Command Approach of a Typical Double-Stage Grid-Connected PV System Under NOM and SGVD

The paper presents a command approach of a typical double-stage grid-connected PV system functioning under Normal Operation Mode (NOM) and Symmetrical Grid Voltage Dips (SGVD). The aim of this proposed command is to contribute to the system stability and ensure connection as long as possible during grid faults. In NOM, the control approach implemented around the double-stage permits to extract the maximum photovoltaic power and regulates, respectively, the dc-link voltage and the inverter output current. Under SGVD, the command approach developed permits to adjust the delivered 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 a 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 control and the operating mode of the MPPT. A case study of a 3 kW solar generator simulated in Matlab/Simulink software is used to illustrate the proposed control.