Neutral Point Voltage Balance in Three-Level Voltage Inverter Based on Space-Vector PWM with Seven-Stage Switching Sequence

Q3 Engineering Russian Electrical Engineering Pub Date : 2024-08-29 DOI:10.3103/s1068371224700524

A. N. Shishkov, M. M. Dudkin, V. K. Le, N. A. Eremin

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Abstract

The voltage imbalance of the neutral point (NP) of the dc link is an inherent limitation in using three-level autonomous voltage inverters with a fixed neutral point in electric-drive systems. To ensure the NP voltage balance within acceptable limits, a control algorithm based on space-vector PWM with a seven-stage switching sequence (SS) is proposed. Compared with the known control methods, the new alternative significantly improves the NP voltage balance by adjusting the fill factor of distributed base vectors in each PWM period based on phase load currents. The algorithm also eliminates the NP voltage imbalance caused by external factors, for example, by the asymmetry of dc capacitors or three-phase load and other factors due to the feedback signal on voltage deviations in two dc link capacitors. A system for calculating the turn-on lengths of basic vectors in a seven-stage SS is presented. The efficiency of the proposed algorithm is confirmed by computer simulation in the MATLAB Simulink suite. The proposed algorithm reduces the average maximal relative error in the NP voltage by 86% over the entire variation range of the modulation coefficient compared to the known method of balancing the NP voltage based on a feedback signal on voltage deviations in two dc link capacitors. This allows efficiently balancing the NP voltage and, as a result, improves the operational reliability of the inverter.

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基于七级开关序列空间矢量 PWM 的三电平电压变换器中的中性点电压平衡

摘要直流链路中性点（NP）电压不平衡是在电力驱动系统中使用具有固定中性点的三电平自主电压逆变器的固有限制。为确保中性点电压平衡在可接受的范围内，提出了一种基于空间矢量 PWM 和七级开关序列 (SS) 的控制算法。与已知的控制方法相比，新的替代方案通过根据相负载电流调整每个 PWM 周期中分布式基向量的填充因子，显著改善了无负压电压平衡。该算法还消除了由外部因素（如直流电容器或三相负载的不对称）以及两个直流链路电容器电压偏差反馈信号等因素造成的 NP 电压不平衡。本文提出了一个用于计算七级 SS 基本矢量开通长度的系统。通过在 MATLAB Simulink 套件中进行计算机仿真，证实了所提算法的效率。与已知的基于两个直流链路电容器电压偏差反馈信号的 NP 电压平衡方法相比，所提出的算法在调制系数的整个变化范围内将 NP 电压的平均最大相对误差降低了 86%。这样就能有效地平衡 NP 电压，从而提高逆变器的运行可靠性。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Russian Electrical Engineering Engineering-Electrical and Electronic Engineering

CiteScore

1.50

自引率

0.00%

发文量

期刊介绍： Russian Electrical Engineering is a journal designed for the electrical engineering industry and publishes the latest research results on the design and utilization of new types of equipment for that industry and on the ways of improving the efficiency of existing equipment.