Introduction
In recent years, initiatives to reduce CO2 emissions in order to protect the environment have been implemented in countries throughout the world. The shift to clean energy, such as to wind power and solar power, which does not rely on conventional fossil fuels, is be coming increasingly prominent.
The use of power electronics devices to conserve energy can be found in a wide variety of applications, from consumer electronics to electric railways, FA systems and the like. Moreover, power electronics are used not only in power-consuming applications, but their use has also spread to the fields of power generation, transmission and supply such as in uninter ruptible power supplies (UPS), wind power generators and solar power generators. In particular, multi-level inverters have been proposed as an efficient way to increase the power conversion efficiency of a UPS or power generation system(1), and neutral-point-clamped (NPC) inverters have been put into practical use. A 3-level inverter*1 having a simpler circuit configuration than this NPC inverter has also been proposed, but when configured with typical insulated gate bipolar transistor (IGBT) and diode, an increase in conduction loss and a high surge voltage due to the wiring inductance were problems.
Fuji Electric has developed circuit systems for in verters and converters, which are power electronics devices, and has contributed to energy conservation mainly in devices in the industrial field. Additionally, by adopting a custom low inductance package using a reverse-blocking IGBT(2) (RB-IGBT), a proprietarily developed power semiconductor, Fuji Electric has developed an IGBT module for use in advanced NPC (A-NPC) circuits that solves the aforementioned problems(3). A UPS that utilizes this module has been in troduced to the market.
Presently, Fuji Electric is aiming to expand its series of IGBT module for A-NPC circuits, and is developing an IGBT module for A-NPC circuits that in tegrates a three-phase A-NPC 3-level inverter circuit and a thermistor into a single package. This paper presents an overview of these efforts.