In the rich-hydropower area with multi-level transmission section limit

the coordinated dispatch for large and small hydropower plants is significant for the overall consumption of hydropower. With large-scale small hydropower access to the power grid

however the problem for power grid security operation is more prominent. Therefore

this paper proposes a short-term coordination model for large and small hydropower consumption considering both the economy and reliability of power systems. The economy of power systems is measured from three aspects: hydropower consumption

power system loss and cascaded power storage. And the loss of load probability(LOLP)is introduced to evaluate the reliability of power systems. For the better description of reliability

the model is evaluated based on real-time state of power systems and simulated by the Monte Carlo method. Then the feasible initial solution is generated by the combined principle of cascaded load partitioning and redistribution

and the improved particle swarm optimization(PSO)algorithm considering constraint tolerance is used to solve the coordination model to improve the search efficiency. The practical application shows that the proposed model can effectively use the regulation potential of large and medium hydropower plants

coordinate the delivery of small hydropower plants in regions

and improve the power system reliability and the overall dispatch benefit of hydropower.