HVDC Energy Buffer Cells for Virtual Inertia and Fault Recovery
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The transition from traditional synchronous generators to renewable energy sources in power systems poses challenges in maintaining stability and recovery from faults due to the different characteristics of renewable energy sources, necessitating alternative means to provide energy buffering and stability support.
Innovation Solution
An energy supporting device for HVDC transmission systems, comprising a series of cells with full-bridge power switches and energy storage devices, allows for energy storage, dissipation, and release, enabling grid forming and virtual synchronous machine capabilities, independent of AC network conditions, and can absorb or dissipate energy quickly to stabilize the grid.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional synchronous generators are replaced by renewable energy sources, then the use of renewable energy increases, but the stability of the power system deteriorates due to lack of natural inertia
Solution Approach 1:
The patent introduces an energy supporting device as an intermediary component between renewable energy sources and the power system. This device includes energy storage devices (capacitors or batteries) that mediate the connection, providing virtual inertia and frequency support to compensate for the lack of natural inertia from synchronous generators, thereby maintaining system stability while enabling high renewable energy integration
Solution Approach 2:
The patent changes the operational parameters of the power system by introducing controllable energy storage devices that can dynamically adjust their impedance and power output. The full-bridge power switch arrangements enable rapid switching between charging and discharging modes, allowing the system to provide synthetic inertia and frequency regulation services that mimic traditional synchronous generators
2Productivity
If power electronic converters are used to transmit renewable energy, then renewable energy transmission is enabled, but the natural inertia and stability support capabilities are lost
Solution Approach 1:
The patent implements preliminary action by pre-charging energy storage devices during normal operation and having them ready to provide rapid support during disturbances. The energy storage devices are maintained in a charged state beforehand, enabling them to immediately provide inertia support and frequency regulation when needed, rather than waiting for a disturbance to occur
Solution Approach 2:
The patent replaces the mechanical inertia of synchronous generators with an electrical/electronic system consisting of energy storage devices and full-bridge power switches. This substitution uses electrical energy storage and rapid switching to simulate mechanical inertia effects, providing synthetic inertia and damping without requiring large rotating masses
3Reliability
If energy storage devices are added to provide stability support, then power system stability improves, but the device complexity increases
Solution Approach 1:
The patent segments the energy supporting device into modular cells, each containing energy storage devices and full-bridge power switch arrangements. These modular units can be independently controlled and combined in series or parallel configurations, allowing the system to provide stability support while maintaining manageable complexity through standardized, replaceable modules
Solution Approach 2:
The patent designs the energy supporting device to perform multiple functions simultaneously: providing virtual inertia, frequency regulation, voltage support, and energy buffering. The same energy storage devices and power switches that provide inertia support also enable bidirectional power flow and grid-forming capabilities, reducing overall system complexity by consolidating multiple functions into a single integrated device
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 energy supporting device enhances the stability and fault recovery capabilities of HVDC transmission systems by providing rapid energy absorption and dissipation, allowing a higher proportion of renewable energy sources to be integrated into the grid, and acts as an energy buffer to manage energy imbalances.
Implementation Method 1
an energy storage device electrically connected to the full-bridge arrangement... in a charging mode, in which the energy storage device of at least one cell of the plurality of cells is receiving electrical energy from the HVDC link... in an energy release mode, in which the energy storage device of at least one cell of the plurality of cells is providing electrical energy to the HVDC link
Implementation Method 2
a resistor electrically connected between the plurality of cells and an electrical reference potential... in a dissipation mode, in which the bypass switch is in an open state for allowing the resistor to dissipate electrical energy from the HVDC link
Data Source
AI summary
An energy supporting device for a high voltage direct current, HVDC, transmission system includes an energy supporting device for providing grid forming and/or virtual synchronous machine, VSM, capabilities to the HVDC transmission system. The energy supporting device comprises a plurality of cells configured to be connected to the HVDC transmission system, and a cell includes a full-bridge arrangement of power switches, an energy storage device electrically connected to the full-bridge arrangement, a resistor electrically connected between the plurality of cells and an electrical reference potential, and a bypass switch configured to allow the resistor to be bypassed. The energy supporting device is configured to be operated in a dissipation mode, in which the bypass switch is in an open state for allowing the resistor to dissipate electrical energy from the HVDC transmission system, and in which the energy storage devices of the plurality of cells are bypassed.