A New Type of Three-phase Asymmetric-LCL Power filter for Grid-Tied Voltage Source Inverter with Step-up Transformer

Power filters have been widely adopted to suppress harmonics caused by the pulse width modulation of grid-connected inverters. In order to save the total inductance, the cost and the size of system, different kinds of power filters had been proposed for the three-phase three-wire grid-connected inverter. However, in industrial applications, due to production cost considerations, the difficulties caused by actual parameter deviations must be considered. In this paper, a new three-phase three-wire power filter is proposed, being with a simple structure almost the smallest total inductance, and strong resistance to the adverse effects of parameter shifts. The design of the filter parameters and the grid-connected system controller is introduced in details. A comparable study on the influence of parameter offset between different types of notch power filters is also given. Simulation and experimental results on a 380 V/50 Hz/6 kW three-phase inverter prototype verify the performance of the proposed power filter