Advanced reconfigurable photovoltaic arrays

Abstract

This thesis describes works relating to advancements in the field of dynamic photovoltaic arrays (DPVA). This subject is becoming extremely active with a flurry of new papers appearing in recent times, all detailing ideas and developments regarding a range of engineering issues. One of the biggest problems with any photovoltaic system is the non-linear reduction in power output caused by the partial shading of the array surface. This is the main focal point of the developments discussed where new techniques regarding the reconfiguration of photovoltaic devices within a topology are identified and used to reduce the negative effects of non uniform insolation.

In particular, the most successful type of dynamic array has been modified (the Irradiance Equalized Dynamic Photovoltaic Array) such that it now exhibits it's maximum flexibility and is able to show complete resilience to partial shading allowing for maximum power extraction. Furthermore, the operational speed of the device has been increased so that it can operate in real time with minimal computational effort and we have investigated the future of the device as source of electricity in a wide range of applications. On top of that, a second completely new type of dynamic array (the Optimise String Dynamic Photovoltaic Array) that demonstrates unique behaviour is presented and tested via a custom made simulator programmed into MATLAB. Both of these developments have included conceiving new sorting algorithms that are particularly rapid in their execution while obtaining a high level of optimisation. Three other classes of arrays found in literature are discussed and their characteristics are identified while concerns with their implementation are cross is examined.

A new classification framework used in identifying all types of dynamic array has been introduced. This is very useful when discussing the main attributes associated with the various contributions made by authors of the literature. Not only this but it also allows for a comparative study between matrix architecture and device flexibility for arrays within the same class.

A simulator that uses standard mathematical models to virtually realise irradiated solar cells and then perform the operations dictated by the sorting algorithms is presented. It reveals in detail the behaviour of featured DPVAs under a complete range of environments. Working with that, a new comprehensive test procedure has been developed that exercises the simulated arrays and documents their expected output under precisely controlled conditions. The resulting graphs are extremely useful in highlighting to the researcher the proficiency's and failings of the arrays under said conditions. This simulation environment interfaces to a real 16 section prototype array so that predictions can be verified by experimentation. The device can be used in such a way that it mimics the simulated dynamic array, while also providing a convenient terminal where more bespoke tests can be conducted. As will be discussed, all market bound DPVA research must be conducted with both a virtual and physical devices because each environment provides an incite that is of great importance to the designer.

A later discussion introduces some abstract but potentially significant ideas about synthesising AC electricity using the switching mechanism. An argument suggesting why an industrially accepted synthesis method is not suitable for photovoltaic use is given and a more suitable solution is hypothesized.

To finish there is a discussion about the remaining unexplored topics in the field which highlights how and why further research is required. The aim of this is to acknowledge that more work is needed but also to show the way to developing a completely new state of the art source of electricity which may one day help society effectively exploit the abundance of power being delivered to us by the Sun.

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