Model predictive control of inverters for both islanded and grid-connected operations in renewable power generations

As the penetration of renewable power generation units connected to the grid increases, high power quality and flexible power regulation have raised much concern. This study proposes a competitive model predictive control strategy for inverters in renewable power generation applications. The controller uses the system model to predict the system behaviour in each sampling interval for each voltage vector, and the most appropriate vector is then chosen according to an optimisation criterion. In islanded mode, the control objectives of the cost function are the a and β components of the voltage so that stable voltage for the local loads can be established. In addition, a fast re-synchronisation scheme is introduced to achieve smooth grid connection. After connected to the grid, a new prediction scheme is developed to fulfill flexible active and reactive power regulation. Furthermore, a switching frequency reduction scheme is presented to reduce switching losses, which are especially significant when considering efficiency for renewable power generations. The effectiveness of the proposed control strategy was tested by simulation using MATLAB/ Simulink and experimentally validated on a laboratory prototype.