Comparison of digital control techniques with repetitive integral action for low cost PWM inverters

Abstract

This paper presents a comparison among digital control techniques with repetitive integral action applied to voltagesource PWM inverters. As a result of the repetitive integral action, these digital control schemes can reduce steady-state errors and distortions caused by unknown periodic disturbances, which usually result from the input source and output load. Moreover, these digital control schemes measure only the output voltage, decreasing the amount of sensors and the overall system cost. The control laws, stability analysis, common and distinguishing features of these control algorithms are discussed. Experimental results from a PWM inverter (110 , 1 kVA) controlled by a low cost microcontroller are presented to demonstrate the control techniques performance under different load conditions, output filters and command strategies.

Design method of single-phase inverters for UPS systems

“…The continuous models (or a simple discrete ZOH models) average the properties of the PWM modulators that are different even for a high frequency ratio (Rymarski 2007). The discrete inverter model taking in account the pulse pattern (Kawamura et al 1998, Rech et al 2003) that corresponds to the discussed continuous model should be used in the design of the digital controller. The characteristic polynomial (9) after substituting z ¼ exp(sT c ) was transformed to its discrete form Equation (10).…”

“…The LC filter design was previously presented separately from the controller design (Dewan and Ziogas 1979;Dahono, Purwadi and Qamaruzzaman 1995) or the LC parameters were connected with feedback parameters (Kusko, Galler and Medora 1990;Kim, Choi and Hong 2000;Ryu, Kim, Choi and Choi 2002) but the research was based on the continuous models of inverters which cannot be directly implemented in a microprocessor based controller. The papers that have presented different types of discrete instantaneous and repetitive controllers (Ben-Brahim, Yokoyama and Kawamura 2003) including choice of pulse patterns (Kawamura, Chuarayapratip andHaneyoshi 1998, Rech, Pinheiro, Grundling, Hey andPinheiro 2003) assigned filter parameters with the L/C filter ratio lower than in papers concerned with the design of an LC filter. The elimination of the output waveform distortions, when the inverter works with the rectifier R O C O load, requires an additional outer control loop with a repetitive controller (i.e.…”

Intelligent voltage control strategy for three-phase UPS inverters with output LC filter

“…However, the transient response appears to be quite sluggish. Repetitive control algorithm (Jiang, Cao, Li, Liu, & Peng, 2012;Rech, Pinheiro, Grundling, Hey, & Pinheiro, 2003a, 2003bTzou, Jung, & Yeh, 1999;Zhang, Kang, Xiong, & Chen, 2003) is a special case of the internal model control method in a single reference frame, which eliminates a periodical tracking error or disturbance whose frequency is less than half sampling frequency. These schemes have been applied to inverter voltage control.…”

Design of plug-in repetitive controllers for single-phase PWM inverters

“…Replacing z by e jωT in (8) and assuming that the spectrum of r and d is composed exclusively for frequencies multiples of the fundamental reference frequency ω 1 =2π/NT, the steady-state error is given by…”

“…For PWM inverter systems, the most attractive and frequently used scheme is the Q-filter algorithm [6][7][8][9][10][11] due to it low coding complexity, fast execution speed and fast convergence. Besides of their widespread use, there is no systematic design procedure for these controllers taking into consideration the parametric variations that the cyclic nonlinear load causes in the dynamic model of the plant.…”