Control of a double-stage-grid connected PV generator under grid faults

This paper presents a command of a typical double-stage grid-connected photovoltaic system functioning under normal and disturbance operation modes. The aim of this proposed command is to contribute to system stability and ensure connection as long as possible during grid faults. Under Normal Operation Mode (NOM), the command extracts the maximum photovoltaic power and regulates, respectively, the dc-link voltage and the inverter output current. Otherwise, under grid Faulty Operation Mode (FOM), the proposed command permits to adjustment of delivered photovoltaic (PV) power with the inverter output power at the Point of Common Coupling (PCC). It changes the command signal from its Maximum Power Point (MPP) voltage to a new voltage corresponding to less power. According to the state of the grid voltage at the PCC and the inverter rating current, the control unit generates instantaneously powers that the inverter can inject to the alternative side. Those powers will be used as references to control the inverter output current, the dc-link voltage and the activation or deactivation of the MPPT. A case study of a 3kW solar generator simulated in Matlab/Simulink software is used to illustrate the proposed control.