Ampere Ratio Research Articles

An Improved Model Predictive Torque Control for Switched Reluctance Motors With Candidate Voltage Vectors Optimization

This paper proposes an improved model predictive torque control (MPTC) strategy for switched reluctance motor (SRM) drives with candidate voltage vectors (CVVs) optimization, which can suppress the torque ripple effectively and enhance the system efficiency. This MPTC method is improved by three aspects. Firstly, the flux linkage calculation is removed compared to conventional MPTC. Secondly, the electric cycle of SRM is divided into six sectors based on the ideal torque contribution profile and the commutation region of the motor is redefined. Finally, CVVs of each sector are adopted based on phase torque characteristics and the total number of CVVs is reduced to 2 or 3 at each control period. The cost function is designed for the torque ripple suppression and copper loss minimization by selecting the optimal voltage vector from CVVs. This improved MPTC method avoids mass useless computation compared to conventional MPTC and no longer relies on hysteresis control loops compared to DTC method. In the simulation and experimental verification on a three-phase 12/8 SRM, the proposed MPTC method effectively reduces the torque ripple, improves the torque–ampere ratio and system efficiency, and improves dynamic response compared to DTC method.

Torque Ripple Reduction Strategy for Doubly Salient Electromagnetic Machine Based on Current Given Function

Torque ripples caused by the particular doubly salient structure of the doubly salient electromagnetic machine (DSEM) restrict its application in the field requiring high performance. This article employs the current given function (CGF) to propose a torque ripple reduction strategy for DSEM to enhance the torque capability. The optimal current profile for minimizing the copper loss is obtained based on the theoretical analysis. It is found that the obtained three-phase currents are distributed according to the phase torque coefficient that represents the torque capability of each phase. Then, to minimize the torque ripple and copper loss, four CGFs are proposed to distribute the reference current of each phase according to the torque characteristics of DSEM. Finally, the influence of overlap angle on the proposed strategy is analyzed to select the reasonable CGF and overlap angle under different operating conditions through simulation, improving the current tracking performance and torque–ampere ratio. The simulation and experimental results demonstrate the effectiveness of the proposed strategy in suppressing torque ripple and improving the torque–ampere ratio.

Energy-Based Control Technique for Monoinverter Dual Parallel PMSM With Different Parameters

This article declares two control strategies, named “ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"/> average-model based <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"/> ” (AMB) and “ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"/> energy-based <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"/> ” (EB) control methods, to control a monoinverter dual parallel surface-mounted permanent magnet synchronous motor (MIDP-PMSM) with different parameters. Up to now, it has been assumed that two parallel PMSMs have the same parameters, so the controller has been designed based on this simplifier assumption. To extend the control subject to MIDP-PMSMs with different parameters, two new methods are proposed and compared in this article. The average value of both motors’ parameters is used in the AMB control design, while in the proposed EB control method, each motor’s parameters separately contribute to designing the control laws. The proposed methods are based on the “ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"/> mean-difference <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"/> ” technique. These methods have been compared by mathematical analysis regarding the torque per total ampere ratio, the copper losses and the dynamic response of motors’ speed. The MATLAB simulation and experimental implementation have been carried out to verify the proposed methods. The results have shown that the EB control method has better performance than the other.

Phase Current Reconstruction Method With an Improved Direct Torque Control of SRM Drive for Electric Transportation Applications

Acquisition of the accurate phase currents is indispensable for the control and protection of switched reluctance motor (SRM) drives for electric transportation applications. Existing phase current reconstruction techniques for SRM are implemented under the current control techniques, which generate large torque pulsations. Therefore, the direct torque control (DTC) method can be adopted to minimize torque pulsations and to enhance transient performance in electrified vehicles. However, the existing current estimation methods cannot be applied to DTC strategies due to the simultaneous conduction of all phases at any switching instant. Furthermore, it offers a lower torque per ampere ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$T/A$</tex-math></inline-formula> ) ratio and draws a high source current. This article addresses the aforementioned concerns by proposing a cost-effective phase current reconstruction method with an improved DTC strategy for a 4-kW four-phase SRM drive. This method employs a 16-sector partition method with a new voltage vector selection by detecting zero-current regions of each phase. As a result, the long-tail currents can be avoided, thereby limiting the simultaneous conduction of all phases. The simulation and test results show that the proposed DTC has minimal torque pulsations, high <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$T/A$</tex-math></inline-formula> ratio, low converter losses, and lower source current ripple in comparison to the existing DTC schemes under various operating conditions. Also, the proposed phase current estimation method effectively reconstructs the phase currents under both steady-state and transient operating conditions.

Direct Torque Control With Phase Commutation Optimization for Single-Winding Bearingless Switched Reluctance Motor

Compared with the traditional control method, the direct torque control and direct force control method significantly reduces the torque ripple and the root-mean-square current of the phase winding in the single-winding bearingless switched reluctance motor. However, due to the unreasonable selection of voltage vectors and full cycle control, this method has some problems, such as too many control objects, excessive switching times, and low torque–ampere ratio. This article proposes an improved method for the abovementioned problems. First, the turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> angle and conduction region of each phase winding are chosen as the control targets, and the operation principle is introduced accordingly. Second, according to the difference of the torque generated by the neighboring phases, the output torque can be distributed more properly to obtain the higher torque–ampere ratio in the commutation region. Finally, the sectors divided in the electrical space are reorganized and the corresponding voltage vectors are optimized. Experimental results show that the proposed method can secure lower torque ripples, fewer switching times, and copper loss. In addition, the torque–ampere ratio is improved as well.

Tork Salınımı Minimizasyonu İçin Modüler Yükseltici-Alçaltıcı Anahtarlamalı Relüktans Makinası Sürücü Sistemi

In this paper, a modular three-phase buck-boost switched reluctance machine (SRM) drive system is proposed. In this topology, the three-phase SRM drive is composed of three single-phase modules that are connected in parallel where each single-phase inverter module is formed with a bidirectional buck-boost DC/DC converter and a cascaded H-bridge inverter. The DC/DC converter generates the rectified form of the phase voltage and the H-bridge inverter alternates and controls the polarity of the output voltage. This structure allows one to adjust the phase voltages independently, which provides faster excitation and demagnetization for a wide range of operating conditions. Since the voltage is always regulated dynamically, the need for bulky DC-bus capacitors is eliminated; hence, the size and the cost of the drive system are reduced. To validate the superiority of the proposed system and compare it with the traditional one, a set of simulations are done in MATLAB®/Simulink®. Not only the torque ripple is reduced, but also a higher torque per ampere ratio is achieved with the proposed system.

Efficiency improvement and torque ripple minimisation of four‐phase switched reluctance motor drive using new direct torque control strategy

The direct torque control (DTC) strategy is one of the most effective techniques, used to control the switched reluctance motor (SRM) with improved dynamic performance and reduced torque ripple. However, this approach draws a higher source current due to an extension of the phase current into the negative torque region, which lowers the net torque per ampere ratio. This study proposes a new DTC strategy for SRM to overcome this issue by modifying the partition of the sectors and appropriate voltage vector selection. Therefore, the proposed method improves the drive efficiency while minimising torque ripple. To implement this method, a non-linear machine model is developed using the torque and flux characteristics obtained from experimental studies on a four-phase 8/6 SRM. The proposed DTC scheme is implemented on a digital control platform and power loss calculations are performed to evaluate the drive efficiency. Test results show that the proposed DTC method has improved performance in terms of efficiency and torque ripple under various operating conditions in comparison to the conventional DTC strategy.

Direct Torque Control for Switched Reluctance Motor to Obtain High Torque–Ampere Ratio

The direct torque control (DTC) method was introduced into the switched reluctance motor to reduce its inherent output torque ripple. However, the conventional DTC method produces negative torque more or less, which reduces the torque–ampere ratio of motors. This paper proposes a new DTC method by three improvements. First, the hysteresis-loop control of flux is removed. New selection rule of voltage vectors is established to reduce the torque ripple. Second, the sectors divided in electrical space are reorganized by their actual positions according to the inductance profile. The boundaries between certain sectors are calculated and updated according to real-time working conditions. Finally, the alternative voltage vectors for increasing or decreasing torque are distinguished by whether any phase is excited. Therefore, the output torque tracks the reference accurately, which reduces the torque ripple. Moreover, the negative torque is avoided by the real-time regulation of the turn- off angle, and the torque–ampere ratio is increased accordingly. Simulation and experimental results verify the demonstrated performance of the proposed DTC method.

Direct torque and flux control of switched reluctance motor with enhanced torque per ampere ratio and torque ripple reduction

A smooth torque control of switched reluctance motor (SRM) is essential to avoid speed fluctuations causing stability problems in vehicular applications. This can be accomplished by an appropriate motor design and/or use of direct control of torque in SRM. It is reported that high RMS current is required to minimise the torque ripple in the conventional direct torque and flux control (DTFC), thereby reducing the torque per ampere ratio. To overcome this issue, a new DTFC technique with improved torque per ampere ratio while minimising torque ripple in an SRM traction drive is presented. Results demonstrated that the proposed DTFC technique reduces torque ripple with enhanced torque per ampere. Finally, the performance of the proposed scheme is compared with conventional DTFC of a four-phase (8/6) SRM to show the improvement in the traction drive.

Performance enhancement of autonomous system comprising proton exchange membrane fuel cells and switched reluctance motor

It is well-known that switched reluctance motor, as a non-linear load, is a source of current ripples which reduces the life time of proton exchange membrane fuel cells and significantly affects their performances. In this work, optimal operations of autonomous stacked proton membrane fuel cells serving a switched reluctance motor are anticipated. Overall model comprising proton exchange membrane fuel cells stack and switched reluctance motor along with necessary interface and control elements are implemented using MATLAB/SIMULINK. Three key objectives are adopted to be optimized either individually or simultaneously such as: i) proton exchange membrane fuel cells stack efficiency, ii) torque per ampere ratio, and iii) torque smoothness factor. Six decision controlling parameters e.g. fuel cells' temperature, air flow rate, air pressure, fuel pressure, and turn on/off angles of switched reluctance motor represent the search space of dragonfly algorithm. Numerical results indicate that the proposed dragonfly algorithm-based method is capable of increasing proton exchange membrane fuel cells stack energy saving, and reducing of hydrogen consumption, ripples in switched reluctance motor torque and current of proton exchange membrane fuel cells stack. Finally, results generated by the dragonfly algorithm are appraised compared to those obtained by genetic algorithm which signifies its value.

Improved performance of PEM fuel cells stack feeding switched reluctance motor using multi-objective dragonfly optimizer

In this article, a switched reluctance motor (SRM) powered by autonomous stacked proton exchange membrane fuel cells (PEMFC)’s stack with the purpose of optimizing their operating performances is addressed. Three key performance indices are examined that include: (1) torque per ampere ratio, (2) torque smoothness factor and (3) average starting torque. The later mentioned adapted indices characterize the objective functions that can be optimized individually and concurrently using a novel application of multi-objective dragonfly approach (MODA). The MODA is applied to generate the optimal turn (on/off) angles of H-bridge converter and the gains of a proportional-integral speed controller. A Pareto front optimal solutions are made, and the final best compromise solution is carefully chosen. The terminal voltage of the PEMFC is fine controlled by a boost converter, to overcome the noticeable decline of its voltage profile with the increase in loading current. The system under study is demonstrated at various loading conditions with necessary comparisons to other recent competing methods complete with subsequent discussions. The cropped numerical results indicate that PEMFC energy saving, reduction in SRM torque ripples and PEMFC current ripples can be enhanced. In addition, higher average starting torque of the SRM is realized.

Improved current control scheme with online current distribution and DFA regulation for switched reluctance generator

In this study, an improved phase current control scheme (CCS) for switched reluctance generator is developed and evaluated. The objective of proposed CCS is to find the most efficient operating point according to output power command directly and shorten the online tuning process. The CCS is augmented with an online phase current distributing block (OCDB) and a dynamic firing angle regulator (DFAR). In OCDB, phase current is distributed online to minimise copper loss by maximising the average-torque–ampere ratio. In DFAR, firing angles are processed according to actual phase current and current command. Improvements in current responses by augmenting DFAR are verified by simulations and experiments. In the end, the proposed CCS is employed in an output power controller for practical applications. Experimental results show that the proposed CCS has good dynamic response and finds the most efficient operating point directly.

Maximum Torque-per-Amp Control for Traction IM Drives: Theory and Experimental Results

A novel maximum torque per Ampere (MTPA) controller for the induction motor (IM) drives is presented. It is shown to be highly suited to applications that do not demand an extremely fast dynamic response, for example, electric vehicle drives. The proposed MTPA field oriented controller guarantees asymptotic torque (speed) tracking of smooth reference trajectories and maximizes the torque per Ampere ratio when the developed torque is constant or slow varying. An output-feedback linearizing concept is employed for the design of torque and flux subsystems to compensate for the torque-dependent flux variations required to satisfy the MTPA condition. As a first step, a linear approximation of the IM magnetic system is considered. Then, based on a standard saturated IM model, the nonlinear MTPA relationship for the rotor flux are derived as a function of the desired torque, and a modified torque–flux controller for the saturated machine is developed. The static and dynamic flux reference calculation methods to achieve simultaneously an asymptotic field orientation, a torque–flux decoupling, and an MTPA optimization in a steady state, is proposed. The method guarantees a singularity free operation and can be used as means to improve stator current transients. Experimental tests prove the accuracy of the control over a full torque range and show successful compensation of the magnetizing inductance variations caused by saturation. The proposed MTPA control algorithm also demonstrates a decoupling of the torque (speed) and flux dynamics to ensure asymptotic torque tracking. In addition, a higher torque per Ampere ratio is achieved together with an improved efficiency of electromechanical energy conversion.

Total Airgap Flux Minimization in Dual Stator Winding Induction Machines

Multiphase machines are gaining attention in specific applications due to their increased reliability and the possibility to split the power between more than one inverter. Dual stator winding machines can be seen under certain conditions as two independent induction machines coupled by the rotor. To ensure control independence of both windings, airgap flux saturation must be avoided. Proper flux synchronization of both windings is required to achieve this goal while maximizing the torque per ampere ratio of the machine. The conditions to obtain proper orientation of the fluxes are discussed in this paper, and the inverter control scheme to perform such orientation is developed.

Total Airgap Flux Minimization in Dual Stator Winding Induction Machines

Multiphase machines are gaining attention in specific applications due to their increased reliability and the possibility to split the power between more than one inverter. Dual stator winding machines can be seen under certain conditions as two independent induction machines coupled by the rotor. To ensure control independence of both windings, airgap flux saturation must be avoided. Proper flux synchronization of both windings is required to achieve this goal while maximizing the torque per ampere ratio of the machine. The conditions to obtain proper orientation of the fluxes are discussed in this paper, and the inverter control scheme to perform such orientation is developed.