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Yuan W.,Guodian Nanjing Automation Co. | Zhu C.,Guodian Nanjing Automation Co.
International Journal of Innovative Computing, Information and Control | Year: 2014

This paper concerns with the problem of robust sampled-data H∞ control for active suspension systems subjected to saturated control input. By using the nature of the sector nonlinear condition, the saturation of the systems' control input is modeled, which is commonly occurred in the practical systems due to the actuator composed by elastic elements. A passenger dynamic is considered in modeling the suspension system wherein the uncertainties aroused from uncertain passengers are assumed to be a polytopic type. Output feedback control strategy is adopted by constructing an output matrix since the measurements of body acceleration and body deflection are unavailable. The controller design is then cast into a convex optimization problem with linear matrix inequalities (LMIs) constraints. An application example is given to illustrate the effectiveness of the developed controller design scheme. © 2014.


Ma W.,Guodian Nanjing Automation Co.
Dianli Zidonghua Shebei/Electric Power Automation Equipment | Year: 2011

For the increasing rate of wind generation capacity, higher requests are brought to the capacity of low voltage ride through for the wind generation on grid. Based on the grid connection guidelines of wind turbine, the operation of DFIG (Doubly-Fed Induction Generator) wind turbine during grid voltage sag is analyzed and it is proposed to apply Crowbar circuit in the protection of rotor excitation source and generator. The wind farm model is built with Matlab/Simulink to validate its effectiveness. Simulative results show that the circuit ensures the safety of system components by limiting the maximum current generated by the rotor circuit during voltage sags, and the AC excitation DFIG can operate in connection with grid to stabilize the grid voltage during fault.


Chen F.,Guodian Nanjing Automation Co.
Dianli Zidonghua Shebei/Electric Power Automation Equipment | Year: 2014

The behavior of distance protection under CT(Current Transformer) disconnection is studied and its influence is analyzed based on the fault-circuit resistance measured by the protection, which shows that the influencing factors are the direction of power flow and the position of faulty phase. At the power-source side, the grounding-fault distance protection tends towards the miss operation when the in-zone fault occurs in the leading phase relative to the phase of CT disconnection and towards the improper operation when the out-zone fault occurs in the lagging phase relative to the phase of CT disconnection, while it behaviors on the contrary at the load side. Combined with the method of CT disconnection detection, an adaptive grounding-fault distance protection scheme is proposed, which is theoretically analyzed and verified by the test. Suggestions are given on the CT circuit and protection configuration. ©, 2014, Electric Power Automation Equipment Press. All right reserved.


Liu Y.,Guodian Nanjing Automation Co.
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2016

This paper takes the merging unit as point cut of smart substation secondary system data source and analyzes the problems of present sampling system. A high reliability sampling way is proposed, based on which a new type of merging unit is designed. The new merging unit owns abnormal sampling data analysis and processing function. It can quickly and accurately distinguish the abnormal data, send information to the relay protection in the substation and help the relay protection to avoid incorrect action. The research can highly improve the reliability of the sampling in the smart substation with analysis and verification. © 2016 Power System Protection and Control Press.


Chen D.,Guodian Nanjing Automation Co. | Xu L.,University of Strathclyde | Yao L.,China Electric Power Research Institute
IEEE Transactions on Power Delivery | Year: 2013

System control for dc microgrids with variable generations and energy storage is proposed in this paper. An autonomous three-level control strategy is proposed for dc microgrids with selective slack terminal(s) assigned to each operation level. The system operational status is acknowledged via the common dc voltage and the transitions between different operational levels are triggered by its variation. A four-terminal sample dc microgrid system with a grid-connected voltage-source converter, a wind turbine, an energy storage system, and dc loads are established and a specific control scheme is outlined to demonstrate the proposed strategy during various operating conditions, such as load step, generation fluctuation, islanding, grid reconnection, load shedding, and generation curtailment. The control strategy and the specific scheme are validated by experimental results conducted on a prototype dc microgrid system. © 1986-2012 IEEE.


Guo X.,Guodian Nanjing Automation Co. | Cai D.,Huazhong University of Science and Technology
Dianli Zidonghua Shebei/Electric Power Automation Equipment | Year: 2013

PLF-CM(Probabilistic Load Flow calculation based on Cumulant Method) performs linearization at the operating point of power system to quickly obtain the distribution of system state variables. Large-scale integration of wind power and photovoltaic power enhances the variation of power system load flow and different series expansions are suitable for different distribution types of system state variable. With a power system with wind/photovoltaic power as the analysis object, the calculative results by Monte Carlo method as the references and the average root mean square of the cumulative distribution of output random variable as the evaluation index, the accuracy of PLF-CM are compared among various input random variables and different series expansions, and the causes of its errors are analyzed.


Hu D.,Guodian Nanjing Automation Co. | Wo J.,Jinhua Electrical Power Bureau
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2010

Considering characteristics of eliminating hard cable circuits in smart substations, implementation of integrated virtual circuit system (VCS) based on network information sharing is proposed. IEC 61850 modeling is used to express design, and system integration, debug and configuration, running repair etc. are all achieved by automatic software tools according to the unified information. For VCS of smart substation it needs to suitably expand and improve IEC 61850 standard. GMRP should be applied to achieve automatically network multicast management, and design and system integration should be fully integrated. Common software of 3rd party may be developed based on the uniform standard, so virtual circuits are easily expressed, understood, implemented and maintained by each professional. Work of information repeat configuration is fully minimized so as to avoid man-made errors. © 2010 State Grid Electric Power Research Institute Press.


Fang G.-Z.,Harbin University of Science and Technology | Yang C.,Guodian Nanjing Automation Co. | Zhao H.,Harbin University of Science and Technology
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2012

In view of the fences phenomenon, spectrum leakage and issues of slow identification and location and weak real-time performance caused by complicated computation that exist in the harmonic detection, a comprehensive harmonic detection method is presented based on FFT and wavelet packet transform. This method uses the excellent amplitude frequency characteristics of FFT to identify the harmonic component, uses the excellent time-frequency characteristics of wavelet packet to locate the time of harmonic occurrence and end quickly and selectively, at the same time extracts the contained harmonic component, so that it can reduce the computation and improve the real-time performance of the harmonic detection. Using Matlab to simulate the comprehensive harmonic detection method, it shows that the comprehensive harmonic detection method is more effective than the common detection methods.


Zhang Y.,Guodian Nanjing Automation Co.
Dianli Zidonghua Shebei/Electric Power Automation Equipment | Year: 2015

The technical routes and methods of digital sampling technology during its development for smart substation are discussed. The principle and application of digital sampling synchronization are described and the problems of existing network sampling methods are analyzed. A technology of sample arrival time prediction based on PLL (Phase Locked Loop) is proposed, which, when the synch clock is lost, can continue the sampling synchronization to avoid the synch failure occurred in normal network sampling methods; and it can also filter the abnormality caused by the switch delay to avoid the unfavourable influences, such as the relay protection blocking. The proposed technology can improve the sample reliability of network transmission and provide the theoretic basis and solution for the popularization and application of network sampling in smart substation. ©, 2015, Electric Power Automation Equipment Press. All right reserved.


Ding Q.,Guodian Nanjing Automation Co. | Li S.,Guodian Nanjing Automation Co.
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2015

For the error introduced by resampling application in smart substation, this paper firstly studies resampling's detailed application background in smart substation, gets the two typical methods as sampling synchronization and frequency conversion. It takes linear interpolation for studying object, through vector modeling analysis and verification testing, then gets linear interpolation's amplitude-frequency characteristic. Result shows that signal's sampling frequency and interpolation positioning are the two main factors affecting resampling's accuracy, measuring and metering functions are affected greatly while protection relay is affected little. By increasing the sampling rate, or improving the techniques of synchronization and interpolation, resampling error can be reduced or even eliminated. © 2015, Power System Protection and Control Press. All right reserved.

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