Fuel Cell Anode Injector Control Algorithm
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Solution Overview
Problem
Existing fuel cell systems face challenges in accurately controlling the injector duty cycle, particularly during transients, due to limitations in pulse width modulation (PWM) control signals, which can lead to hydrogen starvation and instability in fuel cell stacks.
Innovation Solution
A method using discrete output control for the injector, where the processor determines various pulse widths and corresponding close times, selects the pulse width with the lowest error, and adjusts the duty cycle to achieve precise control, allowing for interruptions during power output changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If PWM control signal is used to regulate injector flow, then the injector duty cycle can be controlled, but the control accuracy deteriorates during transients leading to hydrogen starvation
Solution Approach 1:
The system dynamically adjusts the injector control strategy based on operating conditions. During transients, the microcontroller directly controls the injector pulse width with high resolution, while during steady-state operation, PWM control is used. This dynamic switching between control modes maintains accuracy across all operating conditions.
Solution Approach 2:
The invention changes the control parameter from standard PWM duty cycle to a microcontroller-generated pulse width that can be precisely controlled. The microcontroller generates injector control signals with resolution better than PWM can provide, directly controlling the injector open time based on calculated hydrogen demand, thereby achieving superior duty cycle accuracy during transients.
2Ease of manufacture
If PWM firmware is used for injector control, then the control signal can be generated, but the response time increases due to requiring completion of previous command period
Solution Approach 1:
The microcontroller continuously calculates the required injector pulse width based on current hydrogen demand before the previous command completes. This preliminary calculation allows the system to be ready to issue the next control command immediately when needed, eliminating the waiting period inherent in PWM control where the system must complete the current pulse cycle before starting the next one.
Solution Approach 2:
The invention replaces the PWM firmware-based control mechanism with a microcontroller-based direct control system. The microcontroller can generate injector control signals asynchronously, independent of previous command completion, thereby substituting the time-constrained PWM mechanism with a more flexible digital control approach that achieves faster response during transients.
3Ease of operation
If PWM control is used, then the injector can be controlled, but the duty cycle control precision deteriorates at low frequency discrete output
Solution Approach 1:
The system changes from PWM duty cycle control to direct microcontroller-generated pulse width control. The microcontroller calculates the exact pulse width needed based on hydrogen demand and directly controls the injector, achieving precision better than PWM can provide at low frequencies. This parameter change from duty-cycle-based control to time-based direct control eliminates the precision limitations of PWM.
Solution Approach 2:
The microcontroller acts as an intermediary between the hydrogen demand calculation and the injector control. It receives the calculated hydrogen demand, converts it to the precise pulse width required, and generates the control signal. This intermediary processing step allows for higher precision control than direct PWM control, as the microcontroller can account for the specific timing requirements and generate accurate pulse widths even at low frequencies.
Data Source
AI summary
A system and method for controlling an injector in a fuel cell system. The method provides a variety of injector pulse widths for at least one predetermined duty cycle and determines an injector close time for each of the variety of injector pulse widths. The method also determines an error for the at least one predetermined duty cycle based on each of the provided injector pulse widths and uses the injector pulse width with the lowest error for the at least one predetermined duty cycle.