Bidirectional Converter Phase Equalization via Differential Current Sensing
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Solution Overview
Problem
Existing converter control systems face challenges in accurately obtaining and equalizing passing electric power across phases, leading to inefficiencies and delays in responding to load fluctuations in fuel cell power supply systems.
Innovation Solution
A converter control device with differential ammeters to detect current differences across reactors, allowing real-time calculation of passing electric power and implementing an electric power equalization unit to balance phase loads, ensuring accurate and timely adjustments in the number of phases driven.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple converters are connected in parallel to reduce switching element rating capacity, then the device complexity increases, but the reliability and load handling capability improve
Solution Approach 1:
The converter system is segmented into multiple parallel converter phases (first converter phase, second converter phase, third converter phase), each handling a portion of the total load. This segmentation allows the system to distribute the power handling requirement across multiple simpler units, improving reliability while maintaining manageable complexity through modular architecture
Solution Approach 2:
Each converter phase is designed with universal functionality to perform voltage conversion in both directions (charging and discharging modes). The control device can dynamically activate or deactivate specific phases based on load requirements, making the system adaptable to varying power demands while maintaining a standardized modular structure
2Power
If the number of converter phases is increased to handle larger load fluctuations, then the power handling capability improves, but the loss electric power increases when passing electric power is small
Solution Approach 1:
The control device dynamically adjusts the number of active converter phases based on the magnitude of load fluctuation and passing electric power. When load fluctuation is small or passing electric power is low, fewer phases are activated to minimize losses. When load fluctuation exceeds converter capacity or passing electric power is high, more phases are activated to handle the increased demand, optimizing the balance between power handling capability and energy efficiency
Solution Approach 2:
The system changes the operational parameter of the number of active phases based on operating conditions. The control device monitors passing electric power and load fluctuation magnitude, then adjusts the phase configuration accordingly - switching between single-phase, two-phase, or three-phase operation to optimize efficiency across different operating ranges
3Loss of energy
If the number of phases is changed from three phase operation to single phase operation, then the loss electric power decreases when passing electric power is small, but the voltage, current, and electric power fluctuate causing duty ratio adjustments
Solution Approach 1:
The control device implements feedback control by monitoring voltage, current, and power fluctuations when transitioning between phase configurations. When changing from three-phase to single-phase operation, the control device detects the resulting fluctuations and adjusts the duty ratio of the switching elements to compensate, maintaining stable output despite the reduced phase configuration
Solution Approach 2:
The control device performs preliminary adjustments to the duty ratio before and during phase transitions to prevent excessive voltage and current fluctuations. By anticipating the impact of phase changes on system stability, the control device proactively modifies switching parameters to smooth transitions and maintain stable operation
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
Enables real-time determination of electric power and efficient equalization of phase loads, reducing calculation delays and errors, and effectively managing load fluctuations by dynamically adjusting the number of phases in response to changing power demands.
Implementation Method 1
a voltage converter composed of switching elements and reactors is used
Data Source
AI summary
A converter device which is configured by connecting three converter circuits in parallel is provided between a secondary battery serving as a first power supply and a fuel cell serving as a second power supply. Two differential ammeters are placed on three reactors corresponding to the three converter circuits. A control unit includes a passing electric power calculation module which calculates electric power passing through the converter device on the basis of detected values of the two differential ammeters, an electric power equalization module which performs equalization of passing electric power between the respective converter circuits which constitute the converter device, a module for changing the number of drive phases which changes the number of drive phases of the converter device in response to the passing electric power, and a voltage conversion control module which controls the converter device and executes a desired voltage conversion.