基于IEC标准的谐波研究 | 国际电能质量论坛

这种做法, 基本上在欧洲使用, 亚洲, 和许多其他地区, 与 IEEE 方法的不同之处在于其规范结构, 特别是关于测量技术和光谱分组 .

1. IEC 规范框架和基本原则

与 IEEE 方法不同, 重点关注连接点的限制, IEC架构是模块化的. 它清楚地区分了测量方法, 设备排放限值, 和网络分析技术.

1.1 IEC 的结构 61000 Series

用于全面的谐波研究, 您必须了解多个标准之间的相互作用:

符合IEC 61000-4-7: 这是你学习的技术核心. 它定义了测量 “工具箱”: 如何仪器, 样本, 和处理谐波和间谐波信号高达 9 千赫 .
符合IEC 61000-4-30: 这定义了测量仪器的性能等级 (A级进阶学习, guaranteeing the highest accuracy) .
符合IEC 61000-3-2 / -3-12: These set the harmonic current emission limits for individual equipment (≤16A and >16A的相, 分别) .
IEC TR 61000-3-6 / -3-7: Technical reports (non-normative but authoritative) providing principles for determining connection limits for distorting installations in MV, HV, and EHV networks.

1.2 Key Definitions according to IEC 61000-4-7

The IEC introduces specific concepts to handle the non-stationary nature of harmonics:

Spectral Component (Ci): The RMS value of the Discrete Fourier Transform (DFT) output for a given frequency (5 Hz resolution) .
Harmonic Sub-group (HG): To combat spectral leakage effects, the exact harmonic line is grouped with the two immediately adjacent spectral lines. This value is used for comparisons against limits .
Interharmonic Sub-group (IG): The grouping of spectral components located between consecutive harmonics .

Frequency axis — 5 Hz bins (10-cycle window, 50 Hz system)

HG h = 1 (50 赫兹) IG between h=1 and h=2 HG h = 2 (100 赫兹)

$$G_{sg,Ĥ} = \sqrt{\sum_{i=-1}^{+1} C^2_{n \cdot h + 我}}$$

Harmonic subgroup HG

$$G_{isg,Ĥ} = \sqrt{\sum_{i=2}^{N-1} C^2_{n \cdot h + 我}}$$

Interharmonic subgroup IG(N = 10, so i = 2..9, 8 bins)

$$G_{sg,h+1} = \sqrt{\sum_{i=-1}^{+1} C^2_{Ñ(h+1) + 我}}$$

Harmonic subgroup HG (h+1)

Harmonic subgroup (HG) — harmonic bin ± 1 neighbour Interharmonic subgroup (IG) - 8 bins between harmonics

图 1: Harmonic and Interharmonic Grouping according to IEC

Technical note: The harmonic sub-group of order n (HG_Ñ) is the square root of the sum of the squares of the harmonic line n and the two adjacent spectral lines. This method reduces uncertainty due to fundamental frequency fluctuations .

2. Data Acquisition and Modeling

The accuracy of an IEC-based study relies on strict adherence to measurement parameters and detailed source characterization.

2.1 Grid Data and Point of Connection

Grid Impedance: Unlike the American approach, which often uses the short-circuit ratio, the European approach (与英国的 G5/4 或 G5/5 等指南保持一致) 通常需要谐波阻抗. 理想的情况下, 网络运营商提供阻抗位点 作为频率的函数的 .
背景失真: 现场测量根据符合IEC 61000-4-30 A级 (10-cycle window, 精确同步) 在一个有代表性的时期内 (经常一个星期) .

2.2 非线性负载数据 (诺顿模型)

而IEC 61000-4-7 没有规定具体的计算模型, 行业实践和新标准 (像国际电工委员会 61400-27-3 对于可再生能源) 需要稳健的模型 :

谐波电流源 (伊赫): 转换器或负载的发射光谱, 根据 IEC 在实验室测量 61000-3-2.
诺顿阻抗 (Zh): 从负载端子看到的内部阻抗. 对于检测负载与网络之间的谐振现象至关重要.

表 1: 测量参数符合 IEC 61000-4-30 仪器类

范围	A级 (研究)	S级 (调查)
测量不确定度 (电压)	±0.1% (为你> 1% 您_名义)	±1.0%
同步	Robust PLL with frequency tracking	May be less strict
Time aggregation	Very short (3小号) and short (10分钟) values	Identical

For a compliance study intended for a network operator, the use of Class A instruments is mandatory .

3. Step-by-Step Analysis Methodology according to IEC

3.1 Frequency Scan Analysis

Before calculating distortions, identify the resonance frequencies of the combined system (格 + 电缆 + transformers of the installation).

方法: Inject a current of 1 A at a variable frequency and calculate the resulting impedance.
目标: Identify parallel impedance peaks.
Specific IEC Risk: Interharmonic sub-groups (IG) can excite these resonances, even if integer harmonics are filtered.

Impedance |在| (Ž) Inductive ωL Capacitive 1/ωC Resonance (250 赫兹)

f_res = 250 赫兹 — 5th harmonic order 在_高峰 ≈ 38 Ž — parallel resonance Q ≈ 8 — quality factor

图 2: Frequency Scan and Resonance Risk

An impedance peak at 250 Hz 会放大 5 次谐波. 如果峰值位于 275 赫兹, 该频率附近的间谐波分量将成为问题.

3.2 安装贡献的计算 (增量式)

IEC 方法, 被 G5/5 等指南采用, 区分您网站的增量贡献 和总失真.

公式: 使用诺顿模型. $在_{Ĥ, 公司} = \frac{在_{格} (Ĥ) \times 在_{load} (Ĥ)}{在_{格} (Ĥ) + 在_{load} (Ĥ)} \times 我_{Ĥ, 源}$ 在实践中, 软件 (电源工厂, ETAP, EMTP) 求解每个频率的系统.
确认: 该增量电压不得超过背景电压的一定百分比 (经常 1% 至 2% 取决于国家指南).

3.3 谐波子组的计算

这是 IEC 方法中最具特色的步骤. 您没有提供确切的信息 250 赫兹线, 但HG5子组.

对 a 执行 DFT10-cycle window (200 女士 50 赫兹, 〜166.6 毫秒 60 赫兹) .
获得频谱分量 C_i 5 赫兹步长.
计算谐波次数 *n* 的子组:

$Ĥ ĝ_{Ñ} = \sqrt{Σ_{我 = - 1}^{+ 1} Ç_{我}^{2}}$

哪里 $Ç_{0}$ is the exact harmonic line, 和 $Ç_{- 1}$ 和 $Ç_{+ 1}$ are the adjacent lines .

3.4 Time Aggregation and Statistical Evaluation

符合IEC 61000-4-30 requires aggregation to smooth out variations :

Very short values (3 秒): Aggregation of the 15 windows of 200 毫秒.
Short values (10 分钟): Aggregation of the 200 values of 3s.
Comparison: Compliance is generally verified on the short values (10 分钟), ensuring that 95% of the values (或 99% depending on the contract) are below the planned limits.

4. Compliance and Study Report

4.1 Comparison with Compatibility and Planning Levels

IEC TR 61000-3-6 defines three distinct levels :

Emission Level: What your installation injects (the calculated HGs and IGs).
Planning Level: An internal limit for the network operator, stricter than the compatibility level, to maintain a safety margin.
Compatibility Level: The reference disturbance level (例如, THDv = 8%) at which 95% of equipment is expected to function correctly .

您的报告必须证明您的贡献和背景失真的总和低于公共耦合点的规划水平 (PCC).

4.2 缓解和过滤

如果超出限制, 研究必须提出解决方案:

无源滤波器: 针对有问题的谐波子组进行调整 (HG).
有源滤波器: 注入电流实时消除谐波.
失谐: 修改阻抗 (例如, 添加线路电抗器) 将共振峰移离临界频率.

4.3 最终报告的内容

符合 IEC 标准的报告必须包括:

单线图 安装和上游网络.
输入数据: 电网阻抗, 负载电流谱 (具有符合 IEC 的测量或认证证明 61000-3-2).
模拟结果: 正常和应急操作条件下的 HG 和 IG 表.
统计分析: 计算水平与限制相比的累积概率曲线 .

结论: 明确的合规声明或纠正措施计划.