Voltage control and reactive power support in the Spanish transmission network

This paper presents a review of the reactive power support and voltage control management in the Spanish transmission network. This is regulated by two market mechanisms: (i) the network constraint management, and (ii) the voltage control ancillary service. Constraint management is conducted by the SO, who asks generators to modify their outputs to solve power system voltage problems. On the other hand, the ancillary service consists of: (i) an annual auction where reactive regulation capacity VAR resources are agreed, and (ii) the scheduling and real-time operation of these VAR resources. Nowadays, only the first mechanism is fully implemented, while the ancillary service is partially established. Some improvements are proposed for future developments