Control device of neutral-point-clamped power converter apparatus, and control method of neutral-point-clamped power converter apparatus

A control device of a neutral-point-clamped power converter apparatus, comprising:

• a 3-phase/2-phase converter configured to convert three-phase currents flowing to three-phase loads, which are driven by the neutral-point-clamped power converter apparatus that is connected to a DC power supply having three potentials and is capable of outputting voltages of three levels by one-pulse control which switches a switching element in every cycle of an output AC voltage, to a d-axis current and a q-axis current of a rotating coordinate system;
• a 2-phase/3-phase current converter configured to convert a d-axis filter current and a q-axis filter current, which were obtained by passing the d-axis current and the q-axis current through a filter having a time constant which is greater than an inverse number of a fundamental wave frequency of the three-phase currents, to three-phase currents;
• and
• a neutral-point potential controller configured to calculate a sign which determines a switching pattern of one-pulse control that is based on three-phase voltage instruction values for the power converter apparatus, based on signs of the three-phase currents converted by the 2-phase/3-phase current converter, and a sign of a difference between a high-potential-side voltage and a low-potential-side voltage into which a DC input voltage is divided at a neutral point of the power converter apparatus.

A control method of a neutral-point-clamped power converter apparatus which is connected to a DC power supply having three potentials and is capable of outputting voltages of three levels, the method comprising:

• converting three-phase currents flowing to three-phase loads, which are driven by the power converter apparatus, to a d-axis current and a q-axis current of a rotating coordinate system;
• converting a d-axis filter current and a q-axis filter current, which were obtained by passing the d-axis current and the q-axis current through a filter having a time constant which is greater than an inverse number of a fundamental wave frequency of the three-phase currents, to three-phase currents;
• and
• calculating, based on the converted three-phase currents, a zero-phase voltage instruction value for controlling voltages into which a DC input voltage is divided at a neutral point of the power converter apparatus, as an instruction value which is superimposed on three-phase voltage instruction values for the power converter apparatus.