Synchronization signal detection of fundamental voltage under unbalanced and harmonic distorted grid voltage conditions

This paper proposes a novel grid fundamental voltage detection scheme. By means of solving the linear equations that are gained by differentiating the sampled three-phase grid voltage, it is able to calculate the positive and negative sequence components of the fundamental voltage, and the integral and non-integral harmonics in the unbalanced and distorted grid voltage. Based on the fundamental separation method, an improved software phase locked loop (PLL), which is designed to compensate the phase angle jump of the grid voltage, is applied to track the phase angle of the positive sequence component in the fundamental wave rapidly. Simulation and experimental results prove that the proposed algorithm has the characteristic of fast dynamic response and high precision, which provides a reliable basis for the control of various power electronic devices under grid faults.