中性点クランプ電圧形PWMインバータを用いたベクトル制御システム

概要

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This paper describes a vector control system of an induction machine using a neutral-pointclamped voltage source inverter (NPC-VSI) that is one of double series connected inverters.The NPC-VSI is able to output 5 levels step-shaped line to line voltage without output transformers or reactors, and it may reduce harmonic currents corresponding to torque ripples. However, the NPC-VSI has a problem that excessive high voltage is applied to swiching devices when a neutral point of two DC capacitors of the NPC-VSI varies from the center of the DC link voltage, because the neutral point is floating.This paper proposes a current controller to which the space vector theory is applied. This can reduce harmonic currents to 1/4 of those of a conventional voltage source inverter using 6 swiching devices, and regulate the neutral point potential within a preset range. To simplify the current controller, information about voltage space vectors is given from the vector controller to the current controller. Validity of the current controller is confirmed by a prototype using an induction machine of 2.2 kW.
社団法人電気学会の論文