An energy management system (EMS) for grids is the control-room software with which a utility watches its network and keeps the power put in equal to the power taken out, every second. This rule is called grid balancing. If supply and demand drift apart, equipment trips and areas lose power.
The software gets its information from the field. SCADA systems collect readings from substations and lines. Smart meters report how much homes use. Power plants report how much they produce, such as a wind turbine, a gas turbine or a solar inverter. The EMS shows all of this on one screen, often over a map from a geographic information system (GIS), and forecasts demand for the next hours. SCADA only collects the readings and sends simple commands. The EMS is the software that decides what the operators should do with those readings.
In India, the control rooms that use this software are called load despatch centres. Each state has one for its own network. Five regional centres and a national centre watch the power moving between states. The operators are engineers who sit in shifts, because the grid never stops.
Here is a typical case. At 6:45 pm the software sees that demand in a state is rising faster than forecast, because of a heat wave. A control-room engineer sees the warning. The system suggests which power plants should produce more. If needed, it asks a battery energy storage system to discharge, or a virtual power plant to reduce the load of thousands of devices. The engineer approves, and the orders go out.
So the EMS sends orders to breakers and switchgear as well as to plants. It also takes in warnings, for example about a tree close to a line. A related system for buying and selling electricity is power market modelling.
The work is changing because of the grid edge. Millions of rooftop solar panels and chargers now add and take power in ways the operator cannot see directly. So the software needs far more data and faster forecasts than before. Utilities buy this software through tenders and use it for many years, so changing it is slow and expensive.