Ancillary Services Provision with Wind Power Plants in Spain and its Coordination with Congestion Management.

Wind energy has been one on the major sources of electrical energy in the Spanish peninsular system for almost a decade. In 2013, it was even the technology with the highest energy produced and it has consistently provided since then around 20% of the electrical energy in this system. The first steps to achieve this level of wind integration in the Spanish peninsular system were developed into observability and controllability areas. Currently, almost 99% of wind installations can be observed and controlled. These high standards allow to move forward to new objectives related to align the European new requirements with the Spanish electrical system necessities. As a result, regulatory changes introduced in 2014 have adapted also the regulatory framework in order to delete as much as possible the distinctions between renewable energy resources and conventional generation. The two main changes have been the possibility of participation of variable RES in the balancing markets such as the tertiary reserve market and the introduction of market-based downward redispatching for solving congestions on either the TSO or the DSO's network. This paper describes the different ancillary services currently considered in the Spanish electrical system and the participation of RES, focusing particularly on its provision with wind energy. The paper describes the functioning and RES participation on the following topics: • Replacement Reserves or generation-load imbalance market. • Tertiary reserve. • Secondary reserve and AGC connected units. • Voltage control. Additionally, this paper introduces the prequalification processes for those ancillary services, which are a prerequisite for all technologies, including conventional generation, and the state of actual participation in the different services of wind generation in Spain. An important issue on the provision of ancillary services with RES generation which has raised recently some debate in Europe is the crucial coordination between the participation on balancing markets of units that may be affected by congestion management. This issue, while not new at all, since conventional generators may as well be subject to congestion management limits in the transmission network, requires further development when applying to a larger number of renewable generators or these generators are connected to distribution grids. The issue of congestion management for TSO connected and distributed flexibilities has been coordinated by the Control Centre for Renewables (CECRE) in Spain since its commissioning in 2007, but a new degree of coordination needs to be introduced when these resources participate also in the ancillary services markets. The paper describes how this interaction between balancing markets and congestion management is performed in the CECRE on a real-time basis regardless of where congestions arise, whether in the transmission network or in the distribution network. [ABSTRACT FROM AUTHOR]