AN OPTIMAL CONTROL OF GRID CONNECTED MULTILEVEL INVERTER

electrical engineering

In this work a unified control strategy that enables both islanded and grid-tied operations of three-phase three-level inverter in distributed generation controlled by using multilevel space vector pulse width modulation technique, with no need for switching between two corresponding controllers or critical islanding detection. The proposed control strategy composes of an inner inductor current loop, and a novel voltage loop in the synchronous reference frame. The inverter is regulated as a current source just by the inner inductor current loop in grid-tied operation, and the voltage controller is automatically activated to regulate the load voltage upon the occurrence of islanding. Furthermore, the waveforms of the grid current in the grid-tied mode and the load voltage in the islanding mode are distorted under nonlinear local load with the conventional strategy. A unified load current feed forward with proposed control presents the detailed analysis and the proposed system. The effectiveness of the proposed control strategy is simulated by using MATLAB/Simulink software results.

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