Following approval of the new Operating Procedure 7.4 in June, Spain’s System Operator Red Eléctrica has invited renewables plants to submit applications for authorisation to participate in the dynamic voltage control service, which will come into effect on 1 January next year.
According to the regulations, for their authorisation renewable installations must demonstrate their voltage control capability, primarily in real-time voltage setpoint tracking mode, which is essential for responding to rapid voltage variations.
The voltage control capability of these technologies grants them dispatch priority for their generation in the electricity system over installations that do not provide this capability.
In recent weeks, Red Eléctrica has carried out the authorisation tests for the first renewables that will provide dynamic voltage control service, in line with the new Operating Procedure (PO) 7.4 requested by the SO in 2020 and approved in June by the CNMC. The Comisión Nacional de los Mercados y la Competencia, abbreviated as CNMC, is a Spanish independent competition regulator responsible for enforcing competition law. The System Operator is prepared for these installations to begin providing the service from the moment they notify the SO.
Although renewables plants, have been invited them to submit their applications for authorisation to participate, the rate of viable applications received from installations is still low. To date, 168 applications have been submitted, 125 of which correspond to non-dispatchable renewable installations. Of these, 24 are already in a position to begin tests. The rest either declare they cannot follow voltage setpoints or are in the process of completing the necessary documentation.
In addition to non-dispatchable renewable plants, conventional generation plants such as combined cycle or hydroelectric power plants, which are already obliged to provide the dynamic voltage control service in its basic mode, have also submitted applications. Therefore, priority is being given to non-dispatchable renewables in the process, as they are the only ones that can offer new resources to the system.
Among the benefits of participating in this new service, authorised renewables will obtain dispatch priority and the possibility of reducing the maximum ramp rates of change in their generation.
For their authorisation, the new PO regulations establish that installations must demonstrate their technical capability to control voltage in two modes: via reactive power setpoints and via voltage setpoints. This latter mode – real-time voltage setpoint tracking – is what offers flexibility and allows installations to respond to the rapid voltage variations that can occur in an electricity system undergoing a full transformation.
Voltage control in Spain
Voltage levels have not increased in recent years. Average values were higher years ago, but with the commissioning of voltage control elements on the transmission grid, these values are currently lower. The variability of voltages has increased, a variability that must be controlled by the generators that provide the system with effective voltage control.
Red Eléctrica proposed the modification of PO 7.4 with the aim of increasing the volume of resources in the system that are capable of performing voltage setpoint tracking. The generation plants currently participating in the VCS must have the capacity to provide or absorb reactive power equivalent to 30% of their maximum power.
