La qualità della potenza è fondamentale nei moderni sistemi elettrici, Soprattutto nelle strutture che eseguono grandi quantità di carichi non lineari come VFD, Sistemi UPS, e unità industriali. One of the most efficient tools for mitigating harmonic distortion is the Active Harmonic Filter (Ahf).

But how do you determine the right capacity for your system?

Choosing an undersized AHF leads to insufficient harmonic compensation, while oversizing can cause unnecessary investment. This article walks you through the fundamentals of active harmonic filters and provides a simple yet effective approach to determine the correct filter capacity, based on real-world applications and backed by CoEpower’s advanced Active Harmonic Filter technology.

1. What Is an Active Harmonic Filter (Ahf)?

An Active Harmonic Filter is a power electronic device that detects and injects counter-phase currents to cancel out harmonic distortion generated by nonlinear loads. Unlike passive filters, AHFs dynamically respond to load changes and compensate for:

Harmonic currents (typically 3rd to 50th order)

Reactive power

Unbalanced loads

CoEpower’s AHF uses advanced DSP control and real-time FFT algorithms to deliver fast and precise compensation with <200μs response time, achieving THDi <3% in most cases.

Core Functions:

Real-time harmonic detection

Dynamic compensation of harmonic and reactive currents

Bilanciamento del carico

Grid code compliance support (Ieee 519, IEC 61000-3-2/4)

2. How to Determine the Capacity of an Active Harmonic Filter?

Determining the correct capacity (kA or Amperes) of an AHF depends on several electrical parameters and load characteristics. Here’s a step-by-step guide:

Step 1: Measure Total Load Current

Start by identifying the maximum load current at the point of common coupling (PCC), typically in the main distribution panel.

Example: If the total load current is 400A, this is your base value.

Step 2: Analyze Harmonic Content (THDi)

Use a power quality analyzer to check the Total Harmonic Distortion of Current (THDi). Most industrial systems should ideally be below 5%, as per IEEE 519.

Example: Measured THDi = 22%

Step 3: Define Harmonic Compensation Target

Decide how much of the distortion you want to eliminate.

Full compensation: Aim for THDi <5%

Compensazione parziale: Reduce THDi to acceptable utility limits

Step 4: Calculate Required AHF Capacity

Use the following rule of thumb:

AHF Capacity (UN) = Load Current (UN) × THDi (%) × Compensation Rate

Example Calculation:

400UN (carico) × 22% (THDi) × 90% (compensazione) = 79.2A

In this case, select a 100A AHF for some margin.

Step 5: Consider Load Variability & Redundancy

For variable loads: Size the AHF for peak harmonic loads

For critical systems: Use parallel AHFs for redundancy and scalability

For rapid load changes: Ensure fast response time (<1SM)

CoEpower’s AHFs offer parallel operation and modular architecture, making future capacity expansion easy without replacing existing units.

3. Why Proper Sizing Matters？

Properly sizing your active harmonic filter ensures:

Optimal compensation of harmonics and reactive power

System reliability under dynamic loads

Regulatory compliance (Ieee 519, EN 50160)

Improved lifespan of electrical equipment

Insomma, sizing an active harmonic filter is both a technical and strategic decision. It requires accurate load analysis, harmonic measurement, and realistic compensation goals. By following this approach and leveraging intelligent AHF solutions like those from CoEpower, you can improve power quality, reduce system losses, and ensure long-term compliance with harmonic standards.

Explore CoEpower’s Intelligent AHF Solutions:

Active Harmonic Filter – Product Overview

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