Research On Key Technologies Of Communication And Control In Smart Grid

Smart grid additionally incorporates various information technologies and the distributed generation technology on the basis of the traditional grid, which can be able to achieve the functions of state detection and monitoring, the allocation of electricity energy resources as required, etc, and be highly self-healing and self-recovering. Since it is the future development direction of the grid and the critical technical approach of implementing energy-saving, emission reduction, and sustainable development, study on the smart grid is of important theoretical significance and practical application value.The smart grid is mainly related to the two aspects of the communication transmission and control techniques. In transmission, the power line communication technologies are integrated into smart grid for transmission which is very convenient. However the characteristic of the signal in power line is complicated and variable, which causes a strong disturbance to communication reliability. In control, the smart grid is regarded to multiple function tasks to accomplish power configuration, but how to guarantee the performance of task scheduling algorithm is a key to achieve the effective operation of control system. So in this dissertation, the emphasis is put on the basic principle and functional structure of the smart grid, the analysis and prediction of the signal characteristic in power line, the multi-carrier transmission technology based on fountain coding, the hardware construction of smart grid control system, and the embedded multiple task scheduling algorithm. The major contributions are outlined as follows:The first part focuses on the basic functions and network structure. The basic functions of smart grid are reintegrated and defined on the basis of traditional grid. A kind of centralized home network structure is designed for the topological characteristics of RSAN. And some essential system components are designed, of which a new integrated interface structure is presented. The power port, communication port and data collection unit are integrated in the new interface, of which the main working procedure is also presented.The characteristic of the power line signal is first researched and then the corresponding predicted model is developed. The analysis construction regarding the signal characteristic in power line is first designed. Here the schemes of reversed order method, surrogate sequence approach, recurrence plot, and phase space reconstruction theory are utilized to analyze the stationarity, nonlinearity, and certainty. Taking the low-voltage power signal as instance object, it can be obtained that this signal is steady, nonlinear, and definite. Then combining the signal characteristic, the signal prediction model based on the multi-wavelet support vector machine is constructed.The third part focuses on high-reliable multi-carrier transmission technology based on digital fountain code in erasure channel. The system construction of multi carrier transmission with LT code is designed. The peak-to-average power ratio of OFDM signal is controlled, and the information is transmitted reliably through the rateless character of the fountain code. In order to decrease the decoding cost of LT code, Moved-RSD and Truncated-BED are presented on the basis of RSD and BED respectively. A modified switching degree distribution is designed with the combination of Moved-RSD and Truncated-BED, and the switching point is obtained by simulation. The presented degree distribution keeps the balance between big and small degree data packets, which improves the decoding success ratio and decreases the decoding cost.In the fourth part, A novel detection method related to the load status is put forward, and the delay mode of RC-chain circuit is provided. The hardware systems of power resource scheduling and configuration are first explored. And then the load connection status detection method is proposed to realize the check and schedule of the equipment. Additionally directing to the signal delay, the RC-chain delay model with a ramp signal is deduced in a mathematical way, which is highly accurate and low-complexity.For the control system of smart grid, a multi-task scheduling algorithm is proposed in this thesis. According to the functional requirement of the smart grid to the power configuration and control, an embedded multitask scheduling method is constructed and a constraint model is proposed to evaluate the instantaneity of the proposed scheduling algorithm. Besides the simulation test is set up and the relationship between instantaneity which is represented by overtime ratio and task executing time is derived.