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Intelligent Voltage Control Method in Active Distribution Networks Based on Averaged Weighted Double Deep Q-network Algorithm

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Journal of Modern Power systems and Clean Energy 2023年第1期11卷 132-143页

作者： Yangyang Wang Meiqin Mao Liuchen Chang Nikos D.Hatziargyriou Research Center for Photovoltaic System Engineering Ministry of EducationSchool of Electrical Engineering and AutomationHefei University of TechnologyHefei 230009China University of New Brunswick FrederictonNB E3B 5A3Canada National Technical University of Athens Athens 15780Greece IEEE

High penetration of distributed renewable energy sources and electric vehicles(EVs)makes future active distribution network(ADN)highly variable.These characteristics put great challenges to traditional voltage control methods.Voltage control based on the deep Q-network(DQN)algorithm offers a potential solution to this problem because it possesses humanlevel control performance.However,the traditional DQN methods may produce overestimation of action reward values,resulting in degradation of obtained solutions.In this paper,an intelligent voltage control method based on averaged weighted double deep Q-network(AWDDQN)algorithm is proposed to overcome the shortcomings of overestimation of action reward values in DQN algorithm and underestimation of action reward values in double deep Q-network(DDQN)algorithm.Using the proposed method,the voltage control objective is incorporated into the designed action reward values and normalized to form a Markov decision process(MDP)model which is solved by the AWDDQN algorithm.The designed AWDDQN-based intelligent voltage control agent is trained offline and used as online intelligent dynamic voltage regulator for the ADN.The proposed voltage control method is validated using the IEEE 33-bus and 123-bus systems containing renewable energy sources and EVs,and compared with the DQN and DDQN algorithms based methods,and traditional mixed-integer nonlinear program based methods.The simulation results show that the proposed method has better convergence and less voltage volatility than the other ones.

关键词： Averaged weighted double deep Q-network(AWDDQN) deep Q learning active distribution network(ADN) voltage control electrical vehicle(EV)

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Numerical study of conduction and radiation heat losses from vacuum annulus in parabolic trough receivers

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Frontiers in Energy 2022年第6期16卷 1048-1059页

作者： Dongqiang LEI Yucong REN Zhifeng WANG Key Laboratory of Solar Thermal Energy and photovoltaic system Chinese Academy of SciencesBeijing 100190China Institute of Electrical engineering Chinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China Beijing engineering research center of Solar Thermal Power Beijing 100190China

Parabolic trough receiver is a key component to convert solar energy into thermal energy in the parabolic trough solar system.The heat loss of the receiver has an important influence on the thermal efficiency and the operating cost of the power station.In this paper,conduction and radiation heat losses are analyzed respectively to identify the heat loss mechanism of the receiver.A 2-D heat transfer model is established by using the direct simulation Monte Carlo method for rarefied gas flow and heat transfer within the annulus of the receiver to predict the conduction heat loss caused by residual gases.The numerical results conform to the experimental results,and show the temperature of the glass envelope and heat loss for various conditions in detail.The effects of annulus pressure,gas species,temperature of heat transfer fluid,and annulus size on the conduction and radiation heat losses are systematically analyzed.Besides,the main factors that cause heat loss are analyzed,providing a theoretical basis for guiding the improvement of receiver,as well as the operation and maintenance strategy to reduce heat loss.

关键词： parabolic trough receiver vacuum annulus rarefied gas DSMC(direct simulation Monte Carlo) heat loss

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Optimal Allocation of Fault Current Limiter in MMC-HVDC Grid Based on Transient Energy Flow

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CSEE Journal of Power and Energy systems 2023年第5期9卷 1786-1796页

作者： Meiqin Mao Hui Lu Dejian Cheng Zhuang He research Centre for photovoltaic system engineering.MOE Hefei University of TechnologyHefei 230009China

Economical and reliable protection of DC-side shortcircuit faults has become a key technology for promoting the development of module multilevel converters based on the high voltage direct current grid(MMC-HVDC-Grid).The fault current limiter(FCL)can effectively suppress the rapid development of the fault current and reduce the current breaking capacity of the circuit breaker.In this paper,a method based on transient energy flow(TEF)analysis is proposed to optimize the allocation of a resistive and inductive FCL in the MMC-HVDC-Grid.In the proposed method,the electromagnetic TEF is measured first,and then,the TEF suppression rate and suppression efficiency are defined as optimization objectives,and the installation location of the FCL and its impedance parameters as optimization variables.To test the proposed method,two-terminal and four-terminal bipolar MMC-HVDC-Grids with single-pole-to-ground DC faults are modeled in the PSCAD/EMTDC so that the TEF data can be acquired.The optimal FCLs’location and parameter values are determined through investigating the evolution paradigm of TEF along with changes of the FCL position and parameters.The results prove that the selected parameters can effectively slow down the DC fault current rising rate,thus reducing the requirements on tripping current of the DC breakers.

关键词： MMC-HVDC-Grid TEF FCL DC fault protection optimal allocation

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An adaptive control strategy for microgrid secondary frequency based on parameter identification

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Global Energy Interconnection 2023年第5期6卷 592-600页

作者： Yong Shi Yin Cheng Bao Xie Jianhui Su photovoltaic system engineering research center of the Ministry of Education Hefei University of TechnologyHefei 230009P.R.China State Grid Wuhu Power Supply Company Wuhu 241000P.R.China

Complex microgrid structures and time-varying conditions, among other factors, cause problems in the mechanical modeling of microgrids, making model-based controller optimization difficult. Therefore, this study proposed a secondary frequency adaptive control strategy based on parameter identification, which uses an online parameter identification method to identify the parameters in the microgrid in real-time. The identified parameters are then used in the secondary frequency adaptive controller to optimize the real-time controller performance. The proposed method realizes adaptive optimization of the controller in the microgrid operation state and is applied to a microgrid with unknown parameters to adjust the controller parameters. Finally, a simulation experiment was conducted to verify the model accuracy and the frequency regulation effect of the proposed adaptive control strategy.

关键词： Adaptive control Genetic algorithm Microgrid Online identification

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Optical performance analysis of an innovative linear focus secondary trough solar concentrating system

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Frontiers in Energy 2019年第3期13卷 590-596页

作者： Xiliang ZHANG Zhiying CUI Jianhan ZHANG Fengwu BAI Zhifeng WANG Institute of Electrical engineering Chinese Academy of SciencesBeijing 100190China Key Laboratory of Solar Thermal Energy and photovoltaic system of Chinese Academy of Sciences Beijing 100190China Beijing engineering research center of Solar Thermal Power Beijing 100190China University of Chinese Academy of Sciences Beijing 100190China

The parabolic trough solar concentrating system has been well developed and widely used in commercial solar thermal power plants. However, the conventional system has its drawbacks when connecting receiver tube parts and enhancing the concentration ratio. To overcome those inherent disadvantages, in this paper, an innovative concept of linear focus secondary trough concentrating system was proposed, which consists of a fixed parabolic trough concentrator, one or more heliostats, and a fixed tube receiver. The proposed system not only avoids the end loss and connection problem on the receiver during the tracking process but also opens up the possibility to increase the concentration ratio by enlarging aperture. The design scheme of the proposed system was elaborated in detail in this paper.Besides, the optical performance of the semi and the whole secondary solar trough concentrator was evaluated by using the ray tracing method. This innovative solar concentrating system shows a high application value as a solar energy experimental device.

关键词： secondary parabolic trough solar concentrator ray tracing method linear focus concentration ratio optical performance

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Experiment study of a quartz tube falling particle receiver

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Frontiers in Energy 2017年第4期11卷 472-479页

作者： Tianjian WANG Fengwu BAI Shunzhou CHU Xiliang ZHANG Zhifeng WANG Institute of Electrical engineering Chinese Academy of Sciences Beijing 100190 China Key Laboratory of Solar Thermal Energy and photovoltaic system Chinese Academy of Sciences Beijing 100190 China Beijing engineering research center of Solar Thermal Power Beijing 101107 China University of Chinese Academy of Sciences Beijing 100190 China

This paper presents an experimental evaluation of a specially designed falling particle receiver. A quartz tube was used in the design, with which the particles would not be blown away by wind. Concentrated solar radiation was absorbed and converted into thermal energy by the solid particles flowed inside the quartz tube. Several experiments were conducted to test the dynamic thermal performance of the receiver on solar furnace system. During the experiments, the maximum particle temperature rise is 212~C, with an efficiency of 61.2%, which shows a good thermal performance with a falling distance of 0.2 m in a small scale particle receiver. The average outlet particle temperature is affected by direct normal irradiance （DNI） and other factors such as wind speed. The solid particles obtain a larger viscosity with a higher temperature while smaller solid particles are easier to get stuck in the helix quartz tube. The heat capacity of the silicon carbide gets larger with the rise of particle temperature, because as the temperature of solid particles increases, the temperature rise of the silicon carbide decreases.

关键词： solar thermal electricity central receiver,particle receiver experimental research

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Experimental investigation of crossflow characteristics in multi-jets system at small nozzle-to-plate spacing

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排灌机械工程学报 2019年第2期37卷 142-147页

作者： ZHU Keqian SUN Tao YU Pingping LI Meixiang YUAN Ningyi DING Jianning Jiangsu Collaborative Innovation center for photovoltaic Science and engineering Jiangsu Province Cultivation Base for State Key Laboratory of Photovoltaic Science and TechnologyJiangsu Key Laboratory of Green Process EquipmentChangzhou High Technology Research Key Laboratory of Mould Advanced ManufacturingSchool of Mechanical EngineeringChangzhou University Micro/Nano Science and Technology center School of Mechanical EngineeringJiangsu University

To further extend knowledge about the detailed knowledge on the crossflow characteristics in a multi-jets system under a confined space,particle image velocimetry (PIV) was employed to investigate the flow structures together with the distributions of the mean velocity components for Reynolds numbers (Re) ranging from 6 213 to 13 418,nozzle-to-plate spacing (H/D) varying from 0. 20 to1. 25,respectively. Results show that the crossflow configuration is significantly different from those of large nozzle-to-plate spacing. In addition,a turning point H/D=0.50 is revealed in the profile of the normalized maximum radial velocity which is associated with the heat transfer distribution on the impingement plate.

关键词： crossflow multiple impinging jets small nozzle-to-plate spacing Reynolds numbers particle image velocimetry

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Sizing Shared Energy Storage for the Integration of Renewable Generation: A Coalition Game Based Approach

Sizing Shared Energy Storage for the Integration of Renewabl...

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第40届中国控制会议

作者： Chuan Wang Wei Wei Xiaodai Xue Laijun Chen Shengwei Mei Department of Electrical engineering Tsinghua University New Energy (photovoltaic) Industry research center Qinghai University

The integration of renewable generation and energy storage in the power system has significant potential to mitigate undesirable characteristics of the power output such as intermittency and variability, as well as to increase total profits. However,since each generation part and the energy storage owner typically optimize the planning capacity based on their individual gains,it’s challenging to get the system’s optimal planning decision. This paper proposes a cooperative game based model to size shared energy storage for centralized wind and solar generation. We define the value of energy coalitions as the additional profits and allocate the profits of each player according to nucleous of the cooperative game. An iterative method is put forward to calculate the optimal robust capacity of each participant when the objection is to find the highest value of Rate of Return（RoR）,considering uncertainty sets of wind speed. Finally, numerical results verify the effectiveness of the proposed method and the optimal robust capacities of the generators and the energy storage in this cooperative game based model are also obtained.

关键词： Cooperative Game Renewable Energy Nucleous Robust Capacity

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Thermal and hydraulic characteristics of a large-scaled parabolic trough solar field (PTSF) under cloud passages

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Frontiers in Energy 2020年第2期14卷 283-297页

作者： Linrui MA Zhifeng WANG Ershu XU Li XU Key Laboratory of Solar Thermal Energy and photovoltaic system Chinese Academy of SciencesBeijing 100190China Institute of Electrical engineering Chinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China Beijing engineering research center of Solar Thermal Power Beijing 100190China School of Energy Power and Mechanical engineering North China Electric Power UniversityBeijing 102206China

To better understand the characteristics of a large-scaled parabolic trough solar field(PTSF)under cloud passages,a novel method which combines a closed-loop thermal hydraulic model(CLTHM)and cloud vector(CV)is developed.Besides,the CLTHM is established and validated based on a pilot plant.Moreover,some key parameters which are used to characterize a typical PTSF and CV are presented for further simulation.Furthermore,two sets of results simulated by the CLTHM are compared and discussed.One set deals with cloud passages by the CV,while the other by the traditionally distributed weather stations(DWSs).Because of considering the solar irradiance distribution in a more detailed and realistically way,compared with the distributed weather station(DWS)simulation,all essential parameters,such as the total flowrate,flow distribution,outlet temperature,thermal and exergetic efficiency,and exergetic destruction tend to be more precise and smoother in the CV simulation.For example,for the runner outlet temperature,which is the most crucial parameter for a running PTSF,the maximum relative error reaches−15%in the comparison.In addition,the mechanism of thermal and hydraulic unbalance caused by cloud passages are explained based on the simulation.

关键词： parabolic trough solar field(PTSF) thermal hydraulic model cloud passages transients

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Differential Fault Attack on the Stream Cipher LIZARD

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Chinese Journal of Electronics 2021年第3期30卷 534-541页

作者： MA Zhen TIAN Tian QI Wenfeng National Digital Switching system engineering Technological research center

In this paper, we try to give a security evaluation of LIZARD stream cipher in regard to fault attacks, which, to the best of our knowledge, is the first fault analysis on LIZARD. We design a differential engine of LIZARD to track the differential trail of the keystreams. It is shown that the distributions of the keystream differences are heavily biased. Utilizing this characteristic, we propose an improved method to identify the fault location for LIZARD whose success probability approaches 1. Then we use the fault-free keystream and faulty keystreams to generate system of equations in internal state variables and solve it by SAT solver. The result shows that with 100 keystream bits, only 6 different faults are needed to recover the internal state. Finally,the comparison between LIZARD and Grain v1 shows that LIZARD is more resistable than Grain v1 in regard to fault attacks.

关键词： Cryptography Data security Other topics in statistics Other topics in statistics Cryptanalysis stream cipher fault attack SAT solver LIZARD

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