Passivity-based decoupling control strategy of single-phase LCL-type VSRs for harmonics suppression in railway power systems

Abstract

High-frequency harmonics, produced by traditional single-phase voltage source rectifiers (VSRs), frequently lead to high-frequency resonances in railway power systems. The LCL-type filter is well-suited for suppressing such harmonics. To improve the performance of single-phase LCL-type VSR systems, this paper proposes a nonlinear passivity-based decoupling (PBD) control strategy, which improves the power quality of grid-connected systems and is highly robust. The Euler-Lagrange (EL) mathematical model of the single-phase LCL-type VSR system is established in a synchronously rotating frame, decoupling the active- and reactive-power controls. Based on this model, the passivity of the single-phase LCL-type VSR system can be analyzed, and the AC current of the system can be regulated by the proposed PBD controller by adding extra damping terms. A proportional-integral (PI) regulator is used to eliminate static errors in the dc-link voltage. By using the proposed control strategy, the single-phase LCL-type VSR system can have an improved quality of current injected into the traction power grid, a better dynamic performance, and a larger stability margin. The advantages of the proposed control strategy are demonstrated by simulations and experiments.