多馈入交直流系统短路比的定义和应用

Definition and Application of Short Circuit Ratio for Multi-infeed AC/DC Power Systems

随着我国电网的发展,南方电网和华东电网出现了多馈入交直流系统。由于传统短路比不能考虑直流间的相互作用而亟待提出适用于多馈入交直流系统的短路比定义。通过理论分析推导多馈入短路比,证明传统短路比是多馈入短路比的特例。通过提出的多馈入交直流系统的解耦模型推导多馈入临界短路比的函数表达式,证明多馈入临界短路比与电压灵敏因子的等价关系,提出判断多馈入交直流系统强弱的指标。最后,通过理论分析和算例仿真说明利用多馈入短路比指标判断电压稳定、动态过电压、谐波谐振的有效性,证明所提出指标的合理性及在电网规划和运行中的重要作用。

With the development of power grid, multiinfeed HVDC （MIDC） embedded in one AC system has emerged in south China power grid and east China power gird. Because the traditional short circuit ratio （SCR） is not able to reflect the interaction of HVDCs into account, it is urgent to propose a new definition of SCR for MIDC systems. The paper defined multi-infeed short circuit ratio （MSCR） by theoretical analysis and formula derivation, and proved the traditional SCR was a special case of MSCR. Based on it, a decoupled model of MIDC was proposed, and multi-infeed critical SCR （MCSCR） was derived, then the criteria of weak MIDC system were presented. The relationship between MCSCR and nodal voltage sensibility factor （NVSF） was discussed. Further more, MSCR was used to analyze weak MIDC operation problems, for example, voltage stability, transient over-voltage （TOV）, and harmonic resonance. It proved the indices were effective, and can make contribution to power system planning and operation.