Coordination control strategy for LLCL-filter based grid-tied inverter with indirect sliding mode power control and virtual impedance

Abstract

The LLCL filter is widely used in grid-tied inverter systems due to its small size, low cost and good attenuation for high-frequency harmonics. However, the LLCL filter resonance phenomenon and the wide range of impedance may compromise the system stability. In order to solve these problems, a coordination control strategy for LLCL-filter-based grid-tied inverter with indirect sliding mode power control and virtual impedance was presented. The LLCL filter design parameter has been carefully adjusted to ensure the system stable operation under a wide range of grid impedance variations. Comparing with the traditional proportional integral control system through simulation experiment, the output current harmonics of grid-tied inverter are analysed. The proposed strategy is feasible with good control accuracy and tracking performance.

Keywords

• power filters
• power control
• power grids
• electric current control
• invertors
• variable structure systems
• PI control
• harmonics
• stability
• electric impedance
• resonance
• coordination control strategy
• LLCL-filter based grid-tied inverter
• indirect sliding mode power control
• virtual impedance
• LLCL filter resonance phenomenon
• LLCL filter design parameter
• grid impedance variations
• output current harmonics
• proportional integral control system
• system stability