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This article introduces a self-excitation technology for field wound synchronous machines (FWSMs) to eliminate conventional components required by brushless and brushed static excitation systems. This technology is based on the utilization of pre-existing airgap flux harmonics, so no exciter or brush is required. The energy of these airgap harmonics at the slotting frequency is captured using rotor-mounted harvesting coils. A power electronic converter is then used to rectify the induced harvesting coil voltage and regulate the field winding current of the FWSM. Simulation results are presented showing the efficacy of the proposed method for a prototype FWSM under various loading conditions. For demonstration, a full-scale 5.4-MVA synchronous generator is used for design and validation.

This paper focuses on a Quasi-Two-Level (Q2L)converter topology and its use in long cable application, where overvoltage at the motor terminals due to wave reflection threatens the motor and cable insulation. Two operation strategies are proposed to mitigate such undesired effect, by taking advantage of the Q2L multilevel structure. In the first one, the drive works without any output filter, which results in a compact converter design, as capacitance is minimized, while enabling the use for longer cable lengths than those in applications where a $dv/dt$ filter is commonly used. In the second one, a modified $dv/dt$ filter is used in combination with the Q2L operation, when the first operation would require too high accuracy in the converter control. In both of the cases, the aim is to provide a compact solution that does not require the footprint and cost of multilevel converters, nor that of sine filters, and can thus be deployed in long cable applications with particular space constraints.

This work focuses on a Quasi-Two-Level (Q2L) converter topology for medium voltage drives (MVDs). It targets applications where the drive and the motor are connected via a long cable. In such systems a dv/dt filter is usually placed between the drive and motor to increase the rise time of inverter output voltage pulses, and thereby reduce the motor terminal overvoltage. The Q2L converter allows for an intrinsic reduction in the motor terminal overvoltage by dividing the voltage transitions in the inverter output voltage waveform into multiple smaller steps. Simulation results obtained with a distributed parameter cable model are presented, which show that the Q2L converter can offer lower converter capacitor energy and reduced dv/dt filter component values for a given motor terminal overvoltage requirement compared to the 5LANPC, a conventional MVD topology, at the cost of worse WTHD and efficiency. ispartof: pages:488-494 ispartof: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=8507745&isnumber=8502705 pages:488-494 ispartof: International Power Electronics Conference (IPEC) 2018 location:Niigata, Japan date:20 May - 24 May 2018 status: published