Research And Realization Of Intergrated Test Instrument For The Power Quality Of Urban Rail Supply System

With the rapid development of urban rail transit,the interaction between urban rail transit and urban distribution network is increasingly strengthened.Subsequently,power quality problems of urban rail power supply system have emerged.It is essential that important parameters including ripple coefficient,voltage fluctuation and flicker,harmonic and reactive power shall be measured to solve the power quality problems of urban rail power supply system and its impact on urban power network.Therefore,partial research and development work of integrated tester of urban rail power quality has been accomplished in the paper.The specific work is listed as follows.First of all,external power,traction supply,power lighting and power supervisory in urban rail transit power supply system have been introduced among which the traction supply system has been presented explicitly.The illustration is about the supply power mode,operation mode and principle and structure of rectification of urban rail power supply system.Characteristics of the harmonic produced in the rectification system have been pointed out.Secondly,the paper gives an analysis and discussion of several prominent power quality problems of urban rail such as ripple coefficient,voltage fluctuation and flicker,harmonic and reactive power.And the corresponding algorithms have been analyzed combining with their respective characteristics.A type of simplified algorithm has been applied to calculate ripple coefficient due to the influence on direct current exerted by ripple.The application of square demodulation method recommended by IEC is capable of testing the voltage fluctuation and flicker quickly and accurately in consideration of the phenomenon of voltage fluctuation and flicker.An improved FFT algorithm on basis of Kaiser Window has been used in view of the characteristic that the urban rail harmonic power supply system contains much certain sub-harmonic.The amplitude of characteristic sub-harmonic can be exactly figured out through this kind of algorithm.Based on the discussion about different definitions and characteristics of non sinusoidal reactive power,the reason of overcompensation of reactive power compensation calculation has been analyzed;the the validity of the definition of reactive power in IEEE1459 standard has been discussed and the preparation of the relevant procedures has been completed.Thirdly,software and hardware design of urban rail integrated test device has been achieved relying on the LabVIEW virtual instrument software platform while investigating the algorithm.In the software design,the functions of signal acquisition and filtering,the measurement of basic parameters,the measurement of ripple coefficient,the measurement of voltage fluctuation and flicker,the measurement of harmonics and reactive power have been accomplished.In the hardware design,the designation of the conditioning circuit and the selection of the acquisition card,the current clamp and the industrial control computer and the system debugging have been realized.Finally,the system experiment is carried out in the urban rail laboratory to verify the feasibility of the instrument and lay a foundation for further engineering applications.