En-Chih Chang

A High-Efficiency Solar Array Simulator Implemented by an LLC Resonant DC–DC Converter

In this paper, a high-efficiency solar array simulator (SAS) implemented by an LLC resonant dc-dc converter is proposed to save the cost and energy of photovoltaic (PV) system testing. The proposed converter has zero-voltage switching (ZVS) operation of the primary switches and zero-current switczero-current switching (ZCS) operation of the rectifier diodes. By frequency modulation control, the outputhing (ZCS) operation of the rectifier diodes. By frequency modulation control, the output impedance of an LLC resonant converter can be regulated from zero to infinite without shunt or serial resistors. Therefore, the efficiency of the proposed SAS can be significantly increased. The circuit operations are analyzed in detail to derive the theoretical equations. Circuit parameters are designed based on the practical considerations. Finally, an illustrative example is implemented to demonstrate the feasibility of the proposed SAS.

An Integrated High-Power-Factor Converter With ZVS Transition

This paper proposes a single-phase high-power-factor ac/dc converter with soft-switching characteristic. The circuit topology is derived by integrating a boost converter and a buck converter. The boost converter performs the function of power-factor correction to obtain high power factor and low current harmonics at the input line. The buck converter further regulates the dc-link voltage to provide a stable dc output voltage. Without using any active-clamp circuit or snubber circuit, the active switches of the proposed converter can achieve zero-voltage switching-on transition together with high power factor that satisfies the IEC 61000-3-2 standards over a wide load range from 30% to 100% rated power. The steady-state analysis is developed and a design example is provided. A prototype circuit of 60 W was built and tested. Experimental results verify the feasibility of the proposed circuit with satisfactory performance.

A sliding-mode controller based on fuzzy logic for PWM inverters

This paper presents a sliding mode controller that uses a fuzzy logic to achieve a robust tracking of nonlinear systems. Sliding-mode control (SMC) is a robust control method, but does suffer chattering problem around the sliding surface. The pulse-width modulation (PWM) inverter uses SMC with a fuzzified sliding surface, and thus a low total harmonic distortion (THD) sinusoidal voltage in the inverter output can be obtained. The simulation results show that this proposed method is more robust than the conventional SMC

Implementation of a digitally dimming controlled lighting system for two-area fluorescent lamps

The digitally dimming control interface is a new kind of dimming control for a variety of lighting applications, including building, office, and conference room; it also features remote control, real-time dimming control and lamp condition recognition. The conventional RS-232-based digitally dimming lighting system for fluorescent lamps consists of a power-factor corrector and a half-bridge resonant inverter as the main circuit, and a microcontroller-based driver and dimmer as a controller. The drawbacks of this conventional lighting system are its short transmission length and low transmission speed, and that each lighting area needs its own driver and dimmer circuit, which results in large numbers of circuit components and non-cost-effectiveness for multi-area lighting control of fluorescent lamps. Therefore, this paper presents a new digitally dimming control lighting system for fluorescent lamps. The main goal of the paper is to boost the transmission length and speed with use of a new transmission interface. A compact universal-serial-bus (USB)-based lighting system for two lighting areas are developed and measured using the function of remote dimming control in order to improve the transmission speed and to reduce circuit components as compared with the conventional version.

Design and implementation of a two-switch buck-boost typed inverter with universal and high-efficiency features

A typical photovoltaic (PV) grid-connection power system is usually consisted of multi-stage converters to perform multiple functions simultaneously. In order to simplify system configuration, reduce cost, and improve conversion efficiency, this paper proposes to adopt two-switch buck-boost (TSBB) dc-dc converters, and then develops families of buck-boost typed inverters via the connection with an H-bridge unfolding circuit with line-commuted operation. The proposed inverters have both step-up and step-down functions so that they are suitable for the applications with wide voltage-variation range. Depending on the conditions of dc input-voltage and ac output-voltage, the proposed circuits can work functionally as either buck-typed or boost-typed inverter. Due to operating with buck or boost principle, partial energy can be directly delivered to output to improve efficiency. Besides, since only one power switch operates with high-frequency, switching losses can be reduced significantly. Finally, one of the proposed TSBB inverters, named buck-cascaded buck-boost (BuCBB) inverter, is then implemented accordingly to generate 110 Vrms / 60 Hz output voltage. Experimental results have verified the validity of theoretical predictions and the feasibility of proposed inverters.

Discrete-time fuzzy sliding mode control of a UPS inverter feeding nonlinear loads

This paper presents a discrete-time sliding mode controller based on fuzzy logic for high performance single-phase UPS inverters capable of maintaining low harmonic distortion in response to nonlinear loads. The discrete-time sliding mode control suits for digital realization due to its finite sampling frequency. Also, an algorithm for uncertainty estimation, incorporating with fuzzy tuning technique, is developed. The dynamics of the switching function can be driven to the origin and the stability of this control system is guaranteed. The proposed control scheme has been implemented using a dSPACE DSP. Experimental results on a UPS inverter prototype show that the proposed control scheme can achieve low total harmonics distortion during steady-state operation as well as fast transient response.

A Single-Phase DC/AC Inverter using Moving Sliding Manifold Sinusoidal Tracking Control

In this paper, a single-phase DC/AC inverter for uninterruptible power supply using moving sliding manifold (MSM) sinusoidal tracking control is proposed. The characteristic of the MSM over the conventional sliding manifold is capable of ensuring the sliding mode proceeds from an arbitrary initial state and thus achieves the robustness against system uncertainties. The inverter tracking performances of steady-state and transient responses can be improved due to speedup-reaching the sliding manifold. A 60 Hz 400 W prototype is built with MSM control scheme based on dSPACE DSP by sensing the output voltage for the closed-loop feedback. The experimental results show that low total harmonic distortion (THD) output voltages under resistive load or even under rectifier-RC load and fast transient response subject to step change in load are obtained. Design procedures, computer simulations, and experimental results are provided to demonstrate the performance of the MSM controlled inverter.

Modeling and design of the LLC resonant converter used in solar array simulator

An LLC resonant converter has been used to provide the electrical characteristics of solar arrays. In this paper, its small signal model is derived based on the extended describing function concept. The corresponding frequency response can be easily obtained from IsSpice simulation of the equivalent circuit model. Furthermore, a closed-loop compensation controller is designed according to the derived small-signal model. The experimental measurements have really proved that the stable and fast transient response can be achieved in the system. The system output voltage and current can be adjusted simultaneously to match the electrical characteristics of photovoltaic output.

IMPLEMENTATION OF DISCRETE-TIME FUZZY INTEGRAL SLIDING-MODE CONTROL FOR DC-AC INVERTERS

Abstract In this paper, a discrete‐time fuzzy integral sliding‐mode control (DTFISMC) is developed to allow DC‐AC inverters to obtain low‐distortion output voltage. Discrete integral sliding‐mode control achieves zero steady‐state errors, and the fuzzy controller is devoted to the estimation of system uncertainties. Experiments demonstrate the applicability of the proposed controller.

Using the buck-interleaved buck–boost converter to implement a step-up/down inverter

Purpose A typical photovoltaic grid-connection power system usually consists of multi-stage converters to perform multiple functions simultaneously. To simplify system configuration, reduce cost and improve conversion efficiency, this paper aims to develop a buck–boost-type inverter. The proposed inverter has both step-up and step-down functions, so that it is suitable for applications with wide voltage variation. As only one power switch operates with high frequency at one time, switching losses can significantly be reduced. Design/methodology/approach A step-up/down inverter is developed by adopting a buck-interleaved buck–boost (BuIBB) DC-DC converter and connecting with an H-bridge unfolding circuit with line-commutated operation. Finding The proposed circuit can work functionally as either a buck-type or boost-type inverter, so that partial energy can be directly delivered to output to improve efficiency. The input current is shared by two inductors, leading to the reduction of current stresses. Research limitations/implications To apply the proposed inverter to micro-inverter applications in the future, developing a step-up/down inverter with a higher conversion ratio will be considered. Practical implications A laboratory prototype is built accordingly to verify the feasibility of the proposed inverter. The experimental results are presented to show the effectiveness. Originality/value This paper proposes a step-up/down inverter by using the BuIBB converter, which is innovatively studied.