Power converter for an electrically-compensated constant speed drive

An electrically-compensated constant speed drive (CSD) for developing motive power at a constant speed from variable speed motive power developed at an output shaft of a prime mover, comprising:

• a first permanent magnet machine (PMM1) having electrical power windings and a motive power shaft coupled to the prime mover output shaft;
• a second permanent magnet machine (PMM2) having electrical power windings and a motive power shaft;
• a differential speed summer having a first input coupled to the prime mover output shaft, a second input coupled to the motive power shaft of the PMM2 and an output at which the constant speed motive power is produced;
• a first bi-directional AC/DC converter coupled to the electrical power windings of the PMM1;
• a second bi-directional AC/DC converter coupled to the electrical power windings of the PMM2;
• a bi-directional DC/DC converter coupled between the AC/DC converters;
• and
• means for controlling the AC/DC converters and the DC/DC converter so that electrical power developed by one of the permanent magnet machines is delivered to the other of the permanent magnet machines whereby motive power is developed by the motive power shaft of the PMM2 in an amount sufficient to maintain the output of the speed summer at a desired speed.

An electrically-compensated constant speed drive (CSD) for developing motive power at a constant speed from variable speed motive power developed at an output shaft of a prime mover, comprising:

• a differential speed summer having a first input shaft coupled to the prime mover output shaft, a second input shaft and an output shaft at which the constant speed motive power is produced;
• a first permanent magnet machine having a motive power shaft coupled to the prime mover output shaft and electrical power windings;
• a second permanent magnet machine having a motive power shaft coupled to the second input shaft of the differential speed summer and electrical power windings;
• and
• a power converter coupled between the electrical power windings of the permanent magnet machines including
• first and second AC/DC converters coupled to the electrical power windings of the first and second permanent magnet machines, respectively, each AC/DC converter including a plurality of controlled switches connected in a bridge configuration and a plurality of flyback diodes each coupled across and associated with one of the controlled switches, the controlled switches and diodes being connected to at least one input/output bus;
• a bi-directional DC/DC converter coupled between the AC/DC converters and including a bridge inverter, first and second input steering switches coupled between the input/output buses of the first and second AC/DC converters and the bridge inverter, respectively, a rectifier circuit coupled to an output of the bridge inverter and first and second output steering switches coupled between the rectifier circuit and the input-output buses of the first and second AC/DC converters, respectively;
• and
• means responsive to the speed of the prime mover output shaft for controlling the controlled switches, the bridge inverter and the input and output steering switches so that one of the permanent magnet machines operates as a motor and the other of the permanent magnet machines operates as a generator whereby the motive power shaft of the second permanent magnet machine is driven at a speed magnitude and direction which maintains the speed of the output shaft of the speed summer at a desired speed.