Combining a HMM with a Genetic Algorithm for the Fault Diagnosis of Photovoltaic Inverters

Zheng, Hong,Wang, Ruoyin,Xu, Wencheng,Wang, Yifan,Zhu, Wen The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.4

The traditional fault diagnosis method for photovoltaic (PV) inverters has a difficult time meeting the requirements of the current complex systems. Its main weakness lies in the study of nonlinear systems. In addition, its diagnosis time is long and its accuracy is low. To solve these problems, a hidden Markov model (HMM) is used that has unique advantages in terms of its training model and its recognition for diagnosing faults. However, the initial value of the HMM has a great influence on the model, and it is possible to achieve a local minimum in the training process. Therefore, a genetic algorithm is used to optimize the initial value and to achieve global optimization. In this paper, the HMM is combined with a genetic algorithm (GHMM) for PV inverter fault diagnosis. First Matlab is used to implement the genetic algorithm and to determine the optimal HMM initial value. Then a Baum-Welch algorithm is used for iterative training. Finally, a Viterbi algorithm is used for fault identification. Experimental results show that the correct PV inverter fault recognition rate by the HMM is about 10% higher than that of traditional methods. Using the GHMM, the correct recognition rate is further increased by approximately 13%, and the diagnosis time is greatly reduced. Therefore, the GHMM is faster and more accurate in diagnosing PV inverter faults.

Trace surface fluorination and tungsten-intercalation cooperated dual modification induced photo-activity enhancement of titanium dioxide

Yifan Xu,Zhongyuan Liu,Kunlun Wang,Chunyao Niu,Pengfei Yuan,Jin You Zheng,Young Soo Kang,Xiao Li Zhang 한국공업화학회 2022 Journal of Industrial and Engineering Chemistry Vol.108 No.-

General modification that utilizes insoluble tungstic acid or highly toxic hydrofluoric acid to improvecharge separation and transfer in TiO2 results in considerable issues such as uneven doping, significantimpacts on particle size and morphology, as well as environmental hazards. In the present work, an environmentalbenign one-pot dual-modification approach was demonstrated that uses soluble sodium tungstateand only trace-level sodium fluoride as replacements. The photoactivity efficiency for decolorationof methylene blue (MB) solution was improved by 33.6% and 119.5% under ultraviolet and visible light,respectively. Meanwhile, the photocurrent density reached an enhancement by 181.2% by this dualmodification. The dual-modification had negligible influence on the crystal structure and the surface areaof the TiO2 nanoparticles. Density functional calculation suggested the remarkable improvements of thephotocatalysis of TiO2 can be ascribed to the rapid charge separation and transfer owing to the downshiftof conduction band from the tungsten doping and localized spatial charge separation from the surfacefluorination enabled by the dual-modification approach.

Stable and Active Oxidation Catalysis by Cooperative Lattice Oxygen Redox on SmMn₂O₅ Mullite Surface

Zheng, Yongping,Thampy, Sampreetha,Ashburn, Nickolas,Dillon, Sean,Wang, Luhua,Jangjou, Yasser,Tan, Kui,Kong, Fantai,Nie, Yifan,Kim, Moon J.,Epling, William S.,Chabal, Yves J.,Hsu, Julia W. P.,Cho, Kye American Chemical Society 2019 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.141 No.27

<P>The correlation between lattice oxygen (O) binding energy and O oxidation activity imposes a fundamental limit in developing oxide catalysts, simultaneously meeting the stringent thermal stability and catalytic activity standards for complete oxidation reactions under harsh conditions. Typically, strong O binding indicates a stable surface structure, but low O oxidation activity, and <I>vice</I><I>versa</I>. Using nitric oxide (NO) catalytic oxidation as a model reaction, we demonstrate that this conflicting correlation can be avoided by cooperative lattice oxygen redox on SmMn<SUB>2</SUB>O<SUB>5</SUB> mullite oxides, leading to stable and active oxide surface structures. The strongly bound neighboring lattice oxygen pair cooperates in NO oxidation to form bridging nitrate (NO<SUB>3</SUB><SUP>-</SUP>) intermediates, which can facilely transform into monodentate NO<SUB>3</SUB><SUP>-</SUP> by a concerted rotation with simultaneous O<SUB>2</SUB> adsorption onto the resulting oxygen vacancy. Subsequently, monodentate NO<SUB>3</SUB><SUP>-</SUP> species decompose to NO<SUB>2</SUB> to restore one of the lattice oxygen atoms that act as a reversible redox center, and the vacancy can easily activate O<SUB>2</SUB> to replenish the consumed one. This discovery not only provides insights into the cooperative reaction mechanism but also aids the design of oxidation catalysts with the strong O binding region, offering strong activation of O<SUB>2</SUB>, high O activity, and high thermal stability in harsh conditions.</P> [FIG OMISSION]</BR>

A Rendezvous Node Selection and Routing Algorithm for Mobile Wireless Sensor Network

( Yifan Hu ),( Yi Zheng ),( Xiaoming Wu ),( Hailin Liu ) 한국인터넷정보학회 2018 KSII Transactions on Internet and Information Syst Vol.12 No.10

Efficient rendezvous node selection and routing algorithm (RNSRA) for wireless sensor networks with mobile sink that visits rendezvous node to gather data from sensor nodes is proposed. In order to plan an optimal moving tour for mobile sink and avoid energy hole problem, we develop the RNSRA to find optimal rendezvous nodes (RN) for the mobile sink to visit. The RNSRA can select the set of RNs to act as store points for the mobile sink, and search for the optimal multi-hop path between source nodes and rendezvous node, so that the rendezvous node could gather information from sensor nodes periodically. Fitness function with several factors is calculated to find suitable RNs from sensor nodes, and the artificial bee colony optimization algorithm (ABC) is used to optimize the selection of optimal multi-hop path, in order to forward data to the nearest RN. Therefore the energy consumption of sensor nodes is minimized and balanced. Our method is validated by extensive simulations and illustrates the novel capability for maintaining the network robustness against sink moving problem, the results show that the RNSRA could reduce energy consumption by 6% and increase network lifetime by 5% as comparing with several existing algorithms.

Effects of fireworks on air quality in the main urban area of Nanchong City during the spring festival of 2014-2019

Yifan Qian,Xu Yuan,Wen Dou,Jian Hu,Jie Xia,Danyu Li,Qing Zheng,Ping Zhang,Qiumei Quan,Yunxiang Li 대한환경공학회 2023 Environmental Engineering Research Vol.28 No.2

The sources and variation trend of ambient air pollutants, the duration of pollution process and the conditions for decontamination were analyzed in this essay based on the ambient air pollutants data, PM<SUB>2.5</SUB> source analysis data and meteorological factors in Nanchong City during 2014 to 2019. The results indicated that the concentrated discharge of fireworks on New Year’s Eve was the main reason for the sharp deterioration of the ambient air quality. PM<SUB>2.5</SUB> and PM<SUB>10</SUB> concentrations increased significantly after fireworks were set off, and the peak value appeared at about 02:00 on the Lunar New Year’s Day, but the value of PM<SUB>2.5</SUB>/PM<SUB>10</SUB> did not change significantly. The concentration of SO₂ in gaseous pollutants was slightly affected by fireworks, while NO₂, CO and O₃ were not affected basically. Having been affected by fireworks, the concentrations and percentages of K⁺, Cl⁻ and Mg<SUP>2+</SUP> of the water-solubility ions in PM<SUB>2.5</SUB> significantly increased at the 0.01 level. Meanwhile, the concentrations and percentages of the metal elements, including Cu, Pb, Mg, Al, K and Ba, significantly increased at the 0.05 level. Restricted to the topography and meteorological factors, the duration of the pollution was prolonged.

A Novel Control Scheme Based on the Synchronous Frame for APF

Yifan Wang,Hong Zheng,Ruoyin Wang,Wen Zhu 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.6

For the purpose of enhancing the performance of the shunt active power filter (APF), this paper presents a novel Fast Weighted Compound Control (FWCC) strategy based on the synchronous frame. In this control strategy, the proposed new repetitive controller can work faster and more stably by reducing the internal model cycle and introducing a damping coefficient. In addition, the harmonic detector can be removed to simplify the structure of the APF owing to the improvements. Furthermore, a proportional-integral (PI) controller is added to work in parallel with the repetitive controller by using a weighted ratio. Then, a convergence speed analysis and design algorithm are given in detail. Simulation and experimental results show that the harmonic distortion is reduced from 2.91% to 1.89%. In addition, the content for each of the characteristic harmonic orders has decreased by more than three times.

Combining a HMM with a Genetic Algorithm for the Fault Diagnosis of Photovoltaic Inverters

Hong Zheng,Ruoyin Wang,Wencheng Xu,Yifan Wang,Wen Zhu 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.4

The traditional fault diagnosis method for photovoltaic (PV) inverters has a difficult time meeting the requirements of the current complex systems. Its main weakness lies in the study of nonlinear systems. In addition, its diagnosis time is long and its accuracy is low. To solve these problems, a hidden Markov model (HMM) is used that has unique advantages in terms of its training model and its recognition for diagnosing faults. However, the initial value of the HMM has a great influence on the model, and it is possible to achieve a local minimum in the training process. Therefore, a genetic algorithm is used to optimize the initial value and to achieve global optimization. In this paper, the HMM is combined with a genetic algorithm (GHMM) for PV inverter fault diagnosis. First Matlab is used to implement the genetic algorithm and to determine the optimal HMM initial value. Then a Baum-Welch algorithm is used for iterative training. Finally, a Viterbi algorithm is used for fault identification. Experimental results show that the correct PV inverter fault recognition rate by the HMM is about 10% higher than that of traditional methods. Using the GHMM, the correct recognition rate is further increased by approximately 13%, and the diagnosis time is greatly reduced. Therefore, the GHMM is faster and more accurate in diagnosing PV inverter faults.

Sensing formic acid with a water-based chitosan lanthanide luminescence film

Xu Zheng,Xi Chen,Xudong Yu,Yifan Yang 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.125 No.-

A sensitive and selective formic acid sensor could be useful in detecting this corrosive acid in industrial,medical, and environmental settings. Herein, we present a film for detection of formic acid. We introducedchitosan as a film-forming factor to creatively overcome the problem that chitosan dissolves inacids. A carboxylic acid-carbon dot solution was used to replace the strong acid solution and prepare aluminescent film in which the color changed from green to blue when it was exposed to formic acid. Integrated data analysis of the film was used to distinguish vapor from formic acid/water solutions at differentconcentrations and with a detection limit of 0.01% v/v. The selectivity of the sensor was also investigated. After fumigation with ethanol and other common solvents, there was no response similar to thatfor formic acid. It is believed that films based on lanthanide complexes and chitosan could prevent corrosionand injury from formic acid.

A Novel Control Scheme Based on the Synchronous Frame for APF

Wang, Yifan,Zheng, Hong,Wang, Ruoyin,Zhu, Wen The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.6

For the purpose of enhancing the performance of the shunt active power filter (APF), this paper presents a novel Fast Weighted Compound Control (FWCC) strategy based on the synchronous frame. In this control strategy, the proposed new repetitive controller can work faster and more stably by reducing the internal model cycle and introducing a damping coefficient. In addition, the harmonic detector can be removed to simplify the structure of the APF owing to the improvements. Furthermore, a proportional-integral (PI) controller is added to work in parallel with the repetitive controller by using a weighted ratio. Then, a convergence speed analysis and design algorithm are given in detail. Simulation and experimental results show that the harmonic distortion is reduced from 2.91% to 1.89%. In addition, the content for each of the characteristic harmonic orders has decreased by more than three times.

Feature analysis on air quality in the main urban area of Nanchong City in 2015–2018

Xiong Lei,Qing Zheng,Yifan Qian,Jian Hu,Danyu Li,Ping Zhang,Xu Yuan,Qiumei Quan,Yunxiang Li 대한환경공학회 2022 Environmental Engineering Research Vol.27 No.3

This study evaluates the air quality in Nanchong City in 2015–2018 based on automatic monitoring data and meteorological data in the main urban area. Results show that overall air quality in the main urban area of Nanchong was standard and improved from 2015 to 2018. SO₂, NO₂, and CO had slight influences on air quality in the study area, whereas excessive annual average PM2.5 and increasing O₃ concentration challenged the air quality. The monthly average mass concentrations of particulate matters (PM2.5 and PM10), NO₂, and CO generally presented a “U-shaped” distribution pattern while O₃ showed the opposite. The diurnal variation of PM, NO₂, and CO has two peaks related to the morning and evening rush hours. Vehicle exhaust is the main source of local pollution. Over-standard PM2.5 can significantly inhibit O₃ production while O₃ can easily promote the secondary generation of PM2.5 due to its strong oxidization. PM2.5 emission should be controlled strictly in winter, while in summer, the sources of O₃ should be controlled vigorously. Air pollution is comprehensive and complicated and is influenced by various factors, mainly meteorological and human factors. Measures such as artificial rainfall should be included at the appropriate time to cope with adverse meteorological conditions when heavy pollution occurs in winter.