Comparative Study of Discrete PI and PR Controls for Single-Phase UPS Inverter

• Main Authors: Parvez, Mohammad, Elias, Mohamad Fathi Mohamad, Rahim, Nasrudin Abd, Blaabjerg, Frede, Abbott, Derek, Al-Sarawi, Said F.
• Format: Article
• Published: Institute of Electrical and Electronics Engineers 2020
• Subjects: TK Electrical engineering. Electronics Nuclear engineering
• Online Access: http://eprints.um.edu.my/25413/; https://doi.org/10.1109/ACCESS.2020.2964603

This paper presents a comparative study of discrete proportional integral (PI) and proportional resonant (PR) current control for single-phase uninterruptible power supply (UPS) inverters. There is an increasing requirement for current and voltage-controlled UPS inverters with very low or zero steady-state error, improved transient response and lower total harmonic distortion (THD). The most promising type of current regulator for single-phase inverters is PR control because it can introduce an infinite gain at a selected resonance frequency such as the fundamental frequency to eliminate the steady-state error, which cannot be achieved by well-known proportional integral (PI) control. Note that PI control has limitations in terms of the steady-state magnitude and phase errors. In addition, PI control also has limited harmonic rejection capability, unlike the PR control, also can compensate for low-order harmonics. Imperfections in the current and voltage control scheme results in higher harmonic distortion of the output current and voltage. In this paper, performance of PR control parameters (Kp, Ki, and ωc) and filter parameters (Lf and Cf) are optimally tuned to obtain a very low THD current with reduced output voltage ripple and steady-state error. The analysis, design and implementation of both PI and PR current control in single-phase UPS inverter applications through simulations and experiments are also presented in this paper. The performance of both of these control schemes are analyzed in terms of steady-state response, transient response, and level of current harmonics. © 2013 IEEE.