Adaptive Logarithmic State Feedback Control With Quasi One-Switching-Cycle Response Characteristic for Three-Phase Inverter

It is very challenging to improve the dynamic response speed and stability of digital control system, due to the inherent defects of digital controller such as quantization effect and delay in sampling step. This brief proposes an adaptive logarithmic state feedback control (ALSFC) for three-phase grid-tied and off-grid inverters which can be specially applied in digital control system. In the state feedback control system, the feedback coefficient is designed as adaptive logarithmic function of the difference value between the actual state variable and the reference, so as to make the closed-loop system converge to new equilibrium point after about one switching cycle. Comparative experiments verify that the proposed control, carried out by digital controller, has the dynamic response characteristics of quasi one-switching-cycle with its response speed is significantly higher than that of PI control, and has good stability with lower THD.