Abstract: A power conversion device according to an embodiment of the disclosure includes: first paired switching elements including first and second elements coupling, respectively, a first voltage line to a first node and a second voltage line to the first node, second paired switching elements including third and fourth elements coupling, respectively, the first voltage line to a second node and the second voltage line to the second node, third paired switching elements including fifth and sixth elements coupling, respectively, the first voltage line to a third node and the second voltage line to the third node; first and second low-pass filters provided, respectively, in a first path between the first node and a first output terminal and a second path between the second node and a second output terminal; and a control section selectively bringing one of the first and second paired switching elements into an OFF state.

Abstract: A grid independent operation control unit includes a load current estimator to estimate a load current supplied to stand-alone power system in accordance with an output current of the inverter and an output voltage, and a feedback controller configured to PWM control the inverter at a duty ratio feedback calculated to cause the inverter to output an output voltage command value in accordance with the output voltage and the load current. The feedback controller is configured to PWM control the inverter at a duty ratio feedback calculated for output of a normalized output voltage command value obtained by normalizing the output voltage command value with the DC bus voltage in accordance with normalized output voltage obtained by normalizing the output voltage with the DC bus voltage and normalized load current obtained by normalizing the load current with the DC bus voltage.

Abstract: A power conversion device according to an embodiment of the disclosure includes: first, second, third, fourth, fifth, and sixth elements coupling, respectively, a first voltage line to a first node, a second voltage line to the first node, the first voltage line to a second node, the second voltage line to the second node, the first voltage line to a third node, and the second voltage line to the third node; a low-pass filter including two or more reactors provided in respective two or more paths of first, second, and third paths, respectively, coupling the first node and a first output terminal, coupling the second node and a second output terminal, and coupling the third node and a third output terminal, and first and second capacitors; and a control section calculating voltage differences across the respective two or more reactors to control operations of the fifth and sixth elements.

Abstract: A power conversion device according to an embodiment of the disclosure includes: first, second, third, fourth, fifth, and sixth elements coupling, respectively, a first voltage line to a first node, a second voltage line to the first node, the first voltage line to a second node, the second voltage line to the second node, the first voltage line to a third node, and the second voltage line to the third node; a low-pass filter including two or more reactors provided in respective two or more paths of first, second, and third paths, respectively, coupling the first node and a first output terminal, coupling the second node and a second output terminal, and coupling the third node and a third output terminal, and first and second capacitors; and a control section calculating voltage differences across the respective two or more reactors to control operations of the fifth and sixth elements.

Abstract: A power conversion device according to an embodiment of the disclosure includes: first paired switching elements including first and second elements coupling, respectively, a first voltage line to a first node and a second voltage line to the first node, second paired switching elements including third and fourth elements coupling, respectively, the first voltage line to a second node and the second voltage line to the second node, third paired switching elements including fifth and sixth elements coupling, respectively, the first voltage line to a third node and the second voltage line to the third node; first and second low-pass filters provided, respectively, in a first path between the first node and a first output terminal and a second path between the second node and a second output terminal; and a control section selectively bringing one of the first and second paired switching elements into an OFF state.

Abstract: An abnormality detection device for a grid interconnection relay to detect an abnormality of the grid interconnection relay upon switching to grid independent operation, and includes an abnormality detector to execute commercial power system voltage determination of determining whether or not there is a commercial power system voltage, and first voltage determination to be executed if it is determined that there is no commercial power system voltage through the commercial power system voltage determination, of causing the power conditioner to chronologically alternately output monitor voltages having different values in a state where a contact of the grid interconnection relay is controlled to open and executing abnormality determination as to the grid interconnection relay according to whether or not each of the monitor voltages is followed by difference between a voltage of the power conditioner and voltage of the commercial power system with respect to corresponding one of the monitor voltages.

Abstract: A grid connection power conversion device having isolated operation function for connecting a distributed power supply to a commercial power system is provided which comprises an inverter for converting DC power to AC power, a capacitor connected between the inverter and the commercial power system, a commercial voltage amplitude detection circuitry, an amplitude adjustment circuitry to increase an amplitude of an output voltage from the inverter stepwise from a given value to match the amplitude of the commercial system voltage, and a start-up control circuitry to control the grid connection power conversion device so that after the amplitude adjustment circuitry adjusts the amplitude of the output voltage from the inverter, after the start-up, to match the amplitude of the commercial system voltage detected by the commercial voltage amplitude detection circuitry, the start-up control circuitry connects the inverter to the commercial power system to start grid-connected operation.

Abstract: A grid connection power conversion device for connecting a distributed power supply to a three-phase commercial power system is provided. The power conversion device comprises an inverter, an instantaneous voltage detection circuitry to detect a maximum three-phase instantaneous voltage value of the commercial power system, a line voltage detection circuitry to detect a maximum value of each of three line voltages, an instantaneous voltage drop detection circuitry to detect an instantaneous voltage drop, and an output current control circuitry to control an output current value from the inverter. When the instantaneous voltage drop detection circuitry detects an instantaneous voltage drop, the output current control circuitry reduces the output current value from the inverter to an output current value corresponding to a minimum value among the four maximum voltage values which are the maximum three-phase instantaneous voltage value and the maximum values of the three line voltages.

Abstract: A grid connection power conversion device is provided in which an amplitude of an output voltage from an inverter is increased stepwise from 0, after start-up of the power conversion device, to adjust the amplitude of the output voltage from the inverter to match an amplitude of a commercial system voltage as detected, and thereafter the inverter is connected to the commercial power system to start grid-connected operation. This makes it possible to prevent the voltage applied to a capacitor provided between the inverter and the commercial power system from abruptly increasing from 0V to the commercial system voltage at the start-up of the power conversion device, thereby making it possible to reduce an inrush current to the capacitor at the start-up without using an inrush current prevention circuitry.

Abstract: An islanding operation detection device for a distributed power supply comprising an inverter connected to a commercial system power supply comprises: a commercial system frequency measurement circuitry; a reactive power injection amount calculation circuitry to calculate an amount of reactive power injection; a feedback signal generation circuitry; a reactive current control circuitry to feedback-control an output current command value to the inverter; an output current control circuitry to update the reactive current command value when a phase angle of the commercial system voltage is in the range of 90N°±?? so as to control an output current value of the inverter to follow the output current command value; and an islanding operation detection circuitry to detect whether or not the distributed power supply is in islanding mode, based on a commercial system frequency when the reactive power corresponding to the calculated amount of reactive power injection is injected.

Abstract: A relay abnormality detection device to detect an abnormality of a grid interconnection relay upon switching to grid independent operation and includes an abnormality detector to execute commercial power system voltage for determining whether or not there is a commercial power system voltage, if there is commercial power system voltage through the commercial power system voltage determination, first current determination of abnormality determination as to the specific relay according to whether or not there is an input current to the power conditioner in a state where a contact of the specific relay is controlled to open, and if there is no commercial power system voltage through commercial power system voltage determination, second current determination of abnormality determination as to the specific relay according to whether or not there is an output current from the power conditioner in the state where the contact of the specific relay is controlled to open.

Abstract: A grid connection power conversion device for connecting a distributed power supply to a three-phase commercial power system is provided. The power conversion device comprises an inverter, an instantaneous voltage detection circuitry to detect a maximum three-phase instantaneous voltage value of the commercial power system, a line voltage detection circuitry to detect a maximum value of each of three line voltages, an instantaneous voltage drop detection circuitry to detect an instantaneous voltage drop, and an output current control circuitry to control an output current value from the inverter. When the instantaneous voltage drop detection circuitry detects an instantaneous voltage drop, the output current control circuitry reduces the output current value from the inverter to an output current value corresponding to a minimum value among the four maximum voltage values which are the maximum three-phase instantaneous voltage value and the maximum values of the three line voltages.

Abstract: A grid connection power conversion device is provided in which an amplitude of an output voltage from an inverter is increased stepwise from 0, after start-up of the power conversion device, to adjust the amplitude of the output voltage from the inverter to match an amplitude of a commercial system voltage as detected, and thereafter the inverter is connected to the commercial power system to start grid-connected operation. This makes it possible to prevent the voltage applied to a capacitor provided between the inverter and the commercial power system from abruptly increasing from 0V to the commercial system voltage at the start-up of the power conversion device, thereby making it possible to reduce an inrush current to the capacitor at the start-up without using an inrush current prevention circuitry.

Abstract: A grid connection power conversion device having isolated operation function for connecting a distributed power supply to a commercial power system is provided which comprises an inverter for converting DC power to AC power, a capacitor connected between the inverter and the commercial power system, a commercial voltage amplitude detection circuitry, an amplitude adjustment circuitry to increase an amplitude of an output voltage from the inverter stepwise from a given value to match the amplitude of the commercial system voltage, and a start-up control circuitry to control the grid connection power conversion device so that after the amplitude adjustment circuitry adjusts the amplitude of the output voltage from the inverter, after the start-up, to match the amplitude of the commercial system voltage detected by the commercial voltage amplitude detection circuitry, the start-up control circuitry connects the inverter to the commercial power system to start grid-connected operation.

Abstract: A grid independent operation control unit includes a load current estimator to estimate a load current supplied to stand-alone power system in accordance with an output current of the inverter and an output voltage, and a feedback controller configured to PWM control the inverter at a duty ratio feedback calculated to cause the inverter to output an output voltage command value in accordance with the output voltage and the load current. The feedback controller is configured to PWM control the inverter at a duty ratio feedback calculated for output of a normalized output voltage command value obtained by normalizing the output voltage command value with the DC bus voltage in accordance with normalized output voltage obtained by normalizing the output voltage with the DC bus voltage and normalized load current obtained by normalizing the load current with the DC bus voltage.

Abstract: An islanding operation detection device for a distributed power supply comprising an inverter connected to a commercial system power supply comprises: a commercial system frequency measurement circuitry; a reactive power injection amount calculation circuitry to calculate an amount of reactive power injection; a feedback signal generation circuitry; a reactive current control circuitry to feedback-control an output current command value to the inverter; an output current control circuitry to update the reactive current command value when a phase angle of the commercial system voltage is in the range of 90N°±?? so as to control an output current value of the inverter to follow the output current command value; and an islanding operation detection circuitry to detect whether or not the distributed power supply is in islanding mode, based on a commercial system frequency when the reactive power corresponding to the calculated amount of reactive power injection is injected.

Abstract: An abnormality detection device for a grid interconnection relay to detect an abnormality of the grid interconnection relay upon switching to grid independent operation, and includes an abnormality detector to execute commercial power system voltage determination of determining whether or not there is a commercial power system voltage, and first voltage determination to be executed if it is determined that there is no commercial power system voltage through the commercial power system voltage determination, of causing the power conditioner to chronologically alternately output monitor voltages having different values in a state where a contact of the grid interconnection relay is controlled to open and executing abnormality determination as to the grid interconnection relay according to whether or not each of the monitor voltages is followed by difference between a voltage of the power conditioner and voltage of the commercial power system with respect to corresponding one of the monitor voltages.

Abstract: A relay abnormality detection device to detect an abnormality of a grid interconnection relay upon switching to grid independent operation and includes an abnormality detector to execute commercial power system voltage for determining whether or not there is a commercial power system voltage, if there is commercial power system voltage through the commercial power system voltage determination, first current determination of abnormality determination as to the specific relay according to whether or not there is an input current to the power conditioner in a state where a contact of the specific relay is controlled to open, and if there is no commercial power system voltage through commercial power system voltage determination, second current determination of abnormality determination as to the specific relay according to whether or not there is an output current from the power conditioner in the state where the contact of the specific relay is controlled to open.