特高压并联型三端混合直流输电系统功率转带策略

Power Transfer Strategy of Parallel Three-terminal Hybrid UHVDC Transmission System

特高压并联型三端混合直流输电系统作为多端直流输电的一种重要形式,相较于常规特高压两端直流输电系统,其在故障后的功率转带更为灵活和复杂。文中基于中国乌东德多端直流工程,提出了一种适用于特高压并联型三端混合直流输电系统的功率转带策略。基于闭锁前三站各极的功率水平、最小和最大输送功率能力以及所处的控制模式,计算并重新设置各站各极的功率、电流参考值,实现故障极功率的极间转带和站间转带,以减少功率损失,同时兼顾最小化非故障逆变站的接地极电流。通过实时数字仿真,验证了所提策略的有效性。

The parallel three-terminal hybrid ultra-high-voltage direct current(UHVDC)transmission system is one of the most important types of multi-terminal DC transmission systems.Compared with the normal two-terminal UHVDC transmission system,its power transfer strategy after a fault is much more flexible and complicated.Based on Wudongde multi-terminal UHVDC project of China,a power transfer strategy for parallel three-terminal hybrid UHVDC transmission systems is proposed in this paper.The strategy calculates and resets the current and power reference of each pole according to its pre-fault power level,upper and lower power limits,and pre-fault control mode.By this strategy,the power surplus of the fault pole can be transferred to non-fault poles and stations,which helps to minimize the power loss.Moreover,this strategy also minimizes the grounding electrode current of the non-fault stations.The real-time digital simulation results prove the validity of the proposed strategy.