Impact of load dynamics on torsional interactions

Abstract

Abstract-This paper evaluates the impact of load dynamics on torsional interactions by considering a mix of static and dynamic loads aggregated at the bulk transmission level. This is essential to investigate the importance of detailed load modelling for subsynchronous resonance (SSR) studies to accurately assess damping contribution and capture system dynamics. SSR interaction with dynamic loads is investigated for both direct on line and drive connected motor loads. Damping contribution from dynamic loads is also assessed based on their location and size. The interaction of dynamic loads with classical SSR phenomenon is observed and introduced as the new concept of (Subsynchronous Resonance Load Interactions (SSR-LI)). SSR-LI assumes critical importance for scenarios where the load and generation centers are in close electrical proximity and impact of loads on torsional damping is significant. Finally, the scope for using existing converter interfaced motors for torsional mode damping has been discussed.Index Terms-Dynamic load, induction motor, static load, subsynchronous resonance (SSR), variable frequency drive.

Analysis and mitigation of low‐frequency oscillations in hybrid AC/DC microgrids with dynamic loads

“…About ∼80% of the total industrial machine loads are operated as DOL starting mode [32]. In DOL start motors, the stator of the IM is directly connected to the network, hence any voltage/frequency deviations at the motor terminal makes motor vulnerable to instability [33, 34]. With the development of power electronics technology, VFD plays an important role in IM control, and VFD‐based IMs will constitute a significant share in the near future.…”

“…A 100 kW diesel generator is directly connected to the PCC of the AC sub‐grid of the AC/DC hybrid microgrid. About ∼80% of the residential and industrial motor is DOL start type [34], hence two 150 kW DOL start IMs are used as the dynamic load in the hybrid AC/DC microgrid, which amounts to 37.50% of the total load at the AC sub‐grid.…”