Research on the Nonlinear Control Strategy of Three-Phase Bridgeless Rectifier under Unbalanced Grids

Hong Cheng,Cong Wang,Daokuan Yang

doi:10.3390/electronics10243090

Hong Cheng, Cong Wang + Show 1 more

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https://doi.org/10.3390/electronics10243090

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Journal: Electronics	Publication Date: Dec 12, 2021
Citations: 2	License type: CC BY 4.0

Affiliation: China University of Mining and Technology

Abstract

The three-phase Y-connected bridgeless rectifier is essentially a nonlinear system, and it is difficult to obtain superior dynamic performance under the action of traditional linear controller. Under the condition of unbalanced power grids, this paper has established a mathematical model based on Euler–Lagrange (EL) equations with line voltage and line current as state variables. Furthermore, it then designed a passivity-based controller in inner current loop based on the mathematical model. The hybrid nonlinear control strategy consisting of active disturbance rejection controller (ADRC) in the outer voltage loop and passivity-based controller (PBC) in the inner current loop is adopted to control the system, which does not need to consider the positive and negative sequence components. The control structure is simple and can improve the steady-state accuracy, dynamic performance and anti-interference ability. The feasibility of the proposed control strategy is verified by computer simulation, which has a guiding significance for the application of three-phase bridgeless rectifier in practical engineering.

Highlights

Rectifier under Unbalanced Grids.Compared with the traditional two or three level rectifiers, multilevel rectifiers are more and more used in the field of AC/DC-DC/AC power conversion because of its advantages such as lower current distortion rate, lower switching frequency, lower switching device voltage stress and higher power quality [1,2,3]
The H-bridge module in the cascaded H-bridge rectifier can be replaced by the bridgeless module, which can further reduce the number of fully controlled devices in the multilevel rectifiers as well as the cost and control complexity of the system [6,7]
A linear controller was designed for the cascaded bridgeless rectifier with the unbalanced power grids to control its positive and negative sequence components respectively in [13,14]

Summary

Introduction

Compared with the traditional two or three level rectifiers, multilevel rectifiers are more and more used in the field of AC/DC-DC/AC power conversion because of its advantages such as lower current distortion rate, lower switching frequency, lower switching device voltage stress and higher power quality [1,2,3]. The H-bridge module in the cascaded H-bridge rectifier can be replaced by the bridgeless module, which can further reduce the number of fully controlled devices in the multilevel rectifiers as well as the cost and control complexity of the system [6,7]. While the cascaded H-bridge or bridgeless multilevel rectifier is essentially a nonlinear system, and the adoption of linear control strategy requires the establishment of an accurate small signal

Methods

Findings

Discussion

Conclusion