International Journal of Computer Applications (0975 – 8887) Volume 106 – No.10, November 2014 16 P(PV) V(PV) P 1 P 2 dP>0 P 1 P 2 dP>0 P 1 P 2 dP<0 V opt P PV Energy Transfer Optimization in Photovoltaic Conversion by the Maximum Power Point Tracking Samir Mouhadjer URER-MS Research Unit, EPST CDER. Adrar, Algeria Ali Chermitti URMER Research unit, Tlemcen University, Algeria Sid-Ali Chikhi URER-MS Research Unit, EPST CDER. Adrar, Algeria ABSTRACT Of the energy source point of view, for a photovoltaic array (GPV), the power production varies strongly according to insolation level; temperature and nature of the load on which the GPV debits, and according to the characteristics of the latter, a very strong variation can be to find between the potential power of the generator and that really transferred to the load in direct connection mode. Therefore, in order to extract at every moment the maximum of power generated by the GPV and to transfer it to the load, it must be equipped with a switch-mode converter which plays the part of interface between the two elements. This switch-mode can be a Boost (Step-up) or Buck (Step-down) converter according to the applications. General Terms Photovoltaic power generator, Optimization system, Power, Regulation, inverter efficiency. Keywords Photovoltaic, Regulation, Extreme command, Optimization, Power. 1. INTRODUCTION Studies show that a solar panel converts 20-25% of energy incident on it to electrical energy [14]. A Maximum Power Point Tracking (MPPT) algorithm is effectively necessary to use solar array power. The objective of MPPT is to ensure that the system can always harvest the maximum power generated by the PV arrays. There are two main groups of MPPT: those that use analog circuitry and classical feedback control, and others that use a microprocessor to maintain control of the maximum operating point [11]. In this paper, we chose the digital control. The digitally controlled MPPT systems have the advantage that a power point tracking algorithm will not be influenced by changes in temperature and therefore will always be very reliable. 2. THE MPPT ROLE 2.1 Definition: MPPT control is a functional organ of the PV system which makes it possible to seek the optimal operating point of the GPV which depends on the weather conditions and the load variation [10,12]. The regulation concept is based on the automatic variation of the duty cycle α to the optimal value so as to get continuously the maximum power from the PV array. 2.2 Operation principle Let’s take as example, for an incidental power P 1 , the optimal power transferred to the load could be maximal only for well defined duty cycle: α 1opt (P PM1 point on figure 1). If the incidental power changes to P 2 , the new maximum power point is P PM2 , but the operational point of the GPV is P F . To converge towards new point P PM2 , it is necessary to adjust the duty cycle α with the value α 2opt [13]. Therefore, in an independent and autonomous PV system, this regulation must be automatically realized in order to seek the optimal operation point. 2.3 Evolution of the GPV operation point The comparison between two powers (P 1 ) and (P 2 ) respectively measured at the moment (t) and (t-1) served us to seek the maximum power point (figure 2). If the derivative is positive (P 1 < P 2 ), that means that we approach the PPM, and if the derivative of the power is negative (P 1 >P 2 ), that means that we exceeded it. Thus with the system starting up, the research for PPM is done progressively, by seeking the first maximum. Fig. 2: Seeking PPM principle 3. STUDY AND DESIGN OF A REGULATOR OF CHARGE/DISCHARGE OF A BATTERY PROVIDED WITH A DIGITAL MPPT CONTROL The objective of this paper is to build an MPPT to charge a 24-volt lead acid battery by using a field wired 100 Watts PV array. The concrete objectives that we want to reach by this digital realization are the following:  Reduction in production costs compared to analog MPPT.  Reduction of the number of component used for the implementation.  Reduction in the total volume of the printed circuit board.  Reduction in the overall consumption of energy.