High-power cycloconverter drive for double-fed induction motors

Two cycloconverters independently supply stator and rotor windings of a wound rotor induction machine. The control strategy to stabilize this inherently unstable system is derived from the double-fed machine matrix (DFM) and the resulting algorithm is implemented in hardware with a simple field calculator. A practical implementation of a 2 kW drive illustrates the feasibility of the drive, and practical performances of full speed in both directions, as well as speed ramps of up to 700 r/min, are realized. The system benefits from the simplicity of line-commutated converters associated with a relatively high frequency of operation of each individual cycloconverter, thereby avoiding saturation effects appearing at low frequencies, combined with control of harmonic generation using the extra degree of freedom provided by the DFM