As the proportion of renewable energy increases, the receiving-end power grid has gradually formed the typical characteristics of a high proportion of renewable energy and a high proportion of inter-regional DC connection. In the event of DC blockage and commutation failure faults, the demand for voltage support of the receiving-end grid increases greatly. As the proportion of synchronous power gradually decreases, the gap of dynamic reactive power resources gradually increases. The static var compensation capability is weak and the cost of building a new generation condenser is high. Thus adding condenser function in existing thermal power units has become the best technical and economic choice. This paper first analyzes the transient voltage support requirements of the receiving-end power grid and the mechanism of that support by the condenser. A review of domestic and foreign cases of adding/modifying condenser function in thermal power units is provided. Based on the engineering practice of adding condenser function in thermal power unit in the Yahekou power plant, key technologies are proposed for adding condenser function in thermal power unit. An effective technical path is proposed for the improvement of transient voltage support capacity of the receiving end grid in these conditions.