Demanding the accuracy and reliability of the thermal design of high-power density inverter, aluminum substrate has been widely used due to its high thermal conductivity and well insulation performance. This paper provides a complete set of thermal design optimization method: The main power module losses are analyzed. Considering the accurate thermal resistance models for heatsink of variable structural types is hard to modelling, the method of combining finite element simulation and Minitab response surface optimization is mainly used to carry out the multi-objective optimization design with the substrate thickness, fin radius and fin length as the optimization objectives. Finally, it is verified that the heatsink model and optimization method are highly convenient and effective, and can provide a reliable method for structural optimization of heatsink for inverters.
In this paper, a quad active bridge converter for modular photovoltaic inverters is analyzed, which is able to realize the AC/DC power decoupling in the magnetic circuit without increasing the size of the transformer. Besides, a ripple-suppression control strategy is proposed to suppress the voltage ripples caused by the unavoidable parasitic circuit resistance and leakage inductance, so that the bus capacitance can be minimized. Meanwhile, on the basis of this modular structure, a decentralized control system architecture is presented to constitute a decentralized controller for the series-stacked system using the inherent synchronization and power-sharing capabilities of the coupled nonlinear oscillator. The effectiveness of the control strategy was verified through simulation and experiments.
Demanding accuracy and reliability of thermal design for high efficiency and high-power density inverter devices.Integrating heat conduction, convection heat transfer and fluid dynamics theories, a synthetical thermal model based on the characteristic length as the square root of the cross-sectional area and a multi-objective optimization method based on entropy yield minimization theory and electrothermal coupling are proposed for a typical forced air-cooling heatsink system to improve the efficiency of design optimizations in the structure and cost.The fin thickness, fin length, number of fins, and air velocity of the heatsink are used as design variables, and the NSGA-III algorithm applying a prophet population is used to obtain the pareto fronts with minimum thermal resistance, cost and pressure loss as optimization objectives.Enhanced airflow through the heatsink by arranging the columns in a phyllotactic pattern.A temperature rise test by a 100 V/10 kW prototype was designed to prove the accuracy of the model proposed and heatsink optimized.At rated power, the surface temperature of power devices and heatsink has 10 °C reduction.Index Terms-Forced air-cooling
Crossing by Horizontal Directional Drilling (HDD), characterized by short construction period, high quality and little impact on environment, is widely used in pipeline crossing engineering. Deviation between the practical and theoretical exit point, where the bit unthreads, is difficult to control. Excessive deviation could not only cause unconformity of requirement, but also expand the correction and make re-drilling more difficult. In sum, accurate controlling of the drilling direction is the key to the success of the crossing. Fortunately, wired directional control system is fit for the crossing of deep and long pipelines for large or middle scale directional drill rigs due to its high precision. Based on the working principle of the system, possible reasons causing deviation are analyzed, some methods for deviation correction are proposed, and the operation for lateral deviation controlling in a practical construction is studied. The results indicate that, there are many factors that can lead to the deviation, such as the precision of a directional apparatus, theoretical error of the directional crossing, the error of measurement and interference sources on the ground or underground. However, according to the practical situation, the deviation could be confined in a required range as the construction required through the combination of tru-tracker system and some proper control measures.
Wax deposition seriously affects the safe and economic operation of pipelines. Mastering the variation laws of wax deposition thickness is the premise of formulating reasonable pigging schemes. Although the GM (1,1) model (a kind of gray model) is an effective method for predicting wax deposition thickness on pipe walls, its prediction accuracy is easily affected by the smoothness of the original sequence. The improved GM (1,1) was established by introducing the idea of translation transformation, and an optimal weighted combination model based on the traditional gray model and a logarithmic function model was proposed. The differences in the predicted results of the established models were compared and analyzed through indoor wax deposition experimental data. The research results indicate that the optimal weighted combination model has the highest fitting accuracy, followed by the logarithmic function model and the improved GM (1,1), while the fitting accuracy of the traditional gray model is poor. When the number of modeling samples is five, the average relative error and root mean square error of the prediction results of the optimal weighted combination model are 1.313% and 0.021, respectively, which shows the highest prediction accuracy. When the number of modeling samples is six, the average relative error and root mean square error of the optimal weighted combination model are 2.143% and 0.031, respectively, and its prediction accuracy is still the highest. Overall, the optimal weighted combination model has the advantages of high accuracy and easy implementation, and has strong promotion and application value.
The bootstrap gate driver circuits are widely used for bridge-arm-type high-current and high-power-density converters due to their low cost and compact structures. In high-current applications, improper bootstrap parameters and circuit design will cause start-up gate–source voltage oscillation, bridge-arm shoot-through, and gate–source voltage overshoot. Because of the lack of research and detailed model on the above three aspects in high-current applications, this article proposes a full-parameter model of the driver circuit through a detailed analysis of the driver circuit and summarizes a set of systematic design methods, which provides a reference for the parameters and circuit design of bootstrap gate driver for Si-based or GaN-based converters. This article will help tackle the challenges encountered in the bootstrap gate driver circuit design for high-current and high-power-density converters.
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