| The mine hoister is large electromechanical hoisting equipment. To adjust the speedof the hoister in operation, the traditional wound motor was adopted for the step speedadjustment via a serial resistance with its rotor. It has the advantages of simple equipmentstructure and convenient control, but its disadvantages mainly lie in relatively high energyconsumption as the slip power is consumed on the resistance by means of heating, it is alsoof relatively weak mechanical properties as it belongs to the step speed regulation.The load of the mine hoister is of the potential load, which requires the transmissiondevice to run smoothly in the four quadrants, i.e., the energy can flow in a two-way mannerto meet the requirements for handling with the heavy duty (the motor is in the generationstate); it has a strong mechanical property and relatively large starting torque that can meetthe requirements for starting with heavy duty (different from the fan and pump); and thespeed can be regulated in a wide range to meet the various requirements for speed(creeping at low speed and hoisting at high speed).The reproducible transmission device with the full digital AC-DC-AC quadrantstransducer can well meet the above requirements. It has the advantages that theperformance is excellent, the control precision is high, the power factor is1, the pollutionto the grid harmonic waves is small, etc. It will be widely used in the drive system of thehoister step by step. This paper covers the application of ABB ACS6000DTC transducerof energy feedback in the hoister as well as the relevant work principle and operationalcommissioning.The LCL filter can restrain AC voltage distortion and current harmonics. Both theline-side converter and motor-side converter have their own RDCU control units andcontrol programs. The line-side converter rectifies the three-phase AC to DC to supplypower to the middle DC circuit in the drive unit, which thus supplies power to themotor-side converter of the drive motor.The active front end (AFE) power supply in the inverter is a three-phase-voltagePWM rectifying power supply. Due to the application of the full-control switch device (e.g.,IGBT), the AFE converter has become a fully-developed reversible converter, which can maintain the DC busbar voltage to a constant given value. It can serve as both a rectifierand an inverter to operate in the four quadrants at the power side. With the self-turn-offdevice IGBT used and in an appropriate PWM mode, it can control the strength and phaseof AC, and enable the AC input to approximate to a sine wave through the various filteringand energy-reserving functions at the front end. Moreover, its power factor can beregulated to a positive or negative value with1as the mid-value. When the return of themotor-side braking energy through the inverter leads to an increase in the DC busbarvoltage, the phase of the AC input may be regulated to be contrary to that of the supplyvoltage, in order to regenerate power for operation and feedback the regenerative power tothe AC grid. At this moment, the AFE converter operates in the active inverting state.The AFE rectifier/inverter is a new-generation AC-DC converter. It uses theself-turn-off device IGBT as its power device and also utilizes the pulse width modulation(PWM) technology for sine wave, thus avoiding that the rectifier/regenerative feedbackunit of the controlled silicon power component is likely to have an inversion failure due toa fault at the line side, and significantly improving the reliability of AC-DC conversion.Since the waveforms of voltage and current at its front end have been both filtered to thesine waveforms and the phase angle between them may be set within a certain rangeaccording to the requirements, the power factor is adjustable. It may even make an activepower factor compensation for the power supply system.When AFE is initially connected to the grid, IGBT doesn’t operate. The current fromthe line side is rectified through the antiparallel free-wheel diode beside IGBT to chargethe DC capacitor. When the DC voltage Ud increases to the maximum value, PWM beginsto operate. When IGBT is powered on, both the current through the line reactor and theenergy stored in the reactor increase; when IGBT is turned off, the reactor’s energy isreleased to charge the DC capacitor through the free-wheel diode. Thus, Ud is increasedand the line current drops to the origin. The whole system just cycles like this.Based on the DTC principle, the main part of this system is the torque and fluxhysteresis-controllers under the bang-bang control. The given torque value Te*is outputfrom the automatic speed regulator (ASR), and then input into the torque regulator forimplementation of the bang-bang control after a comparison with the observed value Tefrom the torque observer. The torque control inner-loop is set behind Te*, which mayinhabit the effect of flux variation on the subsystem of rotation speed. Meanwhile, theflux’s given value Ψs*and observed value Ψs are compared by the flux regulator, and theoutput flux and torque conditioning signals are input into the switch state selector for regulation. According to the rotation direction, the flux and torque increase or decrease;according to the rotation position of flux vector and based on the DTC principle, anappropriate voltage vector is selected to determine the converter’s switch mode. The switchstate of each switch component of the converter is also under control to achieve thepurpose of controlling the torque and flux.Since the solution described in this article was used for this system, it has workedreliably, thus meeting the requirements for technical improvement. the motor’s speedclosely matches the given control speed. With the capacity of meeting higher requirementsfor performance, e.g., start with heave load, wide-range speed regulation, etc., this systemhas operated reliably since its commissioning. With its power factor reaching1, it has lessinterference with the grid harmonics and an outstanding energy-saving performance in itsfour-quadrant operation. Compared to other hoist drive systems, it has high performance,which is widely applicable. |
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