| In recent years,it has seen a rapid development of the new power system with new energy as the main body,the transit electrification,and the power supply of data centers,so a higher standard for the power density of power electronic equipment has been recommended.To further increase the power intensity of the power electronic equipment,it is important to enhance the accuracy of the thermal model and optimize the thermal design to reduce the volume and weight of the heatsink system that takes up comparative space and weighs in the power electronic equipment.In this paper,the accuracy of thermal modeling and optimization of power electronic equipment have all been investigated thoroughly with the goal of increasing the power density.Firstly,stable-state thermal modeling of the forced-air-cooled heatsink system was proposed based on the theory of fluid mechanics and heat transfer.The core to steady-state thermal modeling is finding the thermal resistance of the forced-air-cooled heatsink system.The low accuracy of the conventional thermal model results from its failure to correctly describe the fluid state of the heatsink and ignore the uneven temperature distribution of the heatsink surface.It pointed out that the fluid state of the forced-air-cooled heatsink system ought to be a developing laminar after the fluid state of the heatsink was investigated.A steady-state thermal model based on the square root of the cross-sectional area as the dimensionless characteristic length considering flow and heat transfer characteristics in the entrance region was proposed.The thermal resistance of fluid temperature rising and spreading are further introduced to improve the accuracy of the steady-state thermal model due to the characteristics of uneven surface temperature distribution of the forced-air-cooled heatsink system dissipated by high-power and multi-power devices.The axial fan’s speed was modified to raise the system’s efficiency during light load conditions in intelligent forced-air-cooled conditioning.The steady-state thermal model of the forced-air-cooled heatsink system with the axial fans at various speeds is developed,which was studied by the similarity principle of fluid mechanics.Secondly,the forced-air-cooled heatsink system’s dynamic thermal modeling was proposed.The forced-air-cooled heatsink system’s time constant,which is produced by multiplying the system’s thermal resistance and capacity,is the key to dynamic thermal modeling.The conventional dynamic thermal model had low accuracy since it only considers the weight of the heatsink and ignores spreading effects when determining the thermal capacity.Based on the steady-state thermal model considering flow and heat transfer characteristics in the entrance region,this research carries out dynamic thermal modeling of the forced-air-cooled heatsink system based on the Cauer thermal network and spreading principle.While the equivalent thermal capacity of the heatsink was analyzed considering thermal storage efficiency.The mathematical analysis of the dynamic thermal modeling proposed predicts the maximum temperature of the heatsink surface quickly and accurately under dynamic working conditions like instantaneous overload operation,burst function,and cycle process.Thirdly,optimization design methods were proposed for forced-air-cooled heatsinks in hopes of tackling the shortcomings of conventional thermal design methods(such as empirical design method,finite element analysis design method,etc.)that cannot balance design efficiency and result accuracy,and application examples were provided for analysis.The simplified forced-aircooled heatsink model was proposed,and relatively correct design results could be acquired with only once calculation by choosing the fan and combining the layout of the power equipment,which could be applied to the heatsink designs that are not sensitive to volume and weight.It is suggested to use an improved thermal design method based on the steady-state thermal model.The method can optimize the heatsink and the fans simultaneously,which has the advantages of high design accuracy and efficiency,which could meet the design requirements of most power electronic equipment heatsinks that operate in steady-state conditions.Due to the excessive volume and weight that will result from the design of power electronic forced air-cooled radiators operating under unique dynamic situations employing optimization techniques based on steadystate thermal models,the volume and weight of a forced-air-cooled heatsink in a power electronic equipment operating under specific dynamic thermal conditions like instantaneous overload operation,burst function,and cycle process could be further optimized using the design method based on the dynamic thermal model.Finally,the proposed thermal model and optimization method are applied to the optimization of power electronic equipment,and an optimization design method trading off heatsinks and filters for power electronic equipment was proposed.A high-power-density 380V/50 k Var Static Var Generator(SVG)is produced using the optimized design.In the optimal design,the loss of common inverter topologies was analyzed that the Si C-two-level inverter has the highest efficiency and minimal volume of the heatsink.Furthermore,a Si C-interleaved two-level inverter topology that offers the benefits of low losses,minimal output ripple,and simple control was proposed.The single inductance filter,LCL filter,and their related inductors are modeled and studied,which indicates that the single inductance filter offers advantages over the LCL filter,including a simpler filter structure,the none of high-frequency resonance peak,and a reduced size when a Si C-inverter with the high switching frequency has been used.A comprehensive optimization method trading off the filter and the heatsink was described.Based on precise thermal and inductance modeling,the method suggested optimizes the switching frequency to reduce the volume of the inverters by trading off the design of the heatsink and inductor volume.The designed 380V/50 k Var-SVG employs a Si C-MOSFET as a power device,has an optimized design volume of 30.2L,and provides a power density that is 200% higher than that of an IGBTSVG operating at the same power level.The peak efficiency of the designed high-power-density380V/50 k Var SVG is 99.03%,and the full load efficiency is 98.75%. |
