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The Impact of PV Inverter Penetration on Voltage Profile and Power Loss in Medium-Voltage Distribution Systems

Waveform of Bus 45 voltage according to active power injected by PV at bus 45 in 56 bus system
Fig. 1. 56 bus system voltage profile with PV at bus 45
Due to environmental problems caused by fossil fuels, the installation of photovoltaic (PV) systems is increasing rapidly worldwide. The impact on the voltage profile of power distribution systems is the most commonly recognized problem caused by high PV inverter use. Accordingly, significant effort has been devoted to assess the static problems produced in distribution systems.

This paper analyzes the impact of PV generators on the voltage profile and power loss in distribution systems, taking into consideration PV inverters of different capacities installed at different locations and with different local reactive power control strategies. To measure voltage impact, sensitivity matrices are used to compare PV generators connected at different locations. After some approximations, it is shown these matrices are only related to the system topology and impedances, results that are also valid for meshed systems. Guidelines are formulated for PV inverters in terms of geographical location and reactive power control scheme.

Compared to centralized PVs, randomly distributed PVs do not necessarily relieve the voltage profile problem. Performance depends on how PV generators are distributed; integration closer to a substation will definitely reduce the possibility of under voltage and overvoltage. Distributed PVs may cause more or less system power loss compared to centralized PVs, depending on the capacity and PV distribution locations. However, if optimally located, distributed PVs yield less system power loss and are less likely to have conflict problems between minimizing power loss and controlling the voltage profile.

Graph to indicate system power loss according to PV power capacity
Fig. 2. IEEE 33 bus system power loss comparison for distributed PV and centralized PV
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