A repetitive-based controller in stationary reference frame for D-Statcom in unbalanced operation

The paper presents a repetitive-based controller for a three-phase three-wire distribution static synchronous compensator (D-Statcom) aimed to compensate reactive power and unbalanced harmonics in the general case of distorted and unbalanced source voltages and load currents. The repetitive scheme involves a negative feedback structure and is aimed to exclusively compensate odd harmonics, thus, reducing the possibility of reinjecting unnecessary distortion into the system. This is in contrast to other repetitive-based works that use traditional positive feedback structures aimed to compensate all harmonics. Therefore, it is expected that the proposed scheme generates cleaner responses in applications of power electronic systems containing mainly odd harmonics. A key observation here is that, there exists an equivalent expression for the negative feedback repetitive scheme in the form of a bank of resonant filters tuned at odd harmonics, therefore the repetitive scheme is in agreement with the well known internal model principle. It is shown that, the proposed controller has a fairly simple implementation. Experimental results in a 2 KVA prototype are provided to illustrate the merits of our solution