Do you have an example of an anti-islanding protection system for a renewable generator based on a Full Scale Converter System?

Dynamic Simulation

The attached project demonstrates the behaviour of a full-scale converter based system while subjected to an islanding event. The converter is implemented in PowerFactory using a static generator element, which is configured to operate as a current controlled voltage source.

The converter currents are controlled using a classical d-q rotating reference system current controller which regulates the active and reactive currents of the unit. Generic values of the negative feedback and feedforward control loop parameters have been selected. Adjust these values according to the actual application.

Given the specific purpose of the study, slow reacting controllers (e.g. outer loop controllers) are not modelled within this unit.

A typical protection scheme is necessary to represent the slow, fast and very fast protection behaviour. The very fast over-voltage protection has been implemented directly in the voltage measurement block as instantaneous values of the voltage are required. Generic values of the protection scheme parameters have been selected. Adjust these values according to the actual application.

This model contains only a passive anti-islanding protection scheme. This scheme is typically sufficient for anti-islanding studies where the power unbalance created as a result of the islanding event main power supply leads to a fast increase of the busbar voltage. This is typical in the case of large WT/PV power plants. In the case of islanding events of full scale converter systems integrated at the distribution level, the power unbalance may be smaller due to the highly probable existence of loads within the network sector which is islanded. If the passive protection does not trip the unit within several hundreds of ms then in practice the active anti-islanding protection will detect the faulty operation and trip the unit. Note that this active anti-islanding protection scheme is not included in the model hence there may exist cases in which the power balance is perfect and the converter system will operate indefinitely within an islanded network by supplying the existing loads.

Quick Notes:

Note that the static generator is set in the load flow page as a Reference Machine.

Note also that the load flow calculation must ensure that the slack machine is within the main supply system (e.g. External Grid). A message like below should be generated by the load flow:
warn - More than one reference machine (' External Grid' and ' Full Scale Converter System') found for separated area of ' PCC'.
info - Element ' External Grid' is local reference in separated area of ' PCC'

In the above, it is critical for correct operation and plausible simulation results that the Full Scale Converter System is not the local reference within the system.

Quick Steps:
- Calculate the initial conditions and run the simulation for 1 second with the already prepared settings. Simulation starts at -0.1s while an islanding event is applied at 0 seconds.
- Observe the converter currents and voltages within plots "WT current" and "voltage WT LV terminal" respectively.
- Identify the point in time when the converter currents are zero.
- Identify also in the output window the moment when the Trip_Converter event has been triggered.
- Observe the maximum voltages in the network.