Abstract
In photovoltaic solar energy systems, power management algorithms (PMAs), usually called maximum power point tracking (MPPT) algorithms, are widely used for extracting maximum available power at every point in time. However, tracking the maximum power has negative effects on the availability of solar energy systems. This is due, mainly, to the created disturbances and thermal stresses on the associated power electronic converters (PECs). This work investigates the effects of PMA on the lifetime consumption, thermal stresses and failures on DC-DC converters used in solar systems. Firstly theoretical analysis and modelling of photovoltaic solar systems including converter’s electro thermal characteristics were developed. Subsequently, experiments on photovoltaic solar systems were carried out using two different PMAs, namely, perturb and observe (P&O) and incremental conductance (IC). Real-time data was collected, under different operating conditions, including thermal behavior using thermal imaging camera and dSPACE. Converters’ thermal cycling was found to be approximately 3 °C higher with the IC algorithm. The steady state temperature was 52.7 °C, for the IC while it was 42.6 °C for P&O. Although IC algorithm offers more accurate power management tool, it causes more severe thermal stresses which, in this study, has led to approximately 1.4 times greater life consumption compared to P&O.
Highlights
Generating electricity using photovoltaic (PV) solar energy modules is getting more popular due to recent advances in PV-cells and power condition circuitries
Ishaque et al [14] stated that the incremental conductance (IC) method is slightly better since it gives 98.5% maximum power point tracking (MPPT) efficiency compared to 98.3% of perturb & observe (P&O), based on a study conducted on a MPPT converter attached to a PV array simulator
The system operated by the IC method was found to be less reliable compared to the one with P&O, when they are operated under the same operating conditions
Summary
Generating electricity using photovoltaic (PV) solar energy modules is getting more popular due to recent advances in PV-cells and power condition circuitries. In the literature, to the best knowledge of the authors of this article, no comparative study has been presented about the electro-thermal effects of the MPPT algorithms on the DC/DC converters employed within PV systems, the temperature influence and importance of the electro-thermal design were mentioned in [22,23] and an improved thermal profile for PV inverters was assessed by power limit control method within the P&O method in [24,25]. This work investigates the effects of IC and P&O PMAs on the thermal stresses and reliability of PEC modules Temperature variations of IGBT were determined when IC and P&O algorithms were applied as MPPT method and these profiles were used in reliability models for lifetime consumption estimation
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