A power conversion apparatus 1 has an inverter for converting DC power into AC power. This control device for the power conversion apparatus includes: a current limiting unit for limiting a target current value to a predetermined limit value or less when the target current value is greater than the limit value; and a control unit for controlling the inverter on the basis of the target current value after the current limiting performed by the current limiting unit.

An electrical assembly includes a converter-based electrical device and a transformer for connecting the converter-based electrical device to an AC electrical network, a first transformer side of the transformer connected to the converter-based electrical device, a second transformer side of the transformer for connection to the AC electrical network, the transformer including a number of taps, the transformer including a tap changer operable to selectively connect to the or each tap to modify a turn ratio of the transformer. The transformer includes a controller configured to selectively operate the tap changer in an AC voltage modification mode, responsive to an abnormal operating state of the electrical assembly, to modify the turn ratio of the transformer so as to modify an AC voltage at the first transformer side.

An electrical assembly includes a converter-based electrical device and a transformer for connecting the converter-based electrical device to an AC electrical network, a first transformer side of the transformer connected to the converter-based electrical device, a second transformer side of the transformer for connection to the AC electrical network, the transformer including a number of taps, the transformer including a tap changer operable to selectively connect to the or each tap to modify a turn ratio of the transformer. The transformer includes a controller configured to selectively operate the tap changer in an AC voltage modification mode, responsive to an abnormal operating state of the electrical assembly, to modify the turn ratio of the transformer so as to modify an AC voltage at the first transformer side.

A power conversion device includes a converter and an inverter that form a power converter to convert a first power into a second power, an input-current sensor to measure a first current value that is a current value of the first power, an output-current sensor to measure a second current value that is a current value of the second power, and a control unit to detect an abnormality of the input-current sensor based on the first current value and the second current value.

A power conversion device includes a converter and an inverter that form a power converter to convert a first power into a second power, an input-current sensor to measure a first current value that is a current value of the first power, an output-current sensor to measure a second current value that is a current value of the second power, and a control unit to detect an abnormality of the input-current sensor based on the first current value and the second current value.

A modified modulated wave acquisition method includes: obtaining a modulated wave u.sub.aba; calculating a difference between the given value i.sub.Nq* and the actual value i.sub.Nq of the q-axis component of a grid side current, inputting the result to a proportional integral (PI) controller, and multiplying an output of the PI controller by cos ωt to obtain a modulated wave offset Δu.sub.aba; and calculating a difference between the modulated wave u.sub.aba and the modulated wave offset Δu.sub.aba to obtain a modified modulation wave u.sub.aba′, where ωt is a grid voltage phase in a sinusoidal case. The MPC method for a single-phase cascaded H-bridge rectifier includes: obtaining the modified modulated wave u.sub.aba′, where the component i.sub.Nq* is 0; and replacing the modulated wave u.sub.aba with the modified modulated wave u.sub.aba′ to perform MPC for the single-phase cascaded H-bridge rectifier.

A modified modulated wave acquisition method includes: obtaining a modulated wave u.sub.aba; calculating a difference between the given value i.sub.Nq* and the actual value i.sub.Nq of the q-axis component of a grid side current, inputting the result to a proportional integral (PI) controller, and multiplying an output of the PI controller by cos ωt to obtain a modulated wave offset Δu.sub.aba; and calculating a difference between the modulated wave u.sub.aba and the modulated wave offset Δu.sub.aba to obtain a modified modulation wave u.sub.aba′, where ωt is a grid voltage phase in a sinusoidal case. The MPC method for a single-phase cascaded H-bridge rectifier includes: obtaining the modified modulated wave u.sub.aba′, where the component i.sub.Nq* is 0; and replacing the modulated wave u.sub.aba with the modified modulated wave u.sub.aba′ to perform MPC for the single-phase cascaded H-bridge rectifier.

An apparatus according to an embodiment includes a control circuit to control operations of an inverter and a switch. The control circuit judges whether or not a power system has a power failure, based on values of the system voltage and a frequency of the power system; and calculates a phase difference between a phase of the output voltage of the inverter and a phase of the system voltage and generate, by means of the phase difference, an output frequency pattern for changing a frequency of the output voltage of the inverter. The control circuit, when it is judged that the power system has recovered from the power failure, controls the inverter to change the frequency of the output voltage of the inverter in line with the output frequency pattern, and closes the switch after the phase difference becomes smaller than or equal to a threshold.

A controller and a plurality of driver circuits may be configured to operate selectively either in a normal mode or in a diagnostic mode. In the normal mode, the controller is configured to transmit a drive signal to each driver circuit via a corresponding drive signal line. Each driver circuit is configured to drive corresponding switching element(s) in response to the drive signal and is further configured to output a failure signal when the driver circuit detects a failure related to the corresponding switching element(s). In the diagnostic mode, the controller is configured to sequentially transmit a request signal to the driver circuits via their corresponding drive signal lines, and each driver circuit is configured to output the failure signal in response to the request signal in a case of having detected the failure during operation in the normal mode.

A controller and a plurality of driver circuits may be configured to operate selectively either in a normal mode or in a diagnostic mode. In the normal mode, the controller is configured to transmit a drive signal to each driver circuit via a corresponding drive signal line. Each driver circuit is configured to drive corresponding switching element(s) in response to the drive signal and is further configured to output a failure signal when the driver circuit detects a failure related to the corresponding switching element(s). In the diagnostic mode, the controller is configured to sequentially transmit a request signal to the driver circuits via their corresponding drive signal lines, and each driver circuit is configured to output the failure signal in response to the request signal in a case of having detected the failure during operation in the normal mode.