DC Power Conversion Device Self-Service Restart Control
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Solution Overview
Problem
In a DC power transmission system, when a DC line experiences an accident, the restart of power conversion devices can be unstable due to random operation without confirming the system's soundness, leading to potential instability in power transmission.
Innovation Solution
A power conversion device with a current breaker and terminal control device that allows for quick and stable restart by controlling the power conversion unit's switching elements based on DC terminal voltage and storage element voltage, eliminating the need for communication with other devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If each power conversion device performs restart operation randomly without communication, then restart speed is improved, but system stability deteriorates
Solution Approach 1:
Each power conversion device independently determines its restart timing by monitoring the DC terminal voltage itself, without needing to communicate with other devices. The control device detects when the DC terminal voltage exceeds a predetermined threshold and autonomously generates a restart instruction, enabling self-service restart operation that achieves both fast restart and system stability
Solution Approach 2:
The control device continuously monitors the DC terminal voltage and uses this feedback information to determine the appropriate restart timing. When the DC terminal voltage exceeds a predetermined threshold value, the control device generates a restart instruction, creating a closed-loop feedback mechanism that ensures restart occurs at the optimal moment for system stability while maintaining fast restart speed
2Reliability
If each power conversion device waits for communication confirmation before restart, then system stability is improved, but restart speed deteriorates
Solution Approach 1:
The power conversion device eliminates the need for communication-based confirmation by using self-service restart determination. The control device monitors DC terminal voltage locally and autonomously decides when to restart based on predetermined voltage thresholds, removing communication delays entirely while maintaining system stability through voltage-based timing
Solution Approach 2:
The system performs preliminary monitoring of DC terminal voltage during the stopped state. When the voltage exceeds a predetermined threshold, the restart condition is pre-established, allowing immediate restart execution without waiting for communication confirmation, thus reducing processing time while ensuring stability
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
Enables rapid and stable restart of power conversion devices without requiring communication with other devices, preventing unstable system operation by ensuring proper synchronization and voltage management during the restart process.
Implementation Method 1
Each cell comprises a plurality of semiconductor switches and a DC capacitor
Data Source
AI summary
A DC power transmission system interconnects a plurality of AC systems via a DC line. A plurality of power conversion devices are connected between the plurality of AC systems and the DC line. One of the plurality of power conversion devices controls the voltage on the DC line, while the remaining power conversion device controls a current input and output to and from the DC line. In a restart which resumes power conversion from a stopped state for controlling a DC current on the DC line, the power conversion device performing current control monitors the voltage on the DC line and starts a restart operation without transmitting or receiving information to or from the other power conversion device.