Rou-Yong Duan

High step-up converter with coupled-inductor

In this study, a high step-up converter with a coupled-inductor is investigated. In the proposed strategy, a coupled inductor with a lower-voltage-rated switch is used for raising the voltage gain (whether the switch is turned on or turned off). Moreover, a passive regenerative snubber is utilized for absorbing the energy of stray inductance so that the switch duty cycle can be operated under a wide range, and the related voltage gain is higher than other coupled-inductor-based converters. In addition, all devices in this scheme also have voltage-clamped properties and their voltage stresses are relatively smaller than the output voltage. Thus, it can select low-voltage low-conduction-loss devices, and there are no reverse-recovery currents within the diodes in this circuit. Furthermore, the closed-loop control methodology is utilized in the proposed scheme to overcome the voltage drift problem of the power source under the load variations. As a result, the proposed converter topology can promote the voltage gain of a conventional boost converter with a single inductor, and deal with the problem of the leakage inductor and demagnetization of transformer for a coupled-inductor-based converter. Some experimental results via examples of a proton exchange membrane fuel cell (PEMFC) power source and a traditional battery are given to demonstrate the effectiveness of the proposed power conversion strategy.

High-Efficiency Power Conversion System for Kilowatt-Level Stand-Alone Generation Unit With Low Input Voltage

This paper mainly focuses on the development of a high-efficiency power conversion system for kilowatt-level stand-alone generation units with a low output voltage, such as photovoltaic modules, fuel cells, and small-scale wind generators, and it aims at having the same output ac voltage, i.e., 110 Vrms/ 60 Hz as the utility power for the utilization of a stand-alone power supply. This high-efficiency power conversion system includes one high-efficiency high-step-up dc-dc converter and one soft-switching dc-ac current-source inverter. This dc-dc converter is capable of solving the voltage spike problem while the switch is turned off, and it can achieve the objectives of high efficiency and high voltage gain. Because the techniques of soft switching and voltage clamping are used in the dc-ac current-source inverter, the conversion efficiency could greatly be improved. The effectiveness of the designed circuits is verified by experimentation, and the maximum efficiency of the entire high-efficiency power conversion system is over 91% based on the experimental measurements.

High-efficiency power conversion for low power fuel cell generation system

This study presents a newly designed topology for a fuel cell energy source conversion in order to supply a highly reliable utility power. Because the fuel cell has the power quality of low voltage as well as high current due to the electrochemical reaction, a high step-up dc-dc converter is utilized for boosting the fuel cell voltage up to a constant dc-bus voltage for the utilization of later inverter. Moreover, a current-source sine-wave voltage inverter is designed in the sense of voltage-clamping and soft-switching techniques to enable the use of a smaller inductor in the current source circuit and the compression of the voltage stress across switches about two times of the dc-bus voltage. In this power conversion scheme, the output voltage has the salient features of lower distortion, fast dynamic regulating speed and insensitivity to load variation, even under nonlinear loads. In addition, experimental results via an example of a proton exchange membrane fuel cell generation system with 250-W nominal power rating are given to demonstrate the effectiveness of the proposed power conversion strategy. According to the experimental measure, the maximum power inverter efficiency is over 95% and the total harmonic distortions for various load conditions are all within 1.1%.

High-Efficiency Bidirectional Converter for Power Sources With Great Voltage Diversity

This study focuses on the development of a high-efficiency bidirectional converter for power sources with large voltage diversity. In conventional bidirectional converters, transformer-based circuit topologies are commonly employed and soft-switching techniques including zero-voltage-switching (ZVS) or zero-current-switching (ZCS) are frequently applied to mitigate corresponding switching losses. Unfortunately, switches of four and upward in these transformer-based schemes increase production costs and reduce conversion efficiency. In this study, a coupled-inductor bidirectional converter scheme utilizes only three power switches to fulfill the objective of bidirectional current control. The high step-up and step-down ratios enable a battery module with a low voltage to be injected into a high-voltage dc bus for subsequent utilization. Some experimental results are given to verify the effectiveness of the proposed bidirectional converter. Since the techniques of voltage clamping, synchronous rectification and soft switching are exploited in this circuit topology, and the corresponding device specifications are adequately fulfilled, it can provide high-efficiency bidirectional power conversion for power sources with large voltage diversity.

High-efficiency Voltage-clamped DC-DC converter with reduced reverse-recovery current and switch-Voltage stress

This paper investigates a high-efficiency clamped-voltage dc-dc converter with reduced reverse-recovery current and switch-voltage stress. In the circuit topology, it is designed by way of the combination of inductor and transformer to increase the corresponding voltage gain. Moreover, one additional inductor provides the reverse-current path of the transformer to enhance the utility rate of magnetic core. In addition, the voltage-clamped technology is used to reduce the switch-voltage stress so that it can select the Schottky diode in the output terminal for alleviating the reverse-recovery current and decreasing the switching and conduction losses. Furthermore, the closed-loop control methodology is utilized in the proposed scheme to overcome the voltage-drift problem of power source under the variation of loads. Thus, the proposed converter topology has a favorable voltage-clamped effect and superior conversion efficiency. Some experimental results via an example of a proton-exchange-membrane fuel cell (PEMFC) power source with a 250-W nominal rating are given to demonstrate the effectiveness of the proposed power-conversion strategy.

Wavelet neural network control for induction motor drive using sliding-mode design technique

This paper addresses an adaptive observation system and a wavelet-neural-network (WNN) control system for achieving the favorable decoupling control and high-precision position tracking performance of an induction motor (IM) drive. First, an adaptive observation system with an inverse rotor time-constant observer is derived on the basis of model reference adaptive system theory to preserve the decoupling control characteristic of an indirect field-oriented IM drive. The adaptive observation system is implemented using a digital signal processor with a high sampling rate to make it possible to achieve good dynamics. Moreover, a WNN control system is developed via the principle of sliding-mode control to increase the robustness of the indirect field-oriented IM drive with the adaptive observation system for high-performance applications. In the WNN control system, a WNN is utilized to predict the uncertain system dynamics online to relax the requirement of uncertainty bound in the design of a traditional sliding-mode controller. In addition, the effectiveness of the proposed observation and control systems is verified by simulated and experimental results.

Robust fuzzy neural network control for linear ceramic motor drive via backstepping design technique

This study presents a robust fuzzy-neural-network (RFNN) control system for a linear ceramic motor (LCM) that is driven by an unipolar switching full-bridge voltage source inverter using LC resonant technique. The structure and operating principle of the LCM are introduced. Since the dynamic characteristics and motor parameters of the LCM are nonlinear and time varying, a RFNN control system is designed based on the hypothetical dynamic model to achieve high-precision position control via the backstepping design technique. In the RFNN control system a fuzzy neural network (FNN) controller is used to learn an ideal feedback linearization control law, and a robust controller is designed to compensate the shortcoming of the FNN controller. All adaptive learning algorithms in the RFNN control system are derived from the sense of Lyapunov stability analysis, so that system-tracking stability can be guaranteed in the closed-loop system. The effectiveness of the proposed RFNN control system is verified by experimental results in the presence of uncertainties. In addition, the advantages of the proposed control system are indicated in comparison with the traditional integral-proportional (IP) position control system.

An ultrasonic motor drive using a current-source parallel-resonant inverter with energy feedback

An ultrasonic motor (USM) drive using a two-phase current-source parallel-resonant inverter is proposed in this study. A single-phase equivalent model of the USM is first described. Then, a detailed theory for the newly designed driving circuit for the USM, in which the inherent parasitic capacitances formed by the polarized piezoelectric ceramic of the USM are parts of the two parallel-resonant tanks, is introduced. Since the dynamic characteristics of the USM are greatly influenced by the variation in the quality factors of the parallel-resonant tanks, two transformers are added to feed the stored energy in the resonant tanks back to the DC source to reduce the quality factors. Detailed experimental results are provided to demonstrate the effectiveness of the proposed driving circuit.

High-efficiency fuel-cell power inverter with soft-switching resonant technique

In order to reduce the capital and overall operating cost of a fuel-cell system, a high-efficiency fuel-cell power inverter with a simple framework is required. The high-order two-inductance two-capacitance (LLCC) resonant technique is adopted in this study to implement a low-frequency 60-Hz sinewave voltage inverter utilized in the proton exchange membrane fuel-cell (PEMFC) system. The methodology for inverting dc voltage into low-frequency ac voltage is usually generated by the pulse-width-modulation (PWM) technique. However, the PWM-type inverter output has high-frequency harmonic components. Although an adequately designed filter could be utilized to overcome this problem, there are still some undesirable effects introduced by the high-frequency switching loss, electromagnetic-interference, harmonic current, and load variation. A novel power inverter via the LLCC resonant technique is designed for inverting dc voltage into 60-Hz ac sinewave voltage in the PEMFC system. This circuit scheme has the merits of low harmonic components, soft switching, high efficiency, and simplified implementation. The effectiveness of the proposed resonant inverter used for the PEMFC system is verified by numerical simulations and experimental results.

Fuzzy neural networks for identification and control of ultrasonic motor drive with LLCC resonant technique

This paper demonstrates the applications of fuzzy neural networks (FNNs) in the identification and control of the ultrasonic motor (USM). First, the USM is derived by a newly designed high-frequency two-phase voltage-source inverter using LLCC resonant technique. Then, two FNNs with varied learning rates are proposed to control the rotor position of the USM. The USM drive system is identified by a fuzzy neural network identifier (FNNI) to provide the sensitivity information of the drive system to a fuzzy neural network controller (FNNC). A backpropagation algorithm is used to train both the FNNI and FNNC on-line. Moreover, to guarantee the convergence of identification and tracking errors, analytical methods based on a discrete-type Lyapunov function are proposed to determine the varied learning rates of the FNNs. In addition, the effectiveness of the FNN-controlled USM drive system is demonstrated by experimental results. Accurate tracking response can be obtained due to the powerful on-line learning capability of the FNNs. Furthermore, the influence of parameter variations and external disturbances on the USM drive system can be reduced effectively.