Advanced Solar Systems Integration
The advanced systems integration activities focus on enabling distributed renewable energy systems, such as solar, to move from their relatively small role in the energy market to a much larger role in the near future.
For distributed renewables to be an active partner in the grid, renewable energy systems must help meet system energy demand and control requirements at all levels. This transition will require improvements in distribution automation, automated load controls, and power quality and reliability-enhancing features.
The Systems Integration subprogram plans to achieve this goal through enhancing existing distribution system and microgrid integration, described below.
Existing Distribution System Integration
Within the unique challenges of integrating large amounts of solar energy into the existing electrical distribution system, the Systems Integration team is focusing on the following seven activities:
- Developing new voltage-regulation schemes for steady-state (slow) regulation, based on communication between transformers, voltage regulators, capacitor banks, and photovoltaics (PV).
- Developing recommended practices for reconciling feeder-voltage control techniques with high penetration of distributed PV.
- Solving the problem of ground-fault overvoltage on subtransmission systems.
- Studying the effective grounding-compatibility problem associated with PV and determining the equipment technologies and system changes to cost-effectively reduce the need to ground PV.
- Finding ways to adapt the distribution-system protective relaying and fusing to deal with fault currents that arise from larger quantities of distributed PV.
- Developing advanced distributed control schemes for distributed renewable systems.
- Developing sectionalizing schemes to allow distributed renewable systems to pick up load during the restoration process.
Microgrid Integration
Microgrids have one or more distributed energy systems operating in parallel with or independent from the electric power system, while providing continuous power to multiple loads. The design and operation of microgrids are complex, so there is a need for standardized design, integration, and operation requirements.
Microgrids can be used to improve system reliability and can be scalable on many service levels—whether for a few customers or for larger applications that include substations.
The fundamental difference between microgrids and the current utility distribution system is that two-way power flow occurs from or to the microgrid and its components, as well as to the interconnected utility.
To better understand microgrids, Sandia National Laboratories (SNL) is working with the developer and utility of a new development, Mesa del Sol, in Albuquerque, New Mexico. Once completed, the community will include 38,000 residences and commercial enterprises. It will have distributed PV systems, cogeneration facilities, and a microgrid, which will all be tied to the power grid. This approach is intended to improve system reliability.
As distributed renewable energy systems become a larger contributor to the electric power system, the distribution itself will need to be changed to accommodate these systems. The advanced system integration activities within the Systems Integration subprogram are designed to help facilitate these changes.
Both SNL and the National Renewable Energy Laboratory can set up and test microgrid systems.