Static Load Model Research Articles

Assessment of the bearing capacity of variable profile piles in soil using static load model tests on a testing apparatus

The paper presents the results of the study of the proposed type of variable profile piles. The proposed type of piles is reinforced concrete driven piles segmented in length. Each subsequent section has a radial displacement along the axis of symmetry relative to the previous section. The positive effect of the performance of the proposed pile is to change the nature of the lateral contact of the pile with the soil, and to increase the drag of the soil. The conducted research is aimed at solving the problem related to the relatively low bearing capacity of traditional square section piles. The research was carried out by the method of model tests of piles on a test bench (tray) at a scale of 1:10. The tests were performed for variant pile types in comparison with a standard square section prismatic pile. The adopted dimensions of the pile model allow the use of this tray without the influence of its boundary conditions on the stress-strain state of the soil. A total of 42 tests were performed, 3 tests for each type of piles compared. Evaluation of pile bearing capacity was performed by static loading of pile models with vertical indentation load until failure. According to the results of the investigations, the resistance values of the compared pile types in the soil were obtained, as well as the dependence of bearing capacity changes on the section dimensions and on the rotation angle. According to the results, the optimal pile solution was selected. The bearing capacity of the proposed optimal pile solution exceeds the bearing capacity of the standard driven pile by 22 %. The results obtained allow us to conclude about the influence of the technological solution of the proposed pile type on its serviceability in soil conditions

A deep dive into enhancing frequency stability in integrated photovoltaic power grids

Voltage control strategies (VCS) and frequency stability analysis (FSA) are essential for power system reliability, particularly during high-load periods. Stable voltage and frequency levels prevent malfunction, power quality deterioration, and supply interruptions. Grid operators must skillfully manage VCS and FSA control to ensure system stability. Nonlinear loads, especially under transient conditions, significantly affect voltage stability (VS), introducing harmonics, waveform distortion, and stability complexities. Accurate modeling of these nonlinear loads is vital when traditional static load models fall short. Frequency fluctuations from power generation-demand imbalances require vigilant monitoring and regulation. Effective frequency control mechanisms are indispensable for preserving desired frequencies. Using a Western Algeria case study, this paper underscores FSA's significance in integrating photovoltaic (PV) systems into power grids. It addresses challenges from frequency fluctuations due to dynamic ZIP load profiles, emphasizing the importance of FSA for reliable grid operation. The study offers insights and practical approaches to enhance VS, FSA control, and energy management (EM), improving grid reliability and ensuring uninterrupted power supply. We must look into FSA's benefits in integrating PV systems to improve performance and lower grid interruptions. This includes looking into its control mechanisms and feedback systems.

Multiparameter Bifurcation Analysis of Power Systems Integrating Large-Scale Solar Photovoltaic and Wind Farms Power Plants

In this paper, we propose a novel codimension-three-parameter bifurcation analysis of equilibria and limit cycles when integrating Renewable Energy Sources (RESs) power plants with an exponential static load model. The study investigates the effect of solar photovoltaic generation margin, wind power generation margin, and loading factor on the local bifurcation of the modified IEEE nine-bus system. The proposed technique considers the real case of the West System Coordination Council (WSCC), the western states of the USA, by using specific models of RES power plants and static loads. The proposed technique helps to create a set of linearly varying parameters for critical operating points of nonlinear systems. The study explores detailed voltage stability analysis through the examination of bifurcation diagrams. The Hopf, limit-induced, and saddle-node bifurcation branches are identified, defining the parameter space’s stable and unstable operational regions. Additionally, the stability regions surrounding the equilibrium points are diligently explored, clarifying the consequences that various bifurcations may exert on these regions. The study offered in this proposed work aids in determining the best ways to monitor and improve these margins while considering system variables and load design.

Design and implementation of controlled load damping factor controller in series connection for power systems with high penetration of renewable energy

As sustainable natural sources such as wind and solar are increasingly integrated into power grids, conventional fossil fuel-based generating units will be gradually replaced, resulting in enormous pressure on frequency regulation of the novel power systems. This paper proposes a method for implementing a cascaded load-damping factor controller based on the controlled load-damping factor controller. Series-type voltage regulators, namely, solid-state transformers or dynamic voltage restorers, can regulate the voltage of the 10 kV feeder within the allowed range. Therefore real-time control of composite load power is realized, which significantly improves the primary frequency regulation capability of novel power systems with renewable energy generation(REG). The effect of actuator regulation time constant is considered, The impact of dynamic loads on the primary frequency regulation of the controller, designed based on a static load model, is analyzed, The effectiveness of the controller on the primary frequency regulation under different renewable energy penetration rates is discussed, The effectiveness of the controller in smoothing short-term power fluctuations of REG is examined. Finally, the effectiveness of the series-connected controlled load-damping factor controller in primary frequency regulation is verified on the RTDS simulation experimental platform. The proposed control system is characterized by a simple structure, easy implementation, and convenient maintenance, which can realize the coordination and unification of reactive-voltage and active-frequency control of the novel power system in the 110 kV customer substation and is beneficial to practical application in engineering.

Comprehensive Analysis of Power System

The contemporary power landscape is marked by escalating complexity driven by surging energy demands, the integration of renewable sources, and the imperative for heightened system performance. In response to these challenges, this paper presents a thorough investigation. Firstly, the load factor Lambda (λ) is expounded upon, emphasizing its significant impact on system stability due to load characteristics. Static load models are employed for voltage stability studies, providing insights into resource allocation and optimization by comparing actual energy consumption to the maximum potential consumption. Secondly, the paper delves into the power balance, a critical aspect that scrutinizes the equilibrium among generation, consumption, and distribution, underscoring its pivotal role in ensuring system stability. Within a 6-node network, the concept of power balance, denoted as "load λ," is illustrated by tracking its variations across iterations, representing the disparity between Power Generator (PG) and Load (PL). To maintain balance during continuous power flow (CPF) analysis, power supply can be finely adjusted using the load factor lambda (λ). Thirdly, the integration of renewable sources introduces active load variation, underscoring the necessity to comprehend load fluctuations over time for ensuring grid reliability. Active load variation is demonstrated based on the number of iterations. Additionally, the paper elucidates the increment factor τ, explaining its impact on the number of correction iterations by selecting the size of the step factor. The graphical representation of the increment factor for iterations 8 and 11 in a network with load nodes provides further clarification. This paper explores the intricate interactions of load factors, power balance, active load changes, and increment factors within power systems. The presented findings contribute to the enhancement of the reliability, efficiency, and sustainability of modern power systems.

Static strength and crashworthiness analysis of a train cowcatcher at a running speed of 160 km/h

The cowcatcher is one of the unique devices at the front end of the train, which can remove obstacles on the track by crashing before the vehicle body to ensure the safety of the train. When a collision accident happens, the cowcatcher serves as the first energy-absorbing structure to dissipate and guide the collision energy. The design of the existing cowcatcher of multiple units generally focuses on the good ability to remove obstacles, while the secondary function, the crashworthiness of orderly deformation under collision, still needs further research. In this study, a finite element model of structural static load and collision analysis was established under standard EN 15227, with the cowcatcher for 160 km/h train as the prototype. Then the solution and simulation process was accomplished under the environment of ANSYS and LS-DYNA. The analysis results showed that the structural static strength of the current cowcatcher met the requirements of the standard EN 15227, and the longitudinal stiffness was evenly distributed. When removing the obstacles with low mass, the impact force was small and the structure would not produce obvious deformation; when removing the obstacles with large mass, the impact force was large and the shear fracture might occur at the connection of the cowcatcher.

Optimal reactive power planning under active and reactive power steady state load model

This research article proposes a unique planning strategy of reactive power (VAr) considering static load model in power transmission system. An exponential static load model of active and/ or reactive power is considered during the study of load flow solution through Newton-Raphson method. This load model is designed with active and reactive exponents on the flow of active and reactive power through the transmission network. The power losses from load flow solution is measured and minimized through the proper placement of compensation devices. Here two types of FACTS (flexible ac transmission systems) are used in order to compensate reactive power. The separate and collective effect of active and reactive power modeling on load flow is also observed during the calculation of total operating cost (TOC) of the system. The TOC is formulated mathematically by adding different cost components such as cost due to real power loss, VAr generation cost component, compensation device cost component. To validate the impetus of the proposed planning strategy small, medium and large transmission systems are considered in this research work.

Probabilistic Assessment of Conservation Voltage Reduction Using Static Load Model Parameter in the Presence of Uncertainties

Higher penetration of solar PV and wind generation in distribution networks may change the conservation voltage reduction (CVR) capabilities. The uncertainties associated with the renewable generations and system loads are neglected in the deterministic CVR assessment. In this paper, a probabilistic framework for CVR assessment has been presented to assess the impact of uncertainties associated with renewable generations and system loads. A theoretical framework has been presented by establishing a mathematical relationship between the probability distribution of renewable generations (solar PV and wind) and the probability distribution of static exponential load model parameters. The simulation results have confirmed that the penetration of non-Gaussian solar PV and wind generation leads to non-Gaussian static exponential load model parameter distribution, which is validated by the normality tests (quantile-quantile plot, skewness, and kurtosis). Subsequently, the magnitude and probability distribution of the CVR capabilities of the network changes with the penetration of renewable generations, where the higher renewable penetration scenarios lead to higher CVR values and non-Gaussian (asymmetric) distribution.

Simulation of Influence of Load Model and Parameters on Frequency and Voltage Stability of Yunnan Power Grid

After fully asynchronous networking with Yunnan Power Grid and China Southern Power Grid, a multi-DC sending-end grid with a relatively weak grid structure and low load level, has prominent frequency and voltage stability, which makes Yunnan Power Grid have complex security and stability problems. Therefore, beginning with the load model and its variable, in this study, the effects of four static load models and four dynamic load models are compared with regard to the frequency and voltage stability of the Yunnan power grid’s asynchronous interconnection system. It simulates and analyzes how load model parameters affect the frequency and voltage stability of the transmitting end power grid of the asynchronous interconnection system while Puqiao DC is experiencing unipolar and bipolar blocking faults.

Parameter identification of photovoltaic discrete-time equivalent model using the bat algorithm

As the development of photovoltaic (PV) power generation continuously accelerated the total installed capacity of PV, the traditional static load model is difficult to meet the needs of the power grid with the increasing penetration of PV. And the dynamic model of grid-connected PV power generation is complicated and there are plenty parameters need to be identified, so the dynamic model of grid-connected PV power generation are extremely challenging to apply in wide-area power system. In this paper, a discrete-time equivalent model of PV (PDEM) is established based on the third-order dynamic differential equation of the PV power generation system and the parameters of the PDEM are identified using the least squares (LS) and the bat algorithm (BA). Besides, the dynamic characteristics of the PV power generation grid connected system with different permeability and the fitting residuals of the two methods is analyzed in the IEEE14-bus system incorporated into the PV system. The applicability of the PDEM is verified by setting short circuit grounding fault and changing the PV permeability and voltage dip. The simulation results demonstrate that the PDEM has a strong adaptability and good applicability in the case of high PV permeability with a wide application. And the applicability of the BA in identification of PDEM are given in this paper.

A reactive power planning model for power transmission systems using meta-heuristics algorithms

The load patterns in electricity markets are changing rapidly worldwide. The power engineers are becoming more vigilant in providing an uninterrupted power supply at different loading conditions. This study proposes a unique planning strategy of reactive power (VAr) considering a static load model in the power transmission system. The active/ reactive power-oriented exponential load model for static load is considered during the study of load flow solution. The load flow solution’s power losses are measured and minimized by properly placing compensation devices. A flexible ac transmission system (FACTS) technology has been applied in this proposed planning strategy to compensate for reactive power. The separate and collective effect of active and reactive power modeling on load flow is also observed during the calculation of the total operating cost (TOC) of the system. The TOC is formulated empirically by adding different cost components such as cost owing to real power loss, VAr generation cost component, and compensation device cost component. A real-world power transmission system is considered in the study to validate the impetus of the proposed planning strategy.

Off-line measuring sampling data identification parameters for digital twins mirroring load modelling and stability analysis

Currently, the methods used to represent loads do not differ between the characteristics that compose them or the nature of these. Therefore, the purpose of this research is to develop digital twins mirroring load models that can be used for more precise studies on power-flows and stability within the National Transmission Grid (NTG). Off-line sampling data of different electric measurements have been used in six substations of the Guayaquil (Ecuador) area. These values were organized by statistical methods and by time periods, to determine the parameters that make up the static load model. Dynamic models are also constructed for the same six substations using the analysis of current and voltage signals obtained from the substations. All data is organized to show a digital twin mirroring visual representation of the disturbances that may occur in the substation buses. A more accurate description of the static and dynamic responses can be obtained by replacing the general model that is currently used by engineers and planners with off-line sampling data. Digital twins help the electric utility businesses gather, visualise, and contextualise data from different sources, and enable to act on data, and to understand what-if modelling stability scenarios.

Mechanical Response Analysis of Asphalt Pavement Structure with Embedded Sensor

Long-term and real-time monitoring of asphalt pavement can be carried out by using embedded sensors to perceive and predict structural damage during pavement operation period, so as to avoid sustained development of damage. However, the influence of embedded sensors on the mechanical properties of asphalt pavement structure and the structural optimization of sensing elements needs to be further studied. Based on the finite element numerical simulation method, static load model and three-point bending test mode were conducted with three “pavement-sensor” coupling model without sensor, with embedded I-shape sensor, with embedded corrugated-shape sensor. Three simulated conditions were studied comparatively of the sensing element embedding effect on the mechanical response of asphalt pavement structure. Results show that the sensing elements embedded with the two structures have a certain influence on the stress and strain field of asphalt concrete. Within the range of 60–100 mm the asphalt mixture is in a state of tension; the stress values increase with depth and show a maximum tensile stress state at the bottom of the beam. In the compression zone, the strain of the I-shape sensing element embedded is closer to that of the strain without the sensing element embedded. Along the axis of the two sensing elements, the axial strain of the I-shape sensing element is smoother and uniform, which ensures the deformation coordination in the road state. The optimal length L of the sensing element is 14 cm, the diameter φ of the sensor is 10 mm, and the I-beam length GL is 10 cm.

Dynamic Equivalents of Nonlinear Active Distribution Networks Based on Hammerstein-Wiener Models: An Application for Long-Term Power System Phenomena

In traditional power systems, the load consumption inside the distribution networks has a relatively passive behavior. Consequently, transmission system operators have commonly aggregated the load centers using static loads such as exponential load models. This is a practical approach for bulk power system stability studies. In modern systems, the impact of distributed generation units on the system dynamics can no longer be neglected. Static load models fall short to represent the highly dynamic behavior of active distribution networks. This paper proposes a methodology for equivalencing such networks while conserving the dynamics of interest for long-term stability studies. The methodology is based on Hammerstein-Wiener models that use only boundary variables measured at the distribution network point of common coupling. Therefore, unlike gray-box models, no previous knowledge about the system is required. Furthermore, the proposed methodology has a transparent relationship to linear systems and a convenient block representation that can be implemented in commercial power system analysis software using only standard elements. This allows for easy implementation, overcoming a barrier for a rather conservative sector such as power systems planning and operation. The conclusions are derived from time-domain simulations on the IEEE test system for voltage stability assessment.

SYNTHESIS OF AN AUTOMATED CONTROL SYSTEM FOR THE FLOW OF ACTIVE POWER ALONG A POWER LINE IN OVERLOAD CONDITION

Currently, there are practically no automated systems for controlling power flow within the specified limits when the power line is overloaded by active power. Regulation is assigned to the dispatchers of the power system or is carried out by means of emergency automation, which disconnects consumers. Therefore, an urgent task is to expand the arsenal of tools for automatic control of active power flow in overload mode. Relevance. A significant increase in electricity consumers leads to a complication of the electric power system. The workload for dispatching personnel is increasing. Maintaining the smooth operation of the elements of the power system is a very important and responsible task. In modern electric power industry, timely warning and elimination of overloads of network elements are relevant. The study aims are development and research of an intelligent automatic control system for the flow of active power along a power line based on the mathematical apparatus of fuzzy logic. The system is based on the use of the regulating effect of the load. Research methodology. Methods of calculating static load model during their actualization were used. The method of fuzzy sets was used in the construction of an intelligence control system for active power flows in overload condition. The effectiveness was estimated by expert methods. Results. The use of artificial intelligence methods for automatic regulation of transformer voltage under load allows up to 5–7 % reducing the flow of active power in overload mode.

SYNTHESIS OF AN AUTOMATED CONTROL SYSTEM FOR THE FLOW OF ACTIVE POWER ALONG A POWER LINE IN OVERLOAD CONDITION

Currently, there are practically no automated systems for controlling power flow within the specified limits when the power line is overloaded by active power. Regulation is assigned to the dispatchers of the power system or is carried out by means of emergency automation, which disconnects consumers. Therefore, an urgent task is to expand the arsenal of tools for automatic control of active power flow in overload mode. Relevance. A significant increase in electricity consumers leads to a complication of the electric power system. The workload for dispatching personnel is increasing. Maintaining the smooth operation of the elements of the power system is a very important and responsible task. In modern electric power industry, timely warning and elimination of overloads of network elements are relevant. The study aims are development and research of an intelligent automatic control system for the flow of active power along a power line based on the mathematical apparatus of fuzzy logic. The system is based on the use of the regulating effect of the load. Research methodology. Methods of calculating static load model during their actualization were used. The method of fuzzy sets was used in the construction of an intelligence control system for active power flows in overload condition. The effectiveness was estimated by expert methods. Results. The use of artificial intelligence methods for automatic regulation of transformer voltage under load allows up to 5–7 % reducing the flow of active power in overload mode.

Modeling of active and reactive power steady state load in optimal reactive power planning

With the flow of time, the load patterns in electricity markets are changing rapidly in world-wide. The power engineers are becoming more vigilant to provide an uninterrupted power supply at any loading conditions. This article proposes a unique planning strategy of reactive power (VAr) considering static load model in power transmission systems. The active and/ or reactive power oriented exponential load model for static load is considered during the study of load flow solution. The power losses from load flow solution is measured and minimized through the proper placement of compensation devices. Series and shunt type FACTS (flexible ac transmission system) devices are used in order to compensate the flow of reactive power. Also, the separate and collective effects of active and reactive power exponents on load flow study are included during total operating cost (TOC) calculation of the system. The TOC is formulated empirically by adding different cost components such as cost owing to real power loss, VAr generation cost component, compensation device cost components and line charging cost. To validate the impetus of the proposed model, IEEE 14, IEEE 39 and IEEE 118 bus transmission systems are considered in this research work.

A Hybrid Algorithm for Parameter Estimation (HAPE) for Dynamic Constant Power Loads

Low-inertia microgrids may easily have a single load that can make up most of the total load, thereby greatly affecting stability and power quality. Instead of a static load model, a dynamic constant power load (DCPL) model is considered here. Next, a hybrid algorithm for parameter estimation (HAPE) is introduced. In order to verify the load model and the HAPE, two experiments are conducted with different DCPLs using a power-hardware-in-the-loop (PHiL) testbed. The PHiL testbed consists of a real-time computer working with a programmable power amplifier in order to perturb the input voltage's amplitude and frequency. Each connected DCPL in two separate experiments serves as the device under test. Using the captured experimental data as a reference, the HAPE is then invoked. The resulting parameter estimates are used to define simulation models. Both resulting DCPL models are simulated to produce waveforms that closely resemble experimental waveforms. Finally, the HAPE's resulting parameter estimates are presented, and the performance of the HAPE is discussed.

Impact of static and dynamic load models on security margin estimation methods

The post-contingency loadability limit (PCLL) and the secure operating limit (SOL) are the two main approaches used when computing the security margins of an electric power system. While the SOL is significantly more computationally demanding than the PCLL, it can account for the dynamic response after a disturbance and generally provides a better measure of the security margin. In this study, the difference between these two methods is compared and analyzed for a range of different contingency and load model scenarios. A methodology to allow a fair comparison between the two security margins is developed and tested on a modified version of the Nordic32 test system. The study shows that the SOL can differ significantly from the PCLL, especially when the system has a high penetration of loads with constant power characteristics or a large share of induction motor loads with fast load restoration. The difference between the methods is also tested for different contingencies, where longer fault clearing times are shown to significantly increase the difference between the two margins.

Research on Application of Multi-Channel Selector in Centrifugal Model Test of Anchoring Slope by Frame Beam

An anchoring frame beam is a very common form of support for reinforced slopes, especially in alpine regions. Centrifugal tests have proved to be an intuitive and effective means of investigating the mechanism of action of frame beams. However, the data acquisition system of the geotechnical centrifuge in service has the problem of a small number of acquisition channels. A multi-channel selector based on the existing acquisition system was proposed, designed, processed, and manufactured, and it was debugged, tested, and applied in a no-load centrifugal test, static pressure model test, and centrifugal model test. The results show that the acquisition mode of the multi-channel selector connected with a maximum of 288 sensors has been changed from “one-to-one” to “one-to-many”. Its influence on various sensor signals is negligible. The multi-channel selector can work normally, which communicates and feeds back with the remote controller in the 1–120 g no-load centrifugal test. In the static load model test, 162 sensor signals were well collected through it. And only 51 channels were used to effectively obtain the signals of 187 sensors in a 70 g centrifugal model test of an anchoring slope with a frame beam. The multi-channel selector can be successfully applied in different use environments, saving time and reducing the cost of obtaining a single set of data.