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最新刊期
卷 49 ， 期 1 ， 2025
- 摘要：To support the efficient utilization of renewable energy and ensure power supply, grid-forming technologies have been initially explored and practiced in various application scenarios within power systems. To promote the large-scale application of grid-forming technologies, their functional positioning and application perspectives in new power systems are discussed. By sorting out the evolution history of grid-forming technologies and existing domestic and foreign standards and specifications, the intrinsic driving demands for developing grid-forming technologies are analyzed, and their functional positioning in different power grid scenarios is clarified. Finally, from the dimensions of static, dynamic, and transient stability analysis, the current challenges faced by grid-forming technologies are analyzed, and the issues that need to be addressed for their large-scale application are prospected.关键词：grid-forming control;grid-forming equipment;new power system;renewable energy;functional positioning6|2|0更新时间：2025-06-16
- 摘要：Under short-circuit faults in the power grid, the transient interaction of renewable energy grid-forming converters operating in parallel is significantly enhanced, which increases the risk of transient synchronous instability of the system. First, this paper establishes a transient interaction model for the parallel system of grid-forming converters. Based on the traditional stability theory of synchronous generators, the mechanism of transient interaction energy affecting the stability of converters is analyzed. It is further revealed that the power angle traction mechanism under the effect of the interaction energy will promote the stability of multiple converters to approach consistency or make the converter with poor stability to accelerate the instability. Therefore, this paper proposes a method for constructing the stability region of the parallel system of grid-forming converters considering current limiting switching. The influence of the operating status and control parameters of the converter on the system transient stability is analyzed through the stability region. Finally, the simulation and experimental results verify the correctness of the theoretical analysis.关键词：grid-forming converter;transient stability;parallel operation;transient interaction energy;stability region;current limiting4|0|0更新时间：2025-06-16
- 摘要：In the heterogeneous system with grid-following photovoltaics and grid-forming energy storage, the influence of grid-forming converters on the heterogeneous system stability can be studied through the impedance analysis method. However, the existing studies do not fully consider the frequency coupling effect between different converters and the frequency coupling effect between the converters and the grid impedance. So it is difficult to accurately evaluate the stability of the heterogeneous system in the weak grid. Therefore, taking a two-generator heterogeneous grid-connected system as an example, this paper deeply analyzes the influence of system internal coupling on the output impedances of grid-following and grid-forming converters. The analysis shows that the grid impedance and the output impedance of the grid-forming/grid-following converter have an additional influence on the output impedance of the grid-following/grid-forming converter. In particular, compared with the converter in the independent grid-connected operation, the output impedance of the grid-following converter in the mid- and low-frequency band is easily affected in the heterogeneous system, while the output impedance of the grid-forming converter is basically unaffected. On this basis, the impedance model of the heterogeneous grid-connected system is established by combining the grid-forming converter and the grid as an equivalent grid, and the small-signal stability is discussed. The results of the hardware-in-loop experiment show that, compared with the traditional impedance model, the stability analysis based on the proposed impedance model realizes the accurate judgment of the small-signal stability of the system in the weak grid.关键词：grid-connected photovoltaic system;heterogeneous system;grid-following photovoltaic;grid-forming energy storage;grid-following converter;grid-forming converter;weak grid;frequency coupling;impedance model;small-signal stability4|1|0更新时间：2025-06-16
- 摘要：The short-circuit ratio (SCR) of renewable energy stations does not take into account the voltage support of the grid-forming power sources, and the critical short-circuit ratio (CSCR) also ignores the power-angle stability constraints, which makes it impossible for them to accurately evaluate the stable operation capability of renewable energy stations in the weak grid. Facing these problems, first, under the constraints of voltage stability and power-angle stability, the SCR and CSCR indicators of grid-following stations are calculated. By comparing the SCR and the CSCR, the stable operation capability of grid-following stations can be evaluated. On this basis, the changes in CSCR quantifies the changes of the stable operation capability of grid-following stations after the grid-forming power source accesses. Thus, the role of grid-forming power source in enhancing the stable operation capability is verified. Finally, through simulation cases of a single grid-following power source, grid-following and grid-forming power sources connected to grid-connected systems, the effectiveness of the proposed stable operation capability evaluation method is verified.关键词：grid-following station;grid-forming power source;critical short-circuit ratio (CSCR);voltage stability;power-angle stability;operation capability evaluation6|2|0更新时间：2025-06-16
- 摘要：The grid-following converters have the risk of sub-synchronous oscillation (SSO) instability in the weak grid. The grid-forming converters can improve the stability of the hybrid parallel system in the sub-synchronous frequency range in the weak grid. The proper configuration of grid-forming units in renewable energy stations can enhance the system stability. Therefore, the ratio of grid-forming and grid-following converters is a key factor influencing the system stability. Aiming at the small-signal stability issue in the hybrid parallel grid-connected system with grid-forming and grid-following converters, this paper studies the influence of converter control system characteristics on the boundary conditions for the ratio of the grid-forming converter. First, the state space model of the hybrid parallel grid-connected system of grid-forming and grid-following converters is established. On this basis, this paper analyzes the influence of key parameters of grid-following/grid-forming control systems and the voltage loop control structures of grid-forming converter on the system stability. From the perspective of maintaining the small-signal stability of the system in the sub-synchronous frequency range, this paper analyzes the key influence factors for the lower limit of the ratio of grid-forming converters in the hybrid parallel system. The stability boundary under the constraint of each influence factor is obtained. In addition, the frequency-domain impedance method is used to explain the influence mechanism of each influence factor. Finally, the accuracy of the theoretical analysis is verified based on the RT-LAB semi-physical platform.关键词：grid-forming converter;grid-following converter;hybrid parallel system;sub-synchronous oscillation;ratio;small-signal stability;stability boundary6|0|0更新时间：2025-06-16
- 摘要：Compared with traditional thermal power-dominated systems, renewable energy bases that lack synchronous power supply support exhibit low immunity and weak support. The use of grid-forming energy storage station (GFMS) is an effective solution. First, the control principle of GFMS is analyzed, the power adjustment ranges of GFMS under steady-state and dynamic conditions are determined, and a GFMS operation model is established. Then, a coordinated optimal reactive power control strategy considering GFMS auxiliary governance is proposed to adapt to reactive power coordinated optimization and real-time voltage support requirements. In the reactive power coordinated optimization stage, day-ahead and intra-day centralized optimization of reactive power sources is carried out with the goal of optimizing economic efficiency and maximizing dynamic reactive power reserve capacity. In the real-time voltage support stage, a GFMS voltage control strategy is proposed based on voltage support requirements of the grid-connected point. A renewable energy base in the northwest region of China that lacks synchronous power supply support is selected as a case for simulation to verify the effectiveness of the proposed strategy. The results show that the proposed coordinated optimal reactive power control strategy effectively improves the security and stability level of the renewable energy base and gives full play to the role of GFMS.关键词：grid-forming energy storage station;renewable energy base;voltage stability;reactive power optimization;voltage support4|3|0更新时间：2025-06-16
- 摘要：Fault equivalent modeling is the basis of system-level response characteristic calculation. However, there are few studies on fault equivalent modeling of grid-forming converters. The traditional short-circuit current calculation method for grid-following power electronic devices connected to AC network is prone to the problem of instability divergence in the flexible DC grid-forming system. Therefore, considering the voltage-frequency grid-forming control strategy and the active voltage reduction strategy of grid-forming flexible DC converters and the low voltage ride-through control strategy of grid-following renewable energy, this paper establishes the fault equivalence model of different types of power electronic devices. On this basis, considering the frequent switching of equivalent models of voltage source and current source for different power electronic devices, a network-wide chain iterative calculation method for fault response characteristics of renewable energy sending-end flexible DC grid-forming transmission system is proposed to realize the fast and reliable convergence of short-circuit current calculation. Based on the PSCAD/EMTDC simulation platform, a simulation model of the renewable energy sending-end flexible DC grid-forming transmission system is built to carry out a large number of simulation tests of various fault types and influencing factors, which fully verify the feasibility, accuracy and superiority of the proposed calculation method.关键词：flexible DC converter;grid-forming control;fault equivalent model;fault response characteristic;chain iteration4|0|0更新时间：2025-06-16
Grid-forming Technology
- 摘要：In response to the urgent need to optimize the overall design of the electricity market under the background of energy transition, this paper proposes a system design of the substitute power product (SPP) market suitable for the new power system, grounded in the fundamental concept of electric energy value. First, the analysis shows that the construction goal of the SPP market system is precisely to adapt to renewable energy resources with low marginal generation costs but high system accommodation costs. Its short-term goal is to enhance system flexibility, and its long-term vision is to promote low marginal regulating costs. Then, based on a reconsideration of electric energy value connotations, this paper proposes the dual-value theory of electric energy, revealing both the production-use value and the power balance value of electric energy as a commodity. It emphasizes that market entities should be classified based on their provided value rather than resource types. Finally, the SPP market system is systematically designed across multiple dimensions including commodity attributes, temporal scales, and spatial scope. This SPP system consists of two main components of the electric energy market and the ancillary service market. The former can be further divided into substitute energy market and regulating energy markets, reflecting production-use value and power balance value of electric energy, respectively. On this basis, this paper also explores the multi-regional SPP market forms and the mode for retailers to participate in the wholesale SPP market. The proposed SPP market system is designed around continuous system energy balance, which is conducive to establishing fair, full-competitive, simple and transparent trading mechanisms.关键词：electricity market;substitute power product;new power system;dual-value of electric energy;substitute energy;regulating energy;renewable energy accommodation4|0|0更新时间：2025-06-16
- 摘要：With the continuous deepening of the reform of the electricity spot market in each province, how large-scale cascade hydropower station can exert its own regulation and storage capabilities in the spot market to respond to the power supply and demand fluctuations caused by the large-scale integration of renewable energy and load uncertainties, has become an important problem that major hydropower generation groups urgently need to solve. The complex market structure, prominent market position, multiple supply and demand uncertainties, and non-convex operation characteristics make the bidding problem in the hydropower spot market extremely complicated. The key lies in the refined modeling of the market environment and the power generation process. Therefore, a bidding model for the cascade hydropower is proposed to respond to the supply and demand fluctuations in the spot market. This model is a bi-level optimization model with a “one leader-multiple followers” structure, where the leader model (upper-level model) is used for bidding decision-making of cascade hydropower, and multiple follower models (lower-level models) simulate the day-ahead and real-time market clearing in multiple scenarios. Considering uncertainties in renewable energy output, load fluctuations, and other power station quotations, three modeling measures are proposed to achieve refined modeling of cascade hydropower and controllable water level fluctuations. By using the Karush-Kuhn-Tucker (KKT) conditions, the strong duality theorem and various linearization techniques, the original model is transformed into a mixed-integer quadratic programming (MIQP) problem that can be solved in finite time. The effectiveness and high performance of the proposed model are demonstrated through a case study based on the Lancang River in China.关键词：cascade hydropower;electricity market;spot market;market bidding;water level control4|0|0更新时间：2025-06-16
- 摘要：As an emerging energy storage operation mode, the shared energy storage plays an important role in reducing the investment cost of prosumers and improving the efficiency of energy storage utilization. However, the current complex interactions and competing interests between prosumers, as well as with the shared energy storage operator (SESO), have exacerbated the difficulty in optimizing and regulating active distribution network. Therefore, a cooperative optimal decision-making method for the active distribution network with shared energy storage leased by prosumers is proposed. Firstly, the framework of the multi-agent cooperative transaction is constructed, which considers the interaction among distribution system operators, prosumers and SESOs. Secondly, a peer-to-peer power sharing trading mechanism that takes into account the participation of shared energy storage is established. And a two-stage pricing strategy for prosumers leasing shared energy storage is proposed accordingly. A bargaining factor indicator is used to quantify the bargaining power of each entity in the pricing process. Then, a game-based optimization model for active distribution network based on the improved Nash bargaining is established, and the bargaining factor is introduced in the index term to set its weight in the objective to achieve a reasonable distribution of benefits. Finally, an improved IEEE 33-bus distribution system is used to simulate and verify the effectiveness of the proposed method.关键词：active distribution network;shared energy storage;prosumer;multi-agent cooperative transaction;peer-to-peer power sharing trading mechanism;improved Nash bargaining;optimization4|3|0更新时间：2025-06-16
- 摘要：The coupled system formed by renewable energy and thermal power units with rapid load adjustment retrofit at the same grid-connected point is an effective means to enhance flexibility in regions such as deserts, gobi, and wilderness, where proportions of renewable energy are high but flexible power generation resources are lacking. To explore the economics and flexibility of the retrofitted thermal power units in the coupled system, this paper proposes a multi-objective optimal scheduling method for wind-solar-thermal coupled systems. First, based on the actual calculated operational coal consumption data of the thermal power units after flexibility retrofitting, a coal consumption calculation formula for the unit ramping process is fitted, and the impact of the improved rapid load adjustment capability on the economy and flexibility of the coupled system is analyzed. On this basis, taking the daily comprehensive operation revenue and the flexibility supply-demand matching degree as objective functions, considering system operation constraints including the ladder-type ramp rate, a multi-objective optimal scheduling model is constructed. By using grouped and linked polynomial mutation operators in the optimization algorithm, the ability to solve multi-objective optimal scheduling problems in power systems with high dimensions and complex constraints is improved. Finally, an optimal scheduling simulation is conducted by using a coupled system in a certain region as an example. Results show that the proposed method can obtain an optimal scheduling scheme for the coupled system with relatively better comprehensive economy and flexibility.关键词：coupled system;peak regulation;rapid load adjustment;ladder-type ramp rate;flexibility supply-demand matching;multi-objective optimal scheduling5|1|0更新时间：2025-06-16
- 摘要：Due to the significant uncertainty of photovoltaic output, the high proportion of distributed photovoltaic integration will pose a huge challenge to the safe and stable operation of the new power system. Accurate and reliable distributed photovoltaic output forecasting is of great significance to improve the security of the new power system operation. Under this background, considering the spatio-temporal coupling characteristics and uncertainty of distributed photovoltaic output, this paper proposes a spatio-temporal cooperative probability forecasting method of distributed photovoltaic output based on the improved quantile regression based dynamic graph attention and the long short-term memory network (iDGA-LSTM). Firstly, considering the spatial correlation of distributed photovoltaic output across a wide area, a distributed photovoltaic spatial feature extraction and aggregation model based on the graph attention network is constructed. Secondly, regarding the extracted distributed photovoltaic spatial correlation features, a distributed photovoltaic spatio-temporal coupling feature extraction model based on the dynamic graph attention and the long short-term memory network is constructed. Then, taking into account the spatio-temporal coupling characteristics of distributed photovoltaic output and combining them with numerical meteorological forecasting features, a probability forecasting model for distributed photovoltaic output based on improved quantile regression is constructed. Finally, the proposed forecasting method is verified with some actual distributed photovoltaic data. The simulation results show that the proposed method improves the reliability and accuracy of distributed photovoltaic output forecasting and provides references for the power system operation strategies with different risk levels.关键词：graph attention network;long short-term memory network;distributed photovoltaic;quantile regression;probability forecasting;spatio-temporal cooperation5|2|0更新时间：2025-06-16
- 摘要：The probability of line outages exerts a crucial influence on the triggering and evolution of cascaded failures. However, the existing study regarding the equilibrium of the distribution of line outage probabilities in power grids suffers from insufficient considerations. In this paper, by integrating the analysis methods of complex network theory and entropy theory, a method for identifying key lines in power grids that comprehensively considers the entropy of outage probability and the entropy of grid structure is proposed, aiming to quantify the comprehensive influence of lines at the levels of the operational state and network state of the power grid. Firstly, based on the line outage probability model, the indicators of the entropy of outage probability distribution and the entropy of outage probability variation are put forward, differentiating the influence of the three states of line power flow within the normal range, between the normal and limit values, and greater than the limit value on the identification results, overcoming the deficiency of insufficient consideration of the direct factors affecting line faults in the existing indicators. Secondly, combined with the improved entropy of grid structure, a comprehensive indicator of key lines reflecting the grid structure and operation state of the power grid is proposed. Then, in combination with the power balance strategy, a method for identifying key lines in the power grid is proposed. Finally, based on the improved network efficiency indicator, simulations are conducted on the IEEE 39-bus system and IEEE 118-bus system, which verify the feasibility and correctness of the proposed method.关键词：line identification;complex network;cascaded failure;entropy;outage probability;network effectiveness4|0|0更新时间：2025-06-16
- 摘要：A dynamic equivalent modeling method for wind farms is proposed. The core idea is to effectively integrate the physical characteristics analysis and data analysis of wind farms, to construct data features reflecting the transient characteristics of wind farms. And a clustering algorithm based on shape-based distance is proposed to address the transient fluctuations with variable characteristics of wind power, achieving clustering equivalence of wind turbines with similar dynamic behaviors within a wind farm. First, based on the multiple spatio-temporal scale characteristics of wind farms, the core factor set are proposed to characterize the dynamic characteristics of the wind farm. Then, considering the correlation between multiple core factors, the denoising autoencoder algorithm is employed to reduce dimensionality and eliminate redundant information to construct data features. In addition, a clustering algorithm based on the shape-based distance is introduced to achieve clustering of power generation units for wind farms. Finally, taking a certain wind farm as a case, the effectiveness of the proposed method is verified through simulation on the PSCAD/EMTDC platform.关键词：equivalent modeling;wind farm;multiple spatio-temporal scales;denoising autoencoder;clustering;physics-data fusion model4|2|0更新时间：2025-06-16
- 摘要：Electromagnetic transient simulation is of great significance for mastering the operating characteristics of DC transformers. However, the current high-speed equivalent modeling methods for modular converters are rarely mentioned for non-isolated transformers. Meanwhile, the existing electromagnetic transient simulation models for non-isolated DC transformers suffer from complex switch-state calculation and a large number of internal nodes, leading to low system simulation efficiency. Therefore, a fast electromagnetic transient equivalent modeling method for non-isolated DC transformers based on switch-state prediction and Thevenin equivalence is proposed. Firstly, a switch-state prediction method for submodules of non-isolated DC transformers is proposed. Secondly, based on the switch states, an equivalent circuit for the bridge arms of the DC transformer is obtained, and the Thevenin equivalence is applied to obtain the two-node equivalent circuit model of the bridge arms. Then, the equivalent circuit model of the autotransformer is established, and the equivalent circuit of the bridge arm and autotransformer is combined to obtain the equivalent circuit of the DC transformer. Based on this, the node voltage equation of the DC transformer is established. Finally, based on the Gaussian elimination, the equation is simplified to achieve the internal node reduction of the simulation model of the non-isolated DC transformer. The case study shows that the proposed equivalent modeling method for fast electromagnetic transient of non-isolated DC transformers has similar accuracy to traditional detailed modeling methods, and the simulation efficiency is significantly improved.关键词：DC transformer;Thevenin equivalence;electromagnetic transient simulation;equivalent modeling;switch-state prediction;internal node reduction4|1|0更新时间：2025-06-16
- 摘要：After a permanent single-phase grounding fault occurs in a flexible grounded system, the switching device of the neutral grounding resistor (a parallel small resistor) is closed with a time delay, in the hope of reliably eliminating the fault. Currently, the application effect of the protection method for the flexible grounded system based on steady-state information is difficult to meet the requirements. Moreover, there is no complete conclusion regarding the transient characteristic analysis when the small resistor is engaged, which restricts the development of the transient protection theory for grounding faults in the flexible grounded system. In this paper, a transient analysis model for the throw-in of a parallel small resistor in the flexible grounded system based on the line distribution parameters is established. The resonant characteristics among various components in the system are investigated. Based on this, a simplified model is proposed. For low-resistance and high-resistance grounding faults, analytical expressions of the transient current and voltage are provided, respectively. The variation laws of the main characteristic values such as resonant frequency, decay time constant, and maximum amplitude with system parameters and fault conditions are analyzed. And the distribution characteristics of the transient zero-sequence current of each line are also analyzed. These are compared with the transient characteristics at the fault moment at the resonant grounding stage. Finally, the correctness of the proposed simplified model for transient characteristic analysis is verified by using digital simulation and field test data.关键词：flexible grounded system;permanent grounding fault;neutral grounding resistor;parallel small resistor;transient characteristic;protection4|2|0更新时间：2025-06-16
Basic Research
- 摘要：High voltage direct current (HVDC) transmission system is the main body of China’s large-scale energy resource optimal allocation. The existing conventional DC power flow reversal is based on the voltage polarity reversal in the DC blocking mode, which is difficult to meet the needs of cross-regional flexible adjustment sharing and transient stability support for the new power system with a high proportion of renewable energy. Combined with the application experience of conventional DC flexible regulation abroad, a new online power flow reversal technology for conventional DC is proposed to meet the demand of domestic cross-regional asynchronous sharing, which can significantly improve the flexible regulation ability of the conventional DC. Based on the standard two-region asynchronous-interconnection system and the southern region extreme scenario, the effectiveness of the proposed online power flow reversal control is verified. The proposed method is of great significance for the construction of DC asynchronous-interconnection cross-regional sharing system.关键词：high voltage direct current (HVDC);cross-regional sharing;high proportion of renewable energy;power flow reversal;flexible interconnection4|2|0更新时间：2025-06-16
- 摘要：Scientific and accurate calculation of variable transmission costs is of great significance for the fair competition of electricity market. Through power flow tracing, it is found that the transmitting power process from the power sources to electricity admittance components also generates active power losses, which in turn affects the final variable transmission cost. Therefore, when calculating the variable transmission cost, it is necessary to consider the physical and economic characteristics of the electricity admittance components. First, a model is established to satisfy the power balance characteristics of active loads and reactive loads such as electricity admittance. Then, by using the principle of cost conservation, a cost calculation model that conforms to economic characteristics is obtained. The variable transmission cost calculated by using the proposed model can provide rich and accurate economic information. Finally, the rationality and the accuracy of the proposed calculation model and results are verified through case study.关键词：variable transmission cost;electricity admittance;power flow;cost conservation;reactive power transmission cost;electricity market4|0|0更新时间：2025-06-16
Engineering Application
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