This brief presents an optimal power management scheme for an electromechanical marine vessel's powertrain. An optimization problem is formulated to optimally split the power supply from engines and battery in response to a load demand, while minimizing the engine fuel consumption and maintaining the battery life, wherein the cost function associates penalties corresponding to the engine fuel consumption, the change in battery's state of charge (SOC), and the excess power that cannot be regenerated. Utilizing the nonlinear optimization approach, an optimal scheduling for the power output of the engines and optimal charging/discharging rate of the battery is determined while accounting for the constraints due to the rated power limits of engine/battery and battery's SOC limits. The proposed optimization algorithm can schedule the operation, i.e., starting time and stopping time for a multiengine configuration optimally, which is a key difference from the previously developed optimal power management algorithms for land-based hybrid electric vehicles. Afterward, a novel load prediction scheme that requires only the information regarding the general operational characteristics of the marine vessel that anticipates the load demand at a given time instant from the historical load demand data during that operation is introduced. This prediction scheme schedules the engine and battery operation by solving prediction-based optimizations over consecutive horizons. Numerical illustration is presented on an industry-consulted harbor tugboat model, along with a comparison of the performance of the proposed algorithm with a baseline conventional rule-based controller to demonstrate its feasibility and effectiveness. The simulation results demonstrate that the optimal cost for electric tugboat operation is 9.31% lower than the baseline rule-based controller. In the case of load uncertainty, the prediction-based algorithm yields a cost 8.90% lower than the baseline rule-based controller.Index Terms-Hybrid electric vehicle (HEV), load estimation, marine powertrain, marine vessel, optimization, power management.
A 20 RVA direct DCILFAC Dual-Active-Bridge (DAB) converter projected for operation at I 0 0 w l z with IGBT switches is presented. It has dual angle, constant frequency phase shift control, and is sofr-switched in a large part of the output V-I-plane. It has a highperformance digital control system. The topology and its properties is presented. The control strategy and regulating loop is examined. Experimental results are shown for both a small-scale-model and a full-scale converter.
When permanent magnet synchronous motors are operated in the flux weakening region, the internal voltage may be much larger than the DC link voltage. If the switching signals are blocked, the freewheeling diodes act as a rectifier and the motor will feed power back into the inverter. This work focuses on the magnitude of the feedback power during such controller failure. Simulations and approximated analysis are used to draw descriptive and comparative curves. Measurements veri ' the computer results but also show that nonlinear effects may have significant influence. INI'HODUC~'IONPermanent magnet excited motors have gained increasingly interest in the last decade due to the discovery of strong and potential low cost permanent magnet materials. Of particular interest are the rugged AC motors. Because of high efficiency, combined with possible compact designs, permanent magnet excited AC motors are well suited for battery fed drives, as in electric traction and remotely operated vehicles [ 1-41. In these applications, the torque requirement is usually high for low speeds, allowing for decreased torque at higher speeds. These requirements are for the high speed region typically met by field weakening in traditional motor drives. In permanent magnet synchronous motors (PMSM), field weakening or more precisely: flux weakening, is obtained by phase advance of the stator currents. The armature reaction then opposes the flux from the magnets and reduces the total stator flux linkages. In inverter fed drives this is obtained by control of the phase of the currents or voltages [ 5 ] . A voltage source inverter (VSI) fed PMsM drive is schematically drawn in Figure 1.The excitation from the magnets alone is constant in flux weakening. The rotational induced voltage from this flux is proportional to speed and may become several times the DC link voltage of the inverter. If for some reason the gate firing signals are blocked or the control is lost, the freewheeling diodes of the inverter behave like a diode rectifier. The motor will act as a generator and feed power back into the DC link. The power can be dissipated in a dumping resistor, or accumulated if the inverter is fed from a battery. If the DC link can not handle the power, the voltage may increase to destructive levels. 42 41, Fax: +47 1 59 42 79 I I I Figwe 1 : A VU fed PMSM drive.In the design of drives with flux weakening, it is essential to predict the magnitude of the power feed-back in failure. It is also necessary to know the influence from motor parameters and the DC link voltage to select the best design. In this work, such failure conditions have been simulated and measured. The results are presented in descriptive curves which show the power during failure vs. speed. Different parameters are compared. An approximate analysis with assumption of continuous currents is perfoxmed. For nonsalient pole motors, this analysis results in a particular simple expression. MODEL DESCRIPTION The motor modelThe state space model for the PMSM is described in synchronous ...
This article presents a mathematical model of a complete diesel-electric propulsion system, including components as diesel generators, distribution network, variable speed thruster-drives, and conventional motor loads. The model is split into two parts: One power generating part where the load is speci®ed with an aggregated active and reactive power load demand. Secondly, a power consumption part where the effects of the different load types as thruster drives, motors and other loads are modelled. The model is written in a state-space form suitable for the purpose of simulation and control design. PID-controllers represent speed governors and automatic voltage regulators.
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