Design Of Optical Storage Power Controller For High-altitude Airship

The high-altitude airship with long flight time across the day and night has the advantages of long time in the air,wide use,strong survivability,reusable,low cost of use and maintenance.It can carry mission system,perform high-resolution earth observation and other tasks,and has high application value in national military and economic construction.Due to the characteristics of high economy and environmental protection,more and more countries have begun to focus on the research and development of airships,and carried out technical research in many related fields.Solar cells are used as the main energy source,and energy storage batteries are used to realize the energy buffer between intermittent power generation and continuous load.In this paper,on the basis of the system bus voltage requirement of up to 600 V,an PV-Battery power controller suitable for high voltage and high power is designed.The main research contents are as follows:In order to design the PV-Battery power supply with high power density,first of all,analyze the circuit topology,control strategy and related hardware equipment of the existing PV-Battery system,sort out and compare the relevant contents,according to the system parameters of this subject,guide the design of the PV-Battery module as the basic unit of the system,multiple modules in series and parallel form the airship power system.Each module can be divided into a photovoltaic control unit and a power output unit according to its function.The photovoltaic power is reasonably utilized in a well-lit or harsh environment.The energy storage units are balanced to ensure the stability of the system bus voltage.Gallium nitride power device with better performance is selected as the main switch element of the controller in the hardware circuit to improve the switching frequency of the system,optimize the parameters of the passive components of the main circuit,and further improve the power density of the device.For coordinated control within the PV-Battery system,multiple PV-Battery modules are connected in series to form a string.The power output unit of each module is controlled by a microprocessor to become a power output module,which can provide load power with a certain degree of redundancy,but will not increase the hardware cost too much.When the input power of the power output module is in an unbalanced state,in order to make the system use the carrier phase shifting PWM technology,it can still achieve the frequency multiplication effect,improve the output voltage quality,and reduce the system ripple.In this paper,two improved carrier phase shift modulation methods are proposed.Theoretic analysis is carried out from two perspectives of string modulation voltage and inductor current respectively,and an improved phase shift angle algorithm is obtained.The effectiveness of the algorithm is proved by MATLAB simulation.For the start-up phase of the power output module,the voltage soft-start method is used to smoothly increase the inductor current to the command value to avoid the problem of inductor saturation failure.In order to improve the stability of the PV-Battery system,analyze the possible failure types of Boost and Buck converter switch tubes,so that the controller can determine whether to take different countermeasures according to the failure signal,as far as possible to ensure the normal operation of the load equipment,and reduce the cause of power failure Adverse effects.The simulation verifies the rationality of countermeasures against failures.In order to optimize the energy management strategy of the PV-Battery system,in the normalized mode where the photovoltaic cell has been tracking the maximum power point,a constant power working mode is added to directly provide the power share required by the load side,reducing the number of charge and discharge of the energy storage unit;Under special working conditions,the power output module selects the through mode to improve the system efficiency;In the calculation of the output index of each half-bridge,the battery SOC factor is added to independently adjust the output power of each PV-Battery module to make the system run intelligently.The effectiveness of the control strategy is proved by the simulink simulation model.