Power Grid Model Research Articles

Fair hierarchical clustering of substations based on Gini coefficient

For the load modeling of a large power grid, the large number of substations covered by it must be segregated into several categories and, thereafter, a load model built for each type. To address the problem of skewed clustering tree in the classical hierarchical clustering method used for categorizing substations, a fair hierarchical clustering method is proposed in this paper. First, the fairness index is defined based on the Gini coefficient. Thereafter, a hierarchical clustering method is proposed based on the fairness index. Finally, the clustering results are evaluated using the contour coefficient and the t-SNE two-dimensional plane map. The substations clustering example of a real large power grid considered in this paper illustrates that the proposed fair hierarchical clustering method can effectively address the problem of the skewed clustering tree with high accuracy.

Blockchain and Internet of Things for Electrical Energy Decentralization: A Review and System Architecture

The decentralization in the electrical power grids has gained increasing importance, especially in the last two decades, since transmission system operators (TSO), distribution system operators (DSO) and consumers are more aware of energy efficiency and energy sustainability issues. Therefore, globally, due to the introduction of energy production technologies near the consumers, in residential and industrial sectors, new scenarios of distributed energy resources (DER) are emerging. In order to guarantee an adequate power management in the electrical power grids, incorporating producers, consumers and producers-consumers (prosumers) together, it is important to adopt intelligent systems and platforms that allow the provision of information on energy consumption and production in real time, as well as for obtaining a fair price for the sale and purchase of energy. In this paper, we analyze the literature to identify the appropriate solutions to implement a decentralized electrical power grid based on sensors, blockchain and smart contracts, evaluating the current state of the art and pilot projects already in place. We also discuss a proposal for a power grid model, with renewable energy production, combining Internet of Things, blockchain and smart contracts.

Spreading of disturbances in realistic models of transmission grids in dependence on topology, inertia and heterogeneity

The energy transition towards more renewable energy resources (RER) profoundly affects the frequency dynamics and stability of electrical power networks. Here, we investigate systematically the effect of reduced grid inertia, due to an increase in the magnitude of RER, its heterogeneous distribution and the grid topology on the propagation of disturbances in realistic power grid models. These studies are conducted with the DigSILENT PowerFactory software. By changing the power generation at one central bus in each grid at a specific time, we record the resulting frequency transients at all buses. Plotting the time of arrival (ToA) of the disturbance at each bus versus the distance from the disturbance, we analyse its propagation throughout the grid. While the ToAs are found to be distributed, we confirm a tendency that the ToA increases with geodesic distance linearly. Thereby, we can measure an average velocity of propagation by fitting the data with a ballistic equation. This velocity is found to decay with increasing inertia. Characterising each grid by its meshedness coefficient, we find that the distribution of the ToAs depends in more meshed grids less strongly on the grid inertia. In order to take into account the inhomogeneous distribution of inertia, we introduce an effective distance r_{mathrm{eff}}, which is weighted with a factor which strongly depends on local inertia. We find that this effective distance is more strongly correlated with the ToAs, for all grids. This is confirmed quantitatively by obtaining a larger Pearson correlation coefficient between ToA and r_{mathrm{eff}} than with r. Remarkably, a ballistic equation for the ToA with a velocity, as derived from the swing equation, provides a strict lower bound for all effective distances r_{mathrm{eff}} in all power grids. thereby yielding a reliable estimate for the smallest time a disturbance needs to propagate that distance as function of system parameters, in particular inertia. We thereby conclude that in the analysis of contingencies of power grids it may be advisable that system designers and operators use the effective distance r_{mathrm{eff}}, taking into account inhomogeneous distribution of inertia as introduced in Eq. (12), to locate a disturbance. Moreover, our results provide evidence for the importance of the network topology as quantified by the meshedness coefficient beta.

Precision timing and communication networking experiments in a real-time power grid hardware-in-the-loop laboratory

The growing wave of digitization in power grids is bringing increased reliance on information and communication technologies (ICT) for the operation of the grid. Such cyber–physical power systems (CPPS) involve the interaction of the physics of the power grid with the performance of other engineered systems, such as communications and time-synchronization. To understand the interplay of such interactions, experimentation is required. However, there are very limited opportunities to perform experiments on actual CPPS systems, due to safety and security concerns. Nevertheless, the demand for more functionalities on cyber components will continue to rise, and thus, other means to understand CPPS behavior for design, implementation and testing are needed. To address this gap, a real-time simulator-based power system laboratory was implemented with the objective of facilitating experiments involving precision timing and communication networking systems which are coupled with power grid models running in real-time. These are integrated in three layers: (a) Precise Timing Layer, (b) Communication/Network Layer, and (c) Electrical Component Layer. This paper reports on detailed experiments performed on the precision timing and communication layers of the laboratory. It shows how to couple the different layers together, and how to conduct experiments to tamper with both the precision timing and communication layers, along with their interactions with the simulated grid. Finally, the paper shows how to validate the Quality of Service (QoS) rules implemented in virtual local area networks (VLANs) in the laboratory environment when using different power system communication protocols.

Control of cascading failures in dynamical models of power grids

In this paper, we introduce a distributed control strategy to prevent dynamically-induced cascading failures in power grids. We model power grids using complex networks and nonlinear dynamics to provide a coarse-grained description of the electro-mechanical phenomena taking place on them (in particular, we use coupled swing equations) and restrict our analysis to cascades of line failures, i.e., failures due to power flows exceeding the maximum capacity of a line. We formulate a distributed control protocol relying on the same topology of the physical layer and apply it to several power grid models, including a small-size illustrative example with five nodes, the Italian high-voltage (380kV) power grid, and the IEEE 118-bus system. Our results indicate that the approach is capable of preventing cascading failures, either controlling each node of the network or a suitable subset of them.

Big Data Cleaning Model of Multi-Source Heterogeneous Power Grid Based On Machine Learning Classification Algorithm

Aiming at the low cleaning rate of the traditional multi-source heterogeneous power grid big data cleaning model, a multi-source heterogeneous power grid big data cleaning model based on machine learning classification algorithm is designed. By capturing high-quality multi-source heterogeneous power grid big data, weight labeling of data source importance measurement, data attributes and tuples, and constructing Tan network based on the idea of machine learning classification algorithm, the data probability value is finally used to complete the classification and cleaning of inaccurate data. Experiments show that the model based on machine learning classification algorithm can effectively improve the imprecise data cleaning rate compared with the traditional model to solve multi-source heterogeneous imprecise data cleaning.

Hierarchical dispatching model of power grid under electrochemical energy storage constraints

Aiming at the hierarchical and zoning operation control of active distribution network, focusing on electrochemical energy storage, theoretical analysis and simulation research are carried out. Firstly, the basic principle of electrochemical energy storage is analyzed, and the working characteristics such as state of charge, power loss and charge discharge power are studied. Secondly, from the perspective of economic indicators, the power consumption cost of electrochemical energy storage is studied, and the objective function of global optimal dispatching of active distribution network is constructed. Then, the energy constraints and power constraints of electrochemical energy storage are studied as an important supplement to the active distribution network optimal scheduling model. Thirdly, the application of electrochemical energy storage in regional autonomous control is analyzed, and the regulation strategy of power fluctuation is studied from the perspective of standby capacity and power deviation. Finally, combined with a specific application example, the simulation analysis is given. The simulation results show that electrochemical energy storage can effectively optimize the hierarchical scheduling of active distribution network.

Optimal Allocation Algorithm of Grid Side Energy Storage Capacity under Large Scale Wind Farm Connection

For grid energy storage capacity configuration is not reasonable, problems such as instability in crossing the river power fluctuations, are proposed based on a large scale wind power grid side under the condition of energy storage capacity of the optimal allocation algorithm, through the use of large-scale wind farm access method to achieve the optimal design of power grid model, so as to quickly solve the micro grid energy storage capacity planning cost and energy consumption data, according to the results. The operation parameters, energy loss and other numerical values of the model in the power grid are controlled, and according to the calculation results. Finally, the experiment proves that the optimization configuration algorithm of the power grid side energy storage capacity under the large-scale wind farm access has higher practicability and accuracy in the practical application process, and fully meets the research requirements.

An open-source extendable model and corrective measure assessment of the 2021 texas power outage

• An open-source Texas power grid model with real blackout data is available. • Model-based simulation captures key characteristics of the 2021 Texas blackout. • The sensitivity of corrective measures on event severity mitigation is quantified. • Per-GW generator winterization has distinct performance. Unprecedented winter storms that hit across Texas in February 2021 have caused at least 69 deaths and 4.5 million customer interruptions due to the wide-ranging generation capacity outage and record-breaking electricity demand. While much remains to be investigated on what, how, and why such wide-spread power outages occurred across Texas, it is imperative for the broader macro energy community to develop insights for policy making based on a coherent electric grid model and data set. In this paper, we collaboratively release an open-source extendable model that is synthetic but nevertheless provides a realistic representation of the actual energy grid, accompanied by open-source cross-domain data sets. This simplified synthetic model is calibrated to the best of our knowledge based on published data resources. Building upon this open-source synthetic grid model, researchers could quantitatively assess the impact of various policies on mitigating the impact of such extreme events. As an example, in this paper we critically assess several corrective measures that could have mitigated the blackout under such extreme weather conditions. We uncover the regional disparity of load shedding. The analysis also quantifies the sensitivity of several corrective measures with respect to mitigating the severity of the power outage, as measured in Energy-not-Served (ENS). This approach and methodology are generalizable for other regions experiencing significant energy portfolio transitions.

The Vulnerability of the Power Grid Structure: A System Analysis Based on Complex Network Theory.

The safety and reliability of the power grid are related to national power security, economic development and people’s daily life. The occurrence of extreme weather changes the external environment greatly. Including generators and transmission lines, many power grid units cannot resist such a huge attack and get damaged easily, which forces units to quit from the power grid running system for a while. Furthermore, if the number of influenced units is high enough, the whole power system will be destroyed by cascading failure caused by extreme weather. Aiming at dealing with the cascading failure emergencies, this paper is trying to improve the traditional power structural vulnerability model so that it can be used to discuss extreme weather and propose a theoretical topological model to help scholars measure the damage caused by extreme cases. Based on previous research in this field, this paper utilizes complex network knowledge to build the power grid topology model. Then, considering extreme cases and the three attack modes simulation process, this paper makes use of the characteristic parameters of the power grid topology model and designs an algorithm, according to the realistic situation of the propagation mechanism of cascading failure of the power grid model as well as extreme weather research. Finally, taking IEEE-30 and IEEE-118 node bus system as examples, which shows that the structural vulnerability method proposed in this paper can properly address the mechanism of unbalanced load of cascading failure of power grid units under extreme conditions and can provide theoretical reference for preventing and reducing the impact of extreme cases on power grid which improves the reliability of the power grid.

Large Scale Wind Power Consumption Model of Power Grid Based on Hydrogen Energy Economy

Large Scale Wind Power Consumption Model of Power Grid Based on Hydrogen Energy Economy

Frequency stability of the Israeli power grid with high penetration of renewable sources and energy storage systems

As countries worldwide are integrating more energy storage systems and renewable energy sources, it is important to examine how these impact the frequency stability of the grid. In this study we explore this question by focusing on Israel in 2025. Based on the Israeli power grid model in 2025, which includes detailed information on the entire transmission network, generation units, and loads, we examine hundreds of different locations and sizes of renewable energy sources and energy storage systems, focusing on the frequency behavior in each scenario following the loss of a large generator. This is done using the industry-standard PSS/E simulator. The results lead to several design-level recommendations. One main conclusion is that the Israeli power system already has the required resources to maintain frequency stability in case a large generation unit is lost. However, to maintain a reliable system, policy makers should encourage that the existing and additional storage will contribute to frequency regulation when there is a risk of instability. We also find that the location of renewable energy sources and energy storage systems has an impact on the frequency stability, and that it is better to place storage systems in the south, and renewable energy sources in the north. However, at least until 2025 this impact is not yet strong enough to be a leading factor in determining the location of these sources.

Partial stability criterion for a heterogeneous power grid with hub structures

One of the priority tasks in studying power grids is to find the conditions of their stable operation. The fundamental requirement is synchronizing all the elements (generators and consumers) of a power grid. However, various disturbances can destroy the synchronization. Moreover, desynchronization occurring in a small part of the grid can lead to severe large-scale power outages (or blackouts) due to numerous cascading failures. Here we consider the model of a heterogeneous power grid with hub structures (subgrids), taking into account arbitrary lengths and impedances of grid’s transmission lines and also their arbitrary amount. Using the auxiliary comparison systems approach, we analyze the dynamics of a hub subgrid. Based on the findings, we develop a novel criterion of partial stability of power grids featuring hub structures. The criterion makes it possible to identify the regions of safe operation of individual hub subgrid elements. First, the criterion allows obtaining parameters’ values that guarantee existence and local stability of either synchronous or quasi-synchronous modes in individual hub subgrid elements, i.e. steady-state stability. Second, the criterion allows obtaining the safe values of abrupt frequency and phase disturbances that eventually vanish, i.e. imply transient stability with respect to state disturbance. Third, the criterion permits determining the safe ranges of parameters’ disturbances that do not lead to catastrophic desynchronizing effects, i.e. imply transient stability with respect to parameters’ disturbance. Also, we discover typical dependences of the safe regions on the parameters of transmission lines. We demonstrate the applicability of the criterion on two test power grids with arbitrary distributions of powers as well as effective lengths and impedances of transmission lines. The results may help optimize stability and contribute to developing new real-time control schemes for smart grids that can automatically recover from failures.

재생에너지 기반 Hybrid 전력망의 주파수 추정

The frequency is one of the very important factors in power grid. It is essential that the frequency of a power grid should be maintained close to its nominal frequency. Recently, under the leadership of the government, interest in the expansion and distribution of renewable energy sources (RES) is increasing. Therefore, technology for stable operation in preparation for grid connection variability of RES is required. There is growing interest in the rapid measurement and accurate estimation of grid frequency for renewable energy monitoring and stability, using GPS based time-synchronous PMU (Phasor Measurement Unit) for wide area blackout prevention. In this paper, FRDWT (Fast Recursive Discrete Wavelet Transform), GCDFT (Gain Compensator Discrete Fourier Transform) and PAD (Phase Angle Difference) are selected as optimal frequency measurement methods for frequency estimation of hybrid power grid based on renewable energy. This study is to evaluate the performance of the proposed technique using domestic 345kV power grid model data by EMTP-RV S/W.

Nonlinear damping effects in a simplified power grid model based on coupled Kuramoto-like oscillators with inertia

In our work, we simulate an uneven balance of produced and consumed energy in an artificially created network that can be considered as a simplified model of the operation of some energy network. The system under consideration has a ring topology consisting of locally connected power generators alternating with power consumers. Each node of the network is represented as a Kuramoto-type phase oscillator with inertia. Oscillatory network equations are transformed in accordance with the efficient network model proposed in [24], and studied numerically. The purpose of the work is to find conditions that prevent the loss of network synchronization. Nonlinear damping of oscillators has been proposed as a possible solution to the problem of stabilizing synchronicity. The maps of regimes constant with constant damping and with time-varying nonlinear damping are compared. In addition, the case of external action on a separate network node in the form of a rectangular pulse is considered. The research results show that nonlinear damping can prevent asynchronous behavior of oscillators and increase the stability of the ensemble to sudden fluctuations in systems. The results obtained can be applied in the field of power systems as a possible tool for increasing the sustainability of power grids. The opposite side of the results is the limitation of the use of nonlinear damping. The adaptive damping has a strong negative effect on the connected power generators, which leads to overheating and failure.

Operation Characteristics of Mechanical DC Circuit Breaker Combined with LC Divergence Oscillation Circuit for High Reliability of LVDC System

DC systems are modernly starting to come into the spotlight again due to the carbon-neutral policy, the development of semiconductor devices for power, and the increase in digital loads. We need to prepare in advance solutions to problems that may arise from fault currents due to transients for future DC power grid models. In the case of DC, there is no current zero-point because there is no frequency. Therefore, a large switching surge is generated when the circuit breaker cuts off the fault current. The possibility of insulation breakdown is greater than that of AC in severe cases. We consider power semiconductors or superconducting current limiters as an alternative. However, DC breaking cannot be safely achieved by itself. For reliable DC breaking, mechanical circuit breakers must be used with them. Among the mechanical shut-off methods, we adopted the divergence oscillation method. It has the biggest advantage compared to other methods in that it has a simple structure by composing passive elements and can artificially create zero current. In addition, it can be applied to a power semiconductor and a superconducting current limiter to perform a high-reliability cut-off operation. In this paper, we conducted simulation analysis by configuring the DC power grid and DC cut-off system through the PSCAD/EMTDC program. Results confirmed that the application of the LC divergence oscillation circuit can reduce the cut-off time and reduce the power burden of the mechanical DC circuit breaker (MCB).

Grid‐supportive electric vehicle charging methodology with energy management for coordinated frequency control

This paper proposes a vehicle-to-grid (V2G) operation methodology of electric vehicles (EVs) for frequency regulation, EV charging, and state-of-charge (SOC) management. This V2G operation methodology exhibits multifunctionality in regard to instantaneous power adjustment of EVs for primary frequency control during charging. The proposed method can stabilize grid frequency under the high penetration of renewable energy by simultaneously managing the desired state-of-charge (SOC) of the batteries. The results indicate that both charging and charged EVs can assist in frequency regulation so that V2G services can help embracing renewable energy sources and stabilize a power system. The feasibility of this method is verified by a practical power grid model to demonstrate the efficacy of EV charging control for SOC management using DIgSILENT/PowerFactory.

Multi-agent deep reinforcement learning strategy for distributed energy

The strong random disturbance issues caused by the large-scale grid connections of distributed energy, such as wind energy, photovoltaic energy storage and electric vehicles, must be resolved. In this paper, we propose a Multi-agent deep reinforcement learning strategy, namely DDQN-CDP, which deeply integrate the improved actor-critic strategy with the neural network. This approach also solves the problem of the lack of continuous action controlling ability of traditional deep reinforcement learning, and obtains an optimal solution by multi-region collaboration. By simulating the modified IEEE standard two-area load frequency control power system model and Hubei power grid model, our results indicate that the proposed strategy can solve the strong random disturbance problem caused by the large-scale grid connections of distributed energy and achieve faster convergence and better control performance than other strategies.

Research on Improved Fault Current Analysis Method for Flexible Direct Current Power Grid Considering Alternating Current Feed

Flexible direct current (DC) grid can realize large-scale renewable energy, wide-area coordinated complementation, and reliable power transmission. It is an important development that can be used to support high-voltage and large-capacity flexible DC transmission in the future. The short-circuit current of the DC line is one of the important bases for the selection of key main equipment parameters such as converter valves, DC circuit breakers, and reactors in the flexible DC grid. In this paper, a flexible DC grid equivalent circuit network model with alternating current (AC) feed-in is established. Aiming at the monopolar ground fault of the flexible DC grid grounded through the metal loop, an optimized traditional matrix calculation method is proposed to obtain the accurate line fault current value. On this basis, with an actual engineering background, the equivalent circuit model of the four-terminal bipolar flexible DC power grid is established, and the influence of grounding position, grounding parameters, and current-limiting reactor on the fault current of the DC line is analyzed. Finally, simulation using the PSCAD software verifies the effectiveness and accuracy of the proposed method. The method proposed in this paper can provide the necessary bases and references for the selection of flexible DC grid equipment.

Research on Risk Assessment of Power Grid Based on Realtime Simulation System

In order to ensure the safe and stable operation of the power system, the importance of power grid calculation in simulation analysis has become more and more prominent. It is particularly important to carry out power system hidden danger investigation and risk assessment for large power grids. This paper builds a "power system full-digital real-time simulation platform" based on ADPSS. Through the modeling of the actual power grid and full fault scanning, the existence and probability of risk, the scope and degree of loss are evaluated and measured, and the operation of the power grid is analyzed. The safety and stability of the power grid, while identifying weak links in the power grid. This assessment method can provide technical support for the investigation and management of hidden dangers in the power grid, and has certain practical significance and positive guidance for the stable operation of the power grid.