This paper presents a novel model of photovoltaic (PV) module which is implemented and analyzed using Matlab/Simulink software package. Taking the effect of sunlight irradiance on the cell temperature, the proposed model takes ambient temperature as reference input and uses the solar insolation as a unique varying parameter. The cell temperature is then explicitly affected by the sunlight intensity. The output current and power characteristics are simulated and analyzed using the proposed PV model. The model verification has been confirmed through an experimental measurement. The impact of solar irradiation on cell temperature makes the output characteristic more practical. In addition, the insolation-oriented PV model enables the dynamics of PV power system to be analyzed and optimized more easily by applying the environmental parameters of ambient temperature and solar irradiance.

۱٫ Introduction

Nowadays, people are much concerned with the fossil fuel consumed at the present high rate as well as the environmental damage caused by the conventional power generation. Renewable energy resources will play a significant role in the world energy supply in the upcoming future. Among the renewable energy resources, solar energy is the most essential and prerequisite resource of sustainable energy because of its ubiquity, abundance, and sustainability. Regardless of the intermittency of sunlight, solar energy is widely available and completely free of cost. Recently, photovoltaic (PV) system is well recognized and widely utilized to convert the solar energy for electric power applications. It can generate direct current (DC) electricity without environmental impact and emission by way of solar radiation. Being a semiconductor device, the PV system is static, quite, and free of moving parts. These characteristics make it need very small operation and maintenance costs. PV cell represents the fundamental conversion unit of a PV power generator system. Solar insolation, PV’s cell temperature and operating voltage strongly influence the output current and power characteristics of PV. With nonlinear characteristics, PV model is first built to design the maximum power point tracker (MPPT) for PV system applications. Many mathematical PV models for in computer simulation have been built for over the past three decades (Angrist, 1982; Tsai et al., 2008). These models elaborately describe the output characteristics mainly affected by the solar insolation, cell temperature, and load voltage. In fact, the infrared (IR) region of the solar spectrum with about 42% solar energy generates waste heat and contributes to the increase of operating temperature in conventional semiconductor- based solar cells. The cell temperature is mainly dependent on the irradiance intensity and ambient temperature (Messenger and Ventre, 2000). In addition, the increase in irradiance would enhance the photocurrent but results in additional temperature degradation of PV current and power outputs (Patel, 1999). The previous work (Tsai et al., 2008) found that all PV models are built without considering the effect of sunlight intensity on cell temperature. This motivates me to develop a sunlight intensity-oriented PV model by taking the insolation effect on cell temperature into consideration. Recently, a number of powerful component-based electronics simulation software packages, such as SPICE and Matlab/Simulink, have become popular in the design and development of power electronics applications. A solar cell library that was new in R2008b is in SimElectronics 1.3 toolbox of Simulink. However, these models implemented by SPICE and Matlab/Simulink are not suitable for real applications because that they do not consider the effect of sunlight intensity on cell temperature. To integrate PV models with the wind turbine models in Matlab/ Simulink SimPowerSystem tool is more suitable for analysis and design of renewable power system. Based on the generalized PV model (Tsai et al., 2008), this paper further implements a novel PV model by directly taking the effect of sunlight intensity on cell temperature. The main contribution of this paper is the implementation of an insolation-oriented PV model, which can justify the user’s strategy of MPPT algorithm by taking account of the sunlight insolation effect on the cell temperature. The verification of the proposed PV model has bee confirmed by conducting a series of measurement through an experimental rig.




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