Impact of Multiple Motor Loads on Dynamic Performance and Stability of Microgrids

Microgrids are becoming integral parts of the new power system structure where induction machines (IMs) constitute a significant portion of the system loads. This paper investigates the dynamic behaviour of various induction machines in microgrids and their related issues such as low-frequency oscillations (LFOs). This study also compare the dynamic performance of multiple parallel small IMs with a large IM of same power rating over a wide range of operating conditions using eigenvalue analysis and non-linear dynamic simulations considering different model parameters and voltage/frequency transients across the IM terminals. The results indicate that the IM rotor resistance is the most significant parameter which affects the dynamic behaviour of the machine while voltage and frequency transients lead to LFOs in the microgrid. Furthermore, the LFO damping capability of large IMs is found to be less than the small IMs while the system frequency with single large IM has shown one dominant LFO compared to multiple low frequency modes of the system with parallel small IMs.