Research On Two-stage Grid-connected Photovoltaic System Based On Model Predictive Control

In recent years,new energy generation technologies represented by photovoltaic power generation technologies have continued to develop.The deterioration of the global environment and people's increasing awareness of environmental protection have led people to focus on the development of new energy technologies.Photovoltaic generation systems have been rapidly developed globally.Photovoltaic generation system is an important carrier for the realization of photovoltaic generation technology.Research on photovoltaic generation system and better use of solar energy resources are of great significance.This paper takes a two-stage grid-connected photovoltaic generation system as the research object,and carries out a detailed analysis of the structure and control strategy of the two-stage grid-connected photovoltaic generation system.A new control strategy based on model predictive control technology for the two-stage grid-connected photovoltaic generation system was proposed.In this paper,the development of photovoltaic generation system is first studied.For the two-stage photovoltaic generation system,there are inherent problems such as limited boost capacity and unbalanced control at the front and back stages.Some improvements have been made in the topology structure.A two-stage photovoltaic generation system structure based on a three-level Boost converter.Compared with the conventional two-stage photovoltaic generation system,the TLB converter can further increase the voltage level of the system and optimize the distribution of the control strategy before and after the level,making the two-stage photovoltaic generation system have better control and operation effects.In the control strategy,this paper optimizes the control strategy of the traditional two-stage photovoltaic power generation system,proposes the model predictive control strategy of the TLB converter,and optimizes the model predictive control strategy of the NPC inverter.This paper analyzes the control application of TLB converter based on the basic principle of model prediction,and establishes the discrete prediction model of TLB converter.The analysis of photovoltaic maximum power point tracking and control of DC side capacitance midpoint potential balance was performed.Combining the improved conductance increment method with the model predictive control algorithm,a TLB converter control strategy based on model predictive control is proposed.In order to achieve the PV maximum power point tracking,the DC point capacitor midpoint potential balance is ensured.The topology and operating principle of NPC inverter are briefly analyzed.The mathematical model and prediction model of the NPC inverter were established and optimized,which made the prediction model still accurate in the case of the unbalanced potential of the midpoint capacitance of the DC side.The optimization of cost function and weight factor design was improved.The NPC inverter realizes grid-side current control and DC bus voltage control,reduces system control complexity,reduces calculation amount,and improves system control accuracy.Based on the Matlab/Simulink platform,the simulation model of the system proposed in this paper was established.The simulation results of the model predictive control strategy of the TLB converter and the NPC inverter were analyzed.Through simulation,it is verified that the proposed model predictive control strategy is effective and enhances the overall performance of the photovoltaic generation system.