1. Stability Analysis on WECC Systems with Wind Penetration and Composite Load Model Introduction The growing complexity of generation and load pattern in power grids requires updates in system representation. Stability limits of renewable and motor penetrated systems need to be re-estimated for safety in operation and planning. Test systems are derived from 200-bus WECC system retaining the details of Pacific Intertie and California. The individual and combined influences of wind penetration and composite load model to system stability are estimated by N-1 transfer capacity based on WECC/NERC standards. Research Questions Where is the weakest part of base case WECC system? How does wind penetration weaken the system ? How do motor loads influence the system security? What is the effect of wind penetration on system incorporated with motor loads? Methodology Conclusion Doubly-Fed Induction Generator (DFIG) Model is used for 11 wind turbines in Case II and Case IV. Composite Load Model with representation of compressor stalling applied in Case III and Case IV. Synchronous condensers are added for local support. Pacific HVDC is represented by constant load. 247 non-fault AC contingencies are analyzed in 20 seconds of transient period and 5 seconds of post- transient period. 8 critical contingencies around Pacific Intertie are identified by post transient voltage check. One of the three AC branches of Pacific Intertie, 111-173 proved to be the weakest part of WECC in base case. Nearby wind turbines weakened the stability of Northwest by making branch outage 66-78 a limiting contingency. Air conditioning compressor stalling caused low voltage issues in California during transient period. Wind Turbine restored transfer capacity reduced by stalling motors by allowing more dynamic VAR around Pacific Intertie. Future Work NERC/WECC Standards Case NumberBus NumberWind PenetrationLoad Model Case I181 bus0%Constant Power Case II197 bus12% ( NW and CA)Constant Power Case III181 bus0%Composite Load Model Case IV197 bus12% (NW and CA)Composite Load Model Testing Cases Description and Summary Fig. 6 Case II AND IV Freq. Standard Violation In Response to Northwest Outage CaseLimiting Transfer Capacity Limiting FactorLimiting Contingency Minimum Violation Value Case I4695.93MWPost-transient Voltage dip Branch outage 111-173 0.949Pu on Bus 172 Case II4643.99MWFrequency DropBranch outage 66-78 59.230Hz on Bus 65 Case III4311.07MWNon-load Voltage Drop on Bus 134 Branch outage 119-134 0.6950Pu on Bus 134 Case IV4643.99MWFrequency DropBranch outage 66-78 59.230Hz on Bus 65 Applying dynamic HVDC model in 200-bus WECC system. Including Monopole DC contingency in N-1 transfer capacity analysis for all test systems. Developing wide area control schemes to restore transfer capacity to compensate for compressor stalling. Fig. 8 Case III Transient Voltage Violation in Response to North California Outage Fig. 7 Case III Transient Voltage Response at Limiting Transfer Capacity Fig. 4 Case I Post-transient Voltage Violation after Pacific Intertie Outage Fig. 3 Case I Non-load Voltage Response at Limiting Transfer Capacity Summary of Transfer Capacities of All Test Systems Fig. 5 Freq. Response to Northwest Outage in Case II and IV at Limiting Transfer Capacity Fig. 1 WECC with Renewable Resource Location Fig. 2 WECC 200-bus System with Wind Penetration Transient VoltageTransient Frequency Post-transient Voltage Minimum 0.75 at load buses or 0.7 at non-load buses Minimum 0.8 for maximum 20 cycles at load buses Minimum 0.96 for 500kV bus voltage following disturbance Minimum 59.6Hz for maximum 6 cycles at load buses Minimum 0.95 at any bus after critical contingencies Transfer Capacity Results with Limiting Contingency Simulation Acknowledgements: This work was supported primarily by the Engineering Research Center Program of the National Science Foundation and the Department of Energy under NSF Award Number EEC-1041877 and the CURENT Industry Partnership Program. Hyungdon Joo 1, Melissa Yuan 2, Yidan Lu 3, Dr. Kevin Tomsovic 3 Farragut High School 1, Oak Ridge High School 2, University of Tennessee 3