DC-DC Converter Control for Vehicle Traction Network Stability
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Solution Overview
Problem
In motor vehicle electrical networks, power transients from the on-board network to the traction network cause instabilities, leading to voltage and torque fluctuations, which can result in the traction electric machine experiencing abrupt voltage variations and potential deactivation, and can lead to energy imbalances.
Innovation Solution
Implementing an auxiliary mode of control for the DC/DC current converter with a current limit that depends on the state of charge of the service battery, where the current limit increases as the battery discharges, thereby damping power dynamics and preventing detrimental variations from propagating to the traction network.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the DC/DC converter operates in nominal mode allowing power transients to propagate from the on-board network to the traction network, then the service battery can be charged and discharged freely, but the traction network experiences voltage fluctuations and instabilities that can cause the electric machine to deactivate
Solution Approach 1:
The control mode of the DC/DC converter is made dynamic by switching between nominal mode and auxiliary mode with current limitation based on real-time detection of power transient conditions. The converter adapts its operating characteristics by adjusting the current limit parameter depending on whether power transients are detected, thereby maintaining reliability while preserving battery flexibility when conditions permit
Solution Approach 2:
The DC/DC converter acts as an intermediary between the on-board network and the traction network. By implementing auxiliary mode control with current limitation, the converter mediates the power flow to prevent harmful power transients from propagating to the traction network while still allowing the service battery to function, thus protecting the electric machine from voltage fluctuations
2Productivity
If the DC/DC converter operates without current limitation to maximize power transfer, then the service battery can be fully charged and discharged, but the electric machine experiences abrupt voltage variations that may cause deactivation
Solution Approach 1:
The control system takes preliminary anti-action by detecting power transient conditions and preemptively applying current limitation in auxiliary mode before harmful voltage variations can affect the electric machine. This preventive approach blocks the propagation of power transients at the source (DC/DC converter output) rather than attempting to correct voltage variations after they occur
Solution Approach 2:
The operating parameters of the DC/DC converter are changed by switching between nominal mode (higher current capability) and auxiliary mode (current-limited). The current limit parameter is adjusted based on detected power transient conditions, allowing the system to optimize power transfer efficiency while preventing harmful voltage variations on the electric machine
Data Source
AI summary
Disclosed is a method for controlling a DC current converter present in an on-board network of a motor vehicle including a service battery, the on-board network being connected, via the converter, to a traction battery that supplies power to a traction network with inverter and electric machine. When a transmission of power transients from the on-board network to the traction network leading to instabilities in the traction network is detected, an auxiliary mode of control of the converter is implemented with a limit on the current output from the converter depending on a state of charge of the service battery, the current limit increasing as the charge of the service battery decreases.