Abstract:
The type-4 wind turbine generators (WTGs) can provide inertial frequency response by
implementing the virtual synchronous generator (VSG) concept. However, unstable torsional
oscillations (TOs) would be induced in the multi-mass-spring drive-train which can
destabilize the entire power system. In this study, participation factor analyses are performed
for a power system inclusive of a thermal unit and aggregated WTG system. The
system’s eigenvalues are characterized and the possible detrimental impacts of TOs on
the inertia provision process and overall power system stability are demonstrated and the
related stability limits are identified. A comprehensive active torsional oscillations damper
(CA-TOD) and a supercapacitor-based energy storage system (ESS) are presented and discussed
to implement the CA-TOD. A state of charge (SoC) regulator is also employed
to set the reference speed difference for the turbine-generator. Small-signal studies and
electro-magnetic transient (EMT) simulations are performed to evaluate the functionality
of the CA-TOD and SoC controller and estimate their impacts on the system’s dynamics.
The robust performance of the CA-TOD is compared to the band-pass filter-based
TOD by sweeping key control parameters of the VSG and emulating drive-train parameter
uncertainty. Key results are cross-verified by EMT simulations of a multimachine power
system.