Analytical Overvoltage and Power-Sharing Control Method for Photovoltaic-Based Low-Voltage Islanded Microgrid

Abstract

Overvoltage instability is a growing concern in a standalone low-voltage (LV) microgrid (MG) with non-dispatchable intermittent renewable energies such as residential and commercial photovoltaic generators (PVGs). Several overvoltage controllers used in PV arrays have adopted the concept of standard deviation from the maximum power point (MPP) to curtail the generated power. However, these solutions lack presenting analytical expression for the MPP deviation size, settings tuning independent of the MG’s/PV’s characteristics, scalability, and accurate power-sharing in the same control structure. To overcome these limitations, this paper proposes a new analytical MPP tracking (MPPT)-based overvoltage and power-sharing control method using the series equivalent resistance of the PV module model. By applying this analytical expression, the size of the PV array voltage shift to the right-hand side of the MPP is obtained in terms of overvoltage level, while all PVGs proportionally curtail the active power output. The effectiveness of the proposed methodology is shown in various low-demand and high-PV generation cases through a real time digital simulator (RTDS) platform. In addition to the fast and accurate performance, the presented method benefits from the straightforward and communication-free structure as it solely exploits the point of common coupling (PCC) voltage. Also, the method’s threshold does not require re- tuning after MG restructure, ensuring scalability. Without relying on other microgrid facilities, the proposed methodology is accordingly an effective solution for practical PV-based LV MGs.

Keywords

• Analytical overvoltage control
• islanded microgrid (MG)
• maximum power point tracking (MPPT)
• photovoltaic generator (PVG)