This thesis focuses on the study, implementation and improvement of a digital Generator Control Unit (GCU) for a high-speed synchronous brushless generator. The control of variable frequency power system, a preferred candidate in More Electric Aircraft (MEA), becomes a big challenge. Compared with conventional analog GCU, digital GCU is a future trend due to the properties such as easy tuning, modification and no aging. Control approaches adopted in the new GCU design is introduced. It has multiloop structure and model-based characteristics. Sensorless rotor position detection was used to finish Park transformation. DSP+FPGA based controller hardware was developed in the lab. A set of hardware was designed to implement the control algorithms. VHDL-based software was developed for FPGA, which is working as a bridge between DSP and peripheral circuits. C-based software was designed to implement control algorithm inside DSP. A testbed system was developed according to the lab capacity of CPES. The complete load transit responses were tested according to the standard ISO1540 and EN8420. Good match between simulation and experiment has been reached. Compared with benchmark controller, great improvement in both steady state and dynamic performance is realized. A feasibility of using digital GCU in the next generation aircraft has been proved preliminarily. However, the challenge of reliability issues in digital system and software still needs further attention. / Master of Science