COMPARATIVE ANALYSIS OF CONTROL STRATEGIES FOR THREE-PHASE BIDIRECTIONAL INTERLEAVED BUCK CONVERTERS IN ELECTRIC VEHICLE APPLICATIONS

Abstract

This thesis studies the modeling, control, and performance of a three-phase interleaved bidirectional buck-boost converter designed for applications requiring high efficiency, low ripple, and flexible power flow, such as electric vehicles and renewable energy systems. Interleaving multiple converter phases allows improved current ripple cancellation, thermal distribution, and faster dynamic response. Bidirectional operation further enables the system to manage both charging and discharging conditions, making it suitable for battery storage and regenerative braking scenarios. A conventional Proportional-Integral (PI) control structure is developed as a baseline. It features loops for voltage regulation, total current control, and current balancing across phases. Stability analysis is conducted using small-signal modeling and frequency-domain techniques under varying input voltages and load conditions. Design points are selected based on gain and phase margins that ensure both robustness and responsiveness. The controller is evaluated under nominal and perturbed inductance values to study its response to component mismatches. To enhance dynamic performance and overcome the limitations of linear PI control, a hybrid Sliding Mode–PI control scheme is proposed. This nonlinear controller combines the robustness and fast transient response of Sliding Mode Control (SMC) with the steady-state precision and smoother control action of PI regulation. The existing current balancing loop is retained, simplifying implementation and maintaining phase symmetry. Results validate the effectiveness of both control strategies in buck and boost modes. The key performance metrics such as output voltage regulation, current ripple, phase balancing, and stability under varying loads are analyzed. The outcomes demonstrate the practical potential of the proposed control methods for efficient, scalable, and bidirectional power conversion.