Yasuhiko Hosokawa

A low loss solid-state transfer switch using hybrid switch devices

The authors have developed an advanced solid-state transfer switching scheme using a novel hybrid switch device, resulting in negligible loss consumption and eliminating the need for cooling equipment. In this paper, the authors present the following aspects and operating characteristics of the proposed SSTS (solid-state transfer switch): (1) construction and operating characteristics of the low loss SSTS using the hybrid switch devices; (2) construction and operating characteristics of the hybrid switch device and its compact design using 12 kV, 1.5 kA thyristor; and (3) analysis of opening and closing characteristics of the hybrid switch device, especially in terms of opening characteristics of the parallel switch and current commutation characteristics from parallel switch to thyristors, along with test results.

Static starting device for the start-up of the gas turbine using position sensorless control method

Static starting devices, also called static frequency converters (SFCs), have been utilized to start gas turbines in gas turbine combined cycle (GTCC) power plants, etc. In general, a gas turbine is started using a generator as a synchronous motor with a single-shaft arrangement that is rotated by the electric power fed from the SFC. Because the rotor position signal of the generator is indispensable for controlling the SFC, a mechanical position sensor is installed beside the rotor shaft. However, such mechanical position sensors require considerable time for installation and adjustment at the site. Therefore, a sensorless control method called the advanced position sensor (APS) has been developed and applied to an SFC. In this paper, we describe an SFC that employs this position sensorless control method. Further, we investigate the applicability of the APS by comparing the pulses of the two systems — APS and the traditional position sensor — observed during start-up.

A novel soft-switching inverter for high power application with simple control

A novel soft-switching inverter with regenerative snubber circuits is proposed. This inverter can be operated in soft-switching condition by simple control, without any additional complicated control. Having a passive clamp circuit, a maximum voltage across main switches is suppressed. In addition, voltage of each dc link capacitor is automatically balanced in a half of dc voltage. In this paper, soft-switching operations and other characteristics are descripted in detail. Numerical simulation and experiment with a 1.7 kVA three-phase model was conducted. Because there is undesirable voltage and current resonance due to parasitic components, measures to deal with these problems are also presented. RC snubbers were designed and applied to the experimental system to eliminate these oscillations.