Open-end Winding Research Articles

A New Approach to the PWM Modulation for the Multiphase Matrix Converters Supplying Loads with Open-End Winding

This article presents three variants of the Pulse Width Modulation (PWM) for the Double Square Multiphase type Conventional Matrix Converters (DSM-CMC) supplying loads with the open-end winding. The first variant of PWM offers the ability to obtain zero value of the common-mode voltage at the load’s terminals and applies only six switches within the modulation period. The second proposal archives for less Total Harmonic Distortion (THD) of the generated load voltage. The third variant of modulation concerns maximizing the voltage transfer ratio, minimizing the number of switching, and the common-mode voltage cancellation. The discussed modulations are based on the concept of sinusoidal voltage quadrature signals, which can be an effective alternative to the classic space-vector approach. In the proposed approach, the geometrical arrangement of basic vectors needed to synthesize output voltages is built from the less number of vectors, which is equal to the number of the matrix converter’s terminals. The PWM duty cycle computation is performed using only a second-order determinant of the voltages coordinate matrix without using trigonometric functions. A new approach to the PWM duty cycles computing and the load voltage synthesis by 5 × 5 and 12 × 12 topologies has been verified using the PSIM simulation software.

Grid-Connected Induction Motor Using a Floating DC-Link Converter Under Unbalanced Voltage Sag

This article proposes a series compensator with unbalanced voltage sag ride-through capability applied to grid-connected induction motors. A conventional three-phase voltage source inverter (VSI) is intended to regulate the motor voltages. The VSI is connected in series with the grid and a three-phase machine with open-ended windings. The proposed system is suitable for applications in which no frequency variation is required, like large pumps or fans. The VSI dc-link voltage operates as a floating capacitor through the energy minimized compensation (EMC) technique, in which there is no dc source or injection transformer. The motor load condition determines the minimum grid voltage positive component (sag severity) to keep EMC operation. Meanwhile, a voltage unbalance may increase the dc-link voltage requirements. A 1.5-hp four-pole induction motor has been used to verify the ride-through capability of the proposed compensator under grid voltage disturbances. A total harmonic distortion (THD) analysis of grid currents demonstrates that the proposed system provides low THD even if no passive filter is used. The operating principle, converter output voltage analysis, pulsewidth modulation technique, control strategy, and components ratings are discussed as well. Simulation and experimental results are presented to demonstrate the feasibility of the system.

Enhanced Performance of Dual Inverter With a Floating Capacitor for Motor Drive Applications

This article studies a dual inverter supplied by a dc-link and a floating capacitor (FC), emerged as a promising inverter topology for motor drive applications. For this type of inverter, the voltage ratio between the dc-link and the FC can be actively controlled. This ratio design is crucial as it essentially defines both the dc-link voltage utilization and the inverter output quality. Several voltage ratios have previously been discussed to enhance the dual inverter performance, but only one aspect, either the voltage utilization or the output quality, is investigated. As a result, although one performance aspect can be improved, the other aspect has been adversely affected. In this article, a comparative study considering both aspects is carried out for all the possible voltage ratios. Based on this analysis, the optimal ratios for different inverter modulation indices are identified. This is followed by proposing a ratio selection strategy to double the voltage utilization without degrading the output quality. This strategy enables an electric drive to work at a higher maximum speed without flux weakening for a given dc-link voltage. The claimed advantages have been proved by experimental tests on an open-end windings induction motor drive.

Comparative analysis of the performance influence of isolated bus open-end winding BLDCM and star-end winding BLDCM

The open-end winding motor (OEWM) system is a hot spot of current scholars’ research due to its advantages of large output power, wide speed range, and strong fault tolerance. Through Maxwell and Simplorer software co-simulation, the open-end winding brushless direct current motor (OEWM-BLDCM) and the star-end winding BLDCM under three-phase six-state control mode are compared and analyzed, including conduct current, torque, speed and mechanical characteristics. The simulation results show that: OEW-BLDCM has faster response speed, smaller torque ripple, and doubled the maximum speed.

Enhanced Voltage Switching States for Direct Torque Controlled Open End Winding Permanent Magnet Synchronous Motor Drive

Direct torque control (DTC) is most popular technique used in industries for adjustable speed of drives. It has simple control algorithm without any pulse width modulation technique and vector transformations involvement. Two level voltage source inverter (VSI)-fed permanent magnet synchronous motor (PMSM) operated with DTC has higher torque and flux ripple problems due to the limited voltage vectors availability, which affects the performance of drive. To alleviate these problems, more number of voltage space vectors should be available for DTC of PMSM drive. In this article, DTC for open-end winding PMSM drive (OEW-PMSM) is proposed. A two level dual VSI-fed OEW-PMSM drive configuration attains three level inversion with an equal dc link voltage to VSIs. Similarly four level inversion can also be attained with an unequal dc link voltage of 2:1 ratio given to dual VSIs. Therefore availability voltage space vectors are increased for PMSM drive operation. The effective voltage switching tables for DTC operated OEW-PMSM drive at different speed conditions are proposed to make its performance more satisfactory, thus achieving less torque and flux ripples and also reduced common mode voltage (CMV). To validate this, Simulink/MATLAB and real time experimentation are performed on 3.7 kW PMSM drive.

Constant and variable switching frequency random PWM strategies for open-end winding induction motor drive

High amounts of harmonics cause noise and electromagnetic interference to nearby systems. Pulsewidth modulation (PWM) techniques are used to reduce the amount of harmonics near the multiples of switching frequencies. To trim down the noise and electromagnetic interference and improve the quality of the output voltages, different types of constant and variable switching frequency random PWM techniques for dual inverter-fed open-end winding induction motor drive configuration are discussed in this study. Moreover, the vector control technique is used along with random PWM techniques to improve the transient response of the dual inverter.

Cascaded Predictive Control of a Single Power Supply-Driven Four-Level Open-End Winding Induction Motor Drive Without Weighting Factors

A dual-inverter can synthesize four-level space vector using a single dc power supply and a floating capacitor by utilizing an open-end winding induction motor (OEWIM). In this article, a cascaded predictive current control (CPCC) method is proposed for this drive that completely avoids weighting factors. Sequential control of multiobjectives by identifying the order of evaluation of individual objectives is introduced. In this article, motor torque and flux are controlled first followed by voltage balancing of floating capacitor to determine the optimal switching combination of the dual-inverter. To improve computational efficiency of the proposed CPCC, a reference voltage vector is used in this article, in place of current prediction for identifying the candidate switching combination. Ruggedness of the envisaged CPCC is demonstrated through simulations and experimental studies covering speeds below and above motor base speeds of operation. Performance of the proposed CPCC is also compared with the existing model predictive control (MPC) methods to showcase torque ripple reduction, improved current total harmonic distortion (THD), reduced inverter switching frequency, improved inverter efficiency, etc. Above all, due to the simplicity of the proposed CPCC, a drastic reduction in the execution times is achieved when compared to the existing MPC methods.

Multiphase Open-End Winding Induction Machine Drive With the Floating Capacitor

A comprehensive control scheme is presented for the multiphase open-end winding induction machine drive topology, where the main inverter (MI) and floating inverter (FI) are supplied by a dc power source and a capacitor, respectively. Under the proposed method, the MI can work with the unity power factor, while the FI provides all the reactive power. Besides, the current waveform quality is improved by the harmonic suppression and current balance control. Moreover, the voltage of the floating capacitor is adjusted to keep the modulation ratio of the FI near one during the operation, which helps to reduce the switching losses of the system. Experimental results are presented to verify that the proposed control scheme is practical in controlling this open-end drive topology and suitable for expansion to high-phase-number occasions.

Single-Phase to Three-Phase Electrolytic Capacitor-Less Dual Inverter-Fed IPMSM for Suppress Torque Pulsation

An electrolytic capacitor-less single-phase to three-phase power converter controls the motor and the input power factor. However, the motor power and the torque are pulsated because the input power of the inverter is irregular. This article proposes a power converter and control method to realize a high input power factor and constant motor torque using a dual inverter without an electrolytic capacitor and an open-end winding machine. The proposed system has the following features. First, the proposed control method achieves a high input power factor by controlling the single-phase ac power without affecting the motor current. Second, the proposed control method compensates the pulsation the of load voltage by using an additional inverter. The proposed circuit configuration and control method contributes to the small size and weight, and high efficiency of the motor drive system with a single-phase power supply. The effectiveness of the proposed system is verified through experiments. The proposed system suppresses torque pulsation by 95.5% compared to the conventional system, and the input power factor is 97.2% at 1.5 Nm and 2500 r/min load condition.

Interrupt-Free Operation of Dual-Motor Four-Wheel Drive Electric Vehicle Under Inverter Failure

This article presents a new open-end winding induction motor (OEWIM)-based dual-motor differential four-wheel drive (D4WD) for the electric vehicle (EV). Constant speed operation through cruise control is achieved using direct torque control (DTC) algorithm. The redundant vectors are used in the switching vector selection of the DTC algorithm to achieve balanced battery currents. Fault-tolerant operation (FTO) of the drive is demonstrated, where the EV will work with full torque even if one of the inverters in rear motor drive or front motor drive or both fail. The dynamic model of the proposed drive is presented. The proposed drive and FTO are verified through simulation as per the FTP-75 driving cycle. An experimental prototype of the proposed drive is developed, and the abovementioned algorithms are verified experimentally as per the FTP-75 and HFET driving cycles. Both the simulation and experimental results are presented, and these results agree with the theoretical observations. Stable operation of EV for the entire test cycle under normal operation, as well as inverter fault conditions, is demonstrated.

Power quality of dual two-level inverter fed open end winding induction motor

<p><span>This paper presents the minimization of the total harmonic distortion (THD) of the current signal for open-end winding induction motor by using dual two-level inverter. In order to obtain a good value of THD, the space vector PWM has been used for switching the dual two-level inverter to improve the output voltage quality, gets a low common mode voltage, reduce the execution time, and to save the memory capacity. The proposed scheme uses two different DC voltage source with two two level inverter in order of minimizing the number of components. As well as it is an important to utilize the energy which increases the application of dual inverter in microgrids. All simulation results are obtained using Matlab/Simulink. </span></p>

Electric Drive Based on an Open-End Winding Surface PM Synchronous Machine With a Floating Capacitor Bridge

A speed control scheme is presented for a three-phase surface permanent magnet synchronous machine with an open-end stator winding fed by a three-phase inverter and a floating bridge inverter. The latter is used to compensate for the reactive power of the main inverter and to maximize the active power received by the motor, without exceeding the available stator current and dc-link voltage. To reduce the switching losses, the dc-link voltage of the floating inverter bridge varies depending on the operating condition of the motor and the controllability requirements of the system. The experimental results show that a significant improvement in the speed range at constant power is achievable, proportionally to the dc-link voltage of the floating bridge inverter.

A Three-Phase Integrated Battery Charger for EVs Based on Six-Phase Open-End Winding Machine

This article presents a new configuration of onboard integrated battery charger for electric vehicles (EVs) using six-phase machine and three-phase ac source. The configuration proposes the utilization of symmetrical six-phase open-end winding machine, twelve-leg inverter, and a dc–dc converter. The charger circuit is constructed by connecting directly the three-phase grid to the middle point of machine's phase winding, where the grid currents split into equal portions and flow in opposite directions, without adding an extra mechanical switch (or relay). From this concept, the proposed system has the advantages of obtaining high-power density with a large value of inductance for grid-side filter during charging and avoiding an electromagnetic torque as well as providing a high fault tolerant capability. Moreover, through proper control strategy, the proposed system is able to operate under unity power factor (UPF) with total harmonic distortion (THD) below 5%. In this article, the possibility of vehicle-to-grid (V2G) mode is also investigated. Detail of the control strategy for charging and V2G are given. Furthermore, simulation and experimental results are provided to validate the theoretical analysis.

Two Novel Open-End Winding Multilevel Unidirectional Six-Phase Rectifiers With Reduced Switch Count

In this article, two new unidirectional multilevel six-phase power rectifier topologies are proposed and investigated. Such topologies may be applied to ac–dc systems such as wind energy conversions systems, aerospace generator drives, telecommunications or any other application where regenerative operation is either not required or prohibited. The first topology is composed of two three-level neutral-point-clamped (NPC) converters connected to the open-end windings of a six-phase permanent magnet synchronous generator, and a three-phase noncontrolled diode bridge converter. The second topology is composed of three modified NPC converters with the substitution of two controlled switches by diodes in each leg. The use of a noncontrolled converter with diodes aims to reduce the controlled switches count, the system complexity, and the costs. However, it makes both systems nonreversible. The system models, operating principles, the space vector pulsewidth modulation strategies, the dc-links balance, and the control system to ensure the elimination of the zero-crossover distortion caused by the use of the diodes are presented. Due to the high number of levels generated, the systems are suitable for high power applications with voltage and current ratings restrictions. A study concerning harmonic distortion and semiconductor losses for both systems is performed, in order to be compared with a standard configuration. The feasibility of the system is demonstrated by simulation and experimental results.

SVPWM control strategy for a three phase five level dual inverter fed open-end winding induction motor

A Space Vector Pulse Width Modulation (SVPWM) control strategy is proposed for a three phase five level dual inverter fed open-end winding induction motor. This system includes 2 three level Neutral Point Clamped (NPC) inverters, which is supplied by two isolated dc power supplies. The conventional SVPWM has more complexity in reference vector identification and switching time calculation. The reference vector for proposed five level SVPWM scheme is tracked using three level voltage vector and offset voltage, where 5-level hexagonal region is divided into seven 3-level hexagonal regions. The proposed SVPWM leads to reduce the complexity in switching time calculation, Total Harmonic Distortion (THD) reduction, Minimization of Common Mode Voltage (CMV) and low voltage stresses across the switching devices. Also this system estimate the phase current of the five level dual inverter fed open-end winding induction motor. The results obtained using simulation and hardware are compared and verified using Digital Signal Processor.

Enhanced predictive torque control of multi-level inverter fed open-end winding induction motor drive based on predictive angle control

ABSTRACT In this article, predictive torque control (PTC) of multi-level inversion (MLI) fed open-end winding induction motor (OEWIM) drive has been developed with predictive angle control technique. The classical PTC of induction motor drive involves direct control of torque and flux. The combination of direct torque control (DTC) with model predictive control (MPC) offers all the features of classical DTC and in addition it is easily implementable for MLI fed induction motor drives. This article introduces predictive angle control strategy for MLI fed OEWIM drive to reduce torque ripple, where as the classical PTC algorithm uses magnitudes of torque and flux. The proposed algorithm is developed by controlling the angle between stator flux and stator current, the voltage space vectors of MLI fed OEWIM drive are classified according to operating frequency range. The proposed PTC algorithm requires same computational time as that of classical PTC. The proposed algorithms are verified through simulation and experimental studies.

Equivalent 3-Level PWM: An Improved Technique to Reduce Torque Ripple in DI-WRIM Analyzed as DI-OWIM

In the supersynchronous mode of double-inverter-fed wound rotor induction machine (DI-WRIM) drive, torque ripple is dependent on the sum of the quadrature ( $q$ ) axis stator and rotor flux ripples (termed as overall flux ripple). Therefore, in the existing method, the torque ripple is reduced by merely changing the slope of one of the flux ripples such that their sum is reduced. However, the torque ripple can be further reduced, as the overall flux ripple in DI-WRIM resembles the $q$ -axis stator flux ripple of a double-inverter-fed open-end winding induction machine which is generally analyzed as a three-level neutral-point-clamped inverter fed squirrel cage induction machine (SQIM) (3L-SQIM) drive. Thus, in this article, the stator and rotor voltage source inverters are switched together and the resemblance is explored to develop stator–rotor pulsewidth modulation (PWM) combinations, such that the overall flux ripple is equivalent to the $q$ -axis flux ripple of 3L-SQIM. The effect of phase shift between the stator and rotor voltage vectors on torque ripple is analyzed and a hybrid PWM combination is also proposed to minimize the same. The reduction in torque ripple, with the proposed combinations, is validated in terms of the estimated instantaneous and RMS torque ripples. The simulation and experimental results further validate this reduction.

Voltage-Injected PWM Variants for a Dual Two-Level Inverter-Fed Open-End Winding Induction Motor Drive

In this article, three new pulsewidth modulation (PWM) methods are proposed for a dual-inverter-fed open-end winding induction motor (OEWIM) drive aimed at reducing voltage harmonic distortions in the inverter output. The proposed PWM variants are devised using appropriate voltage injection to the modulating signals. The proffered PWM variants for the dual inverter are analyzed through rigorous harmonic analysis to arrive at complete harmonic description using double Fourier integral approach (DFIA) to obtain their characteristics. For all the PWM variants, optimal values of voltage injection are also obtained, which yields lower voltage harmonics at the output of the dual inverter. The analytical solutions thus obtained are verified through simulations and experimental results, and the improved harmonic performance compared to the existing PWM techniques is also presented. Identifying the shortcoming of reduced limits of linear modulation of the proposed PWM techniques, a solution to smoothly slide-over to the phase-disposed PWM techniques is also demonstrated. Besides, the impact of the proposed PWM variants on improved motor current ripple and torque ripple performance when used with field-oriented control is presented and compared with some existing PWM methods to showcase their superior performance characteristics and also the usefulness of the envisaged PWM methods.

Space Vector Modulation for Distributed Inverter-Fed Induction Motor Drive for Electric Vehicle Application

A long-driving range of the electric vehicle (EV) is always a primary requirement. To achieve this, a high-efficiency traction motor is designed. The other way to achieve a long-driving range is to connect a higher number of batteries in parallel. However, a large number of batteries connected in parallel will give rise to circulating current within the battery circuit. To overcome this problem, a new distributed inverter-fed induction motor (IM) drive is proposed. In the proposed topology, open-end winding IM (OEWIM) is used, and each phase of OEWIM is fed by a single-phase H-bridge inverter individually. In this way, it reduces the parallel combination of batteries. Space vector modulation (SVM) is developed for inverter switching and analyzed for common-mode voltage (CMV) and zero-sequence voltage (ZSV). The proposed topology is validated through simulation and experimental results.

Decoupled Floating Capacitor Voltage Control of a Dual Inverter Drive for an Open-Ended Winding Induction Motor

A control scheme is presented for a dual inverter drive with a floating capacitor bridge, with decoupled motor and capacitor dynamics. A stator current reference frame is used that decouples the real and reactive power components of the motor and enables the decoupling of the motor and capacitor dynamics. Apart from the high frequency voltage ripple due to the inverter switching pattern, the capacitor voltage can be kept constant even during large step changes in motor speed reference and load torque. This allows for the use of a significantly smaller floating bridge capacitor whose size depends only on the steady-state high frequency voltage ripple. Additionally, the number of PI regulators used compared to previous works and the dc-link voltage requirements are both reduced.