Coordination of Functional Controllers in a Multiterminal MMC-VSC-HVDC System Control

This paper presents a study on coordination of functional controllers equipped on a multi-terminal MMC-VSC-HVDC control system for enhancing grid dynamic performance. The study was carried on in a typical transmission power system embedded with a three-terminal MMC-VSC-HVDC system. The HVDC system control was equipped with Power Oscillation Damping (POD) controller, Primary Frequency Support (PFS) controller and Fast Voltage Support (FVS) controller which were designed for improving small signal stability, supporting load-flow in primary frequency control and enhancing transient stability of the AC power system, respectively. The study results showed that, there were potential incorporated interactions between the POD and FVS controllers equipped on the reactive power modulation channel. Whereas, the POD and PFS controllers equipped on the active power modulation channel were found to be well-coordinated. In this study, a counter measure was also proposed to mitigate the identified incorporated interactions between the FVS and POD controllers.