Operating efficiency enhancement of hybrid energy storage system for IPMSM drives

This paper proposes a control strategy to enhance the operating efficiency of a Hybrid Energy Storage System (HESS) for an Interior Permanent Magnet Synchronous Motor (IPMSM) drive. In this method, the battery and super-capacitor (SC) are connected by an interleaved DC-DC (DD) converter where a bypass DD scheme with the inherent anti-parallel diode of power switches is used to create another shorter path for battery discharge. In this design, an adjustable DC-link voltage is accomplished to fit the characterisations in various motor operating conditions. Then, with the corresponding control design, the proposed HESS can operate in an optimal state to improve efficiency and extend the battery lifetime. To validate the effectiveness of the method, several operation scenarios including acceleration, constant-speed and deceleration of the IPMSM are examined using simulations. This is further supported through the experimental study. The test results obtained under the buck, boost and bypass converter scenarios consolidate the feasibility and practicality of the proposed approach in an attempt for potential electric vehicle applications.