Reduction of THD Using Controlled Inverter for EV Motors

The rapid proliferation of electric vehicles (EVs) has intensified the demand for advanced power electronics systems capable of delivering high efficiency, reliability, and compliance with stringent standards. Inverters, as a critical component in EV powertrains, perform the essential function of converting direct current (DC) from batteries into alternating current (AC) to drive motors. However, conventional inverters often suffer from significant Total Harmonic Distortion (THD), which adversely impacts motor efficiency, exacerbates thermal and electromagnetic stress, and diminishes the overall lifespan of the system. Addressing these challenges, this study introduces an enhanced inverter control strategy combining Sinusoidal Pulse Width Modulation (SPWM) with a Proportional-Integral (PI) controller, specifically optimized to reduce THD and improve system performance under dynamic conditions. The proposed methodology leverages SPWM for high-precision modulation of inverter switches, ensuring smooth and efficient power conversion. The inclusion of a PI controller facilitates real-time adjustment of voltage and frequency, maintaining a constant voltage-to-frequency ratio critical for minimizing harmonic content and ensuring stable motor operation. The controller parameters are meticulously tuned using the Ziegler-Nichols method, achieving optimal proportional and integral gains tailored for dynamic load variations. A comprehensive simulation framework is developed in MATLAB/Simulink, incorporating key EV powertrain components such as a multilevel inverter, a three-phase induction motor, and variable load profiles to emulate real-world conditions. Simulation results demonstrate a significant reduction in THD, from an initial 21.18% without control to a mere 0.49% with the proposed SPWM-PI controller, surpassing the IEEE 519 harmonic standard requirements. Furthermore, the system exhibits improved motor speed regulation, enhanced torque stability, and superior power quality across varying modulation indices and load scenarios. These improvements not only enhance the operational reliability of EV powertrains but also contribute to increased energy efficiency, reduced thermal stress, and prolonged component lifespan. Compared to existing harmonic mitigation techniques, the proposed approach offers a balance between computational efficiency and harmonic suppression, making it suitable for real-time embedded implementations in commercial EVs. This study provides a scalable and cost-effective solution for modern EV applications, addressing the critical challenges of harmonic distortion and powertrain optimization. The findings serve as a foundation for future advancements in adaptive control strategies, further promoting sustainable and high-performing EV technologies.