A new maximum power point tracker of photovoltaic arrays using fuzzy controller

The studies on the photovoltaic system are extensively increasing because of a large, secure, essentially exhaustible and broadly available resource as a future energy supply. However, the output power induced in the photovoltaic modules is influenced by an intensity of solar cell radiation, temperature of the solar cells and so on. Therefore, to maximize the efficiency of the renewable energy syskm, it is necessary to track the maximum power point of the input source. In this paper, a new maxi" power point tracker (MPF'T) u s i y fuzzy set theory is proposed to irnpmve energy conversion efficiency. Fuzzy algorithm based on linguistic rules describing the operator's contml strategy is applied to control step-up converter for MPPT. Fuzzy logic contrul based on coarse and fme mode has been incorporated in order to reduce not only the time required to track the m a x i " power point but also fluctuation of power. MPFT algorithm is implemented by 16 bit single chip 8CC196KI3 microcontroller. Simulation and experimental results show that performance of fuzzy controller in maximum power tracking of photovoltaic array is better than that of controller based upon hill climbw method. attention of a number of researchers in the area of power electronics. The fuzzy logic control is somewhat >easy to implement because it does not need the mathematical model of a system. Since it gives mbust performance, the interest in practical application of fuzzy logic is growing rapidly 131141. In this paper, a new method using fuzzy logic has been applied to step-up maximum power p i n t tracker for PV arrays /51. Particularly, input variables of fuzzy controller are dP,ddiphh(where Pph is PV array output power and iph is PV array output current) and change of it. To reduce the transient response time for hacking maximum power point and force fluctuation of PV array output power to miniize, fuzzy controller has two modes -' coarse and fine modes. Proposd step-up MPPT system is studied by simulation and is implemented by using a microcontroller which controls duty ratio of MOSFET boost converter. Comparisons of proposed MPPT with conventional hill climbing MPPT indicate that the proposed method overcomes the trade-off problem that the smaller change of duty ratio is, the closer maximum power point, however there will be an increase m the tinle required be the system to reach equilibrium in the hill climbing method. II. STEP-UP (BOOST) CONVERTER FOR MPPT I . INTRODUCTION According to the realization of high effEiency and low cost photovoltaic(PV) modules, interest in photovoltaic power generation system has increased over the past decade as a clean and infinite energy. The PV modules have maximum operating points corresponding to the surrounding condition such as intensity of the sunlight, the temperature of the PV modules, cell area, and load. When solar energy is used as a power source, the output power has to be maximizd by irnproving the efficiency of the power conditioning equipment used and implementing an adaptive power controller that automatically tracks the system to the point of maximum power delivered from the solar panel under all conditions. Generally, a hill climbing method demonstrated by Boehringer (1970, Harashima(l987f is used to determine the maximum power point. The instantaneous current and voltage are sampled and multiplied to obtain the power. Futhermore, the input source voltage is sampled to help the controller determine whether the operating point is to the left or right side of maximum power point of the On the other hand, fuzzy logic or fuzzy set theory has received solar array [11,[21. 0-7803-1859-5/94/$4.0