Phuc Huynh with adviser A. Banerjee
Ac-to-dc power conversion is essential in many emerging high-power applications, including wind-power generation and electrified transportation. Collecting electrical energy through a dc form allows the prime mover, such as a wind turbine or a gas turbine, to operate at variable speeds, enabling maximum power point tracking (MPPT) or leading to improved thermal efficiency. Creating ac-to-dc conversion systems at a megawatt power level that exceed the conventional solutions in terms of efficiency, reliability, and compactness has been my research theme. An integrated generator-rectifier system is proposed that integrates highly-efficient diode-bridge rectifiers and an active rectifier into a multi-port permanent magnet synchronous generator, as shown in Figure 7. The rectifier dc outputs are serially connected to form a relatively high-voltage dc-bus while each rectifier provides a portion of the total voltage. Processing most of the power on diode bridges results in a compact system that has high efficiency and high reliability.
Electrical power flow control capability is essential for practical usage of the integrated generator-rectifier systems. Achievement of this capability appears to be challenging because most of the power is processed on the uncontrollable diode bridges. Taking advantage of the serial connection of the rectifier dc outputs, the power flow control is feasible by controlling only the active rectifier. This capability allows MPPT in wind-energy applications, as illustrated in Figure 8, and dc-bus voltage regulation in dc-grid forming applications.
The project has been funded since June 2019 by the Advanced Project Research Agency – Energy (APRA-E) through the prestigious APRA-E Open competition in 2018.