Two-level Five-phase Inverter Research Articles

Torque ripple minimization with modified comparator in DTC based three‐level five‐phase inverter fed five‐phase induction motor

The proposed technology deals with the reduction in torque ripple of five-phase induction motor. The machine is controlled by direct torque control technique and fed by three-level five-phase inverter (TL-FPI). In the fraternity of multiphase induction motor, five phase is the most researched drive, considering complexity of control mechanism and advantages which multiphase machine has offered. The selection of TL-FPI is based on availability of more voltage vectors (243) than two-level five-phase inverter (32). The 41 voltage vectors are employed out of 243 based on simplicity and advantages of multiphase machine. The selected vectors are operated through modified seven-level torque comparator. An increase in levels of the comparator restrains the ripple in a predefined boundary. Here, modification in the predefined boundary of the comparator is suggested which allows the utilization of optimal voltage vectors. According to modification, zero voltage vectors are replaced with small active vectors when actual torque is lower than its reference value. To substantiate the claim various results of simulation and experimentation are given.

Predictive Torque Control Algorithm for a Five-Phase Induction Motor Drive for Reduced Torque Ripple With Switching Frequency Control

This article presents a progressive comparison of predictive torque control (PTC) algorithms for a five-phase induction motor fed with a two-level five-phase inverter. The extension of three-phase PTC to the five-phase motor, introduces current harmonics of the order 10n $\pm$ 3 (n = 0, 1, 2.. .), which are not responsible for torque/flux production. The inherent disadvantage of PTC is being a variable frequency algorithm, which adds complexity to the design of magnetic components. This disadvantage of PTC can be overcome by applying dwell time ( $t_{s}$ ) to the voltage vectors obtained through a minimum torque ripple condition, which is determined based on the ripple equation. In the proposed algorithm, a set of synthetic voltage vectors are generated and used for reducing flux and torque error through cost function. The use of synthetic voltage vector simplifies the cost function and further reduces the computation time. A two-step delay compensation is adopted to improve the precision of the control algorithm further. In each control cycle, an optimal switching time is calculated to reduce the torque ripple and to maintain the constant switching frequency. In this article, a modified PTC is proposed, which targets to achieve constant switching frequency, eliminate the xy-subspace current harmonics, reduce the torque ripple, and minimize the computational burden involved in the conventional predictive torque control algorithm. The experimental study is carried out on a laboratory prototype. The results show compliance with all the experimental study with different PTC algorithms with different sampling frequencies, and the modified cost function.

Finite control set model predictive current control of a five-phase PMSM with virtual voltage vectors and adaptive control set

This paper presents an improved finite control set model predictive current control (FCS-MPCC) of a five-phase permanent magnet synchronous motor (PMSM). First, to avoid including all the 32 voltage vectors provided by a two-level five-phase inverter into the control set, virtual voltage vectors are adopted. As the third current harmonics can be much reduced by virtual voltage vectors automatically, the harmonic items in the cost function of conventional FCS-MPCC are not considered. Furthermore, an adaptive control set is proposed based on voltage prediction. Best control set with proper voltage vector amplitude corresponding to different rotor speed can be achieved by this method. Consequently, current ripples can be largely reduced and the system performs much better. At last, simulations are established to verify the steady and transient performance of the proposed FCS-MPCC, and experiments based on a 2 kW five-phase motor are carried out. The results have validated the performance improvement of the proposed control strategy.

Direct Torque Control of Five-Phase Induction Motor With Common-Mode Voltage and Current Harmonics Reduction

This paper proposes two direct torque control (DTC) strategies to reduce the common-mode voltage (CMV) in the five-phase induction motor driven by three-level five-phase inverter. In each technique, 31 voltage vectors consisting of 30 nonzero voltage vectors, and a zero voltage vector are selected out of available 243 voltage vectors. The selection of these voltage vectors are based on their capabilities of reducing the CMV, eliminating the x–y stator flux and maintaining the torque ripple under control. The ten large, ten small, and a zero voltage vector are same in both schemes, however only difference in designing the control strategy for the two schemes is the utilization of different ten medium voltage vectors. First proposal (DTC-I) reduces the CMV to $3V_{{\rm{dc}}}\,/ 10$ and second proposal (DTC-II) reduces to $V_{{\rm{dc}}}\,/ 10$ . These schemes are compared with DTC technique of five-phase induction motor fed by two-level five-phase inverter in order to judge the capabilities of proposed schemes in context of reducing the CMV. The simulation and experimental results validate the proposed DTC techniques.

Carrier-Based PWM Methods With Common-Mode Voltage Reduction for Five-Phase Coupled Inductor Inverter

Carrier-based pulsewidth-modulation (CBPWM) techniques are popular due to their simplicity, and have been widely researched for various three-phase inverter configurations. In this paper, two CBPWM techniques are proposed to reduce the common-mode (CM) voltage generated by the five-phase inverter. The five-phase inverters have more flexibility in reducing the CM voltage than their three-phase counterparts because they have more phase legs, hence finer control over the star-point voltage of the load. Two methods are proposed for the conventional two-level five-phase inverter to reduce the CM voltage; one utilizing adjacent modulating waveforms and the other utilizing nonadjacent modulating waveforms. The coupled inductor inverter (CII) uses coupled inductors to generate multilevel outputs. As the volt-second balance must be maintained across each coupled inductor, direct application of the proposed methods on the CII inverter will result in overcurrents in the coupled inductors. Hence, the proposed methods are further improved to ensure the volt-second integral over each switching period is zero. Moreover, the two proposed methods are designed to reduce switching events and prevent unexpected states occurring during the switching transitions. The performance and the switching strategy of both methods are verified by both simulations and experiments on a prototype of five-phase CII.

A Space Vector PWM With Common-Mode Voltage Elimination for Open-End Winding Five-Phase Drives With a Single DC Supply

Open-end winding three-phase drive topologies have been extensively investigated in the last two decades. In the majority of cases supply of the inverters at the two sides of the winding is provided from isolated dc sources. Recently, studies related to multiphase open-end winding drives have also been conducted, using isolated dc sources at the two winding sides. This paper investigates for the first time a five-phase open-end winding configuration, which is obtained by connecting a two-level five-phase inverter at each side of the stator winding, with both inverters supplied from a common dc source. In such a configuration it is essential to eliminate the common-mode voltage (CMV) that is inevitably created by usual PWM techniques. Based on the vector space decomposition (VSD), the switching states that create zero CMV are identified and plotted. A space vector pattern with large redundancy of switching states is obtained. Suitable space vectors are then selected to realize the required voltage reference at the machine terminals with zero CMV. The large number of redundant states enables some freedom in the choice of switching states to impress these space vectors. Out of numerous possibilities, two particular switching sequences are chosen for further investigation. Both are implemented in an experimental setup, and the results are presented and discussed.