Frequency Regulation Strategy for AC–DC System During Black Start

Abstract

High-voltage direct current (HVDC) can speed up the recovery of a power system. However, both rectifier and inverter sides of HVDC are weak systems during a black start. To coordinate frequency characteristics of both sides within the frequency deviation constrain, a frequency regulation strategy for AC–DC system during a black start is proposed. First, the mathematical models of asynchronous interconnected AC–DC system are established, and the optimal HVDC transmission power leading to minimum frequency deviation of both sides is obtained based on the linear quadratic optimal control method. To adapt to the continuously changing parameters and configurations of the AC power system during a black start, a Narendra adaptive tracking control method is developed to obtain the control law of the target value of governor, which allows the actual system frequency follow the reference system frequency under the optimal HVDC transmission power. Finally, the simulation model is established using PSCAD/EMTDC software to verify the proposed strategy.