HVDC Transmission Abnormal Voltage Detection via Active Power Ratio
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Solution Overview
Problem
High voltage direct current (HVDC) transmission systems face challenges in quickly detecting abnormal voltage states on DC transmission lines, which can lead to damage due to overcurrent or overvoltage conditions.
Innovation Solution
The implementation of a control method that utilizes active power measurement units to calculate the ratio of second active power to first active power, generating a trip signal to stop the HVDC transmission system when the ratio falls outside a reference range, thereby detecting and addressing abnormal voltage states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional voltage detection methods are used on DC transmission lines, then the system structure remains simple, but the detection speed and reliability are insufficient to quickly identify abnormal voltage states
Solution Approach 1:
The patent introduces active power measurement units as intermediary devices that measure active power at both ends of the DC transmission line. Instead of directly measuring voltage, the system uses active power measurements as intermediaries to infer voltage abnormalities through power ratio calculations, thereby improving detection reliability without adding complex direct voltage sensing equipment to the transmission line
Solution Approach 2:
The control unit continuously receives active power measurement data from both ends of the transmission line, calculates the power ratio, compares it against predetermined thresholds, and provides feedback to determine whether abnormal voltage states exist. This closed-loop feedback mechanism enables rapid and reliable detection of voltage abnormalities
2Measurement precision
If direct voltage measurement devices are installed on the DC transmission line, then voltage detection accuracy improves, but the system complexity and cost increase significantly
Solution Approach 1:
The patent replaces direct electrical voltage measurement devices with an indirect measurement approach using active power measurements. By substituting the mechanical/electrical voltage sensing system with a power-based calculation system, the patent achieves sufficient measurement precision for detecting voltage abnormalities while avoiding the complexity and cost of installing direct voltage measurement equipment on the high-voltage DC transmission line
Solution Approach 2:
Active power measurements serve as intermediary variables that allow the system to infer voltage conditions without directly measuring voltage. The control unit calculates the ratio of active powers from both ends and uses this intermediary metric to detect voltage abnormalities, achieving precise enough measurement without complex direct voltage sensing
3Reliability
If the system operates without rapid abnormal state detection, then the operational complexity is reduced, but the risk of damage from overcurrent or overvoltage conditions increases
Solution Approach 1:
The patent implements preliminary protective action by continuously monitoring active power ratios and comparing them against predetermined threshold values before abnormal conditions can cause damage. The control unit is pre-configured with reference ranges, enabling it to quickly identify and respond to voltage abnormalities before they lead to overcurrent or equipment damage, thus providing reliable system protection with relatively simple control logic
Data Source
AI summary
A high voltage direct current (HVDC) transmission system is provided. The high voltage direct current (HVDC) transmission system includes: a rectifier converting alternating current (AC) power into DC power; an inverter converting the DC power into the AC power; a DC transmission line transmitting, to the inverter, the DC power obtained through conversion by the rectifier; a first active power measurement unit measuring first active power input to the rectifier; a second active power measurement unit measuring second active power output from the inverter; and a first control unit detecting an abnormal voltage state on the DC transmission line based on the first and second active power measured.