Voltage control of stand-alone wind and solar energy system

In this paper wind and solar based stand-alone hybrid energy system is presented for the remote area power system applications. The wind, solar, battery, fuel cell and dump load (i.e., aqua-electrolyzer) are connected to the common dc bus. An ac load is connected to dc bus through a pulse width modulation (PWM) based inverter. Ac voltage at load bus can be maintained at rated value by regulating dc-link voltage (V-dc) at its reference value and by controlling modulation index of PWM inverter. Novel control algorithms are developed to maintain V-dc at its reference voltage irrespective of variations in wind speed, solar irradiance and load. Along with the regulation of V-dc, dc-dc converter (connected between battery and dc-link) acts as a maximum power point tracker (MPPT) for photovoltaic (PV) array. Hence an extra dedicated MPPT circuit is not required to extract maximum power from PV. Control technique for the PWM inverter has been developed to make the line voltages balanced at the point of common coupling (PCC) when the load is unbalanced. Hence, efforts are made to supply quality voltage to the consumers through the stand-alone power system. Detailed modeling of various components of stand-alone system is presented. Extensive simulation results using Matlab/SIMULINK established that the performance of the controllers is quite satisfactory under balanced as well as unbalanced load conditions. Moreover, results with real time digital simulator (RTDS) are presented. (C) 2013 Elsevier Ltd. All rights reserved.