Design of Voltage Synchronous Signal Estimator under Grid Distortion

The grid voltage contains the positive sequence, negative sequence and harmonic component under the complex condition of voltage asymmetry, which can cause the great interference to the detection of synchronous sinusoidal signal of the power grid. Therefore, a detection method in a two-phase stationary reference frame is proposed based on extended kalman filter (EKF). Firstly, the Hilbert transform is combined with the Clark transform, and the positive sequence voltage signal is separated by eliminating the negative sequence component using the simple mathematical operation. Secondly, in order to extract the synchronous signal from the separate positive sequence signal, the positive sequence component in the two-phase stationary reference frame is used as the input signal of EKF. This method can not only estimate the positive sequence component of the fundamental wave, but also eliminate the Gaussian white noise of the system, which can more accurately solve the problem of actual working conditions. In this paper, EKF is used to estimate the amplitude and phase of grid voltage synchronization signal. The maximum error of voltage estimation is obviously reduced, compared with other optimized algorithms. Thus, EKF can better estimate the amplitude and phase of the grid voltage fundamental wave. Then, a closed-loop system is designed in this paper. Finally, the simulation and experimental results show that the proposed algorithm can extract grid sinusoidal signals under complex conditions accuracy, and have good frequency adaption characteristics.