A Controller Improving Photovoltaic Voltage Regulation in the Single-Stage Single-Phase Inverter

While substantial research covers current control and synchronization of grid-connected photovoltaic (PV) inverters, issues concerning control of the PV input voltage deserve more attention, as they equally affect the reliable and stable operation of the system. Hence, this article analyses the PV voltage regulation in the single-stage single-phase PV inverter. In contrast to previous work, the PV source influence on the input voltage dynamic is analytically formalized, exposing a potential instability when the PV source is operating in its constant current region. A traditional proportional-integral PV voltage controller fails to ensure a consistent and stable voltage regulation. On the other hand, this issue is resolved by the proposed feedback linearization based controller. The new controller is validated on a test setup comprising of a PV source emulating a 1.2 kW PV array, interfaced to a single-phase inverter connected to a grid emulator. Confirming the issues predicted by the theoretical analysis, the experiments prove two main advantages of the proposed controller. First, PV voltage regulation instability is eliminated when the PV array operates in its constant current region. Second, the PV voltage transient behavior is now independent of the operating point of the PV source.