scholarly journals Faulty Synchronization of Salient Pole Synchronous Hydro Generator

Energies ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 5491
Author(s):  
Adam Gozdowiak
Keyword(s):  
Phase Shift ◽  
Reactive Power ◽  
Short Circuit ◽  
Full Range ◽  
Point Of View ◽  
System Stability ◽  
Salient Pole ◽  
Three Phase ◽  
Voltage Phase ◽  
Physical Quantities

This article presents the simulation results of hydro generator faulty synchronization during connection to the grid for various voltage phase shift changes in a full range (−180°; 180°). A field-circuit model of salient pole synchronous hydro generator was used to perform the calculation results. It was verified using the measured no-load and three-phase short-circuit characteristics. This model allowed observing the physical phenomena existing in the investigated machine, especially in the rotor which was hardly accessible for measurement. The presented analysis shows the influence of faulty synchronization on the power system stability and the construction components which are the most vulnerable to damage. From a mechanical point of view, the most dangerous case was for the voltage phase shift equal to −120°, and this case was analyzed in detail. Great emphasis was placed on the following physical quantities: electromagnetic torque, stator current, stator voltage, rotor current, current in rotor bars, and active and reactive power. The physical quantities existing during faulty synchronization were compared with a three-phase sudden short-circuit state. From this comparison, we selected the values of physical quantities that should be taken into account during design of new hydro generators to withstand the greatest possible threats during long-term work.

scholarly journals Research on Transient Power Quality of Large-capacity Electric Arc Furnace

2021 ◽  
Author(s):  
Liu Yang ◽  
Qinyue Tan ◽  
Di Xiong ◽  
Zhengguang Liu
Keyword(s):  
Power Quality ◽  
Reactive Power ◽  
Short Circuit ◽  
Electric Arc Furnace ◽  
Electric Arc ◽  
Normal Operation ◽  
Arc Furnace ◽  
Three Phase ◽  
Transient Power Quality

The overrun of transient power quality index caused by the large-capacity electric arc furnace (EAF) has become a prominent problem affecting the safe and stable operation of the power system. (1) In this paper, the relationship between arc furnace volt-age and current is derived based on the different stages of arc combustion, and the random variation of chaotic phenomenon of the arc voltage are simulated. Established an EAF model suitable for the study of transient power quality problems. (2) Take 50t AC EAF as an example to analyze the reactive power impact and the influence on the point of common coupling (PCC) voltage caused by the three-phase short circuit of the electrode. The results show that the experimental results are consistent with the theoretical analysis, verifying the correctness and effectiveness of the model. (3) When the three-phase short-circuit occurs, the reactive power impact is nearly 6 times that of normal operation, the short-circuit current is 2.66 times that of normal operation, and the effective value of the PCC voltage has dropped by 40.37%, which provides a theoretical basis for real-time compensation of impulsive reactive power and improvement of the transient power quality of the EAF.

scholarly journals Modelling of Electric Grid to Enhance Generated Power Evacuation

2021 ◽  
pp. 163-173
Author(s):  
Donald Eloebhose ◽  
Nelson Ogbogu
Keyword(s):  
Power Plants ◽  
Short Circuit ◽  
Flow Analysis ◽  
Load Flow ◽  
System Stability ◽  
Contingency Analysis ◽  
Load Flow Analysis ◽  
Electric Power Grid ◽  
Three Phase ◽  
Rivers State

The study of evacuation of power from the power plants in Rivers State Nigeria, connecting to the 330kV transmission network of the Transmission Company of Nigeria (TCN). The Power World Simulator Educational version was used in the modelling and simulation of the electric power grid. The study of load flow analysis, short circuit, transient and N-1 contingency analysis and their effect on the 330 kV/132kV transmission bus connected to the existing power plants in Rivers State Nigeria namely; Rivers IPP (180MW), Afam III (265.6MW), Afam IV & V (351.00 MW) and Afam VI G. S (650.00 MW) was carried out. From the short circuit study, it is observed that when a bus is faulted with a 3-phase fault, the three-phase voltages of the system drastically become zero in all the phases. The other buses of the network experience an increase in voltage and all the buses fed have the same effect as the bus under fault, though the effect is felt more on the buses. However, with the introduction of substation splitting at Afam III and ongoing Afam IV substations, the short circuit level will be reduced by 15%; leading to improvement in the overall system stability.

scholarly journals Voltage stability analysis using STATCOM

2021 ◽  
Author(s):  
Umang Patel
Keyword(s):  
Power System ◽  
Power Control ◽  
Voltage Stability ◽  
Reactive Power ◽  
Stability Margin ◽  
Power System Stability ◽  
System Stability ◽  
Transmission Network ◽  
Voltage Stability Margin ◽  
Three Phase

Power system stability is gaining importance because of unusual growth in power system. Day by day use of nonlinear load and other power electronics devices created distortions in the system which creates problems of voltage instability. Voltage stability of system is major concerns in power system stability. When a transmission network is operated near to their voltage stability limit it is difficult to control active-reactive power of the system. Our objectives are the analysis of voltage stability margin and active-reactive power control in proposed system which includes model of STATCOM with aim to analyse its behavior to improve voltage stability margin and active-reactive power control of the system under unbalanced condition. The study has been carried out using MATLAB Simulation program on three phase system connected to unbalanced three phase load via long transmission network and results of voltage and active-reactive power are presented. In future work, we can do power flow calculation of large power system network and find the weakest bus of the system and by placing STATCOM at that bus we can improve over all stability of the system

scholarly journals Load Flow Analysis in Hybrid AC-DC Transmission Network

2021 ◽  
pp. 617-624
Author(s):  
Ajith M ◽  
Dr. R. Rajeswari
Keyword(s):  
Power Systems ◽  
Power System ◽  
Transmission Lines ◽  
Power Flow ◽  
Reactive Power ◽  
Short Circuit ◽  
Flow Analysis ◽  
Load Flow ◽  
System Stability ◽  
And Control

Power-flow studies are of great significance in planning and designing the future expansion of power systems as well as in determining the best operation of existing systems. Technologies such as renewables and power electronics are aiding in power conversion and control, thus making the power system massive, complex, and dynamic. HVDC is being preferred due to limitations in HVAC such as reactive power loss, stability, current carrying capacity, operation and control. The HVDC system is being used for bulk power transmission over long distances with minimum losses using overhead transmission lines or submarine cable crossings. Recent years have witnessed an unprecedented growth in the number of the HVDC projects. Due to the vast size and inaccessibility of transmission systems, real time testing can prove to be difficult. Thus analyzing power system stability through computer modeling and simulation proves to be a viable solution in this case. The motivation of this project is to construct and analyze the load flow and short circuit behavior in an IEEE 14 bus power system with DC link using MATLAB software. This involves determining the parameters for converter transformer, rectifier, inverter and DC cable for modelling the DC link. The line chosen for incorporation of DC link is a weak bus. This project gives the results of load flow and along with comparison of reactive power flow, system losses, voltage in an AC and an AC-DC system.

scholarly journals Microgrid Protection Strategy Based on the Autocorrelation of Current Envelopes Using the Squaring and Low-Pass Filtering Method

Energies ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2350 ◽  
Author(s):  
Shazia Baloch ◽  
Saeed Zaman Jamali ◽  
Khawaja Khalid Mehmood ◽  
Syed Basit Ali Bukhari ◽  
Muhammad Saeed Uz Zaman ◽  
...  
Keyword(s):  
Reactive Power ◽  
Short Circuit ◽  
Backup Protection ◽  
Medium Voltage ◽  
Protection Scheme ◽  
High Penetration ◽  
Islanded Operation ◽  
Three Phase ◽  
Low Pass ◽  
Efficient Protection

To resolve the protection issues caused by high penetration of distributed energy resources, this paper proposes an efficient protection scheme for microgrids based on the autocorrelation of three-phase current envelopes. The proposed strategy uses a squaring and low-pass filtering approach for evaluating the envelope of the current signal. Then, the variance of the autocorrelation function is used to extract the hidden information of the distorted envelope to detect the fault signatures in the microgrid. Furthermore, the reactive power is used for determining the fault direction. The performance of the proposed protection scheme was verified on a standard medium-voltage microgrid by performing simulations in the MATLAB/Simulink environment (Version: R2017b). The proposed scheme was shown to be easy to implement and have good performance under looped and radial configuration for both grid-connected and islanded operation modes. The simulation results showed that the scheme could not only detect, locate, classify, and isolate various types of short-circuit faults effectively but also provide backup protection in case of primary protection failure.

Electrical fault diagnosis in induction motors using local extremes analysis

2016 ◽  
Vol 22 (3) ◽  
pp. 321-332 ◽  
Author(s):  
Paulo Cezar Monteiro Lamim Filho ◽  
Fabiano Bianchini Batista ◽  
Robson Pederiva ◽  
Vinicius Augusto Diniz Silva
Keyword(s):  
Induction Motors ◽  
Short Circuit ◽  
Induction Machines ◽  
Time Sequence ◽  
Content Type ◽  
Three Phase ◽  
Unbalanced Voltage ◽  
Voltage Phase ◽  
Detection And Diagnosis ◽  
Original Time

Purpose – The purpose of this paper is to introduce an algorithm based only on local extreme analysis of a time sequence to further the detection and diagnosis of inter-turn short circuits and unbalanced voltage supply using vibration signals. Design/methodology/approach – The upper and lower extreme envelopes from a modulated and oscillatory time sequence present a particular characteristic being of, theoretically, symmetrical versions with regard to amplitude reflection around the time axis. Thus, one may say that they carry the same characteristics in terms of waveforms and, consequently, frequency content. These envelopes can easily be built by an interpolation process of the local extremes, maximums and minimums, from the original time sequence. Similar to modulator signals, they contain more detailed and useful information about the required electrical fault frequencies. Findings – Results show the efficiency of the proposed algorithm and its relevance to detecting and diagnosing faults in induction motors with the advantage of being a technique that is easy to implement in any computational code. Practical implications – A laboratory investigation carried out through an experimental setup for the study of faults, mainly related to the stator winding inter-turn short circuit and voltage phase unbalance, is presented. Originality/value – The main contribution of the work is the presentation of an alternative tool to demodulate signals which may be used in real applications like the detection of faults in three-phase induction machines.

New Control Topology for Railway Static Power Conditioner

2014 ◽  
Vol 596 ◽  
pp. 625-630
Author(s):  
Ying Pan ◽  
Juan Bao
Keyword(s):  
Reactive Power ◽  
Dead Zone ◽  
System Stability ◽  
Loop Control ◽  
Traction Power Supply System ◽  
Power Conditioner ◽  
Three Phase ◽  
Control Scheme ◽  
Static Power ◽  
Traction Power Supply

The traction power supply system of electric railway has the disadvantages of heavy unbalanced three phase, large harmonics and reactive power. Based on back-to-back converter, railway static power conditioner (RPC) can effectively balance the load between two arms, compensate the harmonic current and reactive power. As the conventional PI control is difficult to trace the waveform, a dual-loop control scheme was applied. The control scheme reduces the influences of the factors, such as sampling and calculation delay, dead-zone, parameters’ shift, on the system stability and enhances the robustness of the whole system. It can also eliminate the negative sequence current and three-phase voltage fluctuations of the primary side, improve the power factor and harmonic filter, so that electrified railway power quality problems can be resolved perfectly. The whole design was provided. Analysis and simulation results testify the effectiveness of the proposed control scheme.

scholarly journals Electric Vehicle Ultra-Fast Battery Chargers: A Boost for Power System Stability?

2021 ◽  
Vol 12 (1) ◽  
pp. 16
Author(s):  
Fabio Mandrile ◽  
Davide Cittanti ◽  
Vincenzo Mallemaci ◽  
Radu Bojoi
Keyword(s):  
Power System ◽  
Electric Vehicle ◽  
Reactive Power ◽  
Short Circuit ◽  
Electric Power System ◽  
System Stability ◽  
High Peak Power ◽  
Charging Station ◽  
Fast Charging ◽  
The Impact

As a consequence of the exponential growth of the electric vehicle (EV) market, DC fast-charging infrastructure is being rapidly deployed all around the world. Ultra-fast charging (UFC) stations are starting to pose serious challenges to the electric power system operation, mostly due to their high peak power demand and unregulated discontinuous operation. To address these issues, local energy storage can be installed, ensuring a smoother grid power absorption profile and allowing to provide grid-supporting features. In this work, a control solution for the grid-side AC/DC converter of next-generation EV UFC stations is proposed. A virtual synchronous compensator (VSC) control algorithm is implemented, in order to lessen the impact of the charging station on the utility and to provide the full spectrum of grid ancillary services (i.e., frequency regulation, reactive power compensation, harmonic reduction, short circuit current generation, etc.). The proposed control strategy is verified experimentally on a downscaled 15 kVA three-phase inverter, emulating the grid front-end of the charging station.

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