Implementation of Single-Phase Phase-Locked Loop with DC Offset and Noise Rejection Using Fuzzy Logic Controller

In grid connected applications, grid-connected converters require a precise and accurate detection of frequency, an amplitude and a phase-angle of a grid voltage. For estimation of these grid parameters, a well-known method, Phase-locked loop (PLL) can be used. There are different types of PLLs and all of them have advantages and disadvantages. Most PLL systems are designed with PI regulator within loop filter which is very sensitive to disturbances such as sudden changes of the grid voltage. In this paper, an improved PLL structure is proposed which is capable to estimate precisely voltage grid parameters and to reduce noise and DC offset which could appear in the grid voltage, using an intelligent controller—fuzzy logic controller (FLC) instead of PI regulator. Simulation of the proposed PLL structure is done in Matlab Simulink program, while experimental results in real-time are obtained using multifunctional Humusoft I/O card MF634. Proposed structure should give excellent dynamic performances of estimated grid parameters and good performances of fast reacting to sudden changes of the grid voltage.