Fault ride-through method and device for photovoltaic power generation through flexible direct current transmission system

Abstract

The invention discloses a fault ride-through method and device for photovoltaic power generation through a flexible direct current transmission system, a signal switching unit is configured between a maximum power point tracking unit of a photovoltaic power generation unit and a converter controller, the signal switching unit obtains the running state of a current grid-connected system in real time, and once the grid-connected system breaks down, the current grid-connected system stops running. According to the method, the direct current side voltage of a converter is rapidly and actively increased to be higher than the open-circuit voltage of a photovoltaic array, and the output power of the photovoltaic array is rapidly reduced to be close to zero according to the photovoltaic output characteristics, so that the active power output of a photovoltaic power station and the surplus power in a flexible direct current system during a fault are reduced; a dynamic energy consumption device does not need to be additionally configured in the flexible direct current system, and the technical problems that according to an existing fault ride-through method for photovoltaic power generation through the flexible direct current sending-out system, the dynamic energy consumption device needs to be additionally configured in the flexible direct current system, cost is high, and the space is occupied are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of direct current (DC) transmission systems, and in particular to a fault ride-through method and device for a photovoltaic power generation system via a flexible DC transmission system. Background Art

[0002] For systems where large-scale photovoltaic power generation is connected to the AC grid via flexible direct current transmission, when a fault occurs in the receiving AC grid or the flexible direct current transmission system, even if various control and protection measures can be activated in a short period of time, the continuous output of active power by the photovoltaic power station will still cause an active power surplus in the flexible direct current system, which will in turn cause overvoltage on the DC side and aggravate the development of the fault. Existing solutions generally adopt the method of additionally configuring dynamic energy dissipation devices in the flexible direct current system to quickly absorb the surplus power fed into the flexible direct current system by the photovoltaic power station in the event of a fault. However, configuring additional dynamic energy dissipation devices in the flexible direct current system will cost a lot of money and occupy a lot of space. Therefore, providing a method for fault crossing of photovoltaic power generation through a flexible direct current transmission system that does not require additional dynamic energy dissipation devices in the flexible direct current system is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0003] The present invention provides a fault ride-through method and device for photovoltaic power generation through a flexible direct current transmission system, which is used to solve the technical problem that the existing fault ride-through method for photovoltaic power generation through a flexible direct current transmission system requires additional dynamic energy consumption devices to be configured in the flexible direct current system, which is costly and takes up space.

[0004] In view of this, a first aspect of the present invention provides a fault ride-through method for photovoltaic power generation via a flexible DC transmission system, comprising:

[0005] A signal switching unit is configured between the maximum power point tracking unit of the photovoltaic power generation unit and the converter controller;

[0006] The signal switching unit obtains the grid-connected system operation status signal sent by the flexible DC system sending-end converter station in real time;

[0007] The signal switching unit determines whether the grid-connected system has a fault based on the grid-connected system operation status signal. If so, the preset signal is set as the PV array port voltage command and output to the converter controller. The value range of the preset signal is: , is the number of photovoltaic modules connected in series on the DC side of the photovoltaic power generation unit, is the open circuit voltage of a single photovoltaic module, is the preset signal, It is the maximum DC voltage that various devices on the DC side of the photovoltaic power generation unit can withstand during long-term operation.

[0008] Optionally, it also includes:

[0009] If the grid-connected system does not fail, the signal switching unit sets the output signal of the maximum power point tracking unit as the photovoltaic array port voltage instruction and outputs it to the converter controller.

[0010] Optionally, the grid-connected system operation status signal includes 1 and 0. When the grid-connected system has no fault, the grid-connected system operation status signal is 1; when the grid-connected system has a fault, the grid-connected system operation status signal is 0.

[0011] Optionally, it also includes:

[0012] The signal switching unit stores the grid-connected system operation status signal and the signal output to the converter controller in real time.

[0013] A second aspect of the present invention provides a fault ride-through device for photovoltaic power generation through a flexible DC transmission system, comprising a configuration module and a signal switching unit;

[0014] A configuration module, used for configuring a signal switching unit between a maximum power point tracking unit of a photovoltaic power generation unit and a converter controller;

[0015] The signal switching unit is used for:

[0016] Real-time acquisition of grid-connected system operation status signals sent by the flexible DC system sending-end converter station;

[0017] According to the grid-connected system operation status signal, determine whether the grid-connected system has a fault. If so, set the preset signal as the PV array port voltage command and output it to the converter controller. The value range of the preset signal is: , is the number of photovoltaic modules connected in series on the DC side of the photovoltaic power generation unit, is the open circuit voltage of a single photovoltaic module, is the preset signal, It is the maximum DC voltage that various devices on the DC side of the photovoltaic power generation unit can withstand during long-term operation.

[0018] Optionally, the signal switching unit is further configured to:

[0019] If the grid-connected system does not fail, the signal switching unit sets the output signal of the maximum power point tracking unit as the photovoltaic array port voltage instruction and outputs it to the converter controller.

[0020] Optionally, the grid-connected system operation status signal includes 1 and 0. When the grid-connected system has no fault, the grid-connected system operation status signal is 1; when the grid-connected system has a fault, the grid-connected system operation status signal is 0.

[0021] Optionally, the signal switching unit is further configured to:

[0022] Real-time storage of grid-connected system operating status signals and output signals to the converter controller.

[0023] A third aspect of the present invention provides a fault ride-through device for a photovoltaic power generation system through a flexible direct current transmission system, the device comprising a processor and a memory:

[0024] The memory is used to store program code and transmit the program code to the processor;

[0025] The processor is configured to execute the fault ride-through method for the photovoltaic power generation through a flexible direct current transmission system according to any one of the first aspects according to the instructions in the program code.

[0026] A fourth aspect of the present invention provides a computer-readable storage medium for storing program code, wherein the program code is used to execute the fault ride-through method for a PV power generation system through a flexible DC transmission system as described in any one of the first aspects.

[0027] From the above technical solutions, it can be seen that the fault ride-through method of photovoltaic power generation through a flexible DC transmission system provided by the present invention has the following advantages:

[0028] The present invention provides a fault ride-through method for photovoltaic power generation through a flexible direct current transmission system. A signal switching unit is configured between a maximum power point tracking unit of a photovoltaic power generation unit and a converter controller. The signal switching unit obtains the operating status of the current grid-connected system in real time. Once a fault occurs in the grid-connected system, the DC side voltage of the converter is quickly and actively increased to above the open-circuit voltage of the photovoltaic array. According to the photovoltaic output characteristics, the output power of the photovoltaic array will quickly decrease to near zero, thereby reducing the active output of the photovoltaic power station and the surplus power in the flexible direct current system during a fault. There is no need to additionally configure a dynamic energy dissipation device in the flexible direct current system, which solves the technical problem that the existing fault ride-through method for photovoltaic power generation through a flexible direct current transmission system requires additional dynamic energy dissipation devices in the flexible direct current system, which is costly and takes up space. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying any creative work.

[0030] Figure 1 This is a structural diagram of the existing large-scale photovoltaic power generation flexible DC transmission system;

[0031] Figure 2 This is a schematic diagram of the structure of a single power generation unit in a conventional photovoltaic power station;

[0032] Figure 3 A schematic flow chart of a fault ride-through method for photovoltaic power generation through a flexible DC transmission system provided in an embodiment of the present invention;

[0033] Figure 4 A schematic structural diagram of a photovoltaic power station with an additional auxiliary fault ride-through function provided in an embodiment of the present invention;

[0034] Figure 5 This is a schematic diagram of the output characteristic curve of the photovoltaic module;

[0035] Figure 6 This is a schematic structural diagram of a fault ride-through device for a photovoltaic power generation system through a flexible DC transmission system provided in an embodiment of the present invention;

[0036] Figure 7 The figure is a schematic structural diagram of a fault ride-through device for a photovoltaic power generation system through a flexible direct current transmission system provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0037] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0038] For easier understanding, see Figure 3 and Figure 4 The present invention provides an embodiment of a fault ride-through method for photovoltaic power generation through a flexible DC transmission system, comprising:

[0039] Step S1: configuring a signal switching unit between a maximum power point tracking unit of a photovoltaic power generation unit and a converter controller.

[0040] It should be noted that the structural diagram of the existing large-scale photovoltaic power generation through flexible DC transmission system is as follows Figure 1 As shown in the figure, it mainly includes photovoltaic power stations, sending-end converter stations, DC transmission lines, receiving-end converter stations and receiving-end AC power grids. Large-scale photovoltaic power stations are generally composed of multiple photovoltaic power generation units through multi-stage boosting and collection lines. The structure of a single power generation unit in a conventional photovoltaic power station is as follows: Figure 2 As shown, it includes photovoltaic components, collection lines, maximum power point tracking units, converters and their controls, etc. The converter can adopt single-stage or two-stage structures. PV panels connected in series, It is composed of PV panels connected in parallel. 、 are the terminal voltage and current of the photovoltaic array respectively, It is the voltage command of the photovoltaic array port, that is, the signal output by the signal switching unit to the converter controller.

[0041] Step S2: The signal switching unit obtains in real time the grid-connected system operation status signal sent by the flexible DC system sending-end converter station.

[0042] It should be noted that the sending-end converter station transmits a signal indicating the operating status of the grid-connected system (including the Flexible DC transmission system and the receiving AC grid) to the PV power plant. The PV power plant then distributes this signal to each PV power generation unit within the plant. The signal switching unit receives the grid-connected system operating status signal from the sending-end converter station of the Flexible DC system in real time. The grid-connected system operating status signal can be either 1 or 0. When the grid-connected system is fault-free, the grid-connected system operating status signal is 1; when a fault occurs, the grid-connected system operating status signal is 0.

[0043] Step S3: The signal switching unit determines whether the grid-connected system has a fault based on the grid-connected system operation status signal. If so, the preset signal is set as the photovoltaic array port voltage instruction and output to the converter controller. The value range of the preset signal is: , is the number of photovoltaic modules connected in series on the DC side of the photovoltaic power generation unit, is the open circuit voltage of a single photovoltaic module, is the preset signal, It is the maximum DC voltage that various devices on the DC side of the photovoltaic power generation unit can withstand during long-term operation.

[0044] It should be noted that if Figure 4 As shown, when the grid-connected system operation status signal is 1, that is, when the grid-connected system has no fault, Set to the maximum power point tracking unit output; when the grid-connected system operation status signal is 0, that is, when the grid-connected system fails, Set as . The value must be greater than ,in, is the number of photovoltaic modules connected in series on the DC side of the photovoltaic power generation unit, is the open circuit voltage of a single photovoltaic module; at the same time, The value must be less than the maximum DC voltage that various devices on the DC side of the photovoltaic power generation unit can withstand during long-term operation. .like Figure 5As shown in the figure, the photovoltaic power station uses the grid-connected system operation status signal to obtain the current grid-connected system operation status in real time. Once the grid-connected system fails, the photovoltaic power generation unit quickly and actively increases the DC side voltage of its converter to above the open-circuit voltage of the photovoltaic array. Figure 5 As shown in the photovoltaic output characteristics, the output power of the photovoltaic array will drop rapidly to close to zero, thereby reducing the active output of the photovoltaic power station and the surplus power in the flexible direct current system during a fault.

[0045] In one embodiment, the signal switching unit can also store the grid-connected system operating status signal and the signal output to the converter controller in real time, so as to provide data basis for the subsequent fault ride-through analysis of photovoltaic power generation through the flexible DC transmission system.

[0046] The present invention provides a fault ride-through method for photovoltaic power generation through a flexible direct current transmission system. A signal switching unit is configured between a maximum power point tracking unit of a photovoltaic power generation unit and a converter controller. The signal switching unit obtains the operating status of the current grid-connected system in real time. Once a fault occurs in the grid-connected system, the DC side voltage of the converter is quickly and actively increased to above the open-circuit voltage of the photovoltaic array. According to the photovoltaic output characteristics, the output power of the photovoltaic array will quickly decrease to near zero, thereby reducing the active output of the photovoltaic power station and the surplus power in the flexible direct current system during a fault. There is no need to additionally configure a dynamic energy dissipation device in the flexible direct current system, which solves the technical problem that the existing fault ride-through method for photovoltaic power generation through a flexible direct current transmission system requires additional dynamic energy dissipation devices in the flexible direct current system, which is costly and takes up space.

[0047] For easier understanding, see Figure 6 , the present invention provides an embodiment of a fault ride-through device for photovoltaic power generation through a flexible DC transmission system, comprising a configuration module and a signal switching unit;

[0048] A configuration module, used for configuring a signal switching unit between a maximum power point tracking unit of a photovoltaic power generation unit and a converter controller;

[0049] The signal switching unit is used for:

[0050] Real-time acquisition of grid-connected system operation status signals sent by the flexible DC system sending-end converter station;

[0051] According to the grid-connected system operation status signal, determine whether the grid-connected system has a fault. If so, set the preset signal as the PV array port voltage command and output it to the converter controller. The value range of the preset signal is: , is the number of photovoltaic modules connected in series on the DC side of the photovoltaic power generation unit, is the open circuit voltage of a single photovoltaic module, is the preset signal, It is the maximum DC voltage that various devices on the DC side of the photovoltaic power generation unit can withstand during long-term operation.

[0052] In one embodiment, the signal switching unit is further configured to:

[0053] If the grid-connected system does not fail, the signal switching unit sets the output signal of the maximum power point tracking unit as the photovoltaic array port voltage instruction and outputs it to the converter controller.

[0054] In one embodiment, the grid-connected system operation status signal includes 1 and 0. When the grid-connected system has no fault, the grid-connected system operation status signal is 1; when the grid-connected system has a fault, the grid-connected system operation status signal is 0.

[0055] In one embodiment, the signal switching unit is further configured to:

[0056] Real-time storage of grid-connected system operating status signals and output signals to the converter controller.

[0057] For easier understanding, see Figure 7 The present invention provides an embodiment of a fault ride-through device for photovoltaic power generation through a flexible DC transmission system, the device comprising a processor and a memory:

[0058] The memory is used to store program code and transmit the program code to the processor;

[0059] The processor is used to execute any one of the fault ride-through methods for photovoltaic power generation through a flexible direct current transmission system provided in the embodiments of the fault ride-through method for photovoltaic power generation through a flexible direct current transmission system provided in the present invention according to the instructions in the program code.

[0060] The present invention provides an embodiment of a computer-readable storage medium, which is used to store program code, and the program code is used to execute any one of the photovoltaic power generation through flexible direct current transmission system fault ride-through method embodiments provided in the present invention.

[0061] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0062] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features thereof can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A fault ride-through method for photovoltaic power generation through a flexible DC transmission system, characterized in that: include: A signal switching unit is configured between the maximum power point tracking unit of the photovoltaic power generation unit and the converter controller; The signal switching unit obtains the grid-connected system operation status signal sent by the flexible DC system sending-end converter station in real time; The signal switching unit determines whether the grid-connected system has a fault based on the grid-connected system operation status signal. If so, the preset signal is set as the PV array port voltage command and output to the converter controller. The value range of the preset signal is: , is the number of photovoltaic modules connected in series on the DC side of the photovoltaic power generation unit, is the open circuit voltage of a single photovoltaic module, is the preset signal, It is the maximum DC voltage that various devices on the DC side of the photovoltaic power generation unit can withstand during long-term operation.

2. The fault ride-through method for photovoltaic power generation through a flexible DC transmission system according to claim 1, characterized in that: Also includes: If the grid-connected system does not fail, the signal switching unit sets the output signal of the maximum power point tracking unit as the photovoltaic array port voltage instruction and outputs it to the converter controller.

3. The fault ride-through method for photovoltaic power generation through a flexible DC transmission system according to claim 1, characterized in that: The grid-connected system operation status signal includes 1 and 0. When the grid-connected system has no fault, the grid-connected system operation status signal is 1. When the grid-connected system has a fault, the grid-connected system operation status signal is 0.

4. The fault ride-through method of a photovoltaic power generation system through a flexible DC transmission system according to any one of claims 1 to 3, characterized in that: Also includes: The signal switching unit stores the grid-connected system operation status signal and the signal output to the converter controller in real time.

5. A fault ride-through device for photovoltaic power generation through a flexible DC transmission system, characterized in that: including a configuration module and a signal switching unit; A configuration module, used for configuring a signal switching unit between a maximum power point tracking unit of a photovoltaic power generation unit and a converter controller; The signal switching unit is used for: Real-time acquisition of grid-connected system operation status signals sent by the flexible DC system sending-end converter station; According to the grid-connected system operation status signal, determine whether the grid-connected system has a fault. If so, set the preset signal as the PV array port voltage command and output it to the converter controller. The value range of the preset signal is: , is the number of photovoltaic modules connected in series on the DC side of the photovoltaic power generation unit, is the open circuit voltage of a single photovoltaic module, is the preset signal, It is the maximum DC voltage that various devices on the DC side of the photovoltaic power generation unit can withstand during long-term operation.

6. The fault ride-through device for photovoltaic power generation through a flexible DC transmission system according to claim 5, characterized in that: The signal switching unit is also used for: If the grid-connected system does not fail, the signal switching unit sets the output signal of the maximum power point tracking unit as the photovoltaic array port voltage instruction and outputs it to the converter controller.

7. The fault ride-through device for photovoltaic power generation through a flexible DC transmission system according to claim 5, characterized in that: The grid-connected system operation status signal includes 1 and 0. When the grid-connected system has no fault, the grid-connected system operation status signal is 1. When the grid-connected system has a fault, the grid-connected system operation status signal is 0.

8. The fault ride-through device of the photovoltaic power generation through flexible DC transmission system according to any one of claims 5 to 7, characterized in that: The signal switching unit is also used for: Real-time storage of grid-connected system operating status signals and output signals to the converter controller.

9. A fault ride-through device for photovoltaic power generation through a flexible DC transmission system, characterized in that: The device includes a processor and a memory: The memory is used to store program code and transmit the program code to the processor; The processor is used to execute the fault ride-through method of the photovoltaic power generation through flexible direct current transmission system according to any one of claims 1 to 4 according to the instructions in the program code.

10. A computer-readable storage medium, characterized in that The computer-readable storage medium is used to store program code, and the program code is used to execute the fault ride-through method of the PV power generation through the flexible DC transmission system according to any one of claims 1 to 4.

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