A converter circuit converts AC electric power into DC power. An inverter circuit converts the DC power into AC power. A capacitor is connected in parallel to each of the converter circuit and the inverter circuit between these circuits. The capacitor allows variation of an output voltage from the converter circuit, and absorbs variation of an output voltage from the inverter circuit due to a switching operation. An overvoltage protection circuit includes a resistor and a semiconductor element connected in series to each other. The overvoltage protection circuit is connected in parallel to the capacitor to protect the inverter circuit from an overvoltage. First and second control units respectively control the inverter circuit and the overvoltage protection circuit.

A power converter includes a converter circuit, an inverter circuit, a clamp circuit, a scrubber circuit, and an element including a resistive component. The converter circuit generates from an AC voltage source a DC voltage with AC components superimposed. The inverter circuit has an input connected with an output of the converter circuit. The inverter circuit is configured to convert the DC voltage into an AC voltage by switching, and output the AC voltage to an inductive load. The clamp circuit includes a first capacitor and a first diode connected in series. The clamp circuit is connected between a positive output and a negative output of the converter circuit. The snubber circuit includes a second capacitor and a second diode connected in series. The snubber circuit is connected between the positive output and the negative output of the converter circuit.

A power conversion device is provided, which includes: a power conversion circuit that performs power conversion between a primary power and a secondary power; a buffer data accumulation circuit that, in a predetermined buffer cycle, repeatedly acquires data sets relating to a state of the power conversion circuit and store the data sets in a ring buffer; a state monitoring circuit that generates a trigger signal in a case where a state of a predetermined monitoring target satisfies a predetermined condition; and a data replication circuit that, in a case where a trigger signal is generated, stores, in a data storage circuit, a plurality of the data sets accumulated in the ring buffer in a target storage period including a time before a generation time of the trigger signal.

This disclosure provides systems, methods, and apparatus for multi-level inverters. A hybrid binary cascaded multilevel inverter (BCMLI) is discussed that includes a plurality of H-bridge cells connected in a cascaded formation. DC input voltages of some of the H-bridge cells are provided by DC voltage sources. But inputs of other H-bridge cells coupled with capacitors instead. The H-bridge cells are operated to provide an AC output voltage at the output terminals of the inverter. One or more floating capacitor voltage controllers are used to vary one or more switching instances of the H-bridge cells such that a desirable level or charge is maintained across the one or more capacitors coupled with the input terminals of the H-bridge cells.

A method for controlling a voltage source power converter of a renewable energy power conversion system includes providing the voltage source power converter having, at least, a rotor-side converter and a line-side converter. The method also includes generating, via a converter controller, a first set of switching pulses based on a third-harmonic phase opposition carrier-based pulse width modulation (PO_CB_PWM) scheme. Further, the method includes generating, via the converter controller, a second set of switching pulses based on a third-harmonic in phase carrier-based pulse width modulation (IP_CB_PWM) scheme. As such, the method includes implementing, via the converter controller, a pulse-width modulation scheme for the rotor-side and line-side converters using the first and second sets of switching pulses, respectively, to obtain an output voltage from the voltage source converter to a desired magnitude, shape, and/or frequency.

A motor drive device has an abnormality detection function for a power supply unit between its own device and a power supply, and includes: a forward converter that is inputted AC power from the power supply via the power supply input part, and converts the AC power into DC power; a reverse converter that converts the DC power from the forward converter into AC power; a DC link capacitor provided to a DC link between the forward converter and the reverse converter; a voltage detection part that detects voltage of the DC link capacitor; and an abnormality detection part that obtains a voltage change amount for a predetermined time of the DC link capacitor based on voltage values detected by the voltage detection part, and performs abnormality detection on the power supply input part based on the voltage change amount thus obtained.

A motor drive device has an abnormality detection function for a power supply unit between its own device and a power supply, and includes: a forward converter that is inputted AC power from the power supply via the power supply input part, and converts the AC power into DC power; a reverse converter that converts the DC power from the forward converter into AC power; a DC link capacitor provided to a DC link between the forward converter and the reverse converter; a voltage detection part that detects voltage of the DC link capacitor; and an abnormality detection part that obtains a voltage change amount for a predetermined time of the DC link capacitor based on voltage values detected by the voltage detection part, and performs abnormality detection on the power supply input part based on the voltage change amount thus obtained.

Disclosed is a power conversion device having an AC conversion unit and a control unit that controls the AC conversion unit. The power conversion device also has: a temperature detection unit that outputs temperature data of the power conversion device; a current detection unit that outputs current data of an output of the AC conversion unit; a storage unit that stores specification data indicating a relationship between a rated current and a temperature specification and temperature data output by the detection unit; an overload protection unit that outputs a shutdown command to the control unit on the basis of the rated current and the current data output by the current detection unit; and a rating determination unit that acquires specification data and temperature data from the storage unit, determines a rated current corresponding to the acquired temperature data on the basis of the acquired specification data, and outputs the determined rated current to the overload protection unit.

Disclosed is a power conversion device having an AC conversion unit and a control unit that controls the AC conversion unit. The power conversion device also has: a temperature detection unit that outputs temperature data of the power conversion device; a current detection unit that outputs current data of an output of the AC conversion unit; a storage unit that stores specification data indicating a relationship between a rated current and a temperature specification and temperature data output by the detection unit; an overload protection unit that outputs a shutdown command to the control unit on the basis of the rated current and the current data output by the current detection unit; and a rating determination unit that acquires specification data and temperature data from the storage unit, determines a rated current corresponding to the acquired temperature data on the basis of the acquired specification data, and outputs the determined rated current to the overload protection unit.

A method for operating at least two pulse-width-modulated inverters connected to a direct-current supply network. The pulse-width-modulated inverters are each actuated via an actuation signal and operated in an operating point. A phase difference is generated between the actuation signals of the at least two pulse-width-modulated inverters by adapting the actuation signal of at least one of the pulse-width-modulated inverters as a function of operating point information describing the operating points of the pulse-width-modulated inverters.