Multiphase Fuel Cell Converter Switching Beyond Dead Zone
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Solution Overview
Problem
The accuracy of AC impedance measurement in fuel cell systems is compromised due to the 'dead zone' phenomenon in magnetically coupled converters, where current interruption occurs, making it difficult to measure AC impedance effectively, especially when the fuel cell operates in a discontinuous mode, leading to suboptimal control of the fuel cell's operating state.
Innovation Solution
A fuel cell system with a magnetically coupled converter that includes a controller to manage the operation of switches across multiple phases, ensuring different duty ratios and phase differences to avoid the dead zone by adjusting current values and duty ratios, allowing for accurate AC impedance measurement even in discontinuous modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a magnetically coupled converter is used to reduce converter size, then the converter size is reduced, but the dead zone phenomenon occurs causing measurement inaccuracy
Solution Approach 1:
The patent dynamically adjusts the duty ratio of switching elements based on the operating state of the fuel cell. When the fuel cell operates in a state where the converter enters the dead zone, the controller modifies the duty ratio to shift the operating point away from the dead zone region, thereby maintaining accurate AC impedance measurement capability while using the compact magnetically coupled converter structure.
Solution Approach 2:
The patent changes the duty ratio parameter of the switching elements to avoid the dead zone phenomenon. By monitoring the operating conditions and adjusting the duty ratio accordingly, the system prevents the converter from operating in the dead zone region where measurement accuracy deteriorates, thus resolving the contradiction between compact size and measurement precision.
2Measurement precision
If the duty ratio is changed to measure AC impedance, then measurement can be performed, but in the dead zone the output current remains unchanged making measurement impossible
Solution Approach 1:
The patent implements a feedback control mechanism where the controller monitors the operating state of the fuel cell and the converter. When the system detects operation within the dead zone region, the feedback loop adjusts the duty ratio to move the operating point outside the dead zone, ensuring that duty ratio changes produce corresponding output current changes and enabling accurate AC impedance measurement.
3Device complexity
If switches are operated at the same duty ratio to simplify control, then control is simplified, but the dead zone cannot be avoided
Solution Approach 1:
The patent performs preliminary detection of the operating state before AC impedance measurement is attempted. The controller assesses whether the current operating point lies within the dead zone region, and if so, preemptively adjusts the duty ratio to a value that places the operating point outside the dead zone, thereby ensuring measurement reliability without adding complex real-time control mechanisms.
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 system effectively minimizes the occurrence of the dead zone, enabling precise AC impedance measurement and optimal control of the fuel cell's operating state by ensuring that at least one phase operates outside the dead zone range, thus improving measurement accuracy and operational efficiency.
Implementation Method 1
a reactor comprising coils of n phases (n is an integer of 2 or more), which are magnetically coupled to each other
Data Source
AI summary
To provide a fuel cell system configured to appropriately measure the AC impedance of a fuel cell. A fuel cell system wherein the controller controls ON and OFF of the switches of n phases; wherein the controller operates the switches of the n phases at different phases, and the controller operates the switches of the n phases at the same duty ratio; wherein the controller operates the switches of the n phases at different duty ratios, when the controller determines that a specific condition is met; and wherein the controller measures the AC impedance of the fuel cell from the current waveform and voltage waveform of the fuel cell.