MODELLING AND OPTIMAL CONTROLLERS DESIGN FOR A STAND-ALONE PHOTOVOLTAIC-DIESEL GENERATING UNIT

This papr presents a dynamic model and optiml controllers design for a stand-alone photovoltaicdiesel generating unit. The controller objectives are to limit the continual wariations on load bus voltage and frequency as vel1 as extracting the nmximma photovoltaic generator power. The dynamic behaviour of the closed-loop system folloving connnon disturbances such as load changes, solar insolation mriations and three-phase short circuit is investigated. The use of Photovoltaic (PV) generators in remote areas can pose a problem because solar electricity is generated only during sunny day time hours, while most applications need electricity to be available during cloudy periods and at night. The resolution of this problem Is to use of another back up sources such as a battery enerqy storage and diesel generators t11. The PV/diesel generating unit considered in this paper consists of a PV generator connected to a synchronous generator driven by a diesel engine through a 3-phase line commutated inverter. The tvo generators supply an isolated lmd. Figure 1 shovs the schematic diagram of the PV/diesel generating unit. The PV generator and the 3-phase line commutated inverter vere simulated by nonlinear equatjons !2, 31. These equatiors veze combined vith the nonlinear differential equations of the diesel generator to form the complete 7th order model of PV/diesel unit [41. To simplify the controller design, the reduced 3rd-order linearized model was derived from the complete model by neglecting the transfent of the fast mode state variables. The reduced order mdel form is k=Ax+Bu+rd where