Papers by Author: Ke Jun Li

Abstract: In this paper, the problem about the distribution network planning considering distributed generators is researched. Firstly, distribution network planning model is formulated based on economy and security objectives. Secondly, an improved hybrid algorithm is proposed based on ant colony algorithm and genetic algorithm in order to get better performance. Finally, the method has been tested on a typical radial distribution system to demonstrate the effectiveness of the proposed method.

Abstract: The weight of evaluation index plays a key role in condition assessment and maintenance control of power transformer. A new approach of determination of comprehensive weight is proposed in this paper. The approach combines the entropy objective weight with the expert subjective weight together in a specific form, which not only avoids the situation that single weight determines the overall weight, but considers the primary and secondary problem between the two weights. The comprehensive weight calculated by this approach can reflect the place of every index in condition assessment of power transformer well. Empirical results show that the approach is reasonable and available.

Abstract: On the basis of the analysis of simulating the partial discharge (PD) signals in Gas Insulated Substation (GIS), this paper focuses on discussing the common simulation and realization methods of simulating the partial discharge signals in mechanical and electrical equipments. The characteristics of PD signals and the typical insulation defects of GIS are reviewed. Different simulation methods to simulate the PD signals are considered. Two implementation schemes of simulating the discharge pulse are analyzed and compared with each other. Through the analysis, we find out that the electronic technology will be the most hopeful way to achieve the desired goals, which are to simulate those PD signals. This paper provides a simulation scheme of simulating PD signals, which can be described as multi-stage paralleling of MARX circuit and can provide a reliable reference for engineering practice.

Abstract: This paper studies the root-cause analysis based on the time delays among various signals, for reducing nuisance alarms in modern industrial systems including power grids. Time delays are estimated via the revised nearest neighbor imputation method, and are validated via the subsequent consistency check. Numerical examples including the IEEE 5-node system as a prototype power grid are provided to demonstrate the effectiveness of the proposed time delay estimation method and the subsequent consistency check.

Abstract: The energe storage system with combination of large-scale grid-connected wind farms will be the developing trend of renewable energy in future. The flow battery has becoming the most potential advanced chemical energy storage technology among the storage method. This paper is mainly introducing about the work principle, characteristics and structure of the VRB system. Futhermore, the control mechanism of the power quality and stability used in wind farm connected to power grid by battery energy storage is illustrated in the end of paper.

Abstract: Smart Home technology promises enormous possibilities to our future life. It contains internal network, intelligent control and home automation. The paper describes a novel architecture for the smart home system employing ZigBee technology. Energy conservation is also a feature of smart home system. Based on the time-of-use (TOU) pricing, a new energy saving solution has been proposed.

Abstract: The corona characteristic of HVDC tube bus is the main factor taken into account for choosing tube bus of HVDC converter substation. The intension of corona could affect the electromagnetic environment of converter station and generate audible noise. By establishing the calculation models of electric field strength along the tube bus surface and the electric field strength on ground, the paper computes the corona onset voltage gradient and gives the relation curve of high and electrode spacing of tube bus. If the tube bus in HVDC converter substation is installed at the high and electrode spacing, got by the relation curve, it will not generate corona and its electric field strength will meet the requirements. The control indexes of tube bus corona characteristic parameters for HVDC converter substation are confirmed in combination with calculation results and related standards. Based on the control indexes, the paper gives the collocations of different tube bus types.

Abstract: Since traditional power is non-renewable and unfriendly to environment, renewable energy power which overcomes defects of traditional energy will gradually replace the conventional thermal power. Based on the utilization problem of renewable energy in Smart Grid, this paper builds an Energy Internet which supports real-time, high-speed, two-way transmission of power data and more renewable energy. The Energy Internet achieves reliable two-way transmission of power and realizes intelligent management of the grid. This paper proposes the concept and characteristics of the Energy Internet and completes the design of the Energy Internet network structure and system components. Key issues, such as Renewable Energy Management System, energy storage devices, will be discussed, and finally the paper will point out the direction for further research.

Abstract: The mode-switching control method of thyristor controlled series capacitor (TCSC) is of great importance to power system stability. It is very difficult, if not impossible, to realize mode-switching only by changing firing angles. Considering the impedance characteristics of TCSC, a set of mode-switching control methods is proposed. Simulation and experimental results show that the proposed switching method can make the switching process faster and possess better dynamic performance.

Abstract: One of the most challenging problems in real-time operation of power system is the prediction of transient stability. Fast and accurate techniques are imperative to achieve on-line transient stability assessment (TSA). This problem has been approached by various machine learning algorithms, however they find a class decision estimate rather than a probabilistic confidence of the class distribution. To counter the shortcoming of common machine learning methods, a novel machine learning technique, i.e. ‘relevance vector machine’ (RVM), for TSA is presented in this paper. RVM is based on a probabilistic Bayesian learning framework, and as a feature it can yield a decision function that depends on only a very fewer number of so-called relevance vectors. The proposed method is tested on New England power system, and compared with a state-of-the-art ‘support vector machine’ (SVM) classifier. The classification performance is evaluated using false discriminate rate (FDR). It is demonstrated that the RVM classifier can yield a decision function that is much sparser than the SVM classifier while providing higher classification accuracy. Consequently, the RVM classifier greatly reduces the computational complexity, making it more suitable for real-time implementation.