Power generation - Distribution the key driver for smart grids


Traditionally, the UK's power needs have been met by large, centralised generation  units, with the electricity they produce transported to consumers by very reliable transmission grids feeding into tapered distribution networks. But times are changing. There are concerns today's demands for increased power supplies with higher reliability from cleaner, and preferably renewable, energy sources can be met with today's grid infrastructure. There is a growing consensus of opinion we need an intelligent system that can receive power of all qualities from all sources - both centralised and distributed - and deliver reliable supplies, on demand, to consumers of all kinds. In short, we need a smart grid says Peter Jones, head of technology at ABB (UK)

There is though a great deal of variation within the power industry, and outside it, as to what exactly should be included under the idea of a smart grid. Ask a room full of utility professionals to define the term and you're likely to get a wide range of answers. But most probably the discussion will focus on FACTS (Flexible AC Transmission Systems), WAMS (Wide Area Monitoring Systems) and HVDC (High Voltage Direct Current) technologies. These are of course very important transmission technologies that are already starting to play a significant global role in the development of smart transmission grids.

Ask a room full of consumers, and the talk will probably be about smart meters. Personally though, I am coming to the conclusion the ‘killer' element of the smart grid will be in between these two extremes - at the distribution network level. Distribution networks may well be the key to help manage the impact of the variable nature of generation from  large volumes of wind energy coupled with the dynamic requirements of customer electricity demands.
The increased reliance on an inherently variable source of generation will pose particular challenges in balancing the grid to maintain the high level of reliability and availability expected by consumers. This will be especially true on those days when the weather is cold, and energy demand is high with the additional risk of widespread low wind speeds sometimes seen in an average UK winter.

Since the UK currently has very little energy storage resource, with the notable exception of pumped hydroelectric schemes such as Dinorwig (providing 1800 MW), there are two choices. Either we need to invest in expensive fossil-fuelled plants to act as backup, or we create a smart grid that can take active, dynamic control of demand, storage and distributed generation at the distribution network level.

From passive to active distribution network
To meet this challenge, distribution networks will need to make a radical change from their traditionally passive format (ie, planned for particular peak loads and for use as fit-and-forget networks) to become more active or dynamically adapting networks in order to manage the increasing demands placed on them. This will necessarily be a two-way system where power generated by a multitude of small, distributed sources (CHP and domestic micro generation etc) flows into a grid based on a network rather than a hierarchical structure. Just as the Internet has changed media from a one-to-many paradigm to a many-to-many arrangement, so too will the smart grid enable a similar shift in the flow of electricity. It could also include the connection of smart white grids in the home, such as washing machines, refrigerators and freezers, with the possibility that they can be managed by the local DNO (Distribution Network Operator) to provide active and reactive load control in the local network, taking smart metering to a new level of sophistication.

The smart grid will change the way we look at power distribution. Technologies are already available in the form of switchgear, transformers, reactive power compensation solutions and Scada distribution management systems that enhance the operation of medium- and low-voltage power networks. But, as power generation becomes more distributed, and more power comes from renewable resources, the distribution grid will need to accommodate more fluctuations in power quality, as well as two-way power flow, while also becoming more responsive to changes in consumer demand.  The management of such a complex system will depend on real-time, secure communications and highly adaptive control systems. These will provide utilities and their customers with real-time information from across the network on the performance of grid installations, power flow and consumer demand. They will allow intelligent automated devices to react to imbalances in the system and also improve asset management by enabling improved predictive maintenance programs and faster emergency response times. Improved customer restoration times during system disturbances and network reconfiguration will also be a critical aspect of future smart grids. The incorporation of enterprise-wide information systems and customer response management tools will improve utility operations, enabling better customer relations and the provision of tailored services. The introduction of more intelligent monitoring systems and the extension of substation- and feeder automation in distribution networks will optimise operations, bringing improvements in reliability, availability, security and energy efficiency.

The way forward
Building the next generation of active power delivery networks requires a mixture of: new technology; existing technology deployed in new ways; existing asset infrastructure utilised in an optimum way; and changes in operating practices by electric utilities. Building on existing ideas, progress in such a complex, multi-stakeholder research and development effort requires a collaborative approach such as in the team-based AuRA-NMS project. Autonomous Regional Active Network Management Systems (AuRA-NMS) is a collaborative research and development project, sponsored by the UK Engineering and Physical Sciences Research Council (EPSRC), that seeks to demonstrate new network operation concepts in the UK. In addition to ABB, the consortium includes two major distribution network operators (DNOs) and several UK universities.

The goal of AuRA-NMS is to demonstrate the benefits of active network management using a distributed architecture integrated into existing control and asset infrastructure. It includes the use of innovative battery storage to understand the merits of trading opportunities, the support of constrained capacity related to overhead lines and cables, and stability control of the network due to various types of distributed generation. The project also aims to provide automated solutions for complicated constraint management.

The network management system controller used in the project is ABB's COM 600 series designed to complement the substation automation and network management systems already in service by some UK DNOs. The COM 600 supports the IEC 61850 standard and offers interoperability and expandability as well as providing a certain level of legacy protocol support for the DNOs' existing feeder automation devices.

SVC Light with dynamic energy storage
In coordination with the AuRA-NMS project, ABB is working with EDF Energy Networks on a collaborative research, development and demonstration project to install an SVC Light STATCOM (Static Compensator) with dynamic energy storage in a grid with a high penetration of wind power. The project is being financially supported through industry regulator Ofgem's Innovation Funding Incentive scheme.

The installation will yield dynamic voltage control in an 11 kV distribution system and at the same time enable dynamic storage of surplus energy from wind farms, which can be utilized to level out peaks in grid loading. Using this strategy, the power harnessed from the wind can be put to more efficient use than would otherwise be possible. The SVC Light with dynamic energy storage incorporates a high-tech lithium-ion (Li-ion) 5.2 kV battery system supplied by Saft that can deliver 200 kW for an hour and 600 kW for over 15 minutes.

The smart grid will not be a revolution. It will be a transformation of the distribution networks that have served us for many years into more intelligent, more dynamic and effective, environmentally sensitive networks to provide for our future needs. However, if our environmental targets are to be met this transformation must start now.

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