Coordinated expansion planning of AC network and synchronous condenser for receiving-end grids with multi-infeed UHVDC links

Ultra-high-voltage direct current (UHVDC) transmission links and renewable generation are being increasingly infeed to many regional receiving-end grids in China. To ensure secure accommodation of the intensive high-capacity UHVDC, the AC network strength and Var resource margin of the receiving-end grid should be significantly enhanced. This study proposed a distributionally robust coordinated planning (DRCP) model, which simultaneously considers transmission expansion and synchronous condenser configuration with multi-preconceived UHVDC incident security requirements. Network strength and dynamic Var resources sufficiency, as well as transient frequency and voltage security constraints are comprehensively incorporated within the model to mitigate operating risks caused by UHVDC bi-pole blocking and commutation failures. The proposed model was formulated as a mixed-integer second-order cone programming, and a solution approach based on column-and-constraint generation was developed to solve this problem. The effectiveness of the proposed DRCP model was verified using a modified IEEE 39-bus system and a large-scale provincial grid in China.