Voltage control in low voltage grids with independent operation of on-load tap changer and distributed photovoltaic inverters

Abstract

This paper aims to find the optimal setups of voltage control devices in different configurations of Low Voltage (LV) grids with strong PhotoVoltaic (PV) diffusion by performing dedicated simulations. Distributed PV inverters and On-Load Tap Changer (OLTC) are simulated without considering their coordination, to avoid large investments in new communication infrastructures. Thus, each device independently works to decrease voltage deviations in the respective grid connection point. PV generation and consumption profiles are measured and used in two simulated LV grids, connected to the Medium Voltage (MV) grid by a MV/LV transformer with rated powers of 400 and 250 kVA, respectively. The calculation of the optimal devices setups is addressed as a multi-objective problem, considering objectives of voltage quality, grid losses, and OLTC lifespan increase. Multiple simulations are performed by varying the setup of the voltage controls, and considering different positioning and sizes of the generators. In the hardest case, the ratio between the maximum PV power generation and the maximum load in the whole grid is ≈70%. Pareto analysis is carried out to find the non-dominated solutions and TOPSIS is applied to rank the solutions. Finally, a sensitivity analysis is performed by changing the weights attributed to each objective function.