With the increasing proportion of wind turbines in power grids, they are required to have capabilities of active and efficient virtual inertial response to maintain grid frequency stability. However, the virtual inertial control methods currently used in doubly-fed induction generator (DFIG) units suffer from a secondary frequency drop (SFD) problem. Although the SFD can be inhibited by reducing the active power support strength of the DFIG units during inertia response, it will undoubtedly weaken the virtual inertia of the units. Therefore, how to eliminate the SFD while increasing the virtual inertia of the units is a worthy issue for studying. To solve this issue, a wind-storage combined virtual inertial control system based on quantization and regulation decoupling of active power increments is proposed in this paper. First, by setting the parameters of a proportional–differential (P-D) algorithm, the total active power increments required for virtual inertial response are quantified at the DFIG level. Secondly, a curve-shifting method based on the rate of change of frequency is adopted to adjust the active power output of the DFIG units. Finally, a battery energy storage system (BESS) is used to compensate for the power shortages of the units according to the quantized value of the active power increments. Simulations show that the control method can not only eliminate SFD but also effectively increase the system’s virtual inertia.

Increasing power density and miniaturization in 3D packaged power electronics demand innovative thermal management. Yet, the thermal performance of electrically insulated packages for power electronics is currently limited by the ultralow thermal conductivity of conventional thermal interface materials (TIMs) and their poor ability of directing heat to heat sink. Herein, we have prepared highly thermally conductive and electrically insulating TIMs composite based on boron nitride nanobars (BNNB). The polar characteristics of B-N bond in the BNNB outer tube wall-derived h-BN nanosheets facilitates the adsorption of magnetic particles. Modulating the arrangement of 3D-BNNB by an external magnetic field improves the thermal conductivity of composite up to 3.3 W m-1 K-1 at a concentration of 40 wt%, 17.8 times higher than the pure epoxy and also exhibiting significant anisotropy. Moreover, the composite shows a high stiffness of 510 MPa and a high resistivity of 27.2 MΩ·cm, demonstrating excellently mechanical and electrically insulating characteristics. Infrared thermography results show that the surface temperature of the composite depends on the orientation of BNNB and its interfacial interaction with the epoxy resin. The magnetic field-oriented modulation of 3D-BNNB can offer a promising solution to achieve the efficient thermal management of 3D integrated power packaging.

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heat transfer performance of TIM, and the test methods normally include two categories: steady-state and transient methods. However, the present ITR testing methods still suffer from sample damage and low accuracy. [4] Thus, a non-destructive ITR testing method with high accuracy is urgently needed, which is critical for promoting the development of TIM.Submicron silver has become a promising TIM owing to its high thermal conductivity and strong adhesion, which can greatly reduce the ITR. [5][6][7][8] However, the thermal reliability of the silver-adhesive interface is still a major issue. Numerous studies focused on the degradation of properties, such as mechanical strength, material oxidation, and electrochemical corrosion through the test of high temperature, high humidity, and temperature cycling. [9][10][11][12][13][14] Liu et al. reported that conductive adhesive would undergo further curing, hydrolysis, and oxidation under high temperature and humidity, but it did not provide in-depth theoretical explanations. [15] Lin et al. found that the hydrothermal environment induced the hygroscopic expansion of epoxy resin and weakened the absorption peak of the epoxyfunctional group by Fourier transforming infrared (FTIR) spectrum analysis. [16] Several studies hypothesized that the number, size, and shape of porosity would interrupt the interface thermal conduction path, and thus, decrease the equivalent thermal conductivity. However, the evolution of porosity during the aging process is not investigated. [17][18][19] Skuriat studied the change in micro-morphology under high-temperature aging of Thermal interface materials (TIM) represented by submicron silver adhesive provide a promising solution for ultra-high heat dissipation in chip integration. However, it is difficult to accurately characterize the thermal performance of submicron silver adhesive interfaces, and their high-temperature degradation mechanism still remains unclear. Herein, the accelerated high-temperature aging experiments of submicron silver adhesion interfaces are performed, and a non-destructive testing method is provided to measure the degeneration of interfacial thermal resistance (ITR). After performing the two-sided test, ITR can be extracted with an error of less than 4.6%. Based on scanning electron microscopy and X-ray microstructural analysis, the microstructural evolution of silver adhesive interfaces is presented and its high-temperature degradation mechanism is determined. It is observed for the first time that ITR would change with the aging time following a bathtub curve. Such a degenerative process can be evidently divided into three stages including secondary solidification, fluctuation, and failure. In addition, a physical model is developed to interpret the degradation mechanism of ITR at high temperatures. The change in the trend of submicron silver body and TIM-solid contact thermal resistance at different stages is presented. This work helps promote submicron silver's application as high-performance TIM.