Active Voltage Balancing of Integrated Modular Drive with Series DC-Link Capacitors

In order to reduce the size and weight of transmission cables, high direct current (DC) bus voltage is desired for electrical machine drives used in the hybrid powertrains of more-electric aircraft (MEA). An integrated modular machine drive (IMMD) with DC-link capacitors connected in series is adopted to break down the supply voltage for each drive unit. With lower electrical stress, partial discharge (PD) risks at high altitudes can be significantly reduced. This paper deals with the challenge of active DC-link voltage balancing control in a megawatt-level integrated modular machine drives. Voltage closed-loop control is developed under the challenges of high electrical frequency and limited switching frequency. The impact of drive unit count and component parameter variations has been investigated, highlighting the design tradeoffs of the IMMD with series DC-link capacitors.