Fuel Cell Controller Power Reduction for Battery Overcharge Prevention
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Solution Overview
Problem
Conventional fuel cell systems in vehicles experience delays in reducing power generation in response to rapid changes in motor consumption, leading to overcharging of secondary batteries due to excess power generation during these delays.
Innovation Solution
A fuel cell system with a controller that calculates required and maximum power based on accelerator position, temperature, and state of charge, setting allowable charging power to zero during rapid consumption reductions to prevent overcharging, and adjusting correction factors to manage power generation accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the fuel cell system maintains normal power generation control, then the power generated by the fuel cell matches the command power based on accelerator depression, but during rapid deceleration, a temporal delay occurs causing excess power to be supplied to the secondary battery resulting in overcharge
Solution Approach 1:
The controller predicts rapid deceleration based on current accelerator depression rate and vehicle speed, then proactively reduces the fuel cell command power before the actual rapid deceleration occurs. This preliminary action prevents the temporal delay response issue and avoids secondary battery overcharge by anticipating the power demand reduction.
Solution Approach 2:
The system dynamically adjusts the command power reduction strategy based on real-time detection of rapid deceleration conditions. When rapid deceleration is detected through accelerator depression rate and vehicle speed thresholds, the controller applies enhanced power reduction logic, otherwise maintaining normal control. This dynamic adaptation resolves the contradiction between response speed and normal operation.
2Productivity
If the command power of the fuel cell is reduced in response to motor consumption power reduction, then power generation matches demand, but during rapid deceleration the reduction is delayed causing overcharge of the secondary battery
Solution Approach 1:
The controller predicts rapid deceleration using accelerator depression rate and vehicle speed, then proactively reduces command power before the actual power demand drops. This preliminary power reduction prevents excess power from being generated and supplied to the secondary battery, maintaining both productivity and reliability.
Solution Approach 2:
The system continuously monitors accelerator depression rate and vehicle speed to detect rapid deceleration conditions. Based on this feedback, the controller adjusts command power reduction strategy in real-time, enhancing reliability during critical conditions while maintaining normal productivity during steady-state operation.
Data Source
AI summary
A fuel cell system to be installed on a vehicle includes a fuel cell, a secondary battery, an SOC detector that detects a temperature and a state of charge of the secondary battery, an accelerator position detector that detects an accelerator depressed amount, and a controller that controls power to be generated by the fuel cell. The controller includes: a required generation power calculator that calculates required generation power based on the accelerator depressed amount and the temperature and the state of charge of the secondary battery; and a maximum required power calculator that calculates maximum required power based on the accelerator depressed amount and the temperature and the state of charge of the secondary battery. The maximum required power includes allowable charging power correlated with a maximum value of charging power. If determining that a condition for rapid reduction in consumption power of a motor is satisfied, the controller sets the allowable charging power to zero and calculates the maximum required power. If the required generation power exceeds the maximum required power, the controller makes the fuel cell generate power responsive to the maximum required power.