Digital control time-delays affected controller design of UPS inverter

Abstract:
In order to accurately design control system of the uninterruptible power supply (UPS) inverter, impact of the delay induced by digital control on the inverter performances is analyzed, and the design method of the inverter system controller considering the delay link is proposed. The mathematical model of the inverter system is established based on the state space averaging method, and the influence of the control delay link on the system stability is analyzed. Aiming at the single-phase UPS inverter power supply, the digital PID double-loop control technology is applied, and a singlephase UPS inverter control algorithm with easy parameter setting is obtained. The generalized Z-transformation theory is introduced to describe the delay link of digital control, and the model of the control system is improved. The modified design method of the digital PID controller parameters considering the delay link is given. Finally, experimental verification is carried out by Matlab/Simulink simulation and experiment. The experimental results show that the output voltage regulation accuracy of the UPS inverter control system based on the digital PID is less than 1%, and the THD (total harmonic distortion) is less than 2%. When the load end changes suddenly, the time for the system to return to normal is about 1.2ms. The output performance of the inverter system has been effectively improved.