Modeling and control of a variable-speed constant-frequency synchronous generator with brushless exciter

This paper presents the modeling, control, and implementation of a novel variable-speed constant-frequency power generation system for renewable and distributed energy applications. The generation system consists of a wound rotor generator, a brushless exciter and a low-rating controlled power converter. The advantages of the proposed system are reduced harmonic injection to power grid, wide speed operation range covering both sub-synchronous and super-synchronous speeds, self VAr support and increased reliability. It can be directly applied to wind power generators, small-scale hydroelectric generators, standalone diesel and gasoline generators, aerospace and naval power generation systems where a variable speed turbine/engine is employed. The generation system was first simulated using equivalent circuit approach. Then a mathematical model of a standalone generation system was developed and implemented. An experimental system and control scheme was implemented using embedded real time DSP controller. Measurements of the experimental system validated the system design and readiness for prototyping in a relatively large power range.