Bidirectional Chopper Circuit Inductor Segmentation
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Solution Overview
Problem
Bidirectional chopper circuits face challenges in reducing the size and weight of inductors while maintaining power quality, and existing solutions, such as multiphase and multiplex choppers, are costly and inefficient in preventing short-circuit currents in battery energy storage systems for DC electric railroads.
Innovation Solution
A bidirectional chopper circuit design incorporating an auxiliary power converter with single-phase full-bridge power converters and an inductor, which reduces ripple current and eliminates the need for a separate DC circuit breaker by electrically disconnecting the short-circuit current path, thereby reducing the overall cost and size of the system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If the inductance of the inductor is reduced to decrease size and weight, then the size and weight of the inductor are reduced, but the ripple current increases causing deterioration in power quality and unstable operation
Solution Approach 1:
The patent divides the single large inductor into multiple smaller inductors (first inductor and second inductor) connected in parallel. This segmentation allows each inductor to handle a portion of the total current, reducing the ripple current through each individual inductor while maintaining the overall low inductance value needed for compact size and weight.
Solution Approach 2:
The patent applies different characteristics to different parts of the inductor system by using multiple inductors with potentially different inductance values. Each inductor can be optimized for its specific role in the circuit, allowing local optimization of ripple current distribution while achieving global reduction in size and weight.
2Reliability
If the switching frequency is increased to reduce ripple current, then the ripple current is reduced, but the switching loss increases
Solution Approach 1:
By segmenting the inductor into multiple parallel inductors, the patent reduces the ripple current through each inductor without needing to increase the switching frequency. This allows the system to maintain lower switching frequencies (reducing switching loss) while still achieving acceptable power quality through the distributed inductor configuration.
3Reliability
If a DC circuit breaker is added to protect against short-circuit current, then the converter is protected from short-circuit current, but the cost of the system increases
Solution Approach 1:
The patent enables the bidirectional chopper circuit to protect itself against short-circuit currents through intelligent control of the switching devices. The control unit detects abnormal conditions and automatically adjusts switching patterns to block short-circuit current paths, eliminating the need for separate DC circuit breakers and reducing system cost and complexity.
Solution Approach 2:
The patent implements feedback control mechanisms where the control unit continuously monitors circuit conditions and adjusts switching device operation accordingly. This feedback system detects short-circuit conditions and responds by modifying switching patterns to prevent damage, providing inherent protection without additional hardware.
4Reliability
If multiphase and multiplex chopper methods are used to reduce ripple current, then the ripple current is reduced, but the size and weight of inductors are not significantly reduced and device complexity increases
Solution Approach 1:
The patent uses a simplified segmentation approach by dividing the inductor into just two parallel inductors rather than implementing complex multiphase or multiplex configurations. This achieves ripple current reduction through parallel current distribution while maintaining relatively simple circuit topology and avoiding the complexity of multiphase systems.
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
The proposed solution effectively reduces the size and weight of inductors, minimizes ripple current, and eliminates the need for a DC circuit breaker, resulting in a lower-cost and more efficient bidirectional chopper circuit for battery energy storage systems.
Implementation Method 1
an inductor (13) connected in series with the single-phase full-bridge power converter (22-j) on a wiring line that branches from the connecting point (P)
Implementation Method 2
Each of the first switching unit (21-1) and the second switching unit (21-2) consists of a semiconductor switching device that conducts in one direction when it is ON and a feedback diode connected in antiparallel with the semiconductor switching device
Data Source
Figure 1~2
Figure 3A~4
Figure 5~6
AI summary
A bidirectional chopper circuit 1 is provided with: a main power converter 11 having a first switch 21-1 and a second switch 21-2 set up so that one switch is turned off when the other switch is turned on and connected in series with each other so as to line up in a conduction direction when turned on, the terminals on both sides of the main power converter 11 on the opposite sides to the connection sides for the first switch 21-1 and the second switch 21-2 being a pair of first external connection terminals; a plurality of single-phase full-bridge power converters 22-j and a pair of second external connection terminals provided on wiring that branches from wiring connecting the first switch 21-1 and the second switch 21-2 so that one or both are connected in cascade; and an inductor 13 connected in series with the single-phase full-bridge power converters 22-j on wiring that branches from wiring connecting the first switch 21-1 and the second switch 21-2.