Power conditioning for energy systems in green buildings

Abstract

This research work proposes an improved model of stand-alone renewable energy system for green buildings by using a sinusoidal pulse width modulation (SPWM) multilevel inverter with a smaller number of power switches. The energy sources for this system is photovoltaic (PV) solar panels. The main advantage of using multilevel inverter rather than normal two-level inverter is the reduction in the output voltage harmonics and this leads to a reduction in the filter size. In this case, the number of power switches used as well as the number of the gate driver circuits required is less compared to the cascaded H-bridge multilevel inverter (CHMI), therefore the weight and switching losses due to the inverter is reduced. To test the effectiveness of the proposed model simulations are carried out using MATLAB/Simulink under temperature and irradiance varying conditions. In addition to the use of the multilevel inverter, a perturb and observe (P&O) maximum power point tracking (MPPT) algorithm is used for the PV array and a feedforward control system is used for the output voltage control. This research work is carried out to develop a model of stand-alone renewable energy system which is capable to provide constant 240 volts to the load at 50 Hz irrespective to the disturbances on the PV side. Simulations are carried out for both constant as well as for varying conditions and it is found that the output voltage of the inverter is constant and stable for both the cases at 240 volts, 50 Hz.