Design and Control of a Multi-Functional Energy Recovery Power Accumulator Battery Pack Testing System for Electric Vehicles

In this paper, aiming at the energy loss and harmonic problems in the conventional power accumulator battery pack testing system (PABPTS), an improved multi-functional energy recovery PABPTS (ERPABPTS) for electric vehicles (EVs) was proposed. The improved system has the functions of harmonic detection, suppression, reactive compensation and energy recovery. The ERPABPTS, which contains a bi-directional buck-boost direct current (DC)-DC converter and a bi-directional alternating current (AC)-DC converter with an inductor-capacitor-inductor (LCL) type filter interfacing to the AC-grid, is proposed. System configuration and operation principle of the combined system are discussed first, then, the reactive compensation and harmonic suppression controller under balanced grid-voltage condition are presented. Design of a fourth order band-pass Butterworth filter for current harmonic detection is put forward, and the reactive compensator design procedure considering the non-linear load is also illustrated. The proposed scheme is implemented in a 175-kW prototype in the laboratory. Simulation and experimental results show that the combined configuration can effectively realize energy recovery for high accuracy current test requirement, meanwhile, can effectively achieve reactive compensation and current harmonic suppression.