Characteristics Of Power System Research Articles

A Review of the Research on the Wide-Band Oscillation Analysis and Suppression of Renewable Energy Grid-Connected Systems

With the continuous expansion of the scale of power generated by grid-connected renewable energy, the form and operation characteristics of power grids have undergone significant changes, and the power electronic characteristics of power systems are prominent, resulting in the frequent occurrence of wide-band oscillation problems when renewable energy power generation equipment is connected to a power grid. Oscillation has the characteristics of nonlinearity and has an oscillation frequency ranging from a few hertz to several thousand hertz or more, which seriously threatens the stable operation of power grids. This paper summarizes the wide-band oscillation events that occur worldwide under the background of renewable energy access to power grids, classifies the wide-band oscillation events according to the distribution of oscillation frequency bands, and sorts out the characteristics of various oscillations. From the perspectives of the source side and network side, the existing oscillation suppression measures are classified and prospected.

Exploration of carbon reduction in new municipal power systems

In response to China’s goal of “carbon peak and carbon neutrality”, a large number of new energy sources are connected to the power grid, and Chinese cities are also accelerating the construction of new power systems led by new energy. Taking Lishui City as an example, this paper constructs a low-carbon emission reduction evaluation system to evaluate the carbon reduction effectiveness of the new power system. This paper first introduces the basic technical characteristics of the new power system, and introduces in detail the key technologies involved in the construction of the new power system in Lishui. Then, the projects implemented by Lishui City in promoting the new power system and the current achievements were briefly summarized. After that, a new electric carbon traceability model of Lishui power system was constructed to carry out carbon traceability and carbon tracking for the municipal power grid. Finally, a low-carbon emission reduction evaluation system was constructed, and a number of evaluation indicators were proposed to evaluate the carbon reduction effectiveness of Lishui’s new power system, and the zero-carbon evaluation index was calculated through the historical data of Lishui, and the results showed that the new power system in Lishui City achieved remarkable results in carbon reduction and emission reduction.

Analysis of Factors Affecting Sub-Synchronous Oscillation in Doubly-Fed Wind Power Grid-Connected System Based on Impedance Sensitivity and Research on Suppression Strategy

Aiming at the matter of sub-synchronous oscillation (SSO) of the doubly-fed induction generator (DFIG) series compensation capacitors grid connection, a SSO suppression strategy based on adding damping controllers in rotor-side converter (RSC) is put forwarded. Considering the control parameters of power and current control loops of RSC, the equivalent impedance model of DFIG series compensation grid connection (SCGC) is established, and then combined with the equivalent RLC resonant circuit of the system, the mechanism and factors of SSO are analyzed by impedance method. Calculating the impedance sensitivity of the system impedance to parameters by sensitivity analysis method, so as to identify the leading factor affecting the SSO characteristics of wind power system. Combined with the stability criterion of system impedance characteristics, the parameters are adjusted to meliorate system stability. Based on the leading factor affecting the SSO and the mechanism of the SSO, the damping controllers are added in the RSC to supply positive damping for the system to eliminate the negative damping brought by the RSC and rotor resistance, thus suppressing the SSO of the system. The validity of the put forwarded suppression strategy is proved through PSCAD/EMTDC simulation.

Frequency Control and Optimal Operation of Low-Inertia Power Systems With HVDC and Renewable Energy: A Review

With the integration of large-scale renewable energy sources (RES) and high voltage direct current (HVDC) based inter-regional transmission, modern power systems are facing low-inertia issues and poor frequency regulation capabilities. This paper conducts a comprehensive review on frequency control and optimal operation methods in this context. First, the frequency characteristic of a low-inertia power system is analyzed covering the whole frequency response process. Secondly, the impacts of RES and HVDC integration on system inertia and frequency performance are studied, and the system frequency characteristics considering RES and HVDC are analyzed. Then, the frequency response modes of various frequency regulation resources are compared from the perspective of “source-grid-load-storage”, including their basic control principles and frequency control strategies. Further, from the operation dispatch perspective, the frequency security-constrained power system optimal operation methods are reviewed. Finally, future research trends in this area are discussed.

Inertial issues in renewable energy integrated systems and virtual inertia techniques

The global proliferation of renewable energy drastically altered the characteristics of power systems. Integration of clean energy sources reduces the inherent rotational inertia, making the system precarious and susceptible to various disturbances. The major challenges encountered are fast frequency fluctuations, voltage fluctuations, high rate of change of frequency (RoCoF), and frequency nadir. In order to address and adapt to a future low-inertia scenario, it is crucial to understand the effect of inertia on various parameters. This paper introduces a comprehensive review of the fundamental aspects of inertia and challenges that arise due to the reduction in inertia. Researchers have tackled this issue by employing various virtual inertia (VI) emulation techniques, which also have been extensively reviewed in the literature along with their merits, limitations, and recent developments. The impact of RES penetration on system dynamics is analyzed by simulating an IEEE-9 bus system with renewable energy source (RES) in MATLAB/Simulink. Furthermore, a three-phase fault is also introduced, to emphasize the effect of reduced inertia by observing the rotor angle and frequency deviation. The results validate that RES integration and fault location are observed to have a significant impact on stability parameters, making them extremely unstable.

Life Cycle Assessment of Energy Storage Technologies for New Power Systems under Dual‐Carbon Target: A Review

Aiming at the grid security problem such as grid frequency, voltage, and power quality fluctuation caused by the large‐scale grid‐connected intermittent new energy, this article investigates the life cycle assessment of energy storage technologies based on the technical characteristics and performance indicators. First, the new power system under dual‐carbon target is reviewed, which is compared with the traditional power system from the generation side, grid side, and user side. Based on the power characteristics of the new power system, the energy storage mechanism and energy storage characteristics of mechanical energy storage, electrochemical energy storage, chemical energy storage, electromagnetic energy storage, and thermal energy storage are described. Then, compared with the existing research strategies, a comprehensive life cycle assessment of energy storage technologies is carried out from four dimensions: technical performance, economic cost, safety assessment, and environmental impact. Moreover, the suitable scenarios and application functions of various energy storage technologies on the power generation side, grid side, and user side are compared and analyzed from the working principle, key technologies, advantages and disadvantages, and technical difficulties of energy storage technologies. Finally, combined with the energy storage technologies in the electricity market, four profit models are analyzed.

Unraveling fundamental properties of power system resilience curves using unsupervised machine learning

Power system is vital to modern societies, while it is susceptible to hazard events. Thus, analyzing resilience characteristics of power system is important. The standard model of infrastructure resilience, the resilience triangle, has been the primary way of characterizing and quantifying resilience in infrastructure systems for more than two decades. However, the theoretical model provides a one-size-fits-all framework for all infrastructure systems and specifies general characteristics of resilience curves (e.g., residual performance and duration of recovery). Little empirical work has been done to delineate infrastructure resilience curve archetypes and their fundamental properties based on observational data. Most of the existing studies examine the characteristics of infrastructure resilience curves based on analytical models constructed upon simulated system performance. There is a dire dearth of empirical studies in the field, which hindered our ability to fully understand and predict resilience characteristics in infrastructure systems. To address this gap, this study examined more than two hundred power-grid resilience curves related to power outages in three major extreme weather events in the United States. Through the use of unsupervised machine learning, we examined different curve archetypes, as well as the fundamental properties of each resilience curve archetype. The results show two primary archetypes for power grid resilience curves, triangular curves, and trapezoidal curves. Triangular curves characterize resilience behavior based on three fundamental properties: 1. critical functionality threshold, 2. critical functionality recovery rate, and 3. recovery pivot point. Trapezoidal archetypes explain resilience curves based on 1. duration of sustained function loss and 2. constant recovery rate. The longer the duration of sustained function loss, the slower the constant rate of recovery. The findings of this study provide novel perspectives enabling better understanding and prediction of resilience performance of power system infrastructure in extreme weather events.

APT Attack Detection of a New Power System based on DPI-transformer

Introduction: In recent years, the frequent occurrence of network security attacks in the power field has brought huge risks to the production, transmission, and supply of power systems, and Advanced Persistent Threat (APT) is a covert advanced network security attack, which has become one of the network security risks that cannot be ignored in the construction of new power systems. Objective: This study aims to resist the increasing risk of APT attacks in the construction of new power systems, this paper proposes an attack detection model based on Deep Packet Inspection (DPI) and Transformer. Methods: Firstly, we extracted 606 traffic characteristics from the original traffic data through the extended CIC Flowmeter and used them all to train the Transformer network. Then, we used the DPI-Transformer model and traffic labels to perform feature analysis on the traffic data and finally obtained the APT-Score. If the APT-Score is greater than the threshold, the alarm module is triggered. Results: By analyzing the headers and payloads of the network traffic in the APT-2020 dataset, the experimental results show that the detection accuracy of APT attacks by the DPI-Transformer detection model is significantly higher than that of the current mainstream APT attack detection algorithms. Conclusion: Combined with the characteristics of the new power system and APT attacks, this paper proposes an attack detection model DPI-Transformer, which proves that the model has greatly improved the detection accuracy.

Improving the operational characteristics of electrical power systems of marine vessels

THE PURPOSE. Consider the experience of use and conduct a study of the electrical power systems of sea vessels to determine the possibility of improving their operational characteristics. Obtain data on noise and vibration levels of electrical power systems elements.METHODS. The article analyzes the electrical power systems of the Azipod type steering columns of the Baltika icebreaker. The issue of regulating the rotation speed of propulsion electric motors using frequency control based on a DC link and parallel-connected inverter units on IGBT transistors is considered. Motor control on the frequency converter side can be based on direct torque control, scalar and vector control. There are control modes for reducing and increasing voltage.RESULTS. Typical dependences of structure-borne noise levels of main engines and generators are given. Measurements were taken at various frequencies of engine sound power levels, exhaust gases and vibration of generator sets. Experimental oscillograms of studies of the parallel operation of diesel generator sets were obtained, on which power exchange and common-mode oscillations were recorded.CONCLUSION. It is proposed to use multiphase AC electric motors to improve performance characteristics, including reducing noise and vibration. The existing experience in using frequency converters based on a rectifier section and inverter units in electric rowing installations with Azipod propellers makes it possible to implement such a change. To do this, it is necessary to parallelize the inverters that supply each of the three phases and provide the appropriate phase shifts.

Research on improving low-frequency oscillation characteristics of wind power grid-connected power system with doubly-fed wind generator based on virtual impedance power system stabilizer

Research on improving low-frequency oscillation characteristics of wind power grid-connected power system with doubly-fed wind generator based on virtual impedance power system stabilizer

МОДЕЛЬ ЗБЕРЕЖЕННЯ ПРАЦЕЗДАТНОСТІ ЕЛЕКТРОЕНЕРГЕТИЧНОЇ СИСТЕМИ ЗА УМОВИ ЇЇ НЕБАЛАНСУ

Abstract. The dynamic frequency characteristic of the electric power system in the case of imbalance as a result of a change in generating capacity and the absence of a reserve is constructed. A simulation model of the electric power system has been developed based on object-oriented analysis, which makes it possible to analyze the operation and reaction of the electric power system as a result of the impact of disturbances to ensure the possibility of system operability under certified conditions. As a simulation model, an information model and diagrams of transitions to the states of objects were made, reflecting the interaction of objects, which are an abstract reflection of real electrical installations of the power system. Keywords: power system, operability, frequency regulation, disturbances, imbalance, simulation model, object-oriented analysis.

Cost-efficiency based residential power scheduling considering distributed generation and energy storage

The permeation of renewable energy into smart house is a key characteristic of the future power system that brings a significant challenge to the peak load management in the power sector. In this paper, we propose cost-efficiency based residential power scheduling scheme considering distributed generation and energy storage. In which, a cost-efficiency model designed by the ratio of consumption benefit to its cost is introduced to capture the residential users' electricity consumption behaviors and reflect their economic efficiency. A discomfort cost is constructed to represent the losses associated with power scheduling when facing the incentives given by the smart grid. Specially, not only residential load consumption utility, but also that of the renewable energy generation and energy storage devices are applied to compose the consumption benefit，and an energy storage model to be established to plan the charging and discharging of energy storage batteries. Day-Ahead Bidding Price and Real-time consumption management models are introduced to test the performance of the proposed scheduling scheme. Simulation results demonstrate that the proposed method increases the residential consumer's daily cost efficiency by 1.5834, and reduces its daily electricity bill by 38.43 % and that about 36.86 % of energy is saved in the smart grid while the proposed scheduling strategy for energy consumption can effectively smooth the load curve in smart grid.

Study on operation characteristics of a compact megawatt nuclear power system

A novel compact megawatt nuclear power system with a heat pipe reactor coupled supercritical CO2 Brayton cycle has been proposed. To investigate its transient operational characteristics, this paper conducts open-loop dynamic response analyses and designs control systems for it under the load-following mode and the reactor-following mode. Subsequently, transient operational characteristics analysis of the system under different operating conditions is conducted. The results indicate that under load-following conditions, the rotation speed is highly sensitive to disturbances. The system can achieve a load variation of 0–100 % at a rate of 6 %FP/min, while at higher rates, there may be a decrease in speed due to exceeding the regulating range of the bypass valve. It can also accommodate continuous stepped load variations and operate at any desired load level. Under load rejection conditions, the system experiences significant fluctuations, but it can still maintain a new steady state and keep parameters within a safe range. In reactor-following mode, the system can achieve rapid power changes.

Advantage of battery energy storage systems for assisting hydropower units to suppress the frequency fluctuations caused by wind power variations

The integration of renewable energy sources into power grids has led to new challenges for maintaining the frequency stability of power systems. Hydropower has traditionally played a key role in frequency regulation due to its flexibility in output power. However, the water hammer effect can lead to the phenomenon of inverse regulation, which can degrade the transient characteristics of power systems, particularly in hydropower-dominant systems, such as the Southwest China Power Grid. On the other hand, battery energy storage systems (BESSs) are well-suited for frequency regulation due to their fast response speed, high response accuracy, and flexible control capabilities. Hence, it is a meaningful topic to evaluate the advantage of integrated battery energy storage systems for assisting hydropower units (HPUs) in frequency regulation. First, the frequency dynamic response model of power system with BESSs assisting HPUs to participate in frequency regulation is established. Then, a two-part strategy is presented. The primary frequency regulation strategy for BESSs uses droop control with a variable regulation coefficient and the secondary frequency regulation strategy considers the costs associated with both HPUs and BESSs. Last, a performance assessment is carried out based on the management rules for auxiliary services of power plants in China and the USA. The results of this study demonstrate that the incorporation of the BESS into the HPU can significantly improve the regulating performance, and can provide important economic and technical benefits for the power system. Specifically, the maximum ratio of HPU with BESS to conventional HPU is 33.13 %, 33.85 %, 7.60 % and 41.52 % for the different indicators (difference, delay, distance, and cost). Notably, the implementation of BESS in the HPU not only contributes to the stability of the power system, but it also provides considerable economic benefits by achieving higher evaluations for auxiliary services in the power market. These findings are critical in supporting the transformation and development of conventional HPUs under large-scale new energy grid connection conditions.

Research on the capacity cost allocation and the electricity capacity price optimization method for a power system based on the BARY‐GA algorithm

AbstractUnder the new power system, a high proportion of new energy is widely connected to the power grid, and it is necessary to increase investment in centralized and distributed energy storage, flexible resource regulation, and transmission and distribution grids, resulting in an increase in power system costs. The current electricity capacity price does not reflect the economic value of the added system adequately, and flexible capacity is needed to ensure the safety of the power grid under the new power system. In the context of the transformation of the new power system and investment function, it is increasingly difficult to recover the costs according to the traditional electricity price. It is necessary to establish a coordinated development mechanism for the electricity capacity price and the electricity price that recovers the fixed costs according to the investment function to ensure a reasonable return on investment in flexible resources and to provide effective investment signals. Therefore, this work first studied and proposed a mechanism for the formation of capacity and electricity prices based on the proportion of allowed income and fixed costs at different voltage levels and calculates the level of electricity capacity (demand) prices and electricity consumption prices. Then, using the BARY curve, genetic algorithm, and clustering of user load rates, a collaborative mechanism between the electricity capacity price and the electricity price was designed. With the goal of optimizing the electricity capacity price and considering constraints such as the flexibility and reliability of the new power system, the ratio of the capacity cost allocated to the electricity capacity price by voltage level users to the capacity cost allocated to the electricity price was calculated, and the optimal combination of electricity capacity price and electricity price for different load‐rate intervals was determined. Finally, the effectiveness of the model was verified through numerical simulations. On the basis of the investment characteristics of the new power system, suggestions for a capacity pricing mechanism under the new power system were proposed from the perspectives of transfer capacity function, transfer electricity function, grid reliability, and environmental and social benefits.

Research on the optimal model for the evaluation of new power system investment projects based on the cloud model–DS evidence theory–TOPSIS method

AbstractConsidering that the traditional investment project evaluation system can no longer fully adapt to the characteristics of the new power system under the investment environment of the new power system, this study constructed a new power system investment project evaluation and optimization method based on the combination of the cloud model, evidence theory and the TOPSIS method. First, 16 evaluation indexes were considered based on four dimensions, namely green and low‐carbon, safe and reliable, flexible and intelligent, and economical and efficient, and the optimal evaluation index system of new power system investment projects was designed. Second, the normal cloud model was used to obtain the evaluation membership distribution of each index and turn it into evidence. Considering the conflicts between indicators and the combinational contradictions of traditional evidence theories, an improved DS evidence theory based on a game weight coefficient discount to reduce conflicting evidence was used to fuse the membership information of multiple indicators. On the basis of the evaluation results of each scheme, this study used the TOPSIS method to sort the advantages and disadvantages of each scheme. Finally, the project of planning and putting this model into operation in the 14th Five‐Year project database of a power grid enterprise was selected as an example to carry out empirical analysis, and the effectiveness and superiority of the proposed model were verified.

Optimized Multi Agent System for Stability Enhancement of Inter Connected Power System

Due to the rising use of renewable energy sources and the use of contemporary power electronic equipment, power system stability has become a major challenge in current power systems. Controlling the power system characteristics can increase the stability of the power system. The traditional techniques for improving power system stability, such as the use of FACTS devices, are costly and may not be effective in handling the dynamic changes of the power system. As a result, by optimizing the power system parameters, an optimization-based multi-agent system can improve the stability of the power system. The Grey Wolf Optimizer based Multi Agent System (GWO-MAS) is proposed in this paper to improve power system stability. The control agents of Distributed Generations (DGs) are optimized using GWO algorithm based on the deviations in frequencies of DGs. Particle Swarm Optimization based Multi Agent System (PSO-MAS) and Conventional Multi Agent System performance are compared with the suggested technique's implementation on IEEE 30 bus system and testing in MATLAB/Simulink environment. The outcomes showed that the suggested approach is successfully improving the stability of an interconnected power system.

Rapid ascent trajectory optimization of rocket-based combined cycle hypersonic vehicle

The ascent trajectory design of a rocket-based combined cycle (RBCC) hypersonic vehicle has many typical characteristics, including the complex working mode of the RBCC power system, strong coupling between thrust and flight state, strong nonlinear model and many complex constraints etc. This paper proposes a rapid trajectory optimization method based on sequential convex optimization to optimize the complex ascent trajectory with the RBCC power system. Firstly, a mathematical model for optimizing the ascent trajectory of the RBCC hypersonic vehicle is established to describe the angle of attack control system with and without the second-order lag. Then, the optimization model is made convex and discretized based on the convex optimization theory, and a trajectory optimization strategy is improved. Finally, taking the maximum terminal mechanical energy as optimization objective, the ascent trajectory optimization is simulated in cases with and without the second-order lag in the angle of attack control system. The simulation results show that the proposed mathematical model and the ascent trajectory optimization method are rapid and reliable and that the optimization results meet the characteristics of the RBCC power system and provide reference for the application of a RBCC power system and the design of an angle of attack control system.

Intelligent anomaly detection method for power and electricity data based on cubic exponential smoothing model

During the operation of the power system, abnormal electricity data are inevitably generated. How to efficiently detect and identify these abnormal data is a crucial component of power system state estimation, and it is also the foundation for the safety and stability of power system operation. Traditional anomaly detection methods only focus on specific power system characteristics, and there are problems with high computational complexity and low accuracy. To address the shortcomings of traditional methods for anomaly detection in power and electricity data, a smart anomaly detection method for power and electricity data based on a cubic exponential smoothing model is proposed. The cubic exponential smoothing model uses historical data to predict the current regional electricity consumption and then subtracts the predicted value from the true value to obtain the residual term. Finally, the DBSCAN density clustering algorithm is used to cluster the residual term, achieving the recognition of abnormal electricity data. We conduct an experimental comparison of regional electricity consumption data of a certain power grid. The results indicate that the proposed method has achieved good results in both detection rate and false alarm rate indicators in the intelligent detection of abnormal data in power and electricity consumption.

Preliminary analysis of maximum hypothetical accident for a solid core space nuclear reactor power system

In order to study the safety characteristics of the solid core space nuclear reactor power (SNRP) system under the maximum hypothetical accident, a two-dimensional entire core transient heat transfer analysis model was established, and the key parameters response characteristics of the ultra-small lithium-cooled SNRP under two maximum hypothetical accidents, namely, loss of heat sink (LOHS) and loss of coolant accident (LOCA), were calculated and analyzed. In the maximum hypothetical accidents, the coolant cooling capacity is lost, thus the core decay power is discharged into space only through the radiation of the residual heat removal system and the side surface of the reactor vessel. During the accidents, the heat transfer of the core deteriorated, and the fuel temperature may rise to the melting point, resulting in radioactive leakage. The results show that: (1) In the LOHS accident, the maximum fuel temperature reaches 2150 K at 550 s, and the pressure of the primary system volume accumulator continues to increase to the set system pressure safety limit of 2 MPa, resulting the primary loop overpressure failure. And the fuel matrix temperature is close to the set cladding limit temperature of 2200 K; (2) In the LOCA, the deterioration of heat transfer in the core makes the temperature increase rapidly, reaching a maximum of 3016 K at about 630 s, which is very close to the melting temperature of UN fuel 3123 K. As the decay power decreases, the maximum core temperature decreases to less than 1600 K after 24 h of the accident. The auxiliary cooling system of the solid core SNRP system under the maximum hypothetical accident is optimized, and the design parameters of the auxiliary cooling system meeting the safety requirements are obtained.