Inverter, photovoltaic power generation system and control method thereof

Abstract

The invention discloses an inverter, a photovoltaic power generation system and a control method thereof. The inverter comprises a main power circuit and a protection circuit. The main power circuit comprises a plurality of photovoltaic modules, a plurality of direct current switches, a plurality of DCDC conversion units, positive and negative direct current buses and a DCAC inversion unit; the input end of each DCDC conversion unit is connected with at least one photovoltaic module through at least one DC switch, and the output end of each DCDC conversion unit is connected with a positive and negative DC bus; the direct current input end of the DCAC inversion unit is connected with the positive and negative direct current bus, and the alternating current output end of the DCAC inversion unit is connected with a power grid; a bus capacitor is arranged between the positive and negative DC buses. The control unit is configured to determine whether the photovoltaic power generation system has a fault; and when it is determined that the photovoltaic power generation system breaks down, the execution unit controls the direct-current switch to be switched off. When it is determined that the photovoltaic power generation system breaks down, the execution unit controls the direct-current switch to be switched off; and fault expansion and machine burning caused by fire are avoided.

Description

Technical Field

[0001] The present application relates to the technical field of photovoltaic power generation, and in particular to an inverter, a photovoltaic power generation system and a control method thereof. Background Art

[0002] Photovoltaic power generation systems can convert solar energy into electrical energy and realize the use of renewable energy. The on-site operating environment of photovoltaic power generation systems is relatively harsh, and the working conditions are complex, which can easily cause damage to photovoltaic inverters and other devices. When a photovoltaic inverter fails, it does not have the function of quickly disconnecting the DC-side photovoltaic components, which can easily cause the photovoltaic inverter to burn out, or burn out the photovoltaic components, and even more seriously, it may cause a fire. Summary of the invention

[0003] The present application provides an inverter, a photovoltaic power generation system and a control method thereof, so as to disconnect a DC switch in time when a failure occurs in the photovoltaic power generation system.

[0004] On one hand, the present application provides a photovoltaic power generation system, including a main power circuit and a protection circuit;

[0005] The main power circuit includes a plurality of photovoltaic modules, a plurality of DC switches, a plurality of DCDC conversion units, positive and negative DC bus bars and a DCAC inverter unit; the input end of each DCDC conversion unit is connected to at least one photovoltaic module through at least one DC switch, and the output end of each DCDC conversion unit is connected to the positive and negative DC bus bars; the DC input end of the DCAC inverter unit is connected to the positive and negative DC bus bars, and the AC output end of the DCAC inverter unit is connected to the power grid; a bus capacitor is also provided between the positive and negative DC bus bars;

[0006] The protection circuit includes a control unit and an execution unit. The control unit is configured to determine whether a fault occurs in the photovoltaic power generation system; when it is determined that a fault occurs in the photovoltaic power generation system, the DC switch is controlled to be disconnected through the execution unit.

[0007] On the other hand, the present application provides a control method for a photovoltaic power generation system, the photovoltaic power generation system comprising a main power circuit and a protection circuit;

[0008] The main power circuit includes a plurality of photovoltaic modules, a plurality of DC switches, a plurality of DCDC conversion units, positive and negative DC bus bars and a DCAC inverter unit; the input end of each DCDC conversion unit is connected to at least one photovoltaic module through at least one DC switch, and the output end of each DCDC conversion unit is connected to the positive and negative DC bus bars; the DC input end of the DCAC inverter unit is connected to the positive and negative DC bus bars, and the AC output end of the DCAC inverter unit is connected to the power grid; a bus capacitor is also provided between the positive and negative DC bus bars; the protection circuit includes an execution unit;

[0009] The control method comprises:

[0010] determining whether the photovoltaic power generation system fails;

[0011] When it is determined that the photovoltaic power generation system fails, the DC switch is controlled to be disconnected through the execution unit.

[0012] On the other hand, the present application also provides an inverter for use in a photovoltaic power generation system, wherein the inverter includes a DCAC inverter unit and a protection circuit;

[0013] The DC input end of the DCAC inverter unit is connected to the output end of at least one DCDC conversion unit through positive and negative DC busbars, the input end of the at least one DCDC conversion unit is connected to at least one photovoltaic module through at least one DC switch, and the AC output end of the DCAC inverter unit is connected to the power grid; a bus capacitor is also provided between the positive and negative DC busbars;

[0014] The protection circuit includes a control unit and an execution unit. The control unit is configured to determine whether a fault occurs in the photovoltaic power generation system; when it is determined that a fault occurs in the photovoltaic power generation system, the DC switch is controlled to be disconnected through the execution unit.

[0015] The inverter, photovoltaic power generation system and control method thereof provided in the present application control the DC switch to be disconnected through the execution unit when it is determined that a fault occurs in the photovoltaic power generation system, thereby preventing the fault from expanding or even causing a fire that burns the machine. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic diagram of a photovoltaic power generation system provided in an embodiment of the present application;

[0017] Figure 2 A schematic diagram of a control method for a photovoltaic power generation system provided in an embodiment of the present application.

[0018] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0019] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application clearer and more understandable, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0020] In the description of the present application, it should be understood that the orientations or positional relationships indicated by the terms "center", "upper", "lower", "front", "back", "left", "right", etc. are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0021] like Figure 1 As shown, the photovoltaic power generation system includes a main power circuit 11 and a protection circuit 12 .

[0022] The main power circuit 11 includes multiple photovoltaic modules (shown as PV1~PVn in the figure), multiple DC switches (shown as S1~SN in the figure), multiple DCDC conversion units (shown as DCDC conversion unit 1~DCDC conversion unit N in the figure), positive and negative DC bus bars (shown as BUS+ and BUS- in the figure), DCAC inverter units, circuit breakers, transformer T and power grid.

[0023] The input end of each DCDC conversion unit is connected to at least one photovoltaic module through at least one DC switch, and the output end thereof is connected to the positive and negative DC busbars. The DC switch may be a multi-way switch. Bus capacitors are also connected between the positive and negative DC busbars, such as shown by capacitors C1 and C2 in the figure. For example, the input end of the DCDC conversion unit N is connected to at least one photovoltaic module PVN through a DC switch SN, and the photovoltaic module PVN may be formed by a plurality of photovoltaic cells connected in series and parallel (in series and / or in parallel), and the positive output end of the DCDC conversion unit N is connected to the positive DC busbar BUS+, and the negative output end of the DCDC conversion unit N is connected to the negative DC busbar BUS-. In one example, the DCDC conversion unit N may boost the output voltage of the photovoltaic module PVN and output it to the positive and negative DC busbars; the DCDC conversion unit N may realize the maximum power tracking (MPPT) of the photovoltaic module PVN.

[0024] The DC input end of the DCAC inverter unit is connected to the positive and negative DC busbars, that is, the positive DC input end of the DCAC inverter unit is connected to the positive DC busbar BUS+, and the negative DC input end of the DCAC inverter unit is connected to the negative DC busbar BUS-. The AC output end of the DCAC inverter unit is connected to the grid through a circuit breaker and a transformer T. The circuit breaker can be a multi-way switch.

[0025] The protection circuit 12 includes a control unit, a first drive unit, a second drive unit and an execution unit. The control unit can control the first drive unit to drive the DCDC conversion unit to work, the control unit can control the second drive unit to drive the DCAC inverter unit to work, and the control unit can also control the execution unit to drive the DC switch to disconnect or conduct.

[0026] In actual products, the protection circuit 12 can be integrated with the DCAC inverter unit in the same cabinet, or integrated with the DCDC conversion unit in the same cabinet, or integrated with the DCDC conversion unit and the DCAC inverter unit in the same cabinet. It is understandable that it is also feasible to set the protection circuit 12 independently of the DCDC conversion unit or the DCAC inverter unit.

[0027] In one example, the protection circuit 12 further includes an auxiliary power supply, such as auxiliary power supply 1 and auxiliary power supply 2 in the figure. The auxiliary power supply can be powered by a DC bus (positive DC bus power supply and / or negative DC bus power supply) and / or a grid voltage, and the output voltage of the auxiliary power supply can power components such as a control unit.

[0028] In the above implementation, when a photovoltaic power generation system fails, it is necessary to promptly control the DC switch to disconnect. For example, when a photovoltaic module fails in a short circuit, the short circuit current is large, which can easily lead to the expansion of the fault or even a fire that burns the machine; another example is when the positive and negative connections of the photovoltaic cell are reversed, the input voltage of the DCDC conversion unit will be too high, and the bus capacitor will be over-voltage and explode.

[0029] Based on this, in one example, the protection circuit 12 further includes a first detection unit.

[0030] The first detection unit is used to detect the bus voltage between the positive and negative DC bus bars and / or the bus capacitor ripple current.

[0031] The control unit is configured to control the DC switch to be disconnected through the execution unit when the bus voltage detected by the first detection unit is greater than a preset bus voltage threshold (i.e., it is determined that the photovoltaic power generation system has failed); and / or, when the bus capacitor ripple current detected by the first detection unit is greater than a preset ripple current threshold (i.e., it is determined that the photovoltaic power generation system has failed), control the DC switch to be disconnected through the execution unit.

[0032] In one example, the control unit is further configured to control the DC switch to disconnect through the execution unit when the change rate of the bus voltage detected by the first detection unit is greater than a preset change rate threshold (i.e., it is determined that a fault has occurred in the photovoltaic power generation system).

[0033] Generally, when the DCAC inverter unit is working normally, the bus capacitor voltage remains basically stable. In the standby state, the bus capacitor voltage is also basically equal to the opening voltage of the photovoltaic module. When the DCAC inverter unit has an internal fault and a short circuit occurs, the bus voltage suddenly drops. Therefore, when the bus voltage suddenly drops, the control unit needs to send a drive to segment the DC switch.

[0034] In one example, the protection circuit 12 further includes a second detection unit.

[0035] The second detection unit is used to detect the output voltage of the auxiliary power supply.

[0036] The control unit is configured to control the DC switch to be disconnected through the execution unit when the output voltage of the auxiliary power supply detected by the second detection unit does not meet a preset voltage range (ie, it is determined that a failure occurs in the photovoltaic power generation system).

[0037] For example, the auxiliary power supply includes at least one DCDC converter, which is powered by the grid voltage. If the output voltage of the auxiliary power supply detected by the second detection unit does not meet the input voltage range of the DCDC converter, the DC switch is controlled to be disconnected through the execution unit. In other words, when the auxiliary power supply reports a fault, the DCAC inverter unit must have been damaged, and the AC side of the DCAC inverter unit has been overcurrent, causing the circuit breaker connected to the grid to be segmented. Therefore, in this case, the DC switch needs to be disconnected in time to prevent the energy of the photovoltaic module from being continuously transmitted to the DCAC inverter unit side, thereby expanding the fault and burning the machine.

[0038] In one example, the protection circuit 12 further includes a third detection unit.

[0039] The third detection unit is used to detect the current and / or input voltage of the photovoltaic component.

[0040] The control unit is configured to control the DC switch to be disconnected through the execution unit when the current of the photovoltaic component detected by the third detection unit exceeds a preset component current threshold (i.e., it is determined that the photovoltaic power generation system has failed); and / or, when the input voltage of the photovoltaic component detected by the third detection unit is greater than a preset input voltage threshold (i.e., it is determined that the photovoltaic power generation system has failed), control the DC switch to be disconnected through the execution unit.

[0041] For example, when a DCAC inverter unit fails, there is a short circuit point inside, which will cause the current of the photovoltaic module to be abnormally large. At this time, the DC switch needs to be disconnected in time to protect the DCAC inverter unit and the photovoltaic module.

[0042] For example, during on-site installation, the photovoltaic cells may be connected incorrectly, which may cause the input voltage of the DCDC conversion unit to be too high and exceed the system voltage. Therefore, the input voltage of the photovoltaic module is collected in real time, and when the collected input voltage is greater than the preset input voltage threshold, the DC switch is disconnected.

[0043] In a further implementation, when the DC switch is already in a disconnected state, the photovoltaic power generation system will prompt an alarm and the DC switch cannot be closed.

[0044] Figure 2 This is a schematic diagram of a control method for a photovoltaic power generation system provided in another embodiment of the present application. The photovoltaic power generation system may refer to the above content. The control method comprises the following steps:

[0045] S11, determining whether the photovoltaic power generation system fails;

[0046] S12: When it is determined that the photovoltaic power generation system fails, the DC switch is controlled to be disconnected by the execution unit.

[0047] In one example, when the bus voltage detected by the first detection unit is greater than a preset bus voltage threshold, and / or when the bus capacitor ripple current detected by the first detection unit is greater than a preset ripple current threshold, it is determined that the photovoltaic power generation system has a fault.

[0048] In one example, when the rate of change of the bus voltage detected by the first detection unit is greater than a preset rate of change threshold, it is determined that a fault occurs in the photovoltaic power generation system.

[0049] In one example, when the output voltage of the auxiliary power supply detected by the second detection unit does not satisfy a preset voltage range, it is determined that a fault occurs in the photovoltaic power generation system.

[0050] In one example, when the current of the photovoltaic component detected by the third detection unit exceeds a preset component current threshold, and / or when the input voltage of the photovoltaic component detected by the third detection unit is greater than a preset input voltage threshold, it is determined that the photovoltaic power generation system has a fault.

[0051] In one example, when the DC switch is disconnected, a prompt message is generated to prompt the user not to close the DC switch.

[0052] Another embodiment of the present application provides an inverter, which is applied to a photovoltaic power generation system, wherein the inverter includes a DCAC inverter unit and a protection circuit;

[0053] The DC input end of the DCAC inverter unit is connected to the output end of at least one DCDC conversion unit through positive and negative DC busbars, the input end of the at least one DCDC conversion unit is connected to at least one photovoltaic module through at least one DC switch, and the AC output end of the DCAC inverter unit is connected to the power grid; a bus capacitor is also provided between the positive and negative DC busbars;

[0054] The protection circuit includes a control unit and an execution unit. The control unit is configured to determine whether a fault occurs in the photovoltaic power generation system; when it is determined that a fault occurs in the photovoltaic power generation system, the DC switch is controlled to be disconnected through the execution unit.

[0055] It should be noted that, in this example, the DCAC inverter unit and the protection circuit can refer to the contents described in the above examples.

[0056] The preferred embodiments of the present application are described above with reference to the accompanying drawings, but the scope of the present application is not limited thereby. Any modification, equivalent substitution and improvement made by a person skilled in the art without departing from the scope and essence of the present application shall be within the scope of the present application.

Claims

1. A photovoltaic power generation system, characterized in that: Including main power circuit and protection circuit; The main power circuit includes a plurality of photovoltaic modules, a plurality of DC switches, a plurality of DCDC conversion units, positive and negative DC bus bars and a DCAC inverter unit; the input end of each DCDC conversion unit is connected to at least one photovoltaic module through at least one DC switch, and the output end of each DCDC conversion unit is connected to the positive and negative DC bus bars; the DC input end of the DCAC inverter unit is connected to the positive and negative DC bus bars, and the AC output end of the DCAC inverter unit is connected to the power grid; a bus capacitor is also provided between the positive and negative DC bus bars; The protection circuit includes a control unit and an execution unit. The control unit is configured to determine whether a fault occurs in the photovoltaic power generation system; when it is determined that a fault occurs in the photovoltaic power generation system, the DC switch is controlled to be disconnected through the execution unit.

2. The photovoltaic power generation system according to claim 1, characterized in that: The protection circuit further comprises a first detection unit, which is used to detect the bus voltage and / or bus capacitor ripple current between the positive and negative DC bus bars; The control unit is configured to determine that a fault occurs in the photovoltaic power generation system when the bus voltage detected by the first detection unit is greater than a preset bus voltage threshold and / or when the bus capacitor ripple current detected by the first detection unit is greater than a preset ripple current threshold.

3. The photovoltaic power generation system according to claim 2, characterized in that: The control unit is further configured to determine that a fault occurs in the photovoltaic power generation system when a change rate of the bus voltage detected by the first detection unit is greater than a preset change rate threshold.

4. The photovoltaic power generation system according to claim 1, characterized in that: The protection circuit further includes an auxiliary power supply and a second detection unit, wherein the second detection unit is used to detect the output voltage of the auxiliary power supply; The control unit is configured to determine that a fault occurs in the photovoltaic power generation system when the output voltage of the auxiliary power supply detected by the second detection unit does not satisfy a preset voltage range.

5. The photovoltaic power generation system according to claim 4, characterized in that: The auxiliary power supply is powered by the DC bus and / or the grid voltage.

6. The photovoltaic power generation system according to claim 1, characterized in that: The protection circuit further comprises a third detection unit, and the third detection unit is used to detect the current and / or input voltage of the photovoltaic assembly; The control unit is configured to determine that a fault occurs in the photovoltaic power generation system when the current of the photovoltaic component detected by the third detection unit exceeds a preset component current threshold, and / or when the input voltage of the photovoltaic component detected by the third detection unit is greater than a preset input voltage threshold.

7. The photovoltaic power generation system according to claim 1, characterized in that: The control unit is configured to generate a prompt message when the DC switch is disconnected, so as to prompt the user not to close the DC switch.

8. The photovoltaic power generation system according to claim 1, characterized in that: The main power circuit also includes a circuit breaker and a transformer, and the AC output end of the DCAC inverter unit is connected to the power grid through the circuit breaker and the transformer in sequence.

9. The photovoltaic power generation system according to claim 1, characterized in that: The protection circuit further includes a first driving unit and a second driving unit, and the control unit is configured to control the first driving unit to drive the DCDC conversion unit, and / or control the second driving unit to drive the DCAC inverter unit.

10. A control method for a photovoltaic power generation system, characterized in that: The photovoltaic power generation system includes a main power circuit and a protection circuit; The main power circuit includes a plurality of photovoltaic modules, a plurality of DC switches, a plurality of DCDC conversion units, positive and negative DC bus bars and a DCAC inverter unit; the input end of each DCDC conversion unit is connected to at least one photovoltaic module through at least one DC switch, and the output end of each DCDC conversion unit is connected to the positive and negative DC bus bars; the DC input end of the DCAC inverter unit is connected to the positive and negative DC bus bars, and the AC output end of the DCAC inverter unit is connected to the power grid; a bus capacitor is also provided between the positive and negative DC bus bars; the protection circuit includes an execution unit; The control method comprises: determining whether the photovoltaic power generation system fails; When it is determined that the photovoltaic power generation system fails, the DC switch is controlled to be disconnected through the execution unit.

11. An inverter, applied to a photovoltaic power generation system, characterized in that: The inverter includes a DCAC inverter unit and a protection circuit; The DC input end of the DCAC inverter unit is connected to the output end of at least one DCDC conversion unit through positive and negative DC busbars, the input end of the at least one DCDC conversion unit is connected to at least one photovoltaic module through at least one DC switch, and the AC output end of the DCAC inverter unit is connected to the power grid; A bus capacitor is also provided between the positive and negative DC bus bars; The protection circuit includes a control unit and an execution unit. The control unit is configured to determine whether a fault occurs in the photovoltaic power generation system; when it is determined that a fault occurs in the photovoltaic power generation system, the DC switch is controlled to be disconnected through the execution unit.

Images