scholarly journals Analysis of power system operation at asymmetrical load

2018 ◽  
Vol 19 ◽  
pp. 01029
Author(s):  
Stefan Paszek ◽  
Adrian Nocoń ◽  
Piotr Pruski
Keyword(s):  
Power System ◽  
Short Circuit ◽  
Synchronous Generator ◽  
Angular Speed ◽  
Power Line ◽  
Model Parameters ◽  
System Operation ◽  
Two Phase ◽  
The Impact ◽  
Generator Stator

The paper presents a mathematical model of a power system (PS) consisting of a generating unit (with a synchronous generator) connected by a high voltage (transmission) power line to a bus. The state and output equations of the generator are expressed in the coordinate system d, q, 0 and with the use of phase quantities of the generator stator, the bus and the power line, which is especially useful in the analysis of asymmetrical states. A disturbance of the steady state in the form of a two-phase short-circuit in the transmission line was taken into account in the made calculations. The influence of the excitation system and angular speed control system of the generator as well as the impact of selected generator model parameters on the waveforms were investigated.

scholarly journals Impact of Asymmetry of Over-Head Power Line Parameters on Short-Circuit Currents

2020 ◽  
Vol 5 (4) ◽  
pp. 112-115
Author(s):  
Žaneta Eleschová ◽  
Marián Ivanič
Keyword(s):  
Power System ◽  
Short Circuit ◽  
Power Line ◽  
Ground Fault ◽  
Three Phase ◽  
Calculation Results ◽  
Phase Conductors ◽  
The Impact ◽  
Short Circuit Currents

<span lang="EN-GB">This paper analyses the impact of asymmetry of over-head power line parameters on short circuit currents when three-phase fault and phase-to-ground fault occur. The calculation results with consideration of an asymmetry of the power line parameters are confronted with the calculation in accordance with the Slovak standard STN EN 60909 which does not consider asymmetry of equipment parameters in the power system. The calculation of short-circuit conditions was carried out for two types of 400 kV power line towers on which is a considerably different arrangement of phase conductors.</span>

scholarly journals In-Situ Measurement of Power Loss for Crystalline Silicon Modules Undergoing Thermal Cycling and Mechanical Loading Stress Testing

Energies ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 72
Author(s):  
Sergiu Spataru ◽  
Peter Hacke ◽  
Dezso Sera
Keyword(s):  
Thermal Cycling ◽  
Power Loss ◽  
Stress Testing ◽  
Series Resistance ◽  
Short Circuit ◽  
In Situ Measurement ◽  
Mechanical Degradation ◽  
Model Parameters ◽  
The Impact

An in-situ method is proposed for monitoring and estimating the power degradation of mc-Si photovoltaic (PV) modules undergoing thermo-mechanical degradation tests that primarily manifest through cell cracking, such as mechanical load tests, thermal cycling and humidity freeze tests. The method is based on in-situ measurement of the module’s dark current-voltage (I-V) characteristic curve during the stress test, as well as initial and final module flash testing on a Sun simulator. The method uses superposition of the dark I-V curve with final flash test module short-circuit current to account for shunt and junction recombination losses, as well as series resistance estimation from the in-situ measured dark I-Vs and final flash test measurements. The method is developed based on mc-Si standard modules undergoing several stages of thermo-mechanical stress testing and degradation, for which we investigate the impact of the degradation on the modules light I-V curve parameters, and equivalent solar cell model parameters. Experimental validation of the method on the modules tested shows good agreement between the in-situ estimated power degradation and the flash test measured power loss of the modules, of up to 4.31 % error (RMSE), as the modules experience primarily junction defect recombination and increased series resistance losses. However, the application of the method will be limited for modules experiencing extensive photo-current degradation or delamination, which are not well reflected in the dark I-V characteristic of the PV module.

The Impact of Synchronous Generator on Voltage Sag Mitigation in Power System Network

2021 ◽  
Author(s):  
Umme Kulsum Jhuma ◽  
Saad Mekhilef ◽  
Shameem Ahmad ◽  
Jahurul Islam ◽  
Jahidur Rahman Jesan ◽  
...  
Keyword(s):  
Power System ◽  
Synchronous Generator ◽  
Voltage Sag ◽  
The Impact

scholarly journals Improved Control Strategy of MMC–HVDC to Improve Frequency Support of AC System

2020 ◽  
Vol 10 (20) ◽  
pp. 7282
Author(s):  
Zicong Zhang ◽  
Junghun Lee ◽  
Gilsoo Jang
Keyword(s):  
Wind Turbines ◽  
Wind Farm ◽  
Control Method ◽  
Short Circuit ◽  
Synchronous Generator ◽  
Frequency Stability ◽  
Offshore Wind ◽  
Inertial Response ◽  
Control Evaluation ◽  
The Impact

With the continuous development of power electronics technology, variable-speed offshore wind turbines that penetrated the grid system caused the problem of inertia reduction. This study investigates the frequency stability of synchronous, offshore wind-farm integration through a modular-multilevel-converter high-voltage direct-current (MMC–HVDC) transmission system. When full-scale converter wind turbines (type 4) penetrate the AC grid, the AC system debilitates, and it becomes difficult to maintain the AC system frequency stability. In this paper, we present an improved inertial-response-control method to solve this problem. The mathematical model of the synchronous generator is based on the swing equation and is theoretically derived by establishing a MMC–HVDC. Based on the above model, the inertia constant is analyzed using a model that integrates the MMC–HVDC and offshore synchronous generator. With the new improved control method, a more sensitive and accurate inertia index can be obtained using the formula related to the effective short-circuit ratio of the AC system. Moreover, it is advantageous to provide a more accurate inertial control evaluation for AC systems under various conditions. Furthermore, the impact of the MMC–HVDC on system safety is assessed based on the capacitor time constant. This simulation was implemented using the PSCAD/EMTDC platform.

scholarly journals The impact of selected biofuels on the performance parameters of the Common Rail power system in the utility engine

2018 ◽  
Vol 234 ◽  
pp. 03004 ◽  
Author(s):  
Paweł Krzaczek ◽  
Arkadiusz Rybak ◽  
Andrzej Bochniak
Keyword(s):  
Power System ◽  
Common Rail ◽  
Animal Origin ◽  
System Operation ◽  
Working Pressure ◽  
Load Range ◽  
Power System Operation ◽  
The Common ◽  
Operation Parameters ◽  
The Impact

The aim of the research was to determine the impact of biofuels from waste materials of plant and animal origin on the parameters of the common rail power supply system in the utility engine. The tests included identification of power system operation parameters in the whole load range of the tested engine, taking into account the limit and diagnostic parameters of the injectors operation. Then, for certain parameters, the engine injectors were tested on the test bench: injection pressure in the range of 25-135 MPa, injection time in the range of 200-1600 μs. In the tests, as reference fuel for testing injectors were used diesel fuel and three types of methyl esters of higher fatty acids: vegetable, animal and WCO origin. The measurements for individual fuels were made in the operating temperature range 30-60°C. The tests have shown significant changes in the volume of the fuel injection rates depending on the fuel used. Particularly, visible changes concerned the power system operation parameters for high engine speeds and the maximum working pressure of the common rail system in the engine.

scholarly journals Adaptive Armature Resistance Control of Virtual Synchronous Generators to Improve Power System Transient Stability

Energies ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2365
Author(s):  
Daniel Carletti ◽  
Arthur Eduardo Alves Amorim ◽  
Thiago Silva Amorim ◽  
Domingos Sávio Lyrio Simonetti ◽  
Jussara Farias Fardin ◽  
...  
Keyword(s):  
Adaptive Control ◽  
Power System ◽  
Transient Stability ◽  
Short Circuit ◽  
Stability Margin ◽  
Synchronous Generator ◽  
Synchronous Generators ◽  
Resistance Change ◽  
Clearing Time ◽  
Fault Current Limiters

The growing number of renewable energy plants connected to the power system through static converters have been pushing the development of new strategies to ensure transient stability of these systems. The virtual synchronous generator (VSG) emerged as a way to contribute to the system stabilization by emulating the behavior of traditional synchronous machines in the power converters operation. This paper proposes a modification in the VSG implementation to improve its contribution to the power system transient stability. The proposal is based on the virtualization of the resistive superconducting fault current limiters’ (SFCL) behavior through an adaptive control that performs the VSG armature resistance change in short-circuit situations. A theoretical analysis of the problem is done based on the equal-area criterion, simulation results are obtained using PSCAD, and experimental results are obtained in a Hardware-In-the-Loop (HIL) test bench to corroborate the proposal. Results show an increase in the system transient stability margin, with an increase in the fault critical clearing time (CCT) for all virtual resistance values added by the adaptive control to the VSG operation during the short-circuit.

Studies of the Modelling Accuracy of Steam Turbine Control Systems for Diagnostic Tests of Automatic Synchronizers

2013 ◽  
Vol 199 ◽  
pp. 61-66
Author(s):  
Grzegorz Redlarski ◽  
Janusz Piechocki ◽  
Mariusz Dąbkowski
Keyword(s):  
Angular Velocity ◽  
Control Systems ◽  
Working Conditions ◽  
Synchronous Generator ◽  
Angular Speed ◽  
Velocity Control ◽  
Reliable Operation ◽  
Relevant Field ◽  
The Impact ◽  
Selection Of

One of the important factors that affect the reliable operation of the power system and the rapid restitution after disaster is a quick and effective combining synchronous electric power facilities to operate in parallel [. Hence, diagnostics of automatic synchronizers at every stage of their life, from building a prototype, through the whole life, until removing such devices from the operation, is an extremely important and responsible activity. In ordinary practice, this action is performed by dedicated test of mechatronics systems, called simulators [2, , in close to real - or even more restricted - conditions. One of the major limitations in the relevant field undoubtedly concerns the selection of an appropriate structure and implementation of models of the angular velocity control systems involved in the process of connection. These models must be simple enough to allow computation with a frequency of kHz, and, at the same time, developed enough to be able to form diverse and close to real working conditions. For these reasons, classical approach is not possible, allowing the use of well-known Parks model [ of the synchronous generator and the complex - and often nonlinear [. Hence, considered above-mentioned requirements and indicated constraints, to test the automatic synchronizer the designers of mechatronics systems use a number of simplifications during modeling of the angular speed control systems [. However, models are not detailed enough to study the impact of changes in the shape of relevant characteristics under the influence of changes the angle of phase discrepancy in the process of connecting. Hence, this paper presents the results of the research of the currently used method of modeling the most commonly used control systems of angular velocity, in the respective systems.

scholarly journals Fault Assessment and Mitigation of the 132kV Transmission Line in Nigeria using Improved Resonant Fault Current Limiting (RFCL) Protection Scheme

2018 ◽  
Vol 3 (10) ◽  
pp. 38-44
Author(s):  
D. C. Idoniboyeobu ◽  
S. L. Braide ◽  
Wigwe Elsie Chioma
Keyword(s):  
Power System ◽  
Transmission Line ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Resonant Circuit ◽  
Fault Current ◽  
Protection Scheme ◽  
Current Limiting ◽  
Simulation Results ◽  
The Impact

This research work proposed an improved Resonant Fault Current Limiting (RFCL) protection scheme to reduce the impact of three-phase short-circuit faults in a power system sub-transmission network. The model used an interpolator-extrapolator technique based on a Resonant Fault Current Limiter (RFCL) for automating the procedure of predicting the required reactor value that must be in resonant circuit to limit the short-circuit current values to permissible values. Using the developed model, short-circuit fault simulations on the three phases of the transmission line (Phase A-C) were performed in the MATLAB-SIMULINK environment. Simulation results were obtained by varying the resonant inductance (reactor) parameter of the RFCL circuit for each of the phases to obtain permissible short-circuit current levels and the values used to program a functional interpolator-extrapolator in MATLAB; the resonant values were typically set to values of inductance equal to 0.001H, 0.01H and from 0.1H to 0.5H in steps of 0.1H. Simulation results revealed the presence of very high short-circuit current levels at low values of the resonant inductor. From the results of simulations, there are indications that the RFCL approach is indeed very vital in the reduction of the short circuit current values during the fault and can safeguard the circuit breaker mechanism in the examined power system sub-transmission system. In addition, lower fault clearing times can be obtained at higher values of inductances; however, the clearance times start to converge at inductance values of 0.1H and above.

scholarly journals Method to Evaluate the Impact of Integration of PMSG on Stability of Synchronous Generator Shaft Under Weak Grid Connection

2021 ◽  
Vol 9 ◽  
Author(s):  
Tianyi Zhang ◽  
Haifeng Wang
Keyword(s):  
Power System ◽  
Wind Power ◽  
Synchronous Generator ◽  
Connection Strength ◽  
Continuous Growth ◽  
Grid Connection ◽  
Shaft System ◽  
Ac Power ◽  
The Stability ◽  
The Impact

With the continuous growth in the amount of wind power accessed by the AC grid, the impact of the grid connection of wind-power generators with the power system has gradually increased. In this study, the subsynchronous oscillation of a synchronous generator (SG) shaft caused by the integration of direct-drive permanent-magnet synchronous generators (PMSGs) was investigated. The mechanism governing the effect of the connection strength between the PMSG and AC power system on the stability of the generator shaft system was analyzed based on the complex torque coefficient method. When the connection strength between the PMSG and AC power system weakens, the same voltage variation that occurs at the point of common coupling of the PMSG stimulates more intense power fluctuations in the PMSG, and the electrical damping injected by the PMSG into the SG increases considerably. This may cause the oscillation mode dominated by the generator shaft system to move to the right half of the complex plane, thereby reducing the stability of the generator shaft system. In addition, the evaluation process of the influence of the PMSG on the SG shaft system was summarized, and the proposed method can determine the stability of the AC power system after the integration of the PMSG. Finally, the effectiveness of the proposed method was validated via study cases, and conclusions were drawn. This method is expected to serve as a useful tool for the risk assessment of subsynchronous oscillations in wind farms.

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