Converter Carrier Frequency Control for AC Electric Vehicle Thermal Management
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Solution Overview
Problem
In the CI/SIV integral configuration of AC electric vehicles, the converter is required to constantly operate, leading to increased electrical stress and reduced lifetime due to prolonged power supply, making it difficult to prolong the converter's lifespan by reducing switching frequency without compromising generation loss restrictions.
Innovation Solution
A control device that adjusts the carrier frequency of the converter based on initial temperature and input current of the auxiliary power unit, or the difference between initial and real-time temperatures, to minimize temperature variations of the converter main circuit element, thereby reducing the influence of heat cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If the converter operates continuously to supply power to the auxiliary power unit in CI/SIV integral configuration, then the auxiliary power can be continuously supplied, but the lifetime of the converter main circuit element is reduced due to prolonged operation and increased electrical stress
Solution Approach 1:
The patent applies dynamics by making the converter carrier frequency adjustable rather than fixed. The control device dynamically changes the carrier frequency based on real-time temperature measurements of the converter main circuit element, allowing the system to adapt its operating parameters to current thermal conditions and extend component lifetime.
Solution Approach 2:
The patent changes the operational parameter (carrier frequency) of the converter based on temperature conditions. When the converter main circuit element temperature exceeds a predetermined threshold, the control device increases the carrier frequency, which reduces the duty cycle and consequently reduces the temperature increase, thereby controlling thermal stress on the components.
2Reliability
If the carrier frequency is increased to reduce temperature variation and heat cycle influence, then the lifetime of converter main circuit element is prolonged, but the generation loss of converter increases
Solution Approach 1:
The patent changes the carrier frequency parameter in response to temperature conditions rather than maintaining a fixed high frequency. By adjusting the frequency based on actual thermal state, the system achieves temperature control and lifetime extension while minimizing unnecessary increases in conversion loss that would result from permanently operating at high frequency.
Solution Approach 2:
The patent makes the carrier frequency dynamic rather than static. The frequency is adjusted in real-time based on temperature measurements, allowing the system to operate at lower frequencies when thermal conditions permit (reducing conversion loss) and increase frequency only when necessary to control temperature variations and protect component lifetime.
Data Source
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AI summary
A control device for an AC electric vehicle that is applied to a configuration in which an SIV 7 is connected to an intermediate DC circuit unit 40 between a CONV 3 that converts an AC voltage input through a main transformer 2 to a DC voltage and an INV 4 that converts the DC voltage to an AC voltage, in which a carrier frequency fc of the CONV 3 is changed on the basis of initial temperature (initial value of Tcnv) of a converter main circuit element when a vehicle is stopped and input current Isiv of the SIV 7 such that a temperature variation of a converter main circuit element when the vehicle is stopped is reduced.