IP-ANPC Converter Flying Capacitor Voltage Balancing

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Solution Overview

Problem

Current multilevel converter topologies face challenges in utilizing wide band-gap (WBG) devices effectively due to high device count, cost, and reliability issues, particularly in high-power applications, where parallelization is necessary but undermines reliability and increases costs.

Innovation Solution

The internal parallelization based active neutral point clamped (IP-ANPC) converter architecture, which combines low switching frequency (LSF) and high switching frequency (HSF) modules in parallel, with each HSF module having a current sharing inductor and flying capacitor, allowing for modular design, interleaving, and natural or redundant voltage balancing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If parallelization of converters is used to achieve higher power capacity, then modularity and fault tolerant capability are improved, but reliability is undermined due to high device count

Engineering Contradiction:

Improvepower capacityVSAvoidreliability

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The converter is divided into multiple modular units (first converter unit and second converter unit) that can be paralleled to achieve higher power capacity. Each unit contains its own switching devices and circuit components, enabling independent operation and fault isolation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Redundant switching devices are incorporated in each converter unit to provide fault tolerance. The parallel configuration ensures that if one unit fails, the other unit can continue operating, cushioning against complete system failure.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

2Adaptability or versatility

If parallelization of converters is used to achieve higher power capacity, then modularity is improved, but cost increases due to higher cost of WBG devices

Engineering Contradiction:

ImprovemodularityVSAvoidcost

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

The converter is segmented into modular units that can be independently manufactured and assembled. This modularity enables flexible system configuration and simplifies manufacturing processes while maintaining adaptability for different power requirements.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different parts of the converter system use different device technologies optimized for their specific functions. WBG devices are used in specific switching positions where their high-frequency characteristics provide maximum benefit, while other positions may use more cost-effective devices.

Inventive Principle:

Principle #3Local quality

3Speed

If WBG devices are used in high-power applications, then switching frequency is improved, but device stress increases

Engineering Contradiction:

Improveswitching frequencyVSAvoiddevice stress

Core Design Contradiction:

SpeedVSStress or pressure

Solution Approach 1:

The high-power conversion task is divided across multiple parallel converter units, reducing the current and power stress on each individual WBG device while maintaining high switching frequency operation.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Neutral point clamping circuits with flying capacitors are introduced as intermediary elements to limit the voltage stress on WBG switching devices. These clamping circuits provide voltage clamping and current redistribution, protecting WBG devices from excessive stress during high-frequency switching.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Manufacturing precision

If higher number of voltage levels is used, then output quality and common mode voltage profile are improved, but device count increases

Engineering Contradiction:

Improveoutput qualityVSAvoiddevice count

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The high-level multilevel converter is segmented into multiple parallel three-level converter units. Each unit generates a subset of the voltage levels, and their combined output achieves the desired high number of voltage levels without requiring an exponentially increasing number of devices in a single unit.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Multiple three-level converter units are merged in parallel to collectively produce a high-level multilevel output. The combining of these units achieves superior output quality and common mode voltage profile characteristics while keeping the device count manageable through the parallel architecture.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS10924031B2Internal paralleled active neutral point clamped converter with logic-based flying capacitor voltage balancing

Publication Date: 2021.02.16 THE GOVERNORS OF THE UNIV OF ALBERTA

AI summary

An internal parallelization based active neutral point clamped (IP-ANPC) converter is provided having a low switching frequency (LSF) part and a plurality of high switching frequency (HSF) modules. The HSF modules are connected in parallel and the converter is modular. The converter provides the benefits of modularity, improved reliability and efficiency, interleaving operation, and reasonable utilization of wide band gap (WBG) devices. A logic based flying capacitor voltage balancing scheme is also provided. The balancing scheme includes naturally balancing the voltage of the converter with phase shift pulse width modulation and redundantly balancing the voltage of the converter with redundant switching states.