Analysis of a gas turbine driven hybrid drive system for heavy vehicles

Sammanfattning: The goal of this thesis has been to analyze the performanceand behavior of a gas turbine driven hybrid drive train. Thethesis covers both computer simulations and experimental tests.In two case studies, a number of measurements have been made ongas turbine driven hybrid vehicles that are developed by Volvoand ABB.In the recent years, much effort is currently put into thedesign and analysis of hybrid drive trains. Many studiesinvolve computer simulations, but they are often made on ageneral level. This thesis concentrate on gas turbine drivenhybrids for heavy vehicles, a field that has previously notbeen covered to a large extent in academic studies.A major contribution to the field of hybrid drive traindesign is the development of detailed simulation models thathave a close connection to hybrids that are actually built andtested. The access to detailed gas turbine data has furtherenhanced the possibility to design a dynamic model of the gasturbine driven and the electric circuits. The combination ofsimulations and extensive field experience gains new knowledgeon the properties of gas turbines in hybrid drive trains.Two simulation models have been developed in Matlab andSimulink. One is a quasi-steady state model that can be usedfor drive cycle simulations, e.g. a complete bus line. Theother is a transient model that combines the thermodynamicproperties of the gas turbine, the mechanical properties of thecombined turbine-generator shaft, the electric power circuitand the control system. The transient model has been used tosimulate the power response during accelerations andretardation.An analysis of the internal energy flows and the systemefficiency of a hybrid drive train contributes to theunderstanding of the properties of series hybrid drive trains.An important part of the topology is that the system is basedon a DC/DC-converter that is connected between the battery andthe DC-bus. It controls the DC-bus voltage and by this,indirectly, the speed of the gas turbine. With thisarrangements, an uncontrolled diode rectifier can rectify thegenerator output.The control of the output power requires increased knowledgeon the behavior of this apparently simple circuit: thepermanent magnet synchronous generator that is feeding a dioderectifier with additional shunt capacitors at the generatorterminals for reduction of generator current harmonics. Thiscircuit is highly non-linear and a circuit model hasestablished in Matlab and Power System Blockset for theevaluations of the circuit. The results of the circuitsimulations are important inputs to the transient model.Improved system efficiency is one of the key factors for acommercial success of the gas turbine series hybrids. In thelight of this, design alternatives with a flywheel or a supercapacitor energy storage have been studied. A conclusion isthat a straightforward approach with a controlled rectifier isthe best compromise from technological point of view.Keywords:battery, bus, diode, dc-converter,distribution truck, efficiency, emissions, EV, flywheel, gasturbine, generator, HEV, high-speed, hybrid, inverter, matrixconverter, optimization, permanent magnet, Power SystemBlockset, rectifier, simulation, super capacitor, ultracapacitor, vehicle model.