Network-constructed photovoltaic black start method, photovoltaic power generation device and photovoltaic power generation system

Abstract

The application discloses a network-constructing type photovoltaic black start method, a photovoltaic power generation device and a photovoltaic power generation system, relates to the network-constructing type photovoltaic black start technical field, and comprises the following steps: in the case that the DC side voltage of a main photovoltaic source exceeds a preset threshold value after the main photovoltaic source and an auxiliary photovoltaic source are connected in network, a chopping protection device is controlled to work; wherein the main photovoltaic source and the auxiliary photovoltaic source are connected into the same AC bus, the chopping protection device is connected in parallel between a chopping circuit and an inverter circuit of the main photovoltaic source, and the chopping protection device comprises an energy consumption resistor, which is used for absorbing the transient active impact of the auxiliary photovoltaic source connected in network; in the case that the DC side voltage of the main photovoltaic source and the DC side voltage of the auxiliary photovoltaic source are in a stable state, an extended photovoltaic source and a load are controlled to be connected in network, and the network-constructing type photovoltaic black start is completed. The application can improve the stability and reliability of the network-constructing type photovoltaic station black start process under the condition that there is no energy storage support.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of network-constructed photovoltaic black start technology, and particularly relates to a network-constructed photovoltaic black start method, a photovoltaic power generation device and a photovoltaic power generation system. BACKGROUND

[0002] In related technologies, the black start technology of a network-constructed photovoltaic station generally needs to rely on a storage system or an external stable synchronous power source (such as a diesel generator or a traditional synchronous unit) to provide dynamic power support. In some extreme working conditions (such as storage mismatch or external power source loss), the power system needs to rely completely on the self-network building capability of the network-constructed inverter to reconstruct the voltage / frequency reference, and needs to have the multi-zone cascaded self-starting capability.

[0003] However, in the above extreme working condition without storage support, the photovoltaic station as the only black start source has the characteristic of unidirectional active power flow, and any reverse active transient impact in the black start process will raise the direct current voltage, and the rise of the direct current voltage will cause the direct current protection device to act to cut off the photovoltaic panel and the inverter, which will cause the black start to fail, and therefore it is necessary to seek a network-constructed photovoltaic black start path applicable to the condition without storage support. SUMMARY

[0004] The main purpose of the present application is to provide a network-constructed photovoltaic black start method, a photovoltaic power generation device and a photovoltaic power generation system, and aims to solve the technical problem that the network-constructed photovoltaic station is prone to black start failure due to transient impact in the condition without storage support in related technologies.

[0005] To achieve the above purpose, the present application provides a network-constructed photovoltaic black start method, which can be used for the black start control equipment of a photovoltaic power generation system, and the photovoltaic power generation system further includes a main photovoltaic source, a secondary photovoltaic source and a chopping protection device, which are all connected with the black start control equipment; the main photovoltaic source and the secondary photovoltaic source are integrated into the same alternating current bus; the main photovoltaic source includes a photovoltaic panel, a chopping circuit, an inverter circuit and a step-up transformer connected in sequence; the chopping protection device is connected in parallel between the chopping circuit and the inverter circuit; the chopping protection device includes an energy consumption resistor, which is used to absorb the transient active impact of the secondary photovoltaic source in the grid connection.

[0006] The network-constructed photovoltaic black start method includes the following steps.

[0007] When the direct current side voltage of the main photovoltaic source exceeds a preset threshold value after the main photovoltaic source and the secondary photovoltaic source are connected to the grid, the chopping protection device is controlled to work.

[0008] When the direct current side voltage of the main photovoltaic source and the direct current side voltage of the secondary photovoltaic source are in a stable state, the extended photovoltaic source and the load are controlled to be connected to the grid, and the network-constructed photovoltaic black start is completed.

[0009] In an embodiment, before the step of controlling the chopper protection device to work, the method further comprises:

[0010] controlling the main photovoltaic source to start, and increasing the primary frequency modulation coefficient of the main photovoltaic source and / or reducing the inertia time constant of the main photovoltaic source.

[0011] In an embodiment, the step of increasing the primary frequency modulation coefficient of the main photovoltaic source comprises:

[0012] increasing the primary frequency modulation coefficient of the main photovoltaic source within a preset frequency modulation coefficient range until the main photovoltaic source operates stably.

[0013] In an embodiment, the step of reducing the inertia time constant of the main photovoltaic source comprises:

[0014] reducing the inertia time constant of the main photovoltaic source within a preset inertia time constant range until the main photovoltaic source operates stably.

[0015] In an embodiment, after the step of controlling the main photovoltaic source to start, and increasing the primary frequency modulation coefficient of the main photovoltaic source and / or reducing the inertia time constant of the main photovoltaic source, the method further comprises:

[0016] controlling the auxiliary photovoltaic source to start in a zero-power mode, and reducing the inertia time constant of the auxiliary photovoltaic source;

[0017] controlling the auxiliary photovoltaic source to pre-synchronize and grid-connect based on the amplitude, frequency and phase of the main photovoltaic source.

[0018] In an embodiment, the step of reducing the inertia time constant of the auxiliary photovoltaic source comprises:

[0019] reducing the inertia time constant of the auxiliary photovoltaic source within a preset inertia time constant range until the auxiliary photovoltaic source operates stably.

[0020] In an embodiment, in a case where the direct-current side voltage of the main photovoltaic source and the direct-current side voltage of the auxiliary photovoltaic source are in a stable state, the step of controlling the extended photovoltaic source and the load to grid-connect to complete the network-constructed photovoltaic black start comprises:

[0021] controlling the critical load to grid-connect in a case where the direct-current side voltage of the main photovoltaic source and the direct-current side voltage of the auxiliary photovoltaic source are in a stable state;

[0022] controlling the extended photovoltaic source and / or the non-critical load to grid-connect in a case where the frequency of the power system is in a stable state to complete the network-constructed photovoltaic black start.

[0023] In an embodiment, in a case where the frequency of the power system is in a stable state, the step of controlling the extended photovoltaic source and / or the non-critical load to grid-connect to complete the network-constructed photovoltaic black start comprises:

[0024] In the case that the frequency of the power system is in a stable state, control all extended photovoltaic sources to pre-synchronize and grid-connect in a preset starting sequence;

[0025] After all the extended photovoltaic sources are grid-connected, control the inertia time constant of the non-main photovoltaic source and the primary frequency modulation coefficient of the non-main photovoltaic source to be consistent with the primary frequency modulation coefficient of the main photovoltaic source and the inertia time constant of the main photovoltaic source respectively; the non-main photovoltaic source includes the auxiliary photovoltaic source and all the extended photovoltaic sources;

[0026] Control all non-critical loads to gradually grid-connect.

[0027] In addition, to achieve the above-mentioned purpose, the application further provides a photovoltaic power generation device, which comprises a main photovoltaic source and a chopping protection device; the main photovoltaic source comprises photovoltaic panels, a chopping circuit, an inverter circuit and a step-up transformer connected in sequence;

[0028] The chopping protection device is connected in parallel between the chopping circuit and the inverter circuit, and comprises an energy consumption resistor for absorbing transient active impact.

[0029] In addition, to achieve the above-mentioned purpose, the application further provides a photovoltaic power generation system, which comprises:

[0030] A black start control device, which comprises a memory, a processor and a computer program stored in the memory and executable on the processor, and the computer program is configured to implement the steps of the network construction type photovoltaic black start method as described above; and

[0031] The photovoltaic power generation device as described above is connected with the black start control device.

[0032] The one or more technical solutions provided by the application have at least the following technical effects:

[0033] The network-constructing photovoltaic black start method provided in the application can monitor the DC side voltage of the main photovoltaic source after the main photovoltaic source and the auxiliary photovoltaic source are connected in grid, and control the chopping protection device to work when the DC side voltage of the main photovoltaic source exceeds the preset threshold value; the chopping protection device is arranged between the chopping circuit and the inverter circuit of the main photovoltaic source, and the chopping protection device includes an energy consumption resistor, which can absorb the transient active impact caused by the connection of the auxiliary photovoltaic source in grid when the DC side voltage exceeds the preset threshold value; and under the condition that the DC side voltage of the main photovoltaic source and the DC side voltage of the auxiliary photovoltaic source are in a stable state, the extended photovoltaic source and the load are controlled to be connected in grid, so as to complete the whole process of the network-constructing photovoltaic black start. The configuration of the chopping protection device in the application can avoid the reverse active transient impact of the auxiliary photovoltaic source on the DC side voltage of the main photovoltaic source, so as to avoid the black start failure caused by the misoperation of the DC protection device, thereby providing a network-constructing photovoltaic black start path applicable to the case without energy storage support. BRIEF DESCRIPTION OF DRAWINGS

[0034] The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate embodiments consistent with the present application and, together with the description, further serve to explain the principles of the application.

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the application or the related art, the accompanying drawings needed to be used in the embodiments or the related art description will be briefly introduced. Obviously, those skilled in the art can obtain other drawings from these drawings without creative effort.

[0036] Figure 1 The structural schematic diagram of the photovoltaic power generation system related to the embodiments of the application;

[0037] Figure 2 The black start control device structural schematic diagram of the hardware running environment related to the embodiments of the application;

[0038] Figure 3 The structural schematic diagram of the photovoltaic power generation device related to the embodiments of the application;

[0039] Figure 4 The flowchart provided by the first embodiment of the network-constructing photovoltaic black start method of the application;

[0040] Figure 5 The black start brief flowchart of an example based on the first embodiment;

[0041] Figure 6 The main photovoltaic source power waveform simulation diagram of the black start process without chopping protection;

[0042] Figure 7The simulation diagram of the AC voltage and DC voltage amplitude waveform of the main photovoltaic source in the process of the black start without the chopping protection;

[0043] Figure 8 The simulation diagram of the power waveform of the auxiliary photovoltaic source in the process of the black start without the chopping protection;

[0044] Figure 9 The simulation diagram of the AC voltage and DC voltage amplitude waveform of the auxiliary photovoltaic source in the process of the black start without the chopping protection;

[0045] Figure 10 The simulation diagram of the power waveform of the main photovoltaic source in the process of the black start using the method of the application;

[0046] Figure 11 The simulation diagram of the AC voltage and DC voltage amplitude waveform of the main photovoltaic source in the process of the black start using the method of the application;

[0047] Figure 12 The simulation diagram of the power waveform of the auxiliary photovoltaic source in the process of the black start using the method of the application;

[0048] Figure 13 The simulation diagram of the AC voltage and DC voltage amplitude waveform of the auxiliary photovoltaic source in the process of the black start using the method of the application.

[0049] The implementation, functional features and advantages of the application will be further described with reference to the accompanying drawings. DETAILED DESCRIPTION

[0050] It should be understood that the specific embodiments described herein are only used to explain the technical solutions of the application, and are not used to limit the application.

[0051] In order to better understand the technical solutions of the application, the following will be described in detail in combination with the accompanying drawings and specific embodiments.

[0052] The main solution of the embodiments of the application is that the chopping protection device is controlled to work in the case that the DC side voltage of the main photovoltaic source exceeds a preset threshold after the main photovoltaic source and the auxiliary photovoltaic source are grid-connected; the DC side of the main photovoltaic source is configured with the chopping protection device, and the chopping protection device includes an energy consumption resistor, which is used to absorb the transient active impact of the auxiliary photovoltaic source grid-connected; in the case that the DC side voltage of the main photovoltaic source and the DC side voltage of the auxiliary photovoltaic source are in a stable state, the extended photovoltaic source and the load are controlled to be grid-connected, and the network-constructing photovoltaic black start is completed.

[0053] As new power systems rapidly expand towards higher proportions of renewable energy, grid operation faces multiple challenges: the superposition of uncertainties on both the source and load sides leads to a continuous narrowing of the voltage stability domain, and multi-timescale power fluctuations significantly increase the pressure on system dynamic regulation. Against this backdrop, black-start technology, as one of the core technologies for enhancing grid resilience, can reduce power supply interruption time by rapidly rebuilding system voltage and frequency support, becoming a key technical means to enhance power system resilience and ensure the reliable operation of independent microgrids. Among these, grid-forming photovoltaic power plants, as the core power generation unit of new power systems, can achieve a shift from passive response to active construction through the development of their black-start capabilities, providing important technical support for building highly resilient new power systems.

[0054] However, the implementation path of black-start technology for grid-connected photovoltaic (PV) power plants still has significant limitations. In related technologies, black-start technology for grid-connected PV power plants relies on energy storage systems or external stable synchronous sources (such as diesel generators or traditional synchronous generators) to provide dynamic power support. Typical technical routes include using bidirectional DC / AC converters with energy storage to support the AC bus voltage, or configuring buffer supercapacitors or batteries on the DC bus of the PV system. Under some extreme conditions (such as energy storage mismatch or external power supply failure), the power system must rely entirely on the autonomous grid-connection capability of the grid-connected inverter to achieve voltage / frequency reference reconfiguration, and it needs to have multi-zone cascaded self-starting capability.

[0055] In the extreme operating conditions without energy storage support, the photovoltaic power station will serve as the sole black start source. Due to its unidirectional active power flow, any reverse active transient impact during the black start process will raise its DC voltage. The rise in DC voltage will cause the DC protection device to activate and disconnect the photovoltaic panels and inverter, thus causing black start failure. Therefore, it is necessary to find a grid-type photovoltaic black start path that can be applied to situations without energy storage support.

[0056] This application provides a solution that, after the main photovoltaic (PV) source and secondary PV source are connected to the grid, controls a chopper protection device to operate when the DC-side voltage of the main PV source exceeds a preset threshold. The chopper protection device absorbs the transient active power surge caused by the secondary PV source's grid connection through a power-dissipating resistor. After the DC-side voltages of both the main and secondary PV sources stabilize, the remaining extended PV sources and loads are then connected to the grid, completing the entire black-start process for grid-connected PV systems. The chopper protection device prevents the reverse active power transient surge from the secondary PV source from raising the DC-side voltage of the main PV source, thus avoiding malfunction of the DC protection device and resulting in black-start failure. This provides a black-start path for grid-connected PV systems applicable to situations without energy storage support.

[0057] The following will be explained and described through several examples.

[0058] Reference is made to Figure 1 , Figure 1 is a structural schematic diagram of a photovoltaic power generation system involved in an embodiment of the present application.

[0059] In the photovoltaic power generation system provided by the present application, the photovoltaic power generation system can include a black start control device and a photovoltaic power generation device connected with the black start control device.

[0060] The black start control device includes at least one processor and a memory in communication connection with the at least one processor, wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor to enable the at least one processor to perform the network configuration type photovoltaic black start method in the first embodiment as described below.

[0061] Reference is made to Figure 2 , which shows a structural schematic diagram of a black start control device suitable for being used to implement the embodiments of the present application. The black start control device in the embodiments of the present application can include, but is not limited to, mobile terminals such as notebook computers, digital broadcast receivers, PDAs (Personal Digital Assistant), PADs (Portable Application Description), and the like, and fixed terminals such as desktop computers and the like. Figure 2 The black start control device shown is only an example, and should not bring any limitation to the functions and use range of the embodiments of the present application.

[0062] As Figure 2As shown, the black start control device can include a processing device 1001 (e.g., a central processor, a graphics processor, etc.) that can perform various appropriate actions and processes according to programs stored in a read-only memory (ROM) 1002 or loaded from a storage device 1003 into a random access memory (RAM) 1004. In the RAM 1004, various programs and data required for operation of the black start control device are also stored. The processing device 1001, the ROM 1002, and the RAM 1004 are connected to each other through a bus 1005. An input / output (I / O) interface 1006 is also connected to the bus. Generally, the following systems can be connected to the I / O interface 1006: input devices 1007 including, for example, a touch screen, a touch pad, a keyboard, a mouse, an image sensor, a microphone, etc.; output devices 1008 including, for example, a liquid crystal display (LCD), a speaker, a vibrator, etc.; the storage device 1003 including, for example, a magnetic tape, a hard disk, etc.; and a communication device 1009. The communication device 1009 can allow the black start control device to communicate with other devices wirelessly or by wire to exchange data. Although the black start control device with various systems is shown in the figure, it should be understood that all the systems shown are not required to be implemented or possessed. More or fewer systems can be alternatively implemented or possessed.

[0063] The photovoltaic power generation device can include a main photovoltaic source and a chopping protection device; the chopping protection device can be connected in parallel to the direct current side of the main photovoltaic source, and the chopping protection device includes an energy consumption resistor, which is used to absorb the transient active impact brought by the grid connection of the auxiliary photovoltaic source and the extended photovoltaic source. As shown, Figure 1 As shown, the photovoltaic power generation system can also include an auxiliary photovoltaic source, and the main photovoltaic source and the auxiliary photovoltaic source are both connected to the same alternating current bus, and can cooperate to provide energy support for the system during the black start process; the main photovoltaic source is the core power supply in the black start process, and as the first photovoltaic source connected to the grid in the black start process, the main photovoltaic source needs to have the ability of self-networking, and after the system is completely powered off, the voltage and frequency reference are quickly and stably established; generally, a photovoltaic station with large power generation capacity and stable light conditions is selected as the main photovoltaic source in the black start process; and the auxiliary photovoltaic source is the second photovoltaic source connected to the system after the voltage and frequency reference of the main photovoltaic source is established, and the auxiliary photovoltaic source cooperates with the main photovoltaic source to further stabilize the system and provide support for the subsequent connection of the extended photovoltaic source; the auxiliary photovoltaic source is generally a photovoltaic station composed of a medium-sized photovoltaic array, and the power generation capacity of the auxiliary photovoltaic source is smaller than that of the main photovoltaic source, but is sufficient to provide additional power support in the black start process.

[0064] Figure 3 A structural schematic diagram of the photovoltaic power generation device involved in the embodiments of the present application is shown inFigure 3 As shown, the main photovoltaic source can include photovoltaic panels, a DC-DC chopper circuit on the DC side, a DC-AC inverter circuit on the AC side, and a step-up transformer connected in sequence, and the main photovoltaic source is connected to the AC bus through the step-up transformer. Figure 3 As shown, a chopper protection device can be provided in parallel at the DC-DC chopper circuit on the DC side, and the chopper protection device includes an energy dissipation resistor R and a switch K connected in series with the energy dissipation resistor R; in actual application, after the auxiliary photovoltaic source is connected to the AC bus, when the DC voltage U dc of the main photovoltaic source exceeds the preset threshold, the switch K will be closed, at which time the chopper device is put into operation, and the energy dissipation resistor R will absorb the transient active impact generated when the auxiliary photovoltaic source is connected to the grid, thereby preventing the DC voltage of the main photovoltaic source from rising instantaneously; after the DC voltage region is stabilized, the switch K is disconnected to make the chopper device exit the working state, thereby consuming the transient active impact and stabilizing the DC voltage of the main photovoltaic source, effectively preventing the misoperation of the DC protection device of the main photovoltaic source due to the instantaneous voltage rise, so that the main photovoltaic source can smoothly pass through the transient process of active cut-in, laying a solid foundation for the stable connection of the subsequent black-start photovoltaic source and improving the reliability of the black-start process.

[0065] In addition, the above photovoltaic power generation system can further include an extended photovoltaic source and a load connected to the black-start control device, and the extended photovoltaic source and the load are both connected to the same AC bus; wherein the extended photovoltaic source is one or more photovoltaic sources connected to the system subsequently after the main photovoltaic source and the auxiliary photovoltaic source are successfully connected to the grid, and is mainly used to further expand the power generation capacity of the system to gradually restore full-load operation of the system; the extended photovoltaic source can provide more power when the power demand is large, thereby improving the stability and reliability of the power system; in actual application, the extended photovoltaic source can be a photovoltaic field station composed of small photovoltaic arrays, which has a small power generation capacity and can steadily expand the power generation capacity of the system through step-by-step grid connection. The load can include critical loads and non-critical loads, and after the load connection condition is met during the black-start process, the critical loads can be connected first to ensure that the critical loads can be powered in time to maintain the normal operation of the critical infrastructure, and the non-critical loads can be connected after all photovoltaic sources are connected to the grid, the power system tends to be stable, and the energy supply is sufficient, thereby avoiding affecting the stability of the system black-start.

[0066] It can be understood that, in the photovoltaic power generation system provided by the embodiment, by installing the chopping protection device on the direct current side of the main photovoltaic source, the energy consumption resistor in the chopping protection device can consume the transient active impact caused by the grid connection of the auxiliary photovoltaic source, so as to avoid the transient lifting of the direct current voltage of the main photovoltaic source, thereby effectively preventing the misoperation of the direct current protection device of the main photovoltaic source caused by the transient lifting of the voltage, so that the main photovoltaic source can smoothly pass through the transient process of active cutting-in, and the reliability of the black start process is improved.

[0067] Based on the above photovoltaic power generation system, the embodiment of the application provides a grid-forming photovoltaic black start method, which refers to Figure 4 , Figure 4 FIG. 1 is a flowchart of a first embodiment of the grid-forming photovoltaic black start method of the application.

[0068] In the embodiment, the above grid-forming photovoltaic black start method includes steps S100-S200.

[0069] Step S100, in the case that the direct current voltage of the main photovoltaic source exceeds a preset threshold value after the main photovoltaic source and the auxiliary photovoltaic source are connected in grid, the chopping protection device is controlled to work.

[0070] Step S200, in the case that the direct current voltage of the main photovoltaic source and the direct current voltage of the auxiliary photovoltaic source are in a stable state, the extended photovoltaic source and the load are controlled to be connected in grid, and the grid-forming photovoltaic black start is completed.

[0071] Specifically, in the black start process, the main photovoltaic source serves as the reference energy source connected in grid first, and can establish the initial voltage and frequency reference of the alternating current bus through the grid-forming inverter (Grid-Forming mode), on the basis of which the auxiliary photovoltaic source is controlled to be connected in grid, and the system output power is adjusted by the cooperation of the main photovoltaic source and the auxiliary photovoltaic source, so that the photovoltaic power generation system can efficiently and stably restore power supply in the black start process. However, the auxiliary photovoltaic source may cause a certain transient impact after being connected in grid, and the direct current voltage of the main photovoltaic source may be temporarily lifted due to the transient impact after the auxiliary photovoltaic source is connected in grid, exceeding the protection threshold of the direct current protection device, resulting in the cutting-out of the photovoltaic panel and the inverter from the direct current bus, and the failure of the black start.

[0072] Therefore, the direct current side voltage of the main photovoltaic source can be monitored in real time, and the chopping protection device is controlled to work when the direct current side voltage of the main photovoltaic source exceeds a preset threshold after the main photovoltaic source and the auxiliary photovoltaic source are connected in grid. As described in the foregoing system embodiment part, the chopping protection device is arranged between the chopping circuit and the inverter circuit of the main photovoltaic source, and the energy consumption resistor of the chopping protection device can absorb the transient active impact caused by the connection of the auxiliary photovoltaic source, so that the voltage rise of the direct current side of the main photovoltaic source can be reduced, and the black start failure can be avoided. The preset threshold can be a preset value slightly smaller than the protection threshold, so as to trigger the chopping protection device in advance, discharge the transient active impact, and avoid the direct current protection device from acting first. The chopping protection device can make the main photovoltaic source pass through the active cut-in transient process when the auxiliary photovoltaic source is connected in grid, and maintain the stability of the system. On this basis, the extended photovoltaic source and the load can be controlled to be connected in grid when the direct current side voltage of the main photovoltaic source and the direct current side voltage of the auxiliary photovoltaic source are in a stable state, so as to complete the black start process of the grid-connected photovoltaic system.

[0073] During the black start process, in addition to the main photovoltaic source, the photovoltaic power generation system also includes an auxiliary photovoltaic source and the remaining extended photovoltaic source. If the chopping protection device is arranged on the direct current side of each photovoltaic source, although the transient active impact caused by the connection of each photovoltaic source in grid can be effectively alleviated, and the stability of the system can be maintained, the construction cost of the system will certainly be increased if the chopping protection device is introduced for each photovoltaic source. Therefore, in order to realize the cost-optimal black start control, the chopping protection device is not arranged for the auxiliary photovoltaic source and the extended photovoltaic source, and the chopping protection device is arranged only on the direct current side of the main photovoltaic source. The transient active impact caused by the connection of the remaining photovoltaic sources in grid can be reduced through parameter control, so as to maintain the stability of the system.

[0074] In the power system, the relationship between the inertia time constant and the active power can be expressed as:

[0075]

[0076] wherein, is the active power change amount when the frequency changes, is the inertia time constant, is the rated frequency of 50 Hz, is the frequency change rate, The rated active power of the photovoltaic source; analyzing the relationship can know that the reduction of the inertia time constant can reduce the active variation, thus the transient active impact can be regulated by adjusting the inertia time constant. Therefore, in a feasible implementation mode, before the step S100, the main photovoltaic source can be controlled to start, and the primary frequency modulation coefficient of the main photovoltaic source can be increased and / or the inertia time constant of the main photovoltaic source can be reduced. It can be understood that although the main photovoltaic source is additionally provided with the chopping protection device, the remaining parallelly operated photovoltaic sources are not additionally provided with the chopping protection device, thus in order to maintain the voltage fluctuation of the main photovoltaic source in the allowable range, the primary frequency modulation coefficient of the main photovoltaic source can be increased and / or the inertia time constant of the main photovoltaic source can be reduced; the primary frequency modulation coefficient represents the power adjustment amount corresponding to the unit frequency deviation, under the same frequency deviation, the larger primary frequency modulation coefficient can make the active power adjustment range of the main photovoltaic source larger, thus more power disturbance can be borne; and reducing the inertia time constant of the main photovoltaic source can reduce the active variation of the main photovoltaic source, so as to maintain the stability of the main photovoltaic source.

[0077] In actual operation, the primary frequency modulation coefficient of the main photovoltaic source can be increased in the preset frequency modulation coefficient range until the main photovoltaic source is stably running; after starting the main photovoltaic source, the initial primary frequency modulation coefficient corresponding to the main photovoltaic source can be gradually increased by a first set step, or adjusted by a random step each time, on the basis of the initial primary frequency modulation coefficient, until the main photovoltaic source is stably running; the adjustment range of the primary frequency modulation coefficient should be controlled within the preset frequency modulation coefficient range, that is, the adjusted primary frequency modulation coefficient still remains within the corresponding preset frequency modulation coefficient range, which is an optimal primary frequency modulation coefficient range suitable for the photovoltaic source, and the primary frequency modulation coefficient of the main photovoltaic source out of range may cause aggressive power response and over-regulation phenomenon; it should be noted that the preset frequency modulation coefficient range can be set to 10-50, and the preset frequency modulation coefficient range of 10-50 is mainly determined according to GB / T1994-2024 Technical Regulations for Photovoltaic Power Station Access to Power System, and in actual application, the actual more accurate coefficient range can be determined according to the characteristics of the inverter. The inertia time constant of the main photovoltaic source can also be reduced within the preset inertia time constant range until the main photovoltaic source is stably running (the direct current voltage of the main photovoltaic source is constant, or the voltage fluctuation is within the allowed range); on the basis of the initial inertia time constant corresponding to the main photovoltaic source, the initial inertia time constant is gradually reduced by a second set step, or each time it can also be adjusted by a random step, until the main photovoltaic source is stably running; the adjusted value of the inertia time constant should still be controlled within the preset inertia time constant range; the above-mentioned preset inertia time constant range can be set to 4-14, and this preset inertia time constant range can refer to GB / T36547-2024 Technical Regulations for Electrochemical Energy Storage Power Station Access to Power Grid, and in actual application, the actual more accurate coefficient range can also be determined according to the characteristics of the inverter. By adjusting the primary frequency modulation coefficient and the inertia time constant of the main photovoltaic source and the access of the chopping protection device on the direct current side of the main photovoltaic source, more dynamic power support margin and transient stability guarantee are provided for the grid connection of the remaining photovoltaic sources (secondary photovoltaic sources and extended photovoltaic sources, etc.), to ensure the reliability of the black start process.

[0078] The secondary photovoltaic source can be further incorporated after the main photovoltaic source is regulated, the secondary photovoltaic source is controlled in a zero-power mode to start, and the inertia time constant of the secondary photovoltaic source is reduced; based on the amplitude, frequency and phase of the main photovoltaic source, the secondary photovoltaic source is controlled to pre-synchronize and grid-connect. After the main photovoltaic source starts and the region is stable, the grid-connection operation of the secondary photovoltaic source can be performed, the zero-power mode can reduce the impact when the secondary photovoltaic source starts, and the inertia time constant of the secondary photovoltaic source is reduced so that the active change is smaller, thereby reducing the transient active impact that can be generated; similar to the regulation of the inertia time constant of the main photovoltaic source, the inertia time constant of the secondary photovoltaic source can be reduced within a preset inertia time constant range until the secondary photovoltaic source is stably operated; the adjusted inertia time constant of the secondary photovoltaic source is still maintained within the corresponding preset inertia time constant range; it should be noted that the adjustment of the primary frequency coefficient and the inertia time constant can also be achieved by setting and optimizing the inverter control parameters of the photovoltaic source corresponding to the photovoltaic station, and the adjustment is calculated and optimized according to the actual factors such as the power level of different regions and the station line. After the main photovoltaic source and the secondary photovoltaic source are stably started and operated, the amplitude, frequency and phase of the output can be monitored in real time, and the output frequency and phase of the secondary photovoltaic source are adjusted accordingly to ensure that the secondary photovoltaic source is synchronized with the main photovoltaic source, and the grid-connection impact caused by the difference in frequency and phase is avoided; when the frequency and phase of the secondary photovoltaic source are completely consistent with those of the main photovoltaic source, the secondary photovoltaic source can be smoothly incorporated, and the main photovoltaic source can provide black-start power support together.

[0079] After the main photovoltaic source and the secondary photovoltaic source are successfully grid-connected and stably operated, the remaining extended photovoltaic sources and loads can be connected, so as to complete the whole process of the network-type photovoltaic black-start without energy storage support; it should be noted that the extended photovoltaic source in the embodiment also does not need to be provided with a chopper protection device, and the grid-connection impact is regulated only by adjusting the inertia time constant, which can be referred to the regulation of the inertia time constant of the secondary photovoltaic source. By increasing the primary frequency coefficient of the main photovoltaic source, reducing the inertia time constant of the main photovoltaic source, reducing the inertia time constant of the non-main photovoltaic source, and adding a chopper protection device to the main photovoltaic source, the comprehensive operation of reversely absorbing the transient active impact can enable the main photovoltaic source to bear more transient active impact when other photovoltaic sources are connected, so that even if the other parallelly operated photovoltaic sources do not additionally increase the chopper protection device, the DC voltage fluctuation can be ensured to be maintained within the allowable range, the stability and reliability of the black-start process can be ensured, and the system construction cost can be saved.

[0080] In an implementable embodiment, the critical load can be controlled to be grid-connected when the direct-current side voltage of the main photovoltaic source and the direct-current side voltage of the auxiliary photovoltaic source are in a stable state; the extended photovoltaic source and / or the non-critical load can be controlled to be grid-connected when the frequency of the power system is in a stable state, to complete the network-constructing photovoltaic black start. The critical load refers to a load that needs to be preferentially powered on in the power system once power failure or power interruption occurs, to ensure normal operation of important facilities or services; after the direct-current side voltage of the main photovoltaic source and the auxiliary photovoltaic source is stabilized, the critical load (such as a hospital, communication equipment, important equipment, etc.) can be grid-connected first, to ensure that these important loads are guaranteed and powered. Then, the extended photovoltaic source and / or the non-critical load can be controlled to be grid-connected when the frequency of the power system is in a stable state, to complete the network-constructing photovoltaic black start; the frequency of the power system is a key indicator of power supply and demand balance, and frequency stabilization means that the power system has reached a stable state, and power supply and demand have reached a certain balance, at which time the load of the power grid can be further expanded, and the extended photovoltaic source and some non-critical load can be connected.

[0081] Specifically, all the extended photovoltaic sources can be controlled to be pre-synchronized and grid-connected in a preset starting order when the frequency of the power system is in a stable state; after all the extended photovoltaic sources are grid-connected, the inertia time constant of the non-main photovoltaic source and the primary frequency modulation coefficient of the non-main photovoltaic source are controlled to be consistent with the primary frequency modulation coefficient of the main photovoltaic source and the inertia time constant of the main photovoltaic source, respectively; wherein the non-main photovoltaic source includes the auxiliary photovoltaic source and all the extended photovoltaic sources; all the non-critical loads are controlled to be gradually grid-connected. After the frequency is stabilized, all the extended photovoltaic sources can be sequentially connected in a preset order (such as an order of the extended photovoltaic sources from large to small), to gradually increase the power generation capacity, to avoid connecting too many photovoltaic sources at one time, which causes system frequency fluctuation. After all the extended photovoltaic sources are grid-connected, the inertia time constant of the non-main photovoltaic source and the primary frequency modulation coefficient of the non-main photovoltaic source can be controlled to be consistent with the main photovoltaic source, to ensure the overall coordination of the power system, and then all the non-critical loads are gradually grid-connected, to smoothly transit the system and reduce power grid fluctuation, so that all the photovoltaic sources and loads can be grid-connected, and finally full-capacity black start is completed.

[0082] It can be understood that the network construction type photovoltaic black start method provided by the first embodiment of the present application can control the chopping protection device to work when the direct current side voltage of the main photovoltaic source exceeds the preset threshold after the main photovoltaic source and the auxiliary photovoltaic source are connected in grid; the energy dissipation resistor in the chopping protection device absorbs the transient active impact brought by the connection of the auxiliary photovoltaic source in grid; and after the direct current side voltage of the main photovoltaic source and the direct current side voltage of the auxiliary photovoltaic source are stabilized, the rest of the extended photovoltaic source and the load are connected in grid to complete the whole process of the network construction type photovoltaic black start. The configuration of the chopping protection device can avoid the reverse active transient impact of the auxiliary photovoltaic source to lift the direct current side voltage of the main photovoltaic source, causing the black start failure caused by the misoperation of the direct current protection device, thereby providing a network construction type photovoltaic black start path applicable to the case without energy storage support.

[0083] Exemplarily, in order to help understand the implementation process of the network construction type photovoltaic black start method in the embodiment, the following example is given. Specifically, Figure 5 The black start brief process diagram of the example based on the first embodiment is as shown in Figure 5 The black start whole process as shown in the figure mainly includes the following steps:

[0084] 1) System initialization and load removal: after the microgrid enters the black start state, first cut off all the loads in the system to establish a no-load operation environment;

[0085] 2) Main photovoltaic source voltage and frequency establishment: under sufficient light conditions, the initial voltage and frequency are constructed by the main photovoltaic source of the black start to provide basic power support for the system; on this basis, the primary frequency modulation coefficient and the inertia time constant of the main photovoltaic source can also be adjusted to maintain the stability of the main photovoltaic source, and the specific regulation can refer to the first embodiment part of the foregoing method;

[0086] 3) Auxiliary photovoltaic source pre-synchronization control: control the auxiliary photovoltaic source of the black start to start in zero power mode, and set the inertia time constant and the primary frequency modulation coefficient in the black start mode, and on this basis, the amplitude, frequency and phase of the main photovoltaic source are pre-synchronized;

[0087] 4) Multi-source parallel operation: when the auxiliary photovoltaic source meets the synchronization conditions such as amplitude, frequency and phase, the grid connection closing operation is performed to make it form a coordinated parallel operation mechanism with the main photovoltaic source; after the grid connection, the chopping protection device of the main photovoltaic source can work according to the direct current side voltage of the main photovoltaic source, and when the direct current side voltage exceeds the preset threshold, the energy dissipation resistor in the chopping protection device absorbs the transient active impact brought by the grid connection of the auxiliary photovoltaic source;

[0088] 5) Key load access and frequency stabilization: the key load is preferentially powered or restored to power, and the output of the main photovoltaic source and the auxiliary photovoltaic source is adjusted in proportion according to the primary frequency modulation coefficient to maintain the stability of the system frequency;

[0089] 6) Extension of photovoltaic source grid connection: the remaining black start photovoltaic source (extended photovoltaic source) can refer to the pre-synchronization and parallel control logic of the secondary photovoltaic source, and sequentially complete the grid connection operation;

[0090] 7) Full load recovery and system reconstruction: after all photovoltaic sources complete parallel operation, adjust the inertia time constant and primary frequency modulation coefficient of non-main photovoltaic sources to be consistent with the main photovoltaic source, and can re-distribute power; then gradually access the remaining non-critical load, realize dynamic frequency balance through multi-source collaborative output adjustment, and finally complete the full-capacity black start of the microgrid.

[0091] At the same time, in order to verify the black start effect of the present application, simulation experiments are carried out, Figure 6 、 Figure 7 、 Figure 8 and Figure 9 are the simulation waveform diagrams of the two-stage black start process of the non-energy storage support network type photovoltaic station without setting the chopper protection device; Figure 10 、 Figure 11 、 Figure 12 and Figure 13 are the simulation waveform diagrams of the three-stage black start process of the non-energy storage support network type photovoltaic station using the network type photovoltaic black start method of the present application Figure 6 、 Figure 7 、 Figure 8 、 Figure 9 、 Figure 10 、 Figure 11 、 Figure 12 and Figure 13 In the power waveform diagram, the blue waveform is the waveform of active power Pe, and the green waveform is the waveform of reactive power Qe ; in the voltage amplitude waveform diagram, the blue waveform is the waveform of direct current voltage Vdc_INV_pu, and the green waveform is the waveform of alternating current voltage uqm ).

[0092] The simulation of the two-stage black start process of the non-energy storage support network type photovoltaic station without setting the chopper protection device is mainly an example of directly connecting the secondary photovoltaic source in parallel with the main photovoltaic source after pre-synchronization, and the main photovoltaic source is started at 1.2s, the frequency and voltage are built at 2.2s, and the secondary photovoltaic source is closed and connected to the main photovoltaic source at 4s. The waveform diagram can be obtained; wherein, Figure 6 is the power waveform of the main photovoltaic source, Figure 7 is the alternating current voltage and direct current voltage amplitude waveform of the main photovoltaic source, Figure 8 is the power waveform of the secondary photovoltaic source, Figure 9 is the alternating current voltage and direct current voltage amplitude waveform of the secondary photovoltaic source. From Figure 8The simulation test waveform of the pre-synchronization process shows that although the power impact of the sub photovoltaic source at the moment of closing is about 0.07 pu, which is within a reasonable range, the photovoltaic source can only output active power unidirectionally, and as the only voltage and frequency support source in the system, the 0.07 pu active output power of the sub photovoltaic source can only be absorbed by the main photovoltaic source, so the direct current voltage of the main photovoltaic source is lifted to the protection threshold, Figure 7 The direct current voltage of the main photovoltaic source can reach 2.7 pu, which exceeds the protection threshold of the direct current protection device, and in an actual situation, the direct current protection device may cut off the photovoltaic panel and the inverter, resulting in failure of the black start.

[0093] Therefore, the black start method of the grid-connected photovoltaic power station is improved in the application, which firstly avoids the direct current overvoltage protection action caused by the transient impact of the photovoltaic sequential start, and secondly regulates the multi-zone cooperative control parameters (such as the inertia time constant and the primary frequency modulation coefficient) to ensure the smooth completion of the hierarchical black start. The simulation of the three-stage black start process of the grid-connected photovoltaic power station without energy storage support of the chopper protection device is mainly based on the parallel connection of the main photovoltaic source, the sub photovoltaic source and an extended photovoltaic source (the third photovoltaic source), the main photovoltaic source is started at 1.2 s, the frequency and voltage are built at 2.2 s, the photovoltaic source is closed and connected to the main photovoltaic source after pre-synchronization at 4 s, and the third photovoltaic source is closed and connected to the microgrid system after pre-synchronization at 6 s, and the waveform can be obtained; wherein, Figure 10 the power waveform of the main photovoltaic source using the black start method of the application, Figure 11 the AC voltage and DC voltage amplitude waveform of the main photovoltaic source using the black start method of the application, Figure 12 the power waveform of the sub photovoltaic source using the black start method of the application, Figure 13 the AC voltage and DC voltage amplitude waveform of the sub photovoltaic source using the black start method of the application. From Figure 10 , Figure 11 , Figure 12 and Figure 13 it can be seen that the main photovoltaic source can bear more transient active power after reducing the inertia time constant, and because it has a chopper protection device, it can absorb additional transient active power impact, so it can stabilize the direct current side voltage well, and thus the sub photovoltaic source only bears a small amount of transient active power, so when the third photovoltaic source is connected, its direct current side voltage only has a small fluctuation, and the three-stage photovoltaic power station without energy storage support realizes sequential parallel operation within the allowable range.

[0094] It should be noted that the above examples are only used to understand the application and do not limit the black start method of the grid-connected photovoltaic power station, and more simple transformations based on the technical concept are within the protection scope of the application.

[0095] The above merely describes some embodiments of the present application, and is not intended to limit the protection scope, and any equivalent structure transformation or direct / indirect application in other related technical fields based on the technical concept of the present application and the content of the specification and drawings is included in the protection scope.

Claims

1. A grid-forming photovoltaic black start method, characterized in that, Black-start control equipment for a photovoltaic power generation system, the photovoltaic power generation system further includes a main photovoltaic source, a secondary photovoltaic source, and a chopper protection device all connected to the black-start control equipment; the main photovoltaic source and the secondary photovoltaic source are connected to the same AC bus; the main photovoltaic source includes a photovoltaic panel, a chopper circuit, an inverter circuit, and a step-up transformer connected in sequence; the chopper protection device is connected in parallel between the chopper circuit and the inverter circuit; the chopper protection device includes a power dissipation resistor, the power dissipation resistor being used to absorb transient active power surges when the secondary photovoltaic source is connected to the grid; The grid-type photovoltaic black start method includes: When the DC side voltage of the main photovoltaic source exceeds a preset threshold after the main photovoltaic source and the auxiliary photovoltaic source are connected to the grid, the chopper protection device is controlled to work. When the DC-side voltage of the main photovoltaic source and the DC-side voltage of the auxiliary photovoltaic source are in a stable state, the extended photovoltaic source and the load are controlled to connect to the grid, thus completing the grid-connected photovoltaic black start; Before the step of controlling the chopper protection device to operate when the DC side voltage of the main photovoltaic source exceeds a preset threshold after the main photovoltaic source and the auxiliary photovoltaic source are connected to the grid, the method further includes: Control the main photovoltaic source to start, and increase the primary frequency regulation coefficient of the main photovoltaic source and / or decrease the inertial time constant of the main photovoltaic source; The auxiliary photovoltaic source is started in zero-power mode, and the inertial time constant of the auxiliary photovoltaic source is reduced. Based on the amplitude, frequency, and phase of the main photovoltaic source, the secondary photovoltaic source is controlled to pre-synchronize and connect to the grid.

2. The networked photovoltaic black start method of claim 1, wherein, The step of increasing the primary frequency regulation coefficient of the main photovoltaic source includes: Increase the primary frequency regulation coefficient of the main photovoltaic source within the preset frequency regulation coefficient range until the main photovoltaic source operates stably.

3. The networked photovoltaic black start method of claim 1, wherein, The step of reducing the inertial time constant of the main photovoltaic source includes: The inertial time constant of the main photovoltaic source is reduced within a preset inertial time constant range until the main photovoltaic source operates stably.

4. The networked photovoltaic black start method of claim 1, wherein, The step of reducing the inertial time constant of the secondary photovoltaic source includes: The inertial time constant of the secondary photovoltaic source is reduced within a preset inertial time constant range until the secondary photovoltaic source operates stably.

5. The networked photovoltaic black start method of claim 1, wherein, The steps for controlling the extended photovoltaic source and load to connect to the grid and complete the grid-connected photovoltaic black start, under the condition that the DC side voltage of the main photovoltaic source and the DC side voltage of the auxiliary photovoltaic source are in a stable state, include: When the DC-side voltage of the main photovoltaic source and the DC-side voltage of the auxiliary photovoltaic source are in a stable state, control the grid connection of critical loads; When the frequency of the power system is stable, control the grid connection of extended photovoltaic sources and / or non-critical loads to complete the grid-connected photovoltaic black start.

6. The networked photovoltaic black start method of claim 5, wherein, The steps for controlling the grid connection of extended photovoltaic sources and / or non-critical loads to complete grid-connected photovoltaic black start, under the condition that the frequency of the power system is stable, include: When the frequency of the power system is stable, all extended photovoltaic sources are pre-synchronized and connected to the grid according to a preset startup sequence. After all the extended photovoltaic sources are connected to the grid, the inertia time constant of the non-main photovoltaic source and the primary frequency modulation coefficient of the non-main photovoltaic source are kept consistent with the primary frequency modulation coefficient of the main photovoltaic source and the inertia time constant of the main photovoltaic source respectively; the non-main photovoltaic source includes the auxiliary photovoltaic source and all the extended photovoltaic sources; All the non-critical loads are controlled to be connected to the grid gradually.

7. A photovoltaic power system, characterized by, The photovoltaic power generation system comprises: a black start control device, the black start control device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the computer program being configured to implement the steps of the network construction type photovoltaic black start method according to any one of claims 1 to 6; and a photovoltaic power generation device connected to the black start control device.

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