Series, Parallel and Series-Parallel Configuration of Photovoltaic

Arrays

What is a Solar Photovoltaic Array?

A Solar Photovoltaic Module is available in a range of 3 W P to 300 WP. But

many times, we need power in a range from kW to MW. To achieve such a
large power, we need to connect N-number of modules in series and
parallel.

A String of PV Modules

When N-number of PV modules are connected in series. The entire string

of series-connected modules is known as the PV module string. The
modules are connected in series to increase the voltage in the system.
The following figure shows a schematic of series, parallel and series
parallel connected PV modules.
PV Module Array

To increase the current N-number of PV modules are connected in parallel.

Such a connection of modules in a series and parallel combination is
known as “Solar Photovoltaic Array” or “PV Module Array”. A schematic of
a solar PV module array connected in series-parallel configuration is
shown in figure below.

Solar Module Cell:

The solar cell is a two-terminal device. One is positive (anode) and the
other is negative (cathode). A solar cell arrangement is known as solar
module or solar panel where solar panel arrangement is known as
photovoltaic array.

It is important to note that with the increase in series and parallel

connection of modules the power of the modules also gets added.

Series Connection of Modules

Sometimes the system voltage required for a power plant is much higher
than what a single PV module can produce. In such cases, N-number of PV
modules is connected in series to deliver the required voltage level. This
series connection of the PV modules is similar to that of the connections of
N-number of cells in a module to obtain the required voltage level. The
following figure shows PV panels connected in series configuration.

With this series connection, not only the voltage but also the power
generated by the module also increases. To achieve this the negative
terminal of one module is connected to the positive terminal of the other
module.

If a module has an open circuit voltage V OC1 of 20 V and other connected in

series has VOC2 of 20 V, then the total open circuit of the string is the
summation of two voltages

VOC = VOC1 + VOC2

VOC = 20 V + 20 V = 40 V

It is important to note that the summation of voltages at the maximum

power point is also applicable in case of PV array.

Calculation of the Number of Modules Required in Series and their

Total Power

To calculate the number of PV modules to be connected in series, the

required voltage of the PV array should be given. We will also see the total
power generated by the PV array. Note that all the modules are identical
having the same module parameters.

Step 1: Note the voltage requirement of the PV array

Since we have to connect N-number of modules in series we must know

the required voltage from the PV array

 PV array open-circuit voltage VOCA

 PV array voltage at maximum power point VMA

Step 2: Note the parameters of PV module that is to be connected in the
series string

PV module parameters like current and voltage at maximum power point

and other parameters like VOC, ISC, and PM should also be noted.

Step 3: Calculate the number of modules to be connected in series

To calculate the number of modules “N” the total array voltage is divided
by voltage of individual module, Since the PV module is supposed to be
working under STC the ratio of array voltage at maximum power point
VMA to module voltage at maximum power point VM is taken.

A similar calculation for open-circuit voltage of PV can also be done i.e.

ratio of array voltage at open circuit V OCA to module voltage at open circuit
VOC. Note that the value of “N” can be a non-integer so we have to take
next higher integer and so the value of V MA and VOCA will also increase than
what we desired.

Step 4: Calculating the total power of the PV array

The total power of the PV array is the summation of the maximum power
of the individual modules connected in series. If P M is the maximum power
of a single module and “N” is the number of modules connected in series,
then the total power of the PV array PMA is N × PM.

We can also calculate the array power by the product of PV array voltage
and current at maximum power point i.e.

VMA × IMA

Example:

Now to understand these steps in a more mathematical way. Let’s take an

example of a power plant of 2 MW, in which a large number of PV modules
are connected in series. The 2 MW inverter can take input voltage from
600 V to 900 V.

Determine the number of modules be connected in series to obtain a

maximum power point voltage of 800 V. Also determine the power
delivered by this PV array. The parameters of the single PV module are as
follows;

 Open circuit voltage VOC = 35 V

 Voltage at maximum power point VM = 29 V

 Short circuit current ISC = 7.2 A

 Current at maximum power point IM = 6.4 A

Step 1: Note the voltage requirement of the PV array

 PV array open-circuit voltage VOCA = Not given

  PV array voltage at maximum power point VMA = 800 V

Step 2: Note the parameters of PV module that is to be connected in the

series string

Open circuit voltage VOC = 35 V

Voltage at maximum power point VM = 29 V

Short circuit current ISC = 7.2 A

Current at maximum power point IM = 6.4 A

Maximum Power PM

PM = VM x IM = 29 V x 6.4 A = 185.6 W

Step 3: Calculate the number of modules to be connected in series

N = VMA / VM = 800 / 29 N = 27.58 (Higher integer value 28)

Take higher integer value 28 modules. Due to the higher integer value of
N, the value of VMA and VOCA will also increase.

VMA = VM × N = 29 × 28 = 812 V

Step 4: Calculating the total power of the PV array

PMA = N × PM = 28 × 185.6 = 5196.8 W

Thus, we need 28 PV modules to be connected in series having a

total power of 5196.8 W to obtain the desired maximum PV array
voltage of 800 V.

Mismatch in Series-connected PV Modules

The maximum power in the PV module is the product of voltage and

current at maximum power. When the modules are not connected in
series then the power produced by an individual module is different. Take
the example of table 1 given below.

Table 1
Modules VM in Volts IM in Ampere PM in Watt

Module A 16 4.1 65.6

Module B 15.5 4.1 63.55

Module C 15.3 4.1 62.73

In series =
Total In series = 4.1 191.88
46.8
If the three modules in table 1 are connected in series their voltage is
added but the current remains the same considering all the modules are
identical having the same value of IM = 4.1 A.

The difference in the voltages of the modules A, B, and C connected in

series does not result in the loss of the power produced by the PV module
array considering all the modules are identical having the same value of
IM = 4.1 A.

But if the current producing capacity of the modules connected in series is

not identical then the current flowing through the series-connected PV
modules will be equal to the lowest current produced by a module in the
string. Take an example table 2 given below.

Table 2
Modules VM in Volts IM in Ampere PM in Watt

Module A 16 4.1 65.6

Module B 15.5 3.2 49.6

Module C 15.3 4.1 62.73

Total In Series = 46.8 In Series = 3.2 177.93

If all the modules in table 2 are connected in series, then the current
flowing through the series-connected modules is determined by the
module with the lowest current. In this case module B has the lowest
current of 3.2 A as compared to modules A and C.

So, the current flowing through these three series-connected modules is

3.2 A. Now compare Tables 1 and 2 and the total power produced by both.
Due to unidentical current modules in table 2 the total power produced is
177.93 W which is less than the total power produced by modules in table
1 i.e. 191.88 W.

We can see that due to the mismatch in current the output power
produced by the series-connected modules is widely affected. So, in the
series connection of modules mismatch in voltage is not an issue but
mismatch in current results in loss of power. Hence modules with different
current ratings should not be connected in series.

Parallel Connection of Modules

Sometimes to increase the power of the solar PV system, instead of

increasing the voltage by connecting modules in series the current is
increased by connecting modules in parallel. The current in the parallel
combination of the PV modules array is the sum of individual currents of
the modules.
The voltage in the parallel combination of the modules remains the same
as that of the individual voltage of the module considering that all the
modules have identical voltage.

The parallel combination is achieved by connecting the positive terminal

of one module to the positive terminal of the next module and negative
terminal to the negative terminal of the next module as shown in the
following figure. The following figure shows solar panels connected in
parallel configuration.

If the current IM1 is the maximum power point current of one module and
IM2 is the maximum power point current of other module then the total
current of the parallel-connected module will be I M1 + IM2. If we keep on
adding modules in parallel the current keeps adding up. It is also
applicable for short-circuit current Isc.

Calculation of the Number of Modules Required in Parallel and

their Total Power

To calculate the number of PV modules to be connected in parallel, the

required current of the PV array should be given. We will also see the total
power generated by the PV array. Note that all the modules are identical
having the same module parameters.

Step 1: Note the current requirement of the PV array

Since we have to connect N-number of modules in parallel we must know

the required current from the PV array

 PV array short-circuit current ISCA

 PV array current at maximum power point IMA

Step 2: Note the parameters of PV module that is to be connected in

parallel
PV module parameters like current and voltage at maximum power point
and other parameters like VOC, ISC, and PM should also be noted.

Step 3: Calculate the number of modules to be connected in parallel

To calculate the number of modules N the total array current is divided by

the current of an individual module, Since the PV module is supposed to
be working under STC the ratio of array current at maximum power point
IMA to module current at maximum power point I M is taken.

A similar calculation for short-circuit current of PV can also be done i.e.

ratio of array short-circuit current ISCA to module short-circuit current ISC.

Note that the value of N can be a non-integer so we have to take next

higher integer and so the value of IMA and ISCA will also increase than what
we desired.

Step 4: Calculating the total power of the PV array

The total power of the PV array is the summation of the maximum power
of the individual modules connected in parallel. If P M is the maximum
power of a single module and “N” is the number of modules connected in
parallel, then the total power of the PV array P MA is N × PM. we can also
calculate the array power by the product of PV array voltage and current
at maximum power point i.e. VMA × IMA.

Example:

Let’s take an example, calculate the number of modules required in

parallel to obtain maximum power point current I MA of 40 A. The system
voltage requirement is 14 V. The parameters of the single PV module are
as follows;

 Open circuit voltage VOC = 18 V

 Voltage at maximum power point VM = 14 V

 Short circuit current ISC = 6.5 A

 Current at maximum power point IM = 6 A

Step 1: Note the current requirement of the PV array

 PV array short-circuit current ISCA = Not given

 PV array current at maximum power point IMA = 40 A

Step 2: Note the parameters of PV module that is to be connected in

parallel

Open circuit voltage VOC = 18 V

Voltage at maximum power point VM = 14 V

Short circuit current ISC = 6.5 A

Current at maximum power point IM = 6 A

Maximum Power:

PM = VM x IM = 14V x 6A = 84 W

Step 3: Calculate the number of modules to be connected in parallel

N = IMA / IM = 40 / 6 = 6.66 (Higher integer value 7)

Take higher integer value 7 modules. Due to the higher integer value of N,
the value of IMA and ISCA will also increase.

IMA = IM × N = 6 × 7 = 42 A

Step 4: Calculating the total power of the PV array

PMA = N × PM = 7 × 84 = 588 W

Thus, we need 7 PV modules to be connected in parallel having a total

power of 588 W to obtain the desired maximum PV array current of 40 A.

Mismatch in Parallel-connected PV Modules

In a parallel connection, the issue of mismatch in current is not a problem

but the mismatch in voltage is a problem. In parallel-connected modules,
the voltage will remain the same if the modules have identical voltage
ratings.

But if the voltage rating of parallel-connected modules is different then

the system voltage is determined by the module having the lowest
voltage rating resulting in the power loss.

The effect of voltage mismatch is not as severe as the current mismatch

but care must be taken while choosing the modules. It is recommended
that for series combination modules of the same current rating and for
parallel combination modules of the same voltage rating should be
preferred.

Series – Parallel Connection of Modules – Mixed Combination

When we need to generate large power in a range of Giga-watts for large

PV system plants we need to connect modules in series and parallel. In
large PV plants first, the modules are connected in series known as “PV
module string” to obtain the required voltage level.

Then many such strings are connected in parallel to obtain the required
current level for the system. The following figures shows the connection of
modules in series and parallel. To simplify this, take a look at right in the
following figure.
Module 1 and module 2 are connected in series let’s call it the string 1.
The open-circuit voltage of the string 1 V OC1 is added i.e.

VOC1 = VOC + VOC = 2VOC

Whereas the short-circuit current of string 1 I SC1 is the same i.e.

ISC1 = ISC

Similar to string 1, the modules 3 and 4 make up the string 2. The open-
circuit voltage of the string 2 VOC2 is added i.e.

VOC2 = VOC + VOC = 2VOC

Whereas the short-circuit current of string 2 I SC2 is the same i.e.

ISC2 = ISC

Now string 1 and string 2 are connected in parallel, nowhere the voltage
remains the same but the current is added i.e, open-circuit voltage of the
PV module array

VOCA = VOC1 = VOC2 = 2VOC

And Short circuit current of the PV module array

ISCA = ISC1 + ISC2 = ISC + ISC = 2ISC

The same calculation is applicable for voltage and current at the

maximum PowerPoint.

Calculation of the Number of Modules Required in Series –

Parallel, and their Total Power

Here for the calculation of the number of modules required in series and
parallel, and power we have assumed that all the modules have identical
parameters. Note that;

 NS = Number of modules in series

 NP = Number of modules in parallel

Step 1: Note the current, voltage, and power requirement of the PV array

 PV array power PMA

 PV array voltage at maximum power point VMA

 PV array current at maximum power point IMA

Step 2: Note the PV module parameters

PV module parameters like current and voltage at maximum power point

and other parameters like VOC, ISC, and PM should also be noted.

Step 3: Calculate the number of modules to be connected in series and

parallel

To calculate the number of modules in series N s the total array voltage is

divided by the voltage of an individual module, Since the PV module is
supposed to be working under STC the ratio of array voltage at maximum
power point VMA to module voltage at maximum power point VM is taken.

Similarly, to calculate the number of modules in parallel N p the total array

current is divided by the current of an individual module, Since the PV
module is supposed to be working under STC the ratio of array current at
maximum power point IMA to module current at maximum power point I M is
taken.

Similar calculations for open-circuit voltage and short-circuit current can

be done. Note that the value of N s and NP can be a non-integer so we have
to take next higher integer and so the value of I MA, ISCA, VMA, and VOCA will
also increase than what we desired.

Step 4: Calculating the total power of the PV array

The total power of the PV array is the summation of the maximum power
of the individual modules connected in series and parallel.

If PM is the maximum power of a single module, and N S is the number of

modules connected in series and N P is the number of modules connected
in parallel, then the total power of the PV array

PMA = NP × NS × PM

We can also calculate the array power by the product of PV array voltage
and current at maximum power point i.e.

VMA × IMA

Example:

Now let’s take an example for the mix – combination. We have to

determine the number of modules required for a PV array having the
following parameters;

 Array power PMA = 40 KW

  Voltage at maximum power point of array VMA = 400 V

 Current at maximum power point of array IMA = 100 A

 The module for the design of the array has the following
parameters;

 Voltage at maximum power point of module VM = 70 V

 Current at maximum power point of module IM =17 A

Step 1: Note the current, voltage, and power requirement of the PV array

 PV array power PMA = 40 KW

 PV array voltage at maximum power point VMA = 400 V

 PV array current at maximum power point IMA = 100 A

Step 2: Note the PV module parameters

Voltage at maximum power point of module VM = 70 V

Current at maximum power point of module IM = 17 A

Maximum power PM:

PM = VM x IM = 70V x 17A = 1190 W

Step 3: Calculate the number of modules to be connected in series and

parallel

NS = VMA / VM = 400 / 70 = 5.71 (Higher integer value 6)

Take higher integer value 6 modules. Due to the higher integer value of
NS, the value of VMA and VOCA will also increase.

VMA = VM × NS = 70 × 6 = 420 V

Now,

NP = IMA / IM = 100 / 17 = 5.88 (Higher integer value 6)

Take higher integer value 6 modules. Due to the higher integer value of
NP, the value of IMA and ISCA will also increase.

IMA = IM × NP = 17 × 6 IMA = 102 A

Step 4: Calculating the total power of the PV array

PMA = NS × NP × PM = 6 × 6 × 1190 = 42840 W

Thus, we need 36 PV modules. A string of six modules connected in

series and six such strings connected in parallel, having a total power of
42840 W to obtain the desired maximum PV array current of 100 A and
voltage of 400 V.

Note that due to higher integer value of 6 the maximum PV array current
and voltage is 102 A and 420 V respectively.
Series Connected Solar Panels & Batteries
We may connect two solar panels or batteries by connecting their Negative Terminal
“-” to the Positive “+” Terminal and vice versa. This way, two 6V (or 12 or 24V)
150W, 12.5A solar panels and 12V, 100Ah batteries connected in series would have
the following values.

Currents: I1 = I2 …. = In

i.e., current is same in each branch

12.5Amp = 12.5Amp

Similarly,

Current in series Connected Batteries 100Ah = 100Ah

Voltage: As voltage are additive in parallel connection, this way,

V1 + V2 …… + Vn

i.e., voltage will add up in parallel connection. (Suppose we have 12V PV panels and
batteries).

12V + 12V = 24V.

PV Panels & Batteries in Parallel:
A solar panel or battery can be connected in parallel by connecting the Negative
Terminal “-” of first one to the Negative Terminal “-” of second one and Positive
Terminal “+” of second one to the Positive Terminal “+” of first one. In simple words,
similar terminals are connected by jumper wires. This way, two 6V (or 12 or 24V)
150W, 12.5A solar panels and 12V, 100Ah batteries connected in parallel would
have the following quantities.

Current

Current from solar panel to the charge controller: I1 + I2 …. + In

i.e. 12.5Amp + 12.5Amp = 25A

Similarly, Ah capacity of batteries in series would have: 100Ah + 100Ah = 200Ah.

Voltage

Voltage for solar panel and batteries remains same in parallel connection:

V1 = V2 …… = Vn

i.e., voltage remains the same for both PV panels and batteries. 12V = 12V.
PV Panels & Batteries in Series-Parallel Combination:
The next part is interesting where we will utilize the maximum efficiency of 12V solar
panels and batteries by arranging them in series-parallel combination to increase
both the charging power from solar panels and storage capacity of batteries. This
way, the more power will charge the battery quickly with extra power storage. We
can use this system in tiny projects like 6V batteries and PV panels for 12V systems
or residential applications like 24V or 48V and so on.

Suppose we have the following rated devices.

 4 Nos. of solar panels each having 12V, 150W, 12.5A
 4 Nos. of batteries each having 12V, 100Ah

We need to connect them for an efficient 24V green energy system.

To do this, connect the first 2 solar panels in series and do the same for the rest two
solar panels. In simple words. make two pairs of two series connected solar panels.
Now, connect these two sets of series connected PV panels in parallel as shown in
the following fig. Do the same for batteries to arrange the same series-parallel
connection of batteries. This way, you will get:

Voltage & Current in Series Parallel Connected PV Panels

A set of two series connected solar panels will have = 12V + 12V = 24V and

12.5A = 12.5A

if we connect these series pairs in parallel, you will have to get:

24V = 24V (from previous series (12V + 12V = 24V) and now they are in parallel)

and 12.5A + 12.5A = 25A (from previous series 12.5A = 12.5A and now they are in
parallel).

You can see that we have increased the solar panel voltage from 12V to 24V as well
as the charging power from 12.5A to 25A.

Voltage & Current in Series Parallel Connected Batteries

Likewise, the series-parallel combination of batteries would have the same impact as
mentioned above for solar panels e.g., the batteries bank voltage would increase
from 12V to 24V and storage capacity from 100Ah to 200Ah.
Voltage in a set of two parallel connected batteries: 12V = 12V = 12V and

12.5A + 12.5A = 25A.

If we connect these two sets of series connected batteries in parallel, we will get;

12V + 12V = 24V and 25A = 25A

You can see that we achieved 24V from 12V and 200Ah from 100Ah at once and it
is according to our designed 24V system. So, we can wire them through a solar
charge controller and connect to the load equipment.

Wiring PV Panels & Batteries in Series-Parallel Combo for 24V

System
The following simple wiring shows that four 12V solar panels and 12V, 100Ah
batteries are connected in series-parallel combination. PV panels are connected to
the batteries and DC load through a charge controller. The 120V or 230V AC load is
connected through Inverter. The load can be powered up during normal
sunshine/day and operate via backup power stored in the batteries during
shading/night. This whole 24V system will work automatically as we have used the
uninterruptible power supply (UPS) / inverter i.e. we have used automatic UPS
wiring. It means no need to use additional auto or manual changeover or auto
transfer switch for automatic operation.

Good to know:
 Series connection of batteries or solar panels will increase the level of
voltage e.g two 12V, 5A PV panel or 12V, 100A battery in series will
provide 24V. Where current is the same in both devices i.e., 5A in panels
and 100Ah in batteries.
 Parallel connection of PV panels and batteries will add up the current and
ampere hour rating of battery (storage capacity) e.g., two 12V, 5A PV
panels in series will provide 12V, 10A. Similarly, two 12V, 100Ah batteries
in parallel will provide 12V, 200Ah storage capacity. Where the voltage
remains same in both equipment i.e.,12V.

Important Notes:
Make sure the battery as well as solar panel voltage rating is the same while
connecting them in series, parallel or series-parallel. In other words, a 6V battery
should not be connected in series/parallel with 9V, 12V or other voltage rated
batteries. Same rule is applicable to solar panels e.g., do not connect a 12V solar
panel in series/parallel with 6V or 24V PV panel