An Improved SHM-PAM Technique for Three-Phase Five-Level CHB Inverter Utilizing Both Quarter-Wave and Half-Wave Symmetry Waveforms to Fulfill Some Important Voltage Harmonic Standards

Selective harmonic minimization-pulse amplitude modulation (SHM-PAM) generates a waveform that minimizes some selected low-order harmonics instead of eliminating them completely. This approach is highly beneficial for medium-voltage high-power inverters, where allowable amplitudes for individual harmonics (mentioned in power quality standard) are required with low switching frequencies. This work applies improved SHM-PAM proposing four new types of formulations utilizing quarter-wave (QW) and half-wave (HW) symmetry-based waveforms for three-phase five-level cascaded H-bridge (CHB) multilevel inverter (MLI) to satisfy the requirements of two well-known power quality standards, namely IEC 61000-2-12 and ER G4/5. Recently reported dragonfly algorithm (DA) is used for computing the optimum switching angles and dc-link voltages required to control the CHB MLI. The effectiveness and practicality of the proposed techniques have been investigated through extensive simulations and experimentation on a laboratory scale CHB MLI. While fulfilling the IEC 61000-2-12 and ER G4/5 voltage harmonic standards, the solutions provided by QW and HW symmetry-based waveforms are compared based on several performance indices such as waveform quality and power losses. It is found that HW symmetry waveforms provide better waveform quality and power loss profile than QW symmetry waveforms. The proposed SHM-PAM has also been compared with some existing modulation techniques to justify its mastery. Finally, the practicability of the proposed SHM-PAM technique is verified on an induction motor drive application.