Comparison of Quarter-Wave with Half-Wave Symmetrical Pulse Patterns Applied in Electrical High-Speed Drives

摘要

Typical fundamental frequencies of an electrical high-speed drive range between 1 and 2 kHz. Common switching frequencies from 8 to 16 kHz lead to small pulse numbers and in consequence complicate the closed loop operation of the drive. In addition, the efficiency of these drives which are typically used in pumps, fans, compressors and turbine systems should be further optimized to ensure economic operation. In order to achieve this requirement both the switching frequency of the applied pulse pattern and the total harmonic distortion (THD) of the resulting phase currents should be kept as low as possible while retaining stable operation. In this paper, optimized pulse patterns of quarter-wave and half-wave symmetry are applied in an electrical high-speed drive and compared to sine-triangular pulse width modulation with regard to THD. The principle of the developed control and modulation strategy will be proven by simulation and experimental results. It will be shown that the application of optimized pulse patterns is recommended especially for high modulation degrees resulting in a THD reduction of 20 to 45 percent.