Related Technologies Of Wams And Study On Application Of Voltage Stability

The dispatching&monitoring system such as EMS/SCADA is playing a role inmonitoring steady behaviors of electric power system by the power flow. But thedispatching&monitoring system can't monitor and identify the dynamic behaviors of electricpower system. There are not the related algorithms and necessary communication in somerecording equipments with GPS so as not to realize observing and monitoring the dynamicbehaviors . With the project that power being transmitted from West China to East China andall grids being interlinked being constructed, the dimension of the state grid becomes largerand larger. The dispatching branches urgently need a way of reflecting dynamic behaviors ofthe large power grid.GPS can provide the high-precision synchronous clock for the monitoring equipments soas to realize measuring the phase of the buses. At present, with the optical fiber communicati-on becoming more and more universal, the optical fiber is used as the main channels fortransmitting data in the electric power dynamic monitoring system.WAMS is as the platform for WACS(Wide Area Control System) by using thecommunication technology, computer technology and internet technology. WACS can realizedispatching and controlling the large grids in order to prevent the instability or collapse. Thispaper studies technologies of WAMS and application of voltage stability. They are mainlyconstituted of :1.This paper studies a kind of distributed phasor measurement system. The paper involvesdesign idea, all the parts of system,communication networks and remote management .2.This paper first studies the gateway in distributed phasor monitoring system, andadvances a proposal of developing high-speed digital gateway aiming connecting differentkinds of communication mediums. Subsequently the paper discusses the scheme ofdeveloping gateway about hardware and software in detail. The hardware design adopts highperformance CPU, high-speed Ethernet Controller, the Ethernet optical interface and electricalinterface ,and high-speed serial optical interface. The paper also discusses the real-timeperformance of the gateway from the point of network structure, software design and protocolin detail.3.Because of the difficulty of equipment's debugging, the test software is developed.4.This paper proposes two problems:a large quantity of recorded data is difficult to bestored, and software technique.Aiming at the first problem,the paper takes a detailed discussfrom the point of application such as adopting newfashioned storage technique on harddisk,data compression method,enhancing the compression ratio. Aiming at the secondproblem, this paper adopts the idea of component in order to simply programming and makemaintenance easily. This paper develops the testing software in order to makes debuggingdevice easilier. It has been proved that the recording software is valid in the experiment ofmanual short circuit fault in the Northeast of China.5. A data compression and reconstruction method is proposed. Data are compressed andreconstructed by biorthogonality filters based on linear WT of lifting scheme, and are encodedand decoded by Huffman algorithm. The experiment proved that the method is valid with lessprocessing time and as high as 8.9 times of compression ratio. This method is suitable to thereal-time compression of mass data recorded continuously by dynamic monitoring devices ofpower system.6. Square-root algorithm is used to acquire equivalent parameters of power system in thispaper. The method combines feature and requirement of voltage stability research and usessynchronous phasors informations. The V_Q curve and P_V curve is used to prove thevalidity of the Square-root algorithm. The method has the distinctive physicalmeaning,requires less compution work, has better numerical stability and can deal with theparamter estimation continuously.The results given from IEEE 9-bus system showed theeffectiveness of the algorithm.7. A new algorithm for monitoring against voltage instability is proposed. The algorithmcan distinguish the active overload from lack of reactive power supply. The algorithm canindicate the information of voltage instability. This paper first deduces related formulas. Thealgorithm is simple and easy to be realized by microcomputer. The index can provide an exactreference for protecting the system against voltage instability or voltage collapse.