Hybrid Drive Controller Voltage Reduction for Safe Engine Start
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Solution Overview
Problem
In hybrid vehicle drive systems, the voltage reduction process can result in a high capacitor voltage when the power switch is turned on, leading to false abnormality detection and potential failure to start the engine, especially when an abnormality is detected in the motor.
Innovation Solution
A drive system with a controller that executes a voltage reduction process by driving an electrically-powered device until the capacitor voltage reaches a prescribed level, includes a discharge resistor for natural voltage reduction, and performs a voltage reduction determination process to assess the capacitor voltage before attempting to start the engine, ensuring safe engine startup even with motor abnormalities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the voltage reduction process is executed by driving the DC-DC converter when capacitor voltage is high, then the DC-DC converter is protected from damage, but the capacitor voltage remains higher than necessary causing false abnormality detection
Solution Approach 1:
The system performs preliminary voltage reduction by driving the DC-DC converter before engine startup, ensuring the capacitor voltage is reduced to an appropriate level in advance. This preliminary action prevents both converter damage and false abnormality detection during subsequent operations.
Solution Approach 2:
The controller continuously monitors capacitor voltage and uses this feedback to control the DC-DC converter operation. When voltage exceeds a threshold, the converter is activated to reduce voltage, and operation is terminated when voltage reaches a target level, ensuring precise voltage control without false abnormalities.
2Measurement precision
If the voltage reduction process reduces capacitor voltage to a lower level, then false abnormality detection is prevented, but the DC-DC converter may be damaged when voltage is reduced too much
Solution Approach 1:
The system changes the voltage parameter dynamically by adjusting the DC-DC converter operation based on real-time capacitor voltage measurements. The converter is controlled to maintain voltage within a safe operating range, preventing both overvoltage false detection and undervoltage converter damage.
3Reliability
If the starting check process detects high capacitor voltage, then the system prevents potential damage, but the engine cannot be started even when no abnormality exists
Solution Approach 1:
The system performs preliminary voltage reduction before the starting check is executed. By reducing capacitor voltage in advance through DC-DC converter operation, the system ensures that the voltage is at an appropriate level when the starting check occurs, allowing normal engine startup without false protection triggers.
4Measurement precision
If the voltage reduction process takes longer to execute, then the capacitor voltage is reduced more thoroughly, but the engine startup time is delayed
Solution Approach 1:
The system optimizes the voltage reduction process by dynamically adjusting reduction parameters such as power level and duration. The DC-DC converter is controlled to achieve sufficient voltage reduction in the minimum necessary time, balancing thoroughness with speed to enable timely engine startup.
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 configuration ensures the hybrid vehicle can be safely started by determining the reduced capacitor voltage accurately, preventing false abnormality detection and ensuring engine operation even when motor abnormalities are present.
Implementation Method 1
a capacitor (67) disposed between the system main relay (65) and the inverter (70) in a power supply path from the high-voltage battery (52) to the inverter (70), a first end of the capacitor (67) being connected to the positive power line (61), a second end of the capacitor (67) being connected to the negative power line (62)
Implementation Method 2
a discharge resistor (68) disposed in parallel with the capacitor (67)
Data Source
AI summary
A controller of a drive system is configured to, when a power switch is changed from an on state to an off state in a situation in which it has been diagnosed that an abnormality is occurring in a motor generator, execute a starting check process of checking a drive circuit and an engine starting process of starting an engine. The starting check process includes a voltage reduction process of driving a DC-DC converter until a capacitor voltage becomes lower than or equal to a prescribed voltage. The controller is configured to, on condition that the controller determines through a voltage reduction determination process that the capacitor voltage is reduced as compared to the capacitor voltage at an end of the voltage reduction process, execute the engine starting process.