A Generalized Modulation Method for Common-Mode Voltage Reduction of Dual-Input Three-Level Inverter

Ying Jiang,Xiaoyan Li,Xiangyang Xing,Changwei Qin,Boxue Zhang

doi:10.1109/access.2020.3005288

Ying Jiang, Xiaoyan Li + Show 3 more

Open Access

https://doi.org/10.1109/access.2020.3005288

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Abstract

The dual-input three-level inverter should have the ability to operate in certain areas where the dc-links are unbalanced. This paper proposes a generalized large-medium-zero space vector modulation (GLMZ-SVM) method to obtain high-quality output currents and suppress common-mode voltage (CMV) amplitude simultaneously when the dc-links are unbalanced. In this method, a modified space voltage vector diagram (MSVVD) based on the unbalancing factor is obtained, which is highly asymmetrical compared to the space vector diagram when the dc-links are balanced. Then, a novel sector division method of MSVVD is presented by six medium vectors and six large vectors. In each sector, the large, medium, and zero vectors are used to synthesize the reference voltage vector to reduce the CMV amplitude. The duty cycles of large, medium and zero vectors are calculated based on the modified volt-second balance principle with the unbalancing factor. To further reduce harmonics and avoid switching losses between switching cycles, a symmetrical five-segment switching sequence is designed. Comparisons with conventional methods show that the CMV amplitude of the proposed method is reduced by half and the high-quality output currents are obtained. Both simulation and experimental results validate the correctness of the theoretical analyses and the effectiveness of the proposed scheme.

Highlights

With the rapid consumption of fossil fuels and environmental pollution problems, renewable energy sources such as solar energy and wind energy have become the trend of global power generation [1], [2]
This paper studies the the space vector-based modulation strategy of three-level dual-input inverter, and the proposed scheme is effective for both balanced and unbalanced dc-links
Medium, and zero vectors to synthesize the reference vector, which can solve the problems of common-mode voltage (CMV) reduction and dc-link neutral point voltage balance at the same time [24]

Summary

INTRODUCTION

With the rapid consumption of fossil fuels and environmental pollution problems, renewable energy sources such as solar energy and wind energy have become the trend of global power generation [1], [2]. An improved predictive control method based on two-layer vector selection criteria and a modulation technique using large, medium, and zero vectors were studied respectively in [23] and [24] for CMV reduction These methods are applicable to balanced dc-side conditions, but current distortion occurs when the upper and lower capacitor voltages on the dc side are not equal. Aiming at the unbalanced NP voltage condition, a generalized modulation method adopting large, medium, and zero vectors is proposed in this paper, which can obtain high-quality output currents, and reduce the CMV simultaneously. PROPOSED MODULATION METHOD Since the NP voltage imbalance may occur under certain operating conditions, this requires that dual-input three-level inverters should have the ability to work normally in certain areas where the dc-links are unbalanced.

DUTY CYCLE CALCULATION

SIMULATION RESULTS

CONCLUSION