Power Converter Controller Active Harmonic Cancellation

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Solution Overview

Problem

Harmonic currents generated by non-linear loads in power systems and electrical grids increase heat in equipment, cause unwanted trips, and lead to financial losses due to added maintenance costs and production downtime, with existing passive solutions like filter capacitor banks causing undesirable grid resonance and power dissipation.

Innovation Solution

A power conversion system with a power converter controller that actively cancels harmonic currents by generating a cancellation current equal and opposite to the harmonic current received from the grid, using a control system that combines voltage reference commands with harmonic cancellation commands to reduce harmonic components in the grid current.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-generated harmful factors

If passive filter capacitor banks are used to reduce harmonic currents, then harmonic current reduction is achieved, but grid resonance is caused

Engineering Contradiction:

Improveharmonic currentVSAvoidgrid resonance

Core Design Contradiction:

Object-generated harmful factorsVSReliability

Solution Approach 1:

The patent replaces passive mechanical filter capacitor banks with an active control system that uses power electronic switches (IGBTs) and control algorithms to generate cancellation currents. This substitution eliminates the resonance problems inherent in passive RC filters while maintaining harmonic current reduction effectiveness.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The system employs feedback control by continuously monitoring grid current harmonics through sensors and using this information to dynamically adjust the cancellation current generated by the power converter. The control system processes harmonic information and generates appropriate switching signals to maintain effective harmonic cancellation.

Inventive Principle:

Principle #23Feedback

2Reliability

If resistors are added in series with filter capacitors to dampen resonance, then grid resonance is dampened, but power dissipation increases

Engineering Contradiction:

Improvegrid resonance dampingVSAvoidpower dissipation

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent replaces resistor-based passive damping with active control using power electronic switches. The IGBTs are controlled to generate currents that actively dampen resonance without the continuous power dissipation associated with resistors, achieving resonance control only when needed while minimizing energy loss.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The system uses periodic switching of power electronic devices at specific frequencies to counteract resonance conditions. This periodic active control replaces continuous passive resistor damping, providing resonance suppression only when harmonic conditions require it, thereby reducing overall power dissipation.

Inventive Principle:

Principle #19Periodic action

3Adaptability or versatility

If non-linear loads are connected to the DC to AC inverter, then power conversion capability is improved, but harmonic current is generated

Engineering Contradiction:

Improvepower conversion capabilityVSAvoidharmonic current

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

The patent converts the harmful harmonic currents into a useful control signal. The system detects harmonic currents generated by non-linear loads and uses this information to generate equal and opposite cancellation currents, transforming the harmful effect into an opportunity for active compensation and improved power quality.

Inventive Principle:

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

Solution Approach 2:

The power converter acts as an intermediary between non-linear loads and the electrical grid. It processes the non-sinusoidal current from non-linear loads, extracts harmonic components, and generates compensating currents to cancel these harmonics before they reach the grid, enabling both non-linear load operation and clean power delivery.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS8773873B2Methods and systems for operating a power converter

Publication Date: 2014.07.08 GE GRID SOLUTIONS LLC

AI summary

A power conversion system for providing power to an electrical grid is described. The power conversion system includes a power converter coupled to a power source and the electrical grid. The power conversion system also includes a converter controller coupled to the power converter and configured to control operation of the power converter to actively cancel harmonic current received at the power converter from the electrical grid.