Model-free subspace-based control scheme for grid-connected voltage source inverters

In this paper, both model-free subspace-based LQG control and H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> control schemes are used to investigate the tracking control performance and robustness of grid-connected voltage source inverters (VSIs). The proposed approaches do not require any identification or other modeling process. The controller can be directly derived from the experimental inputs/outputs measurements. Both the subspace-based LQG controller and H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> controller are recursively designed. Simulation results show subspace-based LQG controller has a better tracking control performance than subspace-based H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> controller, whereas, H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> controller has stronger robustness than LQG controller.