World Automation Congress © 2010 TSI Press. Variable Angle Adjustable-High Speed Control with PI for SRM. Maged N. F. Nashed Power Electronics & Energy Conversion Dep., Electronics Research Institute (ERI), Egypt, e-mail: maged@eri.sci.eg ABSTRACT: This paper presents a new approach to control the turn-off angle θ off used to excite the Switched Reluctance Motor (SRM) used in electric vehicles (EV). The controller selects the turn-off angle which will improve the performance of the electric drive system with turn-on angle constant. This control scheme consisting of classical current controller and speed controller depend on lookup table to choose the best result from it. The turn-on angle of the main inverter switches is fixed at 0 o and the turn-off angle is variable depending on the reference speed and PI current controller. The whole system including motor, inverter and control unit are modeled in Simulink to demonstrate the operation of the system. Keywords: Switched Reluctance Motor (SRM), PI Current control, Speed Control, and Turn-off control 1. INTRODUCTION SRM is a motor using reluctance torque which originates from the change of the magnetic resistance in magnetic circuit. The stator and rotor have the salient pole structure, and they are made from the laminated non oriented electrical steel. The concentrated winding coils are installed only in the stator. SRM has solid features and is characterized by its low cost, since SRM has the structure which is very simpler than induction motor and synchronous motor. Also, winding coils and permanent magnet are not used in the rotor. Therefore, SRM has the possibility of standing high-speed rotations and operations in high temperature state. SRM is suitable for application in EV running on roads with inferior condition and subject to impacts and vibration, [1, 2]. The problems of torque pulsation and noise were big in the initial development of SRM drive existed. However, those problems are being solved by development of the power electronics and improvement in the technology [3]. The improvement of basic performance for the SRM drive contributes to the extension of the application field, and the application of SRM to the electric automobile (EV) begins to be examined recently. This paper presents an automatic turn-off angle (θ off ) control that supports Torque operation of the SRM over its entire speed region. On the other hand to be more reliable, I derived the turn-off angle control equation to be valid for all operating conditions. This approach is an alternative to the classic control of speed and the self-tuning approach to optimization of excitation parameters [4]. This method is simulated with 600W SRM as sample machine to compare with experiment in the next paper. II- SRM Control The process of fluxing and de-fluxing is controlled by switching the supply voltage on at θ On and θ off . At low/medium motor speeds almost all supply voltage is available to force the increase in current, subsequently to the low back-EMF. Current control is necessary at low speed. A. Current Control The method of current regulation is a question of timing and width of the voltage pulses. Broadly speaking there are two main methods: current hysteresis control and voltage-PWM. In both cases, as mentioned above, there is a flux building interval from θ On to θ off , called dwell, and the interval where both mosfets are switched off and the flux decays to zero [5, 6, 7]. In this first control method the magnitude of the current flowing into windings is controlled using a control loop with a current feedback. The current in a motor phase winding is directly measured with a current/voltage converter or a current sense resistor connected in series with the phase. The current is compared with a desired value of current, forming an error signal. The current error is compensated via a control law, such as a PID, and an appropriate control action is taken. The block diagram shows in Fig. 1 that both current and position feedback are needed for controlling the SR motor. Position feedback is