Accommodating a High Penetration of PHEVs and PV Electricity in Residential Distribution Systems

by Mohamed ElNozahy

Institution: University of Waterloo
Year: 2015
Keywords: Photovoltaic systems; Energy storage systems; Plug-in hybrid electric vehicles; DC distribution systems
Record ID: 2058056
Full text PDF: http://hdl.handle.net/10012/9258


Global warming is threatening the world’s delicate ecosystems to the point where the extinction of numerous species is becoming increasingly likely. Experts have determined that avoiding such a disaster requires an 80% reduction in the 1990 levels of global greenhouse gas emissions by 2050. The problem has been exacerbated by the booming demand for electrical energy. This situation creates a complex dilemma: on the one hand, energy sector emissions must be decreased; on the other, electrical energy production must be increased to meet the growing demand. The use of renewable emission-free sources of electrical energy offers a feasible solution to this dilemma. Solar energy in particular, if properly utilized, would be an effective means of meeting worldwide electricity needs. Another viable component of the solution is to replace gasoline-powered vehicles with plug-in hybrid electric vehicles (PHEVs) because of their potential for significantly reducing greenhouse gas emissions from the transportation sector. It was once believed that integrating solar electricity into distribution systems would be relatively straightforward; however, when the penetration level of photovoltaic (PV) systems began to increase, power utilities faced new and unexpected problems, which arose primarily due to the weak chronological coincidence between PV array production and the system peak demand. PV arrays produce their peak output at noon, during low demand periods, resulting in individual instances when the net PV production exceeds the system net demand. Power then flows from low voltage (LV) to medium voltage (MV) networks. Such reverse power flow results in significant over voltages along distribution feeders and excessive power losses. For PHEVs, the situation is the direct opposite because peak demand periods coincide closely with the hours during which the majority of vehicles are parked at residences and are thus probably being charged. This coincidence causes substantial distribution equipment overloading, hence requiring costly system upgrades. Although extensive research has been conducted with respect to the individual impacts of PV electricity and PHEVs on distribution networks, far too little attention has been paid to studying the interaction between these two technologies or the resulting aggregated impacts when both operate in parallel. The goal of the research presented in this thesis is to fill this gap by developing a comprehensive benchmark that can be used to analyze the performance of the distribution system under a high penetration of both PV systems and PHEVs. However, the uncertainties associated with existing electrical loads, the PHEV charging demand, and the PV array output complicate the achievement of this goal and necessitate the development of accurate probabilistic models to express them. The establishment of such models and their use in the development of the proposed benchmark represent core contributions of the research presented in this thesis. Assessing the anticipated impacts of…