Reduction of interference currents in a group of synchronized, variable speed electric drives
AssigneeSiemens Aktiengesellschaft
InventorHubert Schierling
Life of this patent
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Abstract
The simultaneous generation of interference currents with the same polarity is prevented in all converters of connected drives, without adversely affecting the time slice synchronization or the uniformity of the dynamic characteristics. This is achieved by taking advantage of the symmetry of the modulation. The triangles of the sinusoidal/triangular modulation do not overlap as in conventional drives; instead, the triangles of one group, corresponding to approximately half the number of drives, are offset by 180°. With control processes operating with phasor modulation, the offset of 180° represents a shift of the switching sequence by interchanging the initial zero phasors and/or the modulation half intervals.
Claims14
A method for reducing interference currents in connected synchronized, variable-speed electric drives, comprising the steps of:
- addressing the connected drives with a common frequency converter having a common line feed and a common intermediate circuit as well as associated inverters, or with separate associated frequency converters,
- selecting switching frequencies of the inverters and respective sampling rates for determining actual values which are identical or integral multiples of each other, and
- preventing a simultaneous generation of interference currents with identical polarity in all inverters by using a modulation symmetry of voltage phasors, without impairing the synchronization of the dynamic characteristics.
Dependencies are inferred from the claim text.