Abstract: In first power transmission in which power is transmitted from a first DC power source to a second DC power source, a control circuit performs on/off drive control of a positive electrode-side switching element and a negative electrode-side switching element in a first bridge circuit and a second bridge circuit and stops on/off drive of a positive electrode-side switching element and a negative electrode-side switching element in a third bridge. For a positive electrode-side switching element and a negative electrode-side switching element of a fourth bridge circuit, when a first power transmission amount by the first power transmission is greater than a predetermined first reference value, the control circuit performs on/off drive control, whereas when the first power transmission amount is smaller than the first reference value, the control circuit stops on/off drive.

Abstract: A power conversion device inputs or outputs a power for changing a state quantity of a distribution grid to which a voltage source device is connected, to or from the distribution grid. A grid control unit calculates a power command value of the power conversion device such that a drooping characteristic is provided for compensating for a deviation from a control target of the state quantity obtained from an output of a detector. A frequency characteristic of control computation for calculating a power command value from the deviation in the system control unit is defined such that a first control gain value in a first frequency range including direct current is set corresponding to a slope of the drooping characteristic, and a second control gain value in a second frequency range including higher frequencies than the first frequency range is set to be lower than the first control gain value.

Abstract: In a DC/DC converter, in first power transmission in which power is transmitted from a first DC power source to a second DC power source, on/off drive of a positive electrode-side switching element and a negative electrode-side switching element is stopped in a third bridge circuit on the power-receiving side. When a power transmission amount by the first power transmission is smaller than a first reference value, a control circuit lowers the switching frequency of the switching elements of a first bridge circuit and a second bridge circuit on the power-transmitting side and a fourth bridge circuit on the power-receiving side, compared with when the power transmission amount is equal to or greater than the first reference value.

Abstract: An insulating transformer includes a plurality of sub-insulating transformers connected in series. Polarity directions of all sub-windings are identical. When a current I flows from a first main terminal to a third main terminal through the first sub-winding, an interphase capacitance, and the second sub-winding, excitation inductance of the first sub-winding and excitation inductance of the second sub-winding are configured to have opposite polarities.

Abstract: A first capacitor and a second capacitor are connected in series through a neutral point on the DC side of an inverter. A first converter receives an input voltage from a power source and outputs a first DC voltage to the first capacitor. A second converter receives a common input voltage and outputs a second DC voltage to the second capacitor. A control circuit controls the first converter such that the first DC voltage is controlled in accordance with a preset first voltage command value and controls the second converter such that the second DC voltage is controlled in accordance with a second voltage command value set equivalent to the first voltage command value.

Abstract: In a DC/DC converter, in first power transmission in which power is transmitted from a first DC power source to a second DC power source, on/off drive of a positive electrode-side switching element and a negative electrode-side switching element is stopped in a third bridge circuit on the power-receiving side. When a power transmission amount by the first power transmission is smaller than a first reference value, a control circuit lowers the switching frequency of the switching elements of a first bridge circuit and a second bridge circuit on the power-transmitting side and a fourth bridge circuit on the power-receiving side, compared with when the power transmission amount is equal to or greater than the first reference value.

Abstract: In first power transmission in which power is transmitted from a first DC power source to a second DC power source, a control circuit performs on/off drive control of a positive electrode-side switching element and a negative electrode-side switching element in a first bridge circuit and a second bridge circuit and stops on/off drive of a positive electrode-side switching element and a negative electrode-side switching element in a third bridge. For a positive electrode-side switching element and a negative electrode-side switching element of a fourth bridge circuit, when a first power transmission amount by the first power transmission is greater than a predetermined first reference value, the control circuit performs on/off drive control, whereas when the first power transmission amount is smaller than the first reference value, the control circuit stops on/off drive.

Abstract: A reactor has one end connected to a neutral point of a transformer and the other end connected to a primary-side power supply. The transformer has almost no effective flux linkage for zero-phase current and has a phase difference between the primary side and the secondary side. A first bridge circuit and a second bridge circuit are connected to both ends of the transformer, and electric power of the primary-side power supply is controlled by the duty ratio of the first bridge circuit. The switching pattern of the second bridge circuit is phase-shifted in the leading direction and the lagging direction with reference to the switching pattern of the first bridge circuit, thereby achieving control such that soft switching operation can be performed even when the voltage ratio between the primary-side power supply and the secondary-side power supply fluctuates and the amount of transmission power is reduced.

Abstract: A reactor has one end connected to a neutral point of a transformer and the other end connected to a primary-side power supply. The transformer has almost no effective flux linkage for zero-phase current and has a phase difference between the primary side and the secondary side. A first bridge circuit and a second bridge circuit are connected to both ends of the transformer, and electric power of the primary-side power supply is controlled by the duty ratio of the first bridge circuit. The switching pattern of the second bridge circuit is phase-shifted in the leading direction and the lagging direction with reference to the switching pattern of the first bridge circuit, thereby achieving control such that soft switching operation can be performed even when the voltage ratio between the primary-side power supply and the secondary-side power supply fluctuates and the amount of transmission power is reduced.