Research And Design Of 3kW Three-phase Photovoltaic Grid-connected Inverter System

In a world facing environmen,tal pollution and energy shortage crisis,Grid-connected PV power,as a kind of renewable energy with low-carbon and widespread features,has captured the world’s attention.Given the economy and reliability of power system,this paper focuses on the control of both maximum power point tracking and current in three-phase PV grid-connected inverter system.First,various architectures of grid-connected PV power generation system were compared and analyzed,and the general planning of this design is ensured.Meanwhile,main circuit topology of three-phase grid-connected inverter system is studied,which leads to conclusions of its advantages and disadvantages,and applicability.Main circuit adopted one with multiply parallel branch,two-stage and non-isolated topology,due to consideration of the general design of system and its practical limits.Second,converting solar energy to maximum electricity needs to track the maximum power of PV array.Therefore,this paper set up a mathematical model of photovoltaic cell,implemented MPPT control of two-stage grid-connected inverter topology,carried out in-depth analysis on various algorithms of MPPT control,and simulated the process of maximum power-tracking of Boost circuit by using Matlab and the perturbation and observation method and improved conductance increment method.Third,grid-side control strategy of inverter is the key part of grid-connected PV power system.Under Synchronous Reference Frame,double closed loop control system is designed according to oriented vector control strategy of grid voltage.In the control system PI controller is adopted,making real-time adjustment of DC bus voltage and grid-connected current.Voltage is proved to be stable,grid-side current wave form is sine and the power factor is unity.Meanwhile,phase lock loop technology and space voltage vector modulation technology are studied deeply,and related simulations are verified.Finally,a grid-connected PV inverter,which is 3kW,three-phase,two-stage and non-isolated,is constructed on basis of chip TMS320F28335.Both type-selecting of hardware circuit and procedures of designing software program are introduced in detail.