Abstract
In this paper, a new hybrid SEPIC dc-dc converter with coupled inductors suitable for photovoltaic applications is presented. First, the way how the new topology was derived will be presented, continuing with its analysis and design equation as a standalone dc-dc topology. The analysis will consist of a steady-state equations derivation, a static conversion ratio calculation based on which the semiconductor voltage and current stresses are evaluated, leading to the continuous conduction mode (CCM) operation conditions. The converter will then be simulated as a first validation of the theory using the dedicated Caspoc power electronics package. To finally validate the theoretical design, a prototype will be built in order to practically demonstrate the feasibility of the proposed solution and to reveal its main practical features and limitations. A comparative study to several other similar topologies will be carried out to identify its most desirable features. Finally, an application of the new hybrid converter will consist of a complete solar energy conversion system using a photovoltaic panel. The maximum power point tracking (MPPT) algorithm will be elaborated. The solar system together with the MPPT will first be modeled, then simulated and practically implemented and tested.
Highlights
The European Union (EU) expects greenhouse gas emissions to be eliminated by 2050 and 100% replaced by renewable energy sources [1,2,3]
In standard test conditions (STC) for a solar irradiance G = 1000 W/m2 and temperature T = 25 ◦C, one PV module has the following parameters: Peak power: Pmax = 20 W Maximum power point current: Imp = 1.14 A Maximum power point voltage: Vmp = 17.49 V Short circuit current: Isc = 1.22 A Open circuit voltage: Voc = 21.67 V The converter was designed according to the following parameters: Input voltage range was between: Vg = 30 ÷ 35 V − correlated to Vmp Maximum output power: Po = 40 W Switching frequency: fs = 100 kHz Output voltage: Vo = 120 V Output voltage peak-to-peak ripple: ∆VC2 = 300 mV Transformer ratio: n = 0.5
The simulation is made in an operating point, considering the input voltage Vg = 30 V, the static conversion M = 4
Summary
The European Union (EU) expects greenhouse gas emissions to be eliminated by 2050 and 100% replaced by renewable energy sources [1,2,3]. Solar energy is considered to be the largest source of energy [3]. In this context, solar energy technologies have experienced an increase in research to offer better efficiency at a lower cost. If the output voltage is required to be higher than the input voltage, a step-up converter needs to be used. The classical Boost topology is the simplest step-up converter with the lowest number of components [13]. One disadvantage of this converter is that if the required output voltage is much higher than the input voltage, this type of conversion cannot be achieved because of the intrinsic non-ideal components losses. On the market, different solutions, beginning with non-isolated high step-up dc-dc converters like: cascaded converters [14,15,16,17], semiquadratic converters [18], quadratic converters [19,20,21], stacked step-up converters [22,23], hybrid converters [24,25,26,27], multiinput converters [28], multiphase converters [17,29] and ending with isolated step-up topologies [30] have been reported
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