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.

Systems and method for controlling electrodynamic machines with a variable frequency drive

Abstract: Systems and method for controlling an alternating current (AC) electrodynamic machine (390) with a variable frequency drive (VFD) (380) include a control system (300) with a phase-locked-loop (PLL) circuit (382) for providing a stator flux angle signal (338) to the VFD (380), the PLL circuit (382) comprising a proportional integral (PI) regulator (332) providing an output signal (334); and a feedforward generator (350) in communication with the PLL circuit (382), wherein the feedforward generator (350) tracks a stator flux position of the AC electrodynamic machine (390) such that the feedforward generator (350) determines a stator frequency signal (352) based on stator flux signals (308, 310, 312) and supplies the stator frequency signal (352) downstream of the PI regulator (332), and wherein the stator frequency signal (352) is summed with the output signal (334) of the PI regulator (332) to provide a dynamically adapted output signal (335) of the PI regulator (332), and wherein the adapted output signal (335) is used to determine the stator flux angle signal (338).

Method for operating a well using a pump assembly with a variable-frequency drive

Abstract: The invention pertains to the oil production and can be used in wells equipped with electric pumps namely electric submersible pumps. The method of exploitation of well by pumping unit with variable-frequency drive comprises periodic repetition of the cycles including pumpdown, search for frequency when delivery stops and accumulation and at the same time to ensure such extraction of fluid from well which is equal to its inflow it is necessary to choose unit with higher capacity in comparison with inflow of fluid from formation into well and during the cycles the pumpdown-accumulation ratio is corrected depending on the results of the previous cycles until the pumpdown-accumulation time ratio stops to change and the torque at which the delivery stops is determined based on the equality of the current torque of the downhole motor shaft and check torque which is pre-determined based on stepwise drop of torque of the downhole motor shaft in the point when delivery stops when supply voltage is decreased. The device for implementation of the method contains pumping unit placed in the production casting string consisting of electrical submersible pump and downhole motor suspended on the downhole pipe string and the is linked with frequency converter and controller located on surface. The device contains also matching transformer, frequency, current, torque, power measurement unit, communication unit, indication and control unit, the conductive cable is linked with the first input-output of the matching transformer, the second input-output of the matching transformer is linked with the input-output of the frequency converter, the second input-output of frequency converter is connected with the power supply unit, the third input-output of the frequency converter is connected with the first input-output of frequency, current, torque, power measurement unit, its second input-output is connected with the first input-output of the communication unit, the second input-output of communication unit is connected with the fourth input-output of the frequency converter, the third input-output of communication unit is connected with the first input-output of controller, the second input-output of the controller is connected with indication and control unit while all signals are transmitted to units located on the surface via conductive cable directly from the downhole motor shaft.

Deduction of Goal-Oriented Minimum-Order Models for Advanced Motion Control on the Example of Large Industrial Drives

Abstract: Adjustable speed drives are used in a wide variety of applications which in many cases include loads with relevant mechanical flexibility. Unwanted mechanical oscillations deteriorate the process quality and threaten to damage the drive train. Due to limited overload capabilities of mechanical components in high power drive systems, the reduction of mechanical strain is considered a crucial control objective. Therfore, acurate models reproducing all important system dynamics of the drive train are required, which, at the same time, have the lowest possible dynamic order to be suitable for online as well as offline optimization and model-based control. Within the scope of this paper, the influence of higher eigenmodes and the shortcomings of two- mass drive train models for controller design and performance evaluation is discussed based on simulative investigations on multi-megawatt rolling mill drives. A strategy for determining all performance-relevant eigenmodes of a drive train is presented.

Solar A/C Direct Motor Drive

Abstract: An electrical device comprising: a high voltage DC power storage system; a variable frequency drive comprising DC terminals, a variable frequency inverter, and a variable drive output, wherein said high voltage DC power source is direct fed to said DC terminals; and an AC motor connected to said variable drive output.

Explosion-proof intrinsically safe variable-frequency drive for mining

Abstract: The invention discloses an explosion-proof intrinsically safe variable-frequency drive for mining. The explosion-proof intrinsically safe variable-frequency drive comprises a rectifier and an inverter. The rectifier comprises a filter unit, a pre-charging unit, a rectification control unit, a power unit, a six-path PWM drive unit, a high-voltage support capacitor unit assembly and a rectification display/keyboard. The inverter comprises an inverting control unit, a power unit, a six-path PWM drive unit and an inverting display/keyboard. The explosion-proof intrinsically safe variable-frequency drive further comprises a power interface board, wherein the power interface board is composed of a rectification power interface board and an inverting power interface board and comprises a detection circuit module. An actual direct-current voltage value detected by a detection circuit is compared with a reference direct-current voltage value by the detection circuit, if the direct-current voltage value is larger than the reference direct-current voltage value and not within a range, it is indicted that a system works in an inverting state, a drive pulse signal is transmitted to a rectification-side power switch triode by a control system, and the power switch triode is normally switched on or switched off; otherwise, the rectification-side power switch triode is in a turn-off state. The explosion-proof intrinsically safe variable-frequency drive alleviates equipment heat dissipation difficulty and improves heat dissipation performance.