Active energy management is an effective way to realize the flexible utilization of distributed energy resources to suit the characteristics of active distribution system.Advanced active energy management strategies n...Active energy management is an effective way to realize the flexible utilization of distributed energy resources to suit the characteristics of active distribution system.Advanced active energy management strategies need to be designed to coordinate the optimization of‘generation,network,load’.An active management model is built for the local distribution system integrated with the generation curtailment mechanism and the charging/discharging management of plug-in electric vehicles.Furthermore,different strategies based on the energy management model are presented.The model and strategies are tested and discussed in a modified distribution system,and the impacts with different load profiles are also analyzed.展开更多
Operating in island mode when failure occurs in sure to maintain an uninterrupted power supply to significant loads. A two-stage approach that integrates optimal island partition and power dispatch is proposed in this...Operating in island mode when failure occurs in sure to maintain an uninterrupted power supply to significant loads. A two-stage approach that integrates optimal island partition and power dispatch is proposed in this paper, considering photovoltaics(PVs), batteries(BEs) and electric vehicles(EVs) as the power sources. In the first stage, energy indices are defined to describe the energy demand and the maximum energy that these distributed energy resources(DERs) can provide, and islands are partitioned based on an energy constraint. Considering the variability the loads and PVs, the energy constraint is a necessary but not sufficient condition for island operation,so in the second stage, a power dispatch model is proposed the active distribution network(ADN) is an effective mea-as a test for the island partition result. Sequential power flow is also simulated to guarantee a feasible and optimized island status. The situations when the tests are not passed are analyzed and classified, and corresponding modifications for the first stage model are provided. Multiple levels of constraints based on the energy index are established for the island partition model. The proposed approach has been validated through simulation using a modified IEEE 69-bus system which is divided into three districts with different load variability characteristics.展开更多
Finite control set-model predictive control (FCS-MPC) is employed in this paper to control the operation of a three-phase grid-connected string inverter based on a direct PQ control scheme. The main objective is to ac...Finite control set-model predictive control (FCS-MPC) is employed in this paper to control the operation of a three-phase grid-connected string inverter based on a direct PQ control scheme. The main objective is to achieve high-performance decoupled control of the active and reactive powers injected to the grid from distributed energy resources (DER).The FCS-MPC scheme instantaneously searches for and applies the optimum inverter switching state that can achieve certain goals, such as minimum deviation between reference and actual power;so that both power components (P and Q) are well controlled to their reference values.In addition, an effective method to attenuate undesired cross coupling between the P and Q control loops, which occurs only during transient operation, is investigated. The proposed method is based on the variation of the weight factors of the terms of the FCS-MPC cost function, so a higher weight factor is assigned to the cost function term that is exposed to greater disturbance. Empirical formulae of optimum weight factors as functions of the reference active and reactive power signals are proposed and mathematically derived. The investigated FCS-MPC control scheme is incorporated with the LVRT function to support the grid voltage in fulfilling and accomplishing the up-to-date grid codes. The LVRT algorithm is based on a modification of the references of active and reactive powers as functions of the instantaneous grid voltage such that suitable values of P and Q are injected to the grid during voltage sag.The performance of the elaborated FCS-MPC PQ scheme is studied under various operating scenarios, including steady-state and transient conditions. Results demonstrate the validity and effectiveness of the proposed scheme with regard to the achievement of high-performance operation and quick response of grid-tied inverters during normal and fault modes.展开更多
The distributed generation (DG) plays an important role in the context of the environmental problems and sustain- able development throughout the world. This paper proposes a DG siting and sizing model in an active di...The distributed generation (DG) plays an important role in the context of the environmental problems and sustain- able development throughout the world. This paper proposes a DG siting and sizing model in an active distribution network (ADN). The objective is to minimize the total cost, including investment, operation and maintenance costs. The proposed model is transferred to a Mixed Integer Second-Order Cone Programming (MISOCP) model based on a distribution network forward backward-sweep power flow and constraint relaxation. The CVX platform and GUROBI solver are used for the solution. The scenario analysis is used for the uncertainties of load and DG. Different numbers of operational scenarios are considered in order to analyze the effect of a non-network solution to the final planning result and total investment. The planning results with and without consideration of active managements, and the planning results with and without taking environmental profits into consideration, are compared and analyzed. The proposed methodology is verified with a modified IEEE 33 example.展开更多
Designing catalysts with capable dual-active sites to drive catalytic hydrogen generation is necessary for the future hydrogen economy.Herein,the interfacial active sites consisting of Co and Co-C on Co-Co_(2)C@carbon...Designing catalysts with capable dual-active sites to drive catalytic hydrogen generation is necessary for the future hydrogen economy.Herein,the interfacial active sites consisting of Co and Co-C on Co-Co_(2)C@carbon heterostructure are designed through annealing and highpressure carbonization.The operating temperature during the high-pressure carbonization under a CO-reducing environment is responsible for the construction and regulation of Co-Co_(2)C@C heterostructure.The optimal catalyst has a high turnover frequency(TOF) of33.1 min^(-1) and low activation energy(E_a) of27.3 kJ-mol^(-1) during the hydrolysis of NH_(3)BH_(3).The catalytic stability of Co-Co_(2)C@C has no dramatic deterioration even after 5 cyclic usages.The interfacial active sites and the carbon on the catalyst surface enhance hydrogen generation kinetics and catalytic stability.The construction of interfacial active sites in Co-Co_(2)C@C prompts the dissociation of reactants(NH_(3)BH_(3) and H_(2)O molecules),leading to an enhanced catalytic hydrogen generation from NH_(3)BH_(3) hydrolysis(Co activates NH_(3)BH_(3) and Co-C activates H_(2)O).The construction of hetero-structural catalysts provides theoretical direction for the rational design of advanced transition metal carbide materials in the field of energy catalysis and conversion.展开更多
Flexibility in energy systems can support the operation of the electricity grid by providing active and reactive power to avoid voltage limit violations or congestion.Active distribution networks can provide this flex...Flexibility in energy systems can support the operation of the electricity grid by providing active and reactive power to avoid voltage limit violations or congestion.Active distribution networks can provide this flexibility by implementing systems to control distributed generators,storage or loads.Additionally,power flow controlling devices can be used to implement operational flexibility in the energy system.This paper presents concepts for planning and forecasting of flexibility,monitoring of energy systems and control of flexibility from active distribution networks(ADNs)to enable the use of flexibility in future power systems.展开更多
The region-based method has been applied in transmission systems and traditional passive distribution systems without power sources. This paper proposes the model of total quadrant security region(TQSR) for active dis...The region-based method has been applied in transmission systems and traditional passive distribution systems without power sources. This paper proposes the model of total quadrant security region(TQSR) for active distribution networks(ADN) with high penetration of distributed generation(DG). Firstly, TQSR is defined as a closed set of all the N-1 secure operation points in the state space of ADN. Then, the TQSR is modeled considering the constraints of state space,normal operation and N-1 security criterion. Then, the characteristics of TQSR are observed and analyzed on the test systems with different DG penetrations. TQSR can be located in any quadrant of the state space. For different DG penetrations,the shape and security features of TQSR are also different. Finally, the region map is discovered, which summarizes the features of different types of distribution networks.展开更多
Optimal reactive power dispatch(ORPD)is a complex and non-linear problem,and is one of the sub-problems of optimal power flow(OPF)in a power system.ORPD is formulated as a single-objective problem to minimize the acti...Optimal reactive power dispatch(ORPD)is a complex and non-linear problem,and is one of the sub-problems of optimal power flow(OPF)in a power system.ORPD is formulated as a single-objective problem to minimize the active power loss in a transmission system.In this work,power from distributed generation(DG)is integrated into a conventional power system and the ORPD problem is solved to minimize transmission line power loss.It proves that the application of DG not only contributes to power loss minimization and improvement of system stability but also reduces energy consumption from the conventional sources.A recently proposed meta-heuristic algorithm known as the JAYA algorithm is applied to the standard IEEE 14,30,57 and 118 bus systems to solve the newly developed ORPD problem with the incorporation of DG.The simulation results prove the superiority of the JAYA algorithm over others.The respective optimal values of DG power that should be injected into the four IEEE test systems to obtain the minimum transmission line power losses are also provided.展开更多
主动配电网(Active Distribution Network,ADN)的源荷强不确定性加剧了其电源规划的难度。文章基于ADN的灵活管控特性提出了考虑主动管理模式的分布式电源多目标双层规划模型。上层模型以最小化系统电源侧的全寿命周期成本为目标,从而确...主动配电网(Active Distribution Network,ADN)的源荷强不确定性加剧了其电源规划的难度。文章基于ADN的灵活管控特性提出了考虑主动管理模式的分布式电源多目标双层规划模型。上层模型以最小化系统电源侧的全寿命周期成本为目标,从而确定DG的安装配置方案;而下层则以最小化DG有功出力切除量为目标,通过采用主动管理中的DG出力控制、有载变压器分接头调节以及无功补偿装置调节等方式实现DG运行优化。利用带自适应变异的改进粒子群(IPSO)算法对上下层模型进行求解,提高了算法的求解速度并有效得到全局最优解。同时,通过对IEEE 33节点系统进行仿真分析,验证了所构建模型的合理性。展开更多
基金This work was supported by National High Technology Research and Development Program of China(No.2014AA051901)the National Science Foundation of China(No.51377111).
文摘Active energy management is an effective way to realize the flexible utilization of distributed energy resources to suit the characteristics of active distribution system.Advanced active energy management strategies need to be designed to coordinate the optimization of‘generation,network,load’.An active management model is built for the local distribution system integrated with the generation curtailment mechanism and the charging/discharging management of plug-in electric vehicles.Furthermore,different strategies based on the energy management model are presented.The model and strategies are tested and discussed in a modified distribution system,and the impacts with different load profiles are also analyzed.
基金supported in part by the National Science Foundation of China(No.51477029)the National Science and Technology Support Program of China(No.2015BAA01B01)the State Grid Corporation of China(No.SGTYHT/14-JS-188)
文摘Operating in island mode when failure occurs in sure to maintain an uninterrupted power supply to significant loads. A two-stage approach that integrates optimal island partition and power dispatch is proposed in this paper, considering photovoltaics(PVs), batteries(BEs) and electric vehicles(EVs) as the power sources. In the first stage, energy indices are defined to describe the energy demand and the maximum energy that these distributed energy resources(DERs) can provide, and islands are partitioned based on an energy constraint. Considering the variability the loads and PVs, the energy constraint is a necessary but not sufficient condition for island operation,so in the second stage, a power dispatch model is proposed the active distribution network(ADN) is an effective mea-as a test for the island partition result. Sequential power flow is also simulated to guarantee a feasible and optimized island status. The situations when the tests are not passed are analyzed and classified, and corresponding modifications for the first stage model are provided. Multiple levels of constraints based on the energy index are established for the island partition model. The proposed approach has been validated through simulation using a modified IEEE 69-bus system which is divided into three districts with different load variability characteristics.
文摘Finite control set-model predictive control (FCS-MPC) is employed in this paper to control the operation of a three-phase grid-connected string inverter based on a direct PQ control scheme. The main objective is to achieve high-performance decoupled control of the active and reactive powers injected to the grid from distributed energy resources (DER).The FCS-MPC scheme instantaneously searches for and applies the optimum inverter switching state that can achieve certain goals, such as minimum deviation between reference and actual power;so that both power components (P and Q) are well controlled to their reference values.In addition, an effective method to attenuate undesired cross coupling between the P and Q control loops, which occurs only during transient operation, is investigated. The proposed method is based on the variation of the weight factors of the terms of the FCS-MPC cost function, so a higher weight factor is assigned to the cost function term that is exposed to greater disturbance. Empirical formulae of optimum weight factors as functions of the reference active and reactive power signals are proposed and mathematically derived. The investigated FCS-MPC control scheme is incorporated with the LVRT function to support the grid voltage in fulfilling and accomplishing the up-to-date grid codes. The LVRT algorithm is based on a modification of the references of active and reactive powers as functions of the instantaneous grid voltage such that suitable values of P and Q are injected to the grid during voltage sag.The performance of the elaborated FCS-MPC PQ scheme is studied under various operating scenarios, including steady-state and transient conditions. Results demonstrate the validity and effectiveness of the proposed scheme with regard to the achievement of high-performance operation and quick response of grid-tied inverters during normal and fault modes.
基金This work was supported in part by the Shanghai Engineering Re-search Center of Green Energy Grid-Connected Technology under Grant 13DZ2251900the Key Laboratory of Control of Power Transmission and Conversion(SJTU),Ministry of Education(2016AA01,2016AA03).
文摘The distributed generation (DG) plays an important role in the context of the environmental problems and sustain- able development throughout the world. This paper proposes a DG siting and sizing model in an active distribution network (ADN). The objective is to minimize the total cost, including investment, operation and maintenance costs. The proposed model is transferred to a Mixed Integer Second-Order Cone Programming (MISOCP) model based on a distribution network forward backward-sweep power flow and constraint relaxation. The CVX platform and GUROBI solver are used for the solution. The scenario analysis is used for the uncertainties of load and DG. Different numbers of operational scenarios are considered in order to analyze the effect of a non-network solution to the final planning result and total investment. The planning results with and without consideration of active managements, and the planning results with and without taking environmental profits into consideration, are compared and analyzed. The proposed methodology is verified with a modified IEEE 33 example.
基金financially supported by the National Natural Science Foundation of China (Nos.52071135, 51871090 and U1804135)the Fundamental Research Funds for the Universities of Henan Province (Nos.NSFRF220201 and NSFRF200402)。
文摘Designing catalysts with capable dual-active sites to drive catalytic hydrogen generation is necessary for the future hydrogen economy.Herein,the interfacial active sites consisting of Co and Co-C on Co-Co_(2)C@carbon heterostructure are designed through annealing and highpressure carbonization.The operating temperature during the high-pressure carbonization under a CO-reducing environment is responsible for the construction and regulation of Co-Co_(2)C@C heterostructure.The optimal catalyst has a high turnover frequency(TOF) of33.1 min^(-1) and low activation energy(E_a) of27.3 kJ-mol^(-1) during the hydrolysis of NH_(3)BH_(3).The catalytic stability of Co-Co_(2)C@C has no dramatic deterioration even after 5 cyclic usages.The interfacial active sites and the carbon on the catalyst surface enhance hydrogen generation kinetics and catalytic stability.The construction of interfacial active sites in Co-Co_(2)C@C prompts the dissociation of reactants(NH_(3)BH_(3) and H_(2)O molecules),leading to an enhanced catalytic hydrogen generation from NH_(3)BH_(3) hydrolysis(Co activates NH_(3)BH_(3) and Co-C activates H_(2)O).The construction of hetero-structural catalysts provides theoretical direction for the rational design of advanced transition metal carbide materials in the field of energy catalysis and conversion.
基金This work was supported in part by the National Natural Science Foundation of China(NSFC)under Grant 51520105011in part by the 111 project of China under Grant B17016,in part by China Scholarship Council(No.201706130143)within the incentive scheme Showcase Intelligent Energy-Digital Agenda for the energy transition(SINTEG)under Grant 03SIN227 as well as the IDEAL project under Grand 03ET7557A provided by the Federal Ministry for Economic Affairs and Energy.
文摘Flexibility in energy systems can support the operation of the electricity grid by providing active and reactive power to avoid voltage limit violations or congestion.Active distribution networks can provide this flexibility by implementing systems to control distributed generators,storage or loads.Additionally,power flow controlling devices can be used to implement operational flexibility in the energy system.This paper presents concepts for planning and forecasting of flexibility,monitoring of energy systems and control of flexibility from active distribution networks(ADNs)to enable the use of flexibility in future power systems.
基金supported in part by National Key Research and Development Program of China (No. 2016YFB0900100)National Natural Science Foundation of China (No. 51877144)China Postdoctoral Science Foundation (No.2020M670668)。
文摘The region-based method has been applied in transmission systems and traditional passive distribution systems without power sources. This paper proposes the model of total quadrant security region(TQSR) for active distribution networks(ADN) with high penetration of distributed generation(DG). Firstly, TQSR is defined as a closed set of all the N-1 secure operation points in the state space of ADN. Then, the TQSR is modeled considering the constraints of state space,normal operation and N-1 security criterion. Then, the characteristics of TQSR are observed and analyzed on the test systems with different DG penetrations. TQSR can be located in any quadrant of the state space. For different DG penetrations,the shape and security features of TQSR are also different. Finally, the region map is discovered, which summarizes the features of different types of distribution networks.
文摘Optimal reactive power dispatch(ORPD)is a complex and non-linear problem,and is one of the sub-problems of optimal power flow(OPF)in a power system.ORPD is formulated as a single-objective problem to minimize the active power loss in a transmission system.In this work,power from distributed generation(DG)is integrated into a conventional power system and the ORPD problem is solved to minimize transmission line power loss.It proves that the application of DG not only contributes to power loss minimization and improvement of system stability but also reduces energy consumption from the conventional sources.A recently proposed meta-heuristic algorithm known as the JAYA algorithm is applied to the standard IEEE 14,30,57 and 118 bus systems to solve the newly developed ORPD problem with the incorporation of DG.The simulation results prove the superiority of the JAYA algorithm over others.The respective optimal values of DG power that should be injected into the four IEEE test systems to obtain the minimum transmission line power losses are also provided.
文摘主动配电网(Active Distribution Network,ADN)的源荷强不确定性加剧了其电源规划的难度。文章基于ADN的灵活管控特性提出了考虑主动管理模式的分布式电源多目标双层规划模型。上层模型以最小化系统电源侧的全寿命周期成本为目标,从而确定DG的安装配置方案;而下层则以最小化DG有功出力切除量为目标,通过采用主动管理中的DG出力控制、有载变压器分接头调节以及无功补偿装置调节等方式实现DG运行优化。利用带自适应变异的改进粒子群(IPSO)算法对上下层模型进行求解,提高了算法的求解速度并有效得到全局最优解。同时,通过对IEEE 33节点系统进行仿真分析,验证了所构建模型的合理性。
