Power Converter Voltage Limiting for Breaker-Failure Overvoltage
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Solution Overview
Problem
In power systems, when a breaker on the output side of a power converter fails, impedance rapidly increases, leading to the potential for overvoltage in the output from the power converter.
Innovation Solution
A control device for a power converter that includes a voltage command value limiting unit and a current feedback control output limiting unit, which restrict each phase component or the absolute value of the voltage and current feedback control outputs to predetermined values, preventing overvoltage when impedance increases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If breaker on output side fails and impedance rapidly increases, then system reliability is compromised, but overvoltage occurs in power converter output
Solution Approach 1:
The control device applies preliminary anti-action by detecting impedance increase and preemptively limiting the voltage command value before overvoltage can occur. The limiting unit restricts the voltage command value to a predetermined safe level when impedance change is detected, preventing the harmful overvoltage effect before it develops
Solution Approach 2:
The control device implements feedback control by continuously monitoring the impedance state on the output side and adjusting the voltage command value accordingly. When impedance increase is detected through feedback, the control device modifies the voltage command to maintain safe operating levels, creating a closed-loop protection mechanism
2Object-affected harmful factors
If voltage command value is limited to prevent overvoltage, then overvoltage is prevented, but voltage control flexibility is reduced
Solution Approach 1:
The control device applies dynamics by making the voltage command value adaptive rather than fixed. The limiting unit dynamically adjusts the voltage command value based on real-time impedance conditions, allowing full control flexibility under normal conditions while automatically applying limits only when impedance increase is detected, thus maintaining adaptability while preventing overvoltage
Data Source
AI summary
A control device for a power converter includes a voltage command value limiting unit configured to limit each phase component or an absolute value of a vector of a voltage command value to be equal to or less than a value set in advance. With such a configuration, the control device for the power converter limits each phase component or the absolute value of the vector of the voltage command value to be equal to or less than the value set in advance. Therefore, it is possible to prevent overvoltage of the output from the power converter when impedance rapidly increases on the output side of the power converter.