Direct Instantaneous Torque Control Research Articles

OCTSF for torque ripple minimisation in SRMs

In this study, a new online compensation of torque sharing function (OCTSF) method is proposed to minimise the torque ripple in switched reluctance motors (SRMs). For SRMs, the torque ripple is a serious issue which is mainly produced by the overlapped conduction phases in the commutation region. In conventional TSF-based direct instantaneous torque control system, the incoming phase torque cannot achieve its reference torque perfectly and the outgoing phase torque also cannot drop down to its torque reference quickly in the commutation region. Hence, in order to minimise the torque ripple, the TSF of the outgoing phase is proposed to realise the positive compensation at the start of the commutation and the TSF of the incoming phase is used to achieve the negative compensation at the end of the commutation. Moreover, compared with the hard-chopping mode in conventional TSF strategies, the hard-chopping and soft-chopping modes are both employed in the proposed scheme to reduce the switching actions and switching loss. The simulation and experiments based on a 750 W three-phase 12/8 SRM are carried out to verify the effectiveness of the proposed OCTSF method.

Control Performance Analysis and Improvement of a Modular Power Converter for Three-Phase SRM With Y-Connected Windings and Neutral Line

In this paper, the control performances of a modular power converter for a three-phase switched reluctance machine (SRM) are analyzed and improved. The converter is implemented by a dual and a six-pack IGBT module, and the phase windings of the SRM are Y-connected and bipolar excited. The performances of the existing control method for this converter are evaluated by simulation and compared with those for the traditional asymmetric half-bridge converter, and the drawbacks, such as big torque ripple and small average torque, are presented. With the new operating modes of phase branch, namely magnetization, freewheeling, and demagnetization, improved basic control methods are proposed, which can effectively enhance the performances, flexibility, and applicability of the converter. Furthermore, the direct instantaneous torque control, which can reduce the torque ripple, is realized with the converter as well. Several simulations and experiments under different working conditions are carried out to verify the performances of the improved control methods.

Comparative Analysis of DITC Based Switched Reluctance Motor Using Asymmetric Converter and Four-Level Converter

High torque ripple is the main draw of Switched Reluctance Motor (SRM) compared to other conventional motor. Torque ripples can be minimized by Direct Instantaneous Torque Control (DITC) technique. DITC responds against the torque error instantaneously by using hysteresis torque controller and regulate the torque output of the motor within hysteresis band.This paper compares the performance of Switched Reluctance Motor in terms of torque ripples with DITC strategy for both Asymmetric converter and Four-level converter. Asymmetric converter has three states namely magnetization, freewheeling and demagnetiztion states. With four-level converter, fast magnetization and fast demagnetization are also possible. Thus, the current build up and decay time is reduced which improves the dynamic performance. SRM is simulated using DITC scheme with Asymmetric converter and Four-level converter in MATLAB/SIMULINK to analyze torque ripples and it is observed that DITC with four level converter is better than that with Assymetrical converter.

Low‐cost direct instantaneous torque control for switched reluctance motors with bus current detection under soft‐chopping mode

This study proposed a low-cost torque distribution function (TSF)-based direct instantaneous torque control (DITC) technique for switched reluctance motors (SRMs) by bus current detection under soft-chopping mode. A three-phase 12/8-pole prototype SRM is employed to analyse the phase currents and operation states, and a new converter connection with bus current sensor placement strategy is presented to replace the phase current sensors in each phase leg. Considering that the conventional bus current contains both the chopping current and demagnetisation current, the current sensor is placed in a new bus to remove all the needless demagnetisation currents. To obtain the chopping current information from the bus current for DITC implementation, pulse-width modulation signals with extremely short turn-off time are injected into the lower transistors to insert the chopping current detection states for brief intervals during each fundamental frequency cycle. The DITC scheme is implemented directly on the detected chopping currents from bus current based on a sinusoidal TSF. The proposed DITC system is more compact and low cost by using just a bus current sensor. The effectiveness of the proposed technique is verified by the simulation and experimental results.

A designed converter for minimizing SRM torque ripple with controlled boost capacitor automatically

Direct instantaneous torque control (DITC) is one way of controlling torque in switched reluctance motors. Despite the presence of DITC control, torque ripple at nominal or higher speeds is considerable due to the back emf increasing. To overcome this drawback, many converters have been proposed. In most convertors proposed for fast excitation in DITC, controlling of boost capacity is an important problem. This paper presents a DITC for a switched reluctance motor using a proposed converter to reduce the torque ripple with controlled boost capacitor automatically. The proposed converter reduces the torque ripple at rated or higher speeds and no controller requires controlling the boost capacitor. The proposed converter is compared with an asymmetric one via simulation results using MATLAB and experimental results.

Direct instantaneous torque control with wide operating range for switched reluctance motors

Owing to the constraint of the supply voltage, there is a theoretically maximum operating range of the smooth-torque operation for a switched reluctance drive (SRD). The maximum operating range can be determined by the authors previous work, based on which a novel direct instantaneous torque control (DITC) is proposed for four-phase 8/6 switched reluctance drive in this study, which can achieve the widest operating range. Compared with the conventional DITC, the proposed DITC does not need the extra optimisation strategy of the switching angle. The performance of the proposed method is identified by simulation and experiment results.

Speed Control of 8/6 Switched Reluctance Motor with Torque Ripple Reduction Taking into Account Magnetic Saturation Effects

This paper presents speed control of switched reluctance motor (SRM) with torque ripple reduction using direct Instantaneous torque control (DITC). The reference values of the instantaneous torque is generated from speed control by PI controller, from the comparison between the reference torques and the estimated torque using hysteresis controller in addition to selects different turn-off angles so that improve the performance of torque ripple, the latter achieves the switching signals needed for the converter to get the desired results. SRM have highly nonlinear for this the static characteristic has been determined using finite element method (FEM) under non-linear magnetic characteristics that makes them difficult to control but gives results closer to the truth. Results obtained from computer are compared for different turn-off angle which improve the performance the torque ripple of SRM.

Torque Smoothing of a Fault Tolerant Segmental Stator Switched Reluctance Motor

The relatively high torque ripples are one of the main disadvantages of the switched reluctance motors. By smoothing their torque they can become more competitive for variable speed drives used in automotive and industrial applications. One of the most promising approaches to reduce the torque ripples of a SRM is the use of a direct instantaneous torque controller. In the paper the effectiveness of this type of control will be proved for a fault tolerant segmental stator SRM. By advanced simulation techniques the working principle of the direct instantaneous torque controlled drive system is illustrated, and its performances are demonstrated.

Minimization of torque ripple in switched reluctance motor drives using direct instantaneous torque control

Torque ripple is an inherent characteristic of switched reluctance motor drives due to its double salient geometry and it is a serious drawback in applications that require smooth torque and high dynamic performances. This paper presents some contributions to the minimization of torque ripple in SRM using direct instantaneous torque control (DITC). Direct torque controller is simulated using Matlab/Simulink and then implemented in a DSPACE ACE kit 1006 CLP that includes a processor board with an AMD OpteronTM running at 2.6 GHz. Finally, experimental results are shown and they are compared with those obtained using conventional angle control.

Control for Polyphase Switched Reluctance Machines to Minimize Torque Ripple and Decrease Ohmic Machine Losses

In this paper, instantaneous torque control for switched reluctance machines (SRMs) with an arbitrary number of phases is introduced. Direct portability of this control to machines with any number of phases is achieved by the developed multiphase-torque-sharing concept. This concept is also useful for SRMs where maximum torque can only be achieved by phase overlap of more than two phases. Furthermore, a new torque-sharing strategy, the low-loss-commutation strategy, for predictive pulsewidth modulation direct instantaneous torque control, is proposed that minimizes ohmic losses during commutation of two phases without the use of precomputed current or torque profiles. Additionally, no precomputed switching angles are required. They are determined online by the low-loss-commutation strategy. The strategy is especially useful for operating areas where copper losses dominate, which is usually the case at low speed. The proposed control strategies are validated by simulations and measurements on a drive test bench.

Torque Ripple Minimization of 4 Phase 8/6 Switched Reluctance Motor Drive with Direct Instantaneous Torque Control

The switched reluctance motor drives has evolved as an alternative to conventional motors in variable speed drives because of advantages like simple and rugged structure, absence of rotor winding, adaptability to harsh environments like coal mining, high speed operation etc. Because of nonlinearity, torque ripple is high in the motor. This paper presents a high dynamic control technique called Direct Instantaneous Torque Control (DITC) where in the torque is maintained within a hysteresis band by changing the switching states of the phases. Thus torque ripple minimization and fast torque response is an inherent property of DITC. This paper analyses performance of the drive mainly in terms of the torque ripple during acceleration and steady state conditions with DITC in MATLAB/SIMULINK environment and results are discussed elaborately.

Direct Instantaneous Torque Control of 4 Phase 8/6 Switched Reluctance Motor

The applications of Switched Reluctance Motor Drives has increased in the recent past because of advantages like simple structure, no rotor winding, high torque to weight ratio, adaptability to harsh environments like coal mining etc. But the main disadvantage is that torque ripple is high because of the double saliency. This paper presents a high dynamic control technique called Direct Instantaneous Torque Control (DITC) where in the torque is maintained within a hysteresis band by changing the switching states of the phases between 1, 0 or -1.Thus torque ripple minimization is an inherent property of DITC. DITC based SRM drive is simulated in MATLAB/SIMULINK environment and results are discussed elaborately DOI: http://dx.doi.org/10.11591/ijpeds.v1i2.102

A Study on the Control Method for Torque Ripple Reduction during Phase Commutation

In this paper, an advanced torque control scheme of Switched Reluctance Motor(SRM) using modified non-linear logical TSF (Torque Sharing Function) with PWM is presented. In the proposed control scheme, a simple calculation of PWM duty ratio and switching rules from DITC(Direct Instantaneous Torque Control) can reduce the torque ripple with fixed switching frequency. The proposed control scheme is verified by the computer simulations and experimental results.

Direct instantaneous torque control of switched reluctance machines using 4-level converters

Direct instantaneous torque control (DITC) of switched reluctance machines (SRMs) using a novel 4-level converter is presented. The described DITC control strategy proposes detailed torque control regions and suitable control schemes. Using the 4-level converter, DITC can overcome voltage limitation of asymmetric converters and has a fast magnetisation and demagnetisation to improve dynamic performance and efficiency. For integrated advantages of DITC and 4-level converters, a suitable control scheme is described and analysed. Finally, the proposed DITC method of SRM drive systems using the 4-level converter is verified by simulation and comparative experiments.

Direct Instantaneous Torque Control in Direct Drive Permanent Magnet Synchronous Motors—a New Approach

In this paper, a novel direct instantaneous torque control scheme for a direct drive (DD) permanent magnet synchronous motor (PMSM) is presented. A hybrid control structure combining the internal model principle and the variable structure control (VSC) approach is proposed. First, a variable structure torque controller is adopted to regulate the torque angle increment according to the torque feedback error. Second, the appropriate control voltage vector is determined using the reference stator flux vector and the estimated dynamic back electromotive force (EMF) vector, as an internal model, in a deadbeat control manner. Subsequently, better disturbance rejection can be obtained with the proposed cascaded control structure. To robustly obtain the instantaneous torque and flux information, a robust adaptive motor model is proposed. The Lyapunov stability theory is used to analyze the stability of the augmented robust adaptive motor model and to give a guideline for tuning model parameters. Experimental results are presented to demonstrate the validity and effectiveness of the proposed instantaneous torque control scheme.

A Novel Direct Instantaneous Torque and Flux Control With an ADALINE-Based Motor Model for a High Performance DD-PMSM

This paper presents a novel direct instantaneous torque and flux controller with an adaptive linear neuron (ADALINE)-based motor model for a high-performance direct drive permanent magnet synchronous motor (DD-PMSM). Usually, high-performance motor drives are characterized by their fast and accurate response, quick recovery from disturbances, and insensitivity to parameter variations. However, the absence of the auxiliary mechanisms in direct drives, such as gears or ball screws, increases the sensitivity of the servo performance to uncertainties in the drive system. Practically, uncertainties are usually composed of torque ripple, parameter variations, external disturbances and un-modeled dynamics. To achieve fast and smooth torque production in a DD-PMSM, the proposed controller has a linear with variable-structure control element to control the torque angle increment and a dynamic internal model element within the flux control loop. With this novel configuration, the controller can embed more frequency modes within the stable closed loop system to cancel the torque ripples. To relax the parameters sensitivity issue, this study proposes an ADALINE-based motor model to robustly extract the instantaneous torque information and unknown motor parameters with low computational demand and high accuracy. Comparative experiments are presented to demonstrate the validity and effectiveness of the proposed control scheme.

Sensorless Direct Instantaneous Torque Control for Switched Reluctance Machines

This paper presents a position-sensorless torque controller for Switched Reluctance Machines (SRMs) based on Direct Instantaneous Torque Control (DITC). An indirect position estimation is developed based on a current-flux-linkage method to eliminate the need of the position encoder. The current-flux-linkage method has advantages of simplicity and requires a relatively short computation time. Therefore, the controller can be implemented with a high control bandwidth. The accuracy of position estimation and influences of estimation errors are studied. The functionality of the developed controller and its performance are investigated and verified by experiments over a wide operating range.

High-Dynamic Four-Quadrant Switched Reluctance Drive Based on DITC

This paper presents the development of a four-quadrant switched reluctance machine (SRM) drive for high dynamic applications. Comprehensive fundamentals and analysis for operating switched reluctance machines in four quadrants are presented. The drive is designed based on a high dynamic control strategy called Direct Instantaneous Torque Control (DITC). The functionality of DITC is discussed in detail for both motoring and generating operation. A methodology to generate switching functions directly by the hysteresis torque controllers for SRMs is proposed. The proposed controller was prototyped and tested on a digital signal processor/field-programmable gate array development platform. High dynamic operation in both motoring and generating mode and the transition between these modes are validated by experimental results presented at the end of this paper.

DITC-direct instantaneous torque control of switched reluctance drives

This paper presents an online instantaneous torque control technique for switched reluctance machines called direct instantaneous torque control. The method comprises two novel aspects. First, torque is estimated as a function of terminal quantities, i.e., flux linkage and phase current. Hence, torque estimation is independent of the rotor position. Secondly, high-bandwidth drive performance is obtained by implementing a digital torque hysteresis controller. Thus, the method works without torque profile functions and auxiliary phase commutating strategies. Therefore, the control algorithm offers a wide drive operating range without the use of a high-resolution shaft position sensor or sensitive position estimation techniques. Experimental and simulation results are presented in this paper.