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PV Solar Module performance enhancement in the field Disclosure Number: IPCOM000204643D
Publication Date: 2011-Mar-08
Document File: 4 page(s) / 147K

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The article covers the module installation improvement in the field by using dynamic string build dependent on individual module performance.

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PV Solar Module performance enhancement in the field


Solar modules do have between 60 and 72 solar cells assembled. The cells are typically serialized to achieve maximum output voltage. The same is with modules installed in the field, meaning the modules are typically serialized. This has the disadvantage, that the weakest performing unit determines the performance of the module or installation. The ability of switching the individual units, cell or module, can improve the overall performance significant. The paper below describes a solution how to enable such a unit or module switching.

Functional description:

PV solar modules can lack performance in the field due to cell matching issues, as well as

problems like:

• Environment
• Location and orientation
• Clouds
• Dust, dirt
• Shading
• Degradation, thermal, material etc.
• Etc.

To optimize thermal issue it might be certainly helpful to have local temperature sensors available to be able to work preventive.

Optimization of module string per inverter. Base idea is to build dynamically strings based on individual module performance, as outlined in the figure below.

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inverter array switching

In case of a field application with 1MW we would talk about 5000 modules and around 200 inverters. This to address the complexity of the matrix. The cabling must be kept as short as

possible to keep DC losses low. Or we have to work with micro inverter per module and

Fig.1: architectural overview of module



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combine the AC voltages in a complex matrix. But this would cause losses due to the bad efficiency of the inverter technology in case of low voltage.

The complex switch array requires an appropriate switch algorithm to enable most efficient string build. The algorithm determines the best strings, real time, realizing maximum power output. Those modules are real time linked together using the advanced switching array. The algorithm can be also used to link modules in parallel as well as serial mode, this only to maximize power output.

The switches used are semiconductor switches which nowadays easy can handle power in the order of several hundred Watt. The base array or high level matrix to switch the module strings together for best output is shown in the figure below.

The array must be able to link the matching modules in series and to one of the inverters. The base concept of switching the modules to the right inverter is shown in the figure below. The switching lines are highlighted in the figure below to demonstrate the serialization of the switching array. The "I's" are the inverters. The array is as flexible as combining any number of modules with a relevant number of inverters. Modules can be switched in serial as well as

parallel mode, see figure below.


Fig.2: example showing modules switched in serial mode to inverter

It has to be considered that the DC contact wires shouldn't be to...