Fuel Cell-Super Capacitor Hybrid Vehicle Startup Sequence Control
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Solution Overview
Problem
Fuel cell-super capacitor hybrid electric vehicles without high-voltage power converters require a separate initial charge device and start-up control method to protect the fuel cell during startup, reduce start-up time, and ensure driver convenience, especially under adverse conditions like cold starts.
Innovation Solution
A startup sequence control method that selectively uses a super capacitor and low-voltage battery, boosting the auxiliary power source voltage using a buck-type converter after fuel cell startup, allowing smooth vehicle starts under various conditions by managing voltage levels and relay operations to optimize fuel cell and auxiliary component power usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high-voltage DC-to-DC converter is employed to compensate voltage difference and control charge/discharge, then voltage matching between fuel cell and battery is achieved, but device complexity increases
Solution Approach 1:
The patent extracts the high-voltage DC-to-DC converter from the system configuration. By removing this complex voltage-matching device, the system simplifies the architecture while relying on the inherent voltage characteristics of the fuel cell and battery to naturally match during operation, thereby reducing device complexity while maintaining operational reliability
Solution Approach 2:
The system enables self-service voltage matching where the fuel cell and battery naturally regulate their own voltages during charge/discharge cycles without requiring external converter intervention. The control strategy allows components to self-adjust based on their electrical characteristics and state of charge
2Reliability
If a precharge resistor and precharge relay are used for initial charge, then super capacitor initial charge is enabled, but start-up time increases
Solution Approach 1:
The patent applies preliminary action by pre-charging the super capacitor through the low-voltage battery before fuel cell startup. This preliminary charging ensures the super capacitor is ready to immediately accept high-voltage power transfer when the fuel cell starts, eliminating the need for slow resistive precharging during the critical startup phase
Solution Approach 2:
The low-voltage battery serves as an intermediary component that enables controlled initial charge of the super capacitor. It mediates the charge transfer process by providing a controlled current path that safely charges the super capacitor without requiring high-voltage converters or slow resistive charging, thereby reducing startup time
3Use of energy by moving object
If auxiliary components are driven using output voltage of fuel cell itself after voltage boost, then system efficiency improves, but voltage stability during transition becomes challenging
Solution Approach 1:
The patent implements dynamic voltage management by continuously adjusting the voltage supply mode based on real-time system conditions. The system dynamically transitions between different voltage sources (battery, super capacitor, fuel cell) and control modes (direct connection, precharge mode, power transfer mode) to maintain voltage stability during transitions while maximizing energy efficiency in steady-state operation
Solution Approach 2:
The control strategy employs feedback mechanisms that monitor voltage levels, current flow, and component states to automatically adjust the power distribution. This feedback control ensures voltage stability during transitions by detecting deviations and correcting them in real-time, while enabling efficient direct fuel cell-to-auxiliary component operation when conditions are favorable
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 smooth and efficient startup of fuel cell-super capacitor hybrid electric vehicles under diverse conditions, including cold starts, by strategically utilizing the super capacitor and low-voltage battery to boost fuel cell voltage, reducing start-up time and enhancing driver convenience.
Implementation Method 1
boosting the auxiliary power source voltage using a buck-type converter after fuel cell startup
Data Source
AI summary
The present invention provides a startup sequence control method of fuel cell-super capacitor hybrid electric vehicles, which can protect a fuel cell at the time of the starting of the fuel cell, reduce the start-up time and promote convenience of a driver in a fuel cell-super capacitor serial hybrid system which does not employ a high-voltage power converter. The startup sequence control method comprises the steps of: determining whether or not a low-voltage auxiliary battery is in a state where its voltage is less than a reference voltage or in a cold start condition after a key-on signal has been input; if the auxiliary battery is in the state where its voltage is less than a reference voltage or in the cold start condition, matching the voltage of a main bus terminal to the voltage of an auxiliary power source through the voltage boost of a power converter; turning on a relay for cutting off the voltage of the auxiliary power source and a main relay of a precharge unit for the auxiliary power source; and turning off the power converter and then driving a fuel cell auxiliary component using the auxiliary power source to thereby boost a fuel cell voltage.