DC Bus Voltage Regulation During Contactor Open Events
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Solution Overview
Problem
Existing hybrid vehicle power systems face instability and reduced power capability during battery contactor open conditions, leading to high impedance and electrical losses, which affect the stability and maximum power capacity of the battery and high-voltage buses, especially with increasing power demands from autonomous and smart mobility systems.
Innovation Solution
The implementation of a control system that includes a voltage converter and PI controllers to regulate the battery and high-voltage bus voltages, maintaining a stable battery bus voltage and controlling the generator speed during contactor open conditions, using a voltage converter to facilitate power transfer between bus networks and reducing impedance by adjusting voltage levels and commanding generator torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the battery contactor is opened to isolate the traction battery, then system reliability is improved by preventing fault propagation, but electrical impedance increases and power capability is reduced
Solution Approach 1:
The voltage converter acts as an intermediary device between the high-voltage bus and battery bus, enabling power transfer without direct battery connection. This mediator allows the system to maintain power capability while the contactor remains open, resolving the contradiction between reliability improvement and power capability maintenance
Solution Approach 2:
The patent replaces the mechanical direct-connection system with an electronic power conversion system. Instead of relying on mechanical contactor closure for power transfer, the system uses electronic voltage conversion and control to achieve the same power transfer function, thereby maintaining power capability while allowing contactor isolation for reliability
2Reliability
If the battery contactor is opened to isolate the traction battery, then fault propagation is prevented, but electrical losses increase due to high impedance
Solution Approach 1:
The voltage converter dynamically adjusts voltage parameters (battery bus voltage, high-voltage bus voltage) to optimize power transfer efficiency. By changing voltage levels adaptively, the system minimizes electrical losses while maintaining fault isolation through the open contactor
Solution Approach 2:
The voltage converter serves as an intermediary that reduces impedance between isolated battery and high-voltage systems. This mediator lowers electrical losses by providing an optimized power transfer path despite the physical separation created by the open contactor
3Power
If generator speed is increased to provide more power during contactor open conditions, then power capability is improved, but system stability deteriorates due to voltage fluctuations
Solution Approach 1:
The control system continuously monitors battery bus voltage and high-voltage bus voltage, using feedback signals to adjust generator torque and voltage converter operation. This feedback mechanism maintains voltage stability even when generator speed increases to provide additional power during contactor open conditions
Solution Approach 2:
The system dynamically adjusts multiple parameters including generator torque, battery bus voltage, and high-voltage bus voltage in real-time. This dynamic control allows the system to respond to changing power demands while maintaining stability, resolving the contradiction between power capability and voltage stability
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 solution provides continuous and stable power supply, enhances transient performance, increases maximum power capability, and reduces resonant current and electrical losses in the voltage converter's inductor, ensuring better power handling and stability during high-power conditions.
Implementation Method 1
controlling a voltage converter to drive a measured voltage of the battery bus toward a first commanded value
Implementation Method 2
controlling the generator to drive a measured voltage of the high-voltage bus toward a second commanded value
Data Source
AI summary
A vehicle power system includes a battery bus between a traction battery and voltage converter, a high-voltage bus between the voltage converter and an inverter, and a controller. The controller, responsive to a contactor between the traction battery and voltage converter opening, controls an engine to maintain a speed of a generator electrically coupled with the inverter within a predefined range, controls the voltage converter to drive a measured voltage of the battery bus toward a first commanded value based on a first difference between the first commanded value and measured voltage of the battery bus, and controls the generator to drive a measured voltage of the high-voltage bus toward a second commanded value different than the first commanded value based on the first difference and a second difference between the second commanded value and the measured voltage of the high-voltage bus.