Control of three phase grid-connected photovoltaic arrays with open loop maximum power point tracking

This paper proposes a control technique for medium and large scale PV arrays connected to the power system grid. The array is interfaced to the grid through power electronic converters to change output voltages and currents from DC to AC quantities. A DC-DC boost converter is used to step up the output voltage of the array and extract maximum power under a given temperature and solar irradiation. A voltage source inverter under current control mode is connected to the DC converter through a DC link capacitor used to store power and act as a fixed DC bus for the inverter. A controller is used to regulate the capacitor voltage and keep it constant by balancing its input and output powers. The inverter is controlled in the rotating (dq) frame to inject AC power into the grid. An open loop maximum power point tracking (MPPT) technique is proposed to quickly locate the maximum power point (MPP) of the PV array under varying weather conditions. This technique is simple to implement and does not require periodic measurements of the array output power as in most closed loop MPPT techniques. MATLAB software was used to simulate the system to confirm the performance and effectiveness of the proposed technique.