Transaction Decision-making Method For Microgrid Considering Power Flow Situational Awareness

In view of the increasing generation of the distributed generation system,the increasing randomness and intermittence of microgrid,the complexity and decentralization of power status information,situational awareness technology in Cyber-Physical Systems(CPS)and automated power trading technology of microgrid have been attracted much attention.The problems of power trading in the microgrid are generally reflected by the following two aspects: on the one hand,when the electricity trading in microgrid are frequent,the real-time transmission of communication instructions is very important and the delay will lead to transaction failure or grid instability;on the other hand,the microgrid mostly adopts the control strategy of master-slave mode now,and the third party is required to supervise the transaction process and process the transaction data during the power transactions,which is difficult to meet the needs of the current power market in the stability and efficiency of the grid transaction.In order to solve the above problems,this paper puts forward the transaction decision-making method for microgrid considering power flow situational awareness.The main research work of this paper is as follows:Firstly,a power flow situational awareness system in communication for microgrid CPS is established.The EtherCat bus technology is used to reconstruct the original communication network in the distributed power microgrid conforming to IEC61850-90-7 standard.All intellectual electronic devices in microgrid system adopt master-slave communication mode.Then,according to the special control command flow and state machine of EtherCat bus,the communication system of microgrid is upgraded.The implementation of communication instructions for mode switching of advanced inverters is accomplished according to the specific definition of IEC61850-90-7 standard.Finally,the microgrid CPS system is connected to the blockchain online cloud platform,so that the users of microgrid can trade electricity online.And the simulation of master-slave communication station of microgrid CPS situation awareness system verifies that the communication delay is minimal,which meets the real-time requirements of microgrid power trading.Secondly,this paper designs a specific flow of power flow situational awareness in the control layer of microgrid CPS.The power flow calculation of microgrid system is carried out to obtain Jacobian matrix under different conditions.Then singular value decomposition of Jacobian matrix of microgrid power flow is carried out to obtain the stability of the system,and then the communication instructions are sent down to the advanced inverter to keep optimal mode operation of microgrid.Finally,the feasibility and efficiency of the transactionmode considering power flow situational awareness are verified by case analysis of power flow situational awareness and simulation of transaction data fitting.Finally,a transaction decision-making method for smart nodes in microgrid based on smart contracts in cloud service platform is proposed.And in the cloud platform,smart contracts are used to reasonably manage the trading order when the stochasticity of distributed generation generates excess or insufficient electricity.Power flow situational awareness is carried out periodically in the microgrid region with balanced power supply and demand to maintain the stability of microgrid system.In the case of electricity transaction demand,the trader obtains probability distribution model through historical data mining in cloud platform database,then it makes decision on the transaction object by using D-S evidence theory.It determines the transaction content and publishes intelligent contracts according to the constraints and specific transaction conditions,and it finally carries out security inspection until the transaction is completed.The transaction data is packaged and transmitted to cloud platform.The proposed transaction decision-making method is applied to a specific microgrid transaction case through simulation operation,and the efficiency and superiority of the method are verified.