Apparatus for controlling first and second rotary electric machines

An apparatus for controlling at least first and second rotary electric machines, the apparatus comprising:

• a PWM control unit configured to cyclically update a command voltage output to a first inverter to cause the first inverter to convert a common system voltage input thereto into a first AC voltage supplied to the first rotary electric machine according to a comparison between the command voltage and a cyclic carrier signal, thus driving the first rotary electric machine to operate in a PWM control mode based on current feedback;
• a rectangular control unit configured to cause a second inverter to convert the common system voltage input thereto into a second AC voltage supplied to the second rotary electric machine, thus driving the second rotary electric machine to operate in a rectangular control mode based on torque feedback;
• a determiner configured to determine whether a ratio of a first electrical frequency of the first rotary electric machine to a second electrical frequency of the second rotary electric machine is within a predetermined specific frequency-ratio range, the specific frequency-ratio range including 1/6n where n is an integer excluding zero;
• and
• an update-cycle controller configured to control an update cycle of the command voltage output to the first inverter according to a result of the determination by the determiner such that the update cycle during a specific drive of the first rotary electric machine is longer than the update cycle during a usual drive of the first rotary electric machine while a cycle of the carrier signal is maintained during both the usual drive and the specific drive of the first rotary electric machine,
• the specific drive of the first rotary electric machine representing drive of the first rotary electric machine while the ratio of the first electrical frequency to the second electrical frequency is within the specific frequency-ratio range,
• the usual drive of the first rotary electric machine representing drive of the first rotary electric machine while the ratio of the first electrical frequency to the second electrical frequency is out of the specific frequency-ratio range.