小电容电机驱动系统的直流母线电压稳定性分析与控制

Analysis and Control of DC-link Voltage Stabilization in Small Capacitor Motor Drive System

对电机驱动系统中采用小电容的直流母线稳定性进行研究。由于在控制过程中驱动电机对直流母线呈现负阻抗的恒功率特性,系统可能存在不稳定的问题,采用阻抗方法对系统的稳定性进行分析。根据直流母线侧LC滤波器的输出阻抗和电压型逆变器——电机驱动系统的输入阻抗,构造出系统的传递函数,并得出相应的系统稳定工作条件,同时探讨阻抗参数对直流母线电压稳定性的影响。基于阻抗特性的分析,提出一种在不增加实际电阻的情况下,使直流母线阻尼虚拟增加的有源阻尼控制方案。该方法可在直流母线电容较小、常规系统稳定性条件不满足时仍能保证直流母线电压稳定,并将所提方法与无源阻尼控制进行对比分析。仿真和实验结果验证了该方法的有效性。

The stability of DC-link with small capacitance in motor drive system had been researched in this paper. Due to the constant power characteristic of negative impedance of the drive motor to the DC-link in the control process, the system may be unstable. Aiming at this problem, impedance method was used to analyze the stability of the system. The output impedance of DC-link LC filter and the input impedance of motor drive system were derived to construct the transfer function of the system, and the stability criterion were obtained. The influence of the parameters of both impedances on the stability of DC-link voltage was discussed. After analyzing the characteristics of impedance, an active damping control method based on virtual resistance was proposed to increase the damping of DC-link without additional real resistor. The control method is able to guarantee the stability of DC-link voltage when the capacitance is small and cannot meet the system stability requirements. The proposed method was compared with the passive damping control method in which a physical resistance was used. The simulation and experimental results verify the effectiveness of the proposed method.