Five-phase Induction Machine Research Articles

Open-Phase Fault-Tolerant Direct Torque Control Technique for Five-Phase Induction Motor Drives

Direct torque control (DTC) has been widely used as an alternative to traditional field-oriented control (FOC) methods for three-phase drives. The conventional DTC scheme has been successfully extended to multiphase drives in recent times, using hysteresis regulators to independently track the desired torque and flux in symmetrical five-phase induction machines (IMs). The fault-tolerant capability of multiphase drives is an interesting intrinsic advantage for safety-critical applications, where recent research has demonstrated the effectiveness of FOC schemes to perform ripple-free postfault operation. In spite of the utility of DTC methods in normal operation of the multiphase machine, no extension to manage the postfault operation of the drive is found in the literature. In this paper, a novel fault-tolerant DTC scheme is presented. The performance of the proposed method is experimentally validated in a five-phase IM drive considering an open-phase fault condition. Provided tests analyze steady and transient states, including the transition from pre- to postfault operation. Obtained results prove the interest of the proposal, which ensures the open-phase fault-tolerant capability of DTC-controlled five-phase IM drives.

Dynamic Modeling of a Five-Phase Induction Machine With a Combined Star/Pentagon Stator Winding Connection

The combined star/pentagon connection of five-phase induction machines was recently demonstrated as a promising compromise between conventional star and pentagon connections. It combines the advantages of both star and pentagon connections without any additional hardware for winding changeover. This connection is based on two five-phase single layer concentrated winding sets shifted in space by π/10 and connected in a combined star/pentagon configuration to provide five-phase terminals. Since the combined star/pentagon connected induction machine is fundamentally an asymmetrical ten-phase machine, the machine mathematical model possesses additional subspaces, which affect the behavior of the machine especially under open line conditions. Starting from the conventional five-phase and m -bar squirrel cage induction machine model, the phase-variable model of the combined star/pentagon connection is introduced in this paper. The corresponding equivalent dq model with five decoupled subspaces, which can account for air gap harmonics up to ninth order, is then derived. Finally, it was shown that the machine model could be simply approximated with only two subspaces similar to a conventional five-phase induction machine with sinusoidally distributed winding, where the flux produced by the nonfundamental subspace could be neglected. The model is verified using a 1 kW prototype five-phase induction machine.

Online Estimation of Rotor Variables in Predictive Current Controllers: A Case Study Using Five-Phase Induction Machines

Predictive current control (PCC) has been recently proposed like an alternative to conventional PI-PWM current control techniques. Implemented solutions are based on inaccurate estimation of the rotor electrical variables to reduce the computational cost of the method. In this study, the utility and computational cost of PCC with different methods for the online estimation of the rotor variables are studied. Experimental results are provided to characterize the obtained benefits and drawbacks, using a five-phase induction machine as a case example.

Open Fault Detection and Tolerant Control for a Five Phase Inverter Driving System

This paper proposes a fault detection and the improved fault-tolerant control for an open fault in the five-phase inverter driving system. The five-phase induction machine has a merit of fault-tolerant control due to its increased number of phases. This paper analyzes an open fault pattern of one switch and proposes an effective fault detection method based upon this analysis. The proposed fault detection method using the analyzed patterns is applied in the power inverter. In addition, when the open fault occurs in the one switch of the induction machine driving system, the proposed fault-tolerant control method is used to operate the induction machine using the remaining healthy phases, after performing the fault detection method. Simulation and experiment results are provided to validate the proposed technique.

Operation of five-phase induction motor after loss of one phase of feeding source

The paper deals with the influence of a loss of one phase of a feeding source on the properties of a five-phase induction machine. The attention is paid to the waveforms of the currents in individual stator phases, the increase in torque pulsations and the decrease of speed in emergency operation after the disconnection of a faulty phase of the source. Machines in star, pentagon and pentacle connections are taken into consideration. The conclusions of the theoretical analysis are verified experimentally.

Steady-State Mathematical Modeling of a Five-Phase Induction Machine With a Combined Star/Pentagon Stator Winding Connection

This paper presents the steady-state mathematical model of a five-phase induction machine with a combined star/pentagon connection. The connection splits the stator winding into two five-phase windings displaced in space by $\pi$ /10 and connected in a combined star/pentagon configuration. Recent work limited to an experimental investigation demonstrated that the connection possesses improved fault tolerance when compared to a conventional star-connected stator, as well as avoids the pentagon connection problems. Although the machine has five-phase terminals, it is intrinsically an asymmetrical ten-phase machine, which introduces additional subspaces in the machine's mathematical model. In order to theoretically investigate and thoroughly assess this connection against conventional connections, this paper introduces the steady-state mathematical model based on vector space decomposition and symmetrical component theory. Finite-element analysis is first used to investigate the different harmonic current components induced in the cage rotor circuit, upon which the effect of different subspaces can be clarified and the required transformation matrix from phase variables to their sequence components can be derived. The model is verified using a 1-kW prototype five-phase induction machine.

Multiphase rotor current observers for current predictive control: A five-phase case study

The use of multiphase drives has gained importance in recent times due to some advantages that they provide over conventional three-phase ones. High performance stator current control can be achieved by means of direct command of voltage source inverter. In this context finite-state model predictive control is a very flexible strategy that has been recently proposed and analyzed. Nevertheless, its implementation must solve the problem of estimating rotor quantities, being the conventional solution a simple backtracking procedure. In this respect, observers appear as an attractive alternative. However, while they have been used with FOC, sensorless drives and for fault detection, they have not been used yet for predictive control of drives as a way to provide rotor values estimates. In this paper the authors propose to incorporate a full-order rotor current observer in a finite-state model predictive controller of a five-phase induction machine. Pole placement design based on Butterworth filters is used. The new estimation scheme and the standard procedure are compared. By means of experimental tests, the differences between both approaches and the benefits of including a rotor observer are illustrated and verified.

Comparative Study of Predictive and Resonant Controllers in Fault-Tolerant Five-Phase Induction Motor Drives

One of the most attractive features of multiphase machines is the fault-tolerant capability due to the higher number of phases. Different postfault control strategies based on hysteresis, proportional integral (PI)-resonant, and predictive techniques have been recently proposed. They all proved their capabilities to withstand fault situations and to preserve the fundamental component of the air-gap field, while achieving minimum losses, maximum torque per ampere, and reducing torque vibrations. Nonetheless, due to their recent introduction, no thorough study has yet appeared comparing the performance of these controllers. In this paper, two open-phase fault-tolerant control schemes are experimentally compared in a real five-phase induction machine. The controllers being compared are based on PI-resonant and predictive control techniques, respectively. The experiments include pre- and postfault situations. Obtained results show that both control methods offer nearly the same performance. When compared, predictive control provides faster control response and superior performance at low-speed operation but is found to be less resilient to fault detection delays and to have higher current ripple. Regarding the controller implementation, it is shown that the transition from prefault to postfault operation involves modeling the nonlinear effects observed when an open-phase fault occurs for the predictive controller and proper retuning of the PI trackers for the PI-resonant controller, to ensure postfault operation.

Steady-State Equivalent Circuit of Five-Phase Induction Machines with Different Stator Connections under Open Line Conditions

The steady-state modeling of multiphase induction machines (IMs) with m phases under open-line fault conditions is usually carried out based on symmetrical component theory. Hence, the estimation of the machine characteristic curves usually involves complex mathematical calculations and inversion of high-order matrices, which complicates the analysis. Moreover, the effect of the different subspaces’ impedances on the machine performance cannot be easily recognized using this modeling technique. Instead, this paper presents the first attempt to derive a simple equivalent circuit for a five-phase IM under open-line conditions that includes the effect of all subspaces in a single circuit. The derivation is carried out for both star and pentagon connections. The equivalent circuit can be a simple technique to explain the advantages obtained from a pentagon connection compared to the star connection under open-circuit faults. It can also be used to derive a simple expression for torque gain and torque ripple magnitude for different stator connections based on the circuit parameters. The derived equivalent circuits are verified using a 1-kW five-phase prototype machine.

An Open-End Winding Four-Level Five-Phase Drive

A four-level five-phase open-end winding (OeW) drive topology is introduced in this paper. The drive comprises a five-phase induction machine with open-end stator windings, supplied using two two-level voltage-source inverters with isolated and unequal dc-link voltages, in the ratio 2 : 1. The topology offers the advantages of a modular structure with fewer semiconductor components and has a greater potential for fault tolerance, as compared with an equivalent single-sided four-level drive. Due to the large number of switching states, development of a suitable space vector pulsewidth-modulation (PWM) method can be challenging. Hence, this paper examines the implementation of two-level-shifted carrier-based PWM methods. The effect of dead time on the drive performance is discussed, and it is shown that simultaneous PWM switching of both inverters can lead to degraded output phase voltage waveforms. Detailed analysis of this phenomenon is presented, a solution is proposed, and the modified modulation techniques are incorporated in an experimental setup, at first in conjunction with $V/f$ control. Once the proof of concept has been provided, full field-oriented control is implemented in this OeW drive topology for the first time; detailed experimental testing is conducted, and results are reported.

An Improved Fault-Tolerant Five-Phase Induction Machine Using a Combined Star/Pentagon Single Layer Stator Winding Connection

One of the main merits offered by multiphase machines is their high fault-tolerant capability. Literature has demonstrated that the performance of multiphase induction machines under fault conditions is affected by the employed stator winding connection. In open-loop controlled five-phase machines, the star connection is favorable under healthy conditions while the pentagon connection is favorable and yields a lower derating factor under the open phase condition. In this paper, a new combined star/pentagon single layer winding layout that combines the advantages of both star and pentagon connections is proposed for a five-phase induction machine. Although the proposed winding is intrinsically an asymmetrical ten-phase machine, the proposed connection allows for only five-phase terminals. Moreover, the proposed winding not only yields better flux distribution compared to a conventional single layer winding, but also provides a complete cancellation of the third-order harmonic flux component caused by the induced third sequence currents due to the saturation effect and/or under unbalanced operation. Hence, the machine losses are decreased, which improves the overall machine efficiency. For the healthy case, the machine is similar to a conventional star connected five-phase machine. However, with one phase open, the proposed connection results in a lower derating factor compared to conventional connections for both open-loop and optimal current control techniques. A 1-kW prototype machine is used for experimental verification.

A Method for Optimization of Five-Phase Induction Machines Based on Genetic Algorithms

The optimization of five-phase induction machines is addressed using a new procedure based on genetic algorithms. A constrained optimization model is introduced which considers the main machine dimensions as free variables. Number of stator and rotor slots, winding pitch, and rotor bar inclination angle are among the free design variables. In addition, the relationship between fundamental and third harmonic component of the airgap induction is also considered as a free variable. This relationship is used to shape the airgap induction making it near to a trapezoid, thus potentially increasing the output torque. The underlying machine model used in the optimization process is detailed in previous works and includes the effect of losses and saturation on the steady state performance. Thus, a mixed-integer optimization problem is defined, in which the continuous variables are codified as integer variables making the optimization problem easier to solve. Three objective functions are defined and tested: efficiency, cost of conductor material, and a weighted combination of efficiency and material costs; other objective functions can be defined, too. The proposed method was applied to the optimization of a 5.5-kW prototype machine, and the results are presented and discussed.

Dynamic Modelling and Simulation of FivePhase Induction Motor

In this paper, a dynamic modelling of five-phase induction motor is described in a step by step approach. A dq model based on transformation theory for five-phase induction machine is presented. A detailed implementation of an indirect-type five-phase field oriented control including the hysteresis-type pulse width modulation (PWM) current regulator is described. Simulations have been carried out for different load conditions.

Effect of Stator Winding Connection of Five-Phase Induction Machines on Torque Ripples Under Open Line Condition

One of the main challenges in designing high-power drive systems is the quality of the developed torque. High-torque-ripple magnitudes result in serious vibration and acoustic noise problems that affect the lifetime of a drive train. Multiphase machines intrinsically offer the torque with higher quality and are also being promoted for their high fault tolerant capability when compared with their three-phase counterparts. During open-phase conditions, the induced nonfundamental sequence current components have a detrimental effect on the machine performance especially under open-loop control. Although optimal current control is usually employed to ensure certain optimization criterion, such as minimizing torque ripples, optimizing flux distribution, or minimizing copper loss, are met, it usually entails a sophisticated current controller. This paper studies the effect of a stator winding connection of a five-phase induction machine on the induced torque ripples. Two possible connections, namely, star and pentagon connections are compared under healthy as well as fault conditions with one-line open. The comparison is conducted using both finite-element simulation and experimental results using a 1.5-Hp five-phase prototype induction machine. The comparison shows that the pentagon connection reduces the machine-induced torque ripples and improves the overall machine performance under fault conditions.

Parameterized Model and Performance of Five-Phase Induction Machines including Losses and Saturation

In this paper, the main electrical and magnetic parameters of five-phase machines are described in terms of the main dimensions and the winding characteristics. An analytical model is presented that accounts for the effects of saturation and losses; both effects have been neglected in most published works on high-phase machines. The model validation is performed through finite element analysis for a five-phase machine operating at steady state. In addition, the proposed model was also validated using experimental data obtained for a prototype five-phase machine working under several distinct load conditions and with varying third harmonic airgap induction. Special attention is given to the determination of the losses, due their influence on the overall performance of the machine. As shown through an example, the model and parameterization presented are well suited for the purposes of analysis design and optimization, as in volume reduction and efficiency maximization. To illustrate the model utilization, a comparison of a five-phase machine operating with sinusoidal and trapezoidal airgap induction is presented. The comparison indicates that the effects of saturation and losses can compromise some of the claimed advantages of this type of machine.

IJIREEICE - Electrical, Electronics, Instrumentation and Control

In this paper a fuzzy logic scheme is applied for direct torque fuzzy control (DTFC) of five phase induction machine (FPIM). The proposed DTFC based on fuzzy logic technique switching table is described and compared with conventional direct torque control (DTC). The proposed fuzzy control strategy is simulated using Matlab/Simulink software. The simulation results show that DTFC method reduces torque ripple and stator flux variation and improves dynamic response. High Phase Order (HPO) multiphase motor a type of AC motor that has been developed in the last decade and due to its advantage over the three phase motor, many scientists and researchers focus on it. Each electrical motor that have over three phase stator winding can be in HPO class. Researcher demonstrated that HPO drive motor many advantage over conventional three phase motor drives. Multiphase Motor drives are mostly proposed for high power application such as traction and hybrid vehicles aircraft and etc. The advantage of multiphase machines, with respect to conventional three-phase machines are reduced torque pulsations, reduced dc-link harmonics, higher torque density, greater fault tolerant, improvement of the drive noise characteristic, reduction in the required rating per inverter leg and achieving a high power motor

Parameter Identification of Five-Phase Induction Machines With Single Layer Windings

Despite the increased interest in multiphase induction machines for safety-critical applications, machine parameter identification for the different sequence planes is still a challenging research point. In most available literature, the effect of nonfundamental sequence planes is overlooked due to the assumption of sinusoidal winding distribution and healthy operation. However, in a single layer or concentric winding layout with an odd number of phases, the effect of flux produced by nonfundamental sequence planes cannot be ignored for the open-phase case. This paper proposes a simple offline method to estimate the parameters of a five-phase induction machine corresponding to different sequence planes. The proposed technique can estimate the stator leakage inductance as well as the magnetizing inductance of both fundamental and third sequences by applying a quasi-square voltage to the stator winding while the machine is running at no-load. Consequently, the rotor circuit parameters of the fundamental sequence plane can be simply obtained by deducting the stator impedance from the blocked rotor machine impedance. For the third sequence plane, an approximate relation to estimate these parameters based on the measured fundamental sequence rotor parameters is also given. An experimental 1.5 Hp prototype machine is used to verify the proposed technique.

Sensorless speed control of a five‐phase induction machine under open‐phase condition

Recently, multiphase machines have been promoted as competitors to their three-phase counterparts in high-power safety-critical drive applications. Among numerous advantages of multiphase induction machine (IM) drives, self-starting and operation under open phase(s) stand as the most salient features. With open phase(s), optimal current control provides disturbance- free operation given a set of objective functions. Although hysteresis current control was merely employed in the literature as it offers a simple controller structure to control the remaining healthy phases, it is not suitable for high-power applications. In the literature, multiple synchronous reference frame (dq) control can be an alternative; however, it requires back and forth transformations with several calculations and additional sophistication. In this paper, a simple technique employing adaptive proportional resonant (PR) current controllers is presented to control a five-phase IM under open-phase conditions. Results for both volt/hertz (V/f) and field oriented control (FOC) systems are presented. Moreover, sensorless operation under fault condition is also demonstrated by estimating the machine speed using a rotor flux-based model reference adaptive system (MRAS) speed estimator. The proposed controllers are experimentally verified and compared. Although FOC provides better dynamic performance, V/f control offers a simpler control structure and a lower number of PR controllers.

High Performances of Five–Phase Induction Machine Feeding by A [3 × 5] Matrix Converter

Abstract In this paper, we study an analytic technique to control matrix converter for a four-quadrant five-phase induction machine drive with use PWM five intervals modulation strategy. The multiphase induction machine is feeding by a matrix converter using a three-phase network. Special emphasis is given to the sinusoidal five phase voltage in the output and five phase voltage input current modulation. Simulation results are presented.

Effect of Stator Winding Connection on Performance of Five-Phase Induction Machines

This paper studies the effect of stator winding configuration on the performance of five-phase induction machines under healthy as well as faulty conditions. The study compares two connections, namely, star and pentagon connections. The comparison is conducted using both simulation and experimental results. The steady-state model based on symmetrical components theory is introduced for both connections with one-line open due to a converter fault, and the corresponding machine characteristic curves are estimated. During faults, two alternatives for machine operation are possible, namely, open-loop control and optimal current control. While the first alternative corresponds to higher torque ripple and unbalanced winding currents, the second option necessitates unbalanced phase voltages and typically an increased dc-link voltage to source the required optimal currents. Consequently, an increase in the employed semiconductor device rating is required, which is a critical design factor particularly in medium-voltage applications. A new V/f control technique is proposed to ensure disturbance-free operation with one-line open for both winding connections. Based on the unbalanced machine model and experimental verification, the derating factors that ensure safe machine operation for both winding connection alternatives are calculated. The comparison between the two connections shows the superiority of the pentagon connection under fault conditions in terms of efficiency, average torque, torque ripples, and derating factor.