Grid-Forming Inverter Control for Stable Renewable Microgrids

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Isolated electrical grids relying on renewable energy sources face challenges in maintaining stable voltage and frequency without combustion engine-driven alternators.

Innovation Solution

A method and system utilizing a controllable inverter coupled to an electric battery, where the inverter operates as a master controller to adjust grid frequency by supplying or withdrawing power from the battery based on frequency deviations, and optionally using an energy bank and alternators to stabilize the grid.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If combustion engine-driven alternators are used to ensure stable voltage and frequency, then grid stability is maintained, but reliance on non-renewable energy sources increases

Engineering Contradiction:

Improvegrid stabilityVSAvoidrenewable energy penetration

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent replaces the mechanical combustion engine-driven alternator system with an electrical system consisting of battery energy storage systems and controllable inverters. The inverter-based system synthesizes stable grid voltage and frequency through electronic control, eliminating the need for mechanical prime movers while maintaining grid stability and enabling full renewable energy integration.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the fundamental operating parameters of the grid forming component from mechanical rotation speed and torque (in combustion engines) to electrical voltage, frequency, and power control (in inverter-based systems). This parameter transformation enables precise digital control of grid stability while accommodating fluctuating renewable energy inputs without combustion processes.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If renewable energy sources are used to reduce carbon emissions, then environmental sustainability improves, but grid frequency stability deteriorates due to fluctuating power output

Engineering Contradiction:

Improverenewable energy penetrationVSAvoidfrequency stability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent introduces battery energy storage systems as an intermediary between fluctuating renewable energy sources and the grid. The batteries absorb excess power when renewable generation exceeds demand and release power when generation is insufficient, acting as a buffer that smooths fluctuations and maintains frequency stability while enabling high renewable penetration.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent implements closed-loop feedback control through controllable inverters that continuously monitor grid frequency and adjust power output accordingly. The inverter-based grid forming controller detects frequency deviations and automatically modulates the battery system's power delivery to restore frequency to nominal values, ensuring stability despite renewable energy variability.

Inventive Principle:

Principle #23Feedback

3Speed

If battery energy storage systems are used to stabilize grid frequency, then response speed improves, but system complexity increases

Engineering Contradiction:

Improveresponse speedVSAvoidsystem complexity

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

The patent designs the inverter-based grid forming system to perform multiple functions simultaneously: it provides frequency regulation, voltage control, power factor correction, and energy storage management through a single integrated platform. This multi-functionality reduces the need for separate specialized devices, thereby limiting the increase in system complexity while maintaining fast response capabilities.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

Enables stable grid frequency and voltage with high renewable energy penetration, allowing fast and robust response to fluctuations using a hybrid energy system.

Implementation Method 1

a controllable inverter (20) coupled to a battery (21)... supplying power from the battery (21) through the controllable inverter (20) to the grid... withdrawing power through the controllable inverter (20) from the grid to the battery

Methodology Applied

Scientific EffectPower conversion:

Data Source

PatentUS20260018894A1Method and system for operating an electrical grid

Publication Date: 2026.01.15 VESTESEN HYBRID ENERGY APS

AI summary

A method and controller are provided for operating an isolated or weakly connected electrical grid supplied by at least one fluctuating renewable energy source, such as wind or photovoltaic generation, in combination with a grid-forming controllable inverter coupled to a battery. The inverter operates as a master controller to regulate grid frequency and voltage, while the renewable sources operate as slaves. Battery charging and discharging are controlled according to deviations in grid frequency and charge level, with slopes defined for smooth power transitions. Additional selectively driven or non-driven alternators may be coupled in parallel with the inverter to stabilize frequency, provide inertia, reactive power, and short-circuit capacity, or support load changes. Control logic further manages integration of combustion engine-driven generators, resistive load banks, and external energy banks, while accounting for battery temperature and charge thresholds, thereby ensuring stable grid operation under fluctuating generation and demand conditions.