Gas generation may be used to manage some of the wind and solar variability. The Macrogrid could schedule the variable energy patterns to HVDC terminals near gas generation clusters
The Macrogrid establishes a stronger transmission infrastructure than the present AC systems.
The Macrogrid has a contingency withstand limit of 5,400 MW compared to the present limit of about 2,700 MW for the AC WECC system.
Figure 5 shows that the cost of building larger scale HVDC lines of the Macrogrid is lower per MW of power delivery capability than the cost of dedicated HVDC merchant lines currently being proposed. The Macrogrid could be expanded with three more HVDC lines to be able to deliver about 60,000 MW of renewable generation. The cost reduction from the current HVDC line offerings by the Macro Grid and the Macrogrid expansion is estimated to be valued at $16B.
Summary for the NREL Seams Study
Design a typical collection system for wind and solar high potential areas-3,000 MW, 800 kV VSC bipoles- estimate of the scaled size of a VSC:
- Estimate the power density of current wind and solar installations per square mile and parcel the NREL renewable data into collection zones.
- Use 345 kV double circuited BOLD design-2000 MW rating or 5,000 MW rating per 500 kV double circuited BOLD line or about 3600 MW per standard double circuit 500 kV line-some reactive compensation may be required away from the terminals and for biasing at the terminal. My estimate is that the 345 kV double circuit Bold design is the least cost by using a set of radial lines from the HVDC terminal.
- Calculate the cross over distances for 345 kV, 500 kV and HVDC for terminal location constraints
- Example calculations should be sufficient to provide input data for the co-optimization program- one collector system probably will stand out for wind and another for solar
- Up to 30,000 MW of renewables connected to the Macrogrid there is no cost for incremental transmission, but each MW of renewable should have an incremental collector cost plus an incremental cost per MW for two HVDC terminals.
- For renewable expansion above 30,000 MW add the incremental cost the collector system, two HVDC terminal incremental cost/ MW and the HVDC line cost/MW based on the line being fully used. The line cost would be from an HVDC terminal.
- Place HVDC terminals with a rating limit of 5,000 MW where the Macro Grid HVDC lines cross the wind and solar high potential zones.
It is expected that the Macrogrid and further co-optimized transmission expansion would satisfy the FERC Order 1000 compliance for the Macrogrid footprint.
The NREL SEAM study funded by the DOE Future Grid Initiative investigates the economic benefits of tying the Eastern Interconnection with WECC with HVDC.
The Macrogrid HVDC network overlay was added to the AC WECC and AC EI grids as the initial starting point for the transmission system. The results may be reported on the SEAM study by the end of 2017. Early results show a benefit to cost ratio for the transmission that enables renewable energy expansion determined by a program tha co-optimizes the cost of generation and transmission expansion to be about 2.5:1. The HVDC transmission tying the EI to WECC is rated at about 20,000 MW. The SEAMS study started less than two years ago.
Designing the Future Grid with a scenario as the Macrogrid is possible today. The quality of the designs should be higher than the “estimates” from Think Tanks. Studies similar to the SEAM study could be used for policy guidance, inputs into more detailed utility level studies and possibly future articles.
Pacific Northwest Laboratory, Argonne National Laboratory, Oakridge National Laboratory, MISO, SPP and WECC conducted a dynamic stability simulation of the EI and WECC tied together with the HVDC Macrogrid network. The frequency drop in WECC for the loss of Palo Verde (2,700 MW) was about half of that of WECC alone for the loss of Palo Verde. The Macrogrid works as predicted.
For more information, please contact Dale Osborn, [email protected].