Current Harmonics in Single phase Inverter

[lxmn]

Hello All,

If you have fundamental current flowing through the dc capacitor in a full bridge single phase Inverter,
why does it cause a second harmonic component of current to flow in the output?

Thanks a bunch.

 

[FvM]

Sketch the waveforms of a full wave rectifier to realize that it acts as frequency doubler.

 

[lxmn]

Sketch the waveforms of a full wave rectifier to realize that it acts as frequency doubler.

Yes, for a full wave rectifier the frequency of the output (dc side) will be twice that of the input(ac side). But, for a dc to ac inverter with let's say with bipolar SPWM switching, why does fundamental component of current in the dc side cause a current in the ac side dominant in 2nd, 4th, 6th harmonics?

 

[FvM]

I presume, you are actually talking about input supply rather than inverter output frequency harmonics. My explanation would be that the bus voltage ripple appears in the output voltage, e.g. because the bus voltage variation is not or not completely compensated in the pwm modulator.

 

[lxmn]

I presume, you are actually talking about input supply rather than inverter output frequency harmonics. My explanation would be that the bus voltage ripple appears in the output voltage, e.g. because the bus voltage variation is not or not completely compensated in the pwm modulator.

Sorry, for misleading.
The scenario i'm referring is not regarding the voltage harmonics but with the current harmonics. Normally with PWM switching the voltage harmonics will be found as a side band of the switching frequency in the output and the current harmonics will also be scaled version of the voltage harmonics but with a different phase angle. Now, the situation i'm talking about is with a fundamental ac current (let's say injected) in input side (the dc) causing dominant 2nd harmonic current in the output.

 

[FvM]

I didn't overhear that you are talking about current.

I presume currents are related to voltages, both on input and output side. But as bus voltage is the link in this case, you would look at bus voltage ripple, though. You are dealing with a voltage switched inverter, isn't it?