# PWM switching in a 3-level inverter

I am new to the pwm switching technique. Here I have the output waveform of a 3 level inverter with normal switching and switching using pwm pulses. (a)Phase-A, (b)Phase-b, (a)LIne-ab
(a)Phase-A, (b)Phase-b, (a)LIne-ab.

But the figure 1 seems to be very noisy than the other. But it says it is more preferable than the second one. Can anybody help me to understand the advantages clearly? And what is the advantage if I increase the switching frequency of the pwm?