WO2021143169A1 - 风电场及其高电压穿越控制方法、系统、mmc及机侧变流器 - Google Patents

风电场及其高电压穿越控制方法、系统、mmc及机侧变流器 Download PDF

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Publication number
WO2021143169A1
WO2021143169A1 PCT/CN2020/115150 CN2020115150W WO2021143169A1 WO 2021143169 A1 WO2021143169 A1 WO 2021143169A1 CN 2020115150 W CN2020115150 W CN 2020115150W WO 2021143169 A1 WO2021143169 A1 WO 2021143169A1
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Prior art keywords
high voltage
ride
source converter
modular multi
voltage source
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PCT/CN2020/115150
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English (en)
French (fr)
Inventor
冯其塔
汤明杰
李昂
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新疆金风科技股份有限公司
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Priority to EP20913645.6A priority Critical patent/EP4080709A4/en
Priority to BR112022014067A priority patent/BR112022014067A2/pt
Priority to AU2020421890A priority patent/AU2020421890B2/en
Priority to CA3165069A priority patent/CA3165069A1/en
Priority to US17/758,922 priority patent/US12100955B2/en
Publication of WO2021143169A1 publication Critical patent/WO2021143169A1/zh
Priority to ZA2022/08018A priority patent/ZA202208018B/en

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/001—Methods to deal with contingencies, e.g. abnormalities, faults or failures
    • H02J3/00125—Transmission line or load transient problems, e.g. overvoltage, resonance or self-excitation of inductive loads
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • H02J3/48—Controlling the sharing of the in-phase component
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/28—The renewable source being wind energy
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/70—Wind energy
    • Y02E10/76—Power conversion electric or electronic aspects

Definitions

  • This application relates to the technical field of wind power generation, and in particular to a wind farm and its high voltage ride-through control method, system, MMC and turbine-side converter.
  • Modular Multilevel Converter Modular Multilevel Converter
  • the transmission distance between the DC wind turbine and the MMC in the prior art may reach tens of kilometers or hundreds of kilometers, and there is no communication between the two, which leads to the realization of the high voltage ride-through control of the flexible DC transmission integrated wind farm. difficulty.
  • the embodiments of the present application provide a wind farm and its high voltage ride through control method, system, MMC, and generator-side converter, which can meet the high voltage ride through requirement of the wind farm.
  • an embodiment of the present application provides a high voltage ride through control method for a wind farm, which is used for a modular multi-level voltage source converter, and the modular multi-level voltage source converter is connected to the DC bus of the wind farm Between and the power grid, the high voltage ride through control method includes:
  • the modular multi-level voltage source converter is controlled to work.
  • the embodiments of the present application provide a high voltage ride through control method, which is used in a generator-side converter of a wind turbine generator set in a wind farm, and the generator-side converter is connected to a modular multi-level voltage source commutation through a DC bus Device.
  • the high voltage ride through control method includes:
  • the amplitude of the DC bus voltage calculate the minimum reactive power that the modular multi-level voltage source converter needs to absorb when the high voltage ride through condition is met;
  • the minimum reactive power and the apparent power of the modular multi-level voltage source converter calculate the minimum allowable duty cycle of the braking circuit of the timing-side converter to meet the high voltage ride through condition
  • the braking circuit is controlled to work according to the preset duty cycle, and the preset duty cycle is greater than or equal to the minimum duty cycle.
  • an embodiment of the present application provides a modular multi-level voltage source converter, which is connected between the DC bus of the wind farm and the power grid.
  • the modular multi-level voltage source converter includes:
  • the grid voltage calculation module is used to determine the magnitude of the grid voltage
  • the first high voltage ride through determination module is configured to determine to enter the high voltage ride through state if the magnitude of the grid voltage exceeds the first threshold
  • Fundamental frequency modulation wave acquisition module used to obtain the fundamental frequency modulation wave of the modular multi-level voltage source converter
  • the third harmonic superposition module is used to superimpose the third harmonic on the fundamental frequency modulation wave to obtain the superimposed modulation wave;
  • the first control module is used to control the operation of the modular multi-level voltage source converter according to the superimposed modulated wave.
  • an embodiment of the present application provides a generator-side converter of a wind turbine generator, and the generator-side converter is connected to a modular multi-level voltage source converter through a DC bus.
  • the generator-side converter of the wind turbine includes:
  • DC bus voltage calculation module used to determine the amplitude of the DC bus voltage
  • the second high voltage ride through determination module is configured to determine to enter the high voltage ride through state if the amplitude of the DC bus voltage exceeds the second threshold;
  • the minimum reactive power calculation module is used to calculate the minimum reactive power that the modular multi-level voltage source converter needs to absorb when the high voltage ride through condition is met according to the amplitude of the DC bus voltage;
  • the minimum duty cycle calculation module is used to calculate the minimum duty allowed by the brake circuit of the timing-side converter to meet the high voltage ride-through condition based on the minimum reactive power and the apparent power of the modular multi-level voltage source converter Compare;
  • the second control module is used to control the braking circuit to work according to the preset duty cycle, and the preset duty cycle is greater than or equal to the minimum duty cycle.
  • an embodiment of the present application provides a high voltage ride-through control system for a wind farm, including: the modular multi-level voltage source converter as described above and a plurality of generator-side converters as described above .
  • an embodiment of the present application provides a wind farm, including: the modular multi-level voltage source converter as described above and a plurality of wind power generators, at least one wind power generator among the plurality of wind power generators It includes the generator-side converter provided by the fourth aspect or any one of its embodiments.
  • an embodiment of the present application provides a computer-readable storage medium that stores a program.
  • the program includes operation instructions for executing the high voltage ride through control method provided by the first aspect or any one of its embodiments, or for executing Operation instructions of the high voltage ride through control method provided by the second aspect or any of its embodiments.
  • the third harmonic is superimposed on the fundamental frequency modulation wave, so that the maximum DC voltage utilization rate can reach 1.
  • the increase in DC voltage utilization can increase the AC outlet voltage of the modular multi-level voltage source converter to match the increased grid voltage during high voltage ride-through, thereby enabling wind farms The high voltage ride through was successful.
  • the wind farm and its high voltage ride through control method, system, MMC, and generator-side converter provided by the embodiments of the present application can meet the high voltage ride through requirements of the wind farm.
  • Figure 1 is a schematic diagram of the topology of a flexible DC transmission integrated wind farm
  • FIG. 2 is a schematic flowchart of a high voltage ride through control method for a wind farm provided by an embodiment of the present application
  • FIG. 3 is a schematic diagram of a fundamental frequency modulated wave superimposed with third harmonics according to an embodiment of the present application
  • FIG. 4 is a schematic flowchart of a method for high voltage ride through control of a wind farm provided by an embodiment of the present application
  • FIG. 5 is a schematic flowchart of a method for controlling high voltage ride through of a wind farm according to an embodiment of the present application
  • FIG. 6 is a schematic diagram of simulation results of DC bus voltage, third harmonic, reactive current, and modulated wave during high penetration period according to an embodiment of the present application
  • Figure 7 is a partial enlarged view of Figure 6;
  • FIG. 8 is a schematic diagram of a simulation result of a transformer grid-side voltage and a valve-side voltage during a high penetration period according to an embodiment of the present application
  • FIG. 9 is a schematic diagram of simulation results of the grid-side current and the valve-side current of the transformer during another high-through period according to an embodiment of the application.
  • FIG. 10 is a schematic structural diagram of a modular multi-level voltage source converter provided by an embodiment of the present application.
  • Fig. 11 is a schematic structural diagram of a generator-side converter of a wind turbine generator provided by an embodiment of the present application.
  • Fig. 2 is a schematic flow chart of a wind farm high voltage ride through control method provided by an embodiment of the present application, which is used in a modular multilevel voltage source converter MMC, which is connected to the wind power Between the DC bus of the field and the grid (see Figure 1).
  • the high voltage ride through control method in this embodiment includes step 201 to step 205.
  • step 201 the magnitude of the grid voltage is determined.
  • step 202 if the magnitude of the grid voltage exceeds the first threshold, it is determined to enter the high voltage ride-through state.
  • step 203 the fundamental frequency modulation wave of the modular multi-level voltage source converter is obtained.
  • step 204 the third harmonic is superimposed on the fundamental frequency modulated wave to obtain the superimposed modulated wave.
  • step 205 the modular multi-level voltage source converter is controlled to work according to the superimposed modulated wave.
  • the first threshold can be determined according to the requirements of the high voltage ride through standard. In an example, when the magnitude of the grid voltage is greater than or equal to 1.1 times, it can be judged to enter the high voltage ride through state.
  • the magnitude of the grid voltage can be represented by the positive sequence component of the grid voltage, and the magnitude of the grid voltage can also be represented by other forms.
  • the fundamental frequency modulation wave It can be a sine wave, which is determined according to the degree of modulation, rotation angle and initial phase angle, and its expression can be equation (1):
  • the third harmonic U 3rd is determined according to the third harmonic coefficient, modulation degree, rotation angle and initial phase angle, and its expression can be equation (2):
  • k is the third harmonic coefficient
  • M is the degree of modulation
  • ⁇ is the rotation angle
  • ⁇ is the initial phase angle
  • the fundamental frequency modulation wave may also adopt other waveforms.
  • the modulation range is [0,1], and the maximum modulation wave amplitude can be 1.
  • the fundamental frequency amplitude of the output phase voltage is Udc/2
  • the fundamental frequency of the output line voltage is Udc/2.
  • Frequency amplitude Udc is a direct current voltage. Calculate according to the ratio of the conventional peak line voltage to the DC voltage: That is, the maximum DC voltage utilization rate can reach 0.866.
  • the superimposed modulated wave appears as a saddle shape.
  • the fundamental frequency amplitude can reach At this time, the output phase voltage reaches
  • the fundamental frequency amplitude of the output line voltage is Calculate according to the ratio of the conventional peak line voltage to the DC voltage: That is, the DC voltage utilization rate can reach up to 1.
  • the DC voltage utilization rate can reach as high as 1.
  • the increase in DC voltage utilization can increase the AC outlet voltage of the modular multi-level voltage source converter to match the increased grid voltage during high voltage ride-through, thereby enabling wind farms The high voltage ride through was successful.
  • formula (3) by combining formula (1) and formula (2), formula (3) can be obtained:
  • the increased DC bus voltage given value and DC bus voltage measurement value can be input to a DC bus voltage controller (such as a PI regulator), and the modular multi-level voltage source can be adjusted through the output of the DC bus voltage controller
  • a DC bus voltage controller such as a PI regulator
  • the fundamental frequency modulation wave of the converter realizes the closed-loop control of the DC bus voltage.
  • the third harmonic can be superimposed on the fundamental frequency modulated wave adjusted by the DC voltage controller closed-loop to obtain the superimposed modulated wave, which can ensure the high voltage of the wind farm from two aspects: improving the utilization rate of the DC bus and raising the DC bus voltage. Successfully traversed.
  • FIG. 4 is a schematic flow chart of a method for controlling high voltage ride through of a wind farm according to an embodiment of the application. It is used for the generator-side converter of a wind generator set, and the output end of the generator-side converter is connected to the DC bus of the wind farm . As shown in FIG. 4, the high voltage ride through control method in this embodiment includes steps 401 to 405.
  • step 401 the amplitude of the DC bus voltage is determined.
  • step 402 if the amplitude of the DC bus voltage exceeds the second threshold, it is determined to enter the high voltage ride-through state.
  • step 403 the minimum reactive power that the modular multi-level voltage source converter needs to absorb when the high voltage ride through condition is met is calculated according to the magnitude of the DC bus voltage.
  • step 404 according to the minimum reactive power and the apparent power of the modular multi-level voltage source converter, the minimum duty cycle allowed by the braking circuit of the wind turbine generator when the high voltage ride through condition is met is calculated.
  • step 404 the braking circuit is controlled to operate according to a preset duty cycle, where the preset duty cycle is greater than or equal to the minimum duty cycle.
  • the DC bus voltage of the wind farm will rise, and the second threshold may be determined according to the requirements of the high voltage ride through standard.
  • u d is the amplitude of the grid voltage
  • U dref is the amplitude of the DC bus voltage
  • the amplitude in this embodiment can be understood as a unit value.
  • the machine-side converter can determine the high voltage ride through state by collecting the DC bus voltage U dref , and, in the high voltage ride through During this period, the maximum allowable output power of the wind turbine can be calculated according to the increase in the DC bus voltage, and then the allowable minimum duty cycle of the braking circuit of the generator-side converter can be calculated, so that the DC bus voltage can be consumed when the DC bus voltage is high.
  • the excess energy accumulated by the voltage ride-through device ensures that the modular multi-level voltage source converter can absorb inductive reactive power in accordance with the requirements of the high voltage ride through standard, thereby ensuring the success of the high voltage ride through.
  • the calculation steps of the minimum reactive power that the modular multi-level voltage source converter needs to absorb when the high voltage ride through condition is met include S1 and S2:
  • the expression of the minimum reactive power Q min that the modular multi-level voltage source converter needs to absorb when the high voltage ride through condition is met is as follows:
  • u d is the amplitude of the grid voltage
  • S is the apparent power of the grid-connected converter.
  • It can be expressed as 1.5 ⁇ (u d -1.1).
  • It can also be expressed as 1.5 ⁇ (u d -1.08), which is greater than the high voltage ride through requirement to further ensure the success of the high voltage ride through.
  • the steps of the minimum duty cycle allowed by the braking circuit of the wind turbine generator when the high voltage ride through condition is met include S3 to S5:
  • the expression of the maximum active power P max that the converter of the wind turbine generator allows to output when the high voltage ride through requirement is met is as follows:
  • the expression of the minimum duty cycle D min allowed by the braking circuit when the high voltage ride through requirement is met is as follows:
  • the high voltage ride-through control method used on the generator-side converter side of the wind turbine generator (see Figure 4) is compared with the high voltage ride-through control method used for the modular multi-level voltage source converter.
  • the traversal control method (see Figure 2) can be executed at the same time or later, which is not limited here.
  • Fig. 5 is a schematic flow chart of a wind farm high voltage ride through control method provided by an embodiment of the present application, which is used to implement the wind farm's high voltage ride through control strategy through the interaction of the MMC converter and the generator-side converter.
  • the high voltage ride through control method in this embodiment includes steps 501 to 507.
  • step 501 to step 505 can be executed by the MMC converter.
  • step 501 the amplitude u d of the grid voltage is detected and it is judged whether u d ⁇ 1.1 is established. If it is established, it means that the MMC converter enters the high voltage ride-through state, otherwise it jumps to the end.
  • step 502 it is determined that the MMC converter enters a high voltage ride through state.
  • step 503 the third harmonic is superimposed on the fundamental frequency modulation wave to improve the utilization of the DC voltage, and the AC outlet voltage of the modular multi-level voltage source converter is increased to match the increased grid voltage during high voltage ride through , While suppressing the overmodulation phenomenon, so that the wind farm high voltage ride through successfully.
  • step 504 the DC bus voltage U dref is raised , and the DC bus voltage is raised to match the increased grid voltage during the high voltage ride through, so that the wind farm high voltage ride through is successful.
  • step 505 the MMC converter is controlled to absorb inductive reactive power in accordance with the requirements of the national standard.
  • step 506 can be executed after step 504, and step 506 and step 507 are executed by the generator-side converter of the wind turbine generator.
  • step 506 the DC bus voltage U dref is detected and it is determined whether U dref ⁇ 1.01667 is established. If it is established, it means that the MMC converter enters the high voltage ride-through state, otherwise it jumps to the end.
  • step 507 the duty ratio of the braking resistor is input according to the DC bus voltage.
  • the machine-side converter can determine the high voltage ride-through state by collecting the DC bus voltage U dref And, during the high voltage ride-through period, the maximum allowable output power of the wind turbine can be calculated according to the increase in the DC bus voltage, and then the allowable minimum duty cycle of the braking circuit of the generator-side converter can be calculated. While consuming the excess energy accumulated by the DC bus voltage in the high voltage ride through device, it ensures that the modular multi-level voltage source converter can absorb inductive reactive power in accordance with the requirements of the high voltage ride through standard, thereby ensuring the success of the high voltage ride through.
  • FIG. 7 is a partial enlarged view of FIG. 6.
  • the amplitude of the modulated wave is up to 0.999364, which is less than 1, and no overmodulation occurs.
  • FIG. 10 is a schematic structural diagram of a modular multi-level voltage source converter provided by an embodiment of the present application, and the explanation in FIG. 2 can be applied to this embodiment.
  • the modular multi-level voltage source converter includes: a grid voltage calculation module 1001 (which may have a function corresponding to step 201), and a first high voltage ride through determination module 1002 (which may have the same function as step 201). 202), the fundamental frequency modulation wave acquisition module 1003 (which may have a function corresponding to step 203), the third harmonic superimposition module 1004 (which may have a function corresponding to step 204), and the first control module 1005 (which may have a function corresponding to step 204) It may have a function corresponding to step 205).
  • the grid voltage calculation module 1001 is used to determine the magnitude of the grid voltage.
  • the first high voltage ride through determination module 1002 is configured to determine to enter the high voltage ride through state if the magnitude of the grid voltage exceeds the first threshold.
  • the fundamental frequency modulation wave obtaining module 1003 is used to obtain the fundamental frequency modulation wave of the modular multi-level voltage source converter.
  • the third harmonic superposition module 1004 is used to superimpose the third harmonic on the fundamental frequency modulation wave to obtain the superimposed modulation wave.
  • the first control module 1005 is used for controlling the operation of the modular multi-level voltage source converter according to the superimposed modulated wave.
  • the third harmonic superposition module 1004 is specifically used to increase the DC bus voltage setting value after determining that it enters the high voltage ride through state to increase the DC bus voltage; according to the increased DC bus voltage setting value and the DC bus voltage The measured value of the bus voltage adjusts the fundamental frequency modulation wave of the generator-side converter to obtain the adjusted fundamental frequency modulation wave; superimpose the third harmonic on the fundamental frequency modulation wave adjusted by the generator-side converter to obtain the superimposed modulation wave .
  • the DC voltage utilization rate can reach a maximum of 1.
  • the increase in DC voltage utilization can increase the AC outlet voltage of the modular multi-level voltage source converter to match the increased grid voltage during high voltage ride-through, thereby enabling wind farms The high voltage ride through was successful.
  • the fundamental frequency modulation wave is not adjusted, overmodulation is likely to occur, leading to current fluctuations, distortion or divergence at the AC outlet of the high-modular multi-level voltage source converter . Since the amplitude of the superimposed saddle-shaped modulation wave is smaller than that of the fundamental frequency modulation wave, the over-modulation problem can be suppressed.
  • Fig. 11 is a schematic structural diagram of a generator-side converter of a wind turbine generator provided by an embodiment of the application, and the explanation in Fig. 4 can be applied to this embodiment.
  • the machine-side converter includes: a DC bus voltage calculation module 1101 (which may have a function corresponding to step 401), a second high voltage ride through determination module 1102 (which may have a function corresponding to step 402) ), a minimum reactive power calculation module 1103 (which may have a function corresponding to step 403), a minimum duty cycle calculation module 1104 (which may have a function corresponding to step 404), and a second control module 1105 (which may have a function corresponding to step 404) Function corresponding to step 405).
  • a DC bus voltage calculation module 1101 which may have a function corresponding to step 401
  • a second high voltage ride through determination module 1102 which may have a function corresponding to step 402
  • a minimum reactive power calculation module 1103 which may have a function corresponding to step 403
  • the DC bus voltage calculation module 1101 is used to determine the amplitude of the DC bus voltage.
  • the second high voltage ride through determination module 1102 is configured to determine to enter the high voltage ride through state if the amplitude of the DC bus voltage exceeds the second threshold.
  • the minimum reactive power calculation module 1103 is used to calculate the minimum reactive power that the modular multi-level voltage source converter needs to absorb when the high voltage ride through condition is satisfied according to the amplitude of the DC bus voltage.
  • the minimum duty cycle calculation module 1104 is used to calculate the minimum duty cycle allowed by the brake circuit of the timing-side converter to meet the high voltage ride through condition based on the minimum reactive power and the apparent power of the modular multilevel voltage source converter Compare.
  • the second control module 1105 is configured to control the braking circuit to work according to a preset duty cycle, and the preset duty cycle is greater than or equal to the minimum duty cycle.
  • the machine-side converter can determine the high voltage ride through state by collecting the DC bus voltage U dref , and, in the high voltage ride through During this period, the maximum allowable output power of the wind turbine can be calculated according to the increase in the DC bus voltage, and then the allowable minimum duty cycle of the braking circuit of the generator-side converter can be calculated, so that the DC bus voltage can be consumed when the DC bus voltage is high.
  • the excess energy accumulated by the voltage ride-through device ensures that the modular multi-level voltage source converter can absorb inductive reactive power in accordance with the requirements of the high voltage ride through standard, thereby ensuring the success of the high voltage ride through.
  • An embodiment of the present application also provides a high voltage ride through control system for a wind farm.
  • the high voltage ride through control system for a wind farm includes: the modular multilevel voltage source converter provided by the embodiment of the present invention and a plurality of such as the present invention.
  • the machine-side converter provided by the embodiment.
  • An embodiment of the present application also provides a wind farm, which includes: the modular multi-level voltage source converter and a plurality of wind power generators as provided in the embodiment of the present invention, and at least one wind power generator of the plurality of wind power generators
  • the generator set includes the generator-side converter as provided in the embodiment of the present invention.
  • the wind power generator set in the embodiment of the present application may be a DC wind power generator set.
  • An embodiment of the present application also provides a computer-readable storage medium that stores a program, and the program includes operation instructions for executing the high voltage ride through control method provided by the embodiment of the present invention.
  • a computer-readable storage medium refers to a non-transitory readable medium.
  • the functional blocks shown in the above-mentioned structural block diagram can be implemented as hardware, software, firmware, or a combination thereof.
  • it can be, for example, an electronic circuit, an application specific integrated circuit (ASIC), appropriate firmware, a plug-in, a function card, and so on.
  • ASIC application specific integrated circuit
  • the elements of the embodiments of the present application are programs or code segments used to perform required tasks.
  • the program or code segment may be stored in a machine-readable medium, or transmitted on a transmission medium or a communication link through a data signal carried in a carrier wave.
  • "Machine-readable medium" may include any medium that can store or transmit information.
  • machine-readable media examples include electronic circuits, semiconductor memory devices, ROM, flash memory, erasable ROM (EROM), floppy disks, CD-ROMs, optical disks, hard disks, fiber optic media, radio frequency (RF) links, and so on.
  • the code segment can be downloaded via a computer network such as the Internet, an intranet, and so on.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Control Of Eletrric Generators (AREA)
  • Control Of Ac Motors In General (AREA)
  • Wind Motors (AREA)

Abstract

一种风电场及其高电压穿越控制方法、系统、MMC及机侧变流器。该风电场的高电压穿越控制方法包括：确定电网电压的幅值（201）；若电网电压的幅值超过第一阈值，则确定进入高电压穿越状态（202）；获取模块化多电平电压源换流器的基频调制波（203）；在基频调制波上叠加三次谐波，得到叠加后的调制波（204）；根据叠加后的调制波控制模块化多电平电压源换流器工作（205）。该技术方案能够满足风电场的高电压穿越要求。

Description

风电场及其高电压穿越控制方法、系统、MMC及机侧变流器
相关申请的交叉引用
本申请要求享有于2020年01月16日提交的名称为“风电场的高电压穿越控制方法、系统、MMC及机侧变流器”的中国专利申请202010046620.4的优先权，该申请的全部内容通过引用并入本文中。
技术领域
本申请涉及风力发电技术领域，尤其涉及风电场及其高电压穿越控制方法、系统、MMC及机侧变流器。
背景技术
近年来，基于模块化多电平电压源变流器(Modular Multilevel Converter，MMC)的柔性直流输电技术应用越来越广泛。参见图1中的柔性直流输电一体化风电场，直流风机通过架空线或者电缆与MMC连接，MMC与电网直接相连。
然而，现有技术中直流风机和MMC之间的输送距离可能达到几十公里或者几百公里，且两者之间没有通信，导致对柔性直流输电一体化风电场的高电压穿越控制实现起来比较困难。
因此，亟需一种新的风电场的高电压穿越控制方法、系统、MMC及机侧变流器，以使柔性直流输电一体化风电场能够满足高电压穿越要求。
发明内容
本申请实施例提供了风电场及其高电压穿越控制方法、系统、MMC及机侧变流器，能够满足风电场的高电压穿越要求。
第一方面，本申请实施例提供一种风电场的高电压穿越控制方法，用于模块化多电平电压源换流器，模块化多电平电压源换流器连接于风电场 的直流母线和电网之间，该高电压穿越控制方法包括：
确定电网电压的幅值；
若电网电压的幅值超过第一阈值，则确定进入高电压穿越状态；
获取模块化多电平电压源换流器的基频调制波；
在基频调制波上叠加三次谐波，得到叠加后的调制波；
根据叠加后的调制波控制模块化多电平电压源换流器工作。
第二方面，本申请实施例提供一种高电压穿越控制方法，用于风电场的风力发电机组的机侧变流器，机侧变流器通过直流母线连接模块化多电平电压源换流器。该高电压穿越控制方法包括：
确定直流母线电压的幅值；
若直流母线电压的幅值超过第二阈值，则确定进入高电压穿越状态；
根据直流母线电压的幅值计算满足高电压穿越条件时模块化多电平电压源换流器需要吸收的最小无功功率；
根据最小无功功率和模块化多电平电压源换流器的视在功率，计算满足高电压穿越条件时机侧变流器的制动电路允许的最小占空比；
根据预设占空比控制制动电路工作，预设占空比大于或等于最小占空比。
第三方面，本申请实施例提供一种模块化多电平电压源换流器，模块化多电平电压源换流器连接于风电场的直流母线和电网之间。该模块化多电平电压源换流器包括：
电网电压计算模块，用于确定电网电压的幅值；
第一高电压穿越判定模块，用于若电网电压的幅值超过第一阈值，则确定进入高电压穿越状态；
基频调制波获取模块，用于获取模块化多电平电压源换流器的基频调制波；
三次谐波叠加模块，用于在基频调制波上叠加三次谐波，得到叠加后的调制波；
第一控制模块，用于根据叠加后的调制波控制模块化多电平电压源换流器工作。
第四方面，本申请实施例提供一种风力发电机组的机侧变流器，机侧变流器通过直流母线连接模块化多电平电压源换流器。该风力发电机组的机侧变流器包括：
直流母线电压计算模块，用于确定直流母线电压的幅值；
第二高电压穿越判定模块，用于若直流母线电压的幅值超过第二阈值，则确定进入高电压穿越状态；
最小无功功率计算模块，用于根据直流母线电压的幅值计算满足高电压穿越条件时模块化多电平电压源换流器需要吸收的最小无功功率；
最小占空比计算模块，用于根据最小无功功率和模块化多电平电压源换流器的视在功率，计算满足高电压穿越条件时机侧变流器的制动电路允许的最小占空比；
第二控制模块，用于根据预设占空比控制制动电路工作，预设占空比大于或等于最小占空比。
第五方面，本申请实施例提供一种风电场的高电压穿越控制系统，包括：如上文所述的模块化多电平电压源换流器以及多个如上文所述的机侧变流器。
第六方面，本申请实施例提供一种风电场，包括：如上文所述的模块化多电平电压源换流器以及多个风力发电机组，多个风力发电机组中的至少一个风力发电机组包括第四方面或其任一实施例提供的所述的机侧变流器。
第七方面，本申请实施例提供一种计算机可读存储介质，存储有程序，程序包括用于执行第一方面或其任一实施例提供的高电压穿越控制方法的操作指令，或者用于执行第二方面或其任一实施例提供的高电压穿越控制方法的操作指令。
根据本申请实施例，在确定进入高电压穿越状态后，对基频调制波叠加三次谐波，最高能够使直流电压利用率达到1。在直流母线电压保持不变的情况下，直流电压利用率的提升能够提高模块化多电平电压源换流器的交流出口电压，以匹配高电压穿越时升高的电网电压，从而使风电场高电压穿越成功。
此外，由于高电压穿越时直流母线电压会升高，如果不对基频调制波进行调整，容易造成过调制，导致高模块化多电平电压源换流器的交流出口的电流波动、畸变或者发散。由于叠加后的马鞍型调制波的幅值相较于基频调制波的幅度较小，因此能够抑制高电压穿越期间的过调制问题。综上，本申请实施例提供的风电场及其高电压穿越控制方法、系统、MMC及机侧变流器，能够满足风电场的高电压穿越要求。
附图说明
从下面结合附图对本申请的具体实施方式的描述中可以更好地理解本申请，其中，相同或相似的附图标记表示相同或相似的特征。对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1为柔性直流输电一体化风电场的拓扑示意图；
图2是本申请实施例提供的一种风电场的高电压穿越控制方法的流程示意图；
图3是本申请实施例提供的一种基频调制波叠加三次谐波的示意图；
图4是本申请实施例提供的一种风电场的高电压穿越控制方法的流程示意图；
图5是本申请实施例提供的一种风电场的高电压穿越控制方法的流程示意图；
图6是本申请实施例提供的一种高穿期间直流母线电压、三次谐波、无功电流和调制波的仿真结果示意图；
图7为图6的局部放大图；
图8是本申请实施例提供的一种高穿期间变压器网侧电压和阀侧电压的仿真结果示意图；
图9是本申请实施例提供的另一种高穿期间变压器网侧电流和阀侧电流的仿真结果示意图；
图10是本申请实施例提供的一种模块化多电平电压源换流器的结构示意图；
图11是本申请实施例提供的一种风力发电机组的机侧变流器的结构示意图。
具体实施方式
下面将详细描述本申请的各个方面的特征和示例性实施例，为了使本申请的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本申请进行进一步详细描述。应理解，此处所描述的具体实施例仅意在解释本申请，而不是限定本申请。对于本领域技术人员来说，本申请可以在不需要这些具体细节中的一些细节的情况下实施。下面对实施例的描述仅仅是为了通过示出本申请的示例来提供对本申请更好的理解。
在本文中，诸如第一和第二等之类的关系术语仅仅用来将一个实体或者操作与另一个实体或操作区分开来，而不一定要求或者暗示这些实体或操作之间存在任何这种实际的关系或者顺序。而且，术语“包括”、“包含”或者其任何其他变体意在涵盖非排他性的包含，从而使得包括一系列要素的过程、方法、物品或者设备不仅包括那些要素，而且还包括没有明确列出的其他要素，或者是还包括为这种过程、方法、物品或者设备所固有的要素。在没有更多限制的情况下，由语句“包括……”限定的要素，并不排除在包括所述要素的过程、方法、物品或者设备中还存在另外的相同要素。
下面将详细描述本申请的各个方面的特征和示例性实施例。在下面的详细描述中，提出了许多具体细节，以便提供对本申请的全面理解。
图2是本申请实施例提供的一种风电场的高电压穿越控制方法的流程示意图，用于模块化多电平电压源换流器MMC，模块化多电平电压源换流器连接于风电场的直流母线和电网之间(参看图1)。
如图2所示，该实施例中的高电压穿越控制方法包括步骤201至步骤205。
在步骤201中，确定电网电压的幅值。
在步骤202中，若电网电压的幅值超过第一阈值，则确定进入高电压穿越状态。
在步骤203中，获取模块化多电平电压源换流器的基频调制波。
在步骤204中，在基频调制波上叠加三次谐波，得到叠加后的调制波。
在步骤205中，根据叠加后的调制波控制模块化多电平电压源换流器工作。
其中，第一阈值可以根据高电压穿越标准的要求确定。在一示例中，当电网电压的幅值大于等于1.1倍时，可以判断进入高电压穿越状态。在一示例中，电网电压的幅值可以用电网电压的正序分量表示，电网电压的幅值也可以用其他形式表示。
在一示例中，参见图3，基频调制波
Figure PCTCN2020115150-appb-000001
可以为正弦波，根据调制度、旋转角度以及初始相位角确定，其表达式可以为式(1)：
Figure PCTCN2020115150-appb-000002
对应地，三次谐波U 3rd根据三次谐波系数、调制度、旋转角度以及初始相位角确定，其的表达式可以为式(2)：
U 3rd＝k×M×cos(3(θ+α))       (2)
其中，k为三次谐波系数，M为调制度，θ为旋转角度，α为初始相位角。
在一些实施例中，根据模块化多电平电压源换流器的实际需求，基频调制波也可以采用其他波形。
当柔性直流电网采用正弦波调制方式时，调制度范围为[0，1]，调制波幅值最大可为1，此时输出相电压的基频幅值为Udc/2，输出线电压的基频幅值为
Figure PCTCN2020115150-appb-000003
Udc为直流电压。按照常规的线电压峰值与直流电压之比计算：
Figure PCTCN2020115150-appb-000004
即直流电压利用率最高可达到0.866。
参见图3，叠加后的调制波呈现为马鞍型。在叠加后的调制波的峰值不大于1的前提下，基频幅值能够达到
Figure PCTCN2020115150-appb-000005
此时输出相电压达到
Figure PCTCN2020115150-appb-000006
输出线电压的基频幅值为
Figure PCTCN2020115150-appb-000007
按照常规的线电压峰值与直流电压之比计算：
Figure PCTCN2020115150-appb-000008
Figure PCTCN2020115150-appb-000009
即直流电压利用率最高可达到1。
因此，对基频调制波叠加三次谐波后，直流电压利用率最高能够达到1。在直流母线电压保持不变的情况下，直流电压利用率的提升能够提高 模块化多电平电压源换流器的交流出口电压，以匹配高电压穿越时升高的电网电压，从而使风电场高电压穿越成功。
此外，由于高电压穿越时直流母线电压会升高，如果不对基频调制波进行调整，容易造成过调制，导致高模块化多电平电压源换流器的交流出口的电流波动、畸变或者发散。由于叠加后的马鞍型调制波的幅值相较于基频调制波的幅度较小，因此能够抑制过调制问题。
在一些实施例中，联立式(1)和式(2)，可得式(3)：
U a＝U a1+U 3rd＝M cos(θ+α)+kM cos(3θ+3α))   (3)
对式(3)中的θ求导，令其等于0，可得式(4)：
-M sin(θ+α)-3M ksin(3α+3θ)＝0    (4)
求解式(4)，可得式(5)：
Figure PCTCN2020115150-appb-000010
将θ代入式(3)，此时U a取得极值，可得：
Figure PCTCN2020115150-appb-000011
对式(6)求导，令其等于0，可得k＝-1/6。
也就是说，k＝-1/6时U a取得最小值
Figure PCTCN2020115150-appb-000012
此时调制度最大，能够达到
Figure PCTCN2020115150-appb-000013
最终调制波U a＝M cos(θ+α)-1/6M cos(3θ+3α))。
在一些实施例中，也可以通过增加模块化多电平电压源换流器的直流母线电压给定值，使直流母线电压抬升，以匹配高电压穿越时升高的电网电压，从而保证风电场高电压穿越成功。
具体地，可以将增加后的直流母线电压给定值和直流母线电压测量值输入至直流母线电压控制器(比如PI调节器)，通过直流母线电压控制器的输出调整模块化多电平电压源换流器的基频调制波，从而实现对直流母线电压的闭环控制。
进一步地，可以将三次谐波叠加在经直流电压控制器闭环调整后的基频调制波上来得到叠加后的调制波，从提高直流母线利用率和抬升直流母线电压两个方面保证风电场高电压穿越成功。
图4为本申请实施例提供的一种风电场的高电压穿越控制方法的流程示意图，用于风力发电机组的机侧变流器，机侧变流器的输出端连接于风电场的直流母线。如图4所示，该实施例中的高电压穿越控制方法包括步骤401至步骤405。
在步骤401中，确定直流母线电压的幅值。
在步骤402中，若直流母线电压的幅值超过第二阈值，则确定进入高电压穿越状态。
在步骤403中，根据直流母线电压的幅值计算满足高电压穿越条件时模块化多电平电压源换流器需要吸收的最小无功功率。
在步骤404中，根据最小无功功率和模块化多电平电压源换流器的视在功率，计算满足高电压穿越条件时风力发电机组的制动电路允许的最小占空比。
在步骤404中，根据预设占空比控制制动电路工作，其中，预设占空比大于或等于最小占空比。
在一些实施例中，高电压穿越时，风电场的直流母线电压会抬升，第二阈值可以根据高电压穿越标准的要求确定。
在一示例中，电网电压和直流母线电压之间有如下关系：
U dref＝0.1667×u d+0.8333      (7)
其中，u d为电网电压的幅值，U dref为直流母线电压的幅值，本实施例中的幅值可以理解为标幺值。
以u d≥1.1时判断进入高电压穿越状态为例，将1.1代入上式(7)可以得到U dref＝1.01667。对应地，若U dref≥1.01667时，则可以判断进入高电压穿越状态。
根据本申请实施例，在MMC换流器和机侧变流器之间没有通信的前提下，机侧变流器能够通过采集直流母线电压U dref判断高电压穿越状态，并且，在高电压穿越期间，能够根据直流母线电压升高值计算出风力发电机组允许输出的最大功率，进而计算出机侧变流器的制动电路的允许的最小占空比，从而能够在消耗直流母线电压在高电压穿越器件集聚的多余能量的同时保证模块化多电平电压源换流器能够按照高电压穿越标准要求吸 收感性无功，进而能够保证高电压穿越成功。
在一些实施例中，满足高电压穿越条件时模块化多电平电压源换流器需要吸收的最小无功功率的计算步骤包括S1和S2：
S1、获取满足高电压穿越要求时模块化多电平电压源换流器需要吸收的最小无功电流。
S2、计算直流母线电压的幅值、最小无功电流和模块化多电平电压源换流器的视在功率的乘积，将该乘积作为满足高电压穿越条件时模块化多电平电压源换流器需要吸收的最小无功功率。
具体地，满足高电压穿越条件时模块化多电平电压源换流器需要吸收的最小无功功率Q min的表达式如下：
Figure PCTCN2020115150-appb-000014
其中，u d为电网电压的幅值，
Figure PCTCN2020115150-appb-000015
为满足高电压穿越要求时所述并网变流器需要吸收的最小无功电流，S为所述并网变流器的视在功率。
以u d≥1.1时判断进入高电压穿越状态为例，
在一些实施例中，
Figure PCTCN2020115150-appb-000016
可以表示为1.5×(u d-1.1)。
在一些实施例中，
Figure PCTCN2020115150-appb-000017
也可以表示为1.5×(u d-1.08)，以大于高电压穿越要求，进一步确保高电压穿越成功。
在一些实施例中，满足高电压穿越条件时风力发电机组的制动电路允许的最小占空比的步骤包括S3至S5：
S3、根据满足高电压穿越条件时模块化多电平电压源换流器需要吸收的最小无功功率和模块化多电平电压源换流器的视在功率，计算满足高电压穿越要求时风力发电机组的变流器允许输出的最大有功功率。
S4、计算最大有功功率和模块化多电平电压源换流器的视在功率的比值。
S5、根据比值得到满足高电压穿越要求时制动电路允许的最小占空比。
具体地，满足高电压穿越要求时风力发电机组的变流器允许输出的最大有功功率P max的表达式如下：
Figure PCTCN2020115150-appb-000018
具体地，满足高电压穿越要求时制动电路允许的最小占空比D min的表 达式如下：
Figure PCTCN2020115150-appb-000019
需要说明的是，高电压穿越期间，用于风力发电机组的机侧变流器侧的高电压穿越控制方法(参见图4)相对于用于模块化多电平电压源换流器的高电压穿越控制方法(参见图2)可以是同时执行或者稍后执行，此处不做限定。
图5是本申请实施例提供的一种风电场的高电压穿越控制方法的流程示意图，用于通过MMC换流器和机侧变流器的交互实现风电场的高电压穿越控制策略。如图5所示，该实施例中的高电压穿越控制方法包括步骤501至步骤507。
其中，步骤501至步骤505可以由MMC换流器执行。
在步骤501中，检测电网电压的幅值u d并判断u d≥1.1是否成立，若成立，说明MMC换流器进入高电压穿越状态，否则跳转至结束。
在步骤502中，确定MMC换流器进入高电压穿越状态。
在步骤503中，在基频调制波上叠加三次谐波，以提高直流电压利用率，通过提高模块化多电平电压源换流器的交流出口电压来匹配高电压穿越时升高的电网电压，同时抑制过调制现象，从而使风电场高电压穿越成功。
在步骤504中，抬升直流母线电压U dref，通过使直流母线电压抬升来匹配高电压穿越时升高的电网电压，从而使风电场高电压穿越成功。
在步骤505中，控制MMC换流器按照国标要求吸收感性无功功率。
本申请实施例不限定步骤503和步骤504的顺序。在步骤504之后可以执行步骤506，步骤506和步骤507由风力发电机组的机侧变流器执行。
在步骤506中，检测直流母线电压U dref并判断U dref≥1.01667是否成立，若成立，说明MMC换流器进入高电压穿越状态，否则跳转至结束。
在步骤507中，根据直流母线电压投入制动电阻占空比。
采用本申请实施例中的高电压穿越控制方法，在MMC换流器和机侧变流器之间没有通信的前提下，机侧变流器能够通过采集直流母线电压U dref判断高电压穿越状态，并且，在高电压穿越期间，能够根据直流母线 电压升高值计算出风力发电机组允许输出的最大功率，进而计算出机侧变流器的制动电路的允许的最小占空比，从而能够在消耗直流母线电压在高电压穿越器件集聚的多余能量的同时保证模块化多电平电压源换流器能够按照高电压穿越标准要求吸收感性无功，进而能够保证高电压穿越成功。
图6-图9为MMC换流器容量为25Mvar，电网电压升高到1.3倍时的仿真结果。其中，图7为图6的局部放大图。
参看图6和图7，将u d＝1.3代入式(7)，得到U dref＝1.05，即MMC会抬升直流母线电压U dref到1.05倍。
参看图6和图7，将u d＝1.3代入表达式：1.5×(u d-1.08)，得到满足高电压穿越要求时MMC需要吸收的最小无功电流I q_ref为0.33。
将
Figure PCTCN2020115150-appb-000020
u d＝1.3，以及S＝25代入式(8)，得到满足高电压穿越要求时MMC需要吸收的最小无功功率率Q min为10.725MVar。
参看图6和图7，注入三次谐波后，调制波的幅值最大为0.999364，小于1，未出现过调制现象。
进一步地，参看图8，注入三次谐波后，高电压穿越期间变压器阀侧电压、网侧电压无过压、无畸变、无发散现象，没有出现过调制现象。以及参看图9，注入三次谐波后，高电压穿越期间变压器阀侧电流、网侧电流无过流、无畸变、无发散现象，没有出现过调制现象，因此能够实现高电压穿越功能。
图10是本申请实施例提供的一种模块化多电平电压源换流器的结构示意图，图2中的解释说明可以应用于本实施例。如图10所示，该模块化多电平电压源换流器包括：电网电压计算模块1001(其可以具有与步骤201对应的功能)、第一高电压穿越判定模块1002(其可以具有与步骤202对应的功能)、基频调制波获取模块1003(其可以具有与步骤203对应的功能)、三次谐波叠加模块1004(其可以具有与步骤204对应的功能)和第一控制模块1005(其可以具有与步骤205对应的功能)。
其中，电网电压计算模块1001用于确定电网电压的幅值。
第一高电压穿越判定模块1002用于若电网电压的幅值超过第一阈值，则确定进入高电压穿越状态。
基频调制波获取模块1003用于获取模块化多电平电压源换流器的基频调制波。
三次谐波叠加模块1004用于在基频调制波上叠加三次谐波，得到叠加后的调制波。
第一控制模块1005用于根据叠加后的调制波控制模块化多电平电压源换流器工作。
在一些实施例中，三次谐波叠加模块1004具体用于在确定进入高电压穿越状态后，增加直流母线电压给定值，以抬升直流母线电压；根据增加后的直流母线电压给定值和直流母线电压测量值调整机侧变流器的基频调制波，得到调整后的基频调制波；在机侧变流器调整后的基频调制波上叠加三次谐波，得到叠加后的调制波。
根据本申请该实施例，在高电压穿越期间，通过对基频调制波叠加三次谐波后，能够使直流电压利用率最高达到1。在直流母线电压保持不变的情况下，直流电压利用率的提升能够提高模块化多电平电压源换流器的交流出口电压，以匹配高电压穿越时升高的电网电压，从而使风电场高电压穿越成功。此外，由于高电压穿越时直流母线电压会升高，如果不对基频调制波进行调整，容易造成过调制，导致高模块化多电平电压源换流器的交流出口的电流波动、畸变或者发散。由于叠加后的马鞍型调制波的幅值相较于基频调制波的幅度较小，因此能够抑制过调制问题。
图11为本申请实施例提供的风力发电机组的机侧变流器的结构示意图，图4中的解释说明可以应用于本实施例。如图11所示，该机侧变流器包括：直流母线电压计算模块1101(其可以具有与步骤401对应的功能)、第二高电压穿越判定模块1102(其可以具有与步骤402对应的功能)、最小无功功率计算模块1103(其可以具有与步骤403对应的功能)、最小占空比计算模块1104(其可以具有与步骤404对应的功能)和第二控制模块1105(其可以具有与步骤405对应的功能)。
其中，直流母线电压计算模块1101用于确定直流母线电压的幅值。
第二高电压穿越判定模块1102用于若直流母线电压的幅值超过第二阈值，则确定进入高电压穿越状态。
最小无功功率计算模块1103用于根据直流母线电压的幅值计算满足高电压穿越条件时模块化多电平电压源换流器需要吸收的最小无功功率。
最小占空比计算模块1104用于根据最小无功功率和模块化多电平电压源换流器的视在功率，计算满足高电压穿越条件时机侧变流器的制动电路允许的最小占空比。
第二控制模块1105用于根据预设占空比控制制动电路工作，预设占空比大于或等于最小占空比。
根据本申请实施例，在MMC换流器和机侧变流器之间没有通信的前提下，机侧变流器能够通过采集直流母线电压U dref判断高电压穿越状态，并且，在高电压穿越期间，能够根据直流母线电压升高值计算出风力发电机组允许输出的最大功率，进而计算出机侧变流器的制动电路的允许的最小占空比，从而能够在消耗直流母线电压在高电压穿越器件集聚的多余能量的同时保证模块化多电平电压源换流器能够按照高电压穿越标准要求吸收感性无功，进而能够保证高电压穿越成功。
本申请实施例还提供一种风电场的高电压穿越控制系统，该风电场的高电压穿越控制系统包括：本发明实施例提供的模块化多电平电压源换流器以及多个如本发明实施例提供的机侧变流器。
本申请实施例还提供一种风电场，该风电场包括：如本发明实施例提供的模块化多电平电压源换流器以及多个风力发电机组，多个风力发电机组中的至少一个风力发电机组包括如本发明实施例提供的机侧变流器。
其中，本申请实施例中的风力发电机组可以为直流风力发电机组。
本申请实施例还提供一种计算机可读存储介质，存储有程序，程序包括用于执行本发明实施例提供的高电压穿越控制方法的操作指令。在本申请的一个实施例，计算机可读存储介质是指非暂态可读介质。
需要明确的是，本说明书中的各个实施例均采用递进的方式描述，各个实施例之间相同或相似的部分互相参见即可，每个实施例重点说明的都是与其他实施例的不同之处。对于装置实施例而言，相关之处可以参见方法实施例的说明部分。本申请实施例并不局限于上文所描述并在图中示出的特定步骤和结构。本领域的技术人员可以在领会本申请实施例的精神之 后，作出各种改变、修改和添加，或者改变步骤之间的顺序。并且，为了简明起见，这里省略对已知方法技术的详细描述。
以上所述的结构框图中所示的功能块可以实现为硬件、软件、固件或者它们的组合。当以硬件方式实现时，其可以例如是电子电路、专用集成电路(ASIC)、适当的固件、插件、功能卡等等。当以软件方式实现时，本申请实施例的元素是被用于执行所需任务的程序或者代码段。程序或者代码段可以存储在机器可读介质中，或者通过载波中携带的数据信号在传输介质或者通信链路上传送。“机器可读介质”可以包括能够存储或传输信息的任何介质。机器可读介质的例子包括电子电路、半导体存储器设备、ROM、闪存、可擦除ROM(EROM)、软盘、CD-ROM、光盘、硬盘、光纤介质、射频(RF)链路，等等。代码段可以经由诸如因特网、内联网等的计算机网络被下载。
本申请实施例可以以其他的具体形式实现，而不脱离其精神和本质特征。例如，特定实施例中所描述的算法可以被修改，而系统体系结构并不脱离本申请实施例的基本精神。因此，当前的实施例在所有方面都被看作是示例性的而非限定性的，本申请实施例的范围由所附权利要求而非上述描述定义，并且，落入权利要求的含义和等同物的范围内的全部改变从而都被包括在本申请实施例的范围之中。

Claims (12)

  1. 一种风电场的高电压穿越控制方法，用于模块化多电平电压源换流器，所述模块化多电平电压源换流器连接于风电场的直流母线和电网之间，所述高电压穿越控制方法包括：
    确定电网电压的幅值；
    若所述电网电压的幅值超过第一阈值，则确定进入高电压穿越状态；
    获取所述模块化多电平电压源换流器的基频调制波；
    在所述基频调制波上叠加三次谐波，得到叠加后的调制波；
    根据所述叠加后的调制波控制所述模块化多电平电压源换流器工作。
  2. 根据权利要求1所述的方法，其中，
    所述基频调制波
    Figure PCTCN2020115150-appb-100001
    根据调制度、旋转角度以及初始相位角确定；
    所述三次谐波U 3rd根据三次谐波系数、所述调制度、所述旋转角度以及所述初始相位角确定。
  3. 根据权利要求1所述的方法，其中，所述在所述基频调制波上叠加三次谐波，得到叠加后的调制波的步骤，包括：
    在确定进入高电压穿越状态后，增加直流母线电压给定值，以抬升直流母线电压；
    根据增加后的直流母线电压给定值和直流母线电压测量值调整所述基频调制波，得到调整后的基频调制波；
    在所述调整后的基频调制波上叠加三次谐波，得到叠加后的调制波。
  4. 一种风电场的高电压穿越控制方法，用于风电场的风力发电机组的机侧变流器，所述机侧变流器通过直流母线连接模块化多电平电压源换流器，所述高电压穿越控制方法包括：
    确定直流母线电压的幅值；
    若所述直流母线电压的幅值超过第二阈值，则确定进入高电压穿越状态；
    根据所述直流母线电压的幅值计算满足高电压穿越条件时所述模块化多电平电压源换流器需要吸收的最小无功功率；
    根据所述最小无功功率和所述模块化多电平电压源换流器的视在功率，计算满足高电压穿越条件时机侧变流器的制动电路允许的最小占空比；
    根据预设占空比控制所述制动电路工作，所述预设占空比大于或等于所述最小占空比。
  5. 根据权利要求4所述的方法，其中，根据所述直流母线电压的幅值计算满足高电压穿越条件时所述模块化多电平电压源换流器需要吸收的最小无功功率的步骤包括：
    获取满足高电压穿越要求时所述模块化多电平电压源换流器需要吸收的最小无功电流；
    计算所述直流母线电压的幅值、所述最小无功电流和所述模块化多电平电压源换流器的视在功率的乘积；
    将所述乘积确定为所述满足高电压穿越条件时所述模块化多电平电压源换流器需要吸收的最小无功功率。
  6. 根据权利要求4所述的方法，其中，所述根据所述最小无功功率和所述模块化多电平电压源换流器的视在功率，计算满足高电压穿越条件时风力发电机组的制动电路允许的最小占空比的步骤，包括：
    根据所述最小无功功率和所述模块化多电平电压源换流器的视在功率，计算满足高电压穿越要求时所述风力发电机组的变流器允许输出的最大有功功率；
    计算所述最大有功功率和所述模块化多电平电压源换流器的视在功率的比值；
    根据所述比值得到满足高电压穿越要求时所述制动电路允许的最小占空比。
  7. 一种模块化多电平电压源换流器，所述模块化多电平电压源换流器连接于风电场的直流母线和电网之间，所述模块化多电平电压源换流器包括：
    电网电压计算模块，用于确定电网电压的幅值；
    第一高电压穿越判定模块，用于若所述电网电压的幅值超过第一阈值，则确定进入高电压穿越状态；
    基频调制波获取模块，用于获取所述模块化多电平电压源换流器的基频调制波；
    三次谐波叠加模块，用于在所述基频调制波上叠加三次谐波，得到叠加后的调制波；
    第一控制模块，用于根据所述叠加后的调制波控制所述模块化多电平电压源换流器工作。
  8. 根据权利要求7所述的模块化多电平电压源换流器，其中，所述三次谐波叠加模块具体用于：
    在确定进入高电压穿越状态后，增加直流母线电压给定值，以抬升直流母线电压；
    根据增加后的直流母线电压给定值和直流母线电压测量值调整所述基频调制波，得到调整后的基频调制波；
    在所述调整后的基频调制波上叠加三次谐波，得到叠加后的调制波。
  9. 一种风力发电机组的机侧变流器，所述机侧变流器通过直流母线连接模块化多电平电压源换流器，所述风力发电机组的机侧变流器包括：
    直流母线电压计算模块，用于确定直流母线电压的幅值；
    第二高电压穿越判定模块，用于若所述直流母线电压的幅值超过第二阈值，则确定进入高电压穿越状态；
    最小无功功率计算模块，用于根据所述直流母线电压的幅值计算满足高电压穿越条件时所述模块化多电平电压源换流器需要吸收的最小无功功率；
    最小占空比计算模块，用于根据所述最小无功功率和所述模块化多电平电压源换流器的视在功率，计算满足高电压穿越条件时机侧变流器的制动电路允许的最小占空比；
    第二控制模块，用于根据预设占空比控制所述制动电路工作，所述预设占空比大于或等于所述最小占空比。
  10. 一种风电场的高电压穿越控制系统，所述风电场包括多个风力发电机组，包括：
    如权利要求7或8所述的模块化多电平电压源换流器，以及
    多个如权利要求9所述的机侧变流器。
  11. 一种风电场，包括：
    如权利要求7或8所述的模块化多电平电压源换流器，以及
    多个风力发电机组，其中，所述多个风力发电机组中的至少一个风力发电机组包括如权利要求9所述的机侧变流器。
  12. 一种计算机可读存储介质，存储有程序，所述程序包括用于执行如权利要求1-3中任一项或者4-6中任一项所述的高电压穿越控制方法的操作指令。
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