In order to mitigate the operation congestion of urban power grids

three unique logical constraints(i. e. sequence constraint

mutual exclusion constraint and orientation constraint)on the high-voltage distribution network are developed. Instead of the conventional breaker-status

the selected variables of 110 kV transfer units are used in the modeling. Then three operation congestion control models

i. e. minimum substation replacement number model

mixed load curtailment model

load balancing model

are developed. By combining with the optimization operation sequence model

a comprehensive strategy is created. Although the variables size is enlarged

the nonlinearity and complexity of the complete model is largely reduced by introducing logical constraints on load transfer

which enable the model to be directly solved by commercial software at a fast computing speed

while avoiding the instability of the conventional algorithm. The proposed model is verified by using part of an actual urban power grid. This work is supported by National High Technology Research and Development Program of China(863 Program)(No. 2014AA051901)and National Natural Science Foundation of China(No. 51207098).