Connecting offshore wind farms over long distances with AC cables leads to significant capacitive reactive power, which must be compensated to meet grid code requirements. While steady-state compensation is often achieved using a variable shunt reactor, requirements resulting from fast voltage dips must be met dynamically. In common configurations, the variable shunt reactor is combined with a static synchronous compensator (STATCOM) to meet these dynamic requirements.
This presentation proposes an alternative topology for dynamic reactive power control using a mechanically switched reactor and an enhanced variable shunt reactor. The variable shunt reactor is enhanced with a power electronic fast-switching module that allows the turns ratio to be adjusted within one grid frequency cycle. To meet the grid code requirements, a coordinated reactive power control scheme is developed and validated against the UK National Grid code.
For this purpose, a controller-hardware-in-the-loop setup is established, using two industrial controllers coupled to the RTDS® real-time simulator to validate the coordinated control scheme. The power plant controller, which calculates the grid code requirements, is implemented on one industrial controller. The reactive power controller is implemented on the second controller and coordinates the compensation devices. Simulation results prove compliance with the UK grid code and validate the concept of the enhanced variable shunt reactor for dynamic reactive power control.
Presented by: Florian Zier, Friedrich-Alexander University