Research Of Key Points In Grid Connected Inverter

This paper mainly investigates several key issues about grid-connected inverters, including the unified pulse width modulation technology, the suppression of circulating current and the phase locked loop for a single-phase in grid-connected power systems. Based on the analysis of space vector in phase vector frame, the unified pulse width modulation technology is obtained, then this paper discusses the relationships between several pulse width modulation methods applied in three-phase power systems.According to the analysis of circulating current circuits in power-feedback systems, this paper studies the parallel system which consists of grid-connected inverters and full-bridge rectifier, and presents a dual carried wave PWM with injections of zero-sequence voltages. Simulations and results are given out to verify PWM proposed can cause smaller circulating current, compared with SPWM and SVPWM. As to the research of the phase locked loop, this paper proposes a new orthogonal signal generator which can suppress the direct-current of input signal. The orthogonal signal generator is get through the analysis of the weight factor of adaptive filter using least square method in time domain in this paper. Finally, the results of experiments are employed to compare the orthogonal signal generator proposed in this paper and the orthogonal signal generator based on second order generalized integrator. the proposed orthogonal signal generator can achieve similar performance compared to the widely applied method with second-order generalized integrator, and also improve the suppression of direct-current in input signal.