Large-signal stabilization of AC grid supplying voltage-source converters with LCL-filters

A robust tool compensating stability problems occurring in interconnected voltage-source rectifier loads with input passive LCL filter is developed. An LCL filter can reduce the harmonics introduced by PWM switching frequency and guarantee low currents THD using small component values comparing to the well-known L filter solution. Nevertheless, the additional poles introduced by the LC part induce resonance in the system and may lead to instability. To deal with this issue, a large-signal stabilizing supervisor based on the direct Lyapunov theorem is proposed in this contribution. The use of Lyapunov theory allows constructing feedback stabilizing signals which keep both the damping performance and robustness of the proposed stabilizer. The stability phenomenon is highlighted and the effectiveness of the proposed solution is validated by experimental results.