Adaptive State-of-Charge Based Battery Balancing Strategy for Cascaded Multilevel Converter Fed PMSM Electric Vehicle Under Variable Road Inclination

Abstract

The increasing adoption of electric vehicles (EVs) has intensified the need for efficient battery energy management systems capable of maintaining reliable vehicle performance under varying operating conditions. Unequal state-of-charge (SOC) distribution among battery modules can lead to reduced energy utilization, shortened battery lifespan, and degraded vehicle performance, particularly during high-load driving conditions such as uphill operation. This paper presents an adaptive SOC-based battery balancing strategy for a cascaded multilevel converter-fed permanent magnet synchronous motor (PMSM) electric vehicle. The proposed method continuously monitors the SOC of individual battery modules and dynamically assigns modulation priorities based on their charge levels, enabling balanced energy utilization without requiring additional balancing circuits. A PI-controlled DC-link voltage regulator is employed to ensure stable converter operation, while the complete electric vehicle drivetrain, including the battery system, multilevel converter, PMSM, and vehicle dynamics, is developed in the MATLAB/Simulink environment. The proposed system is evaluated under different road inclinations to investigate its performance under varying load conditions. Simulation results demonstrate that the proposed control strategy maintains stable DC-link voltage, effectively balances battery utilization, and sustains satisfactory vehicle performance while reducing the impact of increased road gradient on battery energy consumption. The proposed approach provides a simple and computationally efficient solution for enhancing battery management in multilevel converter-based electric vehicles.