Complete state feedback control of quasi direct AC/AC converter

In this paper, a new regulator structure for the input stage of quasi-direct AC/AC power converter based on the multivariable state feedback theory is presented. The cascade control structure consists of the inner loop current regulator and the outer loop DC link voltage regulator. The current regulator ensures true unity power factor operation and the DC link voltage regulator incorporating the integral control regulates the DC link voltage with the high dynamics and the zero steady state error. The internal controller is implemented in the synchronous reference frame and the state feedback is designed to enable fully decoupled control of each current component. In order to evaluate the overall performance attributes of the proposed state feedback regulator, its performance is compared with the PI regulator and the PI regulator with power estimation feedforward. All the above control schemes were implemented in a digitally controlled 7.5 kW prototype of the quasi-direct AC/AC power converter. Simulation and the experimental results confirm the superior performance of the proposed state feedback regulator. A detailed description of the system eigenvalues and eigenvector allocation is given