Energy-efficient Driving Strategies Of Electric Freight Locomotive

The Belt and Road Project has been carried out,together with the successful experiment of the 30000-ton heavy haul train on Datong-Qinghuangdao Railway Line,which marks the rapid development era of China's railway freight transport.The electric locomotive is the power source of the freight train.Due to the advantages of the electric locomotive's high power,large hauling weight and low energy consumption per unit,the electric locomotive is gradually becoming the main locomotive of railway freight transport instead of the diesel locomotive.However,the electric locomotive consumes a large amount of energy while the freight train is operating on the railway line,which accounts for 70% usage of the electricity of the railway system.Meanwhile,the terrain in China is high in the west and descends toward the east coast.And some rail lines consist of multiple long-distance steep downhill(LDSD)sections.From the perspective of the railway sector,it's an economic way to achieve the energy-efficient operation of the freight train according to the track profile.Therefore,considering LDSD sections,the energy-efficient operation of a freight train is studied,which aims at providing a guiding speed trajectory that meets the constraint of safety,punctuality and stability for the train drivers.Based on the optimal control theory,the dissertation focuses on deriving the energy-efficient optimal control strategies of the freight train on the LDSD sections and its adjacent sections,and developing the on-board driver advisory system,which finally realizes the auxiliary operation of the freight train.The main work of this dissertation includes four aspects:(1)Based on the mechanical energy model,the energy-efficient optimal control model is established,which is close to the operation of the real freight train.In accordance with the train traction calculation principle,the force of the freight train is analyzed and the multi-particle model of the train is derived.The real traction/braking force of the train with different adhesion coefficients is calculated.The cause that leads to the distinction of the train adhesion performance is investigated.The mathematical model of the LDSD section is established.Then the air-filled time of the auxiliary reservoir is introduced,which is the constraint that must be met on the LDSD section after the pneumatic braking is applied.Based on the above models,the energy consumption analysis is adopted to study the internal and external factors that influence the train energy consumption.And the simulation is utilized to verify these factors.Then the cost function of the energy-efficient operation of the freight train is constructed.Finally,the optimal control model of the train energy-efficient operation is established,which could deal with the constrained optimal control problem with the air-filled time,the pneumatic braking and wheel-rail adhesion.(2)The periodic braking of the freight train without regenerative braking energy feeding back to the traction power supply system is studied.The pneumatic braking is simplified based on the pressure reduction of 50 k Pa,which is a typical condition during braking.On the basis of the energy-efficient control model,the Pontryagin's maximum principle is adopted to derive the modes of optimal control(full power,partial power,coasting,etc.),which aims at minimizing the energy consumption due to hauling.Meanwhile,the adjoint variable is introduced to analyze the relationship between the adjoint variable and the modes of optimal control,and the two special modes-partial power and partial braking.The theorem about air-filled time constraint is proposed based on Cauchy-Lipschitz Condition,which transforms the time constraint to the speed constraint.To tackle the inequality constraint of the optimal control problem such as speed limit,the complementary slackness factors are introduced.The relationship between the adjoint variable and the complementary slackness factors is investigated.Then the jumping rules of the adjoint variable are proposed.Based on the adjoint variable,the periodic braking of the freight train on the LDSD section is analyzed.And the speed profile linkage between the LDSD section and its adjacent sections is discussed.The simulation results show that the energy consumption based on the optimal linkage rules could be reduced by 9.8% with respect to the fuzzy predictive control,which achieves the goal of the train energy-efficient operation.(3)The periodic braking of the freight train with regenerative braking energy feeding back to the traction power supply system is studied.Based on the Pontryagin's maximum principle,the necessary condition of the energy-efficient operation of the AC drive locomotive is studied.Then the number of the modes of optimal control is increased.Two special modes are studied-partial power and partial electric braking,which indicates that every mode is corresponding to certain constant velocity.Proof by contradiction is utilized to analyze the uniqueness of the control transitions when a train leaves the LDSD section.Then the speed profile linkage between the LDSD section and its adjacent sections is proposed.Based on the results of the field test,the relationship between the efficiency of the train traction system and the constant velocity is studied.The optimality of the periodic braking strategy(full electric braking-full braking-full electric braking)is proved by comparative analysis.Finally,the simulation results show that the energy consumption of the AC drive locomotive based on the optimal linkage rules could be reduced by 6.5% with respect to the fuzzy predictive control,which is more energy-efficient to some extent.(4)The numerical algorithm and engineering-based modified algorithm about the train energy-efficient operation are both studied.The numerical algorithm for the optimal driving solution is proposed.And the simulation is utilized to verify the numerical algorithm.The energy-efficient operation of the train drivers is investigated.Based on the experienced drivers' operation,the numerical algorithm is modified for the engineering application.Then the train operation simulation system is designed.The field test data is compared with the simulation results of the designed simulation system,which aims at proving that the simulation system is more energy-efficient.The comparative results show that the speed trajectory based on the modified algorithm saves 15.0% of the energy consumption comparing with that of the numerical algorithm.The simulation system could provide the operation advice for the train drivers,which achieves the goal of the train auxiliary operation.