Non-isolated Single-phase Impedance Source Inverters

With the development of society,the requirement of industry,there is a growing demand for energy.As we all know,traditional fossil fuels not only cause irreparable pollution to the environment,but are also non-renewable.Therefore,new energy has emerged at the historic moment.At present,the main new energy sources are wind energy,solar energy,water energy,nuclear energy,etc.Among them,solar energy,which is photovoltaic power generation,has been greatly developed and applied.The electricity used in daily life is alternating current(AC),and photovoltaic power generation is direct current(DC),so the inverter plays a vital role,it is a device that converts DC to AC.At present,there are mainly two types of inverters,voltage source inverters(VSI)and current source inverters(CSI),and voltage source inverters are the most common,but traditional voltage source inverters are step-down circuits,usually a step-up DC-DC boost circuit is added before VSI,which will increase losses and reduce system efficiency.At the same time,inverters are divided into isolated inverters and non-isolated inverters.The difference lies in whether there is a transformer in the circuit.In order to reduce the size and cost of the inverter,people tend to study non-isolated inverters.However,due to the lack of transformer in the circuit,it will bring the problem of leakage current without isolation.Therefore,it is important to study high-gain non-isolated inverters.At the same time,the topology to be studied must have the ability to solve leakage current problem.In order to solve the above problems,three kinds of new topologies are proposed in this paper,namely,a Z-source inverter based on CUK circuit,a Z-source inverter based on SEPIC circuit,and a Z-source inverter based on ZETA circuit,respectively.These circuits are formed based on Z-source inverters.Their common feature are inverters with boosting characteristics.In addition,the negative terminal of the DC input and the negative terminal of the AC output of these circuits are directly connected and grounded.This feature can bypass the parasitic capacitance between the photovoltaic panel and the ground,thereby this circuit structure can solve the problem of leakage current from the root cause.Therefore,the proposed topology is non-isolated,has high gain,and can solve the problem of leakage current.In this paper,the modulation methods are designed for the proposed topology,thw operating modes are analyzed,and inductance and capacitance parameters are designed.In addition,their small-signal models are also established,and closed-loop control is designed through the small-signal models.The circuit was simulated and verified by MATLAB / SIMULINK software to prove the correctness of the theoretical analysis.Finally,an experimental platform for three circuits is set up,the control circuits are achieved by DSP and FPGA,and the above circuits are experimentally verified.The experimental results verify the reliability of the theoretical analysis and simulation results.