Modular DC Link Energy Storage for Flexible Grid Inertia Support
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Solution Overview
Problem
Existing DC-DC converters with energy storage capability lack flexibility, reliability, and power transmission capabilities, leading to instability in power grids with reduced inertia due to increased renewable energy sources.
Innovation Solution
An energy storage system comprising modular multilevel converters, individually switchable energy storage devices, and an AC loop device, allowing for flexible power exchange and control, with super capacitors and batteries for quick power bursts or long-term energy storage, respectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional power production resources are replaced with renewable power sources, then environmental sustainability is improved, but system inertia is reduced resulting in grid instability
Solution Approach 1:
The patent introduces an intermediary inertia emulation system comprising power electronic converters and energy storage devices that mediate between renewable power sources and the grid. This intermediary system provides synthetic inertia without requiring conventional synchronous generators, thus maintaining grid stability while enabling renewable energy integration.
Solution Approach 2:
The patent changes the operational parameters of power electronic converters by implementing virtual synchronous machine control strategies. This involves modifying the control algorithms to emulate the inertial response characteristics of conventional generators, thereby providing inertia emulation through parameter adjustment rather than physical hardware changes.
2Power
If DC-DC converters with energy storage capability are implemented, then power transmission capabilities are improved, but design flexibility is reduced
Solution Approach 1:
The patent segments the DC-DC converter into modular components including multiple energy storage devices, power electronic converters, and control systems. This segmentation allows independent optimization of each module while maintaining overall system flexibility, enabling customized configurations for different power transmission requirements.
Solution Approach 2:
The patent implements dynamic control strategies that allow the converter parameters to be adjusted in real-time based on operating conditions. The control system can dynamically modify conversion ratios, power flow directions, and energy storage charging/discharging rates, providing adaptability across varying power transmission scenarios.
3Reliability
If existing DC-DC converters are used for energy storage, then basic energy storage function is achieved, but reliability and availability are reduced
Solution Approach 1:
The patent incorporates energy storage devices as a cushioning element that can absorb power fluctuations and provide backup power before actual failures occur. This prior cushioning capability protects the converter system from stress and potential failures, enhancing reliability without requiring redundant converter hardware.
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
Enhances grid stability by providing flexible, reliable, and efficient energy storage with higher power transmission capabilities, reducing dependency on lowest state of charge and enabling cost-effective operation across varying power demands.
Implementation Method 1
Each energy storage device comprises a cell having power electronic switches, and an energy storage element connected to the cell, wherein the cells are individually switchable
Data Source
AI summary
There is disclosed herein an energy storage system for a direct current (DC) transmission system, the energy storage system being configured to be connected to a DC link. The energy storage system comprises a first system terminal, a second system terminal, a first converter connected to the first system terminal, and a second converter connected to the first converter and the second system terminal. The energy storage system further comprises an AC loop device providing an alternating current (AC) path, and a plurality of energy storage devices connected in parallel with the second converter comprising a cell having power electronic switches, and an energy storage element connected to the cell, wherein the cells are individually switchable. The present disclosure further relates to a method for providing energy storage to a DC transmission system.