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最新刊期
卷 47 ， 期 6 ， 2023
- 摘要：With the promotion of the “carbon emission peak and carbon neutrality” policy as well as the construction of new power systems, renewable sources and novel loads, such as distributed photovoltaics and electric vehicles have developed rapidly and their proportion has reached new heights. Due to the power fluctuation and randomness, these sources and loads bring new requirements and challenges to the safe operation and flexibility of distribution networks. Aiming at the diversity and difference of flexible distribution network construction, this paper analyzes the demand for flexible interconnection at different levels of distribution network, and introduces its core role and research progress in four levels: realizing efficient integration of source and load in low-voltage station area, realizing power transfer and support between interconnected low-voltage station areas, realizing the improvement of power supply capacity and flexibility in medium-voltage line, and realizing source-load “large spatio-temporal” matching and the interconnection and mutual power support between power grids. Focusing on the structure of AC/DC hybrid distribution system, optimal planning, operation control and fault restoration, the future technical development direction of AC/DC hybrid interconnected distribution system is prospected.关键词：new distribution system;AC/DC hybrid distribution network;power support;flexibility;spatio-temporal matching;key technology3|2|0更新时间：2025-06-16
- 摘要：Flexible interconnection technology can realize the flexible control of power flow in the distribution network, which is an important technical means for the new distribution network to realize a strong architecture. This paper summarizes the circuit topology and control technology of flexible interconnection devices for medium-voltage distribution networks. First, the system structure of flexible interconnection device for medium-voltage distribution network is analyzed, including application scenarios and device components. Secondly, the circuit topology of flexible interconnection of the medium-voltage distribution network is compared and analyzed, including modular multi-level high-voltage type and transformer step-down type, and the technical development is discussed. Finally, this paper summarizes the control technologies of the grid-following and grid-forming flexible interconnection devices in the medium-voltage distribution networks and points out the challenges to be faced when the virtual synchronous generator control strategy is applied to the flexible interconnection devices.关键词：distribution network;flexible interconnection device;device system structure;circuit topology;control strategy2|1|0更新时间：2025-06-16
- 摘要：In order to measure the flexibility brought by power electronic devices such as soft open point (SOP) to the distribution network, the concept of flexibility degree for the power-electronized distribution network is proposed. First, the concept of flexibility degree is proposed, which is the relative measurement of the bi-direction continuous flexible power flow control capability of the distribution network after the adoption of flexible power electronic devices. Furthermore, the specific definition and calculation method of flexibility degree are proposed. Flexibility degree is defined by the proportion of flexible range to the whole distribution network taking into account the flexible capacity of power flow control. Secondly, taking the flexible transformation based on SOP as an example, the typical wiring modes and the expanded IEEE RBTS-Bus4 test system are used for verification. Then, the influence rules of SOP on flexibility degree are analyzed by cases: the flexible range in the distribution network is determined by the number of sets and terminals as well as sites of SOPs, while the flexible capacity of power flow control is determined by the total capacity of SOP access to feeders. The configuration principles of SOP are summarized on this basis. Finally, the unit flexibility cost is defined and the economic evaluation method of flexible transformation for the distribution network based on flexibility degree is proposed. The application of flexibility degree in SOP planning and distributed generator accommodation are also shown by cases.关键词：distribution network;soft open point (SOP);power electronic;flexibility degree;flexible transformation;unit flexibility cost2|1|0更新时间：2025-06-16
- 摘要：Under the goal of "carbon emission peak and carbon neutrality", large-scale distributed photovoltaic, electric vehicle charging piles and other zero-carbon and low-carbon elements are connected to the low-voltage distribution network, which brings challenges to the reliable, stable, and economic operation of the terminal power grid. Based on the low-voltage DC technology, the flexible interconnection and energy reciprocity between distribution substation areas are realized, the new topology of terminal power grid under the new power system is constructed, and the energy microcirculation is used to solve a series of prolems in the current terminal power grid. First, the primary topology and secondary networking mode of low-voltage flexible DC interconnection are introduced to meet the resource endowment and differentiated needs of different low-voltage distribution networks. Secondly, several functional morphologies of the terminal energy microcirculation are described to achieve the operation goals of load balancing and fast fault transfer in different distribution substation areas. Finally, the current project situation in China is summarized, and the first low-voltage flexible interconnection and energy microcirculation project in China is introduced in detail. The project operation situation verifies that the system can effectively improve the reliability and economy of the terminal power grid operation.关键词：distribution network;low-voltage DC;distribution substation area;flexible interconnection;energy microcirculation2|0|0更新时间：2025-06-16
- 摘要：As an important development direction of the active distribution network, it is of significant research value to coordinate the active-reactive power resources of the AC/DC distribution network for improving the characteristics of system operation. First, taking the AC/DC distribution network based on multi-terminal soft open point (SOP) as the research object, an active-reactive power dispatch model of the AC/DC distribution network is constructed with the objective of minimum operation cost considering the key equipment operation constraints for the energy storage, flexible load, SOP, photovoltaic inverter, and the constraints of peak-shaving and valley-filling and voltage offset. Secondly, in order to adapt to the uncertainty of photovoltaic output, a data-driven two-stage stochastic-distributionally robust optimization model is constructed. Then, the model is solved based on the column and constraint generation algorithm. Finally, the 72-bus and 38-bus AC/DC distribution networks are used to verify the effectiveness of the proposed model.关键词：AC/DC distribution network;soft open point (SOP);peak-shaving and valley-filling;voltage regulation;stochastic-distributionally robust optimization2|1|0更新时间：2025-06-16
- 摘要：Due to the integration of a large number of distributed genreators to the distribution network, the insufficient regulation and control capacity of the distribution network has led to serious problems such as large voltage fluctuations, low consumption level of renewable energy, and poor economic indicators. Therefore, a collaborative optimization method of soft open point (SOP) and dynamic reconfiguration of the distribution network is proposed to fully mobilize the flexibility resources on the network side, and a double-layer optimization model based on reinforcement learning is constructed. In the upper layer of the model, the generated radial topological structure set is used as the action space of reinforcement learning, and the topological structure is dynamically selected. The lower layer optimizes the operation of controllable active equipment with SOP based on the network structure of the upper layer, excavates the flexible power flow regulation ability of SOP, and continuously modifies the topology selection of the upper layer according to the optimization results, which can effectively solve the multi-time-scale mixed-integer nonlinear programming problem. The convergence speed of the algorithm is accelerated by deleting invalid networks and taking priority sampling of historical information. The example analysis shows that the optimization strategy given by the double-layer collaborative optimization method based on reinforcement learning effectively improves the operation level of the active distribution network, and can adapt to the source-load uncertainty scenarios.关键词：distribution network optimization;dynamic reconstruction;soft open point;reinforcement learning;distributed generator;mixed-integer nonlinear programming2|1|0更新时间：2025-06-16
- 摘要：The flexible interconnection technology based on the soft open point (SOP) brings new opportunities to solve the problems of complex power flows and light and heavy loads in existing distribution networks. However, the existing optimal regulation and control strategy of SOP only takes the lowest line loss as the optimization objective, ignoring the loss variation characteristics of transformers, SOPs and other key equipment, which cannot realize the optimal operation and control of the system. To this end, this paper proposes an optimal regulation and control strategy for flexible interconnected distribution networks considering the loss characteristics of transformers and SOPs. First, the loss characteristics of SOPs and transformers are analyzed to obtain the efficiency characteristic curves of both SOPs and transformers. Secondly, an improved loss sensitivity model is established to determine the optimal access location of SOP. And a two-layer optimization model is established, in which, the lowest annual comprehensive cost and comprehensive system loss are taken as the objectives of the upper and lower layers, respectively. Then, the optimal installation capacity of SOP is determined, and the lower-layer optimization model realizes the comprehensive optimization of the loss of SOPs, transformers and network lines. Finally, the verification is based on the IEEE 22-bus and IEEE 15-bus interconnection system. The results show that the proposed regulation and control strategy is more advantageous than the existing strategies, which can significantly reduce the comprehensive system loss, solve the system light and heavy load problems, and improve the operating economy and reliability of the system.关键词：distribution network;flexible interconnection;soft open point (SOP);loss sensitivity;site and capacity selection;operation optimization2|0|0更新时间：2025-06-16
- 摘要：The transformation for the distribution network by the flexible interconnection device can realize the flexible and efficient interaction between source, grid, load and storage, and solve the problems of load imbalance and power quality caused by the large number of distributed generators. Aiming at the flexible interconnection in low-voltage transformer area, an optimal dispatch model of AC/DC hybrid low-voltage distribution network based on multi-mode flexible interconnection is proposed. First, considering the networking forms of back-to-back and hybrid AC/DC low-voltage flexible interconnection devices, the low-voltage model of the flexible interconnection device and the PV-storage-charge-load element is established. Then, based on the low-voltage model, taking multi-level load imbalance degree, network loss and operation cost as optimization objectives, an optimal dispatch model of AC/DC hybrid low-voltage distribution network based on multi-mode flexible interconnection is proposed. Convex optimization theory is also used to convexize and linearize the model, and Gurobi solver is called to obtain the global optimal solution of the model. Finally, the effectiveness of the proposed model and the solution algorithm is verified by the case of AC/DC hybrid low-voltage distribution network.关键词：flexible interconnection;optimal dispatch;AC/DC hybrid low-voltage distribution network;three-phase four-wire system;load imbalance2|1|0更新时间：2025-06-16
- 摘要：The high proportion of the access of distributed generators makes the voltage control problem of the distribution network more and more urgent. Compared with the traditional voltage regulation devices in distribution networks, the new power electronic devices represented by the energy storage integrated soft open point (ESOP) have more flexible and rapid voltage regulation capability. The actual distribution network parameters are difficult to obtain; the operation scenario is complex and changeable; and the control method based on the physical model is often difficult to adapt to the change of system operation state. Therefore, a data-driven voltage control method of ESOP considering the measured data quality is proposed. First, a data-driven control model of ESOP is established based on the model-free adaptive predictive control method. Then, considering the measurement error of actual measurement data in the data-driven process, the bad data identification and measurement disturbance suppression method are used to process the measurement data. A data-driven voltage control method of ESOP considering the measurement data quality is proposed to reduce the impact of measurement error on the data-driven control process. Finally, a practical distribution network example with a four-terminal ESOP is used for verification analysis. The results show that the proposed data-driven voltage control method of ESOP can effectively solve the problem that distribution network parameters are difficult to obtain accurately, significantly reduce the adverse effects caused by measurement errors, and comprehensively improve the voltage control level of distribution networks.关键词：distribution network;soft open point;energy storage;voltage control;data-driven;measurement data2|2|0更新时间：2025-06-16
- 摘要：Driven by the goal of “carbon emission peak and carbon neutrality”, the penetration of new energy equipment in the distribution network has been significantly accelerated. A more in-depth study of operational optimization control strategies for new distribution systems is necessary. As a new type of equipment, the soft open point (SOP) can realize power smoothing control between feeders and promote feeder load balancing to cope with frequent power fluctuations in the distribution network. First, this paper introduces the consistency algorithm and proposes a weighted average consistency algorithm considering the topological changes of the intelligent agent by combining the SOP with the characteristics of the feeder capacity of the distribution network. Then, the control model of the SOP cluster in the distribution network is established, and the control strategy for the SOP cluster based on the consistency algorithm is proposed. The strategy can realize the coordinated convergence of the SOP clusters in the global scope and improve the feeder balance of the distribution network. Finally, the example of an modified IEEE 33-bus distribution system verifies the effectiveness of the proposed control strategy.关键词：distribution network;soft open point (SOP);consensus algorithm;cluster control;distributed control2|1|0更新时间：2025-06-16
- 摘要：The power of distributed generator fluctuates and the distribution in tegration location is uneven. Its high proportion and large-scale integration to the low-voltage distribution network will lead to the problem of voltage overlimit at the end of the feeder, so how to make full use of the regulation capability of the distribution primary equipment to achieve rapid and flexible voltage regulation is the key to improve the accommodation ability of the distribution network to the distributed generators. This paper builds a flexible interconnected distribution network based on soft open point (SOP) and proposes a voltage regulation scheme based on coordinated active and reactive control of SOP, which has the best voltage regulation performance compared to existing reactive-power-based voltage regulation scheme of the energy storage system and active-power-based voltage regulation scheme of equipment, and can significantly increase the capacity of the distribution network to accommodate distributed generators. Since the active power transmission of SOP will affect the voltage of the interconnection line at the same time, the distribution network operation modes are divided according to the inherent voltage level at the end of each feeder, and the internal energy storage device of SOP is organically combined to propose a voltage regulation control strategy based on multi-modal coordination of SOP, which can simultaneously achieve the voltage overlimit mitigation at the end of interconnected distribution lines. This scheme can be flexibly extended to the multi-terminal flexible interconnection scenario. The feasibility and effectiveness of the proposed control strategy are verified by the built simulation model of the flexible interconnected distribution network.关键词：low-voltage distribution network;soft open point (SOP);flexible interconnection;distributed generator accommodation;voltage overlimit;multi-terminal coordinated voltage regulation2|6|0更新时间：2025-06-16
- 摘要：To solve the end-user low-voltage problem in the distribution system caused by increasing load, a flexible AC/DC switching distribution system is proposed, which can improve the voltage quality and ensure the system operation flexibility. The distribution scheme is designed to operate in DC distribution mode or AC distribution mode as required by installing converters and circuit breaker groups at both ends of the distribution line. First, in view of the power supply reliability of load during the switching process of AC/DC distribution modes, the converter control system and the operation sequence of circuit breakers are designed to realize the seamless transition of load voltage during the switching process. Secondly, in order to avoid the misoperation of circuit breaker groups under extreme conditions, two judgment logics based on event triggering and non-characteristic harmonic detection are proposed to ensure the stable operation of the system under extreme conditions. Finally, in view of the potential short-circuit fault during the wrong switching process, protection measures are designed at the control and hardware levels to avoid system equipment damage. MATLAB/Simulink simulation and experimental results verify the effectiveness of the switching distribution scheme and protection scheme.关键词：low-voltage;flexible DC;AC/DC distribution system;seamless switching;voltage quality;short-circuit protection2|1|0更新时间：2025-06-16
Special Topic onFlexible Interconnection and Morphological Evolution of Smart Distribution Networks
- 摘要：To cope with the challenges brought by the increasing penetration rate of distributed photovoltaic to power grid operation, a short-term power forecasting model of regional distributed photovoltaic station clusters based on affinity propagation clustering and long short-term time-series network (LSTNet) is proposed. First, the affinity propagation algorithm is employed to divide the regional distributed photovoltaic station clusters into different seasons. Pearson correlation coefficient is used to determine the strong correlation between meteorological factors of photovoltaic output, and the bilinear interpolation method is utilized to encrypt the meteorological data of the corresponding photovoltaic station cluster. Furthermore, LSTNet is used to mine the long-term and short-term temporal and spatial dependence of photovoltaic power and meteorological factor series, and linear components of autoregression are superimposed to realize the simultaneous forecasting of multiple photovoltaic stations in the group. Finally, the effectiveness of the proposed method is verified on the measured data set from the National Renewable Energy Laboratory (NREL) of USA. The experimental comparison shows that the forecasting model obtains high forecasting accuracy and robustness.关键词：distributed photovoltaic station cluster;short-term power forecasting;affinity propagation clustering;long short-term time-series network (LSTNet)2|1|0更新时间：2025-06-16
- 摘要：With the increasing proportion of renewable energy, it has gradually become a normal state for new power systems that renewable energy stations participate in dispatching response through power regulation. In order to reduce the steady-state response error to dispatching instructions, it is of great practical significance to study the active power allocation scheme in stations. First, the error function of each inverter in the photovoltaic (PV) power station is established based on the historical operation data; the temporal convolutional network is introduced to conduct deep learning based on the historical data; and the function mapping relationship between dispatching response error of the inverter, the active power output value, the target power value and multiple environmental factors is constructed. Then, based on the error function of each inverter, the active power allocation model is established to minimize the response error of the whole PV power station to the dispatching instruction. Moreover, in order to improve the solving speed of the model, a hierarchical sorting method of inverters is proposed to effectively reduce the number of optimization variables, and the adaptive particle swarm optimization algorithm is used to solve the model. Finally, simulation analysis and field experiments are carried out based on a PV power station in Gansu Province, China, which verify that the developed power allocation module based on the proposed model and algorithm effectively improves the steady-state response accuracy of the PV power station to dispatching instructions.关键词：photovoltaic (PV) power station;power allocation;temporal convolutional network;error function;particle swarm optimization algorithm2|1|0更新时间：2025-06-16
- 摘要：Aiming at the hydrogen producing system powered by renewable energy with uncertain downstream hydrogen load fluctuations, an adaptive power coordinated control strategy based on model predictive control is proposed. First, the basic structure and mathematical model of the hydrogen producing system powered by renewable energy are determined. Then, based on the model predicive control principle, the hydrogen load flow rate, the real maximum output power of the renewable energy sources, and the start-stop status of the electrolyzer are used as the uncertainty interference variables of the system, and the hydrogen producting power of each electrolyzer, the output power of the battery, and the abandoned power from the renewable energy are optimized in a rolling manner through the prediction model. Further, the intraday real-time tracking of the state of charge of the batteries, the pressure of the hydrogen storage tank, and the power grid load, as well as the optimal control of the start-stop status of the electrolyzer are realized. Finally, the effectiveness of the strategy is verified by case simulation, and the sensitivity analysis and robustness analysis are carried out for each parameter.关键词：hydrogen energy;renewable energy;power coordinated control;electrolyzer;model predictive control2|0|0更新时间：2025-06-16
- 摘要：When renewable energy participates in the primary frequency regulation, its dead band in frequency regulation is generally set to achieve a balance between avoiding frequent start-up of the unit and ensuring the frequency regulation performance. Unlike the fixed dead band determined by the equipment performance of traditional synchronous generator governors, the dead band in primary frequency regulation of renewable energy can be flexibly set within a larger range with diverse setting methods. However, the nonlinear influential mechanism of the dead band in the primary frequency regulation of renewable energy is still unclear. Especially in the scenario of the high proportion of renewable energy participating in the frequency regulation, the influence of the dead band on the frequency regulation performance cannot be analyzed. Hence, the system frequency response model considering the dead band in the primary frequency regulation of renewable energy is first analyzed. After analytically solving the frequency dynamic response expression, the influence of key parameters of primary frequency regulation of renewable energy on the important system frequency index is analyzed. And it is pointed out that the ordinary dead band in frequency regulation will weaken the primary frequency regulation capability. Then, in order to reduce the influence of the ordinary dead band on the frequency regulation performance, a coefficient correction strategy for the primary frequency regulation of renewable energy is proposed to improve the primary frequency regulation performance. Finally, the simulation results show that the accuracy of system frequency response model considering the dead band of renewable energy is higher, and the maximum frequency deviation can be reduced and the security of system frequency can be improved by using the proposed coefficient correction strategy for the primary frequency regulation.关键词：dead band;renewable energy;primary frequency regulation;frequency response model2|3|0更新时间：2025-06-16
- 摘要：Accurate assessment of the state of health (SOH) and remaining useful life (RUL) of lithium-ion batteries is extremely important for the safe and stable operation,and the low transparency of the internal operation mechanism of existing prediction models leads to poor assessment reliability. In this paper, an encoding and decoding model of bi-directional long short-term memory network based on dual-stage attention mechanism is proposed for SOH estimation and RUL prediction. The feature attention mechanism on the encoding side and the timing attention mechanism on the decoding side not only improve the model prediction accuracy by dynamically assigning the weights of feature and timing information, but also realize the model interpretability by visualizing the weights. Finally, experimental tests using National Aeronautics and Space Administration (NASA) and Center for Advanced Life Cycle Engineering (CALCE) public battery datasets verify the high accuracy and reliability of the proposed method in this paper.关键词：lithium-ion battery;long short-term memory network;Attention mechanism;state of health (SOH);remaining useful life (RUL)2|1|0更新时间：2025-06-16
- 摘要：A semi-distributed transactive energy market is proposed to overcome the defects of the current distributed and centralized markets for electricity transaction. First, a distributed market pricing mechanism is put forward based on the locational marginal prices of distribution networks. Then, a dynamic and static compound game model is proposed based on the multi-layer market-entity structure of distribution system operators, microgrid managers, and energy prosumers, and the existence and uniqueness of the equilibrium solution of this multi-layer compound game are proven. Finally, the rationality of the proposed pricing mechanism and the convergence condition of the equilibrium point solution algorithm based on the best response are verified by case studies.关键词：transactive energy market;semi-distributed transaction market;distribution network;locational marginal price;game2|0|0更新时间：2025-06-16
Basic Research
- 摘要：As an effective means for monitoring the dynamic change of the system, the dynamic state estimation is of great significance to the stable operation of the power system. However, time-varying non-Gaussian measurement noise and outliers often exist in the collected and transmitted data, which reduces the accuracy of traditional Kalman filter estimation methods based on the mean squared error criterion. To this end, the generalized kernel risk sensitive loss function is defined firstly, and it is introduced into the unscented Kalman filter framework for robust state estimation. Secondly, considering the different condition constraints of the synchronous generator and controller models, the constraints are introduced into the aforementioned estimation algorithm through the pseudo-measurement method to solve the problem that the estimated value is beyond the true value range and produces a large estimation deviation, so as to further improve the estimation accuracy. Finally, the simulation experiments are performed under different conditions to verify the effectiveness of the proposed algorithm in the New England 16-machine 68-bus network model关键词：dynamic state estimation;unscented Kalman filter;extend kernel risk sensitive loss function;pseudo-measurement method;constraint condition2|0|0更新时间：2025-06-16
- 摘要：The dead-zone effect leads to the power transmission characteristics and the operating range of zero-voltage switching of dual active bridge (DAB) converters deviating from the ideal model, so it is of great significance to establish a steady-state model considering the dead-zone effect for optimal control of DAB converters. In this paper, the circuit modes in the dead-zone and the transition process between the modes are analyzed in detail, and the dead-zone calculation model based on the state machine is proposed to realize the quantitative analysis of the incomplete zero-voltage switching phenomenon of SiC metal-oxide-semiconductor field-effect transistor (SiC MOSFET). A steady-state calculation model of the DAB converter based on the discrete-time series method is proposed, which reduces the modeling complexity and realizes the accurate calculation of dead-zone state under the control of triple phase shift. Benefiting from the calculation speed of the DAB steady-state calculation model, the optimal loss control of the 2 kV/150 kW DC transformer module is realized under all the working conditions by the parameters scanning optimization method. The 150 kW DC transformer module prototype is built based on 3.3 kV SiC devices, whose efficiency in the power range from 10% to 100% is higher than 98.0% with the optimal loss control strategy, and the peak efficiency reaches 99.3%.关键词：DC transformer;dual active bridge;dead-zone effect;loss optimization3|1|0更新时间：2025-06-16
- 摘要：Aiming at the problems of the low sensitivity of high resistance grounding fault protection at the far end of flexible DC ring network and serious interference of adjacent non-fault lines, an inverse-time protection method based on the current rising rate is proposed. By calculating the initial value of the fault current and its rising rate, the substantial difference between the fault line and the non-fault line is analyzed and compared. The sliding time window is used to make the current rising rate closest to the actual value, and has certain anti-interference ability. The inverse-time limit method is applied to ensure the reliable delay operation of the protection in case of high-resistance fault by setting a lower starting value. Setting an appropriate instantaneous operation value ensures that the fault can be quickly removed under the condition of low transition resistance. The inverse-time limit characteristic of the method eliminates the interference of non-fault lines and non-fault poles. Finally, the influence of the line distributed capacitance on the current rising rate is analyzed, and the corresponding correction method is proposed. A large number of simulation experiments show that the proposed method has high sensitivity, selectivity and reliability, and has strong ability to withstand transition resistance.关键词：high voltage direct current;flexible DC power grid;current rising rate;inverse-time protection;sliding time window2|0|0更新时间：2025-06-16
Application Research
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