Research On No-communication Control Strategy And Analog Control For Series-connected Photovoltaic Power Optimizer

With the increasing attention to environmental protection,the renewable energy generation has developed year by year.As an important part of renewable energy power generation,photovoltaic power generation has made considerable development in recent years.Among them,the module level power electronic converters with higher illumination utilization rate represent the development direction of future photovoltaic power generation systems,and also occupy an increasing market share in the household photovoltaic field.Power optimizer,the representative of module level power electronic converter,has the problem of high cost.Therefore,this paper studies the related technologies of the photovoltaic power optimizer,including two aspects of no-communication control and analog control,and designs a prototype and experiment.The first chapter introduces the current situation of energy development in the world,and introduces the basic working principle of photovoltaic system and power optimizer.In the second chapter,the no-communication control strategy of series boost power optimizer applied to off-grid system is analyzed.The no-communication control scheme of the series power optimizer is improved.The optimizer can only use local information to realize large-scale series operation,and on this basis,the introduction of over-voltage shutdown,restart after protection have been achieved.In addition,the problem of system startup when using real PV modules at sunrise was solved.In chapter three,the optimal topology of analog control power optimizer is analyzed.Twelve simple DC/DC topologies,including BUCK,BOOST,partial power BUCK/BOOST and partial power flyback,are analyzed.In the process of analysis,a partial power circuit analysis method based on power supply splitting is proposed.Finally,the optimal topology selection under this scenario is proposed,and the feasibility of the whole series system connection scheme is confirmed.In chapter four,the analog control method and grid-connection scheme of the optimizer are studied.The analog control circuit including the analog MPPT module,the converter control loop and the anti-backflow circuit is designed,and the prototype of the analog control power optimizer is made.The experiment verifies the analog control method of the optimizer and the design of the whole system,and realizes the basic function of the power optimizer and the compatibility photovoltaic inverter.