Asymmetrical Half-bridge Converter Research Articles

Fault-Tolerant Performance Analysis of a Modified Neutral-Point-Clamped Asymmetric Half-Bridge Converter for an In-Wheel Switched Reluctance Motor

Reliability is an essential factor for the operation of the Switched Reluctance Motor (SRM) drive. Electric vehicles operate in harsh environments, which may degrade the operation of power converters. These failure modes include transistor open- and short-circuits, freewheeling diode open- and short-circuits, and DC-link capacitor failures. This work presents a performance analysis of an in-wheel SRM for an electric vehicle under short-circuit (SC) and open-circuit (OC) faults of a modified Neutral-Point-Clamped Asymmetric Half-Bridge (NPC-AHB) Converter. The SRM is modeled as an in-wheel electric vehicle. A separate vehicle model attached to the motor is also developed for validation and performance of the NPC-AHB under different faulty scenarios. The performance of the modified NPC-AHB is also compared with that of a conventional AHB under faulty conditions for an in-wheel 8/6 SRM. The performance indicators such as torque, speed, current, and flux are presented from MATLAB/Simulink 2023b numerical simulations.

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.

Analysis and Implementation of a Switched Reluctance Generator in Connection with the Three-Phase Power Grid and Proposal of an Anti-Islanding Strategy

This paper presents a dynamics study of the Switched Reluctance Generator (SRG) dynamics when connected to a three-phase AC power grid. A mathematical model that includes magnetic saturation is used to represent the SRG, which is driven by an asymmetric half bridge converter. Output generated voltage is smoothed with a shunt capacitor leading to a DC link voltage. This voltage is regulated using a PI compensator that controls the magnetizing angle of the generator phases. It is shown that putting a freewheeling stage between the magnetizing and the demagnetizing states per phase, allows the best use for a better usage of the mechanical power in electromechanical conversion process. Injection of active power in the grid is performed by two PI compensators that determine the modulation indexes to each sinusoidal PWM modulators that drive the three phases of the converter. This work also proposes the implementation of an islanding detection method for distributed generation (DG) systems. This method is based on voltage and frequency parameters detection. It proved to be robust and useful to detect the islanding under different load conditions and the output of the power grid.

Study and Implementation of a Computational Platform to Drive a Switched Reluctance Motor 8x6 for Electric Vehicles Applications

This paper aims to develop a computational platform for study and analysis of a Switched Reluctance Machine (SRM) 8x6 operating as motor for electric vehicles applications. In SRM modelling it was used the non-linear approach, which includes the representation of the magnetic circuit saturation through the concept of incremental inductance. For machine drive is used the topology of the asymmetrical half-bridge converter. The proposal is to make the computational representation to simulate of the behaviour of this machine under several operations conditions, guaranteeing safety and reliability of the results. Besides the drive of the SRM, the computational platform allows the study of the various magnitudes and aspects of this machine, such as: inductance, torque, speed profile, power and efficiency. A current control is also implemented, and simulation results are presented and discussed.

A quick demagnetization approach for low torque ripple in three‐phase switched reluctance motor drive system for electric vehicle applications

SummaryElectric vehicles (EVs) have gained a forward approach for achieving the low carbon economy and green transportation. Switched reluctance (SR) motor‐based propulsion mechanisms have been popularly used for EVs due to the wide speed range capability. The conventional phase current regulation technique does not give the satisfactory reduction of torque ripple in SR motor drive, particularly for automotive applications. To overcome the issue, a frontend boost converter (FEBC) is proposed to realize the quick excitation and demagnetization. Initially, the problems associated with the conventional asymmetric half bridge converter are investigated at various levels of phase current. The various operating modes of proposed drive system with FEBC are explained in detail. The proposed FEBC has the significant benefit of being able to provide variable boosting voltages based on the dynamic behavior of the SR motor. The phase voltages are increased during the fast magnetization and demagnetization modes due to the inclusion of FEBC, and hence, quick magnetization and demagnetization have been achieved. The proposed FEBC drive system has been simulated through the Matlab Simulink toolbox. The experimental results are also carried out in order to validate the simulation results.

Double Bus Provider Asymmetrical Half Bridge Converter With a Resonant DCX-Derived Auxiliary Circuit to Supply a LED-Based VLC Postregulator

The wide and settled use of Light-Emitting Diodes (LEDs) in lighting has made Visible Light Communication (VLC) an interesting option. Given the way LEDs are driven in VLC, the Two-Input Buck converter fits perfectly as a post regulator for VLC-LED lamps. Its main drawback is that it needs two input voltages with specific requirements tied to the VLC feature. One needs to be regulated according to the LEDs knee voltage thermal drift, while the other needs to be constant. With the objectives of avoiding complex circuits with cross regulation and using two converters performing the bus provider, the present work proposes a converter with two outputs that meet those voltage requirements. This converter is the integration of an Asymmetrical Half Bridge converter and a resonant unregulated Half Bridge converter. This integration is achieved thanks to the primary side similarity of both converters and the integration of both transformers in one magnetic core, achieving a solution with fewer components. In addition, one output can be fully regulated by a standard control variable while the other remains naturally constant, and is independent from any control variable. This greatly simplifies the control stage, avoiding cross regulation while fully complying with the application requirements. This work presents the circuit concept and how it relates to the intended application. The principle of operation will be explained and used to define the wide operational region where the topology meets the requirements imposed by the application. To validate the proposed topology, a 45-W prototype is built and tested, archiving the output voltage requirements and an overall efficiency near 94%.

Direct Instantaneous Torque Control of SRM Based on a Novel Multilevel Converter for Low Torque Ripple

The torque ripple of a switched reluctance motor (SRM) limits its application in electric vehicles. This paper proposes a DITC system for SRMs based on a novel multilevel converter (MLC), which aims at the problem that the torque ripple cannot be effectively suppressed for the conventional direct instantaneous torque control (DITC) of an SRM due to the limitation of the DC bus voltage in the asymmetric half-bridge converter (AHBC) and the single control strategy formulated in the commutation region. Based on the advantages of fast excitation and fast demagnetization for the proposed MLC and the torque distribution characteristics for each phase winding in the commutation region, a novel torque hysteresis control strategy is developed to improve the torque-following ability of the DITC and achieve the purpose of minimizing the torque ripple in the commutation region. In addition, multiobjective optimization control of the motor is carried out to improve the efficiency of the DITC system while suppressing the torque ripple. The effectiveness of the proposed SRM drive scheme is verified by experiment, which is of great significance for the application of SRMs in electric vehicles.

Bipolar power converter and control of switched reluctance generator system for renewable energy storage

PurposeBecause of the shortage of energy, the development of green and reliable energy is particularly important. As a green and clean energy, wind power is widely used. As the core component of wind power generation, it is particularly important to choose generators with high reliability. Switched reluctance machine is widely used as generators because of its strong fault tolerance and high reliability. Therefore, this paper aims to propose a power converter and its control strategy to improve the efficiency of switched reluctance generators.Design/methodology/approachIn this paper, a full-bridge power converter (FBPC) instead of the asymmetric half-bridge power converter (AHBPC) is adopted to drive the switched reluctance generator (SRG) system. Compare the FBPC with the AHBPC, the FBPC has several advantages including low cost and modularization, and operation process of SRG winding current direction is variable.FindingsThe results show that the SRG system can keep smooth operation by the FBPC with relatively high efficiency.Originality/valueThe FBPC is suitable to drive the SRG system. Meanwhile, this paper introduces two excitation modes of the FBPC as three-phase three-beat mode and six-phase six-beat mode. When the six-phase six-beat control strategy is adopted, the dead band time of the converter can be avoided. At the same time, the SRG has higher efficiency.

Reliability evaluation on SRG with full-bridge power converter considering thermal stress

PurposeQuantitative reliability analysis can effectively identify the time the driving system needs to be maintained. Then, the potential safety problems can be found, and some catastrophic failures can be effectively prevented. Therefore, this paper aims to evaluate the reliability of the switched reluctance generator (SRG) driving system.Design/methodology/approachIn this paper, a method considering different thermal stresses and fault tolerance capacity is proposed to analyze the reliability of an SRG. A full-bridge power converter (FBPC) instead of the asymmetric half-bridge power converter (AHBPC) is adopted to drive the SRG system. First, the primary fault modes of the SRG system are introduced, and a fault criterion is proposed to determine whether the system fails. Second, the thermal circuit model of the converter is established to quickly and accurately obtain the junction temperature of the devices. At last, the Markov models of different levels are established to evaluate the reliability of the system.FindingsThe results show that the two-level Markov model is the most suitable when compared to the static model and the one-level Markov model.Originality/valueThe driving system of SRG will be more reliable after the reliability of the system is evaluated by the Markov model. At the same time, an FBPC is adopted to drive the SRG. The FBPCs have the advantages of fewer switching devices, higher integration and lower cost. The proposed driving strategy of the FBPC avoids the current reversal and the generation of dead zone time, which has the advantage of reliable operation. In addition, a precise thermal circuit model of the FBPC is proposed, and the junction temperature of each device can be obtained, respectively.

An Electrolytic-Capacitor-Less PFC LED Driver With Low DC-Bus Voltage Stress for High Power Streetlighting Applications

This paper presents a single-stage, soft-switching, high power factor, flicker-free LED driver without any electrolytic capacitors for streetlighting application. The proposed LED driver consists of a buck-boost type power factor correction (PFC) circuit integrated with an asymmetric half-bridge LLC resonant converter. The buck-boost type PFC circuit provides a high power factor, low input current harmonics, and low dc bus average voltage. Unlike other methods that use the first harmonic approximation (FHA) analysis or the differential equations in time domain to analysis the LLC circuit, in this paper, a Fourier series-based analysis is proposed. The proposed method provides better accuracy in comparison with the FHA while being simpler than the time domain analyze method. The half-bridge LLC resonant converter is designed such that ZVS is obtained for the entire input voltage range (185 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$-$</tex-math></inline-formula> 265 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$V_{rms}$</tex-math></inline-formula> ), and for 20% to 100% of the full-load power. In addition, a magnetic integration technique is utilized to increase efficiency and reduce converter size. The designed control system enables lowering the output current ripples without using any electrolytic capacitors. To verify the feasibility of the proposed LED driver, a 200 W prototype is implemented. The proposed LED driver achieves maximum efficiency of 94.6%, high PF, and a maximum of 15% output current ripples.

Meta Heuristic Optimization Algorithm based Rectifier Control in Switched Reluctance Generator

A simple, robust, economical and highly efficient 8/6 switched reluctance (SR) generator is connected to a wind turbine to increase the amount of power extracted from the wind. Output power of the generator is fed to the PWM rectifier via a four-phase asymmetric half-bridge (AHB) converter and maximum power point tracking (MPPT) of the rectifier is assisted with torque ripple minimization to present an effective control as it allows torque ripple suppression arising from the SR generator nature while capturing maximum wind power. The wide range of speed variation of the SR generator is minimized using the combination of PI and hysteresis current controller. Further, the output of the AHB converter is directed to the conventional PWM rectifier. The purpose of this research is to deliver ripple-free dc power to a dc grid/load or battery. Hence, in this paper, the GWO-based optimized PI controller is implemented as an MPPT method to maintain the constant dc bus voltage. The inherent ability of GWO optimization-based control of the rectifier system ensures better dynamic control. The simulation is performed in a MATLAB environment for a power rating of 1000W standalone system and tested using an FPGA controller. This paper carries out a stability analysis of the system by varying the wind velocity.

Phase Current Reconstruction Technique for Four-Phase Switched Reluctance Generator With Two Current Sensors

The paper proposes a novel current reconstruction technique with two current sensors to reconstruct the phase currents in a 4-phase switched reluctance generator (SRG). Conventionally with the asymmetric half-bridge converter (AHB), four current sensors are employed, one in each phase for measuring the phase currents in SRG. In the proposed work, the AHB converter’s DC bus is split into the excitation bus and the generating bus. Two current sensors are employed, first in the excitation bus, measuring the energization current of the respective active phase during phase excitation. And the second current sensor is placed in the generating bus, measuring the generating current. The switching functions of the AHB converter are re-designed such that the phase current during free-wheeling and de-energization flows through the generating bus. The proposed current reconstruction technique using linear algebraic equations facilitates the reconstruction of phase currents from two current sensors only. This is the first time a paper experimentally verifies the proposed phase current reconstruction technique for 4-phase SRG, wherein multiple phases are conducting simultaneously. Also, during power electronics switch fault the proposed current reconstruction method successfully reconstructs healthy phase currents after isolating the faulty phase.

Integrated Asymmetric Half-Bridge Converter With Boost Operation for Wide Input Voltage Range

A conventional asymmetric half-bridge (AHB) conve rter with zero dc offset current of the transformer at any operating points was proposed. It has low-voltage stresses on the two diodes that are clamped to the output voltage. However, for a wide input voltage range, it can have a small nominal duty ratio that causes to large conduction loss at the maximum input voltage. Moreover, it has high-voltage stress on one of the secondary diodes that leads to high power loss. In order to improve these problems, in this article, an AHB converter with an integrated boost converter is proposed. The proposed converter has identical operation to the conventional one as well as boost operation for the wide input voltage range. Thus, it has a large nominal duty ratio and low-voltage stress on the secondary diode at the maximum input voltage. Moreover, it has zero dc offset current of transformer and higher efficiency over the entire input voltage range compared with the conventional converter. The proposed converter has been verified for a laboratory prototype with 200–400 V input and 50 V/300 W output.

Single-Phase H-Bridge Rectifier Fed High-Speed SRM System Based on Integrated Power Control

Traditionally, an uncontrollable diode bridge rectifier (DBR) is employed to supply the constant DC voltage for the asymmetric half-bridge (ASHB) converter fed switched reluctance motors (SRMs), which brings about inferior AC side power quality. In this article, a high-speed SRM drive system based on integrated power control scheme is proposed, which not only realizes the regulation of SRM but improves the AC side power quality. For the topology, a single-phase H-bridge rectifier and ASHB converter are connected in a cascade arrangement to form an AC-DC-DC converter to drive the SRM. For the control, the proposed integrated power control scheme governs the rectifier and SRM as one control unit in which stable motor speed and high AC side power factor are realized via regulating the input real and reactive power, respectively. Moreover, the proposed system has bi-directional power flow capability, which means the power can flow out of and into the AC side. Experiments are carried out to investigate the steady-state and dynamic performances of the proposed driving system. The experimental data and performance comparison confirm its effectiveness.

Wireless Power Transmission-Based In-Wheel Switched Reluctance Motor Drive System With an x-Type Converter

This paper proposes a wireless power transmission (WPT)-based in-wheel switched reluctance motor (IWSRM) drive system, which uses an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x-</i> type converter at the motor side with charging function. In this system, a single frequency WPT subsystem with one transmitter coil and one receiver coil is used to completely isolate the DC power side from the motor side, and realize a transmission voltage gain of 1 by incorporating the symmetrical LCC-S network, which has the advantage of constant voltage gain when load changes. Be different from asymmetric half-bridge (AHB) converter, at the motor side an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x-</i> type converter with minimum number of active power switches is employed to connect the WPT subsystem, in which one power switch and one diode are used for each phase with independent control. The number of power active devices are reduced by half compared to AHB converter. Two freewheeling modes are analyzed for the drive system: the resistance freewheeling mode and the battery charging freewheeling mode. An experimental setup for a WPT-based three-phase 18/24-pole IWSRM system was built and tested. The simulation and experiment results of the system under two freewheeling modes are presented to validate the analysis and effectiveness of the system. The DC-to-DC efficiency is achieved over 96% with 100 mm air gap and the system efficiency is achieved up to 82% with the battery charging freewheeling mode.

A Comprehensive Performance Comparison between Segmental and Conventional Switched Reluctance Machines with Boost and Standard Converters

This paper presents the comparisons between two types of switched reluctance machines (SRMs) and SRM converters. An SRM with a segmental rotor is compared with a conventional SRM (CSRM), and an SRM converter containing a passive boost circuit is compared with a conventional asymmetric half-bridge (AHB) converter. The segmental SRM has an asymmetric rotor with a segmented structure. The four rotor segments are made of steel laminations. Two segments are misaligned with the other two by 15 degrees. The torque ripple of the SRM with this structure is decreased, and the static torque is increased compared to a conventional SRM. The boost converter comprises a front-end circuit and a conventional AHB converter. The front-end circuit boosts the voltage level. The boosted voltage accelerates the rising and falling progress of the phase current. In this way, the SRM can obtain a greater speed and a smaller torque ripple. The comparison is conducted in simulation and validated through the experimental results. The experiment results have demonstrated that the segmental SRM obtains a maximum 7% torque ripple reduction at a low-speed range, compared to the CSRM. With the boost converter, both the CSRM and the segmental SRM can achieve a lower torque ripple and a higher maximum speed.

High-Efficiency Asymmetrical Half-Bridge Converter With Linear Voltage Gain

A conventional asymmetrical half-bridge (AHB) converter is one of the widely used topologies in low to medium power applications. However, when it is designed in a wide input voltage range, it operates with a low duty ratio at nominal input voltage. In addition, it has disadvantages, such as a dc offset of magnetizing current, an unbalanced average current of the diode, and a nonlinear voltage gain due to asymmetrical operation. To solve these disadvantages, an AHB converter with linear voltage gain is proposed. The proposed converter has a structure in which a capacitor is added as a voltage source to obtain a symmetrical operation by extending the commutation period. Therefore, it has a narrow range of operating duty ratio and a zero dc offset of magnetizing current. Due to the zero dc offset of magnetizing current, it has a small size transformer and improved zero-voltage switching conditions of the primary-side switches. In addition, it has a low primary rms current and a balanced average current of the diode. Consequently, the proposed converter has high efficiency under the entire load conditions. A 300–400 V input and 48 V/400 W output prototype is tested to verify the feasibility of the proposed converter.

Fault Diagnosis for Power Converter in SRM Drives Based on Current Prediction

This article proposes an online diagnosis scheme for transistor faults of asymmetric half-bridge converter (AHBC) in switched reluctance motor (SRM) drives. In order to extract more information from the phase current to identify faults, based on the conventional current measurement method, two novel current measurement methods are presented by reconstructing current sensors. According to the novel current measurement methods, a current prediction method is raised. The phase current at the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> th sampling time is available so that the estimated current can be calculated. The fault can be detected and located by analyzing the given and actual switching states, which are deduced by comparing the measured and estimated currents. Compared with existing methods, the proposed scheme can be applied to diagnosis of multiple faults in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> -phase AHBC, which can operate at various control strategies and chopping modes. With a single current sensor in each phase, the scheme will not increase the cost and complexity of the SRM drive. Furthermore, the scheme does not require complicated computation, making it easy to implement online. The experimental results confirm the effectiveness and flexibility of the proposed scheme.

Voltage-Sourced Converter Fed High-Speed Switched Reluctance Motor Drive System With Energy Feedback and Near-Unity Power Factor

The diode bridge rectifier fed asymmetric half-bridge converter (AHBC) is conventionally employed to drive switched reluctance motors (SRMs), which leads to poor grid-side power quality. In the proposed system, a topology made up of a voltage-sourced converter and an AHBC is employed to drive the high-speed SRM. Stable SRM operation can be obtained by manipulating the active power flowing to motor side, and on the basis of that, the grid-side power quality is enhanced by directly manipulating input reactive power. Predictive deadbeat control with disturbance observer is employed to follow the power references, thereby achieving controllable speed, energy feedback, near-unity grid-side power factor, and low grid-side current distortion simultaneously. Additionally, an improved asymmetric modulation method is developed for switching frequency reduction. Experiments are carried out to test the proposed drive system in steady and dynamic conditions. Performance comparisons validate the improvement of the proposed high-speed SRM drive system.

Development of a variable‐magnet switched reluctance motor drive

This paper introduces a variable magnet switched reluctance motor (VM‐SRM) drive that can be characterized with adjustable performance. It consists of a switched reluctance (SR) motor with low coercive force (LCF) magnets buried on stator yoke and a modified asymmetric half bridge (AHB) converter. Magnetization level of the LCF magnets is adjusted by injecting a current pulse to a phase winding of the VM‐SRM. The magnetization process does not need any extra coil and provides a simplicity owing to modified AHM converter. Possible magnetic saturation that limits the magnetization level is overcome by injecting current pulses to two phase windings at the same time. Thus, LCF magnets can be used with their full capacity. The presented analysis results demonstrate that proposed VM‐SRM drive provides a variable performance and might be a candidate for future variable speed applications. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.