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

Abstract

With the development of power grid,multi-infeed 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.