Research On Distributed Optimal Dispatch For Security-constrained Unit Commitment Of Multi-area Interconnected Power Systems

The multi-area interconnected power systems(MI-PS)are usually composed of several regional subsystems interconnected by tie-lines.For example,China's southern power grid and northwest power grid are MI-PS composed of multiple provincial power grids.Under the premise of ensuring the safe and stable operation of the power system and reliable power supply,MI-PS can reduce the energy consumption and pollutant emissions in the unit power production.The essential difference between MI-PS and single-area interconnected power system is that a large interconnected power system is usually operated jointly by multiple independent system operators(ISOs),and each operator needs to independently and economically use internal resources within its own operating area.Traditional centralized scheduling is difficult to realize the privacy protection of ISOs and meet the computational requirements of the large-scale of MI-PS.Therefore,it is greatly practical significance to study the distributed method of MI-PS.This dissertation focuses on the distributed method for dynamic optimal power flow,unit commitment and security-constrained unit commitment of MI-PS.The main research results are as follows.Firstly,combined with regularized technology(RT)and primal-dual interior point method(PDIPM),the regularized primal-dual interior point method(R-PDIPM)was designed to realize the efficiently distributed computing of multi-area interconnected AC dynamic optimal power flow(MI-AC-DOPF).The MI-AC-DOPF model was transformed into a block-angle structure by replicating the regional coupling nodes and the multi-area decoupling of the power grid is realized.A block Newton system matrix is easy to be ill-conditioned under the distributed computation of PDIPM.Though introducing the regularized term into the PDIPM,the matrix of block Newton system becomes quasi-definite and strongly factorizable.The robustness of distributed computing of PDIPM is enhanced.The simulation results of 3012 and 3074 node systems showed that the R-PDIPM is more robust than PDIPM in distributed computing,which is suited for the distributed solution of MI-AC-DOPF.Secondly,with the projection and reformulation techniques,a compact and tight mixed-integer quadratic programming(MIQP)formulation for unit commitment(UC)problem is presented.With projecting unit generation level onto [0,1] and reformulation techniques,a two-binary-variables(2-bin)UC formulation is presented.We show that 2-bin formulation is more compact than the state-of-the-art one binary(1-bin)variable formulation and three binary(3-bin)variables formulation.Moreover,2-bin formulation is tighter than 1-bin and 3-bin formulations in the quadratic cost function,and it is tighter than 1-bin formulation in linear constraints.The simulation results of 43 realistic instances indicated that the 2-bin UC formulation is the tightest and most compact model and can be solved most efficiently by CPLEX solver.Thirdly,a hierarchical alternating direction multiplier method(H-ADMM)is proposed and applied to the fully distributed solution of a multi-area interconnected UC(MI-UC)problem.The 2-bin MI-UC model is reconstructed into a two-block problem model,which is solved by the alternating direction multiplier method(ADMM).For the sub-problem of update step with system constraints,the full decoupling of each unit in the update step is realized based on Lagrangian dual theory and consensus ADMM,so that each unit is full decoupled in the solution process of the whole MI-UC problem,thus achieving the protection of unit privacy information.The simulation results show that the H-ADMM can obtain high-quality solutions in a reasonable time,which is suitable for the distributed solution of MI-UC.Finally,based on ADMM and R-PDIPM,an ADMM-R-PDIPM approach is proposed to solve the multi-area interconnected AC security-constrained unit commitment(MI-AC-SCUC).First,the model of MI-AC-SCUC is reconstructed by copying the output variables of the unit,and which is solved by ADMM.The updating step subproblems are similar to AC-DOPF and MI-UC with unit full decoupling.Then,the distributed solution of AC-DOPF subproblem is realized based on R-PDIPM,so as to realize the distributed optimal dispatch of MI-AC-SCUC.In addition,the improved ADMM-R-PDIPM approach reduces the number of iterations and the running time of the approach.The simulation results of the IEEE 38 and IEEE 118 systems show that ADMM-R-PDIPM is suitable for the distributed solution of MI-AC-SCUC.