Sensorless Control of Seven-Phase PMSM Drives Using NSV-SVPWM with Minimum Current Distortion

Abstract

This paper introduces three different algorithms to track the saliency in the seven-phase PMSM to obtain sensorless speed control. These algorithms are based on measuring the amount of change of the stator currents when different active vectors are implemented using the Near Six Vectors-Space Vector Pulse Width Modulation (NSV-SVPWM). Then, a comparison between these algorithms in terms of the Total Harmonics Distortion (THD) associated with implementing each algorithm is presented. The increase in the current distortion in these algorithms is related to the fact that narrow active vectors in these algorithms should be extended to tmin (8us) for proper measurement in the current dynamics due to the oscillation in the currents. However, since the time duration of these active vectors in NSV-SVPWM will be 2.52 times longer than others, it is found that using these long active vectors will result in minimum current distortion. Simulation results are provided to investigate the effect of using the dynamic response of different active vectors on the THD of the current. Moreover, the results demonstrate the effectiveness of the proposed control technique to maintain the performance of the seven-phase PMSM motor drive post the failure in the speed sensor.

Control of 7-phase permanent magnet synchronous motor drive post three failures

“…The proposed FTC technique suggested in the previous section after the loss of phases 'a' and 'c' was implemented using the SABRE simulator as shown in Figure 9. Under healthy operating conditions, the SVPWM technique presented in [36] was utilized. In case of failure of phase 'a', the SVPWM presented in [41] was utilized.…”

“…This procedure is help to enhance the stability of the 7-phase PMSM drive significantly. Unfortunately, the algorithms introduced in [36] and [41] to determine the shaft speed and position in the 7-phase motor running under healthy operating conditions and after a failure of phase 'a', respectively, are no longer applicable after the failure of phases 'a' and 'c'. The reason for this is that the derivative of the stator currents in the faulty phases 'a' and 'c' becomes zero after the fault.…”

“…The idea is to obtain the speed and position of the shaft without using the encoder. The techniques that are used to achieve that are model-based techniques, DTC, and voltage and current excitation methods [32]- [36]. Recently, some techniques have been proposed to maintain the operation of the multiphase drive system post the two types of faults which are: the open-circuit fault in one phase of the multi-phase drive in addition to the fault in the encoder [37], [38].…”

Multi-dimension SVPWM-based sensorless control of 7-phase PMSM drives

“…And few papers used a high-frequency injection method to get the speed and position of the 5-phase motor [16]- [20]. In the past  ISSN: 2302-9285 couple of years, a few papers have been published in the field of the model-based sensorless control of the 7-phase motor [21]- [27] In this year, a new paper has been published in the field of sensorless control of the 7-phase motor based on voltage excitation when a failure in the speed sensor is occurred [28]. The paper has compared three techniques to track the saliency of the 7-phase drive in terms of the current distortion.…”

“…This is because the DC offset of all the saturation saliency position scalars is equal in the new algorithm in all sectors while the dc offset of the position scalars is different in the same sector and between sectors. Finally, the new algorithm can be applied to acquire the saliency position in the 7-phase motor drives when one phase of the motor is lost due to the open-circuit failure while the algorithms published in [28] can't.…”