Research on voltage comprehensive compensation system and control strategy of high-speed railway traction network

High-speed railway, as one of the most important forms of transportation, have been developed rapidly throughout the world. As the people’s living condition improves, the energy demand in China’s transport sector has grown dramatically and will keep increasing in the short term. In order to support the realization of ’ energy conservation ’ vision, it is urgent to adopt energy technology to change the structure of traditional high-speed railway system and realize the green, high efficiency and high elasticity transformation of high-speed railway system. High-speed railway will cause voltage fluctuation of the traction network during driving, which may affect the safety and reliability of high-speed railway in severe cases. In order to improve the voltage fluctuation of traction network caused by high-speed railway, this paper proposes a comprehensive voltage compensation system (VCCS) and its control strategy for high-speed railway traction network. Firstly, the causes of voltage fluctuation in traction network are analyzed, and the existing compensation methods at home and abroad are introduced. Then, the topology and compensation principle of high-speed railway traction network voltage compensation system are introduced, and the corresponding control strategy is proposed. Finally, the correctness of the theoretical analysis is verified by simulation experiments. The experimental results show that the VCCS proposed in this paper can ensure that the high-speed train can maintain full power operation under various typical working conditions, and effectively improve the voltage fluctuation of the traction network

The degradation, biodegradability and toxicity evaluation of sulfamethazine antibiotics by gamma radiation

This study evaluated gamma radiation-enhanced sulfamethazine (SMT) degradation, which belongs to the heterocyclic sulfonamides, in different conditions in aqueous solution. The results showed that gamma irradiation could increase the SMT removal in aqueous solution, and the SMT degradation kinetic follow the modified pseudo-first-order kinetic. The degradation rate was nearly 95% at the absorbed dose of 4 kGy. The removal of total organic carbon (TOC) and total nitrogen (TN) could be also induced. When the radiation dose was 5 kGy, the removal rates were only about 6.8% and 10.5% for TOC and TN, respectively. Some ions including HCOO−, CH3COO− and SO42− released during SMT degradation were studied. The biodegradability and toxicity of intermediate products of the SMT degradation were also proposed in this experiment. The biodegradability of the SMT can be improved by the intermediate products of SMT degradation at the radiation dose of 1, 2 and 5 kGy. Gamma radiation could be used as a pretreatment technology before the biodegradation process of pharmaceutical waste water

Development of Cotton Picker Fire Monitoring System Based on GA-BP Algorithm

Due to the characteristics of the cotton picker working in the field and the physical characteristics of cotton, it is easy to burn during the operation, and it is difficult to be detected, monitored, and alarmed. In this study, a fire monitoring system of cotton pickers based on GA optimized BP neural network model was designed. By integrating the monitoring data of SHT21 temperature and humidity sensors and CO concentration monitoring sensors, the fire situation was predicted, and an industrial control host computer system was developed to monitor the CO gas concentration in real time and display it on the vehicle terminal. The BP neural network was optimized by using the GA genetic algorithm as the learning algorithm, and the data collected by the gas sensor were processed by the optimized network, which effectively improved the data accuracy of CO concentration during fires. In this system, the CO concentration in the cotton box of the cotton picker was validated, and the measured value of sensor was compared with the actual value, which verified the effectiveness of the optimized BP neural network model with GA. The experimental verification showed that the system monitoring error rate was 3.44%, the accurate early warning rate was over 96.5%, and the false alarm rate and the missed alarm rate were less than 3%. In this study, the fire of cotton pickers can be monitored in real time and an early warning can be made in time, and a new method was provided for accurate monitoring of fire in the field operation of cotton pickers

Adsorption and Fenton-like Degradation of Ciprofloxacin Using Corncob Biochar-Based Magnetic Iron–Copper Bimetallic Nanomaterial in Aqueous Solutions

An economical corncob biochar-based magnetic iron–copper bimetallic nanomaterial (marked as MBC) was successfully synthesized and optimized through a co-precipitation and pyrolysis method. It was successfully used to activate H2O2 to remove ciprofloxacin (CIP) from aqueous solutions. This material had high catalytic activity and structural stability. Additionally, it had good magnetic properties, which can be easily separated from solutions. In MBC/H2O2, the removal efficiency of CIP was 93.6% within 360 min at optimal reaction conditions. The conversion of total organic carbon (TOC) reached 51.0% under the same situation. The desorption experiments concluded that adsorption and catalytic oxidation accounted for 34% and 66% on the removal efficiency of CIP, respectively. The influences of several reaction parameters were systematically evaluated on the catalytic activity of MBC. OH was proved to play a significant role in the removal of CIP through electron paramagnetic resonance (EPR) analysis and a free radical quenching experiment. Additionally, such outstanding removal efficiency can be attributed to the excellent electronic conductivity of MBC, as well as the redox cycle reaction between iron and copper ions, which achieved the continuous generation of hydroxyl radicals. Integrating HPLC-MS, ion chromatography and density functional theory (DFT) calculation results, and possible degradation of the pathways of the removal of CIP were also thoroughly discussed. These results provided a theoretical basis and technical support for the removal of CIP in water

Fault detection method for VSC-HVDC System with new energy sources considering fault current limiter

Voltage source converter based high voltage direct current transmission (VSC-HVDC) is widely adopted in the power system with new energy sources, but with the problem of fast rise of fault current. Magnetic saturation fault current limiter (MSFCL) suppresses the rise of short-circuit current by increasing the inductance value, which has the advantages of high speed and no additional control. However, the change of inductance will affect the detection of VSC-HVDC system fault, may leading to missed or incorrect removal of the fault and causing harm. Based on this problem, this paper proposes a fault detection method used in VSC-HVDC system considering MSFCL, which has fast detection speed, high sensitivity and reliability. The proposed method is robust to short-circuit resistance variation and can locate faults external and internal. Firstly, we establish the short-circuit equivalent circuit of VSC-HVDC system. Then we establish the differential equation and solve it, to obtain the analytical expression of voltage across MSFCL. Furthermore, we proposed a short circuit fault detection method based on the rise rate of the voltage across MSFCL. Finally we establish a four port VSC-HVDC system simulation model to prove that the method is effective. The results show that compared with traditional methods, the proposed method has faster detection speed. The proposed method is independent of the power flow direction, can identify the short circuit fault with large short-circuit resistance of 500 Ω and can discriminate the faulty branch from the healthy ones accurately

Application of double core symmetrical phase shifting transformer in power flow regulation of UHV power grid

With the development of society, the demand for electric energy is growing day by day. However, the energy centers and load centers are geographically distributed in a reverse direction, so the power supply and demand are unbalanced. High voltage transmission lines are characterized by long distance and large capacity, and the power flow problems are increasingly prominent. In order to flexibly adjust the line power flow, improve the comprehensive utilization of grid assets, and improve the transmission capacity of the system, this paper analyzes the principle of double core symmetrical phase-shift transformer (DS-PST) and the application of power flow regulation. Firstly, the basic principle of phase shifting transformer is analyzed in detail, and the equivalent mathematical model of DS-PST and the calculation of main parameters are derived. Impedance coefficient and excitation coefficient are introduced to modify the parameter design of DS-PST. Then, an electromagnetic simulation model is established to verify the effectiveness of the design method. Finally, a system simulation model is built to verify the power flow regulation effect of DS-PST by taking 500 kV UHV power grid and IEEE standard multi-node system as examples. DS-PST can transfer the active power transmitted by the lines with high load rate to the lines with low load rate, which makes the power flow distribution of the system more balanced and effectively improves the transmission capacity of the power system

Reconfigurable Surface Plasmon Polariton Wave Adapter Designed by Transformation Optics

This article proposes a reconfigurable surface plasmon polariton (SPP) wave adapter designed by transformation optics, which can control the propagation of SPP waves on un-even surfaces

Inhibition of PRMT1 alleviates sepsis‐induced acute kidney injury in mice by blocking the TGF‐β1 and IL‐6 trans‐signaling pathways

Sepsis‐induced acute kidney injury (SI‐AKI) causes renal dysfunction and has a high mortality rate. Protein arginine methyltransferase‐1 (PRMT1) is a key regulator of renal insufficiency. In the present study, we explored the potential involvement of PRMT1 in SI‐AKI. A murine model of SI‐AKI was induced by cecal ligation and perforation. The expression and localization of PRMT1 and molecules involved in the transforming growth factor (TGF)‐β1/Smad3 and interleukin (IL)‐6/signal transducer and activator of transcription 3 (STAT3) signaling pathways were detected in mouse kidney tissues by western blot analysis, immunofluorescence, and immunohistochemistry. The association of PRMT1 with downstream molecules of the TGF‐β1/Smad3 and IL‐6/STAT3 signaling pathways was further verified in vitro in mouse renal tubular epithelial cells. Cecal ligation and perforation caused epithelial–mesenchymal transition, apoptosis, and inflammation in renal tissues, and this was alleviated by inhibition of PRMT1. Inhibition of PRMT1 in SI‐AKI mice decreased the expression of TGF‐β1 and phosphorylation of Smad3 in the renal cortex, and downregulated the expression of soluble IL‐6R and phosphorylation of STAT3 in the medulla. Knockdown of PRMT1 in mouse renal tubular epithelial cells restricted the expression of Cox‐2, E‐cadherin, Pro‐caspase3, and phosphorylated Smad3 (involved in the TGF‐β1‐mediated signaling pathway), and also blocked IL‐6/soluble IL‐6R, inducing the expression of Cox‐2 and phosphorylated‐STAT3. In conclusion, our findings suggest that inhibition of PRMT1 mitigates SI‐AKI by inactivating the TGF‐β1/Smad3 pathway in the cortex and the IL‐6/STAT3 pathway in the medulla. Our findings may aid in the identification of potential therapeutic target molecules for SI‐AKI