| Increased penetration of solar PV has risen the level of concern among utilities about its potential impact on the system operation and reliability. Reverse powerflow, rise in voltage, unnecessary operations of traditional voltage regulation devices, harmonics, PV islanding, sympathy trips during feeder faults, flicker, etc. are some of the concerns mentioned in 1547.7 which deals with impact of distributed generation (like solar PV) on distribution feeders. One of the main concerns for utility is voltage on a feeder and its regulation.;The studies conducted in this thesis go beyond the current IEEE 1547 practices, 'The Standard for Interconnecting Distributed Resources with Electric Power Systems', which gives recommended practices for DG interconnection. Current standards limit PV Inverters to inject real power only and not participate in voltage regulation. But with several studies showing the benefits of using the readily available capability of inverter to inject reactive power and regulate voltage is being explored which will pave way for the new IEEE 1547 amended guidelines which would allow PV inverters to regulate voltage and supply reactive power. For this study, the PV inverters were allowed to supply reactive power and regulate voltage. In doing so, an investigation of interactions between PV inverters and traditional voltage regulation equipments like tap changing transformer (OLTC), switched capacitor bank (SCB), and step voltage regulator (SVR) were made. The study was conducted on two distinct Florida utility distribution feeders that have high penetration of PV and voltage regulation devices. One of the feeder has single large PV plant (15 MW) while the other feeder has large multiple PV plants (2.6 MW) which amounts to penetration levels of 100% and 35% respectively. Distribution feeder were modeled on an EMTP tool (RTDS) and validated against data provided by the utility. The study focuses on how different PV penetration levels and load levels on the feeder impact operation of voltage regulation devices. In doing so, the study aims at using different operating constraints for OLTC, SCB and SVR. Some candidate methods of operating constraints for OLTC, SCB and SVR are voltage, time, temperature, real power flow, reactive power flow, and combination of any methods mentioned above. As mentioned before, in going beyond the current scope of IEEE 1547, PV inverters were allowed to supply reactive power and different candidate methods currently available on inverter like constant Q, power factor, voltage based and advanced control strategies like German LV std. curve, Volt-VAR curve, Volt-pf curve were used to investigate and mitigate any possible interactions between devices. Possible best suited methods and practices were laid out incase there is an unnecessary interaction between PV inverters and OLTC, SCB and SVR for each feeder. The major observations from this study are: 1. Allowing PV inverters to regulate voltage may not necessarily increase or decrease interactions with voltage regulation devices. 2. Some of the key factors which influence interactions between voltage regulation devices and PV are feeder circuit layout (e.g. overhead line vs. cable,), voltage level, length of feeder, etc), nature of loads, location and size of loads, and location of PV. 3. Based on the cases studied within this work no common trait for defining high penetration PV circuit studies could found. 4. No correlation between PV penetration level, measured by the amount of installed PV capacity vs. feeder loading, and the severity of impact of PV on the circuit operational characteristics could be found in this study.;Concluding from this work is recommended to establish a new set of metrics which truly define the impact severity of PV on distribution feeders, since the current metric of PV penetration level is clearly inadequate. |
