Generator Protection : Generator Monitoring Subsynchronous Resonance

The DVR is one of the most common and effective solutions for protecting critical load against voltage sags [10] [11]. The DVR is a power electronic device used to inject three-phase voltages in series and in synchronism with the distribution feeder voltages in order to compensate for voltage sags. Moreover, it can be efficiently used to augment the fault ride through capability in wind applications. Detection time is an important factor in the voltage restitution process. Fast detection

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:

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).

Power system analysis is important part of power systems. According to the mathematical model we can divide security analysis into two types

Abstract— this paper presents a brief overview of standards for power electronics. All the standards presented in this paper are currently active and are approved by the Institute of Electrical and Electronics Engineer Standards Association (IEEE-SA) and American National Standards Institute (ANSI).

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.

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

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,

The penetration level of distributed generators is increased due to the restructuring in electric power system.

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:

protection are designed to achieve required discrimination by sensing that large second harmonic content [1]. The level of second harmonic component of the inrush current has been reduced due to improving in transformer core material and occur power system changes. Additionally, a large second harmonic can also be found in transformer internal fault currents if a shunt capacitor is connected to a transformer in a long extra high voltage transmission line. Therefore, the methods based on the measurement of the second harmonic are not sufficiently effective for differential protective relays [2].

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].

In the present era of advanced technologies, power electronics devices have wide applications. These devices are important for industrial and domestic uses but they generate the power quality problems [1-2].these problems are created on account of these devices

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].