In today’s dynamic power environments—from industrial facilities to data centres—power quality is non-negotiable. Non-linear loads such as variable frequency drives and computers inject harmonic distortion, impacting efficiency and compliance. Active Harmonic Filters (AHFs) or Active Power Filters (APFs) are advanced solutions engineered to eliminate these distortions by injecting real-time compensating currents—ensuring a clean, sinusoidal waveform. In this blog, we’ll explore the most common types of APFs, their applications, and how CoEpower’s innovative designs can meet your needs.
1. Shunt Active Filters (Shunt APF)
How they work: Connected in parallel with the load, shunt APFs measure harmonic currents and inject counter-currents to cancel them out.
Best for: Eliminating current harmonics, compensating reactive power, and balancing unbalanced loads.
Why choose it: Ideal for improving true power factor and reducing THD (Total Harmonic Distortion). For example, installations have reduced THD from 7% to under 3%.
2. Series Active Filters (Series APF)
How they work: These are placed in series with the supply and inject a compensating voltage to mitigate voltage harmonics.
Best for: Suppressing voltage distortion, regulating terminal voltage, and isolating sensitive loads from supply anomalies.
3. Hybrid Active Filters
What they combine: Hybrid APFs merge shunt, series, and often passive filter components into a single system.
Advantages: This hybrid design tackles both current and voltage harmonics effectively—leveraging active elements for dynamic, high-order mitigation and passive components for fixed, low-order frequencies.
4. Current-Source vs Voltage-Source Active Filters
Current‐source active filter: Injects compensating current—functionally similar to a shunt APF.
Voltage‐source active filter: Delivers compensating voltage in series—akin to a series APF.
5. Adaptive Active Filters
These systems deploy smart algorithms that dynamically adapt to changing harmonic profiles—providing more accurate and efficient filtering in real-time conditions.
6. Control & Compensation Strategies
Technology backbone: APFs typically rely on power electronics such as IGBTs or MOSFETs, paired with DSP or FPGA platforms, enabling rapid switching and precise harmonic cancellation.
Control methods:
Synchronous Reference Frame (SRF) or dq0 transforms simplify harmonic components into DC quantities, aiding in more straightforward filtering.
Instantaneous Reactive Power Theory (pq/IRPT) generates reference compensation currents based on real‐time calculations.
7. Why APFs Outperform Passive Filters
| Feature | Active Harmonic Filters (APFs) | Passive Filters |
|---|---|---|
| Adaptability | Dynamic and responsive to variable loads | Tuned to fixed frequencies—less flexible |
| Harmonic Range | Mitigates multiple orders including high-order harmonics | Typically handles predetermined low-order harmonics only |
| Resonance Risks | Minimal resonance issues | Prone to resonance with system impedance |
| Size & Scalability | Compact, modular, scalable (e.g., rack-mount, wall, cabinets) | Larger footprint, less modular |
8. CoEpower APF Highlights
Leveraging insights from CoEpower’s product offering, here’s what sets their APFs apart:
Installation Flexibility: Available in wall-mounted, rack-mounted, and cabinet-integrated designs to suit a wide range of environments.
Advanced Compensation: Employ FFT-based DSP microchips to identify harmonic orders and generate precise, real-time compensating currents.
Performance: Their AHF systems deliver rapid response speed and can reduce THD to below 5%, critical for stringent power quality targets.
Scalable Rack Options: The Parallel Rack-Mounted AHF Module fits standard 19″ racks—perfect for telecom/data cabinets.
Industrial Standards: Their high-protection class modules are TÜV-CE certified and comply with IEC 61000 & IEC 62477 standards.
In Conclusion, when optimizing power systems, selecting the right type of APF is critical. Shunt APFs are your go-to solution for current harmonics; series APFs safeguard voltage quality; hybrid APFs offer comprehensive coverage; and adaptive APFs provide ongoing, intelligent performance. CoEpower’s APF portfolio meets these needs head-on—bringing modular versatility, intelligent control, and compliance-grade reliability to the table.
Explore our Active Harmonic Filter product page to learn more:
Tags: Filtro Harmônico Ativo (APF), Types of Active Harmonic Filters, Shunt APF, Series APF, Hybrid APF, Adaptive APF, CoEpower Active Harmonic Filter, Power quality improvement, Harmonic mitigation, FFT DSP compensation, Rack-mounted harmonic filter, THD reduction.
