SDK Overmodulation

1. Principle of SVPWM

File:STM32MotorControl:STM32 MC Overmodulation new slide1 1.png

Space vector modulation index is limited to (√3)/2 but there is way to extend this limit with the over-modulation. This technique is required when the modulation index (the length of the reference space vector Us) exceeds the edges of the hexagon.

1.1. Linear mode

In the linear area, V'_cmd can keep both the amplitude and angle of V_cmd ,
then V'_cmd = T'₁ * V₁ + T'₂ * V₂ with T'₁ = T₁ and T'₂ = T₂ .

1.2. TOVM mode 1

There are two cases:

• In the green area: T₁ + T₂ ≤ 1 .
  

V_cmd is unmodified and the timings remain unchanged T'₁ = T₁ and T'₂ = T₂ . In that region V'_cmd follows the circle.

• In the blue area: T₁ + T₂ > 1 .
  

Then In order to keep V'_cmd on the edge of the hexagon and keep the angle 𝜃, | V'_cmd | is shrunk to make T'₁ + T'₂ = 1. V'_cmd = T'₁ * V₁ + T'₂ * V₂ with T'₁ = T₁/(T₁ + T₂) and T'₂ = T₂/(T₁ + T₂).
In that region V'_cmd follows the hexagon edge.

1.3. The detail OVM mode 2

1.4. Example: F4 three shunt with Shinano motor at 4000rpm