Suman Dwari

Fault-Tolerant Control of Five-Phase Permanent-Magnet Motors With Trapezoidal Back EMF

This paper presents fault-tolerant control techniques for five-phase permanent-magnet motors with trapezoidal back electromotive forces under various open-circuit conditions. The proposed fault-tolerant control methods use only the fundamental and third-harmonic current components for the excitation of the healthy stator phases. The control techniques are developed by applying a concept that correlates the currents in the healthy phases based on their symmetry in space with respect to the fault in a machine. Optimum solutions under the single-phase open-circuit fault condition and double-phase open-circuit fault conditions are presented. The presented solutions are derived to increase the average output torque while reducing the torque pulsations and satisfying the zero-neutral-current constraint. Detailed experimental results are presented for the verification of the proposed solutions.

An Efficient High-Step-Up Interleaved DC–DC Converter With a Common Active Clamp

This paper presents a high-efficiency and high-step-up nonisolated interleaved dc-dc converter with a common active-clamp circuit. In the presented converter, the coupled-inductor boost converters are interleaved. A boost converter is used to clamp the voltage stresses of all the switches in the interleaved converters, caused by the leakage inductances present in the practical coupled inductors, to a low voltage level. The leakage energies of the interleaved converters are collected in a clamp capacitor and recycled to the output by the clamp boost converter. The proposed converter achieves high efficiency because of the recycling of the leakage energies, reduction of the switch voltage stress, mitigation of the output diodes reverse recovery problem, and interleaving of the converters. Detailed analysis and design of the proposed converter are carried out. A prototype of the proposed converter is developed, and its experimental results are presented for validation.

An Optimal Control Technique for Multiphase PM Machines Under Open-Circuit Faults

In this paper, an optimal control technique for n-phase permanent-magnet (PM) machines under various open circuit faults is presented. Under the fault conditions, the currents in the healthy phases are controlled to compensate phase loss and to produce the required output torque. The proposed control technique ensures continuous operation of the machines while producing minimum torque ripples and minimum stator ohmic loss. The control technique is based on the instantaneous power balance theory. To set the summation of the phase currents equal to zero, a constraint is incorporated in the derivation of the control technique. A five-phase PM machine is considered to demonstrate the proposed open circuit fault-tolerant control strategy. Simulation and experimental results are provided for validation.

An Efficient AC–DC Step-Up Converter for Low-Voltage Energy Harvesting

The conventional two-stage power converters with bridge rectifiers are inefficient and may not be practical for the low-voltage microgenerators. This paper presents an efficient ac-to-dc power converter that avoids the bridge rectification and directly converts the low AC input voltage to the required high dc output voltage at a higher efficiency. The proposed converter consists of a boost converter in parallel with a buck-boost converter, which are operated in the positive half cycle and negative half cycle, respectively. Detailed analysis of the converter is carried out to obtain relations between the power, circuit parameters, and duty cycle of the converter. Based on the analysis, control schemes are proposed to operate the converter. Design guidelines are presented for selecting the converter component and control parameters. A self-starting circuit is proposed for independent operation of the converter. Detailed loss calculation of the converter is carried out. Simulation and experimental results are presented to validate the proposed converter topology and control schemes.

Design and Implementation of a Direct AC–DC Boost Converter for Low-Voltage Energy Harvesting

In this paper, a direct ac-dc power electronic converter topology is proposed for efficient and optimum energy harvesting from low-voltage microgenerators. The converter utilizes the bidirectional current-conduction capability of MOSFETs to avoid the use of a front-end bridge rectifier. It is operated in discontinuous conduction mode and offers a resistive load to the microgenerator. Detailed analysis and modeling of the converter is presented. In such low-power applications, the power consumption of gate drive and control circuits should be minimal. In this paper, they are specifically designed to consume very low power. A suitable startup circuit and auxiliary dc supply circuit is proposed for the implementation of the converter. A low-voltage microgenerator is used to verify the performance and operation of the converter and the gate drive circuits.

A New Design for Vibration-Based Electromagnetic Energy Harvesting Systems Using Coil Inductance of Microgenerator

In this paper, a new design methodology for low-voltage electromagnetic energy harvesting systems consisting of a microgenerator and power processing circuit is introduced. In the first section of this paper, a simple topology for a resonance-based electromagnetic generator is presented. The microgenerator is capable of producing a voltage of a few hundred millivolts. Since traditional two-stage power conversion schemes cannot be used for such a low ac voltage, a suitable single-stage ac-dc converter is utilized for power processing. The converter boosts the low ac voltage to a nominal dc voltage required by electronic devices. As a part of integrated design, the coil of the microgenerator is fabricated such that it can be utilized both for electromagnetic induction and power processing. Such an arrangement improves efficiency and makes the system compact. The converter is controlled to regulate the output voltage under varying input or load conditions. Simulation and experimental results are presented to validate the operation of the proposed converter with a low-voltage microgenerator.

Dynamics Characterization of Coupled-Inductor Boost DC-DC Converters

Dynamic characterization of the coupled-inductor boost DC-DC converter is presented. Operating of the converter in both continuous conduction mode (CCM) and discontinuous continuous conduction mode (DCM) are studied. A state variable equivalent to the inductor core magnetic flux is defined to avoid the problem with using the discontinuous inductor current as a state variable. Dynamic model of the converter under peak-current control is also developed. Control to output transfer functions are calculated for all the dynamic models and are validated by experimental measurements. A comparison to the conventional boost converter is provided

Design of Halbach-Array-Based Permanent-Magnet Motors With High Acceleration

The Halbach magnetized permanent-magnet (PM) motors can be designed to achieve high torque density and to realize hollow rotor structure with very low rotational inertia. In this paper, the design and analysis of Halbach-array-based PM motors, which can produce high output torque and meet the requirements for very fast dynamic performance, are presented. A design method is proposed to select the optimum dimensions of the Halbach-array-based PM machines. The analysis and design approach for the selection of the suitable stator winding distribution, while considering the effect of the end windings, are also presented. Loss analysis of the machine is carried out, and a simplified 3-D model is proposed for its thermal analysis. Detailed finite-element analysis results are provided for the verification of the performances of the designed machine.

Efficient direct ac-to-dc converters for vibration-based low voltage energy harvesting

In this paper two direct ac-to-dc power electronics converter topologies are proposed for efficient and optimum energy harvesting from low voltage microgenerators. The conventional power electronics converters used for such applications have two stages, a diode bridge rectifier at the front end followed by a dc-dc boost converter. However, the extremely low output voltage of electromagnetic microgenerators does not allow diode bridge rectification. Even if possible, the losses in the front end diode bridge make the conventional power electronic interfaces quite inefficient. The proposed single stage converters directly boost the microgenerator low ac voltage to usable dc voltage level, and hence, achieve higher efficiency. The single stage ac-to-dc power conversion is achieved by utilizing the bidirectional current conduction capability of MOSFETs. Moreover, for optimum energy harvesting the power converter should be able to control the load resistance as seen by a microgenerator. The conventional converters are not conducive for such control. With the proposed converter topologies the optimal energy harvesting can be successfully realized.

Efficient low voltage direct AC/DC converters for self-powered wireless sensor nodes and mobile electronics

The conventional power electronics converters used in the microgenerator based energy harvesting applications have two stages: a diode bridge rectifier and a DC-DC converter. However, in the case of electromagnetic microgenerators, the diode bridge rectification is not normally feasible due to the extreme low output voltage of the microgenerators. Even if possible, the losses in the diode bridge rectifier make the conventional power electronic interfaces very inefficient. In this paper two direct ac-to-dc power electronics converter topologies are proposed for efficient and maximum energy harvesting from low voltage microgenerators. The proposed single stage converters directly boost the microgenerator low ac voltage to usable higher dc voltage, and hence, achieve higher efficiency. The single stage ac-to-dc power conversion is achieved by utilizing the bidirectional conduction capability of MOSFETs. Furthermore, with the proposed converters, the maximum energy harvesting can be successfully realized by controlling the effective load resistance offered to the microgenerators. The conventional power converters are not conducive for implementation of such control. Simulation and experimental results are presented for verification of the proposed converters.