Leakage Current Analysis And Hardware Design Of Non-isolated Photovoltaic Inverter

Recently,with the increasing use of fossil fuels the environment has been greatly polluted.The active promotion,photovoltaic power generation,is used widely in the tens of thousands of households from the initial military because of its clean,extensive and no-pollution.The measures not only solve the energy shortage and environmental pollution problems but also promote the local economic development.Compared with the traditional isolation inverter,system efficiency is the most critical thing in the photovoltaic power generation system.Non-isolated inverter becomes the focus of the study for its small size,high efficiency,power density and other advantages.However,due to the lack of transformer,leakage current which is mainly analyzed in this paper.Firstly,by analyzing the topology of the conventional PV grid-connected system considering the unbalanced bus voltage in the three-level inverter,a topology containing compensation is proposed and analyzed in detail.At the same time,in order to suppress the leakage current of non-isolated inverter,a new topology is proposed.Secondly,the suppression of non-isolated inverter leakage current is next to study.Firstly,the mechanism of the distributed capacitance in the inverter system is analyzed from the source of the leakage current.Secondly,the equivalent mathematical model is established to deduce the resonant circuit in the system when the common mode voltage remains constant in the system and the leakage current is zero.The effects of unipolar modulation and bipolar modulation on the system common-mode voltage and leakage current are compared.Then,the topology and working principle of H6 topology as well as the common mode voltage and leakage current of the system are analyzed.Overall,the new topology proposed in this paper is particularly analyzed from the circuit,the working mode and simulation.Thirdly,filter inductor and auxiliary switching power of the system is designed.By calculating the inductance according to the actual parameters of the system,and then the iterative calculation is used to determine the magnetic ring model and the parameters of the verification.The inductance loss and temperature rise are calculated according to the parameters of the magnetic ring.The auxiliary power supply specially the RCD buffer circuit,feedback compensation circuit,UC3842 and its peripheral circuit parameters are calculated in detail.Fourthly,in order to verify the correctness and rationality of the filter inductor,the auxiliary power supply and the new topology suppression leakage current,the experimental prototype is designed on basis of the theoretical design.The filter current,common mode voltage,leakage current and auxiliary power signal of the system are measured to meet the design requirements.