Multiphase machines have several benefits compared with three-phase machines. Their inherently higher reliability makes them attractive in several applications. For instance, the nine-phase motor can operate with up to six open phases in its stator but with torque ripple production. However, the modeling and control schemes for a balanced motor cannot be used since now the stator is unbalanced. In order to allow the multiphase machine to work magnetically balanced even in open-phase conditions, an adequate dq current control should be employed. To achieve this control scheme, it is necessary to have a synchronous-frame modeling of a nine-phase induction motor under open-phase faults, which is developed here. Using it, a synchronous-frame control is derived, still using proportional controllers in the dq current loops. This is possible due to the use of an appropriate voltage decoupling considering the fault condition. Hence, the unbalanced multiphase induction motor can be controlled very similarly as a balanced one, additionally resulting in the torque ripple minimization. Experimental results characterize the operation with open phases. Simulation and finite-element results show the success of the proposed control scheme.

Synchronous-Frame Modeling and dq Current Control of an Unbalanced Nine-Phase Induction Motor Due to Open Phases

This article proposes a current injection-based simultaneous stator winding and permanent magnet (PM) temperature tracking technique for dual three-phase permanent magnet synchronous machines (PMSMs). The estimation models involving winding and PM temperatures are derived for different control strategies with the cancelation of inductances. To improve the tracking performance, a Kalman filter is used for simultaneous winding and PM temperature estimation. Compared with the existing methods, the proposed simultaneous winding and PM temperature estimation technique is independent of the voltage-source nonlinearity effect and is applicable to various machine operating conditions. The main features of the proposed method are underscored by the cancelation of inductance and the elimination of the need for a lookup table. The test results on a laboratory dual three-phase PMSM are used to validate the proposed method under different speed and torque conditions.

Current Injection-Based Simultaneous Stator Winding and PM Temperature Estimation for Dual Three-Phase PMSMs

The five phase induction motor (FPIM) is a very suitable choice for different industrial applications which require high reliability. This is due to the ability of the motor to keep operating even with open stator phases. However, to ensure the right operation and for achieving the desired dynamic performance in terms of reduced torque fluctuations, a fault tolerant control (FTC) methodology must be applied. Because of this, the paper introduces a novel FTC approach for the FPIM drive based on a backstepping controller. The derivation and explanation of the proposed technique are presented and analyzed in a systematic manner. The validation of the proposed FTC strategy has been carried out experimentally using a dSPACE 1104 control board. The test results approve the validity of the designed controller in achieving the control targets which ensures the highest system reliability of the drive that is mostly required in different automotive and industrial applications.

A novel fault tolerant control approach based on backstepping controller for a five phase induction motor drive: Experimental investigation.

A fault-tolerant hybrid current control is proposed for dual three-phase permanent magnet synchronous machines (PMSMs) with one phase open in this article. The maximum torque control, minimum copper loss control, and single three-phase mode control are unified in the proposed method, which is a combination of single three-phase mode control and maximum torque control with different percentages. When the percentage of single three-phase mode control ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$k$ </tex-math></inline-formula> ) varies from 0% to 100%, the hybrid current control transitions from maximum torque control ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$k \,\,=0$ </tex-math></inline-formula> %) to minimum copper loss control ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$k\,\,=50$ </tex-math></inline-formula> %) and then to single three-phase mode ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$k =100$ </tex-math></inline-formula> %). Therefore, the hybrid current control can be switched among the aforementioned three control methods easily and smoothly. Meanwhile, it can be a mixed mode with a tradeoff between the maximum torque control and the minimum copper loss control, such as the minimum copper loss control for a given torque within the full torque range, which can be achieved by changing <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$k$ </tex-math></inline-formula> . The smoothness of transition among the maximum torque control, minimum copper loss control, and single three-phase mode control is verified by experimental results on a prototype machine. 

Fault-Tolerant Hybrid Current Control of Dual Three-Phase PMSM With One Phase Open

In order to not change the space vector pulse width modulation (SVPWM) control strategy during one phase fault, the five-phase six-bridge arm SVPWM fault tolerant control method for fifteen-phase permanent magnet synchronous motor (PMSM) is proposed in this paper, and the thermal stress of fifteen-phase PMSM under different fault-tolerant operations is analyzed. Firstly, the control model of the fifteen-phase PMSM based on three dq axes is established, the generation mode of the SVPWM is analyzed, and the speed and current loop PI regulators of the control system are designed. Secondly, the fault-tolerant control principle of the five-phase six-bridge arm is analyzed and compared with the hysteresis control strategy of equal amplitude and minimum stator loss. Thirdly, the 3D model of the fifteen-phase PMSM is established, the steady-state temperature and the transient temperature rise considering operating conditions under different fault tolerant operations are analyzed, and corresponding temperature rise results of the stator armature windings are compared separately. Finally, the experimental platform is established, the phase current waveforms tested under load conditions confirm the theoretical analysis of five-phase six-bridge arms and hysteresis control, and the test results of steady-state and transient temperature rise confirm the correctness of the simulation prediction.

Thermal Analysis of Fifteen-Phase Permanent Magnet Synchronous Motor Under Different Fault Tolerant Operations

The high fault-tolerance ability is one important application characteristic of multiphase motors. At present, researches on fault-tolerant control of multiphase motors are focused on open-phase faults. When an open-phase fault occurs for the dual three-phase machine, the α 
–
 β subspace and z 
1–
 z 
2 subspace currents are no longer decoupled, so the mathematical model with open phases should be set up. In this study, the mathematical model of the dual three-phase permanent-magnet synchronous motor (PMSM) with one open phase is set up by the vector space decomposition modelling method, and two optimal current control modes of minimum stator loss and maximum torque output are achieved by vector control strategy. The experimental results demonstrate the effectiveness and feasibility of the proposed strategy.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/joe.2018.0061

Tang Wei

Papers

Control strategy for dual three-phase PMSM based on reduced order mathematical model under fault condition due to open phases