Real-time Dispatch with Flexible Ramping Products in a Power System with High Penetration of Renewable Energy Generation

The variability and uncertainty of the power outputs from renewable energy sources (RESs) impose higher requirements on the operational flexibility of a power system with RESs integrated. The concept of flexible ramping product (FRP) is thus proposed and has attracted widespread attention in academic and industrial communities, which provides a new alternative for the accommodation of high penetration of renewable energy generation. Given this background, a real-time unit commitment/real-time economic dispatch model considering FRP provided by various flexible resources is proposed. The unit commitment here is with respect to those fast-starting units such as natural gas-fired ones. The unit commitment for conventional thermal units especially coal-fired units is determined in the day-ahead electricity market, and will not be addressed in real time. In the proposed model, the objective is to maximize the social surplus with the integration of multiple types of demand response resources taken into account, while the constraints include unit start-up/shut-down periods and ramping up/down rates in continuous periods. A sample system is next employed to demonstrate the proposed method, and the role of FRP in improving the system flexibility and in enhancing the accommodation capability for RESs is illustrated by some operation scenarios of the sample system. The impact of the prediction confidence of the demanded FRP on the system operational flexibility is also investigated through case studies.