Enhancement of the Voltage Control Response in Three-Phase Photovoltaic Inverters With Small DC Capacitors

In the case of photovoltaic (PV) inverters, an adequate dc voltage regulation is fundamental to maximize or limit the power injected into the grid. However, the traditional control requires a large dc capacitance to ensure stability in the whole operating range while the existing alternatives, despite achieving a stable control with a small capacitance, become too slow in the open-circuit area. This paper proposes two control methods to improve this performance. Firstly, a new voltage control with virtual impedance emulation is presented, showing that the response becomes faster in all operating points. Secondly, the control with impedance emulation is combined with a feed-forward compensation, further improving the dynamic response. Both methods are very simple to implement and their superior performance when using a small dc capacitance is verified by means of simulation results.