Research On 3KW Single-phase PV Grid-connected Inverter Based On H6 Bridge

Under the background of energy depletion and serious environmental pollution,people pay more and more attention to the photovoltaic power generation technology.Photovoltaic grid-connected inverter is the core of the entire photovoltaic power generation system to realize the conversion and control of energy.And its performance largely affects the stability and efficiency of the system,so the design of photovoltaic grid-connected inverter is extremely important.In this paper,a 3KW single-phase photovoltaic grid-connected inverter is designed.The inverter adopts two-stage and non-isolated structure,the former stage uses Boost converter to realize the boost of the photovoltaic cell’s output voltage and maximum power point tracking(MPPT),and the latter stage uses the H6 bridge inverter which can reduce the common mode current to complete the inversion.In this paper,some control strategies are compared and analyzed.The system includes booster,inverter and filter parts,they are respectively designed in this paper.The system uses TM320F28035 to control the MPPT,the DC bus voltage,the pulse width of DC/DC and DC/AC,etc.In this paper,photovoltaic cell’s MPPT technology is also studied.After comparing several common MPPT algorithms,an improved variable-step perturbation and observation method is proposed,the effectiveness of the method is verified by Simulink.In addition,the MPPT methods based on fuzzy control and neural network are respectively proposed.Because the perturbation and observation method exists oscillation and erroneous judgment,a MPPT method based on power prediction is proposed.The islanding effect detection of photovoltaic grid-connected system is also studied in this paper,the active frequency drift method is chosen,which is simple、high efficiency,and the effectiveness of the method is also verified by simulation.Based on the theories in this paper,the hardware and software of 3KW single-phase photovoltaic grid-connected inverter are designed.Finally a prototype is made,and the results of the prototype verify the effectiveness of the system’s design and control strategies in this paper.The grid-connected current of the prototype is high-quality and the function of H6 Bridge to reduce the common mode current is also verified,and the indexes,including European efficiency and THD,all satisfy the system’s requirements.