On the damping deterioration of power systems with CIG-based power plants performing PFR under communication delays

The primary frequency response of converter-interfaced generation power plants is a mandatory technical requirement of the grid connection codes. This is the case in Europe, where the grid code EU 2016/631 specifies mandatory frequency sensitive modes for power park modules of medium and high dimension. In this response, the active power output changes as a result of a frequency deviation in order to contribute to the restoration of the nominal frequency. The power plant controller that governs these type of plants isthe responsible to perform this task. Plant-level control latency is primarily caused by communication delays, which increase the plant response time, thereby compromising the damping of network oscillation modes in the range of 0.1 to 1.5 Hz. The case presented here shows that in certain situations the primary frequency response, which is crucial for maintaining frequency stability, can seriously affect the oscillation damping of a power system. This can lead to so-called angle instability. Simulations show that PFR provision by PV plants can worsen damping when delays are present, especially with changes in system inertia or line length.