Determining the appropriate size of PV generation in distribution system considering voltage stability

As photovoltaic (PV) generation starts to play a vital role in distribution network; the requirement to assess the effect of this type of renewable energy source on the system voltage stability becomes important. In this paper, the PV modules model is based on the single-diode five-parameter model considering environmental conditions. The generated power from PV is recorded every time step throughout a defined duration, along with the load data using a time varying load model. At each time step, the steady-state operation of the system is analyzed by AC load flow calculation. From the results of the power flow analysis, the PQ voltage stability index (PQVSI) can be determined to indicate how close the system´s current operating condition to the voltage instability condition. Utilizing this index as a main criterion, this paper shows how to specify the appropriate location, size, as well as control mode of the PV farm. Furthermore, it also demonstrates the benefit of operating the PV generation system at the power factor less than unity.