Hybrid Integrated Propulsion POwertrain (HIPPO-1) Τest-bed

The Hybrid Integrated Propulsion POwertrain (HIPPO-1) test-bed at LME consists of a marine diesel engine in parallel connection to an electric machine (see Fig. 1). In this setup, the thermal and electric engine provide mechanical power simultaneously, with identical rotational speeds.

The prime mover is a production-type, CATERPILLAR 6-cylinder, 10.3-liter marine diesel engine, with a rated power output of 425 kW at 2300 rpm. The electric machine is a standard AC asynchronous-induction 3-phase motor, with a rated power of 112 kW. A frequency inverter unit enables the torque output regulation of the electric motor under closed loop control. A water brake from AVL Zoellner, with a load capacity of 1200 kW and maximum speed of 4000 rpm, applies the desired torque demand, which is regulated by a separate robust controller developed at LME. The water brake is configured so as to simulate a seagoing vessel’s propeller/waterjet demand, with variable speed and torque as well as a generator with constant speed.

Fig. 1. The hybrid diesel-electric test-bed at LME.

Various sensors have been installed in the testbed: for NOx/oxygen (NGK, UniNOx 24V), for exhaust gas opacity (Green Instruments, G1000), for fuel mass flow (ABB Coriolis), for turbocharger speed (micro-epsilon), for in-take manifold pressure, for the torque and speed of electric motor (HBM). The whole testbed is controlled and monitored by a dSPACE DS1103 controller board, programmed under the MATLAB/Simulink environment.

The concept of hybridization of a marine propulsion plant is presented schematically in Fig. 2. The electric motor assists the diesel engine at low-load operation, where the internal combustion engine produces low torque, so as to meet up with the torque demand faster. With this setup the initially small margin (i.e. available torque that the propulsion system has available for acceleration during transient operation) can be significantly increased.

Fig. 2. Effect of hybridization of a marine propulsion plant during transient operation.

Various control methods are investigated in relation to the power split strategies applicable to the HIPPO-1 hybrid diesel-electric test-bed. In a recent work, closed loop of λ (air to fuel-ratio/stoichiometric) was implemented, with system models derived from first principles and system identification.