DC/DC Boost Converter Bus Voltage Derivative Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing fuel cell systems face challenges in reducing disturbances on high voltage buses due to insufficient capacitance, which increases system cost, size, and weight, and is exacerbated by the high ohmic resistance of batteries at low temperatures and the slow reaction of system controllers to disturbances.
Innovation Solution
A system that includes a high voltage battery and a DC/DC boost converter with a current controller, where the converter calculates the time derivative of the bus voltage to adjust the fuel cell stack current set-point, thereby dampening oscillations on the high voltage bus without adding significant capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high capacitance is added to reduce disturbances on the high voltage bus, then the filtering effect is improved, but the system cost, size, and weight increase
Solution Approach 1:
The patent implements a feedback control mechanism where the controller continuously monitors the high voltage bus voltage and adjusts the fuel cell stack current in response to detected voltage deviations. This active feedback loop compensates for disturbances without requiring additional passive capacitance, thereby maintaining reliability while avoiding increased system weight.
Solution Approach 2:
The patent replaces the mechanical/passive approach of adding physical capacitance with an active electronic control system. Instead of relying on passive electrical components (capacitors) to filter disturbances, the system uses active control of the fuel cell current to counteract voltage fluctuations, substituting a control-theoretic solution for a component-based solution.
2Reliability
If high capacitance is added to reduce disturbances on the high voltage bus, then the filtering effect is improved, but the system cost and size increase
Solution Approach 1:
The controller uses feedback control to monitor bus voltage and dynamically adjust fuel cell current, providing active disturbance compensation. This feedback mechanism achieves reliable filtering without requiring additional capacitive components, thereby avoiding increased system complexity and cost associated with larger capacitor banks.
Solution Approach 2:
The patent changes the operational parameters of the existing fuel cell stack by dynamically adjusting its current output based on bus voltage conditions. Instead of adding new components with fixed parameters (capacitance), the system modifies the electrical parameters (current) of an existing component (fuel cell stack) to achieve the desired filtering effect, maintaining system simplicity.
3Weight of stationary object
If battery capacitance is relied upon for filtering, then the system size is reduced, but the filtering effectiveness deteriorates at low temperatures due to high ohmic resistance
Solution Approach 1:
The feedback control system actively compensates for the reduced filtering effectiveness of the battery at low temperatures by detecting voltage disturbances and adjusting the fuel cell current accordingly. This active compensation mechanism maintains reliable disturbance filtering even when the battery's passive capacitance is less effective due to temperature-induced increased ohmic resistance.
Solution Approach 2:
The controller acts as an intermediary that mediates between the battery and the high voltage bus. When the battery's natural filtering capability is insufficient (at low temperatures), the controller introduces corrective action by adjusting the fuel cell current to counteract disturbances, effectively bridging the performance gap without requiring additional capacitance.
4Measurement precision
If system controller reaction time is increased to respond to disturbances, then the control precision is improved, but the response speed deteriorates
Solution Approach 1:
The feedback control system is designed to detect voltage disturbances with high precision and respond with appropriate current adjustments. The feedback mechanism inherently balances measurement precision and response speed by continuously monitoring bus voltage and immediately acting on detected deviations, eliminating the need to compromise between these two parameters.
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
This approach effectively reduces oscillations on the high voltage bus by utilizing the inherent capacitance of the fuel cell stack, maintaining system performance even at low temperatures, and minimizing additional costs and weight.
Implementation Method 1
A voltage signal from the bus is received and a time derivative of the voltage signal is calculated that defines voltage changes on the bus over time
Implementation Method 2
A hydrogen fuel cell is an electro-chemical device that includes an anode and a cathode with an electrolyte therebetween. The anode receives hydrogen gas and the cathode receives oxygen or air. The hydrogen gas is dissociated in the anode to generate free hydrogen protons and electrons.
Implementation Method 3
The battery provides supplemental power to the electrical bus during those times when additional power is needed beyond what the stack can provide, such as during heavy acceleration.
Implementation Method 4
a bi-directional DC/DC converter is sometimes employed to match the battery voltage to the voltage of the fuel cell stack
Data Source
AI summary
A system for reducing oscillations on a high voltage bus. The system includes a high voltage battery electrically coupled to the high voltage bus and a DC/DC boost converter electrically coupled to the high voltage bus and a fuel cell stack. The DC/DC converter includes a current controller that selectively controls the current provided by the fuel cell stack. A system controller provides a stack current set-point to the DC/DC converter. The DC/DC converter includes a voltage device that receives a voltage signal from the bus and provides a time derivative of the voltage signal that defines voltage changes on the bus over time. The time derivative signal is provided to a summer that adjusts the current stack set-point to provide a modified current set-point to the current controller that selectively adjusts the current provided by the fuel cell stack to dampen oscillations on the high voltage bus.