Abstract
The influence of unadjustable-speed AC drive and adjustable-speed DC drive of the drydock main pumps on the network of the Okean shipyard (Ukraine) is investigated in MatLab SimPowerSystems. To accurately simulate deep-bar induction motors, the own method of determining the parameters of the T-shaped equivalent circuit and viscous friction coefficient of a virtual motor according to catalog data is used. This method is based on formulas that correspond to the T-shaped and refined L-shaped equivalent circuit. It is proposed to introduce the corrected values of the initial starting and critical torque ratio into the calculation. The rated power factor is determined indirectly and compared with the catalog value. The dependences of rotor resistance are approximated by elementary functions, which provide almost constant values of these parameters at subcritical slip values. As a result of the simulation, it became clear that even with the alternate starting of unregulated electric pump units, there is a significant voltage drop in the network. The mathematical model of DC drives was built with a common dual-circuit automatic speed control system. A resonance filter is included at the input of each synchronized 6-pulse generator, thereby eliminating possible errors in operation. The simulation results prove that during the operation of DC drives, there are switching voltage variations in the network, substantially non-sinusoidal current consumption and reactive power consumption. Given the stray capacitance of the cable line, high-frequency voltage fluctuations occur, which are dangerous for electric equipment. Through the use of the harmonic filtering and reactive power control device, these negative phenomena can be eliminated, thus, the DC drive will surpass unadjustable-speed induction motor drive in many respects. To minimize reactive power consumption, an automatic control system with an integrated variable gain reactor power controller can be used
Highlights
An integral part of many shipbuilding and ship-repair yards are drydocks or wet dock chambers
Stripping pumps are used for the final drainage of the chamber when the main pumps are switched off and to remove production, rain and drainage water
The major energy consumers at the stations are the main pumps, which in most cases are equipped with direct-on-line unadjustable-speed induction motor drive
Summary
An integral part of many shipbuilding and ship-repair yards are drydocks or wet dock chambers. In [3, 4] it is shown that by switching to adjustable-speed drive of the main pumps, it is possible to achieve significant energy savings in the process of chamber emptying. A rather long transient process caused by significant joint inertia of the electric drive may be accompanied by a marked decrease in supply voltage The latter phenomenon in most cases adversely affects the Eastern-European Journal of Enterprise Technologies ISSN 1729-3774. The urgency of the work consists in reduction of the influence of powerful electric drives of the drydock main pumps on the network of the shipbuilding and ship-repair yard and providing the possibility of speed control of the main pumps
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