Patent ID: 8829829

Claim:
A system for driving an inverter equipped with a first switching element, a first diode connected in antiparallel to the first switching element, a second switching element, and a second diode connected in antiparallel to the second switching element, so that the inverter connects a terminal of a salient-pole rotary machine selectively to one of a positive terminal and a negative terminal of a direct voltage power supply via the respective first and second switching elements to thereby control a controlled variable of the rotary machine, the first and second switching elements being turned on or off with a dead time during which both the first and second switching elements are off, the system comprising: a superimposing element configured to set a command value vector of a high-frequency voltage signal and superimpose the high-frequency voltage signal with the command value vector on a command voltage for an output voltage of the inverter, the high-frequency voltage signal having a frequency higher than an electrical angular frequency of the rotary machine, the command value vector being correlated with a measured high-frequency component value of a current signal flowing in the rotary machine; a calculating element configured to calculate a rotational angle of the rotary machine based on the measured high-frequency component value of the current signal flowing in the rotary machine; and a reducing element configured to control at least one of the inverter and the direct voltage power supply to reduce a deviation of each of the command value vector and the vector of the high-frequency voltage signal to be actually superimposed on the command voltage from a parallel direction of the command value vector and the vector of the high-frequency voltage signal, the deviation being due to an error voltage vector, the error voltage vector being based on a difference between the command voltage vector and the vector of the high-frequency voltage signal to be actually superimposed during the dead time that is generated while a terminal current flowing in the terminal of the rotary machine crosses zero level.