Fuel Cell Power Control for Accurate In-Drive Impedance Measurement
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Solution Overview
Problem
Existing fuel cell systems in vehicles face challenges in accurately diagnosing the internal state during travel due to electric power load fluctuations, which affect impedance measurement, and secondary batteries are prone to overcharge or overdischarge, complicating the process.
Innovation Solution
An electric power control apparatus that stabilizes the generated current of the fuel cell and adjusts the secondary battery's remaining capacity within predetermined limits by charging or discharging before impedance measurement, ensuring accurate diagnosis while preventing battery deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the generated current of the fuel cell is made constant during impedance measurement, then measurement accuracy is improved, but the remaining capacity of the secondary battery may fall below the lower limit value or exceed the upper limit value
Solution Approach 1:
The control apparatus performs preliminary charging or discharging of the secondary battery before impedance measurement to ensure the remaining capacity is within acceptable limits. This preliminary action prevents the battery capacity from falling below the lower limit or exceeding the upper limit during the constant current impedance measurement process.
Solution Approach 2:
The control apparatus dynamically adjusts the fuel cell current between two modes: a first current value during impedance measurement to ensure measurement accuracy, and a second current value at other times to maintain battery capacity within limits. This dynamic switching resolves the contradiction between measurement precision and battery reliability.
2Reliability
If the secondary battery is controlled to maintain remaining capacity within limits, then battery deterioration is suppressed, but the generated current of the fuel cell cannot be made constant during impedance measurement
Solution Approach 1:
Before impedance measurement begins, the control apparatus adjusts the secondary battery charge state through preliminary charging or discharging operations. This ensures that when constant current measurement starts, the battery capacity is already within acceptable limits, allowing both measurement precision and battery durability to be maintained.
Solution Approach 2:
The system dynamically switches between two operational modes: during impedance measurement, the fuel cell operates at a first current value for measurement accuracy; at other times, it operates at a second current value to maintain battery capacity within limits. This dynamic control satisfies both contradictory requirements.
3Productivity
If impedance measurement is performed during vehicle traveling, then real-time diagnosis is achieved, but electric power load fluctuation causes measurement errors
Solution Approach 1:
The control apparatus dynamically controls the fuel cell current to maintain a constant first current value specifically during impedance measurement periods, even when the vehicle is traveling. This dynamic current stabilization eliminates measurement errors caused by load fluctuations while preserving real-time diagnosis capability.
Solution Approach 2:
The control apparatus continuously monitors the fuel cell current during impedance measurement and adjusts it to maintain a constant value. This feedback control eliminates the influence of electric power load fluctuations on measurement accuracy, enabling precise real-time diagnosis during vehicle operation.
Data Source
AI summary
An electric power control apparatus is for a fuel cell system including an impedance measurement unit that measures an impedance of the fuel cell based on a current and a voltage measured when alternating-current electric power is superimposed on output electric power of the fuel cell. A processor of the electric power control apparatus: estimates a remaining capacity of the electric power storage device after execution of a process of measuring the impedance; performs charging and discharging of the electric power storage device before start of the process of measuring the impedance, to make the estimated remaining capacity fall within a predetermined range from a lower limit value to an upper limit value; and controls electric power generation of the fuel cell to make a generated current of the fuel cell constant, during the execution of the process of measuring the impedance.