Research On Model Prediction Strategy Of Single Phase Nine Level Inverter

With the rapid development of new energy power generation,micro-grid,new energy vehicles and other fields,single-phase multilevel inverter has received more and more attention and research.However,the lower level inverter proposed for a long time can not meet the increasingly stringent application requirements.For the improvement of the output wave shape quality of single-phase multilevel inverter,single-phase high-order multilevel inverter emerges as the times require.The single-phase nine level inverter has less harmonics,less switching voltage stress,less common mode voltage and lower switching frequency,which can meet the higher performance requirements.In this paper,the voltage balance problem of flying capacitor and the complex control strategy of single-phase nine level inverter are studied.The main contents of this paper are as follows:1.The development process and research purpose of multilevel inverter are described,the typical topology and control algorithm of multilevel inverter are analyzed,and the research status and key problems of single-phase multilevel inverter are summarized.2.The experimental platform of multilevel converter based on modular design technology is described.The working principle of each part of the experimental platform is analyzed,and the software design flow of DSP + CPLD is given,which lays an excellent foundation for the experimental research of single-phase nine level inverter control strategy.3.the operation mode and voltage vector model of single-phase nine level inverter are briefly described,and the topology model is discretized.4.Aiming at the voltage balance problem of flying capacitor in single-phase nine level inverter,an estimation method of flying capacitor voltage is studied,which can realize flying capacitor voltage control without expensive voltage sensor.On this basis,the voltage control algorithm and output current control algorithm of the bus capacitors are further studied.Compared with the conventional equalization algorithm,this algorithm reduces the cost and volume of the inverter,solves the problem that the flying capacitor voltage sensor is easily affected by noise,and simplifies the structure design of the system.Finally,the proposed algorithm is verified by simulation and experiment.5.On the basis of the previous research,a fast model predictive control strategy is proposed to solve the problem of cumbersome calculation of single-phase high-order multilevel model predictive control strategy.The algorithm reduces the number of voltage vectors needed to be calculated in rolling optimization,reduces the calculation burden of the system,improves the calculation efficiency of the algorithm,and reduces the consumption of the main control chip resources.Finally,the proposed algorithm is verified by simulation and experiment.