Bi-Directional Power Converter Control for Higher-Order Harmonic Mitigation

Solution Overview

Problem

Legacy power converters face challenges in efficiently removing higher-order harmonic disturbances due to their limited bandwidth and switching frequency range, often requiring bulky and costly separate filters, which can reduce efficiency and increase complexity.

Innovation Solution

A bi-directional power converter with an integrated control system that estimates harmonic voltage content at intermediate nodes and controls electronic switches to generate compensating waveforms, reducing harmonic current content without the need for separate filters, and integrates with DC link voltage and AC current regulators to anticipate and compensate for digital delays.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If separate filters are added to remove harmonic disturbances, then power quality is improved, but device complexity and cost increase

Engineering Contradiction:

Improveharmonic disturbancesVSAvoidfiltering system complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent combines the harmonic filtering function with the existing power converter by integrating active harmonic compensation into the converter's control system. The controller monitors intermediate node voltages and adjusts switching signals to actively cancel harmonics, merging two functions (power conversion and harmonic filtering) into a single integrated system, thereby eliminating the need for separate passive filter components.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The power converter performs its own harmonic filtering through self-monitoring and self-correction. The controller measures voltages at intermediate nodes, detects harmonic content, and automatically adjusts switching signals to compensate for detected harmonics. This self-service approach eliminates the need for external filtering components and reduces system complexity.

Inventive Principle:

Principle #25Self-service

2Object-affected harmful factors

If separate filters are added to remove harmonic disturbances, then power quality is improved, but cost increases

Engineering Contradiction:

Improveharmonic disturbancesVSAvoidmanufacturing cost

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The patent combines the harmonic filtering function with the existing power converter by integrating active harmonic compensation into the converter's control system. The controller monitors intermediate node voltages and adjusts switching signals to actively cancel harmonics, merging two functions (power conversion and harmonic filtering) into a single integrated system, thereby eliminating the need for separate passive filter components.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The power converter performs its own harmonic filtering through self-monitoring and self-correction. The controller measures voltages at intermediate nodes, detects harmonic content, and automatically adjusts switching signals to compensate for detected harmonics. This self-service approach eliminates the need for external filtering components and reduces system complexity.

Inventive Principle:

Principle #25Self-service

3Speed

If higher switching frequency is used to improve bandwidth, then harmonic compensation capability is improved, but switching losses increase

Engineering Contradiction:

Improveswitching frequencyVSAvoidswitching losses

Core Design Contradiction:

SpeedVSLoss of energy

Solution Approach 1:

The patent applies partial action by selectively compensating for specific harmonic orders (5th, 7th, 11th, 13th) rather than attempting to eliminate all harmonics across the entire frequency spectrum. The controller calculates compensation signals for dominant harmonic components and applies targeted corrections, achieving effective harmonic mitigation without requiring excessively high switching frequencies that would cause prohibitive switching losses.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS11967891B2Mitigation of harmonic disturbances in a power converter

Publication Date: 2024.04.23 EATON INTELLIGENT POWER LTD

AI summary

A bi-directional power converter includes: a plurality of input nodes, each input node configured to electrically connect to one phase of a multi-phase AC electrical power distribution network; and an electrical network configured to convert alternating current (AC) to direct current (DC) and to convert DC current to AC current, the electrical network including a plurality of electronic switches. The bi-directional power converter also includes a control system configured to: estimate harmonic voltage content at three intermediate nodes in the bi-directional power converter based on a measured electrical quantity; and control the electronic switches to compensate for the estimated harmonic voltage content.