Implementation aspects of Field Oriented Control of an Induction Machine for a Hybrid Electric Vehicle

The aim of this paper is to describe the practical aspects involved with the implementation of field oriented control (FOC) applied to a model hybrid electric vehicle (HEV) [1]. The well-established theory of FOC is described and translated into different implementation steps. In this paper we aspire to fill the gap between theory and practice. The paper starts with deriving the relevant parameters from manufacturer supplied data and some additional tests performed on the motor. These parameters are then translated into set-points and limit values by representing the inverter as a Yconnected voltage source and by investigating the relation between the rated values of the motor and the d/q-components. The implementation steps further include PWM generation with SVPWM and the design of the flux controller and the torque controller with adaptive anti-windup. The input signals are translated into a reference signal for the torque controller. Finally, the power flow management of the series HEV is discussed. For some of the problems encountered during implementation, practical workarounds are presented. EVS25 Copyright Keywords— Field Oriented Control, Hybrid Electric Vehicle, Power Flow Management, SVPWM 1. System description The HEV that is the subject of this paper consists of an induction motor that is connected (delta connection) to a three-phase inverter. The dc-link of the inverter is fed on the one hand from a battery pack through a bi-directional dc-dc converter and on the other hand from a petrol-engine generator through a power-factor-correction (PFC) converter. The rated values of the motor are as follows: PN = 4 kW, nN = 2850 rpm, ηN = 86 %, UN = 420 V, IN = 7.8 A, cos(φN) = 0.91. The maximum allowable line voltage of the motor in Δ-connection (UMAX) is 242 V. The inverter contains three IGBT half-bridges that produce a pulse-width modulated (PWM) output voltage. The PWM values for the output phases are imposed by the control algorithm that is built using MATLAB/SIMULINK. The inverter has a rated power of 23 kVA and is operated at a switching frequency of 10 kHz. The maximum RMS value of the phase current equals 33 A. The dc-link voltage is chosen to be 400 VDC nominally. The torque produced by the induction motor is controlled using field oriented control (FOC). This control technique is also commonly referred to as vector control.