Efficient Fuzzy Switch of Hybrid Wind Energy System

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1 , pp Efficient Fuzzy Switch of Hybrid Wind Energy System Young Hoon Ko Department of Computer engineering, Hyupsung University, Abstract. In these days, there are many countries try to use alternative energy like solar, wind, etc. Especially for wind energy, it is already widely used in Denmark, England, etc. But at the case of small wind turbine for home, it should be used with the ESS and combined with electricity for pleasant usage. So the switch is necessary when the electricity should be connected. This paper suggests the fuzzy inference system which makes this demand real. The fuzzy inference system could be implemented easily by lookup table. Keywords: wind energy, fuzzy inference system. fuzzy switch 1 Introduction Since carbon dioxide emissions in the Kyoto Protocol, agreed in 1997 to reduce by 5.2% in the reference year 1990, the world has tried to create a pleasant global environment. Several problems have been derived from Kyoto Protocol. But the Durban Platform in 2011 has been established. Then Finally the Paris Agreement signed in 2015 to join the ambitious goals by all countries which is to tie into the global mean temperature of 1.5 degrees. Coming into the 21st century, Crude oil has had long-term rise in oil prices up to $ 150 on July 2008, which was accelerating the development of alternative energy. However, from 11 July 2008, it began a sharp decline in oil prices and happened the financial crisis, on his way to find stable at $ 100 oil price. And then oil prices began to decline secondly from July The price of oil had plunged to $ 30 which is almost production costs. This makes ironically to be useless of the alternative energy development. In the future, the alternative energy will be widely spread regardless of the price of crude oil. This paper presents a smart power system using a wind power generation, and suggests an efficient system by introducing a Fuzzy switch. Wind generators need the ESS (energy storage system) because of the nature of the wind blowing deviation. Therefore, to the point of view of power consumption, the wind power source should have the ESS. In the switch for efficient consumption by attempts to control by two parameters. Two parameters are the state of charge in ESS and generated power level of Wind turbine. ISSN: ASTL Copyright 2016 SERSC

2 2 Hybrid Wind Power System 2.1 Wind Power Generation Wind turbines are largely divided into two groups that use the PMSG(permanent magnet synchronous generator) and use of induction. The induction generator has the advantage of being cheap and firm. But it has a low power factor and requires surplus power of AC. So the small wind power system tends to use PMSG. And the structure is showed below. The system is relatively simple that the AC power is simply converted by the rectifier diode without additional control circuit. Fig. 1. PMSG Wind Power Generation Structure 2.2 Fuzzy Switch Wind power generation has a weakness of being unable to generate continuously. Wind is changed strong and weak frequently. So the ESS must be used with the wind generators if you don't want black out. Therefore it should be the hybrid power system which use wind power generator with ESS and the electric power. The residents have to consider about the electric charges. The wind power is free but the electricity is not free. In the view of the residents, they have the energy storage connected to both electric power and wind power. If the wind is strong which makes enough power, it requires no electricity. But sometimes the wind is calm so that the electricity should be used for living. So the ESS needs the switch to electricity. In basic way, the residents turn on the switch when the wind is calm. They turn also on when the state of charge of ESS is low. In other way, they should turn off the switch when there is lots of power stored in ESS or the wind is strong enough. If the switch is controlled by residents, they are going to be annoyed in not long time. In the night time, they cannot sleep because of the wind stopping. Copyright 2016 SERSC 123

3 Fig. 2. The Fuzzy switch between electricity and the ESS 2.3 Fuzzy Algorithm The suggested fuzzy inference system has two inputs which are the state of charge in ESS and the level of power generated by wind turbine. The state of charge is divided into three membership functions. High, low, and middle are the three states. They are normal distribution functions. Practically the normal state is not used. Fig. 3. Input membership functions (level of state of charge) 124 Copyright 2016 SERSC

4 Fig. 4. Input membership functions (power) And the level of power is divided into three membership functions. Strong, middle, and weak are these three states. They are normal distribution functions. Practically the middle state is not used. Fig. 5. Output membership functions (switch) This fuzzy system is the mamdani system so that the output is the center of gravity of proportional shapes of output membership functions. Copyright 2016 SERSC 125

5 Fig. 6. Fuzzy rules in graphics Fuzzy rules are considered which conditions have to use electricity. It is when the state of charge is low or when the power of wind generation is strong. For implementation, this fuzzy rules set into a small circuit by lookup table. The table's index are level and power. And the value is hard-decision value like binary number which means the switch is on or off. The surface plot shows this table, and it shows below. Fig. 7. Surface plot of fuzzy inference system 126 Copyright 2016 SERSC

6 5 Conclusion There are many countries to develop the alternative energy especially like wind energy. But in the view of consumption, there should be combined with steady power like electricity. So the switch is necessary for this wind energy. This paper suggests the fuzzy switch which uses mamdani fuzzy inference system. There are two inputs which are the state of charge in the ESS and the power level generated by wind turbine. The fuzzy rules manage the switch so that the ESS always has the stable state of charge. First, when the state of charge in the ESS is low, the probability of connection to electricity is increasing. In this case, if the wind blow is weak, it is difficult to charge from the wind turbine, So this case the electricity will be connected in the most probability. For implementation, fuzzy rules can easily set into ROM in circuit by lookup table. References 1. Kang, M.-S.: Generation Cost Assessment of an Isolated Power System with a Fuzzy Wind Power Generation Model. In: IEEE Transactions on Energy Conversion, vol. 22, iss. 2, pp (2007) 2. Tan, K.-H.: Squirrel-Cage Induction Generator System Using Wavelet Petri Fuzzy Neural Network Control for Wind Power Applications. In: IEEE Transactions on Power Electronics, vol. 31, iss. 7. pp (2016) 3. Pavan Kumar, A. V., Parimi, A.M., Rao, K.U.: Implementation of MPPT control using fuzzy logic in solar-wind hybrid power system. In: IEEE International Conference on Signal Processing, Informatics, Communication and Energy Systems (SPICES), pp (2015) 4. Putri, A.I., Ahn, M., Choi, J.: Speed sensorless fuzzy MPPT control of grid-connected PMSG for wind power generation. In: International Conference on Renewable Energy Research and Applications (ICRERA), pp: 1--6 (2012) 5. An, A., Yang, G., Zhang, H., Du, P.: PMSG maximum wind power tracking control based on T-S fuzzy method. In: The 27th Chinese Control and Decision Conference (2015 CCDC), pp (2015) Copyright 2016 SERSC 127