Medium Frequency Transformer Reduces Energy Storage Volume

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Solution Overview

Problem

Conventional energy storage devices for high voltage DC transmission grids are bulky and costly due to the need for high-ratio transformers and bidirectional converters, leading to high volume and cost, especially in applications like offshore wind farms where long-distance power transmission is inefficient.

Innovation Solution

The use of a medium frequency transformer and bidirectional AC/DC conversion module in the energy storage device reduces the volume and cost by enabling efficient AC/DC conversion and transmission, allowing for a more compact and economical energy storage solution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a high-ratio transformer and bidirectional converter are used to enable high voltage DC transmission grid connection, then the energy storage device can achieve dispatching and regulating function, but the volume and cost of the device increase significantly

Engineering Contradiction:

Improvedispatching and regulating functionVSAvoidvolume of energy storage device

Core Design Contradiction:

Adaptability or versatilityVSVolume of stationary object

Solution Approach 1:

The patent changes the working frequency parameter of the transformer from conventional 50/60Hz to medium frequency (e.g., 400Hz). This parameter change allows the transformer to achieve the same voltage transformation ratio with a much smaller core and winding size, directly reducing the volume of the energy storage device while maintaining the required dispatching and regulating functions

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

Engineering Contradiction:

Improvedispatching and regulating functionVSAvoidcost of energy storage device

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

By changing the operating frequency to medium frequency, the patent reduces the material requirements (core steel, copper windings) and manufacturing complexity of the transformer. This parameter change leads to lower material costs, reduced manufacturing complexity, and ultimately lower overall device cost while maintaining full functionality

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the conventional large-scale mechanical transformer system with a medium frequency transformer system that uses electromagnetic induction at higher frequency. This substitution enables more efficient energy transfer with smaller components, reducing both manufacturing cost and device complexity

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Adaptability or versatility

If long-distance AC cable transmission is used to connect wind turbine to onshore substation, then the power system can be connected to the electric grid, but the transmission efficiency is low and cost is high

Engineering Contradiction:

Improvegrid connection capabilityVSAvoidtransmission loss

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The patent substitutes AC transmission with HVDC transmission by introducing a bidirectional AC/DC converter. This substitution eliminates the reactive power losses and skin effect losses inherent in AC cable transmission, significantly improving transmission efficiency for long-distance power transfer from offshore wind farms to onshore substations

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

The proposed solution reduces the volume and cost of the energy storage device while enabling flexible energy regulation and dispatching, supporting efficient power transmission and peak-shaving functions, and providing auxiliary power to generators when needed.

Implementation Method 1

The energy storage device uses a medium frequency transformer

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

at least one bidirectional inverter module, wherein a DC terminal of each bidirectional inverter module is electrically connected with the corresponding energy storage element

Methodology Applied

Scientific EffectPower electronic conversion:

Implementation Method 3

at least one bidirectional AC/DC conversion module, wherein an AC terminal of each bidirectional AC/DC conversion module is electrically connected with a second transmission terminal of the corresponding medium frequency transformer

Methodology Applied

Scientific EffectPower electronic conversion:

Data Source

PatentUS11239663B2Energy storage device and power system and control method thereof

Publication Date: 2022.02.01 DELTA ELECTRONICS (SHANGHAI) CO LTD

AI summary

An energy storage device for a power system is provided. The energy storage device is electrically connected with a high voltage DC transmission grid. The energy storage device includes at least one energy storage element, at least one bidirectional inverter module, at least one medium frequency transformer and at least one bidirectional AC/DC conversion module. A DC terminal of each bidirectional inverter module is electrically connected with the corresponding energy storage element. A first transmission terminal of each medium frequency transformer is electrically connected with an AC terminal of the corresponding bidirectional inverter module. An AC terminal of each bidirectional AC/DC conversion module is electrically connected with a second transmission terminal of the corresponding medium frequency transformer. A DC terminal of each bidirectional AC/DC conversion module is electrically connected with the high voltage DC transmission grid.