| The electrified railway has large transportation capacity,high speed and high safety.It is the main mode of transportation in China,developing rapidly in recent years.However,the problem of neutral section restricts the advantages of the electrified railway with single-phase AC 25kV/50 Hz traction power supply system,and the speed loss caused by the power-lossing of Electric locomotive reduces the operating efficiency for the high-speed railway and may lead to the heavy haul railway parking on the ramps.At the same time,there are problems such as transient over-voltage and over-current during phase switching when passing neutral section,which would affect the safety and life of the vehicle equipment.Firstly,the topology of uninterruptible passing scheme for neutral section with circuit connected to the series winding is proposed.Based on the topology of the circuit,the working principle of uninterruptible passing scheme for neutral section is introduced.The "vehicle-net" equivalent circuit of neutral section for its transition zone and neutral zone where the train pantograph is located is analyzed,and the control targets of the different positions of the pantograph are clarified,that is,the current transfer control in the transition zone and the voltage phase shift control at variable frequency in the neutral zone.Next,the judgment basis of the inverter switching between the two control modes is given.Several common current control methods are introduced,and among them,it is determined that the d-q decoupling current control or quasi-PR current control is used as the current control methods.Then,the parameters for current transfer control are calculated.The reference voltage construction method of the voltage phase switching in the neutral zone,based on series topology,is deduced and modified.The double closed-loop control strategy of current inner loop and voltage outer loop is adopted by voltage control.The mathematical models are analyzed and the control parameters are calculated.Finally,based on Matlab/Simulink platform,the traction power supply system model and the uninterruptible passing neutral section model are built.The control strategy of the current transfer in the transition zone and the voltage phase switching in the neutral zone are simulated to verify the effectiveness of the two control modes.At the same time,the high-voltage test platform is built and the test scheme for uninterruptible passing neutral section is designed in the high-voltage laboratory to simulate the on-site operating conditions.The rationality of the judgment for the two control modes of inverter switching and the strategy of current transfer control in the transition zone and voltage phase switching control in the neutral zone is confirmed by the test results. |
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