Autonomous Dual Active Power-frequency Control in Power System with Small-scale Photovoltaic Power Generation

Active power control of the photovoltaic (PV) power generation system is a promising solution to regulate frequency fluctuation in a power system with high penetration of renewable energy. This paper proposes an autonomous active power control of a small-scale PV system for supporting the inertial response of synchronous generators and power-frequency control. In the proposed control approach, an effective grid frequency regulation scheme is realized using slow- and fast-frequency responses. A low-pass filter based frequency measurement is used for slow-frequency response, while direct frequency measurement is used for fast-frequency response. The designed dual droop characteristic-based control is shaped to achieve a smooth transition between slow- and fast-frequency responses. The performance of the proposed control approach is demonstrated for serious disturbance scenarios, i.e., considerable power-load imbalance and generation trip. In the power-load imbalance test scenario, the proposed control approach works properly within the normal frequency deviation region even when the frequency deviation exceeds that region occasionally. In the generation trip test, the frequency deviation is mitigated quickly, and the employed droop control is smoothly transferred from the slow- to fast-frequency responses.