Integrated emergency frequency control method for interconnected AC/DC power systems using centre of inertia signals

An integrated design method for emergency frequency control of interconnected AC/DC power systems with centre of inertia (COI) signals is proposed in this study. It aims to provide emergency power support from reserve-rich area(s) to the disturbed control area(s) through the paralleled AC and DC tie-lines under extreme conditions, when the normal automatic generation control (AGC) is suspended. With the assumption of area COI frequency and the employment of wide-area measurement system (WAMS), the centralised control strategy drives the area COI frequencies to track the overall system COI frequency by virtue of coordination control of emergency generation and high voltage direct current (HVDC) power such that the long-term frequency stability can be promisingly improved. The adaptive backstepping sliding-mode approach holds desired robustness to time-varying generator parameter, modelling error and area load disturbances. Simulations have been conducted on a 3-area-interconnected AC/DC system in computer and the results demonstrate the feasibility and effectiveness of the proposed design method.