A MPPT Approach Using Improved Hill Climbing and Double Closed Loop Control 
Yuhang Liu1,2, Xiangxin Liu1,2, Duofeng Shi3, Yufeng Zhang1,2, Qiuchen Wu1,2, Ziyao Zhu1,2, Xinlu Lin1,2
1The Key Laboratory of Solar Thermal Energy and Photovoltaic System, Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing, China
/2University of Chinese Academy of Sciences, Beijing, China
/3Electric Power College,Inner Mongolia University of Technology, Hohhot, China

The development of Maximum Power Point Tracking (MPPT) control strategy is continuing in order to increase the generated energy from PV module. Many MPPT control strategies can be classified based on three main categories: perturbing current, perturbing duty cycle and perturbing voltage. This paper analysis the output characteristics of the mathematical model of photovoltaic modules under different illumination conditions at first, and then propose a hybrid approach which is a combination of Improved Hill Climbing and Double Closed Loop. The first part ensures the rapidity of the rising stage and the stability at the maximum power point, the second part,, ensures the stability of the output voltage and the output current of the Boost converter. Using MATLAB/Simulink to build various parts of the system model, the simulation results are compared with the two-stage variable step-size disturbance duty cycle. The simulation results show that the proposed algorithm can achieve a good ability of fast rise, stability and response to environmental transformation.