Power conversion device

A power conversion device, comprising:

• a first input/output terminal pair;
• a second input/output terminal pair;
• a DC/DC converter connected to the first input/output terminal pair and the second input/output terminal pair;
• and
• a control unit configured to control the DC/DC converter,
• wherein the DC/DC converter comprises:
• a first switching leg having first and second switching elements connected in series via a first connection point and connected to the first input/output terminal pair;
• a second switching leg having third and fourth switching elements connected in series via a second connection point and connected in parallel to the first switching leg;
• a third switching leg having fifth and seventh switching elements connected in series via a third connection point and connected to the second input/output terminal pair;
• a fourth switching leg having sixth and eighth switching elements connected in series via a fourth connection point and connected in parallel to the third switching leg;
• a first energy storage and conversion unit connected to the first connection point and the second connection point and connected to one winding of a transformer and a first reactor connected in series;
• and
• a second energy storage and conversion unit connected to the third connection point and the fourth connection point and connected to the other winding of the transformer and a second reactor connected in series,
• wherein the control unit is able to execute a first control for causing the DC/DC converter to convert a voltage within a first range applied to the first input/output terminal pair into a voltage within a second range and to output the voltage within the second range from the second input/output terminal pair and a second control for causing the DC/DC converter to convert a voltage within the second range applied to the second input/output terminal pair into a voltage within the first range and to output the voltage within the first range from the first input/output ten final pair,
• wherein the first control is a control for controlling ON/OFF of each switching element in the DC/DC converter so that a state of the DC/DC converter iteratively transitions between, in an order of, a first state in which a current input from the first input/output terminal pair flows through the first reactor, a second state in which a current is able to circulate along a path including the first reactor, a third state in which the current input from the first input/output terminal pair flows through the first reactor in a direction opposite to a direction in the first state, and a fourth state in which a current is able to circulate along a path including the first reactor while flowing through the first reactor in a direction opposite to a direction in the second state, and is a control for causing the state of the DC/DC converter to transition from the second state to the third state after a second reactor current value, which is a result of measuring a value of a current flowing through the second reactor, is within a first current value range if the second reactor current value is not within the first current value range when the state of the DC/DC converter is to be transitioned from the second state to the third state and causing the state of the DC/DC converter to transition from the fourth state to the first state after the second reactor current value is within the first current value range when the second reactor current value is not within the first current value range when the state of the DC/DC converter is to be transitioned from the fourth state to the first state, and
• wherein the second control is a control for controlling ON/OFF of each switching element in the DC/DC converter so that a state of the DC/DC converter iteratively transitions between, in an order of, a fifth state in which a current input from the second input/output terminal pair flows through the second reactor and no current is output from the first input/output terminal pair, a sixth state in which the current input from the second input/output terminal pair flows through the second reactor and a current is output from the first input/output terminal pair, a seventh state in which no current is input from the second input/output terminal pair and no current is output from the first input/output terminal pair, an eighth state in which the current input from the second input/output terminal pair flows through the second reactor in a direction opposite to a direction in the fifth state and no current is output from the first input/output terminal pair, a ninth state in which the current input from the second input/output terminal pair flows through the second reactor in a direction opposite to a direction in the sixth state and a current is output from the first input/output terminal pair, and a tenth state in which no current is input from the second input/output terminal pair and no current is output from the first input/output terminal pair, and is a control for causing the state of the DC/DC converter to transition from the sixth state to the seventh state after a first reactor current value, which is a result of measuring a value of a current flowing through the first reactor, is within a second current value range if the first reactor current value is not within the second current value range when the state of the DC/DC converter is to be transitioned from the sixth state to the seventh state and causing the state of the DC/DC converter to transition from the ninth state to the tenth state after the first reactor current value is within the second current value range if the first reactor current value is not within the second current value range when the state of the DC/DC converter is to be transitioned from the ninth state to the tenth state.