Battery Inverter Ripple Control for Low-Temperature Heating Noise
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Solution Overview
Problem
Existing battery heating methods using high-frequency alternating current generate noise due to the sound pressure level increase in specific frequency regions, which needs to be addressed while efficiently raising the battery temperature.
Innovation Solution
A battery system that includes an inverter driven at a predetermined carrier frequency, with a control device that varies the frequency of the current ripple around the resonance frequency of the battery circuit and randomly adjusts the carrier frequency to efficiently heat the battery while minimizing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the ripple frequency is controlled to the resonance frequency of the battery circuit, then the temperature of the battery can be raised efficiently, but the sound pressure level increases leading to noise generation
Solution Approach 1:
The patent applies dynamics by making the ripple frequency variable rather than fixed. The control device dynamically adjusts the ripple frequency to vary around the resonance frequency of the battery circuit, allowing the system to maintain heating efficiency while avoiding sustained resonance that causes noise. This is achieved by continuously modulating the ripple frequency within a range centered on the resonance frequency.
Solution Approach 2:
The patent changes the frequency parameter of the ripple current from a fixed value to a varying value. By controlling the ripple frequency to fluctuate around the resonance frequency rather than staying at a constant frequency, the system maintains the beneficial heating effect while reducing the harmful noise generation associated with sustained resonance conditions.
2Ease of operation
If the carrier frequency is kept constant for stable inverter operation, then control is simplified, but noise occurs in specific frequency regions
Solution Approach 1:
The patent applies dynamics by making the carrier frequency variable. The control device varies the carrier frequency randomly or pseudo-randomly around a central frequency value, which prevents the system from operating continuously at a single frequency where noise problems occur. This dynamic adjustment maintains operational stability while avoiding sustained noise-generating conditions.
Solution Approach 2:
The patent employs periodic action by introducing periodic variations in the carrier frequency. The carrier frequency is modulated in a periodic manner, creating a time-varying operating condition that prevents continuous resonance and noise generation while maintaining the overall functionality and control simplicity of the inverter system.
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 efficiently raises the battery temperature by maximizing the amplitude of the current ripple through resonance, while randomly varying frequencies reduces noise levels, effectively suppressing sound pressure increases in relevant frequency regions.
Implementation Method 1
the inverter...converts direct-current power stored in the battery into alternating-current power and supplies the alternating-current power to the electric machine
Implementation Method 2
a high frequency alternating current pulse current having a frequency that is half the switching frequency of an insulated gate bipolar transistor (IGBT) generates Joule heat due to the internal resistance of the battery, thus heating the battery
Implementation Method 3
a circuit including the battery has a resonance frequency. When the frequency of current ripple...is controlled to the resonance frequency of the circuit including the battery, the amplitude of the current ripple increases due to resonance
Data Source
AI summary
Direct-current power of a battery is converted to alternating-current power by an inverter to drive a motor generator. A control ECU executes temperature raising control when the battery is at a low temperature. During the temperature raising control, the control ECU superimposes a current ripple for raising the temperature of the battery on a d-axis current command value. A frequency of the current ripple (ripple frequency) varies randomly around a resonance frequency of a battery circuit including the battery. Additionally, a carrier frequency of the inverter varies randomly. As a result, a sound pressure level can be suppressed in regions of the resonance frequency and the carrier frequency during the temperature raising control.