Finite-time composite control scheme for three-phase four-leg inverter under variable operating conditions

Abstract

Three-phase four-leg inverters widely used in microgrid can effectively provide the power for the non-linear/unbalanced loads. Here, the non-linear composite controller is proposed for three-phase four-leg inverter system under [inline-formula] reference frame by integrating a higher order sliding mode observer and finite-time control technique. The observer adopts the soft sensing manner to feedforward compensate external disturbances caused by current variation of AC bus node, which relaxes some physical constraints. Meanwhile, the higher order sliding mode observer realises the decoupling of the inverter system, which paves the way for the construction of the non-smooth finite-time control law. Finally, the simulation results with PI comparison illustrate the feasibility of the proposed method for improving the robustness, stability, and rapid recovery capability of system.

Keywords

• invertors
• control system synthesis
• robust control
• feedforward
• observers
• distributed power generation
• nonlinear control systems
• variable structure systems
• machine control
• higher order sliding mode observer
• finite-time control technique
• ac bus node
• finite-time control law
• three-phase four-leg inverters
• nonlinear composite controller
• four-leg inverter system