Switched Reluctance Machine Research Articles

Soft Computing Techniques for the Control of Switched Reluctance Generator in Wind Energy Systems: a Review

The commercial use of switched reluctance machine as a wind generator is less popular compared to other alternatives such as induction or synchronous machines. This is due to the non-linear behavior and the complex control methods involved in controlling this machine. However, if the control techniques can be made simpler and easier to implement, switched reluctance machine can produce electricity with lower cost and wider operating range of speeds. In this paper, a comprehensive review of recent research trends in soft computing techniques used for the control of switched reluctance generator in wind energy production are discussed. This paper presents the state-of-the-art control techniques for switched reluctance generator as a good guidance for future research. The advantages of soft-computing techniques are reviewed, and this helps to overcome the non-linearity present in the generator. The highlighting features of various intelligent control techniques such as artificial neural networks, fuzzy logic, evolutionary algorithms, etc. are presented in order to encourage the use of SRG in renewable energy generation.

Development of Two Phase H-bridge Converter for 250W Switched Reluctance Machine

Background: Advancements in Power Electronics made a huge breakthrough in the industrial sector majorly in the development of Switched Reluctance Machines (SRM). The main objective of this paper is to develop a two Phase H-bridge converter for 250W SRM and compare its advantages and disadvantages over the other converters. Methods: A time based simulation has been carried out to evaluate the performance of the converter at various loads. Different parameters of the machine and converter are studied and the results are verified experimentally. Results: The obtained test results of the converter performance are found to be in good agreement with the simulation and the efficiency of the converter is compared with the existing R-Dump topology. Conclusion: It is concluded that the proposed H-Bridge converter for a two phase SRM is better than the R-Dump converter in terms of efficiency and reduced size.

Sub‐domain modelling and multi‐variable optimisation of partitioned PM consequent pole flux switching machines

Permanent Magnet Flux Switching Machines (PMFSMs) enclose unique features of permanent magnet (PM) synchronous machine, direct current machine, and switch reluctance machine therefore, applicable for high speed brushless AC applications. However, conventional PMFSMs exhibits demerits of high PM volume V PM , high torque ripples T rip , low average torque T avg , lower torque density T den , power density P den and leakage flux. In this paper, a new topology of 12S-13P and 6S-13P E-Core PM Consequent Pole Flux Switching Machines (PMCPFSM) with flux barrier and partitioned PM is proposed that eliminate leakage flux, enhanced flux modulation effects through flux barriers and reduces the PM volume up to 46.53%. Moreover, due to non-linear behaviour of PM and complex stator structure alternate analytical sub-domain model is utilized for initial design and Multi-Variable Geometric Optimization (MVGO) is opted to investigate influence of design parameters on electromagnetic performances such as T avg , T rip , T den and P den . Analysis and comparison with the existing 12S-10P E-Core PMFSM, 6S-10P E-Core PMFSM, 6S-10P C-Core PMFSM and 12S-14P C-Core PMCPFSM reveals that proposed 6S-13P PMCPFSM produced T avg higher up to 88.8%, suppress T rip maximum up to 14.72% and offer 2.45 times T den and P den capabilities, when compared with the aforesaid state of the art.

A Survey of the Modeling of Switched Reluctance Machines and their Applications

The main objective of modeling a switched reluctance machine is to derive a mathematical function to relate the outputs to the inputs. Due to the nonlinear relationship between the variables of torque, flux linkage, current and angular position of the rotor, Switched Reluctance Machine (SRM) modeling is a very challenging task and an open problem. Modeling is usually done in two situations, modeling a single machine, or modeling a set of machines. Each one must fulfill different requirements. This work presents a survey of different SRM modeling approaches, evaluating its advantages and limitations when modeling a single machine or a set of machines.

Electromagnetic design method for a TLSRG with application in ocean wave energy conversion

The tubular linear switched reluctance machine (TLSRM) has shown potential for applications as generator in direct drive conversion of ocean wave energy devices. However, the design of this type of machine is a difficult task and there is no methodology to provide an explicit solution. This work aims to contribute for the solution of this problem with the proposal of a new procedure to design tubular linear switched reluctance generators (TLSRG). With the proposed procedure the TLSRG can be designed to develop a given linear force and to achieve better generation efficiency. The design is defined as a minimization problem where an optimization process is used to find the optimal solution for the dimensional parameters. Finite element method (FEM) analysis is applied to compute the relevant electromagnetic characteristics. The mathematical model of the generator conversion system is formulated to evaluate its dynamic performance. An H-Bridge asymmetric converter is adopted to control the energy flow in the generator. The electric currents in the generator phases are adjusted with a hysteresis controller. A TLSRG with a maximum mean force of 120 kN is designed by applying the proposed procedure, implemented in Matlab® and combined with MagNet® (FEM commercial software) to compute the electromagnetic characteristics of the machine. The system mathematical model is solved in Simulink®. The dynamic simulations are performed for a constant velocity of 1.3 m/s. For these operating conditions, the generator is characterised with an output power of 126.2 kW and an efficiency of 82.1%. The control proposed to drive the TLSRG is experimentally tested on a small-scale prototype. The experimental results show the effectiveness of the controller in keeping the phase current near the reference value.

A Novel Structure of Switched Reluctance Machine With Higher Mean Torque and Lower Torque Ripple

Switched reluctance motors (SRMs) have a robust and simple structure, high reliability because of the absence of magnetic field source on rotor, low cost and simple cooling system. However, conventional SRMs confront with some challenges such as low mean torque, low torque density and high torque ripples. For wider applications of SRM, the above-mentioned drawbacks must be mitigated. One possible method is changing the structure of SRMs. In this article, a novel 12/14 three-phase SRM with connected C-core structure is introduced which has a short path for the main flux of stator teeth. This brings about core loss reduction. On the other hand, both teeth of the stator phase in C-core develop a positive torque during the movement of the rotor from the unaligned position to the aligned position; this enhances the torque, the mean torque and torque density of the proposed SRM, keeping the volume fixed. Finally, the proposed SRM was prototyped and tested and its torque/rotor angular position characteristic was measured. To verify the novelty and merits of the proposed SRM, its mean and peak torque, torque density, core losses and torque ripples were compared with those of an optimized 12/8 three-phase conventional SRM and a significant match was achieved.

COMPARATIVE ANALYSIS OF TWO HIGH-SPEED SINGLE-PHASE ELECTRICAL MACHINES WITH PERMANENT MAGNETS ON THE STATOR

Purpose: Single-phase machines with permanent magnets on the rotor are widely used in a variety of applications of a low rated power. When these machines are applied in high-speed applications, a retaining ring on the rotor core must be often used. However, it makes the assembly more complex and the high-speed machines become more expensive. On the other hand, machines with magnets on the stator still can be a valuable alternative due to their simple and reliable rotor design. In this paper the comparative study of performances of two single-phase electrical machines with magnets on the stator (flux reversal electrical machine and hybrid switched reluctance machine) is presented. The following performances have been compared: efficiency, weight, active materials cost, value of rated current of switches of the frequency converter. Methodology: Calculation of electrical machines performances using solving two-dimension boundary magnetostatics problems. Results. The theoretical comparison of the flux reversal electrical machine and the hybrid switched reluctance machine has been carried out; the comparison on specific torque and efficiency of the two aforementioned machines have been obtained. The flux reversal machine has a significantly higher efficiency and a fewer weight. In addition, it has a lower value of rated current. On the contrary, the cost of active materials of the hybrid switched reluctance one is much less. Originality: The presented results can assist in selecting the best design alternative of electrical machines in the following applications: electrical blowers, household appliances, fans, pumps and compressors of a low rated power etc. Practical value: The comparisons results of the flux reversal electrical machine and the hybrid switched reluctance machine has been obtained for the first time.

Torque Production Mechanism of Switched Reluctance Machines With Air-Gap Field Modulation Principle

The torque production mechanism of switched reluctance machines (SRMs) is investigated from the perspective of air-gap field modulation principle. The unipolar stator current excitations can be divided into DC and AC components and they induce the air-gap magneto-motive force (MMF) respectively. Meanwhile, thanks to the salient structure in SRMs, the air-gap MMFs induced by the two sources above can be modulated to obtain the synchronized air-gap fields for torque production. It is revealed that a multitude of field harmonics contribute to the torque together. The MMF-permeance model is built and the analytical deduction of the field modulation effect is provided, with which the orders of the field harmonics contributing to the torque output can be identified. Moreover, finite element method is employed to verify the predictions on various SRM topologies. Finally, aprototype machine is fabricated and measured for validation.

Analytical validation of novel consequent pole E‐core stator permanent magnet flux switching machine

Flux switching machines (FSMs) encompass unique features of conventional direct current machine, permanent magnet (PM) synchronous machine and switch reluctance machine. Permanent magnet FSM (PMFSM) is capable of high torque density and applicable for high-speed application, however conventional PMFSM exhibits demerits of high PM volume, high torque ripples and significant stator flux leakage. In this paper, a novel consequent pole E-core stator PMFSM is proposed and compared with conventional topology utilising 2D finite-element analysis (2D-FEA). Finite-element analysis revealed that proposed design enhanced flux modulation effects by introducing flux bridges and flux barriers as a result reduced cogging torque by reducing 46.53% of the total PM volume, reduce torque ripples by reducing PM slot effects and reduce flux leakage utilising flux bridges in the stator. Furthermore, analytical model for flux linkages, cogging torque, mechanical torque, no load and on-load magnetic flux density (MFD) is developed for initial design of conventional and proposed model. 2D analytical methodologies resolve equivalent magnetic circuits for open-circuit flux linkages, Fourier analysis for cogging torque, Laplace equations for MFD and Maxwell stress tensor for mechanical torque. Finally, results obtained from 2D-FEA and analytical methodologies are validated and compared.

Simulation and analysis of improved direct torque control of switched reluctance machine

<span>Direct torque control of electric machines widely used in modern electric drives. Switched reluctance machines (SRM) are different from traditional electric machines, so we cannot apply well-known technical solutions to them. Simulation can provide a powerful approach for investigating the control of switched reluctance machines, and Matlab / Simulink allows it successfully implemented. This paper presents a description of the model and the simulation results of the proposed new algorithms for direct control of the instantaneous torque of SRM in the motor and braking modes. In comparison with the known control algorithms, the proposed algorithm uses one common for all phases relay regulator with a smaller number of switching thresholds and, therefore, it has greater reliability and is easier to set up. </span>

Design of a Novel Modular Axial-Flux Double Rotor Switched Reluctance Drive

Nowadays, there is a renewed interest in switched reluctance machines and especially in axial-flux switched reluctance machines (AFSRM). This paper presents a comprehensive design procedure for modular AFSRM with an inner stator and two exterior rotors that have a new distribution of the stator and rotor poles, resulting in short magnetic paths with no flux reversal. After a description of the proposed machine, the output torque equation is derived from a simplified non-linear energy conversion loop and guidelines for its design are given. Once the preliminary sizing has been carried out the different modules of the AFSRM, the magnetically active parts made with SMC, are reshaped or refined using 3D printing and 3D electromagnetic finite element analysis until they reach their definitive shape and dimensions. Finally, an AFSRM has been built following the proposed design procedure and has been validated by experimental measurements.

Prediction of acoustic noise and vibration of a 24/16 traction switched reluctance machine

This study presents a numerical modelling approach for the prediction of vibration and acoustic noise for a 24/16 traction switched reluctance machine (SRM). The numerical modelling includes the simulation of electromagnetic force in JMAG, the calculation of natural frequencies and the simulation of vibration and acoustic noise in ACTRAN. Considerations in the modelling of geometries, meshing and contacts of the 24/16 SRM are discussed to ensure the accuracy of the numerical simulation. Two-dimensional fast Fourier transform (FFT) is applied to the radial nodal force at the stator pole tip to analyse the dominant harmonics. FFT is also applied to the simulated surface displacement of the housing and the sound pressure at 2000 rpm to analyse their dominant frequency components. The dominant harmonics for the vibration and acoustic noise at 2000 rpm are confirmed. The numerical modelling method presented in this study can also be applied to the other SRMs and electric machines to predict the vibration behaviour and the radiated acoustic noise.

Four-quadrant force control with minimal ripple for linear switched reluctance machines

Linear switch reluctance machine (LSRM) has been tried to act as an alternative generator for direct drive linear wave energy converter (WEC). Many researchers have proposed new topologies of LSRM to improve the power density, efficiency and reliability. However, the control methods for LSRM applied in direct drive WEC have been paid little attention, especially control methods considering the wave energy generator operating characteristics. In this paper, according to the generator control requirements of the direct drive WEC, force control algorithm for LSRM operating in four quadrants without a speed closed loop is put forward. The force ripple of LSRM is suppressed using force sharing function method. The four-quadrant control is easy to realize requiring only phase currents information. Simulation results validate the proposed method and indicate that LSRM is able to be used as the generator for direct drive WEC.

A New Flux Linkage Estimation with Drift Cancellation Technique for Switched Reluctance Machines

Assessing the flux linkage is an important feature for electric machines, including switched reluctance machines. However, sensor calibration errors and noise impose a problem known as drift, which is caused by the integration process used to estimate the flux linkage. This paper proposes a flux linkage estimation with a drift cancellation technique. The technique accounts for the switched reluctance machine’s working and driving principles. Simulation and experimental results are used to validate the proposed method. Additionally, a goodness-of-fit analysis is performed to support the outcomes. A R 2 factor of 0.9823 is found between the experimentally and simulation-estimated flux linkage. The results indicate that the method works properly and may be further used in control techniques and iron losses estimation.

Model Predictive Control of Switched Reluctance Starter/Generator With Torque Sharing and Compensation

To enhance the mechanical safety, guarantee sufficient temperature margin and reduce the high-frequency electromagnetic interference of the starter/generator embedded in the aero engine, a multiobjective optimization control method is proposed for the switched reluctance machine based on the model prediction and the torque sharing function (TSF). For the model predictive control, the instantaneous phase torque is estimated through the Hermite interpolation with the flux-linkage characteristics at the aligned and unaligned rotor position, and the reference phase torque is obtained by the TSF. The error between the estimated and real instantaneous torque, especially around the unaligned rotor position, will result in the performance degradation, which is effectively compensated by the new TSF. The performances of the proposed control method are evaluated in detail by the simulation and experiment, and comparison with other representative methods is carried out as well.

Predicting Temperature Profile on the Surface of a Switched Reluctance Motor Using a Fast and Accurate Magneto-Thermal Model

In this article, a simplified 3D magneto-thermal model to study the temperature distribution over the housing of a Switched Reluctance Machine (SRM) is proposed. The main objective of such model is to study the temperature distribution profile on the body of the machine under various working conditions in order to introduce a temperature based signature to develop condition monitoring procedures. The analysis of fluid flow and heat transfer inside the SRM supports the hypothesis that the effect of turbulent flow of the fluid and the complex heat transfer phenomenon of the rotating parts can be simplified to a heat flux boundary condition representation of the heat loss. The accuracy of the model is validated through simulation and experimental results on a prototype SRM. The developed simplified model can be used as for prediction of temperature profile on SRM surface, well suited for fault diagnosis in SRM. The proposed methodology can be modified applied in developing a thermal model for other types of electric machines.

Four-Quadrant Sensorless Operation of Switched Reluctance Machine over the Wide Speed Range

This paper presents four-quadrant sensorless control in switched reluctance machine (SRM) over the wide speed range. The proposed sensorless control technique could be employed not only at low speed with current chopping control (CCC) but also at high speed with angle position control (APC). At startup and low speed, the narrow voltage pulse is injected into the idle phases and the rotor position zone is determined by comparing the measured flux linkage with four flux linkage-current curves. The same flux linkage-current curves also can be adopted for rotor positions estimation at medium and high speeds. Two flux linkage-current characteristic curves in the inductance rising zone are employed to estimate the rotor position for motoring mode and the other two curves in the inductance falling zone are used to estimate the rotor position for braking mode. The experiments on a three-phase 12/8 pole SRM drive platform are carried out to verify the effectiveness of the proposed sensorless control technique.

High-Strength Rotor Design for Ultra-High Speed Switched Reluctance Machines

High speed machines are gaining popularity in more and more applications. Besides permanent magnet (PM) machines, switched reluctance machines (SRMs) are very competitive candidates for high-speed applications in high-temperature environments due to their single material rotor without PMs. However, the conventional rotor geometries of SRMs are not suitable for the ultra-high speed applications. In this article, a novel high-strength, high-torque-density, high-efficiency rotor design for the ultra-high speed SRMs is proposed. First, a three-dimensional finite-element analysis is conducted to calculate the von-Mises stress distribution of the proposed rotor and shaft. Then, in order to improve the bonding and robustness of the design, proper high-strength adhesives are used and modeled based on the cohesive zone model. A parametric study is conducted to find the optimal length of the rotor stack. A thermal stress case study is also conducted. Finally, several prototypes are built to validate the manufacturing feasibility of the proposed design.

A Multilevel Fault-Tolerant Power Converter for a Switched Reluctance Machine Drive

Reliability in the electrical drives is becoming an important issue in many applications. In this context, the reliability associated to the switched reluctance machine (SRM) is also an important area of research. One of the major problems, that strongly affect its operation, are drive power semiconductors faults. Typical power converter topologies used in SRM drives cannot handle faults in their power semiconductors. So, this paper presents a power converter topology that provides fault-tolerant capabilities to the drive under a switch fault. This power converter will be used considering that a change in the direction of the current that flows in the SRM windings does not affect the behavior of the machine. Besides that, the proposed power converter will allow to generate multilevel phase voltages in order to apply different voltage levels as function of the SRM speed. A laboratory power converter was developed to test the SRM drive in normal and faulty conditions. From the obtained results it was possible to verify the fault-tolerant capability of the drive under switch faults in different devices and failure modes. It was also possible to confirm the multilevel operation of the drive.

Synchronized Switching Modulation to Reduce the DC-Link Current in SRM Drives

Switched Reluctance Machines (SRM) are emerging as a possible alternative in terms of cost and supply stability to rare earth based electric vehicle traction systems. However, because of the huge amounts of energy stored and transferred back and forth between the DC source and the SRM, large DC-link capacitors must be used as buffers, which increases overall costs and size. This paper proposes a novel modulation technique which forces the exchange of energy between phases while decreasing the energy transfer between the DC bus and the SRM. This means lower DC bus currents (capacitor size and cost reduction) and lower Joule-effect conduction losses (better efficiency). The proposed modulation has been validated experimentally in a test bench and compared with the conventional torque-sharing function.