Stability challenges & solutions for power systems operating close to 100% penetration of power electronic interfaced power sources : exchange of experience between hybrid and major power systems

In 2013 the authors presented a paper [1] to the wind integration workshop (WIW), the results of which demonstrated high converter penetration (typically 65-70%) at synchronous area (SA) level could introduce a type of super synchronous instability in RMS models previously unseen by the authors and TSO’s. 2016 saw two related papers [2], [3] presented at a further WIW. These provided in-depth analysis of the specific high frequency instability identified in 2013, as well as considering a wider range of future high penetration stability challenges identified by the wind industry [4]. The two papers reported R&D study results using a proposed holistic approach converter control strategy. Extensive system wide studies with a new (for large power systems) control strategy for power electronic sources were used to explore the possibility of stable operation close to 100% penetration of Power Electronic Interfaced Power Sources (PEIPS). The studies demonstrated that implementation of a Virtual Synchronous Machine (VSM) converter control strategy with added stability controls, applied to about 25% of the power sources, could deliver stable operation, even at 100% penetration for a reduced model of the 2030 GB power system. The solutions explored in the WIW 2016 papers are included in the Grid Forming approach in a pan European Connection Network Code (CNC) Implementation Guidance Document (IGD HPoPEIPS) [5]. This contains significant ideas and experiences arising initially from the world of Hybrid Systems, such as marine power networks. In taking these ideas forward, various questions are raised by manufacturing industry experts about the necessity for this dramatic change in the context of main power systems. Some suggest it is a more fundamental change, even than the introduction of Fault Ride Through (FRT)). Also, it has been suggested that both the time needed to implement the new strategies and the associated cost will be extensive. This paper explores the prospect of finding answers to these questions from experience already gained in the world of hybrid systems. What are the prospects for closer collaboration to establish viable solutions applicable to both small Hybrid Systems and main Synchronous Areas (SA), such as the 5 SAs in Europe as the first SAs progress towards operation sometimes close to 100% PEIPS