Nam-Ju Park

A Power-Control Scheme With Constant Switching Frequency in Class-D Inverter for Induction-Heating Jar Application

In this paper, a simple power-control scheme for a constant-frequency class-D inverter with variable duty cycle at constant frequency is proposed. It is more suitable and acceptable for high-frequency induction-heating (IH) jar applications. The proposed control scheme has the advantages of not only wide power-regulation range but also ease of output-power control. In addition, it can achieve stable and efficient zero-voltage switching in the whole load range. The control principles of the proposed method are described in detail, and the validity is verified through the simulated and experimental results on the 42.8-kHz insulated gate bipolar transistor for an IH rated on 1.6 kW with constant-frequency variable power

A Novel Fault Detection Scheme for Voltage Fed PWM Inverter

This paper presents a new fault detection scheme for voltage fed inverter to improve the reliability of power electronic system, which is of paramount importance in industrial, commercial, aerospace, rolling mill and military applications. The proposed method is achieved by using voltage of lower switches in each phase under the inverter fault condition. The reconfiguration method is achieved by the four-switch topology connecting a faulty leg to the middle point of DC-link using bidirectional switches. The proposed method has a simple algorithm and fast detecting time to detect faults. Also, this method is not influenced hardly for noise. As a result, continuous free operation of the system after faults is achieved by reconfiguration of system topology. The superior performance of the proposed fault detection and tolerance method are proved by simulation

Soft-switching interleaved bidirectional DC-DC converter for Advanced Vehicle Applications

This paper proposes soft-switching interleaved bidirectional DC-DC converter suitable for advanced vehicle Applications. The proposed converter integrates interleaved synchronous buck and ZVT-cell with a single resonant inductor. ZVS is guaranteed with wide load range in CCM as well as wide output voltage range by current injection method. Also, switching losses and reverse recovery effects can be minimized. In addition, it is possible to significantly reduce diode drop voltage occurred during dead time of conventional synchronous buck converter. The validity of the proposed converter is verified through experimental results.

Design of an LCL filter employing a symmetric geometry and its control in grid-connected inverter applications

An inductor-capacitor-inductor (LCL) filter are widely adapted in grid-connected inverter applications. In this paper, the harmonic attenuations of the LCL filter are quantitatively analyzed, and then the design optimization of two inductance values, which are related on a cost and a size, is illustrated. Based on the design optimization, the LCL filter employing a symmetric geometry is proposed. Through the equivalent circuit analysis of the proposed LCL filter, the operating characteristics and validity are presented in detail. In addition, simple proportional-integral (PI) current controller suitable for the LCL Filter is designed to mitigate the resonance problem. From simulation results, it is seen that the proposed LCL filter and control method have a sufficient attenuation and stability for the high frequency distortions and load variations.

A Novel Current Sharing Technique for Interleaved Boost Converter

An efficient DC/DC converter is needed as the interface between a low voltage source and high current application. The converter must be able to boost the input voltage and operate at higher current levels. The interleaved boost converter (IBC) is the proper solution for this kind of application. But, how to balance the current each phase is the most important. This paper introduces a new approach to IBC using carrier slope control. The control is based on master-slave current sharing technique. It is an effective way to distribute the power and load current equally. Moreover, it is also effective even though the rated current of switching components at slave modules is significantly smaller than that of the master module. The simulation and the experimental results are presented to show the validity.

Simple Fault Detection and Tolerant Scheme in VSI-fed Switched Reluctance Motor

The Switched Reluctance Motor (SRM) has magnetic independence of the motor phases, so that it can continue to operate despite partial failures occurring in the motor-converter unit. Such inherent fault-tolerant characteristic is useful to the applications requiring high reliability, such as aircraft. However, on occurrence of fault, speed variation and torque ripple increase and it cause problems in applications. Therefore fault-tolerant SRM drive systems improving these problems are of extreme importance. This paper proposes the novel fault detection/isolation scheme using voltage of lower switches in each phase under the occurrence of inverter faults. It has benefit of simple realization and robustness in load/noise. The SRM operating principle with VSI-fed inverter and the proposed fault detection scheme is analyzed in detail. Also the validity of the proposed method is verified by simulation.

A high efficiency Zero Voltage-Zero Current Transition converter for battery cell equalization

This paper proposes a new ZVZCT (Zero Voltage Zero Current Transition) dc/dc converter for voltage equalization in series connected battery cells. The proposed circuit equalizes the battery cells by principle of voltage-second balance of inductor and transformer coupling. By adding auxiliary resonant cells at the main switching devices such as MOSFET or IGBT, zero current switching is achieved and turned off loss of switching elements is eliminated. In the other hand, zero voltage switching can be applied to switching elements by the voltage/second balancing of the inductor. Transformer coupling between battery cells and ZVZCT switching method allows the fast balancing speed and high frequency operation, which reduces size and weight of the circuit. The validity of the battery equalization is further verified using prototype board involving four lithium-ion battery cells. The experiment result shows that the proposed ZVZCT battery equalization scheme can achieve faster equalization speed and increase the efficiency compare with the conventional battery equalization schemes.

N Interleaved Boost Converter with a Novel ZVT Cell Using a Single Resonant Inductor for High Power Applications

In this paper, the interleaved boost converter (IBC) with ZVT cell using single resonant inductor in continuous conduction mode (CCM) is proposed. The IBC with the proposed ZVT cell has the advantages such as a simple circuit, reduced size and low cost by using single resonant. It is more suitable for high power applications. The proposed ZVT cell circuit and principles for the IBC are explained in detail. The validity of the IBC with proposed ZVT cell is verified through the simulation results

Interleaved Bidirectional DC-DC Converter for Automotive Electric Systems

In this paper, interleaved bidirectional DC-DC converter with ZVT cell using a single resonant inductor in continuous conduction mode is proposed. The proposed interleaved bidirectional DC-DC converter has advantages such as a simple circuit, ZVS during wide load range and minimization of current injection effect by using dual current injection time. Also, it is possible to reduce diode drop voltage occurred during dead time of convectional synchronous buck converter. The validity of the proposed converter is verified through experimental results.

A three-port bidirectional modular circuit for Li-Ion battery strings charge/discharge equalization applications

In this paper, a three-port bidirectional modular circuit applied in charging and discharging equalization for lithium-ion battery strings is proposed. This circuit consists of four MOSFETs and one transformer which provide a simple structure to be easily modularized. Compared to conventional individual cell equalization schemes, it utilizes the transformer as the energy transfer element, allowing direct transfer of energy between arbitrary two cells of three-cell battery module, thus improving the equalization efficiency significantly by using much less number of equalizers for long battery strings. Simulation results are presented to validate the circuit operation and confirm its capability to equalize the three-cell battery module.