DC Feeder Diode Current Limiting for Wind Power Reliability
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Solution Overview
Problem
In wind power generation systems that collect electric powers in the form of DC, accidents can cause excessive current flow, leading to increased costs and equipment scale due to the need for DC breakers to form a current zero point, which is not naturally present in DC currents.
Innovation Solution
The integration of diodes in series with the connection points between feeders and the DC bus prevents excessive currents from flowing, reducing the duty and cost of DC breakers, and optionally using smoothing capacitors and reactors to manage accident currents, allowing for compact and cost-effective DC breaker configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DC breakers are used to protect against accidents in DC feeders, then system reliability is improved, but device complexity and cost increase due to the need for current zero point formation equipment
Solution Approach 1:
The system divides the DC network into multiple independent feeders, each protected by its own DC breaker. This segmentation isolates faults to individual feeders, preventing system-wide outages while allowing each breaker to be relatively simple in design.
Solution Approach 2:
A current zero point generation circuit is introduced as an intermediary component within each DC breaker. This circuit actively creates the necessary current zero point condition for breaker operation, eliminating the need for complex external zero point formation equipment and reducing overall system complexity.
2Reliability
If excessive current capacity is provided in cables and equipment to handle accident currents, then system reliability is improved, but cost and equipment scale increase
Solution Approach 1:
The DC network is segmented into multiple feeders with individual DC breakers. When an accident occurs in one feeder, only that feeder is disconnected while others remain operational. This limits the maximum accident current to the level of a single feeder rather than the total system current, allowing cables and equipment to be sized for normal operating conditions plus a safety margin rather than worst-case scenario currents.
Solution Approach 2:
DC breakers are pre-installed in each feeder to provide immediate protection against accidents. These breakers detect and interrupt fault currents before they can escalate to dangerous levels, preventing the need for oversized equipment designed to withstand extreme accident currents.
3Reliability
If DC breakers with full accident current capacity are installed in each feeder, then system reliability is improved, but device complexity and cost increase due to current zero point formation requirements
Solution Approach 1:
A current zero point generation circuit is introduced as an intermediary component within each DC breaker. This circuit actively creates the necessary current zero point condition for breaker operation, eliminating the need for complex external zero point formation equipment and reducing overall system complexity.
Solution Approach 2:
The current zero point generation circuit is pre-configured within each DC breaker, ready to activate immediately upon fault detection. This preliminary preparation ensures that the breaker can interrupt fault currents effectively without requiring complex real-time zero point formation, simplifying the overall breaker design.
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
This configuration reduces the duty and cost of network instruments, such as DC breakers, by preventing excessive current flow and managing accident currents, thereby minimizing the scale and cost of equipment necessary for protection in wind power generation systems.
Implementation Method 1
a current limiting unit 20 composed of a DC breaker 5 and a diode 6, which are connected in series with a connection point between a plurality of lines 3 of feeders and a DC bus 4
Implementation Method 2
a commutation circuit composed of a capacitor and a reactor is connected in parallel with a breaking part, and an electric charge, which has been pre-charged in the capacitor, is discharged to superpose a current, which is resonant with the reactor, onto a DC current, and thereby to form a current zero point
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A wind power generation system according to the present invention includes: a DC bus (4); a plurality of feeders (3) connected to the DC bus (4) for transmitting DC powers to the DC bus (4); a plurality of wind power generators (1); a plurality of AC/DC converters (2) connected one by one to each of the wind power generators (1) for converting AC powers generated by the connected wind power generators (1), into DC powers, and outputting the DC powers to the feeders (3); and a DC breaker (5) and a diode (6), which serve as a current limiting unit installed on each of the feeders (3) for preventing a DC current from flowing from the DC bus (4) into the feeder (3).