Abstract
A typical electromechanical drivetrain consists of an electric motor, connecting shafts and gears. Premature failures of these shafts and gears have been reported which are mainly due to fatigue caused by extreme loads and torsional oscillations. Overdesign and passive damping are the common approaches taken to increase the fatigue life. Nevertheless, they increase the system cost, weight and volume. Alternatively, active damping through advanced inverter control of the motor drive has been identified as a promising solution that does not require overdesign or alterations to the existing system. Even with the active damping control, oscillations propagate into the dc side of the power converter and subsequently to the upstream power bus. Generally, a large capacitor or an additional energy storage system is placed to suppress these oscillations. This paper proposes to use the clamping capacitors of the capacitor-clamped inverter as energy storage elements and thereby eliminate the need for a large dc side capacitor or an additional energy storage system. The efficacy of the proposed method has been verified with computer simulations. Simulation results show that the clamping capacitors are capable of containing torsional oscillations within the inverter without passing them to the upstream power bus.
Highlights
More electric technologies (METs) play an important role in meeting ever growing demands for energy efficiency and emission reduction in the transportation sector [1]
Conventional mechanical transmission based propulsion and drive systems in ships and aircrafts are gradually being replaced with electromechanical drive systems
The L-drive type azimuth thruster is a good example for this configuration where the motor is connected to the propeller through a vertical shaft, a horizontal shaft and a bevel gear
Summary
More electric technologies (METs) play an important role in meeting ever growing demands for energy efficiency and emission reduction in the transportation sector [1]. Increasing the dc-link capacitance or adding an energy storage is the common solution to prevent the propagation of oscillations into the power system They require large capacitors or additional hardware. The remaining oscillations get propagated into the inverter and appeared in the dc voltage and the input current Both active damping and clamping capacitor support were added to the controller which in turn reduced oscillations in the shaft and smoothened dc voltage and input current. This concept is proven to be feasible as the torsional oscillations can be contained within the converter without passing them on to the shipboard power system
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