A Technique for Better Energy Management of Single-Stage Topology of Stand-Alone Photovoltaic System

Abstract

This paper proposes a technique for the energy management of a stand-alone photovoltaic system. The proposed system employs a power processing inverter that has a high PV voltage at the input to mitigate the magnitude of AC signal at the output, thus eliminating the use of DC-DC converter and reducing the input capacitor size of PV array. To meet the power requirement of load and to maintain the maximum power point operation of PV array, a battery bank is utilized with a bi-directional converter. An impedance model of the complete system is executed. Based on the model, the control architecture is designed which works in four modes: 1) if load demands > MPP of PV, additional current is extracted from the battery; 2) if load demands < MPP of PV array, extra current is given to the battery; 3) only load management is utilized since the battery bank is not available because of overcharging or under-charging; 4) if irradiation varies then the first mode is used for load requirement. The technique is designed which guarantees the maximum power point tracking of the PV system even without using any intermediate stage of a DC-DC converter, hence making it a single-stage system. MPPT is achieved by effectively controlling the bi-directional converter used for battery charging and discharging purposes. To ensure better utilization of dc voltage, enhanced efficiency, and low less harmonic distortion, a sinusoidal PWM technique is used to drive the inverter. Simulation results are carried out for ensuring better energy management along with MPPT operation demonstrated under uniform operating conditions.