What is the type of your power inverter structure? The conventional ones (single or three phase half or full bridge with uni- or bi-polar PWM modulation) could be found in literature, also operating mode at linear, over-modulation and square region will make significant change in output voltage magnitude depending on the modulation index ma

It depends on the type of inverter. Which type inverter are you working in?

Actually your question is incomplete. You must tell about the type of inverter and the PWM scheme. So when you have knowledge about the inverter type and pwm scheme, you can calculate the required dc link voltage for desired ac output.

First of all make sure which type of inverter you want to use and in which type of configuration and application.

I am simulating 3 phase PWM based inverter for renewable based generation which can generate sinusoidal output almost independent to load

there are too many topologies and control methods in 3 phase PWM inverter, you need to read more to have a good selection in this feild

Voltage equation for inverter is

Vdc/2= Vout peak(phase voltage)*(1/m)

where m is modulation index

so 3 phase inverter the dc input can be calculated as

Vdc= 2*sqrt(2)V(line to line)/(sqrt(3)*m)

Dear Rinku,

As we know the strictly job of inverter it's convert direct voltage into alternating voltage , each signal with -ve voltage level and +ve voltage level means alternating wave without focusing on shape of wave such sinusoidal,Square ..etc.

Suppose you have 12v Dc voltage as input to the inverter at T/2 of time you have the +ve level and to other T/2 you have the -ve level and the peak-to-peak voltage 24 V as output AC (+12V,-12V) in domestic application the 24 Ac voltage not sufficient so should use step up transformer to make output as required level by using the transformer ratio to determine the final output voltage.

Regards,

Hamzah Al-Azzawi

Dear Rinku,

welcome,

In the full bridge inverter the output peak voltage of the inverter is equal to the input DC voltage VDC lowered by the voltage drop on the two switching transistors Von. It follows that Vout peak = VDC- 2Von,

In case of half bridge inverter the input voltage VDC is divided into equal parts.

It follows that Voutpeak= VDC/2 - Von since one uses only one transistor for the switching.

Further one has to make Fourier analysis to get the fundamental sinusoidal voltage as the output is in form of rectangular waveform.

Please see the link for more information:Article “Computer-aided analysis of stepped sine wave inverters

Best wishes

Sine Pulse width Modulation(SPWM):

In Sine PWM the maximum voltage possible is =Vdc/2;

Line to neutral or phase voltage =VspwmLNmax (not a rms value but in maximum value)

Modulation Index(M.I)=VspwmLNmax/maximum possible voltage=VspwmLNmax/(Vdc/2)

So, VspwmLNmax= M.I*Vdc/2=0.5*M.I*Vdc 

RMS value of VspwmLNrms=0.5/sqrt(2)*M.I*Vdc

RMS value of line to line voltage VspwmLLrms=0.5*sqrt(3)*M.I*Vdc/sqrt(2)

VspwmLLrms =.612*M.I*Vdc

And, VspwmLLmax=0.612*M.I*Vdc*sqrt(2)

VspwmLLmax=0.8655*M.I*Vdc

****Modulation index value range=[0-1]

Space Vector Pulse Width Modulation (SVPWM):

When the value of reference vector is maximum,  circle formed by refence vector touch the inner part of the hexagon.

So, Maximum value of reference voltage= 2/3*Vdc*cos(30)=Vdc/sqrt(3)

Modulation index,M.I=sqrt(3)*Vref/Vdc

where Vref=value of refence rotating vector or fundamental line to neutral voltage or fundamental phase voltage(not rms)

So, VsvpwmLNmax=M.I*Vdc/sqrt(3)

VsvpwmLNrms=(M.I*Vdc)/(sqrt(2)*sqrt(3))

VsvpwmLLmax=M.I*Vdc

VsvpwmLLrms= 0.707*M.I*Vdc    

****Modulation index value range=[0-1]

So, voltage gain of SVPWM= VsvpwmLLrms/VspwmLLrms=1.155. So 15.5 percent improvement in voltage generation.

Dear professors Abdelhalim abdelnaby Zekry , Zarzisur Rahman Rony - thank you very much for your kind responses. Could you also please clarify the following issue:

- Which is the relation between the carrier frequency and the inverter switching frequency in a SPWM? Are they equal?

Thanks in advance and BR!

Simply you can remember this two equations:

Vph= Ma* (Vdc/2)

Vph= phase voltage

Vdc= input of inverter voltag

Ma= modulation index

Vph-peak= √2* (Vll/√3)

Vll= line to line voltage

For SPWM Tech. Ma is taken as 1

For ZSPWM, SVPWM Tech. Ma is taken as 1.15

This equations are applicable for SPWM, ZSPWM and SVPWM tech. Only change Ma.

Also it is applicable for CHB and all othe tech. Where inverter is used.

I suggest benefit from this research paper:

https://ceng.tu.edu.iq/eed/images/PE_lect17.compressed.pdf

Note that, voltage-sourced inverter (VSI) is a buck topology and thus, to generate 415 V at the AC terminal of the VSI, a DC-link voltage is required to be chosen higher than the peak of the AC voltage.

More specifically, the value of a DC-link capacitor can be computed based on the following expression:

= {2*sqrt(2)*V (Line to Line)}/sqrt(3)*m; where m is a modulation index

= {2*sqrt(2)*415}/sqrt(3)*1; considering m =1

= 677.69 Volts

Hello Professors I had a quick question

Assume the PV array is connected to a boost converter

I want to know the equation for Single stage connection. How to calculate line-to-line inverter output voltage if modulation index and duty cycle is given?

if its a Double stage connection. how the line-to-line inverter output voltage equation changes?

Abdelhalim abdelnaby Zekry , Rinku Kumar , Nirav Patel , Abid E. Mansuri , Ali Hayder Abdul Kareem , Hamzah M. Marhoon , Zarzisur Rahman Rony , and all,

This link will transport you to a new ResearchGate discussion thread question which may be similar to this one and you may have some answers or replies !

https://www.researchgate.net/post/What_is_your_scientific_explanation_of_why_the_sun_is_becoming_stormier_and_how_does_this_affect_a_nations_power_grid