Takeshi Uematsu

A study of the high performance single-phase UPS

To improve the performance of a UPS, one must consider not only its performance but also its size and cost. Basic components of a UPS are a power circuit, an operation controller and a user interface. The purpose of this paper is to investigate the performance improvement of the power circuit and the operation controller and then to realize a high performance UPS in a trial product.

Transient response comparison of voltage mode and current mode control on output-inductorless two-stage DC-DC converter

The two-stage DC-DC converter is developed for power supply of telecommunication application. This converter consists of a buck topology in the first stage and a half-bridge topology in the second stage. In order to reduce the system order, the output inductor is removed form this topology, then this system can be treated as a second-order system in approximation. As a result, the stability and the transient response are improved. Further improvement is required. This paper presents the effect of current mode control on the transient response in an output-inductorless two-stage DC-DC converter. As a result, output voltage drop is reduced by around 25% and the settling time is reduced by around 36% when compared with the voltage feedback control, and the effectiveness of the current mode control is experimentally confirmed.

Utility interactive inverter controllable for a wide range of DC input voltage

The distributed generation system using new energy sources has attracted much attention. Since this distributed generation system links to a commercial source, a utility interactive inverter is required. In this case, some different levels of DC voltage are applied as the input for the inverter because there are new energy sources such as solar batteries and fuel cells, and they provide different DC-voltage levels. We propose a double-bridge (DB) inverter that can operate for a wide range of DC input voltage. We have analyzed the operation mechanism of the DB inverter including the control system. The analysis has been confirmed by simulation.

Steady-State Characteristics of a Novel PFC Converter Operating in DCM

This paper proposes a novel PFC converter topology. The novel PFC converter is a buck-boost type and its output voltage is suppressed up to 200 V. As the result, the withstand voltage of any components can be reduced. That is possible to be higher efficiency and smaller size. Furthermore, the converter is easy to control when the converter operates in the discontinuous conduction mode (DCM). This paper presents the classification of some operation modes and the analysis by the state-space averaging method. The optimum circuit parameters for DCM operation are presented. Steady-state characteristics of the converter are shown analytically and experimentally. From the results, it is clarified that the proposed converter is usable at the worldwide line voltage and is adapted to the international regulation of line-current harmonics