Self-Decoupled Dual Sequence Current Control of D-STATCOM Under Unbalanced Grid Voltage

For the distributed static synchronous compensator (D-STATCOM), the sequence extraction (SE) is generally necessary in dual sequence current controls (DSCCs) based on double synchronous reference frame (SRF), when the D-STATCOM suffers from unbalanced grid voltage. However, the SE will narrow down the control bandwidth and increase the control complexity. In this article, the influences of not using SE on the DSCC are analyzed. On this basis, a self-decoupled dual sequence current control (SDDSCC) is proposed. Accordingly, a novel control parameter design method of SDDSCC is also proposed. The SDDSCC can achieve two types of decoupling. One is the positive and negative sequence current decoupling in double SRF without SE. The other is the
dq
current decoupling without specialized
dq
decoupling method. Due to not using SE and specialized
dq
decoupling method, the control bandwidth of the proposed SDDSCC is larger, and the current dynamic response is faster, and the control structure and implementation are simpler. Besides, the control parameter is easily determined by the novel control parameter design method, without multiple iterations of design. Experimental results verify the proposed scheme.