| With the gradual lack of traditional energy and the aggravation of environmental pollution,new energy and environmental protection are receiving more and more attention.Due to the factors of fuel consumption,pollution and noise,the development of traditional fuel powered drone will be limited in the future.The pure electric drone is pollution-free but limited by the density of current battery energy.So the hybrid UAV emerges as the times require.It not only combines the power of the fuel powered UAV,but also makes up for the lack of the flight time and load capacity of the pure electric UAV.In this paper,the energy management system of hybrid UAV is designed and studied.The key technologies such as generator rectifier system,battery management system and energy management strategy are studied to meet the requirement of power and economy and improve the stability of DC bus voltage of the system.The main research works of this paper are as follows:Firstly,the overall scheme of the hybrid system is designed.The series hybrid structure is selected based on the discussion of three different hybrid structures and the comparison of their advantages and disadvantages.Each energy module is configured and selected for the dynamic characteristics and structural mode requirements of the UAV,such as the engine generator set as the main energy source of the system,and the lithium battery set as the auxiliary power supply.Secondly,the research of permanent magnet synchronous generator rectifier power generation system is carried out.The mathematical model of PMSG and PWM rectifier is built,and SVPWM modulation method is selected.Based on the theoretical study of id=0 and unity power factor control strategy,the steady-state characteristics of PMSG under different control strategies are analyzed.A compound control strategy suitable for series hybrid power system is proposed.Under low load,id=0 control strategy is used to reduce the internal loss of the motor,while under high load,unity power control strategy is used to improve the efficiency and power of the generation system Rate factor.Finally,two control strategies and compound control strategy are simulated to verify the good voltage stability of PMSG systemand the composite control strategy improves the power factor of the power generation system.Thirdly,the management system of energy storage lithium battery is studied.The ampere hour integral method and voltage open circuit method are used to estimate the residual charge of the battery accurately,which can provide accurate reference for battery equalization technology and battery charge and discharge control.In view of the traditional battery equalization technology is difficult to meet the actual problems of the hybrid UAV,an active passive equalization charging control technology is proposed,which can accelerate the equalization speed and reduce the loss of the battery equalization process.The buck-boost converter is selected as the bi-directional energy transmission circuit of the lithium battery pack.Charge and discharge control strategy are studied to meet the switching requirements of the working mode of the lithium battery pack under different load operation conditions,and to improve the dynamic performance of the system in the operation process,which is verified by simulation.Then,the control strategy of the energy management system of the hybrid UAV is designed.In order to reduce the loss caused by the frequent speed change of the engine and the influence on the stability of the system,the combined control strategy of the engine generator power follow is proposed.According to the different working states of the system,the control strategy of the finite state machine is established to control quickly and accurately the working mode of the bidirectional DC/DC converter.The output power of the hybrid is distributed reasonably to ensure the stability of the hybrid system.The feasibility of the control strategy is verified by simulation.Finally,an experimental prototype of the energy management system for the hybrid UAV is built,and the hardware design and software process design of the system are given,including the hardware circuit design and software design process of each module.The experimental results verify the feasibility of the rectifier control strategy,bi-directional DC/DC control method and energy management control strategy. |
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