Two Variable-Weather-Parameter Models and Linear Equivalent Models Expressed by Them for Photovoltaic Cell

Shaowu Li,Xiaohong Ma,Qin Li,Wenhai Qi,Kunyi Chen,Qing Ai

doi:10.1109/access.2020.3029651

Abstract

For the conventional four-parameter model of photovoltaic (PV) cell, to simplify the number of its mathematical equations, in this paper, a variable-weather-parameter cell model (VWP model) is proposed. Furthermore, to decrease the number of its model parameters, a simplified variable-weather-parameter cell model (SVWP model) is also proposed. Based on them, the model parameters of linear equivalent models can be replaced by the conventional four-parameter model parameters, which finds the direct relationships between linear equivalent cell model and four-parameter cell model. Finally, some simulation experiments are done by comparing the proposed VWP and SVWP models with conventional four-parameter model of PV cell. The results show that, on the one hand, their output characteristics almost correspond with each other. On the other hand, these proposed cell models are very accurate under varying irradiance or temperature conditions. Meanwhile, some simulation experiments also verify that the linear equivalent models expressed by the VWP model and SVWP model are feasible, available and reasonable. By this work, both the conventional four-parameter model and linear equivalent models are greatly evolved and improved. On the one hand, the conventional four-parameter model can be greatly simplified, which makes its modeling and application easier. On the other hand, the bridge between it and linear equivalent models can be built successfully, which makes these linear models more standard and practical.

Highlights

Hitherto, many research works on the mathematical models of PV cell, especially for its one-diode model and fourparameter model, have been done
It is obvious that, according to Eq (19), the simplified variable-weather-parameter (SVWP) model of PV cell is only determined by Isc(S, T ), Voc(S, T ), C1 and C2, which makes the VWP model expressed by Eqs. (8)-(10) greatly simplified when S and T keep varying
DIRECTIONS In this paper, a VWP model of PV cell, which can simplify the number of the mathematical equations of the conventional four-parameter model from five to three, has been proposed

Summary

INTRODUCTION

Many research works on the mathematical models of PV cell, especially for its one-diode model and fourparameter model, have been done. [13], a VWP MPPT method for PV system was proposed by a defined characteristic resistance based on PV cell By these works, the mathematical expressions of the fourparameter cell model is still not simplified, especially for the number of its mathematical equations. It is obvious that, according to Eq (19), the SVWP model of PV cell is only determined by Isc(S, T ), Voc(S, T ), C1 and C2, which makes the VWP model expressed by Eqs. According to Ref [20], at the MPP, PV cell can be linearized as the Thevenin equivalent model (Fig.6(a)) and Norton equivalent model (Fig.6(b)) Their model parameters including RsM , VsM and IsM can be expressed by Eqs. In a word, according to Eqs. (29), (32) and (34) or Eqs. (30), (33) and (35), the linear equivalent models shown by Fig. 6 can be expressed successfully by the VWP model parameters Im(S, T ) and Vm(S, T )

LINEAR MODELS EXPRESSED BY SVWP MODEL PARAMETERS

DISCUSSIONS

CONCLUSION AND FUTURE DIRECTIONS