J.A. Riveros

Parameter Identification of Multiphase Induction Machines With Distributed Windings—Part 1: Sinusoidal Excitation Methods

Multiphase induction machines (IMs) are gaining increasing interest in industry due to their numerous advantages over the conventional three-phase ones. A lot of different parameter estimation methods have been developed for three-phase IMs, but the existing literature regarding specific identification techniques for multiphase IMs is almost nonexistent at this point. This paper proposes simple offline methods to estimate the stator resistance and stator leakage inductance of multiphase IMs with distributed windings, under different conditions, utilizing the machines degrees of freedom associated with the nonflux/torque producing current components. Once these parameters are identified, the rotor ones can be easily calculated by combination with the total values obtained from locked-rotor tests. The procedure enables segregation of the stator and rotor parameters in a simple manner, something that is very difficult to achieve in three-phase IMs where, usually, equality of leakage inductances and a constant stator resistance are assumed. In this manner, the magnetizing inductance can be then also more accurately assessed from no-load tests, because the error in its estimation that would be caused by assuming both leakage inductances to be equal is avoided. The proposed methods are experimentally tested on two different five-phase IMs.

Space-Vector PWM With Reduced Common-Mode Voltage for Five-Phase Induction Motor Drives

The growing interest in multiphase electrical drives has required the extension of control schemes and modulation techniques already well known for three-phase drives. Specifically, different and more complex space-vector pulse width modulation (SVPWM) methods have been developed for multiphase machines taking into account the increased number of switching possibilities and the new components resulting from generalized Clarkes transformation. In spite of the intensive work undertaken in the last decade, no SVPWM techniques with common-mode voltage (CMV) reduction have been developed for five-phase drives. This work proposes two SVPWM methods that are capable of reducing the peak-to-peak CMV by 40% and 80% compared to standard five-phase modulation strategies. Reduction of the CMV is done at the expense of higher phase voltage and current distortion. Simulation and experimental results confirm the CMV reduction and quantify the performance penalties of the proposed methods.

Parameter Identification of Multiphase Induction Machines With Distributed Windings—Part 2: Time-Domain Techniques

Multiphase drives are advantageous when high overall system reliability and the reduction in the total power per phase are required. The control strategies for these applications require a good knowledge of the machine parameters to ensure a high quality of the dynamic and steady-state drive performance. Multiphase machines are still not common in industry and it appears that very little work has been done so far in relation to parameter identification techniques. This paper presents and implements a procedure to estimate the parameters of a five-phase induction machine, which can be also extended to other multiphase machines with higher phase numbers. The method is based on standstill time-domain tests and recursive least-squares algorithms. Experimental results are provided to illustrate the developed identification method using tests on two different five-phase induction machines. Correlation with corresponding parameters obtained in Part 1 of this paper is established, where electrical parameters of the same two five-phase inverter-fed induction motor drives were identified using various procedures, based on sinusoidal excitation of the machine.

Multiphase machines in propulsion drives of electric vehicles

Multiphase electric drives have been recently proposed for applications where the highest overall system reliability and power distribution per phase are required. The propulsion drive of an Electric Vehicle (EV) is one of these applications. This paper deals with the use of a five-phase induction machine in the propulsion module of EVs, where the viability of a Predictive Torque Control method (PTC) is analyzed. Simulation results are provided to illustrate the potential of the method, showing fast speed response and low torque ripple.

Estimation of the electrical parameters of a five-phase induction machine using standstill techniques. Part I: Theoretical discussions

The interest in multiphase drives has recently gained attention of the research community due to their applications when high overall system reliability and/or the reduction in the total power per phase are required. The control strategies for these applications require a good knowledge of the machine parameters to avoid deterioration in the drive performance. These electrical machines are very uncommon in the industry, and most researchers must rewind conventional three-phase machines to obtain the multiphase counterparts. However, the rewinding process does not necessarily preserve the original parameters of the machine. This paper presents and validates a procedure to estimate the parameters of a five-phase induction machine. Part I discusses the method which is based on standstill time-domain test and the application of recursive least-square algorithm to the discrete-time model and it can be easily extended to other multiphase machines. Simulation and experimental results are shown in Part II.

Predictive Torque Control for five-phase induction motor drives

Multiphase electric drives have been recently proposed for applications where the highest overall system reliability, combined with a reduction in the total power per phase, are required. Strategies like Field Oriented Control (FOC) and Direct Torque Control (DTC) have been traditionally used in these high performance applications. In this paper, a Predictive Torque Control (PTC) method is introduced as an alternative to FOC and DTC methods. Simulation results are provided to illustrate the potential of the presented control technique, comparing the speed, torque and current performances with those obtained by applying FOC and DTC methods.

Estimation of the electrical parameters of a five-phase induction machine using standstill techniques. Part II: Practical implications

This paper provides a procedure to estimate the parameters of a five-phase induction machine. The standstill time-domain test is used combined with the application of recursive least-square algorithms. Part I discusses the proposed technique. Part II focuses on the validation of the method. A five-phase machine has been obtained rewinding a conventional three-phase counterpart. Simulation and experimental results are shown. The effectiveness of the estimation process is experimentally analyzed using an indirect vector controlled five-phase drive.

Modeling of a five-phase induction motor drive with a faulty phase

Fault-tolerance capability is one of the most attractive characteristics of multiphase machines for industrial applications. Resent research has proven that post-fault ripple-free operation is possible as long as the reference currents generate a smoothly rotating magnetomotive force (MMF). However, the power converter and multiphase machine behaviour and interaction during different types of faults has been hardly studied, modelled and verified. This work analyses the behaviour of a real five-phase induction machine when a fault appear in one phase of the power converter. Two cases are considered, an open-phase fault condition where a power leg of the converter is disconnected, and an open-phase fault condition where the free-wheel diodes continue working. Two models are also presented based on PSIM and SIMULINK for the analytical study of the system under the fault conditions, and verified comparing the obtained results with the real case.

Direct torque control for five-phase induction motor drives with reduced common-mode voltage

Multiphase electric drives have been recently proposed for applications where the highest overall system reliability and the reduction in the total power per phase are required. This is possible thanks to the extension of modulation and control techniques to the multiphase case. However, the design of techniques to reduce the common-mode voltage (CMV) in multiphase drives is still under development. This work analyzes the CMV of a five-phase drive and proposes two direct torque control (DTC) strategies with reduced CMV. Elimination of certain switching states is proposed to obtain good torque and flux response as well as lower peak-to-peak CMV. The reduction of CMV is achieved at the expense of a small increase of the current distortion. Simulation results are provided to confirm the viability of the proposed schemes which reduce for five-phase induction motor drives the peak-to-peak CMV by 40% and 80% compared to the original DTC scheme.

Experimental magnetizing inductance identification in five-phase induction machines

Parameter identification of multiphase machines is a new and interesting topic in the development of multiphase drive systems. Regardless of the applied control technique, an accurate knowledge of the parameters is required to ensure high-performance operation of the machine. This also applies to the magnetizing inductance of the machine. Available identification schemes for multiphase induction machines utilize AC and time-domain methods, some of which require non-conventional winding arrangement or a combination of different procedures that need tests in the non-flux/torque producing plane(s). This paper introduces a simple magnetizing inductance identification technique, which relies on an induced DC voltage test. It is an extension of a procedure previously proposed for the three-phase case to the five-phase induction machine. Experimental results illustrate the reliability and validity of the technique using two different five-phase induction motor drives.