Power Conversion Device DC Current Protection Control
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Solution Overview
Problem
Conventional power conversion devices require long-distance communication lines to transmit information for fault ride-through control, leading to increased costs and design constraints due to the need for large design margins between rated DC voltage and threshold values, especially when the rated voltage is close to the threshold.
Innovation Solution
Implementing a power conversion device that performs protection control based on variations in DC current, allowing for early activation of protection measures before DC bus voltage reaches abnormal threshold levels, thus eliminating the need for long-distance communication lines and reducing design constraints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If protection control is executed based on DC voltage threshold detection, then the power conversion device can respond to voltage abnormalities, but the rated DC voltage must be designed with a large margin from the threshold value, increasing design constraints
Solution Approach 1:
The patent changes the detection parameter from DC voltage to DC current. By detecting DC current variations instead of DC voltage thresholds, the system can initiate protection control without requiring a large design margin between rated voltage and threshold values, thus resolving the contradiction between reliability and design complexity
Solution Approach 2:
The patent enables preliminary detection of grid disturbances through DC current variations before the DC bus voltage reaches abnormal threshold levels. This preliminary action allows protection control to be activated in advance, preventing voltage abnormalities while eliminating the need for large voltage design margins
2Loss of information
If long-distance communication lines are used for fault ride-through control, then information can be transmitted between control devices, but the cost and space requirements increase
Solution Approach 1:
The patent enables the power conversion device to autonomously detect grid disturbances through its own DC current measurements. By using self-service detection rather than relying on external communication of control information, the system eliminates the need for long-distance communication lines, reducing both cost and infrastructure complexity
Solution Approach 2:
The patent uses DC current variations as an intermediary signal that inherently carries information about grid disturbance conditions. This intermediary allows control devices to obtain necessary information without requiring direct communication lines, as the DC current itself serves as the information carrier
Data Source
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Figure 3(a)~3(b)
AI summary
A power conversion device (30) which is connected between an electric generation grid and a demand area grid and performs power conversion includes: a power converter (32) which is connected to an electric generation grid (20) and which converts AC power received from the electric generation grid (20) to DC power and transmits the DC power via DC bus (60); and a control device (31) for controlling the power converter (32). The control device (31) includes a detection unit (38) for detecting DC current of the DC bus (60), and a protection control unit (50) for performing protection control for suppressing an amount of power received from the electric generation grid (20), on the basis of variation in the DC current, thereby continuing operation in the case of disturbance in the demand area grid.