Research On Communication Model Of WSNs With Qos For Smart Distribution Grid

Smart grid is a complex power network which integrates various power equipments through advanced communication technology,high-performance computer technology and intelligent electrical control technology.The realization of seamless connection between transmission network,distribution grid and power unit is one of the necessary means to ensure two-line transmission of power flow and information flow through the use of network communication technology with efficient,safe,reliable and real-time feature.WSNs communication was successfully recommended as one of communication technologies for the regional power grid by"the Development Framework and Roadmap of Smart Grid" in 2011.IEEE802.15.4g was released as an exclusive technology standard communication for WSNs applied to smart distribution power system in 2012.Recently,Researches on WSNs applied to Power Grid communication were supported by National Natural Science Foundation of China,U.S.National Science Foundation,and European Seventh Framework Programme(FP7).The research of wireless sensor networks applied to smart distribution grid has been the focus of attention.When wireless sensor networks(WSNs)is used to high performance communication of smart distribution grid to ensure that index can satisfy the communication specification of electric power industry,the basic research can be attributed to solve the problem between the uncertain process of data transmission and coordinated optimization of multi-objective requirements with QoS index of supremum limitation assurance.The core of the research is to set up the service quality control model with QoS index of supremum limitation assurance to support in-layer optimization and cross-layers coordination.Under the topology of the WSNs is relatively fixed,the coordination optimization for data communication of the WSNs with QoS index of supremum limitation assurance including the real-time and reliability is realized.The proposed method can improve the communication performance of WSNs and provide the basis theoretical support and practical gauge for WSNs applied to smart distribution grid.The main works can be summarized as blow:(1)the MAC-QoS protocol algorithm of queue scheduling to meet the priority demand of power data in MAC layer and unfair competition channel access mechanism(UCCAM)is developed and the mathematical model of the MAC layer performance analysis is also built.According to the different real-time and reliability requirements specified by power industry communication specification for different types of power data and the change of one step chain in power data queue of WSNs node,the mathematical models including the Markov chain buffer queue based on UCCAM among high priority,middle priority and low priority data,and channel competition in neighboring nodes are built.The models including the delay time,channel collision rate and effective throughput to analyze MAC performance are constructed.The simulation results show that:the real-time and reliability of all the different types of power data can be ensured when WSNs is unsaturated state;the real-time and reliability of higher priority data are ensured first when WSNs is saturated state or supersaturated state.The proposed algorithm can provide the service quality to meet the requirements of the power industry communication standard for different types of data without adding to any network overhead.(2)An optimal path selection algorithm regarding the minimum flow of wireless sensor network as an objective function is proposed.Taking supremum limitation of the real-time and reliability requirements specified by the power industry communication specification as the constraint condition and traffic conservation in node as the boundary condition,the objective function to select the optimal path is established,where communication data traffic is maintained minimum.Starting from the necessary condition of extreme value,the method obtaining the optimal solution of the objective function coefficient is constructed.The relationship between the optimal solution of the obtained objective function and the impedance on the optimal link between the current node and the target node is used as the basis to judge whether the current wireless sensor node is on the optimal path of data transmission.The simulation results show that:the proposed optimal path selection algorithm regarding the minimum flow of wireless sensor network as an objective function can realize the effective transmission of power data in the smart distributiongrid to ensure that the real-time and reliability satify power industry communication standard.(3)The congestion control algorithm considering effect of neighboring node is proposed for WSNs applied to smart distribution grid.By taking the transmission efficiency of neighboring nodes as the evaluation amount and using the data window size as the adjustment amount to control the probability of network congestion occurrence,the proposed algorithm can effectively guarantee needs of real-time and reliability specified by power industry communication standard without reducing the network throughput,when congestion occurs at the current node.In order to make up the loss of data and addition of transmission time due to congestion,retransmission and fast recovery are added to the proposed algorithm.Based on the communication model of wired transmission,the mathematical models of congestion window and change rate of queue length are constructed to analyze perfoemance of the congestion control algorithm of WSNs applied to smart distribution grid.In order to effectively ensure the stability of the WSNs operation,the H2/H? hybrid controller is embedded in communication system of WSNs applied to smart distribution grid.Simulation results show that:the proposed congestion control algorithm of WSNs applied to smart distribution grid communication network considering neighboring node effect can effectively reduce the probability of congestion and enhance the real-time and reliability of power data transmission to meet the power industry communication specification.(4)The service quality control model of cross layer cooperation is established for protocol stack of WSNs applied to smart distribution grid.According to structure of IEEE802.15.4 protocol stack,the proposed model can enhance the overall quality of service protocol stack performance to ensure the real-time and reliability of power data meet the communication requirements by adjusting layer resources and coordinating each protocol layer parameters in protocol stack.The fuzzy cognitive graph model of the single node and the corresponding correlation matrix are established for WSNs applied to smart distribution grid.The relationship among the wireless sensor nodes is established by the T-S method,The control system of the WSNs is established,where the conceptual node of the data queue length is used as the controlled variable and the residual concept node are used as the control variables.Simulation results show that:The proposed service quality control model of cross layer cooperation can realize information sharing and cross layer cooperation among multiple protocol layers of protocol stacks to ensure the real-time and reliability of three types of power data are ensured on the network's under-saturation state;the real-time and reliability of higher priority are ensured first on the network's saturated state.(5)The example application.The WSNs' topology construction for smart distribution grid of Huang Shan City is designed.The design idea of multi-unit,multi-form and multi-level is fully considered to suit the actual geographical environment,the actual layout of terminal equipment,distance between communication regional and information management center,the demand of distribution network information management.The MAC-QoS protocol algorithm based on UCCAM,the optimal path selection algorithm regarding the minimum flow of wireless sensor network as an objective function,the congestion control algorithm considering effect of neighboring node and the service quality control algorithm of cross layer cooperation are embedded in designed WSNs communication system for smart distribution grid.The gateway management software is also designed simultaneously.The real-time and reliability to the engineering project data with different priority are tested.The tested results show that:the basic theory researches and the corresponding model algorithms presented in this article can satisfy the index requirements of real-time and reliability of data transmission in smart distribution grid according to the power communication standards,and the prospective goal of high performance data communication in smart distribution grid is achieved.