Low Short-Circuit Strength and Converter Associated Stability Issues

In contrast to the conventional synchronous generators, power electronic converter interfaced renewable power generation, such as wind and solar-PV plants is typically sited in remote geographic locations in the power grid. Therefore, inevitably, the generated power from these sources has to be transmitted through long-distance transmission corridors. In many cases, they are being connected to main power grid at remote locations with a low short-circuit strength creating instability conditions. Furthermore, power electronic converter interfaced sources provide low short-circuit current, and hence they further deteriorate the short-circuit strength at the remote locations of the network. As HVDC transmission links are used in these transmission corridors, they may have to operate under a low short-circuit strength triggering stability concerns. In addition, HVDC transmission links connecting two synchronous regions are also sometimes connected to busbars with a low short-circuit strength, and hence it is essential to investigate these stability issues and develop remedial strategies to overcome these challenges. Moreover, the power electronic converters associated with these HVDC systems are also prone to various emerging stability issues ranging from converter control interaction issues to converter control induced resonance conditions. This chapter investigates these stability and operation issues associated with a low short-circuit strength and power electronic converter control associated stability in hybrid AC/DC power grids. Moreover, various strategies to overcome these stability issues are also discussed in detail within this chapter.