Research On Single-Phase Current Source Grid-Connected Inverter

This paper mainly studies the single-phase current source grid-connected inverter.Firstly,the present research situation and development trend are outlined.Then,paper introduces the key problems of single-phase current source grid-connected inverter,which is mainly analyzed: leakage current problem,system active damping,effect of power grid background harmonics and ripple power problem.The working mode of the conventional single-phase current source inverter is analyzed,and the mathematical model is established.The stability of the system is analyzed,and the various passive damping methods are illustrated and compared.The control strategy of single-phase current source grid-connected inverter is analyzed,and the parameters of system current loop are designed.The common-mode model of current source photovoltaic grid-connected inverter is established,and the generation mechanism of leakage current is analyzed.In this paper,based on the conventional single-phase current source inverter,a novel circuit is proposed to suppress the common-mode leakage current.The mechanism of the proposed circuit structure to suppress leakage current is analyzed,and optimized methods are proposed to reduce the system power loss.Because the damping coefficient of CL filter is very small,the passive damping method is traditionally used to increase the stability of the system.However,this method will affect the high frequency attenuation characteristics of the system,and will lead to additional power loss.In this paper,active damping method of current source inverter is proposed to increase the system stability.The different active damping methods are analyzed and compared.When the grid contains large background harmonics,the grid current will contain the corresponding lower harmonics.Through the transfer function and the control block diagram of system,the generation mechanism of grid current harmonics is analyzed.The grid voltage full feedback method is proposed to suppress the low frequency harmonic of the grid current.The proportional full feedback method is compared with the full feedback method.For single-phase current source grid-connected inverter,there is an inherent limitation in AC-side low-frequency power oscillation,which is twice the grid fundamental frequency.According to the theorem of conservation of power,it transfers to the DC-side and results in the low-frequency DC-link ripple.In this paper,the generation mechanism of the ripple power is analyzed.An active suppression method used to suppress the ripple power is introduced.Finally,a 500 W power grade single-phase current grid-connected inverter platform based on TMS320F28335 DSP and Xilinx XC6SLX9-2TQG144 C FPGA Controller is designed and built.The validity of the control strategy and modulation method is approved.The theoretical studies are verified by the experiment results.