A new approach to design an observer for load current of UPS based on Fourier series theory in model predictive control system

• Published in: International journal of electrical power & energy systems Vol. 104; pp. 898 - 909
• Main Authors: Heydari-doostabad, Hamed, Ghazi, Reza
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.01.2019
• Subjects: 3-Phase inverter; LC filter; Load current observer (LCO); Luenberger observer; Model predictive control (MPC); Uninterruptable power supply (UPS); Model predictive control (MPC); Uninterruptable power supply (UPS); Load current observer (LCO); 3-Phase inverter; Luenberger observer; LC filter
• ISSN: 0142-0615; 1879-3517
• DOI: 10.1016/j.ijepes.2018.07.047

•Design observer with low computation burden, fast dynamic response, high accuracy.•Implementation of the proposed observer in model predictive control system.•Application of the proposed system to control the output voltage in a 3-phase UPS. In this paper, the model predictive control (MPC) system based on the state space is designed to generate the appropriate switching pulses for UPS inverters. The fast dynamic response and the capability in assessment of various cost functions are some advantages of the predictive control system. The equations concerning the control system show that the load current should be measured. To eliminate the required sensor for load current measurement a new observer is proposed, so the amount of cost can be reduced and the reliability of the system also enhanced. Ordinary observers like Luenberger in terms of stability and design encounter several difficulties. The proposed observer is developed based on Fourier series and instantaneous power theories. This observer is doing well in estimating the load current and renders superior performance regarding the dynamic behavior, stability and convergence. Furthermore, in this observer there is no need for any parameters adjustment and the load current is accurately observed using the measured output voltage and the filter current. To examine the operation of the system the necessary simulations and laboratory experimental results are provided on a 3-phase 220 V UPS. The obtained results are then compared to those obtained by the Luenberger observer.