Generator Protection Subsynchronous Resonance
Sokhom Sim
Department of Electrical Engineering
California State University, Long Beach
Long Beach, CA 90840-8303 ericsokhomsim0@gmail.com Abstract-the transmission lines are complex systems and the power generation sources are generally far away from the distributing center. The transmission lines congesting or overloading are always a challenge for utilities protection engineers. As a result, a series compensating capacitors are being used to alleviate the transmission lines, and increased the loads capability. However, adding series compensating capacitors (SCC) to the transmission lines will increase the potential risk of subsynchronous resonance (SSR). In fact, SSR leads to a possible torsional interaction and damage the turbine generator shaft when the mechanical frequency falls below the electrical frequency. In this paper, a brief analysis of SSR phenomenon will be addressed by computing the eigenvalues, eigenvectors, and MATLAB/Simulink for simulation incorporated with the IEEE first and second benchmark Model # 1 system.
Keywords—Subsynchronous Resonance, Torsional oscillation, Series Compensating Capacitor, Transient Torque, generator induction effect.
Introduction
The growing demand of electricity in a large cities increase the need of high power transmission from remote generating stations. Therefore, for reducing the cost-effective in power transmission, series compensating capacitor (SSC) is used to
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The reactive power supplied by the STATCOM for DF improvement is capacitive in nature. Instinctively, the higher the STATCOM’s reactive power, the higher the dc-link voltage of the STATCOM (the higher the voltage requirements of the semiconductor devices).
In India, 400kV Double circuit Transmission line is predominant with Twin Moose / Quad Moose configuration. Similarly 765kV Double circuit Transmission line with Hexa zebra conductor configuration is predominant taking care of bulk power Transfer from remote generating stations and connecting various regional grids. However these lines are under utilized due to stability constraints. Clerici [1] suggested conversion of existing AC line to HVDC line with some modification in the tower structure cross arm
The uncertainty in the generation capacity is then only due to failures (outages) of generator units [9]. Generating units will occasionally fail to operate and the system operator has to make sure that enough reserve is available to be operated when this situation happens, as will be discussed in the following subsection.
Problem statement: As the characteristics of the distribution network and high volume power electronics penetration into the network are significantly different from the conventional power system, several issues are raised. Some of the issues, which are a promising field for future research, are described shortly below:
In the grid new renewable resources are added to extract more power. This adds more power quality issues to grid connection. A Power quality problem is an occurrence manifested as a nonstandard voltage, current or frequency that results in a failure or a mis-operation of end user equipment. This paper investigates the use of a static synchronous compensator (STATCOM) is connected at a point of common coupling with Battery Energy Storage System(BESS)to overcome of a power quality issues of a wind farm equipped with variable speed wind turbines driving Double – Fed Induction Generators (DFIG). A physical control scheme, including four control loops: ac voltage, dc voltage, ac active current and ac reactive current controllers, is pre-specified for the STATCOM. A synthetic algorithm is proposed to embed these physical control loops in the output feedback path. The simulation results demonstrated that under various system disturbances, the proposed mode decoupling STATCOM is effective in regulating IG terminal voltage.
An accurate cost function for the transmission system is formulated where both fixed and variable costs for all planned facilities are includes, in addition to the cost energy losses. The cost function is then minimized, using (BBO) algorithms. We can be used to derive algorithms for optimization. We apply the BBO on the model of IEEE of 6-bus test system.
The penetration level of distributed generators is increased due to the restructuring in electric power system.
The control of active power and frequency in a power system is referred to as load frequency control (LFC). Stable operation of interconnected power system requires both constant frequency and constant tile-line power exchange [1]. An area control error (ACE), defined as a linear combination of tie line power and frequency deviations, is taken as the controlled output of LFC. LFC regulates ACE to zero such that frequency and tie-line power errors are forced to zeros. PID controller is widely used in LFC due to its simplicity but is gives long settling time and produces large frequency deviation [2]. In recent years, active disturbance rejection control (ADRC) developed by J. Han [3] and modified by Z. Gao [4, 5] has been proposed for the LFC controller [6-9].
Reactive power compensation can be in a form of series type. In a power line at rated frequency, series compensation technique uses capacitors to decrease the equivalent reactance. The series capacitor generates reactive power to balance a fraction of line’s transfer reactance and this type of capacitor arrangement results improvement in the power transmission network. It increases the angular stability of the power system, improves the voltage stability of the corridor and also optimizes power sharing between parallel circuits [5]. Series compensation can be also implemented by using voltage or current source devices as shown in Figure A:
Newly, several new protective schemes have been proposed to deal with the previous problem in large power
The power flow analysis involves the calculations of power flows and voltages of a transmission network for specified terminal or bus condition. Such calculations are required for the analysis of steady-state as well as dynamic performance of power systems [1].
This new technology has replaced many of the old ones, bringing many advantages to the user, for example DC & AC drives, soft stators, UPS, etc. Since this new technology is rapidly gaining in the modern industries, power systems are expected to provide an ideal sinusoidal waveforms for currents and voltages,
Anyone can be mean when they’re hiding behind a computer screen, which is why cyberbullying is a big concern for society today. The younger generation often socializes and communicates online, rather than in person. They prefer to text rather than talk on the phone, and often prefer to video chat instead of meeting up in person. The use of technology makes cyberbullying much easier and more common, especially among teenagers. Cyberbullying is the reason for cutting, school shootings, and suicide, but to the bullies it’s just a game on the computer and they can’t see the damage that they are causing. Some kids do it for entertainment, some do it to raise their own self-esteem, while others are just following the crowd. Many people think that everything can be forgotten by a click of a button, but it’s not that simple. Once it’s online, it follows the victim everywhere they go. Cyberbullying greatly affects the victim’s mental and emotional health as well as their ability to do well in class, so schools should have the power to punish cyberbullies even if it was done off of school grounds.
The quality and dependability of power have become an important factor for the enlargement of new technologies with the imminent derestricted environment. The beginning of power- electronic devices have steered a new era of power quality while integrating them with the renewable sources of energy. Distributed generation (DG) systems are projected to play a vital role to meet the energy demand with non-polluted environment. Distributed generation technologies such as wind turbine, photovoltaic systems, fuel cell and diesel engines are used in various places. Of all these diesel engines have fast response time and controllability, they are relatively common for combination with WECS (wind energy conversion systems).