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卷 48 ， 期 8 ， 2024
- 摘要：In the synchronous generator dominant power system, the mechanical rotational inertia is the dominant factor that determines the frequency dynamics, and is referred to as the system inertia. With the increasing penetration of renewable energy sources, the mechanical rotational inertia keeps declining, its leading role is weakened, and the existing cognition of the inertia of the power system is no longer applicable. The paper first reviews the physical nature of inertia as a measure of the ability to hinder the change of state of an object, and models the power system as an energy supply chain containing various energy forms and components at different scales. The inertia is generalized to mechanical rotational inertia, electrical inertia, thermal inertia and fluid inertia. In energy supply chain, the “inertia pair” composed of storage inertia and channel inertia on the same scale determines the dynamics of the scale. On the whole scale, multiple “inertia pairs” at different scales determine the sequential dynamic characteristics in the time domain and the cascading filtering characteristics in the frequency domain. Then, it is further revealed that the source of inertia demand is energy demand, storage units need to have enough instantaneous energy release to cope with the energy supplement lag caused by the transmission channel, and the entire energy supply chain needs to store enough local energy to support decentralized control. The inertia cognition of the power system from the energy perspective is helpful to evaluate the inertia demand of new power systems and provide theoretical guidance for the method design of active power control of new power systems.关键词：inertia;inertia pair;power system;synchronous generator;energy supply chain;multi-scale5|0|0更新时间：2025-06-16
- 摘要：Frequency stabilization is one of the most critical requirements for the operation of new power systems in the future. Energy endowment of China determines that coal-fired thermal power units are the most core and reliable primary frequency regulation resources. However, coal-fired thermal power has begun to show a trend of insufficient primary frequency regulation capability. In order to meet the current and long-term development needs, this paper reviews the challenges, research status and key problems faced by the primary frequency regulation of coal-fired thermal power. Firstly, four significant trends of primary frequency regulation of thermal power are summarized on the background of the development of new power systems, and the shortcomings of next frequency regulation in the operation of power grids and thermal power plants are analyzed. The key challenges of improving the ability of primary frequency regulation and fast and accurate simulation of frequency regulation are extracted. Secondly, from the two-way perspective of power grids and thermal power plant operation, the research status and existing problems of frequency regulation capability improvement and frequency regulation dynamic simulation are reviewed. Finally, combined with the above challenges and bottlenecks, the key technical problems of primary frequency regulation for new power systems in the future are prospected.关键词：new power system;thermal power unit;primary frequency regulation;modeling and simulation;dynamic modeling;cooperative optimization7|1|0更新时间：2025-06-16
- 摘要：The low-inertia operation risk is a major problem in the process of low-carbon transition of electric power, and it has become a pain point and a key bottleneck restricting the sustainable development of new power systems with renewable energy as the main body. Inertia requirement evaluation is the foundation for realizing risk perception and control of low-inertia systems. However, the current concepts related to inertia requirements are still unclear and do not fully consider the influence of fault types and the security defense lines of power grid frequency, resulting in unreasonable evaluation results. This paper studies the inertia requirement analysis of the power system from three aspects: basic concepts, characterization indexes, and evaluation methods. Firstly, considering the multi-stage response characteristics of inertia support power, the basic concept of inertia requirement for the power system is proposed, and quantitative characterization indexes for inertia requirements are presented from the perspective of energy and time sequence. Furthermore, considering the influence of fault types and frequency security control strategies, an inertia requirement evaluation method and grading mechanism applicable to the security defense lines of power grid frequency are constructed. Finally, taking a provincial power grid in China as a case, the proposed method is used to evaluate and analyze the system inertia requirements, verifying the rationality and effectiveness of the proposed method.关键词：inertia;inertia requirement;power system;frequency security;frequency control;evaluation method3|0|0更新时间：2025-06-16
- 摘要：To maximize the use of the support power of wind farms and avoid the resource wastage, it is necessary to quantitatively assess the frequency regulation capability of the wind farm. However, the assessment of frequency regulation capability of the wind farm lacks a clear definition and is difficult to be assessed, and the mechanism of the impact of operational parameters and boundary constraints on support capability is unclear. To address this, indicators across multiple time scales, energy forms, and assessment levels are defined, which can accurately quantify the assessment of frequency regulation capability. Based on the proposed assessment indicators, by analyzing the mechanism of how operational parameters of wind farm affect frequency regulation capability, it is revealed that the rotational speed is the main influencing factor under low wind speed and low load shedding conditions, while load and capacity are the main influencing factors under high wind speed and high load shedding conditions. Furthermore, a method based on a nonlinear programming model is proposed for the precise calculation of assessment indicators. Finally, a case study analysis of a single-machine aggregated wind farm under droop and load shedding control in a four-machine two-area system validates the rationality of the proposed assessment indicators and the accuracy of the assessment method, as well as the correctness of the conclusions of the key influencing factor analysis.关键词：wind farm;frequency regulation capability;droop control;overspeed load shedding;quantitative assessment method;influencing factor analysis5|1|0更新时间：2025-06-16
- 摘要：The power system with high-proportion renewable energy has low inertia level and high uncertainty. The system inertia level is closely related to the dynamic frequency response process. Considering the spatio-temporal correlation of frequency response process between nodes within the system, dynamically quantifying the spatio-temporal correlation of frequency between nodes provides an effective technique for real-time inertia estimation in the new power system. Firstly, a calculation method for inertia of synchronous units and renewable energy generator units is proposed. Secondly, the Granger causality test algorithm is used to dynamically analyze the frequency correlation of different nodes in the system, thereby establishing a time-varying spatio-temporal causal correlation set of system frequency. Furthermore, based on the swing equation of frequency response processes of various nodes in the system, a system inertia-frequency state space model is constructed. Subsequently, a novel method for estimating the inertia of power system with high-proportion renewable energy is proposed using the unscented Kalman filter and fixed-lag smoother. Finally, the proposed method is validated using an improved IEEE 39-node system, demonstrating its effectiveness and applicability. Results show that the proposed method ensures consistent inertia estimation performance in different renewable energy penetration rates and frequency disturbance scenarios, which has engineering application potential.关键词：inertia estimation;power system;renewable energy;causal correlation;state space;frequency response;filtering-smoothing two-stage estimation3|1|0更新时间：2025-06-16
- 摘要：The current quantification methods of power system frequency strength usually assume that the voltage magnitude at each node is constant. However, during the process of frequency disturbance, the voltage at each node is not constant and may affect the system frequency through various pathways such as influencing loads. Therefore, the assumption of constant voltage may lead to the conclusion with the inaccurate quantification results, or even erroneous conclusions. Therefore, a quantification method of power system frequency strength considering voltage dynamics is proposed. First, a frequency response model for the system that considers voltage dynamics is established, in which the influence of voltage dynamics on the system frequency is characterized by a global coupling term, revealing the interaction paths between voltage and frequency. Based on this, the specific effects of various devices and loads that consider voltage dynamics on the system frequency are analyzed, including the grid-forming converters employing hybrid synchronization control, grid-following converters with additional frequency or voltage outer loops, and constant impedance-constant current-constant power (ZIP) static loads and asynchronous motor loads with distinctive voltage characteristics. Next, by partitioning and decoupling the voltage coupling term and performing unified and simplified modeling, the frequency support capability of each zone in the system as well as the overall frequency strength is quantitatively analyzed. Finally, the effectiveness of the proposed method for quantifying frequency strength is validated through simulations.关键词：frequency strength;quantification method;common-mode frequency;voltage-frequency dynamic coupling;unified structure model;frequency stability3|0|0更新时间：2025-06-16
- 摘要：Constructing the equivalent inertia model of wind turbines is a key basis for quantitative analysis and optimal control of wind farm transient support, especially in the scenario of high-proportion renewable energy power grid with reduced of inertia and degraded frequency characteristics. However, the existing model research often focuses on several links in combination with the analysis goal, but does not establish a complete model of the whole links, and does not reveal the relationship between the reduced-order model and the calculation accuracy at different time scales. Firstly, taking direct-drive wind turbine as the object, based on the comparison of the equivalent inertia of wind power and synchronous machine in mechanism and implementation mode, the dynamic influence of mechanical, control and electrical links on the equivalent inertia of wind power is analyzed, and a full-order frequency response model of the wind turbine is established. Then, based on the singular perturbation theory, the equivalent inertia reduction model considering the dynamics of different time scales is derived, and the relationship between the error and the time scale of the model is derived by applying the Vasilyeva theory. Finally, an electromagnetic transient simulation case is used to verify the effectiveness of the full-order mechanism model and the accuracy of different reduced-order models.关键词：wind turbine;equivalent inertia;multi-time-scale;singular perturbation theory;reduced-order model;Vasilyeva theory3|0|0更新时间：2025-06-16
- 摘要：Establishing a wind turbine model that is consistent with the actual frequency response characteristics is the prerequisite and foundation for analyzing the frequency safety and stability of power systems with high proportion of renewable energy. At present, there is little research on frequency simulation modeling of wind turbines, and intelligent algorithms are mostly used to identify control parameters based on the known structure of frequency regulation controllers, lacking universality and engineering practicality. First, a universal electromagnetic transient model that can cover mainstream models of full-power wind turbines in China is established. On this basis, aiming at the feasible frequency regulation control strategy for wind turbines,a comprehensive frequency regulation control system covering all elements is constructed including overspeed de-load control, pitch angle control, virtual inertia control, and droop control. Then, based on the correspondence between the frequency response characteristics of the unit and the frequency control strategy/parameters, a practical identification method is proposed, which adopts the morphology of the measured frequency response characteristic curves of the unit to identify the structure of the frequency regulation controller, and uses the eigenvalues of the measured frequency response characteristic curves of the unit to identify the parameters for the frequency regulation controller. Finally, the effectiveness of the proposed identification method for the frequency regulation controller is demonstrated by comparing the electromagnetic transient model of the unit established by the proposed practical identification method for the frequency regulation controller with the “black box” model of manufacturers and the frequency regulation response characteristics of on-site tests.关键词：full-power wind turbine;electromagnetic transient modeling;frequency regulation;control structure identification;control parameter identification4|0|0更新时间：2025-06-16
- 摘要：The renewable energy inertia response is gradually becoming a new requirement of grid connection regulations and a new product in the auxiliary service market. The testing of inertia response performance and the evaluation of inertia time constant can help meet the corresponding requirements of grid connection regulations and clear the economic benefits of auxiliary service products. However,the evaluation method for the inertia time constant is not involved in the test standard of inertia response performance. Therefore, this paper proposes an evaluation method for the inertia time constant of renewable energy based on delay compensation. Firstly, the rate of change of frequency and the frequency offset that may exist in the system are generated based on the power grid simulator, and the time nodes for full dynamic process analysis are reasonably selected according to the key evaluation indicators of inertia to improve the analysis accuracy. Secondly, the active power-frequency delay link in the inertia response process is calculated and compensated to eliminate the evaluation error caused by the delay. Finally, a continuous inertia evaluation algorithm based on the differential synchronous machine swing equation is designed to accurately evaluate the inertia of renewable energy. A renewable energy inertia evaluation experimental environment is built on the RT-LAB semi-physical platform to verify the accuracy of the evaluation results with the proposed algorithm in different delay scenarios.关键词：renewable energy;inertia response;evaluation method;delay compensation5|1|0更新时间：2025-06-16
- 摘要：Model analysis based frequency response analysis after the power disturbance is important for the security assessment and emergency control of power systems. When the power grid fault occurs, the magnitude drop of the grid-connected voltage of direct-drive wind turbine (DDWT) causes the transient response of the controller . Meanwhile, the sudden change in the voltage phase triggers the transient response of the phase-locked loop (PLL), which generates the power control error through the converter control conduction. And the power control error may lead to a large deviation in the existing frequency characteristic analysis targeting the sudden load change scenarios. Therefore, a quantification method for the phase-locked deviation of DDWT under the power grid fault is proposed. The conduction paths of phase-locked deviation through converter control of DDWT are analyzed. Also, the mechanism and calculation method for the power control error of DDWT caused by the transient response of the PLL are proposed. The frequency response model of the power system with DDWT under the power grid fault is established, and the calculation method for the rate of change of frequency and the maximum frequency deviation under the influence of the transient response of the PLL is proposed. The frequency dynamic response characteristics of the power system considering the power control error of DDWT under the power grid fault are analyzed. Finally, the effectiveness of the proposed method is verified through case studies.关键词：direct-drive wind turbine (DDWT);frequency dynamic response;power grid fault;phase-locked loop (PLL);transient response;power control5|2|0更新时间：2025-06-16
- 摘要：The high proportion of power electronic equipment connected to the grid changes the frequency response characteristics of the power system, resulting in significant frequency dynamic heterogeneity of each node, leading to problems such as low system inertia and weak frequency stability. The virtual inertia provided by the power electronic equipment is one of the effective ways to improve frequency stability. In order to improve the frequency response performance of the new power system dominated by renewable energy sources, a configuration optimization method of virtual inertia considering the spatial distribution difference of the system frequency response is proposed. Firstly, based on the frequency divider theory, a system frequency response model reflecting the difference characteristics of the spatial distribution of frequency is constructed. Secondly, in order to quantitatively describe the influence of inertia distribution on nodal frequency response, the deviation indices of nodal inertia and nodal kinetic energy are proposed. Then, considering the spatial distribution characteristics of frequency, aiming at optimizing the energy imbalance of each node after the disturbance, a configuration optimization model of virtual inertia is established. Finally, the validity of the nodal inertia index and the improvement effect of the proposed virtual inertia configuration method on the nodal frequency stability of the system are verified by simulations.关键词：virtual inertia;configuration optimization;frequency stability;spatial distribution;nodal inertia4|0|0更新时间：2025-06-16
- 摘要：The large-scale integration of renewable energy significantly reduces the inertia of the AC system, and the participation of grid-connected converters in the frequency control has become an important means to improve frequency stability. Based on the transfer function model, the dynamic inertia of grid-connected converter with additional frequency control is derived. It is observed that the dynamic inertia exhibits time-varying characteristics due to the combined influence of inertia design parameters and other control elements. However, simplifying it to a constant similar to the rotational inertia of synchronous generators will lead to analysis errors. Therefore, for the two mainstream grid-connected converter control methods of constant DC voltage control and constant power control, the quantitative evaluation method of dynamic inertia for grid-connected converter with additional frequency control is proposed. The influence mechanisms of different factors such as control parameters, operation conditions, and system characteristics on inertia are analyzed. It is concluded that the outer loop of active power control will significantly change the original design inertia, and it is necessary to focus on the inertia deviation caused by its control parameters. Finally, based on the time-domain simulation model built in Simulink, the correctness and effectiveness of the transfer function model and quantitative evaluation method of inertia are verified.关键词：renewable energy;grid-connected converter;frequency control;inertia;quantitative evaluation4|1|0更新时间：2025-06-16
- 摘要：To improve the frequency stability of power systems after being subjected to a major disturbance, the wind turbine (WT) is required for the ability of active frequency support. However, the existing WT frequency support control is mostly a direct imitation of the inertia and frequency regulation characteristics of synchronous generators, which limits the control flexibility of the WT. Given this deficiency, originating from the core demand for improving the frequency nadir, an optimal frequency support control of the WT is proposed, which considers the primary frequency regulation characteristics of the system. First, with the control objective of maximizing the frequency nadir, the general form of the optimal system frequency trajectory is proposed and strictly proven. Then, the quantitative expression of the energy recovery characteristics of the WT is constructed, and the optimal frequency support control of the WT is deduced reversely by combining the system frequency response model. Finally, the simulation and comparison results demonstrate that the proposed method significantly improves the frequency nadir by cooperating with the original frequency regulation characteristics of the system, and shows better robustness to different operation conditions and power disturbance levels.关键词：frequency stability;wind turbine (WT);frequency trajectory;system frequency response;frequency nadir4|1|0更新时间：2025-06-16
- 摘要：In the power system with high-penetration renewable energy, a single short-circuit fault easily causes large-scale renewable energy into the low voltage ride-through condition, impacting the system with the high-capacity short-time power. This may result in the transient maximum frequency deviation exceeding the low-frequency load shedding threshold and lead to load losses. Including electrochemical energy storage in the emergency control triggered by the power grid fault events is an effective means to address issues of transient frequency over-limitation under the short-time power impact. To achieve this, this paper constructs a system frequency response analysis model considering the emergency power control using energy storage under the short-time power impact of renewable energy. Then, the impact of release power and duration of the energy storage on the frequency characteristics of the system under short-time power disturbances is analyzed and summarized. Based on this theoretical foundation and considering both transient low-frequency and high-frequency safety under the short-time power impact, this paper proposes a method for calculating the minimum emergency release energy of the energy storage to avoid low-frequency load shedding. The power and duration emergency control strategies using energy storage that meet the requirements are provided. Finally, the accuracy of the analysis results is validated in the IEEE 10-machine 39-bus system.关键词：emergency control;frequency nadir;electrochemical energy storage;low voltage ride-through (LVRT);short-time power disturbance4|0|0更新时间：2025-06-16
- 摘要：Aiming at the problems of insufficient system frequency regulation capability and frequency secondary dip caused by frequency regulation energy overdraft brought about by large-scale wind power integration, a frequency support control strategy with dynamic and differentiated timing synergy for multiple wind farms is proposed. Firstly, the principle of wind power frequency regulation under integrated inertia control is elaborated, and the kinetic energy change process of wind farm groups is analyzed based on the theory of energy conservation in the frequency response stage, which reveals the influence mechanism of frequency regulation timing for multiple wind farms on the effect of frequency regulation. Furthermore, the risk of secondary frequency dip that may be triggered by the simultaneous frequency regulation of multiple wind farm groups is considered, and the frequency regulation timing and task division of wind farm groups are reverse-designed from the perspective of field-station interaction. The input sequence is dynamically adjusted according to the real-time frequency regulation capability of wind power to ensure the safety demand of inertia at the initial moment, and to improve the frequency minimum point and suppress the risk of serious secondary dip caused by the withdrawal of frequency regulation. Finally, the proposed control strategy is simulated and analyzed by the 3-machine 9-bus test system and a case of a real power grid, and the validity and practicability of the proposed strategy are validated by the results.关键词：multiple wind farms;dynamic and differentiated timing;inertia;cooperative control;frequency regulation;secondary dip4|2|0更新时间：2025-06-16
Control Theory and Application of Inertia-Power-Frequency in New Power System
- 摘要：Current research on microgrid (MG) energy management based on federated deep reinforcement learning has not considered the problem of multiple types of energy conversion and power trading among MGs, while frequent interaction of model parameters leads to large communication latency. Based on this, an MC including multiple types of energies such as wind, solar, electricity, and gas is studied. An energy management model that allows for inter-MG electricity trading and intra-MG energy conversion is constructed. A federated dueling deep Q-network (Dueling DQN) learning algorithm based on the sine cosine algorithm (SCA) is proposed, and a multi-microgrid energy management and optimization strategy considering energy conversion and trading is designed based on the proposed algorithm. The simulation results show that the proposed energy management strategy can achieve higher rewards to maximize microgrid economic benefits while protecting data privacy and reducing communication latency.关键词：microgrid (MG);federated learning;dueling deep Q-network;sine cosine algorithm;energy management4|1|0更新时间：2025-06-16
- 摘要：Shared energy storage addresses the challenges of high cost and low utilization through the reuse of energy storage resources. Furthermore, rapidly developing demand-side resources have the potential to be applied in the shared energy storage, but the issue of their uncertainty requires urgent resolution. A virtual energy storage model for electric vehicles and thermal control loads is introduced, integrated with the physical energy storage, this model is employed to construct a comprehensive shared energy storage model that takes uncertainties into consideration, along with the corresponding optimization algorithms to determine the optimal capacity configuration of the physical energy storage. Shared energy storage operators optimize the configuration of multiple types of energy storages based on user demands and design the satisfaction compensation for virtual energy storage holders to safeguard their user experience and economic interests. Additionally, the Wasserstein distance is used to characterize the uncertainty associated with electric vehicles and temperature-controlled loads, in conjunction with the utilization of a risk-value-based distributionally robust chance-constrained algorithm for optimization. The results of the case study demonstrate that the utilization of the generalized shared energy storage model and the distributionally robust optimization algorithm allow for a comprehensive consideration of uncertainty, leading to a substantial reduction in energy consumption costs for users and energy storage configuration costs for operators.关键词：shared energy storage;electric vehicle;thermal control load;distributionally robust optimization;virtual energy storage4|1|0更新时间：2025-06-16
- 摘要：Power electronic transformers (PETs) are key devices for power conversion in flexible DC distribution networks. Due to the limitation of simulation resources, the scales of existing electromagnetic transient (EMT) real-time simulations for PETs are small, which can not meet the demand of hardware-in-loop test and fast simulation for the large-capacity system. This paper proposes a real-time low-consumption equivalent modeling algorithm for dual active bridge (DAB) based PETs. Firstly, the binary input admittance characteristics of the high-frequency link port decoupling model (HFL-PDM) of the DAB are deeply explored and elaborated from the perspective of numerical analysis and physical significance. Based on this, the HFL-PDM of the PET with the N+1 characteristics is constructed. Secondly, a low-memory-occupancy EMT solution scheme using limited storage, a compact low-latency simulation framework, and a hardware implementation scheme using packet-based parallel pipeline computing are designed, which reduce the demand for the storage memory, the computing clock, and the hardware resource during the real-time simulation. Finally, the real-time low-consumption equivalent simulation model at a time step of 250 ns is developed based on Verilog language in RT-LAB. The simulation accuracy and resource utilization of the established model are tested.关键词：electromagnetic transient real-time simulation;power electronic transformer (PET);dual active bridge (DAB);high-frequency link port decoupling;low resource consumption;RT-LAB4|2|0更新时间：2025-06-16
- 摘要：The large-scale development of the electric vehicles (EVs) will increase the pressure of peak and frequency regulation of power grids. The market-based operation of the battery swapping stations (BSSs) can effectively stimulate the BSSs to make full use of the EV swapping demand and the battery flexibility resources of BSSs, alleviating the pressure of peak and frequency regulation of power grids. Therefore, the cooperative bidding strategy and a two-stage optimization model for BSS participating in the electricity energy market and the frequency regulation market are proposed. In the first stage, the battery swapping price is set according to the demand of the frequency regulation market, and EVs are guided to adjust the battery swapping demand. The number and time sequence of redundant batteries are optimized to be consistent with the trend of frequency regulation demand, and the frequency regulation service revenues of BSS are improved. In the second stage, the market bidding strategy is formulated considering the demand response of BSS and the market peak regulation and frequency regulation demands. The proposed biding strategy can reduce the charging costs of BSS and improve the revenues of the frequency regulation service, helping the power grid to fulfill the peak and frequency regulation, while meeting the EV battery swapping demand preferentially. Case simulation results verify the effectiveness of the proposed bidding strategy.关键词：electric vehicle (EV);battery swapping station (BSS);electricity market;frequency regulation;ancillary service;bidding strategy7|0|0更新时间：2025-06-16
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