HVDC control and protection systems are complex systems to model and may include black-box models. This can make the models difficult to maintain and can lead to long computation times. The complexity and difficulty in maintaining the models inevitably leads to differences between the modelled controllers and the actual controllers in the field.
The National HVDC Centre will use replica hardware of HVDC schemes. Replicas are a direct copy of the control and protection systems used. Using replicas allows the actual controls to be implemented into the simulations, removing a major source of modelling uncertainty.
This facilitates complex studies where accuracy is critical, and provides an opportunity to improve and validate the controllers. Having HVDC control and protection replica’s allows control changes to be first tested in a safe environment before being rolled out in the field.
The Centre will combine use of Replicas with a Real Time Digital Simulator (RTDS®). The RTDS® allows detailed power system models to be simulated in real-time, meaning the simulations able to keep in synchronism with a real-world clock. This is very important as real protection and control hardware is synchronised to a clock and executes calculations at regularly spaced points in time. Having both the RTDS® platform and physical hardware time-synchronised, means that the control and protection equipment can be interfaced with software models and their interactions studied.
The major benefit of a RTDS® is that physical hardware, like HVDC protection and control cubicles, can be directly connected to detailed and accurate power system models, removing the uncertainty involved in modelling these systems. In principle, the RTDS® simulations executed in real-time provide a very similar response to what would be observed in the field, and therefore is a very comprehensive method for studying interactions between HVDC controls and the interconnected power system.
The National HVDC Centre has the first worldwide installation of the new RTDS® NovaCor™ system.