PWM Phase Control for Battery Heat-Up in Parallel Converters
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Solution Overview
Problem
In power supply systems for electromotive vehicles with parallel-connected direct-current power supplies, fluctuations in output currents from step-up converters lead to increased heat-up time of batteries, especially at low temperatures, due to inefficient PWM control methods.
Innovation Solution
A power supply system that includes a controller to change the phases of pulse width modulation control signals for two step-up converters from synchronous to asynchronous and back, reducing the heat-up time of batteries by adjusting the phase change period based on the total current threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If synchronous PWM control is used for parallel-connected step-up converters, then output current fluctuations are reduced, but battery heat-up time increases at low temperatures
Solution Approach 1:
The patent applies dynamics by making the PWM control mode changeable based on operating conditions. The controller dynamically switches between synchronous PWM control (for stable operation) and asynchronous PWM control (for rapid heating), allowing the system to adapt its control strategy according to temperature conditions and current requirements, thus resolving the contradiction between stability and heat-up speed
Solution Approach 2:
The patent changes the phase relationship parameter between PWM control signals of parallel converters. By adjusting the phase difference between carrier waves from 0° (synchronous) to non-zero values (asynchronous), the system can control the degree of current fluctuation叠加, enabling both stable operation and rapid heating modes through parameter adjustment
2Loss of time
If asynchronous PWM control is used to rapidly heat batteries, then heat-up time is reduced, but output current fluctuations increase
Solution Approach 1:
The system dynamically adjusts the PWM control phase relationship based on temperature conditions. When rapid heating is needed, asynchronous control is activated; when stability is prioritized, synchronous control is used. This dynamic adaptation resolves the contradiction by allowing the system to operate in different modes as needed
3Loss of time
If phase change period is shortened to increase heating speed, then heat-up time is reduced, but control stability decreases
Solution Approach 1:
The patent implements feedback control by monitoring the total output current and comparing it against thresholds. Based on this feedback, the controller adjusts the phase change period and switching frequency, ensuring that heating operations remain within stable control boundaries while achieving rapid temperature increase when conditions permit
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 approach effectively reduces the heat-up time of batteries by stabilizing current fluctuations, ensuring efficient battery warm-up even at low temperatures, while preventing excessive current oscillations that could lead to control instability.
Implementation Method 1
a first voltage converter configured to bidirectionally convert voltage between a first battery and an output line in accordance with first pulse width modulation control; a second voltage converter connected to the output line in parallel with the first voltage converter, the second voltage converter being configured to bidirectionally convert voltage between a second battery and the output line in accordance with second pulse width modulation control
Implementation Method 2
the controller being configured to, when one or both of temperatures of the first and second batteries are lower than a predetermined temperature, change phases of the pulse width modulation control signals such that the first pulse width modulation control signal and the second pulse width modulation control signal change from a synchronous state to an asynchronous state
Implementation Method 3
when fluctuations in output currents from the two step-up converters overlap with each other, fluctuations in the output current of the power supply system increase... when the temperatures of batteries are low, the charge-discharge characteristics decrease. Therefore, for example, when the electromotive vehicle is started up in a low temperature state, sufficient charge-discharge characteristics need to be ensured by quickly raising the temperatures of the batteries
Data Source
AI summary
A power supply system includes: a first voltage converter configured to bidirectionally convert voltage between a first battery and an output line in accordance with first pulse width modulation control; a second voltage converter connected to the output line in parallel with the first voltage converter, the second voltage converter being configured to bidirectionally convert voltage between a second battery and the output line in accordance with second pulse width modulation control; and a controller configured to control the first and second voltage converters by generating first and second pulse width modulation control signals, the controller being configured to, when one or both of temperatures of the first and second batteries are lower than a predetermined temperature, change phases of the pulse width modulation control signals such that the first second pulse width modulation control signals change from a synchronous state to an asynchronous state.