Friday, 8 March 2013

SMART POWER GRIDS





Even as the demand for electricity grows, new guidelines could help improve power grid reliability and reduce electricity cost, researchers say.


"An imperative condition for the functioning of a power-grid network is that its power generators remain synchronized. Disturbances can prompt de-synchronization, which is a process that has been involved in large power outages. Here we derive a condition under which the desired synchronous state of a power grid is stable, and use this condition to identify tunable parameters of the generators that are determinants of spontaneous synchronization. Our analysis gives rise to an approach to specify parameter assignments that can enhance synchronization of any given network, which we demonstrate for a selection of both test systems and real power grids. These findings may be used to optimize stability and help devise new control schemes, thus offering an additional layer of protection and contributing to the development of smart grids that can recover from failures in real time."



a, Representation of the physical network of transmission lines.
b, Representation of the network of effective admittances.


Barack Obama, in this year’s State of the Union address, talked about the future of energy and mentioned “self-healing power grids”—a grid that is able to keep itself stable during normal conditions and also to self-recover in the event of a disturbance caused, for example, by severe weather. But as national power-grid networks become larger and more complex achieving reliability across the network is increasingly difficult. 

Now scientists have identified conditions and properties that power companies can consider using to keep power generators in the desired synchronized state and help make a self-healing power grid a reality. The design for a better power grid could help reduce both the frequency of blackouts and the cost of electricity, as well as offer an improved plan for handling the intermittent power sources of renewable energy, such as solar and wind power, which can destabilize the network. 




"Some damage to physical infrastructure is inevitable during severe weather and other disasters, but a smart grid with the ability to anticipate, respond to and isolate damage could mitigate the impact and speed recovery", said Massoud Amin, professor of electrical and computer engineering at the University of Minnesota.
Amin, describes a self-healing grid as “a system that uses information, sensing, control and communication technologies to allow it to deal with unforeseen events and minimize their adverse impact.”

The current power grid faces serious challenges. The increase in power demand is outstripping capacity, and the deregulation and the fragmentation of the industry means no single company is in charge of the infrastructure within a region, so there is less incentive for investment in upgrades to improve reliability. A fragmented regulatory environment also complicates things, with federal oversight of bulk distribution and state oversight of regional transmission and local delivery. 

But a 21st century Smart Grid could help enable the self-healing system envisioned by Amin. Here’s how it could work: 
  1. A computer monitoring conditions at a control center can simulate various system-wide corrective actions in less than half a second and send instructions to control computers throughout the system. When a failure in one place is detected, circuit breakers are triggered to isolate the problem and prevent other lines from being damaged. 
  2. Opening circuit breakers protects substations from damage from power surges, but some areas are cut off from power. Generation is automatically increased at a second location to supply the increased demand in affected areas. 
  3. This increased load to the second generator could cause damage, so within a half-second of the initial problem, the second generator can be shut down to prevent excessive acceleration. 
  4. To compensate for loss of this generator, large non-vital customers can be taken offline to lower demand, preserving power for critical functions such as streetlights and hospitals. 
  5. Even with compensation, voltage could become unstable in parts of the system because of increased demand, threatening to damage equipment. Within seconds of the initial problem, instructions can be given to the remaining online generators to increase power and reduce demand in users rather than shutting down transmission lines. 
  6. Within a minute, additional power is being brought in from an adjacent area to make up for the off-line generator and protect remaining infrastructure. The adjacent area automatically compensates for the exported power, and the undamaged portions of the system are stabilized. 
  7. When the original damage is repaired, the offline generator and the lines taken out of service by circuit breakers are brought back online.Damage and outages are not completely eliminated, but they are controlled so that physical damage does not spread and disruptions are minimized. 

The idea of systems and networks capable of defending and/or healing themselves is beginning to take hold.

— Source: GCN


HF

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