PSS Parameters Research Articles

Increased proportion of CD226 + CD14 + monocytes correlates with clinical features and laboratory parameters in patients with primary Sjögren's syndrome.

CD226 is widely expressed on the surface of immune cells as a co-stimulatory receptor, which is involved in the development of many autoimmune diseases. The purpose of this study was to investigate the proportion of CD226 on CD14 + monocytes in the peripheral circulation of patients with primary Sjögren's syndrome (pSS) and the clinical significance of pSS. The proportion of CD226 on the surface of CD14 + monocytes was measured by flow cytometry in 45 pSS patients and 25 healthy controls (HC). The correlations between the proportion of CD226 + CD14 + monocytes and the clinical features and laboratory parameters of pSS were analyzed. Meanwhile, we analyzed the change in proportion of CD226 + CD14 + monocytes before and after treatment, and the clinical significance of pSS was evaluated. The proportion of CD226 on CD14 + monocytes markedly increased in pSS patients compared to HC (p < .01). We found the proportion of CD226 + CD14 + monocytes was positively correlated with the disease activity and severity of pSS patients. The proportion of CD226 + CD14 + monocytes in pSS patients with decayed tooth, fatigue, interstitial lung disease (ILD), low WBC, high IgG, anti-Ro60, and anti-SSB positive increased compared to that in negative patients (p < .05). Furthermore, the proportion of CD226 + CD14 + monocytes was significantly higher in active patients than in nonactive patients (p < .01). Additionally, the proportion of CD226 + CD14 + monocytes decreased in seven pSS patients after treatment (p < .01). Our study suggested that an increased CD226 proportion on CD14 + monocytes was associated with the clinical manifestations, disease activity, and prognosis of pSS patients. CD226+ CD14 + monocytes may present a potential target and a biomarker for the prognosis and therapy of pSS patients.

Decreased expression of TIGIT on CD14 + monocytes correlates with clinical features and laboratory parameters of patients with primary Sjögren's syndrome.

The purpose of this study was to investigate the expression of T-cell immunoglobulin and ITIM domain (TIGIT) in peripheral circulation of primary Sjögren's syndrome (pSS) and its role in the development of pSS. The expression of TIGIT on T cells, B cells, natural killer (NK) cells, and CD14 + monocytes was detected by flow cytometry in pSS and healthy control (HC). The correlations between expression of TIGIT and clinical features and laboratory parameters of pSS were analyzed. Meanwhile, we analyzed the change in expression of TIGIT before and after treatment, and its role in the prognosis of pSS treatment was evaluated. The expression of TIGIT on CD3 + , CD4 + , and CD8 + T cells increased and decreased on CD14 + monocytes in pSS compared to HC; however, there was no significance of B lymphocytes and NK cells. The correlation analysis between the expression of TIGIT on T lymphocytes and CD14 + monocytes and clinical features of pSS showed that the decrease in TIGIT expression on CD14 + monocytes was more closely related to pSS. The expression of TIGIT + CD14 + monocytes negatively correlated with the disease activity of pSS. The expression of TIGIT + CD14 + monocytes of pSS with arthralgia, fatigue, decayed tooth, xerostomia, interstitial lung disease, anti-Ro52 positive, and high IgG decreased compared to that in negative patients. Furthermore, it was significantly lower in active patients than in nonactive patients. After treatment, the expression of TIGIT + CD14 + monocytes tended to increase. Our study suggested that decreased TIGIT expression on CD14 + monocytes was associated with the clinical manifestations, disease activity, and prognosis of pSS patients. TIGIT + CD14 + monocytes may present as a potential target and a biomarker of the prognosis for immunomodulatory therapy in pSS. Key Points • The expression of TIGIT+CD14+ monocytes significantly decreased in pSS patients compared to HC. • There was a negative correlation between TIGIT+CD14+ monocytes and the disease activity of pSS. • TIGIT+CD14+ monocyte expression was associated with the clinical manifestations, autoantibodies, IgG, and prognosis of pSS patients.

Real-Time Solution of PSS Parameter Tuning by GA-ANFIS in Stabilizing the Electrical Power System

Real-Time Solution of PSS Parameter Tuning by GA-ANFIS in Stabilizing the Electrical Power System

Efficient Multi-objective Optimizers by Meta-heuristics for Power System Control

This paper proposes the Meta-heuristics approaches using genetic algorithms (GA) and particle swarm optimization (PSO) for tuning power system stabilizer PSS parameters. In this work we have proposed a multi-objective function based on two objectives: first maximize the stability margin by increasing the damping factors and second minimize the eigenvalues real parts. For the effectiveness function proposed check, we compared it with mono-objective function. The simulation results, by comparative study between genetic algorithms and particle swarm optimizations techniques via multi objective and mono objective functions proved the efficiency of the PSS adapted by multi-objective function based genetic algorithms in comparison with particle swarm optimization, it’s enhanced stability of power system works under different operating modes and different network configurations. The simulation results obtained under developed graphical user interface (GUI).

Digital image analysis of intraepithelial B-lymphocytes to assess lymphoepithelial lesions in salivary glands of Sjögren's syndrome patients.

Salivary glands of primary SS (pSS) patients characteristically harbour periductal infiltrates, in which lymphoepithelial lesions (LELs) can develop. LELs are composed of hyperplastic ductal epithelium with infiltrating lymphocytes and may assist in the challenging diagnostic process of pSS. As manual identification of LELs remains difficult, we aimed to identify LELs by using an objective digital image analysis (DIA) algorithm that detects intraepithelial lymphocytes. A virtual triple-staining technique developed for this study was used to count intraepithelial lymphocytes in consecutive slides stained for CD3 (T-lymphocytes), high-molecular-weight cytokeratin (hmwCK) (striated ducts) and CD20 (B-lymphocytes) in labial and parotid gland biopsies in a diagnostic cohort of 109 sicca patients. Patients were classified as having pSS or non-SS according to the ACR-EULAR classification criteria. T-lymphocytes were detected in almost all analysed ducts of pSS and non-SS sicca patients, whereas intraepithelial B-lymphocytes were present in 59-68% of labial and parotid gland biopsies of pSS patients, against only 2-3% of patients classified as non-SS. Intraepithelial B-lymphocytes were found in almost all striated ducts with hyperplasia (LELs). Remarkably, ∼25% of analysed striated ducts without hyperplasia of pSS patients also contained B-lymphocytes (precursor-LELs). Furthermore, presence of intraepithelial B-lymphocytes was associated with clinical parameters of pSS (i.e. serology). The presence of intraepithelial B-lymphocytes in salivary gland biopsies of sicca patients is a clear indicator of pSS and can be used as an objective alternative to LEL scoring. Therefore, identification of B-lymphocyte-containing ducts should be added to the diagnostic histopathological work-up of patients suspected of pSS.

Recommendations of Optimal Sampling Rates for Periodic Output Feedback Based Discrete Mode PSS

In this paper, an attempt is made to recommend the optimal sampling time period for Periodic Output Feedback (POF) based discrete mode power system stabilizer (DPSS). Various collection of input and output sampling time interval has been used in the designing of POF based DPSS. The Particle Swarm Optimization (PSO) technique is used to obtain the optimal gain matrix of the POF controller as well as the optimal sampling time intervals. The effectiveness of POF based DPSS over continuous mode lead-lag PSS is certified using small-signal stability studies. The parameters of lead-lag type continuous mode PSS is also tuned using the PSO technique. The PSS is designed using POF technique for single machine infinite bus (SMIB) system, considering a variety of sampling time intervals at input-output port. Finally, a trial is made to propose an optimum input and output sampling time period for SMIB test power system, through simulation studies.

Coordinated Optimization of Parameters of PSS and UPFC-PODCs to Improve Small-Signal Stability of a Power System with Renewable Energy Generation

AbstractThe ever-increasing penetration of intermittent renewable energy generation from wind farms (WFs) and photovoltaic (PV) plants has significant impacts on the stability of the power system c...

Amended GWO approach based multi-machine power system stability enhancement

The conception of electromechanical oscillations initiates in the power network when there is an installation of the generator in parallel with the existent one. Further, the interconnection of multiple areas, extension in transmission, capricious load characteristics, etc. causes low-frequency oscillations in the consolidated power network. This paper proposes variants of a booming population-based grey wolf optimization (GWO) algorithm in the tuning of power system stabilizer parameters of a multi-machine system in damping low-frequency oscillations. The parameters have been tuned by framing an objective function considering the improving damping ratios for the system states with lesser damping ratios and shifting the system eigenvalues towards the left-hand side of s-plane for the improved settling characteristics for the oscillations in the system. The requisites of stabilizer strategy are mapped with the hallmarks of prevalent algorithms and designed hybrid versions of GWO for the enhancement of the multi-machine power system stability. Four variants of GWO technique are nominated based on the competent stabilizer performance namely, modified grey wolf optimization (MGWO), hybrid MGWO particle swarm optimization (MGWOPSO), hybrid MGWO sine cosine algorithm (MGWOSCA) and hybrid MGWO crow search algorithm (MGWOCSA) for the designed multi-machine power network. The proposed methods have been realized with the statistical analysis on the 23 benchmark functions. Nonparametric statistical tests, namely, Feidman test, Anova test and Quade tests, have been performed on the test system, further analysed in detail. A detailed comparative analysis under the self-clearing fault is presented to illustrate the suitability of the proposed techniques. For the analysis purpose, the location of system eigenvalues has been observed along with their oscillating frequencies and corresponding damping ratios. Further, the damping nature offered with considered system uncertainty for the system states also presented with the PSS parameters obtained by the proposed algorithms.

Application of Prony Algorithm Based on EEMD for Identifying PSS Parameters

Some problems may caused by controller poor optimal control performance because of PSS parameters are hard for debugging, this paper proposes EEMD (Ensemble Empirical Mode Decomposition) and Prony algorithm combined online identification method for power system low-frequency oscillation. Firstly the EEMD is used to deal with the unstable signal and select the IMF (Intrinsic Mode Function). Secondly the model parameters of low-frequency oscillation in power systems are obtained by analyzing the IMF with Prony algorithm. Finally the PSS parameters have calculated through the residue method base on oscillation system dominant mode. Simulative results of case study show that it is better to identify the dominant mode of the signal. The proposed method has a certain reference value for engineering application.

PSS Parameter Optimization Based on Comprehensive Damping Effect Method Aiming at Actual Grid Characteristics in Northern China

In this paper, we proposed the comprehensive damping effect method to optimize the PSS parameters. Different from other studies, the optimization in this paper is based on both the amplitude-frequency and the phase-frequency properties, while other studies mainly focus on the phase-frequency characteristics. The actual grid data in Northern China are employed to verify the optimization effect in the multimachine system. The proposed method is compared with the engineering method, the existing optimization method, and the commercial software. The comparison shows that the PSS parameters obtained by the proposed method in this paper are superior to those obtained by the engineering experience, the phase-frequency optimization method, and the commercial software. In the cases of different phase-frequency range requirements, the wider the phase-frequency range is, the better the damping effect of the obtained parameters will be.

Impact of PSS Tuning Methods on Grid Connected DFIG System

Abstract-The multi-machine power system is a non-linear dynamic system. Increased demand, economical and ecological woes have driven researchers to discover newer better means of generating electrical energy. In this energy demand race actually the energy production by WT by using DFIG is the most acceptable because it presents greater benefits for a reduced conversion structure, increases damping of oscillations and hence improving stability. This work has also provides an overview of the interaction between variable speed DFIG wind turbines and the power system subjected to disturbance such as short circuit faults. In this study the impact of DFIG on Three-area six-machine test power system is analyzed, the dynamic stability improvement behaviors of the wind turbines during grid faults has been assessed by various PSS controllers like conventional PSS and MB-PSS, on the Matlab/Simulink platform. The selection of PSS parameters are determined by using various techniques like Residual Method and the GEP Transfer Function Method.

Influence of moment of inertia on electric power system security and stability control

The moment of inertia is the basic parameter of the generator and also the basic data of PSS parameter tuning. The parameter setting of PSS will increase the damping of the unit and improve the small disturbance stability of the system. When the rotational inertia parameter is not consistent with the real rotational inertia of the unit, the PSS parameter setting will not increase the damping of the unit, but sometimes it will cause the oscillation of the unit. Here, the correlation analysis is carried out with the small signal stability analysis program, and the field test is carried out in Qinghai Kang Yang power plant. The influence of moment of inertia on PSS is analysed by small disturbance analysis and field test.

Coordinated Tuning of the Parameters of PSS and POD Controllers Using Bioinspired Algorithms

This paper presents a technique based on the novel bat algorithm (NBA) for the design of the parameters of power system stabilizers and the generalized Unified power flow controller-power oscillation damping in a multimachine power system. The objective is to ensure minimal damping rates to low-frequency electromechanical oscillation modes. Simulations were carried out on the New England system to compare the performance of the NBA with three other techniques: particle swarm optimization, bacterial foraging optimization oriented by particle swarm optimization, and the bat algorithm. For the cases analyzed in this paper, the NBA produced results superior to other techniques. Moreover, the proposed methodology was able to obtain solutions with high damping levels, which showed to be robust when a wide range of loading conditions of the power system were considered.

Power System Transient Stability Enhancement by Tuning of SSSC and PSS Parameters Using PSO Technique

In this paper, the tuning design of SSSC and PSS was examined in increasing the damping of system oscillations and improve the stability of the power system during disturbances. The design problem of the SSSC controller and PSS is designed as problem of optimization and the technique uses (PSO) technique to find for optimal control parameters. By minimizing the objective function based on the speed deviation and time domain, which deliberately deviates at the oscillation angle of the alternator rotor to improve performance of transient stability of the system. The proposed controllers are tested on the system of weak bonding ability exposed to severe disturbance. Nonlinear simulation results are presented to demonstrate the proposed controller's effectiveness and its ability to give efficient damping. It is also noted that the proposed controllers of SSSC and PSS greatly improves the power system stability.

Optimal Tuning of PSS Parameter Using HACDE Based on Equivalent SMIB Model

This paper proposesthe optimal tuning of PSS parameter using the Hybrid Adaptive Chaotic Differential Evolution (HACDE) based on equivalent SMIB model in spite of the complex interconnection multi-machine system. The interconnection of power systems has some advantages such as the increase in power system reliability and maximum power transfer but, on the other hand, these interactions make the systems difficult to analyze because it becomes larger and more complex. To simplify the analysis, first the multi-machine system is converted into an equivalent Single Machine to Infinite Bus (SMIB) model which is formed by determining the equivalent impedance obtained from the network reduction method using the losses concept based on power flow tracing. This model is fairlyenough to represent the setting of generator control equipment. Afterward, the PSS parameters is tuned using HACDE optimization methods in the SMIB system. The HACDE method is able to increase the damping of generator oscillation. The PSS tuning by using HACDE is compared with the DE and RD-PSO methods. Based on time domain and ITAE simulation results, the PSS tuned using HACDE gives better damping than by using the other methods.

Adaptive Fuzzy Gain of Power System Stabilizer to Improve the Global Stability

The lead-lag power system stabilizer has several parameters to be optimized.In fact, the number of these latter increases with the number of generators constituting the multi-machine system.In this work, we propose anew approach of an adaptive and robust PSS; it achieves encouraging results by adjusting the gain using fuzzy logic and in the same time we use the same PSSs for each machine. In the first place, we could check that the gain is among the most critical parameters of the lead lag PSS. The parameters are globally optimized by the genetic algorithm, after that an expertise on the speed and the gain variations allow the value prediction according to the velocity deviation. To validate our results, a robustness test was made on a multimachine system IEEE (3 machines 9 bus), for different loads and the results showed good performance and robustness of the presented PSS.

Optimal Tuning and Placement of Power System Stabilizers Based Eigenvalue

&lt;p&gt;In this paper, an eigenvalue assignment based Particle Swarm Optimization and Participation Factor for Optimal tuning and placement of power system stabilizers is proposed. The proposed approach presents a two-step methodology to find optimal location and parameters of PSS. The Participation Factor method is computed using the modal analysis toolbox from DIgSILENT, and used to determine the power system stabilizers optimal location. A Particle Swarm Optimization algorithm is written in MATLAB to search the power system stabilizers optimal parameters. Two eigenvalue-based objective functions to ensure a maximum damping of the inter-area modes as well as of the local modes by assigning them in a robust stability area are considered. The performance of the proposed approach is tested and examined on the four-machine two-area power system. Linear modal analysis and non-linear time domain simulations show the robustness of the proposed approach.&lt;/p&gt;

Optimal Parameters Tuning of Power System Stabilizer via Bees Algorithm&lt;sup&gt;&lt;/sup&gt;

This paper presents a new approach for designing the Power System Stabilizer. As in power system network, low frequency oscillation always occurs for a long period of time that will decrease the power transfer capability. Power System Stabilizer known as PSS is being installed as one of the control devices in a generating unit. The conventional PSS (CPSS) is the most commonly used in power system, which uses lead-lag compensation. The lack in CPSS has drawn an interest of designing the new approach of PSS to outperform the conventional one. Thus, Bees Algorithm (BA) which is known as one of the numerous intelligent optimization methods is proposed in this paper. It is appears to aid the system stability by optimizing the PSS parameters tuning. The PSS with the BA approach is labelled as BA-PSS and being tested on single machine infinite bus system (SMIB) in Matlab/Simulink environment. BA-PSS performance is compared with CPSS as to validate the ability of the proposed method to achieve great performance in power system stability enhancement. Different type of mechanical input is being injected into the system and the result shows that BA-PSS is capable to optimize the parameters tuning of PSS. BA-PSS also improved the unstable or poorly stable modes as the system achieve the stability with lower overshoot and less time settling. The superior response of BA-PSS controller proved the ability of BA approach in which is capable to solve the lack in CPSS with better performance in enhancing the system stability.

Lead-Lag PSS Design Based on H Control Theory and Genetic Algorithm

The aim of this paper is to explain the way to scale back the dimension of an influence system stabilizer (PSS) supported H∞ management theory. In recent years, sturdy PSS styles that adopt associate in nursing H∞ controller are investigated so as to ensure the performance once the state of the system configuration and power flow modification. However the H∞ controller has not been wide adopted into sensible use attributable to the tangled nature of its theory and structure. We tends to think about the H∞ management downside below the condition that PSS structure is mounted to be a lead-lag compensator. Infinity norm of transfer function from disturbance to output is subjected to be minimized via searching and evolutionary computation. The resulted optimal parameters make the system stable and also guarantee robust performance. We applied the evolutionary robust controller to a pneumatic servo system. For performances comparison, three controllers; PID with derivative first order filter controller, PI controller and H- loop shaping controller are investigated. We tends to optimize the parameters of the Lead-Lag PSS by a genetic algorithm program that has associate in nursing analysis perform that takes under consideration a closed-loop system H∞ norm and a desired response. During this manner, we tends to design a PSS that encompasses a standard managementler structure and guarantees its control performance.

Design of power system stabilizers based on μ-controller for power system stability enhancement

The problem of the poorly damped low-frequency (0.1–0.4Hz) oscillations of power systems has been a matter of concern to power engineers for a long time, because they limit the power transfer capability in power systems. The power systems stability is also affected by these poorly damped oscillations and can lead to the system instability. The paper presents a design PSSs based on μ-controller to enhance power systems stability and improve power transfer capability. MATLAB dynamic model was developed for a power system and lead-lag PSS structure is considered in the model. Damping torque technique is applied to tune the PSS parameters. The results of this technique have been verified by eigenvalue analysis and time-domain simulations. The optimal sampling time was determined for transferring the s-domain of PSS model to digital (z-domain) model and then it was implemented on μ-controller chip. The peripheral interface controller (PIC) μ-controller type was used and the developed MATLAB model was interfaced with the μ-controller. The simulations results show that the system time responses under different operating conditions are well damped with the designed PSS. Moreover, the proposed PSS based μ-controller is relatively simple and suitable for real-time applications in the future smart power grid where the stabilizing signals to the PSSs will be provided by wide-area measurement signals using the new technology of synchrophasors.