Novel Fractional-Order Repetitive Controller Based on Thiran IIR Filter for Grid-Connected Inverters

Abstract

The proportional-integral multi-resonance repetitive controller (PIMR-RC) can track the reference current signal of the grid-connected inverter without static error, suppress low-frequency harmonic disturbance signals, and have a fast dynamic response. However, when the grid frequency fluctuates, the performance of reference signal tracking and harmonic suppression will decrease. Based on PIMR-RC, this paper proposes a novel fractional-order repetitive controller (NFO-RC) based on the Thiran infinite impulse response (Thiran IIR) filter, which can automatically track the change of grid frequency. Firstly, the frequency domain analysis of PIMR-RC is given. Then, the realization method based on the Thiran IIR filter is designed, and the structure of NFO-RC system is presented. Moreover, the stability and harmonic suppression analysis of NFO-RC system based on Thiran IIR filter are given. Finally, experimental results on a single-phase LCL grid-connected inverter verify excellent harmonic suppression performance of the proposed NFO-RC system under grid frequency fluctuations.

A Performance Evaluation of Repetitive and Iterative Learning Algorithms for Periodic Tracking Control of Functional Electrical Stimulation System

“…Another control method for perfect tracking of repetitive trajectory is called Repetitive Control (RC). Recently, RC has been used for leg exoskeleton control [56], 1-DOF Lagrangian system [57], industrial wide-format printing [58], contouring control of micro-stereolithography [59], magnetically suspended rotor system [60], [61], [62], control of linear actuator [63], functional electrical stimulation [64], [65], grid-connected inverters [66], [67], [68], [69], [70], nanometer-order contouring [71], dynamical galvanometerbased raster scanning [72], atomic force microscopy (AFM) scanner [73], mechanical ventilation [74], permanent magnet synchronous motor (PMSM) [75]- [77], servo motor [78], plug-in electric vehicle (PEV) charger [79], piezoelectric nano positioning stage [80], hydraulic press system [81], robotic manipulator [82], [83], and electric spring [84]. The RC is based on the idea of internal model principle by Francis and Wonham [85] stated that by incorporating model of reference/disturbance then perfect reference tracking or disturbance rejection can be achieved.…”

Fractional-Order Phase Lead Compensation Multirate Repetitive Control for Grid-Tied Inverters

“…Selecting an appropriate k p is crucial to expanding the stability region and enhancing the error tracking accuracy [40]. According to condition 1 , all the roots of equation 1 + k p P(z m ) = 0 should be located within a unit circle at low sampling rates.…”