Transient Analysis and Modelling of Sixphase Asynchronous Machine

One of the main challenges of voltage source converter based high voltage direct current (VSC-HVDC) transmission systems is the AC faults at the grid side. This work introduces the integration of multiphase induction machine (IM) based flywheel energy storage systems (FESS) with VSC-HVDC systems for AC side fault ride through purposes employing modular multilevel converters (MMC). MMCs have become suitable candidates for medium/high power energy conversion systems due to the capability of simply extending the levels of the converter while retaining high levels of reliability. In order to enhance the storage system reliability, a dual three phase IM is used to drive the FESS due to its fault tolerance capability. In this paper, the performance of the FESS is investigated under the operation of a dual three phase IM being driven by two three-phase MMCs. To step-down the DC-link voltage of the HVDC system to a proper voltage level for IMs, the DC-link voltage is divided into two series connected capacitor, and each capacitor voltage is fed as an input DC voltage for each three- phase MMC. The control strategies of the MMCs and the IM are presented, in addition to the IM mathematical model. Simulation case studies are performed using MATLAB/Simulink to validate the proposed system.

The interest in multiphase drives has been steadily growing during the last decade due to the promising potentials offered by multiphase machines over conventional three-phase counterpart. In this context, six-phase induction machines are preferably used in many diversified high-power applications. Generally, thanks to its improved flux distribution, the asymmetrical six-phase winding topology fed from two three-phase voltage source inverters (VSIs) is commonly employed with isolated neutral points to prevent the flow of zero sequence currents and to limit the number of current controllers to four instead of five when neutral points are connected. In this paper, an innovative design of a six-phase dc-ac inverter is proposed for such type of six-phase ac machines based on the single-ended primary-inductance converter (SEPIC) topology. The proposed topology employs only four active-legs with eight switches with the same output voltage magnitudes as in conventional VSIs and without the mandatory dead-time between switches in the same-leg. Also, it naturally delivers a pure sinusoidal waveform at the output stage. The principle of operation of the proposed inverter topology is investigated in details and assessed through a detailed simulation study of an open-loop control system.

This paper presents an indirect rotor-field oriented control (IRFOC) algorithm for symmetrical six-phase double-winding induction machines with four three-phase sub-winding sets. The presented algorithm introduces the ability to control the power flow between different sub-winding sets. Multiple three-phase induction machines are utilised for critical applications such as more-electric aircrafts, due to their high reliability and fault tolerant capabilities. In this paper, the proposed control scheme is utilising the auxiliary currents of each six-phase sub-motor to achieve full control of the sub-winding sets current amplitudes and consequently the power flow direction for each sub-winding set. A six-phase induction machine with double winding is utilised to validate the proposed control scheme. Four isolated voltage source inverters (VSIs) are used to supply each winding set of the machine. The double-winding six-phase induction machine controlled by the proposed IRFOC algorithm is simulated using Matlab/Simulink. Presented simulation results validate the ability of the algorithm to appropriately control the power flow of each sub-winding set.

Multiphase induction machines have gained more attentions due to their superior fault tolerant capabilities. This work aims to assess the Broken Rotor Bar (BRB) faulty operation of asymmetrical six-phase Induction Machine (IM). Additionally, a comparison in terms of BRB fault feature between the mentioned machine and conventional 3-phase IM has also been performed. Assessment process has been performed initially using Finite Element Algorithm (FEA). Then, a prototype has been re-wound for semi-12-phase arrangement which is an alternative name of asymmetrical 6-phase IM. It has been confirmed experimentally that the BRB fault indicators, the Side Band Harmonic Components (SBHC) of stator current for asymmetrical 6-phase IM, are greater than those of their 3-phase counterparts. Analysis has been concluded with various BRB fault scenarios including single and double BRB cases with variable loading conditions. Furthermore, a fault classifier has also been proposed which could detect and classify the BRB fault for asymmetrical 6-phase IM.

In this paper efficiency improvement of a Six-phase Induction Machine (6PIM) with fuzzy Anfis method is presented. Six phase induction machine is supplied by SPWM (Sine Pulse Width Modulation). The motor efficiency in low speed or low load conditions (under nominal point) is low. The purpose of this paper is to reduce core losses of six phase induction motor in these conditions. Fuzzy flux search controller is a simple technique and robust against parameter changes that can be easily implemented. Loss minimum point of six phase induction motor is related to stator current, thus by decreasing of current the loss is decreased. Results are presented in the paper to verify the effectiveness of the proposed approach. DOI: http://dx.doi.org/10.5755/j01.eee.19.10.5895

With the accelerated development in semiconductor power devices along with the dictated rigorous reliability standards in some industrial sectors, the application of a medium-voltage high-power multiphase induction machine with multiple three-phase windings is now considered as a leading technology in high-power safety-critical applications. This paper proposes a parameter-independent postfault control scheme for an asymmetrical six-phase induction machine based on simple scalar V/f control, which can successfully ensure the most common postfault scenarios used in this respect, namely, equal stator copper loss and minimum copper loss modes. Moreover, the proposed controller can effectively be used in either open-loop or closed-loop speed control modes. The proposed controller is experimentally validated using a 1.5-kW prototype induction machine. The effect of the neutral arrangement on the dynamic performance is also explored.

A new circuit-oriented model for the analysis of six-phase induction machine performances

One of the peculiar studies on the induction machine is the aberrant behavior of the induction machine with stator inter turn faults. These are usually caused by short circuit of few turns on stator winding. In this paper transient model of three phase induction motor using d-q axis theory in stationary reference frame, is proposed to estimate the transient performance of the motor, with such faults. Simulation results as obtained on a test machine are compared with the experimental results and the closeness between the two shows the accuracy of the model as proposed. This paper presents simulation results of induction machine when operated with stator inter turn faults.

In this paper, a new direct torque control (DTC) algorithm for six phase induction machines (6PIM) when one phase is lost will be introduced. The machine has two sets of three phase windings spatially shifted by 60deg electrical degrees. A general decoupled model of the induction machine with up to four open phases is given. Fixed switching frequency and low torque ripple are obtained using this method. Simulation results show good dynamic and steady state performance. Experimental results are carried out to validate the proposed method.

Computer aided design tools are nowadays important for a variety of engineering fields. One of the most used tool is MATLAB/Simulink®, which has a broad variety of libraries and is recognized by its reliability. This paper presents a toolbox library for simulation and prototyping of control techniques for three and five phase induction machines, developed in MATLAB/Simulink®and to be used with dSPACE®DS-1104 platform. The software tools and the hardware platform are both described and provide an integrated environment which allows the user to develop and evaluate control techniques for induction machines by means of pure simulation as well as executing them on an underlying hardware platform connected to the machine. The transition from simulation to a hardware platform are done transparently for the user using rapid prototyping tools.

Field-oriented control techniques for a multi-phase induction machine with an unbalanced stator winding structure is presented in this paper. An unbalanced stationary to synchronous reference frame transformation for stator current was developed in this paper to deal with the asymmetrical structure and thus make the field-oriented control techniques developed from balanced machine winding structure become applicable. Experimental tests were conducted on a dual three phase induction machine with an open phase to verify the proposed analytical modeling and control techniques.

Flywheels as energy storage systems are good candidates for numerous power system applications such as voltage support, serving fluctuating loads, frequency regulation and renewable energy utilization. Most of these applications utilize flywheel energy storage systems (FESSs) at medium voltage ranges. This paper discusses the optimization of the medium voltage high power converters interfacing the FESS with the grid. A dual three phase induction machine (IM) is proposed to drive the flywheel and is controlled via two series-connected three phase voltage source front end converters (VSCs). The proposed configuration is believed to reduce the converters ratings by a half compared to the conventional configuration where three-phase IM with single three-phase VSC is employed. The machine modelling and control are presented, in addition to converters DC links balancing technique. The performance of the proposed system is verified via simulation using MATLAB/Simulink.

Novel methodology of synchronized pulsewidth modulation (PWM) has been disseminated for control of six-phase (dual-three phase) induction machine drives fed by two three-phase inverters with both single and separate DC voltage sources. Control algorithms are based in this case on the 30deg-phase-shifting of control and output signals of two standard voltage source inverters. Four basic schemes of synchronized PWM, applied for control of six-phase drives, have been analyzed and compared. Simulations results are given for continuous, discontinuous and combined versions of synchronized PWM. The spectra of the phase voltage of the six-phase drives with algorithms of synchronized PWM do not contain even harmonics and sub-harmonics, which is especially important for the high power/current applications

In addition to simplicity, the DTC of the IM allows a good torque control in steady-state and transient operating conditions. However, high torque ripple is produced, which is reflected in speed estimation responses. It also increases acoustical noise and makes the voltage source inverter operated in high and variable switching frequency, requiring a high sampling frequency. In this paper, a simple effective ANN-based DTC of the induction machine is proposed. Neural networks with a simple architecture are designed and implemented in influential points of the direct torque control block of the three phase induction machine in order to improve its dynamic performance while preserving the DTC structure simplicity as much as possible. In particular, this paper proposes to reduce, on the one hand, the torque ripple and commutation frequency. Neural comparators are used to select the appropriate bandwidth for the torque and flux hysteresis controllers. Their aim is to optimize the ripple level in the developed torque and flux. On the other hand, a neural speed controller is designed in order to improve the system ability to respond rapidly to changes in process variables and mitigate the effects of external perturbations. The performance of the proposed control are tested in simulation and highlighted by comparing to the conventional DTC control based on conventional hysteresis comparators and conventional PI speed controller. The obtained results show the feasibility and good performances of the proposed control.

This paper analyzes a six-phase two-motor drive, consisting of a six-phase voltage-source inverter (VSI), a six-phase induction machine, and a three-phase induction machine. Stator windings of the two machines are connected in series in an appropriate manner. This enables full decoupling of the dynamics of the two machines by means of vector control. Detailed mathematical modeling of the system is performed and the set of d-q equations, describing the two machines connected in series to a six-phase VSI, is developed. The resulting model clearly shows the possibility of independent vector control of the two machines, although a single VSI is used as the supply. An experimental rig is constructed and existence of the decoupled dynamic control of the two machines supplied from a single VSI is fully verified by extensive experimental testing.