Adjustable Speed Drive System Comparison VSI and LCI for High Power Applications: Copyright Material IEEE, Paper No. PCIC-2018-16

The current development of adjustable speed drives has made voltage source inverter technology available to high power applications such as large axial compressors. Hence, the comparison of voltage source inverter technology to the traditional way of controlling large rotating equipment with load-commutated inverters is of interest. This paper compares the adjustable speed drive systems for shaft powers of 20 MW and more. A drive system includes the drive, the supply network connection and the motor behavior. System reliability and availability are the main drivers, while system efficiency and costs are an additional motivation for the technology positioning. In general, the simple scalability of the load-commutated inverter leads to maximum reliability, especially for very high power. Voltage source inverter technology comes with a higher degree of flexibility in terms of possible output frequencies, cable lengths and type of motor.