Fast control of PWAM boost-converter-inverter system for HEV/EV motor drives

This paper introduces a fast closed-loop control strategy for a pulse width and amplitude modulation (PWAM) boost-converter-inverter system for HEV/EV motor drives. The PWAM boost-converter-inverter system, in which the dc-link voltage is controlled to have a 6ω fluctuation following the output peak voltage envelop, provides several advantages over the traditional PWM boost-converter-inverter system, such as less switching loss, less dc-link capacitor, higher power density and lighter weight. The boost converter is responsible for generating the fluctuating dc-link voltage, thus needs fast control especially when the output fundamental frequency of the inverter is high. However, the boost converter suffers from low bandwidth due to the existence of a right-half-plane (RHP) zero. First, the traditional control method (voltage-mode control and multiloop control) will be analyzed and compared. Their problems will be identified. Then, a multiloop feedback linearized control strategy is adopted to realize the fast dynamic control requirement. A 1-kW prototype has been built and tested. Theoretical analysis, simulation and experimental results are provided to verify the principle of the fast control strategy.