Research On Suppressing Common-mode Voltage In Five-level Active Neutral Point Clamped Inverter

Multilevel inverter has the advantage of high quality output voltage waveform, low harmonic rate, lower voltage across the switches than dc bus voltage. It is widely applied in new energy power generation, electrical drive, high voltage dc transmission and other fields. The harm caused by the common-mode voltage has received increasing attention. High frequency common-mode voltage will induce high shaft voltage on the motor shaft, shorten the service life of the motor, and generate strong EMI (Electro-Magnetic Interference). The EMI will disturb other lectronic equipment operation. In this paper, the essential relationship between SHEPWM and SVPWM is introduced on the basis of the suppression strategy of the common-mode voltage in multi-level inverter. This paper proposes a suppression strategy of the common-mode voltage based on SHEPWM in five-level active neutral point inverter. The main contents of this paper are as follows:1. Based on the research background, the history of power electronic and multi-level inverter is systematically reviewed and the harms of the common-mode voltage are expounded in this paper. At the same time, this paper also discusses the common multi-level inverter topology and pulse width modulation method used in multi-level inverter.2. The research is mainly focused on the five-level ANPC inverter working principle. On the basis of the above study, the common-mode voltage of five-level inverter is deeply analyzed and the root cause of common-mode voltage is revealed. The common method of suppressing common-mode voltage is also introduced.3. The relationship between SHEPWM and SVPWM is analyzed and the task to suppress common-mode voltage by SHEPWM control strategy is completed in the five-level ANPC inverter in this paper. Meanwhile, SHEPWM three-phase output switch status can be put into vector. Common-mode voltage in five-level ANPC inverter is suppressed by selecting the appropriate redundancy vector and dynamic transforming SHEPWM three-phase output switch state.4. The simulation model of five-level inverter is built with Matlab/Simulink software, and the effectiveness of the proposed method is demonstrated. An experimental test bench based on DSP and CPLD is set up. The feasibility and effectiveness of the method are verified by simulation and experiment results.