the second bus voltage, the first controller 113 controls the duty cycle of the controllable switches in the first DC-DC converter circuit 111 or the second DC-DC converter circuit 112 to reduce the difference between the first bus voltage and the second bus voltage, thereby achieving half-bus voltage balance. Subsequently, the second controller 13 controls the inverter circuit 12 to invert the DC power output from the power conversion device 11 into AC power that meets the requirements of the AC power grid.

[0134] Understandably, by connecting two bus capacitors C1 and C2 in series between the positive DC bus BUS+ and the negative DC bus BUS-, and connecting the two output terminals of the first DC-DC converter circuit 111 to the first bus capacitor C1, and the two output terminals of the second DC-DC converter circuit 112 to the two ends of the second bus capacitor C2, the voltage drop across each of the two DC-DC converter circuits can be reduced, thereby reducing the circuit cost of the two DC-DC converter circuits, and consequently reducing the cost of the power supply system 1, further enhancing the market competitiveness of the power supply system 1. Furthermore, by dynamically adjusting the duty cycle of the controllable switch of at least one of the two DC-DC converter circuits using closed-loop control, half-bus voltage balance can be achieved. This control method requires no additional components or circuits, effectively reducing the cost of the power supply system 1.

[0135] Furthermore, in addition to adjusting the duty cycle of the controllable switches in the first DC-DC converter circuit 111 or the second DC-DC converter circuit 112, this can also be achieved by adding a bus voltage balancing circuit to the power conversion device 11.

[0136] See Figure 8 , Figure 8 This is another structural schematic diagram of the power supply system provided in this application. For example... Figure 8 As shown, the power supply system 1 includes an inverter circuit 12 and Figure 6a The power conversion device 11 is shown. The first output terminal out1 and the second output terminal out2 of the power conversion device 11 are respectively connected to the first input terminal in of the inverter circuit 12. 51 Second input terminal in 52 The first output terminal out of inverter circuit 12 51 Second output terminal out 52Connect to the AC power grid. Optionally, the inverter circuit 12 also includes a third bus capacitor C6, a fourth bus capacitor C7, and a third input terminal in of the inverter circuit 12. 53 The third bus capacitor C6 is located at the first input terminal of inverter circuit 12. 51 and the third input terminal in 53 Between, the fourth bus capacitor C7 is located at the third input terminal in of inverter circuit 12. 53 Second input terminal in 52 Between. Among them, inverter circuit 12 is a multi-level inverter circuit. For a description of other parts of the power conversion device 11, please refer to... Figure 6a The descriptions of the corresponding parts of the illustrated embodiments will not be repeated here.

[0137] The power supply system 1 also includes a second controller 13. The second controller 13 can be the same controller as the first controller 113 in the power conversion device 11, or they can be two independent controllers; this application does not impose any restrictions on this. It should be noted that the inverter circuit 12 can be located within the same device as the power conversion device 11 to jointly constitute an inverter. In this case, the second controller 13 and the first controller 113 are the same controller. Alternatively, the inverter circuit 12 can be located separately within the inverter, and the inverter and the power conversion device 11 are independent of each other. In this case, the second controller 13 can be a controller within the inverter, independent of the first controller 113.

[0138] In an optional embodiment, where the inverter circuit 12 and the power conversion device 11 together constitute an inverter: after the power supply system 1 starts working, the second controller 13, in addition to controlling the power conversion device 11 and the inverter circuit 12 to convert the DC power from the DC power supply connected to the input terminal of the power conversion device 11 into AC power that meets the AC requirements of the AC power grid, also acquires the first bus voltage of the first bus capacitor C1 and the second bus voltage of the second bus capacitor C2. If there is a deviation between the first bus voltage and the second bus voltage, the second controller 13 controls the bus voltage balancing circuit 114 to transfer electrical energy between the first bus capacitor C1 and the second bus capacitor C2, thereby reducing the difference between the first bus voltage and the second bus voltage, and thus achieving half-bus voltage balance. For a detailed explanation of how the second controller 13 achieves half-bus voltage balance by transferring electrical energy between the first bus capacitor C1 and the second bus capacitor C2, please refer to [link to relevant documentation]. Figures 6a to 6e Description of the corresponding parts in the illustrated embodiment.

[0139] In another alternative embodiment, where the inverter circuit 12 is located solely within the inverter: after the power supply system 1 starts operating, the first controller 113, in addition to controlling the power conversion device 11 to convert the DC power from the DC power source connected to the input terminal of the power conversion device 11 to DC, also acquires the first bus voltage of the first bus capacitor C1 and the second bus voltage of the second bus capacitor C2. If a deviation occurs between the first bus voltage and the second bus voltage, the first controller 113 controls the bus voltage balancing circuit 114 to transfer electrical energy between the first bus capacitor C1 and the second bus capacitor C2, thereby reducing the difference between the first bus voltage and the second bus voltage, thus achieving half-bus voltage balancing. Afterwards, the second controller 13 controls the inverter circuit 12 to invert the DC power output from the power conversion device 11 into AC power that meets the requirements of the AC power grid.

[0140] Understandably, by connecting two bus capacitors C1 and C2 in series between the positive DC bus BUS+ and the negative DC bus BUS-, and connecting the two output terminals of the first DC-DC converter circuit 111 to the first bus capacitor C1, and the two output terminals of the second DC-DC converter circuit 112 to the two ends of the second bus capacitor C2, the voltage drop across each of the two DC-DC converter circuits can be reduced. This reduces the circuit cost of the two DC-DC converter circuits, thereby reducing the cost of the power supply system 1 and further enhancing its market competitiveness. The bus voltage balancing circuit 114 achieves half-bus voltage balancing, enabling decoupling control from each DC-DC converter circuit. This ensures flexible energy control of the DC-DC converter circuits, allowing for flexible management of the DC power supply, such as without sacrificing the MPPT of the photovoltaic panels or the maximum energy utilization of the energy storage battery.

[0141] See Figure 9 , Figure 9 This is another structural schematic diagram of the power supply system provided in this application. For example... Figure 9 As shown, the power supply system 1 includes an inverter circuit 12 and Figure 4a The power conversion device 11 is shown. The first output terminal out1 and the second output terminal out2 of the power conversion device 11 are respectively connected to the first input terminal in of the inverter circuit 12. 51 Second input terminal in 52 The third input terminal of inverter circuit 12 is in 53 Connect the midpoint M1 of the busbar to the first output terminal out of inverter circuit 12. 51 Second output terminal out 52 It is connected to the AC power grid. The inverter circuit 12 is a multi-level inverter circuit. For a description of the other parts of the power conversion device 11, please refer to [link to relevant documentation]. Figure 4a The descriptions of the corresponding parts of the illustrated embodiments will not be repeated here.

[0142] The power supply system 1 also includes a second controller 13. The second controller 13 can be the same controller as the first controller 113 in the power conversion device 11, or they can be two independent controllers; this application does not impose any restrictions on this. It should be noted that the inverter circuit 12 can be located within the same device as the power conversion device 11 to jointly constitute an inverter. In this case, the second controller 13 and the first controller 113 are the same controller. Alternatively, the inverter circuit 12 can be located separately within the inverter, and the inverter and the power conversion device 11 are independent of each other. In this case, the second controller 13 can be a controller within the inverter, independent of the first controller 113.

[0143] In an optional embodiment, when the inverter circuit 12 and the power conversion device 11 together constitute an inverter: after the power supply system 1 starts working, the second controller 13, in addition to controlling the power conversion device 11 and the inverter circuit 12 to convert the DC power from the DC power supply connected to the input terminal of the power conversion device 11 into AC power that meets the requirements of the AC power grid, also acquires the first bus voltage of the first bus capacitor C1 and the second bus voltage of the second bus capacitor C2. If there is a deviation between the first bus voltage and the second bus voltage, the second controller 13 controls the inverter circuit 12 to output the electrical energy stored in the first bus capacitor C1 and the second bus capacitor C2 to the AC power grid. Specifically, the bus capacitor corresponding to the larger bus voltage outputs more electrical energy to the AC power grid than the bus capacitor corresponding to the smaller bus voltage. This reduces the difference between the first bus voltage and the second bus voltage, thereby achieving half-bus voltage balance.

[0144] In an optional embodiment, when the first bus voltage is greater than the second bus voltage, during the positive half-cycle of the AC circuit, the second controller 13 controls the inverter circuit 12 to connect to the first input terminal in of the inverter circuit 12. 51 The connected upper bridge arm switch is turned on for a fifth preset time and then turned off. After the upper bridge arm switch is turned off, the control and inverter circuit 12's third input terminal in... 53 The connected intermediate bridge arm switch is turned on for a sixth preset time and then turned off. During the negative half-cycle of the AC circuit, the second controller 13 controls the second input terminal in of the inverter circuit 12. 52 The connected lower bridge arm switch is turned on for a seventh preset time and then turned off. After the lower bridge arm switch is turned off, the control and inverter circuit 12's third input terminal in... 53The connected intermediate bridge arm switch is turned on for an eighth preset time and then turned off. The fifth preset time is longer than the seventh preset time. It should be noted that the fifth, sixth, seventh, and eighth preset times can be understood as the turn-on time in traditional PWM control. The second controller 13 can flexibly and dynamically adjust the times of the fifth, sixth, seventh, and eighth preset times, and through multiple controls of the switching devices, achieve half-bus voltage balance control of the power conversion device 11.

[0145] During the conduction of the upper bridge arm switch, the electrical energy stored in the first bus capacitor C1 is output to the AC power grid; during the conduction of the lower bridge arm switch, the electrical energy stored in the second bus capacitor C2 is output to the AC power grid. Since the conduction time of the upper bridge arm switch is longer than that of the lower bridge arm switch, more of the electrical energy stored in the first bus capacitor C1 is fed into the AC power grid compared to the second bus capacitor C2. This reduces the voltage of the first bus capacitor C1, thereby reducing the difference between the first bus voltage and the second bus voltage, and ultimately achieving half-bus voltage balance.

[0146] In another optional embodiment, when the first bus voltage is lower than the second bus voltage, the second controller 13 controls the fifth preset duration to be less than the seventh preset duration. This ensures that the electrical energy stored in the second bus capacitor C2 can be fed into the AC power grid more than that in the first bus capacitor C1, thereby reducing the voltage of the second bus capacitor C2 and reducing the difference between the first bus voltage and the second bus voltage, thus achieving half-bus voltage balance.

[0147] In another alternative embodiment, where the inverter circuit 12 is located solely within the inverter: after the power supply system 1 starts operating, the first controller 113 controls the power conversion device 11 to convert the DC power from the DC power source connected to the input terminal of the power conversion device 11 into DC power that meets the requirements of the DC bus. The second controller 13 acquires the first bus voltage of the first bus capacitor C1 and the second bus voltage of the second bus capacitor C2. If there is a deviation between the first bus voltage and the second bus voltage, the second controller 13 controls the inverter circuit 12 to ensure that the bus capacitor corresponding to the larger of the first and second bus voltages outputs more electrical energy to the AC power grid than the bus capacitor corresponding to the smaller bus voltage, thereby ensuring that the power supply system 1 can not only output AC power that meets the requirements of the AC power grid but also achieve half-bus voltage balance.

[0148] Understandably, by connecting two bus capacitors C1 and C2 in series between the positive DC bus BUS+ and the negative DC bus BUS-, and connecting the two output terminals of the first DC-DC converter circuit 111 to the first bus capacitor C1 and the two output terminals of the second DC-DC converter circuit 112 to the two ends of the second bus capacitor C2, the voltage drop across each of the two DC-DC converter circuits can be reduced, thereby reducing the circuit cost of the two DC-DC converter circuits, and thus reducing the cost of the power supply system 1, further enhancing the market competitiveness of the power supply system 1. Furthermore, by controlling the inverter circuit 12 to achieve half-bus voltage balance, no additional components or circuits are required, effectively reducing the cost of the power supply system 1. Moreover, since the DC-DC converter circuit and the inverter circuit 12 share the first bus capacitor C1 and the second bus capacitor C2, the number of bus capacitors used in the power supply system 1 can be reduced, further reducing the cost of the power supply system 1.

[0149] Since the half-bus voltage balancing capability of inverter circuit 12 is limited, in practical applications, the half-bus voltage balancing capability can still be further improved by adding bus voltage balancing circuit 114.

[0150] See Figure 10 , Figure 10 This is yet another structural diagram of the power supply system provided in this application. For example... Figure 10 As shown, the power supply system 1 includes an inverter circuit 12 and Figure 6a The power conversion device 11 is shown. The first output terminal out1 and the second output terminal out2 of the power conversion device 11 are respectively connected to the first input terminal in of the inverter circuit 12. 51 Second input terminal in 52 The third input terminal of inverter circuit 12 is in 53 Connect the midpoint M1 of the busbar to the first output terminal out of inverter circuit 12. 51 Second output terminal out 52 It is connected to the AC power grid. The inverter circuit 12 is a multi-level inverter circuit. For a description of the other parts of the power conversion device 11, please refer to [link to relevant documentation]. Figure 6a The descriptions of the corresponding parts of the illustrated embodiments will not be repeated here.

[0151] The power supply system 1 also includes a second controller 13. The second controller 13 can be the same controller as the first controller 113 in the power conversion device 11, or they can be two independent controllers; this application does not impose any restrictions on this. It should be noted that the inverter circuit 12 can be located within the same device as the power conversion device 11 to jointly constitute an inverter. In this case, the second controller 13 and the first controller 113 are the same controller. Alternatively, the inverter circuit 12 can be located separately within the inverter, and the inverter and the power conversion device 11 are independent of each other. In this case, the second controller 13 can be a controller within the inverter, independent of the first controller 113.

[0152] In an optional embodiment, where the inverter circuit 12 and the power conversion device 11 together constitute an inverter: after the power supply system 1 starts working, the second controller 13, in addition to controlling the power conversion device 11 and the inverter circuit 12 to convert the DC power from the DC power supply connected to the input terminal of the power conversion device 11 into AC power that meets the AC requirements of the AC power grid, also acquires the first bus voltage of the first bus capacitor C1 and the second bus voltage of the second bus capacitor C2. If there is a deviation between the first bus voltage and the second bus voltage, the second controller 13 controls the bus voltage balancing circuit 114 to transfer electrical energy between the first bus capacitor C1 and the second bus capacitor C2, thereby reducing the difference between the first bus voltage and the second bus voltage, and thus achieving half-bus voltage balance.

[0153] After the bus voltage balancing circuit 114 has been operating for a preset period, if a deviation still exists between the first bus voltage and the second bus voltage, the second controller 13 controls the inverter circuit 12 to output the electrical energy stored in the first bus capacitor C1 and the second bus capacitor C2 to the AC power grid. Specifically, the bus capacitor corresponding to the larger bus voltage outputs more electrical energy to the AC power grid than the bus capacitor corresponding to the smaller bus voltage. This reduces the difference between the first and second bus voltages.

[0154] In another alternative embodiment, where the inverter circuit 12 is located solely within the inverter: after the power supply system 1 starts operating, the first controller 113, in addition to controlling the power conversion device 11 to convert the DC power from the DC power source connected to the input terminal of the power conversion device 11 to DC, also acquires the first bus voltage of the first bus capacitor C1 and the second bus voltage of the second bus capacitor C2. If a deviation occurs between the first bus voltage and the second bus voltage, the first controller 113 controls the bus voltage balancing circuit 114 to transfer electrical energy between the first bus capacitor C1 and the second bus capacitor C2, thereby reducing the difference between the first bus voltage and the second bus voltage, thus achieving half-bus voltage balance. The second controller 13 controls the inverter circuit 12 to invert the DC power output from the power conversion device 11 into AC power that meets the requirements of the AC power grid.

[0155] After the bus voltage balancing circuit 114 has been operating for a preset period, if the second controller 13 detects that there is still a deviation between the first bus voltage and the second bus voltage, the second controller 13 controls the inverter circuit 12 to output the electrical energy stored in the first bus capacitor C1 and the second bus capacitor C2 to the AC power grid. Specifically, the bus capacitor corresponding to the larger bus voltage outputs more electrical energy to the AC power grid than the bus capacitor corresponding to the smaller bus voltage. This reduces the difference between the first bus voltage and the second bus voltage.

[0156] Understandably, by connecting two bus capacitors C1 and C2 in series between the positive DC bus BUS+ and the negative DC bus BUS-, and connecting the two output terminals of the first DC-DC converter circuit 111 to the first bus capacitor C1, and the two output terminals of the second DC-DC converter circuit 112 to the two ends of the second bus capacitor C2, the voltage drop across each of the two DC-DC converter circuits can be reduced, thereby reducing the circuit cost of the two DC-DC converter circuits, and thus reducing the cost of the power supply system 1, further enhancing the market competitiveness of the power supply system 1. Furthermore, by controlling the bus voltage balancing circuit 114 and the inverter circuit 12 to achieve half-bus voltage balancing, the limited half-bus balancing capability of the inverter circuit 12 can be compensated for, further improving the control accuracy of half-bus voltage balancing. Moreover, the bus voltage balancing circuit 114 can further control and reduce the voltage ripple of the half-bus, that is, reduce the voltage ripple of the bus capacitors C1 and C2, improving the grid connection quality on the inverter side.

[0157] See Figure 11 , Figure 11 This is a schematic flowchart of a bus voltage control method for a power conversion device provided in this application. The bus voltage control method for a power conversion device provided in this application is applicable to… Figures 4a to 5fThe power conversion device 11 is shown. The bus voltage control method for the power conversion device may include the following steps:

[0158] S101, obtain the first bus voltage of the first bus capacitor and the second bus voltage of the second bus capacitor.

[0159] In one alternative embodiment, after the power conversion device starts working, the power conversion device begins to acquire the first bus voltage of the first bus capacitor and the second bus voltage of the second bus capacitor.

[0160] S102, when there is a deviation between the first bus voltage and the second bus voltage, adjust the duty cycle of the first switching device in the first DC-DC converter circuit and / or the duty cycle of the third switching device in the second DC-DC converter circuit.

[0161] In an optional embodiment, when the first bus voltage is greater than the second bus voltage and the current of the power conversion device flows from the DC power supply to the load, the power conversion device increases the duty cycle of the first switching device and / or decreases the duty cycle of the third switching device.

[0162] In another alternative embodiment, when the first bus voltage is less than the second bus voltage and the current of the power conversion device flows from the DC power supply to the load, the power conversion device increases the duty cycle of the third switching device and / or decreases the duty cycle of the first switching device.

[0163] In another alternative embodiment, when the first bus voltage is greater than the second bus voltage and the current of the power conversion device flows from the load to the DC power supply, the power conversion device reduces the duty cycle of the first switching device and / or increases the duty cycle of the third switching device.

[0164] In another alternative embodiment, when the first bus voltage is less than the second bus voltage and the current of the power conversion device flows from the load to the DC power supply, the power conversion device reduces the duty cycle of the third switching device and / or increases the duty cycle of the first switching device.

[0165] In specific implementation, further details regarding the operations performed by the power conversion device in the bus voltage control method of the power conversion device provided in this application can be found in [reference needed]. Figures 4a to 5f The implementation method of the power conversion device 11 shown will not be described in detail here.

[0166] In this embodiment, the power conversion device 11 can achieve half-bus voltage balance by dynamically adjusting the duty cycle of the controllable switch of at least one of the two DC-DC converter circuits through closed-loop control. This control method does not require the addition of extra components or circuits, effectively reducing the cost of the power conversion device 11.

[0167] See Figure 12 , Figure 12 This is another schematic flowchart of the bus voltage control method for the power conversion device provided in this application. The bus voltage control method for the power conversion device provided in this application is applicable to... Figures 6a to 6e The power conversion device 11 is shown. The bus voltage control method for the power conversion device may include the following steps:

[0168] S201, obtain the first bus voltage of the first bus capacitor and the second bus voltage of the second bus capacitor.

[0169] S202, when there is a deviation between the first bus voltage and the second bus voltage, the electrical energy stored in the bus capacitor corresponding to the larger bus voltage is transferred to the bus capacitor corresponding to the smaller bus voltage.

[0170] In one optional embodiment, when there is a deviation between the first bus voltage and the second bus voltage, the power conversion device transfers the electrical energy stored in the bus capacitor corresponding to the larger bus voltage to the energy storage element, and transfers the electrical energy stored in the energy storage element to the bus capacitor corresponding to the smaller bus voltage, thereby reducing the voltage value of the larger bus voltage and thus reducing the difference between the first bus voltage and the second bus voltage, to achieve half-bus voltage balance. The energy storage element includes a power inductor and a resonant capacitor.

[0171] In an optional embodiment, when the first bus voltage is greater than the second bus voltage, the power conversion device transfers the electrical energy stored in the first bus capacitor to the energy storage element, and transfers the electrical energy of the energy storage element to the second bus capacitor, so as to reduce the difference between the first bus voltage and the second bus voltage, thereby achieving half-bus voltage balance.

[0172] In another optional embodiment, when the first bus voltage is less than the second bus voltage, the power conversion device transfers the electrical energy stored in the second bus capacitor to the energy storage element, and transfers the electrical energy of the energy storage element to the first bus capacitor, so as to reduce the difference between the first bus voltage and the second bus voltage, thereby achieving half-bus voltage balance.

[0173] In specific implementation, further details regarding the operations performed by the power conversion device in the bus voltage control method of the power conversion device provided in this application can be found in [reference needed]. Figures 6a to 6e The implementation method of the power conversion device 11 shown will not be described in detail here.

[0174] In this embodiment, the power conversion device 11 achieves energy transfer between the first bus capacitor and the second bus capacitor through the bus voltage balancing circuit 114, thereby achieving half-bus voltage balancing. Achieving half-bus voltage balancing through the bus voltage balancing circuit 114 allows for decoupling control from various DC-DC converter circuits, ensuring flexible energy control of the DC-DC converter circuits and thus enabling flexible management of the DC power supply. For example, it avoids sacrificing the MPPT of the photovoltaic panel or the maximum energy utilization of the energy storage battery.

[0175] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A power conversion device, characterized by, The power conversion device includes a first set of input terminals, a second set of input terminals, a first DC-DC converter circuit, a second DC-DC converter circuit, a positive DC bus, a negative DC bus, a first bus capacitor, a second bus capacitor, and a first output terminal and a second output terminal. The first set of input terminals and the second set of input terminals are respectively connected to a DC power supply, and the first output terminal and the second output terminal of the power conversion device are connected to a load. The first set of input terminals includes a first set of first input terminals and a first set of second input terminals, and the second set of input terminals includes a second set of first input terminals and a second set of second input terminals, wherein: The first bus capacitor and the second bus capacitor are connected in series between the positive DC bus and the negative DC bus, and the positive DC bus and the negative DC bus are respectively connected to the first output terminal and the second output terminal of the power conversion device; The input terminal of the first DC-DC converter is connected to the first input terminal of the first group, and the output terminal of the first DC-DC converter is connected to both ends of the first bus capacitor. The input terminal of the second DC-DC converter is connected to the second group of second input terminals, and the output terminal of the second DC-DC converter is connected to both ends of the second bus capacitor. The second input terminal of the first group is connected to the negative DC bus, and the first input terminal of the second group is connected to the positive DC bus.

2. The power conversion device according to claim 1, characterized in that, The power conversion device further includes a first input capacitor and a second input capacitor. The input terminal of the first DC-DC converter includes a first input terminal and a second input terminal. One end of the first input capacitor is connected to the first input terminal of the first DC-DC converter and the first group of first input terminals. The other end of the first input capacitor is connected to the second input terminal of the first DC-DC converter or the first group of second input terminals. The input terminals of the second DC-DC converter circuit include a first input terminal and a second input terminal. One end of the second input capacitor is connected to the first input terminal and the second group of second input terminals of the second DC-DC converter circuit, and the other end of the second input capacitor is connected to the second input terminal or the second group of first input terminals of the second DC-DC converter circuit.

3. The power conversion device according to claim 2, characterized in that, The first DC-DC converter circuit includes a first output terminal and a second output terminal. The first DC-DC converter circuit includes a first switching device, a second switching device, and a first power inductor. The second switching device and the first power inductor are connected in series between the first input terminal and the first output terminal of the first DC-DC converter circuit, or the second switching device and the first power inductor are connected in series between the second input terminal and the second output terminal of the first DC-DC converter circuit. One end of the first switching device is connected to the first input terminal or the second input terminal of the first DC-DC converter circuit, and the other end of the first switching device is connected to the connection point between the second switching device and the first power inductor. The second DC-DC converter circuit includes a first output terminal and a second output terminal. The second DC-DC converter circuit includes a third switching device, a fourth switching device, and a second power inductor. The fourth switching device and the second power inductor are connected in series between the first input terminal and the first output terminal of the second DC-DC converter circuit, or the fourth switching device and the second power inductor are connected in series between the second input terminal and the second output terminal of the second DC-DC converter circuit. One end of the third switching device is connected to the first input terminal or the second input terminal of the second DC-DC converter circuit, and the other end of the third switching device is connected to the connection point between the fourth switching device and the second power inductor.

4. The power conversion device according to claim 3, characterized in that, The first and third switching devices are both controllable switching transistors, while the second and fourth switching devices are either controllable switching transistors or uncontrollable diodes.

5. The power conversion device according to claim 3 or 4, characterized in that, The power conversion device also includes a bus voltage balancing circuit; The first, second, and third terminals of the bus voltage balancing circuit are respectively connected to the connection point between the first bus capacitor and the second bus capacitor, the positive DC bus, and the negative DC bus, and are used to transfer the electrical energy stored in the first bus capacitor to the second bus capacitor, or to transfer the electrical energy stored in the second bus capacitor to the first bus capacitor, so as to reduce the difference between the first bus voltage of the first bus capacitor and the second bus voltage of the second bus capacitor.

6. The power conversion device according to claim 5, characterized in that, The bus voltage balancing circuit includes an energy storage element; The bus voltage balancing circuit is used to transfer the electrical energy stored in the first bus capacitor to the energy storage element, and transfer the electrical energy of the energy storage element to the second bus capacitor; or to transfer the electrical energy stored in the second bus capacitor to the energy storage element, and transfer the electrical energy of the energy storage element to the first bus capacitor.

7. The power conversion device according to claim 6, characterized in that, The energy storage element is a third power inductor. The bus voltage balancing circuit also includes a fifth switching device and a sixth switching device. One end of the third power inductor is connected to the first end, and the other end of the third power inductor is connected to the second end and the third end respectively through the fifth switching device and the sixth switching device.

8. The power conversion device according to claim 6, characterized in that, The energy storage element is a resonant capacitor. The bus voltage balancing circuit further includes a seventh switch device, an eighth switch device, a ninth switch device, a tenth switch device, and a resonant inductor. The seventh switch device and the eighth switch device are connected in series to form a first switch bridge arm. The two ends of the first switch bridge arm are respectively connected to the second end and the first end, and the first end of the seventh switch device is connected to the second end. The ninth switch device and the tenth switch device are connected in series to form a second switch bridge arm. The two ends of the second switch bridge arm are respectively connected to the first end and the third end, and the first end of the ninth switch device is connected to the first end. The resonant inductor and the resonant capacitor are connected in series between the midpoint of the first switch bridge arm and the midpoint of the second switch bridge arm.

9. A control method for controlling the power conversion device as described in any one of claims 3-8; The method includes: When there is a deviation between the first bus voltage of the first bus capacitor and the second bus voltage of the second bus capacitor, the duty cycle of the first switching device and / or the duty cycle of the third switching device are adjusted to reduce the difference between the first bus voltage and the second bus voltage.

10. The method according to claim 9, characterized in that, When there is a deviation between the first bus voltage of the first bus capacitor and the second bus voltage of the second bus capacitor, adjusting the duty cycle of the first switching device and / or the duty cycle of the third switching device includes: When the first bus voltage is greater than the second bus voltage and the current of the power conversion device flows from the DC power supply to the load, the duty cycle of the first switching device is increased and / or the duty cycle of the third switching device is decreased.

11. The method according to claim 9, characterized in that, When there is a deviation between the first bus voltage of the first bus capacitor and the second bus voltage of the second bus capacitor, adjusting the duty cycle of the first switching device and / or the duty cycle of the third switching device includes: When the first bus voltage is less than the second bus voltage and the current of the power conversion device flows from the DC power supply to the load, the duty cycle of the third switching device is increased and / or the duty cycle of the first switching device is decreased.

12. The method according to claim 9, characterized in that, When there is a deviation between the first bus voltage of the first bus capacitor and the second bus voltage of the second bus capacitor, adjusting the duty cycle of the first switching device and / or the duty cycle of the third switching device includes: When the first bus voltage is greater than the second bus voltage and the current of the power conversion device flows from the load to the DC power supply, the duty cycle of the first switching device is reduced and / or the duty cycle of the third switching device is increased.

13. The method according to claim 9, characterized in that, When there is a deviation between the first bus voltage of the first bus capacitor and the second bus voltage of the second bus capacitor, adjusting the duty cycle of the first switching device and / or the duty cycle of the third switching device includes: When the first bus voltage is less than the second bus voltage and the current of the power conversion device flows from the load to the DC power supply, the duty cycle of the third switching device is reduced and / or the duty cycle of the first switching device is increased.

14. A control method for controlling the power conversion device as described in any one of claims 5-8; The method includes: When there is a deviation between the first bus voltage of the first bus capacitor and the second bus voltage of the second bus capacitor, the bus voltage balancing circuit is controlled to transfer the electrical energy stored in the bus capacitor corresponding to the larger bus voltage to the bus capacitor corresponding to the smaller bus voltage.

15. The method according to claim 14, characterized in that, The bus voltage balancing circuit includes an energy storage element; When there is a deviation between the first bus voltage of the first bus capacitor and the second bus voltage of the second bus capacitor, controlling the bus voltage balancing circuit to transfer the electrical energy stored in the bus capacitor corresponding to the larger bus voltage to the bus capacitor corresponding to the smaller bus voltage includes: When there is a deviation between the first bus voltage and the second bus voltage, the bus voltage balancing circuit is controlled to transfer the electrical energy stored in the bus capacitor corresponding to the larger bus voltage to the energy storage element, and to transfer the electrical energy of the energy storage element to the bus capacitor corresponding to the smaller bus voltage.

16. The method according to claim 15, characterized in that, The energy storage element is a third power inductor; When there is a deviation between the first bus voltage and the second bus voltage, controlling the bus voltage balancing circuit to transfer the electrical energy stored in the bus capacitor corresponding to the larger bus voltage to the energy storage element, and transferring the electrical energy of the energy storage element to the bus capacitor corresponding to the smaller bus voltage, includes: When the voltage of the first bus is greater than the voltage of the second bus, the fifth switching device is turned on for a first preset time and then turned off. During the turn-on process of the fifth switching device, the electrical energy stored in the first bus capacitor is transferred to the third power inductor. After the fifth switching device is turned off, the sixth switching device is controlled to turn on for a second preset time and then turn off. During the process of the sixth switching device being turned on, the electrical energy stored in the third power inductor is transferred to the second bus capacitor.

17. The method according to claim 15, characterized in that, The energy storage element is a resonant capacitor; When there is a deviation between the first bus voltage and the second bus voltage, controlling the bus voltage balancing circuit to transfer the electrical energy stored in the bus capacitor corresponding to the larger bus voltage to the energy storage element, and transferring the electrical energy of the energy storage element to the bus capacitor corresponding to the smaller bus voltage, includes: When the first bus voltage is greater than the second bus voltage, the seventh and ninth switching devices are turned on for a third preset time and then turned off. During the turn-on process of the seventh and ninth switching devices, the electrical energy stored in the first bus capacitor is transferred to the resonant capacitor. After the seventh and ninth switching devices are turned off, the eighth and tenth switching devices are turned on for a fourth preset time and then turned off. During the turn-on process of the eighth and tenth switching devices, the electrical energy stored in the resonant capacitor is transferred to the second bus capacitor.

18. A power supply system, characterized in that, The power supply system includes an inverter circuit and a power conversion device as described in any one of claims 1-8, wherein the first output terminal and the second output terminal of the power conversion device are respectively connected to the first input terminal and the second input terminal of the inverter circuit, and the output terminal of the inverter circuit is connected to the power grid.

19. The power supply system according to claim 18, characterized in that, The inverter circuit further includes a third bus capacitor, a fourth bus capacitor, and a third input terminal of the inverter circuit. The third bus capacitor is connected between the first input terminal and the third input terminal of the inverter circuit, and the fourth bus capacitor is connected between the third input terminal and the second input terminal of the inverter circuit.

20. The power supply system according to claim 18, characterized in that, The inverter circuit also includes a third input terminal, which is connected to the connection point between the first bus capacitor and the second bus capacitor. The inverter circuit is used to output the electrical energy stored in the first bus capacitor and the second bus capacitor to the power grid when there is a deviation between the first bus voltage of the first bus capacitor and the second bus voltage of the second bus capacitor. The electrical energy output to the power grid by the bus capacitor corresponding to the larger bus voltage is greater than the electrical energy output to the power grid by the bus capacitor corresponding to the smaller bus voltage.

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