Bidirectional Single-Stage Zeta-SEPIC DC-AC Converter for Traction BLDC Motors

Abstract

Low battery voltage and the possibility of regeneration of braking energy are an additional important advantages of electric vehicles (EV) of low and medium power, in which simple and efficient brushless DC motors (BLDCM) are mainly used. Such results can be ensured by applying DC voltage regulation of the BLDCM using a step down/up DC-DC converter. In this work, the already known topology of the single-stage DC-AC converter based on Zeta-type converter is used, however it was developed for bidirectional ability with the obtaining of a SEPIC-type converter for the regenerative braking mode. The main attention in the work is focused on the development of a simple control system for the received object, which is described by high-order nonlinear equations. To regulate the electromagnetic torque, a single-loop current control system is proposed, which changes its structure in traction and braking modes. To compensate the dependence of this system on the angular velocity, as well as the nonlinear dynamics of the speed control loop, appropriate correctors are applied. Conducted simulations of the studied electric drive system operation at different speeds showed the effectiveness of the proposed solutions, as well as the high efficiency of the single-stage DC-AC converter.