Three-phase VSI supplied by renewable energy sources and controlled in voltage and power modes for grid-tie operation

This paper presents a strategy to control the terminal voltage produced by the voltage source inverter (VSI) as well as, the power delivery or absorbed from the grid independently of the local load. The terminal voltage is controlled by means of double cascade PI controllers. The resonant controller is placed in parallel to the classical voltage PI to improve its performance. To enhance the resonant structure dynamic response, an adaptive resonant controller based on the modification of their coefficients is used. Additionally, the paper exhibits the reactive power control at the grid changing the voltage amplitude synthetized by the VSI, and the active power control by means of the management of the angle of displacement between the grid voltage and the VSI terminal voltage. To the power control operates adequately two controllers in decoupled mode of operation (one with faster dynamic response and other with slower time response) are employed. To prove all statements proposed in this paper a set of experimental results are presented.