Wind energy is rapidly growing in recent years. Among different types of wind turbines, due to several advantages, permanent magnet synchronous generator (PMSG) is attractive concept. Since the penetration level of wind power in the grid is increased, therefore, wind power can influence to the grid and vice versa. Some of the important problems in the grid are fault condition and voltage sags. These conditions may affect the operation of wind turbine. In order to enhance low voltage ride through (LVRT) capability in PMSG-based wind turbines, various approaches have been proposed in the last years. In this paper, the review and comparison of several LVRT capability enhancement methods is performed. The two foremost types of LVRT capability enhancement methods are external devices based methods and modified controller based methods. The main objectives of this paper are to introduce performances of different LVRT capability enhancement methods and use of some LVRT capability enhancement methods in PMSG based wind turbine which are applied in other kind of wind power generators. The external devices based methods can be effective but some of these methods are of significant cost. According to the literatures, modified controller based methods can reduce the LVRT capability enhancement cost. Several modified controller based methods have been proposed for LVRT capability enhancement. To compare the mentioned methods, several simulations are performed in MATLAB software. From the review of simulation results, series connection of FACTS devices and modification of back-to-back converter controllers are the highly efficient LVRT capability enhancement approaches.

A review of low-voltage ride-through enhancement methods for permanent magnet synchronous generator based wind turbines

http://www.scielo.org.mx/pdf/jart/v15n1/2448-6736-jart-15-01-36.pdf

Technical comparison of FACTS controllers in parallel connection

Research of grid connected wind turbines has gained great interest in the recent years. This led to introduce guidelines and regulations regarding the connection of large wind farms to the electrical network. One of such guidelines is low voltage ride-through capability (LVRT). In this paper, a survey on recent LVRT solutions for permanent magnet synchronous generators (PMSG) is carried out along with a brief explanation of grid codes. Among those solutions is the control of fully rated converters, blade pitch angle control and capacitor sizing. Other solutions such as active crowbar rotor circuit and the DC bus energy storage circuit are illustrated. The survey extends to provide possibilities for the development of further LVRT research at the wind farm level using high power FACT devices.

A review on recent low voltage ride-through solutions for PMSG wind turbine

Enhancement of voltage profile by incorporation of SVC in power system networks by using optimal load flow method in MATLAB/Simulink environments

Stabilization of wind farm (WF) is considered one of the major serious issues for developing power systems based on renewable energy sources. A comparison of dynamic performances for FACTS devices like STATCOM and SVC is presented in this paper. Such devices are employed to stabilize WF integrated with multi-machine power system (WFMPS). Fuzzy logic controller (FLC) has been employed for controlling FACTS devices to enhance WFMPS performance under different abnormal conditions. Three-phase to ground short circuit fault has been taken into consideration in different locations of system. MATLAB/Simulink is used to perform the modeling and simulation of WFMPS. The obtained results demonstrate the effect of both SVC- and STATCOM-based FLC on damping the system oscillations and improving the system dynamic performance in the post-fault duration. The comparison confirms superior dynamic performance and fast fault recovery of STATCOM-based FLC through different fault conditions compared with SVC-based FLC.

A comprehensive comparison of STATCOM versus SVC-based fuzzy controller for stability improvement of wind farm connected to multi-machine power system

One of the major causes of voltage instability is the reactive power limit of the system Improving the systempsilas reactive power handling capacity via flexible AC transmission system (FACTS) devices is a remedy for prevention of voltage instability and hence voltage collapse In this paper, the effects of four FACTS controllers, SVC, STATCOM, TCSC, and UPFC, on voltage stability will be studied The IEEE-14 bus system is simulated to test the increasing loadability With continuation power flow feature of PSAT and accurate model of these controllers, voltage stability of the test system is investigated and bifurcation points are detected

Comparison of SVC, STATCOM, TCSC, and UPFC controllers for Static Voltage Stability evaluated by continuation power flow method

One of the major causes of voltage instability is the reactive power limit of the system. Improving the system's reactive power handling capacity via Flexible AC transmission System (FACTS) devices is a remedy for prevention of voltage instability and hence voltage collapse. In this paper, the effects of SVC and STATCOM in Static Voltage Stability Margin Enhancement will be studied. AC and DC representations of SVC and STATCOM are used in the continuation power flow process in static voltage stability study. The IEEE-14 bus system is simulated to test the increasing loadability. It is found that these controllers significantly increase the loadability margin of power systems.

/pdf/comparison-of-svc-and-statcom-in-static-voltage-stability-3ri2pdjbz3.pdf

Comparison of SVC and STATCOM in Static Voltage Stability Margin Enhancement

According to the increasing utilization in power system, the transmission lines and power plants often operate in stability boundary and system probably lose its stable condition by over loading or occurring disturbance According to the reasons that are mentioned, the prediction and recognition of voltage instability in power system has particular importance and it makes the network security strongerThis paper, by considering of power system contingencies based on the effects of them on Mega Watt Margin (MWM) and maximum loading point is focused in order to analyse the static voltage stability using continuation power flow method The study has been carried out on IEEE 14-Bus Test System using Matlab and Psat softwares and results are presented

/pdf/static-voltage-stability-assessment-considering-the-power-2ebjmof9ix.pdf

Static Voltage Stability Assessment Considering the Power System Contingencies using Continuation Power Flow Method

Power transformers are vital and expensive components of electric power systems and it is necessary to protect them from internal faults. Differential protection is based on differential current. Occurrence of some phenomena such as inrush current, over excitation, saturation of current transformers and mismatch of current transformers cause the differential relay to operate incorrectly. In this paper, fuzzy logic is used as a powerful mathematic tool. In this method of protection, algorithm is based on ruled out non-internal fault phenomena. The results of simulations show that fuzzy protection system is able to detect occurrence of fault in less than half a cycle and this method improves protection system, satisfactorily.       

	 

	Key words: Differential protection, power transformer, fuzzy logic.

/pdf/detection-of-internal-fault-in-differential-transformer-31nkr5qk3l.pdf

Detection of internal fault in differential transformer protection based on fuzzy method

Determining maximum loading margins is an important issue in power system operation, as system operators must take proper preventive actions to avoid stability problem. This paper presents a study of parallel FACTS devices and series FACTS devices on steady-state voltage and power stability. Their steady state modeling and effects on power system performance have been studied. It also studies static stability improvement of the power system and hence power flow improvement in the network. Effects of FACTS on system loadability have been discussed and presented here. A method based on the concept of maximum loading point index has been used to compare FACTS devices. The study has been carried out on the IEEE 14 bus test system. The line power transfer capability and loadability of the system and therefore, the stability of the system is increased. It has also been observed that for the improvement of these parameters, the parallel FACTS devices are more adequate than the series FACTS devices.

Mostafa Alinezhad

Papers

Comparison of SVC, STATCOM, TCSC, and UPFC controllers for Static Voltage Stability evaluated by continuation power flow method

Comparison of SVC and STATCOM in Static Voltage Stability Margin Enhancement

Static Voltage Stability Assessment Considering the Power System Contingencies using Continuation Power Flow Method

Detection of internal fault in differential transformer protection based on fuzzy method

Comparison between Parallels and Series FACTS devices on static voltage stability using MLP index