stability is one of the important factors which we have to consider improving performance of wind generator. The stator windings of DFIM wind generator is interfaced to grid because of that reason transient faults arises in grid. Even in fault conditions also wind generator remain connected in accordance with grid code necessity, to achieve the transient stability improvement for DFIM wind generator a bridgetypefaultcurrentlimiter is proposed. Here to check the efficiency of BFCL in transient stability improvement, both symmetrical and unsymmetrical faults were applied to test system. To prove the strength of BFCL in transient stability improvement it should be compared with Series Dynamic Braking Resistor (SDBR).Simulation can be done in MATLAB or in the SIMULINK. The results show the effectiveness of BFCL than SBDR for transient stability improvement in DFIM wind generator.
In this paper, a 2 MW 690V DFIG variable speed wind generator system has been modeled to analyze the transient stability. The simple construction of DFIG is connected to the grid through step up transformer and double circuit transmission line as shown in Fig 1[ ]. Temporary symmetrical fault were applied at the most vulnerable point of the system. In order to see how much effective the proposed approach is, its performance is compared with that of the series dynamic resistor (SDBR) and bridgetypefaultcurrentlimiter (BFCL). Simulation was carried out using the MATLAB/Simulink software.
ABSTRACT: This system proposes a controllable resistive typebridgetypefaultcurrentlimiter (CR-FCL) to enhance the transient stability of a hybrid power system consisting of a photovoltaic (PV) power generation source, a doubly-fed induction generator (DFIG)-based wind energy system, and a synchronous generator (SG).The CR-FCL is designed such a way that it can provide sufficient damping characteristics to the studied power system. Appropriate resistance generation of the BFCL during a grid fault to provide better transient stability is the main contribution of the work. The effectiveness of the proposed CR-FCL in improving the transient stability and enhancing the dynamic performance of the hybrid power system is verified by applying faults in the power network.. Simulation results obtained from the Matlab/Simulink software show that the proposed FCL is effective in maintaining stable operation of the PV, wind generator, and synchronous generator during the grid fault.
In this work, the bridgetypefaultcurrentlimiter (BFCL) is introduced to mitigate the voltage sag as well as to limit the faultcurrent. By using IGBT as a semiconductor switch in the dc current path instead of thyristors at the bridge part, the BFCL has high speed. This type of FCL is useful for the power quality improvement because of voltage sag and phase angle jump mitigation. The performance of the proposed BFCL is analyzed with the help of a three
ABSTRACT : In this paper Transient stability is a major sympathy toward doubly fed induction machine (DFIM).A DFIM-based wind generator is promptly influenced by shortcomings at the network side as its stator windings are interfaced to grid. Be that as it may, the wind generators need to stay connected and proceed with operation during flaws at the grid side as indicated by the network code prerequisites. Along these lines, it is imperative to improve the transient soundness of the DFIM-based wind generators. To accomplish upgraded transient steadiness of the DFIM, a bridgetypefaultcurrentlimiter (BFCL) is proposed through FLC in this paper. Symmetrical as well as unsymmetrical faults were applied to test system efficiency of the BFCL in transient stability enhancement. Simulations were carried out in Matlab/Simulink environment. To demonstrate the effectiveness of the proposed BFCL ,its performance is compared with series dynamic braking resistor(SDBR). Simulation results of BFCL gives better stabilization of DFIM.
Abstract: Fault ride-through (FRT) is necessary for large wind farm in most power systems. Fixed speed wind turbines (FSWTs) are a fading but important sector in the fast-growing wind turbine (WT) promote. State-of-art technique applied to assemble grid needs for FSWT wind farm is blade pitching and dynamic reactive power compensation (RPC). Blade pitching is controlled by the difficult mechanical loads forced on a wind turbine during quick power re-establishment. Dynamic RPC is forced by its high capital cost. These present technologies can therefore be limiting, particularly when linking to smaller power systems. A new choice equipment is projected that insert series resistance into the generation circuit. The series dynamic braking resistor (SDBR) dissipates active power and boost generator voltage, potentially displacing the need for pitch control and dynamic RPC. In this project we use a delegate wind farm model to study the useful effect of SDBR. The relations between wind turbines and grid results in rising short-circuit level and fault ride-through (FRT) capacity problem throughout fault situation. In this paper, the bridgetypefaultcurrentlimiter (FCL) with discharge resistor is used for solve these trouble. For this FCL, a control system is planned, which use the dc reactor current as control changeable, to change the terminal voltage of induction generator (IG) without measure any parameter of scheme. In this paper, the wind energy conversion system (WECS) is a fixed-speed system able to with a squirrel-cage IG. The drive train is representing by a two-mass model. The analytical and simulation studies of the bridge-type FCL and proposed control system for restraining the faultcurrent and recovering FRT ability are offered and compare with the force of the request of the series dynamic braking resistor (SDBR).
The use of shunt FACTS controllers to improve the fault ride-through of induction generators (IGs) by RPC. The RPC method, which can be provide by STATCOM and SVC, can only control the reactive power after fault happening. Thus, the RPC method is able only to reduce voltage fluctuations of the IG after fault happening . The pitch control system is the cheapest key for the wind generator stabilization, but its reply is slow. As a result, the pitch control system cannot be considered as a useful stabilization means for wind energy conversion system (WECS). In series dynamic braking resistor (SDBR) has been standard and used as a gainful calculate for the improvement of FRT. In direct link of SDBR and dynamic RPC has been represent. The simulation results conclude that a 0.05 per unit (p.u.) SDBR is equivalent to 0.4 p.u dynamic RPC. It means that the SDBR is more helpful than RPC. A significant mean issue for SDBR is its quick addition and early switch out of the dynamic resistor. The bridge-typefaultcurrentlimiter (FCL) with discharge resistor is used for solving trouble of the interface of WECS and power grid. The increase of the faultcurrent is limited by dc reactor without any wait. This characteristic of the bridge-type FCL suppress the immediate voltage drop and it is able to develop transient performance of WECS in fault instant, which is the main advantage of the bridge-type FCL to other FRT improvement techniques. On the other hand, the discharge resistor of the bridge-type FCL aims to raise the voltage at the terminals of the generator, thereby justifying the destabilize electrical torque and power during the fault. The WECS is careful as a fixed-speed system able to with a squirrel-cage IG. The simulation results show that not only the faultcurrent is limited but also FRT ability of WECS is improved. Also, a relative study of bridge-type FCL and SDBR for improving FRT ability is accepted out. 
In this paper, transient stability improvement using bridgetypefaultcurrentlimiter (FCL) is presented in single machine infinite bus (SMIB) system with a double circuit transmission line. Three single-phase sets of the proposed FCL are installed at the beginning of feeder. The proposed FCL inserts an inductance and a resistance in the faultcurrent pass. The insertion inductance and resistance not only limits the faultcurrent level in an acceptable value but also improves transient stability of power system by consuming excessive energy of synchronous generator during fault. To reach maximum transient stability, the optimal resistor value of the proposed FCL is calculated. Analytical analysis and simulation results using PSCAD/EMTDC software are presented to show the current limiting future and transient stability enhancement using the proposed FCL in SMIB.
Transient stability is one of the main problems for the Doubly-Fed Induction Generator (DFIG) based variable speed Wind Generator (WG) system during the fault, as DFIGs stator windings are straight forwardly associated with the grid. In this paper, a resistive type solid state faultcurrentlimiter (R-type SSFCL) with fuzzy logic controller is proposed to expand the transient stability of the DFIG based variable speed WG system. A three-line-to-ground (3LG), twofold line-to-ground (2LG) and single-line-to-ground (1LG) deficiencies were connected to one of the doubled circuit transmission lines of the test system to explore the R-type SSFCL transient stability execution. Furthermore, a BridgetypeFaultCurrentLimiter (BFCL) and a LR-type Solid State FaultCurrentLimiter (SSFCL- LR) are additionally considered to contrast their execution and the proposed R-type SSFCL. Simulations were done in MATLAB/Simulink programming. Simulation results demonstrate that the SSFCL upgrades the transient stability of the DFIG system. Besides, this R-type SSFCL with fuzzy logic controller works superior to the R-type SSFCL with pi controller, BFCL, and LR-SSFCL in every prospect.
In this paper, inrush current limitation of transformer using a bridgetypefaultcurrentlimiter (FCL) as inrush currentlimiter is proposed. The proposed ICL consists of three single phase sets of diode bridge, small non-superconductor and semiconductor switch parallel with a resistor. Because of quick damping of inrush current by resistance, this topology inserts a resistance in power system. By simple control circuit and fast operation of the proposed ICL, the maximum peak value of inrush current decreases in an acceptable level. Using small value of non-superconducting dc reactor reduces voltage drop on the FCL as inrush currentlimiter (ICL) and construction cost. PSCAD/EMTDC software is used for getting simulation results. These results show good capability of the proposed ICL to limit the inrush current of transformers.
A simple and effective method for tracking stator and rotor current is proposed in . An inductance control is proposed in  for lowering the magnetizing current. There are many modified control methods, that have been presented: demagnetizing current in [12,13], virtual flux damping control [14,15], sliding mode control (SMC) , robust control (RC) .. A unified interphase power controller (UIPC) is explained and implemented in [18,19], dynamic voltages restorer (DVR) which maintains the rated voltage is presented in [20,21]. Few more solutions in the form of stator damping resistor (SDR)  were used to operate under LVRT for DFIG based wind turbine. Though STATCOM [24,25] is used for improving LVRT capability, this cannot limit the DC link voltage and also faultcurrent through RSC of DFIG on the occurrence of a fault. The DVR, UIPC, and SGSC offer greater series voltage injection for restoring stator voltage of DFIG and are presented in [18-22]. For protecting DC-link, energy storage solutions are proposed for limiting the DC link voltage and a series dynamic braking resistor (SDBR) are presented in [23,24]. A supercapacitor type storage device is implemented in  for LVRT enhancement and in  supercapacitor is connected at DC link of STATCOM for controlling grid side voltage under a grid fault condition. In  stator damping resistor, including rotor current control scheme has been explained. In [28,29] a superconducting faultcurrentlimiter is introduced, as the cost is high, it is not implemented commercially. Similar work has been investigated in for estimating recovery time for a 440kV/1.2kA system. A bridgetypefaultcurrentlimiter [30-32] for voltage recovery under a fault condition for LVRT is presented. In  for the first time, faultcurrentlimiter with DC reactor is introduced but, due to the cost of a DC reactor and transformer, some limitations are present in it. Recently superconducting typefaultcurrentlimiter which has magnetic storage ability has been implemented for LVRT , resonant faultcurrent limiters  have been proposed and examined for limiting faultcurrent under transient conditions. In this paper, a ————————————————
Abstract- In recent world the trend of using electrical energy is increased, which results in increased power demand and hence the occurrence of abnormal events. Superconducting faultcurrentlimiter is an innovative protection device which is used to reduce the magnitude of faultcurrent in high voltage system. In this paper the application of resistive type superconducting faultcurrentlimiter is explained, which is used to reduce the magnitude of faultcurrent. As the electrical power system is very wide, the chance of occurrence of any kind of fault is very common, due to that high magnitude of current flows through the system. This may harm the mechanical equipments of the power system. As the equipment’s in power system are expensive, so it is essential to protect from the abnormal events. It is not possible to eliminate these faults completely, but it is possible to lower their harmful effects, by decreasing the level of faultcurrent. The application of the faultcurrentlimiter (FCL) would not only decrease the stress on network devices, but also can offer a connection to improve the reliability of power system. There are various types of FCL’s, which are made of different superconducting materials and have different designs. They are categorized into three broad types: the resistive type, the inductive type and bridgetype SFCL. We discussed the operating characteristics of SFCL introduced into a simplified power transmission model system. It was finally revealed that SFCL could satisfactorily bring about the functions of faultcurrent suppression and power system stability improvement. In order to evaluate the impact of faultcurrentlimiter in power system performance, simulation work is performed by using Mat lab/Simulink tool.
In normal operation of power system, self turn off switch is ON and small dc reactor is charged to the peak of line current and behaves as short circuit. Neglecting small voltage drop on diodes and self turn off switch, total voltage drop on FCL becomes almost zero and therefore, FCL does not affect normal operation of power system. As fault occurs, dc reactor limits increasing rate of short circuit current and starts to charge. When the line current reaches to the pre-defined value that can be set by system operator, control system turns off the self turn off switch. So, the bridge retreats from utility. At this moment, free wheeling diode turns on and provides free path for discharging the dc reactor. When the bridge turns off, faultcurrent passes through the resonance part of the proposed FCL.
another dc reactor FCL which is on the secondary side of the transformer is explained in. This FCL has two coils one is reactor and another is resistor called as damping resistor connected in series .both of this is connected in shunt with IGBT like those bypass switches suppress the transients inrush current by affecting the reactor impedance. If real-time current value increased beyond the set value the damping resistor comes into picture and limits faultcurrent by switching off of IGBT. But disadvantages of this FCL are conduction losses, switching overvoltage, complex control strategy, and cooling system also required .It can withstand with high current with limited time also due to saturation of core it loose its fault limiting capability. FCL having ac reactor may consist of mechanical or power electronic switches.some of the type of FCL use LC tank circuit in their structure. During normal operation as a capacitor and the inductor are in resonance condition the impedance offered is negligible or small but when a fault occurs the capacitor in a series pass by switches. This will detune the LC tank circuit and impedance is inserted in the path of faultcurrent. As those FCL have a good capability of limiting the faultcurrent but on other hands in normal condition, it has high power loss and unacceptable over switching voltage. Arrestor in parallel can be used as a solution for the switching overvoltage. The equivalent resistance of the LC tank circuit is considerable as it produces losses which are unavoidable. The solid-state CBs are described in ,.Advantages of those CBs over mechanical CBs that they are faster than mechanical CBs. As we consider the dc reactor the work well during normal operation as when a fault occurs they not successful to limit the faultcurrent while on the other hand considering ac reactor during normal operation there is huge power loss but when it comes to limit the faultcurrent in successfully limit the faultcurrent .also when switching from one mode to another mode switching losses occurs. If we combine those FCL then advantages of both we can get FCL with superior advantages.
limiters (FCL) are regarded as the suitable solution to solve excessive faultcurrent problems. Active superconducting faultcurrentlimiter (ASFCL) voltage compensation type is a novel topology of FCL. This type SFCL not only preserves the merits of bridgetype SFCL such as the automatic switch to the current limiting mode and without the quench of the superconductor, but also has the particular abilities of controlling the steady faultcurrent and compensating active and reactive power for AC main circuit in the normal state. In view of that the introduction of a SFCL can impact the coefficient of grounding, which is a significant contributor to control the induced overvoltage’s amplitude, the change of the coefficient may bring positive effects on restraining over voltages. We have proposed a voltage compensation type active SFCL.
FCL, resonant circuit and SFCL (Superconducting FaultCurrentLimiter) have been proposed and developed . SFCL offers a solution to limit faultcurrent with many significant advantages. The application of the SFCL would not only decrease the stress on device but can also improve reliability, improve power quality, limit the inrush current of transformers, reduce the transient recovery voltage (TRV) across the CBs and improve transient stability of power systems by reducing the faultcurrent. There are different types of SFCLs which are based on different superconducting materials and designs such as, flux-lock, transformer, resistive and bridge-types SFCL [36-38]. The transformer-type SFCL has zero impedance under normal conditions and large impedance under fault conditions (the same as other FCLs) [39-43]. But, it has significant advantages as follow:
on theprotected feeder. As pointed, some of previously proposedFCL structures have ac power losses at the resonant circuitin the normal condition, because of placing a large inductorin the line current path. However, the proposed structure inthis paper has very low losses in the normal condition,because the inductor is bypassed by the bridge part. Also,by choosing proper values for the resonant circuit, the proposed FCL limits the faultcurrent in a way that thepower system is not affected by the fault. In such condition, there will not be any considerable voltage sag onthe PCC voltage as shown in Fig.5.
The faultcurrent limiters (FCL) are regarded as the suitable solution to solve excessive faultcurrent problems. Active superconducting faultcurrentlimiter (ASFCL) voltage compensation type is a novel topology of FCL. This type SFCL not only preserves the merits of bridgetype SFCL such as the automatic switch to the current limiting mode and without the quench of the superconductor, but also has the particular abilities of controlling the steady faultcurrent and compensating active and reactive power for AC main circuit in the normal state . In view of that the introduction of a SFCL can impact the coefficient of grounding, which is a significant contributor to control the induced overvoltage’s amplitude; the change of the coefficient may bring positive effects on restraining over voltages. We have proposed a voltage compensation type active SFCL. In previous work and analyzed the active SFCL’s control strategy and itsInfluence on relay protection .
In consideration of the techniques mentioned above, another common idea to reduce the faultcurrent levels is faultcurrent limiters (FCLs). In  and , different types of the FCLs are employed to enhance the FRT capability of the FSWT. The bridgetype FCLs (BFCLs) have been utilized in [27, 28] to enhance the FRT of the FSWT during the fault. However, in  and  only fixed impedance has entered the FSWT faultcurrent path. This procedure helps to limit the faultcurrent. However, not only in this literature but in almost all studies, the most important issue has been omitted; in fact, the impact of the pre-fault conditions has not been considered in the FRT capability of the FSWT. It means that the fault location and the wind speed variations, which cause variable output active power, are not included in both analysis and simulation.
Superconducting FaultCurrentLimiter (SFCL) is innovative electric equipment which has the capability to reduce the faultcurrent level within the first cycle of faultcurrent . The first-cycle suppression of faultcurrent by a SFCL results in an increased transient stability of the power system carrying higher power with greater stability. The concept of using the superconductors to carry electric power and to limit peak currents has been around since the discovery of superconductors and the realization that they possess highly non-linear properties. More specifically, the current limiting behavior depends on their nonlinear response to temperature, current and magnetic field variations. Increasing any of these three parameters can cause a transition between the superconducting and the normal conducting regime. The term ―quenchǁ is commonly used to describe the propagation of the normal zone through a superconductor. Once initiated, the quench process is often rapid and uncontrolled. Though once initiated the quench process is