Characteristics Of Switched Reluctance Motor Research Articles

A simple approach for the computation of magnetic characteristics of 4-phase switched reluctance motor

Switched reluctance motor (SRM) is non-linear in nature due to non-uniform air gap between stator and rotor that is produced from doubly salient poles. To control the operation of non-linear motor, a precise modelling of magnetic characteristic is essential. Traditionally magnetic equivalent circuit, finite element method (FEM) and experimental approaches have been used to derive magnetic characteristics of SRM. These methods involve complex computational steps and numerous assumptions for its calculations. To avoid this complexity, a simple approach is suggested in this paper to compute magnetic characteristics of 4-phase SRM. In this approach, SRM phase inductance is measured directly to identify the location of rotor with respect to stator from unaligned to aligned position. Then, single phase of SRM is excited through asymmetric converter and voltage and currents of corresponding phase is recorded with rotor being blocked using indexing head. Later recorded values are used to compute the magnetic characteristics from unaligned to aligned position. The proposed method is carried out using field programmable gate array (FPGA) controlled 8/6, 4-phase SRM. Further, accuracy of obtained magnetic characteristic is verified using FEM. In addition, fidelity of the magnetic characteristic is also validated by developing a dynamic model of SRM in MATLAB/Simulink

Modified switching control of SRM drives for electric vehicles application with torque ripple reduction

The switched reluctance motor (SRM) offers extensive prospects, particularly within the realm of electric vehicles (EVs). Its robust construction, wide speed range, high torque density, and efficiency provide significant advantages that surpass other motors. Nonetheless, controlling these motors is more intricate when compared to conventional DC brushed or AC motors. This complexity arises due to the non-linear inductance characteristics of SRMs, resulting in undesirable effects like torque ripple, vibrations, and noise. Using the conventional full-bridge inverter, three switching approaches are highlighted for various operating modes of an EV. This aims to reduce costs and the number of switching pulses, leading to a more compact system, elimination of dead time, and switching losses. The MATLAB/Simulink platform was utilized to examine the operational effectiveness of a three-phase 6/4 poles SRM drive. Additionally, this paper focuses on mitigating torque ripple concerns by employing an adaptive neuro-fuzzy inference system (ANFIS) controller that has better efficiency and superior responses compared to conventional controllers such as fuzzy logic control (FLC) and proportional integral (PI) control. The results of the simulation encourage the practical implementation of the system, which is the next step in the author’s research.

Dynamic measurement of magnetic characteristics of switched reluctance motor

Introduction. Switched reluctance motor (SRM) is a type of electric motor featuring nonlinear magnetic characteristics. The flux linkage or inductance profile of SRM is usually required for the purpose of high control performance, and can be normally obtained through conventional static test by using DC or AC method when the rotor is locked. Problem. However, it is not practical to use the conventional method of measurement when the specific apparatus for locking the rotor is unavailable. Besides, due to the magnetic nonlinearity of SRM, the saturation effect makes it difficult to obtain the saturated magnetic characteristics, and the conventional static AC test fails to address this problem. Novelty. In this paper, a dynamic measurement method of the magnetization curves of SRM is proposed which allows the measurement take place while the motor is running with load. Methodology. Based on the conventional static AC test, the proposed measurement handles the saturation problem successfully by introducing a DC offset in the high frequency AC voltage. Phase inductance with different rotor positions and currents can be obtained by analyzing simple equivalent circuit. Practical value. Simulation is conducted in MATLAB/Simulink environment and the results have verified that the proposed dynamic measurement can effectively obtain the magnetic characteristics of SRM.

SR Motor T-I Characteristics Performance Simulation Validation through Experimental Results

This article presents T-I (Torque–Current) characteristics performance of switched reluctance motor (SRM), simulation validation through experimental results. SRM has a simple construction, high fault tolerance capability, reliability, and low cost considered for the study. It works on the principle of reluctance. The simulation using MATLAB/SIMULINK for 8/6 SRM and experimentation tests in the laboratory is essential to find performance. Advance speed control technique of SRM drive using Digital Signal Processor (DSP-28335) controller and hardware setup for experimentation is utilized, for testing the performance. SRM is applicable in automation, electric vehicle, and industry. The characteristics study is a very important need in all applications. The simulation model for SRM is built in MATLAB/SIMULINK using proportional-integral controller. Experiments are conducted in the laboratory on SRM by load tests with a digital storage oscilloscope. Test data along with waveform are recorded for simulation and experimentation. Torque–Current characteristics performances are plotted. Finally, all results of both experimental and simulation are validated and presented. T-I characteristics of SRM are compared in both simulation and experimentation are very close to comparable.

Electromechanical Coupling Braking Control Strategy Considering Vertical Vibration Suppression for Vehicles Driven by In-Wheel Motors

To improve the comprehensive performance of the electromechanical coupling braking system (CBS) and suppress vertical vibration caused by the unbalanced radial forces of in-wheel motors, a CBS control strategy based on multiobjective optimization on the control parameters of switched reluctance motor (SRM) drive system is proposed in this article. First, the electromagnetic coupling and eccentricity characteristics of SRM are analyzed, and a multiobjective optimization strategy (MOOS) for the SRM-drive system is proposed to comprehensively improve the endurance mileage, battery life, and braking comfort. Then, switch angles and required regenerative braking force are optimized by the combination of MOOS and genetic algorithm, and the corresponding optimized controllers are established. Furthermore, the braking performance of optimized CBS is analyzed and compared to the other three single-objective optimization strategies (SOOSs), and the results indicate that the control strategy with MOOS can improve vehicle comprehensive performance, although the strategies with SOOSs have a great improvement for corresponding objectives. Meanwhile, based on the strategies, comprehensive switchable control logic is proposed to improve the overall performance of vehicles under different braking modes. Finally, the results from the simulation and processor in loop test are analyzed and compared, which validates the real-time performance and effectiveness of the control strategy.

Investigation on Torque Sharing Function for Torque Ripple Minimization of Switched Reluctance Motor: A Flower Pollination Algorithm Based Approach

ABSTRACT Switched reluctance motor (SRM) drive has outstanding features like robust construction, double saliency, fault tolerance capability, and heat withstanding capability. Despite these, torque ripple is an intrinsic characteristic of SRM because of double salient geometry, air gap length, and switching sequence of motor phase currents, making it unsuitable for slick torque and high dynamic performances applications. This paper discusses the novel Torque Sharing Function (TSF) implementation and the flower pollination algorithm-based intelligent controller to minimize the torque ripples in Switched Reluctance Motor (SRM). TSF values depend on commutation angles during turn on, turn off, and overlapping angles. The proposed TSF and flower pollination algorithm evaluates the performance parameters using the machine model and controls the torque ripples for a wide range of speeds. Additionally, optimal results are obtained using three TSFs functions with valuable guidance provided for TSF selection. The proposed TSF with flower pollination algorithm-based intelligent controller finds its suitability for online evaluation of optimal turn on, turn off, and overlapping angles. The performance of the proposed method has effectively reduced the torque ripple in SRM than the Differential Evolution (DE) algorithm.

A High-Performance Indirect Torque Control Strategy for Switched Reluctance Motor Drives

This paper proposes a high-performance indirect control scheme for torque ripple minimization in the switched reluctance motor (SRM) drive system. Firstly, based on the nonlinear torque-angle characteristic of SRM, a novel torque sharing function is developed to obtain the optimal current profiles such that the torque ripple is minimized with reduced copper losses. Secondly, in order to track current accurately and indirectly achieve high-performance torque control, a robust current controller is derived through the Lyapunov stability theory. The proposed robust current controller not only considers the motor parameter modeling errors but also realizes the fixed frequency current control by introducing the pulse width modulation method. Further, a disturbance-observer-based speed controller is derived to regulate the motor speed accurately, and the load torque is considered an unknown disturbance. The simulations and experiments on a 1.5 kW SRM prototype are carried out to demonstrate the effectiveness of the proposed high-performance indirect torque control strategy. Results verify the superiority of the proposed strategy with respect to the torque ripple suppression, system efficiency, and antidisturbance.

Output Delay Sliding Mode Tracking Control of SRM based on Multi-innovation Model Identification

The drive system of switched reluctance motor (SRM) is a complex nonlinear system that is composed of many links. The delay in the measurement of the speed and position signal of SRM is caused by the factors that affect the measuring sensor. To effectively improve the influence of the SRM rotor position and speed signal delay on the system performance, a sliding mode position tracking method based on output delay observation was proposed in this study. First, the model was discretized according to the structure and characteristics of SRM and the mathematical parameters of the system were identified using a multi-innovation stochastic gradient (MISG) algorithm. Second, a delay state observer was constructed on the basis of an SRM system model with output delay. Then, the sliding mode tracking control method based on the delay state observation compensation was proposed and combined with sliding mode control theory. Lastly, the effectiveness of the designed model parameter identification, delay state observation, and output delay control methods were compared through numerical simulation. Results show that when uncertain factors, such as noise, are present in the system, the MISG identification method can rapidly and accurately identify the parameters of the SRM model compared with the stochastic gradient identification method; the identification accuracy of the former is four times higher than that of the latter. Similarly, the sliding mode position tracking control method based on output delay observer can rapidly and accurately track the position and speed within 0.5 s. However, its position (0.2 rad) and velocity (0.233 rad/s) tracking exhibit large steady-state errors when no delay observation compensation is present. The proposed method not only demonstrates high position tracking accuracy, but also possesses strong robustness to output delay.

Modeling, Simulation and Experimental Verification of Four-Phase 8/6 Switched Reluctance Motor Considering Interactive Excitation

In the single-phase excitation mode of a four-phase 8/6 switched reluctance motor (SRM), the switch angle for each phase is usually high enough to improve the performance of the SRM, which can directly result in overlapping in excitation periods of each adjacent phase. Ignoring the torque variation caused by magnetic coupling between adjacent charged phases during excitation overlap period, which is a general method to establish the model of SRM currently, would greatly influence the accuracy of the simulation model. Aiming at the problem of the general modeling method, a new SRM ontology modeling method is proposed by considering overlapping excitation, based on nonlinear mathematical model established by means of mutual inductance which could influence the electromagnetic characteristics of SRM. Firstly, the reason of interactive excitation and the distribution of the magnetic field are analyzed by (FEM), and the mathematical model is also developed. Then, the detailed static characteristics including mutual inductance and torque are analyzed based on the results of FEM, which are compared with those of the model without considering the effects of interactive excitation. Furthermore, the dynamic simulation model of SRM drive system (SRD) is built, and the simulation results are analyzed and compared with those of the traditional model. Finally, a static experiment is designed and performed to verify the mutual inductance and static torque under long magnetic circuit (LMC) and short magnetic circuit (SMC) in interactive excitation. The comparison results show that the data from experiment are greatly consistent with those from FEM, and the characteristics of mutual inductance and torque under interactive excitation should be considered when establishing the model of SRM.

Quad Sampling Incremental Inductance Measurement Through Current Loop for Switched Reluctance Motor

Magnetic characteristics of a switched reluctance motor (SRM) determine the modeling accuracy, the performance of a position sensorless control, and the torque ripple reduction control. Due to double saliency structure and core saturation, the magnetic characteristics of SRM is dependent on both the rotor position and the winding current amplitude, which makes it difficult to measure the actual incremental inductance or flux linkage. This article presents the magnetic characteristics identification method. A quad current sampling technique is proposed to capture the derivative of the winding current at a specific rotor position and current amplitude. The flux linkage, co-energy, and torque are calculated from the obtained incremental inductance profile. The proposed method can be easily implemented on digital signal processor-based SRM drive without any extra circuit. The LCR meter and torque sensor measurements are provided to validate the proposed incremental inductance measurement method.

Flux linkage optimization for direct torque control of switched reluctance motor based on model predictive control

In this paper, to solve the problem of large torque ripple in a switched reluctance motor (SRM), a new control strategy based on model predictive flux control is proposed in the direct torque control (DTC) algorithm. First, the flux linkage value in the next period is calculated from the discrete time model of the SRM. Second, to reduce the computation burden and increase the dynamic response, a torque hysteresis controller is embedded in the system to select three candidate voltage vectors for the cost function. Finally, based on flux linkage minimization, the best voltage vector is selected and applied to the system. The proposed direct torque and predictive flux control (DTPFC) method perfectly suits the nonlinear magnetic characteristics of SRM, and shows better steady‐state and dynamic‐state performances compared to DTC. Furthermore, since DTPFC has only one variable in the cost function, the huge task of obtaining the best weighting factor is eliminated. Simulation and experiments are carried out on a three‐phase 12/8 SRM with the proposed control algorithm and DTC. The results demonstrate the validity of the new control approach. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

A Novel Method for Modeling the Electromagnetic Characteristics of Switched Reluctance Motors

Accurate measurement and determination of the electromagnetic characteristics of the switched reluctance motor (SRM) are indispensable to their advanced control and performance analysis. This paper proposes a novel method for modeling the flux-linkage characteristics of SRM. This strategy without rotor locking, includes three steps, namely measuring, estimating and calculating steps. In the first step, flux linkage curves with current at four equilibrium positions are obtained by an indirect measurement method. In the second step, the flux-linkage characteristic of SRM in the middle position is estimated by its two adjacent flux-linkage curves. In the third step, a decoupled analytical model based on the five-order Fourier series is developed to construct the entire flux-linkage characteristics. The proposed method can not only eliminate the requirements on rotor clamping devices or position sensors, but also achieve fast and accurate modeling for the electromagnetic characteristics of SRM. Comparative studies are carried out between the proposed method and the conventional rotor clamping method, and the results demonstrate that the proposed method has a good agreement with the conventional rotor clamping method. Moreover, the simulation model is established in MATLAB/Simulink software based on the entire electromagnetic characteristics calculated by the proposed method. The accuracy of the proposed method is further verified by comparing the simulation and experimental results under different operating modes of the SRM.

Accurate model of switched reluctance motor based on indirect measurement method and least square support vector machine

The accurate model of switched reluctance motor (SRM) is critical for performance prediction. However, due to the doubly salient structure, the flux linkage of SRM is a non-linear function with phase current and rotor position, which makes the determination of the characteristic of SRM very difficult. In this study, indirect measurement method is used to obtain the sample data and least square support vector machine (LSSVM) is used for the prediction of flux linkage. First, the basic principles of indirect measurement and the exact methods of realisation are presented. Second, the errors in the indirect measurements are analysed and post-processing is given to reduce them. Third, the entire static electromagnetic characteristics are obtained by the prediction of improved LSSVM. The results are compared with those of using artificial neural network and those of using less training data by LSSVM, which shows both strong learning ability and generalisation ability. Finally, a simulation model is built up using MATLAB/Simulink and the results are compared between simulation and measurement. The good agreement shows that the proposed model has good accuracy. In addition, the LSSVM does not need any prior knowledge which is much easier for modelling than the existing literatures.

Solar PV-Powered SRM Drive for EVs With Flexible Energy Control Functions

Electric vehicles (EVs) provide a feasible solution to reduce greenhouse gas emissions and thus become a hot topic for research and development. Switched reluctance motors (SRMs) are one of the promised motors for EV applications. In order to extend the EVs’ driving miles, the use of photovoltaic (PV) panels on the vehicle helps to decrease the reliance on vehicle batteries. Based on the phase winding characteristics of SRMs, a tri-port converter is proposed in this paper to control the energy flow among the PV panel, battery, and SRM. Six operating modes are presented, four of which are developed for driving and two for standstill onboard charging. In the driving modes, the energy decoupling control for maximum power point tracking (MPPT) of the PV panel and speed control of the SRM are realized. In the standstill charging modes, a grid-connected charging topology is developed without a need for external hardware. When the PV panel directly charges the battery, a multisection charging control strategy is used to optimize energy utilization. Simulation results based on MATLAB/Simulink and experiments prove the effectiveness of the proposed tri-port converter, which have potential economic implications to improve the market acceptance of EVs.

Torque modeling of Switched Reluctance Motor using LSSVM-DE

An accurate and precised model of Switched Reluctance Motor (SRM) captures the performance of the machine. The model is highly nonlinear and complicated due to its doubly salient structure. In this paper, a nonparametric regression model for torque parameter of SRM was developed using Least Square Support Vector Machine (LSSVM) applying the concept of kernel based learning. Hyperparameters of LSSVM improves the model accuracy and generalization ability. The optimal values of hyperparameters were obtained by using Differential Evolution (DE) and high accuracy was observed. The regression model was developed using the magnetic characteristics of SRM by 2-D Finite Element Methods (FEM). The results obtained have been compared with the other optimization algorithms such as Genetic Algorithm (GA) and Particle Swarm Optimization (PSO).

Modeling of a Switched Reluctance Motor Under Stator Winding Fault Condition

A new method for modeling stator winding fault with one shorted coil in a switched reluctance motor (SRM) is presented in this paper. The method is based on artificial neural network (ANN), incorporated with a simple analytical model in electromagnetic analysis to estimate the flux-linkage characteristics of SRM under the stator winding fault. The magnetic equivalent circuit method with ANN is applied to calculate the nonlinear flux-linkage characteristics under stator winding fault condition. A stator winding fault 12/8 SRM prototype system is developed to verify the effectiveness of the proposed method. The results for a stator winding fault with one shorted coil are obtained from the proposed method and from the experimental work on a developed prototype. It is shown that the simulation results are close to the test results.

Sensitivity Analysis of Geometrical Parameters of a Switched Reluctance Motor with Modified Pole Shapes

A major problem in Switched Reluctance Motor (SRM) is torque ripple, which causes undesirable acoustic noise and vibration. This work focuses on reducing the undesirable torque ripple in SRM by modifying stator and rotor geometry. This paper presents a comparative study on torque ripple minimization in SRM with modified pole shapes such as stator pole taper, stator pole face with non-uniform air gap and pole shoe attached to rotor pole. Further this paper presents a detailed sensitivity analysis of the effect of different geometrical parameters that alter the pole face shapes on the performance of SRM. The analysis is performed using finite-element method considering average torque and torque ripple as performance parameters. Based on the analysis, a design combining stator pole taper with non-uniform air gap is proposed to improve the torque characteristics of SRM. The dynamic characteristics of the proposed design are simulated and the results show satisfactory reduction in torque ripple.

Sensorless Control of Switched Reluctance Motor Based on Phase Inductance Vectors

A new sensorless control method based on phase inductance vectors of switched reluctance motor (SRM) is presented in this paper. To implement this method, the following was done. First, based on the pulse injection technique, a new method called phase current slope difference is proposed for identifying the full-cycle phase inductance of each phase. Second, the phase inductances are considered as vectors with fixed phase difference and the composed vector is rotated with the varied rotor position. Combining the composed vector orthogonal decomposition method and a new inductance subregional method, the rotor position can be estimated. This method can realize sensorless control of SRM from starting up at standstill to high-speed operation and is quite easy to implement. No additional hardware or complex computation is required and no a priori knowledge on magnetic characteristics of SRM is necessary. To verify the performance of the proposed sensorless scheme, the following experiments have been performed: 1) the initial rotor position at standstill and rotating shaft conditions are estimated for sensorless startup control; and 2) the rotor position and rotational speed are estimated at different reference speeds for sensorless speed closed-loop control and the dynamic performance is fully validated.

FEM ANALYSIS OF ANGULAR MISALIGNMENT FAULT IN SRM MAGNETOSTATIC CHARACTERISTICS

This paper proposes magnetostatic analysis of Switched Reluctance Motor (SRM) under angular misalignment fault to evaluate the performance of the motor under difierent operating conditions. In this analysis three-dimensional flnite element method (FEM) is used to simulate reliable and precise model by considering the complex motor magnetic geometry, end efiects, axial fringing efiects as well as nonlinear properties of the magnetic materials. The FE analysis is performed to obtain the static magnetic characteristics of SRM including ∞ux density, ∞ux linkages, terminal inductance and mutual inductance proflle under difierent rotor positions for difierent varying degree of faults. Consequently, it presents assessing the features of mutual inductance in inactive phases to study the variations of diagnosis index. The results obtained present useful information regarding the detection of fault and its direction as well as the amount of angular misalignment fault in the motor. To the best knowledge of the authors, such an analysis has not been carried out previously.

DSP-Based Automated Error-Reducing Flux-Linkage-Measurement Method for Switched Reluctance Motors

The switched reluctance motor (SRM) has received considerable attention from researchers for its many inherent advantages, and thus, it has become a popular research topic in the field of variable-speed drives as well as servo drives. Research on SRMs mainly includes their design, modeling and performance analysis, control, as well as applications. However, for verification of design, performance prediction, as well as development of a high-performance sensorless control algorithm, accurate measurement of the magnetic characteristics of the SRM is most critical. Hence, one of the most important problems in the field of SRMs is a practical and accurate instrumentation system for the measurement of the SRM magnetic characteristics. This paper first describes an accurate and fully automated digital method for the measurement of the magnetic characteristic of SRMs, which includes online offset-error removal and winding resistance estimation. In this method, a digital-signal-processor-based virtual instrumentation for measurement of flux linkage is developed. Then, the results of the measurement conducted on a four-phase SRM are presented. The accuracy of the measurement system is verified by comparing with that found via a magnetic analyzer. Finally, the various sources of errors and their contributions to the errors are discussed. The scheme can also be used, in general, for transformers or inductors.