Control method for keeping thermal stability of parallel IGBTs based on frequency inflection point

Abstract

The invention belongs to the technical field of power electronic devices, and particularly relates to a control method for keeping the thermal stability of parallel IGBTs based on a frequency inflection point. The method comprises the following steps: step 1, selecting two IGBTs with the same model, connecting the IGBTs in parallel for powering on, recording the switching frequency f and the junction temperature difference delta T of the parallel IGBTs, and obtaining a conduction loss difference delta Econd; and step 2, obtaining a frequency inflection point f0 of the parallel IGBTs accordingto the conduction loss difference delta Econd and the switching loss difference delta Esw, and controlling the switching frequency f of the parallel IGBTs to be smaller than or equal to the frequencyinflection point f0. According to the invention, the relation between the switching frequency of the parallel IGBTs and the thermal stability limit is constructed, the switching frequency is controlled to be lower than or equal to the maximum value of the frequency inflection point, and the loss difference of the parallel IGBTs is reduced along with the rise of the temperature difference, so thatthe junction temperature of the high-temperature IGBTs is further reduced, and finally, the thermal stability of the parallel IGBTs is realized.

Description

technical field [0001] The invention belongs to the technical field of power electronic devices, and in particular relates to a control method for maintaining thermal stability of parallel IGBTs based on a frequency inflection point. Background technique [0002] High-voltage IGBT power modules are one of the core components of high-voltage direct current transmission technology, flexible AC power transmission technology, intelligent switch technology, and high-voltage frequency conversion technology. 100 amps or more. [0003] However, there is an increasing gap between the output capacity of high-voltage IGBT power modules and the required capacity for high-power conversion applications. Combining factors such as reliability and economy, directly selecting the highest-grade IGBT is sometimes not the best solution. Therefore, multiple IGBT chips are usually used in parallel to achieve a specific current capacity and power level. The parallel connection in power electroni...

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Problems solved by technology

[0004] The inventors have discovered that the switching process of the commonly used IGBT is the main source of device loss, and it needs to be strictly controlled under high-frequency and high-current conditions. At the same time, it is especially necessary to pay attention to the consistency of current and junction temperature distribution between parallel devices; in addition, The discreteness of the IGBT's own parameters, the asymmetry of the layout of the drive and the main circuit circuit, and the existence of temperature differences will all affect the current sharing in parallel applications, causing inconsistencies in heat generation and loss between devices, making parallel connections The operating junction temperature of IGBTs is different, and the resulting junction temperature difference will affect the switching loss and conduction loss of the IGBT, and further affect the distribution of its current and junction temperature. In severe cases, the device will even be overheated and damaged. The safe operation of the flow device brings serious hidden dangers

[0005] In the existing technology, the influence of temperature on power loss is mostly concentrated on the circuit layout level, and less involved on the internal carrier level of the device.

Moreover, most studies on the temperature characteristics of IGBTs focus on a single power module, and there are few reports on the interaction between parallel modules.

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