HV Load Power Management at Low Battery SOC in EVs
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Solution Overview
Problem
During low state of charge (SOC) conditions in electrified vehicles, the engine and electric motor may fail to meet the demand on the high voltage (HV) bus, leading to potential shutdowns and discomfort due to disabled high voltage loads, such as HVAC systems.
Innovation Solution
An energy management system that uses sensors to monitor SOC and HV loads, determining if the electric motor is a generator or consumer, calculating a power offset based on the power difference, and controlling HV loads to ensure minimum power is provided to critical loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the engine and electric motor operate at maximum capacity to meet HV bus demand during low SOC conditions, then power supply to HV loads is improved, but the battery SOC depletes further and vehicle shutdown risk increases
Solution Approach 1:
The system dynamically adjusts the operating mode of the electric motor (generator vs. consumer) based on real-time SOC levels and load conditions. When SOC is above threshold, the motor operates as a generator to charge the battery. When SOC is below threshold, the motor switches to consumer mode to reduce battery discharge, demonstrating dynamic adaptation to changing system states
Solution Approach 2:
The control system changes the power offset value parameter based on SOC conditions and motor operating mode. The power offset is calculated differently when the motor is a generator versus when it is a consumer, allowing the system to optimize power distribution by adjusting this key parameter in response to changing battery state and load requirements
2Reliability
If HV loads are reduced or disabled during low SOC conditions to preserve battery charge, then battery SOC is maintained, but driver comfort and vehicle functionality deteriorate
Solution Approach 1:
Instead of completely disabling HV loads during low SOC conditions, the system applies partial action by calculating a power offset that allows critical loads to continue operating at reduced capacity. This partial maintenance of load functionality preserves driver comfort while still prioritizing battery charge preservation
Solution Approach 2:
The control system continuously monitors SOC levels and adjusts the power offset applied to HV loads in real-time. This feedback mechanism ensures that loads are not completely disabled but rather modulated to an appropriate power level that balances battery preservation with maintaining acceptable vehicle functionality and comfort
3Reliability
If the electric motor operates as a generator to recharge the battery during low SOC conditions, then battery SOC is improved, but the available power for vehicle propulsion and HV loads decreases
Solution Approach 1:
The system dynamically switches the electric motor between generator and consumer modes based on real-time assessment of SOC thresholds and power balance conditions. This dynamic mode switching allows the system to optimize between battery recharging and power availability for propulsion and loads
Solution Approach 2:
The control system changes the calculation method for power offset based on the motor's operating mode. When the motor is a generator, the power offset is calculated as the difference between generated power and HV loads. When the motor is a consumer, a different calculation is used, allowing flexible parameter adjustment to balance battery charging needs with power availability
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
Maintains vehicle operation and provides comfort by ensuring critical loads receive minimum power, preventing temporary shutdowns and enhancing the driving experience.
Implementation Method 1
operating one of the electric motors associated with an internal combustion engine as a generator, thereby converting the mechanical energy generated by the engine into electrical energy for the HV bus
Implementation Method 2
electric motor connected to an internal combustion engine... provides electrical power to respective electric motors
Data Source
AI summary
Electrified vehicle energy management techniques include determining when a state of charge (SOC) of a high voltage (HV) battery system is below an SOC threshold and, in response, determining whether an electric motor is operating as a generator or a consumer, when the electric motor is operating as a consumer, calculating a power offset value based on a difference between an available power of the HV battery system and a set of HV loads, when the electric motor is operating as a generator and its generated power is less than the set of HV loads, calculating the power offset value based on a difference between the generated power and the set of HV loads, and controlling the set of HV loads using a final output power calculated based on the power offset value and a minimum power for the set of HV loads.