جستجوی مقالات مرتبط با کلیدواژه « small signal stability » در نشریات گروه « برق »

Due to the ever-increasing development of the electricity industry and the growth of consumption demand, the use of clean energy sources is increasing. In this regard, the use of wind energy as a clean and free source for the production of electrical energy is expanding day by day, and according to predictions, 20% of the world's energy will be obtained through wind by 2030. But in addition to all the advantages of wind energy, using them in the form of wind turbines in power grids in order to provide the required power can be considered a negative factor from the point of view of stability in power systems. The purpose of this article is to use the predictive control method based on logger functions to check the small signal stability of a hybrid network, including synchronous generators, wind farms and parallel STATCOM compensator. In this method, by using logger functions, the computational time in model-based predictive control has been reduced, so that the accuracy of tracking control signals can be increased and the stability of the system can be improved. The proposed method for controlling the active and reactive powers in the rotor side converter related to DFIG and the type of compensator used has been done in such a way that the performance of the power system can be increased by applying appropriate switching in the corresponding inverter. The simulation results using MATLAB software have been evaluated in the time domain, and its superiority has been clearly shown in order to improve the damping of power system fluctuations.

With the increasing expansion of power systems, random factors affecting the performance of these systems have also increased. Rising demand for electrical energy, along with the aforementioned random factors, has led to uncertainty analysis methods being of particular importance in analyzing the small signal stability of the power systems. In this paper, a method based on polynomial approximation for probabilistic small signal stability analysis of the power systems is presented. Since the correct determination of unknown coefficients has a direct effect on the accuracy of the polynomial approximation method, this paper presents a method that is able to determine these coefficients with more coverage on the probable input space of the problem and in addition, is able to maintain its efficiency even by increasing the number of random input variables. After determining unknown coefficients, the load flow results and system state matrix are determined for random changes of all loads and based on Hermitchr('39')s polynomial approximation. Then, the eigenvalues ​​of the system are determined and the stability of the small signal of the system is probabilistically studied. In order to evaluate the accuracy and effectiveness of the proposed method, the IEEE 14-bus benchmark system is simulated in MATLAB software and the results of the proposed method is compared with the results of the two conventional methods of Point Estimation and Monte Carlo. Examination of the results has shown that the proposed method in this paper, in addition to validity, has good accuracy and high computational speed.

The safe operation of power system depends on its stability and security supply in all times. The dynamic instability (small signal instability) is one of phenomena that results in power system instability and has been discussed as a challenge in power system control and operation from a long time ago. Commonly the dynamic instability appears as undamped low frequency electromechanical oscillations or with insufficient damping. In order to damp these oscillations and improve dynamic stability, the use of Power System Stabilizer (PSS) in excitation systems is the most effective option. In this paper the impact of PSSs of various units of a real power plant on Iran grid dynamic stability is investigated and its performance is improved. In this way first the excitation system and PSS model of the power plant are identified and verified, and then the main parameters of PSSs are optimally retuned using the proposed method based on Particle Swarm Optimization (PSO) algorithm. In the following, power plant operation is considered in different disturbances with respect to the retuned PSSs, so that, the effect of optimal parameters on local and inter-area oscillation modes damping is taken into account, not only within time domain analysis, but also within frequency domain analysis. The results of proposed flexible and comprehensive analysis display the suitable performance of retuned PSSs.

In this paper, the modal analysis of a grid connected doubly-fed induction generator (DFIG) using small signal stability analysis is presented and effect of variation in system parameters such as mutual inductance, stator resistance, line reactance, shaft stiffness and wind speed on the eigenvalues, stability and damping ratio of different modes of system are studied. This analysis shows that which parameters variation can deviate the system from normal working conditions as well as which parameters variation can improve the system behavior. For evaluating the stability and different controllers design, the simulation results show the effects of parameters variations.