A Droop-Based Diesel Generator Emulator for Microgrid Frequency Control Studies

In laboratory-scale studies, researchers usually prefer to use diesel generator emulator, instead of real diesel generator due to its flexibility in parameters design. Using diesel generator emulator, the behavior of a real diesel generator is emulated by a voltage source converter with voltage and current control loops in d – q frame. In this paper, an inverter-based prototype of a simple diesel generator emulator is presented for frequency variation studies in laboratory-scale microgrids. The proposed control system includes two separated paths for frequency and voltage. In the first path, two cascaded voltage and current control loops in d – q frame are employed to regulate the voltage like AVR system. In the second path, a proposed transfer function and a P – f droop curve are used to generate the reference frequency for inverse park transformation considering the transfer functions of prim-mover, governor and synchronous machine. The real diesel generator and the diesel generator emulator are simulated in MATLAB/Simulink software and compared to investigate the proposed control system. Also the experimental results verify the performance of the implemented prototype of the proposed diesel generator emulator in AUT microgrid.