Bidirectional DC-DC Converter with Two-Step Voltage Transformation
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Solution Overview
Problem
Conventional bidirectional DC-DC converters require a large number of battery cells connected in series due to low voltage conversion ratio, leading to high costs and instability issues caused by leakage inductance.
Innovation Solution
A bidirectional DC-DC converter employing a magnetically coupled inductor with a two-step voltage transformation process, switching between boost and buck converter modes to achieve high gain through a magnetically coupled inductor and a charging/discharging voltage storage unit, with switch units to manage energy transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional bidirectional buck booster-type DC-DC converter is used, then the basic structure is simple, but the voltage conversion ratio is low requiring a large number of battery cells connected in series
Solution Approach 1:
The patent divides the voltage conversion process into two distinct stages: a first voltage conversion stage using a buck converter topology and a second voltage conversion stage using a boost converter topology. This segmentation allows each stage to operate optimally within its voltage range, achieving high overall voltage conversion ratio while using a manageable number of battery cells connected in series.
Solution Approach 2:
The patent introduces a dual-stage conversion architecture that adds a temporal dimension to the voltage conversion process. Instead of attempting single-stage conversion, the system performs sequential conversion through two distinct operational phases, effectively solving the voltage ratio problem by distributing the conversion task across time and stages rather than requiring excessive battery cell series connections.
2Power
If a conventional bidirectional flyback-type DC-DC converter is used, then voltage gain can be controlled by transformer turn ratio, but leakage inductance causes voltage spikes degrading stability
Solution Approach 1:
The patent extracts and removes the transformer component from the conventional flyback topology, replacing it with a dual-stage converter architecture using separate inductors for each stage. This extraction eliminates the source of leakage inductance problems while maintaining the ability to control voltage gain through duty cycle modulation in each stage, thereby improving stability without sacrificing power conversion capability.
Solution Approach 2:
Instead of attempting to suppress voltage spikes caused by leakage inductance, the patent fundamentally eliminates the harmful leakage inductance effect by replacing the transformer with magnetically uncoupled inductors in a dual-stage architecture. This converts the potential harm of voltage instability into a benefit of inherent stability, while voltage gain control is achieved through controlled switching duty cycles in each stage.
3Power
If magnetically coupled inductors are used to implement high voltage conversion ratio, then voltage gain is improved, but sudden change of leakage inductance current causes high voltage spikes
Solution Approach 1:
The patent converts the potential harm of magnetic coupling and leakage inductance into a benefit by using magnetically uncoupled inductors in a dual-stage architecture. This eliminates voltage spikes caused by sudden leakage inductance current changes, while the two-stage conversion process maintains high voltage conversion ratio capability through sequential voltage transformation.
Solution Approach 2:
The patent segments the magnetic energy storage and transfer functions into two separate inductors operating in distinct stages, eliminating the magnetic coupling that causes leakage inductance problems. Each inductor operates independently with controlled current waveforms, preventing the harmful voltage spikes while achieving the desired voltage conversion through coordinated two-stage operation.
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 solution reduces the number of battery cells needed, enhances voltage conversion efficiency, and minimizes the impact of leakage inductance, resulting in a cost-effective and stable energy conversion system with a broader voltage range.
Implementation Method 1
a magnetically coupled inductor configured to store electrical energy supplied from a battery power supply or output electrical energy stored therein in a boost converter mode, and charge the battery power supply with electrical energy stored therein or store electrical energy supplied from a DC link power supply in a buck converter mode
Data Source
AI summary
The present invention relates to a technique for implementing a bidirectional DC-DC converter applied to an energy storage system.The bidirectional DC-DC converter includes a magnetically coupled inductor and a charging/discharging voltage storage unit between a DC link power supply and a battery power supply, and implements a high gain through a two-step voltage transformation process when a charging process or discharging process is performed. Thus, the bidirectional DC-DC converter can reduce the construction cost of the battery cell, guarantee a high voltage available range, and reduce the influence of leakage inductance.