Research On Grid-connected Control Strategy Of Three Level Inverter Based On Internet Of Things

With the economic and social demand for green energy,renewable energy and photovoltaic power generation and wind power generation are becoming more and more popular.Distributed generation has the characteristics of small capacity and dispersed distribution.In view of the problem that the distributed generation equipment is difficult to monitor,dispatch and maintain,this paper uses the Internet technology and the concept of smart grid to monitor and control the distributed generation equipment by using the method of Internet of things,so that the distributed generation equipment can participate in the operation of the power grid flexibly.The principle of the neutral point clamped three level grid connected inverter is analyzed and the mathematical model of the three level inver ter is established.The output filter of inverter is improved,and the LLCL filter with passive damping is adopted.By combining theoretical analysis with simulation,the parameters of each component in the LLCL filter are designed.According to the requir ements of inverter experiment platform,the hardware parameters of inverter are designed.The relationship between Internet of Things technology and inverter grid connected control strategy is analyzed under the background of smart grid application.According to the mathematical model of the inverter in the dq coordinate system,the parameters of the inverter’s current closed loop controller and the power closed loop controller are designed in turn,and the inverter is connected with the constant active power and constant reactive power.The three-phase independent control strategy of inverter is proposed to realize the three phase output power of three level inverter under three-phase four wire system condition.A space vector modulation method for three level inverter is simplified.The imbalance of neutral point potential of DC capacitor in three level inverter is analyzed.According to the different output states of the inverter,the fluctuation of the middle point potential of the three level inverter in the two operating conditions of the three-phase three wire system and the three-phase four line system is derived respectively.A neutral point potential balancing algorithm based on the mean value of neutral point in the switching period is proposed to realize the balance control of neutral point potential in three-phase three wire system.Built Internet of Things controller and three level inverter experiment platform.Built the software code of the Internet of Things controller and inverter respectively,and realize the necessary communication protocol for data interaction with the Internet of Things platform.The experiment is carried out under the control of the platform of the Internet of Things.Through remote monitoring and remote control of the platform of the Internet of Things,the mode switching and the given change of the inverter are realized,and the conclusion of the mid point potential analysis and the middle point potential balance algorithm are verified.