Unipolar and Bipolar SPWM Voltage Modulation Type inverter for Improved Switching Frequencies

This paper attempts an in-depth analysis of switching loss, waveform quality and voltage linearity characteristics of the modern PWM methods. SPWM or sinusoidal pulse width modulation is widely used in power electronics to initialize the power so that a sequence of voltage pulses can be generated by the on and off of the power switches. SPWM techniques are characterized by constant amplitude pulses with different duty cycle for each period. The width of this pulses are modulated to obtain inverter output voltage control and to reduce its harmonic content. In SPWM a unipolar and bipolar SPWM voltage modulation type is selected because these types of methods offers the advantage of effectively doubling the switching frequency of the inverter voltage, thus making the output filter smaller, cheaper and easier to implement.