Research On Coordinated Optimal Scheduling Of Multi-microgrids Considering Multiple Stakeholders

With the continuous development of microgrids(MGs),multiple MGs in a local district are connected to each other to form multi-microgrids(MMGs)system,which is beneficial to their coordinated control and improves operational stability and economy.Compared with the single microgrid,the MMGs system has the characteristics of multiple stakeholders,the MMGs' energy dispatching center needs to coordinate the interests of all parties to optimize the operation plan.The traditional optimal dispatching adopts the centralized optimization,which requires centralized collection of operation parameters and prediction data of all electrical equipment layer by layer.The centralized optimization problem is large in scale,which requires a high level of communication system and control system,and has the risk of leakage of the stakeholders' privacy information.The research on the coordinated optimization method of MMGs is helpful to reduce the data pressure of communication system and the calculation pressure of control system,and to protect the information security of the stakeholders in MMGs.Therefore,it has important engineering value and practical significance.This paper focuses on the coordinated optimization method of MMGs with multiple stakeholders and the main contents are as follows:1)The network structure and control system structure of MMGs are studied.On the basis of hierarchical control,two control system structures of MMGs are proposed,concentrative decentralized MMGs and hierarchical distributed MMGs.Then,the mathematical models of common source-load-grid units in MMGs are established,such as the controllable distributed generators,shiftable loads and sub-microgrids(SMGs).Finally,the economic dispatching models of SMG user stakeholders and MMGs operation stakeholder,with the lowest operating cost as the optimization objective,are proposed.2)To counter the characteristics of the optimal scheduling problem of the control system of concentrative decentralized MMGs,a coordinated optimization algorithm based on analytical target cascading(ATC)is proposed.In this method,the tie-line power data is taken as coupling variables.The centralized problem is relaxed based on the augmented Lagrangian penalty function,and decoupled into independent optimization models of SMGs user stakeholders and MMGs operation stakeholder.The global optimal solution is obtained by the dual-layer iterative solution.Finally,a numerical experiment is given to illustrate the convergence characteristics and rationality of the optimal scheduling algorithm based on ATC,the comparison with the centralized optimization method about the calculation time,iteration times and optimization results are given.The feasibility and effectiveness of ATC for the coordinated optimization of concentrative decentralized MMGs are verified.To counter the characteristics of the optimal scheduling problem of the control system of hierarchical distributed MMGs,a coordinated optimization algorithm based on alternating direction method of multipliers(ADMM)is proposed.In this method,the tie-line power data is also taken as coupling variables.The centralized problem is relaxed based on the augmented Lagrangian penalty function,and decoupled into independent optimization models of SMGs user stakeholders and MMGs operation stakeholder.After autonomous decision-making,the agent of SMGs and the agent of MMGs exchange the expected interactive power with the adjacent agent.According to different ways of coordinated solutions,the ADMM solutions can be divided into serial mode and parallel mode.Finally,a numerical experiment is given to illustrate the convergence characteristics and rationality of the optimal scheduling algorithm based on serial and parallel ADMM.Compared with the centralized optimization method,the coordinated optimal algorithm based on ADMM has the advantages of good convergence and fast computation,and reduces data transmission to ensure the privacy of communication.