Admittance-Dissipativity Analysis and Shaping of Dual-Sequence Current Control for VSCs

This article analyzes the admittance-dissipativity of dual-sequence current control for grid-connected voltage-source converters (VSCs). The output admittance model of dual-sequence current control is first developed in the stationary reference frame by using complex vectors. Impacts of digital filters used within current control and voltage-feedforward (VFF) control loops, and of the delay compensation at the fundamental frequency, are then evaluated. It is found that the cascaded use of sequence-decomposition filter (SDF) and the low-pass filter (LPF) in the VFF control loop adds a nondissipative region in the output admittance, and the fundamental-frequency delay-compensation further worsens the dissipativity. An analytical design method for the LPF is then developed to mitigate the nondissipative region, which lowers the instability risks and improves the stability robustness of dual-sequence current control under different grid conditions. Lastly, simulations and experimental results corroborate theoretical analyses.