Problem Summary

As per the International Renewable Energy Agency (IRENA) solar installed capacity worldwide is around 23 GW in 2018 which is 8 times higher from 2014, looking at the figures the implementation and success of solar are the highest amount other existing renewable energy sources. [1]. With the increase in population and the use of fuels as primary energy source is increasing which add up the air pollution due to burning of fossil fuel such as coal, and other, which increase the green house effect and global warming, the use of such fuels needs to be minimized using alternate energy sources such as photovoltaic, wind, fuel cell, tidal, geothermal, biogas, electric vehicles etc. Another issue with fossil fuel is depleting at fast rate, conservation is needed to save or utilize such fuels in important task or processes. The readily and easily available source is solar energy which can be utilize in many applications using small setups such as solar collector for cooking purpose, solar base water tube for water heating, use of solar for vehicles and solar panels for electricity. However, the efficiency and the conversion rate is low for electricity use. Small residential home requires to setup panel of at least 2kW for all time use with back of battery which increase the overall cost of setup of solar for home use. One of the reasons for least acceptance of solar is high cost of installation and maintenance requirement, how ever cost of maintenance is less.

Figure 1 Solar movement summer and winter

Shading is the big issue with the photovoltaic system, it ultimately decreases the efficiency and performance of the array and may also cause damage to arrays. Whenever subjected to shades the current would go to lower value.  So basic construction is in such a way if one of the arrays subjected to shades and all the cells carrying the same amount of current due to shading on one array entire string will have reduced current at the same time power rating also get reduced. Some types of shading are avoidable while other are natural like clouds, and change in position of the sun in winter and summer need to change the panel direction or angle.

In this report literature survey is carried out on use of solar and fault detection methods for industrial and solar plants. After performing literature review research gaps and research objective were finalized.

Literature Review

The report aim is to find the characteristic and function of the photovoltaic panels, there behavior under different types of faults, monitoring and the detection of faults which are subjected in photovoltaic arrays.

The whole study of the project is focused on monitoring of photovoltaic panel it is very important to understand and target the project on the monitoring and fault detection methods of photovoltaic array. Since solar energy readily come from solar though efficient and effective method is needed to collect and concentrate the energy at one place. The use of solar minimize the pollution and other issues compared to the other fossil fuel base technology. Solar panels are place on rooftop or the ground surface area where the solar energy is available without any shadow. Most of area around the world has the availability of solar for average 8-10 hours and during peak time sufficient energy is available to cater the load and also to store the energy in the form of battery backup for later use. In its place on rooftop the panels are less its easy to analyze the panel faults by visual inspection method, by checking the hot spots, wiring connections, fuses, charge controller faults, and inverter faults. But for large size of solar plants of capacity in terms of kW to MW it becomes very difficult to analyze the faults using visual inspection method, in such case aerial thermal imaging, drone technology, data base analysis etc. are the feasible solution.

The use of data for the primary analysis is very important, research here conducted is initial stage based on existing literature, realistic data, and analysis of data. It is broadly classified as qualitative research and quantitative research,

The model is derived from the mechanism of its working in energy conversion mode and various parameter need to be considered while making an electrical equivalent model of the photovoltaic cells. The figure below shows the equivalent circuit of a photovoltaic system.

Figure 2 Solar cell modeling

It consists of nonlinear equation and the current quantity the equation in terms of voltage can be given as

T is the junction temperature  unit is  K

V is the PV terminal voltage unit is V

k is the  Boltzmann’s constant = 1.38×10⁻²³ (J/K)

I is the PV cell terminal current unit is A

Vt – PV cell thermal voltage (V)

If – photocurrent (A)

Io – dark saturation current (A)

Project Aim and Objective

Rs – cell series resistance (Ω)

A is the p-n junction ideality factor

q is the electronic charge = 1.6×10−19 (C)

Figure 3 I-V characteristics

The blue line is the I(V) characteristic and the red line shows the power characteristic. Maximum power is achieved at MPP point at that time array produces the upper limit of output power and the condition can be given as The current and voltage also given aas

The array which is subjected to constant irradiance shows unique point rather than the photovoltaic array which is subjected to shading, it shows multiple MPP.

The fill factor for that is given as

The efficiency of the array given as

The more conscious and accurate model of PV cell can be given as below figure

Figure 4 Accurate PV modeling

The practical solar cell is not ideal so its modeled with shunt resistance with series component, now the current equation can be written as

Where I, is nothing but the output current, generated current due to photons,  is current through diode anthe d lastly  is the shunt current.

The value of the current is controlled by voltage available across them and given as

Where  is volta age between resistor and diode, V- output voltage I is output current and Rs is the value of series resistance.

By writing the equation of Shockley diode and the current which taken the path of the diode is given as

Where is the saturation current in reverse, n- diode factor, T is absolute temperature, k-Boltzmann’s constant, q-elementary charge.

Again value of shunt current is given as

Substitute all the values of current into to initial current equation

Since Rs is not 0, so the equation is solved by Lambert W function

In the case when the value of Rsh infinite the result for V for any value of I is less than I_L+I₀

Or it is solved for V using lambert W function and given as

In case of the value of Rsh is high best approach is to solve original equation.

When the array is not connected to other circuit means its open circuit and the currentis I=0, the voltage available across the output terminal is the open circuit voltage given as

And in the case when the array is short circuited the voltage almost becomes zero and the current is equal to the load current so it is

The size of array ultimately decides the output and the internal parameters of the Photovoltaic panel. Like value of R_s, R_sh, I_L, I_o etc depends on size of PV. When the size of cell is doubled the value of I_L, I_o also gets double which is holding a direct proportional relationship. The equation for current density or we can say the current produced per unit area is given as

Research Strategy

According to Lysen and Halle, the utilization of solar based vitality is on the ascent around the globe as analysts are always endeavoring to discover practical wellsprings of vitality that won’t just be eco-accommodating however will likewise not go away for a lot of time. With respect to the reasons, the specialists have expressed that the current wellsprings of vitality incorporate coal, oil, oil, and others that have significant negative effects on nature. This is primarily in light of the fact that the ignition of the petroleum derivatives makes a tremendous measure of lethal gases that influences the adjacent creatures as well as the general condition in general, causing an unnatural weather change. With the exponential increment in the utilization of non-renewable energy sources broadly all through the planet, the degree of contamination is likewise expanding step by step. Once more, the wellsprings of these fills are restricted and are rapidly becoming scarce around the globe. It is normal that inside the following couple of decades, the wellsprings of oil far and wide will become scarce totally.

Kamat and Christians stated that the world needs another wellspring of vitality that won’t just be reasonable yet will likewise be close to boundlessness to be possible for use for a huge time of future course of events. Besides, the wellspring of vitality will be to such an extent that it won’t bring on a contamination in the earth. solar powered vitality is thought to be only that wellspring of vitality since there is relatively boundless measure of vitality originating from the solar  and won’t become scarce at any point in the near future. Solar based vitality additionally does not hurt the earth at all and does not require burning or launch of poisonous gases.

Sahay, Sethi, Tiwari and Pandey discussed a portion of the principle hindrances of solar powered vitality that have been the primary explanations for the absence of adequate use of solar based vitality around the globe yet. The principle disadvantage identified with solar based vitality is that there isn’t any reasonable innovation for catching solar based vitality is mass sums. Albeit solar based arrays have been created for catching solar based vitality amid the daytime, they are as yet not ready to catch an adequate measure of vitality. With a specific end goal to expand the proficiency in gathering of the solar oriented vitality and accumulation of the vitality in appropriate scale, for the most part, a substantial number of solar oriented arrays are introduced together and put in lines and sections. This outcomes in taking a tremendous measure of room and furthermore unreasonable costs bringing about the procedure regularly being not attainable. Another real issue of the solar powered vitality is that it is just accessible amid the daytime and there is certifiably not a reasonable innovation accessible to store the solar based vitality for use amid the evening.

Zeng, Klabjan and Arinez stated that specialists have been attempting to build up a controllable framework that will catch solar based vitality according to required just and furthermore store the vitality for use amid the evening. Keeping in mind the end goal to satisfy this prerequisite, IoT has been utilized for checking and controlling the solar based arrays. IoT is additionally being utilized for the observing of the solar powered photovoltaic cells that catch the daylight and utilizations it to create usable types of vitality like power. With a specific end goal to catch expansive scale daylight for creation of vitality, extensive scale photovoltaic cells are being introduced far and wide. Be that as it may, since these cells and the solar based arrays take up a lot of room, they are for the most part introduced in extremely remote and blocked off areas keeping in mind the end goal to abstain from seizing up usable spaces. The burden of putting the cells in remote areas is that they can’t be controlled physically at the area effectively. Thus, IoT gadgets have been produced that assistance to control and screen the working of the cells. These IoT gadgets are worked with microchips and sensor circuits that are straightforwardly connected with the photovoltaic cells and solar oriented arrays. Moreover, these IoT gadgets are remotely associated with a remote checking gadget that can be utilized to identify solar oriented vitality caught by the array/cell, working productivity of the array and others. Once more, the remote gadget can be utilized to change the working of the arrays like lessening the measure of vitality should have been caught, increment in the catching rate amid the season of prerequisites and others.

Hu et al. has done experimental set up with keeping in mind the end goal to screen the working of the IoT gadgets on the solar powered panels and photovoltaic cells. The test setup incorporates the solar based array that will catch the solar energy-based vitality, temperature sensors for breaking down the measure of solar based vitality caught by the arrays, voltage transducers, microcontrollers (PIC18F46K22), GPRS module for controlling the working of the IoT gadget, converters, and interfaces. Moreover, the analysts have additionally utilized the assistance of PC programming like Matlab so as to recreate the whole situation and mimic the outcomes likewise. In the application, the creators built up a theoretical system display in which, the IoT gadgets are controlled from a remote area and are likewise associated with an online cloud database for different reasons. The creators disclosed that the association with the database is primarily because of various particular and imperative capacities as takes after.

Design and Installing Solar Panels Layouts

• Surveying a roof usually requires companies to send out surveyors to gather manual tape measurements, that which they have to clamber across rooftops for about 2 to 3 hours.
• To reduce the workload we are using drones that which are powered by 3D mapping software like Drone Deploy that can reduce the design cycle of solar energy projects by as much as 70%, and increase team productivity along the way.
• Drone captures measurements from the safety of the ground. Capable of flying close to any site and deliver precise measurements consistently and helps surveyors to generate accurate 3D models for further inspection.
  • Creating Valuable Deliverables

Various stakeholders are involved in solar plants such as owner of the solar plant which may be private or government authority, field technicians, workers, managers, and lastly the users of solar energy. It’s very important to optimize the use of assets and maximize the profit to the all the stakeholder involved with the project and lastly the overall energy cost to the users should be less.

• Value of Thermal Imaging in PV System Inspections:

Aerial thermal imaging recognizes PV framework peculiarities from the inverter (vast) level down to the string, module (array), and cell levels. At the point when territories in the PV framework are damaged, the vitality from the solar isn’t changed over into electrical vitality, bringing about an expansion in temperature. Also, changes in the surface properties of a module show as a distinction in emissivity, which is identified with a warm camera. The aftereffects of flying warm imaging illuminate resource administration and spare 2– 5 times the work cost in the field. Each and every module is breaking down, and site condition is quantitatively followed after some time.

• Planning Inspections

It is critical to know the motivation behind the PV framework review and comprehend the level of detail a customer needs before information accumulation. You ought to likewise verify whether there is satellite symbolism of the PV framework; if not, plan on catching shading (RGB) pictures to for an orthostatic. Regardless of whether there are satellite symbolism, shading (RGB) pictures enhance the nature of the report. Make a point to take note of the module innovation (e.g., polycrystalline, CeTe), wiring (e.g., number of modules per string), and other relevant data.

• Plant Monitoring

The most vital capacity of utilizing an association with the database is checking of the plant that is required so as to guarantee the solar powered arrays are filling in as required and anticipated. The IoT gadgets will screen the working of the arrays and will promptly send data to the database at a consistent premise.

• Maintenance Works

 For support works, it is vital to decide the faults or issues the PV array are confronting or whether upkeep is required basically as a result of the aging structures. All the data can be resolved and found from the database in view of the data sent by the appended IoT gadgets and reasonable moves can be taken accordingly.

• Data Analytics

 Information investigation is the most critical capacity that is particularly essential for this specific research. According to the analysts who built up this reasonable structure, information can be gathered straightforwardly from the cloud database that can be associated with the IoT gadgets. From this gathered information, information investigation programming can be run and appropriate ends can become to in regards to the working of the solar-based arrays.

• Fault Monitoring

The monitoring of faults needs to carried out on continuous or Realtime basis, use of IoT devices, RTU, SCADA can be used for such task.

• Fault Detection Methods

Fault detection is the very important part of the Photovoltaic operation and maintenance routine. There are lots of fault detection method proposed by researchers listed and briefly described below.

• Model-based Method:

It’s the simplest method where the output power of the array is compared with the reference or set value of power whenever some deviation occurs it gives an alarm or information to the operator. Usually, link with a satellite system to know weather condition.

• Current-Voltage analysis:

In this method track of operation points of the Photovoltaic array is checked. By this method, it is easy to find the type of fault whether its mismatch loss, reduced voltage or current, shunt losses or series losses. In the figure below, various points are shown.

Figure 5 Loss spots of PV

• Performance ratio method

This method is based on the normalizing the parameter of photovoltaic array, and performance ratio is found using the equation given below

Where the Yr is the reference and Yf is the final.  And above performance ratio is a dimensionless unit. Where Yf is the normalize AC energy output and given as

Where in case the Yr is the irradiance normalized factor and given as

• Machine learning based methods:

Machine learning is the area of artificial intelligence where it automatically tracks knowledge of the designed Photovoltaic system and its data are gathered at central processor using supervised learning process. The amount of data varies and depends on the system and its size and data collected also various types. Few are labeled data and few unlabeled data.  Using various ANN based technique data can be analyzed and fault can be detected. Figure below, shows the basic flow chart of machine learning techniques.

Figure 6 Machine learning basic flow chart

• Statistical method:

Fault detection using the of the statistical method is by applying two method, one of them is descriptive and other is informal statistical method. Covariance of the parameters are determined. Using minimum covariance determinant (MCD) PV module fault can be determined using robust distance calculation.

• Research Gap:

The major fault detection techniques are covered in the previous section and according to a study on fault detection methods, the very common and effective method is Aerial Thermal imaging.

As per NREL, use of aerial thermal imaging method is effective for the detection of three type of faults which are described below

• Module faults: module faults are detected whenever cells of the photovoltaic array are subjected to diode failures, coating, fogging, shattered, junction box heating or the dirty modules
• String faults: String faults are detected whenever there is an issue with the wiring by a technician, by mistake connection is of reverse polarity, cable termination issues or the controller used for charging or may involve faults in the inverter and the fuse links use at converter stages
• Racking and balance of system: racking and balancing of the photovoltaic panel is a very important task and such faults are detected if the modules are not mounted properly with proper angle and foundation.
• Methodology

The monitoring of photovoltaic panel and its data from the sensor need to carried out on a continuous basis. The output of panel generally available at day time during the availability of sun light but during night time if sufficient battery backup is available output power can be delivered to load side, end users or directly to the distribution grid.

Figure 7 Sensors and meter connection with photovoltaic plant

The above diagram shows the solar panel connected with the inverter in between an the intermediate stage can be connected to Boost converter or charge controller. The output of inverter connected to the solar generation meter which can be helpful to monitor output power from solar and having data of voltage, current, power, and harmonics. In the next stage, its synchronized to the grid where bidirectional meters are places to measure power exchange between grid and household or solar plants. And the last stage it delivered to end users. At each point, various sensors are placed and using controller data are processed and delivered to mobiles or Data acquisition systems. Where an operator can analyse the data and can take corresponding corrective actions.

4.11 Design:

• Design part include the simulation and hardware testing
• Initial stage is based on simulation of photovoltaic with Maximum power tracking
• In simulation fault is to be analyzed, various faults on panel and converters to be analyzed.
• In next stage, case study is to be done for the realistic photovoltaic plant.
• The data gathered from the photovoltaic plant will be analysed based on statistical data analysis technique.
• Project Time line

Figure 8 Project Gantt chart

• Resource Requirements

To complete the study of the report and topic the main resources use are mention below

• Papers from IEEE, science direct and other international reputed journals
• Library and book materials
• Survey method
• Using electrical/electronic software tools
• And fund required for completing the research work
• Response to Feedback
• Conclusion

Photovoltaic is the best suitable solution towards the energy crisis and environmental issues. Monitoring, control, and the fault detection are important and key practice need to be done for proper operation and function of the photovoltaic system. There are lots of techniques exist for monitoring and fault detection. Data recording and logging is an important aspect of any method applied for photovoltaic fault detection. The growth of PV utilization if double and size of the plant are too large with manual or technicians its difficult to analyze using visual inspection or onsite monitoring, the best-suited solution is using drone technology to analyze photovoltaic for operation and maintenance (O & M).

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