Fast dc Link Voltage Controller under Large Irradiance Variations in a PV Single- Phase Grid-Connected Inverter

A simple approach to increase the bandwidth of the dc link voltage controller of a grid connected single-phase photovoltaic (PV) power inverter is proposed in this paper. The operation of the converter implies the presence of a second order frequency component in the dc link voltage, and the increment in the conventional voltage controller bandwidth causes total harmonic distortion of the output current to be deteriorated due to this component. The proposed method is based on the design of a lead compensator and a ripple voltage estimator. The former is used to attenuate the low order harmonic content and to increase the bandwidth, the latter is intended to reduce the ripple component in the feedback loop of the dc link voltage controller. The procedure to obtain the lead compensator is discussed and fully validated via simulation results, as well as the ripple estimator which is derived from the power balance on the dc link, for different sudden changes of the solar irradiance.