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This paper reviews different types of maximum power point tracking (MPPT)

This paper proposes a three-phase inverter combined with two LLC resonant tanks series resonant DC-DC boost converter with variable frequency control. The three-phase inverter side of the proposed circuit is connected to identical two-level LLC tanks to ensure balanced resonant currents. The proposed converter requires less switching devices and transformers as compared to the conventional interleaved LLC resonant converter, which competitively offers higher efficiency and reduced size and cost. Furthermore, the proposed converter works above the resonant frequency to achieve zero voltage switching (ZVS) for the entire operating frequency range (42.5kHz

Solar energy is becoming popular and has drawn lots of attention from researchers nowadays. However, the output power of the photovoltaic (PV) arrays varies with solar irradiation and temperature, which affect the efficiency of PV arrays. Therefore, Maximum Power Point Tracking (MPPT) IntroductionFulfilling the energy demand from the people all over the world would be not enough if the energy sources are only limited to utilization of non-renewable sources such as fuel, gas and coal. Besides, most non-renewable energies cause pollution and less non-environmentally friendly. Hence, renewable energies are introduced in the past two decades to fulfill the energy demand. One of the popular renewable energies is solar energy which is extracted by converting sunlight into electrical power using the photovoltaic system. However, the conversion efficiency is relatively low with the range of only from 12% up to 20%, and it is highly dependent on the solar irradiation and panel temperature [1]. Thus, in this paper, Maximum Power Point Tracking (MPPT) control technique is explained which can increase the efficiency of the overall Photovoltaic (PV) system by extracting the maximum available power from the PV arrays [1][2][3].There are many MPPT techniques that have been introduced and elaborated extensively by researchers. Reference [4] stated that at least 19 distinct methods have been promoted, developed and implemented to improve solar photovoltaic. Each method differs in theirs complexity, number of sensors used, cost and effectiveness.The simplest technique that can be used is fixed duty cycle method [5] since it does not need any feedback to be implemented; but when the operation environment changes, the efficiency will become low. Fractional open circuit voltage (OCV) and fractional short circuit current (SCC) are also said to be the easiest offline methods for MPPT [3,4], [6][7][8]. As for the OCV method, the voltage at MPP (V MPP ) is approximately equal to the open circuit voltage (V OC ) of PV array with the factor of k 1 such that V MPP ≈ k 1 V OC , where k 1 ranges between 0.71 and 0.78 [9]. Similar with SCC method, the current at MPP (I MPP ) is approximately linearly related to the short circuit current (I SC ) of PV array, such that IMPP ≈ k 2 I SC, where k 2 ranges between 0.78 and 0.9 [4]. Regardless of their simplicity, the Maximum Power Point (MPP) obtained from these methods is not true due to the imprecise MPP tracking. Plus, the constants k 1 and k 2 are not valid during partial shading condition. It have been improved by sweeping the PV array voltage or current in order to update k 1 and k 2 , respectively. However, sweeping leads to complexity and incurs more power loss.

This study highlights a new construction of SEPIC DC-DC converter. The proposed converter aims for some features such as high voltage gain, continuous input current and reduce stress on the power switch. In addition, the circuit construction ensurs the simplicity in design along with signicant cost saving, since its components are readily available and smaller in size compared to the off-shelf components. This type of converter can adjust the DC voltage to maintain its output voltage to be constant. Typically, SEPIC operated in equipment that uses battery and also in wide range input voltage DC power supply. The converter is designed for renewable energy application where it is able to regulate the output voltage of the Photovoltaic (PV). The converter has been analysed based on different switching frequencies and duty cycle. Thus the outcome of the proposed converter can be achieved by using D=0.45 and fs=30 kHz. The proposed converter is supplied by 26V as an input voltage and produces 300V output and gives 94% of efficiency.

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