The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
This paper investigates sub-synchronous resonance (SSR) phenomena inside a doubly-fed induction generator (DFIG) based wind farm, considering the impact of the spatial distribution of wind speed. Firstly, the impedance model of a one-DFIG aggregated model based wind farm is presented to analyze the induction generator effect. Then, a two-DFIGs aggregated impedance model, considering DFIGs in both...
At standstill and low-speed, signal-injection methods are required to estimate the rotor position of a permanent magnet synchronous machine (PMSM). Therefore, usually either the resistance- or inductance-based saliency is examined. Although the latter case can be found most in literature, it is possible that the sensorless performance can be improved by exploiting the position information of both...
In squirrel cage rotors of induction machines with unconventional end region structure, the three-dimensional effects can be more pronounced as compared to conventional induction machines. As a result, the rotor impedance and machine power factor are affected by the design of the end ring and its supporting structure. To be able to account for this effect, three-dimensional finite element (3D FE)...
The loss of a single phase of a voltage can occur from multiple causes such as the loss of a fuse, failed connections or downed conductors. This condition will cause negative sequence current to flow in motor circuits and may damage those motors. It is desirable to detect the loss of a voltage phase from a utility source and trip an industrial facility before the unbalanced voltages can damage motors...
Up to the date, high frequency signal injection sensorless control techniques normally assume a purely inductive behavior of the machine at high frequency, the rotor position-dependent differential inductance being the term tracked and from which the rotor position is estimated. However, certain machine designs show a rotor position-dependent high frequency resistance, which can also be used for sensorless...
In this paper, the transient characteristics of double-fed induction generator (DFIG) are analyzed. Based on this, the fault current contribution of DFIG with and without crowbar are compared. Comparison result shows that fault current of DFIG under different ride-through conditions differs widely from each other. Under unsymmetrical fault, the DFIG with a crowbar is converted to squirrel case induction...
This paper proposes a method to find the equivalent circuit parameters, moment of inertia, and friction coefficient of an induction machine. The reference data include time-varied signals of voltage, current and rotor speed. By the time-varied voltage and current, a time-varied impedance can be found. The parameters of equivalent circuit can be found from the variation of impedance to the rotor speed...
A simple method involving only a quadratic equation has been developed for calculating the minimum and maximum values of excitation capacitance that will sustain self-excitation in an induction generator meant for isolated power supplies. This approach has also been further extended for the determination of maximum load of a given power factor that could be applied to the generator without losing...
This paper uses time-varied signals of voltage, current and rotor speed to compute the equivalent circuit parameters, moment of inertia, and friction coefficient of an induction machine. A time-varied impedance can be found by the time-varied voltage and current. From the variation of impedance to the rotor speed, the parameters of steady equivalent circuit can be found. According to the equivalent...
In a synchronous machine rotor is the most important part. Excitation system size, earth fault levels, efficiency of the machine and reactive power required by the system depend upon the parameters of the rotor. This paper presents novel method of reducing the size of the excitation system thus improving the excitation system and reduced vulnerability to the earth faults, increasing efficiency, reducing...
When operating three phase induction motor with single phase supply the motor behavior becomes complicated, owing to the emergence of negative and zero sequence components in winding currents. This paper analyzes the behavior of small rating three phase induction motor connected to one phase supply taking into account the variation of rotor resistance with slip for different stator connections. The...
This paper analyzes the effects of the transient resistances in saliency tracking-based sensorless control methods of PM synchronous machines. A high frequency model of the PM synchronous machine including both stator and rotor transient resistance is presented. From this model, potential sources of error in the estimated position due to the transient resistances are analyzed, and their compensation...
The paper proposes an identification method for the inductances of induction machines, based on signal injection. Due to magnetic saturation, a saturation-induced saliency appears in the induction motor, and the total leakage inductance estimate depends on the angle of the excitation signal. The proposed identification method is based on a small-signal model that includes the saturation-induced saliency...
The authors describe a method for calculating equivalent circuit constants of synchronous generators using open and shorted operational impedances obtained by the DC decay tests. In the proposed method, it is possible to find all constants only by a stationary test, including the armature leakage reactance. This method makes it possible to improve transient analysis accuracy on not only the armature...
It is of great importance to study the dynamic behavior of distributed generation (DG), which might affect the fault level and protection system of distribution network greatly. In this paper, the transient stability of asynchronous type of DG is comprehensively analyzed. The critical shedding time and corresponding slip of DG are calculated. It is pointed out that the fault clearing time of existing...
This paper describes a simple graphical method for the finding a reasonably-accurate value for the efficiency of any balanced multiphase motor for any arbitrarily-selected value of operating current. The method assumes the following routine conditions: the motor operates at rated voltage and frequency; the stray load loss and the rotor core loss are negligible; the no load speed of the motor is known...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.