Grid-Tie Inverter Architecture for Variable AC Renewable Inputs

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Solution Overview

Problem

Current non-solar renewable energy generation systems face challenges in meeting power grid requirements and certification standards, particularly due to the variability of energy sources like wind, hydro, and wave energy, which results in market entry barriers and limited market expansion.

Innovation Solution

A grid-tie system is developed using a solar inverter as the front end, coupled with a variable frequency drive (VFD) as the back end, which converts variable AC power to stable DC and then to grid-matched AC power, ensuring compliance with standards like UL 1741 and IEC 62109, and includes a ground isolation monitor interrupter circuit for safe operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If non-solar renewable energy systems (wind, hydro, wave) are connected directly to the power grid, then energy generation can proceed, but the systems fail to meet power grid requirements and certification standards due to power variability

Engineering Contradiction:

Improvecompliance with power grid standardsVSAvoidhandling of variable energy input

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent introduces a solar inverter as an intermediary device between the non-solar renewable energy source and the power grid. This inverter acts as a mediator that accepts variable AC power from generators (wind, hydro, wave), converts it to DC, and then converts it back to grid-matched AC power with stable frequency and voltage, thereby enabling compliance with UL 1741 and IEC 62109 standards while handling variable energy input

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If complex conversion systems are implemented to meet grid standards, then compliance is achieved, but system complexity and cost increase

Engineering Contradiction:

Improvegrid connection certificationVSAvoidsystem architecture

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent leverages the universal design of solar inverters, which are already certified for grid connection under UL 1741 and IEC 62109 standards. By using a solar inverter for non-solar renewable energy sources, the system achieves grid compliance without requiring separate complex conversion equipment. The solar inverter's multi-functionality allows it to handle various AC inputs and output grid-compliant power, reducing overall system complexity

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent essentially copies the proven solar inverter architecture and applies it to non-solar renewable energy systems. This copying approach allows the system to inherit the solar inverter's certified design, control algorithms, and grid interface capabilities, achieving compliance without reinventing the conversion system

Inventive Principle:

Principle #26Copying

3Object-affected harmful factors

If ground isolation monitoring is added for safety, then operational safety improves, but additional circuitry and complexity are required

Engineering Contradiction:

Improveground isolation safetyVSAvoidmonitoring circuitry

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The solar inverter inherently includes ground isolation monitoring capabilities as part of its safety design. The inverter's control system continuously monitors ground isolation status and can detect ground faults, eliminating the need for separate external monitoring circuits. This self-service approach integrates safety functionality into the existing inverter architecture without adding significant complexity

Inventive Principle:

Principle #25Self-service

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 solution enables efficient conversion and control of renewable energy, allowing for safe and certified grid connection, reducing market barriers and enhancing the viability of non-solar renewable energy systems by meeting power grid standards and providing additional functionalities like motoring and regenerative capabilities.

Implementation Method 1

a solar inverter as the front end, coupled with a variable frequency drive (VFD) as the back end, which converts variable AC power to stable DC

Methodology Applied

Scientific EffectRectification:

Implementation Method 2

converts variable AC power to stable DC and then to grid-matched AC power

Methodology Applied

Scientific EffectInversion:

Implementation Method 3

includes a ground isolation monitor interrupter circuit for safe operation

Methodology Applied

Scientific EffectGround isolation monitoring:

Data Source

PatentUS11791634B2Grid-tie system for AC generators

Publication Date: 2023.10.17 XFLOW ENERGY CO

AI summary

An exemplary renewable-energy system including a back end system coupled to an isolated DC power source and a generator powered by a renewable energy source and including first circuitry configured to convert first AC power from the generator to DC power and to provide the DC power to a DC power bus, the first circuitry further configured to initiate operation using power from the isolated DC power source. The example system further includes a front end system comprising an inverter coupled to an isolated DC power source generator. The inverter includes a ground isolation monitor interrupter (IMI) circuit coupled to the DC power bus and configured to receive the DC power and convert the DC power to second AC power for provision to a power grid. The isolated power source generator ground-isolates third AC power of the power grid for conversion to DC power for the isolated DC power source.