WO2022078527A1 - 一种特高压混合直流输电系统暂态电压控制方法及装置 - Google Patents

一种特高压混合直流输电系统暂态电压控制方法及装置 Download PDF

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WO2022078527A1
WO2022078527A1 PCT/CN2021/131625 CN2021131625W WO2022078527A1 WO 2022078527 A1 WO2022078527 A1 WO 2022078527A1 CN 2021131625 W CN2021131625 W CN 2021131625W WO 2022078527 A1 WO2022078527 A1 WO 2022078527A1
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voltage
lcc
cosα
output
vsc
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PCT/CN2021/131625
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French (fr)
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彭忠
曹森
李泰�
赵静
荆雪记
胡永昌
苏进国
李艳梅
张艳浩
肖龙
申帅华
鲁庆华
孙攀磊
程晓磊
李玉龙
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许继电气股份有限公司
许继集团有限公司
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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
    • H02J3/36—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
    • H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
    • 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
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

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  • the invention relates to the technical field of ultra-high voltage direct current transmission, in particular to a transient voltage control method and device of an ultra-high voltage hybrid direct current transmission system.
  • LCCs grid-commutated converters
  • the inverter station For the UHV hybrid DC transmission system, the inverter station generally uses a voltage source converter VSC or a combined topology of LCC and VSC.
  • the voltage source converter has the advantages of no commutation failure, independent control of active power and reactive power, and no need to configure an AC filter.
  • the LCC and VSC hybrid cascade topology of the inverter station can prevent the commutation failure to a certain extent and suppress the system power interruption caused by the commutation failure. voltage, and overvoltage occurs on the pole bus during system recovery. How to limit the overvoltage of the pole bus during the fault recovery process of the inverter side AC system has become a difficult problem.
  • the existing inverter-side pole control system is equipped with an LCC DC voltage controller and a VSC DC voltage controller, which jointly control the pole bus voltage of the rectifier station under steady-state operating conditions.
  • LCC and VSC DC voltage controller For inverter station LCC and VSC mixed cascade topology, LCC and VSC voltage balance operation, so LCC and VSC DC voltage reference value is equal. Under the fault condition, the DC voltage reference values of LCC and VSC are basically maintained at the level before the fault.
  • the VSC output active power is limited, and the VSC DC side power surplus, resulting in VSC DC voltage increase.
  • the LCC is likely to fail commutation, the DC current increases, and the VSC DC side has more power surplus, which increases the VSC DC overvoltage, which may reach 1.3 times the overvoltage (the typical reference value is 400kV) , or even higher.
  • the conventional LCC constant DC voltage control method quickly controls the LCC DC voltage to 400kV (typical value), resulting in the pole bus voltage reaching 1.15 times the overvoltage (reference value is 800kV, typical value).
  • the voltage of the pole busbar of the rectifier station may reach 1.25 times (the reference value is 800kV, typical value), or even higher, which endangers the insulation safety of the equipment.
  • the purpose of the present invention is to provide a method and device for transient voltage control of an ultra-high voltage hybrid DC power transmission system in view of the deficiencies of the prior art.
  • the present invention adopts the following technical scheme to realize:
  • a first aspect of the present invention provides a transient voltage control method for an ultra-high voltage hybrid DC power transmission system
  • the ultra-high voltage hybrid DC power transmission system includes a rectifier station and an inverter station
  • the inverter station includes grid commutation of a high-end valve group.
  • the voltage source converter VSC of the current converter LCC and the low-end valve group, the transient voltage control method controls the DC voltage of the inverter station LCC, including the following steps:
  • the difference between the actual DC voltage U dcLCC and the final LCC DC voltage reference value is input to the PI controller for adjustment, and the trigger angle cosine value is output;
  • the LCC DC voltage reference value U dcref output by the upper-level control is superimposed on the voltage adjustment amount ⁇ U dcLCC processed by the transient voltage controller, and the output final LCC DC voltage reference value includes:
  • the transient voltage controller If U acposmin >U set1 , it indicates that the AC system fault has been cleared, or when the commutation failure of the LCC is not detected, the transient voltage controller outputs the voltage regulation amount ⁇ U dcLCC according to the VSC overvoltage condition.
  • the output voltage adjustment amount ⁇ U dcLCC of the transient voltage controller according to the VSC overvoltage condition includes:
  • the adjustment by the PI controller includes limiting the output trigger angle cosine value between cos ⁇ min and cos ⁇ max , when cos ⁇ >cos ⁇ max , the output is cos ⁇ max ; when cos ⁇ cos ⁇ min , the output is cos ⁇ . min ; when cos ⁇ min ⁇ cos ⁇ cos ⁇ max , the output is cos ⁇ ; where ⁇ is the trigger angle, cos ⁇ max is the maximum cosine value of the trigger angle, and cos ⁇ min is the minimum value of the trigger angle cosine.
  • a second aspect of the present invention provides a transient voltage control device for an ultra-high voltage hybrid DC power transmission system
  • the ultra-high voltage hybrid DC power transmission system includes a rectifier station and an inverter station
  • the inverter station includes grid commutation of high-end valve groups.
  • the voltage source converter VSC of the converter LCC and the low-end valve group including:
  • Transient voltage controller superimpose the LCC DC voltage reference value U dcref output by the upper-level control with the voltage adjustment value ⁇ U dcLCC processed by the transient voltage controller, and output the final LCC DC voltage reference value;
  • Difference calculator carry out a difference calculation between the actual DC voltage U dcLCC and the final LCC DC voltage reference value
  • PI controller input the result of the difference calculation into the PI controller for adjustment, and output the cosine value of the trigger angle;
  • Arc cosine calculator Calculate the cosine value of the output trigger angle through arc cosine, and output the trigger angle of the inverter station.
  • the transient voltage controller performs the following control to obtain the output voltage regulation amount ⁇ U dcLCC :
  • the transient voltage controller If U acposmin >U set1 , it indicates that the AC system fault has been cleared, or when the commutation failure of the LCC is not detected, the transient voltage controller outputs the voltage regulation amount ⁇ U dcLCC according to the VSC overvoltage condition.
  • the output voltage adjustment amount ⁇ U dcLCC of the transient voltage controller according to the VSC overvoltage condition includes:
  • the PI controller limits the output trigger angle cosine value between cos ⁇ min and cos ⁇ max , when cos ⁇ >cos ⁇ max , the output is cos ⁇ max ; when cos ⁇ cos ⁇ min , the output is cos ⁇ min ; When cos ⁇ min ⁇ cos ⁇ ⁇ cos ⁇ max , the output is cos ⁇ ; where ⁇ is the trigger angle, cos ⁇ max is the maximum value of the cosine of the trigger angle, and cos ⁇ min is the minimum value of the cosine of the trigger angle.
  • the present invention provides a method and device for transient voltage control of an ultra-high voltage hybrid DC power transmission system, the method comprising: superimposing the LCC DC voltage reference value U dcref output by the upper-level control and processing the transient voltage controller.
  • the voltage adjustment amount ⁇ U dcLCC outputs the final LCC DC voltage reference value; the difference between the actual DC voltage U dcLCC and the final LCC DC voltage reference value is input to the PI controller for adjustment, and the trigger angle cosine value is output; after the arc cosine Calculate and output the trigger angle of the inverter station.
  • the LCC transient voltage controller appropriately reduces the voltage reference value according to the VSC overvoltage condition and the DC line voltage drop, so that the LCC of the inverter station operates at low voltage during the system recovery process, thus limiting the system. Pole busbar overvoltage.
  • FIG. 1 is a schematic topology diagram of an ultra-high voltage hybrid DC power transmission system according to an embodiment of the present invention
  • FIG. 2 is a schematic flowchart of a transient voltage control method for an ultra-high voltage hybrid DC transmission system according to an embodiment of the present invention
  • FIG. 3 is a block diagram of an LCC voltage controller of an inverter station of an ultra-high voltage hybrid DC transmission system according to an embodiment of the present invention
  • FIG. 4 is a block diagram of transient voltage control of an ultra-high voltage hybrid DC power transmission system according to an embodiment of the present invention.
  • LCC grid commutation converter
  • VSC voltage source converter
  • ACF AC filter
  • DCF DC filter
  • U dcref LCC DC voltage reference value calculated by the superior control function
  • U dcLCC DC voltage of LCC
  • U dcVSCref DC voltage reference value of VSC
  • U dcVSC DC voltage of VSC
  • U acposmin minimum value of positive sequence voltage of AC bus of each converter of inverter station
  • ⁇ U dcLCC transient voltage controller Output voltage regulation amount
  • cos ⁇ max maximum cosine trigger angle
  • cos ⁇ min minimum trigger angle cosine
  • U dcVSCref DC voltage reference value of VSC
  • U dcVSC DC voltage of VSC
  • U deadband VSC overvoltage dead zone
  • U min VSC overvoltage minimum limit value
  • U set1 AC system fault judgment threshold
  • U exc Extra voltage limiting component
  • U c1 Voltsine
  • FIG. 1 is a topological structure diagram of an ultra-high voltage hybrid DC power transmission system provided by the present invention.
  • the rectifier station (transmission end) of the UHV hybrid DC power transmission system is the same as the conventional UHV, including the grid commutation converter (LCC), the LCC valve group is connected with a DC filter (DCF) in parallel, and the AC input end is provided with a grounded AC Filter (ACF).
  • the high-end valve group of the inverter station (receiving end) is a grid commutated converter (LCC).
  • the LCC valve group is connected with a DC filter (DCF) in parallel, and the AC output end is provided with a grounded AC filter (ACF).
  • the valve group is three parallel voltage source converters VSC (respectively VSC1, VSC2, VSC3), and the DC side of the VSC valve group is connected in parallel with a controllable arrester.
  • a first aspect of the present invention provides a transient voltage control method for an ultra-high voltage hybrid DC power transmission system, the ultra-high voltage hybrid DC power transmission system includes a rectifier station and an inverter station, and the inverter station includes grid commutation of a high-end valve group.
  • the transient voltage control method controls the DC voltage of the inverter station LCC, as shown in Figure 2, including the following steps:
  • Step S100 superimposing the LCC DC voltage reference value U dcref output by the upper-level control with the voltage adjustment amount ⁇ U dcLCC processed by the transient voltage controller to output the final LCC DC voltage reference value;
  • Step S200 the difference between the actual DC voltage U dcLCC and the final LCC DC voltage reference value is input to the PI controller for adjustment, and the trigger angle cosine value is output;
  • Step S300 output the firing angle of the inverter station after arc cosine calculation.
  • FIG. 3 is a block diagram of the LCC DC voltage control of the inverter station of the UHV hybrid DC power transmission system provided by the present invention.
  • the LCC DC voltage reference value U dcref calculated by the superior control function is superimposed on the voltage regulation amount ⁇ U dcrefLCC calculated by the transient voltage controller to obtain the final LCC DC voltage reference value.
  • the present invention adds a transient voltage controller. After the fault is cleared, the reference value of the LCC DC voltage is reduced according to the VSC overvoltage condition and the DC line voltage drop, so as to limit the overvoltage of the pole bus during the system recovery process. voltage shock.
  • the LCC DC voltage reference value U dcref output by the upper-level control is superimposed on the voltage adjustment amount ⁇ U dcLCC processed by the transient voltage controller, and the output final LCC DC voltage reference value includes:
  • the transient voltage controller If U acposmin >U set1 , it indicates that the AC system fault has been cleared, or when the commutation failure of the LCC is not detected, the transient voltage controller outputs the voltage regulation amount ⁇ U dcLCC according to the VSC overvoltage condition.
  • the output voltage adjustment amount ⁇ U dcLCC of the transient voltage controller according to the VSC overvoltage condition includes:
  • FIG. 4 is a block diagram of a transient voltage controller of an ultra-high voltage hybrid DC power transmission system provided by the present invention.
  • the inverter station control system collects the AC bus voltage of the converter in operation, and calculates the minimum value U acposmin of the positive sequence component of the AC bus voltage. By comparing with the voltage threshold U set1 , it is determined whether an AC system failure has occurred. If U acposmin ⁇ U set1 indicates that the AC system is faulty, and it is detected that the commutation failure of the LCC occurs, the voltage regulation amount ⁇ U dcLCC output by the transient voltage controller is equal to 0.
  • the transient voltage controller outputs the voltage regulation amount ⁇ U dcLCC according to the VSC overvoltage condition.
  • the VSC DC voltage U dcVSC increases.
  • U exc is used to limit the overvoltage of the rectifier station pole busbar caused by the line inductive reactance during the rapid recovery of the system.
  • the LCC transient voltage controller appropriately reduces the voltage reference value, so that during the system recovery process, the LCC of the inverter station operates at low voltage, thereby limiting the overvoltage of the system pole bus.
  • the adjustment by the PI controller includes limiting the output trigger angle cosine value between cos ⁇ min and cos ⁇ max , when cos ⁇ >cos ⁇ max , the output is cos ⁇ max ; when cos ⁇ cos ⁇ min , the output is cos ⁇ . min ; when cos ⁇ min ⁇ cos ⁇ cos ⁇ max , the output is cos ⁇ ; where ⁇ is the trigger angle, cos ⁇ max is the maximum cosine value of the trigger angle, and cos ⁇ min is the minimum value of the trigger angle cosine.
  • a second aspect of the present invention provides a transient voltage control device for an ultra-high voltage hybrid DC power transmission system
  • the ultra-high voltage hybrid DC power transmission system includes a rectifier station and an inverter station
  • the inverter station includes grid commutation of high-end valve groups.
  • the voltage source converter VSC of the converter LCC and the low-end valve group including:
  • Transient voltage controller superimpose the LCC DC voltage reference value U dcref output by the upper-level control with the voltage adjustment value ⁇ U dcLCC processed by the transient voltage controller, and output the final LCC DC voltage reference value;
  • Difference calculator carry out a difference calculation between the actual DC voltage U dcLCC and the final LCC DC voltage reference value
  • PI controller Input the result of the difference calculation into the PI controller for adjustment, and output the cosine value of the trigger angle;
  • Arc cosine calculator Calculate the cosine value of the output trigger angle through arc cosine, and output the trigger angle of the inverter station.
  • the present invention provides a method and device for transient voltage control of an ultra-high voltage hybrid DC power transmission system, the method comprising: superimposing the LCC DC voltage reference value U dcref output by the upper-level control and processing the transient voltage controller.
  • the voltage adjustment amount ⁇ U dcLCC outputs the final LCC DC voltage reference value; the difference between the actual DC voltage U dcLCC and the final LCC DC voltage reference value is input to the PI controller for adjustment, and the trigger angle cosine value is output; after the arc cosine Calculate and output the trigger angle of the inverter station.
  • the LCC transient voltage controller appropriately reduces the voltage reference value according to the VSC overvoltage condition and the DC line voltage drop, so that the LCC of the inverter station operates at low voltage during the system recovery process, thus limiting the system. Pole busbar overvoltage.

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Abstract

一种特高压混合直流输电系统暂态电压控制方法及装置，该方法包括：将上级控制输出的LCC直流电压参考值U dcref叠加经过暂态电压控制器处理的电压调节量ΔU dcLCC，输出最终的LCC直流电压参考值；直流电压实际值U dcLCC与所述最终的LCC直流电压参考值作差后输入PI控制器进行调节，输出触发角余弦值；经过反余弦计算，输出逆变站触发角。该方法在交流系统故障清除后，LCC暂态电压控制器根据VSC过电压情况和直流线路压降，适当降低电压参考值，使得系统恢复过程中，逆变站LCC低电压运行，从而限制了系统极母线过电压。

Description

一种特高压混合直流输电系统暂态电压控制方法及装置 技术领域
本发明涉及特高压直流输电技术领域，具体涉及一种特高压混合直流输电系统暂态电压控制方法及装置。
背景技术
常规特高压直流输电系统使用电网换相型换流器LCC，存在逆变侧换相失败造成系统传输功率中断的缺陷。对于特高压混合直流输电系统，逆变站一般使用电压源型换流器VSC或者使用LCC与VSC的组合拓扑。电压源型换流器具有无换相失败，有功功率和无功功率独立控制，无需配置交流滤波器等优点。逆变站LCC与VSC混合级联拓扑结构可以在一定程度预防换相失败和抑制换相失败导致的系统功率中断，但是逆变侧交流系统故障过程中，VSC直流侧功率盈余，导致VSC出现过电压，并且系统恢复过程中极母线出现过电压。如何限制逆变侧交流系统故障恢复过程中极母线过电压成为一个难题。
现有的逆变侧极控系统配置LCC直流电压控制器和VSC直流电压控制器，稳态工况下，共同控制整流站极母线电压。对于逆变站LCC与VSC混合级联拓扑结构，LCC与VSC电压平衡运行，因此LCC与VSC直流电压参考值相等。故障工况下，LCC与VSC直流电压参考值基本维持在故障前水平。
对于逆变站为LCC与VSC混合级联拓扑结构，逆变侧交流系统故障时，VSC输出有功功率受限，VSC直流侧功率盈余，导致VSC直流电压升高。逆变侧交流系统故障过程中，LCC很可能换相失败，直流电流增大，VSC直流侧功率盈余更多，增大了VSC直流过电压，可能达到1.3倍过电压(典型基准值为400kV)，甚至更高。当故障清除后，常规的LCC定直流电压控制方法，将LCC 直流电压快速控制到400kV(典型值)，导致极母线电压达到1.15倍过电压(基准值为800kV，典型值)。系统快速升功率过程中，由于线路感抗的作用，整流站极母线电压可能达到1.25倍(基准值为800kV，典型值)，甚至更高，危害设备绝缘安全。
发明内容
本发明的目的在于针对现有技术的不足，提供一种特高压混合直流输电系统暂态电压控制方法及装置，在逆变侧交流系统故障已清除，系统快速恢复功率过程中，根据VSC过电压情况和直流线路压降，降低逆变站LCC直流电压参考值，从而限制系统极母线过电压。
为实现上述目的，本发明采用如下的技术方案实现：
本发明的第一方面提供了一种特高压混合直流输电系统暂态电压控制方法，所述特高压混合直流输电系统包括整流站和逆变站，逆变站包括高端阀组的电网换相换流器LCC和低端阀组的电压源型换流器VSC，所述暂态电压控制方法对逆变站LCC直流电压进行控制，包括如下步骤：
将上级控制输出的LCC直流电压参考值U dcref叠加经过暂态电压控制器处理的电压调节量ΔU dcLCC，输出最终的LCC直流电压参考值；
直流电压实际值U dcLCC与所述最终的LCC直流电压参考值作差后输入PI控制器进行调节，输出触发角余弦值；
经过反余弦计算，输出逆变站触发角。
进一步的，所述将上级控制输出的LCC直流电压参考值U dcref叠加经过暂态电压控制器处理的电压调节量ΔU dcLCC，输出最终的LCC直流电压参考值包括：
实时采集逆变站投运换流器交流母线电压，计算得到交流母线电压正序分量最小值U acposmin；通过与电压阈值U set1进行比较，判断是否发生交流系统故障：
如果U acposmin＜U set1，则表明交流系统故障，并且检测到LCC发生换相失败 时，暂态电压控制器输出的电压调节量ΔU dcLCC＝0；
如果U acposmin＞U set1，则表明交流系统故障已清除，或者未检测到LCC发生换相失败时，暂态电压控制器根据VSC过压情况输出电压调节量ΔU dcLCC。
进一步的，所述暂态电压控制器根据VSC过压情况输出电压调节量ΔU dcLCC包括：
当逆变侧交流系统发生接地故障时，VSC直流电压U dcVSC升高；
当交流系统故障清除或者LCC换相正常后，如果U dcVSC大于VSC直流电压参考值U dcrefVSC与VSC过压死区值U deadband之和，则ΔU dcLCC为VSC电压偏差分量和额外限压分量U exc之和，ΔU dcLCC＜0，其中VSC电压偏差分量处于U min至0区间，U min为VSC过电压最小限幅值；
当U acposmin＜U set1并且LCC换相失败时，额外限压分量U exc从0平滑变化到U c1，U c1为限压参数，U c1＜0；
当交流系统故障清除或者LCC换相正常，经过一段延时后，U exc由U c1平滑变化到0。
进一步的，所述PI控制器进行调节包括将输出的触发角余弦值限定在cosα min和cosα max之间，当cosα＞cosα max时，输出为cosα max；当cosα＜cosα min时，输出为cosα min；当cosα min≤cosα≤cosα max时，输出为cosα；其中，α为触发角，cosα max为触发角余弦最大值，cosα min为触发角余弦最小值。
本发明的第二方面提供了一种特高压混合直流输电系统暂态电压控制装置，所述特高压混合直流输电系统包括整流站和逆变站，逆变站包括高端阀组的电网换相换流器LCC和低端阀组的电压源型换流器VSC，包括：
暂态电压控制器：将上级控制输出的LCC直流电压参考值U dcref叠加经过暂态电压控制器处理的电压调节量ΔU dcLCC，输出最终的LCC直流电压参考值；
作差计算器：将所述直流电压实际值U dcLCC与所述最终的LCC直流电压参考值进行作差计算；
PI控制器：将作差计算的结果输入PI控制器进行调节，输出触发角余 弦值；
反余弦计算器：将输出触发角余弦值经过反余弦计算，输出逆变站触发角。
进一步的，所述暂态电压控制器进行如下控制以得到输出的电压调节量ΔU dcLCC：
实时采集逆变站投运换流器交流母线电压，计算得到交流母线电压正序分量最小值U acposmin；通过与电压阈值U set1进行比较，判断是否发生交流系统故障：
如果U acposmin＜U set1，则表明交流系统故障，并且检测到LCC发生换相失败时，暂态电压控制器输出的电压调节量ΔU dcLCC＝0；
如果U acposmin＞U set1，则表明交流系统故障已清除，或者未检测到LCC发生换相失败时，暂态电压控制器根据VSC过压情况输出电压调节量ΔU dcLCC。
进一步的，所述暂态电压控制器根据VSC过压情况输出电压调节量ΔU dcLCC包括：
当逆变侧交流系统发生接地故障时，VSC直流电压U dcVSC升高；
当交流系统故障清除或者LCC换相正常后，如果U dcVSC大于VSC直流电压参考值U dcrefVSC与VSC过压死区值U deadband之和，则ΔU dcLCC为VSC电压偏差分量和额外限压分量U exc之和，ΔU dcLCC＜0，其中VSC电压偏差分量处于U min至0区间，U min为VSC过电压最小限幅值；
当U acposmin＜U set1并且LCC换相失败时，额外限压分量U exc从0平滑变化到U c1，U c1为限压参数，U c1＜0；
当交流系统故障清除或者LCC换相正常，经过一段延时后，U exc由U c1平滑变化到0。
进一步的，所述PI控制器将输出的触发角余弦值限定在cosα min和cosα max之间，当cosα＞cosα max时，输出为cosα max；当cosα＜cosα min时，输出为cosα min；当cosα min≤cosα≤cosα max时，输出为cosα；其中，α为触发角，cosα max为触发角余弦最大值，cosα min为触发角余弦最小值。
综上所述，本发明提供了一种特高压混合直流输电系统暂态电压控制方法及装置，该方法包括：将上级控制输出的LCC直流电压参考值U dcref叠加经过暂态电压控制器处理的电压调节量ΔU dcLCC，输出最终的LCC直流电压参考值；直流电压实际值U dcLCC与所述最终的LCC直流电压参考值作差后输入PI控制器进行调节，输出触发角余弦值；经过反余弦计算，输出逆变站触发角。该方法在交流系统故障清除后，LCC暂态电压控制器根据VSC过电压情况和直流线路压降，适当降低电压参考值，使得系统恢复过程中，逆变站LCC低电压运行，从而限制了系统极母线过电压。
附图说明
图1是本发明实施例的特高压混合直流输电系统拓扑示意图；
图2是本发明实施例的特高压混合直流输电系统暂态电压控制方法的流程示意图；
图3是本发明实施例的特高压混合直流输电系统逆变站LCC电压控制器框图；
图4是本发明实施例的特高压混合直流输电系统暂态电压控制框图。
附图标记：LCC:电网换相换流器；VSC:电压源型换流器；ACF:交流滤波器；DCF:直流滤波器；U dcref:上级控制功能计算的LCC直流电压参考值；U dcLCC:LCC的直流电压；U dcVSCref:VSC的直流电压参考值；U dcVSC:VSC的直流电压；U acposmin:逆变站各换流器交流母线正序电压最小值；ΔU dcLCC:暂态电压控制器输出的电压调节量；cosα max:触发角余弦最大值；cosα min:触发角余弦最小值；U dcVSCref:VSC的直流电压参考值；U dcVSC:VSC的直流电压；U deadband:VSC过电压死区值；U min:VSC过电压最小限幅值；U set1:交流系统故障判定阈值；U exc:额外限压分量；U c1:限压参数；ΔU dcLCC:暂态电压控制器输出的电压调节量。
具体实施方式
为使本发明的目的、技术方案和优点更加清楚明了，下面结合具体实施方式并参照附图，对本发明进一步详细说明。应该理解，这些描述只是示例 性的，而并非要限制本发明的范围。此外，在以下说明中，省略了对公知结构和技术的描述，以避免不必要地混淆本发明的概念。
图1是本发明提供的特高压混合直流输电系统拓扑结构图。该特高压混合直流输电系统的整流站(送端)与常规特高压相同，包括电网换相换流器(LCC)，LCC阀组并联有直流滤波器(DCF)，交流输入端设置有接地的交流滤波器(ACF)。逆变站(受端)高端阀组为电网换相型换流器(LCC)，LCC阀组并联有直流滤波器(DCF)，交流输出端设置有接地的交流滤波器(ACF)；低端阀组为三个并联的电压源型换流器VSC(分别为VSC1、VSC2、VSC3)，VSC阀组直流侧并联可控避雷器。
本发明的第一方面提供了一种特高压混合直流输电系统暂态电压控制方法，所述特高压混合直流输电系统包括整流站和逆变站，逆变站包括高端阀组的电网换相换流器LCC和低端阀组的电压源型换流器VSC，所述暂态电压控制方法对逆变站LCC直流电压进行控制，如图2所示，包括如下步骤：
步骤S100，将上级控制输出的LCC直流电压参考值U dcref叠加经过暂态电压控制器处理的电压调节量ΔU dcLCC，输出最终的LCC直流电压参考值；
步骤S200，直流电压实际值U dcLCC与所述最终的LCC直流电压参考值作差后输入PI控制器进行调节，输出触发角余弦值；
步骤S300，经过反余弦计算，输出逆变站触发角。
具体的，如图3所示，图3是本发明提供的特高压混合直流输电系统逆变站LCC直流电压控制框图。上级控制功能计算的LCC直流电压参考值U dcref叠加暂态电压控制器计算的电压调节量ΔU dcrefLCC，得到最终的LCC直流电压参考值。LCC的直流电压实际值与参考值作差后，经PI控制器调节，并通过反余弦计算，输出触发角。相对于常规特高压电压控制，本发明增加了暂态电压控制器，在故障清除后，根据VSC过电压情况和直流线路压降，降低LCC直流电压参考值，限制系统恢复过程中极母线的过电压冲击。
进一步的，所述将上级控制输出的LCC直流电压参考值U dcref叠加经过暂态电压控制器处理的电压调节量ΔU dcLCC，输出最终的LCC直流电压参考值包 括：
实时采集逆变站投运换流器交流母线电压，计算得到交流母线电压正序分量最小值U acposmin；通过与电压阈值U set1进行比较，判断是否发生交流系统故障：
如果U acposmin＜U set1，则表明交流系统故障，并且检测到LCC发生换相失败时，暂态电压控制器输出的电压调节量ΔU dcLCC＝0；
如果U acposmin＞U set1，则表明交流系统故障已清除，或者未检测到LCC发生换相失败时，暂态电压控制器根据VSC过压情况输出电压调节量ΔU dcLCC。
进一步的，所述暂态电压控制器根据VSC过压情况输出电压调节量ΔU dcLCC包括：
当逆变侧交流系统发生接地故障时，VSC直流电压U dcVSC升高；
当交流系统故障清除或者LCC换相正常后，如果U dcVSC大于VSC直流电压参考值U dcrefVSC与VSC过压死区值U deadband之和，则ΔU dcLCC为VSC电压偏差分量和额外限压分量U exc之和，ΔU dcLCC＜0，其中VSC电压偏差分量处于U min至0区间，U min为VSC过电压最小限幅值；
当U acposmin＜U set1并且LCC换相失败时，额外限压分量U exc从0平滑变化到U c1，U c1为限压参数，U c1＜0；
当交流系统故障清除或者LCC换相正常，经过一段延时后，U exc由U c1平滑变化到0。
具体的，如图4所示，图4是本发明提供的特高压混合直流输电系统暂态电压控制器框图。逆变站控制系统采集投运换流器交流母线电压，计算得到交流母线电压正序分量最小值U acposmin。通过与电压阈值U set1进行比较，判定是否发生交流系统故障。如果U acposmin<U set1表明交流系统故障，并且检测到LCC发生换相失败，暂态电压控制器输出的电压调节量ΔU dcLCC等于0。如果U acposmin>U set1表明交流系统故障已清除，或者未检测到LCC换相失败，暂态电压控制器根据VSC过压情况输出电压调节量ΔU dcLCC。当逆变侧交流系统发生接地故障时，VSC直流电压U dcVSC升高。交流系统故障清除或者LCC换相正常 后，如果U dcVSC大于VSC直流电压参考值U dcrefVSC与过压死区值U deadband之和，ΔU dcLCC将包含VSC电压偏差分量(处于U min至0区间)和额外限压分量U exc，ΔU dcLCC<0。当U acposmin<U set1并且LCC换相失败时，额外限压分量U exc从0平滑变化到U c1(U c1<0)。当交流系统故障清除或者LCC换相正常，经过一段延时后，U exc由U c1平滑变化到0。U exc用于限制系统快速恢复过程中线路感抗造成的整流站极母线过电压。交流系统故障清除后，LCC暂态电压控制器适当降低电压参考值，使得系统恢复过程中，逆变站LCC低电压运行，从而限制了系统极母线过电压。
进一步的，所述PI控制器进行调节包括将输出的触发角余弦值限定在cosα min和cosα max之间，当cosα＞cosα max时，输出为cosα max；当cosα＜cosα min时，输出为cosα min；当cosα min≤cosα≤cosα max时，输出为cosα；其中，α为触发角，cosα max为触发角余弦最大值，cosα min为触发角余弦最小值。
本发明的第二方面提供了一种特高压混合直流输电系统暂态电压控制装置，所述特高压混合直流输电系统包括整流站和逆变站，逆变站包括高端阀组的电网换相换流器LCC和低端阀组的电压源型换流器VSC，包括：
暂态电压控制器：将上级控制输出的LCC直流电压参考值U dcref叠加经过暂态电压控制器处理的电压调节量ΔU dcLCC，输出最终的LCC直流电压参考值；
作差计算器：将所述直流电压实际值U dcLCC与所述最终的LCC直流电压参考值进行作差计算；
PI控制器：将作差计算的结果输入PI控制器进行调节，输出触发角余弦值；
反余弦计算器：将输出触发角余弦值经过反余弦计算，输出逆变站触发角。
综上所述，本发明提供了一种特高压混合直流输电系统暂态电压控制方法及装置，该方法包括：将上级控制输出的LCC直流电压参考值U dcref叠加经过暂态电压控制器处理的电压调节量ΔU dcLCC，输出最终的LCC直流电压参考 值；直流电压实际值U dcLCC与所述最终的LCC直流电压参考值作差后输入PI控制器进行调节，输出触发角余弦值；经过反余弦计算，输出逆变站触发角。该方法在交流系统故障清除后，LCC暂态电压控制器根据VSC过电压情况和直流线路压降，适当降低电压参考值，使得系统恢复过程中，逆变站LCC低电压运行，从而限制了系统极母线过电压。
应当理解的是，本发明的上述具体实施方式仅仅用于示例性说明或解释本发明的原理，而不构成对本发明的限制。因此，在不偏离本发明的精神和范围的情况下所做的任何修改、等同替换、改进等，均应包含在本发明的保护范围之内。此外，本发明所附权利要求旨在涵盖落入所附权利要求范围和边界、或者这种范围和边界的等同形式内的全部变化和修改例。

Claims (8)

  1. 一种特高压混合直流输电系统暂态电压控制方法，所述特高压混合直流输电系统包括整流站和逆变站，逆变站包括高端阀组的电网换相换流器LCC和低端阀组的电压源型换流器VSC，所述暂态电压控制方法对逆变站LCC直流电压进行控制，其特征在于，包括如下步骤：
    将上级控制输出的LCC直流电压参考值U dcref叠加经过暂态电压控制器处理的电压调节量ΔU dcLCC，输出最终的LCC直流电压参考值；
    直流电压实际值U dcLCC与所述最终的LCC直流电压参考值作差后输入PI控制器进行调节，输出触发角余弦值；
    经过反余弦计算，输出逆变站触发角。
  2. 根据权利要求1所述的特高压混合直流输电系统暂态电压控制方法，其特征在于，所述将上级控制输出的LCC直流电压参考值U dcref叠加经过暂态电压控制器处理的电压调节量ΔU dcLCC，输出最终的LCC直流电压参考值包括：
    实时采集逆变站投运换流器交流母线电压，计算得到交流母线电压正序分量最小值U acposmin；通过与电压阈值U set1进行比较，判断是否发生交流系统故障：
    如果U acposmin＜U set1，则表明交流系统故障，并且检测到LCC发生换相失败时，暂态电压控制器输出的电压调节量ΔU dcLCC＝0；
    如果U acposmin＞U set1，则表明交流系统故障已清除，或者未检测到LCC发生换相失败时，暂态电压控制器根据VSC过压情况输出电压调节量ΔU dcLCC。
  3. 根据权利要求2所述的特高压混合直流输电系统暂态电压控制方法，其特征在于，所述暂态电压控制器根据VSC过压情况输出电压调节量ΔU dcLCC包括：
    当逆变侧交流系统发生接地故障时，VSC直流电压U dcVSC升高；
    当交流系统故障清除或者LCC换相正常后，如果U dcVSC大于VSC直流电 压参考值U dcrefVSC与VSC过压死区值U deadband之和，则ΔU dcLCC为VSC电压偏差分量和额外限压分量U exc之和，ΔU dcLCC＜0，其中VSC电压偏差分量处于U min至0区间，U min为VSC过电压最小限幅值；
    当U acposmin＜U set1并且LCC换相失败时，额外限压分量U exc从0平滑变化到U c1，U c1为限压参数，U c1＜0；
    当交流系统故障清除或者LCC换相正常，经过一段延时后，U exc由U c1平滑变化到0。
  4. 根据权利要求1所述的特高压混合直流输电系统暂态电压控制方法，其特征在于，所述PI控制器进行调节包括将输出的触发角余弦值限定在cosα min和cosα max之间，当cosα＞cosα max时，输出为cosα max；当cosα＜cosα min时，输出为cosα min；当cosα min≤cosα≤cosα max时，输出为cosα；其中，α为触发角，cosα max为触发角余弦最大值，cosα min为触发角余弦最小值。
  5. 一种特高压混合直流输电系统暂态电压控制装置，所述特高压混合直流输电系统包括整流站和逆变站，逆变站包括高端阀组的电网换相换流器LCC和低端阀组的电压源型换流器VSC，其特征在于，包括：
    暂态电压控制器：将上级控制输出的LCC直流电压参考值U dcref叠加经过暂态电压控制器处理的电压调节量ΔU dcLCC，输出最终的LCC直流电压参考值；
    作差计算器：将所述直流电压实际值U dcLCC与所述最终的LCC直流电压参考值进行作差计算；
    PI控制器：将作差计算的结果输入PI控制器进行调节，输出触发角余弦值；
    反余弦计算器：将输出触发角余弦值经过反余弦计算，输出逆变站触发角。
  6. 根据权利要求5所述的特高压混合直流输电系统暂态电压控制装置，其特征在于，所述暂态电压控制器进行如下控制以得到输出的电压调 节量ΔU dcLCC：
    实时采集逆变站投运换流器交流母线电压，计算得到交流母线电压正序分量最小值U acposmin；通过与电压阈值U set1进行比较，判断是否发生交流系统故障：
    如果U acposmin＜U set1，则表明交流系统故障，并且检测到LCC发生换相失败时，暂态电压控制器输出的电压调节量ΔU dcLCC＝0；
    如果U acposmin＞U set1，则表明交流系统故障已清除，或者未检测到LCC发生换相失败时，暂态电压控制器根据VSC过压情况输出电压调节量ΔU dcLCC。
  7. 根据权利要求6所述的特高压混合直流输电系统暂态电压控制装置，其特征在于，所述暂态电压控制器根据VSC过压情况输出电压调节量ΔU dcLCC包括：
    当逆变侧交流系统发生接地故障时，VSC直流电压U dcVSC升高；
    当交流系统故障清除或者LCC换相正常后，如果U dcVSC大于VSC直流电压参考值U dcrefVSC与VSC过压死区值U deadband之和，则ΔU dcLCC为VSC电压偏差分量和额外限压分量U exc之和，ΔU dcLCC＜0，其中VSC电压偏差分量处于U min至0区间，U min为VSC过电压最小限幅值；
    当U acposmin＜U set1并且LCC换相失败时，额外限压分量U exc从0平滑变化到U c1，U c1为限压参数，U c1＜0；
    当交流系统故障清除或者LCC换相正常，经过一段延时后，U exc由U c1平滑变化到0。
  8. 根据权利要求5所述的特高压混合直流输电系统暂态电压控制装置，其特征在于，所述PI控制器将输出的触发角余弦值限定在cosα min和cosα max之间，当cosα＞cosα max时，输出为cosα max；当cosα＜cosα min时，输出为cosα min；当cosα min≤cosα≤cosα max时，输出为cosα；其中，α为触发角，cosα max为触发角余弦最大值，cosα min为触发角余弦最小值。
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