Dynamic Modeling of Prime Mover on Microgrid Testbed Using Induction Motor Inverter Drive

Microgrid testbed is a prototype of a large scale microgrid system. This paper discusses a microgrid testbed simulation consisting of one synchronous generator, two induction generators, three induction motors, busbar, and load. The induction motor is used as prime mover which controlled by inverter. The operation of microgrid testbed, both in stand-alone as well as parallel operation, can affect frequency. The speed of prime mover is used to maintain the frequency of the system at 50 Hz (±1 %). The method used to control the speed of prime mover is by changing the frequency of the power source. The best stand-alone operation frequency (50 Hz) of induction generator is achieved by setting the power source frequency to 46 Hz to get the motor speed of 0.85 pu, while synchronous generator operation achieved with setting the power source frequency to 45 Hz and the motor speed of 0.9 pu. The oscillation occurred shortly when induction generator 1 and 2 connected to the system in parallel operation. This happens because the induction generator not only acts as an active power supply, but also absorbs reactive power from the system, so it affects the changes of frequency. The synchronous generator as the primary generator can reduce oscillation because it acts as both active and reactive power supply to the system, so it can stabilize the frequency.