Research On The Urban Rail Transit Permanent Magnet Synchronous Motor Control System Considering The DC-link Oscillation

ABSTRACT:In the urban rail transit, the permanent magnet synchronous traction drive system consists of the DC traction network, filter circuit, traction converters, Permanent Magnet Synchronous Motor (PMSM) and controller. Voltage and current oscillation on the DC-link of traction converter is easily stirred by traction network voltage fluctuation, by limited configuration of LC filter parameters, and by negative impedance characteristic due to certain traction control scheme, affecting system stability finally.Firstly, this paper comes up with PMSM model in d-q axis coordinate system, id=0and MTPA introduced as examples of the PMSM vector control methods. Then on the basis of the permanent magnet synchronous traction drive system model, the equation dealing with the output admittance of LC filter and the input admittance of converter-motor is induced, with which the close loop transfer function of the system is established. This paper analyzes the system stability with the capacitor, inductance, working point and the controller parameters changing by using Logarithmic-frequency criterion and Nyquist criterion.This paper also researches the DC-link oscillation inhibition strategy of permanent magnet synchronous traction drive system, and the basic principle is extracting the capacitor voltage and putting into the controller. Combined with the characteristics of the oscillation signal, the second-order band-pass filter is used to extract the oscillation signal. This paper researches the different injecting location of the compensation signal, which are reference current-based compensation (RCC) and reference voltage-based compensation (RVC), which both can improve the system performance. However, the speed sensitivity and the current sensitivity of q-axis caused by RVC are smaller than those caused by RCC.This paper sets up a simulation model of PMSM drive system in MATLAB/Simulink, verifies the effectiveness of RCC and RVC in solving the oscillation problem, and proves that the system robustness of RVC is better than RCC. And the7.5kW traction PMSM drive system experimental platform based on DSP28335is set up, which verifies the accuracy and feasibility of compensation.