Design In System About Power Supply From Single-Phase To Three-Phase In The Railway

There are a large number of various types of electricity load along the electrified railway, However, different electrical equipments require different powers. those electrical equipments operate and maintain in the electrification of railway between the beginning of construction of the electrification of railway and the entire operation it is directly related to the safety and stable operation of the electrical railway.Firstly, This paper analyzes the pulse rectifier which have two-level and four-quadrant mode. according to the phase relationship between the source current and the voltage, we can divided the four quadrant converter into the state of rectifier, the state of inverter, the state of reactive power compensation, and the state of any operation.No matter what the state, the circuit structure of the pulse rectifier is the same, and therefore the mathematical model is also the same, so we use mathematical models to analyze the control method of the four-quadrant converter, which adopts the control scheme of the transient current, the feedback the inductor current of network's side is to stabilize the DC voltage and to make up for shortcomings of the poor dynamic response and to achieve better performance of transient tracking.Designing and calculating the inductance of AC side, the purpose is to filter harmonic currents in the catenary and meet the following performance of the transient current control, and the purpose of using capacitors is to reduce the ripple voltage of DC rectifier and limit the DC voltage ripple when the load is mutation, so we select the capacitor, due to the the advantages heavy and chemical technology can reduce rectifier harmonic pollution in the catenary of dual technology we use the it.Using the software of Matlab to simulate the feasibility of pulse rectifier device and reduce the harmonic pollution in the catenary. The Voltage source inverter is to convert the DC power into three-phase AC power, to Provide power for the three-phase Symmetrical load or asymmetric load, however in order to maintain the three-phase symmetrical voltage source, we have to adjust the time by feedback control.Therefore, we analyzed the Voltage type inverter mathematical model In the three-phase stationary a-b-c coordinates and two-phase synchronous rotating d-q coordinate, According to the characteristics of the characteristics of its mathematical model, we choice methods to control it, especially the model in the d-q model coordinate system, because of the Coupling relationship at the times of making feedback control, we must be decoupled it. Since the voltage type inverter obtain DC component by decomposition in the d-q Coordinate system, so it easy to control. according to some successful examples, we adopte Control methods in the d-q coordinate system.Using the PI control to adjusted tracking and determine the Control method in unbalanced loads, using the double-feedback control of the positive sequence and negative sequence, due to the symmetry of the structure, the system structure and the PI controller have the same parameters between the positive sequence and negative sequence in the feedback control, so it provided convenience in the process of design, reduce the computational difficulty.Therefore, we designed two- loop control based on the Voltage outer loop and current inner loop, the Voltage outer loop is to determine the voltage value of AC, however the inner loop is mainly function to achieve the purpose of the fast-track the current reference, and realize fast following, using design method of PI parameters with pole assignment, of the parameters, establish the direct relationship between the. indicators of expected performance and the PI controller and the system structure.Using the matlab software of simulation system to built the AC-DC-AC voltage inverter control model of the 17.5kVA. conducting the simulation of the control system under the symmetrical and asymmetrical load, under the inductive, capacitive, resistive load, and between a wide range of verification of series and parallel.