PMSM current controller block

Hello

I am using the IPMSM Velocity Control example (IPMSM Velocity Control - MATLAB & Simulink - MathWorks India) to test a PMSM for electric vehicle application. In the example , Inside the current control subsystem, the PMSM current controller takes in Vph max as one of the inputs of the block. i want to know why the Vph max is taken as . Is the maximum peak to peak phase voltage or is it the rms value ; and Is the max voltage we can get out of the inverter irrespective of the type of PWM scheme we use ( SVPWM vs Sine PWM).

My second question is whether the value of is equal to the rms value of the stator voltage of the motor. where Vd and Vq are the outputs of the PMSM current controller. What is the relation between the Vph max and the Vd and Vq voltages because in the simulation results, i see that the saturates at Vph max.

I have inserted the pic of the block . Thanks in advance

Answer 1

[Aman Banthia]

Hello @Sriram M A,

I understand that you want to know why the Vph_max is taken as (Vdc)/√3 and if the RMS value of Stator Voltage is √(Vd²+Vq²)and the maximum value of the same.

Vph_max is dependent on the modulation technique used. If we have Space Vector Modulation the maximum amplitude of the phase voltage is Vdc/√3. If we have Sinusoidal Modulation, then Vph_max=Vdc/2. The maximum amplitude can be increased in the overmodulation region, for example in six-step operation we can get (2/pi)*Vdc.

The root mean square (RMS) value of the stator voltage in terms of Vd and Vq can be calculated using the following equation:

Vrms = √(Vd²+Vq²)

Here, Vd and Vq represent the magnitudes of the direct-axis and quadrature-axis voltage components, respectively. The RMS value of the stator voltage is the square root of the sum of the squares of Vd and Vq.

This equation assumes that Vd and Vq are sinusoidal waveforms with the same frequency and phase relationship. If the waveforms are not sinusoidal or have different frequencies or phase relationships, the calculation of the RMS value may differ.

In an ideal scenario, the magnitude of the voltage vector formed by Vd and Vq. √(Vd²+Vq²) should not exceed the magnitude of Vph_max. This is because the maximum voltage that can be applied to each phase (Vph_max) sets an upper limit on the voltage that can be generated in the motor.

In simulation results, if you observe that √(Vd²+Vq²) saturates at Vph_max, it indicates that the control strategy or implementation is limiting the magnitude of the voltage vector to not exceed Vph_max. This saturation occurs to ensure that the generated voltage does not exceed the maximum voltage that the motor can handle.

The specific control strategy and implementation details will determine how Vd and Vq are controlled and limited to ensure they do not exceed Vph_max. This could involve techniques such as scaling, voltage clamping, or modulation schemes to ensure the generated voltage stays within the motor's limits.

Hope that the above solution answers all your doubts.

Thank-you

Aman Banthia