Improved Predictive Current Control for Grid Connected Inverter Applications with Parameter Estimation

This paper proposes predictive current control strategy based on predictive direct power control strategy for grid connected three phase voltage source inverter applications. The Proposed strategy uses a symmetrical 4+4 voltage vectors´ sequence which selects two effective and two zero voltage vectors and determines concatenated voltage vectors´ sequence. The time derivatives of currents for each of selected voltage vectors are used in order to calculate application times that minimize objective function. In this way, constant switching frequency and high quality currents are obtained. The drawback of predictive current control is the mathematical based approach, which is sensitive to parameters changes. A real time parameter estimator is added in order to estimate the filter inductance and equivalent series resistance. The estimation is achieved using the least square estimation method, and as a result, the robustness of the control system for filter parameter changes is improved.