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In order to improve the compensation performance and harmonic suppression ability of active power filter (APF), the SMC-PBC strategy with reaching law sliding mode control (SMC) in voltage outer loop and passivity based control (PBC) in current inner loop was proposed. Compared with the PI-PBC strategy combining proportion integration (PI) and PBC, the PI-HCC strategy combining PI and hysteresis current control (HCC), SMC-PBC strategy can make the compensated current of APF closer to sine wave when load changes. The simulation results of MATLAB/Simulink experimental platform show that the SMC-PBC strategy is effective and feasible.

New energy power generation devices are mostly located in weak power grid areas, where the grid voltage harmonic content is high. Affected by the grid voltage harmonics and switching characteristics, the current of the grid-connected inverter is prone to distortion, which affects the system stability. To solve this problem, a selective harmonic current suppression method based on passivity-based control is proposed for three-phase grid-connected inverters in this paper. Firstly, the Euler-Lagrange (EL) mathematical model of the three-phase grid-connected inverter is established, and the current loop passivity-based controller is designed. Then, combined with the multiple reference frame (MRF) method, an error voltage compensation loop is introduced to independently control the harmonic current. Finally, a simulation model of the system is built and a comparative simulation study is performed with the conventional proportional integral (PI) control and passivity-based control. The simulation results show that the proposed control method which has the advantages of passivity-based control, can effectively suppress the harmonic current of the grid-connected inverter and reduce the design requirements of the filter, thus improving the adaptability of the grid-connected inverter to the weak grid.

The evaluation of system performance plays an increasingly important role in the reliability analysis of cyber-physical systems. Factors of external instability affect the evaluation results in complex systems. Taking the running gear in high-speed trains as an example, its complex operating environment is the most critical factor affecting the performance evaluation design. In order to optimize the evaluation while improving accuracy, this paper develops a performance evaluation method based on slow feature analysis and a hidden Markov model (SFA-HMM). The utilization of SFA can screen out the slowest features as HMM inputs, based on which a new HMM is established for performance evaluation of running gear systems. In addition to directly classical performance evaluation for running gear systems of high-speed trains, the slow feature statistic is proposed to detect the difference in the system state through test data, and then eliminate the error evaluation of the HMM in the stable state. In addition, indicator planning and status classification of the data are performed through historical information and expert knowledge. Finally, a case study of the running gear system in high-speed trains is discussed. After comparison, the result shows that the proposed method can enhance evaluation performance.

Using the differential game model, this study examines the impact of the digital economy and regional cooperative innovation on green innovation efficiency. Additionally, based on the two-stage Super-NSBM model, this study evaluates the effects of the digital economy on green innovation efficiency, its spatial spillover effects, and the moderating role of regional cooperative innovation. The findings of the study indicate that (1) the digital economy significantly enhances green innovation efficiency but has negative spatial spillover effects on surrounding regions. (2) Regional cooperative innovation positively moderates the promotional effect of the digital economy on green innovation efficiency. Moreover, the moderating effect exhibits a single-threshold effect. (3) The influence of the digital economy on green innovation efficiency is more significant in regions with advanced industrialization, robust transportation infrastructure, and high R&D intensity. The coordinated development of digital industrialization and governance is crucial for effectively promoting the development of green innovation. [ABSTRACT FROM AUTHOR]

In this paper, CuZnSnS thin films are prepared by sol-gel method. Firstly, precursor solution is prepared using copper acetate (Cu(CH3COO)2 • H2O), zinc acetate (Zn(CH3COO)2 • H2O), strenuous chloride (SnCl2 • H2O) and thiourea (CH4N2S) in a certain ratio. Then triethanola mine (C6H13NO3) and ethanola mine (C2H73NO) are as stabilizers to prepare Cu2ZnSnS4 thin films. The surface morphology, phase structure, composition and optical properties of the films are characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray energy dispersive spectroscopy (EDS) and UV-visible-infrared spectroscopy. The effects of sintering temperature, rotating speed and stabler addition on the morphology, phase structure and optical properties of copper, zinc, inn and sulfur (CZTS) films are investigated. The results show that the Cu2ZnSnS4 phase structure films are obtained when the concentration of precursor solution 0.2 mol/L in the condition of 1 000 r/min spin speed and 10 s coating time, and the sintering temperature set as 280 °C. When concentration is set as 0.3 mol/L and the spin speed set as 3 500 min with 15 s coating time, the surface appearance of CZTS films prepared by adding ethanola mine (MEA) stabilizer at sintering temperature of 260 C is greatly improved. The granular morphology of CZTS films prepared by adding 1.5 mL tiethanola mine (TEA) and ethanola mine (MEA) stabilizer is observed, and the surface uniformity of CZTS films is improved. However, the crystal quality of the thin film not as good as that of the sample prepared by 0.2 mol/L solution. The loss of Sn and S elements founded and leads to the formation of other phases, reselling in a large bandwidth of the thin film. In add-on, the crystallization of the sample becomes better with the extension of sintering time, but no large size grains are formed. [ABSTRACT FROM AUTHOR]