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.