Current Chopping Control Research Articles

A Hybrid Analysis of Brushless DC Motor

Brushless DC (BLDC) motors and derives have gained popularity because of numerous advantages. This motor application is achievable since permanent magnet (PM) technology has advanced. It has higher efficiency, reliability, and power with less maintenance due to the absence of brushes. A higher torque-to-mass ratio and long life are two of the most attractive characteristics making it appropriate for high-performance applications. This study describes the hybrid methodology for analyzing a three-phase, four-pole, 1500 W, brushless DC (BLDC) motor with an inner rotor. PI controllers and PWM in Matlab /Simulink, and the chopped current control in Maxwell 2d ae used. BLDC motor modeled by rotation machine export (RMxprt) analytical software and analyzed with a finite element method (FEM) Maxwell 2D software to calculate motor performance, such as torque, speed, and efficiency. The FEM results were verified by comparing them with the results taken from the Matlab/Simulink program and with the aid of the RMxprt software to supply some missing data. The motor torque and efficiency results from Maxwell 2D and Matlab show good agreement. A hybrid FEM-analytical approach is successfully applied to study a BLDC motor using three software packages RMxprt, Maxwell 2D, and Matlab/Simulink despite the lack of motor test data. The RMxprt program offers missing data like stator resistance, stator inductance, and torque constant. It is provided in the design sheet to help us with motor modeling. The successful adoption of the proposed hybrid FEM-analytical methodology will provide a good starting point for future BLDC motor research work

An enhanced current chopping control strategy for SRM drives using Harris Hawks optimization algorithm

This research proposes an Optimized Current chopping Control (CCC) approach for SRM drives. The goal is to implement a simple SRM drive that can effectively meet electric vehicle requirements, comprising minimized torque ripple to reduce vibrations and acoustic noises, maximized output torque to enhance vehicle acceleration, and improved efficiency, which contributes to extending the EV's battery life. Therefore, an optimization problem is formulated and solved offline, incorporating a CCC-based SRM drive model. The control variables for this optimization problem are the switching angles of the SRM. A multi-objective function is chosen to combine three performance indices: torque ripple, average torque, and efficiency. The Harris Hawks Optimization (HHO) method is utilized in this paper to solve the optimization problem and find the optimal switching angles based on the selected objective function. HHO demonstrates a strong search capability that can effectively handle the nonlinear magnetization characteristics of SRMs. Constraints on the switching angles are also included in the optimization problem to control the phase current's RMS value and power consumption. The optimized switching angles are applied to a current chopping control (CCC) strategy and an asymmetric half-bridge converter to implement the proposed HHO-based CCC drive. Moreover, to demonstrate the effectiveness of the proposed HHO-based CCC drive, a comparative analysis based on simulations and experimental measurements is presented against other CCC approaches for SRM drives, including modified particle swarm algorithm (MPSO)-based CCC drives and analytical-based CCC drives.

A Novel Diagnosis Method for Interturn Short-Circuits in SRMs by Tracking Post Turn-Off Phase Currents Under Current Chopping Control

Current chopping control (CCC) is widely preferred for low and medium-speed applications in switched reluctance motor drives. With precise current regulation, the consequence of inter-turn short-circuits is not reflected much in the faulty phase current. Also, the fault features are difficult to extract in the online mode for minor short-circuits. Moreover, ITSCs are responsible for hot spots in the defective winding, ultimately leading to a complete winding short-circuit due to persisting heating effect. Even the associated complications of SRMs like torque ripple, noise and vibrations are amplified to a greater extent under ITSCs. Therefore, diagnosing ITSCs is critical to shun such unwanted characteristics and failures. This article proposes a simple and novel method to diagnose ITSCs even with minor short-circuits in SRMs operating under CCC. With the reduction in the inductance due to ITSCs, the decay time of the faulty phase current post turn-off also reduces. This variation is monitored for all the phase currents within their respective aligned rotor positions to diagnose ITSC. The proposed method has better detection reliability regarding diagnosis under varying load conditions. The scheme is validated experimentally on a test setup of a customized four-phase SRM having winding taps for emulating ITSCs.

Integrated optimization of the in-wheel motor driving system considering the ride comfort of the electric vehicle under multiple operating conditions

In this paper, a multi-objective optimization scheme integrating structural parameters with control parameters is proposed to address the adverse effects of an unbalanced magnetic pull of the wheel motor on vehicle dynamics. Firstly, the unbalanced magnetic pull under the air gap eccentricity of a switched reluctance motor is analyzed using both Maxwell’s stress method and the principle of virtual displacement. Then, a current chopper control strategy for the in-wheel motor is developed, and the influence of relevant control parameters on the output characteristics of the motor driving system under different driving conditions is discussed. Finally, a multi-objective optimization model of a motor under multiple operating conditions is developed with the aid of multidisciplinary optimization software. Integration of structural and control parameters for optimization. The results show that the motor design parameters determined by the integrated optimization scheme can improve the vehicle’s response characteristics under a wide range of operating conditions. In particular, the negative effect caused by an unbalanced magnetic pull during the operation of the vehicle is greatly suppressed.

An Analytic Method of Segmented PWM Duty Cycle for Switched Reluctance Motor

In view of the large current peak and torque ripple in the actual current chopping control of switched reluctance motor, a segmented PWM duty cycle analysis method of switched reluctance motor based on current chopping control is proposed in this paper. The method realizes the control of the winding current by adjusting the average voltage of the two ends of the winding in one cycle through the PWM duty cycle. At the same time, according to the inductance linear model, the conduction phase is divided into a small inductance region and an inductance rising region, and the analytical formulas of PWM duty cycle in the two regions are deduced respectively. Finally, through matlab/simulink simulation and motor platform experiment, the current chopping control is compared with the segmented PWM duty cycle analysis method in this paper. Simulation and experimental results show that the segmented PWM duty cycle analysis method can effectively reduce the current peak and torque ripple, and has high practical application value.

Transient modelling and simulation of a switched reluctance machine in different operating modes

An appropriate numerical computational method and simplest model captures the performance of Switched Reluctance Machines (SRMs). Several papers and computer software-based simulation models are reported in the literature. Each model has its own merits and demerits. This paper proposes a mathematical model, based on a combination of voltage and mechanical equations, suitable for the transient running of a switched reluctance machine. The simulation results of current, torque and speed profile of SRM are produced under current chopping control and voltage pulse width modulation control. The proposed work has used experimental data of flux linkage and static torque in the mathematical model for best performance and control of the machine. The obtained simulation results are verified with experimental results. This model can be extended to a range of rotor position where the machine can be switched at decreased and increased inductance region which gives motoring and generating operation mode.

Mechanism analysis and optimum control of negative airgap eccentricity effect for in-wheel switched reluctance motor driving system

In this paper, the generation mechanism of the negative airgap eccentricity effect for the in-wheel switched reluctance motor (SRM) driving system is analyzed. An independent current chopping control strategy is proposed to achieve optimum control between the response characteristic of the in-wheel motor driving system and the dynamic performance of electric vehicle (EV). Firstly, the electromagnetic characteristic of the studied SRM under airgap eccentricity is studied based on electromagnetic coupling model and circuit driving equation, and the radial electromagnetic force under different airgap eccentricity is verified by adopting the built experiment device. Then, combined with the excitation characteristics of the radial electromagnetic force, the negative dynamic effect of the in-wheel motor driving system is analyzed in the time–frequency domain. Finally, an independent current chopping control strategy for the in-wheel SRM driving system based on vehicle vibration feedback is proposed. The controller parameters including the turn-off angle and chopping current threshold are optimized by data interpolation. Results show that the proposed control strategy can achieve the optimum control between the response characteristics of the in-wheel motor driving system and the vehicle dynamic performance, especially to suppress the vehicle sprung mass acceleration and tire bounce while starting EV.

Design of high power switched reluctance motor controller

This paper takes the high power Switched Reluctance Motor (SRM) as an example, and designs the control system of the SRM according to the structure and operation characteristics of the high power SRM. The control system takes STM32 MCU as the core, and is composed of driving circuit, current detection circuit and protection circuit. The control methods commonly used in SRM include current chopper control (CCC), voltage chopper control (VCC) and Angle position control (APC). In addition, PI closed-loop control strategy is used to optimize the system performance, which verifies the feasibility and stability of the design of the motor control system.

A single-winding BSRMWR direct instantaneous torque control and direct levitation force control method

The stator and rotor of the bearingless switched reluctance motor are both double salient pole structures, when the traditional current chopping control method is used, the torque and levitation force of the motor will have large fluctuations. To solve this problem, this paper studies a direct instantaneous torque control and direct levitation force control (DITC&DFC) method suitable for single-winding bearingless switched reluctance motors. This method takes the instantaneous torque and the instantaneous levitation force of the motor as the directly controlled object, eliminates the current loop, and simplifies the control algorithm while suppressing the fluctuation of the motor torque and levitation force. A 12/8-pole singlewinding bearingless switched reluctance motor with wide rotor teeth drive system is constructed, the Matlab/Simulink system simulation verifies the effectiveness and feasibility of the method.

Nonlinear Modeling of a C-Core Connected Two-Phase Switched Reluctance Motor

The main idea of this paper is to offer a continuous C-cores unique configuration for switched reluctance motor (SRM) and to present an analytical model for its analysis. The advantages of this structure are having a short path for the main part of the magnetic flux, resulting in less core losses and as well as less negative torque. On the other hand, there is less leakage flux in the proposed structure. Another advantage of this structure is that it has a high mean torque compared to conventional structures, so that this increase in mean torque also increases a small amount of torque ripple, which is negligible. However, power density at a constant volume increases relatively much. The proposed SRM is analyzed by the finite element method (FEM) and by employing a magnetic flux density pattern and magnetic fluxes path, its magnetic equivalent circuit (MEC) is obtained. In this MEC model, the main fluxes and leakage fluxes are fully modeled. After its complete analysis, electromagnetics torque, inductance, flux-linkage, mean torque, and peak torque are evaluated. Static and dynamic performances are then determined. Finally, the proposed SRM was prototyped and tested. The experimental results consisting of static torque, flux-linkage, voltage, and current waveforms and input power are compared with the corresponding results in the MEC model and FEM. The comparisons verify the accuracy and validity of the introduced analytical model. Besides, static torque, flux-linkage characteristics, and dynamic performance at a nominal speed of 1000 rpm and the current chopping control mode with chopping 5A under the load of the proposed SRM are compared with the conventional SRM and its merits are observed.

A Novel Power and Signal Composite Modulation Strategy for CCC-Based SRG in Distributed Microgrid

Switched Reluctance Generator (SRG) possesses the advantages of simple structure, low cost, high reliability and high fault tolerance. For promoting the intelligence of SRG based distributed power network, reliable communication is the key to achieve system monitoring, remote control, fault protection, etc. Power and Signal Composite Modulation (PSCM) methods are newly proposed to realize power-line communication (PLC) for SRG-based distributed microgrid. Two signal modulation methods are implemented on the basis of Current Chopping Control (CCC) by modulating either chopping references or chopping threshold of phase currents, so as to obtain voltage ripples with different frequencies to carry signals. Fast Fourier Transform (FFT) method is adopted for demodulating the transmitted data on receiving side. The proposed PSCM strategies are experimentally tested for SRG system with phase failure in distributed microgrid.

Direct Torque Control Based on a Fast Modeling Method for a Segmented-Rotor Switched Reluctance Motor in HEV Application

This article proposes a fast-nonlinear modeling method for the direct torque control (DTC) of a segmented-rotor switched reluctance motor (SSRM), excluding the rotor clamping device. First, the torque-balanced method is used to measure the flux-linkage values at five crucial positions. The flux-linkage profile of the SSRM is represented by the fourth-order Fourier series based on the measured values. Then, the Kriging model is employed to further describe flux linkage and torque characteristics based on the Fourier series. A combination of Fourier series and Kriging model can greatly incorporate their merits and improve the accuracy of the models. Compared with the conventional methods, the finite-element analysis data are not required for the modeling process in the proposed method. Finally, the simulations and experiments of the DTC and the current chopping control (CCC) methods based on the modeling method are carried out. The amplitude of flux linkage under DTC can be well controlled, while that under CCC is increased with the enlargement of load torque. Compared with the CCC mode, DTC greatly reduces the torque ripple and exhibits the better speed response, while the torque per ampere with CCC mode is higher.

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.

Modeling and simulation of three-phase 6/4 switched reluctance motor speed control system

To improve the response ability of the motor and reduce the torque ripple, we take the three-phase 6/4 SRM as the research object, according to the structure and characteristics of the SRM speed control system, the SRM speed and current double closed-loop control system are established and the current chopping control mode is adopted to change the motor speed. According to the mathematical model of SRM, then the model of each module of the speed control system is established by Matlab/Simulink. The simulation and performance analysis are carried out. The results show that the simulation model double closed loop control method can improve the system response ability, improve the stability of the motor and reduce the torque ripple.

Development of a digital control system for a belt-driven starter generator segmented switched reluctance motor for hybrid electric vehicles

A novel four-phase 16/10 belt-driven starter generator segmented switched reluctance motor has been proposed in a previous work to reduce torque ripple and increase the fault tolerance ability. Based on the previous research, the segmented switched reluctance motor digital control system is designed and presented. The digital control system including a power converter, detection circuits, and protection circuits is introduced in detail. For detection circuits, the half-detection method is employed to decrease the cost of the system. In addition, based on MicroAutoBox DS1401, a rapid control prototype platform is established. With this software system, it is easy to transfer control models and realize real-time control directly. Then, the speed closed closed-loop control for the segmented switched reluctance motor is applied to verify the proposed system. It contains current chopper control at a low speed and angle position control at a high speed. The simulation results are given, including the flux, current, torque, and efficiency range over the entire speed range of the segmented switched reluctance motor. Finally, the experimental results are presented to verify the simulation results and the effectiveness of the system. It can be found that the simulation and experimental results are consistent and acceptable, which means that the proposed digital system can operate naturally and accurately under speed closed loop control. Hence, the proposed digital system has high compatibility and practicability.

Novel Bearingless Switched Reluctance Motor With Wide Flat Inductance Region to Simplify the Control of Torque and Levitation Force

In conventional 12/8 bearingless switched reluctance motors (BSRMs), the generation and control of torque and levitation forces are always coupled and interacted, which increases the complexity of the current control algorithm. In this paper, a novel BSRM with 12 stator poles and 4 rotor poles is proposed to simplify the control of torque and levitation, which has wide flat inductance region. Through allocating the generation of torque and levitation forces to different inductance regions of each phase, the levitation control can be similar as that of magnetic bearings, and the torque control can adopt the methods of conventional switched reluctance motors, e.g. current chopping control and angle position control. Accordingly, the current control algorithm of proposed BSRM becomes very easy and flexible. Extensive experiments were completed to verify the demonstrated performance of proposed motor.

Modeling and analysis of radial electromagnetic force and vibroacoustic behaviour in switched reluctance motors

In this paper, the radial electromagnetic force and vibroacoustic behaviour of a switched reluctance motor (SRM) are predicted and analysed in detail. First, the radial force with the spatial–temporal distribution characteristics is derived analytically and verified by the 2D Fourier transform. Second, a multiphysics model, which not only includes the electromagnetic field, the mechanical field, and the acoustic field, but also takes into account the structural orthotropy and the non-uniformly distributed electromagnetic force, is established to predict the electromagnetic vibration and noise of a SRM. Third, based on the spatial and temporal orders of the force harmonics, the vibroacoustic mechanism of a SRM is revealed. Finally, the electromagnetic force and vibration under two control strategies, which include the angle position control (APC) and the current chopping control (CCC), are compared and analysed, respectively. The results show that the electromagnetic vibration and noise of a three-phase 12/8 SRM are mainly caused by the force harmonics with the spatial order of 4 and the temporal orders of 3 N0 ± 1 (N0 = 0, 1, 2···). Besides, under the two control strategies, the orders of the electromagnetic force and vibration are the same, but the amplitudes are different.

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.

One special current waveform of toothed pole doubly salient permanent magnet machine for marine current energy conversion system

Marine current energy becomes more and more attractive because of its remarkable advantages. In this paper, one toothed pole doubly salient permanent magnet (DSPM) machine is proposed for marine current energy conversion system. This kind of machine has a simple structure, good fault tolerance, reliable operation, and high power density, which make it very suitable for marine tidal current applications. However, DSPM machine is conventionally operated by means of current chopping control and angle position control in a different region due to the trapezoidal back electromotive force (EMF) waveform. While for this toothed pole DSPM machine, the PM flux-linkage, inductance, and back EMF have more sinusoidal waveforms, which make the sinusoidal current be possible. Unfortunately, the classic sinusoidal current generates a relatively large torque ripple owing to the special inductance. Consequently, the primary purpose of this paper was to design one special current waveform to further reduce the torque ripple. Firstly, the model of the toothed pole DSPM machine is presented. Secondly, the torque distribution theory is proposed without taking into account mutual inductance effect. The mathematic expressions of the currents are deduced subsequently. Thirdly, several fitting currents are analyzed and compared based on the theoretical currents. Moreover, the simulation results verify the torque distribution theory and allow proposing the optimal current waveform (fundamental and second harmonic) in comprehensive consideration of the voltage, powers, and torque ripple. Finally, some robustness analysis is also presented to show the good performances of this current.

Reliability Analysis on Power Converter of Switched Reluctance Machine System Under Different Control Strategies

In this paper, a novel reliability assessment scheme is presented to achieve the optimal selection of control strategies for switched reluctance machine system from the perspective of reliability. To begin with, a combination model of k-out-of-n :G model and Markov model is proposed to lower the complexity and enhance the accuracy of system-level reliability assessment. As for the component-level reliability assessment, the three-dimensional coupled thermal circuit model of power converter is built to achieve the precise and fast prediction of junction temperature that is necessary for calculation of failure rate. Then the static and dynamic reliability analyses are carried out under voltage chopping control (VCC), current chopping control (CCC), and angle position control (APC) strategies, which indicates that the implementation scope of the APC strategy should be broadened. Compared with the VCC strategy, the CCC strategy is strongly recommended even if current sensors boost the extra failure rate. Besides, the increase in redundancy levels on power converter is certified as the most powerful measure for reliability enhancement of the SRM system and the most cost-effective redundancy level can also be quantitatively obtained. The experiments of fault-tolerance capability and thermal stress indirectly verify the validity of reliability analysis.