低开关频率下三相PWM整流器电流解耦控制研究

Current decoupling control strategy for three-phase PWM rectifier at low switching frequency

在中高压大功率PWM整流器中,功率器件工作在较低开关频率下,这造成了PWM发波和采样延时增加,使得控制时dq轴电流分量交叉耦合严重,不利于系统控制。为解决这一问题,基于传递函数阵模型,定义耦合度函数对系统耦合进行分析。分析表明,随着开关频率的降低,系统耦合愈加严重,传统解耦控制已无法适用。结合串联解耦和状态反馈,提出一种新型的解耦控制策略。该策略在不同的开关频率下,均能有效地消除系统的交叉耦合,实现dq轴电流的独立控制。同时,解耦后系统得到了简化,利于控制器设计,提高系统的控制性能。实验结果验证了理论分析的正确性与所提解耦控制策略的可行性。

The switching frequency of power devices is reduced to improve the capacity of high voltage PWM （pulse-width modulation, PWM） rectifier. However, this leads to heavy cross coupling between the dq current components, and it is not conducive to system control. In order to overcome this problem, the coupling degree function was established to analyse the coupling degree of the system, which is based on the transfer function matrix model. Analysis shows that with the decrease of the switching frequency, the coupling of the system becomes so serious that the traditional decoupling control is not suitable any more. And a novel decoupling control strategy was proposed, which is based on series deeoupling and state feed- back. Cross coupling of the system was eliminated at different switching frequencies, and independent con- trol was achieved for the dq current components. At the same time, the decoupling system was simplified, which is beneficial to controller design, and the control performance of the system was improved. Experi- mental results verify the correctness of the theoretical analysis and the feasibility of the proposed decou-pling control strategy.