Research on Modeling and Simulation of

Detailed Model of Photovoltaic Power

Generation System Yuyu Liu1,2,a,*, Xueshun Ye2, Keyan Liu2, Hairong Luo3

1North China University of Water Resources and Electric Power, Jinshui District, Zhengzhou City, Henan Province, China.

2China Electric Power Research Institute, Haidian District, Beijing Municipality, China 3Electric Power Research Institute of State Grid NingXia Electric Power Company,Jinfeng District,

Yinchuan City, NingXia Autonomous Region, China. a email: lyy9365@126.com

Keywords: Photovoltaic array, MPPT, Photovoltaic Inverter Control Strategy, Digital ana-log Hybrid Simulation Management System

Abstract: With the photovoltaic, fan and other new energy in the proportion of distribution network is growing, the photovoltaic power generation system and the process of accurate simulation is of great significance. Based on Matlab / Simulink, a detailed model of PV ar-ray, detailed model of MPPT controller and detailed model of PV inverter control strategy are established according to the actual principle of grid connection, and the process of grid connection of photovoltaic power generation system is simulated. The photovoltaic grid connected waveforms of the mixed-mode simulation system of distribution network of China Electric Power Research Institute are compared with Simulink model simulation waveforms, and the accuracy of the model is verified. The experimental results show that the detailed simulation model of photovoltaic power generation system can accurately re-flect the grid connection process of photovoltaic power generation system.

1. Introduction

In recent years, with the traditional energy shortage and environmental problems become increasingly serious, and the rapid development of clean energy and distributed power generation technology, photovoltaic, fan and other new energy distributed power generation technology in the proportion of distribution network increased dramatically. Among them, the photovoltaic power generation system because of its flexible application, convenient and so on, in the distribution network has a very good application prospects. The modeling and simulation of the grid-connected process of the photovoltaic power generation system has a guiding effect on the actual photovoltaic power generation system. Therefore, it is very important to establish a realistic simulation model of PV power generation system for the development of PV power generation system.

The 3rd International Conference on Intelligent Energy and Power Systems (IEPS 2017)

Published by CSP © 2017 the Authors 172

Researchers at home and abroad have carried out some research on the modeling and simulation of photovoltaic power generation system. The photovoltaic power generation model is reviewed in [1]. Literature [2] ~ [5] carried out preliminary modeling work on PV array and MPPT. In the literature [6], the characteristics of PV arrays under different conditions were analyzed. The control strategies of the inverter are discussed in [7] ~ [10]. Among them, the control strategy of PQ, V / f and Droop is the focus of these four literatures.

2. Mathematical Model of Photovoltaic System and Simulink Model

As shown in Figure 1, the solar photovoltaic array of photovoltaic power generation system of light into DC power, the boost circuit MPPT controller, and then through the DC / AC inverter con-trol strategy into alternating current through the filter and isolation transformer into the power grid.

SPWMControl Strategy

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MPPT controller

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Distribution network

~Isolation

transformer

Figure 1 PV power generation structure.

The detailed Matlab / Simulink model of each part of the grid-connected model of the photovoltaic power generation system will be established in order to carry out the next step-by-step process simulation study.

2.1. Photovoltaic array mathematical model and Simulink model

2.1.1. Mathematical model of photovoltaic array

Based on the theory of electronics, photovoltaic panels are affected by light to produce photovoltaic effects, solar energy into electrical energy. The equivalent circuit diagram of the PV array is shown in the following figure:

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Figure 2 Photovoltaic array equivalent circuit.

In Figure 2, is the current generated by the photovoltaic effect, is the current flowing into the diode, is the photovoltaic array capacitance, is the photovoltaic parallel resistance, is the photovoltaic series resistance, the photovoltaic array equation:

1 (1)

Formula: q is charge, K is Boltzmann constant, T is temperature. Since some of the parameters in (1) are difficult to determine, the mathematical model commonly

used in the project is:

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As can be seen in Figure 4, if you want the photovoltaic inverter in the photovoltaic power generation system to output the maximum power, the voltage needs to take the red dot position in the figure. Since the light intensity S and the photovoltaic array temperature T have a significant effect on the curve, in practice, S and T are in a state of constant change in general. Therefore, need to constantly track the maximum power point to ensure that the photovoltaic power generation system to maximize the output power.

2.2.1. MPPT controller algorithm

The maximum power MPPT controller research tracking algorithm commonly used constant voltage tracking method (Constant Voltage Tracking CVT (Perturbation), And Observation interference observation method referred to as P&O), the incremental conductance method (Incremental Con-ductance method referred to as INC), the incremental conductance method based on variable step size gradient. In this paper, the MPPT controller is designed based on the incremental conductivity method. The overall flow of the incremental conductivity algorithm is shown in the following figure:

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As shown in Fig. 13, the oscilloscope shows the waveform time: 251.001s to 291.001s, which is the PV output voltage current and the grid current change during the PV stabilization process.

Figure 13 Photovoltaic Grid - Connected Steady Process Voltage Current and Grid - Connected Current Variation Waveform.

It can be seen from the figure that the photovoltaic output voltage and the grid current are not changed obviously, and the PV output current has obvious change process. Affected by the inverter, three-phase current amplitude in a period of time to stabilize in a smaller value, after the A-phase current amplitude in the negative half-axis has a significant fluctuation after a slight increase and stability of about 10s, and then instantaneous increase and stability of about 20s, and then gradually increased 10s after the reduction to 10s before the amplitude, and finally gradually Increase and stabilize.

4.4. Comparison of simulation results

By comparing the results of the two simulations, we can see that Simulink simulation of the photovoltaic output current stability faster, but the process and digital analog hybrid simulation results are basically the same. In addition, the simulation results of grid connected PV system are consistent with the simulation results of the digital analog hybrid simulation. Therefore, the detailed model of the photovoltaic power generation system described in this paper can accurately realize the simulation of the real process of the photovoltaic power generation system.

5. Conclusion

In this paper, Simulink modeling is carried out for the detailed model of photovoltaic power generation system, and the process of grid connection of photovoltaic power generation system is simulated. Based on the distribution network digital analog hybrid simulation management system, the digital analog hybrid simulation of the grid - connected process of the photovoltaic power generation system was carried out. By comparing the waveforms of the two simulation results, the feasibility of the detailed model of the photovoltaic power generation system described in this paper is proved.

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Acknowledgements

This work was supported by Project of Electric Power Research Institute of State Grid NingXia Electric Power Company (PDB11201601764) and Project of National High Technology Research and Development Program (863 Program) funded projects (2015AA050102)

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