IESO Tool Change for Variable Generator Dispatch Instructions
October 10, 2017
The IESO will be making a change to its dispatching tool to identify that any variable generator (VG) involved in a line security constraint as being security constrained. This will ensure that the IESO respects all security limits and contribute positively toward the reliability of Ontario’s electricity system. This change will occur on October 11.
What this means for Variable Generators
Currently, if a VG is involved in a line security constraint and its offer is economic, they will receive a release dispatch to follow their forecast. As of October 11, the VG will now receive a mandatory dispatch to their forecast. If a VG is uneconomic, the VG will continue to receive a mandatory dispatch to 0 MW.
Additionally, a VG may experience an increase in the number of mandatory dispatches if its resource is security constrained.
Background
This change is intended to address operational problems that have arisen when dispatching VGs that are involved in line security constraints. Typically, not all of these VGs are constrained when resolving the detected security violation. Consequently, they are free to operate as per the ambient weather conditions. Due to under forecast error, this has resulted in the violation of security limits in real-time operation.