Abstract: A harmonic current compensator is connected in parallel with a harmonic generating load to a system power supply and supplies a compensation current Ia to limit a harmonic component contained in a load current IL to be input from the system power supply to the harmonic generating load. The harmonic current compensator includes: a load current detector that detects the load current IL; a compensation current detector that detects the supplied compensation current Ia; a control amount computing portion that computes a control amount of the compensation current Ia based on the harmonic component contained in the load current IL detected by the load current detector and the compensation current Ia detected by the compensation current detector; and a limiter that limits an upper limit of the compensation current Ia.

Abstract: Provided is a power conversion device including: a step-up converter unit, including a reactor to which a DC voltage is to be input, a switching element connected to the reactor in parallel, and a backflow prevention element connected to the reactor in series; a smoothing capacitor configured to smooth an output voltage from the step-up converter unit; an inverter unit configured to convert the output voltage smoothed in the smoothing capacitor into an AC voltage; a dew condensation state detection unit configured to detect a state of dew condensation, which occurs due to a cooler configured to cool the step-up converter unit and the inverter unit; and a control unit configured to control an operation of the step-up converter unit, wherein the control unit includes: a determination unit configured to determine the state of dew condensation detected by the dew condensation state detection unit; and a step-up control unit configured to control a step-up operation of the step-up converter unit based on a result

Abstract: A heat pump device includes an inverter control unit for controlling an inverter. The inverter control unit includes a constraint-energization control unit that, during operation standby of a compressor, determines whether heating to the compressor is necessary, on the basis of a refrigeration stagnation amount in the compressor, and, when having determined that heating to the compressor is necessary, selects, according to the refrigeration stagnation amount, any one of direct-current energization for supplying a direct-current voltage to the motor and high-frequency energization for supplying a high-frequency voltage having a frequency higher than a frequency during a normal operation to the motor, so as to output a constraint energization command for carrying out constraint energization of the motor; and a driving-signal generating unit that generates a driving signal on the basis of the constraint energization command.

Abstract: Provided is a power conversion device including: a step-up converter unit, including a reactor to which a DC voltage is to be input, a switching element connected to the reactor in parallel, and a backflow prevention element connected to the reactor in series; a smoothing capacitor configured to smooth an output voltage from the step-up converter unit; an inverter unit configured to convert the output voltage smoothed in the smoothing capacitor into an AC voltage; a dew condensation state detection unit configured to detect a state of dew condensation, which occurs due to a cooler configured to cool the step-up converter unit and the inverter unit; and a control unit configured to control an operation of the step-up converter unit, wherein the control unit includes: a determination unit configured to determine the state of dew condensation detected by the dew condensation state detection unit; and a step-up control unit configured to control a step-up operation of the step-up converter unit based on a result

Abstract: Provided is a power conversion device configured to convert electric power from a power source to a load, including: a boosting device including a boost rectification unit configured to prevent backflow of a current from the load side to the power source side, the boosting device being configured to change a voltage of power from the power source to a predetermined voltage based on a drive signal; a commutation device configured to perform commutation operation in which a current flowing through the boosting device is caused to flow into an other path based on a commutation signal; and a signal generating module device configured as a module to generate and send an output signal based on an input signal that is input thereto. The input signal has an on-pulse width greater than a length of time where the output signal generated by the signal generating module device is turned on.

Abstract: A power converter includes a transformation circuit configured to transform a rectified voltage, and a converter control unit configured to control a switching element of the transformation circuit. The converter control unit calculates a current command value based on a line voltage or the phase voltage, calculates a current deviation between the current command value and the reactor current, and calculates a switching command value from the current deviation. The converter control unit includes a plurality of integrators for the respective different phase angles of a power supply voltage. The integrator corresponding to a power supply phase angle is caused to accumulate the current deviation, and the integrator corresponding to a phase angle that is advanced by a set delay phase from the power supply phase angle is caused to output the control amount. A switching signal is generated with use of the control amount and the switching command value.

Abstract: A backflow preventing device includes a backflow preventing element connected between a power source and a load, for preventing a backflow of a current from the load side to the power source side, a commutation device configured to perform a commutation operation of causing a current to flow through an other path connected in parallel to the backflow preventing element, and a controller configured to change a pulse width of a commutation drive signal for controlling the commutation device to perform the commutation operation based on a current flowing through the backflow preventing element, and transmitting the commutation drive signal having the changed pulse width to the commutation device. The controller transmits the pulse to the commutation device only for a necessary time period so that the commutation device performs the commutation operation, to thereby reduce electric power relating to the commutation operation not contributing to the power conversion.

Abstract: A power conversion device is provided that includes a rectifier, a booster circuit configured to boost an output voltage of the rectifier, a smoothing capacitor configured to smooth an output voltage of the booster circuit, and an inverter circuit configured to convert a DC voltage of the smoothing capacitor to an AC voltage and drive a motor forming a part of a device supplied with the voltage after the conversion. In addition, a reactor, a first backflow prevention element, a second backflow prevention element, a first switching element, a second switching element, an intermediate capacitor, and a controller configured to control the first switching element and the second switching element, are included.

Abstract: A power conversion apparatus, including: an MLC circuit configured to boost an input voltage from a three-phase rectifier; a smoothing capacitor configured to smooth an output of the MLC circuit; an inverter control unit configured to generate a PWM signal; an inverter circuit configured to convert a DC voltage of the smoothing capacitor into an AC voltage based on an input of the PWM signal and to supply the AC voltage to a motor; a boost mode switching unit having at least three boost modes in which a boost level of the input voltage is selected and configured to switch among the at least three boost modes depending on an operation status of the motor determined for the purpose of controlling a refrigeration cycle; and an MLC control unit configured to control the MLC circuit based on the switching by the boost mode switching unit.

Abstract: A motor drive control apparatus according to the present invention includes: a three-phase rectifier to rectify an AC voltage supplied from a three-phase AC source; a booster circuit including a reactor, a switching element, and a backflow preventing element, to boost a DC bus voltage supplied from the three-phase rectifier; a smoothing capacitor to smooth an output of the booster circuit; and an inverter circuit to convert the DC bus voltage smoothed by the smoothing capacitor into an AC voltage and supplying the AC voltage to a motor. During a starting operation of a boosting operation of the booster circuit or a stopping operation of the boosting operation thereof, a rotation speed of the motor is fixed.

Abstract: A heat pump device includes: a compressor including a compression mechanism compressing a refrigerant and a motor driving the compression mechanism; an inverter unit applying a voltage for driving the motor; an inverter control unit generating a driving signal for driving the inverter unit; and temperature sensors detecting temperatures of the compressor, wherein the inverter control unit includes a normal operation mode in which a refrigerant is compressed by performing a normal operation of the compressor and a heating operation mode in which a heating operation of the compressor is performed by applying, to the motor, a high-frequency voltage, and in the heating operation mode, the inverter control unit determines an amplitude and a phase of a voltage command for generating the high-frequency voltage on a basis of a temperatures detected by the temperature sensors and a necessary amount of heat specified in advance.

Abstract: An object of the present invention is to maintain a heating amount constant when a compressor is heated at the time of shutdown of the compressor, regardless of the influences of production tolerance and environment variations. An inverter control unit causes an inverter to generate a high-frequency AC voltage having a de-energized section in which a voltage applied from the inverter to a motor is zero between a section in which the voltage is positive and a section in which the voltage is negative. At this time, the inverter control unit detects a value of a current flowing to the inverter in a detection section residing from immediately before a start of the de-energized section to immediately after an end of the de-energized section, and causes the inverter to generate a high-frequency AC voltage adjusted according to the detected current value.

Abstract: A heat pump device includes an inverter control unit outputting PWM signals to an inverter; a current detection unit detecting a current value flowing in the inverter and outputting the current value after reducing a current value having a first frequency or higher in detected current value; and a drive-signal stop unit that, when the current value output from the current detection unit is equal to or larger than an interruption level, stops output of PWM signals to the inverter. Particularly, the inverter control unit generates a voltage command value such that the voltage command value becomes a value equal to or larger than a lower limit determined according to the first frequency and generates PWM signals based on generated voltage command value and a carrier signal, thereby causing a voltage output time to the motor to be a predetermined time or longer.

Abstract: A motor drive control device includes a three-phase rectifier; a boosting circuit including a reactor, a switching element, and a backflow preventing element and boosts a direct-current bus voltage supplied from the three-phase rectifier; a smoothing capacitor; an inverter circuit; a boosting control unit; an inverter control unit; and a circuit protecting unit suppresses a ripple current flowing through the smoothing capacitor. In the circuit protecting unit, a correlation of an on-duty ratio of the switching element included in the boosting circuit, the output power of the inverter circuit, and an estimated ripple current are set. On the basis of the on-duty ratio of the switching element, output power of the inverter circuit, and the correlation, the circuit protecting unit determines an estimated ripple current flowing through the smoothing capacitor. When the estimated ripple current exceeds a preset threshold, the circuit protecting unit suppresses the ripple current.

Abstract: A heat pump device capable of efficiently and reliably preventing a liquid refrigerant from stagnating in a compressor an air conditioner, a heat pump water heater, a refrigerator, and a freezing machine including the heat pump device. The configuration is such that, when the compressor is under operation standby, a high-frequency voltage synchronizing with a carrier signal is supplied to the compressor motor to carry out the locked energization of the compressor motor. From respective inter-phase voltages, respective phase voltages, or respective phase currents of the compressor motor for a plurality of high-frequency energization cycles, the detection values for one high-frequency energization cycle are restored. A power value calculated using the restored detection values for one high-frequency energization cycle is controlled to coincide with a heating power command necessary for discharging the liquid refrigerant stagnated in the compressor to the outside of the compressor.

Abstract: A heat pump device includes: a compressor that compresses a refrigerant; a motor that drives the compressor; a wiring switching unit that switches a wiring structure of the motor; an inverter that applies a desired voltage to the motor; and an inverter control unit that generates a PWM signal for driving the inverter, that includes, as an operation mode, a heating operation mode in which a heating operation is performed on the compressor and a normal operation mode in which a refrigerant is compressed by performing a normal operation on the compressor, and that controls a switching operation of the wiring switching unit in accordance with an operation mode.

Abstract: A power converter for converting electrical power from a power source to a load, including: a boosting device including a boost rectifier configured to prevent a backflow of a current from the load to the power source, the boosting device being configured to change a voltage of electrical power from the power source to a predetermined voltage; and a commutation device including: a commutation operation device configured to perform a commutation operation of directing a current flowing through the boosting device to an other path; and a commutation rectifier including a plurality of rectifiers and connected in series on the other path, the commutation rectifier being configured to rectify a current relating to commutation, thereby reducing a capacitance component.

Abstract: A heat pump device includes a compressor including a compression mechanism that compresses a refrigerant and a motor that drives the compression mechanism, an inverter that applies a voltage for driving the motor, a converter that applies a voltage to the inverter, an inverter control unit that generates a driving signal for driving the inverter, and a converter control unit that generates a driving signal for driving the converter. The inverter control unit includes a heating-operation-mode control unit that controls a driving-signal generating unit such that the driving-signal generating unit outputs, as inverter driving signals, PWM signals for heating the compressor without rotationally driving the motor by feeding a high-frequency current that the motor cannot follow in a heating operation mode.

Abstract: A power conversion device located between an AC power source and a load includes: a rectifier circuit unit that rectifies a voltage of the AC power source; a smoothing unit that smooths a DC voltage on the load side of the rectifier circuit unit; a short-circuiting unit that short-circuits the AC power source; a step-up reactor—located on the AC power source side of the short-circuiting unit; at least one of a reactor current detecting unit—that detects the current of the step-up reactor and a bus voltage detecting unit that detects an output voltage of the smoothing unit; a counterflow preventing element that prevents a counterflow of the current from the smoothing unit to the AC power source; a switching control unit that outputs a control signal for the short-circuiting unit; and a switching frequency changing unit that changes a frequency of the control signal using a logic operation.

Abstract: A power conversion device includes: a rectifier, a converter unit including a reactor, a backflow prevention element, and a switching element, the converter unit being configured to boost a DC voltage rectified by the rectifier, a smoothing capacitor, a reactor current detection unit, a bus voltage detection unit, a temperature detection unit, and a control unit. The control unit includes a converter control unit configured to calculate a switching command value for driving the switching element, on the basis of a target command voltage which is the bus voltage to be targeted, the bus voltage detected by the bus voltage detection unit, and the reactor current detected by the reactor current detection unit, and a temperature correction unit configured to correct the temperature of the switching element detected by the temperature detection unit, on the basis of the switching command value calculated by the converter control unit.