Study on LCL-type Grid-connected VSC Based on Optimized Active Damping with NBPF for SMES System

The superconducting magnetic energy storage (SMES) is with the features of quick system adjustment and transient stability enhancement for grid-connected voltage source converter (VSC). To suppress the resonant peak generated by LCL topology, the active damping method utilizing internal model is employed. But the active damping could result in noise amplification and the system delay, which will affect the damping effect. Thus the multi-loop feedback control in static coordinate system is established by using second-order generalized integral, and the negative band pass filter (NBPF) and the delay compensation with optimized Newton interpolation are presented to reduce the resonance peak. And the quasi-proportional resonant (QPR) regulator is adopted for inner current loop to realize the sinusoidal current without static error, and also the quasi-direct power control (QDPC) based on the instantaneous power model is employed in the outer current loop. Through simulation and experimental verification, the presented strategy in this paper significantly reduces the total harmonic distortion (THD) of line current, and realizes unity power factor. Additionally, it improves the power quality with well dynamic and static response characteristics.