DC Link Power Supply Assembly for Distant Fault Ride-Through
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Solution Overview
Problem
In power supply assemblies, long load wiring and faults distant from the load converter can cause current drawn by the fault to be below the load converter's upper limit current value, leading to a power surplus at the source converter, which fails to maintain the DC link voltage, potentially resulting in DC link collapse and shutdown.
Innovation Solution
The power supply assembly decreases the load converter's current below its capable value during faults, reducing the source converter's power and allowing it to maintain the DC link voltage, using a control system to dynamically adjust the control limit current and potentially employing an energy saving transfer route to bypass the source converter and load converter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the load converter operates at its upper limit current value, then the source converter can transfer maximum power to the DC link, but during distant faults the DC link voltage cannot be maintained and the system shuts down
Solution Approach 1:
The control system dynamically adjusts the control limit current of the load converter based on real-time monitoring of DC link voltage and power balance. During normal operation, the load converter operates at its upper limit current value for maximum power transfer. When a fault is detected (DC link voltage deviation or power imbalance), the control system automatically reduces the control limit current to maintain voltage stability, preventing system shutdown while maintaining operational continuity.
Solution Approach 2:
The control system continuously monitors the DC link voltage and power transfer status, and uses this feedback to adjust the control limit current of the load converter. When the DC link voltage deviates from the predetermined value or when the source converter power exceeds its upper limit, the control system reduces the load converter current accordingly. This closed-loop feedback mechanism ensures that the system can detect and respond to fault conditions, maintaining stability during distant faults while preserving maximum power transfer capability under normal conditions.
2Device complexity
If the protection system uses only current-based fault detection, then simple fault detection is achieved, but faults far from the load converter are not detected and the DC link collapses
Solution Approach 1:
The control system performs multiple functions: it controls the load converter current during normal operation, detects fault conditions through power balance monitoring, and adjusts the control limit current to maintain DC link voltage stability. By making the control system multi-functional, the patent avoids adding separate complex protection devices while achieving reliable fault detection and response, solving both the simplicity and reliability requirements.
3Adaptability or versatility
If long load wiring is used to extend the service area, then the service coverage is increased, but wire resistance causes voltage drop and DC link collapse during faults
Solution Approach 1:
The control system proactively monitors the power balance and DC link voltage before the fault causes system collapse. When it detects that the source converter power exceeds its upper limit or that the DC link voltage deviates from the predetermined value, it preemptively adjusts the control limit current of the load converter to prevent voltage collapse. This preliminary action allows the system to maintain stability even with long load wiring extending service coverage.
Data Source
Figure 1~2
AI summary
A power supply assembly comprising a source converter (81), a load converter (82) having an upper limit current value (I82,lim), a DC link (2) comprising DC link capacitance, direct current connections of the source converter (81) and the load converter (82) being electrically connected to the DC link (2), and a control system (909) adapted to control the load converter (82) such that current of the load converter (82) is less than or equal to a control limit current value (Icmax,82). During normal operating conditions, the control limit current value (Icmax,82) is equal to the upper limit current value (I82,lim) of the load converter (82). As a response to a predetermined fault situation, the control limit current value (Icmax,82) is decreased to a value lower than the upper limit current value (I82,lim) of the load converter (82).