Capacitor-Clamped Inverter Based Transient Suppression Method for Azimuth Thruster Drives

The more-electric trend is there in almost all the corners of the automotive industry. The same trend is followed by the maritime transportation industry and as a result, conventional mechanical propulsion systems are gradually being overtaken by electric propulsion systems. An azimuth thruster driven by an electric motor is a common configuration found in modern electric propulsion systems. Due to the tight speed control and stiff drivetrain in these propulsion systems load transients easily get propagated into the dc-link of the motor drive and subsequently into the upstream power bus as well. These transients can cause disturbances to the other loads connected to the power system. In the worst case, stability of the shipboard power system gets affected by the transients. This paper proposes to use the capacitor-clamped inverter based motor drive itself to absorb such transients and thereby prevent the propagation into the power bus. The efficacy of the proposed concept is verified through computer simulations. Simulation results show that the capacitor-clamped inverter is capable of absorbing load transients without passing them to the upstream power bus.