Advanced Frequency Support Strategy of Double-Stage Grid-Connected PV Generation

With an increasing penetration of PV generation in the electrical grid, the increasing replacement of large conventional synchronous generators by PV generation will result in deteriorated frequency regulation performance due to the reduced system inertia response. It is urgent for PV generation to take part in frequency regulation. In this paper, three virtual inertial control strategies are proposed for double-stage grid-connected PV generation: virtual inertial control based on the dynamics of phase-locked loop (PLL), virtual inertial control based on the dynamics of low voltage DC capacitor, virtual inertial control based on the dynamics of high voltage DC capacitor. The influence of control parameters on virtual inertial control strategies is also analyzed. Besides, in order to get an even better frequency behavior, a coordinated control strategy between PV generation and conventional synchronous generators (SGs) is also proposed. Finally, the theoretical analysis and control strategies are verified by simulation results.