| When the subway train is running,the auxiliary converter is responsible for supplying power to various auxiliary equipment such as ventilation motors,compression motors,air conditioners and others,which is an indispensable part of the train.When the auxiliary converter is disturbed by the DC input voltage and load disturbance,instability will appear on the DC side,which is manifested in the voltage oscillation of the supporting capacitor on the DC side,which affects the safe operation of the train.Based on the research project of Zhuzhou CRCC Times Electric,this paper studies the instability mechanism and the solving strategy of the DC side instability of auxiliary converter.The main research work includes:First,the dynamic model of three-phase inverter is established.According to the structure and working principle of three-phase inverter,the dynamic mathematical model of circuit in ABC coordinate system,?? coordinate system and dq coordinate system is established,and the mathematical relationship between the circuit parameters in different coordinate system is obtained.The analysis of discontinuous system is transformed into that of continuous system.Second,the control strategy of three-phase inverter is studied.The double closed-loop control strategy based on dq coordinate system is analyzed.The closed-loop control system model of three-phase inverter is established.The controller parameters are designed.The dynamic performance and stability of the system are analyzed and verified by simulation.By cascading the three-phase inverter which under the closed-loop control and the LC input filter,the stability performance of the cascaded system is tested by simulation.The results show that under the closed-loop control,the three-phase inverter that can operate independently and stably will oscillate on the DC side when cascaded with the LC input filter.Third,the DC-link instability mechanism and its suppression strategy of the auxiliary converter system are studied.The stability of the cascade system composed of the LC input filter and three-phase inverter is analyzed when the three-phase inverter is equivalent to constant power load.The stability criterion is deduced according to the damping coefficient,and it is concluded that the negative impedance characteristic of the three-phase inverter is the reason for the system instability.Based on the impedance analysis method,the stability of the auxiliary converter system under dq feedforward decoupling control is studied.The factors which affecting the system stability are analyzed,including the output power of the threephase inverter,the parameters of the DC side LC input filter,the parameters of the steady-state operating point of the system,and the structure and parameters of the three-phase inverter controller.The effectiveness of reducing the inductance of LC input filter and reducing the PI parameters of controller on DC-link oscillation suppression is analyzed and verified by simulation.A control algorithm with adaptive DC side capacitor voltage disturbance feedforward is designed to suppress DC-link oscillation,changing the controller structure and making the system stable.The effectiveness of the algorithm is verified by simulation.Finally,the DC-link oscillation suppression measures are verified by experiments.On the1 k VA low-power experimental platform,the effects of three-phase inverter output power,DC side filter inductance,DC side input voltage and PI regulator parameters on DC-link oscillation are tested,and the feasibility of introducing adaptive DC side capacitor voltage disturbance feedforward control algorithm to suppress DC-link oscillation is verified.The effectiveness of the DC-link oscillation suppression algorithm is further verified on the product prototype of the auxiliary converter with 750 V input and 220 KVA capacity of Zhuzhou CRCC Times Electric. |
PDF Full Text Request