Dongli Jia

Study on technology system of self-healing control in smart distribution grid

Smart distribution grid is an important part of smart grid, which connects the main network and user-oriented supply. As an “immune system”, self-healing is the most important feature of smart grid. Major problem of self-healing control is the ‘uninterrupted power supply problem’, that is, real-time monitoring of network operation, predicting the state power grid, timely detection, rapid diagnosis and elimination of hidden faults, without human intervention or only a few cases. First, the paper describes major problems, which are solved by self-healing control in smart distribution grid, and their functions. Then, it analysis the structure and technology components of self-healing control in smart distribution grid, including the base layer, support layer and application layer. The base layer is composed of the power grid and its equipments, which is the base for smart grid and self-healing control. The support layer is composed of the data and communication. High-speed, bi-directional, real-time and integrated communications system is the basis of achieving power transmission and the use of high efficiency, reliability and security, and the basis for intelligent distribution network and the key steps of self-prevention and self-recovery in distribution grid. The application layer is composed of Monitoring, assessment, pre-warning/analysis, decision making, control and restoration. Six modules are interconnected and mutual restraint. The application layer is important means of self-prevention and self-recovery in distribution grid. Through the research and analysis on the relationship and the technical composition of six modules in the application layer, the paper divides running states of smart grid distribution grid having self-healing capabilities into five states, which are normal state, warning state, critical state, emergency state and recovery state, and defines the characteristics and the relationship of each state. Through investigating and applying self-healing control in smart distribution grid, smart distribution grid can timely detect the happening or imminent failure and implement appropriate corrective action, so that it does not affect the normal supply or minimize their effects. Power supply reliability is improved observably and outage time is reduced significantly. Especially in extreme weather conditions, the distribution grid will give full play to its self-prevention and self-recovery capability, give priority to protecting peoples life and provide electricity for the people furthest.

Classification of Massive User Load Characteristics in Distribution Network Based on Agglomerative Hierarchical Algorithm

In order to improve primary energy utilization, achieve economical operation of distribution network, comprehensively consider the concentration / compensation needs of various groups under typical load levels, and to gain understanding of characteristics of different types of user loads, the present paper proposes a hierarchical cluster algorithm to enhance the cohesion of a distribution feeder load characteristic clustering algorithm circumstances. This will serve to ultimately provide effective guidance for electricity energy conservation as well as to better realize peak load shifting. By cutting distribution network load time sequence data in longitudinal manner, relevant feature were extracted to achieve user load characteristics classification based on hierarchical clustering algorithm. Such classification will therefore assist to optimize distribution network scheduling. It is therefore an effective way to enhance accuracy and effectiveness of relevant power distribution decision-making.

A system identification method for smart distribution grid

With the development of the smart distribution grid, risk assessment, early risk warning, fault diagnosis and self-healing control have put forward a requirement of getting the precise impedance parameters of a distribution line. In order to solve the problem, a method for online virtual metrology of distribution line impedance is proposed. The paper builds the voltage drop linear equivalent computiong model by using probability theory. Then based on the collected three-phase currents and voltages data at the head and end of the line, it uses mathematical method, such as regression analysis method and the average value of solving equations method, to analyze and calculate the coefficients of the voltage drop linear equivalent calculative model. The coefficient of terminal current corresponding is the impedance of the line. The method can be used to calculate the impedance of a running distribution line. The calculation result and the actual impedance were compared and analyzed. The analysis result shows that it is feasible and effective and has the advantages of a fast calculation speed and a good real-time performance.

Research on model system architecture of smart distribution grid

In order to solve the problem of optimizing operation and control under complicated network connections in distribution grid, and to provide better support for the distribution network running economically and efficiently, the paper constructs an model system structure which includes three model types, six kinds of business models and three levels. The paper also designs a distribution network model library. It includes six sub-model libraries, has functions of scheduling control for each model, input and output, model analysis, user interaction, and can provide user interface for other modules. Model system structure and distribution network model library provide basic support for smart distribution network development of planning, operation, and control. And they have important theoretical and practical significance too.