Boletín Técnico, Vol.55, ssue 3, 2017, pp.329-334 Simulation of Solar Generation System for MPPT Xiao Xue School of Electronic and Electrical Engineering, Nanyang nstitute of Technology, Nanyang 474304, Henan, China Yangbing Zheng* College of Mechanical and Electronic Engineering, Nanyang Normal University, Nanyang 473061, Henan, China *Corresponding author(e-mail: zhengyb505@163.com) Jiantao Yu School of Electronic and Electrical Engineering, Guangxi Normal University, Guilin 474304, Guangxi, China Abstract This research mainly uses the platform of MATLAB software to imitate and simulate the characteristics of PV cell, maximum power point (MPPT) tracking of solar energy, control of inverter and grid-connected systems in the entire PV generation syste First of all, a simulation model of the solar cell is established; secondly, incremental conductance is used for MPPT control strategy program; thirdly, modeling and simulation are set for MPPT (Maximum Power Point) strategy as well as SPWM (Sinusoidal Pulse-Width Modulation) and boost module. At last, SPWM double-loop control program is adopted for strategy in PV grid-connected. The simulation results show that the strategies in the study have greatly enhanced the overall performances of solar power system, and improved the efficiency of solar power circuit. Key words: PV generation, Maximum Power Point (MPPT), nverter Grid, Dual-loop Control Strategy 1. NTRODUCTON The so-called solar generation system is to convert the energies of solar energy with the special materials into the electric energies for application. The PV system is divided into the off-grid and grid-connected generation systems. The grid-connected solar generation system is the systematic simulation mainly introduced in this article. Energies from the PV generation are directly transmitted to the grid, where the entire electric energy shall be distributed by the grid syste Existing studies have shown that, at the case of single-phase grid-connected, the researches and algorithms are limited in improving the performances of solar power circuits and cannot solve the circuit performance problems completely (Li, 2010; Li, Zhou and Liu, et al., 2008; Miu and Li, 2011). So, in the article, the study mainly fuses on the modeling, simulation and analysis of the control strategies, output characteristics of solar panel, MPPT, boost converter, PV inverter, grid-connected etc. with the simulink function in MATLAB. 2. PRNCPLES AND CHARACTERSTC ANALYSS ON PV CELL As the energy source of the whole system, solar panel converts the solar radiation energy into the electric energy that we can make use of, during which the photo voltaic effect has played the core role. Establish the mathematical formula model is established by means of deduction and calculation, on basis of which, establish the simulation model with the MATLAB and work out the initial illumination and temperature as 1000W/ m2 and 25, the light intensity R =1000W/m 2, cell temperature T =25 ; Set the short-circuit current as SC, open-circuit voltage as V OC; m and V m are respectively used to represent the current and voltage corresponded to the maximum power point of the PV cell while the output voltage is V, so that the output current shall be: VR C2V (1 C ( e 1)) D 1 (1) n which, ( Vm ) m C2V C1 (1 ) e (2) 329
Boletín Técnico, Vol.55, ssue 3, 2017, pp.329-334 Vm m C2 ( 1) / ln(1 ) (3) V V V ( T T ) R D (4) R s D R ( T T ) ( R 1) (5) n this formula, α is the temperature coefficient of current (Amps/ ); B is the temperature coefficient of voltage (V/ ); n the actual test, the specific values of monrystalline silicon or polycrystalline silicon are: 0.0012 (6) 0.005V (7) Rs is the electric resistance (Ω) of the solar panel which is deduced by the following formula: R s N N P R s. N N ( A ln(1 )... ) / s V m V P. A Tc V V. N Tc 3 n which, ε- energy band on the panel of cell panel is 1.12 ev (silicon);, V -Current and Voltage at the maximum power point;., V. -Short-circuit current and Open-circuit voltage;, V -Temperature coefficients corresponded to short-circuit current and open-circuit voltage; N-Number of TJC; N S- Number of TJC Array; N P- Number of Parallel Photovoltaic Array Module; Tc - Reference Temperature. 3 MPPT TECHLOGY ANALYSS ON SOLAR CELL Solar cell outputs different voltages and currents under different external conditions. When the system output is at the maximum power point, the electric energy is output at the maximum conversion efficiency. f we could monitor in real time and control the cell to be in this state all time regardless the different external environments, the real-time solar generation system can be output at the maxim power so as to improve the energy conversion efficiency to a great extent and this is the so-called maximum power point tracking (MPPT). The MPPT includes constant voltage method, perturbation & observation method and incremental conductance. Upon the comprehensive analysis, incremental conductance is adopted in this design as the MPPT control method (Cui, Cai, Li et al., 2015). 3.1. MPPT Control Model in ncremental Conductance ncremental Conductance is to deduce the maximum power point by means of derivation as its basic principle so as to propose the MPPT algorithm applied in this design. Fig. 1 has provided the curve graph of the power changing with the voltage. From this figure, it can be seen that the output of solar PV dell only has one peak value, which means it has one maximum only, namely dp / du 0 ; this point is the maximum power point where we seek. (8) (9) 330
Boletín Técnico, Vol.55, ssue 3, 2017, pp.329-334 Figure 1. Diagram of PV Cell P-U Output and ts Derivative The output power of the solar cell panel here is: P U (10) Conduct the derivation calculation on the voltages at both sides of the equality sign, we can obtain: Obviously, when the derivative is equal to 0 as we seek, so that: dp du Ud (11) du d du (12) U d Theore, we can tell the state of the system directly from whether the specific value of is du U greater, smaller or equal to 0. The entire system is at the place of the maximum power only when it is equal to 0. The control flow is as shown in Figure 2. Run Yes U=U+dU Samples Upv and pv and calculates pv du=0? d/du=-/u? d/du>-/u? U=U-dU Yes d=0 d>0 U=U-dU U=U+dU Po=PdV,Uo=Upv,o=pv Over Figure 2. Flow Chart of Control Algorithm in ncremental Conductance 3.2. Boost nverter Model For the DC voltage inverter, we can regulate the voltage matching of solar cell by changing the output duty ratio of PWM. We mainly adopt boost to achieve the function of matching the voltage for two major benefits, the first one is Boost converter could reduce the energy loss; the second one is that in terms of the inverter grid- 331
Boletín Técnico, Vol.55, ssue 3, 2017, pp.329-334 connected, the program in this design requires higher start-oillating DC voltage (Mao, Yu and Su, 2015; Wang, Ye, Sinha and Yuan, 2013). ts simulation model is as shown in Figure 3: 4. PV GRD-CONNECTED CONTROL STRATEGY Figure 3. BOOST Simulation Model n this section, we will realize functions of inverter and PV grid-connected by means of modeling and simulation. We select the full-bridge inverter and the program of LC filtering for control and regulation in the current-mode input control method. We adopt the program of voltage source for input and current supply for output to simulate and analyze the contravariant at the same time of choosing the method of triangle wave comparison for analog simulation; the control program of double closed loop is adopted while the grid feedforward control program is added. The modeling of grid-connected part is as shown in Figure 4 (Li and Zhu, 2012; Yu and Pan, 2015; Purk, Kirn and Yu, 2009). Figure 4. Schematic Figure of Grid-connected Part 4.1. Result of System Simulation The simulation results of all system modules are as follows: Figure 5. P,V, Diagram of Output of PV Cell Figure 6. Result Diagram of MPPT Module Output 332
Boletín Técnico, Vol.55, ssue 3, 2017, pp.329-334 Figure 7. Output Diagram of Boost Circuit Output Figure 8. Reactive Power (purple) and Active Power of the Power Grid Figure 9. Grid-connected Output Voltage Figure 10. Grid-connected Output Voltage Frequency 5 CONCLUSON Figure11. THD Harmonic Component Content Electric energy is the most widely applied energy utilization pattern in the modern siety. n case of the increasingly exhausted current energy resources, the development of new clean energy has become an effective approach to solve the energy and environment problems. n this design, it fuses on analyzing and simulating the grid-connected application of PV generation while solving the issues of control strategy for the solar energy MPPT. Here are the main contents of this research: (1) Taking various influencing factors, it adopts the M Simulink function to conduct the modeling and simulation analysis on the solar cell. (2) t adopts the increment conductance as the control method for this design to establish the MPPT simulation model and the final results prove that this program could well achieve the maximum power point tracking. 333
Boletín Técnico, Vol.55, ssue 3, 2017, pp.329-334 (3) t analyzes and introduces the several modulation hemes of the photovoltaic inverter and verifies the correctness of the selected control strategies by means of simulation. ACKWLEDGEMENTS This work was supported by the Henan Provincial Key Scientific Research Project in 2017 (Grant No. 17A480008), by the ndustry-university-research projects of Henan Provincial Department of Science and Technology: Study of the Dynamic Monitoring system for Underground Coal Preparation Chamber and Study of the Wireless Head Movement Mobile System, and by the Youth Project for Theoretical Science Foundation of Nanyang Normal University, China (Grant No. QN2017063). REFERENCES Cui Yan, Cai Binghuang, Li Dayong, Hu Hongli, Dong Jingwei (2015) Comparative Studies on the MPPT Control Algorithms of Solar Energy Photovoltaic System, Acta Ecologica Sinica, 27(6), pp. 533-539. Li Anding (2010) Solar Energy Photovoltaic System Engineering, Beijing University of Technology Publishing House, pp. 101-103. Li Qiuhua, Zhou Lin, Liu Qiang, Zhang Feng, Wu Jian (2008) Simulative Research of MPPT for Photovoltaic Power System, Electric Power Automation Equipment, 28(7), pp. 21-25. Li Wei, Zhu Xinjian (2012) The control simulation model of MPPT control for PV system, Computer Simulation, 23(6), pp. 239-243. Minwon Purk. Bong-Tue Kirn, n-kmn Yu (2009) A Novel Simulation Method for PV Power Generation Systems Using Real Weather Conditions. EEE SE, pp. 526-530. Miu Renjie, Li Shulan (2011) Solar Energy Utilization Status and Development Prospect, Applied Energy Technology. 20(3), pp. 28-31. Mao Meiqin, Yu Shijie, Su Jianhui (2015) Versatile Matlab Simulation Model for Photovoltaic Array with MPPT Function. Journal of System Simulation, 17(5), pp. 1248-1251. Wang T C Y, Ye Z H, Sinha G, Yuan X M.(2013) Output filter design for a grid-interconnected three-phase inverter. Pr. PESC, pp. 779-784. Yu Huajun, Pan Junmin (2015) Simulation Analysis of Output Features and the Maximum Power Point Tracking of PV Cells, Computer Simulation, 22 (6), pp. 248-252. 334