Hitachi, Ltd.

Kouji Yasuda

Masato Suzuki

Kiyoshi Nakata

Eiichi Toyota

Tokunosuke Tanamachi

Mutsuhiro Terunuma

Kiyoshi Nakamura

Yoshio Tsutsui

Satoru Inarida

Takeshi Ando

Wataru Miyake

Apparatus and method for controlling induction motor

In a pulse width modulation control method and system for an electric power converter, in order to suppress the occurrence of lower order harmonics and fractional order harmonics in a direct current component even in a condition where a carrier frequency is several times as small as the frequency of a command value, pulse width modulation pulses for driving semiconductor elements in the electric converter are calculated by comparing a command signal from a command value generating means with a carrier signal having a continuous triangular-wave and a constant period. For this purpose, there is provided a means for separately calculating a time product of a command value of the command signal from the command value generating means and a time product of the pulse width modulation pulses and for calculating a difference value representing a difference between both time products. The pulse width modulation pulse is then calculated using the calculated difference value to compensate the command signal received from the command value generating means.

Pulse width modulation control system for electric power converter

A two level inverter having a switching element the switching frequency of which is higher than that of GTO, and providing a continuous control substantially over a full range of output voltages wherein the two level inverter comprises as its pulse modes an asynchronous bipolar modulation mode, a multi-pulse mode of an overmodulation mode, and a one pulse mode, and wherein advantageously the multi-pulse mode and the one pulse mode are arranged to be changed, thereby to enable a continuous control of its output voltage and reduce tone changes in the magnetic noise as well.

Electric power conversion equipment

An electric power converting apparatus equipped with a 3-level PWM control in which the output voltage can be continuously and smoothly controlled from zero to a maximum voltage. The electric power converting apparatus includes a multi-pulse generating unit arranged for a dipolar modulation, a unipolar modulation, and an overmodulation; a 1-pulse generating means; and a unit for controlling the transfer operation among these modulation regions.

Electric power converting apparatus

Growing community of inventors

Hitachinaka, Japan

Kouji Yasuda