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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. [ABSTRACT FROM AUTHOR]

Multiphase dc-excited Vernier reluctance machine (DC-VRM) exhibits the merits of robust structure, small torque ripple, and good fault-tolerant ability. Developing advanced sensorless drive methods can further promote its application in the safety-critical system. In this article, pulse injection sensorless drive methods are optimized in a six-phase DC-VRM parallel H-bridge drive system to strengthen their acceleration performance and fault-tolerant ability. The acceleration performance studied in this article corresponds to the acceleration speed during the startup stage. By the full-phase alternative pulse injection method (APIM), each phase can be excited independently to avoid mutual-inductance influence on position estimation, but this method suffers from a long communication delay and relatively poor acceleration performance. A reduced-phase APIM can reduce detection time, but the lack of detected phase may influence position estimation accuracy and fault-tolerant ability. To solve these problems, a novel vertical-axis synchronous pulse injection method is proposed and compared with previous methods in this article. The key is to inject detection pulses into vertical-axis phases simultaneously, thus reducing the detection time and improving the torque generation. It is proved that the influence of mutual inductance on position estimation can be ignored, and the detection accuracy and acceleration performance can be improved without deterioration of fault-tolerant ability. [ABSTRACT FROM AUTHOR]

High gradability and wide operating speed range are critical requirements for heavy-duty trucks and off-road electric vehicles. The motor power rating used for such applications can be reduced by selecting a motor with a wide constant power speed range (CPSR). However, permanent magnet synchronous motors (PMSMs) with wide CPSR have limited overloading capability. The operating speed range, as well as the overloading capability, can be improved by increasing the base speed of a low CPSR three-phase PMSM, which results in overdesign. Further, using multigear transmission to achieve a wide operating speed range with a low power motor increases system weight, drivetrain complexity, and maintenance requirement. This article proposes a dual three-phase interior PMSM with an unequal split winding configuration and zero degree winding displacement (uneq0-PMSM) to extend the constant power region and improve the overloading capability without any machine overdesign. The winding split ratio for the proposed configuration is decided to achieve the desired torque-speed characteristic shape for a given requirement. Further, a transition algorithm for smooth changeover between two-winding operation during low-speed and one-winding operation for high-speed is also proposed. The proposed concepts are experimentally validated on a 1.5-kW uneq0-PMSM with 1:3 winding split ratio. [ABSTRACT FROM AUTHOR]

This article reviews the state-of-the-art back electromotive force (EMF) based sensorless schemes for synchronous machines. Field-oriented control (FOC) of a synchronous machine requires real-time rotor position for decoupled torque and flux control. Extraction of rotor position without a sensor or sensorless control has been an enabling technology for the past few decades. Sensorless control using back EMF voltage induced by rotor movement is the most widely used method. However, the connections and differences between different methods have not been thoroughly investigated and documented. This article first reviews basic sensorless methods. The two implementation forms of an observer are examined to facilitate analysis. A detailed analysis puts in evidence the connections behind different methods in both stationary and synchronous reference frames. A summary is drawn that is meant to offer a few key points regarding different sensorless methods. Finally, a conclusion is given to summarize the major contributions of this article. [ABSTRACT FROM AUTHOR]

This article presents an optimal direct torque control (DTC) strategy with variable flux for a switched reluctance motor using the improved linear active disturbance rejection control (LADRC) plus the hybrid optimization algorithm (HOA). First, the constant flux amplitude is substituted by the variable flux DTC (VF-DTC) to reduce the torque ripple. Then, the LADRC with the improved extended state observer applied in speed controller is utilized instead of the conventional PI control to improve the speed of the observer, antidisturbance ability, and robustness. Moreover, the HOA is employed to search for the optimal control parameters and acquire satisfactory dynamic performances. Finally, the optimal VF-DTC system is implemented on a 12/8 SRM. Simulation and experimental results are carried out to compare the performances of the conventional DTC, the VF-DTC with LADRC, the VF-DTC with PI using HOA, and the proposed optimal VF-DTC using HOA. The results show that the proposed control method has a faster speed response, superior antidisturbance ability, and lower torque ripples. [ABSTRACT FROM AUTHOR]

Signal-injection sensorless control for low speeds region are usually assisted with compensation techniques to support the heavy load operations beyond rated conditions. For the standard $d$ -axis pulsating voltage injection, this article analyzes the prospect of using $q$ -axis current-model flux instead of the $q$ -axis current for decoupled position estimation. Through convergence analysis, the feasibility of operation at overload is evaluated for the decoupled scheme against the state-of-art compensation technique and is shown to be a promising candidate for its simplicity and the lack of preprocessing of flux-map. All claims are experimentally validated on a 1.1 kW synchronous reluctance machine test-bench. [ABSTRACT FROM AUTHOR]

This article proposes a phase current reconstruction strategy for open-winding synchronous reluctance motor (OW-SynRM) drives with the dual-inverter topology and common dc bus. The traditional reconstruction strategy cannot be applied in OW motor drives because the dual-inverter modulation and zero-sequence current suppression strategies complicate the vector combinations and shorten their durations. Besides, additional sampling is required because the sum of the three-phase current is not zero. To solve these issues, the edge alignment algorithm is proposed to extend the duration of certain vector combinations, and the phase-shift strategy for the third sampling is proposed to obtain extra current information. In the case of the reconstruction failure in immeasurable regions, the corresponding compensation strategy is investigated. With the proposed reconstruction strategy, the system cost can be significantly reduced and the reliability can be improved, where only one current sensor is required. Besides, the single sensor can be reused for power detection and protection for the whole system by selective installation. Moreover, the proposed strategy is compatible with both the 180° and 120° assignment schemes, increasing the flexibility of application. Finally, experiments are carried out on an OW-SynRM to verify the high accuracy and feasibility of the proposed strategy. [ABSTRACT FROM AUTHOR]

This article presents the application of model predictive control (MPC) in high-performance drives. A wide variety of machines have been considered: Induction machines, synchronous machines, linear motors, switched reluctance motors, and multiphase machines. The control of these machines has been done by introducing minor and easy-to-understand modifications to the basic predictive control concept, showing the high flexibility and simplicity of the strategy. The second part of the article is dedicated to the performance comparison of MPC with classical control techniques such as field-oriented control and direct torque control. The comparison considers the dynamic behavior of the drive and steady-state performance metrics, such as inverter losses, current distortion in the motor, and acoustic noise. The main conclusion is that MPC is very competitive concerning classic control methods by reducing the inverter losses and the current distortion with comparable acoustic noise. [ABSTRACT FROM AUTHOR]

This article from a discrete-time model and stability analysis is developed using a Lyapunov approach, taking into account the one sample implementation delay present in digital control applications. Experimental results are provided to demonstrate the effectiveness of the proposed approach, where a conventional hysteresis controller is used as a benchmark. Results show that the proposal is able to deliver adequate reference tracking while using significantly lower sampling frequencies. Moreover, when compared to the hysteresis controller, superior tracking is observed at low speeds, while maintaining a similar level of computational complexity. [ABSTRACT FROM AUTHOR]

In this article, a new fault-tolerant control strategy for a triple redundant 3 × 3 phase permanent magnet assisted synchronous reluctance motor under a single-phase open-circuit fault has been proposed. In order to reduce the cost of the system, a two-level three-phase inverter is constructed to drive the parallel-connected motor under normal and fault-tolerant conditions. In normal operations, the current and torque are equally distributed to the three modules of the motor, while in a fault-tolerant state, they should be redistributed according to a specific ratio. The optimal ratio is obtained by investigating the control strategy of minimum copper loss and minimum torque ripple. The torque ripple of the normal module is increased to offset the torque ripple of the fault module, thereby reducing the total electromagnetic torque ripple after the failure. It means that no auxiliary switching devices need to be added even if the failure happened, which can significantly reduce the complexity and improve the reliability of the control system. To verify the theoretical analysis, simulations and experiments have been conducted. The results are in good agreement with that of theoretical analysis. [ABSTRACT FROM AUTHOR]

In this article, a time-efficient torque shaping technique for the switched reluctance machines is proposed to reduce the torque ripples while optimizing the copper loss. To reduce the computational time for solving the time-consuming bi-objective optimization problem, an efficient and desirable linear space for the SRM is utilized through the torque mapping between the linear space and nonlinear space. The feasible regions and properties of this torque mapping for SRM are studied in detail first. Then, based on this torque mapping, the current reference is generated by solving a convex optimization problem in the linear space and later converted to the current reference in nonlinear space. Compared to the traditional method that only adopts nonlinear space, the proposed current reference generation method requires less than 10% of the time. Furthermore, the proposed method saves more than 70% time consumed by the traditional method for the bi-objective optimization problem but possesses the similar torque ripple reduction performance. The effectiveness of the proposed method has been verified by extensive simulation and experimental tests on a four-phase 5.1 kW 8/6 SRM setup. [ABSTRACT FROM AUTHOR]

Noise, vibration, and harshness (NVH) issue in switched reluctance machines (SRMs), originating from their doubly salient structure and unique principle of operation, is addressed in this work by proposing a structural design modification in the stator, which increases stiffness to mass ratio of the structure. A 24-slot 16-pole (24s/16p) SRM designed with the aim of automotive application is studied here for the NVH optimization, at different target operating points, using stator pole bridges. Stator pole bridges link consecutive stator teeth to provide additional stiffness to the stator structure. Average torque reduction due to flux shorting in stator pole bridges is tackled by proposing a low-permeability material, with considerable stiffness, which has not yet seen its’ application in SRM NVH domain. Multiphysics aspects of stator pole bridge design encompassing electromagnetic radial force, mechanical stress, steady-state temperature distribution, and acoustic noise analyses are presented in this article. Possible manufacturing issues are considered during the design phase and appropriate measures are implemented to facilitate easier construction of two 100-kW prototypes. The final design with stator pole bridges and a baseline design without any stator pole bridges are prototyped, after rigorous multiphysics optimization, for extensive testing. Experimental results verify simulation outputs and report a maximum noise reduction of 12.52 dBA in the stator pole bridge model compared to the baseline SRM. [ABSTRACT FROM AUTHOR]

Finite control set model predictive torque and flux control of ac motor drives commonly selects optimum inverter switching states through a cost function with a required weighting factor. The weighting factor should be well-tuned in accordance with the motor specifications and operating points. Additionally, the control performance of the drive is degraded under the parametric uncertainties. In this article, a predictive torque and flux control method is proposed for interior permanent magnet synchronous motor drives without a cost function. As a result, the tuning of the weighting factor is avoided. Besides, an estimation scheme based on a data-driven model is adopted, which enhances the robustness of the drive against parametric uncertainties. Instead of directly using the motor parameters, the input and output data of the control system, i.e., voltage and current, are used for estimating three new coefficients employed in the predictions. The performance of an interior permanent magnet synchronous motor drive under the proposed control method is evaluated and compared with those under the conventional predictive torque control method and a recently developed predictive torque control method without a weighting factor. The results confirm the effectiveness of the proposed control method and its superiority over the other two methods. [ABSTRACT FROM AUTHOR]

This article proposes a simplified dual-electric-port drive for a flux-modulated switched reluctance machine (SRM) with flexible charging capability for electric vehicle applications. In the driving mode, the developed flux modulation control can be achieved by directly employing the modular three-leg converter compared to the conventional open-winding topology. The zero-sequence current excitation can be flexibly controlled between the dual port and the number of power switches is also significantly reduced. The corresponding carrier-based pulsewidth modulation method and harmonic current suppression strategy are both developed to improve the machine performance. In the standstill condition, flexible battery charging can be easily achieved by the drive circuit, including both the dc and ac charging, without using any additional passive components and power devices. Then, the current distribution control scheme and power factor correction strategy are further developed for the dc and ac charging, respectively. Compared with existing drive topologies, advanced flux-modulated control and flexible energy control both can be achieved with machine performance improvement and drive cost reduction. Experiments are carried out on a three-phase 12/8 SRM prototype to verify the effectiveness of the proposed SRM drive and control strategies. [ABSTRACT FROM AUTHOR]

To develop a high-performance synchronous reluctance motor (SynRM) drive system, a novel maximum power factor control (MPFC) using a current angle controller with stator resistance and stator flux estimators is proposed. First, a traditional maximum power factor control system using a saliency ratio of the SynRM to generate a fixed current angle command is described. Since the saliency ratio requires offline prepreparation and cannot be adjusted automatically, it is difficult to improve the performance of the MPFC in different operating regions because of the increasing of manufacturing cost and time-consumption. Therefore, an intelligent-maximum power factor searching control (MPFSC) using a recurrent Chebyshev fuzzy neural network (RCFNN) current angle controller is developed for the speed control of a SynRM. In order to search the online optimal power factor (PF) points of the SynRM under different operating conditions, the RCFNN current angle controller is designed to produce the compensated current angle command. Moreover, a proportional-integral speed controller is adopted to generate the stator current magnitude command, and the proposed intelligent-MPFSC is employed to generate the current angle command. Furthermore, the proposed intelligent-MPFSC system is implemented in a 32-bit floating-point TMS320F28075 digital signal processor. Finally, from the experimental results, the current angle commands of the optimal PF can be effectively obtained online at different speed operating commands with varied load torque. [ABSTRACT FROM AUTHOR]

This article studies the rotational movement and charging torque in a new reconfigured on-board charger during the charging process. Recently, the reconfigured on-board charger becomes attractive because the propulsive units are engaged in the charging system to reduce the cost and volume. Since the unbalanced currents flow through the three-phase permanent-magnet synchronous machine, the rotational movement and charging torque are generated. The charging torque may be equal to the rated propulsive torque at some special rotor positions, which is unsafe and may lead to the rotational movement, extra noise, and motor wear. In order to reduce the influence of charging torque and rotational movement during the charging process, the charging torque is analyzed based on the magnetic coenergy. It is found that the charging torque is related to the unbalanced current, differential-mode current, and current ripple in motor windings. Thus, the mutual inductances of motor windings during the charging process are decoupled into the differential-mode and common-mode inductances. Furthermore, a solution is provided to significantly minimize the charging torque based on the control methods of the ac/dc side and dc/dc side. Finally, the experimental results are provided to verify the correctness of the suppression of rotational movement and the charging performance. [ABSTRACT FROM AUTHOR]

This article proposes a novel current control technique for three-phase switched reluctance motor (SRM) drives with harmonic current suppression, based on developed flux modulation principle. For conventional SRM control systems, the unsmooth and discontinuous stator current cause serious torque ripple, vibration, and noise, due to the doubly salient motor structure. In order to overcome shortcomings in conventional drives, the developed flux modulation principle is employed for the SRM in this article, where the working principle is investigated in detail, including the excitation magnetic field, flux modulator, and armature magnetic field. Then, a new control strategy is presented to generate the dc-biased sinusoidal current, by employing the modular open-winding converter. Furthermore, a harmonic current suppression strategy is put forward for the new drive to improve the motor performance, by employing a developed vector proportional integral control scheme. Compared to existing SRM drives, the torque ripple and motor vibration can be both significantly reduced, the motor structure and winding arrangement do not need to be changed, and the robustness of the motor system is improved. Finally, experiments are carried out on a three-phase 12/8 SRM prototype to verify the effectiveness of the proposed SRM drive and control strategy. [ABSTRACT FROM AUTHOR]

Relatively high torque ripple limits the further development of the switched reluctance machine, and the application of the ripple suppression method will reduce the efficiency of the system. To simultaneously improve the efficiency and torque ripple of the switched reluctance machine, a new commutation and online optimization strategy is proposed. According to the torque per ampere characteristics of the machine, two rotor position angles are defined, which are the boundaries for the high and low torque per ampere operation modes of the two adjacent phases, respectively, and for different operating modes, specific torque hysteresis control schemes are performed. Furthermore, an objective function is constructed with the efficiency and torque ripple coefficient, and during the operation of the machine, the defined boundary angles are online optimized by the genetic algorithm to maximize the value of the objective function. The effectiveness of the method is verified by detailed simulation and experiment under different operating conditions. [ABSTRACT FROM AUTHOR]

In order to construct a high-performance synchronous reluctance motor (SynRM) drive system, an intelligent maximum torque per ampere (MTPA) tracking control using a recurrent Legendre fuzzy neural network (RLFNN) is proposed in this study. First, a traditional MTPA (TMTPA) control system based on FOC is introduced. Since the reluctance torque of the SynRM is highly nonlinear and time-varying, the MTPA tracking control is very difficult to achieve by using the TMTPA control in practical applications. Then, an adaptive computed current (ACC) speed control using the proposed RLFNN for the MTPA tracking control of a SynRM drive system, which does not use a lookup table and can effectively obtain the optimal current angle command of MTPA online, is described in detail. The ACC speed control is applied to generate the stator current magnitude command, and an adaptation law is proposed to online adapt the value of a lumped uncertainty in the ACC control. Moreover, the adaptation law is derived using the Lyapunov stability theorem to guarantee the asymptotic stability of the ACC speed control. Furthermore, the proposed RLFNN is employed to produce the incremental command of the current angle. In addition, the ACC speed control and RLFNN are implemented in a TMS320F28075 32-bit floating-point digital signal processor for a 4 kW SynRM drive system. Finally, the robustness and effectiveness of the proposed intelligent MTPA tracking control are verified by some experimental results. [ABSTRACT FROM AUTHOR]

Control issue in electrical drives mainly deals with the dynamic behavior, which is based on the deviation of variables. The deviations play a straightforward role in presenting the various capabilities and merits of the electric drive systems. This paper describes, for the first time, a deviation-based torque control of synchronous reluctance motor (SynRM) drives with no need to know the motor parameters. The proposed control system is designed by using a normalized deviation model to derive linear and simple relationships amongst different machine signals. Therefore, the commonly used proportional–integral current regulators are replaced by novel deviation equations. As a result, the proposed approach provides facilities to electric drives, including control system simplicity, parameter independency, and no need for controller tuning. The theoretical findings are verified by those experiments. The obtained results are reported for a typical SynRM drive. In addition, performance comparison of the control system with a general PI controller-based field-oriented control scheme is carried out. It is expected that the proposed approach contributes to other electrical drives to simplify the machine equations, reduce control complexities, such as the number of conventional controllers, and overcome the problem of machine parameter dependency. [ABSTRACT FROM AUTHOR]

In this paper, a simplified control scheme is introduced for permanent magnet synchronous motors (PMSMs). The control strategy consists of a direct voltage controller that capitalizes on the motor's model to achieve accurate speed tracking. As such, no explicit currents loop regulation is needed which simplifies the control structure and unlike other control strategies, no motor's parameter knowledge, voltage or current transducer is required. But, the absence of current regulation loops yields higher energy consumption, which limits the motor's range of operation. Therefore, a genetic algorithm is presented to determine control gains with optimal current consumption ensuring operation at the full range of the machine. Simulation and experimental results for different situations highlight the performance of the proposed controller in transient, steady-state, and standstill conditions. Furthermore, the simplicity of the control scheme makes it a good candidate for a low-cost implementation of real-time PMSM drives. [ABSTRACT FROM AUTHOR]

This paper proposes a modular multilevel converter (MMC) based switched reluctance motor (SRM) drive with decentralized battery energy storage system for hybrid electric vehicle applications. In the proposed drive, a battery cell and a half-bridge converter is connected as a submodule (SM), and multiple SMs are connected together for the MMC. The modular full-bridge converter is employed to drive the motor. Flexible charging and discharging functions for each SM are obtained by controlling switches in SMs. Multiple working modes and functions are achieved. Compared to conventional and existing SRM drives, there are several advantages for the proposed topology. A lower dc-bus voltage can be flexibly achieved by selecting SM operation states, which can dramatically reduce the voltage stress on the switches. Multilevel phase voltage is obtained to improve the torque capability. Battery state-of-charge balance can be achieved by independently controlling each SM. Flexible fault-tolerance ability for battery cells is equipped. The battery can be flexibly charged under both running and standstill conditions. Furthermore, a completely modular structure is achieved by using standard half-bridge modules, which is beneficial for market mass production. Experiments carried out on a three-phase 12/8 SRM confirm the effectiveness of the proposed SRM drive. [ABSTRACT FROM AUTHOR]

An offline torque sharing function (TSF) is introduced in this paper for torque ripple reduction in switched reluctance machines (SRM). This TSF uses static flux linkage characteristics of the machine obtained from finite element analysis or experiments that describe the machine dynamics to determine optimal current profiles such that the torque ripple reduction is achieved with minimal copper losses. Due to this feature, the proposed TSF performs well across a wide speed range. Additionally, the objective function of the proposed TSF uses only one weight parameter, which facilitates the use of this TSF. In this paper, an intuitive justification for the selection of this weight parameter is given, and the performance of this TSF is validated in simulation and experimentally on a 5.2 kW, four phase SRM. To baseline its performance, the proposed TSF has been compared to the offline TSF in the literature, which shows that it has better current tracking performance at higher speeds due to the inclusion of flux linkage characteristics. Finally, it has been compared to conduction angle control at speeds above the base speed to show that it can be a viable alternative for the control of SRM even in an operation region normally not considered for TSF. [ABSTRACT FROM AUTHOR]

In order to have direct and better control of reducing the torque/flux ripples of interior permanent magnet synchronous motor (IPMSM), this paper presents an online torque and flux estimation-based nonlinear torque and flux control (NTFC) scheme of IPMSM drive considering motor electromagnetic developed torque and stator air-gap flux linkage as virtual state variables. For conventional nonlinear controller, thed—q-axis currents ($i_{d}$ , $i_{q}$) are considered as state variables that indirectly controls the torque/flux which may not be suitable for high-performance drives. On the other hand, conventional direct torque and flux control (DTFC) scheme suffers from significant torque ripples. The proposed work overcomes the major drawback of both the conventional nonlinear and DTFC schemes through the significant reduction in torque ripples. Stability of the proposed drive is also demonstrated through Lyapunov's stability criterion and global asymptotic stability is assured through the application of criterion supported by Barbalat's lemma. Reduced torque ripples and robustness of the proposed NTFC scheme is validated through comparative simulation and experimental results with classical nonlinear controller and DTFC-based IPMSM drive. The proposed NTFC scheme achieves the lowest possible torque ripples in steady state at different operating conditions. [ABSTRACT FROM AUTHOR]

The hybrid electric bus (HEB) presents an emerging solution to exhaust gas emissions in urban transport. This paper proposes a multiport bidirectional switched reluctance motor (SRM) drive for solar-assisted HEB (SHEB) powertrain, which not only improves the motoring performance, but also achieves flexible charging functions. To extend the driving miles and achieve self-charging ability, photovoltaic (PV) panels are installed on the bus to decrease the reliance on fuelsbatteries and charging stations. A bidirectional front-end circuit with a PV-fed circuit is designed to integrate electrical components into one converter. Six driving and five charging modes are achieved. The dc voltage is boosted by the battery in generator control unit (GCU) driving mode and by the charge capacitor in battery driving mode, where the torque capability is improved. Usually, an extra converter is needed to achieve battery charging. In this paper, the battery can be directly charged by the demagnetization current in GCU or PV driving mode, and can be quickly charged by the PV panels and GCUAC grids at SHEB standstill conditions, by utilizing the traction motor windings and integrated converter circuit, without external charging converters. Experiments on a three-phase 128 SRM confirm the effectiveness of the proposed drive and control scheme. [ABSTRACT FROM AUTHOR]

A maximum torque per ampere (MTPA) control based on virtual signal injection for an interior permanent magnet synchronous motor with fast dynamic response is proposed in this paper. A small square wave signal is mathematically injected into the current angle for accurately tracking MTPA points. The extracted derivative of electromagnetic torque is utilized to compensate the initially set current angle to the real MTPA operation current angle. Due to the absence of bandpass and low-pass filters, which are essential in the sinusoidal injected signal scheme, this method shows good dynamic response. By incorporating a modified equation for the torque after signal injection, the steady-state accuracy is also enhanced. The $d$ - and $q$ -axis current references are obtained through the current vector magnitude and optimal current angle instead of using the torque equation with nominal motor parameters, which guarantees the accuracy of the output torque. The proposed scheme is parameter independent, and no real signal is injected to the current or voltage command. Thus, the problems of the high-frequency signal injection method are avoided. A prototype is set up, and experiments are carried out to verify effectiveness and robustness of the proposed control scheme. [ABSTRACT FROM AUTHOR]

This paper proposed a simple strategy for parameters identification of switched reluctance motor (SRM) direct instantaneous torque control. This strategy without rotor locking includes measuring and calculating steps. In the measuring step, flux linkage curves with current at three critical positions are obtained. At the intermediate position, flux linkage curve is measured under current chopper control (CCC). At the aligned and unaligned position, flux linkage curves are measured when the winding is given a voltage pulse. In the calculating step, the whole flux-linkage characteristics with current and position can be calculated based on the measured critical curves. Then torque curves are calculated for direct instantaneous torque control. Meanwhile, the i-Ψ loci curves during CCC operation are analyzed for identifying adjusting advance angle. In this way, the entire flux linkage characteristics and adjusting advance angle parameters under different operating area are obtained. This strategy is applied to a 7.5 kW 12/8 SRM for direct instantaneous torque control (DITC). Experiments have been carried out to verify the effectiveness and accuracy of the proposed method. [ABSTRACT FROM PUBLISHER]

This paper proposes a sensorless control scheme for synchronous reluctance (SyR) motor drives based on the direct-flux vector control (DFVC) method. The control operates in stator-flux-oriented coordinates, using constant switching frequency. A hybrid position and speed observer is proposed, based on the combination of the active flux concept and high-frequency signal injection and demodulation. The two methods are fused together to form a unique position and speed estimate signals, with seamless transition between the two models based on reference speed. The proposed observer covers a wide speed range, from standstill operation at full load to flux weakening (FW). Furthermore, it is inherently immune from position estimation error caused by cross saturation, as proven mathematically and experimentally. The motor is operated according to the maximum torque per ampere (MTPA) law. Specific issues related to MTPA around zero torque are addressed in this paper. The proposed control technique extends the range of application of the DFVC to encoderless drives, and can be usefully adopted in those applications where both zero-speed and FW speed range operations are necessary, such as home appliances, or automotive and aerospace actuators and generators. A 2.2-kW SyR motor prototype was tested to verify the feasibility of the proposed method. Key tuning aspects are addressed in this paper. [ABSTRACT FROM PUBLISHER]

Hybrid-excitation switched reluctance motors (HESRMs) have attracted considerable attention for various drive applications due to their simple structure, low cost, and high-torque/power capabilities. This paper comprehensively evaluates and compares a high-torque segmented-stator HESRM drive with a conventional SRM drive in terms of static magnetic and dynamic performances. The stator of the segmented HESRM consists of six individual U-shaped segments; each one has two teeth associated with a permanent magnet (PM) installed between them. The static magnetic characteristics of a segmented HESRM and a conventional SRM, including flux distribution, phase flux linkage, electromagnetic torque, are analyzed and compared. The total fluxes created by the PM and by the excited current are strongly coupled. The details of mathematical model as well as dynamic performances of the segmented HESRM is derived and compared with the conventional SRM. Finally, a segmented HESRM and a conventional SRM of the same size are prototyped for experimental verification. From the comparative study, it is indicated that the segmented HESRM has better characteristics than the conventional SRM, such as less iron consumption, higher static and dynamic average torque production, lower torque ripple, higher power and torque densities, higher efficiency, and stronger starting capability. The measured results of static magnetic characteristic, steady-state and transient performances, and torque–speed characteristic of two SRM drives verify the finite-element analysis, modeling, and corresponding predictions. [ABSTRACT FROM PUBLISHER]

This paper presents an effective closed-loop control approach for a stepper motor. The proposed approach consists of motor parameter identification, closed-loop current control, closed-loop position control, and damping control. The presented implementation achieves accurate position, high torque, and smooth speed. By using an improved proportional-integral current control algorithm, this approach not only guarantees the current tracking performance but also increases the bandwidth during the speed response. The advanced position controller achieves both high torque and the synchronous condition of the motor after a loss of synchronism occurs. In addition, this method applies an effective speed damping method to remove resonance at low speed and reduce vibration at high speed. All the proposed algorithms were implemented on an industrial test-bench. The experimental results demonstrate the validity of the proposed approach for practical applications. [ABSTRACT FROM PUBLISHER]

This paper presents an integrated multilevel converter of switched reluctance motors (SRMs) fed by a modular front-end circuit for plug-in hybrid electric vehicle (PHEV) applications. Several operating modes can be achieved by changing the ON–OFF states of the switches in the front-end circuit. In generator driving mode, the battery bank is employed to elevate the phase voltage for fast excitation and demagnetization. In battery driving mode, the converter is reconfigured as a four-level converter, and the capacitor is used as an additional charge capacitor to produce multilevel voltage outputs, which enhances the torque capability. The operating modes of the proposed drive are explained and the phase current and voltage are analyzed in details. The battery charging is naturally achieved by the demagnetization current in motoring mode and by the regenerative current in braking mode. Moreover, the battery can be charged by the external ac source or generator through the proposed converter when the vehicle is in standstill condition. The SRM-based PHEV can operate at different speeds by coordinating the power flow between the generator and battery. Simulation in MATLAB/Simulink and experiments on a three-phase 12/8 SRM confirm the effectiveness of the proposed converter topology. [ABSTRACT FROM AUTHOR]

A robust field-weakening method for direct-torque-controlled (DTC) synchronous reluctance motors is presented in this paper. The proposed algorithm achieves smooth transition between the constant torque and field-weakening regions. Maximum torque per ampere is utilized below base speed, while both the current and voltage limits of the drive system are satisfied in the field-weakening region. The proposed method is robust to the variations in the machine dq -axis inductances. This ensures the system stability during field-weakening operation, especially along the maximum torque per flux trajectory. The proposed algorithm is incorporated into the duty ratio regulation-based DTC to achieve high-performance torque and flux control in the field-weakening region. Experimental results included in this paper confirm the veracity of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, a PWM current controller for the switched reluctance motor drives is proposed and digitally implemented. Parameter adaption is employed to guarantee both fast dynamics and robustness of the proposed current controller. The relationship between the proposed controller and the conventional controllers including PI and dead-beat controller is also presented. An improved sampling method is designed to avoid PWM delay in the control loop. Simulation and experimental results show that the proposed controller keeps similar dynamic response and accuracy as hysteresis controller under various testing conditions. However, compared with the hysteresis controller, the proposed current controller needs much lower sampling rate and has a constant switching frequency. [ABSTRACT FROM AUTHOR]

This paper proposes the novel control method for a monoinverter dual parallel (MIDP) drive system with interior permanent magnet synchronous machines (IPMSMs). It includes maximum torque per ampere (MTPA) control to elevate drive efficiency and active damping control to alleviate inherent stability problem of an MIDP motor drive system. Due to the combination of reluctance and electromagnetic torques, the d- and q-axis currents of IPMSM are coupled unlike those of induction and surface-mounted permanent magnet machines. For this reason, MTPA and active damping control of a MIDP IPMSM drive system are far more complex than those with nonsalient motors. In this paper, model-based mathematical analysis about MTPA and active damping control for MIDP IPMSM drive system are provided. Experimental results with two 1.6-kW IPMSMs are presented to verify the proposed algorithm. [ABSTRACT FROM AUTHOR]

The mutually coupled dual three-phase switched reluctance motor (DTPSRM) is a new type of special 12/8 SRMs, which possesses high-reliability and fault-tolerant feature. In the past researches, the model, analysis, and fault-tolerant operation were mainly focused on the classical single three- and four-phase SRMs. This paper is mainly to analyze and investigate the fault-tolerant performances of a 12/8-pole mutually coupled DTPSRM drive under various open-circuit operations. First, the static magnetic characteristics of DTPSRM with single- and two-phase excitations are calculated by finite-element analysis. Then, the mathematic model of the DTPSRM drive under open-circuit condition is developed with a combination of state and fault functions. The simulation model of the DTPSRM drive system with a fault-tolerant control strategy is established for dynamic analysis. The faulty characteristics and fault-tolerant performances of the DTPSRM with diverse open circuits are predicted. Finally, a 12/8 DTPSRM is prototyped and an experimental setup is built for verification. The experimental normal results and diverse open-circuit operations and self-starting capability under lack of phases are presented, validating the accuracy of the analysis and simulation as well as fault-tolerant characteristics of the DTPSRM drive system. [ABSTRACT FROM AUTHOR]

In this paper, speed and torque control modes (SCM and TCM) of synchronous reluctance motor (SynRM) drives are proposed based on emotional controllers and space vector modulation under an automatic search of the maximum-torque-per-ampere (MTPA) strategy. Furthermore, in order to achieve an MTPA strategy at any operating condition, after recognition of transient state by two new indicators, a search algorithm changes the stator flux magnitude automatically. The indicators operate based on slip effect generated at transient conditions in a SynRM with cage. The performance of the proposed controller is compared with an optimized conventional PI controller under different operating conditions. Simulation and experimental results demonstrate the benefits of the proposed approach. This structure shows superiority of the proposed method, such as fast dynamic, simple implementation and robustness to parameter variations and external disturbances in both TCM and SCM. In addition, the proposed MTPA strategy shows a reliable and fast response to operating point change. [ABSTRACT FROM AUTHOR]

An approach to eliminate mutual flux effect on rotor position estimation of switched reluctance motor drives at rotating shaft conditions without a prior knowledge of mutual flux is proposed in this paper. Neglecting the magnetic saturation, the operation of conventional self-inductance estimation using phase current slope difference method can be classified into three modes: Mode I, II, and III. At positive-current-slope and negative-current-slope sampling point of one phase, the sign of current slope of the other phase changes in Mode I and II, but does not change in Mode III. Theoretically, based on characteristics of a 2.3 kW, 6000 rpm, three-phase 12/8 SRM, mutual flux introduces a maximum ±7% self-inductance estimation error in Mode I and II, while, in Mode III, mutual flux effect does not exist. Therefore, in order to ensure that self-inductance estimation is working in Mode III exclusively, two methods are proposed: variable-hysteresis-band current control for the incoming phase and variable-sampling self-inductance estimation for the outgoing phase. Compared with the conventional method which neglects mutual flux effect, the proposed position estimation method demonstrates an improvement in position estimation accuracy by 2°. The simulations and experiments with the studied motor validate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, an extended-speed low-ripple torque control of switched reluctance motor (SRM) drives using torque sharing function (TSF) is proposed. Two operational modes are defined for the online TSF during commutation: In Mode I, absolute value of rate of change of flux linkage (ARCFL) of incoming phase is higher than outgoing phase; in Mode II, ARCFL of outgoing phase is higher than incoming phase. In order to compensate the torque error produced by imperfect tracking of phase current, a proportional and integral compensator with torque error is added to the torque reference of outgoing phase in Mode I and incoming phase in Mode II. Therefore, the total torque is determined by the phase with lower ARCFL rather than the phase with higher ARCFL as in conventional TSFs. The maximum torque-ripple-free speed of the proposed TSF is increased to more than ten times as the best case in conventional TSFs. Finally, the proposed TSF is verified by both simulations and experiments with a 2.3 kW, 6000 rpm, three-phase 12/8 SRM operating in both linear magnetic and saturated magnetic regions. Results show that the proposed TSF has higher average torque, and much lower torque ripples compared to conventional TSFs. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive method for eccentricity fault diagnosis in switched reluctance machine (SRM) during offline and standstill modes. In this method, the fault signature is achieved by processing the differential currents resulted from injected high-frequency diagnostic pulses to the motor windings. For feasibility assessment of the proposed method, the correlation between differential current and eccentricity occurrence is analytically demonstrated. A 3-D transient finite-element method is utilized to analyze the proposal, and its results are validated by experimental tests on a prototype machine in the laboratory. According to the obtained results by experimental as well as numerical analysis, a pattern is introduced in order to detect fault presence. In this stage, an algorithm with two methods is proposed for the detection of fault location or faulty phase. Furthermore, the direction of fault is recognized by a simple comparative technique. Next, a normalized indicator is proposed in order to estimate the eccentricity fault severity as well as its occurrence. This indicator is not dependent of the healthy motor information, which makes it reliable and applicable tool for all sizes of SRMs. Finally, a simple procedure based on achieved pattern and indicator is implemented to distinguish the static, dynamic, and mixed eccentricity in the SRM. [ABSTRACT FROM AUTHOR]

Small variable speed drives intended for mass-market applications like hand-held power tools and household appliances have to be inexpensive and efficient. Doubly salient reluctance motors are known to be cheap and robust, but their use in such mass market applications has been hindered by the cost and limitations of their associated power converters. A new converter concept is proposed in this paper. The new converter has the ability to apply higher voltages across the machine windings than could be obtained with standard circuits to achieve high-speed operation. The demagnetization of the machine coils is load independent ensuring fast current decay and consequently a stable high-speed operation at higher loads. The fast rate of current decay allows a longer duration of positive torque pulses resulting in less pulsating torque. A detailed analysis of the proposed converter is presented and design guidelines are laid out. A 1-kW prototype converter is designed and constructed to experimentally validate the operation of the new circuit. [ABSTRACT FROM AUTHOR]

A novel Lyapunov function-based direct torque controller for minimization of torque ripples in a switched reluctance motor (SRM) drive system is reported in this paper. SRM magnetization characteristics are highly nonlinear, where torque is a complex and coupled function of the phase currents and rotor position. The direct torque control (DTC) scheme avoids the complex process of torque-to-current conversion as required in indirect torque control scheme. The traditional DTC scheme uses a hysteresis-type torque controller and it leads to large amount of torque ripples when implemented digitally. The proposed controller is intended to take care of the nonlinear system dynamics of magnetic characteristics associated with accurate torque control using DTC scheme for the SRM drive system. In the Lyapunov function-based controller, the feedback gain is varied using a heuristic technique. The stability of the proposed controller is ensured by the direct method of Lyapunov. Experimental results for a 1-hp, 4-phase SRM are provided to demonstrate the efficacy of the proposed torque control scheme. [ABSTRACT FROM AUTHOR]

A concept of an integrated and distributed inverter for switched reluctance machines is introduced. The application at hand is an outer-rotor direct drive designed for railway traction applications. A five-phase switched reluctance machine was developed and is used to demonstrate the function of the integrated and distributed inverter. The distribution is achieved by supplying each phase coil with its own modular inverter. Each inverter module is placed evenly around the end of the stator stack next to its dedicated coil. This increases the redundancy of the drive significantly. The likelihood of phase-to-phase faults is reduced, because no overlapping end-turns are necessary. Also, the integration of machine and inverter is simplified, because the semiconductors can be evenly distributed around the machine. The concept reduces the amount of terminals between drive and vehicle to communication, power supply, and cooling, independent of the number of machine phases. With the integrated and distributed inverter new control strategies can be developed to influence machine vibration and radiated noise. In this paper, the design of the prototype, the direct torque control of the five-phase machine, and the behavior in the case of a fault inside a module is analyzed. [ABSTRACT FROM AUTHOR]

In this paper, instantaneous torque control for switched reluctance machines (SRMs) with an arbitrary number of phases is introduced. Direct portability of this control to machines with any number of phases is achieved by the developed multiphase-torque-sharing concept. This concept is also useful for SRMs where maximum torque can only be achieved by phase overlap of more than two phases. Furthermore, a new torque-sharing strategy, the low-loss-commutation strategy, for predictive pulsewidth modulation direct instantaneous torque control, is proposed that minimizes ohmic losses during commutation of two phases without the use of precomputed current or torque profiles. Additionally, no precomputed switching angles are required. They are determined online by the low-loss-commutation strategy. The strategy is especially useful for operating areas where copper losses dominate, which is usually the case at low speed. The proposed control strategies are validated by simulations and measurements on a drive test bench. [ABSTRACT FROM AUTHOR]

This paper presents a control technique for torque-ripple minimization in the switched reluctance motor (SRM) drive, based on a torque-sharing function (TSF) concept. In the proposed method, the reference torque is directly translated into the reference current waveform using the analytical expression. Optimization criteria of a TSF that are concerned with secondary objectives, such as minimization of copper losses or maximization of drive performance, are described. In addition, a novel family of TSFs is introduced. An optimal TSF can be easily extracted from the proposed family to satisfy one of the secondary objectives or to create balance between more of them. Control performances of the two extracted TSFs and the two optimized conventional (linear and sinusoidal) TSFs are compared. These four TSFs keep the copper losses to nearly the theoretical minimum. Each of them provides approximately the same operation efficiency of the considered three-phase 6/4 SRM drive. However, due to extension of the commutation angle between adjacent phases, TSFs from the proposed family provide better torque-speed characteristics. Moreover, one of them expands the possible speed range of torque-ripple-free drive operation, and another one, which provides the best torque-speed characteristics, reduces the peak phase current. [ABSTRACT FROM AUTHOR]

This paper presents the design and an encoder-based starting strategy for a low-cost single-phase switched reluctance machine (SRM). The single-phase SRM cannot produce a continuous torque over one revolution. Therefore, applications that do not require a continuous torque, e.g., pumps and fans, are especially suitable. Another issue of single-phase machines is start up. The starting direction is affected by the initial rotor position. Due to the functional concept of SRM the machine produces no torque at aligned and unaligned position of the rotor and consequently, cannot be started from these positions. To start up from every rotor position a saturation-based starting method is used. The design of the rotor with the saturable area is shown and the principles of an encoder-based starting strategy for a fast start-up under 0.5 s are introduced. Finally, the build prototype and experimental results of the starting strategy are shown. [ABSTRACT FROM AUTHOR]

A bearingless switched-reluctance motor (BSRM) has a complicated nonlinear character; therefore, its control strategy is very important to a stable operation. This paper presents a new control strategy for rotating and levitating a 12/8 BSRM with two sets of windings. This strategy can enhance not only the availability of winding currents in producing the radial force to suspend a rotor, but also decrease the torque ripple and stator vibration. First, influences of different combinations of winding magnetomotive force on the radial suspension force and torque are analyzed, and the optimal combination of winding magnetomotive force is gained. Second, based on the optimal combination, the theoretical equations of winding currents are obtained. Consequently, this paper gives the flowchart to calculate the advanced angle and winding currents. Moreover, the torque ripple and stator vibration of BSRM in the new control strategy are analyzed. Finally, simulation model and control system of BSRM with 12/8 poles are designed. Dynamic simulation and experimental results proved the theoretic conclusions. [ABSTRACT FROM PUBLISHER]

Abstract-Radial force and torque are the control objectives that determine the machine performance of levitation and rotation in a bearingless switched reluctance motor (BSRM). This paper proposes a control scheme for rotating and levitating a 12/8 BSRM. The motor average torque and radial force are independently controlled with hybrid excitations in main windings and levitation windings. First, the mathematical relationship between radial force and currents, which is utilized in this paper, is derived by using the Maxwell stress tensor method. Then, the proposed control scheme is analyzed. The average torque of each phase generated in the levitation region equals zero for its symmetry of the aligned position. Accordingly, the current calculating algorithm is deduced to minimize the magnitude of instantaneous torque in the levitation region. The principle and realization of the proposed scheme are demonstrated with finite-element (FE) analysis. Experimental results show that the proposed scheme is effective for a stable levitation. [ABSTRACT FROM AUTHOR]

Due to its special structure, the shaft radial force and torque of a switched reluctance motor can be separately controlled when all of the pole currents are independently controlled. In this paper, a control scheme for self-bearing operation of a 12 / 8 pole SRM drive is proposed. The rotor needs only one bearing for rotation and constraining the axial movement. The other end can move freely in the radial direction but is balanced with the radial force produced by the motor. A model for torque and radial force is derived and used to design the controller. Mutual inductance between the stator poles is included in the analysis to improve the model accuracy. The conduction phase pole currents are energized with phase-shifted sinusoidal currents. Depending on the requested radial force and torque, a descending-inductance phase may also be energized to increase radial force production. The requested force and torque are synthesized from the force and torque produced by these phases. The experimental results demonstrate successful SRM self-bearing operations. The rotor can be effectively balanced to the center of the air gap. The maximum radial position error was about 0.07 mm when the motor was rotating at 1500 r/min under full load torque. [ABSTRACT FROM AUTHOR]

This paper proposes the use of iterative learning control (ILC) in designing a torque controller for switched reluctance motors (SRMs). The demanded motor torque is first distributed among the phases using a torque-sharing function. Following that, the phase torque references are converted to phase current references by a torque-to-current converter and the inner current control loop tracks the phase current references. SRM torque is a highly nonlinear and coupled function of rotor position and phase current. Hence, the phase current references for a given demanded torque can not be obtained analytically. Assumption of linear magnetization characteristics results in an invertible torque function. However, the nominal phase current references obtained using this torque function will lead to some torque error as motor enters into magnetic saturation. For a constant demanded torque, the error in the phase current references will be periodic with rotor position. Hence, we propose to use ILC to add a compensation current to the nominal phase current references so that torque error is eliminated. Similarly, current tracking for the nonlinear and time-varying system is achieved by combining a simple P-type feed- back controller with an ILC controller. The proposed scheme uses ILC to augment conventional feedback techniques and hence, has better dynamic performance than a scheme using only ILC. Experimental results of the proposed scheme for an 8/6 pole, 1-hp SRM show very good average as well as instantaneous torque control. [ABSTRACT FROM AUTHOR]

Parasitic torque pulsations exist in permanent magnet synchronous motors (PMSMs) due to nonsinusoidal flux density distribution around the air-gap, errors in current measurements, and variable magnetic reluctance of the air-gap due to stator slots. These torque pulsations vary periodically with rotor position and are reflected as speed ripple, which degrades the PMSM drive performance, particularly at low speeds. Because of the periodic nature of torque ripple, iterative learning control (LLC) is intuitively an excellent choice for torque ripple minimization. In this paper, first we propose an ILC scheme implemented in time domain to reduce periodic torque pulsations. A forgetting factor is introduced in this scheme to Increase the robustness of the algorithm against disturbance. However, this limits the extent to which torque pulsations can be suppressed. In order to eliminate this limitation, a modified ILC scheme implemented In frequency domain by means of Fourier series expansion is presented. Experimental evaluations of both proposed schemes are carried out on a DSP-controlled PMSM thin platform. Test results obtained demonstrate the effectiveness of the proposed control schemes in reducing torque ripple by a factor of approximately three under various operating conditions. [ABSTRACT FROM AUTHOR]