| 摘要 |
PURPOSE: To obtain a control device which can suppress a change in a neutral potential by a method wherein a voltage correction amount which suppresses an alternating change in the neutral potential is found by a computing operation. CONSTITUTION: A phase selection means 18 compares the magnitude relationship between three-phase voltage instructions Vu*, Vv*, Vw*. A phase at a maximum value out of the three-phase voltage instructions is designated as an x-phase, a phase at an intermediate value is designated as a y-phase, and a phase at a minimum value is designated as a z-phase so as to select the respective phases. A correction computing means 19 outputs, as a correction amount Vc, either of two correction amounts Vc1, Vc2 computed by expressions by using voltage instructions Vx*, Vy*, Vz* at the x-, y- and z-phases decided by the phase selection means 18 and by using detection currents Ix, Iy, Iz. The correction amount Vc is added to the three-phase voltage instructions Vu*, Vv*, Vw* by using respective adders 15u, 15v, 15w, corrected voltage instructions Vuc*, Vvc*, Vwc* are pulse-width-modulated by a PWM circuit 16, and the switching element of an NPC converter 1 is controlled. |
