Power Converter Harmonic Compensation at AC Sub-Network Connection

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Solution Overview

Problem

AC sub-networks in industrial settings experience harmonic distortions that exceed THD limits, preventing automatic connection to higher-level supply networks, and existing solutions like passive filters and STATCOMs are inefficient or costly.

Innovation Solution

A method and control circuit using a power converter with a bridge circuit to generate compensation voltage and current, reducing harmonic distortion by detecting network voltage and adjusting the bridge circuit's clocking to counteract harmonic currents, with optional galvanic isolation and integration of a DC source for self-consumption and network-friendly compensation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If passive filters are used to compensate harmonics, then harmonic distortion is reduced, but the system is designed for specific loads and lacks adaptability

Engineering Contradiction:

Improveharmonic compensation precisionVSAvoidload adaptability

Core Design Contradiction:

Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

The patent implements dynamic harmonic compensation by continuously measuring the load current and generating compensation currents that adapt to changing load conditions. The control unit dynamically adjusts the compensation parameters based on real-time harmonic content, enabling the system to maintain effectiveness across varying load scenarios rather than being fixed for specific loads.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system employs feedback mechanisms where the load current is continuously measured and analyzed for harmonic content. This measured information feeds back to the control unit, which then generates appropriate compensation signals. This closed-loop feedback ensures the compensation remains accurate and adaptive to changing load conditions.

Inventive Principle:

Principle #23Feedback

2Reliability

If STATCOM with current control system is used, then reactive power and harmonics are compensated, but the device complexity increases

Engineering Contradiction:

Improvepower qualityVSAvoidcontrol system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent creates a multi-functional device that simultaneously performs active power factor correction, reactive power compensation, and harmonic filtering. By integrating these functions into a single power electronics-based system rather than separate devices, the solution reduces overall system complexity while maintaining comprehensive power quality improvement.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The invention replaces traditional mechanical/passive filtering approaches with electronic control methods. Instead of using complex passive filter networks or mechanical switches, the system uses power electronics switches controlled by digital signal processing to achieve the same or better power quality results with reduced mechanical complexity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If active power factor correction is implemented, then power quality improves, but harmonic distortion current increases

Engineering Contradiction:

Improvepower factorVSAvoidharmonic distortion current

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent converts the harmful harmonic currents generated by active power factor correction circuits into beneficial compensation signals. The system measures the harmonics produced by the PFC circuit and generates equal and opposite compensation currents to cancel them out, thereby eliminating the harmful effect while preserving the beneficial power factor improvement.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The system implements preliminary anti-action by proactively generating compensation currents that counteract the harmonic distortion before it propagates into the power network. The control unit anticipates the harmonic content based on the switching patterns of the PFC circuit and applies compensating signals in advance to prevent harmonic pollution.

Inventive Principle:

Principle #9Preliminary anti-action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Improves network voltage and current quality, reduces harmonic power flows, and meets regulatory requirements while minimizing the need for additional AC network filters, enabling cost-effective compliance with THD limits.

Implementation Method 1

A power converter is clocked with a bridge circuit between a DC unit and an AC sub-network. A control circuit determines a compensation voltage and/or a compensation current which is/are to be generated by the power converter

Methodology Applied

Scientific EffectElectromagnetic Induction: Electromagnetic Induction

Data Source

PatentUS20250392129A1Method and control circuit for reducing harmonic power flows, and sub-network having control unit

Publication Date: 2025.12.25 SMA SOLAR TECH AG

AI summary

A method for reducing harmonic power flows via a connection point at which a sub-network is connected to a higher-level AC supply network and via which a network current flows between the sub-network and the higher-level AC supply network is disclosed.