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最新刊期
卷 47 ， 期 12 ， 2023
- 摘要：Urban energy systems not only need to have high reliability for small-scale and large-probability daily failure events, but also need to have high resilience to cope with large-scale and small-probability extreme disaster events. With the increasing coupling of cross-energy forms and power electronization, the urban energy system is expected to improve system resilence through coordinated cross-system energy transfer and rapid regulation of massive power electronic devices. First, this paper proposes a two-stage resilience operation model for urban energy systems under extreme disaster events, which integrates the modeling and coordination of fast dynamic characteristics of power electronic devices and slow dynamic characteristics of multi-energy networks. Then, to address the problems of multiple constraints and high solution complexity of the resilience model, a data-driven urban energy system security rule extraction method based on space-weighted inclined decision tree theory is proposed. The method transforms the complex resilience model into a small number of mixed-integer linear constraints, namely security rules, and embeds them into the system normal operation model. Finally, the effectiveness of the proposed method and its advantages in computational efficiency over the traditional model-driven methods are verified by case analysis.关键词：urban energy system;integrated energy system;resilience;optimal operation;security rule;energy hub;multi-energy network12|1|0更新时间：2023-06-19
- 摘要：In recent years, the typhoon become a major natural disaster affecting the safe operation of the receiving-end grid in coastal cities. This paper proposes a resilience enhancement strategy for multi-stage collaboration including the prevention stage, resistance-response stage and recovery stage by considering the response characteristics of the receiving-end grid under the typhoon disaster, including load, external power, various units, energy storage, and power transmission channels. The resilience of the grid is quantified by the difference between the actual and ideal operation curves, and the resilience of the urban grid is evaluated. The resilience enhancement model and the ideal aims to minimize the total cost of investment and operation and maximize the grid resilience, and includes three types of measures: power transmission channel reinforcement, unit commitment, and additional restoration teams, covering three phases of grid state changes during typhoon transit. Finally, the validity of the model is verified by selecting the actual receiving-end grid of a Chinese city and combining it with typhoon data from the Tropical Cyclone Center of the China Meteorological Administration.关键词：receiving-end grid;typhoon disaster;extreme weather;resilience;renewable energy;energy storage;multi-stage collaboration4|1|0更新时间：2023-06-19
- 摘要：In recent years, extreme events and uncertainty of wind power generation have brought serious challenges to the security operation of power systems. This paper proposes an adaptive robust optimization model to enhance the resilience of the power system considering wind power generation uncertainty under extreme events. Firstly, an adaptive robust polyhedral uncertainty set is constructed by considering the wind power generation uncertainty. Secondly, considering the threat of extreme events to the power system, a resilience enhancement model of power system considering wind power output uncertainty in the defense-attack-defense framework is proposed. Finally, the model is simulated and verified on the IEEE RTS-79 and IEEE RTS-96 test systems, which is solved by the column-and-constraint generation (C&CG) algorithm. The simulation results fully verified the effectiveness of the proposed model and solution method.关键词：resilience;renewable energy;power system;extreme event;uncertainty set;column-and-constraint generation (C&CG) algorithm5|0|0更新时间：2023-06-19
- 摘要：In recent years, frequent extreme disasters have caused huge losses to the distribution network, so it is extremely important to improve the resilience of the distribution network. With the large increase of DC sources and loads such as distributed photovoltaic, energy storage and electric vehicles, the form of urban distribution network is transforming from AC distribution network to AC/DC hybrid distribution network. DC lines have the advantage of flexible interconnection, which can break the bottleneck in the radial operation of AC distribution networks and achieve flexible networking after disasters, thus effectively improving the resilience of distribution networks. Aiming at the urban AC/DC hybrid distribution network with photovoltaic-storage-charging integrated station (PSCIS), a power supply recovery strategy that fully considers the characteristics of flexible DC interconnection and regulation ability is proposed. First, considering the distribution of critical loads and local resources after disasters, a topology generation method for emergency power supply recovery with DC lines as the core is proposed. Secondly, based on the AC/DC recovery topology, a two-stage resilience improvement optimization model for the distribution network is established. In the first stage, the load recovery sequence is optimized with the objective of maximizing the power supply of critical loads. In the second stage, the emergency power supply output of the PSCIS is optimized with the objective of minimizing the network loss. The simulation results show that the proposed strategy can make full use of the DC flexible interconnection capability and power support capability of PSCIS to restore critical loads, and the two-stage fault recovery method has good feasibility and adaptability.关键词：AC/DC hybrid distribution network;resilience;photovoltaic-storage-charging integrated station;fault recovery5|0|0更新时间：2023-06-19
- 摘要：For the actual cyber-physical power system with one-to-one correspondence, identifying and reinforcing its disaster-resistant backbone grid can improve the reliability of the cyber-physical power system under natural disasters or cyber attacks. Therefore, this paper proposes a multi-objective optimization model for backbone network identification. The proposed model comprehensively considers the economy, anti-destruction and recovery of the entire system, and satisfies important load constraints, network connectivity constraints, network scale constraints, and power flow constraints. First, the multi-objective optimization model is solved by using the improved non-dominated sorting genetic algorithm-Ⅱ (NSGA-Ⅱ), and each objective function is assigned a weight by using the entropy weight method in multi-objective decision-making. Then, the optimal solution in the Pareto solution set is filtered by using the approximately ideal solution ranking method. Finally, the effectiveness of the proposed backbone network identification algorithm for the cyber-physical power system is verified by taking the IEEE 39-bus system and an actual 500 kV power grid in a region of China as examples.关键词：cyber-physical system;backbone network;non-dominated sorting genetic algorithm-Ⅱ (NSGA-Ⅱ);multi-objective optimization;entropy weight-TOPSIS4|1|0更新时间：2023-06-19
- 摘要：The distribution system is evolving into an integrated trading platform for multiple energy including electricity, gas and heat, which is necessary to meet the demand of point-to-point energy transaction. However, the existing dendritic radiation structure of distribution system is difficult to meet the demand. The networking structures and operation modes of honeycomb integrated energy distribution system (HIEDS) are proposed in this paper. First, the networking structures of HIEDS are proposed, including the flexible interconnection mode between microgrids and key equipment such as integrated energy base stations. Then, the optimal operation models of HIEDS aiming at operation economy and load balance are proposed. Finally, the operation characteristics of HIEDS in different scenarios are analyzed through cases, and compared with other typical microgrid interconnection structures. The results show that HIEDS operates more flexibly and can improve the economy and reliability of system operation. The research in this paper provides a theoretical basis for the structural optimization of integrated energy distribution systems.关键词：honeycomb topology;integrated energy;distribution system;microgrid;networking;operation mode3|0|0更新时间：2023-06-19
- 摘要：Power loss and phase unbalance of three-phase voltage in active distribution networks (ADNs) become more and more serious due to the increasing unbalance of three-phase loads. As a kind of power electronic equipment which can replace the traditional tie switch, soft open point (SOP) provides a potential solution to reduce power loss and alleviate the unbalance problem. Therefore, a three-phase four-wire back-to-back voltage source converter is introduced as the topology of SOP, and the corresponding phase-switching control strategy is designed for the topology. On this basis, a multi-objective operation optimization model of ADNs based on three-phase four-wire phase-switching SOP is proposed to reduce the power loss and alleviate the voltage unbalance. The symmetric semi-definite programming algorithm is used to transform the original non-convex nonlinear model into a semi-definite programming model which is easy to solve by convex relaxation. This model can be used for three-phase decoupling and analysis of three-phase power grid. Finally, a case study is carried out in an improved IEEE 123-bus system to verify the feasibility and effectiveness of the proposed model and its solving algorithm.关键词：soft open point;phase-switching control;symmetric semi-definite programming algorithm;active distribution network;three-phase unbalance3|1|0更新时间：2023-06-19
- 摘要：In the simulation of modern distribution network with high-density distributed generators, the traditional numerical integration algorithm is difficult to meet the fast and stable simulation requirements, so an event triggering based improved variational algorithm is proposed. First, the variational iteration method (VIM) is introduced to obtain the approximate solution corresponding to the typical state variables of the bipolar photovoltaic power station in the distribution network. Then, the numerical stability of the algorithm is verified, and its limit step size is deduced. Aiming at the problem that the calculation of partial state variables consumes more simulation resources, the event triggering mechanism is introduced, and the triggering condition of the locked value is deduced by using the norm of error to reduce the calculation frequency and improve the simulation efficiency of the system. Finally, the numerical stability and event triggering effect of the algorithm are simulated and verified. The results show that the event triggering based variational algorithm improves the simulation speed while maintaining high accuracy, and the efficiency advantage is more obvious with the expansion of node scale.关键词：active distribution network;variational iteration method;event triggering;numerical stability;efficient simulation3|2|0更新时间：2023-06-19
- 摘要：The high cost of transporting pure hydrogen is one of the factors hindering the development of renewable energy accommodation technology through power to hydrogen. The direct injection of hydrogen into the natural gas pipeline by using hydrogen enriched compressed natural gas (HCNG) technology can effectively reduce the transportation costs. Aiming at the control of hydrogen mix ratio and the capacity configuration of hydrogen production equipment while hydrogen is injected into pipelines, a wind-hydrogen-HCNG coupled network is established. Based on analyzing the overload efficiency characteristics of the electrolyzer monomer, the operation characteristics of the power to hydrogen system with modular integration of multiple electrolyzers are analyzed, and the coordinated operation strategy of double-layer rotation of multiple electrolyzers is further proposed. With the objective of maximizing system revenue and considering the constraints of the power-hydrogen balance and operation of each equipment, a capacity configuration model of hydrogen energy system that can meet the demand for hydrogen mix is established, and CPLEX in MATLAB is used for solution. The economy and feasibility of pipeline hydrogen mix in the long-distance hydrogen transportation are verified through case analysis and comparison. The double-layer rotation strategy based on the operation characteristics of the electrolyzer can balance the running time of the electrolyzer, and reduce the capacity configuration demand and the investment cost.关键词：hydrogen energy storage;hydrogen enriched compressed natural gas;alkaline electrolyzer;coordinated operation;capacity optimization4|0|0更新时间：2023-06-19
- 摘要：Under the goals of carbon emission peak and carbon neutrality, the analysis of spatial-temporal distribution rules of travel and charging demand of electric vehicles (EVs) is foundational for the coordinated operation of the traffic and power systems. However, few existing studies can systematically describe the spatial-temporal distribution mechanism of private EVs and their charging demand. Starting from the source of travel demand, firstly, the relevance between travel and charging behaviors of EV users is analyzed in a multi-modal transportation system. Secondly, considering the bounded-rationality decision-making behaviors and the heterogeneity of travelers, a tolerance-based dynamic activity-travel assignment (DATA) model is established to depict the spatial-temporal evolution mechanism of EVs and their charging demand. Finally, the case analysis is carried out based on the route-swapping algorithm. The results show that the proposed model can describe the spatial-temporal distribution rules of EVs and their charging demand. Moreover, the charging price, initial state of charge, and the existence of other travel modes have a significant influence on the spatial-temporal evolution rules of charging demand.关键词：coupled traffic-power system;activity-travel demand;charging demand;spatial-temporal evolution;dynamic traffic assignment model;heterogeneity;bounded rationality6|2|0更新时间：2023-06-19
- 摘要：The inherent time delays in the control loops of power systems will affect the performances of controllers and even endanger the stable operation of the system. Therefore, an eigenvalue calculation method based on the partial infinitesimal generator discretization with implicit Runge-Kutta (PIGD-IRK) is proposed for analyzing the effect of time delays on small disturbance stability of large-scale power systems. Firstly, the bottlenecks that restrict the computational efficiency of infinitesimal generator discretization with implicit Runge-Kutta (IGD-IRK) are analyzed. Secondly, by applying the partial spectral discretization idea, the dimension of the infinitesimal generator discretization matrix constructed by IGD-IRK is greatly reduced. Thirdly, the echelon block discretization matrix is further transformed into the product of the inverse of a constant matrix and an upper triangular block matrix by taking advantage of its structural characteristics, thus the sparsity of the discretization matrix and system augmented state matrix can be fully used in the process of eigenvalue calculation. Finally, the accuracy and high efficiency of the proposed method are verified on a two-area four-machine system and two actual power systems.关键词：time delay;small disturbance stability;spectral discretization;infinitesimal generator;implicit Runge-Kutta method3|2|0更新时间：2023-06-19
Basic Research
- 摘要：Aiming at the power grid security problems caused by the competitive charging behavior of large-scale electric vehicles under the dynamic electricity price mechanism, a congestion management model of electric vehicle aggregator considering power grid security constraints is proposed. Firstly, the lossless linearization model of distribution network and the cluster model of the electric vehicle aggregator are established. Secondly, a competitive game model among electric vehicle aggregators considering power grid security constraints is proposed under the dynamic electricity price mechanism. Thirdly, the existence of equilibrium solution and the uniqueness of variational decomposition of the game model are proven based on the theory of variational inequality. Finally, the gradient descent algorithm and the proximal decomposition algorithm are used to solve the proposed game model. Numerical results show that the proposed model can ensure the power grid security when large-scale electric vehicles are competing for charging.关键词：electric vehicle;charging;congestion management;dynamic electricity price;game model4|1|0更新时间：2023-06-19
- 摘要：From the perspective of reducing the control time, based on the propagation mechanism of overload-dominated cascading failures, this paper develops a blocking control method against cascading failures, which takes into account economy and rapidity. First, the line overload protection model is used to quantify the line tripping time. The line with the minimum tripping time is tripped as the next fault link. Based on this, the prediction method for propagation paths of cascading failures is established considering the hidden failure of relay protections. Then, a blocking control model to minimize control cost and blocking time is presented, and the risk importance index of faulty links is defined to select the optimal position for applying the blocking control strategy. Finally, the IEEE 39-bus system and the IEEE 118-bus system are used as cases for simulation. The results show that the proposed model can ensure the rapidity of the implementation of the blocking control strategy while taking into account the economy, effectively preventing the spread of failures and reducing load loss.关键词：cascading failure;blocking control;tripping time;overload protection model;emergency control;transient stability3|1|0更新时间：2023-06-19
- 摘要：In the new power system, the uncertainty of both sides of the source and load makes the power flow fluctuation increase significantly. The power system security correction control can eliminate the system power flow over-limit and ensure the safe operation of the power grid. However, the traditional security correction control methods have many constraints and complex calculation, and it is difficult to make real-time multi-step decisions for large-scale power grids. Therefore, this paper proposes a two-stage training method based on deep deterministic policy gradient (DDPG) to determine the security correction control strategy. Firstly, combining the security correction control problem with deep reinforcement learning, the Markov decision process (MDP) model of the security correction is constructed by designing the state, action and reward function of reinforcement learning. Secondly, a two-stage training framework is proposed to obtain the optimal correction strategy. In the pre-training stage of the imitation learning, based on the expert strategy, the imitation learning is used to provide the initial neural network for agents and improve the training speed. In the training stage of the reinforcement learning, the agent is further trained through the continuous interaction between DDPG agent and the environment. The trained agent can be applied in real time to obtain the optimal decision. Finally, the effectiveness of the proposed method is verified by a simulation case based on a provincial power grid of China.关键词：deep reinforcement learning;security correction control;imitation learning;power flow over-limit2|0|0更新时间：2023-06-19
- 摘要：The integration of a large number of renewable energy power generation equipment has significantly changed the dynamic characteristics of modern power grid, which brings the challenges to the security and stability of the power grid. The subsynchronous/supersynchronous oscillation problem caused by the mismatch between the phase-locked loop bandwidth and the power grid strength is particularly serious. The previous studies have shown that grid-forming converters whose external characteristics are similar to the voltage sources can reduce the small-signal stability problems of renewable energy power systems dominated by PLL and provide strong voltage support capability for the system. However, the mechanism of effect of energy storage system based on grid-forming converters on the stability of the multi-renewable-energy-infeed system and the optimal siting and sizing method are still unclear. Therefore, this paper reveals the mechanism of the energy storage system based on the grid-forming converters for improving the small-signal stability of the multi-renewable-energy-infeed system. Then, from the perspective of improving the system stability margin, the optimal siting and sizing method of energy storage systems based on grid-forming converters is studied. Finally, the effectiveness of the proposed method is verified by the example.关键词：grid-forming converter;energy storage system;small-signal stability;siting and sizing4|2|0更新时间：2023-06-19
- 摘要：When an asymmetric fault occurs in the AC collection line of offshore wind power through a flexible DC transmission system, the line has weak fault characteristics due to the negative-sequence suppression strategy adopted by the inverters on both sides, resulting in a decrease in the performance of conventional power frequency AC protection. This paper first analyzes the faulty circuit when an asymmetric fault occurs on the offshore AC collection line, as well as the distribution of negative-sequence current under internal and external faults. It is found that there is a significant difference in the negative-sequence current between the faulty line connected to the same bus and the non-faulty line. Furthermore, by constructing the accumulation of negative-sequence current and amplifying the difference in negative-sequence current amplitude between faulty and non-faulty lines, a protection scheme for AC collection lines based on the ratio of transient negative-sequence current accumulation is proposed. The proposed scheme can achieve rapid and accurate identification of fault lines, and has a certain ability to withstand transition resistance. Finally, simulation verification is conducted on the PSCAD/EMTDC platform, and the results show that the proposed scheme is feasible and effective.关键词：offshore wind power;AC collection line;protection;negative-sequence current;accumulation4|0|0更新时间：2023-06-19
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Marketization Operation Mechanism and Clearing Model of Day-ahead Market for Pumped Storage Stations
摘要：Under the background of the electricity spot market, the pumped storage power stations are facing the challenges of how to operate to meet the demand of power systems with high-proportion renewable energy. To this end, this paper proposes the marketization operation mechanism that the capacity tariff of pumped storage power stations is preserved, and the pumped storage power stations act as the price recipients without price and capacity offer. Based on the above operation mechanism, the optimal clearing model of day-ahead markets embedding the participation of pumped storage power stations is further proposed. The rationality and feasibility of the proposed marketization operation mechanism and optimal clearing model of the pumped storage power stations are demonstrated by case study. The analysis results show that the proposed mechanism can solve the unreasonable operation problems of some pumped storage power stations.关键词：pumped storage power station;marketization operation mechanism;day-ahead market;clearing model4|2|0更新时间：2023-06-19 - 摘要：The high-resistance grounding fault current in the distribution network is weak, and the measurement accuracy of zero-sequence current transformers (CTs) directly affects the ability of grounding protection to withstand the transition resistance. The requirements of zero-sequence CT for grounding protection in small-current grounding system are analyzed. Based on the equivalent circuit and electromagnetic parameters of the CT, the relationship between the measurement error of the CT and the primary current is analyzed. The theoretical analysis results are verified through experiments, and the measurement accuracies of 11 types of zero-sequence CTs for weak current signals are compared. Based on the measurement error of zero-sequence CT and the zero-sequence current of high-resistance grounding fault, the impact of measurement error of zero-sequence CT on the resistance to transition resistance of grounding protection is analyzed. Finally, the guidance on the selection of zero-sequence CTs is provided, and the measures to improve their measurement accuracy and protection against transition resistance are introduced.关键词：distribution network;high-resistance grounding fault;transition resistance;zero-sequence current transformer;measurement accuracy4|1|0更新时间：2023-06-19
Application Research
- 摘要：Virtual distribution transformers and virtual distribution feeders organically incorporate conventional distribution transformers and distribution feeders with controllable power electronic conversion circuits and series-parallel energy storage units, respectively. They are vital means to explore new scenarios for the integration and development of energy storage, build clean, low-carbon, safe and efficient distribution network, and realize a high proportion of distributed renewable energy accommodation in multiple regions. This paper defines the concept of virtual distribution transformer and virtual distribution feeder with the fundamental idea of “function virtualization” of distribution network equipment, and elaborates their functional architectures. On this basis, the relevant research status and engineering practice at home and abroad are summarized, the key technologies of virtual distribution transformers and virtual distribution feeders are discussed, and the future research directions are prospected, The aim of this paper is to provide useful references for the future research and application of virtual distribution transformers and virtual distribution feeders.关键词：virtual distribution transformer;virtual distribution feeder;active distribution network;function virtualization3|1|0更新时间：2023-06-19
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