The direct torque control (DTC) method was introduced into the switched reluctance motor (SRM) to reduce its inherent output torque ripple. However, the conventional DTC method produces negative torque more or less, which reduces the torque-ampere ratio of motors. This paper proposes a new DTC method by three improvements. Firstly, the hysteresis-loop control of flux is removed. New selection rule of voltage vectors is established to reduce the torque ripple. Secondly, the sectors divided in electrical space are reorganized by their actual positions according to the inductance profile. The boundaries between certain sectors are calculated and updated according to real-time working conditions. Finally, the alternative voltage vectors for increasing or decreasing torque are distinguished by whether any phase is excited. Therefore, the output torque tracks the reference accurately which reduces the torque ripple. Moreover, the negative torque is avoided by the real-time regulation of turn-off angle, and the torque-ampere ratio is increased accordingly. Simulation and experimental results verify the demonstrated performance of proposed DTC method.

Because of the current commutation and the double-salient pole structure of single-winding bearingless switched reluctance motors (SWBSRMs), the torque and radial forces have large ripples when present control methods are used. In order to solve those problems, a novel solution is proposed in this paper, which can achieve direct torque control (DTC) and direct force control (DFC) simultaneously. With the hysteresis-loop control of torque and flux linkage, the power switches of converter can be directly controlled based on the proposed space voltage vectors. First, the basic space voltage vectors are transformed correspondingly to realize DTC for BSRMs. After that, considering the generation principle of levitation forces, the basic space voltage vectors are transformed into equivalent space voltage vectors to facilitate the implementation of DFC. As a result, the torque and levitation forces can be controlled at the same time only with the developed equivalent space voltage vectors. The complicated current control algorithm is not needed, which is necessary for conventional methods. Moreover, the levitation performance is improved with the proposed method. Experimental results show that the torque ripple and radial displacements of SWBSRMs can be reduced approximately by 80% and 29%, respectively.

The direct torque control (DTC) and direct force control (DFC) method were introduced to reduce the torque and levitation force ripple in single-winding bearingless switched reluctance motors (SWBSRMs). However, it still has some disadvantages. Firstly, the flux-linkage control is not suitable for the DTC method in SWBSRMs. On the one hand, it can increase the torque ripple. On the other hand, the RMS current can be increased and then the torque-ampere ratio is decreased. Secondly, the vectors selection is also unreasonable, which can increase the torque ripple further. In order to solve these problems, an improved control method based on DTC and DFC method for SWBSRMs is proposed in this paper, which can obtain high torque-ampere ratio and low torque ripple simultaneously. In the proposed method, the flux-linkage loop control is not needed and the space voltage vector table is improved. The experimental results show that the torque ripple is reduced by 66.7%, the torque-ampere ratio is increased by 200% and the switching times in one electrical period are reduced by 47.3%.

In order to take advantage of conventional switched reluctance motors (SRMs), the SRM is integrated with the bearingless motor technology and then a reluctance type of bearingless motor is created, named as bearingless SRM (BSRMs). Not only electromagnetic torque but also the levitation forces should be controlled in BSRMs, which is different from SRMs. The levitation forces should always exist even when winding fault occurs. Therefore, the absent levitation forces that ought to be produced by the fault winding should then be compensated by other winding. This paper proposes the compensation strategy of levitation forces for BSRMs when one stator winding is short circuited. The short-circuit fault is investigated and the short-circuit current is expressed for the derivation of radial forces. Then, the winding compensation rule and the mathematical model of levitation forces are developed to facilitate the compensation control for the motor levitation. After that, the proposed compensation strategy is verified by simulation results in MATLAB/Simulink. Experimental results are also presented to demonstrate the performance.

The least cell state-of-charge (SOC) in a battery pack directly determines the left runtime of the total battery pack. Hence, an equalizing strategy is often needed to balance the battery cells, especially for lithium-ion batteries. In this paper, it is shown that this can be achieved with a simple equalizing circuit, which only needs a power semiconductor switch and an inductor for each cell. To avoid the intensive requirement on the processing power of existing control algorithms, two simple control schemes are proposed to obtain better modular performance. First, the operating modes under different switching states are illustrated with a four-cell battery module. After that, the required duty cycles to operate the switches are obtained by comparing the SOC of the relevant cells and the average SOC of all cells. By fixing the maximum of the duty cycle of the highest SOC cell, the inductor can be easily designed and the rated currents of switches and cells can also be regulated. Moreover, the multilayer and modular concept is developed to speed up the balancing process and modularize the design of equalizing circuits. Finally, experiments were completed to demonstrate the proposed scheme.

Compared with the traditional control method, the direct torque control and direct force control method significantly reduces the torque ripple and the root-mean-square current of the phase winding in the single-winding bearingless switched reluctance motor. However, due to the unreasonable selection of voltage vectors and full cycle control, this method has some problems, such as too many control objects, excessive switching times, and low torque–ampere ratio. This article proposes an improved method for the abovementioned problems. First, the turn- on angle and conduction region of each phase winding are chosen as the control targets, and the operation principle is introduced accordingly. Second, according to the difference of the torque generated by the neighboring phases, the output torque can be distributed more properly to obtain the higher torque–ampere ratio in the commutation region. Finally, the sectors divided in the electrical space are reorganized and the corresponding voltage vectors are optimized. Experimental results show that the proposed method can secure lower torque ripples, fewer switching times, and copper loss. In addition, the torque–ampere ratio is improved as well.