Three-Phase Microinverters for Photovoltaic Modules

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Solution Overview

Problem

Conventional solar power systems require large, costly inverters due to high capacitance and inductance needs, increasing installation costs and complexity, as they convert direct current from solar panels to alternating current for grid compatibility.

Innovation Solution

Integration of microinverters with photovoltaic modules, specifically three-phase microinverters with reduced capacitance and inductance, allowing for parallel connection of multiple microinverters to reduce power rating and inductance, and interleaved microinverters to cancel current ripple and reinforce fundamental waveforms, enabling smaller, more efficient power conversion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If conventional large inverters are used to convert DC from solar panels to AC for grid compatibility, then power conversion capability is achieved, but inverter size and cost increase due to large capacitance and inductance requirements

Engineering Contradiction:

Improvepower conversion capabilityVSAvoidinverter size

Core Design Contradiction:

PowerVSVolume of stationary object

Solution Approach 1:

The patent divides a single large inverter into multiple smaller microinverters, each handling a portion of the total power conversion task. This segmentation allows each microinverter to use smaller capacitance and inductance components, reducing individual inverter size while collectively achieving the required power conversion capability through parallel operation

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the electrical parameters of the microinverters by operating them in parallel with interleaved switching patterns. This parameter change allows the system to achieve equivalent power conversion while using significantly reduced capacitance and inductance values compared to a single conventional inverter

Inventive Principle:

Principle #35Parameter changes

2Power

If conventional large inverters are used with high capacitance and inductance, then power conversion is achieved, but installation cost and complexity increase

Engineering Contradiction:

Improvepower conversion capabilityVSAvoidinstallation complexity

Core Design Contradiction:

PowerVSDevice complexity

Solution Approach 1:

By segmenting the inverter function into multiple independent microinverters, each unit can be independently installed and configured on individual photovoltaic modules, simplifying the overall installation process compared to installing one large centralized inverter with complex wiring and mounting requirements

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The microinverters are designed as universal, standardized units that can be applied to various photovoltaic module configurations. This multi-functionality allows the same microinverter design to be used across different installations, reducing installation complexity through standardization

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Loss of energy

If multiple microinverters are connected in parallel with interleaved switching, then current ripple is cancelled and fundamental waveforms are reinforced, but system complexity increases

Engineering Contradiction:

Improveconduction lossesVSAvoidcontrol complexity

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent employs periodic interleaved switching patterns where multiple microinverters operate with phase-shifted switching cycles. This periodic action causes current ripple from individual microinverters to cancel each other out while reinforcing the fundamental power frequency waveforms, reducing energy losses without requiring complex real-time control adjustments

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The interleaved microinverter system uses feedback control to synchronize switching patterns and maintain optimal phase relationships between parallel microinverters. This feedback mechanism ensures continuous ripple cancellation and waveform reinforcement while adapting to varying load conditions

Inventive Principle:

Principle #23Feedback

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

This approach reduces the size and cost of inverters, simplifies installation, and enhances efficiency by integrating microinverters within photovoltaic modules, improving power conversion and reducing conduction losses, while maintaining high output quality.

Implementation Method 1

solar cells that can be microsystems-enabled photovoltaic (MEPV) cells

Methodology Applied

Scientific EffectPhotovoltaic effect: Photovoltaic Effect

Data Source

PatentUS9143053B1Microinverters for employment in connection with photovoltaic modules

Publication Date: 2015.09.22 NATIONAL TECHNOLOGY & ENGINEERING SOLUTIONS OF SANDIA LLC

AI summary

Microinverters useable in association with photovoltaic modules are described. A three phase-microinverter receives direct current output generated by a microsystems-enabled photovoltaic cell and converts such direct current output into three-phase alternating current out. The three-phase microinverter is interleaved with other three-phase-microinverters, wherein such microinverters are integrated in a photovoltaic module with the microsystems-enabled photovoltaic cell.