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Joint Optimization of Planning and Operation in User-side Multi-energy Systems
CUI Quansheng, BAI Xiaomin, DONG Weijie, HUANG Biyao
Proceeding of the CSEE    2019, 39 (17): 4967-4981.   DOI: 10.13334/j.0258-8013.pcsee.181874
Abstract288)      PDF(pc) (560KB)(397)       Save
Building user-side multi-energy systems (USMES) is of great significance for promoting the energy revolution in China. However, USMES contain multiple forms of energy coupling, therefore its optimal planning is a challenging problem. So, the joint optimization model of planning and operation in USMES was proposed. This model takes simultaneously into account the optimization of equipment configuration, network and energy storage, and the full utilization of renewable energy. And it also integrates the operation optimization considering seasonal variation and intra-day time sequence. Equipment type combination, equipment capacity, equipment location, energy distribution network planning and operation strategy can be obtained by solving this model. In a multi-energy system comprised of several buildings in one city block, this model is utilized and the optimization results prove the effectiveness of the proposed model and its solution method.
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Maximum Operation Duration Assessment of Isolated Island Considering the Uncertainty of Load Reduction Capability of Air Conditioner
XIAO Tianying, PEI Wei, CHEN Naishi, WANG Xiaohui, PU Tianjiao, SUN Hongjian
Proceeding of the CSEE    2019, 39 (17): 4982-4994.   DOI: 10.13334/j.0258-8013.pcsee.181449
Abstract263)      PDF(pc) (953KB)(319)       Save
The maximum duration that an island can operate without affecting the electricity users' comfort reflects its operational capability, which has a certain guiding role for the division and operation optimization of the island formed after the fault. In order to assess the maximum operation duration of the island formed after the fault, the probability model of air conditioner load reduction capability under the state-queuing control strategy was established according to the thermal parameter model of air conditioner, which considered the uncertainty of initial control temperature and the prediction error of the outdoor temperature. Then based on the probabilistic models, which included prediction errors of wind turbine power, photovoltaic power and load power, and the air conditioning load reduction capability, a bi-level optimization model designed for assessing the maximum operation duration and power deficiency probability of the island was established. Then the maximum operation duration under different power deficiency probability thresholds, the probability of maximum power shortage under different operating durations, and the probability of running different durations of the island were evaluated. The efficiency of the proposed model was verified through the improved IEEE 13 node system. The simulation results show that the proposed model can evaluate the system's operation duration more realistically, and improve the credibility of the evaluation results.
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Impact of Model Resonance Caused by Current Flow Control of VSC-MTDC on the Stability of System
FU Qiang, DU Wenjuan, WANG Haifeng
Proceeding of the CSEE    2019, 39 (17): 4995-5004.   DOI: 10.13334/j.0258-8013.pcsee.180599
Abstract262)      PDF(pc) (454KB)(359)       Save
In this paper, the impact of model resonance caused by current flow control on the stability of VSC-MTDC system was studied. The linearized model of VSC-MTDC and current flow control (CFC) were established respectively. Based on the linearized model, the characteristics of two model resonances, open-loop resonance and closed-loop resonance, were analyzed and compared. It is concluded that these model resonances are differently mathematical description of the same phenomenon. They can both reduce the damping of the oscillation modes. In addition, the impact of open-loop model resonance on the stability was more significant than the closed-loop model resonance. Hence, the parameters should be carefully tuned to avoid the model resonances. Finally, the voltage source converter based HVDC (VSC-MTDC) system with CFC was established in Matlab. The simulation results indicate that the model resonances can occur between VSC-MTDC and CFC or CFCs. The stable parameters area of CFC is calculated, which can be referred by engineering.
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A New Series Compensation Control Strategy of Power Factor Corrector Without Electrolytic Capacitor by Power Decoupling
WANG Liqiao, WANG Haixu, CUI Shumin, SHEN Hong
Proceeding of the CSEE    2019, 39 (17): 5195-5204.   DOI: 10.13334/j.0258-8013.pcsee.181497
Abstract260)      PDF(pc) (897KB)(356)       Save
In order to remove the electrolytic capacitor and improve the life of the converter, a new series-type power decoupling PFC topology without electrolytic capacitor was proposed. The single-phase full-bridge inverter circuit was selected in series between the Boost-type PFC circuit and the load as a decoupling circuit. According to the principle of voltage compensation and power decoupling, a new voltage compensation open-loop control strategy was proposed for the decoupling circuit. This method is not sensitive to load changes, which improves the stability and reliability of the system. The switching device in the circuit is subjected to a lower voltage value, and the current sampling step is not required in the circuit, which reduces the size and cost of the converter. In order to further improve the input current quality of the circuit, a closed-loop control strategy suitable for the decoupling circuit was proposed. The simulation results show that the closed-loop control can optimize the input current quality and reduce the harmonic pollution, but compared with the voltage compensation open-loop control strategy, the cost and the complexity is higher than the open loop control strategy. Finally, the open-loop and closed-loop control strategies of series-type decoupling circuit were experimentally verified. The experimental results prove the correctness of the theory.
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A Method of Frequency Curve Prediction Based on Deep Belief Network of Post-disturbance Power System
ZHANG Yichao, WEN Da, WANG Xiaoru, LIN Jintian
Proceeding of the CSEE    2019, 39 (17): 5095-5104.   DOI: 10.13334/j.0258-8013.pcsee.181821
Abstract258)      PDF(pc) (491KB)(331)       Save
In order to quickly and accurately predict the dynamic frequency of the post-disturbance power system, this paper proposed a method for predicting the dynamic frequency of the power system based on deep belief network. The method considered the 22-dimensional data as the input features of the deep belief network, including the electromagnetic power and the mechanical power, the maximum output limit of each generator, and the influence factor of each generator on the dynamic frequency. The New England 39-bus system and the South Carolina 500-bus system were used as the simulation systems. Compared with the simulation results in PSS/E, it is proved that the deep belief network can quickly and accurately predict the dynamic frequency of the post-disturbance power system. The method is applicable to online stability analysis of frequency, and it can provide a basis for setting frequency stability control measures which is important to prevent frequency collapse.
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Identifying Inrush Current for Wind Farm Outgoing Transformer Based on MEMD-MMFE
LI Chunyan, ZHOU Niancheng, LIAO Jianquan, WANG Qianggang, MENG Xiaoxiao
Proceeding of the CSEE    2019, 39 (17): 5061-5073.   DOI: 10.13334/j.0258-8013.pcsee.181001
Abstract255)      PDF(pc) (1002KB)(336)       Save
When an internal fault occurs in the wind farm outgoing transformer during the low voltage ride through of the doubly-fed wind farm, there are larger second harmonic in the differential current of the transformer, which can cause the differential protection to be turned down. Based on the multivariate empirical mode decomposition-multiscale multivariate fuzzy entropy (MEMD-MMFE), this paper proposed a method to identify the inrush current. Firstly, the current was decomposed by the multivariate empirical mode. By discriminating the monotonicity of the residual function in the decompositions, whether to remove the residual function from the original function was determined. Then, the multiscale multivariable fuzzy entropy transformation was carried out for the processed original function, and the area of the multiscale multivariate fuzzy entropy value or the entropy area for short was obtained. Finally, the relationship between the entropy of the current on both sides of the transformer and the size of the given brake area was used to distinguish the inrush current and the fault current. Taking a wind farm connected to the main grid as an example, several operating conditions for transformer were investigated. Through comparing with the second harmonic restraint algorithm, the effectiveness of the proposed algorithm in this paper was verified.
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A Monthly Balancing Mechanism Based on Pre-bidding and Its Multi-period Generation Schedule Optimization Model
XU Chuanlong, ZHANG Lizi, CHEN Dayu, TANG Chengpeng
Proceeding of the CSEE    2019, 39 (17): 5085-5094.   DOI: 10.13334/j.0258-8013.pcsee.181092
Abstract252)      PDF(pc) (262KB)(329)       Save
Under the medium- and long-term power direct trading market in China, the traditional monthly balancing mechanism mainly focuses on flexibility and does not fully consider economy. As the scale of direct trading continues to expand, the traditional way can hardly meet the dual needs of market operation for fairness and economy. A new balancing mechanism based on pre-bidding was designed to deal with monthly energy deviation, which can minimize the cost of monthly deviation adjustment and replace the generation of high-cost units with low-cost units, thus effectively improving the economy of system operation. Under the designed balancing mechanism, a multi-period model including monthly generation schedule rolling model, day-ahead generation schedule optimization model and intraday generation schedule adjustment model was established, considering the factors of load forecast deviation, unit operation constraints and grid operation constraints. Finally, the effectiveness of the method and the model is verified through the IEEE 30-bus system simulation.
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Proceeding of the CSEE    2019, 39 (17): 4965-4965.  
Abstract252)      PDF(pc) (227KB)(323)       Save
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Closing Performance of Phase-control Circuit Breakers in Ultra-high Voltage Networks
DUAN Xiongying, ZHANG Fan, LIAO Minfu, ZOU Jiyan
Proceeding of the CSEE    2019, 39 (17): 5271-5278.   DOI: 10.13334/j.0258-8013.pcsee.182534
Abstract252)      PDF(pc) (406KB)(326)       Save
Theoretically controlled switching is an effective strategy to reduce over-voltages due to ultra-high- voltage (UHV) transmission line closing. But in practice, the pre-breakdown characteristic, the mechanical dispersion of the circuit breaker, and the topological structure of the UHV line have a significant impact on the effect of controlled switching. The quantitative relationship between the closing performance of circuit breakers and the risk of failure of transmission lines is not explicit by the traditional method. According to the data calculated by the statistical method, an adaptive network-based fuzzy inference system (ANFIS) model for forecasting closing performance of circuit breakers was presented. The ANFIS model was employed to map the closing performance of circuit breakers, line parameters and the failure risk of the UHV transmission line. The calculation and analysis show the results of the model meet the accuracy requirements of UHV systems. On one hand, the ANFIS model can forecast the risk of failure in different pre-breakdown characteristic and mechanical dispersion of circuit breakers and line parameters. On the other hand, it is easy to analyze the closing performance of circuit breakers in different failure risk requirements.
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Thrust Fluctuation Suppression of Permanent Magnet Synchronous Linear Motor by Using Electromagnetic Damping-spring System
ZHAO Jiwen, HE Zhongyan, DONG Fei, WANG Lijun, SONG Juncai, WANG Hui
Proceeding of the CSEE    2019, 39 (17): 5237-5246.   DOI: 10.13334/j.0258-8013.pcsee.181841
Abstract250)      PDF(pc) (1336KB)(329)       Save
The thrust fluctuation of permanent magnet synchronous linear motor (PMSLM) limits its application in precision machining equipment. In this paper, an electromagnetic damping-spring system was designed with the structure and motion characteristic of PMSLM for thrust fluctuation suppression. First, the kinetic model of the PMSLM and electromagnetic damping-spring system was established, and the vibration suppression principle of the vibration suppression device was analyzed. Then, the thrust fluctuation as the excitation of the electromagnetic damping-spring system, the Hooke's law was used to analyze elastic force and the electromagnetic damping force was analyzed by the principle of virtual work. Therefore, the suppression force of the vibration suppression system was obtained. Next, the correctness of the analysis was verified by simulation analysis. And the optimized relevant structural parameters of electromagnetic damping-spring system were selected. Finally, prototype experiments verified that the proposed method can effectively suppress the thrust fluctuation under different speeds and loads.
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Fuel Cell System Online Identification and Real-time Maximum Efficiency Sliding Mode Control Method
WANG Tianhong, LI Qi, YIN Liangzhen, SU Bo, HUANG Wenqiang, CHEN Weirong
Proceeding of the CSEE    2019, 39 (17): 5118-5128.   DOI: 10.13334/j.0258-8013.pcsee.181559
Abstract250)      PDF(pc) (624KB)(315)       Save
In order to guarantee the fuel cell system working at maximum efficiency point without disturbance under the varying load conditions. This paper proposed a method based on forgetting factor recursive least square (FFRLS) online identification and Super-Twisting sliding mode control algorithm for tracking the real-time maximum efficiency point of fuel cell system. The proposed method is based on the nonlinear curve fitting principle, according to the real-time data of the system, the maximum efficiency point power of the fuel cell can be estimated in real time within the unit control period. Then, the Super-Twisting sliding mode algorithm was used to ensure that the fuel cell system can still operate at the maximum efficiency point under the varying load conditions. On the test bench, a multi-index performance test and comparative analysis were carried out. The experimental results show that, the proposed real-time maximum efficiency point tracking method has obvious advantages compared with the traditional disturbance observation (P&O) method. A comparative experiment with the traditional PID algorithm was carried out. The results show that, under the large disturbances in input, the converter controlled by the Super-Twisting sliding mode algorithm has stronger robustness, which is beneficial to the long-term stable operation of the fuel cell power system.
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Series-capacitor Based Interleaved Buck PFC Converter With High Power Factor
ZHANG Chenyu, WU Yunfeng, CHEN Zhangyong, TANG Yuanhong, ZHANG Changhua
Proceeding of the CSEE    2019, 39 (17): 5205-5215.   DOI: 10.13334/j.0258-8013.pcsee.181658
Abstract249)      PDF(pc) (1054KB)(318)       Save
Conventional buck power factor correction (PFC) converter has the problem of dead zone angle of input current. In order to solve the problem, a series-capacitor based interleaved buck PFC converter with high power factor was proposed in this paper. By effectively regulating the charge and discharge time to effectually control the energy transferred to the load, the proposed PFC converter had the character of ultrahigh step down ratio, namely ultralow output voltage which can mitigate the dead zone angle. Meanwhile, the intermediate energy storage capacitance worked at discontinuous capacitor voltage mode (DCVM) for automatic PFC and the capacitor peak voltage was clamped to the input voltage without increasing the voltage stress of the power switches. In addition, working at DCVM, the proposed PFC converter can realize the soft turn-off of power switches and soft turn-on of diodes. The operational principle, performance analysis and parameter design principle were given in this paper. Finally, a 220V ac input, 60W/15V output experimental prototype was built to verify the validity of the theoretical analysis.
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The Modeling and Characteristic Analysis of Harmonic Current of DFIG Based Wind Turbine in Grid-connected Mode
NIAN Heng, ZHOU Qi, WU Chao, ZHU Qiongfeng
Proceeding of the CSEE    2019, 39 (17): 5037-5048.   DOI: 10.13334/j.0258-8013.pcsee.181612
Abstract248)      PDF(pc) (860KB)(363)       Save
With the increased renewable energy power capacity and increased requirement for power quality assessment of renewable power station, the mathematical model of harmonic current including the output from the stator winding and grid side converter of the doubly-fed induction generator based wind turbine was developed, in which the harmonic current caused the background harmonic components in the power grid and dead time effect of convertor were considered. Based on the harmonic current model, the amplitude-phase characteristic of integer frequency and non-integer frequency component in harmonic current could be accurately described. Also, the influence mechanism of different factors such as the amplitude and phase of harmonic voltage in grid, operation situation and control delay on the harmonic current were analyzed. Finally, the correctness of the harmonic current model was verified by the simulation results and experimental tests.
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Parallel Calculation of Load Margin in Bulk Power Grid Using CPU-GPU Architecture
LI Xue, LIU Ye, JIANG Tao, CHEN Houhe, LI Guoqing
Proceeding of the CSEE    2019, 39 (17): 5105-5117.   DOI: 10.13334/j.0258-8013.pcsee.181172
Abstract248)      PDF(pc) (361KB)(339)       Save
To quickly and accurately achieve the load margin of the power system, this paper proposed a parallel algorithm for load margin calculation using CPU-GPU hybrid architecture on the basis of the direct load margin calculation method. Firstly, according to the characteristics that the power flow Jacobi matrix was singular at the voltage stability critical point and the eigenvector corresponding to the zero eigenvalue was not 0, a set of nonlinear equations that characterize the critical point of voltage stability was constructed. To reduce the computational cost, the modified equations were reduced into four groups of low dimension linear equations with the same coefficient matrix in the process of solving the nonlinear equations using Newton method. On this basis, in order to improve the coefficient matrix eigenvalue distribution, this paper combined Jacobi preconditioner and incompleted LU decomposition preconditioner (ILU) into a two-step preconditioner and preconditiond the coefficient matrix of the reduced linear equations. In addition, a GPU-accelerated biconjugate gradient stabilized (BICGSTAB) iterative linear solver was used to solve these linear equations parallelly. Multiple test systems were further used to evaluate the performance of the proposed method. The results validate that the proposed method can improve the computational efficiency of the load margin calculation.
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Electric-thermal-stress Oriented Multi-objective Optimal Design of Power Module Package
ZENG Zheng, LI Xiaoling, LIN Chaobiao, RAN Li
Proceeding of the CSEE    2019, 39 (17): 5161-5171.   DOI: 10.13334/j.0258-8013.pcsee.180965
Abstract247)      PDF(pc) (828KB)(346)       Save
Due to the common applications of power modules and increasing penetration of wide bandgap devices, low parasitic, low thermal-resistance, and high reliability packaging for power modules is urgently needed. Focusing on the coupling principles among electric-thermal-stress multi-physics in power modules, characteristics of parasitic, thermal-resistance, power-cycling and thermal-cycling based life-times are modeled and quantified. To achieve an advanced power package, the trade-off among parasitic inductance, thermal resistance, and reliability were revealed, then a multi-objective optimal model was proposed to balance the electric-thermal-stress trade-off. Non-dominated sorting genetic algorithm (NSGA-II) was employed to obtain the Pareto-based optimal solutions. According to the multi-objective model, the effect principles of solders, ceramics, and baseplates by using different materials were comprehensively compared. Additionally, the specifications of packaging materials in each layer were represented. The proposed theories and approaches are of reference value for the optimal design of power module package.
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A PWM Scheme for Regenerative Braking of Brushless DC Motor
BIAN Chunyuan, DUAN Pengfei, XIAO Hongquan, LI Xiaoxia, ZHANG Zhenqiang
Proceeding of the CSEE    2019, 39 (17): 5247-5256.   DOI: 10.13334/j.0258-8013.pcsee.181248
Abstract247)      PDF(pc) (507KB)(326)       Save
Based on regenerative braking principle, the paper indicated the advantages and disadvantages of half bridge pulse width modulation (PWM) and whole bridge PWM of brushless DC Motor (BLDCM) respectively, and presented a detailed analytical study of half bridge PWM of BLDCM This half bridge PWM method would cause diode freewheeling of inactive phase when motor operated in braking mode, thus affect operation characteristics of the motor. Through theoretical and mathematical analysis, a new PWM approach called PWM-OFF-PWM was proposed,which could eliminate the diode freewheeling of the inactive phase, improve the current waveform, decrease the torque ripple, get larger and stabler braking torque, and realize efficient regenerative braking. Simulation and experimental results were provided to demonstrate the validity of the proposed method.
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Correlation Analysis Between Oscillation Mode and Impact Factor of Doubly-fed Induction Generator
MIAO Jierong, XIE Da, WANG Xitian, ZHANG Yanchi, ZHU Miao
Proceeding of the CSEE    2019, 39 (17): 5049-5060.   DOI: 10.13334/j.0258-8013.pcsee.181386
Abstract246)      PDF(pc) (594KB)(338)       Save
The research on wind power oscillation modes is usually based on system modeling of wind power system with limited external factors considered. The more accurate model means more complicated solution of the model. This paper would analyze the measured data of the wind generation system to mine the correlation between oscillation modes and factors (including wind speed and voltage fluctuation). The output power of wind generating machine sets was segmented first. Each segment was decomposed by the Prony algorithm and the important oscillation modes were extracted according to the results of small signal analysis. Meanwhile, the K-Means algorithm was adopted to cluster the data according to wind and voltage factor. The Apriori algorithm was finally used to discuss the association rules between wind speed/voltage clusters and oscillation modes and to predict the oscillation modes. The results of association analysis show that the wind speed/voltage clustering number has a great influence on the association rules. Under the optimal value, some clusters can analyze some specific oscillation components of the power and the prediction results are consistent with the actual situation.
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On-line Abnormal State Identification of Pitch System Based on Transitional Mode for Wind Turbine
WANG Shuangxin, GUO Tingting, LI Meng
Proceeding of the CSEE    2019, 39 (17): 5144-5152.   DOI: 10.13334/j.0258-8013.pcsee.182500
Abstract246)      PDF(pc) (516KB)(346)       Save
Pitch system of wind turbine is often switched under different operating modes due to random fluctuation of wind speed and strong coupling between subsystems, which makes it difficult to detect and locate faults precisely in real time. Therefore, supervisory control and data acquisition (SCADA) system in practice running has a high false alarm rate for pitch system. Accounting for these problems, this paper proposed an abnormal status monitoring and recognition system online. First, because the contribution rate of characters to state is discrepant under different modes, the paper put forward reduction model based on the entropy-optimized neighborhood rough set (ENRS) under different operating modes, and a mining strategy of state characteristic parameters of pitch system in all operating modes. Then, the multi-model state monitor based on a small-world particle swarm optimized entropy weighted learning vector quantization (SWPSO- Entropy LVQ) with reduction data set as input sample is constructed to realize locate faults precisely. Finally, above models were trained the based on actual wind field data. Simulations and test results indicate that the SWPSO-Entropy weighed LVQ based on ENRS can accurately and real-time reflect the abnormal state pattern recognition of the pitch system under transitional operating modes.
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Microstructure and Its Evolution of Two Candidate Alloys Used for A-USC Power Plant
DANG Yingying, ZHAO Xinbao, YANG Zheng, ZHANG Xingxing, YIN Hongfei
Proceeding of the CSEE    2019, 39 (17): 5137-5143.   DOI: 10.13334/j.0258-8013.pcsee.190069
Abstract245)      PDF(pc) (772KB)(292)       Save
The key to realize 700℃advanced ultra- supercritical technology is the development of materials with long term safe operation. Investigations were made on In 740H the most promising alloy among the whole candidates and HT1 a new candidate developed domestic by thermodynamic simulation, long term exposure test, microstructure characterization and micro-hardness analysis. The results show that the microstructures of In 740H and HT1 after standard heat treatment are both constituted of γ matrix, γ' and a quantity of carbides. With the increase of exposure time, the coarsening of γ' follows Ostwald ripening theory. During the whole thermal aging no eta and sigma phases are observed. Due to the different growth rate of γ', room temperature microhardness increases to a maximum at the first 500h to ~1000h and then softening proceeds. However, the hardness decreases slowly with time from ~1000h to 3000h aging, which implies that superior properties can be maintained during long term service. The changes of microstructure and hardness indicate that both of In 740H and HT1 have good phase stability.
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DC Voltage Target Predetermined Control of Hybrid MMC to Handle Line Fault of Overhead DC Grid
ZHOU Meng, XIANG Wang, ZUO Wenping, WEN Jinyu, LIN Weixing
Proceeding of the CSEE    2019, 39 (17): 5015-5024.   DOI: 10.13334/j.0258-8013.pcsee.181491
Abstract244)      PDF(pc) (529KB)(332)       Save
With the plan for HVDC projects based on hybrid/full-bridge modular multilevel converter (MMC), the research on DC fault ride through control of hybrid MMC is an urgent demand for engineering application. To reduce the peak value of DC fault current, and accelerate the recovery of the DC power, this paper proposed a DC voltage predetermined control for hybrid MMC. It optimized the transient characteristics of the DC voltage station after the DC fault. The fundamental principle and design method of DC voltage predetermined control were disclosed in this paper. The selection principle of DC voltage reference during the DC fault was discussed in the view of the application both in two-terminal HVDC system and DC grids. The influence of different DC voltage predetermined curves on the drop of DC bus voltage, the peak of DC current, and the recovery of DC power transmission were analyzed. Simulation analysis shows that the DC voltage predetermined control can reduce the peak value of DC fault current to a certain extent, and significantly accelerate the DC power recovery after DC fault, which has certain engineering application prospects.
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Distributionally Robust Unit Commitment Based on Imprecise Dirichlet Model
ZHANG Yumin, HAN Xueshan, YANG Ming, WANG Mingqiang, ZHANG Li, YE Pingfeng, XU Bo
Proceeding of the CSEE    2019, 39 (17): 5074-5084.   DOI: 10.13334/j.0258-8013.pcsee.181279
Abstract244)      PDF(pc) (529KB)(334)       Save
Cope with the uncertainty of wind power in the decision-making of unit commitment (UC), the stochastic process of wind power is difficult to express for exact probability density and distribution function. In order to solve this problem, a distributionally robust unit commitment optimization model and solving method based on imprecise Dirichlet model (IDM) was proposed. The core of this method is as follows. Firstly, based on historical information, IDM is adopted to construct ambiguity set containing all possible probability distributions of wind power. Secondly, according to the ambiguity set, the uncertainty interval of wind power was deduced at a certain confidence level. In this way, it can be connected with the traditional adaptive robust optimization model. Therefore, the distributionally robust optimization decision model was constructed, which was solved by C&CG (column and constraint generation) algorithm. Finally, case studies on the modified IEEE 118 bus system demonstrates the effectiveness and efficiency of the proposed method.
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Reaction Thermodynamics of Overthermal Decomposition of C6F12O
TANG Ju, LEI Zhicheng, WAN Zhaofeng, YAO Qiang, GAO Keli, ZENG Fuping
Proceeding of the CSEE    2019, 39 (17): 5257-5262.   DOI: 10.13334/j.0258-8013.pcsee.182599
Abstract243)      PDF(pc) (349KB)(305)       Save
The greenhouse effect caused by SF6 in the power industry cannot be ignored anymore. The environmentally friendly insulating gas C6F12O has the potential to replace SF6 in the medium and low pressure gas insulated switchgear C-GIS, but the thermostability problem has not been revealed so far when a partial overthermal fault occurs in C-GIS. For this purpose, this paper firstly carried out the C6F12O partial overthermal decomposition experiment on the existing decomposition experimental system of gas insulating medium. Combined with theoretical calculations, it can be seen that the main products of C6F12O decomposition at high temperature are CO, CF4, C2F4, C2F6, C3F6, C3F8, C4F8, C4F10, C5F12, C6F14. Based on the experimental research, the molecular geometry optimization of C6F12O and main decomposition products was carried out by the density functional theory Hybrid:B3LYP method, and the various bond energies in the C6F12O were calculated. From the perspective of bond energy, the sequence and possibility of bond breaking of C6F12O in overthermal state were analyzed in detail. The thermodynamic characteristics of the overthermal decomposition of C6F12O under overthermal state were calculated in detail. The thermal stability of C6F12O was revealed at the molecular level, which laid a theoretical foundation for the future study of C6F12O insulation thermostability.
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Proceeding of the CSEE    2019, 39 (17): 4966-4966.  
Abstract243)      PDF(pc) (6587KB)(312)       Save
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Study on the Biomass Gasification Process in Fluidized Bed Based on Discrete Element Method
CHEN Juhui, SONG Meiqi, WANG Shuai, HU Ting, LIN Feng, YIN Weijie
Proceeding of the CSEE    2019, 39 (17): 5129-5136.   DOI: 10.13334/j.0258-8013.pcsee.180991
Abstract242)      PDF(pc) (903KB)(319)       Save
Based on discrete element method, the control equations of gas and solid phases were proposed. The reliability of the model was verified by simulating the evaporation process of droplets in wet air, and the model was presented for simulating the biomass gasification process in the fluidized bed. The simulation results show the instantaneous distribution of the flow and reaction characteristics of biomass particles in the reactor, and the bubbles periodically generate and float up and eventually break in the bed. The biomass particles entering the reactor periodically floated up and sink with the bed particles, then biomass is fully mixed with the bed material and evenly distribute in the bed materials. After the fuel particles entered the reactor, it would pyrolysis the volatiles rapidly and be carried out by the air flow from the top outlet. The simulations show the instantaneous distribution of mass fraction of gas products. The gas species CH4, CO, CO2, and H2 are basically the same distribution, and the proportion of CO and CO2 is slightly higher. The distribution of N2 and O2 was contrary to the former four distribution rules. The distribution of H2O gas species was slightly different, and the concentration gradient near the inlet was lower.
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Analysis and Direct Torque Control of a Disc Permanent Magnet Synchronous Motor for Contra-rotating Propellers
RAO Zhimeng, HUANG Shoudao, LUO Derong, JIANG Yan, CHENG Shuangyin, HUANG Zhong
Proceeding of the CSEE    2019, 39 (17): 5225-5236.   DOI: 10.13334/j.0258-8013.pcsee.181603
Abstract240)      PDF(pc) (2118KB)(323)       Save
It is usual that adopting gas turbine with a mechanical transmission device to drive contra-rotating propellers (CRP), but the device has many problems such as complex structure, huge volume, noise pollution and so on. A novel disc contra-rotating permanent magnet synchronous motor (DC-PMSM) for electric propulsion contra-rotating propeller was designed. Firstly, based on the analysis of the structure and working principle of the new DC-PMSM, the magnetic circuit characteristic of the motor was studied. And superposition characteristics of back EMF and dual-rotor torque characteristics of the DC-PMSM were examined by three-dimensional finite element method (3D-FEM). Secondly, aiming at the unusual structure of a single-stator-double-rotor of the DC-PMSM, a direct torque control (DTC) algorithm based on torque angle time-sharing control was proposed. The algorithm can suppress the uncontrollable speed of the DC-PMSM when the load torques were unbalanced, and synchronous operation of double-rotor was realized. Finally, the effectiveness of the designed DC-PMSM and the feasibility of the proposed torque angle time-sharing control algorithm were verified by 3D-FEM and prototype experiments.
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State Split Multi-objective Dynamic Programming Algorithm for Dynamic Reconfiguration of Active Distribution Network
LI Zhenkun, LU Qun, FU Yang, SU Xiangjing, GE Xiaolin
Proceeding of the CSEE    2019, 39 (17): 5025-5036.   DOI: 10.13334/j.0258-8013.pcsee.181681
Abstract240)      PDF(pc) (405KB)(325)       Save
A large quantity of DG has caused much operation risk for distribution network by its uncertainty. The day-ahead dynamic reconfiguration of active distribution network was studied in this paper and its operational risk was fully considered. The multi-objective dynamic reconfiguration model was established, which takes into account both operational economy and operational risk. A comprehensive operational risk index of the system was proposed. To solve the multi-objective dynamic reconfiguration model, a state split multi-objective dynamic programming algorithm was proposed. Firstly, after obtaining the Pareto optimal static solution set at each time, the allowable state set of each time period was obtained by adopting state locking measure. Then the state of each period was split into multiple sub-states according to the size of Pareto optimal front of sequence distance vector. And Pareto optimal day-ahead dynamic reconstruction scheme was obtained based on the expanded sets. Finally, the dynamic reconfiguration of IEEE 33 node power distribution network including wind turbines and photovoltaic was carried out. The day-ahead Pareto optimal reconfiguration scheme was obtained, and the validity of the proposed model and algorithm was verified.
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Experimental Study on Synergistic Heat Transfer on Plate Between Ion Wind and Incoming Flow
ZHANG Li, YANG Lanjun, HAN Jiayi, LIU Shuai, ZHAN Wei, YU Menghan, GUO Shenghui
Proceeding of the CSEE    2019, 39 (17): 5263-5270.   DOI: 10.13334/j.0258-8013.pcsee.182356
Abstract240)      PDF(pc) (421KB)(321)       Save
Synergistic heat transfer between ion wind and incoming flow was studied. Three different-shaped electrodes including the wire electrode, the needle electrode and the needle-ring electrode on the heat dissipation of the plate were compared. The effects of incoming wind speed and applied voltage on heat exchange performance under different electrode spacing and energy consumption were investigated. The experimental results show that when the incoming flow speed is less than 1.5m/s and act simultaneously with the ion wind, on the one hand, the ion wind can cause local turbulence on the surface of the heating plate to improve the local heat exchange capacity. On the other hand, the heat is transported away in time to further enhance the heat transfer. The synergy between the two can make the heat transfer coefficient reach 60W/(m2·℃) or more, which is 3.5~4.5 times of natural convection heat dissipation. Moreover, compared with the wire electrode and the needle electrode, a needle-ring electrode can provide better heat exchange effect and relatively lower energy consumption. The electric field calculation indicates that the ring of the needle-ring electrode can enhance the body force strength between the discharge electrode and the ground plane, which is beneficial to enhance the heat exchange effect of the ion wind.
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Review on Artificial Intelligence in Power System Transient Stability Analysis
TANG Yi, CUI Han, LI Feng, WANG Qi
Proceeding of the CSEE    2019, 39 (1): 2-13.   DOI: 10.13334/j.0258-8013.pcsee.180706
Abstract240)      PDF(pc) (376KB)(557)       Save
Control and analysis methods in power system transient stability assessment (TSA) evolved fundamentally with the trends of power electronic domination, cyber-physical integration and large-scale power system interconnection. In order to satisfy the urgent requirements of TSA, artificial intelligence (AI) with the advantage in data mining was widely studied. This paper analyzed new features in TSA from the aspects of information, theory, simulation, analysis and control in detail. Moreover, based on the review of progress in the field of applying AI to TSA, the existing problems in data source, sample generation and algorithm application were analyzed for further improvements. Finally, a conclusion on current research progress was made.
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Overall Structure Optimization of Mist Eliminator
CHEN Hongwei, XU Jifa, FENG Xupeng, JIA Jiandong, LIU Tuo
Proceeding of the CSEE    2019, 39 (17): 5153-5160.   DOI: 10.13334/j.0258-8013.pcsee.182085
Abstract237)      PDF(pc) (655KB)(322)       Save
In order to improve the demisting efficiency of the baffle demister, the influence of the demister blade pitch, turning angle, turning height, flow velocity, different droplet diameter and other factors on the demisting efficiency were studied, and the evaluation parameter KpPiRe2 was introduced. Reasonable structure enables the defogger to have higher defogging efficiency when the induced draft fan is used at lower power consumption. The results show that the efficiency of the defogger is proportional to the droplet diameter and flow velocity, and inversely proportional to the turning angle and the blade pitch. The effect of the defogger turning height on the efficiency of the defogger is small. The optimized structure parameters of the final defogger are determined as θ=40°, H3=25mm, D=20mm. When the flow rate is 2~3m/s, the efficiency of the defogger of the optimized structure is about 16%, which is optimized at 4m/s. The defogging efficiency of the structure is increased by an average of about 11%. At 5 to
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A Novel Dual-rotor Induction Motor Based on Electromagnetic Coupling Applied for Energy Storage and Driving
WANG Peilong, SHI Liming, DU Yumei
Proceeding of the CSEE    2019, 39 (17): 5216-5224.   DOI: 10.13334/j.0258-8013.pcsee.181887
Abstract237)      PDF(pc) (1656KB)(310)       Save
A novel dual-rotor induction motor (DRIM) applied for energy storage and driving was proposed in this paper. It was based on electromagnetic coupling and fly-wheel energy storage mechanism. DRIM adopted dual-rotor structure, which consisted of an external rotor (master rotor) for energy storage and an internal rotor (slave rotor) for driving load. The structure feature and operation mechanism of DRIM had been presented firstly in this paper. Then the transient working characteristics of DRIM operating on driving model had been analyzed by finite element method (FEM). And the influence of both energy storage speed of master rotor and exciting voltage on DRIM working characteristics had also been studied. Finally the feasibility of DRIM and theory analysis results of the working characteristics had been verified by experiment of a prototype. The theory study and experiment results have demonstrated that DRIM is characterized by low ratio of required exciting power to output power and simple structure and control method, all of which make DRIM be a novel energy storage and driving integration motor scheme for the instantaneous large power mechanical load accelerating system.
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