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SUMMARYAn indirect control variable for improving the control-to-output characteristics of a Pulse Width Modulation (PWM) buck-boost converter is introduced in this letter. The voltage gain and the small-signal model of the buck-boost converter are reviewed. The actual voltage command at one input of the PWM comparator is from the proposed indirect control variable and the peak value of the high-frequency PWM carrier. The resulted voltage gain function appears proportional to this indirect control command. Also the dependence of the DC gain of the control-to-output transfer function on the duty cycle is eliminated. Experimental results conform well to the theoretical analysis.

The Photovoltaic Array has a best optimal operating point where the array operating can obtain the maximum power. However, the optimal operating point can be compromised by the strength of solar radiation, angle, and by the change of environment and load. Due to the constant changes in these conditions, it has become very difficult to locate the optimal operating point by following a mathematical model. Therefore, this study will focus mostly on the application of Fuzzy Logic Control theory and Three-point Weight Comparison Method in effort to locate the optimal operating point of solar panel and achieve maximum efficiency in power generation.The Three-point Weight Comparison Method is the comparison between the characteristic curves of the voltage of photovoltaic array and output power; it is a rather simple way to track the maximum power. The Fuzzy Logic Control, on the other hand, can be used to solve problems that cannot be effectively dealt with by calculation rules, such as concepts, contemplation, deductive reasoning, and identification. Therefore, this paper uses these two kinds of methods to make simulation successively. The simulation results show that, the Three-point Comparison Method is more effective under the environment with more frequent change of solar radiation; however, the Fuzzy Logic Control has better tacking efficiency under the environment with violent change of solar radiation. PrefaceWith the energy crisis that is looming over modern civilization, the development and application of renewable energy sources have become a major issue around the world. In the recent years, Taiwan has seen an avid development in solar energy. Solar energy has the benefit of being reusable, sustainable, and produces no pollution. With the island of Taiwan situated in the subtropical regions and its adequate amount of sunshine, Taiwan is an ideal location for solar energy development. However, the solar panels, even produced by the highest industry standard could convert 23% of the solar energy into electricity, and the optimal conversion rate fluctuates with the change in environment and load. To optimize the conversion rate in the constantly changing