Black-start method suitable for wind power plant through LCC-MMC hybrid DC power transmission system, electronic equipment and computer readable storage medium
By adopting the black start method of the LCC-MMC hybrid DC transmission system in offshore wind farms, and using equipment such as grid-type wind turbines and static reactive power compensation devices, coordinated black start between the internal equipment of the wind farm is achieved, solving the problem of how to independently establish an AC system after the offshore wind farm power outage, and improving the power quality and starting efficiency.
Patent Information
- Application Number
- CN202510077124.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-17
- Publication Date
- 2025-04-25
AI Technical Summary
After an offshore wind farm has power outage, how to establish the voltage frequency of the offshore AC system through internal equipment of the wind farm to achieve black startup of the system, especially when it does not rely on external power sources such as the onshore power grid.
A black start method suitable for wind farms through LCC-MMC hybrid DC transmission system is adopted. By installing a grid-type wind turbine on each feeder, and using a static reactive power compensation device and a static synchronous compensator in the LCC-MMC hybrid DC transmission system, the mutual coordinated black start between the grid-type wind turbine, the DC system, the static reactive power compensation device and STATCOM is achieved.
It improves the power quality during the system black startup process, improves the startup efficiency and wind energy utilization rate, and has good economic benefits.
Smart Images
Figure CN119891339A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of wind power generation, and in particular to a black start method, electronic equipment and computer-readable storage medium applicable to a wind farm via an LCC-MMC hybrid direct current transmission system. The present invention can realize a black start in coordination between a grid-type wind turbine set, a direct current system, a static reactive power compensation device and a STATCOM (static synchronous compensator). Background Art
[0002] With the proposal of green, environmentally friendly and low-carbon lifestyles and the gradual saturation of offshore wind power resources, the development of the offshore wind power industry and the gradual saturation of offshore wind power development in offshore areas, large-capacity offshore wind power transmission technology has gradually become one of the research hotspots. The AC transmission scheme cannot meet the needs of large-scale deep-sea offshore wind power development. The flexible DC transmission technology platform based on the MMC topology is large in size and weight, and has a high cost. In contrast, the LCC-MMC hybrid DC transmission technology is mature, large in capacity and low in cost, and is expected to become one of the future offshore wind power transmission solutions. The offshore LCC converter station relies on the grid voltage to achieve phase switching and cannot power the passive network. Therefore, after the offshore wind farm is out of power, how to establish the voltage frequency of the offshore AC system by the equipment with black start capability inside the wind farm to achieve the black start of the system without relying on external power sources such as the onshore power grid has become a key issue that needs to be solved urgently. At present, domestic and foreign scholars have carried out relevant research, such as the following published documents: [1] Jin Yanqiu, Zhang Zheren, Wu Hongyuan, et al. Offshore wind farm black start strategy based on grid-connected wind turbines and diode rectifier units[J]. High Voltage Engineering, 2023, 49(09): 3730-3740. [2] Jianhui Meng, DongxuWang, Yi Wang, et al. An improved dampingadaptive grid-forming control for black start of permanent magnet synchronousgenerator wind turbines supported with battery energy storage system [J]. IETGeneration, Transmission&Distribution, 2023, 17(2): 354-366. Reference [1] proposed a grid-connected wind farm black start strategy with diode rectification. This strategy mainly emphasizes the single-machine black start method of wind turbines. No corresponding strategy is given for the grid-connected impact problem of wind turbines during sequential startup and process. In addition, the wind turbines in the wind farm are started in series, which is inefficient. The coordinated control of wind turbines and reactive power compensation equipment in the DC converter station is not considered. Therefore, this startup scheme still has a lot of room for improvement. Reference [2] proposed a grid-connected wind turbine black start process equipped with energy storage, which achieved smooth black start through control and mode switching. This scheme has only been simulated and verified in an isolated microgrid, and the wind turbines use virtual synchronous mechanism network technology. The operating characteristics of the DC system and the impact of reactive power compensation equipment in the converter station are not considered. The applicability of its black start strategy in this scenario is still unclear. Summary of the invention
[0003] In view of the above-mentioned deficiencies in the prior art, the purpose of the present invention is to propose a black start method, electronic device and computer-readable storage medium suitable for a wind farm via an LCC-MMC hybrid DC transmission system. The present invention can achieve a black start that is coordinated between a grid-type wind turbine, a DC system, a static VAR compensation device and a STATCOM, improves the power quality during the black start of the system, and has a high start-up efficiency and wind energy utilization rate.
[0004] The technical solution of the present invention is achieved in this way: A black start method applicable to a wind farm via an LCC-MMC hybrid DC transmission system, wherein a plurality of grid-forming wind turbines are installed on each feeder, all feeders are connected to the same busbar, and then connected to the power grid via the LCC-MMC hybrid DC transmission system, and the LCC converter station in the LCC-MMC hybrid DC transmission system is matched with a static reactive power compensation device and a static synchronous compensator; the grid-forming wind turbines in different feeders are started in sequence according to the principle of average wind speed of feeders in an offshore wind farm from large to small, and all grid-forming wind turbines in the same feeder are started in parallel; the grid-forming wind turbines on the first feeder are completed, and the grid-forming wind turbines on the first feeder are started in parallel; ... After black start and establishment of AC voltage, the static synchronous compensator is put into operation. The static synchronous compensator adopts grid voltage-oriented vector control to suppress AC voltage fluctuations in the wind farm and balance reactive power during the system black start process. The starting conditions of the LCC-MMC hybrid DC transmission system are detected in real time and the LCC-MMC hybrid DC transmission system is started when the conditions are met. The static reactive power compensation device is controlled according to the harmonic content and output reactive power of the wind farm, so as to achieve a coordinated black start among the grid-connected wind turbines, the LCC-MMC hybrid DC transmission system, the static reactive power compensation device and the static synchronous compensator.
[0005] Furthermore, the grid-connected wind turbine achieves maximum wind energy tracking through machine-side converter control, the grid-side converter achieves grid control through reactive power synchronization and outputs active power by controlling DC voltage, and the grid-connected wind turbine has two control modes: no-load operation and maximum wind energy tracking.
[0006] Furthermore, the grid-type wind turbine maintains no-load operation during the black start process. The black start process of the grid-type wind turbine sequentially includes starting the machine-side converter, starting the grid-side converter to realize the ramp-up of the AC voltage, and pre-synchronizing the amplitude, frequency and phase between the AC voltage output by the grid-side converter and the grid voltage.
[0007] Furthermore, the starting condition of the LCC-MMC hybrid DC transmission system is that the output active power capacity of the grid-connected wind turbines that have completed black start reaches 10% of the rated power of the LCC-MMC hybrid DC transmission system.
[0008] Furthermore, when the LCC-MMC hybrid DC transmission system is started, the MMC converter station in the LCC-MMC hybrid DC transmission system is started first, and then the LCC converter station in the LCC-MMC hybrid DC transmission system is started; the MMC converter station adopts grid voltage-oriented double closed-loop vector control of constant DC voltage and reactive power to charge the LCC-MMC hybrid DC transmission system and stabilize the system DC voltage, thereby realizing a black start of the LCC-MMC hybrid DC transmission system.
[0009] Furthermore, when the LCC converter station is started, the trigger pulse of the thyristor converter valve is turned on, and the fixed trigger angle control mode is maintained to achieve active power transmission after the black start of the LCC-MMC hybrid DC transmission system.
[0010] Furthermore, the feeders in the offshore wind farm are numbered sequentially from 1 according to the average wind speed from high to low, and all the grid-type wind turbines in the same feeder are black-started in parallel in the order of the feeder numbers from small to large; after the black-start of the grid-type wind turbines in the same feeder is completed, once the trigger pulse is detected, all the grid-type wind turbines in the feeder are switched in parallel from the no-load operation mode to the maximum wind energy tracking control mode.
[0011] Furthermore, the static reactive power compensation device is a plurality of devices connected in parallel, and each static reactive power compensation device includes a characteristic subharmonic filter, a parallel reactor and a parallel capacitor, wherein the characteristic subharmonic filter is used for harmonic suppression, and the parallel reactor and the parallel capacitor are used for suppressing the output reactive power; the devices are grouped and put into use according to the harmonic content of the AC system on the wind farm side and the size of the output reactive power, the more the harmonic content, the more characteristic subharmonic filters are put into use; the greater the output reactive power, the more parallel reactors and parallel capacitors are put into use.
[0012] The present invention also provides an electronic device, comprising a memory and a processor, wherein a computer program is stored in the memory, and the processor implements the above-mentioned black start method when executing the computer program.
[0013] The present invention also provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the black start method is implemented.
[0014] Compared with the prior art, the present invention has the following beneficial effects: The present invention does not require any additional devices, but only changes the control methods of the wind turbine generator set, the DC system, the static VAR compensation device and the STATCOM. By giving priority to parallel starting of the wind turbine generator sets in the feeder with a higher average wind speed, and controlling the input of the static VAR compensation device and the operation of the STATCOM according to the harmonic content of the wind farm and the output reactive power, a black start that is coordinated between the grid-forming wind turbine generator set, the DC system, the static VAR compensation device and the STATCOM can be achieved, thereby improving the power quality during the black start of the system, the starting efficiency of the system and the wind energy utilization rate, and having better economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Figure 1 It is a structural schematic diagram of the wind farm sent through the LCC-MMC hybrid DC transmission system.
[0016] Figure 2 This is a flow chart of the system black start method proposed by the present invention.
[0017] Figure 3 This is the simulation waveform of the system during startup. DETAILED DESCRIPTION
[0018] The present invention is used to realize the black start of the grid-type wind turbine, the DC system, the static reactive power compensation device and the STATCOM in coordination with each other, so as to improve the power quality during the black start of the system and the starting efficiency and wind energy utilization rate of the system. Figure 1 It is a structural schematic diagram of the wind farm sent through the LCC-MMC hybrid DC transmission system. Figure 2 The flowchart of the system black start method proposed in the present invention is as follows. By giving priority to starting the wind turbines in the feeder with higher average wind speed in parallel, and controlling the input of the static reactive power compensation device and the operation of STATCOM according to the harmonic content and output reactive power of the wind farm, a coordinated black start between the grid-type wind turbines, the DC system, the static reactive power compensation device and the STATCOM is achieved, the power quality during the system black start process, the system startup efficiency and the wind energy utilization rate are improved, and good economic benefits are achieved.
[0019] The invention discloses a black start method applicable to a wind farm through an LCC-MMC hybrid DC transmission system. A plurality of grid-forming wind turbine sets are installed on each feeder, all feeders are connected to the same collecting bus, and then connected to the power grid through the LCC-MMC hybrid DC transmission system. The LCC converter station in the LCC-MMC hybrid DC transmission system is matched with a static reactive power compensation device and a static synchronous compensator. When starting, the grid-forming wind turbine sets in different feeders are started in sequence according to the principle of the average wind speed of the feeders in the offshore wind farm from large to small, and all the grid-forming wind turbine sets in the same feeder are started in parallel. The grid-forming wind turbine sets on the first feeder are started in parallel. After the group completes the black start and establishes the AC voltage, the static synchronous compensator is put into operation. The static synchronous compensator adopts grid voltage-oriented vector control to suppress the AC voltage fluctuation of the wind farm and balance the reactive power during the system black start process; the starting conditions of the LCC-MMC hybrid DC transmission system are detected in real time and the LCC-MMC hybrid DC transmission system is started when the conditions are met, and the static reactive compensation device is controlled according to the harmonic content and output reactive power of the wind farm, so as to achieve a coordinated black start between the grid-forming wind turbine group, the LCC-MMC hybrid DC transmission system, the static reactive compensation device and the static synchronous compensator.
[0020] Among them, the grid-type wind turbine sets realize maximum wind energy tracking through machine-side converter control, the grid-side converter realizes grid control through reactive power synchronization and realizes active power output by controlling DC voltage. The grid-type wind turbine sets have two control modes: no-load operation and maximum wind energy tracking.
[0021] The black start process of the grid-type wind turbine of the present invention is as follows: the grid-type wind turbine maintains no-load operation during the black start process, and the black start process of the grid-type wind turbine sequentially includes starting the machine-side converter, starting the grid-side converter to realize the ramp-up of the AC voltage, and pre-synchronizing the amplitude, frequency and phase between the AC voltage output by the grid-side converter and the grid voltage.
[0022] Furthermore, the starting condition of the LCC-MMC hybrid DC transmission system is that the output active power capacity of the grid-connected wind turbines that have completed black start reaches 10% of the rated power of the LCC-MMC hybrid DC transmission system.
[0023] Specifically, when the LCC-MMC hybrid DC transmission system is started, the MMC converter station in the LCC-MMC hybrid DC transmission system is started first, and then the LCC converter station in the LCC-MMC hybrid DC transmission system is started; the MMC converter station adopts grid voltage-oriented double closed-loop vector control of fixed DC voltage and reactive power to charge the LCC-MMC hybrid DC transmission system and stabilize the system DC voltage, thereby realizing a black start of the LCC-MMC hybrid DC transmission system.
[0024] Furthermore, when the LCC converter station is started, the trigger pulse of the thyristor converter valve is turned on, and the fixed trigger angle control mode is maintained to achieve active power transmission after the black start of the LCC-MMC hybrid DC transmission system.
[0025] Furthermore, the present invention numbers the feeders in the offshore wind farm in sequence from 1 according to the average wind speed from high to low, and black-starts all the grid-type wind turbines in the same feeder in sequence from small to large in parallel; after the black-start of the grid-type wind turbines in the same feeder is completed, once the trigger pulse is detected, all the grid-type wind turbines in the feeder are switched in parallel from the no-load operation mode to the maximum wind energy tracking control mode.
[0026] Furthermore, the static reactive power compensation device is a plurality of devices connected in parallel, and each static reactive power compensation device includes a characteristic subharmonic filter, a parallel reactor and a parallel capacitor, wherein the characteristic subharmonic filter is used for harmonic suppression, and the parallel reactor and the parallel capacitor are used for suppressing the output reactive power; the devices are grouped and put into use according to the harmonic content of the AC system on the wind farm side and the size of the output reactive power, the more the harmonic content, the more characteristic subharmonic filters are put into use; the greater the output reactive power, the more parallel reactors and parallel capacitors are put into use.
[0027] The present invention further provides an electronic device, comprising a memory and a processor, wherein a computer program is stored in the memory, and when the processor executes the computer program, any one of the aforementioned black start methods is implemented.
[0028] The present invention also provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, any of the above-mentioned black start methods is implemented.
[0029] Effect description of the present invention: Figure 3 The time domain simulation results of the wind farm through the LCC-MMC hybrid DC transmission system under the black start method proposed in this invention are given. Taking the start of the wind turbines on feeders 1 to 5 as an example, the simulation results are as follows: Figure 3As shown. At t=4s, the wind turbines on feeder lines 1 to 4 have completed black start and are in no-load operation, and STATCOM has been connected to the grid. At t=4s, the trigger pulse of the LCC converter station is unlocked, and the units that have completed black start are switched to the optimal wind energy tracking control. The control switching of the wind turbines causes fluctuations in the DC bus voltage, which brings certain fluctuations to the AC voltage. At t=4.1s, it is detected that the harmonic content on the AC side of the wind farm is too high, and two small groups of filters are put into use. Due to the excess reactive power after the filters are put into use, a small group of shunt reactors are put into use at the same time. The reactive balance of the system is mainly borne by STATCOM, and the reactive fluctuation of the wind turbines is small. Similar to t=4.1s, due to the increase in harmonic current in the wind farm and the excess reactive power after the filters are put into use, at t=4.5s and t=5s, two small groups of filters and a small group of reactors, and a small group of filters and a small group of reactors are put into use at the same time, respectively. The AC voltage fluctuation of the wind farm is about 0.02pu, and the voltage can be stabilized at about 1p.u. After the system is started and reaches a steady state, each feeder wind turbine hardly bears reactive power. Under the control of the reactive-frequency link, the system frequency can reach 1 p.u., verifying the effectiveness of the black start method proposed in the present invention.
[0030] It can be seen that the black start method proposed in the present invention can achieve mutual coordination among the grid-connected wind turbines, DC systems, static VAR compensation devices and STATCOM, ensuring the stable operation of the system during the black start process, while improving the power quality during the black start process of the system as well as the starting efficiency and wind energy utilization rate of the system, and has good economic benefits.
[0031] Finally, it should be pointed out that the specific examples mentioned above are only used to explain the present invention and do not constitute a limitation on the embodiments of the present invention. Although the present invention selects preferred examples and makes relevant descriptions, for those skilled in the art, other forms of adjustments and improvements can be made based on the above explanations. It is impossible to list all possible implementation schemes here. Any direct or indirect adjustments and improvements within the scope of the technical solution of the present invention can be regarded as the protection scope of the present invention.
Claims
1. A black start method applicable to a wind farm via an LCC-MMC hybrid DC transmission system, wherein a plurality of grid-type wind turbines are installed on each feeder, all feeders are connected to the same collection bus, and then connected to the power grid via the LCC-MMC hybrid DC transmission system, and the LCC converter station in the LCC-MMC hybrid DC transmission system is matched with a static reactive power compensation device and a static synchronous compensator; characterized in that: The grid-connected wind turbines in different feeders are started in sequence according to the principle of average wind speed of feeders in the offshore wind farm from large to small, and all grid-connected wind turbines in the same feeder are started in parallel; after the grid-connected wind turbines on the first feeder complete the black start and establish the AC voltage, the static synchronous compensator is put into operation. The static synchronous compensator adopts grid voltage-oriented vector control to achieve the suppression of AC voltage fluctuations in the wind farm and the balance of reactive power during the system black start process; the starting conditions of the LCC-MMC hybrid DC transmission system are detected in real time and the LCC-MMC hybrid DC transmission system is started when the conditions are met, and the static reactive compensation device is controlled according to the harmonic content and output reactive power of the wind farm, so as to achieve a coordinated black start between the grid-connected wind turbines, the LCC-MMC hybrid DC transmission system, the static reactive compensation device and the static synchronous compensator.
2. A black start method applicable to a wind farm via an LCC-MMC hybrid DC transmission system according to claim 1, characterized in that: The grid-type wind turbine achieves maximum wind energy tracking through machine-side converter control. The grid-side converter achieves grid control through reactive power synchronization and outputs active power by controlling DC voltage. The grid-type wind turbine has two control modes: no-load operation and maximum wind energy tracking.
3. The black start method applicable to a wind farm via an LCC-MMC hybrid DC transmission system according to claim 1, characterized in that: The grid-type wind turbine maintains no-load operation during the black start process. The black start process of the grid-type wind turbine includes starting the machine-side converter, starting the grid-side converter to realize the ramp-up of the AC voltage, and pre-synchronizing the amplitude, frequency and phase between the AC voltage output by the grid-side converter and the grid voltage.
4. A black start method applicable to a wind farm via an LCC-MMC hybrid DC transmission system according to claim 1, characterized in that: The starting condition of the LCC-MMC hybrid DC transmission system is that the output active power capacity of the grid-connected wind turbines that have completed black start reaches 10% of the rated power of the LCC-MMC hybrid DC transmission system.
5. The black start method applicable to a wind farm via an LCC-MMC hybrid DC power transmission system according to claim 1, characterized in that: When the LCC-MMC hybrid DC transmission system is started, the MMC converter station in the LCC-MMC hybrid DC transmission system is started first, and then the LCC converter station in the LCC-MMC hybrid DC transmission system is started; the MMC converter station adopts grid voltage-oriented double closed-loop vector control of fixed DC voltage and reactive power to charge the LCC-MMC hybrid DC transmission system and stabilize the system DC voltage, thereby realizing a black start of the LCC-MMC hybrid DC transmission system.
6. A black start method applicable to a wind farm via an LCC-MMC hybrid DC power transmission system according to claim 5, characterized in that: When the LCC converter station is started, the trigger pulse of the thyristor converter valve is turned on, and the fixed trigger angle control mode is maintained to achieve active power transmission after the black start of the LCC-MMC hybrid DC transmission system.
7. A black start method applicable to a wind farm via an LCC-MMC hybrid DC power transmission system according to claim 6, characterized in that: The feeders in the offshore wind farm are numbered sequentially from 1 according to the average wind speed from high to low, and all the grid-type wind turbines in the same feeder are black-started in parallel in the order of the feeder numbers from small to large; after the black start of the grid-type wind turbines in the same feeder is completed, once the trigger pulse is detected, all the grid-type wind turbines in the feeder are switched in parallel from the no-load operation mode to the maximum wind energy tracking control mode.
8. The black start method applicable to a wind farm via an LCC-MMC hybrid DC transmission system according to claim 1, characterized in that: The static reactive power compensation devices are multiple and connected in parallel, and each static reactive power compensation device includes a characteristic subharmonic filter, a parallel reactor and a parallel capacitor, wherein the characteristic subharmonic filter is used for harmonic suppression, and the parallel reactor and the parallel capacitor are used for suppressing the output reactive power; the grouping is realized according to the harmonic content of the AC system on the wind farm side and the size of the output reactive power, the more the harmonic content, the more characteristic subharmonic filters are put into use; the greater the output reactive power, the more parallel reactors and parallel capacitors are put into use.
9. An electronic device comprising a memory and a processor, wherein a computer program is stored in the memory, wherein: When the processor executes the computer program, the black start method applicable to a wind farm through an LCC-MMC hybrid DC transmission system as described in any one of claims 1 to 8 is implemented.
10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, a black start method applicable to a wind farm through an LCC-MMC hybrid DC transmission system according to any one of claims 1 to 8 is implemented.