Inverter control device, electric power steering system, and electric vehicle system
An inverter control device includes a pulse width modulation (PWM) pulse generation unit that generates a PWM pulse signal for controlling an inverter in every predetermined control cycle, wherein the PWM pulse generation unit generates the PWM pulse signal to meet a pulse generation condition that at least three or more pulses exist in one cycle of a fundamental of an output voltage from the inverter and a state of the PWM pulse signal is switched between on and off at a zero crossing point at which the fundamental changes across zero while generating a PWM pulse signal asynchronous with the control cycle.
1 . An inverter control device comprising:
a pulse width modulation (PWM) pulse generation unit that generates a PWM pulse signal for controlling an inverter in every predetermined control cycle,
wherein the PWM pulse generation unit generates the PWM pulse signal to meet a pulse generation condition that at least three or more pulses exist in one cycle of a fundamental of an output voltage from the inverter and a state of the PWM pulse signal is switched between on and off at a zero crossing point at which the fundamental changes across zero while generating a PWM pulse signal asynchronous with the control cycle, wherein the PWM pulse generation unit calculates percentage modulation of the output voltage and sets pulse widths of the PWM pulse signal based on the percentage modulation.
2 . The inverter control device according to claim 1 , wherein
the PWM pulse generation unit includes
a percentage modulation calculation unit that calculates the percentage modulation,
a pulse phase angle calculation unit that calculates a pulse phase angle for switching an on or off state of the PWM pulse signal, based on the percentage modulation,
a voltage phase calculation unit that calculates a voltage phase in accordance with a phase angle of the output voltage,
a phase variation width calculation unit that calculates a phase variation width of the output voltage in the control cycle, and
a pulse setting unit that sets a switching timing of the on or off state of the PWM pulse signal based on the pulse phase angle, the voltage phase, and the phase variation width.
3 . The inverter control device according to claim 1 , wherein
the inverter is connected to a motor, and
the PWM pulse generation unit selectively outputs either a first PWM pulse signal that meets the pulse generation condition or a second PWM pulse signal based on a comparison between a voltage command to the inverter and a carrier signal that periodically changes in a predetermined carrier cycle, based on an operation state of the motor.
4 . The inverter control device according to claim 1 , wherein the PWM pulse generation unit generates the PWM pulse signal so that a number of pulses existing in one cycle of the fundamental of the output voltage is an odd number.
5 . An electric power steering system comprising:
the inverter control device according to claim 1 ;
the inverter that is controlled by the inverter control device; and
an alternating current (AC) motor that is driven by the inverter,
wherein the AC motor controls steering of a vehicle.
6 . An electric vehicle system comprising:
the inverter control device according to claim 1 ;
the inverter that is controlled by the inverter control device; and
an alternating current (AC) motor that is driven by the inverter,
wherein the AC motor causes the electric vehicle system to travel using a drive force.