Modular Flywheel Grid Interface for Fast Frequency Support
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Solution Overview
Problem
Existing energy storage systems for frequency support in AC power grids face challenges such as high self-discharge rates due to mechanical friction and limited short circuit contribution, particularly in utility applications.
Innovation Solution
A bi-directional DC/AC power electronic converter interface connects energy storage modules in series and parallel configurations, allowing flexible adaptation of output voltage and providing redundancy, with each module having its own converter for efficient energy transfer and reduced spatial footprint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional synchronous condenser is used, then reactive power and active power support can be provided, but the reactive power response is voltage dependent and relatively slow
Solution Approach 1:
The patent replaces the conventional synchronous condenser's mechanical/electromagnetic operation with a power electronics-based flywheel energy storage system. The flywheel converter system provides voltage-independent reactive power support and faster response times by using power electronic conversion instead of relying on voltage-dependent electromagnetic fields and mechanical inertia alone.
Solution Approach 2:
The system changes the operational parameters by decoupling the flywheel rotation speed from grid frequency, allowing the flywheel to rotate at optimal speeds for energy storage while the power electronics interface handles frequency conversion. This enables independent optimization of energy storage efficiency and grid support response characteristics.
2Speed
If power electronics-interfaced synchronous condenser is used, then reactive/active power support with fast response is achieved, but the short circuit contribution is limited
Solution Approach 1:
The patent segments the system into multiple parallel-connected flywheel modules, each with its own converter. This modular architecture allows individual modules to contribute to short circuit support independently, and the collective contribution of multiple parallel modules provides enhanced short circuit support capability while maintaining fast response characteristics.
3Duration of action of stationary object
If kinetic energy storage with ball bearings is used, then long lifetime and lower environmental impact are achieved, but high self-discharge rate due to mechanical friction occurs
Solution Approach 1:
The patent replaces mechanical ball bearing support with magnetic bearing technology. Magnetic bearings eliminate mechanical contact and friction, thereby dramatically reducing energy losses from mechanical friction while maintaining the long lifetime and environmental benefits of kinetic energy storage systems.
4Adaptability or versatility
If series connected ES groups with parallel ES modules are used, then flexibility and redundancy are improved, but device complexity increases
Solution Approach 1:
The patent divides the energy storage system into multiple standardized modular units, each comprising a flywheel, magnetic bearings, and a power electronic converter. These modular units can be connected in series to achieve different voltage levels and in parallel to provide redundancy, allowing flexible configuration without proportionally increasing overall system complexity due to the standardized modular design.
Solution Approach 2:
Each modular flywheel unit is designed as a universal building block that can perform multiple functions: energy storage, frequency support, voltage support, and short circuit contribution. This multi-functionality reduces the need for separate specialized components, thereby limiting the increase in device complexity while providing adaptability.
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 solution enhances frequency stability by reducing friction losses, improving modularity, reliability, and reducing power electronics costs, while offering fast and efficient active power support with increased redundancy and lower losses compared to conventional systems.
Implementation Method 1
a bi-directional DC/AC power electronic converter interface configured for connecting the ES arrangement with the grid
Implementation Method 2
Energy storage to buffer the imbalance between the generation and load, and mitigate the frequency excursions
Implementation Method 3
with the use of magnetic bearings, this problem can be mitigated
Data Source
AI summary
A frequency support system arranged for providing frequency support to an AC grid. The system includes an ES arrangement, and a bi-directional DC/AC power electronic converter interface configured for connecting the ES arrangement with the grid. The ES arrangement includes a plurality of series connected ES groups, each ES group including a plurality of parallel connected ES modules, each ES module including an energy storage interfaced by a bi-directional power electronic ES converter configured for connecting the ES with a DC side of the converter interface.