Design And Optimization Of Independent Photovoltaic Inverter Systems

With the continuous development of modern science and technology,environmental pollution has become increasingly serious,especially in the field of power generation.Traditional methods of power generation will cause great detriment to the environment.Considering all kinds of energy shortage,people have begun to use such clean and renewable energy as solar energy,wind energy and so on.In the past few years,photovoltaic technology has attracted worldwide attention,and has become a hot research direction in the field of scientific research,which has realized large-scale commercial applications.In recent years,wide band gap semiconductor technology has gained widespread attention,which is due to the wide band gap of silicon carbide materials that can greatly improve power conversion efficiency.Photovoltaic power generation is an important application field of silicon carbide devices,which can effectively reduce the volume of photovoltaic inverter,improve the power density,and greatly reduce the power loss.In this dissertation,a single phase independent photovoltaic inverter system is designed to invert DC power into the 220V sinusoidal AC power.The system includes photovoltaic array,DC-DC converter,DC-AC inverter,and filter.The innovation of this dissertation can be concluded as follows.In the design of topology structure,studied the structure of traditional photovoltaic inverter based on Si devices.Proposed a two-stage inverter topology and a new LLC soft switching resonant DC-DC converter and DC-AC inverter based on SiC devices.In the design of experiment methods,considering the influence of temperature,parasitic parameters of the system,compared the new SiC photovoltaic inverter with the traditional Si inverter device.Analyzed the loss and efficiency of the designed inverter,highlighted its advantages,and optimized it.In the design of control method,proposed a modified control method of output current based on SPWM in DC-AC inverter part which has realized the output target.In this dissertation,parameter designing and device selection of each part of system,contrast test and efficiency analysis of silicon and SiC devices have been accomplished.The experiments are based on Matlab/Simulink and LTspice software platform and hardware platform.Excitation current,harmonic current,output voltage,output current and a series of results are obtained.The calculation shows that the maximum efficiency of PV inverter system based on silicon carbide devices can reach 97.6%,which is 57.3%lower than that based on silicon devices.The superiority of silicon carbide device using in photovoltaic system has been verified,and the goal of system optimization and efficiency improvement have also been achieved.