Division B Limited frequency sensitive mode overfrequency

In addition to the requirements of Article 11 the following shall apply with regard to limited frequency sensitive mode — overfrequency (LFSM-O):

1. (a)

   the HVDC system shall be capable of adjusting active power frequency response to the AC network or networks, during both import and export, according to Figure 3 at a frequency threshold f₁ between and including F150.2 Hz and F250.5 Hz with a droop S₃ adjustable from F30.1 % upwards;

2. (b)

   the HVDC system shall be capable of adjusting active power down to its minimum HVDC active power transmission capacity;

3. (c)

   the HVDC system shall be capable of adjusting active power frequency response as fast as inherently technically feasible, with an initial delay and time for full activation determined by the relevant TSO and notified to the regulatory authority in accordance with the applicable F4... regulatory framework;

4. (d)

   the HVDC system shall be capable of stable operation during LFSM-O operation. When LFSM-O is active, hierarchy of control functions shall be organised in accordance with Article 35.

The frequency threshold and droop settings referred to in point (a) of paragraph 1 shall be determined by the relevant TSO and be notified to the regulatory authority in accordance with the applicable F5... regulatory framework.

Figure 3: Active power frequency response capability of HVDC systems in LFSM-O. ΔΡ is the change in active power output from the HVDC system and, depending on the operational conditions, either a decrease of import power or an increase of export power. f_n is the nominal frequency of the AC network or networks the HVDC system is connected to and Δf is the frequency change in the AC network or networks the HVDC is connected to. At overfrequencies where f is above f₁ the HVDC system shall reduce active power according to the droop setting.