Taylor series expansion based repetitive controllers for power converters, subject to fractional delays

• Published in: Control engineering practice Vol. 64; pp. 140 - 147
• Main Author: Nazir, R.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.07.2017
• Subjects: Finite impulse response; Fractional delay filter; Infinite impulse response; Repetitive controller; Taylor Series expansion; Repetitive controller; Fractional delay filter; Finite impulse response; Taylor Series expansion; Infinite impulse response
• ISSN: 0967-0661; 1873-6939
• DOI: 10.1016/j.conengprac.2017.03.013

Digital repetitive controllers are widely employed to track/reject the periodic signals with zero steady-state error. Their implementation involves the use of single or multiple digital delay elements. Practically, the delay element is implemented by the use of memory locations, where samples are held and released after a specific number of sampling periods, equivalent to the desired time delay. A problem arises when the desired time delay becomes a non-integer multiple of the sampling time. Such time delays can be accurately realized by employing a fractional delay filter This paper presents a Taylor Series expansion based digital repetitive controller designed to implement any (integer, non-integer) delay in the control of power converters, occurring due to uncontrollable variations in the reference frequency. The T3644aylor Series expansion transforms the fractional delay filter design problem to a differentiator/sub-filter design. Finite impulse response (FIR) and infinite impulse response (IIR) fractional delay (FD) filter concepts can be applied to realize the required fractional delay. This structure provides efficient on-line tuning capabilities i.e. FD can easily generate any required fractional delay without redesigning the filter when the delay parameter varies. An example is demonstrated to show the effectiveness of this approach, for a single-phase power inverter feeding a passive load. •A Taylor Series expansion based Repetitive (advanced) controller is developed to work under variable frequency environment.•Taylor Series expansion based RC of single-phase inverter is implemented.•Advanced repetitive control is compared with the conventional repetitive control and Fractional order repetitive control.•Results indicate that advanced RC control provides frequency adaptability whereas the other techniques fail to do so.