Analysis and compensation of inverter nonlinearity for three-level T-type inverters

This paper analyzes the inverter nonlinearity effect resulting in issues such as narrow pulses and the even order harmonics in three-level T-type inverters. These issues make the compensation of the inverter nonlinearity be difficult. Based on the analysis of the output voltage distortion, carrier-based PWM methods to avoid these issues and to balance dc-link voltages simultaneously are proposed using the concept of the offset voltage. The proposed PWM methods can be easily implemented by adding appropriate offset voltages to output voltage references. Also, a compensation method to alleviate inverter nonlinearity effects is proposed based on the modeling of the inverter nonlinearity. The effectiveness of proposed methods is verified by experimental results. Through the proposed algorithms, not only even harmonics but also 5th and 7th harmonic components of current are conspicuously reduced. At the same time, the neutral voltage of the inverter can be balanced effectively by the proposed PWM methods.

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