Reactive power management stretegy for photovoltaic based distributed generators operating under nonuniform conditions

Photovoltaic (PV) based distributed generators (DGs) are generally controlled as current source to deliver only active power generated by PV source to the grid. However, reactive power transfer capability of such DGs must be utilized to satisfy load reactive power requirement or to provide reactive power support to the grid. Reactive power management for several such PV based DGs operating in parallel is a challenging task as the available reactive power capacity of each depends on the environmental conditions and may vary continuously. The proposed control strategy considers the effect of environmental conditions on the active power generated by the DGs and accordingly assigns reactive power references for the inverters after computing the available capacity of the inverters. Hence, irrespective of variation in active powers of the DGs, the proposed algorithm not only helps to avoid the overloading of the inverters but also operates all inverters at same apparent power rating to ensure that all inverters are utilized equally. The algorithm is evaluated in terms of its capability to obtain the best solution that gives the least standard deviation of utilization factors of the inverters. Simulation results obtained using MATLAB/Simulink are included to confirm its effectiveness over other algorithms.