scholarly journals The.main types of wind turbines-generators in the power supply system

2022 ◽  
Vol 23 (5) ◽  
pp. 71-85
Author(s):  
V. A. Novobritsky ◽  
D. S. Fedosov
Keyword(s):  
Second Harmonic ◽  
Short Circuit ◽  
Separation Of Variables ◽  
Harmonic Component ◽  
Relay Protection ◽  
Short Circuit Current ◽  
Current Transformer ◽  
Correct Operation ◽  
Protection Devices ◽  
Dc Component

THE PURPOSE. This paper considers the problem of relay protection functioning when the current transformer reaches the saturation mode which is provided by transient processes.METHODS. MATLAB Simulink software environment allows reproducing the method of statespace representation by using structural blocks. The model is verified by comparison the time to saturation, obtained by calculation and according to the graphical data of the model. The separation of variables method extracts and graphically displays the investigated components.RESULTS. This paper reveals that applying the requirements of IEC 61869-2:2012 standard, which determines the worst combination of series of unfavorable factors for current transformers in transient mode, can influence a serious impact on the correct operation of relay protection based on current, reactance or differential principle of action. Saturation of the current transformer can lead to both negative results: false operation of relay protection devices and their failure.CONCLUSION. According to the results of the study, it was determined that the presence of a DC component in the primary short-circuit current has the greatest effect on the protection operation. The delays in the restoration of the RMS value of the short-circuit current reached up to 0.3 seconds, which is comparable with the response time of the second protection zones for microprocessor-based relay protection devices. The DC component of the primary current and the presence of residual magnetic induction of the current transformer provides the largest content of the magnetization current, the largest angular error and also the largest content of the second harmonic component in the secondary short-circuit current.

scholarly journals INTELLIGENT RELAY PROTECTION

2020 ◽  
pp. 30-37
Author(s):  
A. N. Shilin ◽  
A. A. Shilin ◽  
P. V. Dikarev ◽  
O. O. Ahmedova
Keyword(s):  
Smart Grids ◽  
Short Circuit ◽  
Relay Protection ◽  
Short Circuit Current ◽  
Weather Conditions ◽  
External Factors ◽  
Current Voltage ◽  
Environment Temperature ◽  
Protection Devices ◽  
Time Of Year

Currently, with the introduction of electrical smart grids, one of the main problems is increasing the authenticity of turning on the relay protection devices during emergency modes. This is due to the fact that the short circuit current, and therefore setpoint, is affected by large number of external factors, such as the humidity of the earth and the atmosphere, external environment temperature, soil state, terrain, etc. Therefore, the relay protection devices must to take account of the influence of these factors and to introduce automatic correction for the setpoint current, i.e. the device must be intelligent. For solution this problem, the intelligent device was developed, containing a microprocessor and a set of sensors of physical quantities of external factors. A more accurate calculation of the relay protection parameters will allow to increase a sensitivity and to avoid the failures of turning on or false turning on of protection. The results of the research can be applied to create a multidimensional mathematical model allowing automatic to select the relay protection settings based of the initial data on weather conditions, time of year, resistance of the soil, current, voltage, etc.

Research on Adaptive Current Protection of Wind Farm

2012 ◽  
Vol 260-261 ◽  
pp. 257-262
Author(s):  
Feng Ting Li ◽  
Chang Sheng Su
Keyword(s):  
Wind Farm ◽  
Short Circuit ◽  
High Sensitivity ◽  
Short Circuit Current ◽  
Phase Selection ◽  
Wind Generators ◽  
Attenuation Characteristic ◽  
Sample Data ◽  
Dc Component ◽  
Current Sample

In allusion to the problems of convention current protection when it was used to collect circuit of wind farm, the relay protection should consider the short-circuit current of wind generators; The principle of adaptive current protection was described, the fault current and attenuation characteristic of asynchronous wind generator was studied, the scheme of adaptive current protection was proposed for wind farm operation. Taking PSCAD/EMTDC as the platform, simulation and record the voltage and current sample-data of different wind farm operation which can guarantee high sensitivity phase selection, the high accuracy wind generators impedance measure method based on FFT filter DC component is presented , and using MATLAB program achieved the scheme of adaptive current protection. Simulation results demonstrate that collect circuit adaptive current protection is adaptive wind farm operation model, and enhance the operation benefit of wind farm.

scholarly journals Control Strategy Based on Arm-Level Control for Output and Circulating Current of MMC in Stationary Reference Frame

Energies ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4160
Author(s):  
Waqar Uddin ◽  
Tiago D. C. Busarello ◽  
Kamran Zeb ◽  
Muhammad Adil Khan ◽  
Anil Kumar Yedluri ◽  
...  
Keyword(s):  
Reference Frame ◽  
Control Method ◽  
Second Harmonic ◽  
Harmonic Component ◽  
Effective Control ◽  
Level Control ◽  
Circulating Current ◽  
Stationary Reference Frame ◽  
Pr Controller ◽  
Dc Component

This paper proposed a control method for output and circulating currents of modular multilevel converter (MMC). The output and circulating current are controlled with the help of arm currents, which contain DC, fundamental frequency, and double frequency components. The arm current is transformed into a stationary reference frame (SRF) to isolate the DC and AC components. The AC component is controlled with a conventional proportional resonant (PR) controller, while the DC component is controlled by a proportional controller. The effective control of the upper arm and lower arm ultimately controls the output current so that it delivers the required power to the grid and circulating current in such a way that the second harmonic component is completely vanished leaving behind only the DC component. Comparative results of leg-level control based on PR controller are included in the paper to show the effectiveness of the proposed control scheme. A three-phase, five-level MMC is developed in MATLAB/Simulink to verify the effectiveness of the proposed control method.

scholarly journals Use of Discharge Resistor to Improve Transient De-Excitation in Brushless Synchronous Machines

Energies ◽  
2019 ◽  
Vol 12 (13) ◽  
pp. 2528
Author(s):  
Emilio Rebollo ◽  
Carlos A. Platero ◽  
David Talavera ◽  
Ricardo Granizo
Keyword(s):  
Short Circuit ◽  
Short Circuit Current ◽  
Static Field ◽  
Normal Operation ◽  
Synchronous Machines ◽  
Correct Operation ◽  
Negative Voltage ◽  
Output Field ◽  
First Moment ◽  
Winding Insulation

The discharge resistor is only used in case of electrical trip to reduce the field current as fast as possible and to minimize the damages produced by the short-circuit current supplied by the synchronous machine. The connection of the discharge resistor is done by opening the field breaker and it implies a large negative voltage in the field winding. This negative voltage is limited to 80% of the winding insulation voltage. On the other hand, in case of a transient de-excitation, at the first moment, the automatic voltage regulator (AVR) reduces the field voltage to the minimum. In case of one-quadrant rectifier type AVR, the minimum voltage is zero and in case of two-quadrant rectifier AVR, the minimum voltage is close to the ceiling voltage with negative polarity. In both cases, the minimum voltages are much smaller than the negative voltage produced by the connection of the discharge resistor. This paper presents a new system that improves the transient de-excitation of synchronous machines using the discharge resistor by an additional static field breaker (SFB). The control of the static field breaker and consequently the connection and disconnection of the discharge resistor is done based on the output field voltage supplied by the AVR. This allows the exciter field current to be reduced in a faster way and continue with the normal operation of the machine after the transient. In this study, the correct operation of the additional static field breaker (SFB) has been validated by computer simulations and experimental test in a 15 MVA generator comprising a commercial one-quadrant rectifier AVR type obtaining excellent results.

Research and Improvement of Fourier Algorithm in the Microcomputer Relay Protection

2013 ◽  
Vol 347-350 ◽  
pp. 1945-1948
Author(s):  
Jian Xu ◽  
Xin Yao
Keyword(s):  
Power System ◽  
Harmonic Component ◽  
Relay Protection ◽  
High Accuracy ◽  
Computer Algorithms ◽  
Full Wave ◽  
Dc Component ◽  
Fourier Algorithm ◽  
Improved Algorithm ◽  
Microcomputer Relay Protection

Fourier algorithm can be effective utilized in the Microcomputer relay protection to filter out Harmonic component in the AC signal .but the drawback is that not filter attenuation DC component. it may be affect the computation accuracy of the entire system .and it is also reduce the efficiency of the system. In this paper ,we combined with the actual project ,on the basis of analysis of the full-wave Fourier algorithm ,for the problem of it can not filter decaying a periodic component ,we proposed an improved algorithm, and combined with MATLAB simulation ,the results show that the improved algorithm has the advantages of high accuracy and the algorithm is simple. In the microcomputer relay protection of the power system need to handle all kinds of signals, provide the necessary information for the implementation of protection. however, With the rapid development of computer technology and the continuous research of computer algorithms, a lot of actual power system protection device has been widely used in our life, on the one hand, these devices reduce the complexity of building hardware circuit, on the other hand ,it can make full use of the filter function about some algorithms have itself. The most important is that it can avoid the problem of instability and low efficiency with some filter circuit. But, this characteristic need the algorithms has a high precision [2,3]. The algorithm is set up in the microcomputer protection is a mathematical model for achieve some specific function. and write the corresponding computer applications according to this model. Then do some specific mathematical operations with these digital signals will achieve the purpose of protection. At present, the widely used full wave Fourier algorithm has a function of filtering DC component and harmonic component[4],but it can not filtering the decaying DC component in the system. It will be cause a certain interference and influence to the whole system in the practical application, the result is that led to the precision of the operation drop and lose the meaning of the protecting. In this paper, combined with specific engineering example give an improved calculation method. Through example of simulation has proved that using this algorithm can accurately figure out fundamental component and harmonic component, and it has the advantage of algorithm simple and high accuracy [5].

Relay Protection Setting Calculation and Analysis of Auxiliary Power System for Hydropower Plants

2014 ◽  
Vol 574 ◽  
pp. 324-328
Author(s):  
Nian Fang ◽  
Xian Shan Li ◽  
Hao Xu ◽  
Yu Long Du
Keyword(s):  
Power System ◽  
Short Circuit ◽  
Relay Protection ◽  
Short Circuit Current ◽  
Hydropower Plant ◽  
System Protection ◽  
Auxiliary Power ◽  
Hydropower Plants ◽  
Actual Operation ◽  
Setting Calculation

The configuration and setting calculation of auxiliary power protection are directly related to the regular and safe operation of the equipments, thereby affecting the security and stability of the power plant. The system features are analyzed in depth according to the operational requirements of auxiliary power system protection in Xiangjiaba hydropower plant ,the system model is built on the basis of the actual project, and a variety of short-circuit current calculations are carried out. At last, the setting of the auxiliary power system relay protection is completed. This thesis also proposes solutions to the emerging problems in the process of protection setting. The results of the setting have been applied to the actual operation and no misoperation or maloperation caused by improper constant setting value has occurred so far in Xiangjiaba hydropower plant.

scholarly journals Improved Short-Circuit Current Calculation of Doubly Fed Wind Turbines With Uninterrupted Excitation

2021 ◽  
Vol 9 ◽  
Author(s):  
Jun Yin
Keyword(s):  
Short Circuit ◽  
Relay Protection ◽  
Control Unit ◽  
Short Circuit Current ◽  
Doubly Fed Induction Generator ◽  
Transient Model ◽  
Real Time Digital Simulator ◽  
Doubly Fed ◽  
Current Calculation ◽  
Actual Control

With the enlarging scale of a doubly fed induction generator (DFIG) connected to a power system, the influence of short-circuit current on the system relay protection could not be ignored. Setting and configuring relay protection would be affected by an imprecise short-circuit current calculation. However, some existing studies only consider the condition that the input is the Crowbar and the rotor excitation is blocked. China's new network standard requires the output reactive support current of a DFIG and will change the characteristics of short-circuit current. To solve this problem, on the basis of analyzing the characters of the transient equivalent potential of a DFIG, the transient model of a DFIG with uninterrupted excitation is provided. Based on the characteristics of a non-abrupt change of flux linkage and the requirement of a new grid standard reactive support current, the short-circuit current calculation method of a DFIG with uninterrupted excitation is put forward. Based on the real-time digital simulator (RTDS), a digital-analog experimental platform containing the actual control unit of the DFIG converter is founded, the proposed short-circuit current root mean square (RMS) value calculating method is validated.

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