Synchronization signal detection method in synchronous reference frame through sinusoidal amplitude integrators

The synchronization signal is necessary for the control of three-phase grid-tied converters, and so also is for the separation of positive and negative sequence components. Under unbalanced grid condition, the traditional synchronous reference frame phase-locked loop(SRF-PLL) can not work well because of the influence of the fundamental negative sequence component. By analyzing the characteristic of the SRF-PLL under unbalanced grid voltage condition, this paper proposes a separation method for the fundamental positive and negative sequence components which is based on the sinusoidal amplitude integrator phase-locked loop(SAI-PLL). Not only can this method eliminate the influence of the fundamental negative sequence component, it also can obtain the negative sequence component at the same time. In this paper, an overall block diagram of the SAI-PLL is shown, on the basis of its operation principle, a mathematical model is built and the parameters are designed. Compared with other existed methods, this method has advantages in the performance. The simulation and experimental results show that the proposed method can extract the synchronization signal quickly and precisely under the unbalanced and distorted conditions. ©, 2015, Chinese Machine Press. All right reserved.