http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
Control Strategy of MMC-HVDC under Unbalanced Grid Voltage Conditions
Jianpo Zhang,Chengyong Zhao 전력전자학회 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.6
High voltage direct current transmission based on modular multilevel converter (MMC-HVDC) is one of the most promising power transmission technologies. In this study, the mathematical characteristics of MMC-HVDC are analyzed in a synchronous rotational reference frame. A hybrid current vector controller based on proportional integer plus resonant is used to uniformly control the DC and double-base frequency AC currents under unbalanced grid voltage conditions. A corresponding voltage dependent current order limiter is then designed to solve the overcurrent problems that may occur. Moreover, the circulating current sequence components are thoroughly examined and controlled using a developed circulating current suppressor. Simulation results verify the correctness and effectiveness of the proposed control schemes.
Chunyi Guo,Chengyong Zhao,Maolan Peng,Wei Liu 전력전자학회 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.5
A hybrid HVDC system that is composed of line commutated converter (LCC) at the rectifier side and voltage source converter (VSC) in series with LCC at the inverter side is studied in this paper. The start-up strategy, DC fault ride-through capability, and fault recovery strategy for the hybrid HVDC system are proposed. The steady state and dynamic performances under start-up, AC fault, and DC fault scenarios are analyzed based on a bipolar hybrid HVDC system. Furthermore, the immunity of the LCC inverter in hybrid HVDC to commutation failure is investigated. The simulation results in PSCAD/EMTDC show that the hybrid HVDC system exhibits favorable steady state and dynamic performances, in particular, low susceptibility to commutation failure, excellent DC fault ride-through, and fast fault recovery capability. Results also indicate that the hybrid HVDC system can be a good alternative for large-capacity power transmission over a long distance by overhead line.
Yafeng Li,En Li,Chengyong Yu,Chong Gao,Gaofeng Guo,Yong Gao 대한금속·재료학회 2020 ELECTRONIC MATERIALS LETTERS Vol.16 No.2
In this paper, the microwave characteristics of typical photosensitive material InP under diff erent light irradiation are studied. The measurement sensor is a refl ection-type hemispherical quasi-optical resonator with an operating frequency range from 20to 40 GHz, an operating mode of TEM 00q , and a quality factor of 18,000 or more. For the short-time irradiation experiment,the variation of InP microwave characteristics with the irradiation power of 20 mW, 60 mW, 100 mW, and 200 mW, is studiedby frequency-domain and time-domain scanning methods, respectively. The measurement results indicate that the microwavecharacteristics of InP change signifi cantly even under weak light irradiation. Taking 100 mW and 200 mW irradiation poweras examples, the long-time irradiation experiment performed on InP lasting 1.5 min is carried out. The measurement resultcurves clearly show the infl uence of the thermal and non-thermal eff ects on the InP microwave characteristics at the instantof the monochrome light source opening and closing and during irradiation. Furthermore, the temperature distribution ofInP during 200 mW irradiation is real-time imaged by a thermal infrared imager to verify the existence of thermal eff ectduring irradiation. The measurement results are in good agreement with the theoretical analysis.
Control Strategy of MMC-HVDC under Unbalanced Grid Voltage Conditions
Zhang, Jianpo,Zhao, Chengyong The Korean Institute of Power Electronics 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.6
High voltage direct current transmission based on modular multilevel converter (MMC-HVDC) is one of the most promising power transmission technologies. In this study, the mathematical characteristics of MMC-HVDC are analyzed in a synchronous rotational reference frame. A hybrid current vector controller based on proportional integer plus resonant is used to uniformly control the DC and double-base frequency AC currents under unbalanced grid voltage conditions. A corresponding voltage dependent current order limiter is then designed to solve the overcurrent problems that may occur. Moreover, the circulating current sequence components are thoroughly examined and controlled using a developed circulating current suppressor. Simulation results verify the correctness and effectiveness of the proposed control schemes.
Guo, Chunyi,Zhao, Chengyong,Peng, Maolan,Liu, Wei The Korean Institute of Power Electronics 2015 JOURNAL OF POWER ELECTRONICS Vol.15 No.5
A hybrid HVDC system that is composed of line commutated converter (LCC) at the rectifier side and voltage source converter (VSC) in series with LCC at the inverter side is studied in this paper. The start-up strategy, DC fault ride-through capability, and fault recovery strategy for the hybrid HVDC system are proposed. The steady state and dynamic performances under start-up, AC fault, and DC fault scenarios are analyzed based on a bipolar hybrid HVDC system. Furthermore, the immunity of the LCC inverter in hybrid HVDC to commutation failure is investigated. The simulation results in PSCAD/EMTDC show that the hybrid HVDC system exhibits favorable steady state and dynamic performances, in particular, low susceptibility to commutation failure, excellent DC fault ride-through, and fast fault recovery capability. Results also indicate that the hybrid HVDC system can be a good alternative for large-capacity power transmission over a long distance byoverhead line.
Efficient metaheuristic-retrofitted techniques for concrete slump simulation
Yinghao Zhao,Chengzong Bai,Chengyong Xu,Loke Kok Foong 국제구조공학회 2021 Smart Structures and Systems, An International Jou Vol.27 No.5
Due to the benefits of the early prediction of concrete slump, introducing an efficient model for this purpose is of great importance. Considering this motivation, four strong metaheuristic algorithms, namely electromagnetic field optimization (EFO), water cycle algorithm (WCA), teaching-learning-based optimization (TLBO), and multi-tracker optimization algorithm (MTOA) are used to supervise a neural predictive system in analyzing the slump pattern. This supervision protects the network against computational issues like pre-mature convergence. The overall results (e.g., Pearson correlation indicator larger than 0.839 and 0.807 for the training and testing data, respectively) revealed the competency of the proposed models. However, investigating the rankings of the models pointed out the superiority of the WCA (MAE<sub>train</sub> = 3.3080 vs. 3.7821, 3.5782, and 3.6851; and MAE<sub>test</sub> = 3.8443 vs. 4.0326, 4.1417, and 4.0871 obtained for the EFO, TLBO, and MTOA, respectively). Moreover, the high efficiency of the EFO in terms of model complexity and convergence rate, as well as the adequate accuracy of prediction, demonstrated the suitability of the corresponding ensemble. Therefore, the neural systems trained by these two algorithms (i.e., the WCA and EFO) are efficient slump evaluative models and can give an optimal design of the concrete mixture for any desirable slump.
Atiq Ur Rehman,Chunyi Guo,Chengyong Zhao,Wen Jiang 대한전기학회 2019 Journal of Electrical Engineering & Technology Vol.14 No.2
This paper compares the performance of diff erent dynamic reactive power compensators (DRPCs) on transient characteristics of LCC based UHVDC system under hierarchical connection mode (LCC-UHVDC-HCM). The diff erent DRPCs considered are Synchronous Condenser (SC), STATCOM and combination of both SC and STATCOM (hybrid dynamic reactive power compensator, HDRPC). Various transient indices like commutation failure immunity index (CFII), commutation failure probability index (CFPI) and fault recovery time (FRT) of LCC-UHVDC-HCM system are undertaken in order to evaluate the comparative performance of various DRPCs. The LCC-UHVDC-HCM system along with diff erent DRPCs is developed in PSCAD/EMTDC and numerous simulations are done to observe the transient phenomena. The results indicate that performance of DRPCs changes during various AC disturbances such as single phase to ground fault and three phase to ground fault for diff erent fault severity. It is examined that STATCOM is better than other dynamic compensators in improving CFII and CFPI. SC and HDRPC show almost same behavior in improving CFII. However, in case of CFPI, HDRPC is superior to SC. The performance of SC is better than STATCOM and HDRPC in improving FRT under severe fault conditions. However, under low fault conditions, all DRPCs have equal performance in reducing FRT.
Hybrid Double Direction Blocking Sub-Module for MMC-HVDC Design and Control
Jianpo Zhang,Diqiong Cui,Xincheng Tian,Chengyong Zhao 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.6
Dealing with the DC link fault poses a technical problem for an HVDC based on a modular multilevel converter. The fault suppressing mechanisms of several sub-module topologies with DC fault current blocking capacity are examined in this paper. An improved half-bridge sub-module topology with double direction control switch is also designed to address the additional power consumption problem, and a sub-module topology called hybrid double direction blocking sub module (HDDBSM) is proposed. The DC fault suppression characteristics and sub-module capacitor voltage balance problem is also analyzed, and a self-startup method is designed according to the number of capacitors. The simulation model in PSCAD/EMTDC is built to verify the self-startup process and the DC link fault suppression features.