7/31/2019 Control of Permanent Magnet Assisted Synchronous Reluctance Generators

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Control of Permanent Magnet Assisted Synchronous Reluctance Generators (PMa-SynRG) with Current-Fed Drive

The growth of embedded generation and portable electrical installations has led to an increased

demand for low cost, flexible and reliable generator systems for military and commercial

applications. An interior permanent magnet (IPM) machine has high power density due to itsreluctance torque and magnetic torque components so it can produce a large constant power-speed

range. However, IPM needs demagnetizing current at high-speed during the flux-weakening region

and thus develops an inverter shutdown problem in an uncontrolled generator mode operation. In

order to overcome the disadvantages of IPM, the permanent magnet assisted synchronous

reluctance generator (PMa-SynRG) can be a good solution for low cost, high efficiency reliable

generator systems. A PMa-SynRG can produce a high efficiency drive by util izing the proper amount

of magnet and reluctance torque. This work suggests PMa-SynRG with two flux barriers and

permanent magnets embedded in the second layer of the rotor. NdFeB was used as permanent

magnets in the rotor to prevent demagnetization. Finding the minimum amount of magnet is one of

the goals of the optimization process.

The objectives of this work are to build an optimal design for the 3kW generator and advanced

power electronics converter for the PMa-SynRG drive system. In order to find the optimized 3kW

machine, Lumped Parameter Model (LPM) was used to achieve fast computation and Differential

Evolution Strategy (DES) was used to embed the LPM in an efficient numerical optimization routine

to identify optimum designs. Finite Element Analysis (FEA) was used for test performance of

optimum designs. On the basis of differences between LPM and FEA, model predictions were used

to fine tune the LPM model. For new optimum design converges, numerical optimizations and

iterations were performed to produce LPM and FEA predictions.

For the drive system, the thyristor based, current-fed drive is much simpler and has lower losses

compared to the pulse width modulation (PWM) drive. Eliminating the requirement for self-controlled

switches is a distinct advantage for lower cost. Another feature of the developed current-fed drive is

its inherent capability to provide generating action by making the PMa-SynRG operate as a

generator, rectifying the phase voltages by means of the three-phase rectifier and feeding the power

into the load. These features make the current-fed drive a good candidate for driving any type of

synchronous generators including the proposed PMa-SynRG.