Power Transfer Protocol for Variable Frequency Aircraft Electrical Power Systems

Since the early days of aviation, when an AC-type generator became a primary source of electrical power for all aircraft systems, the demand for electrical power has steadily grown. Following rapid technology and scientific advancements in the aerospace industry, the complexity and criticality of all aircraft systems have increased to the point where multiple independent and isolated electrical power sources are required. In such an environment, with two or more variable-frequency AC-type generators that can be simultaneously activated to provide electrical power to the aircraft power distribution system, a safe power transfer process becomes a major priority. This means that any two independent aircraft AC power sources with different frequencies or phase angles cannot be connected simultaneously to a common power bus. For this purpose, a power transfer protocol has been developed to prevent any aircraft parallel power sourcing and to provide a reliable AC generator connection to single or multiple aircraft power buses. This article presents one approach to an aircraft power transfer protocol, design, and implementation. Going further and considering the possibility that a specific group of hardware-type system failures can prevent power transfer in a particular aircraft bus power configuration, the presented algorithm includes an additional logic design structure permitting safe and reliable power transfer for a limited type of failure conditions. An algorithm for a power transfer protocol was allocated to the generator control unit. The protocol itself relies on data communication between the bus power control unit and generator control unit through analog discrete and digital bus communication interfaces. A SIMULINK model was created to demonstrate a normal and a single-failure power transfer process. With time sequences, simulation results are included to illustrate that the presented power transfer protocol is fault-tolerant and independent of the aircraft power distribution architecture.