Division 1 When operating in frequency sensitive mode (FSM):

the HVDC system shall be capable of responding to frequency deviations in each connected AC network by adjusting the active power transmission as indicated in Figure 1 and in accordance with the parameters specified by each TSO within the ranges shown in Table 2. This specification shall be subject to notification to the regulatory authority. The modalities of that notification shall be determined in accordance with the applicable F1... regulatory framework;

the adjustment of active power frequency response shall be limited by the minimum HVDC active power transmission capacity and maximum HVDC active power transmission capacity of the HVDC system (in each direction);

Figure 1: Active power frequency response capability of an HVDC system in FSM illustrating the case of zero deadband and insensitivity with a positive active power setpoint (import mode). ΔΡ is the change in active power output from the HVDC system. f_n is the target frequency in the AC network where the FSM service is provided and Δf is the frequency deviation in the AC network where the FSM service is provided.

Table 2: Parameters for active power frequency response in FSM

the HVDC system shall be capable, following an instruction from the relevant TSO, of adjusting the droops for upward and downward regulation, the frequency response deadband and the operational range of variation within the active power range available for FSM, set out in Figure 1 and more generally within the limits set by points (a) and (b). These values shall be subject to notification to the regulatory authority. The modalities of that notification shall be determined in accordance with the applicable F3... regulatory framework;

as a result of a frequency step change, the HVDC system shall be capable of adjusting active power to the active power frequency response defined in Figure 1, in such a way that the response is:

1. (i)

   as fast as inherently technically feasible; and

2. (ii)

   at or above the solid line according to Figure 2 in accordance with the parameters specified by each relevant TSO within the ranges according to Table 3:

   • the HVDC system shall be able to adjust active power output ΔΡ up to the limit of the active power range requested by the relevant TSO in accordance with the times t₁ and t₂ according to the ranges in Table 3, where t₁ is the initial delay and t₂ is the time for full activation. The values of t₁ and t₂ shall be specified by the relevant TSO, subject to notification to the regulatory authority. The modalities of that notification shall be determined in accordance with the applicable F4... regulatory framework;

   • if the initial delay of activation is greater than F50.5 second, the HVDC system owner shall reasonably justify it to the relevant TSO.

   

   Figure 2: Active power frequency response capability of an HVDC system. ΔΡ is the change in active power triggered by the step change in frequency.

   Parameters	Time
   Maximum admissible initial delay t 1	F60.5 seconds
   Maximum admissible time for full activation t 2, unless longer activation times are specified by the relevant TSO	30 seconds

   Table 3: Parameters for full activation of active power frequency response resulting from frequency step change.

for HVDC systems linking various control areas or synchronous areas, in frequency sensitive mode operation the HVDC system shall be capable of adjusting full active power frequency response at any time and for a continuous time period;

as long as a frequency deviation continues active power control shall not have any adverse impact on the active power frequency response.