Cascade Multi-level Inverter Control Technology

This paper first introduces a multi-level inverter status and the development of further detailed study of three different topologies of multi-level inverter. Which multi-level cascade inverter DC side of their mutual separation of the use of DC power supply, voltage balance does not exist, and the H bridge module of the modular design of the structure is more suitable for more than 7 levels of multi-level inverter occasions. Therefore, this article focuses on the multi-level cascade inverter PWM modulation technique, commonly used in the comparative study of several PWM modulation techniques, the proposed two types of PWM switching frequency modulation technique to improve the methods of optimization and the design of a variety of modulation technology to generate PWM wave circuit.For the nonlinear harmonic components of high impact, through simulation studies comparing the number of different levels, different carrier frequency, different modulation and different than the method of the PWM modulation of the inverter output harmonic distribution. At the conclusion of the inverter output waveform harmonic distribution on the basis of a practical low-pass filter design method, and through simulation experiments show that the filter has a simple and practical features of the economy.Multi-level cascade inverter output waveform control strategy using a digital PID-based control technology to control and repeat the combination of control methods. The PID control method has a number of control strategies in response to repetitive control speed and static characteristics of good advantages. The controller through the system performance analysis and simulation output waveform of the study results show that the transient case, the ratio of the number of PID in the link role to ensure the rapid response system; in the steady-state cases, the duplication of controller no static error, and ensure the steady-state system indicators.