A Fault-Tolerant Control Method for a PMSM Servo Drive System with a Four-Leg Inverter

Round 1

Reviewer 1 Report

This paper presents the theoretical analysis, simulation and experimental validation of a fault-tolerant control method for PMSM using a four-leg inverter. The paper is generally well-organized and easy to follow. I have a couple of questions/comments to hopefully help improve the manuscript further:

1. "torque current" is more commonly referred to as "torque-producing current".

2. The 3rd and 4th paragraphs of the introduction section is too long. I would recommend breaking them into shorter paragraphs to benefit the fast readers.

3. Section 2 and Section 3 have the same title "Proposed control method".

4. With this 4-leg converter and the fault-tolerant control method, how much power can be delivered under faulty conditions? A percent relative to the rated power should be sufficient.

The English writing needs further check to avoid grammatic errors.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

This paper studies the torque ripple suppression under open-phase fault in three phase four legs PMSM drive systems. In fault conditions, the three order harmonics are considered, SPWM is used instead of SVPWM. Meanwhile, the mathematical model in fault conditions is built and the new current reference considering the three order harmonics is given. Experiments are conducted to verify the effectiveness of the proposed method. However, the contribution of this paper is not quite clear. To end this, following issues should be carefully addressed.

1. What is the difference between the proposed method and the method in [10]? It is stated that the third harmonic flux linkage was taken into account to suppress the torque ripple after open phase fault in [10].

2. What is the difference between the methods for torque ripple suppression in normal condition and fault condition.

3. The current reference expressed by (11) only considers the third order harmonics in back EMF or flux linkage. However, other factors also contribute to the torque, for example, cogging torque, current sampling error, inverter nonlinearities, etc. More details can be found in the recommended references [1]-[3]. The authors are suggested to suppress the torque ripple shown in Fig. 6.

4. In Fig. 6, the time scale should not be 1 s/div because the mechanical frequency at 500 r/min is 8.33Hz and the electrical frequency is 41.67Hz. I believe the torque ripple is not caused by the low precision mechanical assembly and system friction. The authors should do more experiments to figure out the source for the torque ripple.

5. The authors are suggested to analysis the spectrum of the torque ripple so that readers can easily find which harmonic is suppressed. The results shown in Fig. 6 - Fig. 8 are not enough to verify the effectiveness of the proposed method.

6. In the paragraph above Fig. 1, the TR should be turned off in healthy condition while turned on in fault condition. The expression “broken” and “closed” are not professional. The authors are suggested to check the full paper thoroughly about the expression.

Recommended references:

[1] N. Nakao and K. Akatsu, “Suppressing pulsating torques: Torque ripple control for synchronous motors,” IEEE Ind. Appl. Mag., vol. 20, no. 6, pp. 33–44, Nov./Dec. 2014.

[2] J. Ou, Y. Liu, R. Qu, and M. Doppelbauer, “Experimental and theoretical research on cogging torque of PM synchronous motors considering manufacturing tolerances,” IEEE Trans. Ind. Electron., vol. 65, no. 5, pp. 3772–3783, May 2018.

[3] Y. Zuo, X. Zhu, X. Si, and C. H. T. Lee, “Fault-Tolerant Control for Multiple Open-Leg Faults in Open-End Winding Permanent Magnet Synchronous Motor System Based on Winding Reconnection,” IEEE Trans. Power Electron., vol. 36, no. 5, pp. 6068–6078, May 2021.

In the paragraph above Fig. 1, the TR should be turned off in healthy condition while turned on in fault condition. The expression “broken” and “closed” are not professional.

The authors are suggested to check the full paper thoroughly about the expression.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf