Several studies on voltage stability analysis of electric systems with high photovoltaic (PV) penetration have been conducted at a power-transmission level, but very few have focused on small-area networks of low voltage. As a distribution system has its special characteristics-high R/X ratio, long tap switching delay, small PV units, and so on-PV integration impacts also need to be investigated thoroughly at a distribution level. In this paper, the IEEE 13 bus system has been modified and extended to explore network stability impacts of variable PV generation, and the results show that a voltage stability issue with PV integration does exist in distribution networks. Simulation comparisons demonstrate that distribution networks are traditionally designed for heavily loaded situations exclusive of PVs, but they can still operate under low PV penetration levels without cloud-induced voltage-stability problems. It is also demonstrated that voltage instability can effectively be solved by PV inverter reactive power support if this scheme is allowed by the standards in the near future.
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