In this paper, a new control structure is proposed for grid-tied photovoltaic (PV) systems where the dc bus voltage is regulated by the dc/dc converter controller, whereas the maximum power point tracking (MPPT) function and the power flow control are embedded into the dc/ac converter controller. A PV voltage-regulation is designed to build the linkage between MPPT function and power flow control. In this way, the dc/dc converter controller and the dc/ac converter controller are decoupled, which naturally provides the dc bus voltage protection. In particular, an uncertainty and disturbance estimator (UDE)-based current-mode controller (CMC) is proposed for accurate voltage regulation of the dc/dc converter. And a bounded-voltage power flow control strategy is proposed for the dc/ac converter to improve the existing UDE-based robust power flow control for ac voltage protection. The effectiveness of the proposed method is experimentally validated in a lab-environment grid-tied PV system platform with the fault ride-through capabilities. In addition, simulation studies are also provided to demonstrate the need of the PV voltage-regulation between MPPT and power flow control, and the advantages of the bounded-voltage design in the power flow control.
- Bounded-voltage power flow control
- dc bus voltage protection
- fault ride-through
- grid-tied photovoltaic (PV) systems
- uncertainty and disturbance estimator (UDE)