A New Modulation Technique to Improve the Power Loss Division Performance of the Multilevel Inverters
IEEE Transactions on Industrial Electronics
Multilevel inverters (MLIs) have offered significant contributions toward the implementation of energy conversion units used in industry and renewable energy applications. However, the switching devices in MLIs are associated with power loss division problems. The pulsewidth modulation (PWM) techniques greatly influence the peak, average, and ripple values of the device junction temperature. Thermal tension in the devices may be raised due to increased power loss caused by additional switching or uneven distribution of losses due to unbalanced gate pulses. Higher thermal stress accelerates the life degradation process of the power devices, and, eventually, leads to permanent damage of the MLI. Therefore, a new loss balancing two-pole clamped PWM technique for a single-phase MLI is proposed in this article. In the proposed PWM technique, in each half line cycle, symmetrical and equal duration of nonswitching zone is placed on the two reference signals alternately. Due to symmetrical and equal duration of clamping action, the unbalanced gate pulses become balanced after each half line cycle. The proposed technique extends the reliability of the power devices by improving the loss division performance and the junction temperature characteristics. Moreover, the reduction of neutral point potential swing reduces the output total harmonic distortion. The improved performance of the proposed technique is validated by simulation in MATLAB/Simulink and experimental results from downscale laboratory prototype test platform.
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