Research On Prototype For Active Protection Against Low Frequency Conducted EMI

With the rapid development of China’s high-speed railways,the safety and reliability of high-speed trainsets had received widespread attention.The onboard train operation control equipment has an important influence on the operational reliability and safety of high-speed trainsets.With limited space on high-speed trainsets,the complete isolation between strong current and weak current electric vehicle equipment and its wiring is difficult.Conducted electromagnetic interference from strong current equipment can easily couple to weak current sensitive equipment through power or signal cables,causing electromagnetic interference to the onboard train operation control equipment and threatening the safe operation of trains.Filtering is an effective anti-interference technology,however traditional filtering technology is based on the difference in frequency between the useful signal and the interference signal and filtered out the interference signal outside the useful signal band to achieve the purpose of interference suppression.However,traditional filtering technology cannot effectively filter out the electromagnetic interference signal in the same frequency band as the useful signal.To solve the above technical difficulties,this paper focused on low-frequency conducted interference that affects the onboard train control equipment of high-speed trainset,and developed an active protection hardware platform that can effectively filter out the electromagnetic interference signals with the same frequency by using advanced signal processing techniques,and completed the laboratory validation of the filtering effect of the platform.The main tasks are as follows.(1)An adaptive filter was used as a solution for the same frequency conducted interference problem,and the step factor and iteration parameters of the classical LMS algorithm are optimized to increase the convergence speed and improve the steady state performance of the classical algorithm and reduce the complexity of the implementation of the algorithm.(2)An active interference protection simulation platform for same-frequency conducted interference was built through the MATLAB software platform,and the short-time Fourier transform was used to analyze the frequency components of the interference signal within a certain time window and generate the reference signal of the noise at the corresponding frequency.The parameters of the optimized LMS algorithm are simulated and debugged to achieve the optimal estimation and real-time suppression of the interfering signal,and the performance of the algorithm is verified by simulation results.(3)The active protection algorithm for same-frequency conducted EMI selects a DSP chip that meets the requirements of the algorithm as a carrier for verification,and the test verification platform for active protection against conducted interference with the same frequency as the useful one is designed and implemented,and the effect of interference protection of the platform was verified by experimental test.The theoretical analysis and validation tests show that the active protection algorithm for the same-frequency conducted EMI proposed in this paper can achieve an electromagnetic protection effectiveness greater than 7d B.By reasonably selecting the DSP hardware platform,a low-cost and highly flexible solution for active protection against same-frequency conducted interference in onboard train operation control equipment can be realized.Furthermore,the algorithm proposed in this paper can also be ported to digital signal processing platforms with higher performance,thus providing more general practical engineering applications.