English Version Journal Login
EN
最新刊期
卷 49 ， 期 2 ， 2025
- 摘要：The system exhibits the characteristics of low inertia and weak support with high proportion of renewable energy integrated into power systems. The power-synchronization grid-forming converters can effectively provide active frequency and voltage support by emulating the operation characteristics of synchronous generators. However, different from synchronous generators, the power electronics in converters show limited overcurrent and overheat tolerance capability, and the interaction caused by current limiting control among the multiple control loops in power-synchronization grid-forming converters is severe, which will lead to transient synchronization instability and windup problems, and severely restrict the role of safe and stable operation and active support capability of grid-connected systems based on power-synchronization grid-forming converters. Moreover, the characteristics of high nonlinearity in the synchronization loop of power-synchronization grid-forming converters make it hard to analyze and quantify the transient synchronization stability of its grid-connected system, posing new challenges to the optimal control of transient synchronization stability. The system modeling, analysis, and stability boundary quantification methods are summarized and induced for the transient instability problems of the grid-connected system based on power-synchronization grid-forming converters without considering the fault current limiting, as well as the problems of transient instability and windup considering the fault current limiting. Based on the analysis and induction results of transient instability and windup problems, the transient synchronization stability control methods of grid-connected systems based on power-synchronization grid-forming converters are summarized. Finally, the future research directions for transient synchronization stability analysis and control of grid-connected systems based on power-synchronization grid-forming converters are prospected.关键词：grid-forming converter;grid-connected system;transient stability;power grid fault;faulty current limiting;windup;synchronous generator5|3|0更新时间：2025-06-16
- 摘要：With good active support characteristics and weak grid adaptability, grid-forming converters have become a hot topic. However, the transient stability performance of grid-forming control (GFMC) under grid faults is a key issue restricting its operation. The existing studies mainly focus on the transient synchronization stability of GFMC strategy under symmetric faults, with limited in-depth studies on transient synchronization stability under asymmetrical AC faults. According to the latest hybrid-synchronization based grid-forming control methods, firstly, combining the positive and negative sequence decoupling module and hybrid-synchronization control structure, the hybrid-synchronization control can be applied to asymmetric faults. Secondly, a detailed dynamic model of the system under asymmetric faults is established, based on which the influence of positive and negative sequence current on transient stability is qualitatively analyzed, and the mathematical relationship between positive and negative sequence current and transient instability boundary is quantitatively analyzed based on the phase diagram model. Finally, based on electromagnetic transient numerical simulation and hardware-in-the-loop experiments, the effectiveness of the proposed control strategy and the accuracy of the transient synchronization stability analysis under asymmetric faults are verified.关键词：asymmetric fault;transient stability;grid-forming converter;hybrid-synchronization control;phase portrait;current stability boundary4|4|0更新时间：2025-06-16
- 摘要：The introduction of current limitation link significantly changes the transient synchronization mechanism and dynamic characteristics of grid-forming converters. In order to study the influence of current limitation link on the transient synchronization stability of grid-forming converters under large disturbance faults, the dynamic characteristics of the traditional d-axis priority limiting strategy under fault conditions are analyzed based on the power-angle curve. In the condition that the power grid voltage dips and the fault is not removed in time, the converter will "lock" in the limiting control mode. To address this issue, an adaptive limiting method is proposed, and the adaptive coefficient is introduced to adjust the power-angle curve of the grid-forming converter in the limiting state. First, the range of values for the adaptive coefficient is determined to ensure that the converter can return to normal operation state in various conditions. Then, the optimal value of the adaptive coefficient is selected using the equal-area criterion, so that the converter can obtain the maximum critical clearing angle and critical clearing time. Finally, the correctness of the theoretical analysis and the effectiveness of the adaptive limiting control strategy are verified through PSCAD/EMTDC simulations.关键词：voltage source converter;grid-forming converter;current limitation;transient stability;power-angle curve;equal-area criterion4|3|0更新时间：2025-06-16
- 摘要：In the power system where the power electronization level is progressively increasing, grid-forming converters are extensively studied due to their capability of autonomously establishing the terminal voltage and the frequency. Among them, the grid-forming converter without the inner-loop is widely used for its strong voltage source characteristics and simple control structure. However, this converter is prone to low-frequency oscillation when the system damping is weak. To enhance the low-frequency stability of the grid-connected converter without the inner-loop, this paper employs a complex torque coefficient analysis method to reveal that the low-frequency instability mechanism of the grid-forming converter without the inner-loop lies in the lack of lag characteristics of the constant virtual impedance in the low-frequency range, thus making it difficult to provide low-frequency damping torque to the system. Moreover, the increase in the virtual impedance can lead to an increase in the negative damping in the reactive power loop. Therefore, in response to the insufficient low-frequency damping torque provided by constant virtual impedance strategies when facing disturbances, this paper proposes a virtual impedance strategy based on low-pass filters to increase the damping torque and suppress low-frequency oscillations. Finally, the effectiveness of the proposed low-pass virtual impedance strategy is validated through the MATLAB/Simulink simulation and the StarSim semi-physical experiment.关键词：grid-forming converter;low-frequency oscillation;complex torque coefficient;damping;virtual impedance6|2|0更新时间：2025-06-16
- 摘要：The parallel grid-forming and grid-following inverter system is widely used in the islanded AC microgrid with distributed integration of renewable energy. The power-frequency droop control loop of grid-forming inverter and the phase locked loop (PLL) of grid-following inverter both generate fundamental frequency small-signal dynamics. Consequently, there exists the strong fundamental frequency interaction between the parallel power loops and PLLs, which has a considerable effect on the stability of the system. Regarding the above mentioned issue, first, based on terminal impedances and frequency-domain frequency-current terminal characteristics, the accurate small-signal frequency-domain models are constructed for the grid forming inverter, the grid-following inverter and the parallel inverter system, which include the main circuit dynamics, the voltage and current inner-loop dynamics, the power loop and PLL frequency dynamics, and the interaction dynamics. Furthermore, based on the frequency-domain model, the characteristics and effects of frequency dynamics are analyzed, and a simplified stability criterion based on the principal diagonal entries of the return-ratio matrix for the parallel system is derived using the Gerschgorin circle theorem under the typical operation conditions. Finally, simulation and experimental results validate the accuracy and effectiveness of the proposed frequency-domain model and simplified stability criterion.关键词：grid-forming inverter;grid-following inverter;islanded microgrid;parallel system;small-signal stability;impedance model;frequency dynamics;stability criterion5|1|0更新时间：2025-06-16
- 摘要：With the increase of penetration of renewable energy sources, the complexity of the power grid also escalates. Grid-forming (GFM) converters face the grid-connection environment with a wide range of short-circuit ratio of the power grid. In order to study the potential stability issues of the GFM converter and enhance its adaptability in the power grid with a wide range of short-circuit ratio, this paper establishes an impedance model considering power control, coordinate transformation, and voltage-current control. By analyzing the order-reduced impedance model, the instability mechanism of the GFM converter interacting with a strong power grid is revealed. Then, a hybrid virtual impedance method is proposed to improve the grid-connection stability of GFM converters over a wide frequency range and enhance the adaptability in complex grid environments. Finally, the correctness of the impedance characteristic analysis and the effectiveness of the proposed control strategy are verified through the experiment.关键词：grid-connection stability;grid-forming converter;sub-synchronous resonance;small-signal modeling;impedance reshaping;wide-range short-circuit ratio6|2|0更新时间：2025-06-16
- 摘要：When traditional grid-following (GFL) wind turbines are integrated into weak AC grids, there is a risk of small-signal instability. In contrast, grid-forming (GFM) wind turbines can enhance the system stability margin to some extent, which may lead to the emergence of hybrid wind farms with a mixture of GFL and GFM wind turbines in the future. However, when the proportions of GFL and GFM wind turbines are different, it is worth exploring how the stability domain of hybrid wind farms changes. First, a detailed mathematical model is established for the grid-connection system of wind farms with hybrid direct-drive GFL and GFM wind turbines. A method for calculating the system grid-connection stability domain is proposed, which comprehensively considers both the steady-state operation constraints and the small-signal stability constraints, and the grid-connection stability operation domain of the hybrid direct-drive wind farms under multi-dimensional constraints is quantitatively evaluated. Then, feasible ranges of grid short-circuit ratio (SCR) for the hybrid direct-drive wind farm under varying proportions of GFM wind turbines are determined at specific wind farm power outputs. Furthermore, when the output of wind farms and the length of collector line from wind turbines to the point of common coupling (PCC) vary, the trend of changes in the grid-connection stability domain of the hybrid direct-drive wind farms is explored. Finally, the accuracy of the obtained grid-connection stability domain of the hybrid direct-drive wind farms is verified through electromagnetic transient simulations in PSCAD/EMTDC.关键词：grid-following (GFL) wind turbine;grid-forming (GFM) wind turbine;hybrid direct-drive wind farm;stability domain7|1|0更新时间：2025-06-16
- 摘要：Due to economic advantages, diode-rectifier-unit based high-voltage direct current (DRU-HVDC) transmission system has a good application prospect in the field of DC transmission of the renewable energy base. However, most of current studies on the large disturbance stability of grid-forming converters rely on a large-capacity synchronous generator or a strong grid to support the frequency and phase of the fault point, and set the fault current reference value by a look-up table. There is a lack of research on the system where the fault point frequency of grid-forming wind turbines is controlled by the converter and the fault current reference value is dynamically adjusted in the DRU-HVDC system. In order to solve the above problems, first, a high-order nonlinear differential equation model considering current limitation and frequency control is established. Then, the analytical expression of the equilibrium point of the system after the fault is derived, and the advantages of q-axis priority current limiting strategy and frequency control in ensuring the existence of the equilibrium point after large disturbances are demonstrated. Finally, the Lyapunov function is constructed based on Takagi-Sugeno method and the estimated domain of attraction (EDA) for the system is obtained. The influence of the key control parameters of the converter on the transient stability is analyzed and compared with the simulation cases in PSCAD/EMTDC to verify the accuracy of the transient stability analysis.关键词：grid-forming wind turbine;transient stability;estimated domain of attraction (EDA);current limitation;diode-rectifier-unit based high-voltage direct current4|1|0更新时间：2025-06-16
Grid-forming Technology
- 摘要：At present, the global response analysis of power system frequency usually adopts the common mode frequency of the system. However, as the proportion of renewable energy in the power system continues to increase, the characteristics of system inertia reduction and uneven distribution of frequency regulation resources are becoming increasingly apparent. The frequency deviation index between nodes can reflect the distribution differences of system frequency in time and space. To obtain the accurate measurement values of frequency deviation between nodes, a power measurement method is proposed. With this method, the frequency variation of the system can be obtained by measuring the power fluctuation in the condition that the internal structure and control parameters of the unit are unknown, and the frequency spatial-temporal distribution characteristics of the system can be analyzed.Firstly, the frequency spatial-temporal distribution characteristics and influencing factors of the system with high proportion of photovoltaics after disturbance are analyzed using the frequency deviation between nodes obtained through simulation models. Secondly, the inter-node frequency deviation obtained by power measurement method is compared with the inter-node frequency deviation measured by phase-locked loop and synchrophasor measurement unit to verify its accuracy. Finally, the frequency deviation between nodes obtained by the proposed method can effectively reflect the spatial-temporal distribution characteristics of the system frequency through simulation and experimental tests.关键词：renewable energy;photovoltaic;differential mode frequency;frequency deviation;frequency spatial-temporal distribution;common mode frequency;power measurement;inertia6|0|0更新时间：2025-06-16
- 摘要：Aiming at the problem of insufficient inertia in the power system with high penetration of wind power, a hierarchical cluster cooperative frequency control strategy for large-scale wind power bases considering differential frequency regulation dead zones is proposed. First, based on the frequency control strategy of the unit, the time-domain analysis method is used to analyze the frequency response characteristics of multiple wind farm clusters inside and outside the frequency regulation dead zone, and the influence mechanism of frequency regulation dead zone parameters on the system frequency regulation effect is revealed. Then, taking into account the influence of dead zone parameter settings, differential multiple frequency regulation dead zones are designed with the dead zone width as the main control line. According to the frequency regulation energy demand, the task division of wind power base hierarchical clusters is reversely planned, the number of unit clusters participating in frequency regulation is adaptively adjusted, the lowest point of system frequency is increased and the risk of secondary drop is suppressed, which avoid frequent actions of the unit and extend the working service life. Finally, the proposed control strategy is simulated and analyzed using a modified 4-machine 11-bus testing system and an actual power grid case, and the results verify the effectiveness and practicality of the proposed strategy.关键词：wind power base;dead zone;hierarchical cluster;primary frequency regulation;secondary drop6|3|0更新时间：2025-06-16
- 摘要：Wind farms are affected by factors such as wind speed changes, and the output is prone to large fluctuations, resulting in problems such as voltage fluctuations and increased network losses, which affect the safe and efficient operation of wind farms. The current scheduling and control schemes of wind farms are mostly based on the traditional mathematical optimization model, and the day-ahead output forecasting data of the wind turbine are required. Hence, the introduction of the unavoidable day-ahead forecasting error leads to the reduction of the effectiveness of the day-ahead optimization control scheme, which increases the difficulty of intraday wind turbine control. Therefore, this paper gives full play to the decision-making ability of reinforcement learning model and proposes a decision-making scheme for topology reconfiguration of wind farm without forecasting based on improved deep Q network (DQN), which is developed using DQN as the framework. First, the state space based on historical data is constructed, and then the action space optimization method based on the decoupling of action value pairs of spanning tree is proposed. The optimization evaluation system is established with the goal of minimizing voltage deviation and network loss, and the mapping relationship from historical actual output data to decision-making is completed. The day-ahead optimal control of wind farms is realized without introducing forecasting error. Finally, an experience playback strategy based on multi-level experience guidance is designed to improve the training performance of the algorithm and ensure the applicability of the algorithm. According to the actual wind power operation data, the simulation is carried out. The innovation and effectiveness of the proposed method are verified by comparing and analyzing the influence of the improved technology on the DQN algorithm and the operation state of the wind farm before and after the optimal control.关键词：wind farm;forecasting;deep Q network;topology reconfiguration;voltage control;optimization;reinforcement learning7|0|0更新时间：2025-06-16
- 摘要：To reduce carbon emissions and improve the operating economy of port areas, considering the hydrogen-electricity load characteristics in port areas, an energy management method to coordinate the imbalance of supply and demand of hydrogen-electric energy of the port areas is proposed. In the traffic scheduling stage of the port areas, in order to obtain the daily hydrogen-electricity load curve of the port areas, according to the production process of the port areas, the power load model of the port areas is firstly obtained through the berth-quay crane optimal scheduling model. Then, with the goal of minimizing the total hydrogen consumption of container transportation, a hydrogen load model based on yard optimal scheduling is formulated. In the stage of energy scheduling in the port areas, the total daily operation cost model of the port areas considering the carbon emission cost is established to obtain the day-ahead energy scheduling strategy of the port areas. The simulation results based on historical data show that, the total operation cost of the port areas obtained by the proposed method is significantly reduced compared with that in scenarios using only lithium batteries and only power to hydrogen equipment. At the same time, the carbon emissions are significantly reduced compared with those the scenarios upgrading only fixed logistics equipment and only mobile logistics equipment.关键词：energy management;carbon emission;berth-quay crane optimal scheduling;port area;renewable energy accommodation;multi-energy load;power to hydrogen (P2H)6|1|0更新时间：2025-06-16
- 摘要：Electricity/hydrogen hybrid energy storage plays an important role in the power regulation capability of off-grid wind and photovoltaic power generation systems, but the comprehensive performance of energy management is not fully considered. Given the problems above, an improved energy management strategy based on dynamic optimization cycles is proposed. Firstly, the day-ahead optimization is carried out with the goal of minimizing the system operation cost. Then, the weight factor is adaptively adjusted in the process of intraday rolling optimization to reasonably coordinate the short-term power stabilization and long-term state optimization, and the rolling optimization cycle is dynamically adjusted to improve the real-time response ability of the controller and reduce redundant adjustment. Finally, in the real-time correction layer, the successive variational mode decomposition and the double-layer fuzzy control are used to perform the initial distribution and secondary distribution of the hybrid energy storage power respectively, so as to make full use of the operation characteristics of the hybrid energy storage and improve the robustness of the system. The case analysis shows that compared with the traditional strategy, the improved energy management strategy can reduce the system operation cost, energy imbalance rate and calculation time by 38.3%, 63.1% and 57.9% respectively, which improves the economy, reliability and real-time performance of the system energy management.关键词：electricity/hydrogen hybrid energy storage;energy management;adaptive weight;dynamic optimization cycle;successive variational mode decomposition;double-layer fuzzy control4|0|0更新时间：2025-06-16
- 摘要：In view of the difficulty in dealing with multiple uncertainties and multi-agent interactions in electricity-hydrogen-transportation system, a multi-agent game operation strategy of electricity-hydrogen-transportation system considering the hydrogen refueling uncertainty of hydrogen fuel cell vehicles (HFCVs) is proposed. Firstly, the interaction mechanism and game framework of energy and benefits among distribution network operator, hydrogen producing and refueling station (HPRS) operator and HFCV users are constructed. Secondly, considering the traffic flow of real-time traffic network, a refined modeling method for HFCV users' travel and hydrogen refueling behavior is proposed, and the uncertainty model of HFCV hydrogen refueling load is established based on Wasserstein distance. Then, a double-layer master-slave game distributionally robust operation model is constructed with the goal of maximizing the benefits of each agent among distribution network operator, HPRS operator and HFCV users, and is solved by using duality principle and Slater conditional transformation. Finally, a coupling system consisting of IEEE 69-bus distribution network and TN 25-bus transportation network is used to verify the effectiveness of the proposed model.关键词：Hydrogen fuel cell vehicle;electricity-hydrogen-transportation system;uncertainty;multi-agent game;distributionally robust4|0|0更新时间：2025-06-16
- 摘要：The coordinated optimization scheduling problem of transmission and distribution networks presents the characteristics of multi-time scale coupling and non-convex nonlinear, which is essentially a non-deterministic polynomial-hard problem. With the increase of the system adjustable resources, the control variables exponentially increase, and the phenomenon of the curse of dimensionality becomes more and more obvious. It is difficult for the solution strategy based only on physical model to balance the calculation accuracy and solution efficiency. Therefore, a multi-time scale coordinated optimal scheduling method of transmission and distribution networks based on the improved multi-agent twin delayed deep deterministic policy gradient (IMATD3) and Peaceman-Rachford (PR)-analytical target cascading (ATC) method is proposed. Based on the PR splitting method, the information iteration strategy of main-subsystem in ATC method is improved, and a PR-ATC based transmission and distribution coordinated day-ahead scheduling method is proposed. Through the offline interaction between multiple agents and the transmission and distribution networks, the sequential features of the continuous scheduling strategy are extracted, and the scheduling problems of each system are calculated in parallel based on the physical model. A joint scheduling and decision-making method combining offline training based on deep reinforcement learning and online application based on physical model is formed. The T6-D7-D7 and IEEE 118-D9-D33-D69 transmission and distribution networks are taken as examples and the effectiveness of the proposed method is verified.关键词：multi-agent system;coordinated optimal scheduling;transmission network;active distribution network;Peaceman-Rachford-analytical target cascading method;deep reinforcement learning;parallel computing7|0|0更新时间：2025-06-16
Basic Research
- 摘要：Most of the traditional power supply restoration strategies of the distribution network are divided into islands first and then dynamically reconstructed, which lacks the common consideration for both. However, the global reconstruction also has some problems such as poor economic efficiency and high operational difficulty. Therefore, a robust power supply restoration method with coordination of main grid and distribution networks based on reconstruction level identification is proposed. First, based on the fault situation of the distribution system, according to the principle of local autonomy and low-level priority reconstruction, the multilevel reconstruction requirements of the main grid (substation level) and distribution networks (distribution line level) are quickly determined. Then, islands are divided and reconstructed for different levels of regions. Next, in order to solve the problem that the convex hull polyhedron set describing the uncertainty of distributed photovoltaic output is conservative in the shrinking process, the hyperplane method is used to cut the convex hull set and an improved convex hull set model is established. Furthermore, the robust power supply restoration model of distribution network is constructed, and the column and constraint generation algorithm is used to solve the robust power supply restoration model. Finally, the simulation results of the improved 78-bus system show that the robust power supply restoration method with coordination of main grid and distribution networks based on reconstruction level identification can reduce conservatism and improve the robustness of power supply restoration results.关键词：distribution network;main grid;reconstruction;convex hull polyhedron;power supply restoration;robust optimization7|0|0更新时间：2025-06-16
- 摘要：Under typhoon meteorology, the load of the power grid will experience severe fluctuations, posing a threat to the safe and stable operation of the power grid. An effective method is urgently needed to generate corresponding load demand scenarios. A typhoon load scenario generation method is proposed based on interpretability conditional generative adversarial network (CGAN) for rare historical samples. First, the historical typhoon load is adjusted and classified based on the information such as typhoon landfall locations and levels. Then, a two-stage data augmentation strategy is proposed to address the issue of data scarcity. The first stage utilizes the horizontal and vertical correlation information between historical typhoon daily load sequences for sample augmentation, while the second stage utilizes the residual information between typhoon and non-typhoon daily loads for further sample augmentation. Finally, a CGAN causal interpretation method based on feature influence indicators is proposed, which characterizes the regulation degree of different features on the model results. Numerical cases show that the proposed model and method are effective and progressive.关键词：typhoon meteorology;artificial intelligence;load demand;scenario generation;interpretability;conditional generative adversarial network6|5|1更新时间：2025-06-16
- 摘要：At the initial stage of the commissioning and operation of Zhangbei flexible DC project of China, the high-frequency oscillation from 600 Hz to 3 900 Hz in the converter station at the sending end occurred many times. This paper briefly describes the oscillation mechanism of the flexible DC converter station using the dual-loop control strategy and determines that the negative damping of high-frequency oscillation comes from the delay of the control link and the current control link. The single-loop control strategy is applied to the islanded converter station, and the current control link is eliminated. A mathematical model of the impedance of the flexible DC converter considering the dynamic process of the primary circuit and the single-loop control strategy is established. Based on the simplified model, the characteristic of single-loop voltage control in the high-frequency range is deduced. The direct amplitude limiting scheme is adopted to achieve fast and accurate suppression of the transient fault current, and the control switching criteria and transient current evolution laws are provided. The proposed control strategy has been validated through field tests and long-term stable operation in Zhangbei flexible DC project, which solves the problem of high-frequency oscillation under all operating conditions on the engineering site.关键词：flexible DC transmission;high-frequency oscillation;negative damping;current control;voltage control;delay;direct amplitude limiting5|0|0更新时间：2025-06-16
Application Research
- Technical support is provided by Beijing Founder electronics co., LTD 京ICP备09064830号-19
京公网安备11010802024621 - It is recommended to read the content of this site in Chrome&IE9+. Please switch to extreme mode in browser 360.
- Cookies We use cookies to help provide and enhance our service and tailor content. By continuing, you agree to the use of cookies.
0