Coupling Analysis on Current Control at Low Switching Frequency for the Three-Phase PWM Converter Based on RGA and a Novel Output Feedback Decoupling Method

With the increase of the rated power, the sampling and switching frequencies of the high-power pulse-width-modulated (PWM) converter tend to be lower so that a challenging scenario is arising in current control system design. This strongly affects the stability and control performance of the current control system due to the undesirable dynamic coupling of the dq current components. From this perspective, this paper presents a systematic procedure for accurately evaluating the coupling of current control systems, which is based on static and dynamic relative gain array (static relative gain array and dynamic relative gain array). Unfortunately, the dynamic coupling of these systems is so serious at low-frequency band, and the parameter variation makes it easier for these systems to lose stability, when a classical proportional integral regulator with feed-forward decoupling or nondecoupling is employed. Hence, a novel output feedback decoupling control method is proposed, which is based on linear control for multiple-input-multiple-output system. Considering the amplification of the first-order differential, the decoupling unit is further improved by replacing the differential with high-pass filter. Experimental results in a small-power converter are presented to support the theoretical analysis and demonstrate the feasibility of the proposed method.