Coordinated primary control reserve by flexible demand and wind power through ancillary service-centered virtual power plant

With the steady increase of intermittent renewable power generation in generation portfolio of some power systems with limited hydro power generation and reduced access to synchronized controllable units such as thermal power plants, enabling participation of flexible loads to provide primary control reserve has recently gained attention. In this paper, a virtual power plant (VPP) as an aggregator of demand response (DR) resources and wind farms is developed. It facilitates providing primary control reserve by aggregation of DR resources and coordination of the primary reserve between those aggregated DR and wind farms. As a result, wind farms can be operated with less available capacity allocated for primary control reserve. This approach contributes to reduction of greenhouse gas emissions in a power system with a high proportion of wind-thermal units in the generation portfolio. Decentralized activation of DR for providing primary control reserve is proposed. For the VPP, an intraday and a near real-time scheduling algorithm in compliance with the German electricity market regulations are devised. The selection method of the DR resources, the adaptive power-frequency droop characteristics of resources, the aggregation process of the resources, and coordination of the primary reserve between wind farms and the DR resources are described. Demand response also effectively contributes to grid frequency stability by providing inertia response to frequency deviations, in addition to the steady-state primary control reserve. The simulation results of a representative high voltage transmission network model confirm the added value of the proposed VPP in enhancing the integration of wind power generation.