The interruption of a power supply is one of major technical issues for rotation-angle sensorless control of PMSMs. This causes the inverter operation to stop owing to the voltage drop in the filter capacitor (FC). In order to solve this technical issue, a method is proposed to continue the rotation-angle estimation over a wide speed range and for all types of powe-supply losses. The proposed method is to control the FC voltage in order to continue the operation of the inverter. This method is also applicable, even in the field-weakening control range, by preventing the increase in the FC voltage after power-supply interruption. Experimental results verify that the PMSMs are able to continue operation, even after power-supply interruption over a wide speed range. The results contribute to the increase in opportunities for the application of simple and high-performance PMSM drive systems to various fields.
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