M. Rizwan Khan

A Novel Three-Phase to Five-Phase Transformation Using a Special Transformer Connection

The first five-phase induction motor drive system was proposed in the late 1970s for adjustable speed drive applications. Since then, a considerable research effort has been in place to develop commercially feasible multiphase drive systems. Since the three-phase supply is available from the grid, there is a need to develop a static phase transformation system to obtain a multiphase supply from the available three-phase supply. Thus, this paper proposes a novel transformer connection scheme to convert the three-phase grid supply to a five-phase fixed voltage and fixed frequency supply. The proposed transformer connection outputs five phases and, thus, can be used in applications requiring a five-phase supply. Currently, the five-phase motor drive is a commercially viable solution. The five-phase transmission system can be investigated further as an efficient solution for bulk power transfer. The connection scheme is elaborated by using the simulation and experimental approach to prove the viability of the implementation. The geometry of the fabricated transformer is elaborated in this paper.

MRAS-based sensorless control of a five-phase induction motor drive with a predictive adaptive model

Multi-phase ac motor drives are nowadays considered for various applications, due to numerous advantages that they offer when compared to their three-phase counterparts. Variable speed induction motor drives without mechanical speed sensors at the motor shaft have the attractions of low cost and high reliability. This paper analyses operation of a Model Reference Adaptive System (MRAS)-based sensorless control of vector controlled five-phase induction machine. A linear neural network is designed and trained online by means of back propagation network (BPN) algorithm. Moreover, the neural adaptive model is employed here in prediction mode and in simulation mode. The ANN-MRAS-based sensorless operation of a three-phase induction machine is well established and the same principle is extended in this paper for a five-phase induction machine. Performance, obtainable with hysteresis current control, is illustrated for a number of operating conditions on the basis of simulation results. The results obtained with prediction and simulation mode are compared on the basis of various parameters. Full decoupling of rotor flux control and torque control is realised in both predictive and simulation mode. However, predictive method is shown to provide better dynamics.

Three-Phase to Seven-Phase Power Converting Transformer

Multiphase (more than three-phase electric power) electric drive system is the focus of a significant research in the last decade. Multiphase power transmission system is also investigated in the literature because multiphase transformers are needed at the input of rectifiers. In the multiphase power transmission and multiphase rectifier systems, the number of phases investigated is a multiple of three. However, the variable speed multiphase drive system considered in the literature are mostly of five, seven, nine, eleven, twelve, and fifteen phases. Such multiphase drive systems are invariably supplied from power electronic converters. In contrast, this paper proposes technique to obtain seven-phase output from three-phase supply system using special and novel transformer connections. Thus, with the proposed technique, a pure seven-phase sine-wave voltage/current is obtained, which can be used for motor testing purposes. In addition, a seven-phase power transmission and rectifier system may benefit from the proposed connection scheme. Complete design and testing of the proposed solution is presented. Analytical analysis, simulation, and experimental verifications are presented in the paper.

Extended Kalman filter based speeds estimation of series-connected five-phase two-motor drive system

Abstract The multi-phase machines enables independent control of a few number of machines that are connected in series in a particular manner, and the supply is fed from a single voltage source inverter (VSI). The idea was first implemented for a five-phase series-connected two-motor drive system, but is now applicable to any number of phases. The number of series-connected machines is a function of the phase number of VSI. Variable speed induction motor drives without mechanical speed sensors at the motor shaft have the attractions of low cost and high reliability. To replace the sensor, information of the rotor speed is extracted from measured stator currents and voltages at motor terminals. Open-loop estimators or closed-loop observers are used for this purpose. They differ with respect to accuracy, robustness, and sensitivity against model parameter variations. This paper analyses operation of an EKF-based sensorless control of vector controlled series-connected two-motor five-phase drive system with current control in the stationary reference frame. Results, obtained with fixed voltage and fixed frequency supply fed and hysteresis current control, is presented for various operating conditions on the basis of simulation. The purpose of this paper is to report first time, the simulation results on a sensorless control of a five-phase two-motor series-connected drive system using EKF estimator.

Carrier based PWM technique for a novel three-to-seven phase matrix converter

Multi-phase (more than three-phase) converters are required mainly for feeding variable speed multi-phase drive systems. This paper presents one such solution by using direct ac-ac converter that can be used to supply a seven-phase drive system. Simple Pulse width modulation (PWM) technique is developed for the proposed matrix converter configuration. The developed modulation technique is based on the comparison of high frequency carrier signal with the duty ratios. Although carrier-based scheme is widely employed for control of voltage source inverter, it is very recently being used for controlling a three-phase to three-phase matrix converter. The similar concept is extended in this paper for controlling a three-phase to seven-phase matrix converter. Two techniques are proposed, one outputs 0.75 of the input magnitude and the output reaches 0.7694 of the input with the other method. This is the maximum value of the output voltage in the linear range that can be achieved in this configuration of the matrix converter. The viability of the proposed control techniques is proved using analytical, simulation and experimental approach.

Self regulating three phase-self excited induction generator for standalone generation

This paper presents a simple and effective method for the voltage control of a three phase self excited induction generator (SEIG). The paper is divided into two sections; first section deals with modeling of self compensated SEIG. In the second section a detailed performance analysis of SEIG without and with compensation is carried out. Each of the two models is subjected to different operating conditions by changing excitation and series capacitances, load etc., for a range of different power factor loads. The mathematical model of SEIG is developed in terms of simple quadratic equation rather than traditional nonlinear equation. Therefore, the implemented method does not require numerical solution of the modeled equations. The simulations are carried out by generating programming codes in MATLAB M-file and the veracity of proposed method is established through experimental tests on a 3 phase, 400 V induction motor. The optimum shunt and series capacitances to achieve best output profile are reported in the paper for present case.

Sensorless control of a vector controlled three-phase induction motor drive using artificial neural network

The sensorless drive system is more versatile due to its small size and low cost. Therefore it is advantageous to use the sensorless system where the speed is estimated by means of a control algorithm instead of measuring. This paper presents a new model reference adaptive system (MRAS) speed observer for high-performance field-oriented control induction motor drives using neural networks. The proposed MRAS speed observer uses the current model as an adaptive model. The neural network has been then designed and trained online by employing a back propagation network (BPN) algorithm. In the estimator design using motor parameters and monitored stator voltages and currents also taking the motor speed as a variable. Performance analysis of speed estimator with the change in motor parameters especially resistances of stator and rotor is presented. Its performance under fault condition is also examined. The estimator was designed and simulated in Matlab/Simulink. Simulation result shows a good performance of speed estimator especially under fault condition.

Generalized Theory and Analysis of Scalar Modulation Techniques for a

The basic requirement of all the scalar modulation strategies employed for matrix converter, is to define the desired output voltages. The output phase voltages, if not optimized, results in underutilization of semiconductor device ratings. For better utilization, the output reference phase voltages are modified such that the sinusoidal nature of line voltages is not altered. Multiphase drives are in consideration and much work is being done and reported on multiphase matrix converter-based system. New modulation strategies for such systems are being formulated. Most of these new strategies are based on scalar approach; which in contrast to the space vector pulse width modulation, require addition of friendly harmonics in order to achieve optimized output reference phase voltages and maximum utilization of the matrix converter semiconductor switches. On the other hand, in space vector pulse width modulation, the maximum voltages are inherently achieved. This paper presents a generalized theory, explained in mathematical as well as graphical manner, defining the optimized output reference phase voltages for any number of input and output phases, whether odd or even, for m × n matrix converter. Further, this paper also explores the Venturini method for m × n case. It is found that the method is extendable to 3 × n matrix converters only. Finally, a simple and generalized algorithm, applicable to all m × n matrix converter configurations, is discussed. Results for 3 × 5 matrix converter are validated by simulation and experimental results.

m {\;\times\;} n

Wind and mini/micro hydro electric generation systems are gaining popularity due to their self sustaining attributes. The Self Excited Induction Generators (SEIGs) are most viable generating machines for such applications due to certain merits of these machines. However, in-spite of carrying excellent fault tolerant and rugged construction, their biggest drawback is an inherently poor voltage regulation. This paper presents a simple method for voltage control of a single phase, capacitor excited induction generator. The voltage control strategy adopted for the modeling is based on series connected static capacitor compensation in the main winding of SEIG. The excitation (shunt) capacitance is accommodated in the auxiliary winding to facilitate voltage buildup of the generator. The simulations are carried out by generating programs in MATLAB M-file to get various performance characteristics of SEIG. In order to verify the optimality of the derived model, experimental verification of results of shunt model is carried out on a 1 hp, 220/230 V, single phase induction motor working as SEIG. Reasonable agreement between simulated and experimental results is observed. The obtained results explicitly exhibit the improved voltage regulation and substantially enhanced steady state loading limit of SEIG.

Matrix Converter

Multi-phase self excited induction generators (SEIGs) are increasingly being considered for standalone renewable energy generation due to better fault tolerance and ruggedness offered by them compared to the poly-phase counterparts. This paper presents modeling and analysis of a self voltage regulating, short shunt six-phase SEIG (6Ph-SEIG) supplying RL load. Mathematical model of the 6Ph-SEIG is developed in decoupled dual d-q axes in stationary reference frame. The developed model is then implemented in terms of a simulation model to carry out no-load and on-load analysis of SEIG with a loading of 0.9 lagging power factor. An open stator winding induction machine is integrated with necessary equipments to obtain a 6Ph-SEIG test rig which is used for experimental validation of results. The simulated and experimental results are found to be in good agreement.