摘要
在交流系统故障或者甩负荷等暂态过程中,由于有功功率不平衡,电压源换流器型高压直流(VSC-HVDC)输电系统直流侧会出现过电压或者欠电压现象,危及换流阀、直流电容器和直流电缆等设备的安全。为了限制暂态过程中直流电压波动幅度,提出了一种改进的控制策略,即在外环有功功率控制器中增加了一个依赖于直流电压的电流指令限制单元(VDCCOL),它通过内环电流控制器有功电流指令的变化来反映直流电压的变化。当直流电压异常时,VDCCOL根据预设的特性迅速修正外环功率控制器输出的有功电流指令值,减缓有功功率的不平衡,从而达到限制直流过电压/欠电压的发展、保护设备安全运行和避免频繁切机等目的。仿真研究表明,文中提出的控制策略能有效地抑制故障条件下直流电压波动幅度,提高系统的运行特性。
During the transients caused by the AC faults or load rejections, the DC link of voltage source converter based high voltage DC （VSC-HVDC） system may experience under-voltage or over-voltage because of the active power unbalance, which endangers the safety operation of the valves, DC capacitors and cables. To keep the DC voltage in the safety limits under the steady and transient conditions, a novel control strategy is proposed. It introduces a DC voltage dependent current order limiter （VDCCOL） into the outer active power controller. ＂VDCCOL changes the inner active current orders according to the DC voltage fluctuations. When the DC voltage is abnormal, VDCCOL rapidly modifies the outer control loop current setting points according to pre-set characteristics, to mitigate the active power unbalance, therefore the DC under-voltage or over-voltage is suppressed and the risk of tripping the whole system is reduced. Simulation results show that the proposed control strategy can effectively suppress the variations of the DC link voltage during the transients and enhance the system＇ s operational characteristics. This work is supported by State Grid Corporation of China （No. SGKJ [2007] 249） and Natural Science Foundation of Zhejiang Province, China （No. Y106164）.
出处
《电力系统自动化》
EI
CSCD
北大核心
2008年第22期41-46,共6页
Automation of Electric Power Systems
基金
国家电网公司科技项目(SGKJ[2007]249)
浙江省自然科学基金资助项目(Y106164)~~
关键词
高压直流输电
电压源换流器
直流电压控制
依赖于直流电压的电流限制单元
甩负荷
high voltage DC （HVDC）
voltage source converter （VSC）
DC voltage control
DC voltage dependent current order limiter （VDCCOL）
load rejection
