  Coordinated optimal dispatch is of utmost importance for the efficient and
secure operation of hierarchically structured power systems. Conventional
coordinated optimization methods, such as the Lagrangian relaxation and Benders
decomposition, require iterative information exchange among subsystems.
Iterative coordination methods have drawbacks including slow convergence, risk
of oscillation and divergence, and incapability of multi-level optimization
problems. To this end, this paper aims at the non-iterative coordinated
optimization method for hierarchical power systems. The theory of the
equivalent projection (EP) is proposed, which makes external equivalence of the
optimal dispatch model of the subsystem. Based on the EP theory, a coordinated
optimization framework is developed, where each subsystem submits the EP model
as a substitute for its original model to participate in the cross-system
coordination. The proposed coordination framework is proven to guarantee the
same optimality as the joint optimization, with additional benefits of avoiding
iterative information exchange, protecting privacy, compatibility with
practical dispatch scheme, and capability of multi-level problems.
