Stepping motors are normally operated without feedback and may suffer from loss of synchroni-zation. The permanent magnet stepper motor (PMSM) is generally two-phase. In this paper, the nonlinear dynamic equations governing the performance of the permanent magnet stepper motor are linearized at an operating point for small signal stability studies. Small signal stability is the system ability to maintain synchronism when a small disturbance occurs. It is based on the state space averaging approach. A detailed description of the method, results, and conclusions are also presented. Finally, simulation results for three motors have been reported and compared Manuscript profile

Wind energy is one of the renewable energy sources. Using the maximum power available in the wind is necessary to achieve the performance of the wind turbine at maximum pow-er. One of the ways to control the voltage at the connection point of the wind turbine to the power grid is to use flexible ac transmission systems (FACTS) controller. In this paper, the effect of static synchronous compensator (STATCOM) in a distribution system with induc-tion generator wind farm is analyzed and simulated. The studied system consists of a 9 MW wind farm connected to a 25 kV distribution system that delivers power to the grid through a 25 kV feeder. The results show that the STATCOM can, in addition to providing active power in short-circuit fault conditions, adjust the voltage changes at the common connection point between the wind farm and the grid in normal and fault conditions Manuscript profile

Sensitive loads cannot tolerate voltage sags and swells in power distribution networks and lots of problems are engendered for them. Therefore, dif f e rent instruments are pla nn ed to compensate volt a ge swells and sags. Between them dynamic voltage restorer (DVR) has found special import a n c e, because it operates better than others for this purpose and restores voltage to its initial value conveniently. A DVR is a power-electronic controller that can protect sensitive loads from disturbances in the supply system. The DVR is installed in series to the network. In this paper 9 level cascaded inverters with cas ca d ed transfor m e r s are used in DVR internal circuit, but the difference in magnetic flux in cascading transformers has adverse effects on the plan. Therefore, a new switching pattern is used Manuscript profile

Low changes in active power demand cause changes in the frequency of the power system. The purpose of using a load frequency control (LFC) system is to maintain the frequency balance in the power system, using active power control to minimize frequency changes to achieve acceptable power system stability. In this paper, the linearized model of a gas power plant has been studied and simulated to check the small signal stability and load frequency control. The frequency depends on the parameters of the power system, and small changes in the parameters cause slight deviations in the frequency of the power system. To provide good quality output power, LFC should have good robustness against uncertainty of power system parameters and sudden changes. The initial order equations of the system in the state space have been used in MATLAB software to simulate the dynamic behavior. The effect of changes in different parameters on frequency deviation and stability of the power system has been investigated. Analysis of system modes show the correctness of the simulation results. Manuscript profile