Direct drive permanent magnet generator fed AC-DC active rectification and control for more-electric aircraft engines

This study examines one of the principle candidates for jet engine electrical power generation in future more-electric aircraft, which is variable-speed multi-spool direct drive architecture with a DC distribution bus. New analysis of the behaviour of the system and a novel algorithm for the control of a variable speed dual-fault-tolerant permanent magnet generator (PMG)-fed AC-DC rectifier system is presented. Control objectives of DC voltage regulation, generator load sharing and minimisation of reactive power transfer are addressed. The controller is designed to facilitate unbalanced operation of the PMGs, thereby fault-tolerant operational capability of the system is supported. The AC-DC rectifier control algorithm is formulated such that the reactive power transfer is minimised, yielding reduced overall copper losses. The DC link voltage regulation is achieved via generator-rectifier phase angle control with a PI technique specially augmented to facilitate generator-rectifier load sharing control. Controller gain selection and direct implications on hardware limitations are discussed. Input/output stability is established and the control algorithm is validated via simulations.