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Master of Science Thesis in Electric Power Engineering - page 29 / 114

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VOLTAGE ORIENTED CONTROL – SIMULATION

3.3 PWM Simulation

A description of the sinusoidal PWM implemented here is available in section “2.4 Pulse Width Modulation”.

3.3.1 Simulink implementation of PWM

 PWM block using switch

The amplitude of triangular wave should be Vdc/2. But Vdc is not constant in our case. We should first normalized the reference value by Vdc/2 and compare this value with a triangular wave with an amplitude of 1. The following figure show the Simulink block diagram.

Figure 3.3 : Simulink PWM block

 PWM block without switch

We can also use a PWM block without switching to create the switching pattern. The reference voltage is normalized by Vdc/2 to obtain a signal within a range [ 1 ; +1], then divide by 2 and translate to get signal in the range [0 ; +1] like the switching function Sabc. This simple model can be useful in Simulink to reduce the simulation time if needed. In a complete simulation with controller, the behavior of the system is similar using Figure 3.3 or Figure 3.4.

Figure 3.4 : Simulink PWM block without triangular wave

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