Four-phase Switched Reluctance Motor Research Articles

Direct Torque Control of a Four-Phase Switched Reluctance Motor for Electric Vehicle Drives

Direct Torque Control of a Four-Phase Switched Reluctance Motor for Electric Vehicle Drives

Modeling of nonlinear characteristics of switched reluctance motor based on optimized RBF neuron network

The strong nonlinearity of switched reluctance motor (SRM) makes it difficult to establish an accurate mathematical model of its electromagnetic characteristics. In this paper, an artificial neural network modeling method is adopted to estimate the nonlinear flux linkage characteristics of a four-phase SRM. Based on the samples obtained by experimental measurement, a radial basis function neural network is trained and further optimized using the K-Means algorithm. The modeling accuracy of the optimized flux linkage model is analyzed in detail and also verified by dynamic simulation of a direct instantaneous torque control system of the motor.

Analysis of Skewing Effects on Radial Force for Different Topologies of Switched Reluctance Machines: 6/4 SRM, 8/6 SRM, and 12/8 SRM

Reducing vibration and noise in electrical machines for a given application is not an easy task, especially when the application imposes some restrictions. There are many techniques for reducing vibration based on design or on control. Switched reluctance motors (SRMs) have a double-saliency structure, which results in a radial pulsation force. Consequently, they cause vibration and acoustic noise. This paper investigates the correlation between the radial force and the skew angle of the stator and/or rotor circuits. The analysis is computed from two-dimensional (2D) transient magnetic finite-element analysis (FEA) of three machine topologies, namely the 12/8 three-phase SRM, the 6/4 three-phase SRM and the 8/6 four-phase SRM. Compared to SRM, these topologies have the same basic dimensions (stator outer diameter, rotor outer diameter, and length) and operate in the same magnetic circuit saturation. The flux linkage and torque characteristics of the different motors are presented. The radial force distributed on the stator yoke under various skewing angles is studied extensively by FEA for the three machines. It is also demonstrated the effect of skewing angles in the reduction of radial force without any reduction in torque production.

Fully Integrated Multilevel Power Converter for SRM Drive With Charging Capabilities (G2V) for Electric Vehicle Application

This article presents a fully integrated multilevel power converter topology (IML-PCT) with integrated battery charging capability for a switched reluctance motor (SRM) drive. The battery charger is integrated within the IML-PCT, which eliminates the requirement of any additional module for charging purposes. The proposed IML-PCT applies higher energization and de-energization voltages during the driving mode, which leads to an enhanced constant torque region for SRM drive. For the battery charging mode, the proposed IML-PCT exhibits the characteristics of an onboard charger (OBC) capable of charging the battery energy storage system directly via a standard ac outlet. The OBC functionality is realized by reconfiguring the proposed IML-PCT into an interleaved bridgeless boost power factor correction circuit (IBB-PFCC). The charging inductors for IBB-PFCC are realized by reutilizing/reconfiguring all the windings of the four-phase SRM. Also, with the proposed IBB-PFCC configuration, the charging current in the windings leads to an average zero torque production. Thus, the rotor is kept stationary during battery charging mode without any external braking mechanism. Detailed simulation and experimental studies on a 1.1-kW laboratory prototype four-phase SRM demonstrate ac level-1 (120 V/240 V) charging performance of the proposed IML-PCT.

A Simple Four-Phase Switched Reluctance Motor Drive for Ceiling Fan Applications

A simple four-phase switched reluctance motor (SRM) drive for a ceiling fan is presented in this paper. Here, an asymmetric bridge converter is preferred due to its independent phase control and simple design. The proposed four-phase asymmetric bridge converter based SRM drive has no speed and current feedback loops, thereby eliminating the use of current sensors and complex computational logic. Position sensing is carried-out using hall-effect sensors in the proposed drive. Analytical and simulation studies are carried-out on the proposed drive and the results are presented. To verify the efficacy of the drive a prototype of motor and drive are fabricated. Experimental results show that the proposed SRM drive has low current ripple and acoustic noise as required in ceiling fan applications.

An Economical Solar Water Pump With Grid and Battery Backup for Continuous Operation

In this article, the design and control of an efficient solar-powered, reduced-stage water supply system with both grid and battery backup for enhanced reliability are presented. The water pumps with permanent magnet and induction motors have demagnetization and reliability issues under harsh environments. Therefore, a reduced-component four-phase switched reluctance motor drive is utilized to improve the cost-effectiveness and reliability of the system. The back-up battery together with the grid supply will contribute to the uninterruptable power supply of the standalone solar water pump. The provision to feed the solar power back into the grid can offer an additional benefit to the consumers: to earn revenue. A single-phase voltage source converter is employed to preserve the desired power quality at the grid side. In the proposed structure, an intermediate maximum power point tracking dc–dc converter for the solar panel is removed to make the system more compact and efficient. Based on the converter's absence, a new control scheme is developed and presented. MATLAB/Simulink-based simulation is carried out first to validate the developed system and control strategy. The simulation results are further validated through experimental results obtained via a developed prototype.

An Integrated Driving/Charging Four-Phase Switched Reluctance Motor Drive With Reduced Current Sensors for Electric Vehicle Application

This article proposes an integrated power converter (IPC) with driving/charging capabilities for four-phase switched reluctance motor (SRM) drive-based electric vehicle (EV) application. With the proposed IPC, only two current sensors are employed for measuring phase currents under all operating conditions. The proposed IPC integrates three circuits. First, during the SRM driving mode, the proposed IPC is utilized as an improved Miller converter. Second, during battery charging mode, the proposed IPC is utilized as an on-board battery charger, which is based on a bridgeless boost power factor correction circuit (PFCC) that incorporates two dc–dc boost converters. The on-board battery charger is realized by utilizing the existing power electronic switches in the proposed IPC and all the phase windings as charging inductors. Third, a front-end bidirectional dc–dc converter is employed for maintaining voltage and current balance between IPC dc-bus and battery. During driving mode, the front-end converter boosts the battery voltage to the IPC dc bus voltage. And during regeneration/braking, the stored magnetic energy is used to charge the battery in constant-current (CC) mode via the front-end converter. During battery charging via ac grid, the bridgeless boost PFCC and the front-end converter operating in buck mode charge the battery in CC/constant-voltage (CV) modes without stepping down the ac grid voltage. The claims of the proposed IPC are validated through simulation and experimental verifications.

Phase Current Reconstruction Method With an Improved Direct Torque Control of SRM Drive for Electric Transportation Applications

Acquisition of the accurate phase currents is indispensable for the control and protection of switched reluctance motor (SRM) drives for electric transportation applications. Existing phase current reconstruction techniques for SRM are implemented under the current control techniques, which generate large torque pulsations. Therefore, the direct torque control (DTC) method can be adopted to minimize torque pulsations and to enhance transient performance in electrified vehicles. However, the existing current estimation methods cannot be applied to DTC strategies due to the simultaneous conduction of all phases at any switching instant. Furthermore, it offers a lower torque per ampere ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$T/A$</tex-math></inline-formula> ) ratio and draws a high source current. This article addresses the aforementioned concerns by proposing a cost-effective phase current reconstruction method with an improved DTC strategy for a 4-kW four-phase SRM drive. This method employs a 16-sector partition method with a new voltage vector selection by detecting zero-current regions of each phase. As a result, the long-tail currents can be avoided, thereby limiting the simultaneous conduction of all phases. The simulation and test results show that the proposed DTC has minimal torque pulsations, high <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$T/A$</tex-math></inline-formula> ratio, low converter losses, and lower source current ripple in comparison to the existing DTC schemes under various operating conditions. Also, the proposed phase current estimation method effectively reconstructs the phase currents under both steady-state and transient operating conditions.

A Fault-Tolerant Power Converter With Multi-Switch Fault Diagnosis and Repair Capability for 4-Phase 8/6 SRM Drives

In this article, a modular fault-tolerant power converter for 8/6 four-phase switched reluctance motor (SRM) drives is presented. The proposed converter can work for both open-circuit (OC) and short-circuit (SC) fault conditions in the power semiconductor switches. A semiconductor switch module and a relay circuit are used for achieving the fault tolerance feature. The proposed converter is modular and provides independent fault-tolerant control for all phases. It also uses a minimum number of switches when compared with other fault-tolerant converter topologies. The proposed converter is tested for a fault in single as well as multiple phases using MATLAB/Simulink software and is validated experimentally on a 0.6 hp 8/6 SRM using an FPGA-based hardware setup developed in the laboratory. Detailed results are presented and compared with existing fault-tolerant converter topologies. A fault repair time of 2 ms has been achieved for both open and SC faults.

Fast Discharging (N+1) Switch Converter With Regenerative Flyback Operation for N-Phase SRM Drives

This article proposes a converter topology that can provide fast discharging for any N-phase switched reluctance motor (SRM) drive. The proposed converter achieves fast discharging with only (N+1) switches for an N-phase SRM drive. The discharging can also be varied and made faster as per requirement. The proposed converter achieves fast discharging by dumping the winding energy to a capacitor and feeding it back to the source through a flyback transformer. The proposed converter uses fewer switches, is easy to control, and has variable discharging voltage which can be made much greater than the supply voltage. The proposed converter has been implemented with a four-phase SRM drive using MATLAB/Simulink software and the results are presented. A hardware prototype of the proposed converter is developed in the laboratory and tested on a four-phase SRM. The corresponding experimental results are presented at different operating conditions. The proposed converter is also compared with other existing SRM converters with respect to different performance metrics and a detailed comparison table is presented. Using the proposed converter, a minimum discharge time of 0.32 ms has been achieved at 3 A reference current.

Torque Ripple Suppression Method of Switched Reluctance Motor Based on an Improved Torque Distribution Function

Currently, torque ripple is a crucial factor hindering the application of the switched reluctance motor (SRM). Hence, it is of crucial importance to suppress this undesirable torque ripple. This paper proposes a new torque ripple suppression method of SRM based on the improved torque distribution function. Firstly, the electromagnetic characteristic model of a 8/6-pole four-phase SRM is established, and the cerebellar model articulation controller (CMAC) is used to complete the learning of each model. Then, the improved torque distribution function is planned based on the torque model to give the reference torque of each phase, and the inverse torque model is used to realize the mapping of the reference torque to the reference flux linkage. Finally, the duty of each phase voltage PWM wave modulation is output based on the PID control theory. The proposed accurate model-based planning scheme is implemented on the simulation platform, and the results shows that the maximum torque fluctuation of the output results is reduced to within 3%, and the average error is reduced to within 1%, which is much lower than the error of 15% under the traditional direct torque control method.

A Mathematical Torque Ripple Minimization Technique Based on a Nonlinear Modulating Factor for Switched Reluctance Motor Drives

This article presents a method to reduce the torque ripple in an 8/6 four-phase switched reluctance motor (SRM). The proposed scheme introduces a nonlinear modulating factor dependent on the rotor position and magnitude of the phase currents. This factor manipulates the currents in two adjacent phases during commutation and reduces the torque ripple effectively. Unlike the conventionally available torque-sharing functions, the proposed method instantaneously modulates every phase current obtained mathematically based on the other phase current in order to maintain the net torque constant. The proposed method requires minimal offline analysis and offers maximum possible torque with a minimal ripple. The method is simple and easy to implement due to a low computational burden. The proposed algorithm is implemented using MATLAB/Simulink software and is also validated experimentally on a 0.6-hp 8/6 SRM using a field-programmable-gate-arrays-based hardware setup developed in the laboratory. Typical results are presented and compared with the existing techniques. A torque ripple of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\approx 8\%$</tex-math></inline-formula> has been achieved.

A Novel Fault Diagnosis Technique of Interturn Short-Circuit Fault for SRM in Current Chopper Mode

The interturn short-circuit fault of stator winding is a common failure mode in switched reluctance motors (SRMs), which can severely harm the operation of the motor. In this article, a novel method for diagnosing the interturn short-circuit fault in the current chopping mode is proposed, which is suitable for online monitoring and protection of SRMs. The proposed method achieves a fast response and high sensitivity and can mitigate the interference of load conditions on detection reliability. Moreover, this method is based on phase currents, which does not require additional sensor or detection circuits. Meanwhile, the effects of interturn fault location in the stator winding on the motor flux and motor parameters are analyzed in detail through finite-element analysis, which is helpful to establish a reliable diagnostics technique for various fault conditions. Experimentations based on an 8/6 four-phase SRM with special windings designed to simulate interturn short circuit conditions are conducted, and the results have verified the effectiveness of the proposed method.

Multi-Battery Block Module Power Converter for Electric Vehicle Driven by Switched Reluctance Motors

To improve the endurance and charging flexibility of electric vehicle battery packs, this paper proposes a multi-battery block module (MBM) topology for four-phase switched reluctance motors (SRMs), which not only allows flexible electric vehicle operation, but also achieves fast demagnetization and excitation. By integrating the multi-battery block module and photovoltaic (PV) panel into an asymmetrical half-bridge (AHB) converter, the MBM topology is designed to supply a multilevel bus voltage for the SRM drive. To improve the endurance of battery packs, a PV panel is also added to the topology to charge battery packs when the system is stationary. According to the different operation requirements, multiple power supply modes and charging modes can be realized by controlling the power devices in the proposed MBM topology. The simulation results based on the MATLAB/Simulink platform and the experimental results on a four-phase 8 / 6 switched reluctance motor verify the effectiveness of the proposed design.

Evaluation of DC-Link Capacitor RMS Current in Switched Reluctance Motor Drive

In this article, a method to evaluate the dc-link capacitor rms current of a switched reluctance motor (SRM) drive under different operating conditions is presented. Square current reference in both hard and soft chopping modes of pulsewidth-modulated current control is considered. By approximating the current controller response and using a recently proposed flux linkage model, the switching-cycle-average phase voltage and current are evaluated over an electrical cycle. The phase voltage and current are further used to obtain the rms values of dc-link current and capacitor current. The proposed method is also used to determine the capacitor current for low-torque-ripple current reference and single-pulse operation. The analytical predictions pertaining to different control methods under different operating conditions are verified by simulation and experimental results obtained from a 4 kW, 1500 r/min, four-phase SRM drive. While the capacitor current is found to be maximum at the lowest operating speed with hard chopping, the maximum capacitor current is observed at an intermediate speed with soft chopping, both for a given magnitude of square wave current reference. The proposed method is useful to size the dc-link capacitor and evaluate its loss in an SRM drive. Furthermore, closed-form expressions for capacitor rms current are also derived, assuming perfect tracking of square wave current reference at low speeds. These expressions bring out the dependence of capacitor rms current on the machine characteristics.

Efficient solar‐powered water pump with single‐input dual‐output DC–DC converter employing four‐phase SRM drive

The present work deals with the design of an efficient and inexpensive autonomous photovoltaic array-based water pumping system utilising a new configuration of a single-input balanced dual supply buck–boost DC–DC converter. A four-phase switched reluctance motor (SRM) drive is selected to pump the water effectively and to make the system reliable. The utilised DC–DC converter can provide two balanced outputs using a single solar power source. It offers continuous output supply with minimum ripple to the SRM pump. The new control logic is also discussed in this work to provide equal voltages for two capacitors of the split converter in both starting and steady-state conditions. An improved perturb and observer-based maximum power point tracking control is also utilised to enhance the solar output power at varying irradiance. Moreover, owing to the pulse-width modulation switching of a split converter, a reduction is achieved in the size of split DC-link capacitors. The MATLAB/Simulink-based simulation is done to validate the real-time implementation of a developed system. These obtained responses are again validated through test results obtained via the developed prototype.

Torque Ripple Reduction of SRM Drive Using Improved Direct Torque Control With Sliding Mode Controller and Observer

The industrial application of the switched reluctance motor (SRM) is limited by its high torque ripples caused by the doubly salient structure. In this article, an improved direct torque control (DTC) with sliding mode controller and observer is developed to reduce the torque ripples of a four-phase SRM. First, a sliding mode controller based on a new reaching law is developed for designing a sliding mode speed controller (SMSC) for the DTC system. An antidisturbance sliding mode observer (ADSMO) is then proposed and combined with the SMSC to build a composite antidisturbance speed control strategy. Moreover, detailed simulation validations are carried out to reveal the effectiveness of the new reaching law, SMSC and ADSMO. Finally, experiments are conducted to verify the performance of the proposed SMSC–ADSMO in a DTC system with a four-phase SRM prototype.

Proposal of a New Coil Arrangement for a Four-Phase Switched Reluctance Motor

This article proposes a new coil arrangement for a four-phase switched reluctance motor (SRM) which can be applied to a 12-slot and its multiple-slot motors. Two patterns of coil arrangement for a four-phase SRM have been proposed. However, these coil arrangements can be applied for eight-slot and its multiple-slot motors because of their magnetic symmetry. The conventional and proposed coil arrangements are compared in a four-phase SRM with 24 slots. The torque and radial force characteristics are compared using finite-element analysis. Finally, the motor efficiency is compared.

DC‐biased sinusoidal excited switched reluctance motor

In this study, a DC-biased sinusoidal excited control method is proposed for a traditional four-phase switched reluctance motor (SRM). Based on the proposed method, the torque ripple is smaller than that of traditional square excitation. First, the mathematical model of four-phase SRM with DC-biased sinusoidal excitation in dq-axis rotating coordinate system is established and the instantaneous torque is analysed. It is found that the torque is proportional to q-axis current and does not contain reluctance torque component with DC-biased sinusoidal excitation for four-phase SRM. Then the current control methods for torque component and magnetic field component are studied. The torque component is controlled by the sinusoidal pulse-width modulation (PWM) method, and the magnetic field component is controlled by the current hysteresis tracking method. Finally, the proposed method is verified by finite element simulation and experiment results. Compared with the square wave excitation, the torque ripple is reduced by about 40%.

Online Calibration of Sensorless Position Estimation for Switched Reluctance Motors With Parametric Uncertainties

This article proposes an online calibration strategy of sensorless position estimation for switched reluctance motors (SRMs) with parametric uncertainties. For conventional sensorless SRM drives, the voltage drops on power devices and the winding resistance changing with the current and temperature are neglected, which affects the accuracy of the estimated position. In this article, an inductance calculation scheme is proposed to improve the real-time position estimation with these parametric uncertainties. First, the calculation errors of the flux linkage and inductance are both investigated and the error correction of the estimated rotor position is analyzed in detail. Then, the inductance values of the current overlapped phases are calculated. The dc component of the phase inductance is online adjusted, where all three phase inductances can be easily obtained accordingly. Finally, the real-time rotor position is acquired by the coordinate transformation of the calculated three-phase inductance during the current overlapped region. Compared to conventional SRM sensorless drives, the error of the estimated position due to parametric uncertainties can be significantly reduced without pulse injection, extra hardware, and prestored flux linkage and inductance profiles. The simulation and experiments are carried out on three-phase and four-phase SRMs to validate the effectiveness of the proposed scheme.