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Technical specifications of the generating units affect their primary frequency reserve activation amounts (capacity) and quality (speed and maintaining), which have significant effects on power system security and reliability. This paper discusses the technical value of generating units, participating in primary frequency control, based on all their influential parameters. Initially, the formulation of the active power calculation of the generating units, in response to frequency variations, is developed. The concept of Weighted Average of Frequency Active Power Change (WAFAPC) is introduced, and its continuous and discrete formulation with different types of weighting function are proposed afterwards. Also, a novel general frequency profi
The design and manufacture of structural nodes for gridshell structures are complicated due to complex geometries and loading conditions. The validation of the design concepts of these nodes is even more challenging, because complex design loads are difficult to be applied in a laboratory test. In this paper, a testing rig is proposed and manufactured to test two different additively manufactured nodes. The two nodes are symmetrical and each connecting three members. These nodes are designed to sustain pure axial loads and pure out-of-plane bending moments, respectively. The results of the experiments show the importance of the bolt tolerance in the design of such a testing setup. Subsequently an innovative and inexpensive experimental setu
In this study, the mechanical responses of an assembly plate made of topologically interlocking concrete bricks with rubber as soft interfaces are investigated. The principle of topological interlocking is combined with the concept of hybrid material design. A series of quasi-static tests are conducted to compare the mechanical behaviour of the hybrid interlocking assembly plate with those obtained from the monolithic plate and the interlocking assembly plate without soft interfaces. The results show that the hybrid assembly plate has a remarkable flexural compliance with less damage in the bricks compared to the other two. The effect of lateral confining load on the structural behaviour of the hybrid interlocking assembly plate is also inv
In this study, the mechanical responses of an assembly plate made of topologically interlocking concrete bricks with rubber as soft interfaces are investigated. The principle of topological interlocking is combined with the concept of hybrid material design. A series of quasi-static tests are conducted to compare the mechanical behaviour of the hybrid interlocking assembly plate with those obtained from the monolithic plate and the interlocking assembly plate without soft interfaces. The results show that the hybrid assembly plate has a remarkable flexural compliance with less damage in the bricks compared to the other two. The effect of lateral confining load on the structural behaviour of the hybrid interlocking assembly plate is also inv
A large number of power system equipment and their various operating conditions could make the system-wide model validation process a rigorous and time-consuming task. This paper presents a new approach for parameter identification in large-scale power system networks by estimating each group of the parameters through a different event during the dominant intervals of the process time. This technique provides a faster convergence in order to achieve the lowest mismatch between the simulation and measured disturbance responses. The proposed method is implemented on the 18-machine 118-bus system model. Governor droop, ramp rate, and dead band parameters are estimated using the Particle Swarm Optimization algorithm (PSO) coupled with the genet
Nowadays, an Energy Management System (EMS) located at power grid control centers plays a critical role in ensuring the reliable operation of a grid. The State Estimator (SE) serves as the main interface of EMS with the power grid and because of that, other EMS functionalities rely on its provided data. Recent studies show that the state estimator is vulnerable to various types of cyber-attacks. Among different types of such attacks, the False Data Injection Attacks (FDIAs) are proven to be one of the most stealth ones and attracted much attention. Various countermeasures have been proposed to detect such kind of attacks. However, these approaches are generally based on some assumptions, such as being limited to detecting a specific type of
Frequency security is an essential issue in power system operation and planning, especially with the increasing penetration level of intermittent and non-synchronous energy sources, which causes insufficiency of inertial and primary frequency responses. Therefore, various studies must observe the frequency security in the problem formulation as objective function and/or constraints. This letter proposes a Frequency Security Index (FSI), which determines the frequency security based on all aspects of the frequency profile. This index presents a quantitative percentage for the frequency security in order to specify the relative distance from the insecure (0%), secure (100%), and absolute secure (200%) conditions. The FSI considers transient a
In this chapter, the theoretical aspects of a framework for power system model validation from frequency viewpoint, including formulations and methods, are presented and described. This framework is applicable to large power systems and uses a quantitative method for comparing the measured and the simulated responses. In order to reduce the unnecessary complexities and efforts, the proposed framework is based on two main approaches and for each, uses the maximum capability of turbine-governor models. Since the framework considers the manual actions of the system operators and other emergency actions after an incident, the time frame of the validation can be chosen arbitrarily based on the availability of data. It should be ment
In this chapter, the effects of different affecting parameters and improving measures on frequency validation are investigated by developing various scenarios based on the validated simulation. These scenarios are developed in three main groups which are the parameters of the loads (voltage and frequency dependency), the parameters of the turbine-governors?(participation in primary frequency control, droop, dead band, practical powers, activity range, frequency ramp rate, and various turbine and governor time constants), and the improving measures of the framework (pre-incident frequency correction, secondary and tertiary emergency actions, static data correction, and the use of accurate governor parameters). Qualitative and qu
In this chapter, the proposed validation framework in Chap. 3 is applied to a large and interconnected test grid by modelling all known parameters affecting the frequency behaviour, including the parameters related to the active load and the generating units and also implementing the improving measures of the framework. This chapter aims to illustrate the step-by-step implementation of the validation framework for a large power system and demonstrates the effectiveness of the framework, its methods and formulations. It is concluded that for the investigated test grid, first approach (using existing models) is not sufficient to validate the frequency behaviour due to non-modelling
Condition Based Maintenance (CBM) using inspection data is one of the available maintenance approaches for power system equipment. In Inspection Based Maintenance (IBM) as a specific type of CBM, decisions about the time and type of the maintenance tasks are made after determining the deterioration condition of the equipment. In this paper, an IBM model is proposed for yearlong transmission equipment maintenance scheduling. In order to quantify the effect of the inspection and maintenance tasks, the probability distribution of the deterioration condition is calculated using the transition probability matrix of the Markov process. The problem of system level maintenance scheduling is formulated with binary variables as weekly inspection time
This paper proposes a quantitative model validation framework from the frequency perspective in which some of the technical issues of the process are solved. Two influential parameters of the process, namely the frequency ramp rate and activity range are introduced. A new quantitative assessment method including indices development and threshold calculation method is proposed. In order to reduce the complexities and efforts, all the capabilities of the existing models are initially tried (as approach 1) and upon its failure, more complex models are developed and employed (as approach 2). After discussing the theoretical aspects, the implementation steps and effectiveness of the process are demonstrated by applying the framework to a large a
Gridshells, also called lattice shells or reticulated shells, are lightweight spatial structures. Their organic shape, column-free space, free-form surface and maximised transparency have provided limitless design freedom for architects and structural eng
In this chapter, the concepts regarding frequency, as a basic parameter of power systems are described. Initially, the physical phenomenon, based on that, this parameter is affected and how it can be controlled are explained. A short historical view on frequency is then followed. It is then discussed how the players in a power system may be affected by frequency. A more detailed description of the affecting parameters on power system frequency related to the generating units (primary frequency participation, droop, dead band, practical powers, operating point, activity range, frequency ramp rate, time constants, and inertia) and loads (frequency and voltage dependency), is then given. The final sections are devoted to various f
Turbine-governor is one of the key elements in the dynamic performance of electric power systems. The accurate modeling of turbine-governor has great importance in analyzing the transient behavior of power systems. This paper proposes a hybrid method combining Particle Swarm Optimization (PSO) and Sensitivity Analysis (SA) for dynamic parameter identification of turbine-governor model in multi-machine power systems. The proposed method utilizes the frequency and turbine powers responses following some events. In each event, to recognize the validity of the estimated parameters, sensitivity analysis technique is applied. Also, considering the results of the sensitivity analysis, the impact of type and magnitude of events and also upper/lower
Microgrid is a distribution system consisted of loads and Distributed Generators (DGs) which are operating as a single power system to supply local area loads. DGs can provide various environmental and economical benefits but their presence in network poses great technical challenges in control, stability and protection sides which become a noticeable issues associated with the growing penetration of DGs in recent years. Power electronic interfaced DGs are of especial concern in microgrid control side as their control systems play a principal role in the DGs behaviors and subsequently microgrid stability. In this paper a hierarchical structure for multimode control system of inverter based DGs is presented which adaptively switches between
Background:Type 2 diabetes mellitus (DM) and chronic periodontitis (CP) show common pathophysiological features. We investigated the serum levels of IL-23 and IL-35 in people with type 2 DM and CP.Methods:In a cross-sectional study, 72 patients were divided into four equal groups: group A, participants without type 2 DM and CP; group B, patients with type 2 DM without CP; group C, patients with CP and without type 2 DM; and group D, patients with type 2 DM and CP. Demographic data were obtained and periodontal conditions including clinical attachment loss, bleeding on probing, plaque index, gingival index, and probing depth was evaluated on all existing teeth. Fasting blood sugar (FBS) levels, hemoglobin (Hb) A1c, erythrocyte sedimentation