摘要
针对电网不平衡时电压源换流器高压直流输电(voltage source converter based high voltage direct current transmission,VSC-HVDC)的直流电压2倍频波动及交流系统低频谐波问题,建立基于正向dq坐标系的正负序VSC-HVDC动态模型,研究其运行特性,并提出一种新型统一矢量控制策略。该策略外环基于谐振积分器及谐振滤波器方案实现直流系统2倍频波动抑制,降低不平衡运行对电网电流的低频谐波影响;内环为两相静止坐标下的正负序矢量电流统一控制,避免因相序分解可能引起换流站交流侧电压含奇次低频谐波分量的问题。PSCAD/EMTDC仿真研究表明:统一矢量控制不仅能抑制直流系统2倍频波动,而且降低了交流电网低频谐波水平,增强了VSC-HVDC的不平衡运行能力。
Based on the models presenting the dynamic behavior of voltage source converter based high voltage direct current transmission（VSC-HVDC） system in the unique positive synchronously rotating reference（dq＋） frame with respect to both the positive-and negative-sequence components,this paper proposed a novel unified control strategy to restrain the DC-link ripple along with the reduction of low-order harmonics in each grid under unbalanced grid conditions.The resonant integrator and filter based scheme in the outer loop enables the restraint of the DC-link ripple and mitigates harmonics in the current references due to the imbalance.In the inner loop,the unified positive-and negative-sequence current control in the stationary ？？ frame avoids the sequence component decomposition which will cause the odd low-order harmonics in the converter output voltage.The simulation studies in PSCAD/EMTDC verified the improved performance of VSC-HVDC system regarding the power quality and the operational capability in the imbalance.
出处
《中国电机工程学报》
EI
CSCD
北大核心
2012年第34期50-57,9,共8页
Proceedings of the CSEE
关键词
高压直流输电
电压源换流器
不平衡
谐振积分器
电能质量
high voltage direct current transmission（HVDC）
voltage source converter（VSC）
unbalanced operation
resonant integrator
power quality
