Abstract: When a snubber capacitor is charged to a level greater than or equal to a predetermined voltage, a protection circuit renders a clamp diode conductive to complete charging of the snubber capacitor.

Abstract: A power conversion device includes: a DC current calculation unit for calculating a circulating current component for each phase which circulates between the phases through first arms and/or second arms not via an AC power supply and a DC power supply; and a circulating current control unit for controlling the circulating current component for each phase so as to follow a predetermined circulating current command value, thereby reliably suppressing variation in voltages of DC capacitors of unit cells among the phases even in such a case where an impedance is additionally inserted in a DC circuit.

Abstract: A cell block including a plurality of cell converters connected in cascade and each including switching elements and a capacitor is provided. The cell block includes external connection terminals for connecting to another cell block in cascade, and a bypass circuit is connected to the external connection terminals.

Abstract: A thyristor starting device includes: a converter which converts AC power supplied from an AC power source into DC power; a DC reactor which smooths a DC current; an inverter which converts the DC power provided from the converter into AC power, and supplies the AC power to a synchronous machine; a gate pulse generation circuit which generates a gate pulse to be provided to thyristors of the converter and the inverter; a control unit which sets a phase control angle of the gate pulse to be provided to the thyristors of the converter, by controlling a current of the converter such that the DC current flowing into the DC reactor matches a current command value; and an abnormality detection unit which compares a detection value of the DC current with the current command value, and determines an abnormality in the gate pulse based on a comparison result.

Abstract: A power conversion device includes a converter, a DC reactor, and an inverter. A control unit controls the converter according to a sum of a feedback control amount and a feedforward control amount, the feedback control amount being calculated based on a deviation between a current command value and the DC current flowing into the DC reactor, the feedforward control amount being set in accordance with a DC voltage provided from the converter through the DC reactor. When an output frequency of the inverter is in a first region, the control unit reduces a control gain used to calculate the feedforward control amount, as compared to when the output frequency is in a second region having a frequency lower than that of the first region.

Abstract: An electric power converter for converting AC to DC power or DC to AC power is disclosed. The converter includes a circuit for controlling the voltage and the circuit for controlling the current separately. The voltage is controlled by the switching modules and the up-side controller using the calculated target voltage. The current is controlled by the current controller using the calculated target current.

Abstract: This thyristor starter includes a control angle operation portion including a function or a table showing relation between a rotation speed of a synchronous machine and a phase control angle of an inverter and finding a phase control angle having a value in accordance with the rotation speed of the synchronous machine found by a speed operation portion. The phase control angle varies from a minimum value to a maximum value in accordance with the rotation speed of the synchronous machine, and a rate of increase in phase control angle relative to the rotation speed of the synchronous machine is varied in a plurality of steps in accordance with the rotation speed of the synchronous machine.

Abstract: An electrical power converter includes: AC voltage terminals U, V, and W; DC voltage terminals P and N; a converter cell series unit composed of one or more converter cells connected in series between the AC voltage terminals U, V, and W and the DC voltage terminals P and N, each converter cell including a semiconductor element and a capacitor; and a first inductance connected in series to the converter cell series unit, between, of the DC voltage terminals P and N, a DC voltage terminal at the lowest potential with respect to the ground, and the AC voltage terminals U, V, and W.

Abstract: In a synchronous machine starting device, a timing detection unit outputs a first position signal indicating a timing at which a value of an armature voltage passes a prescribed reference level. A feedback operation unit calculates an error of an estimated phase based on the estimated phase, an estimated rotational speed of a rotor, an armature voltage, and an armature current, updates the estimated phase and the estimated rotational speed based on the calculated phase error, and outputs a second position signal indicating the updated estimated phase. A frequency detection unit detects a current rotational speed of the rotor based on the first position signal, as an initial value of the estimated rotational speed. A selector circuit selects the first position signal and the second position signal in this order, and outputs a selected position signal to the power conversion control unit.

Abstract: In a thyristor control device which converts a first AC voltage to a DC voltage and converts the DC voltage to a second AC voltage to be supplied to a synchronous motor, a DC voltage detector is configured to detect the DC voltage, and is provided with an AC voltage detector configured to detect the second AC voltage and an arithmetic circuit configured to determine the DC voltage on the basis of the second AC voltage detected by the AC voltage detector. As a result, there is no need to separately provide a DV voltage detector, which makes it possible to make the device compact in size and cheap in price.

Abstract: In the ground fault detecting circuit, one terminals of first to third resistance elements are connected to first to third AC lines, respectively, the other terminals of the first to third resistance elements are commonly connected to one terminal of a fourth resistance element, and the other terminal of the fourth resistance element is connected to a line of a ground voltage. On the basis of a voltage across the terminals of the fourth resistance element, the ground fault detecting circuit detects whether a ground fault has occurred or not. Since a current does not flow through the fourth resistance element in the normal state and flows through the fourth resistance element after the occurrence of a ground fault, it is possible to detect the occurrence of the ground fault at a high accuracy.

Abstract: When a snubber capacitor is charged to a level greater than or equal to a predetermined voltage, a protection circuit renders a clamp diode conductive to complete charging of the snubber capacitor.

Abstract: A power conversion apparatus including a three-phase transformer interconnected to a three-phase power system, the three-phase transformer including a primary winding group that receives three-phase electric power of the three-phase electric power system, a first secondary winding group and a second secondary winding group that receive electric power transferred from the primary winding group, and a first converter group and a second converter group connected to the first and second secondary winding groups, respectively, the power conversion apparatus further including a DC output terminal group connected to at least one of other ends of the first to third converter arms provided in the first converter group, and connected to at least one of other ends of the fourth to sixth converter arms provided in the second converter group.

Abstract: When a snubber capacitor is charged to at least a predetermined voltage, a protection circuit renders conductive a clamp diode provided on current paths to complete the charging of the snubber capacitor.

Abstract: A synchronous-machine starting device includes an electric power conversion unit for converting supplied electric power into AC power for supply to the armature of the synchronous machine, a rotor position detection unit for detecting a position of the rotor of the synchronous machine based on an AC voltage in the armature of the synchronous machine detected by an AC voltage detection unit, an electric power conversion control unit for controlling the electric power conversion unit based on the position of the rotor detected by the rotor position detection unit, and an abnormality detection unit detecting a rotation abnormality of the synchronous machine based on the AC voltage detected by the AC voltage detection unit after supply of the field current to the rotor of the synchronous machine is started.

Abstract: A power converter converts DC power supplied from a first DC power supply and a second DC power supply into AC power and supplies the AC power to a load. The power converter includes a protection circuit for allowing a charging current, which is possibly to flow from the first DC power supply and the second DC power supply to a first snubber capacitor or a second snubber capacitor, to flow to another current path, when a voltage applied to the first snubber capacitor becomes a predetermined value or more or when a voltage applied to the second snubber capacitor becomes a predetermined value or more.

Abstract: A synchronous-machine starting device includes an induction voltage operating unit calculating an induction voltage induced to an armature of a synchronous machine based on an estimated phase representing a position of a rotor, an estimated rotational speed of a rotor, an AC voltage signal, and an AC current signal, and outputting an induction voltage signal representing the calculated induction voltage, a selection unit selecting and outputting one of the induction voltage signal received from the induction voltage operating unit and the AC voltage signal received from the AC voltage detection unit, and a feedback operating unit outputting a speed signal representing the calculated estimated rotational speed based on calculated phase error to the induction voltage operating unit, and outputting a position signal representing the calculated estimated phase to the electric power conversion control unit and the induction voltage operating unit.

Abstract: A synchronous machine starting device in which AC power is supplied to an armature of a synchronous machine, the supplied AC voltage is detected to determine a rotor position of the synchronous machine, and the supplied power is controlled based on the detected rotor position. To detect rotor position, a first position signal indicating a timing at which a level of AC voltage supplied to the armature of the synchronous machine reaches a prescribed value is output. An error of an estimated phase is calculated based on the estimated phase indicating the rotor position and the detected AC voltage, and the estimated phase is calculated based on the calculated error to produce a second position signal indicating the calculated estimated phase. A selected of first and second position signals is output to indicate the rotor position of the synchronous machine for control of AC power supplied to the armature.

Abstract: A control circuit, during a positive period in which current flows from a power conversion apparatus to a load, causes a second snubber capacitor to discharge by controlling a second auxiliary switch to be turned on while a second main diode is turned on, and during a negative period in which current flows from the load to the power conversion apparatus, causes a first snubber capacitor to discharge by controlling a first auxiliary switch to be turned on while a first main diode is turned on.

Abstract: In a synchronous machine starting device, a timing detection unit outputs a first position signal indicating a timing at which a value of an armature voltage passes a prescribed reference level. A feedback operation unit calculates an error of an estimated phase based on the estimated phase, an estimated rotational speed of a rotor, an armature voltage, and an armature current, updates the estimated phase and the estimated rotational speed based on the calculated phase error, and outputs a second position signal indicating the updated estimated phase. A frequency detection unit detects a current rotational speed of the rotor based on the first position signal, as an initial value of the estimated rotational speed. A selector circuit selects the first position signal and the second position signal in this order, and outputs a selected position signal to the power conversion control unit.