Hitachi, Ltd.

The Kansai Electric Power Co., Inc.

Tadao Kawai

Akira Bando

Hiroto Nakagawa

Mitsuyasu Kido

Chikara Tanaka

Eizo Kita

Tomio Chiba

Keiji Saito

Keiichi Mitsuhashi

Tomoharu Nakamura

Junzo Kawakami

Hiroyuki Kudo

Yasuteru Oono

Hiroo Konishi

Takeichi Sakurai

Yasuteru Ohno

Kiyoshi Goto

A power signal processing system and method for protection of a power system has a signal input unit for receiving a signal representing a condition of a power system; a plurality of processing units cooperating to apply to the received signal a predetermined process including a series of predetermined different computations thereby producing a control signal for controlling operation of the power signal processing system. The respective processing units operate to perform the predetermined different computations, respectively. A control unit is provided for controlling transfer of data among the processing units so that the different computations are applied, successively, to the received signal thereby producing the control signal which is used to cause, for example, the issue of a cut-off command to a circuit breaker.

Digital control and protection equipment for power system

A semiconductor power conversion system comprising a multiphase bridge circuit which includes semiconductor devices having a controllable firing function and a reverse blocking characteristic, a gate control circuit which gives firing commands to the semiconductor devices, a short circuiting switch in which switching devices having a controllable firing function and a reverse blocking characteristic are connected in parallel with a DC output side of the multiphase bridge circuit, and a protection control device for performing a control for protecting the multiphase bridge circuit. The protection control device includes a device for detecting a commutation failure of the multiphase bridge circuit, and a device in response to the detection of the commutation failure for producing a blocking command for blocking the firing of the semiconductor devices of the multiphase bridge circuit and producing a short-circuiting command for firing the switching device which is short-circuited which bypasses current of the commutation failure. The protection control device further includes a device for detecting ending of a short-circuit based on the ceasing of current conduction of the short circuiting switch and for halting the blocking of the firing of the semiconductor devices of the multiphase bridge circuit.

Fault protection for a multiphase bridge power converter

Analog signals are sampled and converted into digital data which is then filtered by a digital filter. The filtered digital data is then subjected to an arithmetic operation. The blocking band of the digital filter is set to a frequency band which is above the pass band of the analog signal components. Frequency of sampling, as well as the frequency of noise caused by the sampling, is elevated, so that the noise frequency falls within the blocking band of the digital filter.

Digital signal processing method and system, electric power system

An improved electric power conversion system comprising a multi-phase bridge circuit composed of semiconductors such as thyristors and an associated firing circuit. It is so constructed that: if the AC input current Iac flowing in the bridge circuit is equal to or larger in value that the DC output current Idc flowing out of the bridge circuit, it will be decided than an inner defect or fault is caused, and possible expansion of inner defect will be prevented by disabling the firing circuit to extinguish the thyristors in the bridge circuit, and if the AC input current Iac is smaller than the DC output current Idc in value, the bridge is permitted to continue the operation of power conversion, thus eliminating unnecessary interruption which otherwise would be caused by exterior disturbances. Also, an improved electric power conversion system may be equipped with a device to prevent an adverse effect from being caused by abnormal rise of thyristors' temperature.

Semiconductor electric power conversion system enabling fault and/or

Two rectifiers and two inverters are operated under the state under which they are connected in parallel by common transmission lines. These rectifiers and inverters are controlled an independent control apparatus respectively which can selectively apply either the constant current control or the constant voltage control. The control apparatus of each converter has bestowed thereon the reference value of a current to flow through the particular converter and the reference value of a terminal voltage of the particular converter. A signal for lowering the current reference value is added to the control apparatus of one or all of the converters which are to be operated as the inverters. On the other hand, a signal for essentially rendering the terminal voltage of the converter smaller than the voltage reference value is added to the control apparatus of the converter which is to be operated as the converter for determining the voltage of a direct current system.

Converter control apparatus for parallel connected multi-terminal direct

A ground detecting device for detecting a ground fault in a DC circuit, through which a DC power produced by converting a poly-phase AC power by an AC-DC converter is transmitted and which is connected at an earth point to the earth, is arranged to detect an earth current flowing through the earth point and extract a DC component, if any, from the detected earth current and to judge whether a ground fault has occurred or not by comparing the level of the DC component with a predetermined reference level.

Ground fault detecting device for use with a DC circuit

Growing community of inventors

Katsuta, Japan

Tadao Kawai