Method For Switched Reluctance Motor Research Articles

Improved indirect instantaneous torque control based torque sharing function approach of SRM drives in EVs using hybrid technique

This manuscript proposes an improved indirect instantaneous torque control (IITC) based torque sharing function (TSF) method of switched reluctance motor (SRM) drives in electric vehicles (EVs) using a hybrid system. The proposed hybrid techniques are joint performance of both Reptile Search Algorithm (RSA) and Honey Badger Algorithm (HBA), hence it is named as Enhanced RSA (ERSA) method. Here, an IITC method of SRMs for EVs is utilized. It achieves the requirements of the vehicle, like minimum torque ripple, improved speed range, high effectiveness, and maximal torque per ampere (MTPA). To precisely specify the switched reluctance motor and its magnetic features are measured by the proposed method. The modified Torque sharing function compensates the torque error along with incoming phase, which contains the minimal rate of change of flux linkage. Finally, the ERSA method is implemented to define the best control parameters. Then, the proposed ERSA system is performed on the MATLAB platform and the performance is compared to different existing systems. The MSE for case 1 and case 2 using proposed system attains 0.01093 and 0.01095. The voltage deviation for case 1 and case 2 using proposed system reaches 5 and 5. The power factor for case 1 and case 2 reaches a value of 50 and 40 using the proposed system.

Robust-Oriented Optimization of Switched Reluctance Motors Considering Manufacturing Fluctuation

For electric drive systems, high robustness is the key performance in the design and optimization stage. Switched reluctance motor (SRM) is considered as an ideal candidate for industrial applications like electric vehicles (EVs), due to its superior thermal and mechanical performances. This article proposes an effective robust-oriented design optimization method for SRMs considering manufacturing tolerances for better finding the optimal robust design solution. A segmented-rotor SRM is taken as a design example, and the finite-element model (FEM) results are verified by the experiments. In the implementation, first, the optimization problem including the optimization objectives and constraints is defined. Sensitivity analysis is performed for the selection of strong-sensitive parameters, and the tolerance-affected parameter is considered in the optimization to ensure that the obtained optimal solution exhibits high robustness. Then, for the traditional Taguchi method, an orthogonal array (OA) is established based on the preset of design levels, and the optimal solution is determined by selecting the highest signal/noise ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S/N$ </tex-math></inline-formula> ) ratios. An improved sequential Taguchi optimization method (STOM) is proposed by combining the process in the traditional Taguchi method with the space reduction method inside the iteration process. The optimal solution can be found with the reduction of design space until meeting the preset condition. Finally, a comprehensive comparison of the initial, Taguchi, and STOM designs is presented for the SRM. Compared with the initial and Taguchi designs, the proposed STOM can obtain a robust design solution with more centralized performance distributions.

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.

Improved Position Estimation Method for SRM Considering Current Measurement Errors

Saturation and current measurement errors will decrease the accuracy of rotor position estimation for switched reluctance motor (SRM). To avoid the drawbacks, a rotor position estimation method based on the unsaturated inductance reconstruction is proposed considering current measurement errors. Firstly, the incremental, apparent and unsaturated inductances are analyzed. The unsaturated inductance is calculated with the similar triangle solution in normal condition during the linear inductance rising region. To avoid the pulse injection, the linear regression algorithm is used to calculate the virtual unsaturated inductance in the linear inductance falling region of adjacent phase. Then the complete rotor position in each electric period is obtained by combining the estimated position of three phases. Secondly, the influence of current measurement errors on rotor position estimation is analyzed. The offset error is directly avoided by detecting the zero-value region of phase currents. The scaling error is compensated by balancing the amplitudes of three phase unsaturated inductances. The proposed method does not need additional hardware and can avoid the influence of saturation and current measurement errors simultaneously. Experimental results validate the effectiveness of the proposed method.

Phase Current Reconstruction With Dual-Sensor for Switched Reluctance Motor Drive System

Due to the rugged construction, high starting torque, wide speed range, inherent fault-tolerance and high operating efficiency, switched reluctance motors (SRMs) have been used in many fields such as household appliances, electric vehicles and industrial drives. At low and medium speeds, the current chopping control (CCC) are usually used for SRMs. The current sensors must be connected in series with each phase winding for detecting the phase current, and the number of sensors is usually equal to the number of motor phases. In order to reduce the number of current sensors and the cost of the drive system, this paper propose a general phase current reconstruction method for SRM drive system with two current sensors. Firstly, the excitation, freewheeling and demagnetization circuits of the asymmetric half-bridge power converter are separated into two different paths. The sensors placement method, winding connection method and calculation formula of each phase current are introduced in detail. Then the influence of the turn-off angles on the overlap interval of each phase current is analyzed, and the proposed reconstruction method is further extended to multi-phase SRM. This method can simplify the current decoupling process and is easy to implement without changing the asymmetric half-bridge topology and operating states. Finally, the feasibility of the proposed phase current reconstruction algorithm is verified by simulation and experiment.

Improved general modelling method of SRMs based on normalised flux linkage

The modelling of a switched reluctance motor (SRM) is indispensable owing to its inherent non-linear characteristics. In this study, a general flux linkage model for SRMs developed by normalising the magnetic saturation levels and magnetic structures are described. On the basis of this general model, entire flux linkage characteristics of a specific SRM can be calculated easily with only need for the flux linkage at the aligned and unaligned rotor positions. In addition, a radial basis function neural network is adopted for high-precision modelling of the general flux linkage model. The flux linkage characteristics of five prototype motors were also analysed using both the finite element method and the proposed general modelling strategy. The results demonstrate perfect agreement, which verify the feasibility and practicality of the proposed general modelling method.

Minimising torque ripple of SRM by applying DB‐DTFC

Since the traditional direct torque control (DTC) of switched reluctance motors (SRMs) has the shortcomings of large torque ripple and non-constant switching frequency, this study proposes the deadbeat-direct torque and flux-linkage control (DB-DTFC) method for SRM. By analysing the basic principles of SRM, a discrete-time model is established to predict the future states of the SRM drive system. With DB-DTFC, the stator flux and torque can be manipulated during each pulse-width modulation cycle to minimise torque ripple during operation. As a result, the proposed DB-DTFC can minimise the torque ripple as well as apply space-vector modulation with a constant switching frequency. Finally, to verify its effectiveness, DB-DTFC was applied to the 15 kW three-phase 12/8-pole SRM test bench in real time and the results are compared with conventional DTC.

Rotor position tolerant detection method for SRM drive system with misaligned position sensors

Accurate rotor position is necessary for the control of switched reluctance motors (SRMs). Generally, three position sensors are ideally installed 120 electrical degrees apart for three-phase SRMs. However, the placement of position sensors may be inaccurate, particularly in small-size SRMs, and there is no method reported to deal with this problem up to now. Firstly, the position signals and the influence of the misaligned sensors on the detected rotor position are investigated. Then a novel method is developed to identify the misaligned position sensors with dynamic time warping (DTW) algorithm. The DTW distance versus the misaligned angle is calculated, and the relationship between them is described with linear regression analysis algorithm. Then the rotor position tolerant detection method is realised by compensating the misaligned angle in real time. Finally, comparative experiments are carried out on a three-phase 12/8 SRM drive system, and it can be found that the proposed strategy is capable of providing an accurate rotor position for the SRM drive system. The presented method is easy for online implementation and can be integrated into the control system conveniently.

Unipolar sinusoidal excited switched reluctance motor control based on voltage space vector

In order to improve the operation performance and decrease the torque ripple of switched reluctance motor (SRM), a new current control method for SRM based on voltage space vector was proposed. In which the stator windings are excited by sinusoidal current with a DC offset to realise the unipolar current excitation. In this control system, zero vectors were used to control zero-sequence current alone and non-zero voltage space vector was selected to control d–q-axis current considering coupling. The reluctance torque component was offset by injecting third harmonic current into the DC bias current, and copper loss was minimised by selecting appropriate current ratio. Experiences verified that the new method can effectively control SRM current. The torque ripple can be reduced with third times harmonic current injection, but the efficiency is also decreased. Compared with the traditional control method, the proposed method is simple, easy to implement, and can effectively suppress torque ripple.

An improved sensorless driving method for SRM using a phase-shift circuit technique

This paper presents an improved sensorless driving method for switched reluctance motor (SRM) using a phase-shift circuit technique. The conventional method consists of impressing short voltage pulses during unenergized phases, measuring the phase current pulses, and finding the correlation between the filtered current signals and rotor position. However, the filtering process causes a signal phase delay which varies with motor speed. This delay must be compensated for in providing the sensorless signal which is proper to the rotor position. A solution for this phase delay compensation, based on a simple analog and digital circuit, is proposed in this paper.

Novel sensorless driving method of SRM with external rotor using impressed voltage pulse

The paper presents an improved impressed diagnostic pulse-voltage method to estimate the rotor position of a switched-reluctance motor (SRM) with an external rotor. The fundamental method of impressed diagnostic pulse voltage is to impress pulse voltage at the inactive phases of a SRM that has an external rotor. Because the variations of inductance are dependent on the rotor position, and because the characteristic current values produced from the pulse voltage are dependent on the inductance, the rotor position can be inferred by observing the characteristic-current value. If the inductance of the SRM does not vary obviously, noise in the characteristic-current signal may cause failure of the sensorless-position-estimation method. Therefore, an improved impressed diagnostic pulse-voltage method is presented to increase the variations of characteristic current and estimate rotor position. First, the structure, characteristics, operational principles and mathematical model of the SRM with an external rotor are introduced. Then the improved impressed diagnostic pulse-voltage method is utilised to implement the sensorless position estimation for commutation control.