Investigations of multi-carrier pulse width modulation schemes for diode free neutral point clamped multilevel inverters

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Chokkalingam B.
Bhaskar M.S.
Padmanaban S.
Ramachandaramurthy V.K.
Iqbal A.
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Korean Institute of Power Electronics
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Multilevel Inverters (MLIs) are widely used in medium voltage applications due to their various advantages. In addition, there are numerous types of MLIs for such applications. However, the diode-less 3-level (3L) T-type Neutral Point Clamped (NPC) MLI is the most advantageous due to its low conduction losses and high potential efficiency. The power circuit of a 3L T-type NPC is derived by the conventional two level inverter by a slight modification. In order to explore the MLI performance for various Pulse Width Modulation (PWM) schemes, this paper examines the operation of a 3L (five level line to line) T-type NPC MLI for various types of Multi-Carriers Pulse Width Modulation (MCPWM) schemes. These PWM schemes are compared in terms of their voltage profile, total harmonic distortion (THD) and conduction losses. In addition, a 3L T-type NPC MLI is also compared with the conventional NPC in terms of number of switches, clamping diodes, main diodes and capacitors. Moreover, the capacitor-balancing problem is also investigated using the Neutral Point Fluctuation (NPF) method with all of the MCPWM schemes. A 1kW 3L T-type NPC MLI is simulated in MATLAB/Simulink and implemented experimentally and its performance is tested with a 1HP induction motor. The results indicate that the 3L T-type NPC MLI has better performance than conventional NPC MLIs. � 2019 KIPE.
Balancing; Diodes; Field programmable gate arrays (FPGA); Harmonic distortion; Induction motors; Pulse width modulation; Voltage control; Wave filters; 3-level inverters; Multi carrier pulse width modulation; Multilevel inverter; Total harmonic distortion (THD); Xilinx system generator; Electric inverters