Variable-frequency drive

About: Variable-frequency drive is a research topic. Over the lifetime, 837 publications have been published within this topic receiving 5691 citations. The topic is also known as: VFD.

An Analysis on the Effectiveness of Harmonics Reduction for Variable Frequency Drive by Reactors

Abstract: Recently, due to the rapid development of Power Electronics, the usage of Non Linear Load variable frequency drivers (VFDs) is increasing in the electric propulsion vessels and offshore plants. And harmonics which is generated by the variable frequency drives is an important issue should be solved. Ac line reactors and dc link reactors are widely used in variable frequency drives to improve the drive performance such as reducing input current harmonics, elevating input power factor, and protecting the drives from surges, etc. The effectiveness of both types of reactors in reducing input harmonics is affected by the loading of the drives and the system source impedance. And it considered that inductance of DC link reactors should be about 1.7 times of AC line reactors for same effect. The rules to evaluate the needs and effectiveness using ac line or dc link reactors are proposed for practical appications. In this paper, a simulation is performed to investigate of such factors using software PSIM.

Experimental study of the VFD's speed stabilization processes under torque disturbances

Abstract: Maintaining speed with various jumps and changes in load torque is one of the main tasks of variable frequency drives (VFD). The article considers the operation of the VFD under the influence of periodic perturbations of variable frequency and amplitude. The dependence of the transient function of the VFD and the family of frequency characteristics associated with it on the frequency of the stator voltage and slip underlies the methodology for experimental studies of such drives. The traditional method is based on the response to harmonic stimulation and works well for a non-linear system. In the course of the work, it was found that the introduction of dynamic positive feedback (DPF) allows to compensate for disturbances of varying frequency and amplitude. Experiments with a sinusoidal change in the load torque have shown the effectiveness of introducing the DPF in front of conventional sensorless control systems (vector and scalar).

Correction of Scalar Control Systems for Frequency Induction Electric Drives to Change the Mutual Orientation of the Torque-Generating Vectors of Engine Variables

Abstract: The inclusion of corrective elements in the frequency control systems of an induction electric drive makes it possible to achieve the best energy and dynamic performance of an induction electric drive. To build correction systems, it is necessary to use observers of variables of an induction motor that are inaccessible for measurement. The most convenient and versatile variables for building correction systems are the angles between any two torque-generating variables of an induction motor. It is not possible to measure these angles between vector variables in a scalar control system, but they can be determined indirectly using the instantaneous values of other engine variables available for measurement. For systems of scalar frequency-current control of an induction electric drive, such calculations are rather complicated and have a large error due to the need to filter the stator voltage pulse signals. When using an induction motor with a phase wound, the solution to the problem of constructing a correction system for a frequency electric drive is simplified due to the possibility of determining the required angle based on measuring the instantaneous values of the stator and rotor current using standard current sensors. Such a correction system is effective and workable. thanks to the ability to determine the required angle based on the measurement of the instantaneous values of the stator and rotor current using standard current sensors. Such a correction system is effective and workable. thanks to the ability to determine the required angle based on the measurement of the instantaneous values of the stator and rotor current using standard current sensors. Such a correction system is effective and workable. The mechanism for correcting the control signal between the stator current and the main flux linkage is considered on the basis of a calculation based on a comparison of the values of the stator and rotor currents.

Medium voltage variable frequency drive with artificial intelligence

Abstract: A variable frequency drive system includes a power converter with a plurality of power cells supplying power to one or more output phases, each power cell having multiple switching devices incorporating semiconductor switches; a plurality of sensors monitoring values of the power converter; and a control system in communication with the power converter and controlling operation of the plurality of power cells, the control system comprising a processor configured via executable instructions to access a first reduced order model of the power converter; receive the values provided by the plurality of sensors; analyze the values in connection with the first reduced order model to determine one or more operating modes; and output one or more determined operating modes of the power converter.