Synchronous machine field excitation utilizing a single phase matrix converter excited rotary transformer

This paper introduces a single-phase matrix converter (SPMC) excited rotary transformer system to replace the slip rings of traditional wound field synchronous machine (WFSM). Compared to an inverter excited rotary transformer system, the matrix converter is compact due to the absence of a bulky DC Link capacitor. In this paper, the proposed SPMC uses a new constant volts per Hz modulation method that generates a medium frequency voltage waveform to reduce the size and loss of a rotary transformer. The new modulation method maintains the flux in the rotary transformer over each switching cycle to be a nearly constant value so that the loss and the size of the rotary transformer are minimized. A new commutation strategy is also developed by the authors to ensure safe commutation of the converter switches. Simulation results for the proposed excitation system are discussed and verified by hardware prototypes of the matrix converter with two different types of topologies.