DC-to-DC Converter Control for Hybrid Vehicle Voltage Stability
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Solution Overview
Problem
In hybrid vehicles, power fluctuations in the low-voltage network can cause instability in the high-voltage network, risking engine stalling due to the combustion engine's slower dynamics compared to electrical machines, necessitating effective damping mechanisms without additional components.
Innovation Solution
A control device for a DC-to-DC converter that adjusts its operation based on an operating mode signal, switching between voltage and current control modes to limit output voltage and regulate current, ensuring power fluctuations are damped and transmitted to the high-voltage network in a controlled manner, utilizing existing electrical components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the DC-to-DC converter operates in conventional voltage control mode, then the output voltage is regulated, but power fluctuations in the low-voltage network are transmitted to the high-voltage network causing instability
Solution Approach 1:
The control device changes the control parameter from voltage to current when operating in generator mode. The current control amount is determined based on the output voltage of the DC-to-DC converter, creating a dependent relationship that dampens power fluctuations while maintaining reliable operation of the high-voltage network.
Solution Approach 2:
The control device uses feedback by determining the current control amount based on the output voltage of the DC-to-DC converter. This feedback mechanism allows the system to respond to voltage variations and transmit only damped power fluctuations to the high-voltage network, improving stability.
2Object-generated harmful factors
If additional damping components are added to the system, then power fluctuations can be reduced, but device complexity increases
Solution Approach 1:
The DC-to-DC converter serves itself by using its own output voltage as the basis for determining the current control amount. This self-service approach allows the system to dampen power fluctuations without requiring additional external damping components, maintaining simplicity while reducing harmful fluctuations.
Solution Approach 2:
The control device performs multiple functions: it regulates power transmission, damps fluctuations, and adapts to different operating modes (battery mode and generator mode) all within a single integrated system, eliminating the need for separate damping components.
3Speed
If the electrical machine responds quickly to power fluctuations, then voltage stability is maintained, but the combustion engine cannot respond fast enough causing stalling
Solution Approach 1:
The system changes the control parameter to current when the electrical machine operates in generator mode. This parameter change, combined with determining the current control amount based on output voltage, creates a damping effect that slows down the transmission of rapid fluctuations to the combustion engine, preventing stalling while maintaining voltage stability through the electrical machine's fast response.
Data Source
AI summary
The invention relates to an electrical drive system of a hybrid vehicle, comprising: a traction battery (1), a high-voltage intermediate circuit (2), a pulse-controlled inverter (3) which is coupled to the high voltage intermediate circuit (2), an electrical machine (5) which is coupled to the pulse-controlled inverter (3); a DC-to-DC converter (6) which is coupled to the pulse-controlled inverter (3) and the high-voltage intermediate circuit (2) and is designed to convert a high voltage (UE) from the high-voltage intermediate circuit (2) into a low voltage (UA) for a vehicle electrical system; a low-voltage battery (8) which is coupled to the DC-to-DC converter (6); a plurality of selectively-connectable electrical consumers (9a, 9b) of the vehicle electrical system, which are coupled to the low-voltage battery (8) and the DC-to-DC converter (6); and a control device (7) which, in the event of a traction battery failure, is designed to operate the DC-to-DC converter (6) in a current-controlled manner using the electrical machine so as to supply said vehicle electrical system consumers (9a, 9b).