Grid Harmonics Suppression for Three Phase Dual-Frequency Grid-Connected Inverter Based on Feedforward Compensation

Zhigang Chen; Dongkai Ma; Liyong Yang; Shuo Liu; Chaonan Tong; Yifan Zhao

doi:10.3390/sym15081517

Symmetry (Aug 2023)

Grid Harmonics Suppression for Three Phase Dual-Frequency Grid-Connected Inverter Based on Feedforward Compensation

Zhigang Chen,
Dongkai Ma,
Liyong Yang,
Shuo Liu,
Chaonan Tong,
Yifan Zhao

Affiliations

Zhigang Chen: School of Automation and Electrical Engineering, University of Science and Technology Beijing, Beijing 100083, China
Dongkai Ma: College of Electrical and Control Engineering, North China University of Technology, Beijing 100144, China
Liyong Yang: College of Electrical and Control Engineering, North China University of Technology, Beijing 100144, China
Shuo Liu: College of Electrical and Control Engineering, North China University of Technology, Beijing 100144, China
Chaonan Tong: School of Automation and Electrical Engineering, University of Science and Technology Beijing, Beijing 100083, China
Yifan Zhao: College of Electrical and Control Engineering, North China University of Technology, Beijing 100144, China

DOI: https://doi.org/10.3390/sym15081517
Journal volume & issue: Vol. 15, no. 8
p. 1517

Abstract

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Using a low pulse ratio, the electromagnetic interference and switching loss of an inverter can be effectively reduced, particularly in high-power applications. However, due to variations in grid impedance, it is a challenging task to achieve stable operation of an LCL-type grid-connected inverter (GCI) using the active damping method with low pulse ratio. Thus, a novel three-phase dual-frequency GCI is presented to ensure the symmetry of the output power and the stable operation of the system address stability issues. The proposed inverter topology in this article is composed of two inverters in parallel, which are, respectively, a power inverter unit (PIU) and an auxiliary harmonic elimination unit (AHEU). To reduce the switching loss and improve the inverter efficiency, the switching frequency of the PIU is relatively low, injecting current into the grid. Moreover, the feedforward compensation method is used in AHEU. AHEU operates at high switching frequency to generate a current component that is symmetrical with the ripple com-ponent, improving the power quality, without extracting the current harmonic as the current reference. The operating principle of feedforward compensation is explained, and a proper parameter design procedure is presented in this paper. Since L filters are used for the proposed inverter, the system can operate stably where the ratio of switching frequency to fundamental frequency is low. A 10 kW laboratory prototype was built. The experimental results showed that the grid current ripple could be effectively eliminated and the THD of the grid current was 3.01%. The proposed inverter has good stability in a weak grid, and the efficiency of the proposed inverter is 95.98% at rated current, which is 0.81% higher than the traditional GCI, effectively increasing the efficiency of the system.

Published in Symmetry

ISSN: 2073-8994 (Online)
Publisher: MDPI AG
Country of publisher: Switzerland
LCC subjects: Science: Mathematics
Website: http://www.mdpi.com/journal/symmetry/

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