Explanation of the control parameters

The exemplary simulation shows the potential response of grid-forming inverters to various grid events. The time range t = [0 s, 180 s] reproduces the course of the grid frequency and voltage amplitude at the time of system disconnection on 24.07.2021, measured in La Cereal, Spain, in the center of the Iberian Peninsula. In the following trajectory, frequency and voltage amplitude were held constant with a voltage dip of 0.05 pu for t = [250 s, 300 s], as well as a positive phase jump at tθpos = 350 s and a negative phase jump at tθneg = 380 s. The phase jumps are reproduced by pulses in the frequency response with ∆f = θstep*∆T.

The simulation is based on a simplified model in which coupling terms between active and reactive power are neglected. The power of the inverter is 100 kW. Two approaches are shown for the provision of active and reactive power by the grid-forming inverter:

1. P-controller: proportional power controller (parameterizable via Ta,set and Kq)
2. D-controller: differential power controller (parameterizable via Kp and Kq)

For comparison, the reactions of a synchronous generator (SG) with different settings can be shown:

1. P_SG without primary control power: Provision of active power as instantaneous reserve with Ta = 12 s
2. P_SG with primary control power: Provision of active power as PRL with droop = 0.035
3. Q_SG with const. U: Provision of reactive power without Q(U) control
4. Q_SG with Q(U) droop controller: Provision of reactive power with Q(U) control