Generalized switching strategies for current source inverters/converters

This paper presents generalized techniques for realizing PWM patterns which provide selective harmonic elimination and current magnitude modulation (SHEM) for current source inverters/power converters (CSI/C). Recently, PWM-SHEM patterns for CSI/C have been presented which utilize a combination of chops and short circuit pulses to selectively eliminate lower order harmonics besides achieving current magnitude modulation with minimum switching frequency. In the present paper, these PWM-SHEM patterns are reviewed and development of any arbitrary PWM-SHEM is discussed in detail. In particular, the requirements of maximum inverter/power converter utilization are examined and different modes of operation (i.e., rectifying and inverting) are explained. Furthermore, the generalized equations for the input/output AC currents for the CSI/C are utilized to derive a generalized equation for the DC input/output voltage of the CSI/C. Generalized waveforms and tables which show the relationship of various PWM-SHEM parameters to the position of short circuit pulses and the number of chops per 30°, are provided and discussed in detail