Eui-Cheol Nho

An electrolytic capacitor‐less AC/DC converter for high‐brightness LED driving is proposed. It is possible for the proposed scheme to be implemented in more cost‐effective and small‐sized system compared with the conventional electrolytic capacitor‐less converters with additional devices. The reliability, efficacy, and lifetime of the LED driven by the suggested converter can be improved by about 6% compared to those of the conventional converter using harmonic injection method. Experiments are carried out to show the validity of the proposed converter.

A test circuit for modular multilevel converter (MMC)‐based voltage‐sourced converter valves in high‐voltage direct current (HVDC) system is dealt with. The proposed scheme has an ability to provide a submodule current having DC component as well as AC component to represent real operating condition of HVDC transmission system. There is no need of extra power supply to provide the DC current component because the scheme has inherent circulating DC current between rectifier and inverter valves. Therefore, only one small power rated DC power supply is necessary. Experiments are carried out to show the validity of the proposed test circuit.

This paper presents the MPPT (maximum power point tracking) and PCC (point of common coupling) current control strategy for photovoltaic (PV) grid-connected generating system using the quasi-Z-source inverter (QZSI). At first, in order to explain the above controllers, the characteristic of QZSI is analyzed. And then, the MPPT control technique with a modified P&O method, the PCC current control one for the regulation of DC-link capacitor voltage, and the PWM methods for the proposed system are explained. The feasibility of the propose algorithm is verified through the simulation and experiment with 3 kW system.

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.

A novel high voltage DC power supply for neutral beam injector (NBI) is proposed. An acceleration power supply of NBI will experience frequent load short-circuits owing to the spark downs in the load. The output DC voltage of the proposed scheme can be quickly disconnected from the short-circuit load. In addition, the DC voltage is applied to the load immediately after the fault has been cleared without causing any voltage overshoot. The proposed scheme has the characteristics of a simplified structure, reduced cost and volume. Experimental results are presented to verify the usefulness of the proposed scheme.