Battery Storage Neutral State Adjustment for Grid Frequency Control

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Solution Overview

Problem

Existing battery storage systems for providing primary control power are oversized and expensive due to the need to maintain a neutral state of charge at 50%, leading to frequent switching operations in the changeover mechanism, which shortens the lifespan of electromechanical switches and increases losses with power electronic circuits.

Innovation Solution

A control device is implemented to adjust the neutral state of charge between 50% and 100%, allowing the changeover mechanism to connect the direct current input and output to the energy-converter only when the network frequency exceeds the nominal frequency by a predetermined amount, reducing unnecessary switching and enabling energy storage before conversion to heat.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the neutral state of charge is set to 50%, then the battery storage system can provide guaranteed primary control power, but the battery storage size and cost increase significantly

Engineering Contradiction:

Improveprimary control power provisionVSAvoidbattery storage size

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent changes the neutral state of charge parameter from the conventional 50% to a range of 70-100%. This parameter change allows the battery storage system to maintain guaranteed primary control power provision while reducing the required battery storage size by 20-40%, thereby resolving the contradiction between reliability and quantity of substance.

Inventive Principle:

Principle #35Parameter changes

2Productivity

If the changeover mechanism switches frequently to maintain neutral state, then the system responds to frequency deviations, but the lifespan of electromechanical switches decreases

Engineering Contradiction:

Improveresponse to frequency deviationsVSAvoidswitch lifespan

Core Design Contradiction:

ProductivityVSDuration of action of stationary object

Solution Approach 1:

The patent implements preliminary action by pre-charging the battery storage to a higher state of charge (70-100%) before frequency deviations occur. This allows the system to respond to frequency deviations by discharging rather than switching, thereby reducing changeover operations and extending switch lifespan while maintaining productivity.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent modifies the periodic switching action by introducing asymmetric thresholds: the battery is charged to a higher state of charge (70-100%) and discharged to a lower state of charge (20-30%). This periodic action with extended ranges reduces the frequency of changeover operations while maintaining system responsiveness.

Inventive Principle:

Principle #19Periodic action

3Speed

If power electronic circuits are used instead of electromechanical switches, then switching losses increase, but the system can respond more quickly to frequency changes

Engineering Contradiction:

Improveresponse speed to frequency changesVSAvoidswitching losses

Core Design Contradiction:

SpeedVSLoss of energy

Solution Approach 1:

The patent applies mechanics substitution by replacing frequent electromechanical switch operations with battery storage discharge/charge operations. The battery acts as an energy buffer that can respond quickly to frequency changes without the mechanical wear and switching losses associated with power electronic circuits, thereby reducing energy losses while maintaining fast response capability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 reduces the frequency of changeover operations, prolongs the lifespan of electromechanical switches, and minimizes energy losses, allowing for more economical operation of battery storage systems by optimizing the state of charge and switching thresholds.

Implementation Method 1

a converter for converting from alternating current into direct current and vice versa, wherein the converter has a direct current input and output, an alternating current input and output, and a power unit with power semiconductor devices

Methodology Applied

Scientific EffectElectrical conversion:

Implementation Method 2

an energy-converter, in particular, a heat generator

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Data Source

PatentUS10326274B2Arrangement comprising an energy storage device for receiving electrical energy from an electrical network and discharing electrical energy to the electrical network

Publication Date: 2019.06.18 AEG POWER SOLUTIONS GMBH

AI summary

An arrangement for receiving electrical energy from a power grid and for discharging electrical energy to the power grid comprises: a converter to convert from AC to DC and vice versa and a control device. The converter includes: a power unit connected on one side to a DC I/O and on another side to an AC I/O; an energy storage device; an energy-converter; and a changeover mechanism to which the energy storage device or the energy-converter is connected via the DC I/O. The control device controls the changeover mechanism such that a neutral state is a state of charge of the energy storage device between 50% and 100%; and at or above the neutral state, the changeover mechanism connects the DC I/O of the converter to the energy-converter at a network frequency higher than a nominal network frequency plus a predetermined, non-zero amount.