 If there are any questions, please let me know. My question was is it possible to integrate the inverter mode with each P module and then add the output of all the inverters? This is the question since yesterday you have been asking right? Yeah. From Calicut. And I said yes. You can. At the AC side you have to synchronize. What are the issues in the sense? See, for every module you have put a small inverter, you have converted that AC to DC, okay? Sorry, you have converted this DC to AC, now there are a large number of them, you have to synchronize them. You just can't connect. You just can't connect, you have to synchronize them. You have to synchronize all the inverters with the grid. And in the morning we discussed how to synchronize one inverter to the grid. And the procedure you have to follow with others, is that okay? Okay. If there are any other questions, any other remote centers, both of us are here, please go ahead and ask. You can also put your question in chat. Sir, in case of multi-level inverters, for when it is, when we are considering two different PV strings, actually it becomes two different sources for multi-level inverters. So in that case, what would be the resultant output voltage of that particular inverter? Say, for example, PV string of one, PV string is giving somewhere around, after boosting somewhere around 80 or 60 volts and the other string is also giving around 60. So actually I should get what output voltage at the multi-level inverter, will there be a combination since they are put in series? Could you please elaborate, in the sense you have two multi-level inverters, input voltages are different. So, input voltage. Five level inverter, for example. Let us now go to five level, let us do three level first, okay. Number of level does not, number of level does not matter, okay. Number of level matters only when it comes to number of switching frequency on THD, okay. Now we have two multi-level inverters, input voltages are different? Yes sir, input voltages are different. Input voltages are different. When the input voltages are, yes. Okay, input voltages are different now. So should I go for a power balance? No, no, no. See, I do not know, this is what you mean. Number of levels, whether it is a two level or multi-level, it does not matter. You have an inverter, one, you have an inverter, two, there is a DC link, there is a DC link. You have an AC here, then what next? V1, V2, then? No, V1 is not equal to V2, okay. What is your doubt? This is the configuration. When V1 is not equal to V2, in which part of the controller should I make... No, no, from the inverter, what are you doing? What exactly are you doing to the inverter output? What are you... Input, I just want the voltage around RMS voltage. What are you doing with the inverter output? Is it being connected to the load or are you feeding it to the grid? Sir, to the grid only, sir. Okay, TK, what is the grid voltage? What is the voltage around 120 or 120, sir? No, no, ma'am, you tell me one value. 120. Excellent, okay. This is 120 volts, three phase. 50 hertz. Single phase. Okay. Single phase, 50 hertz. Now we just see, you have... What is the order of V1 and V2? V1 and V2 are 60 volts. V1 and V2 is equal to 60 volts. Not exactly. Okay, fine, V1 is 60, V2 is equal to 80. My question to you is, with this configuration, can you get 120 AC? See, you get a... See, it is like this. Now, small inductor is connected to the grid. Here, you have 120 volts RMS. 120 into root 2 is the peak of the AC. Okay? Now, what should be the fundamental... What should be the peak of the fundamental of the inverter output voltage? V1 is equal to 120 volt RMS and this is V2. DC link is 60 volts. You may not be able to do. See, the first condition is V1 should be higher than the peak of the input. So, if I use a boost converter, I can... So, don't worry about boost or something like that. You first talk about DC link voltage. DC link voltage you maintain at a suitable value so that you can get or you can feed the power to a grid of 120 volts AC. And you try to get that voltage from the given solar panel using a suitable DC to DC converter. Are you with me? See, you have... This is the grid voltage. That's what you are saying, 120 volts. This is V2 whose peak is proportional to the DC link voltage V2. To feed the power to 120 volts grid, the peak of the DC link voltage should be much higher than 120. The DC link voltage should be VDC min. At least 180 volts around, sir. Wait a minute. I do not know from where to where 120 into root 2. 120 into 1.414. 120, I hope it is line to line. How do you get that 120 volt line to line? I do not know anyway. These are the figures that are given by you. Now, that should be the DC link voltage. Now, how to get that DC link voltage from the given solar panel? You choose a suitable DC to DC converter. What is this black box that I have taught you? Depending upon VDC solar and VDC in, you have to choose a suitable power circuit configuration here. If the ratio is too high, then you may have to use a transformer with DC to DC converters with a transformer. If the ratio is less than 7, you may be able to use the conventional buck boost or buck boost or whatever. So, you have to tell the exact figures. Then we may be able to suggest possible circuit configuration. With 60 volts DC, you may not be able to get 120 volts AC. How can you possibly get? See here, you have straight away gone to three levels. I am just in half bridge. If I do just a square wave inversion, what is VAB? VAB is VDC by 2, VDC by 2. Its fundamental is as a sinusoid, this peak is 4 by pi into VDC by 2. This all I did in the class, is not it? If total is 60, this would be around 30, 30. How can you get? Numbers do not match. Now what I am saying is do not be in a hurry, take a paper and a pencil and determine the values. You can find a solution. What a problem? Sir, I want to ask it, when we are manufacturing, when we are manufacturing solar cell, it is depositing emitter through various functions. And does not it have any effect on the concentration due to increased temperature or combination, recombination rate, generation rate? So when, what is your question? If you deposit the solar cell at different temperature, does not it has an impact on the recombination? That is what you are saying? Yes sir. Does not it affect the concentration on peak, on that substrate which is made of peak and then when we are depositing end layer or emitter layer, does not it have any, high temperature, does not have any effect on the concentration? Okay, so when you have, when you are actually depositing the layer or when you are making actually a solar cell, so you start with a p substrate and let us say you are doing diffusion to get an end layer, your temperature will be high. So you are saying that at that high temperature, your carrier generation and recombination will be higher. Yeah, but I mean you are just making the device. You are not, you are not extracting the power at that time. You are just making the device. Because your temperature is higher, in principle your intrinsic carrier concentration will be very high at the time of diffusion, but it will not affect the performance in any way. So when the device is ready, temperature is normal to the room temperature, your behavior of your semiconductor will be as if you know that you are operating at 25 degree centigrade or whatever is the temperature. There is some question on chat. What is the different method to generate dead time in inverter? What are the different methods to generate dead time in inverter means what? College of Engineering. These are the pulses coming out of the controller. There is no dead time. They are perfectly complementary. Now what do I need to do? This is turning it off. The device is turning off. Another device here, S1, S4. So this could be S4. S4 is turning off and S1 has to be turned on. These are the controller outputs. Now what do I need to do? S4 should turn off. After some time, S3 should be turned on. Similarly, S1 then afterwards, S4 is turned on. Then first, S1 has to be turned off. S1 has to be turned off and after some time, S4 has to be turned on. This is dead time. Now how do I generate this dead time? Dead delay. Maybe using an RC circuit, something like this, to charge the capacitor through R and discharge the capacitor by passing that R. Because you want a delay in only one side, not on both the edges, not on both the edges rising as well as falling. You need a delay only when the device has to turn off and then the incoming device has to be turned on. So the rising edge has to be delayed. Rising edge of the incoming, the rising edge of the incoming device should be delayed. So what I will do is, I will give it to a RC circuit. It charges through R, I am getting delayed. And while discharging, it discharges through this diode. So this could be one of the methods. You can implement this philosophy using the gates also. That is not a problem. So I do not have an answer to what are the different methods to generate dead time in inverter. Else you can have a software also. What you do is, at the rising edge, at the rising edge you raise an interrupt, go to the interrupt routine, wait for some time, say 2 to 3 microsecond and output it. It is possible. At the rising edge, you raise an interrupt, go to the ISR, wait for some time. When you come out of it, output it and come. Because you have to have a dead time only at the rising edge of the clock. So you can do that using software as well as hardware. So these are the two methods I know. Maybe there are other methods as well. You find out any other question. There is one question from AVVC. Can I use multi-level inverter for UPS application? Why make life complicated by using multi-level inverters? Why you use multi-level inverters for what application? Multi-level inverters generally preferred for high voltage. What is the output voltage of the UPS? If you want to have 230 volts output from the UPS, why we need to use multi-level inverter? No, it does not make sense. These are my views. Multi-level inverters are generally preferred for high power application. Because at high power, I cannot switch the device at high frequency. To have the same harmonic spectrum, instead of having two levels, I will have multi-levels. Now if you want the output voltage of 230, it does not make sense to use a multi-level inverter. You need to make a choice. Our final call depends on you. I cannot suggest. Thank you. With that, I will wind up.