A power conversion system and control method

Abstract

The application discloses a power conversion system and a control method. The power conversion system is provided with a photovoltaic DC / DC conversion circuit between each photovoltaic group string and a DC bus. An independent current detection device and an independent switching device are arranged between the branch cable corresponding to each photovoltaic DC / DC conversion circuit and the DC bus. The controller can locate a fault branch according to the branch output current detected by the current detection device, control the corresponding switching device to be disconnected, realize the isolation of the fault branch, and the remaining normal photovoltaic DC / DC conversion circuits continue to work. The application can realize the positioning and isolation of the photovoltaic DC / DC conversion circuit fault, reduce the influence of the fault branch on the power conversion system, and improve the operation reliability and power supply continuity of the power conversion system.

Description

Technical Field

[0001] This application relates to the field of energy conversion technology, specifically to a power conversion system and control method. Background Technology

[0002] In renewable energy supply scenarios such as photovoltaics and energy storage, power conversion systems are used to convert electrical energy. For example, in photovoltaic scenarios, the power conversion system includes a photovoltaic inverter, which converts the direct current (DC) from the photovoltaic system into alternating current (AC) for grid connection. In energy storage scenarios, the power conversion system includes an energy storage converter, which converts the DC power from the battery into AC power for grid connection, and can also convert the AC power from the grid into DC power to charge the battery.

[0003] However, the integration level of current power conversion systems is not high enough, and the protection mechanisms need to be improved. Summary of the Invention

[0004] In view of this, this application provides a power conversion system and control method that can improve the integration of the power conversion system and provide effective protection.

[0005] To solve the above problems, the technical solution provided in this application is as follows: This application provides a power conversion system, including: a controller, a DC bus, multiple photovoltaic DC / DC conversion circuits, multiple DC / AC conversion circuits, multiple switching devices, and multiple current detection devices; the first terminals of the multiple photovoltaic DC / DC conversion circuits are respectively used to connect to corresponding photovoltaic strings, and the second terminals of the multiple photovoltaic DC / DC conversion circuits are connected to the DC bus through branch cables; the DC bus is also used to connect batteries; the DC sides of the multiple DC / AC conversion circuits are respectively connected to the DC bus, and the AC sides of the multiple DC / AC conversion circuits are connected in parallel; corresponding switching devices and current detection devices are provided between the branch cables and the DC bus; the controller is configured to, based on the output current of the corresponding photovoltaic DC / DC conversion circuit detected by the current detection device, control the corresponding switching device to disconnect the connection between the corresponding photovoltaic DC / DC conversion circuit and the DC bus when a fault is detected.

[0006] One possible implementation is that the switching device includes a first type of switch and a second type of switch connected in series, the first type of switch including a mechanical switch and the second type of switch including an energized fuse or a semiconductor switch; the controller is configured to, in the event of a fault, first control the second type of switch to open and then control the first type of switch to open.

[0007] One possible implementation is that each of the DC / AC conversion circuits has a corresponding current detection device and a third type of switch between its DC side and the DC bus; the third type of switch includes an excitation fuse or a semiconductor switch; the controller is also configured to, based on the DC side current of the corresponding DC / AC conversion circuit detected by the current detection device, determine that a fault has occurred, and control the corresponding third type of switch to open, thereby disconnecting the connection between the corresponding DC / AC conversion circuit and the DC bus.

[0008] One possible implementation also includes: an energy storage DC / DC converter circuit; the first terminal of the energy storage DC / DC converter circuit is used to connect to the battery, and the second terminal of the energy storage DC / DC converter circuit is connected to the DC bus.

[0009] One possible implementation is that the second terminal of the energy storage DC / DC converter circuit is connected to the DC bus via a corresponding fourth type switch; the fourth type switch includes an excitation fuse or a semiconductor switch.

[0010] One possible implementation also includes: a load DC / DC converter circuit; the first end of the load DC / DC converter circuit is connected to a DC bus, and the second end of the load DC / DC converter circuit is used to connect to a DC load.

[0011] One possible implementation also includes: a load switch; and a controller configured to control the load switch to disconnect in the event of a DC load failure.

[0012] One possible implementation is that each of the multiple DC / AC conversion circuits has a corresponding current detection device and a fifth type switch on its AC side; the controller is also configured to, based on the AC side current of the corresponding DC / AC conversion circuit detected by the current detection device, determine that a fault has occurred, and control the fifth type switch on the AC side of the corresponding DC / AC conversion circuit to open, the fifth type switch including an excitation fuse or a semiconductor switch.

[0013] One possible implementation is that, when the AC side of multiple DC / AC conversion circuits is equipped with corresponding Class 5 switches, and the AC side of multiple DC / AC conversion circuits is three-phase, Class 5 switches are respectively installed on at least two phases of the AC side of multiple DC / AC conversion circuits.

[0014] One possible implementation is that the controller is configured to determine whether a short-circuit fault or overcurrent fault has occurred on the AC side of the corresponding DC / AC conversion circuit based on the AC side current detected by the current detection device.

[0015] One possible implementation is that the controller is configured to, upon determining that a reverse connection fault or a short circuit fault has occurred, first control the second type of switch to open, and then control the first type of switch to open.

[0016] One possible implementation also includes an AC bus; the AC side of each DC / AC conversion circuit is connected to the AC bus via a corresponding Class 5 switch; the AC bus is used to connect at least one of the mains port and the AC load port.

[0017] One possible implementation also includes: a redundant DC / AC conversion circuit; in the event of a faulty DC / AC conversion circuit in the system, a controller is used to control the redundant DC / AC conversion circuit to replace the faulty DC / AC conversion circuit.

[0018] This application also provides a control method for a power conversion system, comprising: determining, based on the current of the photovoltaic DC / DC conversion circuit, that in the event of a fault, controlling a corresponding switching device to disconnect the connection between the corresponding photovoltaic DC / DC conversion circuit and the DC bus; the first terminal of the photovoltaic DC / DC conversion circuit is used to connect to a photovoltaic string, and the second terminal of the photovoltaic DC / DC conversion circuit is connected to the DC bus through a corresponding switching device; the DC bus is also used to connect to a battery; the DC side of the DC / AC conversion circuit is connected to the DC bus, and the AC sides of multiple DC / AC conversion circuits are connected in parallel.

[0019] One possible implementation is that the switching device includes a first type of switch and a second type of switch connected in series. The first type of switch includes a mechanical switch, and the second type of switch includes an excitation fuse or a semiconductor switch. Controlling the corresponding switching device to disconnect the corresponding photovoltaic DC / DC converter circuit from the DC bus includes: first controlling the second type of switch to open, and then controlling the first type of switch to open, so as to disconnect the corresponding photovoltaic DC / DC converter circuit from the DC bus.

[0020] One possible implementation involves installing corresponding current detection devices and third-type switches between the DC side and the DC bus of multiple DC / AC conversion circuits; the third-type switches include excitation fuses or semiconductor switches; the control method further includes: based on the DC side current of the corresponding DC / AC conversion circuit detected by the current detection device, if a fault occurs, controlling the corresponding third-type switch to open to disconnect the connection between the corresponding DC / AC conversion circuit and the DC bus.

[0021] The power conversion system provided in this application embodiment includes photovoltaic DC / DC conversion circuits between each photovoltaic string and the DC bus. Independent current detection devices and independent switching devices are installed between the branch cables corresponding to each photovoltaic DC / DC conversion circuit and the DC bus. This allows the controller to locate the faulty branch based on the branch output current detected by the current detection device, control the corresponding switching device to disconnect, and isolate the faulty branch. The remaining normal photovoltaic DC / DC conversion circuits continue to operate. This application can achieve fault location and isolation of photovoltaic DC / DC conversion circuits, reduce the impact of faulty branches on the power conversion system, and improve the operational reliability and power supply continuity of the power conversion system. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of a first power conversion system provided in an embodiment of this application; Figure 2 This is a schematic diagram of a second power conversion system provided in an embodiment of this application; Figure 3 This is a schematic diagram of a third power conversion system provided in the embodiments of this application; Figure 4 This is a schematic diagram of a fourth power conversion system provided in the embodiments of this application; Figure 5 This is a schematic diagram of the fifth power conversion system provided in the embodiments of this application; Figure 6 A schematic diagram of the sixth power conversion system provided in the embodiments of this application; Figure 7 A schematic diagram of the seventh power conversion system provided in the embodiments of this application; Figure 8 This is a flowchart of a method for a power conversion system provided in an embodiment of this application. Detailed Implementation

[0023] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the embodiments of this application will be further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0024] See Figure 1 The figure is a schematic diagram of a power conversion system provided in an embodiment of this application.

[0025] The power conversion system provided in this application includes a controller 20, a DC bus 10, multiple photovoltaic DC / DC conversion circuits, multiple DC / AC conversion circuits, multiple switching devices, and multiple current detection devices.

[0026] DC bus 10 includes positive DC bus 10+ and negative DC bus 10-.

[0027] The first terminals of multiple photovoltaic DC / DC converter circuits are respectively used to connect to the corresponding photovoltaic strings, and the second terminals of multiple photovoltaic DC / DC converter circuits are connected to the DC bus 10 through branch cables; the DC bus 10 is also used to connect batteries; the DC side of multiple DC / AC converter circuits is respectively connected to the DC bus 10, and the AC side of multiple DC / AC converter circuits is connected in parallel; corresponding switching devices and current detection devices are set between the branch cables and the DC bus 10; the controller 20 is configured to control the corresponding switching device to disconnect the connection between the corresponding photovoltaic DC / DC converter circuit and the DC bus 10 when a fault is detected based on the output current of the corresponding photovoltaic DC / DC converter circuit detected by the current detection device.

[0028] The battery is connected to the DC bus 10 and can provide power to the DC bus 10 together with multiple photovoltaic DC / DC conversion circuits. The DC power generated by the photovoltaic string and the battery is uniformly dispatched through the DC bus and output after centralized inversion through a shared DC / AC conversion circuit, which can improve the integration of the power conversion system and the flexibility of energy management.

[0029] The photovoltaic string and the battery share the same DC / AC conversion circuit, eliminating the need for separate inverters, which simplifies the circuit structure and reduces the cost of the power conversion system.

[0030] This application does not specifically limit the number of batteries connected to the DC bus 10, and can be set according to actual application requirements. For ease of understanding, Figure 1 The diagram illustrates the case where DC bus 10 is connected to N batteries. In this case, batteries 801 through 80N are all connected to DC bus 10.

[0031] The embodiments of this application do not specifically limit the circuit topology of the photovoltaic DC / DC converter circuit, which can be determined according to functional requirements. For example, it can be a unidirectional DC / DC converter circuit or a bidirectional DC / DC converter circuit. When the photovoltaic DC / DC converter circuit only needs to realize the unidirectional transmission of photovoltaic energy to the DC bus 10, a unidirectional DC / DC converter circuit can be used; if it is necessary to realize the reverse injection of energy into the photovoltaic to realize functions such as photovoltaic health detection or module snow melting, then the photovoltaic DC / DC converter circuit can be a bidirectional DC / DC converter circuit.

[0032] The embodiments of this application do not specifically limit the circuit topology of the DC / AC conversion circuit. For example, any one of the following can be used: two-level topology, neutral point clamping three-level topology, flying capacitor three-level topology, or cascaded H-bridge multi-level topology.

[0033] This application does not specifically limit the location of the switching device, and the location can be flexibly selected according to the actual application scenario. For example, the switching device can be installed inside the cabinet where the photovoltaic DC / DC conversion circuit is located or in a separate switch cabinet, as long as the location of the switching device can realize the controllable switching function of the corresponding branch. Similarly, this application does not specifically limit the location of the current detection device, as long as the location of the current detection device can realize the current detection function of the corresponding branch.

[0034] For example, both the switching device and the current detection device can be located inside the cabinet where the DC / AC conversion circuit is located, such as inside the inverter.

[0035] This application does not specifically limit the number of photovoltaic cells connected to the DC bus 10 or the number of DC / AC conversion circuits. For ease of understanding, the following description uses a power conversion system comprising M photovoltaic DC / DC conversion circuits, M switching devices, M current detection devices, and i DC / AC conversion circuits as an example, where M is a positive integer greater than or equal to 2, and i is a positive integer greater than or equal to 2.

[0036] The first terminal of the first photovoltaic DC / DC converter circuit 301 is used to connect to the corresponding first photovoltaic string 401, and the second terminal of the first photovoltaic DC / DC converter circuit 301 is connected to the DC bus 10 through a branch cable; a corresponding first switching device 501 and a first current detection device 601 are provided between the branch cable and the DC bus 10; until the first terminal of the Mth photovoltaic DC / DC converter circuit 30M is used to connect to the corresponding Mth photovoltaic string 40M, and the second terminal of the Mth photovoltaic DC / DC converter circuit 30M is connected to the DC bus 10 through a branch cable; a corresponding Mth switching device 50M and an Mth current detection device 60M are provided between the branch cable and the DC bus 10.

[0037] The DC sides of the first DC / AC conversion circuit 701 up to the i-th DC / AC conversion circuit 70i are all connected to the DC bus 10, and the AC sides of the first DC / AC conversion circuit 701 up to the i-th DC / AC conversion circuit 70i are connected in parallel. Multiple DC / AC conversion circuits are used to convert the DC power on the DC bus 10 into AC power output.

[0038] To facilitate understanding, the working principle of the power conversion system will be introduced below using the fault in the branch where the first photovoltaic DC / DC conversion circuit 301 is located as an example.

[0039] In this embodiment, the first current detection device 601 is used to detect the output current from the first photovoltaic DC / DC converter circuit 301 to the DC bus 10. The controller 20 determines whether a fault has occurred in the corresponding branch based on the output current detected by the first current detection device 601. When the controller 20 determines that a fault has occurred in the branch where the first photovoltaic DC / DC converter circuit 301 is located, it controls the first switching device 501 to open, thereby disconnecting the first photovoltaic DC / DC converter circuit 301 from the DC bus 10 and isolating the faulty branch; the branches corresponding to the remaining photovoltaic DC / DC converter circuits continue to be connected to the DC bus 10, thereby continuing to supply power to the DC bus 10.

[0040] Since each photovoltaic DC / DC conversion circuit is equipped with an independent switching device and an independent current detection device, the controller 20 can accurately locate the faulty branch according to the output current of each branch and disconnect the faulty branch. Therefore, it can reduce the impact of the faulty branch on the DC bus 10 and other normal branches, protect the components in the normal branches from the fault, and allow the remaining normal photovoltaic DC / DC conversion circuits to continue to work, thereby improving the operational reliability and power supply continuity of the power conversion system.

[0041] The power conversion system provided in this application embodiment includes photovoltaic DC / DC conversion circuits between each photovoltaic string and the DC bus. Independent current detection devices and independent switching devices are installed between the branch cables corresponding to each photovoltaic DC / DC conversion circuit and the DC bus. This allows the controller to locate the faulty branch based on the branch output current detected by the current detection device, control the corresponding switching device to disconnect, and isolate the faulty branch. The remaining normal photovoltaic DC / DC conversion circuits continue to operate. This application can achieve fault location and isolation of photovoltaic DC / DC conversion circuits, reduce the impact of faulty branches on the power conversion system, and improve the operational reliability and power supply continuity of the power conversion system.

[0042] The following is combined Figure 2 This application provides a detailed description of the switching device provided in the embodiments.

[0043] See Figure 2 The figure is a schematic diagram of a second power conversion system provided in an embodiment of this application.

[0044] Figure 2 and Figure 1 The difference is that, Figure 2 The switching device includes a first type of switch and a second type of switch connected in series.

[0045] In the power conversion system provided in this application embodiment, the switching device includes a first type of switch and a second type of switch connected in series; the first type of switch includes a mechanical switch, and the second type of switch includes an excitation fuse or a semiconductor switch; the controller 20 is configured to, in the event of a fault, first control the second type of switch to open, and then control the first type of switch to open.

[0046] For ease of understanding, this application describes the embodiments using a second type of switch as the excitation fuse as an example.

[0047] The excitation fuse has an external trigger disconnection function. The controller 20 can send a trigger signal to the excitation fuse to make the excitation fuse melt within milliseconds, thereby realizing the rapid disconnection of the circuit and improving the fault response speed and operation reliability of the switching device.

[0048] The triggering methods for the excitation fuse include, but are not limited to, electromagnetic triggering, electronic triggering, or thermal triggering. The controller 20 can send trigger signals through communication methods such as optical fiber, CAN bus, and Ethernet.

[0049] The activating fuse is used to achieve rapid disconnection after a fault occurs, while the mechanical switch is used to achieve electrical isolation of the branch after the activating fuse has opened. By adopting the method of the second type of switch acting first and the first type of switch acting later, both rapid fault isolation and reliable electrical isolation can be achieved, and the arcing and contact losses caused by the mechanical switch breaking under load can be reduced.

[0050] For example, when the controller 20 determines that a fault has occurred in the branch where the first photovoltaic DC / DC conversion circuit 301 is located based on the output current detected by the first current detection device 601, the controller 20 first controls the corresponding second type of switch to operate, so that the faulty branch is quickly disconnected; then controls the first type of switch to open, so that the faulty branch is isolated from the DC bus 10, which facilitates subsequent maintenance or replacement of faulty components.

[0051] The power conversion system provided in this application embodiment sets up a mechanical switch and an excitation fuse, or a mechanical switch and a semiconductor switch in series, and controls the operation in the order of priority action of the second type of switch and subsequent action of the first type of switch. This can achieve both rapid fault clearing and reliable electrical isolation, and improve the fault handling capability of the branch circuit.

[0052] In one possible implementation, in the power conversion system provided in this application embodiment, the controller 20 is configured to, upon determining that a reverse connection fault or a short circuit fault has occurred, first control the second type of switch to open, and then control the first type of switch to open.

[0053] In this embodiment, the current detection device detects the output current of the photovoltaic DC / DC converter circuit. The controller 20 determines whether a reverse connection fault or a short circuit fault has occurred based on the output current detected by the current detection device. When a reverse connection fault or a short circuit fault is detected, the controller 20 first controls the corresponding second-type switch to operate, so that the faulty branch is quickly disconnected; then it controls the first-type switch to open, so that the faulty branch is electrically isolated.

[0054] The power conversion system provided in this application adopts a control method that prioritizes the second type of switch and then disconnects the first type of switch for reverse connection faults and short circuit faults, which helps to improve fault clearing efficiency and system operation reliability.

[0055] This application does not specifically limit the specific placement of the first type of switch and the second type of switch in the embodiments. The following description, in conjunction with... Figure 3 Let me introduce it.

[0056] See Figure 3 This figure is a schematic diagram of a third power conversion system provided in an embodiment of this application.

[0057] In the power conversion system provided in this application embodiment, taking a mechanical switch as the first type of switch and an excitation fuse as the second type of switch as an example, the first type of switch can be set between the photovoltaic module and the positive DC bus 10+, or between the photovoltaic module and the negative DC bus 10-; or the first type of switch can be set between the photovoltaic module and the positive DC bus 10+, and between the photovoltaic module and the negative DC bus 10-. The excitation fuse is similar.

[0058] Figure 3 The illustration shows a scenario where an excitation fuse is installed between the photovoltaic module and the positive DC bus 10+, and a first-type switch is installed between the photovoltaic module and the positive DC bus 10+, as well as between the photovoltaic module and the negative DC bus 10-.

[0059] In one possible implementation, the DC / AC conversion circuit provided in this application embodiment can also be connected to a corresponding current detection device and switch, as described below. Figure 4 Let me introduce it.

[0060] See Figure 4 This figure is a schematic diagram of the fourth power conversion system provided in the embodiments of this application.

[0061] The following section introduces the implementation method of setting up corresponding current detection devices and third-type switches between the DC side and DC bus 10 of the DC / AC conversion circuit.

[0062] In the power conversion system provided in this application embodiment, a corresponding current detection device and a third type of switch are provided between the DC side of multiple DC / AC conversion circuits and the DC bus 10; the third type of switch includes an excitation fuse or a semiconductor switch.

[0063] The embodiments of this application do not specifically limit the specific location of the third type of switch, and will not be described in detail here.

[0064] The controller 20 is also configured to, based on the DC-side current of the corresponding DC / AC conversion circuit detected by the current detection device, determine that a fault has occurred, and control the corresponding third-class switch to open, thereby disconnecting the connection between the corresponding DC / AC conversion circuit and the DC bus 10.

[0065] The following explanation uses the first DC / AC conversion circuit 701 as an example.

[0066] The DC side of the first DC / AC conversion circuit 701 is connected to the DC bus 10 through a corresponding third-type switch, and the current detection device is used to detect the DC side current of the first DC / AC conversion circuit 701.

[0067] The controller 20 determines whether the first DC / AC conversion circuit 701 is faulty based on the DC-side current detected by the current detection device. When the controller 20 determines that the first DC / AC conversion circuit 701 is faulty, it controls the corresponding third-type switch to open, thereby disconnecting the first DC / AC conversion circuit 701 from the DC bus 10, while the other normal DC / AC conversion circuits continue to operate.

[0068] The power conversion system provided in this application embodiment is equipped with an independent current detection device and a third-class switch on the DC side of each DC / AC conversion circuit. This enables the controller to locate the faulty DC / AC conversion circuit, disconnect the faulty branch in a timely manner, reduce the impact of the faulty branch on the DC bus and other normal DC / AC conversion circuits, and improve the operational reliability of the power conversion system.

[0069] The following describes the implementation of the corresponding current detection device and the fifth type of switch on the AC side of the DC / AC conversion circuit.

[0070] In the power conversion system provided in this application embodiment, a corresponding current detection device and a fifth type switch are provided on the AC side of multiple DC / AC conversion circuits; the controller 20 is also configured to control the fifth type switch on the AC side of the corresponding DC / AC conversion circuit to open when a fault is detected based on the AC side current of the corresponding DC / AC conversion circuit detected by the current detection device; the fifth type switch includes an excitation fuse or a semiconductor switch.

[0071] The embodiments of this application do not specifically limit the specific location of the fifth type of switch, and will not be described in detail here.

[0072] The following explanation uses the first DC / AC conversion circuit 701 as an example.

[0073] The first DC / AC conversion circuit 701 is equipped with a corresponding current detection device and a fifth-type switch on its AC side. The current detection device is used to detect the AC side output current of the first DC / AC conversion circuit 701.

[0074] The controller 20 determines whether the first DC / AC conversion circuit 701 is faulty based on the AC output current detected by the current detection device. When the controller 20 determines that the first DC / AC conversion circuit 701 is faulty, it controls the corresponding fifth-class switch to open, thereby disconnecting the first DC / AC conversion circuit 701 from the AC side, while other normal DC / AC conversion circuits continue to operate in parallel.

[0075] The power conversion system provided in this application embodiment is equipped with a current detection device and a fifth-class switch on the AC side of each DC / AC conversion circuit. This enables the controller to locate the faulty branch based on the AC side current of the DC / AC conversion circuit, isolate the faulty DC / AC conversion circuit in a timely manner, reduce the impact of the faulty branch on other normal branches, and improve the reliability of system operation.

[0076] In one possible implementation, in the power conversion system provided in this application embodiment, the controller 20 is configured to determine whether a short circuit fault or overcurrent fault has occurred on the AC side of the corresponding DC / AC conversion circuit based on the AC side current detected by the current detection device.

[0077] In this embodiment, the current detection device detects the AC side current of the corresponding DC / AC conversion circuit and sends the detection result to the controller 20.

[0078] The controller 20 determines whether a short circuit or overcurrent fault has occurred on the AC side of the corresponding DC / AC converter circuit based on the AC side current. When a short circuit or overcurrent fault is detected, the controller 20 controls the corresponding Class V switch to open, thereby disconnecting the faulty DC / AC converter circuit from the AC side.

[0079] The power conversion system provided in this application uses the AC side current of the DC / AC conversion circuit to determine whether a short circuit fault or overcurrent fault has occurred on the AC side of the DC / AC conversion circuit, which helps to improve the accuracy of fault identification and the speed of fault response.

[0080] One possible implementation involves setting corresponding Class 5 switches on the AC side of multiple DC / AC conversion circuits. When the AC side of the multiple DC / AC conversion circuits is three-phase, Class 5 switches are set on at least two phases of the AC side of the multiple DC / AC conversion circuits.

[0081] In this embodiment of the application, when the AC side of the DC / AC conversion circuit adopts a three-phase output, a fifth type of switch can be set in at least two of phases A, B and C respectively.

[0082] For example, a fifth-class switch can be installed in any two phases of the three-phase system, or a fifth-class switch can be installed in phases A, B, and C. This application does not specifically limit this.

[0083] When any two phases on the AC side of the DC / AC conversion circuit are equipped with a fifth-class switch, the phase without a fifth-class switch may be equipped with a mechanical switch. This application does not specifically limit this.

[0084] When any two of the three phases (A, B, and C) on the AC side are equipped with a Class 5 switch, for example, if the Class 5 switch is installed on phases A and B on the AC side, when the controller 20 determines that the DC / AC conversion circuit is faulty, the controller 20 sends a trigger signal to the Class 5 switch of phase A and the Class 5 switch of phase B. The Class 5 switch of phase A and the Class 5 switch of phase B blow, the three-phase circuit is cut off, the connection between the faulty DC / AC conversion circuit and the AC side is disconnected, and the faulty DC / AC conversion circuit is isolated.

[0085] When all three phases on the AC side are equipped with Class 5 switches, when the controller 20 determines that the DC / AC conversion circuit is faulty, the controller 20 sends a trigger signal to the Class 5 switches of the three phases, the Class 5 switches of the three phases blow, the three-phase circuit is cut off, and the connection between the faulty DC / AC conversion circuit and the AC side is disconnected.

[0086] For ease of understanding, Figure 4 This illustrates how a DC / AC converter circuit can be configured with two phases on the AC side using Class 5 switches and the third phase using a mechanical switch.

[0087] The power conversion system provided in this application embodiment can quickly disconnect the AC side of the faulty DC / AC conversion circuit by setting a fifth type of switch on at least two phases of the three-phase AC side, thereby improving the fault isolation capability.

[0088] The power conversion system provided in this application embodiment has a third-class switch on the DC side and a fifth-class switch on the AC side of the DC / AC conversion circuit. When the controller determines that a fault has occurred in the DC / AC conversion circuit, the controller can control the switches on the DC side and the AC side to be disconnected, thereby achieving electrical isolation between the faulty DC / AC conversion circuit and the DC bus and the AC side.

[0089] See also Figure 4In this embodiment of the application, when there are many DC / AC conversion circuits, the controller 20 can adopt a master-slave control structure. The master controller is used to coordinate and control the operating status of each DC / AC conversion circuit to achieve stable operation and stable output of multiple DC / AC conversion circuits.

[0090] In one possible implementation, to improve the continuity of system power supply and operational reliability, the power conversion system provided in this application embodiment further includes redundant DC / AC conversion circuits.

[0091] In the event of a faulty DC / AC conversion circuit in the power conversion system, the controller is used to control a redundant DC / AC conversion circuit to replace the faulty DC / AC conversion circuit.

[0092] In this embodiment, the redundant DC / AC conversion circuit has the same or compatible functions as the normally operating DC / AC conversion circuit.

[0093] During normal operation, the redundant DC / AC converter circuit is in standby mode. When the controller detects a fault in the DC / AC converter circuit, after isolating the faulty DC / AC converter circuit, the controller activates the redundant DC / AC converter circuit to replace the faulty DC / AC converter circuit and continue to perform power conversion.

[0094] When the controller puts the redundant DC / AC converter circuit into operation, the controller can first close the corresponding switch on the DC side of the redundant DC / AC converter circuit, and the redundant DC / AC converter circuit is first connected to the DC bus. Then the controller closes the corresponding switch on the AC side of the redundant DC / AC converter circuit, and the redundant DC / AC converter circuit is then connected to the AC bus. This achieves a smooth start-up and reduces the disturbance caused by the start-up process of the redundant DC / AC converter circuit to the normal operation of the power conversion system.

[0095] The embodiments of this application do not specifically limit the number of redundant DC / AC conversion circuits, and one or more redundant DC / AC conversion circuits can be configured according to the system reliability requirements.

[0096] For example, redundant DC / AC converters can be configured with T+1 redundancy, meaning one additional redundant DC / AC converter is configured on top of the T required DC / AC converters for normal operation; or they can be configured with T+L redundancy, meaning L additional redundant DC / AC converters are configured on top of the T required DC / AC converters for normal operation to cope with the extreme case of multiple DC / AC converters failing simultaneously. When a DC / AC converter fails, the controller can select the redundant DC / AC converter with the best condition from among the multiple DC / AC converters to put it into operation.

[0097] The power conversion system provided in this application embodiment is additionally configured with redundant DC / AC conversion circuits to replace faulty conversion circuits and continue to work. The failure of the conversion circuit will not cause the power conversion system to stop or interrupt the output, thereby improving the power supply continuity, system reliability and maintainability of the power conversion system. It is suitable for application scenarios with high requirements for power supply reliability.

[0098] The following is combined Figure 5 This paper introduces the working principle of the energy storage side in a power conversion system.

[0099] See Figure 5 This figure is a schematic diagram of the fifth power conversion system provided in the embodiments of this application.

[0100] The power conversion system provided in this application embodiment also includes an energy storage DC / DC conversion circuit; the first terminal of the energy storage DC / DC conversion circuit is used to connect to the battery, and the second terminal of the energy storage DC / DC conversion circuit is connected to the DC bus 10.

[0101] Taking the DC bus 10 connecting N batteries as an example, the first terminal of the first energy storage DC / DC converter circuit 901 is used to connect to the first battery 801, and the second terminal of the first energy storage DC / DC converter circuit 901 is connected to the DC bus 10; until the first terminal of the Nth energy storage DC / DC converter circuit 90N is used to connect to the Nth battery 80N, and the second terminal of the Nth energy storage DC / DC converter circuit 90N is connected to the DC bus 10.

[0102] Since the battery needs to both obtain power from the DC bus 10 and release power to the DC bus 10, the first energy storage DC / DC converter circuit 901 to the Nth energy storage DC / DC converter circuit 90N all adopt bidirectional DC / DC converter circuits.

[0103] The embodiments of this application do not specifically limit the specific topology of the first energy storage DC / DC converter circuit 901 to the Nth energy storage DC / DC converter circuit 90N. For example, a bidirectional Buck-Boost converter circuit, a dual active bridge converter circuit, or other DC / DC converter circuits that can realize bidirectional energy flow can be used.

[0104] The working principle of the energy storage DC / DC conversion circuit is introduced below, taking the branch where the first battery 801 is located as an example.

[0105] In this embodiment, the first energy storage DC / DC conversion circuit 901 is used to establish an energy transmission channel between the first battery 801 and the DC bus 10, so that the first battery 801 can supply power to the DC bus 10 or absorb electrical energy from the DC bus 10 according to the operating requirements of the power conversion system.

[0106] For example, when the photovoltaic string outputs sufficient power, the DC power generated by the photovoltaic string can be transmitted to each DC / AC conversion circuit via the DC bus 10; or, the first energy storage DC / DC conversion circuit 901 can control the first battery 801 to absorb the remaining electrical energy on the DC bus 10 for energy storage.

[0107] Since the DC power generated by the photovoltaic string can directly charge the battery through the DC bus 10 without going through the DC / AC conversion process, the number of energy conversion stages is reduced and the energy conversion efficiency of the power conversion system is improved.

[0108] When the output power of the photovoltaic string is insufficient or the photovoltaic string does not generate electricity at night, the first energy storage DC / DC conversion circuit 901 can control the first battery 801 to release electrical energy to the DC bus 10, providing a stable DC input for multiple DC / AC conversion circuits, and realizing energy storage to support the power supply of the load or the power grid.

[0109] The power conversion system provided in this application embodiment enables the battery to establish an energy interaction channel with the DC bus by setting an energy storage DC / DC conversion circuit, thereby realizing the coordinated operation between photovoltaic power generation and energy storage, and improving the power supply stability and energy utilization efficiency of the power conversion system.

[0110] In one possible implementation, in the power conversion system provided in this application embodiment, the second terminal of the energy storage DC / DC conversion circuit is connected to the DC bus 10 through a corresponding fourth type switch; the fourth type switch includes an excitation fuse or a semiconductor switch.

[0111] The embodiments of this application do not specifically limit the specific settings of the fourth type of switch, and will not be described in detail here.

[0112] The fourth type of switch is used to controllably disconnect the connection between the energy storage DC / DC converter circuit and the DC bus 10.

[0113] In one possible implementation, a current sensing device can be installed between the second terminal of the energy storage DC / DC converter circuit and the DC bus 10. The current sensing device is used to detect the output current from the energy storage DC / DC converter circuit to the DC bus 10.

[0114] When the controller 20 determines that a fault has occurred in the branch where the energy storage DC / DC converter circuit is located based on the output current detected by the current detection device, it can control the corresponding fourth type switch to open, thereby disconnecting the energy storage DC / DC converter circuit from the DC bus 10, thus isolating the faulty branch and reducing the impact of the faulty branch on the operation of the DC bus 10 and other normal branches.

[0115] The power conversion system provided in this application embodiment can isolate the faulty energy storage branch by setting a fourth type of switch between the energy storage DC / DC conversion circuit and the DC bus, which helps to reduce the scope of the fault and improve the operational reliability of the power conversion system.

[0116] In one possible implementation, the DC bus provided in this application embodiment can also be connected to a DC load, as described below. Figure 6 Let me introduce it.

[0117] See Figure 6 This figure is a schematic diagram of the sixth power conversion system provided in the embodiments of this application.

[0118] The power conversion system provided in this application embodiment may further include a load DC / DC conversion circuit 100; the first end of the load DC / DC conversion circuit 100 is connected to the DC bus 10, and the second end of the load DC / DC conversion circuit 100 is used to connect to the DC load 110.

[0119] This application does not specifically limit the number of DC loads connected to the DC bus 10, but for ease of understanding... Figure 6 This illustrates the case where a DC load 110 is connected to a DC bus 10.

[0120] The load DC / DC converter circuit 100 is used to establish an energy transmission channel between the DC bus 10 and the DC load 110 to meet the power supply requirements of different types of DC loads.

[0121] For example, DC load 110 may include DC loads such as DC charging piles, DC lighting systems or DC motors, and this application embodiment does not specifically limit this.

[0122] Once a stable DC voltage is established on the DC bus 10, the load DC / DC converter circuit 100 converts the DC power on the DC bus 10 into the corresponding voltage level and outputs it to the DC load 110 according to the working requirements of the DC load 110.

[0123] The power conversion system provided in this application embodiment enables the DC bus to directly supply power to the DC load by setting up a load DC / DC conversion circuit, which further expands the application scenarios of the power conversion system and improves the integration and energy utilization flexibility of the power conversion system.

[0124] In one possible implementation, the power conversion system provided in this application embodiment further includes a load switch 120; the controller 20 is also configured to control the load switch 120 to disconnect in the event of a fault in the DC load 110.

[0125] The load switch 120 is used to controllably disconnect the connection between the DC load 110 and the load DC / DC converter circuit 100. When the controller 20 determines that the DC load 110 has a fault, the controller 20 can control the load switch 120 to disconnect the faulty DC load 110 from the DC bus 10.

[0126] The embodiments of this application do not specifically limit the type of fault that occurs in the DC load 110. It can be any fault state that causes the DC load 110 to fail to work properly, such as load abnormality, line abnormality, overload, short circuit or other abnormal operating state.

[0127] The power conversion system provided in this application embodiment, by setting a load switch, controls the load switch to disconnect when a DC load fault occurs, which helps to reduce the impact of the faulty load on other parts of the power conversion system and improves the operational reliability of the power conversion system.

[0128] One possible implementation is that a load switch 120 and a corresponding current detection device can be set between the DC load 110 and the load DC / DC conversion circuit 100. The current detection device is used to detect the current of the load DC / DC conversion circuit 100. The controller 20 can determine that the DC load 110 has failed based on the current detected by the current detection device. This will not be elaborated further here.

[0129] One possible implementation is that the AC side of each DC / AC conversion circuit provided in the embodiments of this application can be connected to an AC bus, as described below. Figure 7 introduce.

[0130] See Figure 7 This figure is a schematic diagram of the seventh power conversion system provided in the embodiments of this application.

[0131] The power conversion system provided in this application embodiment may further include an AC bus 130.

[0132] For ease of understanding, this application will use a three-phase AC bus 130 as an example for illustration.

[0133] The AC busbar 130 includes phase A AC busbar, phase B AC busbar and phase C AC busbar.

[0134] Each DC / AC converter circuit's AC side is connected to AC bus 130 via a corresponding Category 5 switch.

[0135] AC bus 130 is used to connect at least one of power grid port 140 and AC load port 150.

[0136] The power grid port 140 is used to connect to the power grid to realize the power exchange between the power conversion system and the power grid; the AC load port 150 is used to connect AC load devices, such as lighting systems, AC motors or other AC electrical equipment, to realize the power supply of AC loads.

[0137] In practical applications, one or more AC load ports can be configured according to actual load requirements.

[0138] For ease of understanding, Figure 7 The example shown illustrates the configuration of an AC load port 150, but is not limited in any way.

[0139] In this embodiment of the application, when the AC bus 130 is connected to the grid port 140, the power conversion system can feed the DC power provided by the photovoltaic string or battery into the grid after DC / AC conversion to realize the grid-connected power generation function; or it can obtain AC power from the grid and charge the battery after DC / AC conversion.

[0140] When AC bus 130 is connected to AC load port 150, the power conversion system can convert DC power to AC power and directly supply power to the AC load, realizing off-grid power supply or emergency power supply functions. When AC bus 130 is connected to both grid port 140 and AC load port 150, the power conversion system can flexibly schedule the flow of energy between the grid, load and DC side according to the grid status, load demand and DC side energy conditions.

[0141] Therefore, the power conversion system has both grid-connected and off-grid power supply capabilities. It can both connect photovoltaic strings or battery power to the grid and meet the power demand of the load. In the event of a grid fault or power outage, the power conversion system can switch to off-grid operation mode and continue to supply power to critical loads through the AC load port, improving the power continuity of important loads, further enriching application scenarios, and enhancing the power supply flexibility and operational reliability of the power conversion system.

[0142] One possible implementation is that appropriate protection devices, such as circuit breakers, fuses, or contactors, can be installed on the connection lines between the power grid port 140 and the AC bus 130, and on the connection lines between the AC load port 150 and the AC bus 130, according to actual application requirements, to realize the connection, disconnection, and fault protection functions of the corresponding lines.

[0143] Based on the power conversion system provided in the above embodiments, this application also provides a control method for the power conversion system.

[0144] See Figure 8 The figure is a flowchart of a control method for a power conversion system provided in an embodiment of this application.

[0145] The control method for the power conversion system provided in this application includes: S801: Based on the current of the photovoltaic DC / DC converter circuit, if a fault occurs, control the corresponding switching device to disconnect the corresponding photovoltaic DC / DC converter circuit from the DC bus.

[0146] The first terminal of the photovoltaic DC / DC converter circuit is used to connect to the photovoltaic string, and the second terminal of the photovoltaic DC / DC converter circuit is connected to the DC bus through a corresponding switching device; the DC bus is also used to connect the battery; the DC side of the DC / AC converter circuit is connected to the DC bus, and the AC sides of multiple DC / AC converter circuits are connected in parallel.

[0147] The control method for the power conversion system provided in this application locates the faulty branch based on the current of the photovoltaic DC / DC conversion circuit and controls the corresponding switching device to disconnect the faulty branch, which helps to reduce the impact of the faulty branch on the overall operation of the power conversion system and improves the operational reliability of the power conversion system.

[0148] In one possible implementation, the control method for the power conversion system provided in this application embodiment includes a switching device comprising a first type of switch and a second type of switch connected in series. The first type of switch includes a mechanical switch, and the second type of switch includes an excitation fuse or a semiconductor switch.

[0149] Controlling the corresponding switching device to disconnect the corresponding photovoltaic DC / DC converter circuit from the DC bus includes: first controlling the second type of switch to open, and then controlling the first type of switch to open, so as to disconnect the corresponding photovoltaic DC / DC converter circuit from the DC bus.

[0150] The control method for the power conversion system provided in this application improves fault handling efficiency and branch isolation reliability by adopting a control sequence that prioritizes the second type of switch and then disconnects the first type of switch.

[0151] In one possible implementation, the control method for the power conversion system provided in this application embodiment includes a corresponding current detection device and a third type of switch between the DC side and the DC bus of multiple DC / AC conversion circuits; the third type of switch includes an excitation fuse or a semiconductor switch. The control method also includes: based on the DC-side current of the corresponding DC / AC conversion circuit detected by the current detection device, if a fault occurs, controlling the corresponding third-class switch to open, so as to disconnect the connection between the corresponding DC / AC conversion circuit and the DC bus.

[0152] The control method for the power conversion system provided in this application controls the opening of the corresponding third-type switch based on the DC-side current of the DC / AC conversion circuit, thereby achieving rapid isolation of the faulty DC / AC conversion circuit and improving the operational reliability and power supply continuity of the power conversion system.

[0153] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0154] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A power conversion system, characterized in that, include: Controller, DC bus, multiple photovoltaic DC / DC conversion circuits, multiple DC / AC conversion circuits, multiple switching devices, and multiple current detection devices; The first terminals of the plurality of photovoltaic DC / DC conversion circuits are respectively used to connect to the corresponding photovoltaic strings, and the second terminals of the plurality of photovoltaic DC / DC conversion circuits are connected to the DC bus through branch cables; The DC bus is also used to connect batteries; The DC sides of the plurality of DC / AC conversion circuits are respectively connected to the DC bus, and the AC sides of the plurality of DC / AC conversion circuits are connected in parallel. The branch cable is provided with a corresponding switching device and a current detection device between it and the DC bus. The controller is configured to, based on the output current of the corresponding photovoltaic DC / DC converter circuit detected by the current detection device, control the corresponding switching device to disconnect the connection between the corresponding photovoltaic DC / DC converter circuit and the DC bus when a fault is detected.

2. The transformation system according to claim 1, characterized in that, The switching device includes a first type of switch and a second type of switch connected in series. The first type of switch includes a mechanical switch, and the second type of switch includes an energizing fuse or a semiconductor switch. The controller is configured to, in the event of a fault, first control the second type of switch to open, and then control the first type of switch to open.

3. The transformation system according to claim 1, characterized in that, Each of the multiple DC / AC conversion circuits is provided with a corresponding current detection device and a third type of switch between the DC side and the DC bus; the third type of switch includes an excitation fuse or a semiconductor switch. The controller is further configured to, based on the DC-side current of the corresponding DC / AC conversion circuit detected by the current detection device, determine that a fault has occurred, and control the corresponding third-type switch to open, thereby disconnecting the connection between the corresponding DC / AC conversion circuit and the DC bus.

4. The transformation system according to claim 1, characterized in that, Also includes: Energy storage DC / DC converter circuit; The first terminal of the energy storage DC / DC converter circuit is used to connect to the battery, and the second terminal of the energy storage DC / DC converter circuit is connected to the DC bus.

5. The transformation system according to claim 4, characterized in that, The second terminal of the energy storage DC / DC converter circuit is connected to the DC bus via a corresponding fourth type of switch; the fourth type of switch includes an excitation fuse or a semiconductor switch.

6. The transformation system according to any one of claims 1-5, characterized in that, It also includes: load DC / DC conversion circuit; The first terminal of the load DC / DC converter circuit is connected to the DC bus, and the second terminal of the load DC / DC converter circuit is used to connect to the DC load.

7. The transformation system according to claim 6, characterized in that, Also includes: Load switch; The controller is also configured to control the load switch to disconnect in the event of a DC load failure.

8. The transformation system according to any one of claims 1-5, characterized in that, The AC side of each of the multiple DC / AC conversion circuits is equipped with a corresponding current detection device and a fifth type of switch; The controller is further configured to, based on the AC side current of the corresponding DC / AC conversion circuit detected by the current detection device, determine that a fault has occurred, and control the fifth type of switch on the AC side of the corresponding DC / AC conversion circuit to open, the fifth type of switch including an excitation fuse or a semiconductor switch.

9. The transformation system according to claim 8, characterized in that, When the AC side of the plurality of DC / AC conversion circuits is respectively provided with the corresponding fifth type of switch, when the AC side of the plurality of DC / AC conversion circuits is three-phase, the fifth type of switch is respectively provided on at least two phases of the AC side of the plurality of DC / AC conversion circuits.

10. The transformation system according to claim 8, characterized in that, The controller is configured to determine whether a short circuit fault or overcurrent fault has occurred on the AC side of the corresponding DC / AC conversion circuit based on the AC side current detected by the current detection device.

11. The transformation system according to claim 8, characterized in that, The controller is configured to, upon determining that a reverse connection fault or a short circuit fault has occurred, first control the second type of switch to disconnect, and then control the first type of switch to disconnect.

12. The transformation system according to claim 8, characterized in that, It also includes AC busbars; The AC side of each of the DC / AC conversion circuits is connected to the AC bus via a corresponding fifth-type switch; The AC bus is used to connect at least one of the power grid port and the AC load port.

13. The transformation system according to claim 3, characterized in that, Also includes: Redundant DC / AC conversion circuit; In the event of a faulty DC / AC conversion circuit in the system, the controller is configured to control the redundant DC / AC conversion circuit to replace the faulty DC / AC conversion circuit.

14. A control method for a power conversion system, characterized in that, include: Based on the current of the photovoltaic DC / DC converter circuit, if a fault occurs, control the corresponding switching device to disconnect the photovoltaic DC / DC converter circuit from the DC bus. The first terminal of the photovoltaic DC / DC converter circuit is used to connect to the photovoltaic string, and the second terminal of the photovoltaic DC / DC converter circuit is connected to the DC bus through the corresponding switching device; the DC bus is also used to connect the battery; the DC side of the DC / AC converter circuit is connected to the DC bus, and the AC sides of multiple DC / AC converter circuits are connected in parallel.

15. The control method according to claim 14, characterized in that, The switching device includes a first type of switch and a second type of switch connected in series. The first type of switch includes a mechanical switch, and the second type of switch includes an energizing fuse or a semiconductor switch. Controlling the corresponding switching device to disconnect the corresponding photovoltaic DC / DC converter circuit from the DC bus includes: First, control the second type of switch to open, then control the first type of switch to open, so as to disconnect the corresponding photovoltaic DC / DC conversion circuit from the DC bus.

16. The control method according to claim 14, characterized in that, Each of the multiple DC / AC conversion circuits is provided with a corresponding current detection device and a third type of switch between its DC side and the DC bus; the third type of switch includes an excitation fuse or a semiconductor switch. The control method further includes: based on the DC-side current of the corresponding DC / AC conversion circuit detected by the current detection device, if a fault is detected, controlling the corresponding third-type switch to open to disconnect the connection between the corresponding DC / AC conversion circuit and the DC bus.

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