A voltage sensorless phase locked loop structure for single phase grid connected converter system

The popularly used current controlled architecture for grid connected converter systems needs a phase locked loop (PLL) for its operation. The PLL generates the unit vectors required for desired current reference generation. This paper proposes to eliminate the grid voltage sensor and presents a method to estimate the unit vectors and grid frequency without a dedicated grid voltage sensor. The estimation method is based on the active and reactive power delivered by the converter to the grid. In addition, it also gives an estimation of the fundamental component of the grid voltage. Simulation and experimental results are presented to confirm the feasibility of the proposed scheme.