Modulation (Current Control Module) - Renesas RA6T2 Application Note

Sensorless vector control for permanent magnetic
synchronous motor - 1shunt current detection

3.1.3 Modulation (current control module)

A modulated voltage can be output to improve the efficiency of voltage usage. The modulation operation is
set from the API of the current control module.
(a) Sine wave modulation (MOD_METHOD_SPWM)
The modulation factor m is defined as follows.
m：Modulation ratio V：Reference voltage E：Inverter input voltage
(b) Space Vector Modulation (MOD_METHOD_SVPWM) *
In vector control of a permanent magnet synchronous motor, generally, the desired voltage command value
of each phase is generated sinusoidally. However, if the generated value is used as-is for the modulation
wave for PWM generation, voltage utilization as applied to the motor (in terms of line voltage) is limited to a
maximum of 86.7% with respect to inverter bus voltage. As such, as shown in the following expression, the
average of the maximum and minimum values is calculated for the voltage command value of each phase,
as the modulation wave. As a result, the maximum amplitude of the modulation wave is multiplied by √ 3 2
and the value obtained by subtracting the average from the voltage command value of each phase is used
while voltage utilization becomes 100% and line voltage is unchanged.
∵ ΔV = −
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: Command values of U-, V-, and W-phases for PWM generation (modulation wave)
The modulation factor m is defined as follows.
m：Modulation ratio V'：Reference phase voltage for PWM
E：Inverter input voltage
R01AN6840EJ0100 Rev.1.00
May 23, 2023
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For Renesas Flexible Motor Control Series
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Page 34 of 73
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