Research On Photovoltaic Grid-connected Inverter Based On Model Predictive Direct Power Control

New energy power generation reduces carbon emissions and environmental pollution.It can promote the realization of carbon neutrality.Among them,photovoltaic energy is widely used in micro-grid systems,charging piles,etc.due to its safe and clean characteristics.The core of new energy power generation is the grid-connected inverter,and the research on its performance is a hot topic in the field of power electronics.This article has carried out research and analysis on the control strategy of the grid-connected inverter,and the main contents completed are as follows:(1)The research context of PV power generation both here and abroad and the kinds of PV power generation systems are described.The current research status of grid-connected inverters is also discussed.(2)The output characteristics of PV cells is stated,and the maximum power point tracking technology(MPPT)is analysed.In three coordinate systems,a mathematical model of the grid-connected inverter is built,the basic principles of feedforward decoupling control and model predictive direct power control(MPDPC)are analyzed in detail,and a simulation model is built.Combined with the mathematical model,the basic principles of feedforward decoupling control and model predictive direct power control(MPDPC)are analyzed in detail,and the simulation results show that MPDPC has more excellent dynamic performance,which can neglect the complicated PI parameter design and SVPWM modulation.(3)Two MPDPC methods,multi-coefficient frequency reduction and variable coefficient frequency reduction,are adopted to solve the problem of high switching frequency in traditional MPDPC.Among them,the multi-factor frequency reduction improves the system performance by increasing the number of cost functions,but too many functions will cause the system calculation to increase greatly;and the variable coefficient frequency reduction strategy can adaptively determine the switching action function based on the power deviation.coefficient.The simulation conclusions verify that the two control methods have impressive control effects.(4)A new strategy that combines frequency reduction MPDPC and virtual flux orientation is proposed.This strategy reduces the switching frequency of the system and improves the anti-interference performance of the system by introducing virtual flux orientation technology and improving the switching action function at the same time.A simulation model of MPDPC(VF-MPDPC),three-factor frequency reduction MPDPC(VF-3FFDMPDCP),seven-factor frequency reduction MPDPC(VF-7FFDMPDCP)and variable coefficient frequency reduction MPDPC(VF-VCFDMPDCP)based on virtual flux orientation was built,The simulation results verify the feasibility of various strategies.(5)The design of the three-phase photovoltaic grid-connected inverter system experimental platform was completed,and related software algorithms based on DSP28335 were written.The laboratorial conclusions proved the precision and feasibility of the frequency reduction method.