Ongoing & Completed Research Projects 

Sponsored by Replus Engitech Pvt Ltd.

Sponsored by Ministry of Education under AI Center of Excellence, seed fund at IIT Gandhinagar.

Funded by Electrical Research and Developement Association, ERDA Vadodara

Funded by Defense Research and Devleopment Organization, DRDO

Funded by Enotrac UK Ltd.

If the light seen by different PV modules in a series string of PV installation is different, it leads to the reduction in the output of the system and can potentially damage the system in long run if it is not protected. This phenomenon called partial shading occurs from near by trees, buildings, moving clouds, bird droppings etc. Also dust deposited on panels can aggravate this problem. Availability of water in hot regions of India is a challenge for routine cleaning of PV arrays and therefore despite of shading, the system should be able to control itself in a way that the maximum possible power is produced. This is known as the global maximum power point tracking (MPPT), wherein the system control is smartly designed to automatically work at the maximum power point despite of varying ambient conditions in real time.

Most of the commercial PV converters fail to extract the maximum power from PV arrays under partial shading conditions. Such conditions are common in dense PV installations and presence of low passing clouds. Due to non-uniform irradiation, output characteristics present several local maxima. Failure of system control to track the global maximum can lead to considerable fall in system efficiency. Several GMPPT algorithms proposed in literature are based on artificial intelligence: making them complex in implementation; or are based on curve tracing: causing a slow response. We propose a novel GMPPT algorithm based on module voltage sensing and fundamental output characteristics, which is fast and easy to implement.

This algorithm is much faster than commercial methods as all homework in maximum computation is done is background, which means that you will not loose power when your neighbour shadows your panels as the system will keep settling to new operating points as soon as the irradiation changes unlike the situation where by the time the system settles to the maximum, the shading condition or solar irradiation itself has changed, in which situation a lot of energy gets wasted in transition delay. Another major advantage of this approach is its retrofit ability. It can be coded in existing PV systems and made to work in tandem with the existing local maximum power tracking algorithms. Use of the proposed GMPPT control results in: longevity of solar panels, more power production and prevention of potential safety hazards. GMPPT enabled system can detect partial shading and shifts automatically to a safe operating point, while giving the maximum possible power output in a given ambient condition. This technology has been patented recently and soon will find its way from our laboratory to fields, via solar energy start-ups, where people will be directly benefited.

More details about our novel GMPPT method are well-covered in the video of our IEEE Access article here:  https://ieeexplore.ieee.org/document/9395445

The performance of photovoltaic (PV) systems is greatly affected by shading and faults during operation. This reduces the system output and leads to reliability concerns. This research developed new approach of module level voltage sensing in PV modules wherein the PV installation autonomously diagnoses the performance deterioration using real-time measurements. Correlations between the module voltage, irradiation, and temperature are developed by utilizing PV characterization models. When the differential module voltages are detected in the PV string, a partial shading condition or a fault such as a hotspot is anticipated. The proposed solution provides energy yield optimization along with improved system reliability by incorporating sensing, communication, modelling and control in tandem.

This work was funded by IUSSTF under collaboration of IISc, Bengaluru with Northeastern University, Boston in 2019

Millions of people lack access to basic electricity, while a large majority of world population still relies on poor quality state electrification in the developing countries. This work proposes the much-needed interface problem between the on- and off-grid solution for the last mile electrification towards the fulfilment of the sustainable development goal 7 of the United Nations: to provide reliable universal energy access to all in a sustainable way. The grievous repercussions of the climate change are being felt throughout the globe, driving the urgent need to switch to renewable energy resources. World energy leaders have acknowledged that it is easier to develop green energy infrastructure in developing countries rather than transforming existing carbon-emitting energy nexus in the developed countries. Due to high flexibility and growing energy needs of the developing communities the focus of the proposed green microgrids is the developing nations. 

More details on this are awaiting sponsor permissions to be released in public domain.

Modern infrastructure in developing and developed nations reflects an energy nexus of multiple carriers such as gas, electricity, water and air. Different energy systems have been modelled by unique tools and methods in the past several years however they often suffer from complexity, high computational burden, and low accuracy due to lack of measured data for system modelling. Most of these methods involve closed tools, making them inapplicable for other energy systems. In order to solve global energy crisis, reduce carbon emissions and save costs, a unified modelling approach, which can interface different energy carriers under a common umbrella of modelling variables, is the need of the hour. 

More details on this are awaiting sponsor permissions to be released in public domain.

In last one decade there has been active interest in PV fault diagnosis as large PV deployments are facing field related performance issues. Several real time fault detection mechanisms have been proposed in literature involving observation of electrical parameters of PV power converters. However the problem with these methods is that many faults such as hotspots go undetected with  only electrical parameter performance evaluation, but later may lead to catastrophic failures. To detect such faults: thermal and electroluminescence (EL) related tests are commercially practiced, but these are typically very expensive and time consuming in nature. During some recent experiments at IISc we have discovered that: Infra Red thermography along with electrical parameter observation, can lead to conclusive results on preventive fault diagnosis.  The impact of non uniform irradiation on PV module temperature is modelled and the phenomenon of hotspot formation on healthy PV modules is explained and experimentally verified to study the impact of partial shading on system safety. The introduction of subcell model of solar cells under non uniform irradiation now gives a method of studying the effect of diffused light and non uniform temperature distribution within a cell.

We developed a solar irradiation meter in-house that measures sunlight and cell temperature and is at least twenty times cheaper than the commercial pyranometers but offers comparable performance. As this meter is based on solar cells and therefore has matching spectral response with respect to the actual PV panels, the calibration cost and time are largely saved. This solution was highly appreciated by the Instrument Society of India and is now used across the country by several solar energy start-ups.

A PV characterization set up was developed using which the output of a given PV array could be captured. This further helped in the modelling of PV systems, shading analysis, defect detection, etc. As a second step we performed extensive characterisation of PV modules under varying ambient conditions and generated data. Based on this data a novel PV modelling parameter extraction method was derived which incorporates parameter variation with ambience.  To study the effect of partial shading conditions on PV output, shading conditions were emulated using shades of different translucence. A novel subcell model is proposed which can physically explain the effect of shading of PV module and its impact on output.

We designed Indian-centric power converters and developing their control mechanisms which work with storage in presence or absence of grid and are optimized in size and cost so that they are more affordable and are robust enough to work in tropical weather conditions. This is achieved by using novel design of converter components such as magnetics at high frequency. As magnetics are often the bulkiest and costliest component in an inverter, this approach optimizes both size and cost. Layout of the converter is designed with high density for size reduction with state of the art power electronic devices arranged in a novel circuit topology. As converters are made compact, the thermal management issues have been closely looked into for reliable operation. This is achieved by using an electro-thermal holistic design approach wherein heat-sinks are fabricated using the concepts of heat flow and heat generation is calculated using the power loss estimation during converter operation. Also the converter is designed for with minimal losses during operation using zero voltage switching and low drop switches, which ensures while switching from on to off state switching losses are minimized in power semiconductor devices and also while their current conduction operation.

The annual energy that Earth receives from Sun is more than the combined energy of all fossil fuel reserves in mankind’s awareness. Yet Solar energy does not make even 10% of the global energy mix. Why? What went wrong with our engineers and scientists? The reason is very simple, though not very convincing! Solar energy is a diffused source of energy and it takes more effort to make it usable. But since conventional sources of energy are depleting, we have no choice but to go the renewable way. And India being a tropical country, it receives a lot of Solar energy. In last few decades, thanks to the climate activists, the awareness about solar energy has increased and more and more people want to adopt it. Major installations of solar photovoltaic (PV) energy systems have happened country-wide where Sun’s light is transformed into electricity. Unlike conventional energy sources, a PV plant can be placed on someone’s rooftop and is therefore both a centralised and a decentralised source of energy. Therefore every individual can be empowered to make their own electricity along with the central electricity utility support. Major components of a solar PV installation includes a PV array consisting of PV modules or panels, which are connected to an inverter for DC to AC conversion. However a major challenge here is the high investment cost and limitations of the available technologies specially when applied to our country. Let us take a closer look at these issues. Firstly, most of the PV modules and inverters that are involved in solar energy generation are imported. When the PV modules, converters and control technology are made in India, the cost of the entire PV installation will significantly drop. Secondly, the energy conversion systems available in market are mostly grid-tied, which give a good energy yield when grid is always available. This condition is true in western countries however in India, grid outages are commonplace specially in rural areas. Unless storage is provided with PV converters they are not of much use in present Indian electric ecosystem. To prove this we considered the cost of energy of a 3 kW grid-tied PV inverter and a dual-mode PV converter of same ratings but with additional storage, such that both these systems can individually cater to a medium household. With increasing number of grid outage hours in day time, the cost of energy for grid-tied energy system increased exponentially as compared to the dual-mode technology. This cost benefit analysis clearly shows that the grid-tied PV systems without storage are not successful in all parts of India, as when grid is out they cannot produce any energy, resulting in the loss of Solar power.

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