Research On The Quality Monitoring System Of Train On-board Power Supply

Due to the complexity of railway signal system,signal equipment may be affected to malfunctions by many factors,among which electromagnetic disturbance is one of the important factors.With the development of some high-power on-board devices towards integration,the distance between devices in the vehicle is gradually reduced.Meanwhile,the amount of signal lines and power lines of devices are increasing,and the electromagnetic environment in the vehicle is becoming more and more complex.In such an electromagnetic environment,different forms and kinds of disturbance sources seriously affect the normal operation of equipment through different coupling ways.On locomotives and EMUs,the power of on-board signal equipment is mainly supplied by on-board battery pack and secondary power supply apparatus.Since there are many on-board equipment connected in parallel on the power bus,the common impedance coupling between them is obvious,that is to say,the disturbance emission from any equipment’s power port will be mapped to the others’ power ports via the bus,act as power supply noises.These noises are always characterized by high frequency components,which are different from conventional power quality parameters such as power harmonic and voltage fluctuation.Therefore,for vehicle-mounted signal power supply,its quality degradation mainly includes the high-frequency noise and transient phenomena such as surge pulse on the power line,which deteriorates the power quality on the power line,and then affects the normal operation of on-board equipment.This thesis analyzed the power quality of the on-board equipment’s power port,and designed a power monitoring system,which can acquire the basic power quality parameters and high-frequency noise on the equipment’s power port.According to the analyzed characteristics of the monitored noise,the source can be diagnosed efficiently,and the hidden riskto the equipment can be found to solve.The main contents of this paper include:1)Designed and manufacturedthe sampling interface circuit for the power quality monitoring system,and realized synchronous sampling of three parameters: port voltage,differential mode current and common mode current.2)Constructed a high-speed real-time voltage and current acquisition platform based on a NI PXIe data acquisition system.Based on virtual instrument technology,realized high-frequency noise detection and triggering with up to 8MHz bandwidth.Based on the FPGA co-processing,realized the time-frequency analysis of for transient and high-frequency disturbance.3)Based on variable sampling rate processing,different power quality parameters are measured at different statistical cycles and time slots.For example,the processing time slot of the judgment condition for triggering is 100μs(@20MS/s real-time sampling),while conventional power quality parameters such as voltage/current frequency,peak value,average value,RMS value and ripple are measured in a time window of 500ms(@1k S/s eqv.sampling)or 1min(@2S/s eqv.sampling).Multiple parallel data flow queues are adopted between each processing step,which realizes non-blocking between modules and ensures real-time performance.4)Realized continuous logging of the conventional parameters,and block storage of the time and frequency domain characteristic analysis results of captured high-frequency transient power supply noise.The logging viewing and playback programs are developed to provide a review toolkit.5)Designed several corresponding calibration tests,to implement the system functional verification and characteristics tests.