In addition to system inertia, the number of on-line diesel generator units and the corresponding spinning reserve margin may also affect the lowest system transient fre- quency. The more diesel generator units running, the larger the corresponding spinning reserve margin is, and the less the drop of the lowest system transient frequency would be. In other words, to prevent low transient fre- quency from triggering an under-frequency load shed- ding relay as a principle during an incident, the number of running diesel generator units should be increased appropriately. However, the issue of low power genera- tion efficiency and accelerated depreciation when power output of each single generator unit is too low should also be considered. Therefore, a set of appropriate oper- ating modes for diesel generators to meet the system re- liability and economic is important. Generally, the de- termination of the maximum wind power penetration will be determined by the following limit criterions: minimal and maximum power production criterion of the conven- tional diesel plants, ramp rate of the diesel plants, dy- namic penetration limit for transient frequency and vol- tage stability, power quality impact, and protection schemes and load management.
Ayodele et al. (2016) focused on improving transientstability of Nigerian 330kV Transmission Network using Static VAR Compensation (SVC). It considered the response of the transmission network to three phase balance fault in terms of Critical Clearing Time (CCT) and its effect on generator, bus voltage magnitudes and phase angle. Load flow analysis was performed to determine the steady state of the network before it was subjected to large disturbances. Critical lines were identified and generator that fell out of synchronism was also located when the system three phase faults were applied. The investigation was carried out with and without SVC and a commercially available Dig Silent Power Factory was used for the analysis. It was observed that the CCT was improved tremendously, voltage profile at seven (7) buses were improved to acceptable limit of the reference value while positive effect was noted on the phase angle. The study also showed that generators that were closer to the critical lines operated in synchronism. However, the study did not address power loss in the transmission system.
Unlike coal and other conventional resources used for power generation, some renewable energy, such as wind power, is random, intermittent and uncontrollable. Acci- dent of grid or the tripping of wind farm will increase the difficulty of system recovery with significant penetration of wind power, even leading to the grid collapse. During the past decades, wind power penetration limit has been exceeded from about 5 percent to 20 percent in many countries based on the reactive power compensators and reinforcement of networks. The choice of wind gen- erator has been an important technical and economic target to power system because analysis results show that parameters of induction motor, such as stator reactance, initial rotor slip, have influence on power system tran- sient stability. Effect of mechanical parameters of induction generator (IG) and doubly-fed induction gen- erator (DFIG) has been analyzed in conference. Com- parative analysis between IG, DFIG and direct-drive permanent magnetism synchronous generator (PMSG) on power system transientstability shows that variable speed wind generator is a better choice to meet the re-
A self-excited two-phase reluctance generator (SETPRG) with balanced stator winding is presented. A unique balanced two-phase stator winding was designed with emphasis on obtaining a stator MMF waveform with minimum space har- monics. Then a mathematical model by which the dynamic behavior of the gener- ator can be successfully predicted under various operating conditions is developed. The model developed accommodates balanced and unbalanced loading conditions. Self-excitation is achieved via capacitors connected across the two terminals of the stator windings. The performance of the generator under various loading conditions is studied. It is realized that the generator can simultaneously supply good voltage through its terminals, in both balanced and unbalanced load conditions within its rating. It is also observed to have a good voltage regulation. Further- more, it was determined that the generator can accept a sudden addition of load without any transients in its output variables. However, slight transient behavior is noticed in the output variables when the generator loses load. These transients increases with increasing load power factor. The presence of these transients will not jeopardize performance as the magnitude is indeed small, nor does it pose a threat to the connected load for the same reason. The generator is also capable of re-building up its voltage after a short circuit fault is cleared.
The larger the penetration level of hybrid distributed generation (HDG) in a power system, the more difficult it becomes to predict, to model, to analyze and to control the behavior of such system . Some HDG using induction generators are not grid friendly because they consume reactive power instead of generating it. Most power converters do not have adequate control mechanism to actively support DG integration. The system inertia for some of them (e.g., solar PV or fuel cell) is extremely low. They are weather dependent with constant daily load variation . Also, existing protection mechanism might not be able to take care of the problem of bi-directional power flow that takes place due to DG connection in radial networks. New design controllers are needed to effectively manage the multi-energy sources distributed generation in other to service remote villages.
proposed CBD power system analysis application. The application is developed from the components given in Table 1. The window shows the IEEE 300 bus single line diagram. The application has many facilities that makes it user friendly. The main application window contains features needed by the software application such as main menu, tool bar, image list, etc. The software application uses multiple document interfaces. More than one drawing forms can be opened within the main application window at the same time. In the dialog box that is shown in Fig. 3, which is marked as D, a slack bus and a calculation method needs to be selected. The slack bus is chosen from a combo box containing all of the available busses in the diagram. The calculation methods, i.e. load flow or fault calculation, unbalanced power flow…etc. are chosen from another combo box as well. Other parameters, i.e. as base for MVA, maximum iteration, and tolerances, need to be keyed in. After keying in the parameters, the calculate button is clicked to start any power system analysis calculation.
Modern power system is a complex network comprising of numerous generators, transmission lines, variety of loads and transformers. As a consequence of increasing power demand, some transmission lines are more loaded than the planned capacity when they were built. With the increased loading of long transmission lines, the problem of transientstability after a major fault can become a transmission limiting factor. Now power engineers are much more concerned about transientstability problem due to blackout in North East United States, Scandinavia, England and Italy . Transientstability refers to the capability of a system to maintain synchronous operation in the event of large disturbances such as multi-phase short-circuit faults or switching of lines. The resulting system response involves large excursions of generator rotor angles and is influenced by the nonlinear power angle relationship. Stability depends upon both the initial operating conditions of the system and the severity of the disturbance. Recent development of power electronics
Abstract—UPFC is a versatile FACTS controller that can regulate the Power Flow through the Line by controlling its Series and shunt parameters. In shunt it is having STATCOM and in series SSSC are employed can independently control the Line Power Flow. Two Converters improves the flexibility and provide additional degree of freedom in Power System. With the application of UPFC, Transientstability of the system can be Improved. This Paper shows that how TransientStability of the Inter Area system is Improved. The Mathematical Model of TransientStability is also given in this Paper.
system stability. The difference lies in modelling, that is, in dynamic stability, excitation systems, turbines, and generators modelled by providing flux variations in engine slit water, while the stability of steady state generators is represented as a constant voltage source [1-2]. While transientstability is the ability of the power system to achieve stable conditions under acceptable new operating conditions after the system experiences a large scale disruption in the period during the first 1 swing assuming the AVR and the governor have not functioned .
 M.J. Hossai, H.R. Pota, R.A. Ramos 2012. “Improved low-voltage-ride-through capability of fixed speed wind turbines using decentralized control of STATCOM with energy storage system” Generation, Transmission & Distribution, IET Volume:6 , Issue: 8 Page(s): 719 – 730.  Liang Liu, Haiming Li, Siqing Sheng and Huan Li 2015. “Research for transient-voltage stability based on doubly-fed wind power generation system” Applied Mechanics and Materials Vols. 738-739 pp 1251-1255.  M. Stiebler 2012. “PM Synchronous Generator with Diode Rectifier for Wind Systems Using FACTS Compensators” Power Electronics, Electrical Drives, Automation and Motion (SPEEDAM), International Symposium on Date of Conference: 20-22 June 2012 Page(s): 1295 – 1300.
The multi-agent theory is introduced and applied in the way to strike the control amount of emergency control accord- ing to stability margin, based on which an emergency control strategy of the power system is presented. The multi-agent control structure which is put forward in this article has three layers: system agent, areal agent and local agents. System agent sends controlling execution signal to the load-local agent according to the position and the amount of load shed- ding upload from areal agent; The areal agent judges whether the power system is stable by monitoring and analyzing the maximum relative power angle. In the condition of instability, determines the position of load-shedding, and the optimal amount of load-shedding according to the stability margin based on the corrected transient energy function, upload control amount to system agent; local-generator agent is mainly used for real-time monitoring the power angle of generator sets and uploading it to the areal agency, local-loads agent control load by receiving the control signal from system agent. Simulations on IEEE39 system show that the proposed control strategy improves the system stability. Keywords: Multi-agent; Corrected Transient Energy Function; Emergency Control; Stability Margin
The comparison of the SVC, STATCOM and UPFC, controller applications. The detailed models of the SVC, STATCOM, and UPFC were implemented and tested in the EMT (electro-magnetic transients). The models are relevant for transientstability analysis, and cover broader range of frequency oscillations and voltage control. The STATCOM give better performance than SVC for reactive power, voltages and loading capacity. For STATCOM reactive power compensated from 13.11 MVAR (SVC) to 15.83 MVAR (STATCOM) and voltage injected from 464.4 kv (SVC) to 469.8 kv (STATCOM) at bus 2.another relation with UPFC give better-quality performance than STATCOM for reactive power, voltages and loading capacity. For UPFC reactive power compensated from 15.83 MVAR (STATCOM) to 22.26
Thorough research works are going on in finding newer concepts for minimizing the reason of voltage collapse. Minimizing reason of voltage collapse means increasing power system stability (Dynamic, transient and steady- state stability), voltage margin and voltage security in the system . Voltage collapse occurs in a system when transmission lines are heavily loaded, power demand is increased, faults occurring in a system etc. So, many methods are used for determining voltage stability. There are three types of voltage stability: static voltage stability, dynamic voltage stability and transient voltage stability . Ref.  investigates the enhancement of steady-state voltage stability for a secure power system using SVC (static VAR compensator) and TCSC (Thyristor controlled series capacitor). To investigate the effectiveness of the FACTS (Flexible A.C transmission system) controller under different fault conditions the equal area-criteria is applied and simulation is conducted in . In , performance of the UPFC for power system stability (dynamic stability) improvement is compared with the other FACTS devices (SVC, TCSC and SSSC) by using two-area criteria. Power electronic based controllers are now-a-days being used for solving instability problem. Effectiveness of SVC and STATCOM in improvement of voltage security of a multi-bus power network has been studied in .
Transientstability enhancement of induction generator is one of the main issues in wind powergenerator. Fault or any of sudden disturbances on power system may cause rotor speed instability and voltage instability. This paper investigates for transientstability enhancement of induction generator after fault. For transientstability enhancement, the method used in which unique property of reversing the rotating flux of stator field is employed. In this method, after clearing fault for short time rotating field of stator is reversed results in opposition between stator rotating field and mechanical torque. It is nothing but changing operating mode from generating to plugging. This operation avoids rotor from further acceleration. Simulation result shows that proposed method is efficient for enhancing transientstability. Since in this method, no need of any external equipment, proposed method is more attractive than previous methods, from economic point of view.
There are various forms of FACTS devices, some of which are connected in series with the line and the others are connected in shunt or a combination of series and shunt . A Static Synchronous Series Compensator (SSSC) is a member of FACTS family which is connected in series with a power system. It consists of a solid state voltage source converter which generates a controllable alternating current voltage at fundamental frequency. When the injected voltage is kept in
Wavelet transform (WT) a mathematical technique, has a special feature of variable time- frequency localization, which is different from the windowed Fourier transform. Wavelet algorithms Process data at different scales so that they may provide multiple resolutions in frequency and time, these mainly being used in this study to detect and classify faults. This property of multi resolution is particularly useful for analyzing fault transients, which contain localized high frequency components superposed power frequency signals. The basic concept in wavelet analysis is to select a proper wavelet, called mother wavelet (analyzing wavelet or admissible), and then perform an analysis using its translated and dilated versions. In this report, the Daubechies five wavelet transform is used to analyse the speed deviation measured on each of the generator in the test system.Faults were created at a distance of 10kms from both the buses. Different types of faults were simulated using Electromagnetic Transient Analysis in Mi power package. Different types of faults were created and the transients were recorded for analysis. Simulation is carried out for Phase-A,
ABSTRACT: Transientstability of a power system is concerned with the system’s ability to remain in synchronism after the disturbance is cleared. Oc- currence of a fault in a power system causes transients. The disturbances subjected to the system may be occurrence of fault, sudden change in load etc. This paper describes the improvement of transientstability with phase shift insertion by phase shifting transformer. A 3-phase to ground fault is created on the line to analyze the effect of fault and to find the critical clearing time. Then by inserting phase-shifting transformer, a series of simulations are carried out to find the appropriate angle of PST to achieve rotor angle stability using MiPower Software.
ABSTRACT: The increasing pressure on the power system increases the complexity that is becoming a concern for the stability of the power system and mainly for transitory stability. To operate the system in the event of faults, Flexible AC Transmission System (FACTS) devices that provide opportunities to control the power and damping oscillations are used. This paper presents the enhancement transientstability of the Multi-Machine power system (MMPS) with Unified Power Flow Controller (UPFC) by using Artificial Neural Network (ANN) controller. Performance the power system under event of fault is investigating by utilizes the proposed the strategy to simulate the operational characteristics of power system by the UPFC using Artificial Neural Network (ANN) controller. The simulation results show the behavior of power system with and without UPFC, that the proposed (ANN) technicality has enhanced response the system, that since it gives undershoot and over-shoot previously existence minimized in the transitions, it has a ripple lower. The use (MATLAB R2014a) in all simulations carried out.
If the load requires more power than its maximum power allocation, it may consume the additional power however it will be treated as a regular consumer load. In this case additional generating capacity may be started in order to maintain the spinning reserve of the system. The MGC600L provides information about the status of a pump/heater/crusher or other controllable (major) load and is able to control the load by either turning the whole device on/off, switching individual elements within the device or even sending power consumption setpoints.