Operation of a Three-phase Soft Phase Locked Loop Under Distorted Voltage Conditions Using Intelligent PI Controller

The phase angle of the utility voltage plays a most important role for the operation of FACTS (Flexible AC Transmission System) and renewable energy systems, and PLL (Phase Locked Loop) should be accurate, fast and robust. Operation of a vector-based soft phase locked loop system under distorted utility conditions is presented in this paper. An intelligent PI controller is proposed to solve the conflict between tracing speed and filtering characteristics, which is to regulate the parameters of PI controller based on the phase error input. All analytical results are verified by simulations and experiments. The merits of high-speed, robust and strongly restraining ability to distorted voltage make it could be widely used in FACTS and renewable energy control systems.