SYSTEM AND METHOD FOR CONTROLLING SPEED OF AC MOTOR AND POWER INVERSION UNIT EMPLOYED THEREIN

摘要

PURPOSE: To suppress fluctuation in the output voltage from a power inverter due to abrupt variation of speed command in a system for controlling the speed of an AC machine by feeding inverted AC power thereto. CONSTITUTION: The power inverter unit comprises a power converter 11 and a power inverter 14 and controls an AC rotating machine 15 by feeding AC rotating machine 15 with AC power of desired frequency obtained by inverting power from an AC power supply 10. The power inversion unit further comprises a speed control system 20 for the power inverter 14 and a voltage control system 30 for the power converter 11. In the speed control system 20, a speed command delay unit 22 receives a speed command Wr* and outputs the speed command Wr* with a predetermined time lag, while at the same time, an acceleration/ deceleration current operating unit 23 and a power operating unit 24 calculate an inverter output power Pconv. In the voltage control system 30, a power supply current operating unit 34 operates a power supply current compensation command value Idc* from the inverter output power Pconv. The Idc* is added to a control output Id* from a voltage control operating unit 32 determined from the difference between a voltage command V* and the voltage Vfb across a smoothing capacitor 13 thus producing a power supply current command value Id* for controlling the output from the power converter 11 stably.