Distributed Voltage Clamping for Renewable Sending-End Grid Stability
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Solution Overview
Problem
The 100% renewable-energy sending-end grid faces stability issues due to multiple voltage levels and long electrical distances, leading to poor voltage support and potential overvoltage, particularly in large-scale onshore and offshore wind power generation bases, where conventional direct-current transmission technologies struggle with power-frequency overvoltage and black start conditions.
Innovation Solution
A distributed voltage clamping method is introduced, involving the selection of key nodes in the grid, installation of dynamic reactive power compensation devices, and adjustment of voltage levels using a voltage-reactive droop control algorithm to maintain stable voltage within specified limits, ensuring the grid meets operational requirements even under varying conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional direct-current transmission technology is used, then the system can transmit power over long distances, but it suffers from serious power-frequency overvoltage and black start problems under islanding conditions
Solution Approach 1:
The patent replaces conventional current-source converter-based DC transmission with voltage-source converter-based DC transmission. This substitution fundamentally changes the control mechanism from current-based to voltage-based control, enabling the system to maintain stable operation under islanding conditions while preserving long-distance transmission capability. The voltage-source converter can independently control active and reactive power, providing stable voltage support during islanded operation.
2Productivity
If the 100% renewable-energy power-generation base occupies large area with long electrical distance, then more renewable energy can be integrated, but the voltage support strength at grid-connected points becomes weak
Solution Approach 1:
The patent introduces a reactive power compensation device as an intermediary component at the grid-connected point. This device acts as a mediator between the renewable energy base and the grid, providing local reactive power support to strengthen voltage stability. The compensation device decouples the voltage support function from the distance-dependent grid connection, enabling strong voltage support even for large-scale, geographically dispersed renewable energy bases.
Solution Approach 2:
The patent employs voltage-reactive droop control that dynamically adjusts the reactive power output based on voltage deviations. When voltage drops, the compensation device automatically increases reactive power injection; when voltage rises, it reduces or absorbs reactive power. This dynamic parameter adjustment maintains optimal voltage levels and provides adaptive voltage support strength regardless of the electrical distance from renewable energy sources.
3Reliability
If dynamic reactive power compensation devices are installed at multiple key nodes, then voltage stability is improved, but the device complexity and cost increase
Solution Approach 1:
The patent applies reactive power compensation selectively at strategically identified key nodes rather than uniformly across all nodes. The voltage-reactive droop control is implemented locally at each selected node, providing targeted voltage support where it is most needed. This localized approach maintains voltage stability while minimizing the total number of compensation devices required, as each device operates autonomously based on local voltage conditions.
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 method enhances the operational stability and universality of the renewable-energy sending-end grid, preventing overvoltage and ensuring reliable power transmission across different topological structures, offering a practical solution for engineering applications.
Implementation Method 1
installation of dynamic reactive power compensation devices, and adjustment of voltage levels using a voltage-reactive droop control algorithm
Data Source
AI summary
A distributed voltage clamping method for a 100% renewable-energy sending-end grid, including: selecting key nodes from the 100% renewable-energy sending-end grid, including their voltage levels and positions; installing a dynamic reactive power compensation device on each key node, where the dynamic reactive power compensation device is controlled by a constant alternating-current (AC) voltage effective value, and the instruction value of the constant AC voltage effective value is adjustable according to an operation mode; according to AC voltage variation of the sending-end grid under a typical working condition, judging whether the key nodes meet the checking requirements; if not, selecting more key nodes.