Comparative study on Lyapunov-function-based control schemes for single-phase grid-connected voltage-source inverter with LCL filter

Abstract

This study deals with various Lyapunov-function-based control (LFBC) schemes proposed for a single-phase grid-connected voltage source inverter with LCL filter. Use of LCL filter causes resonance which may adversely affect the controller's stability. The conventional (CLFBC) scheme employing the inverter-side current guarantees the asymptotic global stability, but it is not able to damp the resonance. As a remedy to the poor resonance damping, the adoption of grid-current and capacitor-voltage feedback schemes have been investigated. Although the former offers a globally asymptotically stable system, it cannot improve the poor resonance damping. However, the CLFBC with capacitor-voltage feedback scheme not only preserves the global stability, but also improves the resonance damping substantially. The analytical equations of the closed-loop poles for each control scheme are provided which can be used to compute the pole positions and the damping ratio needed for a desired response. Furthermore, the effect of changing controller gains on the loci of closed-loop poles is also studied. Simulation and experimental results obtained from 3.3kW system demonstrate that the CLFBC with capacitor-voltage feedback scheme not only offers a global stability, but also leads to good quality sinusoidal grid current with reasonable total harmonic distortion and fast dynamic response.