Subsynchronous resonance assessment for a large system with multiple series compensated transmission circuits

Abstract

Generators connecting to a series compensated transmission system can be exposed to subsynchronous resonance (SSR) and require a comprehensive vulnerability assessment. This study presents an SSR assessment framework and tools to more efficiently assess all types of generation in a large system with multiple generators and meshed series capacitors. The developed framework covers torsional interaction, torque amplification, and induction generator effect/control interaction and includes three assessment stages: topology screening, frequency scan, and detailed electromagnetic transient study. Topology screening based on max-flow min-cut theorem is applied to identify the set of transmission outages forming radial connections between generators and series capacitors. Frequency scan analysis is then conducted to further analyse the SSR vulnerability with all the possible combinations of transmission outages identified in the topology screening results. Nearby generators are modelled by frequency-dependent impedance tables, which consider the equivalent impedance looking into the generators over the range of 1-120 Hz. An electromagnetic transient simulation will be required to confirm the SSR vulnerability identified in the frequency scan analysis. The developed framework and tools have successfully been applied to a large power system with multiple series compensated circuits to ensure reliable generation interconnection and operation.

Vector‐fitting‐based quantitative SSCI analysis for series‐compensated wind power systems

“…Once all the elements of a k and c k are solved, d and e in (11) can be determined. To this end, a new least-square problem is formulated, as expressed in (17). In this case, B is the same as that in (16), and A and x can be expressed as…”

“…Then the aggregation technique is applied on the network admittance/ impedance matrix to establish two subsystems. To study the SSCI, one subsystem should consist of all the wind farms of interest, and the other should represent the series-compensated network [17]. Finally, the SSCI risk can be assessed considering the equivalent impedances of two subsystems.…”

“…More importantly, with the continuous integration of wind power, the utility may wish to install multiple series capacitors in a wind power system [22][23][24][25]. For example, ERCOT completed the Competitive Renewable Energy Zone transmission project in 2013, resulting in the system consisting of multiple series capacitors to accommodate an increase of 11,553 MW in the wind generation capacity in West Texas [17]. Therefore, it is questionable whether the RLC fitting can be applied to such systems to yield a sufficient accuracy.…”

Impedance Analysis and PHIL Demonstration of Reactive Power Oscillations in a Wind Power Plant Using a 4-MW Wind Turbine

“…These problems manifest as oscillations or resonance, which have resulted in significant equipment damage and disruption in the operation of wind power plants around the world (Gross, 2010;Brendel and Traufetter, 2014;Buchhagen et al, 2016;Sun et al, 2017;Xie et al, 2017;Liu et al, 2018). Resonance is classified either as subsynchronous resonance (Gross, 2010;Cheng et al, 2013Cheng et al, , 2019Sun et al, 2017;Xie et al, 2017;Liu et al, 2018) or super-synchronous resonance (Brendel and Traufetter, 2014;Buchhagen et al, 2016;Lyu et al, 2016), depending, respectively, on whether the frequency of oscillations is lower or higher than the fundamental frequency. In addition to the frequency of oscillations, however, it is also important to note whether the oscillations are measured in phasor variables-active and reactive power flows, and frequency, magnitude, and angle of bus voltages and currents-or phase variables-three-phase voltages and currents; subsynchronous oscillations in phasor variables appear as a combination of subsynchronous and supersynchronous oscillations in phase variables (Shah and Parsa, 2017).…”

Evaluating the Impacts of Transmission Expansion on Sub-Synchronous Resonance Risk

“…Apart from manual computation approach for these outage counts which could be time consuming for a highly interconnected region with large number of generations, other methodologies have also been proposed in literature. In [9] and [10], a topology screening methodology has been presented in which contingencies resulting in the shortest path (in terms of the number of buses) between the generation Point of Interconnection (POI) and the series compensated lines is determined using the Ford-Fulkerson max-flow min-cut theorem. However, this approach provides the contingency set only for the shortest path neglecting other paths that might satisfy the underlying planning criteria.…”