Multiphase Machines Research Articles

Comparative performance analysis of different controllers for five-phase induction motor drive

In many situations where it is necessary to reduce the total power consumption per phase while maintaining high overall system dependability, multiphase machines are widely acknowledged as an appealing substitute for traditional three-phase machines. Recent years have seen an acceleration in the field's advances, and a significant body of knowledge has been produced. Fuzzy controllers are an effective method for managing complex processes. However, its characteristic changes across wide variations in parameters' ranges. Our research addresses this problem by using a fuzzy adaptive controller. To improve vector controlled induction Motor drive robustness and guarantee that the five-phase asynchronous machine operates consistently even in the face of disruptions (abrupt changes in the load, rotor resistance variations, and rotor inertia variations, and other factors.), control behavior model (CBM) is applied. The simulation's findings demonstrate that fuzzy adaptive control performs well and is more reliable (Rotor resistance Rr = 200%Rrn, Lm = 0.8*Lmn and J = 200%Jn) when compared to the conventional fuzzy Logic Control and as a classic controller.

Evaluative assessment of a five-phase and three-phase permanent magnet synchronous machine at varied loads and fault conditions

Multiphase machines are very essential for industrial applications that require high reliability of operation. In this paper, a comparative study of three-phase and five-phase inverter fed permanent magnet synchronous motors (PMSMs) was evaluated with respect to their performance characteristics under a healthy state and during transient disturbances such as varied load and double line to ground faults. To avert inherent high oscillations in speed and torque ripples during fault condition, the machine load was significantly reduced to 1/4th of the full load and a post fault current limiting series dynamic braking resistance (SDBR) with a bypassed switch was introduced to enhance the machine fault tolerant level and improve its operational performance. Spectral analyses were carried out to determine the magnitude of harmonic distortion during these conditions. The simulation results show that the five-phase PMSM achieved a reduced oscillatory transient and a faster settling time of speed and torque under a varied load. It also exhibited good harmonic profiles as indicated in the respective % THD values when compared to the three phase PMSM which is prone to high harmonic overheat. However, when subjected to a double line to ground fault, their various %THD values in speed and torque increased with five-phase PMSM still having a reduced %THD values over the three-phase PMSM. Therefore, for a higher fault tolerant capability, greater efficiency with proven reliability, a five-phase PMSM with a fault current limiting series dynamic braking resistance is a better substitute when compared with the three-phase PMSM in industrial applications where safety and loss minimization is a top priority. All simulation processes in this paper were achieved in MATLAB 2015.

Control of dual star induction generator based on multi-level inverter used in wind energy conversion system

This paper presents vector control of dual star induction generator (DSIG) integrated into variable speed wind energy and supplied by three-level NPC converters. Now the DSIG is the most common among multiphase machines when used in high power generation systems, which is associated with two converters. Maximum power point tracking (MPPT) for extracting a maximum of power fluctuating wind speed is illustrated. In order to decrease the fluctuations that appear in the currents generated by DSIG to the electrical network, we propose the NPC structure three-level inverter. Simulation results of a 1.5 MW Wind turbine are presented to illustrate the validity of this application.

Current Control for Multi-Phase Machine under Multiple Open-Faults Condition Using Orthonormalized Extended Clarke Transformation

Current Control for Multi-Phase Machine under Multiple Open-Faults Condition Using Orthonormalized Extended Clarke Transformation

Study on Winding Design of Dual Three-Phase Electrical Machines for Circulating Current Harmonics and Vibration Suppression

The dual three-phase electrical machines (DTP-EMs) have significant advantages and application potential in large-power and high reliability electromagnetic drive system. Nevertheless, one of the main operating challenges of DTP-EMs is the significant high-frequency circulating current harmonics when supplied with voltage-source inverters (VSIs), which will bring unexpected vibration and loss. This paper provides a thorough study on the mutual magnetic coupling effect and design criterion of dual three-phase winding. First, the mathematical model of DTP-EMs is established. Then, the internal mechanism of mutual magnetic coupling and the relationship among the mutual leakage inductance in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$x$</tex-math></inline-formula> - <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$y$</tex-math></inline-formula> subspace, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\alpha$</tex-math></inline-formula> - <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\beta$</tex-math></inline-formula> subspace and stator leakage inductance is revealed. Furthermore, the winding design criterion for DTP-EMs considering high-frequency circulating current harmonics and vibration suppression is proposed. It is drawn that full pitch is required for DTP-EMs to minimize the high-frequency current harmonics and vibration. Finally, two prototypes of the DTP-EM are built and tested to validate the theoretical analysis. This paper provides an effective winding design guide of DTP-EMs for the high-frequency current harmonics suppression and can also be expand to other multi-phase machines.

TUNING OF PI SPEED CONTROLLER IN DIRECT TORQUE CONTROL OFDUAL STAR INDUCTION MOTOR BASED ON GENETIC ALGORITHMS AND NEURO-FUZZY SCHEMES

Thanks to the positive characteristics of the double stator machine (DSIM), its high reliability, and reduced rotor torque ripples, it has become among the most important multiphase machines included in industrial applications. This article aims to apply the two techniques of artificial intelligence represented by the adaptive neuro-fuzzy inference systems (ANFIS) and the genetic algorithm (GA) for direct torque control (DTC) of the DSIM to improve the performance of the machine. The ability to learn and the parallelism of operation characteristics made exploiting the GA to control the machine possible instead of using the proportional integral controller (PI). Fixed switching frequency obtained, given with the vector selection table and hysteresis, allowed the inclusion of the ANFIS technique in the DTC strategy. Two-level inverters are included to feed the DSIM. Several results prove that the two techniques applied, ANFIS and GA, improve the quality of the electromagnetic torque and flux and the dynamic responses of the DSIM.

Field-Weakening Strategy with Modulated Predictive Current Control Applied to Six-Phase Induction Machines

The predictive current controller has arisen as a practicable technique for operating multiphase machines due to its fast dynamic response, control flexibility, and overall good performance. However, this type of controller has limitations, e.g., it tends to suffer from steady-state tracking errors in (d−q) currents; high computational burden; and high (x−y) currents, which become more pronounced at higher speeds, thereby worsening its sustainability. While some proposals have addressed these limitations by incorporating modulation stages and new cost functions, there is still room for improvement, particularly at higher speeds. In line with the pursuit of sustainable advancements, this article explores the integration of a field-weakening strategy with a modulated predictive current controller applied to a six-phase induction machine to improve its performance at current tracking for higher speed ranges. Experimental tests were conducted to validate the effectiveness of the proposed controller, assessing stator current tracking, reduction in the (x−y) currents, and the total harmonic distortion.

Power Quality Analysis of Six Phase Indirect Matrix Converter Based on Multi Phase Generator

Nowadays, multiphase machine drives are considered in many applications, especially for medium and highpower applications. This paper focuses on the topology of the six to three phase (hexaphase) indirect matrix converter (IMC). The matrix converter (MC) is designed based on twelve bidirectional switches for the rectifier stage and six single switches for the inverter stage. It is interfaced to a high-performance, fault-tolerant multiphase permanent magnet synchronous generator (PMSG) on one side and to the grid on the other side. In the literature, the most common MCs are of the three-phase type and papers on multiple input converters (N&gt;3) are not common. This paper deals with all possible configurations of SVM that can be deduced in a hexaphase MC to determine the modulation indexes and then to assess the VTR (Voltage Transfer Ratio). Simulations are performed on a pure inductive load and THD analysis are performed on the input currents of the MC to show the impact of the studied configurations on the system.

Analysis, simulation and experimental strategies of 5-phase permanent magnet motor control

This paper presents a study of control strategies for 5-phase permanent magnet synchronous motors (PMSMs) supplied by a five-leg voltage source inverter. Based on the vectorial decomposition of the multi-phase machine, fictitious machines, magnetically decoupled, allow a more adequate control. In this paper, our study focuses on the vector control of a multi-phase machine using a linear proportional-integral-derivative (PID) current regulator in the cases of sinusoidal and trapezoidal back-electromotive force (EMF) waveforms. In order to determine currents' references, two strategies are adopted. First one aims to minimize copper losses under constant torque, while the second one targets to increase torque for a given copper losses. These techniques are tested under a variable speed control strategy based on a proportional-integral (PI) regulator and experimentally validated.

Hybrid Flatness-Based Control of Dual Star Induction Machine Drive System for More Electrical Aircraft

Abstract This paper develops a precise method control system for tracking control of a power drive system based on a multi-phase machine under motor parameter and load torque variations. By adding a simple feedforward term based on the flatness theory, a conventional flux oriented control (FOC) can be enforced to have a perfect tracking performance under model parameter and load torque variations. Hence, a hybrid flatness-based control (HFBC) technique is applied to the control of a dual star induction machine (DSIM) and compared to a classical vector control strategy regarding tracking behaviour, robustness, and perturbations rejection. Finally, the simulation and experimental results are provided to verify the effectiveness of the proposed HFBC under uncertainties such as motor parameter and load torque variations. Furthermore, an enhancement of the drive system’s control performances is demonstrated by the improvement of the technique of separation of the objectives of tracking and disturbance rejection. The simulation and experimental results are presented, demonstrating the superiority of the HFBC.

General Design Rules for Space Harmonic Cancellation in Multiphase Machines with Multiple Converters and Star-Polygonal Windings

General Design Rules for Space Harmonic Cancellation in Multiphase Machines with Multiple Converters and Star-Polygonal Windings

DIRECT TORQUE CONTROL SCHEME FOR LESS HARMONIC CURRENTS AND TORQUE RIPPLES FOR DUAL STAR INDUCTION MOTOR

Multi-phase machine drives are widely used in high-power applications such as naval propulsion and railway traction. In the control context, direct torque control (DTC), based on the large voltage vectors, is the most used control for a dual-star induction motor. However, these techniques suffer from steady-state errors and torque ripples. Therefore, the stator phase currents have a non-sinusoidal waveform, which leads to high losses and reduces the drive efficiency of the system caused by considerable harmonic currents. This paper presents a modified direct torque control (MDTC) based on two steps to select the appropriate vector to supply the dual star induction motor (DSIM) and effectively reduce the harmonic currents. Moreover, this paper deals with a comparative study of 3-level, 5-level, and modified 5-level torque regulators to reduce the steady-state error and torque ripple. In addition, a PI controller is incorporated for the modified five-level torque regulator to reduce the torque error at low, medium, and high speeds. Moreover, an investigation of switching and core losses has been done for the DSIM drive. Finally, validation results have been presented to prove the effectiveness of developed direct torque control of the dual star induction motor (DSIM) under different operating conditions.

Validation of FEM-Based Parameter Estimation for Variable Phase-Pole Induction Machines

In multiphase electric machines, high-performance control strategies require suitable electrical parameter estimation. This aspect is particularly true for the class of multiphase machines known as variable phase-pole induction machines. This work analyzes, calculates, and experimentally validates different parameter estimation methods for a wound independently-controlled stator coil induction machine, which can dynamically change the phase-pole configuration during real-time operation. The parameter estimation methods are a conventional finite-element analysis-based stator impedance calculation and an implementation of the harmonic plane decomposition theory. Experimental verification illustrates the proposed estimation technique in different machine configurations. Comparing the two analyzed methods, the estimation of all machine parameters based on the harmonic plane decomposition theory well agrees with the practical results. The results indicate that using the proposed method as the initial parameter estimate in a commissioning process for a variable phase-pole drive is possible and beneficial for the reduced computing time.

General Online Current-Harmonic Generation for Increased Torque Capability With Minimum Stator Copper Loss in Fault-Tolerant Multiphase Induction Motor Drives

This paper proposes a current-reference generation method including current harmonic injection (CHI) for enhancing the torque capability of multiphase induction machines (IMs) with negligible space-harmonic effects, which is useful, e.g., during transient overload in electric vehicles. The admissible torque is increased because the harmonics reduce the phase-current peaks, so that the instantaneous peak-current constraint of the drive, usually associated with the converter ratings, is respected. The harmonics are injected in the so-called <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x-y</i> subspaces of the IM, which do not produce torque, so that no torque ripple is introduced. The optimum harmonics are found online for each load, making it possible to minimize the stator copper loss (SCL) per torque in the entire torque range, ensuring full-range minimum loss (FRML). The method is suitable for healthy operation or open-phase faults, and for multiphase machines of any phase number and with either symmetrical or asymmetrical windings. Compared with FRML methods without CHI, higher torque is achieved. Although some techniques were available for increasing the torque capability by CHI, FRML was not attained, laborious offline optimization was needed, or they were only suitable for specific drives or for healthy conditions, unlike the proposal. Experimental results with a symmetrical six-phase IM are provided.

Data-Driven-Based Vector Space Decomposition Modeling of Multiphase Induction Machines

For contemporary variable-speed electric drives, the accuracy of the machine's mathematical model is critical for optimal control performance. Basically, phase variables of multiphase machines are preferably decomposed into multiple orthogonal subspaces based on vector space decomposition (VSD). In the available literature, identifying the correlation between states governed by the dynamic equations and the parameter estimate of different subspaces of multiphase IM remains scarce, especially under unbalanced conditions, where the effect of secondary subspaces sounds influential. Most available literature has relied on simple RL circuit representation to model these secondary subspaces. To this end, this paper presents an effective data-driven-based space harmonic model for n-phase IMs using sparsity-promoting techniques and machine learning with nonlinear dynamical systems to discover the IM governing equations. Moreover, the proposed approach is computationally efficient, and it precisely identifies both the electrical and mechanical dynamics of all subspaces of an IM using a single transient startup run. Additionally, the derived model can be reformulated into the standard canonical form of the induction machine model to easily extract the parameters of all subspaces based on online measurements. Eventually, the proposed modeling approach is experimentally validated using a 1.5 Hp asymmetrical six-phase induction machine.

Simple Predictive Current Control of Asymmetrical Six-Phase Induction Motor With Improved Performance

Despite the intensive research work on the application of model predictive control (MPC) for multi-phase machines, there are many challenges still to be handled such as high circulating currents, variable switching frequency, and high computation burden. This paper proposes a simple, yet efficient predictive current control (PCC) for six-phase induction motor (IM) that reduces considerably circulating current, computation cost, and switching frequency. In the proposed method, a group of four candidate voltage vectors (VVs) is formed in each control sample. Unlike similar methods reported in literature, these candidate vectors are generated based on a simple lookup table and the previous optimal VV. The lookup table is designed such that it allows only one commutation in each control sample. The performance of the proposed method is assessed experimentally using a one kW asymmetrical six-phase induction motor (A6PIM). Different performance indices are investigated to compare the proposed method against two different PCC methods in literature at different operating conditions. The experimental results confirm that about 50% reduction in average switching frequency and 15% in current total harmonic distortion at different speed ranges are observed with the proposed method compared to the conventional one.

A Seven-Phase qZsource Inverter Based on PWM Maximum Constant Boost Control Technique

In the last decade multiphase machines and inverters have attracted much attention from research teams, where excellent overall system reliability and an overall reduction in total power per phase are required, multiphase machines are widely recognized as a promising alternative to traditional three-phase machines. Multiphase inverters are commonly used in various applications, including Electric vehicles (EVs), Renewable energy systems, Motor drives and Aerospace applications. These inverters provide several advantages, including enhanced power quality, lower harmonic distortion, higher power density, and better fault tolerance. By distributing power across multiple phases, these inverters can achieve smoother power delivery, reduced voltage ripple, and higher power transmission capacity. This paper presents a novel inverter design named two-level Seven Phase qZsource inverter based on maximum constant boost control algorithm, The simulations results obtained in this work prove the quality of the improved performances of the proposed topology.

Online Diagnosis and Discrimination of Stator Faults in Six-Phase Induction Motors Based on Voltage Symmetrical Components

In recent years, multiphase machines have been presented as a good alternative to the classical three-phase machines, mainly due to their ability to operate smoothly under fault conditions. Due to multiple stator phase arrangements, existing fault diagnostic (FD) methods are not sufficiently universal and cannot be applied to the multiple configurations of multiphase machines. In this regard, the current research proposes a universal and effective online diagnostics technique based on the computation and monitoring of a relevant severity factor, which is defined as the ratio of the zero, negative and positive voltage symmetrical components. The Short Time Least Square Prony’s (STLSP) approach is used to implement this method online in LabVIEW environment. In addition to the wide applicability of the method, the obviation of any motor parameter estimation and limited requirements regarding variables measurements make the proposed approach extremely advantageous for motors with high number of phases. This article addresses at stator faults in symmetrical six-phase induction machines (6PIM). The proposed method’s experimental results on six-phase motor drive platforms demonstrate the excellent generalization capability of the proposed method, as well as high accuracy and robustness, along with the ability to accurately distinguish between the occurrence of Inter-Turn Short Circuit (ITSC) faults and the presence of Unbalance Supply Voltage (USV) conditions. A 6PIM is put through its paces in both healthy and faulty conditions. The obtained results demonstrate the effectiveness of the proposed method for diagnosing the occurrence of ITSC faults and USV operating conditions with high reliability, fastness and high precision.

DC-Signal Injection for Stator-Resistance Estimation in Symmetrical Six-Phase Induction Motors Under Open-Phase Fault

Multiphase machines are often chosen due to their enhanced fault tolerance. Six-phase ones are especially convenient because they may be fed by off-the-shelf three-phase converters. In particular, those with symmetrical windings offer superior postfault capabilities. On the other hand, estimation of the stator resistance is important for purposes such as thermal monitoring and preserving control performance. Resistance estimation by dc-signal injection provides low sensitivity to parameter deviations compared with other techniques. It has previously been shown that the dc signal can be added in the non-torque-producing (<inline-formula><tex-math notation="LaTeX">$x$</tex-math></inline-formula>-<inline-formula><tex-math notation="LaTeX">$y$</tex-math></inline-formula>) plane of a six-phase machine to avoid the torque disturbances that typically arise in three-phase machines. However, extending this method to the case of an open-phase fault (OPF) is not straightforward, because of the associated current restrictions. This paper addresses dc-signal injection in a symmetrical six-phase induction motor with an OPF. It is shown that, in contrast to healthy operation, the postfault dc injection should be carefully performed so that minimum copper loss, peak phase current and zero-sequence braking torque are achieved. A solution that attains optimum performance in all these aspects simultaneously is proposed. Adapted controller and resistance estimation are also presented. Experimental results confirm the theory.

Bearing Current and Shaft Voltage in Electrical Machines: A Comprehensive Research Review

The reliability assessment of electric machines plays a very critical role in today’s engineering world. The reliability assessment requires a good understanding of electric motors and their root causes. Electric machines mostly fail due to mechanical problems and bearing damage is the main source of this. The bearings can be damaged by mechanical, electrical, and thermal stresses. Among all stresses, the researcher should give special attention to the electrical one, which is bearing current and shaft voltage. This review paper introduces a comprehensive study of bearing current and shaft voltage for inverter-fed electric machines. This study aims to discuss several motor failure processes, as well as the sources and definitions of bearing current and shaft voltage. The different kinds of bearing currents are addressed and the parasitic capacitances, which are the key component to describe bearing current, are determined. Several measurement approaches of bearing current will be discussed. Furthermore, modeling of bearing current will be covered together with the machine’s parasitic capacitances. Moreover, the different bearing current mitigation techniques, as described in many papers, will be thoroughly addressed. The use of rewound multiphase machines for mitigation of bearing current will be proposed and compared to a three-phase machine. Finally, various pulse width modulation techniques of multiphase systems that reduce bearing current and shaft voltage will be investigated, and the findings described in the literature will be summarized for all techniques.