The implementation of modular multilevel converters (MMC) in an electric ship to create a medium voltage direct current (MVDC) energy conversion system that is efficient, small, dependable, and easily scalable has garnered considerable interest. In this research, an improved two-step nearest level control (E-NLC) is presented for MMC with a three-level submodule (3L-SM) as the rectifier of the electric ship power generation units in order to ease the economical and reliable operation of MMCs in MVDC systems. To achieve DC fault-clearing capability, the use of MMC with 3L-SM minimizes the number of switching devices when compared to the regular MMC topology. The suggested E-NLC scheme aims to reduce total harmonic distortion (THD) and achieve the nearest zero common mode voltage (CMV). The output voltage vector of the three phases is tuned using eight candidate vectors capable of suppressing CMV rather than the nearest-level vector, and the rounding function is modified to improve harmonic performance by increasing the approximation between stepped and modulated waves. The generator-connected MMC with THD reduction and CMV elimination maximizes the mover's protection in the generating unit of the electric ship's MVDC system. Simulation and experiment results validate the efficacy of the suggested approach with respect to steady-state and dynamic-state performance.
{"title":"Enhanced Two-Step Nearest Level Control with Enhanced Power Quality for Electric Ship System","authors":"Hui Hwang Goh;Jiaru Sun;Xue Liang;Dongdong Zhang;Wei Dai;Shaojian Song;Tonni Agustiono Kurniawan;Kai Chen Goh","doi":"10.17775/CSEEJPES.2023.00740","DOIUrl":"https://doi.org/10.17775/CSEEJPES.2023.00740","url":null,"abstract":"The implementation of modular multilevel converters (MMC) in an electric ship to create a medium voltage direct current (MVDC) energy conversion system that is efficient, small, dependable, and easily scalable has garnered considerable interest. In this research, an improved two-step nearest level control (E-NLC) is presented for MMC with a three-level submodule (3L-SM) as the rectifier of the electric ship power generation units in order to ease the economical and reliable operation of MMCs in MVDC systems. To achieve DC fault-clearing capability, the use of MMC with 3L-SM minimizes the number of switching devices when compared to the regular MMC topology. The suggested E-NLC scheme aims to reduce total harmonic distortion (THD) and achieve the nearest zero common mode voltage (CMV). The output voltage vector of the three phases is tuned using eight candidate vectors capable of suppressing CMV rather than the nearest-level vector, and the rounding function is modified to improve harmonic performance by increasing the approximation between stepped and modulated waves. The generator-connected MMC with THD reduction and CMV elimination maximizes the mover's protection in the generating unit of the electric ship's MVDC system. Simulation and experiment results validate the efficacy of the suggested approach with respect to steady-state and dynamic-state performance.","PeriodicalId":10729,"journal":{"name":"CSEE Journal of Power and Energy Systems","volume":"11 4","pages":"1670-1680"},"PeriodicalIF":5.9,"publicationDate":"2024-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10520188","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144831932","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-03-03DOI: 10.17775/CSEEJPES.2023.04990
Feng Hong;Yalei Pang;Weiming Ji;Lu Liang;Fang Fang;Junhong Hao;Jizhen Liu
Frequency stability and security have been a vital challenge as large-scale renewable energy is integrated into power systems. In contrast, the proportion of traditional thermal power units decreases during the decarbonization transformation process, resulting in poor frequency support. This paper aims to explore the potential of frequency regulation support, dynamic assessment, and capacity promotion of thermal power plants in the transition period. Considering the dynamic characteristics of the main steam working fluid under different working conditions, a nonlinear observer is constructed by extracting the main steam pressure and valve opening degree parameters. The real-time frequency modulation capacity of thermal power units can provide a dynamic state for the power grid. A dynamic adaptive modification for primary frequency control (PFC) of power systems, including wind power and thermal power, is proposed and improved. The power dynamic allocation factor is adaptively optimized by predicting the speed droop ratio, and the frequency modulation capability of the system is improved by more than 11% under extreme conditions. Finally, through the Monte Carlo simulation of unit states of the system under various working conditions, the promotion of the frequency regulation capacity with high wind power penetration (WPP) is verified.
{"title":"Assessment and Enhancement of FRC of Power Systems Considering Thermal Power Dynamic Conditions","authors":"Feng Hong;Yalei Pang;Weiming Ji;Lu Liang;Fang Fang;Junhong Hao;Jizhen Liu","doi":"10.17775/CSEEJPES.2023.04990","DOIUrl":"https://doi.org/10.17775/CSEEJPES.2023.04990","url":null,"abstract":"Frequency stability and security have been a vital challenge as large-scale renewable energy is integrated into power systems. In contrast, the proportion of traditional thermal power units decreases during the decarbonization transformation process, resulting in poor frequency support. This paper aims to explore the potential of frequency regulation support, dynamic assessment, and capacity promotion of thermal power plants in the transition period. Considering the dynamic characteristics of the main steam working fluid under different working conditions, a nonlinear observer is constructed by extracting the main steam pressure and valve opening degree parameters. The real-time frequency modulation capacity of thermal power units can provide a dynamic state for the power grid. A dynamic adaptive modification for primary frequency control (PFC) of power systems, including wind power and thermal power, is proposed and improved. The power dynamic allocation factor is adaptively optimized by predicting the speed droop ratio, and the frequency modulation capability of the system is improved by more than 11% under extreme conditions. Finally, through the Monte Carlo simulation of unit states of the system under various working conditions, the promotion of the frequency regulation capacity with high wind power penetration (WPP) is verified.","PeriodicalId":10729,"journal":{"name":"CSEE Journal of Power and Energy Systems","volume":"10 4","pages":"1371-1383"},"PeriodicalIF":6.9,"publicationDate":"2024-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10520152","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141966166","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Composite insulators have been widely used in transmission lines. After being removed from transmission lines, their housing silicone material cannot degrade naturally. To tackle this problem, this paper proposes an effective method to recycle waste insulators by pyrolysis to obtain mullite $(mathbf{3}mathbf{Al}_{2}mathbf{O}_{3}cdot mathbf{2}mathbf{SiO}_{2})$