The Reasearch On Hybrid Type Of Power Filter For Electrified Railway

With the development of electrified railway, electric traction loads increase quickly . The safe and economic operation of power systems and of other users in points of common coupling is badly influenced by the harmonic which is produced by electric traction loads. It is more and more urgent to eliminate power system's harmonic and improve power factor. Therefore, the research on harmonic elimination scheme for electric traction load is becoming a hot subject at present.It is an ideal scheme to suppress harmonic of electrified railway by using hybrid power filter consisting of passive power filter and active power filter at present. Because passive power filter can endure higher voltage level and reach bulkier capacity, and active power filter has good dynamic compensating performance and can compensate reactive power continuously. In order to reduce active filter rate ofhybrid power filter, this thesis presents a novel hybrid power filter topology——Resonant Impendent Type Hybrid Active Filter (RITHAPF).This thesis introduces several common harmonic current detecting methods used in APR The simple arithmetic and realization,little delay and quick response velocity of the harmonic current detecting method based on the phase distinguishing technology are improved by theoretical analysis. The detecting method is on fit for harmonic current detecting of the electrified railway.In order to guarantee dynamic compensation performance of APF, Reasonable and simple delay solution is critical for further using of APF. So, this thesis presents delay solution based on LMS adaptive filter against Shunt Active Power Filter(SAPF). And then, By simulating for delay solution presented in this thesis, the result show that delay solution presented has excellent compensation effect.To verify the feasibility of the harmonic current detecting method and harmonic compensation characteristic of RITHAPF, This thesis modeled and simulated for RITHAPF used in the electrified railway traction supply system in MATLAB7.0. The simulative result shows that RITHAPF can filter a majority of the electric locomotive harmonic current and lower THD of the source current. Furthermore, RITHAPF possesses excellent dynamic performance and can track the changes of compensation current in real-time. The control strategy of RITHAPF is simple and hasn't the problem of stability. So, RITHAPF has good application prospects in harmonic suppress of electrified railway.