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voltage control of magnetization switching and dynamics

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Chinese Physics B 2018年第6期27卷 443-447页

作者：文宏玉夏建白 The State Key Laboratory of Superlattices and Microstructures Institute of SemiconductorsChinese Academy of Sciences

The voltage controlled magnetic switching effect is verified experimentally. The Landau–Lifshitz–Gilbert（LLG）equation is used to study the voltage controlled magnetic switching. It is found that the initial values of magnetic moment components are critical for the switching effect, which should satisfy a definite condition. The external magnetic field which affects only the oscillation period should be comparable to the internal magnetic field. If the external magnetic field is too small, the switching effect will disappear. The precessions of mx and my are the best for the tilt angle of the external magnetic field θt = 0？, i.e., the field is perpendicular to the sample plane.

关键词： magnetic switching voltage control spin transfer torque Landau-Lifshitz-Gilbert （LLG） equa- tion

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)

Automatic voltage control of Differential Power Grids Based on Transfer Learning and Deep Reinforcement Learning

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CSEE Journal of Power and Energy Systems 2023年第3期9卷 937-948页

作者： Tianjing Wang Yong Tang Laboratory of Power Grid Safety and Energy Conservation China Electric Power Research InstituteBeijing 100192China School of Electrical and Electronic Engineering Nanyang Technological UniversitySingapore

In terms of model-free voltage control methods,when the device or topology of the system changes,the model’s accuracy often decreases,so an adaptive model is needed to coordinate the changes of input.To overcome the defects of a model-free control method,this paper proposes an automatic voltage control(AVC)method for differential power grids based on transfer learning and deep reinforcement learning.First,when constructing the Markov game of AVC,both the magnitude and number of voltage deviations are taken into account in the reward.Then,an AVC method based on constrained multiagent deep reinforcement learning(DRL)is developed.To further improve learning efficiency,domain knowledge is used to reduce action space.Next,distribution adaptation transfer learning is introduced for the AVC transfer circumstance of systems with the same structure but distinct topological relations/parameters,which can perform well without any further training even if the structure changes.Moreover,for the AVC transfer circumstance of various power grids,parameter-based transfer learning is created,which enhances the target system’s training speed and effect.Finally,the method’s efficacy is tested using two IEEE systems and two real-world power grids.

关键词： Deep reinforcement learning differential power grids transfer voltage control

Cluster voltage control method for “Whole County” distributed photovoltaics based on improved differential evolution algorithm

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Frontiers in Energy 2023年第6期17卷 782-795页

作者： Jing ZHANG Tonghe WANG Jiongcong CHEN Zhuoying LIAO Jie SHU School of Energy Science and Engineering University of Science and Technology of ChinaHefei 230026China Guangzhou Institute of Energy Conversion Chinese Academy of SciencesGuangzhou 510640China Jiangsu Collaborative Innovation Center of Photovoltaic Science and Engineering Changzhou 213001China

China is vigorously promoting the “whole county promotion” of distributed photovoltaics (DPVs). However, the high penetration rate of DPVs has brought problems such as voltage violation and power quality degradation to the distribution network, seriously affecting the safety and reliability of the power system. The traditional centralized control method of the distribution network has the problem of low efficiency, which is not practical enough in engineering practice. To address the problems, this paper proposes a cluster voltage control method for distributed photovoltaic grid-connected distribution network. First, it partitions the distribution network into clusters, and different clusters exchange terminal voltage information through a “virtual slack bus.” Then, in each cluster, based on the control strategy of “reactive power compensation first, active power curtailment later,” it employs an improved differential evolution (IDE) algorithm based on Cauchy disturbance to control the voltage. Simulation results in two different distribution systems show that the proposed method not only greatly improves the operational efficiency of the algorithm but also effectively controls the voltage of the distribution network, and maximizes the consumption capacity of DPVs based on qualified voltage.

关键词： distributed photovoltaics(DPVs) cluster partitioning improved differential evolution algorithm voltage control consumption capacity of distributed photovoltaics

Model Predictive control Based Coordinated voltage control for Offshore Radial DC-connected Wind Farms

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Journal of Modern Power Systems and Clean Energy 2023年第1期11卷 280-289页

作者： Wu Liao Qiuwei Wu Hesong Cui Sheng Huang Yusheng Gong Bin Zhou College of Electrical and Information Engineering Hunan UniversityChangshaChina Electrical Technology and Economics of Machinery Industry Institute of Beijing BeijingChina Department of Electrical Engineering Technical University of DenmarkLyngbyDenmark Electric Power Research Institute State Grid Hunan Electric Power Co.Ltd.ChangshaChina

In this study,a coordinated voltage control strategy based on model predictive control(MPC)is proposed for offshore radial DC-connected wind farms.Two control modes are designed in this strategy.In the economic operation mode,the wind farm controller generates optimal active power references as well as bus voltage references of medium-voltage collector for DC-connected wind turbine(DCWT)systems and high-voltage DC/DC converters,where the goal is to minimize power losses inside the wind farm and ensure that voltages are within a feasible range,all while tracking the power references.In the voltage control mode,the main control objective for the wind farm controller is to minimize voltage deviations from the rated voltage.With the MPC,the control objective and operation constraints can be explicitly represented in the optimization problem while considering the dynamic response of the DCWT system.In addition,a sensitivity coefficient calculation method for radial DC-connected wind farms is developed to improve computational efficiency.Finally,DC-connected wind farms with 20 wind turbines are used to demonstrate the performance of the proposed strategy.

关键词： Wind farm DC/DC converter model predictive control(MPC) voltage control

Coordinated voltage control of Distribution Network ConsideringMultiple Types of Electric Vehicles

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Energy Engineering 2024年第2期121卷 377-404页

作者： Liang Liu Guangda Xu Yuan Zhao Yi Lu Yu Li Jing Gao State Grid Jibei Electric Power Research Institute(North China Electric Power Research Institute Co. Ltd.)Beijing100045China

The couple between the power network and the transportation network(TN)is deepening gradually with the increasing penetration rate of electric vehicles(EV),which also poses a great challenge to the traditional voltage control scheme.In this paper,we propose a coordinated voltage control strategy for the active distribution networks considering multiple types of EV.In the first stage,the action of on-load tap changer and capacitor banks,etc.,are determined by optimal power flow calculation,and the node electricity price is also determined based on dynamic time-of-use tariff mechanism.In the second stage,multiple operating scenarios of multiple types of EVs such as cabs,private cars and buses are considered,and the scheduling results of each EV are solved by building an optimization model based on constraints such as queuing theory,Floyd-Warshall algorithm and traffic flow information.In the third stage,the output power of photovoltaic and energy storage systems is fine-tuned in the normal control mode.The charging power of EVs is also regulated in the emergency control mode to reduce the voltage deviation,and the amount of regulation is calculated based on the fair voltage control mode of EVs.Finally,we test the modified IEEE 33-bus distribution system coupled with the 24-bus Beijing TN.The simulation results show that the proposed scheme can mitigate voltage violations well.

关键词： Electric vehicle transportation network voltage control queuing theory

voltage control of ferromagnetic resonance

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Journal of Advanced Dielectrics 2016年第2期6卷 27-38页

作者： Ziyao Zhou Bin Peng Mingmin Zhu Ming Liu Electronic Materials Research Laboratory Key Laboratory of the Ministry of Education&International Center for Dielectric Research Xi'an Jiaotong University Xi'an 710049P.R.China

voltage control of magnetism in multiferroics,where the ferromagnetism and ferroelectricity are simultaneously exhibiting,is of great importance to achieve compact,fast and energy efficient voltage controllable magnetic/microwave devices.Particularly,these devices are widely used in radar,aircraft,cell phones and satellites,where volume,response time and energy consumption is critical.Researchers realized electric field tuning of magnetic properties like magnetization,magnetic anisotropy and permeability in varied multiferroic heterostructures such as bulk,thin films and nanostructure by different magnetoelectric(ME)coupling mechanism:strain/stress,interfacial charge,spin–electromagnetic(EM)coupling and exchange coupling,etc.In this review,we focus on voltage control of ferromagnetic resonance(FMR)in multiferroics.ME coupling-induced FMR change is critical in microwave devices,where the electric field tuning of magnetic effective anisotropic field determines the tunability of the performance of microwave devices.Experimentally,FMR measurement technique is also an important method to determine the small effective magnetic field change in small amount of magnetic material precisely due to its high sensitivity and to reveal the deep science of multiferroics,especially,voltage control of magnetism in novel mechanisms like interfacial charge,spin–EM coupling and exchange coupling.

关键词： Multiferroics magnetoelectric coupling ferromagnetic resonance voltage control thin films

Multi-objective optimization for voltage and frequency control of smart grids based on controllable loads

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Global Energy Interconnection 2021年第2期4卷 136-144页

作者： Yaxin Wang Donglian Qi Jianliang Zhang College of Electrical Engineering Zhejiang UniversityHangzhou 310027P.R.China

The output uncertainty of high-proportion distributed power generation severely affects the system voltage and frequency.Simultaneously,controllable loads have also annually increased,which markedly improve the capability for nodal-power control.To maintain the system frequency and voltage magnitude around rated values,a new multi-objective optimization model for both voltage and frequency control is proposed.Moreover,a great similarity between the multiobjective optimization and game problems appears.To reduce the strong subjectivity of the traditional methods,the idea and method of the game theory are introduced into the solution.According to the present situational data and analysis of the voltage and frequency sensitivities to nodal-power variations,the design variables involved in the voltage and frequency control are classified into two strategy spaces for players using hierarchical clustering.Finally,the effectiveness and rationality of the proposed control are verified in MATLAB.

关键词： Multi-objective optimization voltage control Frequency control Power flow controllable loads Game theory

Steady-state voltage Security-constrained Optimal Frequency control for Weak HVDC Sending-end AC Power Systems

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JOURNAL OF MODERN POWER SYSTEMS AND CLEAN ENERGY 2024年第2期12卷 658-669页

作者： Wang, Qiangqiang Yao, Liangzhong Xu, Jian Zheng, Yuping Li, Wei Wang, Wei Wuhan Univ Sch Elect Engn & Automat Wuhan 430072 Peoples R China Wuhan Univ Hubei Engn & Technol Res Ctr AC DC Intelligent Dis Wuhan 430072 Peoples R China NARI Grp Corp State Grid Elect Power Res Inst State Key Lab Smart Grid Protect & Control Nanjing 211106 Peoples R China

Due to the fact that a high share of renewable energy sources (RESs) are connected to high-voltage direct current (HVDC) sending-end AC power systems, the voltage and frequency regulation capabilities of HVDC sending-end AC power systems have diminished. This has resulted in potential system operating problems such as overvoltage and overfrequency, which occur simultaneously when block faults exist in the HVDC link. In this study, a steady-state voltage security-constrained optimal frequency control method for weak HVDC sending-end AC power systems is proposed. The integrated virtual inertia control of RESs is employed for system frequency regulation. Additional dynamic reactive power compensation devices are utilized to control the voltage of all nodes meet voltage security constraints. Then, an optimization model that simultaneously considers the frequency and steady-state voltage security constraints for weak HVDC sending-end AC power systems is established. The optimal control scheme with the minimum total cost of generation tripping and additional dynamic reactive power compensation required is obtained through the optimization solution. Simulations are conducted on a modified IEEE 9-bus test system and practical Qing-Yu line commutated converter based HVDC (LCC-HVDC) sending-end AC power system to verify the effectiveness of the proposed method.

关键词： HVDC transmission voltage control Reactive power Steady-state Power system stability Frequency control Power system dynamics Renewable energy source (RES) high-voltage direct current (HVDC) AC power system optimal frequency control steady-state voltage security dynamic reactive power compensation OPTIMIZATION STRATEGY STABILITY GRIDS DFIG