Hybrid power plant control to enhance voltage stability in weak grid

• Hybrid power plants enhance voltage stability in converter-dominated weak grids. • Analytical criteria for maximum power transfer are developed and validated. • Voltage stability limits shown to be independent of short-circuit ratio. • Q control point shift in HPPs improves maximum power evacuation capability. • HPPs enable higher renewable penetration than individual plant operation. This paper presents the potential of hybrid power plants (HPPs) to improve voltage stability in weak grids. Moving towards converter-based generations, installation capacity of the available renewable sources is significantly limited by weak grids. While designed as hybrid power plants, it is shown that more renewable generation capacity can be installed and stably operated in weak grids as opposed to individual technology power plants as the first contribution of this paper. Additionally, this study focuses on the power evacuation limits while ensuring voltage stability in weak grids. It is verified that the maximum power evacuation capability depends on the grid short circuit power (SCP) levels and roughly equals SCP/2 while renewables are controlled individually. As another contribution, it is shown that HPP can transfer more power than individual connection of renewable sources. The main reason behind this improvement in power evacuation capability is the change in reactive power control point between these two methods. Finally, the paper highlights the invulnerability of maximum voltage stability limits towards grid strength indicated by short circuit ratio.