A brutal storm ripped through southwestern Minnesota in April and snapped 2,000 power poles. Worthington Public Utilities kept the lights on with a seat-of-the-pants microgrid.
Greening the Local Grid
Smart solutions for distributed renewables.
The ability to link the disparate applications together to enhance performance and increase system optimization is extremely powerful. As an example, the integration of the load and DG forecasting capability (along with accuracy enhancing short- and long-term weather forecasting) with real-time power flow capability, a detailed network model and load management capabilities provides the foundation for a complete grid optimization solution. The new DMS solutions and remote monitoring devices are designed to bring the automated protection and control schemes out to the grid to automatically change settings to support relay reach and operation when feeders reconfigure themselves to allow DG to remain on-line.
The voltage-enhancing capabilities of the smart grid and DMS are an example of the future potential. The utility has traditionally been tasked with maintaining voltage within acceptable range at the end-customer delivery point. In a radial system, utilities developed a framework to accomplish this task. With a large volume of distributed generation, this becomes increasingly difficult. Older, traditional voltage regulators and capacitor banks that form the basis of current utility distribution system voltage management are inadequate for the future state. The response times of these devices are too slow to support the anticipated dynamic conditions. In addition, voltage regulators or booster controls traditionally operate in one direction while the future state system will be bidirectional due to the distributed sources.
As the utility portion of the power requirements is reduced, in favor of third-party or customer distributed sources, the complex interactions on the power grid can result in inadequate voltage support. As utilities still have ultimate responsibility for providing service within regulatory bounds, solutions need to be developed to manage voltage and reactive support in real time. It’s a delicate balance of ensuring that distributed generators aren’t harmed by power disturbances, while also trying to keep them on-line for transitory conditions, as they can support the grid when most needed.
Supporting these DMS solutions are the communication networks that are evolving to support smart grid field devices, backhaul smart meter networks and enable direct-connect monitoring. There’s no single network capable of meeting all the requirements of the smart grid, but a network of networks will combine to address bandwidth and latency requirements for the wide variation of unique applications, including system monitoring, distribution automation (DA), local control solutions and protection and control schemes. These include uWave, fiber and public and private WIMAX (and similar) networks, as well as smart meter networks.
The Inevitable Reality
Notwithstanding all the market and regulatory issues, the increase in distribution connected renewable generation is a reality. The advancements in renewable technologies, coupled with design and manufacturing cost improvements, are resulting in large-scale wind being competitively priced to coal-fired generation sources. And while solar thermal and PV remain high cost compared with fossil fuels, they continue on a downward trend. As the technology and cost efficiencies are translated down into the smaller scale installations, the widespread penetration of renewables on the distribution network is inevitable.
In parallel, utilities are increasingly exploring the evolving area of smart grid applications and integrated solutions, especially DMS. In