Dielectric capacitors are the key components in advanced electronics and electrical systems owing to their highest power density among the electrical energy devices. [1][2][3][4][5][6][7] While ceramic dielectrics are of large dielectric constants and high thermal stability, [8][9][10][11][12] polymer dielectrics possess high tolerance to voltage, great reliability, scalability, and light weight, and therefore are preferred for high-energy-density high-power film capacitors. [13][14][15][16][17] However, the current polymer dielectrics are unable to match the temperature requirements of the emerging applications of electrical energy storage and conversion in harsh environments [18][19][20][21][22] because of their inherently poor thermal stability. For example, while the near-engine-temperature in electric vehicles can reach to above 120 °C, [23] the operating temperature of biaxially oriented polypropylene (BOPP), which is the best commercially available polymer dielectric and currently used in power inverters of electric vehicles, is below 105 °C. [24] The wide bandgap semiconductors like silicon carbide (SiC) and gallium nitride that are well positioned to replace traditional silicon power devices boost the operating temperatures of next-generation capacitors beyond 150 °C. [19] To address these urging needs, a variety of engineering polymers with high thermal stability, such as polyimides (PIs) and fluorene polyesters (FPEs), have been exploited as high-temperature dielectric materials. [20,25] Unfortunately, all the polymers show poor charge-discharge efficiencies under elevated temperatures and high applied fields, [26] which is due to sharply increased electrical conduction attributable to various temperature-and field-dependent conduction mechanisms, e.g., charge injection at the electrode/dielectric interface. [27,28] Ceramic dielectrics are relatively insensitive to temperature and able to maintain the energy-storage performance throughout a broad temperature range, [8][9][10][11][12] but they still suffer from considerable energy loss under high electric fields and elevated temperatures. [29] More recently, the addition of 2D wide bandgap nanostructures such as boron nitride nanosheets (BNNSs) into the polymer has been demonstrated to effectively reduce the conduction loss and largely improve the charge-discharge High-temperature capability is critical for polymer dielectrics in the nextgeneration capacitors demanded in harsh-environment electronics and electrical-power applications. It is well recognized that the energy-storage capabilities of dielectrics are degraded drastically with increasing temperature due to the exponential increase of conduction loss. Here, a general and scalable method to enable significant improvement of the high-temperature capacitive performance of the current polymer dielectrics is reported. The high-temperature capacitive properties in terms of discharged energy density and the charge-discharge efficiency of the polymer films coated with SiO 2 via plasma-enhanced chemical...

Dielectric polymers for electrostatic energy storage suffer from low energy density and poor efficiency at elevated temperatures, which constrains their use in the harsh-environment electronic devices, circuits, and systems. Although incorporating insulating, inorganic nanostructures into dielectric polymers promotes the temperature capability, scalable fabrication of high-quality nanocomposite films remains a formidable challenge. Here, we report an all-organic composite comprising dielectric polymers blended with high-electron-affinity molecular semiconductors that exhibits concurrent high energy density (3.0 J cm −3) and high discharge efficiency (90%) up to 200°C, far outperforming the existing dielectric polymers and polymer nanocomposites. We demonstrate that molecular semiconductors immobilize free electrons via strong electrostatic attraction and impede electric charge injection and transport in dielectric polymers, which leads to the substantial performance improvements. The all-organic composites can be fabricated into large-area and high-quality films with uniform dielectric and capacitive performance, which is crucially important for their successful commercialization and practical application in high-temperature electronics and energy storage devices.

We present in this paper a model for forecasting short-term electric load based on deep residual networks. The proposed model is able to integrate domain knowledge and researchers' understanding of the task by virtue of different neural network building blocks. Specifically, a modified deep residual network is formulated to improve the forecast results. Further, a two-stage ensemble strategy is used to enhance the generalization capability of the proposed model. We also apply the proposed model to probabilistic load forecasting using Monte Carlo dropout. Three public datasets are used to prove the effectiveness of the proposed model. Multiple test cases and comparison with existing models show that the proposed model is able to provide accurate load forecasting results and has high generalization capability.Index Terms-Short-term load forecasting, deep learning, deep residual network, probabilistic load forecasting.

terms of a graceful failure. [1] These devices have been applied in many high-tech fields such as hybrid electric vehicles, electrical defibrillators, pulsed power systems, and power grids. Nevertheless, the inferior energy density of the polymer dielectrics significantly restrains the development of film capacitors in the future applications. For instance, the commercial benchmark poly mer dielectric biaxially oriented polypropylene (BOPP) only possesses an energy density of <4 J cm −3 , [2] which leads to the cumbrous volume and cost in the practical applications. For example, film capacitors occupy ≈35% the volume and ≈40% the cost of the power inverters in hybrid electric vehicles. [3] The energy density (U e ) of dielectric materials can be derived from U e = ∫EdD , where E is the applied electric field and D denotes the electrical displacement. For linear dielectrics, the formula evolves into U e = 1/2ε 0 ε r E b 2 , where ε 0 is the vacuum permittivity, and ε r and E b are the dielectric constant and breakdown strength of dielectrics, respectively. Clearly, U e depends on the dielectric constant and breakdown strength of dielectrics, where E b is more important because of its quadratic relationship to U e .Boron nitride nanosheets (BNNSs), a 2D nanomaterial with a wide bandgap (≈6 eV), have proved to be an intriguing dopant in dielectric polymer nanocomposites for the interest of enhancing dielectric strength and energy efficiency, because they are of high intrinsic breakdown voltage, can serve as efficient scattering centers for charge carriers, and possess large electrical resistance, in addition to their great thermal conductivity and mechanical strength. [4] To make use of the exceptional effects of BNNSs on dielectric polymers, a straightforward approach is to homogeneously disperse such nanosheets in the polymer matrices to impede charge conduction. In princi ple, with increasing the population density of BNNSs in the polymer matrices, the transport of charge carriers becomes increasingly constrained by these 2D topological barriers, leading to better dielectric performance. A strain forced orientation (i.e., mechanical stretching) of the BNNSs along the film direction is usually applied as an extra step to further enlarge the coverage of the embedded nanofillers in the transverse plane direction, and hence improve the dielectric performance of the composite film. [5] However, with increasing the feed Polymer dielectrics such as poly(vinylidene fluoride) (PVDF) have drawn tremendous attention in high energy density capacitors because of their high dielectric constant and ease of processing. However, the discharged energy density attained with these materials is restrained by the inferior breakdown strength and electric resistivity. Herein, PVDF composite films with a nanosized interlayer of assembled boron nitride nanosheets (BNNSs) that is aligned along the in-plane direction are prepared through a simple layer-by-layer solution-casting process. Compared to the pristine PVDF, the composite films ...

Achieving high output performance is the key in the development of triboelectric nanogenerators (TENGs) for future versatile applications. In this study, a novel TENG assembled with porous cellulose paper and polydimethylsiloxane is demonstrated. Through dielectric modulation of the friction materials by the nanoparticles (i.e., BaTiO3, Ag), the triboelectric outputs increase significantly with the permittivity increase, which is attributed to the enhancement of the charge trapping capability and the surface charge density of the friction materials. The dielectric modulated TENG demonstrates a high output voltage of 88 V and a current of 8.3 µA, corresponding to an output power of 141 µW. Acting as a sensor unit, the TENG can successfully operate in a wireless transmission system, which can remotely monitor the machine operation and deliver the messages associated with finger movements. Moreover, the TENG can also perform as an efficient power source in an electropolymerization system for electropolymerizing polyaniline on a carbon nanotube electrode, holding a great potential to synthesize a high capacitance electrode for supercapacitors. This work provides a simple and efficient way to construct high performance TENGs and promotes their practical applications in the fields of wireless transmission and electropolymerization systems.

Epoxy-based model insulators were manufactured and fluorinated under a F2/N2 mixture (12.5% F2) at 50 °C and 0.1 MPa for 15 min and 60 min. Surface charge accumulation and decay behavior were studied with and without dc voltage application. The effect of direct fluorination on surface charge migration as well as on flashover voltage was verified. The obtained results show that the charge decay of epoxy-based insulators is a slow process, but the decay rate increases when an outer dc electric field is applied. The surface charge distribution is changed when a streamer is triggered on the insulator surface. The existence of heteropolarity surface charges can decrease the dc surface flashover voltage to some extent, while the surface flashover voltage is almost unchanged when charges of the same polarity accumulate on the insulator surface. The short time fluorinated insulator can modify the surface resistivity, and the rate of surface charge dissipation is greatly increased under a dc electric field.

A comprehensive review on the methods used for fault detection, classification and location in transmission lines and distribution systems is presented in this study. Though the three topics are highly correlated, the authors try to discuss them separately, so that one may have a more logical and comprehensive understanding of the concepts without getting confused. Great significance is also attached to the feature extraction process, without which the majority of the methods may not be implemented properly. Fault detection techniques are discussed on the basis of feature extraction. After the overall concepts and general ideas are presented, representative works as well as new progress in the techniques are covered and discussed in detail. One may find the content of this study helpful as a detailed literature review or a practical technical guidance.

Spacers are key components that are used to support high voltage conductors in gas-insulated substations or gas-insulated lines. The analysis of the surface charge patterns on spacers remains a difficult task, which requires a comprehensive understanding of the physical mechanism of the gas-solid interface charging phenomenon. In this letter, we reported a field dependent property of surface charge accumulation patterns on spacers under DC stress. We verified this finding through experiment, and further, we put forward a field-dependent charging model based on dominant charge transport behavior under different electric fields. It was found that the charging characteristics of the spacer are dominated by the Ohmic conduction from the volume below an electric field of 2.5 kV/mm. When the electric field stress is higher than 2.5 kV/mm, the charging property of spacers is dominated by the enhanced gas ionization according to Townsend's law. The correctness of this model was verified by surface charge measurement results in literature studies, and a method for determining the dominant mechanism of charge accumulation under different electric fields was proposed.