In-Dong Kim

New Bidirectional ZVS PWM Sepic/Zeta DC-DC Converter

Bidirectional DC-DC converters allow transfer of power between two dc sources, in either direction. Due to their ability to reverse the direction of flow of power, they are being increasingly used in many applications such as battery charger/dischargers, dc uninterruptible power supplies, electrical vehicle motor drives, aerospace power systems, telecom power supplies, etc. This paper proposes a new bidirectional Sepic/Zeta converter. It has low switching loss and low conduction loss due to auxiliary communicated circuit and synchronous rectifier operation, respectively. Because of positive and buck/boost-like DC voltage transfer function (M=D/1-D), the proposed converter is desirable for use in distributed power system. The proposed converter also has both transformer-less version and transformer one.

Analysis and Design of a Soft-Switched PWM Sepic DC-DC Converter

This paper proposes a new soft-switched Sepic converter. It has low switching losses and low conduction losses due to its auxiliary communicated circuit and synchronous rectifier operation, respectively. Because of its positive and buck/boost-like DC voltage transfer function (M=D/(1-D)), the proposed converter is desirable for use in distributed power systems. The proposed converter has versions both with and without a transformer. The paper also suggests some design guidelines in terms of the power circuit and the control loop for the proposed converter.

Novel constant frequency PWM DC/DC converter with zero voltage switching for both primary switches and secondary rectifying diodes

A zero-voltage-switching (ZVS) DC/DC converter operating at constant frequency and having wide linearity is proposed. ZVS operation is achieved not only for the primary switches but also for the secondary rectifier diodes to reduce the switching stresses and losses. The converter overcomes other shortcomings of the conventional resonant DC/DC converters, among which are the high VA ratings of devices and passive components and load-dependent DC characteristics. >

Module-type switching rectifier for cathodic protection of underground and maritime metallic structures

Cathodic protection is widely used to prevent corrosion of steel materials buried underground and in seawater. As a rectifier for cathodic protection, the conventional phase-controlled rectifiers with 50- or 60-Hz isolation transformers have been used so far in spite of such shortcomings as large volume, heavy weight, and poor power factor. In order to overcome such disadvantages, this paper proposes a new module-type switching rectifier for cathodic protection, which is composed of two parts, namely, ac/dc converter and module-type dc/dc converter. The ac/dc converter is a single-phase insulated gate bipolar transistor pulsewidth-modulation rectifier, thus resulting in almost unity power factor and controlled dc output voltage. The module-type dc/dc converter operates under zero-voltage switching/zero-current switching condition to permit high-frequency switching operation. It enables the use of a high-frequency transformer for electrical isolation, thus reducing volume and weight of the overall system and improving system efficiency. It is anticipated that the proposed rectifier techniques will apply to the similar technical areas such as multiple-module power supply systems and modular converter-fed dc motor drives.

Cost-effective power quality disturbance generator for the performance test of custom power devices

This paper describes a new sag-swell generator for the test of custom power devices such as UPS, DVR, DSTATCOM, SSTS, etc. The proposed scheme has good features of simple structure, high reliability, wide range of voltage sag and swell variation, and easy control. Outage, harmonic distortion, notches, and voltage unbalance also can be generated. The operation principle of the proposed scheme is described and the characteristics are analyzed through simulation. The usefulness of the scheme is verified through experiments.

Design of bidirectional PWM Sepic/Zeta DC-DC converter

Bidirectional DC-DC converters allow transfer of power between two dc sources, in either direction. Due to their ability to reverse the direction of flow of power, they are being increasingly used in many applications such as battery charger/dischargers, dc uninterruptible power supplies, electrical vehicle motor drives, aerospace power systems, telecom power supplies, etc. This paper proposes a new bidirectional Sepic/Zeta converter. It has low switching loss and low conduction loss due to auxiliary communicated circuit and synchronous rectifier operation, respectively. Because of positive and buck/boost-like DC voltage transfer function (M=D/1-D), the proposed converter is desirable for use in distributed power system. The proposed converter also has both transformer-less version and transformer one. The paper also suggest some design guide line for the proposed converter.

A new ZCS turn-on and ZVS turn-off unity power factor PWM rectifier with reduced conduction loss and no auxiliary switches

This paper presents a new ZCS turn-on and ZVS turn-off unity power factor PWM rectifier, which features soft switching with no auxiliary switches and reduced conduction losses. The ZVS and ZCS switching are achieved by using a simple commutation circuit with no auxiliary switches, and reduced conduction losses are achieved by employing a single converter, instead of a typical front-end diode rectifier followed by a boost rectifier. Furthermore, thanks to good features such as simple PWM control at constant frequency, low switch stress and low VAr rating of commutation circuits, it is suitable for high power applications. The principle of operation is explained and analyzed, and the design considerations and experimental results of the new converter are included.

A new snubber circuit for multilevel inverter and converter

This paper proposes a new snubber circuit for multilevel inverter and converter. The snubber circuit makes use of the Undeland snubber as a basic snubber unit and can be regarded as a generalized Undeland snubber. The proposed snubber keeps such good features as fewer number of components, improved efficiency due to low loss snubber, capability of clamping overvoltage across main switching devices, and no unbalance problem of blocking voltage. Furthermore, the proposed concept of constructing a snubber circuit for multilevel inverter and converter can apply to any kind of basic snubber unit such as Holtz nondissipative snubber, McMurray efficient snubber, Lauritzen lossless snubber, etc. which have been utilized for a two-level inverter.

A new boost type rectifier for a DC power supply with frequent output short circuit

This paper describes a new boost type rectifier. The proposed converter output DC capacitors do not discharge even in a load short circuit condition. When a load short circuit occurs, the capacitors become a floating state immediately. The stored capacitor energy is supplied to the load again as soon as the short circuit has been cleared. This feature satisfies the requirement of a DC power supply for a load with frequent output short circuits. The proposed converter has the characteristics of a simplified structure, a reduced cost, weight and volume compared with conventional power supplies with frequent output short circuits. Experimental results are presented to verify the usefulness of the proposed converter.

A Novel DC Solid-State Circuit Breaker for DC Grid

According to developed distributed generators, Solid State Circuit Breaker(SSCB) is essential for high power quality of DC Grid. In this paper, a simple and new structure of DC SSCB with a fast circuit breaker and fault current limiter is proposed. It can help to choice low specification of elements because of the limiting of fault current and achieve economic efficiency for minimizing auxiliary SCRs. Also all of SCRs have little switching loss because they operate under ZVS and ZCS. Through simulations and experiments of short-circuit fault, the performance characteristic of proposed circuit is verified and a guideline is so suggested that the DC SSCB is applied for a different DC grid using formulas.