The behaviour of virtual synchronous machine (VSM) based converters in front of non-saturable faults

Power converter penetration has increased substantially in the last 20 years bringing new challenges from the system protection perspective. The power network is undergoing a major transformation as the major part of new installed power comes from non-synchronous sources such as wind or solar. These changes might lead to malfunction of the conventional protection schemes such as overcurrent protection or distance protection relays. At the same time, the reduction of the system inertia might cause the tripping of the Loss of Main protection due to a very aggressive Rate of Change of Frequency. To enhance the grid voltage source characteristic and mitigate the loss of inertia, a new set of converter controllers known as Grid forming Converter or Virtual Synchronous Machine has been suggested in recent years. The performance of VSM could provide a potential advantage compared to traditional power converter controllers when a large frequency deviation occurs helping to keep the system stable. This article quantifies and compares the performance of different converter control algorithms including Current Vector Control, Virtual Synchronous Machine and Power Synchronisation Control in front of different frequency events