According to an embodiment of the invention, a power conversion device that includes a power converter, a direct current capacitor, a voltage sensor, a rectifying element, an electromagnetic contactor, and a control circuit is provided. The power converter includes a pair of direct current terminals connected to a direct current power supply, includes multiple alternating current terminals connected to an electric power system of alternating current, converts direct current power input from the direct current power supply into alternating current power, and supplies the alternating current power to the electric power system. The direct current capacitor is connected between the pair of direct current terminals. The voltage sensor detects a voltage value of the direct current capacitor. The rectifying element is provided between the direct current capacitor and the direct current power supply and suppresses a reverse flow of electrical power from the power converter and the direct current capacitor into the direct current power supply. The electromagnetic contactor is connected in parallel with the rectifying element. The control circuit controls operations of the power converter and the electromagnetic contactor. In the case where the voltage value of the direct current capacitor detected by the voltage sensor is a prescribed value or more, the control circuit engages the electromagnetic contactor and supplies active power from the power converter to the electric power system; and in the case where the voltage value of the direct current capacitor detected by the voltage sensor is less than the prescribed value, the control circuit opens the electromagnetic contactor and supplies a reactive power from the power converter to the electric power system.

According to an embodiment of the invention, a power conversion device that includes a power converter, a direct current capacitor, a voltage sensor, a rectifying element, an electromagnetic contactor, and a control circuit is provided. The power converter includes a pair of direct current terminals connected to a direct current power supply, includes multiple alternating current terminals connected to an electric power system of alternating current, converts direct current power input from the direct current power supply into alternating current power, and supplies the alternating current power to the electric power system. The direct current capacitor is connected between the pair of direct current terminals. The voltage sensor detects a voltage value of the direct current capacitor. The rectifying element is provided between the direct current capacitor and the direct current power supply and suppresses a reverse flow of electrical power from the power converter and the direct current capacitor into the direct current power supply. The electromagnetic contactor is connected in parallel with the rectifying element. The control circuit controls operations of the power converter and the electromagnetic contactor. In the case where the voltage value of the direct current capacitor detected by the voltage sensor is a prescribed value or more, the control circuit engages the electromagnetic contactor and supplies active power from the power converter to the electric power system; and in the case where the voltage value of the direct current capacitor detected by the voltage sensor is less than the prescribed value, the control circuit opens the electromagnetic contactor and supplies a reactive power from the power converter to the electric power system.

The invention relates to power supply systems. There is provided an apparatus and a method for supplying electric power to an electric device. In the method an indication of a desired power level to be supplied to the electric device is obtained. Electric power is received as DC power by a constant current regulator unit, which inverts the DC power to AC power and supplies the AC power to a reactance (T1) to be transformed to an output power. The output power is supplied from the reactance (T1) to the electric device. The method further comprises adjusting the AC power supplied to the reactance (T1) by using at least two of the following: voltage level of the AC power; the frequency of the AC power; a waveform of the AC power.

The invention relates to power supply systems. There is provided an apparatus and a method for supplying electric power to an electric device. In the method an indication of a desired power level to be supplied to the electric device is obtained. Electric power is received as DC power by a constant current regulator unit, which inverts the DC power to AC power and supplies the AC power to a reactance (T1) to be transformed to an output power. The output power is supplied from the reactance (T1) to the electric device. The method further comprises adjusting the AC power supplied to the reactance (T1) by using at least two of the following: voltage level of the AC power; the frequency of the AC power; a waveform of the AC power.

A method and device is disclosed for charging and/or maintenance of lead-acid and alkaline accumulator batteries, allowing a charge, discharge, or recovery in control-conditioning cycles of these batteries. To increase efficiency of the battery recovery process, its charge is created by a reversible current in consecutive stages. Correction of the charging mode is provided based on voltage and temperature of the accumulator battery.

A method and device is disclosed for charging and/or maintenance of lead-acid and alkaline accumulator batteries, allowing a charge, discharge, or recovery in control-conditioning cycles of these batteries. To increase efficiency of the battery recovery process, its charge is created by a reversible current in consecutive stages. Correction of the charging mode is provided based on voltage and temperature of the accumulator battery.

A modular multilevel power converter includes first electric components on a first vehicle and second electric components on a second vehicle. The first vehicle and the second vehicle are placed at a spacing distance from each other. The first electric components and the second electric components are electrically interconnected by a plurality of first connecting conductors.

An electric power conversion apparatus includes: a heat-generating element; a case having a cooling wall portion on which the heat-generating element is held and accommodating the heat-generating element; a flow passage cover having an opening formed therein and covering a surface of the cooling wall portion on the opposite side to the heat-generating element; a standing portion standing from the cooling wall portion and inserted in the opening; a flow-passage side wall portion formed in one of the cooling wall portion and the flow passage cover to protrude toward the other; a coolant flow passage surrounded by the cooling wall portion, the flow passage cover and the flow-passage side wall portion; and a sealant that seals both a gap between the cooling wall portion and the flow passage cover at a periphery of the coolant flow passage and a gap between the standing portion and the flow passage cover.

A power conversion system includes a first capacitor, an isolated type converter circuit, and a control circuit. The first capacitor is connected to the direct-current power supply via an inrush current prevention circuit. The inrush current prevention circuit is switchable at least between a high-impedance state and a low-impedance state. The converter circuit includes a transformer, and the first capacitor is connected to a primary winding wire of the transformer. The control circuit controls the inrush current prevention circuit and the converter circuit to cause the converter circuit to start operating, and then, the control circuit switches the inrush current prevention circuit from the high-impedance state to the low-impedance state.

A power conversion system includes a first capacitor, an isolated type converter circuit, and a control circuit. The first capacitor is connected to the direct-current power supply via an inrush current prevention circuit. The inrush current prevention circuit is switchable at least between a high-impedance state and a low-impedance state. The converter circuit includes a transformer, and the first capacitor is connected to a primary winding wire of the transformer. The control circuit controls the inrush current prevention circuit and the converter circuit to cause the converter circuit to start operating, and then, the control circuit switches the inrush current prevention circuit from the high-impedance state to the low-impedance state.