Implementation of PWM Control of DC Split Converter Fed Switched Reluctance Motor Drive

Received Jul 27, 2016 Revised Mar 4, 2017 Accepted Mar 20, 2017 The phase winding of Switched Reluctance Motor is excited during the positive increasing region of the phase inductance to get the motoring action. This is performed through a converter. This paper presents the speed control of DC Split converter fed 4 phase 8/6 Switched Reluctance Motor drive using PWM controller. The speed of the motor is controlled by varying the duty ratio of the PWM controller. Simulation results are verified with hardware implementation of the controller. The Hall sensors provided in the motor provide signals corresponding to the position of the rotor. The pulses to the IGBT switches are generated by TMS320F2407A DSP controller. The waveforms of the PWM signals and Hall sensor signals are captured by means of Digital Storage Oscilloscope. Motor phase currents, phase voltages and associated numerical values are captured and analyzed by Power Analyzer. Steady state analysis of the drive has been carried out. Keyword:


INTRODUCTION
Switched Reluctance Motor (SRM) is considered as an alternative to conventional motors because of its advantages like high speed, robustness, high reliability, low cost and high rotor temperature handling capability. The phase winding is excited during the positive increasing region of the phase inductance to get the motoring action through a converter [1][2][3][4]. The conventional asymmetrical converter has the advantages of both hard chopping and soft chopping [1], [2]. The disadvantage of the asymmetrical converter is that it requires two switches in a phase. Two switches per phase can be eliminated by DC split converter [5]. The control strategies of SRM are mainly the Hysteresis Current Control, PWM Control and the Single Pulse Voltage Control. Hysteresis Current Control and PWM Control are used for low and medium speed operations. The Single Pulse Voltage Control controls the speed and torque by regulating the turn-on and turn-off angles. This is suitable for high speed operation, but not to low speed operation because of high current peaks [6][7][8]. The speed control of asymmetrical converter fed 4 phase SRM using DSP is investigated experimentally in [9].
This paper presents the speed control of DC Split converter fed 4 phase 8/6 Switched Reluctance Motor drive using PWM controller. The speed is regulated through a PWM controller [10], [11] in which, the average phase voltage during the conduction period is controlled by varying the duty ratio of the switches. The simulation results are verified and validated through the experimental setup.

SIMULATION OF PWM CONTROLLED DC SPLIT CONVERTER FED SRM DRIVE
The performance of the PWM controlled DC Split converter fed drive is analyzed through simulation. The specifications of the motor are given in Appendix A. In this simulation, the MATLAB inbuilt SRM model is used. The simulation is performed at 2000 rpm & 4000 rpm for three different load torques i.e at no load, 0.5 Nm and 0.75 Nm. Figure 1(a) shows the simulation diagram of drive with PWM control. Figure 1 The simulation waveforms of the PWM controlled DC Split converter fed drive at a speed of 4000 rpm and for a load torque of 0.75 Nm are shown in Figure 2. PWM gate signals applied to IGBTs S 1 to S 4 are shown in Figure 2(a). The sensor signals are shown in Figure 2(b). The motor currents in four phases is shown in Figure 2

HARDWARE IMPLEMENTATION OF PWM CONTROLLED SRM DRIVE
In order to verify the simulation results, experiments have been performed at 4000 rpm and 2000 rpm at same load torques as executed in simulation. The specifications of the SRM are given in Appendix A. The PWM signals applied to IGBTs and Hall sensor output signals are captured by Digital Storage Oscilloscope. The waveforms of the phase currents, phase voltages and various associated numerical values are measured, captured and analyzed by Power Analyzer. The practical waveforms are shown for 4000 rpm at three different load torques. The load is applied by means of Eddy current loading.
The practical waveforms of the PWM controlled DC Split converter fed drive at 4000 rpm & T L = 0.75 Nm are shown in Figure 3. PWM gate signals applied to IGBTs S 1 to S 4 are shown in Figure 3(a). Switching frequency is 14.47 kHz. The sensor signals are shown in Figure 3(b). The motor currents in four phases is shown in Figure 3(c). The peak current and average current in each phase are 23.00 A and 8.45 A respectively. The motor voltages in four phases is shown in Figure 3(d). The expanded view of current and voltage of one phase is shown in Figure 3 The peak current, average current, peak voltage and average voltage obtained through simulation and experiment for 2000 rpm and 4000 rpm at three different load torques is tabulated in Table 1.