An Adaptive Control System for Three-Phase Photovoltaic Inverters Working in a Polluted and Variable Frequency Electric Grid

Abstract

Index Terms-Digital control, linear feedback control systems, power system harmonics, power quality, three-phase electric power, adaptive signal processing, adaptive filters, lattice filters.

Power quality improvement of single-phase photovoltaic systems through a robust synchronization method

“…Some interesting PLL techniques have been presented in the recent literature, which enable the robustness of the synchronization against low-order harmonics. Those techniques are based on adaptive or notch filters [27]- [28], or apply repetitive and multi resonant controllers on the PLL and/or on the current controller [29]- [32] of the PV system. Although the aforementioned techniques achieve to overcome the harmonics effect, the dynamic response of the synchronization is slightly affected.…”

Power controllability of three-phase converter with unbalanced AC source

“…When the voltages become distorted and unbalanced under faults or disturbances, the unbalanced AC voltages have been proven to be a great challenge for the control of DC-AC converters in order to keep them normally operating and connected to the AC sources [2], [14], [15]. Special control methods which can regulate both the positive and negative sequence currents have been introduced to handle these problems [2], [16]- [21]. However, the resulting performances by these control methods are not satisfactory: either distorted load currents or power oscillations will be introduced, and thereby not only the grid/generator but also the power converter will be further stressed.…”

Control of Grid-Connected Inverters Using Adaptive Repetitive and Proportional Resonant Schemes

“…Different controllers and topologies have been proposed (e.g., [1]- [4]) to provide high-quality output currents that comply with national and international standards [5], [6]. Proportional-resonant (PR) controllers have also been widely used [7]- [13]. Theoretically, a PR controller has infinite gain at selected frequencies.…”

“…The frequency output from a phase-locked loop (PLL) can be used as input in PR controllers to have adaptive tuning with respect to the grid frequency, as suggested in [12] and [13]. However, all controller parameters must be adaptive, which makes the practical implementation of such mechanisms complicated, especially when a bank of resonant controllers is used to reject a high number of harmonics.…”