Abstract：Quasi-Z-source inverter is a single-stage system, which has buck/boost characteristic. It achieves performance of the Z-source inverter, while has extra benefits such as continuously input current, low voltage stress of quasi-Z-source capacitor, etc. In this paper an adjustable speed drives system based on quasi-Z-source inverter is presented. The operation modes and the equivalent circuit of the system are discussed. The adjustable speed drives system can overcome the disadvantages and the limitations of the traditional adjustable speed drives(ASD). It can realize buck/boost capability(0-380VAC), which meets the operating conditions of induction motor rated voltage and provides ride-through during voltage sag. The reduction in energy storage unit (capacitor, supercapacitor, etc.) connected in series, results with the significant decrease in voltage stress of capacitors in dc-link, reduces the hardware cost and the faults rate. The control strategy takes full advantage of the quasi-Z-source inverter, adds boost voltage function when needed, increases modulation index M, improves utilization of dc-link input voltage, decreases voltage stress of the active devices, and decreases the iron losses increment of induction motor. The theoretical analysis is verified by simulation and experimental results.
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2012, Vol. 27 
