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.
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.
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 diode's 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.
Common-mode voltage (CMV) caused by switching operations of power converters can significantly degrade the system's stability and performance. Since the effects of the CMV are more prominent in the ...wide-bandgap-based applications that require fast-switching slew rates, many research articles have been proposed to mitigate CM noise generated by the CMV. In addition, as topologies and control methods of the power converters become more complicated for better performance, more advanced CM noise attenuation methods are required accordingly. Therefore, this article proposes a CM noise attenuation method using a multilevel active CM noise power filter in a five-level inverter system. In this article, detailed control methods and considerations of the proposed multilevel system are presented, and the validity of the proposed multilevel active CM noise power filter has been verified through experimental results.
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.
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.
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.
Pulsewidth modulation (PWM)-based power electronics inverters are being widely used for various applications, including motor drives. However, the common-mode voltage (CMV) resulting from switching ...operations in the PWM inverters causes significant performance degradation of the system and can cause potential damage to motors. Since the effects of the CMV can be more severe in wide bandgap (WBG) and high switching frequency-based converter systems, various methods have been proposed to mitigate the CM noise issues. This work presents a multi-level inverter system composed of a multi-level inverter with a proposed multi-level active power filter (APF). For attenuating the CMV in multi-level inverters using multi-carrier-based PWM methods, a novel PWM method is presented for the proposed multi-level APF. The three-phase five-level active-neutral-point-clamped (ANPC) II-type inverter using the apparent switching frequency doubling (ASFD) PWM is used as an example of the multi-level inverters and carrier-based PWM methods to analyze and verify the proposed CMV attenuation method. The APF generates and injects the APF voltage equal to the CMV to attenuate the CM noise accurately. Various key challenges, including the dead-time compensation, are addressed through the proposed advanced PWM techniques to improve the CMV attenuation performance. Simulation and experimental results are provided to verify the comparison and effectiveness of the proposed CMV attenuation method.
In this paper, an improved dead-time effect compensation is proposed for WBG multilevel inverters to eliminate dead-time voltage errors by zero-current clamping (ZCC) conditions. Conventional ...dead-time compensation methods based on the current direction can eliminate the dead-time voltage errors in the conventional dead-time methods. However, with the conventional dead-time compensation approaches, dead-time voltage errors remain uncompensated during the control cycles that include the ZCC point and its next control cycle. To address this issue, an additional improvement is proposed based on a prediction of the ZCC condition. is proposed to solve this issue. In this proposed method, the output current values of the next control cycles can be estimated by using the voltage references and feedback current information. Utilizing the estimated current, the proposed control scheme can predict each ZCC case and regenerate updated voltage references that can produce accurate output voltages without any dead-time voltage error. The proposed method is successfully implemented in a digital controller and verified through simulation and experiments.
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.
