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Liu Y.,University of Jinan | Sun T.,Integrated Electronic Systems Laboratory Co.
Dianwang Jishu/Power System Technology | Year: 2016

Computation burden of non-recursive Fourier algorithm is well-known heavy, limiting its application in numerical relays. Although recursive form of Fourier algorithm reduces computation burden greatly, errors caused by finite word-length effect and truncated data bits seriously affect accuracy and long-term stable operation because the errors will be cumulated step by step. Based on sources and characteristic analysis of cumulative errors mentioned above, the paper proposes an improved method calculating alternatively using recursive and non-recursive forms to minimize cumulative errors. Moreover, employing distribution and synchronous calculation technology for weighted product terms, the improved method maintains inherent advantages of recursive algorithm, whose calculation amount only increases 2 additions compared with continuous recursive algorithm. The proposed method is applied in busbar protection and substation-area protection for smart substation requiring access of large number of analog channels. Digital simulation and prototype long-term running experiments show that the improved method can effectively reduce cumulative errors and drastically decrease computation burden in comparison to non-recursive algorithm. © 2016, Power System Technology Press. All right reserved.

Zhao H.,Shandong University | Wang X.,Shandong University | Yang Z.,Integrated Electronic Systems Laboratory Co.
DRPT 2011 - 2011 4th International Conference on Electric Utility Deregulation and Restructuring and Power Technologies | Year: 2011

With the development of digital substation, the devices of the substation put forward higher demands on clock synchronization. The standard of the IEEE1588 provides a protocol that enables precise synchronization of clocks in measurement and control systems, and the precision of its network is sub-microsecond level which can satisfy the need of clock synchronization of the substation. This paper makes a brief analysis of the principles of clock synchronization and the protocol state machine, and achieves the clock synchronization by programming. Under the Linux operating system, the design of software contains the protocol engine module, transmission control module and receipt control module. Eventually it is transplanted into the platform of ARM9 and tested. The results show that the precision of time synchronization this paper designed can meet the requirements of the synchronous units of digital substation. © 2011 IEEE.

Qi M.,Shandong University | Wang X.,Shandong University | Yang Z.,Integrated Electronic Systems Laboratory Co.
DRPT 2011 - 2011 4th International Conference on Electric Utility Deregulation and Restructuring and Power Technologies | Year: 2011

IEEE1588 is a Precise Time Protocol (PTP), which is of potentially wide application in control and measurement networks. Stamping PTP messages accurately in physical layer taking advantage of hardware circuits, it is one of important key technologies to achieve the object of high precision time synchronization of IEEE1588. This paper analyzes the content of IEEE1588 standard in detail, and proposes a method of "Cyclone II FPGA + MAC + PHY", a hardware solution that stamps the time of PTP messages' arrival and departure. It permits to obtain messages from Media Independent Interface (MII) between MAC and PHY layers by using "DM9000 + LXT971A", while FPGA monitors these signals and timestamps synchronization messages. To validate the solution, a test platform was built. The result shows that the solution can detect the sent and received synchronization messages accurately. This work laid a solid foundation for developing high-precision network clock based on the IEEE1588 standard. © 2011 IEEE.

Liu Y.,Shandong University | Liu Y.,Integrated Electronic Systems Laboratory Co. | Gao H.,Shandong University | Gao W.,Shandong University
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2011

A novel approach to data processing for relay protection is proposed based on analysis of basic requirements of data processing in digital substation. The new scheme involves three major steps, applying the Fourier algorithm immediately to equal-interval sampling data from merging unit, amending the sine/cosine items in accordance with the real-time frequency, and finally acquiring the signal's true root mean square value and phase. The new scheme not only obtains high precision frequency with the phase-shift-cycle measurement algorithm, but also adapts to phasor based protection without using interpolation or sampling rate conversion. The concrete implementation of novel data processing approach and related issues (e. g. how to deal with startup with sampled values) are given in detail. The feasibility and validity of proposed approach have been verified with ATP based simulation. © 2011 State Grid Electric Power Research Institute Press.

Wang X.-L.,University of Science and Technology of China | Wu Z.-H.,Integrated Electronic Systems Laboratory Co.
Communications in Theoretical Physics | Year: 2014

Using an improved homogeneous balance principle and an F-expansion technique, we construct the new exact periodic traveling wave solutions to the (3+1)-dimensional Gross - Pitaevskii equation with repulsive harmonic potential. In the limit cases, the solitary wave solutions are obtained as well. We also investigate the dynamical evolution of the solitons with a time-dependent complicated potential. © 2014 Chinese Physical Society and IOP Publishing Ltd.

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