State of the Art of Repetitive Control in Power Electronics and Drive Applications

Abstract

Power electronic systems present a non-linear behavior mainly due to their switching nature. This is often combined with their interaction with non-linear systems, such as other switching converters, diode rectifiers, motor drives, etc. and with possible non linearities of the power grid in the case of grid connected systems. The major effect of these non-linear interactions is the generation of harmonic distortion on voltages and currents (both in DC and AC), which needs to be compensated to achieve high power quality systems. The use of passive filters is often the simplest and most immediate solution; however, this decreases converter efficiency and increases its weight and volume. Thus, the use of a control strategy capable of tracking periodic signals, rejecting periodic disturbance and largely improving steady state behavior and harmonic distortion with a limited bandwidth is a very desirable feature. Repetitive Control (RC) represents an extremely practical and efficient solution for the aforementioned issues, and it is widely employed in many different applications. This paper focuses on state of the art of RC used in power electronics and drives. RC basic concepts, different control structures, design methods, fixed and variable frequency operating conditions, etc. are investigated. Furthermore, many example applications and existing control approaches developed in recent years for power electronics and drive systems based on RC, have also been discussed in detail.INDEX TERMS Repetitive control, control design, reviews, power electronic converters, electric drives, gridtied, off grid.

Constant Delay-Line Repetitive Control Analysis for Variable Frequency Operation

“…This gives the minimum amount of time the CA lags the PWMM synch signal for a certain output fundamental frequency. 1 1…”

“…It results in very complicated control structures, which in many cases tend to favor alternative control strategies. On the other hand, Repetitive Control (RC) at a fixed frequency could offer much better performance combined with implementation simplicity [1]. Moreover, the RC can be combined with additional controller topologies to build very high-performance structures as in [2] - [3].…”

“…harmonics) are present in the output waveform. In fact, a non-integer result will cause the same MaMS to not appear with the same period every time: there are two distinct periods T1 (1) and T2 (1). Under the operating condition of output fundamental frequency equal to F0=49.91 Hz, Figure 10 illustrates T1(1) and T2(1) periods, which can be evaluated as in ( 27) and (28) for the very first beating (h)=1:…”

“…That specific operating condition was selected to make the effects graphically visible. With reference to the first beating effects (h)=1, the number of events p(1) between the two synchronous events where the MaMS appears with a period equal to T1 (1), and the number of events r (1) where the MaMS appears with a period equal to T2(1), can be obtained from ( 29) and (30) without lacks of generality for the higher beatings:…”

“…According to the first beating frequency, the output waveforms are affected by a harmonic whose magnitude is related to the MaMS and whose period can be calculated as the weighted average of T1(1) and T2 (1) where the weights are represented by p(1) and r(1). Regarding Figure 10, when a non-integer RMM is considered, the triggers mismatch at the end (Final-Mismatch, FM) of T1 (1) or T2(1) periods is not equal to that one at the beginning (Starting-Mismatch, SM) of T1(1) or T2 (1). Moreover, the difference between the Final-Mismatch (FM) and the Starting-Mismatch (SM) during T1(1) will differ from the same difference appearing during T2(1).…”