Minnesota Renewable Energy
Integration and Transmission
Prepared for: The Minnesota Utilities and
Transmission Companies ,
The Minnesota Department of
Commerce
Prepared by: GE Energy Consulting, with contributions
by:
–The Minnesota Utilities and Transmission Companies
–Excel Engineering, Inc.
–MISO
Study period: 11.13’ – 10.14’.
The Target
■ Increase Renewable Energy Standard to 40% by 2030
■ More Increment afterwards
■ Still maintain System Reliability
Study Tasks.
Study Tasks
 Develop Study Scenarios; Site Wind and Solar Generation
 Perform Production Simulation Analysis
 Perform Power Flow Analysis; Develop Transmission Conceptual
 Evaluate Operational Performance
 Evaluate stability related issues
 Identify and Develop Mitigations and Solutions
Scenarios
Study Scenarios
Wind and Solar Resource
Allocations for Study Scenarios
Scenarios
Major Assumptions for Production Simulation
Analysis of Study Scenarios
Wind Plant Siting
Minnesota region
 Wind plant siting was based on MISO Transmission Expansion plan 2013 (MTEP13)
siting principles in the baseline model scenario, addition of 1931 MW into the
Minnesota-centric area in scenario 1 and increasing by 610MW above Scenario 1 in
Scenario 2.
 The siting locations (Minnesota-centric area) includes all of Minnesota, parts of
North Dakota and South Dakota as well as northern Iowa.
MISO (non-MN) Wind
 Siting for the baseline Scenario 6900MW was added beyond the wind included in
the MTEP13, no addition of wind capacity was included for Scenario 1 and beyond
the baseline 13,026MW was added for Scenario 2
 Siting locations includes all MISO states other than the Minnesota-centric area.
Transmission System Study.
■ Simulation program: Siemens Power Technology PSS/E. Steady state thermal
analysis.
■ Method of Modeling: Generation to Generation. This method involves adding new
generation and simultaeously turning off an equal amount of existing generation to
keep the system balanced where generation equals load (plus system losses)
Scenario 1 / Transmission Mitigation
Scenario 2 /Transmission Expansion /Transmission Mitigation
Study Findings. Total Costs.
Production Simulation Process
Model Used:PLEXOS
This model captures the forecast uncertainties realized between a Day-Ahead and RealTime Markets
Baseline Scenario: Generation, transmission and market system in 2028 if current
industry and economics trends continue.
Scenario 1 (S1): Baseline conditions continue, and additional 40% of renewable
penetration.
Scenario 2 (S2): Baseline trends continue, increasing renewables penetration to 50%.
Study footprint / MISO Market footprint
■ Data about wind energy profile
was given by the National
Renewable Energy Lab (NREL)
WIND ENERGY Data
■ Two different Wind forecast (ND and 4 hours ahead). The 4 Hour wind forecast was
used as this more accurately approximates the final generation commitment MISO
would have going into the Real time market.
LOAD (Day Ahead load forecast)
Dinamic Performace. On line generation (MW).
All scenarios produce stable response and voltage recovery.
All studies consider a wide range of contingences.
Dynamics Analysis
 Analysis data obtained from the MTEP13 data set and
converted to GE PSLF format
 Benchmark contingencies simulation for dynamic data
 Dynamic load Model (GE PSLF Composite model CMPLDW)
- added at all loads greater than 5 MW
- all loads classified in their service territory
- modelling based on WECC parameters
Dynamic Models for Renewables
 Interconnection between new wind plants, utility-scale PV plants and distributed PV
 Utility PV and Wind plants both modelled with ±0.9 power factor but at inverter
transformer and 690V bus respectively
 Wind and Utility PV both set to regulate the 690V bus
 Distributed PV modelled with no voltage regulation capability but as lumped
generation in central locations.
 Inertial and frequency response controls considered inactive
Renewable generation topology in Powerflow Model
Operation Performance
Annual Energy
Annual Load, Wind and Solar Energy for
Minnesota-Centric Region
Annual generation in TWh by unit type for
Minnesota-Centric region
Annual Committed Capacity and Dispatch Energy for
Coal and Combined-Cycle Units in the MinnesotaCentric Region
Operation Performance
Wind and Solar Curtailment. WHY?
- Local Congestion
- Minimum Generation
 In all scenarios curtailment happens mostly at nighttime hours as a result of Minimum
generation
 Curtailment reduction by decommiting some baseload generation via economic signals.
Operation Performance
Cycling Coal Units
 Most plants were designated as “must run” - Scenario 1 & 2
 Scenarios 1a & 2a assumed coal plants as “not must run” (economically
dispatch/committed)
 Utilization of a day ahead forecast instead of longer term forward market
 No examination of wear and tear impacts of plant cycling
Cycling Combined-Cycle Units
 Better cycling capabilities than coal plants
 About 200 start/stop cycles per year
 Cycling decreases as wind and solar increases
System stability and related issues
 No angular stability, oscillatory stability or wide-spread voltage recovery issues were
observed over the range of tested study conditions.
 Overall dynamic reactive reserves are sufficient and all disturbances examined for
Scenarios 1 and 1a show acceptable voltage recovery.
 Weak system (low CSCR) issues assessed:
- Local pockets of a few wind and solar plants in regions with limited transmission
and no nearby synchronous generation (e.g. plants in North Dakota fed from
Pillsbury 230 kV near Fargo)
- Larger areas such as Southwest Minnesota (Buffalo Ridge area) with a very high
concentration of wind and solar plants and no nearby synchronous generation
System stability and related issues
Mitigations for Weak System Issues
 Improve the inverter controls, either by carefully tuning the equipment control
functions or modifying the control functions to be more compatible with weak
system conditions.
 Strengthen the ac system, resulting in increased short-circuit MVA at the locations of
the wind/solar plants. This approach increases CSCR.
 A combination of both works best!
Conclusions
 With wind and solar resources increased, production simulation and
transient/dynamic stability analysis results indicate that the system can be
successfully operated for all hours of the year with no unserved load and minimal
curtailment of renewable energy.
 Stability simulations evaluated using different criteria (first swing and angular
stability, separation and cascading outage conditions)
 Dynamic simulation results indicate that there are no fundamental system-wide
dynamic stability or voltage regulation issues introduced by the renewable generation
assumed in Scenario 1 and 1a.
 No dynamic analysis was performed for the study scenarios with 50% renewable
energy for Minnesota (Scenarios 2 and 2a) due to study schedule limitations and this
analysis is necessary to ensure system reliability.
Thank You!