Research On An Integrated Single-Phase Single-Stage DC/AC Boost Photovoltaic Converter

Energy and environmental issues have been widely concerned by the international community.Especially in recent years,with the adjustment of national energy policies,the trend of replacing traditional energy with new energy represented by solar energy has become more and more obvious,and its development scale is showing a blowout growth trend.In the photovoltaic power generation device,DC/AC converter is the key equipment in the process of electric energy transmission and conversion.Its performance will directly affect the efficiency,safety performance and production benefit of the power generation device and even the whole system.Therefore,DC/AC converter with the characteristics of high efficiency and high reliability has important research significance and research value.From the current research and development process and future development trend of DC/AC converter,the main performance of competitive DC/AC converter is reflected in volume,cost,efficiency and safety.The traditional single-stage full bridge photovoltaic inverter has simple structure and convenient control.It has been widely used in the field of photovoltaic power generation.However,its AC output voltage is lower than the DC side power supply voltage.Therefore,multiple groups of photovoltaic panels are usually connected in series on the input side to improve the DC input voltage to meet the demand of AC side output standard voltage.However,after multiple groups of photovoltaic panels are connected in series,they are easy to be shaded,which leads to problems such as the reduction of photovoltaic power generation efficiency.In addition,the traditional full bridge inverter is easy to produce leakage current and reduce the safety performance of the system.Based on the above factors,an integrated single-phase single-stage DC/AC boost photovoltaic converter topology is proposed in this paper.The AC output voltage of this structure can be higher than the DC input voltage.At the same time,it has the ability to suppress the leakage current,and avoids the through problem of the bridge arm,which is conducive to improving the reliability of the system.In this paper,the working principle,various modulation strategies and steady-state characteristics of the converter are analyzed in detail,the loss analysis process of the converter is given,and its main parameters are theoretically calculated and designed.In this paper,LCL and LRCL filters are applied to the proposed converter,the corresponding mathematical models are established by using the state space average method,the root locus diagrams of inverter side and grid side current control strategies in continuous domain and discrete domain are drawn respectively,and the performance of the converter is analyzed.Further considering the time-delay effect of the switching signal in the converter device,the digital controller of the system is designed,which provides a basis for the production of the actual prototype.Then,aiming at the practical application of the proposed photovoltaic inverter,this paper analyzes a variety of control strategies,and studies the grid connected current control method with maximum power tracking technology,which is simulated and verified by MATLAB software.Finally,the hardware circuit parameters of the main circuit,sampling circuit and driving circuit are designed.Taking the high-performance digital signal processor stm320f2812 DSP as the controller core,the experimental prototype is built,and the experimental results are given to verify the correctness and effectiveness of the theoretical analysis.