Centralized vs distributed (power optimizer) PV system architecture field test results under mismatched operating conditions

Abstract

The number of Building Integrated Photovoltaic (BIPV) system installations is increasing as different new and specific solar cells and modules are developed. The great advantages of BIPV systems should be enough to achieve their massive implantation, but the difficult working conditions of the urban environment reduce the energy yield and increase the payback period of investment.In order to boost the energy yield of BIPV systems distributed PV system architectures seem to be the solution. In this sense, TECNALIA developed a new distributed DC-DC converter PV system architecture. These electronic devices, commonly called power optimizers, eliminate almost all the mismatching losses between modules and increase the system energy output.The performance of these distributed architectures is much better than centralized ones for high mismatched PV systems. However, for no mismatched cases centralized architectures present higher overall system efficiencies and energy yields. This makes the decision of which architecture is the most suitable one not so easy.In order to quantify the advantages and disadvantages in the performance of these types of architectures, the present abstract summarizes the experimental results of both architectures in real and identical working conditions. The tests have been performed in two independent PV fields, one with distributed architecture and the other one with the typical centralized one.The work carried out has consisted in generating different type of mismatching situations common in an urban environment. The tested working conditions are related to different irradiation levels, type of irradiation, orientation and inclination, shadows, dirtiness and reflexions conditions. Other aspects related to the double operation of MPPT systems (inverter and power optimizers) have also been tested.The energetic test result are presented and analyzed, showing the strengths and weaknesses of each PV system architecture.The work carried out is comprised under the Government of Bizkaia funded research project EMAITEK-FOTO. BACKGROUND

The Optimized-String Dynamic Photovoltaic Array

“…This topology was considered economic and simplistic as it requires one high power converter operating at a high DC voltage to facilitate grid tied power inversion. However, recent studies have shown that centralized conversion strategies are generally less effective at converting incident sunlight into electricity than the decentralized conversion topologies within urban environments [1]. This is due to their being less current limitation within the smaller multiple stringed systems than with a single stringed system operating under identical conditions.…”

“…A recent attempt to reduce the partial shading issue involves changing the topology of the PV plant. The most shade robust arrangement is the Module Integrated (MI) topology which involves connecting micro-converter or micro-inverters to each module in the array and a yield in excess of 240% have been reported [1]. This approach allows flexible plant design, lower hardware prices due to mass production and lower minimum array size, however the effectiveness of MI schemes can still be limited as incoherence within a module can still exist.…”

MPPT Control System for PV Generation System with Mismatched Modules

“…But, under the condition of mismatch (modules of different output power, shadows, dirtiness, etc. ), this structure of system can led to the problem of mismatch losses [1][2][3].…”

Photovoltaic grid-connected outdoor LED lighting with zero energy consumption

“…1). It can significantly reduce the negative impact of shading panels and increase the efficiency of the whole system by optimizing of operating conditions of each solar panel [3,4].…”