Inverter Control Unit Switching Frequency Optimization
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Solution Overview
Problem
The existing rotary electric machine driving devices for hybrid and electric vehicles face challenges in reducing the size and weight of smoothing capacitors while maintaining effective voltage and current smoothing, leading to increased pulsation and potential degradation of batteries and switching elements due to the high voltage and capacitance requirements.
Innovation Solution
Incorporating an inverter control unit that sets the switching frequency of the inverter to a value higher than the resonance frequency, based on the frequency characteristics of the direct-current side voltage and current gains, to minimize pulsation by optimizing the capacitance of the smoothing capacitor relative to the induction component.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If the capacity of the smoothing capacitor is reduced to decrease size and weight, then the physical dimensions and mass are improved, but the pulsation of voltage and current increases causing degradation of battery and switching elements
Solution Approach 1:
The patent changes the operating parameter (switching frequency) to a value higher than the resonance frequency of the RLC circuit. This parameter change allows the system to operate in a frequency range where the impedance characteristics minimize pulsation, enabling the use of a smaller smoothing capacitor while maintaining reliable voltage and current smoothing performance.
2Volume of stationary object
If the capacity of the smoothing capacitor is reduced to decrease size, then the volume is improved, but the pulsation of voltage and current increases causing degradation of battery and switching elements
Solution Approach 1:
The patent changes the operating parameter (switching frequency) to a value higher than the resonance frequency of the RLC circuit. This parameter change allows the system to operate in a frequency range where the impedance characteristics minimize pulsation, enabling the use of a smaller smoothing capacitor while maintaining reliable voltage and current smoothing performance.
3Ease of manufacture
If the capacitance of the smoothing capacitor is reduced, then the cost is improved, but the pulse component cannot be sufficiently reduced causing degradation of battery and switching elements
Solution Approach 1:
The patent changes the operating parameter (switching frequency) to a value higher than the resonance frequency of the RLC circuit. This parameter change allows the system to operate in a frequency range where the impedance characteristics minimize pulsation, enabling the use of a smaller, lower-cost smoothing capacitor while maintaining reliable pulse component reduction performance.
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 allows for a reduction in the capacity of the smoothing capacitor while effectively reducing voltage and current pulsation, thereby enhancing the durability of batteries and switching elements, and achieving a more compact and lightweight rotary electric machine driving device.
Implementation Method 1
the value of the direct-current side voltage gain increases as the frequency increases from zero, reaches the maximum value (resonance point) at a resonance frequency, and decreases as the frequency increases based on the resonance point serving as an inflection point
Data Source
AI summary
A rotary electric machine driving device that drives and controls an alternating-current rotary electric machine, the rotary electric machine driving device including: an inverter that is electrically interposed between a direct-current power supply and the rotary electric machine, and converts electric power between a direct current and an alternating current; a smoothing capacitor that is electrically interposed between the direct-current power supply and the inverter, and is connected between a positive pole and a negative pole on a direct-current side of the inverter; and an inverter control unit that controls switching of a switching element of the inverter according to a predefined switching frequency.