Investigation of Model Reference Parameter Adaptive SRM Drives EPE-PEMC ‘04 Conference Laszlo Szamel Department of Electric Power Engineering Budapest University of Technology and Economics 1111 Budapest, Egry József u. 18, Hungary Phone (49) 1 4632971 Fax (49) 4633600 E-Mail: szamel@eik.bme.hu WWW: http://www.vgt.bme.hu Abstract - Nowadays switched reluctance motor (SRM) drives have been widely used in the field of controlled electric motor drives. The paper proposes a model reference adaptive control method for SRM drives. The main goal of the drive control is to improve dynamical performance by compensating for the motor nonlinearities. The ripple free operation can be realize only with an current waveform depending on the angle, speed and torque. The proposed ripple reduced method changes only the turn-on and the turn-off angle in function of the speed and current reference. One of the advantages of using the ripple –reduced method that it does not need the real-time calculation or measuring the motor torque. So it can be implemented on a cheap microcontroller. The test of this control method was performed in an experimental drive system. A SRM of 6/8 pole and 4 kW rated power was used. Simulation and experimental results are presented. I. INTRODUCTION In motion control systems are robustness against parameter changes and disturbance rejection of main interest. The model reference adaptive control has the following features: − It makes the compliance of the system with varying operational conditions possible and ensures the behavior of the controlled system according to the prescribed reference model. − It means such a special type of adaptive systems which results in nonlinear control systems. This is the reason why the analytical analysis is completed by Lyapunov stability criterium or by hyper- stability principle. − Its planning and application is closely related to the using of computer methods. − Simple realisation of the control algorithm. In this paper the application of a model reference parameter adaptive control to switched reluctance motors is presented. II. DRIVE SYSTEM The block scheme of the examined drive system is shown in Fig.1. A SRM of 6/8 pole and 4 kW rated power was used. The supply unit consists of three main blocks, namely the RECTIFIER, the FILTER and the INVERTER. The inverter is a pulsed width modulated (PWM) one, marked with QP in the figure and it contains one-one switching transistor per phase and a brake chopper, not shown in the figure. The common point of phase windings is supplied by the PWM inverter. It is of autonomous operation and has an inner current control loop. The other ends of phase windings are connected to the phase switching transistors. It follows from the operational principle of SRM [1] [3] that its phase windings are to be excited at a well determined angle of the rotor position in an appropriate order. This is why a Rotor Position Sensor is to be mounted on the shaft of the motor. In our case the position sensor is a resolver. It can be calculated from the pole numbers that the phase switchings have to follow each other by 15 degree. The resolver is supplied by an oscillator circuit, their signals are evaluated by a Position Decoder. Fig.1. Block scheme of drive system The Position Decoder has two outputs: the Angle and Speed signals. Based on the two signals, the Angle Controller composes the Control signals for the phase switching transistors. Fundamentally, SRM drives have two control loops, the outer one is the speed loop, Speed Controller and the inner one is the current loop, Current Controller. The output signal of the Speed Controller serves for a Current reference signal of the Current Controller. The hardware and software tools together fulfil the two-loop control. The Current Controller produces the control signal for the PWM inverter, and receives the Current signal from the PWM inverter at the same time. The fundamental part of the control unit is a single-chip microcontroller. It contains a clock generator with 12 MHz, an 256x8 on-chip RAM, four 16 bit timer/counters, a fast 32 bit division unit and a 16 bit multiplication unit, 12 multiplexed input 8-bit A/D converter with programmable reference voltage, two full duplex serial interfaces, a compare/capture unit. The microcontroller executes the instructions of program stored in EPROM memory. The actual values of program parameters and variables are stored in the inner, 256x8-bit RECTIFIER Mains FILTER INVERTER Reluctance Motor Switched Rotor Position Sensor signal Torque limit Speed signal Angle Position Decoder Current Controller Controller Speed Control signals signal Current signal + _ Angle Controller Speed reference Current reference QP brought to you by CORE View metadata, citation and similar papers at core.ac.uk provided by Repository of the Academy's Library