Investigating BESS-based control of over-voltage in stand-alone PV systems

Department of Electrical and Computer Engineering, University of Namibia, Ongwediva, Namibia

Abstract

Over-voltage events pose significant challenges to the operation and reliability of stand-alone solar photovoltaic (PV) systems, particularly in rural off-grid communities. This research investigates Battery Energy Storage System (BESS)-based control as a voltage regulation strategy for mitigating over-voltage conditions in stand-alone PV systems. The study addresses the critical problem of DC bus voltage instability occurring when solar power generation exceeds load consumption during periods of high irradiance, resulting in voltage levels exceeding 110% of nominal values as defined by IEEE/IEC power quality standards. To carry out the investigation, this study encompasses the design and simulation of a 3.12 kW stand-alone PV system in MATLAB Live Editor, incorporating Canadian Solar CS6P-260P modules in a 4S×3P array, a DC-DC boost converter with Perturb and Observe (P&O) MPPT, and a lithium-ion battery system with PI-controlled bidirectional converter. Three simulation scenarios were evaluated: baseline under Standard Test Conditions without BESS, varying irradiance (0-1800 W/m²) without BESS, and varying irradiance with integrated BESS control. The scenario without BESS considered resulted in peak voltages reaching 2,433.16 V with over-voltage lasting 149.996 s. With BESS-based control enabled, the DC bus voltage was maintained at 370 V (±0.10% stability), within the required 340-400 V range, thereby eliminating the over-voltage condition entirely. The findings of this investigation validate BESS-based control as an efficient, loss-free solution compared to Active Power Curtailment, with direct application to rural electrification in Namibia.