Evaluation of repetitive control for power quality improvement of distributed generation

Small-scale distributed generation (DG) is often not a natural 50 or 60 Hz AC source and so employs an inverter for the interface to the utility grid. Here, repetitive control is examined as a means of also using a DG inverter to improve the distortion of a local grid where a large proportion of the load is non-linear. The proposed controller can offer better waveform quality in balanced and unbalanced conditions than PI controllers in either stationary or rotating reference frames. The inverter also requires a control loop to regulate the exported power. A decoupled P and Q controller is applied and compared to a traditional amplitude and angle controller. The controllers are tested for disturbance rejection of variations in grid voltage, DC-link voltage and load power.