Comprehensive Analysis of High-Speed Cascaded H-Bridge (CHB) Medium-Voltage Adjustable Speed Drives

Abstract

High-speed medium-voltage (MV) adjustable speed drives (ASDs) are essential for gearless direct drive systems, offering reduced size and maintenance. High-speed applications include off-shore compressors in oil and gas industry, wind energy generation, and fly-wheel energy storage systems. This paper will cover the implications to cover a higher speed range (120-500Hz), arising from retrofitting existing MV 50/60 Hz cascaded H-bridge (CHB) ASDs. An essential requirement for the ASD is to remain within the Total Harmonic Distortion (THD) and Harmonic Voltage Factor (HVF) constraints set by standards. Key-aspects affecting CHB performance at high speeds are switching frequency and number of voltage levels. Another key-aspect is the CHB power cell DC-Link operational stress, power loss, and size. A unique comprehensive analysis covering all mentioned aspects is performed to provide a view of the MV high-speed application demands and needed High-Speed CHB design considerations.