Transient stability improvement: a review and comparison of conventional and renewable-based techniques for preventive and emergency control

This paper aims at reviewing and summarizing the vast variety of techniques to improve transient stability of power systems. A qualitative comparison of the techniques is presented and the future outlook is discussed. The techniques are categorized into conventional and renewable-based techniques. Conventional techniques are well established and have been employed in the past. Renewable techniques investigate how generators based on renewable energy sources (RES) can contribute to improving stability. Moreover, it is distinguished between techniques applying preventive and emergency controls. For preventive control, re-dispatch of generators and series compensation are extensively used in practice, whereas for emergency control, a great share of the techniques aim at voltage support during fault conditions. Regarding preventive control using RES-based generation, one approach which temporarily increases the voltage setpoint of the units in order to increase the synchronizing power, is reported. Regarding renewable energy source based emergency control, low voltage ride-through (LVRT) capability including voltage support is a well established method. Nevertheless, it is also highlighted that high voltage ride-through (HVRT) capability plays a critical role. The findings show that distributed generation must be included in existing control schemes for preventive control, and new improvement techniques taking full advantage of them need to be developed.