| 摘要 |
A method of determining the switch-over instants of static converters, which are connected in parallel opposition and free of circular currents, of a multiphase controlled inverter feeding asynchronous motors at variable frequency in four-quadrant operation, serves to ensure that a correctly timed switching-over of the converters takes place without having to take into account the operating frequency during a smoothing of the current measurement value. For this purpose the Fourier transforms of the fundamental oscillation of the currents are formed in component form from the temporal courses of the individual currents of the multiphase system with the use of auxiliary magnitudes, which are of constant amplitude and free of harmonic oscillations, as multiplier function. Subsequently, the Fourier transforms of the fundamental current oscillations of all phases are added separately according to the active and the reactive components. The quotient of the temporally smoothed sum values or its arc tagent is compared with the running time angles and the switching-over of the parallel opposition circuit is initiated at each instant of the equality. <IMAGE> |
