میکرو اینورتر خنک کننده ترموالکتریک برای کاربردهای PV Thermoelectric cooling micro-inverter for PV application

1. Introduction As the photovoltaic solar energy is as well promising as other renewable energies, much research and development are underway, to improve the performance of an installation. These improvements are made at the same level of PV modules manufacturing but the PV systems are less efficient because of the climatic conditions that alter their performance. For this reasons, the ‘MLPEs’ (Module-Level Power Electronic) include as a solution, not only to make a good harvest of the maximum power delivered by the PV, but also to adapt the DC output of the PV to the load or the grid voltage. The modules have generally a power up to 500 W. Each PV module integrates its power optimizer or Micro-Inverter that makes it more effective. The use of the multiple modules allows having a greater power if it is needed (Fig. 1). Photovoltaic generators have a nonlinear characteristic; therefore their electrical power has a maximum that must be tracked. MPPT [1] controllers are then used for this purpose. A MPP tracker is an electronic circuit built around a DC-DC converter. DC-DC converters are mostly used for interconnections between two DC networks with different voltage levels. There are many different topologies which vary according to the complexity of circuits, stress on used components and quality of input and output power [2,3]. Generally, a single-inductor, single-switch boost converter topology and its variations exhibit a satisfactory performance in the majority of applications where the output voltage is greater than the input voltage. The performance of the boost converter can be improved by implementing a boost converter with multiple switches and/or multiple boost inductors [2]. The two inductor boost converter exhibits benefits in high power applications [3–10]: high input current is split between two inductors, thus reducing I 2 R power loss in both copper windings and primary switches. Furthermore, by applying an interleaving control strategy, the input current ripple can be reduced [6]. Implementation of the topology can be in either non isolated [11] or isolated format. The isolated boost topology, which is shown in Fig. 2 [12], is attractive in applications such as power optimizer with isolation to extract the maximum power and generate high output voltage from low input voltage [11–14]. When a PV module integrates its own Micro-Inverter, its efficiency becomes more significant. Many methods are used to design Modular Integrated Converter (MIC) or also called micro-inverter. The method used in this paper to design a Micro-Inverter is based on two steps. First, the DC panel voltage is stepped up, using an interleaved isolated boost converter topology, to a much higher voltage. Then, this high DC voltage is converted into an AC signal and then filtered using an LCL filter. The cooling of the power electronics components is ensured by using a thermoelectric model developed at MAScIR. The thermoelectric technology exploited to date by the industry is based essentially on the Peltier and Seebeck effects, the first being that which produces a heat flux from an electric current and the second one that produces an electrical voltage from a difference of heat. The generation of electricity by this new technology is based on the Seebeck effect of n and p type thermoelectric semiconductors consisting of pairs electrically connected in series and thermally in parallel by a conductive material whose thermoelectric power is assumed to be zero. The merit coefficient is given by: ZT = S2CT/K with K = Kres + Kpor, Where; S: Seebeck coefficient, K; thermal conductivity, C: electrical conductivity, ZT; merit coefficient. In this paper the detailed information about total and local density of states of a system based on Bi2Te3 material doped with Sb and Se, will be presented, using ab-initio calculations based on full-potential linearized augmented plane wave (FP-LAPW) method, as implemented in the Wien2k code.