 So, now let us look at the experiment and experiment number 2 of PV modules for this laboratory kit for 1000 teachers training program. In this experiment the basic objective of the experiment is to make the series and parallel connections of the PV module and see how does the current and voltage gets a data. So, the title of the experiment number 2 is to make series and parallel connections of PV modules. And as I said the whole idea is that to make the series connections of the PV modules and parallel connections or combination of series and parallel connections and see how does the characteristic of the whole combination changes. So, when you make various modules in series and parallel it is called the PV array or the photovoltaic array. So, the idea of this experiment is to characterize make a PV array and the characterize it. Characterize means find out what is the total power that PV array can give, find out what is the voltage that PV array can give, what is the current that can it can give and what is the maximum power etcetera. Why do we connect various modules in series and parallel? The idea of connecting more modules in series and parallel to increase the current and voltage output and therefore, increase the total power also. Many times the modules that we require for let our application may be like 500 watt, 1 kilo watt, 2 kilo watt, but the modules which are available in the market may be only 50 watt, 100 watt, 200 watt and therefore, there is always a need to connect the PV modules in series and in parallel if required. When we connect the modules in series the total voltage increases while the current remains same, while when we connect the modules in parallel the current increases and the voltage remains same. So, let us have a look at this. So, for example, if I have a PV module 1 and then PV module 2 assuming all of them are identical module the same module. In your laboratory kit 4 modules are provided which are which characteristic of those module is almost identical in nature. So, when let us say you have module 1 and you have PV module 2 you have the plus point of the module minus point of the module plus point of the module minus point of the module. Suppose, you want to connect them in series what is a series connection plus of a module goes to the minus of the module. So, you have one terminal here minus of the module goes to the plus of the module and you have another terminal here. Now, this is the series connection of the modules in this case. Suppose, the module 1 has suppose the module 1 and this is module 2 module 1 has following parameters. So, for example, it has ISC 1, short circuit current 1, VOC 1, VM 1 and then IM 1. And PM 1 and the module 2 has the following parameter it has IC 2, VOC 2, IM 2, VM 2 and PM 2. These are the parameters of one module these are the parameters of the second module. Now, you want to connect now you have connected them series what will happen to the combination. So, now we want to look at what will happen to the whole combination. So, this is my PV array now this is my PV array. Now, this whole PV array which is under the blue box will now behave as if one bigger module and what will happen to this terminal voltage. So, this is now my plus terminal and this is my minus terminal and what and the voltage of this 2 now will be the sum of this 2 voltage. So, voltage of this and voltage of this module. So, if I actually if I look at the PV array now. So, because 2 modules are connected in series my open circuit voltage VOC of array will be sum of open circuit voltage of module 1 plus sum of the open circuit voltage of the module 2. This will be the behavior of this combination. Similarly, my short circuit current of array short circuit current of array will be because they are connected in series. So, same current flows in the both the modules and we are assuming that the ISC 1 is equal to ISC 2. So, short circuit current will be ISC 1 which is equal to ISC 2 because all the modules are similar rating. So, my short circuit current will be the same it will not double. So, what will is happening to the open circuit voltage VOC 1 and VOC 2 they are all equal. So, because they are the same module VOC 1 and VOC 2 are equals. So, overall it will become 2 VOC and this will remain same as ISC. So, because of the series combination because of the series combination the open circuit voltage has doubled, but the short circuit current remains same. Fine. Now, you can also connect them in parallel. You can also connect them in parallel. When I am saying both the modules are identical means ISC 1 is equal to ISC and ISC 2 also is ISC same current. VOC 1 is equal to VOC and VOC 2 is also VOC. VM 1 is VM and this is also VM. IM 2 is IM and this is also IM. PM 1 is PM and PM 2 is also PM. So, voltage gets added up same thing again coming back to the series connection voltage gets added up same thing will also happen to VM of array. What will happen to VM of array that is VM 1 plus VM 2 which is nothing but VM plus VM. So, it becomes 2 VM. Same thing what will happen to IM of array because they are connected in series IM will remain same as IM of a single module. What will happen to PM of array? PM will get added. So, you will get PM 1 plus PM 2 which is equal to PM plus PM which is equal to 2 PM. So, basically power gets added and series voltage gets added both open circuit voltage will get added and voltage at the maximum power point will also get added and this way you can actually have the. So, when now you want to measure now you want to measure the series combination of the PV module and this parameter you should measure. You know the individual parameter. So, what you will do now? Again same thing you will actually have let me draw it again. So, what is your experimental arrangement? Again you want to do the same thing. So, this is the for the series connection this is your current axis, this is your voltage axis. What is this point you expect? This point you expect is the 2 VOC. This point you expect to be a ISC and you want other points to be measured. So, same thing as we have as we have done in earlier case what you need to do is you need to connect a rheostat across the module. So, if I if I if I draw the 2 modules again in series here 2 modules in series. So, one connection comes here series plus. So, let us say this minus plus minus plus ok. What I have to do? I have to connect a meter in series which is connected to variable raster and then I have to complete my circuit and between these 2 point I have to also measure my voltage. So, if I have this kind of arrangement I can I can find out the overall I V characteristic of a 2 PV modules which are connected in series right. Now, there are 4 PV modules you can actually connect them 2 in series, 2 in parallel, 2 in series and 2 such series in parallel and various combination 1 can try. For example, let me show you now for example, there are 4 PV modules given to you in the laboratory kit and let us let us that we want this 4 PV modules to be connected together in a such a way that 2 modules are connected in series and 2 such series are then connected in parallel ok. So, if I if I go back and draw this diagram again. So, I have PV module 1, PV module 2 there is a plus and minus there is a plus and minus then I have and I also have PV module 3 and PV module 4 ok. So, this is number 3, this is number 4 here also you have plus and minus you have plus and minus. What I said first we will connect this 2 in series this 2 also in series and then both are will connected in parallel. When you put the modules in series your voltage is added up when you put 2 modules in parallel your current is added up ok. So, before I give this I will come back and show you what happens in the parallel arrangement. So, suppose if I have a PV module like this another PV module like this plus minus plus minus module 1, module 2 if I if I have this is connections. So, if I take this point and connect to this point, if I take this point and connect to this point in in this case my both the PV modules are now connected in parallel. So, what will happen if I now if I want to measure the current here at this point between this point if I take the short circuit current the current from this module and current from this module is added again assuming that both the modules are identical in nature. So, the current that is generated at this module that is I m and the current is also generated by this module I m. So, if I measure the short circuit current here. So, short circuit current of this array will be 2 I m right because both the currents are added they are in connected in parallel. But what will happen to the open circuit voltage of array it will not change and open circuit voltage of this array will remain same as open circuit voltage of module which is either VOC here or VOC here. And same thing will also happen you can also may have the similar parameter. What will happen to the P m of this array? P m because now your current has double voltage remains same. So, your power will also become double. So, your P m will remain P m plus P m which is true P m. So, either you make a series connection or parallel connection your power gets added up in series connection your voltage is added up current remains same in parallel connection your current becomes double, but your voltage remains same. So, coming back here I want two of them to be connected in series and then two such series in parallel. So, for example, I have these are the leads coming in these are the leads coming in from here I want to connect them in series. So, the plus of one module is connected to the minus of other module and this is my series connection completed same thing I want to do for this. This is one lead coming here this is another lead coming here again plus of one module is connected to the minus of other and I have the series connection lead. So, from my earlier discussion we can find out that if I take the voltage across this two point the voltage will double and current will remain same. If I take the voltage across this two point voltage will be double and current will remain same because they both are in series. Now, we can actually connect this together. So, you connect this point together and this is a one point you connect this point together and this is another point. So, now, this is your one PV array this is your one PV array you can consider this arrangement is a one big module connected within which you are connected two modules in series and two such series are connected in parallel. Now, I want to measure what will happen across this two point what will happen across this two point. So, what will happen let us to the open circuit voltage of array open circuit. So, when modules in a large PV array when there are a lot of combination of series in parallel one single series combination is known as string. So, you can call it a string 1 and you can call it a string 2. So, in string 2 in a string 1 PV string 1 2 modules are connected in series and because the voltage will be added up right. So, voltage of module 1 plus voltage of module 2 and we know that all modules are identical. Let me put very clearly I am assuming that all four modules are identical which means the parameters of all four modules are identical which means that open circuit voltage of all four modules are same short circuit current of all four modules are same power of all four modules are same right. So, what does it mean VOC 1 is equal to VOC 2 is equal to VOC 3 is equal to VOC 4 which is equal to VOC same thing you can say I am current at maximum power point of module 1 is equal to current at maximum power point of module 2 which is equal to I am 3 which is equal to I am 4 which is equal to I am you can also say that PM 1 is equal to PM 2 which is equal to PM 3 which is equal to PM 4 which is equal to PM which means that all PV modules are all PV modules are identical right. So, because of this when I say PV array this module and this module is connected in series. So, I will get the sum of two voltages VOC 1 and VOC 1, VOC 1 and VOC 2 which is both of them are VOC. Because of that the total voltage I will get out of here and this two are connected in parallel. So, only series connection adds to the voltage parallel connection do not adds to the voltage right. So, the basically the overall voltage that I will get is only sum of this two voltage and which will be equal to 2 VOC. Now, what will happen to the short circuit current of array? The short circuit current of array is the current that is generated by this string this is string string number 1 and the current that is generated by this string right. Because this modules are connected in series same current will flow here and come here this modules are connected in string same current will flow here and come here. So, what will happen if I measure the short circuit current at this two different point it will be the sum of the current coming from here and the current coming from here and this current will be sum of the two current and because it is ISC plus ISC. So, you will get the two ISC because in this case we have two modules connected in series and two series is connected in parallel our current is getting added up our voltage is also getting added up same thing will also you can extend the analogy and you can say what will happen to V m of array will get added up and you will get 2 V m what will happen to I m of the array again it will get added up and you will get 2 I m what will happen to P m of the array what will happen to the power of the array power of the array is basically current at maximum point and the voltage at maximum point right. So, then we have 2 m into 2 I m which is 4 V m into I m what is V m into I m 4 V m into I m is the power of 1 PV module. So, therefore, you get the power which is 4 times. So, either you do the series or parallel connection your power is always added up in series connection voltage is added up in parallel connection current is added up. So, in this way you will actually the current and voltages that you can get for this combination of the PV module array will be double then as compared to the single double as compared to the single voltage of a single PV module and current will also going to be double as compared to a single PV module. Again you need to find out the overall current voltage characteristic of this. So, what you need to do if you want to find out the current voltage current voltage characteristic of this again very simple. What you have to do is you have to connect a meter in series and then you have to connect your variable resistance make this circuit complete this your variable resistance and because you also want to measure the voltage at two different points you connect one voltmeter and then connect to this point. When you make this arrangement you can do the same plotting of IV characteristic of a PV array in which two modules are connected in series and two such series are connected in parallel eventually same thing you will get this kind of curve. This point is your two ISC point this point is your two VOC point and by varying the value of resistance you can get a different point. In terms of the measurement same thing you have to do you have to measure various values of I various values of V and power you can calculate by multiplying V into I again you do the same measurement current and voltage multiply the power by measuring V into I you will find somewhere maximum power point. So, again you have to do the same draw the V I V versus I curve you draw the power versus V curve or I versus V curve basically find out the maximum power point find out the efficiency of the overall PV array find out the other factors V m I m fill factor etcetera. Again if you need to find out the efficiency your P m divided by P in into area and again P in needs to be measured this can be measured either by pyrometer or using a solar cell. So, in this way you can also find out the efficiency of the the combination you can also find out the power of the combination and and also you need to compare the rating of the measured values the measured value as compared to the ratings of the PV module and see how does it how is it different than the rated value. One has to note that rated value are given at the solar radiation condition of 1000 watt per meter square and in practice when you are doing the measurement you may not get 1000 watt per meter square and therefore your measurement value power value may be lower than the actual and the actual rated value and those values you have to compare and how it is different. Again at the end of your manual various questions are given regarding this experiment. So, you are requested to do this experiment measure this values and try to answer all the questions that are given at the end of manual. Thank you for your attention. So, now let us do the another experiment in which we are going to measure the series and parallel combination of voltages modules that are connected either in series and parallel. In series combination when you connect old modules in series your voltage gets added up, but your current remains same while in parallel combination your current gets added up and voltage remains same. So, in your lab kit there are four PV modules you can actually connect various combination of that normally you can connect four of them in series you can connect four of them in parallel two in series two in parallel or you can only measure the two modules. In this case I am giving a example of only two modules. So, this two modules data cables are connected to the two points of the module here there is another cable connected to the another module both the modules are identical. So, if you look into the detail you can see the various parameters of this module is same as the various parameters of this module. So, both modules are identical in nature their maximum power point is same their current is same their voltages are same everything is same. So, now let us see the example what happens when two modules are connected in parallel with each other. So, for example, let me so what happens when two modules are connected in parallel I will show you the open circuit voltage of both the modules individually short circuit current of the both the modules individually and then we will put them together and find out what is the open circuit voltage and short circuit current of a combination I am going to show you the parallel combination of two modules, but you can connect series combination and parallel combination or any other combination that you wish to perform. So, for example, if I take this module this is in a multi this is a so this is in a old meter condition I am just connecting this and it is giving me open circuit voltage of one module. So, it open circuit voltage is about 19.35 volt. Now, let me take another module which is this cable again I will connect the red here to this and then I will connect the black here and this module again open circuit voltage is 19.32 volt. Now, let me put in a short circuit let me measure the short circuit current of this module. So, I will put this in a current and then I will change the north to the other point when I put this one here for this module. So, I am measuring the module 1 when I put here this gives me current. So, the current in this case is 0.31 ampere. So, current in this case is 0.31 ampere of one module this is a short circuit current of the module 1 this you can record. Now, let me take the module 2 and find out what is the short circuit current. So, I connect the red cable here and I connect the black cable here and you can see here this module also giving me 0.31 ampere. So, basically both the modules are identical and they are performing same. So, both open circuit voltage and short circuit current of individual modules are same and you must make a reading note take a reading of this in your notebook. Now, I want to connect them in parallel as I said I want connect them in parallel. So, the plus of this. So, basically red cable is should be connected to the red cable which is here. So, red is connected to the red and the black cable of one module is connected to the black cable of other. So, I have connected them in parallel now you can see here the two modules are now connected in parallel. Modules are connected in parallel and let me see what happens to the short circuit current. So, this multimeter is still in a short current a meter mode. So, you have the red knob here which is pointing for the current and this is a 10 ampere. So, if I take the current measurement of this combination now what do you expect because it is a parallel combination current must be added up. So, let me see the total current now total current is exactly 0.62 ampere because both the modules are in parallel and now current is getting added up. We can also now do the measurement for the voltage. Let me put into the voltage measurement mode. So, I am putting it 20 volt position and knob I am changing here. So, I want to measure the open circuit voltage earlier current measurement of the short circuit kind of combination which was double than the individual modules. Now, because the modules are connected in parallel I do not expect any change in voltage. So, if I put them here and the black knob here with this connection. So, what do you see the voltage remains same that is of a individual modules in your noting you might have noted this value. So, combination open circuit voltage of two modules is about 19.28 volt because they are connected in parallel only current is doubling voltage is not doubling. Now, these are the points at the open circuit voltage and short circuit of the combination, but now let us measure the overall I V characteristic of this combination. If I want to find out the overall I V characteristic you need to measure the various data points and again we need to use the again we need to use the real state. So, that we can vary the resistance from one point to other point and you can measure the current. So, what I what we need to do is again is what I am doing here is in this diagram two modules are connected in series two in series and they are in parallel, but I in our case we have only two modules and they are in parallel. So, arrangement is like this two modules are in parallel your emitter goes back circuit completed and your voltmeter is in parallel with this arrangement. So, now we need to make this arrangement only for two modules that I am showing here, but you can do the same by considering the four modules also. So, let us make the connection. So, that we can measure the another data points which is current in voltage for two combination of parallel connected solar PV modules.