Control And Modulation Algorithm Of Railway Electrical Traction Converter

With the successive operation service of Beijing-Tianjin, Wuhan-Guangzhou, and Beijing-Shanghai High Speed Railway(HSR) special for passenger transport, Chinese HSR has been developing fast. As the key technology of HSR Electricity Multiply Units (EMU), research focused on control scheme of AC electrical traction system is significant for theory and engineering design.This paper is supported by national science and technology support projects, and the electrical traction converter of high-speed EMU is the research objective. Focused on the harmonics characteristics of AC side rectifier, control and modulation algorithms of AC side rectifier, control algorithm of traction motor for lightweight design DC-link of traction converter and so on, the theoretical research has been carried out in depth. This work can not only provide the theory reference for engineering design, but also lay a reliable foundation for railway traction control system, which is the key technology of high-speed EMU. Modulation algorithms of AC side rectifier consist of Carrier-Based Pulse Width Modulation (CBPWM) and Space Vector Pulse Width Modulation (SVPWM) for single-phase three-level rectifier, and control algorithm of traction motor for lightweight design DC-link of traction converter is the beat-less control algorithm of traction motor while LC resonant filter is discarded in the DC-link of traction converter. Specific contents are as follows:In the field of control algorithms for single-phase converter: the operation principle and mathematical modeling of single-phase two-level and three-level rectifier is discussed. On basis of this, firstly, two close-loop controllers of the adopted rectifier are designed and derived from the classical control theory point of view. Secondly, transient current control and predictive current control schemes are analyzed and compared with each other, which are widely used for control of single-phase rectifier. At last, active current and reactive current decoupled control in the d-q synchronous reference frame is adopted for the rectifier under the fluctuation condition of power supply voltage, which is verified by computer simulation.In the field of the line current harmonics for single-phase converter: to study harmonic characteristics of the line current, the lower and higher order harmonic characteristics of the line current are derived and analyzed theoretically, respectively. The influence of the harmonics of power supply and the line current and DC-link voltage of the adopted rectifier is analyzed. The low order and high order harmonic elimination schemes is shown, which are verified by computer simulation, respectively.In the field of CBPWM algorithms for single-phase three-level rectifier:the research object is single-phase three-level unipolar CBPWM algorithm. Considering the unbalance problem of neutral point voltage for three-level rectifier, two single-phase three-level unipolar CBPWM algorithms based on Zero-Sequence Voltage Injection (CBPWM-ZSVI-I and CBPWM-ZSVI-II) are proposed firstly, and the design method and value range of the zero-sequence voltage are derived in details. On basis of this, when zero-sequence voltage is the maximum value, two single-phase three-level unipolar CBPWM algorithms based on Zero-Sequence Maximum Voltage Injection (CBPWM-ZSMVI-I and CBPWM-ZSMVI-II) are shown, respectively. At last, these four CBPWM algorithms are verified and compared by computer simulations and experimental tests, respectively. These four CBPWM algorithms can control the neutral point voltage effectively.In the field of SVPWM algorithms for single-phase three-level rectifier:the research object is single-phase three-level SVPWM algorithm. Considering the unbalance problem of neutral point voltage for three-level rectifier, three single-phase three-level SVPWM algorithms are proposed. Theoretical analysis and design of three SVPWM algorithms are shown in details. Neutral point voltage control function is embedded in the three SVPWM algorithms. The relevance and consistency between the three SVPWM and CBPWM algorithms are proved theoretically. The effectiveness and feasibility of the three SVWPM algorithms are verified by computer simulations and experimental tests.In the field of beat-less control algorithm for traction inverter-motor:voltage fluctuation with twice the line frequency comes out at DC-link of traction converter while LC resonant filter is discarded in the DC-link of traction converter, which causes beat phenomenon of motor. The beat harmonics frequency characteristic of motor stator voltage is derived theoretically. Beat-less control algorithms based on One Cycle Control (OCC) theory are proposed for multi-PWM region and square wave control region, respectively. These beat-less control algorithms are both verified by computer simulation.In order to verify the effectiveness and feasibility of these proposed algorithms, single-phase three-level rectifier experimental prototype in low power is designed, and inverter-motor experimental prototype based on OCC Controller is designed, too. The hardware and software design methods of these two prototypes arc shown. There are many experimental tests for these two prototypes.