Analysis of voltage distortion for parallel PWM inverters with L filter

When multi-parallel inverters with L filter are connected to the grid through a long cable, the voltage at the point of common coupling (PCC) will be distorted due to the superposition of the voltage harmonic which are generated by different inverters. In order to solve this problem, the causes of voltage distortion are analyzed in this paper primarily. The correlation of the harmonic between the voltage in the PCC and the pulse width modulation (PWM) wave the output of the inverters is deduced, including the peak voltage, voltage harmonic, and the total harmonic distortion (THD). And then the solution of adding capacitor in the PCC is presented in this paper. Combined with the practical requirement, the method on the design the capacitor is listed. Finally, for illustration, the problems and solution for paralleled inverters are tested by simulation and experiments and the results provide the support to aforementioned theory and analysis.