Optimal allocation and sizing of Synchronous Condensers in weak grids with increased penetration of wind and solar farms

The increasing number of weak-grid-connected renewable energy resources in power systems has created various challenges in recent years. Some examples include un-damped voltage oscillations in the ERCOT and sub-synchronous resonance in the North-China power grid. Several solutions for these challenges have been proposed, such as Static Compensators and Synchronous Condensers (SynCons). SynCons, being synchronous machines without a prime mover, provide several benefits in weak power systems, such as frequency support, system strength, and voltage regulation. Although SynCons are widely-utilized to mitigate the weak grid integration challenges, their installation/operation costs make them a costly solution. Additionally, their lead-time can be more than a year, which means their initial sizing and allocation must be optimal. In this paper, a method for the optimal allocation and sizing of SynCons is proposed. The main objective of this method is maintaining Short Circuit Ratio (SCR) in the system greater than pre-defined values while the investment and operation costs of SynCons, and voltage deviation in the system are minimized. Three meta-heuristic optimization algorithms are used to implement the proposed method, and its performance is evaluated via Electromagnetic Transient (EMT) time-domain simulation in a modified IEEE 39-bus system. The PSCAD/EMTDC software is used for the time-domain simulation. The simulation results confirm that with optimized allocation and sizing, the SCR of the network in all areas is more than pre-defined values, and also, all renewable energy resources can ride through disturbances and comply with given grid codes.