Hybrid Vehicle Controller Stabilizing Inverter Voltage During Battery-Less Travel
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Solution Overview
Problem
During battery-less travel control in hybrid vehicles, the shift from pulse width modulation (PWM) to rectangular wave voltage control leads to unstable inverter output voltage due to poor control accuracy, causing imbalances in input and output electric powers between the motor and generator, especially at high vehicle speeds.
Innovation Solution
A vehicle control method that uses a controller to switch between PWM and rectangular control based on vehicle speed, with additional processes to limit the rate of variation in accelerator operation and torque, ensuring balanced electric powers by filtering the accelerator pedal operation or vehicle required torque, and maintaining a minimum torque level, thereby stabilizing the inverter output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If rectangular control is used to increase motor output at high vehicle speeds, then motor output is improved, but control accuracy deteriorates and inverter output voltage becomes unstable
Solution Approach 1:
The patent dynamically switches between PWM control and rectangular control based on vehicle speed conditions. At low speeds, PWM control is used for high precision; at high speeds, rectangular control is used for high output. This dynamic adaptation resolves the contradiction by allowing the system to optimize for the appropriate parameter depending on operating conditions.
Solution Approach 2:
The patent changes the control parameter (control method) based on the vehicle speed parameter. By monitoring vehicle speed and switching control methods accordingly, the system achieves both high precision when needed and high output when needed, resolving the fundamental trade-off between these two parameters.
2Adaptability or versatility
If the battery is isolated during battery-less travel control, then the system can operate without battery, but the balance of input and output electric powers is lost and voltage stability deteriorates
Solution Approach 1:
The patent implements feedback control by continuously monitoring the balance between generator input power and motor output power. When operating in battery-less mode, the system uses this feedback to detect imbalances and trigger appropriate responses, maintaining voltage stability through active monitoring and adjustment.
Solution Approach 2:
The patent prepares for potential power imbalances by implementing monitoring mechanisms before critical failures occur. The system detects early signs of imbalance between generator input and motor output, allowing preventive actions to be taken before voltage instability becomes severe.
3Reliability
If the rate of variation in accelerator operation amount is limited, then the balance of electric powers is maintained, but the responsiveness to driver input is reduced
Solution Approach 1:
The patent applies rate limiting only partially - specifically during battery-less travel control at high speeds when rectangular control is active. During other operating conditions, the full accelerator input response is maintained. This selective application maintains power balance when critical while preserving responsiveness during normal operation.
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
The solution effectively suppresses the application of unstable voltage to the motor during battery-less travel control, maintaining power performance during PWM control and stabilizing the inverter output voltage even when shifting to rectangular control, ensuring continuous vehicle operation.
Implementation Method 1
a generator that generates electric power using power of the engine
Implementation Method 2
the motor is driven by using the electric power generated by the generator
Data Source
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AI summary
In a vehicle that includes an engine, a motor, a generator, a battery electrically connected to the motor and the generator, and a transmission provided between the motor and an output shaft coupled to a drive wheel, an ECU executes "battery-less travel control" in which, at the time of a failure of the battery, the battery is isolated from the motor and the generator, the generator is caused to generate electric power by generating a torque, corresponding to an accelerator pedal operation amount (A), from the generator, and the vehicle is caused to travel by driving the motor using the electric power generated by the generator. The ECU suppresses losing a balance of input and output electric powers between the generator and the motor by filtering the accelerator pedal operation amount (A) (S25) when a vehicle speed (V) exceeds a limit vehicle speed (Vsh) (YES in S24) during the battery-less travel control (YES in S20).