LCL filter design and control for grid-connected PWM converter

This paper describes LCL filter design and control for grid-connected PWM converter. To attenuate switching harmonics on grid side with an LCL filter, cost effectiveness must be considered to select filter parameters. This paper proposes a filter design method based on a computer simulation tool. Depending on user's optimal cost function, filter parameters are chosen without tedious and repetitive mathematical calculations. On the other hand, damping factors must be introduced in control of LCL filter to suppress the inherent resonant characteristics. Since the resonance phenomenon is minimized by increasing the ratio of switching frequency to fundamental grid frequency in most conventional researches, it is difficult to be employed in high power system due to the limited switching frequency of power semiconductors in the converter. In this paper, a novel current controller with generalized gain determination is suggested. Discrete time controller based on only grid voltages and currents information is introduced, which yields desirable dynamic response even in lower switching frequency of PWM converter. Simulations and experimental results are presented to validate the proposed design and control procedures.