Abstract
Fault tolerance has been known as one of the main advantages of multiphase drives. When an open-circuit fault happens, smooth torque can be obtained without any additional hardware. However, a reconfiguration strategy is required to determine new reference currents. Despite advantages of non-sinusoidal electromotive forces (NS-EMFs) such as high torque density, multi-harmonics existing in NS-EMFs cause more challenges for control, especially under faulty conditions. Therefore, to guarantee high-quality vector control of multiphase drives with multi-harmonic NS-EMFs, this two-part study proposes control schemes using adaptive linear neurons (Adalines) to adaptively eliminate torque ripples. The proposed simple Adalines are efficient because of taking advantage of the knowledge of rotor position and of torque harmonic rank induced by the NS-EMFs. The control scheme using an Adaline for healthy mode was described in part I of this study. In this second part, the control scheme using another Adaline for an open-circuit operation, under the impacts of multi-harmonics in NS-EMFs, is proposed. Notably, smooth torque and similar copper losses in the remaining healthy phases can be obtained. Experimental tests are carried out on a seven-phase permanent magnet synchronous machine (PMSM) with a high total harmonic distortion (THD = 38%) of NS-EMFs. A demonstration video is provided with this paper.
Highlights
Stage 1: The conventional rotor field-oriented control (RFOC) scheme with maximum torque per ampere (MTPA) strategy is used in healthy condition (“MTPA_HM”) as explicitly described in the first part of this study; Stage 2: Phase A is opened without any reconfigurations; Stage 3: The RFOC scheme is preserved but MTPA_Fault is applied (Figure 1); Stage 4: The proposed control scheme using Adaline_Fault and equal copper losses (ECL) strategy (Figure 2), briefly called Adaline_Fault, is applied
(a) rotating speed variations; and (b) reference torque variations. This part of the study has proposed a control scheme to adaptively improve the quality of non-sinusoidal electromotive forces (NS-EMFs) multiphase drives with an open-circuit fault
The proposed scheme has been validated on a seven-phase permanent magnet synchronous machine (PMSM) with a high THD of NS-EMFs
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. In faulty mode, the existing MTPA strategy used in the conventional RFOC scheme with PI controllers will be utilized to compare with the proposed control scheme in this study In this part of the study, a control scheme is proposed for multiphase machines considering multi-harmonics of NS-EMFs in a post-fault operation. Compared with the conventional RFOC using MTPA strategy [9,10], ECL strategy used in the proposed Adaline-based control scheme allows more similar copper losses in the remaining healthy phases, avoiding the overheating of the remaining phase windings. The proposed Adaline-based control scheme using ECL strategy is numerically and experimentally tested on a seven-phase PMSM with a high THD of NS-EMFs. As previously mentioned, the proposed scheme is compared with the conventional RFOC using the MTPA strategy to prove its superiority.
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