6545(Print), ISSN (Online) Volume 4, Issue 1, January- February (2013), IAEME & TECHNOLOGY (IJEET)

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1 INTERNATIONAL International Journal of Electrical JOURNAL Engineering OF ELECTRICAL and Technology (IJEET), ENGINEERING ISSN 0976 & TECHNOLOGY (IJEET) ISSN (Print) ISSN (Online) Volume 4, Issue 1, January- February (2013), pp IAEME: Journal Impact Factor (2012): (Calculated by GISI) IJEET I A E M E WIND AND SOLAR INTEGRATED TO SMART GRID USING ISLANDING OPERATION K.Raja 1, I.Syed Meer Kulam Ali 2, P.Tamilvani 3, K.Selvakumar 4 1 (Assistant Professor, Dept of EEE, Knowledge Institute of Technology, Salem smartraja13@gmail.com) 2 (Assistant Professor, Dept of EEE, EBET Group of Institutions, Tirupur syed24may@gmail.com) 3 (Assistant Professor, Dept of EEE, EBET Group of Institutions, Tirupur tamilvani.eee@gmail.com) 4 (Assistant Professor, Dept of EEE, Muthayammal Engineering College, Rasipuram selvakse@gmail.com) ABSTRACT Utility grid is disconnected for any reason; the distributed generation still supplies the required power to that section of local loads. This Phenomenon is called islanding operation. When an islanding occurs, the voltages and frequencies in the islanded area cannot be controlled by the grid system. This may lead to damage of electrical equipments and pose a danger to the working personnel. To avoid the occurrence of islanding phenomena, many control schemes have been proposed and devised to sense the islanding. A basic distribution system consists of Distributed Generators such as Photovoltaic panels, Wind turbines and other forms of renewable energy. As these renewable sources produce a Direct current, a DC to AC inverter is needed to convert the Direct current to an Alternating current with the right frequency and harmonics in relative to the AC coming out of the utility grid. A battery storage system can be inculcated into the system to store the excess energy. Due to big disturbance in a micro grid, voltage and frequency fluctuation occurs during transition from emergency mode to islanding mode. However, due to the power fluctuation from renewable energy sources, voltage and frequency deviations occur in islanded power systems. This work presents an islanding operation method of AC smart grid. The power system consists of photovoltaic, wind generators and controllable loads. In this work, the bus voltage and frequency fluctuations of AC grid are reduced by the photovoltaic, the wind generators and the controllable loads. Therefore, the AC bus voltage is maintained within the acceptable range by applying the power control of the photovoltaic and pitch angle control of wind turbine. 27

2 Keywords - Wind Turbine Generator, Photovoltaic, Maximum Power Point Tracker, Permanent Magnet Synchronous Generator, Smart Grid. 1. INTRODUCTION This paper presents about renewable energies such as photovoltaic s and wind energy is important for greenhouse gas reduction and oil substitution. Renewable power resources are safe, clean, and abundant in nature. However, due to the power fluctuation of renewable energy sources, voltage and frequency deviations are occurred in island power systems whose ability to maintain stable supply-demand balance is low. Therefore, it is necessary to control the system frequency and voltage at the supply-side. At supply-side, installation of storage equipment and pitch angle control of wind generator has been proposed for control of distribution power system. However, the installation of storage equipment that needs large storage capacity and the cost of maintenance for battery degradation are not expected. Hence, in case of using the renewable energy plants connected to power system, the supply-side control has limitations. Therefore, the mutual cooperation control with the demand-side is required because it is difficult to maintain the power quality by only the supply-side control. Therefore, the study on the islanding operation of AC smart grid is important. In this paper, an islanding operation of AC smart grid is presented. The proposed AC smart grid consists of PVs, a wind turbine generator (WTG), a generator-side converter, and controllable loads. The AC bus voltage and frequency fluctuation due to the renewable power plants (WTG and PV) and loads is suppressed by the consumed power control of controllable loads based on droop characteristics and the power control of the renewable power plants. The renewable power plants are operated to suppress the AC bus voltage fluctuation by reducing the output power when the controllable loads reach at the rated power. By using the proposed method, stable power supply can be achieved even in the islanding operation. Besides, power companies can expect high quality power supply and can reduce the cost by cooperative control between supply side and demand side. 2. AC SMART GRID CONFIGURATION AND CONTROL SYSTEM 2.1 System Configuration The configuration of the AC smart grid is shown in Fig. (1). The WTG is a gearless 2MW permanent magnet synchronous Generator (PMSG). PMSG has a simple structure and high efficiency and is expected to be installed in next generation WTG systems. The AC smart grid also consists of PV generators, a generator-side converter, a grid-side inverter, controllable loads (Batteries and EWHs) and variable load. The system is connected to a 10MVA diesel generator and variable AC load through the grid side inverter and the transformer. Wind power energy obtained from the windmill is sent to the PMSG. In order to generate maximum power, the rotational speed of the PMSG is controlled by the PWM converter. PMSG s output power and PV s output power are supplied to the AC load through the AC distribution line. And, the remaining power of the PMSG is supplied to the AC load through the grid-side inverter. 28

3 Fig 1 Block Diagram = (, ) Π (1) = (, ) Π (2) Fig 2 Generator-Side Converter Control System 2.2 PMSG Model The windmill output power Pw and the windmill torque are given by the following equations: =0.22( 4 5). Γ (3) Γ Γ=.. where, Vw is the wind speed, ρ is the air density, R is the radius of the windmill, Cp is the windmill power coefficient, λ = ωwr/vw is the tip speed ratio, ωw is the angular rotor speed for the windmill and β is the pitch. The Fig (2) shows the generator side converter controls the rotational speed of the PMSG in order to achieve variable speed operation with maximum power The Fig (3) shows the pitch angle control system of wind turbine. (4) Fig 3 Pitch angle control system 29

4 Where, φf is the permanent magnetic flux, Ld and Lq are the dq-axis inductance, and i1q is the q-axis current. The error between the dq-axis current commands, i1d and i 1q, and the actual dq-axis currents is used as the input of the current controller. The current controller produces the dq axis voltage commands v 1d and v 1q after decoupling. The rotor position θe used for the transformation between abc and dq variables is calculated from the rotational speed of PMSG. MPPT control is applied when the wind speed Vw is less than the rated wind speed Vwref=12m/s. When the wind speed Vw is greater than the rated wind speed Vwref, then the output power of the PMSG is controlled by the pitch angle control system. For the wind speed range between 5m/s and the rated wind speed, the pitch angle is selected to be β=2 because the energy of the windmill is largest at β=2. When the wind speed is between the rated wind speed and 24m/s, Pw is 1 pu so that pitch angle β is selected to keep the windmill output Pw=1 pu. For the other wind speed range, Pw is 0 pu and the pitch angle is fixed at β=90. Fig. 3 shows the pitch angle control system that determines the pitch angle β, where the output power error e is used as the input of the PI controller. The pitch angle control system includes a hydraulic servo system. The system has nonlinear characteristics and can 3. AC DISTRIBUTION VOLTAGE AND FREQUENCY CONTROL BY DROOP CHARACTERISTICS This section describes the control of decentralized controllable loads according to droop characteristic. By using the droop control, the AC network needs no central control and no communication between the different elements of the network. In the AC grid, AC bus voltage fluctuations occur due to the output fluctuation produced by WTG, PV and loads. The suppression of this fluctuation is achieved by controllable loads connected to the AC grid. Determination of the power consumption command is needed for each controllable load which has different capacity. Therefore, the controllable loads are controlled according to the droop characteristics and load is shared according to the capacities of controllable loads. The droop characteristics of EWHs for AC bus voltage are shown in Fig (4). When the AC bus voltage rises, the droop characteristics are configured such that the bigger the capacity. When the DC bus voltage rises, the droop characteristics of batteries are configured such that the bigger the capacity of battery is, the more the charging power of battery are. Additionally, when the DC bus voltage falls, the droop characteristics are also configured such that the bigger the capacity of battery is, the more the discharging power of battery are. The droop characteristics of EWH and battery are presented by the following equations: = (5) = (6) Fig 4 Droop characteristic of controllable loads 30

5 Where RE and RB are expressed by the following equations = (7) = (8) The grid side inverter control system with the feedback loop, here voltage and frequency is maintained. Bus voltage and frequency maintained within the acceptable range by applying power control of photovoltaic's and wind generator. 4. SIMULATION DIAGRAM The Fig 5 shows the voltage and frequency fluctuations are reduced by Photovoltaics and varying pitch angle of wind generator. In that wind turbine and photovoltaic are connected to AC bus through the converter and inverter circuit the controllable load is connected to Ac bus. When a big grid disturbance occurs, voltage and frequency fluctuate during transition from emergency mode to islanding mode of a micro grid so we can control the power of wind turbine and PV cell. Fig 5 Simulink diagram Thus the overall simulation diagram as shown in Fig 5. In this simulation model consists of Solar and Wind power generation. And also hybrid inverter placed in the output of the simulation diagram. Fig 6 shows the Simulink diagram for Wind Power generation. In this simulation consists of Wind Turbine, Asynchronous Generator and Controller. 31

6 Fig 6 Simulink Model for Wind Power Generation And Fig 7 and Fig 8 shows Simulink model of Boost Converter and Simulink model of inverter for Photo Voltaic in the Smart Grid system. Fig 7 Simulink Model for Boost Converter PWM inverter model is shown in Fig 8. There are used six IGBT switches in normal PWM inverter. Fig 8 Simulink Model for Inverter for PV 5. RESULTS AND ANALYSIS From the simulation model, PV array generating 22V after that 22V boosted to 257V using boost converter and wind turbine output 440V, the output of the boost converter DC voltage, DC voltage converted into AC.Finally PV generating voltage and wind turbine generating voltage are integrated to grid so we can avoid the voltage and frequency fluctuation in the grid. 32

Fig 9 shows the output voltage of Photo Voltaic Cell. It generates 22.265 V. Fig 9 Output of PV Cell Thus the input voltage of 22.265 V to the boost converter. This is shown in Fig 10.

7 Fig 9 shows the output voltage of Photo Voltaic Cell. It generates V. Fig 9 Output of PV Cell Thus the input voltage of V to the boost converter. This is shown in Fig 10. Fig 10 Input of Boost Converter Output of the boost converter output voltage is shown in Fig 11. It produces V and given to the normal PWM Inverter. Fig 11 Output of Boost Converter Wind generator generates 440 V. This is shown in Fig 12. Fig 12 Wind Turbine Output Waveform 33

Fig 13 Output Waveform The Fig 13 shows the overall output waveform. After integration of solar and wind turbine the deviation of output voltage can be reduced.

8 Fig 13 Output Waveform The Fig 13 shows the overall output waveform. After integration of solar and wind turbine the deviation of output voltage can be reduced. By controlling the pitch angle and boosting of PV system. 6. CONCLUSION Due to big disturbance in a micro grid, voltage and frequency fluctuation occurs during transition from emergency mode to islanding mode. The AC bus voltage and frequency fluctuation is suppressed considerably by the use of renewable energy sources, such as wind turbine and PV array. Voltage and frequency fluctuations caused are reduced by applying power control of photovoltaic and varying pitch angle of wind generator. Stable power supply can be achieved even during islanding operation. REFERENCE [1] Tomonobu Senjyu, Ryosei Sakamoto, Tatsuto Kinjo, Katsumi Uezato, and Toshihisa Funabashi, Output Power Leveling of Wind Turbine Generator by Pitch Angle Control Using Generalized Predictive Control, The Papers of Joint Technical Meeting on Power Engineering and Power Systems Engineering, IEE Japan, PE-04-77/PSE-04-77, pp , (in Japanese) [2] Tomonobu Senjyu, Tatsuto Kinjo, Katsumi Uezato and Hideki Fujita, Terminal Voltage and Output Power Control of Induction Generation by Series and Parallel Compensation Using SMES, T. IEE Japan, vol. 123-B, no. 12, pp , (in Japanese) [3] Youichi Ito, Zhongqing Yang, and Hirofumi Akagi, A Control Method of a Small-Scale DC Power System Including Distribution Generators,T. IEE Japan, vol. 126-D, no. 9, pp , (in Japanese). [4] E. B. Muhando, Tomonobu Senjyu, Atsushi Yona, Tatsuto Kinjo, and Toshihisa Funabashi, [5] Disturbance rejection by dual pitch control and self-tuning regulator for wind turbine generator parametric uncertainty compensation, IET Control Theory And Applications, vol. 1, pp , [6] Ming Yin, Gengyin Li, and Ming Zhou, Modeling of the Wind Turbine with a Permanent Magnet Synchronous Generator for Integration, IEEE Trans. on Power Electronics, vol. 6, no. 25, pp , [7] Tomonobu Senjyu, Ryosei Sakamoto, Naomitsu Urasaki, Toshihisa Funabashi, Hideki Fujita, and Hideomi Sekine, Output power leveling of wind turbine generator for all operating regions by pitch angle control, IEEE Trans. on Energy Conversion, vol. 21, no. 2, pp ,

[8] De Battista, H., Puleston, P.F., Mantz, R.J., and Christiansen, C.F., Sliding mode control of wind energy systems with DOIG power efficiency and torsional dynamics optimization, IEEE Trans.

949 958. [10] Haider M. Husen, Laith O. Maheemed and Prof. D.S.

182-196, Published by IAEME. [11] Nadiya G. Mohammed, Haider Muhamad Husen and Prof. D.S.

9 [8] De Battista, H., Puleston, P.F., Mantz, R.J., and Christiansen, C.F., Sliding mode control of wind energy systems with DOIG power efficiency and torsional dynamics optimization, IEEE Trans. Power Syst., 2000, 15, (2), pp [9] Bhowmik, S., Spee, R., and Enslin, J, Performance optimization for doubly-fed wind power generation systems, IEEE Trans. Indust. Appl., 1999, 35, (4), pp [10] Haider M. Husen, Laith O. Maheemed and Prof. D.S. Chavan, Enhancement Of Power Quality In Grid-Connected Doubly Fed Wind Turbines Induction Generator, International Journal of Electrical Engineering & Technology (IJEET), Volume 3, Issue 1, 2012, pp , Published by IAEME. [11] Nadiya G. Mohammed, Haider Muhamad Husen and Prof. D.S. Chavan, Fault Ride- Through Control For A Doubly Fed Induction Generator Wind Turbine Under Unbalanced Voltage Sags, International Journal of Electrical Engineering & Technology (IJEET), Volume 3, Issue 1, 2012, pp , Published by IAEME. [12] Dr. Damanjeet Kaur, Smart Grids and India, International Journal of Electrical Engineering & Technology (IJEET), Volume 1, Issue 1, 2010, pp , Published by IAEME. K.Raja received B.E (Electrical and Electronics) & M.E (Power System) in 2010and 2012, respectively. Now he is working as an Assistant Professor in Knowledge Institute of technology in the Dept of Electrical and Electronics Engineering. His areas of interest are Power-Electronic applications in Renewable Energy Systems, Hybrid Renewable Systems, Isolated Wind Electric Generator and Power Quality. I.Syed Meer Kulam Ali was born in Tamil Nadu, India. He received B.E degree in Electrical and Electronics Engineering and M.E degree in Power System Engineering in Anna University Chennai. Now he is working as an Assistant Professor in EBET Group of Institutions, Tirupur in the Dept of Electrical and Electronics Engineering. His areas of interest are Power Electronic and its applications, Renewable Energy Systems and Power System. P.Tamilvani was born in Tamilnadu, India. She received B.E degree in Electrical and Electronics Engineering in Bharathiyar University and M.E degree in Power Electronics and Drives in Anna University Coimbatore. Now she is working as an Assistant Professor in EBET Group of Institutions, Tirupur in the Dept of Electrical and Electronics Engineering. Her areas of interest are Power Electronic and its applications and Renewable Energy Systems. K.Selvakumar received B.E degree in Electrical and Electronics Engineering in Anna University Chennai and he pursuing the M.E degree in Power System Engineering in KSR College of technology, Tiruchengode. He is currently working as a Assistant Professor in Muthayammal Engineering college, Rasipuram. His research interests include Unit Commitment, Economic Dispatch, Power System Optimization and smart grid, Distributed generation in power system. 35

International Journal of Advanced Research in Electrical, Electronics and Instrumentation Engineering. (An ISO 3297: 2007 Certified Organization)

International Journal of Advanced Research in Electrical, Electronics and Instrumentation Engineering. (An ISO 3297: 2007 Certified Organization) Modeling and Control of Quasi Z-Source Inverter for Advanced Power Conditioning Of Renewable Energy Systems C.Dinakaran 1, Abhimanyu Bhimarjun Panthee 2, Prof.K.Eswaramma 3 PG Scholar (PE&ED), Department