抛物线PWM电流控制稳定性分析

On the Stability of Parabolic PWM Current Control Technique

抛物线脉宽调制(pulse-width modulation,PWM)电流控制方法采用一对特定的抛物线函数曲线,以控制电压型变换器电流跟踪误差的正负峰值和PWM开关时刻,实现与滞环控制相媲美的高精度、快速电流跟踪控制,并能保持开关频率基本恒定。但该方法也存在与峰值电流控制类似的动态稳定性问题。从理论上详细分析抛物线PWM电流控制方法在各种工况下的动态稳定性以及影响稳定性的因素,导出PWM占空比与稳定性及动态调整时间之间的关系,结果表明:抛物线法电流控制满足全局动态稳定性条件。仿真和实验结果验证了上述结论的正确性。

The parabolic pulse width modulation （PWM） current control method employs a pair of specified parabolic PWM carders, a positive one and a negative one, as to directly control the peak of current tracking error and the switching instants in a voltage-source converter （VSC）. Compared with the traditional hysteresis control, the proposed parabolic current control scheme features a reasonably fast response, outstanding performance of average current tracking as well as an almost constant switching frequency. However, the parabolic control method may also subject to dynamic stability issues similar to the peak current control method. This paper analyzed the convergence and stability behaviors of the parabolic control method as well as relative influential factors under different operating conditions, and the relationship between the PWM duty ratio and the dynamic setting time of current tracking error was furthei deduced. The research indicates that the parabolic control method can well satisfy the specific conditions of global stability, and both simulation and experimental results verify validity and correctness of the above conclusions.