﻿ 新型中性线谐波电流抑制器

# 新型中性线谐波电流抑制器New Harmonic Current Suppressor

Abstract: This article is based on the improvement of the existing neutral-line harmonic filters. It is pro-posed that the conventional zig-zag transformer cannot suppress the zero-sequence harmonic current generated by unbalanced grid voltage, and the neutral line voltage offset problem that is easily caused by a simple neutral-line series filter is proposed. A novel neutral-line harmonic current suppression method combining a zero-sequence filter and a series-neutral-line filter is proposed. This method combines the zero-sequence filter based on zigzag transformer and the series neutral filter, which not only solves the problem of filtering the third harmonic, but also plays a good role in suppressing the midline zero-sequence current, and has little effect on the load.

1. 引言

2. 滤波器结构

2.1. 零序滤波器

2.2. 串联中线滤波器

Figure 1. Structure of Zero-sequence filter

Figure 2. Structure of Serial midline filter

${Z}_{f}=\frac{{X}_{L1}{X}_{C}}{{X}_{L1}+{X}_{L2}+2{X}_{M}+{X}_{C}}$

3. 等效电路分析

3.1. 零序等效电路

${i}_{sn}=\frac{{Z}_{zn}}{{Z}_{sn}+3{Z}_{f}+{Z}_{s}+{Z}_{z}+{Z}_{zn}}{i}_{s0}+\frac{1}{{Z}_{sn}+3{Z}_{f}+{Z}_{s}+{Z}_{z}+{Z}_{zn}}{u}_{s0}$

${i}_{zn}=\frac{{Z}_{sn}+3{Z}_{f}+{Z}_{s}+{Z}_{z}}{{Z}_{sn}+3{Z}_{f}+{Z}_{s}+{Z}_{z}+{Z}_{zn}}{i}_{s0}-\frac{1}{{Z}_{sn}+3{Z}_{f}+{Z}_{s}+{Z}_{z}+{Z}_{zn}}{u}_{s0}$

$\frac{{Z}_{sn}+3{Z}_{f}+{Z}_{s}+{Z}_{z}}{{Z}_{sn}+3{Z}_{f}+{Z}_{s}+{Z}_{z}+{Z}_{zn}}{i}_{s0}\gg \frac{{Z}_{zn}}{{Z}_{sn}+3{Z}_{f}+{Z}_{s}+{Z}_{z}+{Z}_{zn}}{i}_{s0}$

${u}_{zn}=\frac{\left({Z}_{sn}+3{Z}_{f}+{Z}_{s}+{Z}_{z}\right)\left({Z}_{zn}\right)}{{Z}_{sn}+3{Z}_{f}+{Z}_{s}+{Z}_{z}+{Z}_{zn}}{i}_{s0}-\frac{{Z}_{zn}}{{Z}_{sn}+3{Z}_{f}+{Z}_{s}+{Z}_{z}+{Z}_{zn}}{u}_{s0}$

$\frac{\left({Z}_{sn}+3{Z}_{f}+{Z}_{s}+{Z}_{z}\right)\left({Z}_{zn}\right)}{{Z}_{sn}+3{Z}_{f}+{Z}_{s}+{Z}_{z}+{Z}_{zn}}\approx {Z}_{zn}$

${u}_{zn}=\frac{\left({Z}_{sn}+3{Z}_{f}\right)\left({Z}_{zn}\right)}{{Z}_{sn}+3{Z}_{f}+{Z}_{s}+{Z}_{z}+{Z}_{zn}}{i}_{s0}+\frac{{Z}_{sn}+3{Z}_{f}}{{Z}_{sn}+3{Z}_{f}+{Z}_{s}+{Z}_{z}+{Z}_{zn}}{u}_{s0}$

Figure 3. Zero sequence equivalent circuit

3.2. 三次谐波等效电路

${i}_{sn}=\frac{{Z}_{zn}}{{Z}_{sn}+{Z}_{f}+{Z}_{s}+{Z}_{z}+{Z}_{zn}}{i}_{3s}+\frac{1}{{Z}_{sn}+{Z}_{f}+{Z}_{s}+{Z}_{z}+{Z}_{zn}}{u}_{3s}$

4. 仿真分析

4.2. 仿真结果分析

Figure 4. Third harmonic equivalent circuit

Figure 5. Neutral harmonic current suppressor simulation model

Figure 6. System simulation waveform and FFT analysis without any filtering device

Figure 7. System simulation waveform and FFT analysis only with zero-sequence filter

Figure 8. Neutral harmonic current suppressor simulation waveform and FFT analysis

5. 结论

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