DC-DC Converter Control for Hybrid Gear Shift Voltage Stability
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Solution Overview
Problem
During gear changes in hybrid vehicles, the interruption of thermal torque can cause discomfort for drivers and passengers due to torque rupture, and existing solutions like decreasing the available torque are unacceptable as they negatively impact performance.
Innovation Solution
A control process for a hybrid motor vehicle that detects gear changes and adjusts the power supply by calculating and providing a minimum power output through the DCDC converter, ensuring the low-voltage network remains adequately powered and voltage stable.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the available torque is reduced during gear changes, then the torque interruption felt by driver and passengers is mitigated, but the vehicle performance is negatively impacted
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the voltage supplied to the inverter during gear changes. Instead of reducing torque, the system increases voltage from the nominal 450V to a higher level (up to 540V) to compensate for the thermal engine torque interruption, thereby maintaining both comfort and performance through electrical parameter modification rather than mechanical torque reduction
Solution Approach 2:
The control device predicts the upcoming gear change event and prepares the electrical system in advance by adjusting voltage levels before the actual gear change occurs. This preliminary action ensures that the inverter has sufficient power availability ready to compensate for the thermal torque interruption, preventing the performance loss that would occur with reactive torque reduction
2Power
If the battery relays are opened to increase inverter supply voltage, then the power available to the electric machine increases, but the voltage regulation of the high-voltage network is disrupted
Solution Approach 1:
The patent implements feedback control by continuously monitoring the high-voltage network voltage and dynamically adjusting the HSG (hybrid starter-generator) torque to maintain voltage stability. When battery relays are opened to increase inverter voltage, the control device uses feedback from voltage sensors to regulate HSG output, ensuring that voltage regulation is maintained despite the changed electrical configuration
Solution Approach 2:
The HSG acts as an intermediary element between the battery and the inverter during gear changes. When battery relays are opened, the HSG provides the necessary power and voltage stabilization to the high-voltage network, mediating the transition and ensuring continuous reliable operation without direct battery connection
3Reliability
If the DC/DC converter draws energy from the high-voltage network to maintain low-voltage battery charge, then the low-voltage network remains powered, but the power available to the electric machine decreases
Solution Approach 1:
The control device predicts the gear change event and temporarily reduces or suspends the DC/DC converter power draw before the gear change occurs. This preliminary action ensures that maximum power is available from the high-voltage network to the inverter and electric machine during the critical gear change period, while still maintaining low-voltage network reliability through advance preparation
Solution Approach 2:
The patent applies dynamics by making the DC/DC converter power draw variable rather than constant. The converter's power extraction from the high-voltage network is dynamically adjusted based on the operational phase - reduced during predicted gear changes when electric machine power is needed, and increased during normal operation when low-voltage battery charging is the priority
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 effectively maintains a stable voltage in the low-voltage network during gear changes, preventing discomfort for vehicle occupants and ensuring the proper functioning of low-voltage equipment without risking damage.
Implementation Method 1
a DC-DC converter (12) capable of supplying the low-voltage electrical network from the high-voltage network
Implementation Method 2
the battery relays (16) and (16') are opened to raise the voltage across the inverter capacitors (15)
Implementation Method 3
the high-voltage alternator-starter, abbreviated HSG, connected alternately to the first or second input shaft of the gearbox, which can act as a generator and receiver of electrical energy
Data Source
Figure 1
Figure 2
AI summary
A method for controlling an electrical assembly for a hybrid motor vehicle comprising a hybrid transmission gearbox, a high-voltage electrical network (1) comprising a bank of electrical accumulators (13), a high-voltage alternator-starter connected to an inverter (11), an electrical machine connected to another inverter (10), the hybrid motor vehicle further comprising a low-voltage electrical network (14, 17), and a DC-DC converter (12) able to power, from the high-voltage network (1), the low-voltage electrical network (14), the method comprising a step (21) of detecting a change of mode or of gear on said gearbox, requiring the opening of the battery relays, the method being characterised in that, when such a change of gear or of mode is detected, it further comprises: - a step (22) of acquiring voltage and current values at the terminals of the DC-DC converter (12); - a first step (23) of computing the input power of the DC-DC converter (12) as a function of the acquired values of the voltages and currents; - a second step (24) of computing a minimum power value as a function of said input power and of a correction value; - a step (25) of controlling the DC-DC converter (12) so as to supply said minimum computed power as output.