3 kva Inverter for UPS

[syed sajjad ali]

Hello people
can anyone help me in designing 3 kva UPS inverter . i will also used PWM in this by serial communication RS232 port.
In this UPS i will use double conversion topology.
please help me in designing schematic Or give me the link for 3kva inverter for the above mentioned UPS.
thank you

 

[Tahmid]

I doubt anyone will give you the complete design of a 3kva inverter for UPS with all features needed. What you could do is, try to build it yourself and ask us for help.

 

[syed sajjad ali]

thank you tahmid, check this link :

Inverter Circuit Diagram

this is 500w circuit (let 0.6 power factor) means 500/0.6 equal to 833.33va.
for 3 kva i 'll enhance this circuit 4 times. . but what should i do for 3kva ?
increase 'TIP 35' 4 times in parallel only or any thing else?

 

[Tahmid]

I wouldn't use that circuit for more than 100W.

For 500W, you should use MOSFET. This will give you much lower losses.

Instead of CD4047, you should use a PWM chip such as SG3525. You can then control the output and maintain a fixed output by keeping it regulated through PWM. The output voltage of the circuit you referenced will change with change in load and battery voltage and you very well know that this is not good. You need to keep the output regulated. If not completely tightly, it should atleast be within a set range. eg 200V-230V

There is one circuit diagram for SG3525 I posted here:
While you can not copy it completely, you can use it to learn how to use the SG3525. Next, you should go through the datasheet. You should also look for designs using SG3525. This will give you a better idea.

Here is a circuit that should help you in your design:

Hope this helps.
Tahmid.

 

[syed sajjad ali]

now, i have some bright picture of my design :smile:
but tahmid i have still a confusion.
i will use PWM technique through serial communication before this inverter.
SO, this PWM is not enough to control output voltage near 220vac..
Instead of this PWM, load can change the Output voltage?
It means should i also consider proper regulation during my inverter design?

 

[Tahmid]

If you can properly implement regulation with SG3525, you will have fixed output that will not change with change in battery voltage or load. So, using PWM and proper feedback, you can have 220VAC output with 11V battery voltage with 100W load and also near 220VAC output with 13.5V battery voltage and 1000W load (or more). I hope you get the idea.

In short, the PWM is enough for controlling output voltage and keeping it fixed near 220VAC. The design you posted using CD4047 is not enough. But if you use SG3525 and implement feedback, you can have fixed output.

What do you mean by serial communication? Does it need to communicate with the PC? In that case, you would need a microcontroller.

Hope this helps.
Tahmid.

 

[syed sajjad ali]

yes, i am using PIC 16f877A for serial communication.
As i am designing a UPS (or Line Conditioner) by using Double conversion topology.
i have to control frequency by using PWM and select a proper duty cycle according to the input.
SO, as you told that PWM can also be done by using SG3525. in this case controller is required or not?

 

[Tahmid]

SG3525 is the PWM controller. You can use it for DC-DC conversion.

From your post, I understand that you are designing an online UPS. For generating the sine wave output, you have to use a microcontroller and a full-bridge converter that is driven by the SPWM generated by the microcontroller. You can have the DC bus regulated with the SG3525 by sensing output sine wave voltage and taking feedback from that. You can use the 16F877A for SPWM. You can use the CCP module for that. It would be easier if you used a microcontroller with ECCP like 16F887, but 16F877A's CCP module can be used, provided you can utilize it.

By controlling frequency, do you need to change the frequency as well? Do you need to change frequency as well as voltage or fixed frequency (50Hz/60Hz)?

If you need to change the frequency along with voltage, then, things get tricky. I doubt you can make use of the 16F877A in that case. I would go for something like a dsPIC33. While it is not impossible to do this with a PIC16, you would need to be a hell of a programmer to be able to do that. You could just use the dsPIC33 as it's meant for such applications and the hardware modules (such as the motor control module) make control of frequency and voltage (on-the-fly) control quite easy.

Hope this helps.
Tahmid.

 

[syed sajjad ali]

thank you Tahmid.
i want frequency change as well by using PIC 16f877A.. i think it can be posssible.
i have a product of compony in which they use 16 series for this specific application.
check this link:
https://obrazki.elektroda.pl/100_1329969248.jpg
This is my complete project diagram and i am now working on inverter block.

 

[Tahmid]

May I know the model number of that device?

The block is fine. The trick is in the inverter portion. Controlling voltage and frequency while maintaining a clean output and keeping out audible noise and providing a smooth change of voltage and frequency with the 877A might be a difficult job. It's good if you can do it. But I would do it with a dsPIC33.

Hope this helps.
Tahmid.

 

[syed sajjad ali]

what do you mean by model number?
is this company name or Product number.
This is SOLID STATE LINE CONDITIONER basically.

 

[Tahmid]

What is the company name and product number? I would like to take a look.

 

[syed sajjad ali]

what do you mean by model number?
is this company name or Product number.
This is SOLID STATE LINE CONDITIONER basically.

---------- Post added at 09:29 ---------- Previous post was at 09:23 ----------

SYSTEK
i have basically a line interactive UPS and i want to convert it into Solid state Line conditioner (double conversion topology).

 

[Tahmid]

By model number, I meant the product. Eg your cellphone has a model, eg it could be an iPhone 4, it could be a Samsung Galaxy S or it could be SE Xperia Arc S, etc
Then, I could search on Google and take a look at the device.

 

[tarqasf]

SG3525 is the PWM controller. You can use it for DC-DC conversion.

From your post, I understand that you are designing an online UPS. For generating the sine wave output, you have to use a microcontroller and a full-bridge converter that is driven by the SPWM generated by the microcontroller. You can have the DC bus regulated with the SG3525 by sensing output sine wave voltage and taking feedback from that. You can use the 16F877A for SPWM. You can use the CCP module for that. It would be easier if you used a microcontroller with ECCP like 16F887, but 16F877A's CCP module can be used, provided you can utilize it.

By controlling frequency, do you need to change the frequency as well? Do you need to change frequency as well as voltage or fixed frequency (50Hz/60Hz)?

If you need to change the frequency along with voltage, then, things get tricky. I doubt you can make use of the 16F877A in that case. I would go for something like a dsPIC33. While it is not impossible to do this with a PIC16, you would need to be a hell of a programmer to be able to do that. You could just use the dsPIC33 as it's meant for such applications and the hardware modules (such as the motor control module) make control of frequency and voltage (on-the-fly) control quite easy.

Hope this helps.
Tahmid.

Hello Tahmid,
have you a hex file of 16f877a,if you have pl send on the e-mail:-
tarqasf@yahoo.com
Regards.

---------- Post added at 11:45 ---------- Previous post was at 11:35 ----------

I wouldn't use that circuit for more than 100W.

For 500W, you should use MOSFET. This will give you much lower losses.

Instead of CD4047, you should use a PWM chip such as SG3525. You can then control the output and maintain a fixed output by keeping it regulated through PWM. The output voltage of the circuit you referenced will change with change in load and battery voltage and you very well know that this is not good. You need to keep the output regulated. If not completely tightly, it should atleast be within a set range. eg 200V-230V

There is one circuit diagram for SG3525 I posted here:
While you can not copy it completely, you can use it to learn how to use the SG3525. Next, you should go through the datasheet. You should also look for designs using SG3525. This will give you a better idea.

Here is a circuit that should help you in your design:

Hope this helps.
Tahmid.

the circuit diagram you posted on above thread is incomplete without showing the operational amplifiers.Plz show the remaing cct. Moreover will its output be a sinusoidal wave or square wave.

 

[ALERTLINKS]

https://www.edaboard.com/threads/96053/

 

[Tahmid]

Hello Tahmid,
have you a hex file of 16f877a,if you have pl send on the e-mail:-
tarqasf@yahoo.com
Regards.

I don't have any code for 16F877A for an inverter.

the circuit diagram you posted on above thread is incomplete without showing the operational amplifiers.Plz show the remaing cct. Moreover will its output be a sinusoidal wave or square wave.

Yes, it is meant to be only a block to help you design the circuit yourself. The 1st link gives a circuit with a high voltage DC output. The 2nd link gives a sinusoidal output.

Hope this helps.
Tahmid.

 

[syed sajjad ali]

Tahmid,
in this figure,where is labeled fig5 and fig 2?