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.

Operational optimisation of water supply networks using a fuzzy system

Abstract: This paper presents a fuzzy system to control the pressure in a water distribution network, by using valves and controlling the rotor speed of the pumping systems. The variable frequency drive tracks the minimum head of the pumping system, while the control valves have the function of eliminating the excess pressure at various points of the network. The control system can track any reference pressure value and there is no limit for the number of monitored points. Experiments were carried out to demonstrate the fuzzy system’s efficiency. By extrapolating the results achieved in the experimental setup to a real hydraulic network with leakages and no pressure control, the volumetric losses could be reduced by more than 56%. The experiments showed that the system is robust enough to control the pressure of an experimental setup of water distribution. Besides, the proposed system can be easily applied to similar water supply systems and would help to reduce the consumption of water and electricity, as well as to reduce the maintenance costs.

The application of a 3500 HP variable frequency drive for pipeline pump control

Abstract: AEC Pipelines has expanded the capacity of its bitumen blend Cold Lake pipeline from 130000 barrels/day (bpd) to 185000 bpd by the installation of a new midpoint booster pump station utilizing a 3500 HP adjustable speed drive. The unit is a variable frequency induction motor drive (VFD) utilizing gate turn-off thyristors (GTOs). It was the first of its type in Canada and was the largest induction motor variable frequency drive in a crude oil pipeline application in North America. The authors justify the use of the VFD, describe the equipment, and address application complications. >

Method for boosting the output voltage of a variable frequency drive

Abstract: A sine wave filter including an inductor for each phase (three inductors) and three delta- or Y-connected capacitors is employed within a borehole power system, coupled within a three phase power system at the surface between the output of a variable frequency drive and a three phase power cable transmitting power to a borehole location, and boosts the output voltage of the drive The sine wave filter is designed to have a resonant frequency higher than the maximum operational frequency of the drive, and a Q such that, at the maximum operational frequency of the drive, the filter provides a voltage gain equal to the ratio of the desired voltage to the drive's maximum output power at the maximum operational frequency The sine wave filter also smooths the voltage waveform of a pulse width modulated variable frequency drive

A variable-frequency electric drive with power supply by two independent inputs

Abstract: Excessive sensitivity to interruptions of power supply is a disadvantage of variable frequency drives: short-term power cutoffs or voltage depressions. Within the period of integration of the frequency changing circuit at essential units of a thermal power stations, this can result in increasing risk of electrical power unit blackout. To compensate for this disadvantage, variable frequency drives with electrical supply from two independent inputs have been developed. A frequency-changing circuit with two rectifiers connected on the direct current side has been taken as the basic one. To prevent uncontrolled switching over between inputs, priority of one input should be provided. In this case, increasing the voltage on the input that has been taken as primary is not an efficient solution. Continuous operation of the electric drive should be provided with automatic switching over the reserve input at the loss of supply voltage on the primary input. We propose an arrangement based on two groups of identical frequency-changing circuits connected in parallel on the direct current side. The arrangement also contains a voltage adjuster equipped with an automatic control system, which must provide steady operation of the electric drive with primary input supply. The power unit of the adjuster is constructed based on the active field-bus module (ALM) realized on fully controllable switch contacts. A frequency drive with a simplified main circuit and with a diode rectifier and a group of the active field-bus module ALM has been developed. To carry out experimental investigations of its modes, an experimental prototype of an electric drive with a fast response STATCOM model voltage (power) switch converter has been developed and manufactured. This converter acts as a voltage adjuster of ALM. Experimental investigations of the electric drive with simulation of blackout on one of the inputs and gradual voltage load transfer between inputs and other modes have been conducted. The oscillograms of the main coordinates have been presented. It is shown that the required quality of the transient phenomena is provided in all modes. Thus, automatic switching of the frequency changing circuit over the reserved input practically has no effect on the operation of the electric drive. Thus, we can draw the conclusion that the technological mode of the basic unit will not be affected. Generally, experimental investigations have confirmed that steady operation is maintained of the variable frequency drive under conditions of voltage changes or switching off one of the inputs.

Low stress soft charge circuit for diode front end variable frequency drive

Abstract: A variable frequency drive comprises a diode rectifier receiving multiphase AC power from a source and converting the AC power to DC power. An inverter receives DC power and converts the DC power to AC power to drive a load. A link circuit is connected between the diode rectifier and the inverter and comprises a DC bus to provide a relatively fixed DC voltage for the inverter. A bus capacitor is across the bus. A soft charge circuit limits inrush current to the bus capacitor. The soft charge circuit comprises an inductor connected between the source and the link circuit and a switch circuit in the link circuit for selectively providing a semiconverter configuration or a full bridge converter configuration to provide two stage charging of the bus capacitor.