A Three-Phase Power Flow Approach for Integrated 3-Wire MV and 4-Wire Multigrounded LV Networks With Rooftop Solar PV

Abstract

With increasing level of rooftop solar photovoltaic (PV) penetration into low voltage (LV) distribution networks, analysis with realistic network models is necessary for adequate capturing of network behavior. Traditional three-phase 3-wire power flow approach lacks the capability of exact analysis of 4-wire multigrounded LV networks due to the approximation of merging the neutral wire admittance into the phase wire admittances. Such an approximation may not be desirable when neutral wire and grounding effects need to be assessed, especially in the presence of single-phase solar power injection that may cause a significant level of network unbalance. This paper proposes a three-phase power flow approach for distribution networks while preserving the original 3-wire and 4-wire configurations for more accurate estimation of rooftop PV impacts on different phases and neutrals. A three-phase transformer model is developed to interface between the 3-wire medium voltage (MV) and the 4-wire LV networks. Also an integrated network model is developed for an explicit representation of different phases, neutral wires and groundings of a distribution system. A series of power flow calculations have been performed using the proposed approach to investigate the impacts of single-phase variable PV generation on an Australian distribution system and results are presented. Abstract-With increasing level of rooftop solar PV penetration into LV distribution networks, analysis with realistic network models is necessary for adequate capturing of network behavior. Traditional three-phase 3-wire power flow approach lacks the capability of exact analysis of 4-wire multigrounded LV networks due to the approximation of merging the neutral wire admittance into the phase wire admittances. Such an approximation may not be desirable when neutral wire and grounding effects need to be assessed, especially in the presence of single-phase solar power injection that may cause a significant level of network unbalance. This paper proposes a three-phase power flow approach for distribution networks while preserving the original 3-wire and 4-wire configurations for more accurate estimation of rooftop PV impacts on different phases and neutrals. A three-phase transformer model is developed to interface between the 3-wire MV and the 4-wire LV networks. Also an integrated network model is developed for an explicit representation of different phases, neutral wires and groundings of a distribution system. A series of power flow calculations have been performed using the proposed approach to investigate the impacts of single-phase variable PV generation on an Australian distribution system and results are presented.Index Terms-Thee-phase distribution networks, 3-wire and 4-wire multigrounded systems, Three-phase power flow, Rooftop solar PV impacts.

Alleviation of Neutral-to-Ground Potential Rise Under Unbalanced Allocation of Rooftop PV Using Distributed Energy Storage

“…3. In a previous work [17], authors developed a power flow approach for integrated 3-wire and 4-wire multigrounded networks and investigated the PV impact on an Australian distribution system where the neutral grounding resistances in the LV feeders are elevated because of the bonding of the earth wire with the non-metallic water reticulation system [2]. The results show that the neutral voltage can exceed the acceptable level of 0.5 V [3] in a feeder with an unbalanced allocation of PV, as shown in Fig.…”

Community Energy Storage for Neutral Voltage Rise Mitigation in Four-Wire Multigrounded LV Feeders With Unbalanced Solar PV Allocation

“…Modeling and simulation of the test system is performed using a MATLAB based three-phase power flow analysis tool [28] developed by the authors which is capable to deal with low and medium voltage distribution networks with different wiring configurations, including solar PV and energy storage systems. Simulation time step is determined based on the resolution of the measured PV data.…”

A New Method to Monitor the Primary Neutral Integrity in Multi-Grounded Neutral Systems

“…However, in this method, the multiple grounding electrodes were represented by only one node. Other research about the MGN system mainly focuses on the power flow analysis or ground fault analysis [7][8][9][10][11], and the research on the broken neutral integrity monitoring is relatively little. Some researchers have proposed the method of measuring the primary neutral impedance, such as "fall of potential"-based methods [12] and "staged fault"-based methods.…”