HVDC Rectifier Protection via Power Tracking Controller
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Solution Overview
Problem
HVDC systems face instability and rectification failures due to overloading or generator dropping, limiting stabilization and efficiency in power transmission.
Innovation Solution
A high voltage direct current (HVDC) power increase controller that outputs a current command value with a step waveform, adjusting based on comparisons of AC voltage and DC power levels to maintain stability and track the maximum power point, preventing rectification failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the current command value is increased to transmit more power, then the power transmission efficiency is improved, but the system stability deteriorates and rectification failures occur
Solution Approach 1:
The controller continuously monitors AC voltage levels and DC power levels, comparing them against reference values (lowest AC voltage causing rectification failure, estimated DC power level). Based on these feedback comparisons, the controller dynamically adjusts the current command value to maintain optimal operation without exceeding stability limits or causing rectification failures.
Solution Approach 2:
The controller changes the current command value parameter dynamically based on operating conditions. By adjusting this key parameter according to AC voltage and DC power level comparisons, the system optimizes power transmission efficiency while preventing rectification failures and maintaining stability under varying load conditions.
2Productivity
If the current command value is adjusted dynamically to track maximum power point, then the power transmission efficiency is improved, but the control complexity increases
Solution Approach 1:
The controller uses feedback from AC voltage and DC power level comparisons to automatically adjust the current command value, enabling dynamic tracking of the maximum power point without requiring complex algorithms. The feedback mechanism simplifies the control logic by using direct comparisons against predefined reference values.
Solution Approach 2:
The controller performs self-adjustment by comparing its own output (DC power level) and input (AC voltage level) against reference values, and automatically modifies its current command value accordingly. This self-service capability enables maximum power point tracking without external intervention or complex computational algorithms.
3Reliability
If the AC voltage drops below the lowest level causing rectification failure, then the rectification stability deteriorates, but the system can still operate at reduced power
Solution Approach 1:
The controller takes preliminary action by monitoring AC voltage levels and comparing them against the lowest voltage threshold that causes rectification failure. Before the voltage drops below this critical threshold, the controller adjusts the current command value to prevent rectification failure, thereby maintaining stability while allowing operation at reduced power capacity.
Solution Approach 2:
The controller performs preliminary adjustments to the current command value based on AC voltage level comparisons before rectification failure occurs. By proactively adjusting operating parameters when voltage approaches critical levels, the system maintains rectification stability and prevents failure while continuing to transmit power at the maximum safe capacity.
Data Source
AI summary
An HVDC power increase controller includes a command output unit for outputting a current command value according to a disturbance signal to a main controller; a voltage drop determiner receiving an alternating current (AC) voltage and comparing a level of the AC voltage to a lowest level of a voltage causing a rectification failure; and a power tracking determiner receiving a direct current (DC) power and comparing a level of the DC power to an estimated power level corresponding to the current command value. The command output unit adjusts the current command value according to a comparison result of the voltage drop determiner and the power tracking determiner.