Study On Measurement And Analysis Syetem For Power Quality In Suqian Area

With the far-ranging application of power electronics commutating technology and high power thyristor device in all kinds of electric equipments,the problem of power quality becomes more and more serious.The harmonics contamination affects the safe operation of power system and the normal supply of power in the industry and agriculture.In the Suqian area ,with many companies of mine,smelting,mechanical treatment,a mass of harmonics have been injected into power system.This paper analyses and compares the advantage and disadvantage of several analytic methods of the power quality. The principle diagram of power quality monitoring in the thesis can monitor and classify almost all of the important problems of power quality. The discrete Fourier transform algorithm can analyze time-domain's stationary disturbance signal effectively and confirm the signal's distributing in the frequency domain.Wavelets transform is used to aim at correlative problems of power quality.The results show that the transient and non-stationary signal can be detected and classified using wavelet transform,which can also used in denoising and filtering. So it is effective to analyze and detect stationary and non-stationary disturbance by the integration of the above two methods.Aiming at the demand of power department and the practical applications,we put forward a kind of integrated supervisor which can measure and analyze power quality issues(admissible deviation of supply voltage,permissible deviation of frequency,harmonics in public supply network,voltage fluctuation and flicker,admissible three-phase voltage unbalance factor and disturbance).Such system is composed of the measure device on substation terminal and the software platform of the supervisory center. The design principle has been presented for the device of substation distributed power quality monitoring and controlling.The high performance harmonics inspecting devices have been realized by the high performance DSP and the software has been programmed.A high-speed and high-precision distributed data acquisition and processing system is designed based on DSP in this paper.The synchronous data sampling of the supervising system is realized by multi-channel collection retaining and A/D transformation circuit.Data between the master and slave DSPs can be transferred by dual-port RAM.According to the special characters of the electronic power system,the algoritllnl implementation of digital signal processor is presented.The software development adopts blocking design method.It includes three blocks:interface block,communication block and database block.It becomes possible that analyze,store and manage a great deal of measure data of power quality by using IBM DB2 database. This software can synthetically statistics,figure displaying,report print and so on,aim at the many issues of power quality.The system can provide comprehensive and accurate recording data for all kinds of issues of power quality.Besides,the software realizes various functions,such as various displays of results,database management and so on.The effective methods and measures for deleting the harmonics have been discussed.