Investigation of Impacts of Solar PV on Transmission System Voltage Stability Considering Load Characteristics and Protection

Paper in proceeding, 2017

This paper presents an investigation on possible effects of large scale integration of solar photovoltaics (PVs) on the voltage stability of the transmission grid. The time-domain simulation approach has been used in a case study using the Nordic-32 test system which approximately represents the Swedish transmission system. The simulation study has been carried out in PSS/E for different penetration levels of solar PVs and solar irradiance conditions considering different load characteristics and detailed model of distance relays. The main question to be addressed by the study is how the location and size of the PV plants, load characteristics and the transmission system distance protection can adversely affect the post-disturbance voltage recovery time and thereby the overall voltage stability. It has been found that the post-disturbance voltage recovery time increased by 100% with 30% PV penetration. Another interesting finding is that in the case of high PV penetration, the PV plants can either support or adversely affect the voltage stability of the system, depending on changes in the irradiance and the load level during the day. That is that during periods when the PV plants produce their rated active power, the system was more prone to voltage instability after being subjected to a disturbance compared to the periods where the PV plants produce only reactive power which supports the voltage stability.