Research On The Topology Of Single-Stage Buck-Boost Common-Grounded Inverter

As the core part of photovoltaic power generation systems,the technological innovation of photovoltaic inverters is of great significance.However,due to the presence of parasitic capacitance between the two ends of the photovoltaic inverter and the ground,serious leakage current problems can occur when the common mode voltage at both ends of the parasitic capacitance changes at high frequencies,leading to distortion of the grid connected current and increased losses in the photovoltaic system.In addition,in order to match photovoltaic systems with a wide range of input voltage variations,it is usually necessary to use more power switching devices to achieve voltage rise and fall functions,which can lead to significant switching losses and conduction losses,leading to a decrease in system efficiency.In order to solve the above problems,this article proposes two types of single stage common ground voltage up and down inverters.Inverters with a common ground structure can bypass the parasitic capacitance between the photovoltaic cell and the ground,thereby eliminating leakage current.Topology I is a single stage non isolated Zeta-Cuk common ground inverter,while topology II is a high gain three state three switch common ground Z-source inverter.The two inverters have the function of single stage voltage regulation and the structural characteristics of dual end common ground,which can solve the leakage current problem of photovoltaic systems.In addition,the proposed topology has fewer power switches,simple control,and does not require high-frequency dead zones.Among them,topology I only has one high-frequency switch within half a power frequency cycle,with less switching loss.Compared with the same type of topology,topology II has higher voltage gain and lower switching current stress.In this paper,the operating mode and modulation scheme of the proposed inverter are firstly introduced,and the steady-state expressions for the voltage gain and device stress of the proposed inverter are derived based on the analysis of the operating mode,and the parameters are designed.The stability is analyzed by small-signal modeling and the closed-loop control strategy is designed.MATLAB/Simulink is used to simulate the proposed two inverters to demonstrate the lifting capability of the proposed inverters and to verify the rapidity,stability and grid-connected power generation capability of the closed-loop system.Finally,the experimental platform used to verify the topology is introduced,and the experimental verification of topology I and topology Ⅱ are carried out by Star Sim HIL hardware-in-the-loop experimental platform,and the experimental results further verify the feasibility of the proposed topology and the proposed scheme.