The joint MISO–SPP Interregional Planning Stakeholder Advisory Committee (IPSAC) met November 14 to review interregional flowgates, HVDC coordination issues, long-term joint transmission planning needs, and cross-seam queue impacts. This meeting is central to aligning both RTOs on modeling assumptions and planning priorities for the 2026–2027 cycles. Below is a brief overview of key topics and discussions.
Interregional Flowgates
Both RTOs shared updated performance data on key flowgates:
- Seasonal Flow Influences: High wind output in SPP North and MISO West continues to cause flowgate overloads under shoulder-season and winter conditions.
- East–West Transfer Sensitivities: Increased solar and storage adoption in SPP South is driving new flow patterns affecting MISO Midwest.
- Congestion Mitigation Options: RTOs reviewed potential short-term operational mitigations and long-term infrastructure upgrades.
Stakeholders emphasized the importance of aligning production-cost modeling assumptions across both RTOs.
HVDC Coordination and Modeling
HVDC ties remain a central source of interregional modeling complexity.
Key updates included:
- Control-Mode Consistency: Different control-mode assumptions between SPP and MISO affect both stability and operational results.
- Short-Circuit Behavior: HVDC contributions in fault scenarios remain an area of uncertainty requiring improved modeling standards.
- Inverter Interactions: As IBR penetration increases, HVDC–IBR interaction studies are becoming more critical.
Developers requested standardized modeling guidelines across both RTOs to eliminate conflicting requirements.
Joint Transmission Planning Advancements
IPSAC reviewed interregional transmission needs:
- Joint Project Screening: Both RTOs walked through progress on conceptual projects designed to alleviate flowgate constraints.
- Production-Cost Model Alignment: The RTOs discussed aligning renewable profiles, load forecasts, and resource retirements.
- Policy Drivers: State-level decarbonization policies remain key inputs affecting interregional flows.
Stakeholders asked both RTOs to provide more transparency around cost allocation procedures for joint projects.
Queue Impacts Across the Seam
Developers continue to face queue delays due to:
- Conflicting modeling assumptions
- Affected-system triggers across both RTOs
- Stability study backlogs tied to hybrid facilities
- Load-modifier inconsistencies requiring joint review
IPSAC acknowledged these challenges and noted planned reforms in 2026. Access more on MISO, SPP and joint efforts for 2026.
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