Bidirectional Converter with Multi-Stage Voltage Doubler for Cell Equalization
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Solution Overview
Problem
Existing charge-discharge systems for series-connected electricity storage cells require separate equalization circuits and chargers, leading to complex and costly configurations with high current capacity requirements, and lack a built-in discharging function.
Innovation Solution
A charge-discharge device incorporating a multi-stage voltage doubler rectifier circuit and a bidirectional converter that uses a rectangular waveform voltage to equalize voltages across series-connected capacitors, allowing for simultaneous charging and discharging while reducing the number of switches and circuit size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate equalization circuit is equipped in addition to a charge-discharge device, then voltage equalization among series-connected electricity storage cells is achieved, but the system complexity and cost increase
Solution Approach 1:
The patent combines the equalization circuit and charge-discharge device into a single integrated system. The converter unit serves dual purposes: it functions as both the charge-discharge device and the equalization circuit by selectively connecting to different groups of electricity storage cells. This merging eliminates the need for separate equipment, reducing system complexity while maintaining voltage equalization capability.
Solution Approach 2:
The converter unit is designed with multi-functionality, capable of operating in different modes to perform both charging/discharging operations and voltage equalization. By controlling the switching elements, the same converter can connect to the first group of cells for charge-discharge operations or to the second group of cells for equalization operations, making a single component serve multiple functions.
2Reliability
If a charger with equalization function is configured to supply charging electric power individually to each cell, then voltage equalization is achieved, but the circuit size and cost increase due to large current capacity requirements
Solution Approach 1:
The patent divides the electricity storage system into two groups: a first group of cells for charge-discharge operations and a second group of cells for equalization operations. By segmenting the cell groups and using the same converter alternately for different purposes, the circuit components only need to handle the current required for equalization when connected to the second group, rather than being oversized for individual cell charging, thus reducing circuit size.
Solution Approach 2:
The equalization operation is performed partially by dedicating only a portion of the cells (second group) to equalization while the rest (first group) handles the main charge-discharge operations. This partial action approach allows the converter to be sized appropriately for equalization current rather than requiring excessive current capacity for simultaneous individual cell charging.
3Reliability
If conventional equalization circuits using multiple switches are employed, then voltage equalization is achieved, but the number of switches and circuit complexity increase
Solution Approach 1:
The converter unit is designed as a universal component that performs both charge-discharge and equalization functions. By using the same converter and switching elements for both operations, the patent eliminates the need for additional switches that would be required in conventional separate equalization circuits, reducing the total number of switches while maintaining equalization capability.
4Device complexity
If a charger with equalization function is designed, then system simplification is achieved, but the device lacks discharging function requiring separate equipment
Solution Approach 1:
The converter unit is designed with bidirectional capability, allowing it to function as both a charger and a discharger. The same converter that performs charging operations can also perform discharging operations by reversing the current flow direction through appropriate switching control. This multi-functionality ensures that the integrated system maintains both charging and discharging capabilities without requiring separate equipment.
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 enables a compact, cost-effective charge-discharge system with integrated equalization, reducing the need for separate equalization circuits and chargers, and supports both charging and discharging operations efficiently.
Implementation Method 1
a converter having a switching element to which a rectangular waveform voltage is applied during operation
Implementation Method 2
multi-stage voltage doubler rectifier circuit in which two series-connected diodes are connected in parallel, respectively, to series-connected 1st to nth capacitors
Data Source
AI summary
The disclosure describes a charge device capable of charging electricity storage cells while eliminating a voltage variation among the electricity storage cells without a need for at least a circuit section playing a role in voltage equalization among the electricity storage cells to be designed to have a large current capacity, and describes a charge-discharge device constructed by additionally equipping a discharging function with the charge device. Provided are a charge device and a charge-discharge device each of which comprises a convertor, an input circuit, and a multi-stage voltage doubler rectifier circuit. An element in the convertor configured to be applied with a rectangular waveform voltage is connected to the multi-stage voltage doubler rectifier circuit via the input circuit to thereby realize a voltage equalization function, and an output section of the convertor is connected to the multi-stage voltage doubler rectifier circuit to thereby realize a charging-discharging function.