Fuel Cell Compressor Control for Bypass Valve Stability
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Solution Overview
Problem
Conventional fuel cell systems face issues with repeated opening and closing of the bypass valve, leading to abnormal noise and electrolyte membrane drying due to inconsistent cathode gas flow rates, which cannot be precisely controlled to match target flow rates.
Innovation Solution
The fuel cell system sets a target compressor supply flow rate based on either the stack request or system request, and controls the bypass valve to fix or limit its operation when the actual stack supply flow rate deviates from the target, ensuring optimal gas flow and preventing membrane drying.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the bypass valve is repeatedly opened and closed to control the stack supply flow rate to reach the target flow rate, then the flow rate control precision is improved, but abnormal noise is generated and the valve reliability deteriorates
Solution Approach 1:
The control system performs preliminary action by predicting the stack supply flow rate based on the relationship between compressor supply flow rate and stack supply flow rate. This prediction allows the system to determine the appropriate bypass valve opening in advance, preventing the need for repeated opening and closing operations to achieve target flow rate, thereby eliminating abnormal noise and improving valve reliability
Solution Approach 2:
The control system uses feedback by detecting the actual stack supply flow rate and comparing it with the target flow rate. Based on this feedback and the predicted flow rate relationship, the system adjusts the bypass valve opening to achieve precise flow rate control without repeated operations, resolving the contradiction between control precision and valve reliability
2Reliability
If the bypass valve is fixed to prevent repeated opening and closing, then the valve reliability is improved, but the cathode gas flow rate becomes excessive and causes electrolyte membrane drying
Solution Approach 1:
The control system performs preliminary calculation of the predicted stack supply flow rate based on the compressor supply flow rate and their established relationship. This preliminary action allows the system to determine the precise bypass valve opening needed to achieve target flow rate before operation begins, ensuring accurate flow control without excessive gas flow that would cause membrane drying
Solution Approach 2:
The control system changes the operating parameters by using the predicted flow rate relationship to determine the appropriate bypass valve opening position. This parameter adjustment ensures that the bypass valve is set to the correct opening degree that prevents both repeated operations and excessive flow rate, thereby preventing electrolyte membrane drying while maintaining valve reliability
3Device complexity
If the bypass valve opening resolution is coarse, then the device complexity is reduced, but the stack supply flow rate cannot coincide with the target flow rate and causes repeated valve operation
Solution Approach 1:
The control system performs preliminary prediction of the stack supply flow rate based on the compressor supply flow rate and their relationship. This prediction compensates for the coarse opening resolution by calculating the appropriate bypass valve opening in advance, allowing the system to achieve precise flow rate control without requiring fine resolution valve steps or repeated operations
Solution Approach 2:
The predicted stack supply flow rate acts as an intermediary that bridges the gap between coarse bypass valve opening resolution and precise flow rate control requirements. By using this predicted value in conjunction with feedback control, the system can achieve accurate flow rate matching without requiring complex fine-resolution valve mechanisms
Data Source
AI summary
A fuel cell system sets the larger one of a stack request compressor supply flow rate calculated based on a request of a fuel cell stack and a system request compressor supply flow rate calculated based on a request by the fuel cell system as a target compressor supply flow rate and controls a compressor according to the target compressor supply flow rate. The fuel cell system also controls a bypass valve based on a stack supply flow rate and a target stack supply flow rate to be supplied to the fuel cell stack. The fuel cell system fixes the bypass valve or limits the drive of the bypass valve when the system request compressor supply flow rate is set as the target compressor supply flow rate and the stack supply flow rate becomes smaller than the target stack supply flow rate.