Research on Photovoltaic Power Plant Participating in Primary Frequency Regulation of Power Grid with Variable Control Gain Based on Describing Function Method

With the increasing proportion of photovoltaic and other new energy in the power grid operation, the overall frequency modulation ability and inertia level of the system decline, so it is urgent for new energy to participate in the primary frequency modulation of the power grid. The gain of frequency regulation control (the reciprocal of the regulation coefficient) is the key parameter of the primary frequency regulation control system, a frequency regulation system can run with smaller control gain under small disturbance, when the frequency deviation in power grid is large due to the large load disturbance in the system, if the original control gain is switched to the greater control gain, it is excepted to bring better control effect of frequency regulation. So the use of variable gain control is a subject worth studying. For this reason, this paper studies the variable gain control problem of photovoltaic power plant participating in primary frequency modulation. Firstly, the primary frequency modulation control analysis model of photovoltaic power plant is established. What's more, the value of original control gain is given referring to the actual operation experience of the power system. Then based on the nonlinear Nyquist stability criterion, the range of control gain can be obtained that ensure the stability of the system. Finally, the optimal control gain is obtained by using Particle Swarm Optimization(PSO). Simulation results show the effectiveness of the proposed method.