Research On An Optimized Modulation Arithmetic Of Multilevel Inverters

High power electronic inverter has a wide range of applications in the national economy, such as high-power inverters, high-power active power filters, inverters used in MW wind turbines and other fields.For high-power inverter, there is a contradiction between the handled power capability and the switching frequency, and the greater the power, the lower the switching frequency.Restricted by the switching frequency, it is difficult to apply traditional PWM techniques to improve the performance of large-capacity inverter and people tend to hope that the power electronic inverters can work at a switching frequency as high as possible to improve the quality of the output waveform.In order to enhance the capacity of power electronic inverters and improve its performance at the same time, the circuit topology and control strategy of power inverters can be investigated in. A good topology together with a good control strategy can make the system more valuable. Therefore, the research in high-power inverters have not only theoretical value but also of practical importance. Paper introduces the topology of multi-level inverters and the working principles. The main topologies are the diode-clamped, the flying-capacitor clamped, and the cascaded.Analyze the differences between the clamped and the cascaded multilevel inverters and summarize the advantages and disadvantages for each of them.Secondly, do research in the traditional PWM algorithms used in multilevel-level inverters: step wave modulation and multi-carrier phase shift modulation and analyze the modulation principles and their characteristics.Summarize the suitable fields of the two PWM control methods.Thirdly, the cause of switching loss and the need to reduce it are analyzed and the optimized modulation algorithm is introduced. Then, set up simulation blocks for the five cells cascaded multi-level and the optimized modulation algorithm.Make a detailed introduction to sub-modules includes:triangular wave, the optimized modulation algorithm and the basic power unit.Finally, five cells cascaded inverters with the frequency multiples of 100 and 200 and the ten cells cascaded inverter with a frequency multiple of 100 is simulated in the article. The PWM algorithms include Carrier Phase-Shifted PWM, step wave modulation and the optimized modulation algorithm based on the reduction of switching loss. Make comparisons among them and verify the superiority of the optimization algorithm.