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...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。展开更多
We have given a straightforward method to solve the problem of noncentral anharmonic oscillator in three dimensions. The relative propagator is presented by means of path integrals in spherical coordinates. By making ...We have given a straightforward method to solve the problem of noncentral anharmonic oscillator in three dimensions. The relative propagator is presented by means of path integrals in spherical coordinates. By making an adequate change of time we are able to separate the angular motion from the radial one. The relative propagator is then exactly calculated. The energy spectrum and the corresponding wave functions are obtained.展开更多
文摘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。
文摘We have given a straightforward method to solve the problem of noncentral anharmonic oscillator in three dimensions. The relative propagator is presented by means of path integrals in spherical coordinates. By making an adequate change of time we are able to separate the angular motion from the radial one. The relative propagator is then exactly calculated. The energy spectrum and the corresponding wave functions are obtained.
