With the rapid development of high-speed and high-power railway system in China, power quality such as the negative sequence current and harmonic current caused by electric locomotives becomes more and more critical. This paper proposes a half-bridge-converter-based railway static power conditioner (RPC) (HBRPC) which consists of two half-bridge converters connected by two capacitors in series. Compared with the traditional RPC, the HBRPC requires only a pair of power switch legs and two capacitors. Under the premise of accomplishing the same function of RPC, the proposed conditioner can reduce half of the power switches, which can make it with lower cost and hardware complexity. A double-loop control is proposed for HBRPC to keep the dc-link voltage stable and achieve the dynamic tracking of the current reference signals, while a balanced voltage control is proposed to eliminate the error of two capacitor voltages and maintain the normal operation of HBRPC. Finally, simulation and experiment results have verified the proposed structure and its control method effectively.

A Simplified Power Conditioner Based on Half-Bridge Converter for High-Speed Railway System

In this paper, a family of zero-voltage-transition (ZVT) pulsewidth-modulated converters with synchronous rectifier (SR) is introduced. The SR decreases the conduction losses, while it increases the achieved soft switching range. In this family of converters, zero-voltage-switching (ZVS) condition is attained for the main and rectifier switches. Also, zero-current switching is achieved for the auxiliary switch. In addition, the applied ZVS technique can eliminate the reverse recovery losses of the rectifier switch body diode. The ZVT buck converter with SR is analyzed, and the presented experimental results confirm the theoretical analysis.

Zero-Voltage-Transition PWM Converters With Synchronous Rectifier

This paper proposes the design of a 2.5-kW 400/12 V high-efficiency isolated dc/dc converter for electric vehicles. The designed system accommodates the wide-range input voltage (450 V–220 VDC) and output voltage (16 V–6 VDC). An LLC half-bridge topology is adopted as the primary side of the dc/dc converter. For the secondary side, a novel synchronous rectification control (SRC) strategy is developed to switch metal oxide semiconductor field effect transistors (MOSFETs) through accurately tracking the target switching moments. Experimental results were carried out to charge the on-board 12-V battery and validate the proposed control algorithm. The maximum system efficiency is 93.2%. System power loss is also itemized.

Design of a 2.5-kW 400/12-V High-Efficiency DC/DC Converter Using a Novel Synchronous Rectification Control for Electric Vehicles

The objective of this paper is to implement a two-phase, interleaved, bidirectional DC/DC converter topology with an improved voltage conversion ratio for electric vehicle (EV) and DC-microgrid systems. In this study, a two-phase interleaved charge-pump topology is introduced to achieve a high voltage conversion ratio with very simple control circuits. In discharge mode, the circuit topology acts as a voltage-multiplier boost converter to achieve a high step-up conversion ratio (48 V to 240 V). In charge mode, the circuit topology acts as a voltage-divider buck converter to achieve a high voltage step-down conversion ratio (240 V to 48 V). The circuit configuration, operating principle, steady-state analysis and the closed-loop control of the proposed converter are presented. Experiments conducted on a laboratory prototype with 500 W power-rating are presented to verify the effectiveness. The maximum efficiency levels in discharge and charge modes are about 97.7% and 98.4% respectively.

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Study and Implementation of a Two-Phase Interleaved Bidirectional DC/DC Converter for Vehicle and DC-Microgrid Systems

The use of battery–cell equalizers is mandatory in order to assure that all the cells connected in series are charged to its maximum capacity, even when they present small differences in this parameter due to several factors, such as aging, manufacturing, or temperature. Active equalizers, with a higher efficiency in comparison to passive ones, have the disadvantage of using a considerable number of components. Moreover, in the case of active equalizers with very high performance, this number can be even higher. In this paper, the use of the wave-trap concept, widely used in telecommunication systems, is studied. This concept allows the battery–cell equalizer to use its switching frequency as the control variable that decides which cell is being charged. Hence, it is not necessary to use a complex system based on a high number of controlled switches in order to determine which cell is being charged. In this way, the number of switches (and the corresponding driving signals) can be strongly minimized without reducing the performance of the system. In order to proof the validity of this concept (i.e., wave traps) in the design of battery–cell equalizers, a topology based on a half-bridge structure is also proposed in this paper. It uses only two controlled switches in order to decide which cell is charged. Experimental results are provided for a four-cell equalizer as a proof of concept.

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Practical Application of the Wave-Trap Concept in Battery–Cell Equalizers

This study presents a high efficiency asymmetrical half-bridge flyback converter using a new voltage-driven synchronous rectifier that operates over a universal input voltage range (75-265-V) with a fixed 5-V DC output voltage. Both power semiconductor switches of the proposed converter primary operate asymmetrically under zero voltage switching to achieve high efficiency and low switch voltage stress. Because the proposed converter uses the transformer leakage inductance as its resonant inductance, its structure is simplified. The proposed synchronous rectifier can cover a universal input voltage range and can maintain control in a narrow switching period, features that are essential in converters with universal input voltage. The synchronous rectifier switch of the proposed converter conducts under zero voltage/zero current switching conditions with a discontinuous conduction mode. The operational principle and steady state analysis of the proposed converter are explained, and a design example for a 100-W prototype is discussed in detail. Experimental results for the designed prototype converter with universal input voltage are shown. The author also shows that the efficiency of the proposed converter can be improved significantly.

High efficiency asymmetrical half-bridge flyback converter using a new voltage-driven synchronous rectifier

A novel high efficiency asymmetrical half-bridge converter using a self-driven synchronous rectifier is presented. The proposed converter improves the system efficiency using the characteristics of the asymmetrical half-bridge converter and the self-driven synchronous rectifier. The synchronous rectifier applied to the proposed converter is the new topological synchronous rectifier, which is a slightly modified type of the conventional synchronous rectifier used in the conventional asymmetrical half-bridge converter. The type of the new topological synchronous rectifier slightly changes the transformer structure and the synchronous switch connection in the asymmetrical half-bridge converter with a conventional self-driven synchronous rectifier. The operational principle of the proposed converter is explained in detail. Since the proposed converter utilises the transformer leakage inductor as its resonant inductor, its structure is simplified. A design example for a 90 W (12 V/7.5 A) prototype is discussed in detail. Experimental results are shown for the designed prototype converter under universal AC input voltage (180-265 V). It is shown that the efficiency of the proposed converter can be significantly improved.

G.-Y. Jeong

Papers

High efficiency asymmetrical half-bridge flyback converter using a new voltage-driven synchronous rectifier

High efficiency asymmetrical half-bridge converter using a self-driven synchronous rectifier