基于混合双馈入直流输电系统有功无功协调的后续换相失败控制方法

Subsequent Commutation Failure Control Method Based on Coordination Between Active and Reactive Powers in Hybrid Dual-infeed HVDC System

基于电网换相换流器的高压直流输电(LCC-HVDC)系统的换相失败是威胁电网安全的关键因素,但是受自身调节能力的限制,目前LCC-HVDC后续换相失败的抑制效果有限,甚至对电网产生不利的影响。为此,充分考虑影响LCC-HVDC换相失败的因素,提出了利用基于电压源换流器的高压直流输电(VSC-HVDC)系统无功控制能力并兼顾直流有功传输对换相失败影响以及交流有功缺额对电网安全影响的混合双馈入直流输电系统换相失败控制方法。建立了LCC-HVDC逆变站关断角、LCC-HVDC直流电流和VSC-HVDC输出无功的关联模型;计及VSC-HVDC和LCC-HVDC运行约束,提出了基于LCC-HVDC直流电流与VSC-HVDC无功坐标平面的混合双馈入直流输电系统换相失败可控域;建立了以直流系统传输功率变化量最小为目标函数和以换相失败可控域为约束的优化模型,提出了考虑LCC-HVDC有功与VSC-HVDC无功协调的后续换相失败控制方法。仿真算例表明,该方法不仅能够提高LCC-HVDC的换相失败免疫能力,还能最大限度地降低直流传输有功的变化,有利于交直流电网的安全稳定运行。

Commutation failures,occurring in line commutated converter based HVDC(LCC-HVDC),is a key factor threatening security of power grid.However,restricted by its own regulation capability,its suppression effect on subsequent commutation failures is limited.Therefore,considering the factors affecting commutation failure,in this paper,a commutation failure control method based on full use of the reactive power control capacity of voltage source converter based HVDC(VSC-HVDC)in hybrid dual-infeed HVDC system was proposed with both the impacts of HVDC active power transmission on commutation failure and active power shortage on power gird taken into account.A correlation model among the extinction angle and DC current of LCC-HVDC inverter and the output reactive power of VSC-HVDC was deduced.Furthermore,by combining the constraints of control variables in VSC-HVDC and LCC-HVDC,a controllable operation region for commutation failure was proposed for hybrid dual-infeed HVDC transmission system based on the coordinate plane of LCC-HVDC DC current and VSC-HVDC reactive power.Then,an optimization model was established with the minimum variation of the transmitted active power in hybrid dual-infeed HVDC system as objective function and the controllable operation region for commutation failure as constraint.A subsequent commutation failure control method based on coordination of LCC-HVDC active power and VSC-HVDC reactive power was proposed.Simulation results show that this method is effective in improving immunity of commutation failure,able to farthest minimize the variation of DC system transmission power,and conducive to security and stability of AC grid.