Power control method on VSC-HVDC in a hybrid multi-infeed HVDC system

Multi-infeed HVDC (MIDC) system connected with VSC-HVDC links and LCC-HVDC links is a new structure in modern power systems, which can be called hybrid multi-infeed HVDC (HMIDC) system. The paper presents the voltage stability analysis of a HMIDC system modeled from a possible future Danish power system and proposes a power control method to improve the system voltage stability. Dynamic loads are considered in the studied system and represented by induction machines. The paper analyses voltage recovery process of an induction machine during a fault and gives the necessary condition of the voltage stability of the system with induction machine loads. The proposed power control method based on a VSC power circle makes fully use of the VSC-HVDC capacity to support system voltage during fault situations. Simulation model of the studied HMIDC system is built in PSCAD. Simulation studies under different disturbances verify that the proposed power control method can improve the system voltage stability. The comparison with traditional control method has also been made.