Smart Grid Technologies-Microgrids, Demand Response and Communication Systems in Distribution Network

The modern day power system is transforming over the recent years from the traditional unidirectional (Generation to Distribution to Consumers) power flow to an inter-connected grid, with distributed generation injecting power into the grid at different levels (sometimes even at the consumer point) within the system. Variability of solar and wind power in a small geographical domain calls for quickly controllable back up generation or storage such as battery systems to fill in shortfalls. In urban scenario, the loads may peak during morning and evening hours when there is no solar generation. It also makes sense to encourage shifting the loads to a time of the day when there is surplus energy available in the system through ‘Demand Response’.

As the percentage or penetration of renewables increase in a power system, it becomes imperative to have grid level power balancing using energy storage systems. Microgrids are expected to form an inherent component in the grid system with localized generation and storage as close to the load centers as possible. They can be differentiated from major power grids in the sense that they are usually integrated at the distribution system of the power system, limited to integration at low or medium voltage levels of the grid. They are limited in geographical reach unlike power grids, and they lack bulk power transmission capabilities. Microgrids are thus more localized where the generation and consumption happens within a small area.

Another technique that can be used to assist power balance would be Demand Response (DR), which encourages customers to shift the load from one time of the day to another. This helps in reducing the peak demand during particular times of a day. As peak shave off is more important from the utilities perspective to maintain the operating conditions of the grid, incentive payments are normally included to encourage end customers to volunteer and subscribe to the program.

While distributed generation is changing the traditional grid connectivity, the distribution system needs implementation of technologies to improve its operational efficiency like energy availability, power quality and system responsiveness. To achieve this, a smart utility has to not only monitor the system components at every location of the distribution system but also plan ‘automatic’ reconnection of disconnected customers, when technically feasible, within a short time. The automation solutions include applications like SCADA/DMS, Outage Management System (OMS), Advanced Metering Infrastructure (AMI), Smart Metering and advanced applications like Demand Response etc. For implementation of such Distribution Automation (DA) systems, communication network is the backbone to interconnect the field devices to the control system applications. There are different communication technologies that are available today, with each one having its advantages and limitations. While it is comparatively easier to select a particular technology for transmission grid automation, the distribution grid automation faces a challenge of choosing a right and reliable technology.