Abstract
Dynamic voltage instability (DVI) issues are the primary concern in low-voltage distribution network (DN) due to growing integration of low-inertia compressor motor loads such as air-conditioner and refrigerator. The concern of DVI is likely to increase owing to high penetration of rooftop type single-phase photovoltaic (PV) units in DN. On the other hand, DNs are inherently unbalanced as a result of load and line characteristics along with unbalanced PV penetration. This paper examines the impact of imbalance on the dynamic voltage stability (DVS) in DN and provides solutions to mitigate any adverse effects. Dynamic models of the single-phase PV units are developed and utilised in the paper. The degree of unbalanced is defined first, and then its impact on the DVS is investigated. From the investigation, it is observed that degree of instability is increased with the increment of imbalance. The paper has also proposed a mitigation strategy i.e. reactive power injection by PV inverter. Case studies are conducted on modified IEEE 4 bus system which represents a low-voltage DN. Results reveal that reactive power injection by PV inverter can improve the DVS by mitigating the impact of unbalance.
Highlights
The need for clean and affordable energy due to the concern of climate change and increasing energy demand has been leading the power system towards renewable
As the main motivation of this paper is to explore the impact of dynamic voltage stability (DVS) on unbalanced distribution network (DN) with high PV penetration, an average model of the PV systems is developed by replacing the inverter switching, DC link, and PV with an ideal voltage source
Modifications have been accomplished by accommodating PV systems and induction motor (IM) loads at bus 4 through a transformer (Tr2)
Summary
The need for clean and affordable energy due to the concern of climate change and increasing energy demand has been leading the power system towards renewable. Very few studies have discussed the impact of high PV power on the short-term voltage stability (STVS), which is known as DVS [13,14,15,16,17]. In [14, 17], STVS has been investigated for different control strategies of PV systems Both papers [14, 17] have concluded that DVI is likely to occur with high PV penetration without LVRT capability, while it can be enhanced if PV units provide dynamic voltage support. To reduce the impact of imbalance, mitigation strategies are discussed and one of them, namely, reactive power injection by PV inverter is implemented. It has been shown that DVI problems due to increased imbalance can be mitigated by providing reactive power support from PV inverters.
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