Mitsubishi Denki Kabushiki Kaisha

Shikoku Research Institute Incorporated

Masayoshi Kumano

Takafumi Maruyama

Fumihiko Ishikawa

Hiromasa Higasa

Hiroshi Mitsuoka

Shigenori Matsumura

Sueo Sakata

In a method of controlling the output voltage of a three-phase three-level inverter having a plurality of switching elements by pulse width modulation in each of three-pulse and one-pulse modes, the upper limit of the percentage modulation is set to a value equal to or smaller than the maximum percentage modulation determined by the minimum switching element off time to output a three-level voltage as an inverter output voltage in each phase if each of the switching element is turned of and off one time during one inverter output period.

Method of controlling an inverter

In a power interconnection system between an electric power system and a power converter which makes AC power from a DC power source, a positive feed-back loop is constituted so as to include a frequency deviation detector, a band-pass filter, an inert zone circuit, an amplifier, an adder, a phase controller, an inverter controller, an inverter and an interconnection reactor. Thereby a sufficiently great frequency fluctuation is made after opening of a branch line switch, so as to produce a frequency abnormality signal to be given to a disconnection switch; and disconnection is made certainly.

Interconnection for electric power system

A power source device according to this invention comprises a voltage and phase detector for detecting the voltage and phase of a power supply system, a first controller for controlling an inverter so that an output of the inverter may agree with either a reference voltage and a reference phase or with the voltage and the phase of the power supply system, a second controller for switching the inputs of the first controller from the reference voltage and phase to the power supply system voltage and phase, or vice versa, when the phases of a reference oscillator and the power supply system have agreed, and a third controller for switching the power to a load from the inverter to the power supply system, or vice versa, when the synchronism between the inverter output and the power supply system has been detected.

Power source device for a load with a stand-by power supply system

A capacitor charged with a voltage across anode and cathode of a thyristor after the voltage division and rectification is connected across gate and cathode of the thyristor through a switch while a diode with or without a series reactor is connected across the anode and gate through the same switch. Alternatively a primary winding of an insulating transformer may be connected across the anode and cathode and its secondary winding is operative to charge the capacitor through diodes. The switch is preferably a light switch.

Device for firing thyristor

A circuit for reducing thyristor turn-off time includes a thyristor connected between a power source and a load. A voltage source is connected between the anode and the cathode of the thyristor for applying across the anode and the cathode of the thyristor, upon actuation of a switch, an electrical signal sufficient to block the forward current of the thyristor. A rectifier and an impedance connected between the gate and the cathode of the thyristor cause a reverse current to flow in the gate of the thyristor upon application of the voltage source.

Growing community of inventors

Amagasaki, Japan

Masayoshi Kumano