【作者】 蔡伟；

【导师】 刘开培；

【作者基本信息】 武汉大学 ， 电力系统及其自动化， 2013， 博士

【摘要】 电力线载波通信技术因其良好的经济性和便利的应用性而成为智能电网通信的重要手段之一。在智能配电网中为提高供电可靠性而将出现新的环形和格状网络拓扑；各种分布式电源也将大量接入智能配电网中,使得网络组成元件的阻抗特性发生较大变化,从而影响载波通信信道传输特性。因此,研究对各种网络拓扑结构具有通用性的信道传输特性建模方法,研究分布式电源呈现出的阻抗特性,在此基础上分析各种影响因素对信道传输特性的影响规律,能够为设计智能配电网中电力线载波通信技术的调制方式,提高电力线载波通信技术的实用化程度提供必要的理论依据和分析方法。本文首先提出了信息节点的概念,以此为基础建立了适用于任意网络拓扑结构的电力线信道建模方法。该方法首先将每条电力线看成一个子网络,求出各条电力线的电压电流传输关系式,然后求出网络组成元件连接节点处电力线、负载及电源之间的电压电流关系式；最后根据这些关系式求出信号发射点到信号接收点之间的传输特性。通过物理试验验证了该建模方法的有效性和普遍适用性,为解决环形和格状等任意网络结构的信道建模提供了必要的方法。基于上述信道建模方法,本文利用数值仿真方法,对影响树形网络和环形网络信道传输特性及输入阻抗特性的因素及其影响规律进行了研究。主要影响因素包括电力网络中主干长度、分支长度、负载阻抗和分支位置及数量等。结果表明：主干线路长度主要影响信道传输的相频特性；分支线路长度主要影响信道传输的幅频特性；支路负载的阻抗主要影响信道的幅频特性；分支线路数量主要影响信道幅频特性中衰落谷的大小和相频特性。随着电力拓扑的改变,输入阻抗特性也会随之改变,但是在信号幅值衰落峰处,输入阻抗均稳定在一个固定值附近。本文还分析了对称环网在闭环与开环两种运行方式下,信道传输特性的区别。结果表明：对称环网闭环运行时信道传输幅频特性中的衰落峰频率点,在开环运行方式下仍然为衰落峰。本文建立了单相光伏发电系统并网的阻抗模型。通过对单相光伏发电系统运行原理的分析得出并网滤波器是光伏系统接入电力网的最后一个环节,通过仿真得出光伏发电系统在电力载波通信网络中相当于开路。本文分析了异步电动机的高频阻抗模型,并对异步电动机接入载波通信系统对载波通信信道特性的影响规律进行了分析。分析结果表明异步电动机负载在低频段呈现开路特性,而在高频段表现为短路特性。本文还建立了RG316和SYV75-4两种同轴通信电缆的阻抗特性模型,并利用开短路阻抗法测量出电缆的开路阻抗和短路阻抗,进而求出电力线的特性阻抗和传播常数。与通过建模所仿真得到的结果进行比较,验证了同轴通信电缆阻抗模型的正确性。上述工作为提高信道化输特性研究的准确性提供了必要的依据。本文最后针对电力线信道中噪声严重的问题,分析了电力线信道噪声的类型和特点,并建立了智能配电网中大量存在的与电网频率同步的周期脉冲噪声的模型。对不同时间点实验室低频段和高频段的噪声情况分别进行了测量,分析了电力线信道不同频率段的噪声特性和时变性。更多还原

【Abstract】 Due to the good economy and convenient, the power line communication (PLC) technologies are often used for smart grid communication. Ring topology and mesh topology would appear in the smart distribution grid to improve the power supply reliability, and all kinds of distributed generation would be connected to the smart distribution grid, which will change the impedance characteristics of the grid. All of the changes will affect the PLC channel transmission characteristics. Therefor it is necessary to establish a PLC channel modling method for arbitrary topology. The impedance characteristics and the effect to PLC system also should been studied.The paper has proposed the concept of information nodes, and then the power line channel modeling method for arbitrary topology has established. Firstly, taken each power line as a subnetwork and obtain the power line transmission relationship of each power line, and then obtain the voltage-current relationship of conneting nodes between power line, load and source by the basic circuit theory, lastly obtain the transmission characteristics from the signal launching point to the signal receiving point. The effectiveness and universal applicability of this method are verified by actual measurement.Using the channel modeling method based on information nodes, the simulation has carried out to analyze the influence of line length, load impedance and topology to channel transmission characteristics and input impedance characteristics in tree topology and ring topology. Simulation results show the trunk line length and branch line length has heavy effect on amplitude-frequency characteristics and phase-frequency of channel respectively. The number of branch has heavy effect on the notchs and phase-frequency characteristics. The input impedance changes greatly with topology, but the input impedance of amplitude-frequency characteristics peak pointes maintained in a fixed value. The paper also has analyzed the difference channel transmission characteristics of symmetric ring topology in closed ring operational mode and open ring operational mode. Simulation results show the peaks frequency points in closed ring operational mode are also the peaks in open ring mode.The paper has analyzed the influence of the single-phase photovoltaic systems connect to the power line communication system. It is summarized that the filter is the junction device between photovoltaic systems and power system. And basis on this summary, the influence of the single-phase photovoltaic systems connect to the power line communication system has simulinked in the paper. Simulation results show the photovoltaic system equivalent to open-circuit in power line communication network. The high frequency impedance model of the asynchronous motor has been analyzed in the paper, and the influence of the asynchronous motor connect to the power line communication system has been analyzed in the paper. Analysis results show that the asynchronous motor load equivalent to open-circuit in low frequency and short-circuit in high frequency. The paper has established the impedance characteristics model of coaxial communication cables. The open circuit impedance and short-circuit impedance of the cable are measured by open short-circuit impedance method, and then the characteristic impedance and propagation constant of cables are obtained basis the measure results. The correctness of the cables model is verified by the comparison of measure results and the simulink results. The above work is the basis of improving the accuracy of channel transmission characteristics.According to serious impact of the power line channel noise, the paper has analyzed the type and characteristics of the power line channel noise, and established the model of periodic impulse noise asynchronous to the mains freauency. These impulse noises are abundant in the smart distribution network. Aim to analysis the noise characteristes and time variation of power line channel, the paper has measured the lower frequency and high frequency power line channel noise in our laboratory at different time points.更多还原