scholarly journals Load Capacity Analysis of Self-Excited Induction Generators Based on Routh Criterion

Energies ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3953
Author(s):  
Jia Li ◽  
Xinzhen Wu ◽  
Xibo Yuan ◽  
Haifeng Wang
Keyword(s):  
Power Systems ◽  
Stability Criterion ◽  
Critical Loads ◽  
Load Capacity ◽  
The State ◽  
Induction Generator ◽  
Special Focus ◽  
State Matrix ◽  
Load Impedance ◽  
Induction Generators

In this paper, the Routh criterion has been used to analyze the stability of a self-excited induction generator-based isolated system which is regarded as an autonomous system. Special focus has been given to the load capacity of the self-excited induction generator. The state matrix of self-excited induction generators with resistor-inductor load has been established based on transient equivalent circuits in the stator stationary reference-frame. The recursive Routh table of self-excited induction generators is established by the characteristic polynomial coefficients of the state matrix. According to the Routh stability criterion, the necessary and sufficient condition to predict the critical loads of self-excited induction generators is deduced, from which the critical load impedance can be calculated. A simple self-excited induction generator-based isolated power system has been built up with a 2.2 kW self-excited induction generator. The theoretical analysis and experiments were all carried out based on this platform. In the range determined by the minimum excitation capacitance (Cmin) and the maximum excitation capacitance (Cmax), the critical loads under various power factors have been calculated. The agreement of the calculated theoretical results and experimental results demonstrate the effectiveness and accuracy of the proposed analysis method. The conclusions achieved lay a foundation for further application of Routh stability criterion in self-excited induction generator-based power systems analysis.

Research on Voltage Stability in Grid-Connected Large Wind Farms

2011 ◽  
Vol 354-355 ◽  
pp. 989-992
Author(s):  
An Lin
Keyword(s):  
Power Systems ◽  
Voltage Stability ◽  
Wind Farm ◽  
Reactive Power ◽  
Low Voltage ◽  
Wind Farms ◽  
System Stability ◽  
Induction Generator ◽  
Induction Generators ◽  
Large Wind

Squirrel-cage induction generator (SCIG) has been widely utilized in large wind farms in China. However, the large wind farm composed of induction generators will cause obvious power system stability problems due to the dependency on reactive power. Doubly-fed induction generator (DFIG) has excellent dynamic characteristics of wind farm operations. With the increasing of wind power penetration in power systems, more and more wind farms use both SCIG and DFIG. This paper firstly analyzes the the dynamic characteristic of wind farm on power systems, especially in terms of the voltage stability. Then the interaction between the SCIGs and DFIGs is also investigated. A detailed simulation model of wind farms is presented by means of MATLAB. The simulation results demonstrate that the DFIG applications will improve the voltage stability of the wind farm largely and the low voltage ride through characteristics of SCIG to some extend.

scholarly journals A simplified linearized dynamic model for voltage collapse assessment in power systems

2003 ◽  
Vol 16 (1) ◽  
pp. 145-154
Author(s):  
Dragan Tasic ◽  
Miodrag Stojanovic
Keyword(s):  
Power Systems ◽  
Dynamic Model ◽  
The State ◽  
Voltage Collapse ◽  
State Matrix ◽  
Time Constants ◽  
Load Change ◽  
Collapse Assessment

A simplified linearized dynamic model for fast assessment of voltage collapse is developed in this paper. The simplification was made under assumption that the voltages at generator nodes are constant, which means that only power changes at load nodes are considered in analysis. Dimensions of the state matrix, which eigenvalues are used for voltage collapse assessment, decrease under this assumption. Appropriate transformations of linearized state matrix prove that knowledge of values of the dynamical load change time constants is not required for this model.

Overview of Subsynchronous Oscillation in Grid-connected Wind Farm

2020 ◽  
Vol 13 (7) ◽  
pp. 969-979
Author(s):  
Xu Pei-Zhen ◽  
Lu Yong-Geng ◽  
Cao Xi-Min
Keyword(s):  
Power Systems ◽  
Wind Turbine ◽  
Large Scale ◽  
Wind Farm ◽  
Wind Farms ◽  
Induction Generator ◽  
Future Research ◽  
Stable Operation ◽  
Subsynchronous Oscillation ◽  
Different Types

Background: Over the past few years, the subsynchronous oscillation (SSO) caused by the grid-connected wind farm had a bad influence on the stable operation of the system and has now become a bottleneck factor restricting the efficient utilization of wind power. How to mitigate and suppress the phenomenon of SSO of wind farms has become the focus of power system research. Methods: This paper first analyzes the SSO of different types of wind turbines, including squirrelcage induction generator based wind turbine (SCIG-WT), permanent magnet synchronous generator- based wind turbine (PMSG-WT), and doubly-fed induction generator based wind turbine (DFIG-WT). Then, the mechanisms of different types of SSO are proposed with the aim to better understand SSO in large-scale wind integrated power systems, and the main analytical methods suitable for studying the SSO of wind farms are summarized. Results: On the basis of results, using additional damping control suppression methods to solve SSO caused by the flexible power transmission devices and the wind turbine converter is recommended. Conclusion: The current development direction of the SSO of large-scale wind farm grid-connected systems is summarized and the current challenges and recommendations for future research and development are discussed.

scholarly journals Methodology for Implementing the State Estimation in Renewable Energy Management Systems

Energies ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2301
Author(s):  
Yun-Sung Cho ◽  
Yun-Hyuk Choi
Keyword(s):  
Renewable Energy ◽  
Power Systems ◽  
State Estimation ◽  
Measurement Errors ◽  
Large Scale ◽  
Test System ◽  
The State ◽  
Inner Function ◽  
Outer Function ◽  
Bad Data

This paper describes a methodology for implementing the state estimation and enhancing the accuracy in large-scale power systems that partially depend on variable renewable energy resources. To determine the actual states of electricity grids, including those of wind and solar power systems, the proposed state estimation method adopts a fast-decoupled weighted least square approach based on the architecture of application common database. Renewable energy modeling is considered on the basis of the point of data acquisition, the type of renewable energy, and the voltage level of the bus-connected renewable energy. Moreover, the proposed algorithm performs accurate bad data processing using inner and outer functions. The inner function is applied to the largest normalized residue method to process the bad data detection, identification and adjustment. While the outer function is analyzed whether the identified bad measurements exceed the condition of Kirchhoff’s current law. In addition, to decrease the topology and measurement errors associated with transformers, a connectivity model is proposed for transformers that use switching devices, and a transformer error processing technique is proposed using a simple heuristic method. To verify the performance of the proposed methodology, we performed comprehensive tests based on a modified IEEE 18-bus test system and a large-scale power system that utilizes renewable energy.

Operation Characteristics of Zone 3 Distance Protection in Wind Power Systems with Fixed-Speed Induction Generators

2011 ◽  
Vol 12 (4) ◽  
Author(s):  
Shenghu Li
Keyword(s):  
Power Systems ◽  
Wind Power ◽  
Reactive Power ◽  
Flow Analysis ◽  
Load Flow ◽  
Synchronous Generators ◽  
Induction Generators ◽  
Load Flow Analysis ◽  
Wind Power Systems ◽  
Operation Characteristics

The induction generators (IGs) are basic to wind energy conversion. They produce the active power and consume the reactive power, with the voltage characteristics fragile compared with that of the synchronous generators and doubly-fed IGs. In the stressed system states, they may intensify var imbalance, yielding undesirable operation of zone 3 impedance relays.In this paper, the operation characteristics of the zone 3 relays in the wind power systems is studied. With the theoretical and load flow analysis, it is proved that the equivalent impedance of the IGs lies in the 2nd quadrature, possibly seen as the backward faults by the mho relays, i.e. the apparent impedance enters into the protection region from the left side. The undesirable operation may be caused by more wind power, larger load, less var compensation, and larger torque angle.

scholarly journals Dual Stator Winding Induction Generator (DSWIG) used for hybrid micro grid power systems

2021 ◽  
Vol 1781 (1) ◽  
pp. 012038
Author(s):  
M Topor ◽  
S I Deaconu ◽  
F Bu ◽  
G N Popa ◽  
L N Tutelea ◽  
...  
Keyword(s):  
Power Systems ◽  
Induction Generator ◽  
Stator Winding ◽  
Micro Grid

scholarly journals Load Forecasting Based on LSTM Neural Network and Applicable to Loads of “Replacement of Coal with Electricity”

2021 ◽  
Author(s):  
Zexi Chen ◽  
Delong Zhang ◽  
Haoran Jiang ◽  
Longze Wang ◽  
Yongcong Chen ◽  
...  
Keyword(s):  
Power Systems ◽  
Short Term Memory ◽  
Load Capacity ◽  
Load Forecasting ◽  
Forecasting Method ◽  
Adequate Accuracy ◽  
Model Time Series ◽  
Power System Faults ◽  
Long Short Term Memory ◽  
Electric Loads

AbstractWith the complete implementation of the “Replacement of Coal with Electricity” policy, electric loads borne by urban power systems have achieved explosive growth. The traditional load forecasting method based on “similar days” only applies to the power systems with stable load levels and fails to show adequate accuracy. Therefore, a novel load forecasting approach based on long short-term memory (LSTM) was proposed in this paper. The structure of LSTM and the procedure are introduced firstly. The following factors have been fully considered in this model: time-series characteristics of electric loads; weather, temperature, and wind force. In addition, an experimental verification was performed for “Replacement of Coal with Electricity” data. The accuracy of load forecasting was elevated from 83.2 to 95%. The results indicate that the model promptly and accurately reveals the load capacity of grid power systems in the real application, which has proved instrumental to early warning and emergency management of power system faults.

scholarly journals Transnational Lived Citizenship – The Case of the Eritrean Diaspora

2021 ◽  
Vol 56 (1) ◽  
pp. 3-18
Author(s):  
Tanja R. Müller ◽  
Milena Belloni
Keyword(s):  
The State ◽  
Special Focus ◽  
Diaspora Studies ◽  
Historical Events ◽  
Everyday Practices ◽  
Key Questions

This special focus section analyses state–diaspora relationships with a focus on the case of Eritrea, a paradigmatic example, as we show in this introduction, to elaborate on the following key questions: What determines loyalty between diaspora and the state? How can we understand the dynamics of co-optation, loyalty, and resistance that characterise many diaspora–state relationships? What is the role of historical events and memory in building alliances as well as divides among different generations and different groups in the diaspora? How do diaspora citizens interpret and enact their citizenship in everyday practices of engagement? By engaging with both citizenship and diaspora studies, this introduction shows the significance of analysing these questions through the lens of “transnational lived citizenship.” This concept enables a look at the intersections between formal aspects of citizenship as well as the emotional and practical aspects related to feelings of belonging, transnational attitudes, and circulation of material cultures.

STATE-LEVEL DIETARY DIVERSITY AS A CONTEXTUAL DETERMINANT OF NUTRITIONAL STATUS OF CHILDREN IN INDIA: A MULTILEVEL APPROACH

2017 ◽  
Vol 50 (1) ◽  
pp. 26-52 ◽  
Author(s):  
Kakoli Borkotoky ◽  
Sayeed Unisa ◽  
Ashish Kumar Gupta
Keyword(s):  
Nutritional Status ◽  
Dietary Diversity ◽  
State Level ◽  
The State ◽  
Sample Survey ◽  
Special Focus ◽  
Consumer Expenditure ◽  
Multilevel Regression ◽  
Effective Measure ◽  
Nutritional Status Of Children

SummaryThis study aimed to identify the determinants of nutritional status of children in India with a special focus on dietary diversity at the state level. Household-level consumption data from three rounds of the Consumer Expenditure Survey of the National Sample Survey Organization (1993–2012) were used. Information on the nutritional status of children was taken from the National Family Health Survey (2005–06). Dietary diversity indices were constructed at the state level to examine diversity in quantity of food consumed and food expenditure. Multilevel regression analysis was applied to examine the association of state-level dietary diversity and other socioeconomic factors with the nutritional status of children. It was observed that significant variation in childhood stunting, wasting and underweight could be explained by community- and state-level factors. The results indicate that dietary diversity has increased in India over time, and that dietary diversity at the state level is significantly associated with the nutritional status of children. Moreover, percentage of households with a regular salaried income in a state, percentage of educated mothers and mothers receiving antenatal care in a community are important factors for improving the nutritional status of children. Diversity in complementary child feeding is another significant determinant of nutritional status of children. The study thus concludes that increasing dietary diversity at the state level is an effective measure to reduce childhood malnutrition in India.

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