Frequency-Adaptive Multiresonant LQG State-Feedback Current Controller for LCL-Filtered VSCs Under Distorted Grid Voltages

This paper combines the well-known linear quadratic Gaussian (LQG) control and frequency-adaptive resonators and presents a frequency-adaptive multiresonant LQG state-feedback current controller for LCL-filtered voltage-source converters connected to a distorted grid. The paper also provides a design guideline and procedure based on robust control criteria, which, in combination with the linear quadratic regulator technique, offers flexibility in the control structure and automatizes the design of the controller. The frequency-adaptive resonators, based on second-order IIR resonators and on an online tuning algorithm, and the robustness criteria considered for the design process offer robustness in the face of grid voltage disturbances. The controller is evaluated and validated in a 9-kVA voltage-source converter (VSC) setup configured as a rectifier.