Microgrid Essay Example

Microgrid Essay Modelling and Simulation of Microgrid Application at RCET Rana A. Jabbar1, Azah Mohamed2, Muhammad Junaid1, Muhammad Ashraf1, Ihsan Ullah1 1Rachna College of Engineering and Technology, Gujranwala, Pakistan 2Universiti Kebangsaan Malaysia (UKM) [emailprotected] edu. pk ABSTRACT Renewable energy resources have got vital importance in present era as fossil fuel reserves are depleting and their prices are fluctuating drastically. The role of these resources in generation of electricity is inevitable in the developing countries like Pakistan, where energy crisis has become a burning issue due to short fall of electricity. Presently the country is suffering from repeated and shocking black outs. Therefore, the generation of electricity through other than traditional resources has become indispensable. In this research paper an innovative concept has been imparted for the development of Microgrid, based upon locally available renewable energy resources, keeping in view the geographical location of Rachna College of Engineering Technology (RCET), Gujranwala-Pakistan. These available renewable energy resources have been integrated to function as a single generating unit for forming Microgrid. The comprehensive modelling and simulation of Microgrid has been performed using MATLAB. The objective behind the development of this proto type model of Microgrid is to design a standby power for RCET Library in case of electricity failure from National Grid. Alternative Energy Development Board (AEDB) of Pakistan is looking for viable solution to compensate the National Grid and emergency need of individual sensitive consumers since long. Simulation and implementation of this developed model will really be very helpful for all stake holders of power industry nationally and internationally. We will write a custom essay sample on Microgrid specifically for you for only $16.38 $13.9/page Order now We will write a custom essay sample on Microgrid specifically for you FOR ONLY $16.38 $13.9/page Hire Writer We will write a custom essay sample on Microgrid specifically for you FOR ONLY $16.38 $13.9/page Hire Writer KEY WORDS Renewable Energy Resources; Microgrid; MATLAB 1. Introduction Microgrid is actually assembly of renewable energy resources able to be operational paralleled or independently from National Grid having capacity up-to Distributed Generation (DG). Microgrid is more modern way for utilizing the available potential of DG, not only in remote area electricity development but also in over coming the short-fall of electricity commercially. Most commonly available renewable energy resources, used for the development of Microgrid, are Solar, Biomass, Micro-hydro, Wind, Fuel Cell etc [1, 2, 3, 4]. Like other developing countries, Pakistan is also suffering from acute energy crisis. The present sources for generation of electricity in Pakistan include Hydro (33%), Natural Gas (35. 7%), Oil (28. 7%), Coal (0. 3%) and Nuclear (2. 3%). Despite the massive availability of renewable energy resources, their contribution towards generation of electricity in Pakistan is negligible. The Maximum demand of electricity in Pakistan is about 15,000 MW, whereas supply demand gap is about 3000 – 4000 MW. The renewable resources used in this research work are Solar, Biomass, Micro-hydro and Fuel Cell. Pakistan located in the Sun Belt is ideal for taking advantage of solar energy. The mean global irradiation falling on horizontal surface is about 200–250 watt/ m2 per day, equivalent to about 1500–3000 sun shine hours and 1. 9 – 2. 3 MWh/ m2 annually [5]. Being an agriculture country, sufficient live stock is available for producing enough animal dung to be utilized in the production of biogas. Following the latest statistical data of AEDB, the available micro-hydro potential in Pakistan is about 2000 MW. Moreover, there is an immense potential to utilize the flow of water in world’s largest canal network, particularly in province of Punjab, Pk [6]. This paper presents a novel approach of Microgrid development in which micro-level energy generation resources are first incorporated with each other to form one generating station controlled by a central unit and simultaneously integrated with National Grid for both way power flow [7]. Conventionally, these DG resources are not integrated with each other and separately run the load, controlled by individual switches [8, 9, 10, 11, 12]. The power quality issues involved during the conversion from dc source to ac for Microgrid operation have become the subject of research. Moreover, the study of intelligent control for Microgrid is also in progress [13, 14, 15]. In this research paper, the single control unit is responsible for overall functioning of the developed model of Microgrid supported by the physical location of RCET Grw, Pk, where a Marala Nokhar Link Canal flows adjacent to the college. The complete simulation of Microgrid has been performed using MATLAB Simulink for supplying power to RCET library. 2. Geographical Location of RCET Fig. shows the geographical location of RCET indicating the renewable energy resources and library (load). Fig. 1. Geographical location of RCET Detail of Library load (8 kW) is given in Table I. TABLE I Library Load detail |S/No. |Item |Rating (kW) |No. |kW | |1 |AC |2. 60 |02 |5. 20 | |2 |Tube Light |0. 04 |12 |0. 48 | |3 |PC |0. 45 |04 |1. 80 | |4 |Fan |0. 08 |04 |0. 32 | |5 | CFL |0. 02 |10 |0. 0 | |Total Load (kW) |8. 00 | Shaded portion of RCET power distribution network as shown in Fig. 2, is indicating the location of library being fed from the developed Microgrid. [pic] Fig. 2. Single line diagram of RCET power distribution network 3. Real Models of Renewable Energy Resources at RCET The project for Microgrid development at RCET is divided into two main phases: Firstly, modelling and simulation of Microgrid and secondly, implementation of simulated model practically. For this purpose, three real models have been focused at RCET. Fig. shows the practical Biomass arrangement to produce methane gas (CH4) used directly as input to Fuel Cell or the same methane gas can be decomposed to get hydrogen. In this research work hydrogen Fuel Cell is used for simulation purpose. Fig. 3. Biomass plant at RCET Fig. 4 is indicating the PV Array which is available at RCET for solar energy generation. [pic] Fig. 4. PV Array Fig. 5 is showing the Micro-hydro resource which will be utilized for generation of electricity through Microgrid while implementing the simulated model. [pic] Fig. 5. View of Nokhar Canal flowing adjacent to RCET 4. Block diagram of Proposed Microgrid Block diagram of proposed Microgrid is given in Fig. 6. Fig. 6. Block diagram of Microgrid PV Array and Fuel Cell are dc sources where the Micro-hydro is an ac source of power supply. So, for synchronization the both afore mentioned resources will also be converted in ac supply. Two methods are used to convert the dc sources into ac supply. First is the Pulse Width Modulator (PWM) inverter to convert dc supply into ac supply. The second method is the use of Motor-Generator set, in which dc motor is run by dc supply and then that motor will be used as prime mover for generator to provide ac output at the terminals of generator. Their results are also compared in this research work. Moreover, this combined generating unit of Microgrid is also integrated with National grid for both way flow of power. Whenever the generation exceeds the load requirement, the extra power will be supplied to distribution network of National grid, otherwise it will be supplied by National grid 5. Modelling and Simulation Comprehensive modelling and simulation of Microgrid to run 8 kW load of RCET Library has been performed using MATLAB software. The detail of mentioned software used for simulation is as under: MATLAB  ®, the Language of Technical Computing Version: 7. 6. . 324 (R 2008a), February 10, 2008 License Number: 161051 Fig. 7 shows the Interconnected Microgrid in which all the three renewable energy resources are connected to run the Library load. Moreover, this generating unit is further interconnected with Power distribution system (National Grid) for both way power supply. [pic] Fig. 7. Microgrid Simulation Model Br ief description of resources (PV Array, Fuel Cell and Micro-hydro) used in simulation is as under: 5. 1. PV Array For simulation purpose, PV Array is replaced with a 12 v dc battery, which is boosted up by use of DC/DC Boost Converter up to 320 v dc as shown in Fig. . [pic] Fig. 8. DC Battery DC/DC Boost Converter Fig. 9 is indicating the PWM operation, to convert 320 v dc supply into 400 v ac. [pic] Fig. 9. PV Array Simulation Model using PWM Inverter The above simulation is also performed using Motor-Generator set. Fig. 10 is the Simulink model for PV Array based ac supply generating unit in which Motor-Generator set is used for dc to ac conversion. Output of PV Array is 12 v dc which is boosted up to 240 v dc using DC/DC Boost Converter to run the dc motor. [pic] Fig. 10. PV Array Simulation Model using Motor-Generator Set 5. 2. Fuel Cell Fuel Cell is also dc generation source like PV Array. Here dc is again required to convert into ac supply for integration among the renewable energy resources and also with National grid. For this purpose both PWM Inverter technique as well as the Motor-generator set are used. Fig. 11 shows the hydrogen Fuel Cell in which dc supply is boosted up through DC/DC Boost Converter and after that the same mechanism of PV Array, as shown Fig. 9, is used to convert up to the required ac voltage level [pic] Fig. 11. Hydrogen Fuel Cell Fig. 12 shows the internal model of Motor-Generator set for dc to ac conversion used in Fuel cell. pic] Fig. 12. Fuel Cell Simulation using Motor-Generator set PWM inverter is commonly used for dc to ac conversion. However, Motor-Generator set has also been practiced during this research work. Due to certain inherited characteristics, like increase in technical losses, vibration at starting etc, PMW is preferred considering operational and economic comparison. 5. 3. Micro-hydro Micro-hydro is an ac source of power supply. For simulation purpose, Micro-hydro is replaced with a synchronous generator. Fig. 13 indicates the internal model of Micro-hydro. [pic] Fig. 13. Micro-hydro simulation structure 6. Comparison of PWM and Motor-Generator Set output In the following sections, comprehensive comparison of PWM and Motor-Generator set techniques is given graphically along with tabular form. This comparison reveals that the latter mechanism is suffering from unavoidable fluctuation initially, resulting in undue operational and economic constrains. Keeping in view the above scenario, PWM technique is more advantageous. 6. 1. PWM Inverter The results for PV Array obtained in result of simulation performed using Fig. 7 are given in Fig. 14. Fig. 14. PV Array output Vinv shows the 320 v ac PWM output. VLoad is the desired level of voltage that appears at the load terminals. PL is the Library load. During time interval (0–0. 4) sec, PV Array shares 2. 67 kW (out of 8 kW) of Library load and rest of the 3. 3 kW is supplied to National grid. From (0. 4–1. 0) sec PV Array is supplying total generating power (6 kW) to National Grid. The results for Fuel Cell got in result of simulation performed using Fig. 7 are given in Fig. 15. [pic] Fig. 15. Fuel Cell results During time interval (0–0. 4) sec Fuel Cell shares 2. 7 kW of Library load and supplies 3. 3 kW to National Grid. From (0. 4–0. 7) sec it shares 4 kW of Library load. From (0. 7–1. 0) sec it provides total generated power (6kW) to National Grid. Following the previous pattern, results regarding Micro-hydro are shown in Fig. 16. Fig. 16. Micro-hydro output During time interval (0–0. 4) sec Micro-hydro shares 2. 67 kW of Library load. From (0. 4–0. 7) sec it shares 4 kW and from (0. 7–1. 0) sec it provides all 6 kW to Library Load and reaming 2 kW are contributed from National Grid. The previous results are summarized in Table II: TABLE II Microgrid Power Flow using PWM Inverter |Time |PV Array (kW) |Fuel Cell (kW) |Micro-hydro ( kW) | |Interval | | | | | |PL |Psys |PL |Psys |PL |Psys | |(0–0. 4) sec|2. 67 |-3. 30 |2. 67 |-3. 30 |2. 67 |-3. 30 | |(0. 4 –0. 7) |0 |-6. 0 |4. 0 |-2. 0 |4. 0 |-2. 0 | |sec | | | | | | | |(0. 7 – 1. 0)|0 |-6. 0 |0 |-6. 0 |6. |2. 0 | |sec | | | | | | | 6. 2. Motor-Generator Set Simulation referring to Fig. 7 using dc Motor-Generator set in comparison with PWM inverter is described graphically in this section. Results are also summarized in tabular form. Figs. 17, 18 and 19 are the graphical results of PV Array, Fuel Cell and Micro-hydro respectively using Motor-Generator set for dc to ac conversion where required. Results discussed earlier indicate the initial fluctuation in case of Motor-Generator set is prominent. Fig. 17. PV Array output (Motor-Generator Set) [pic] Fig. 18. Fuel Cell output (Motor-Generator Set) [pic] Fig. 19. Micro-hydro output (Motor-Generator Set) The results are tabulated as under: TABLE III Microgrid Power Flow using Motor-Generator set |Time |PV Array (kW) |Fuel Cell (kW) |Micro-hydro ( kW) | |Interval | | | | | |PL |Psys |PL |Psys |PL |Psys | |(0–6. 5) |2. 67 |-3. 30 |2. 67 |-3. 3. 0 |2. 67 |-3. 3. | |sec | | | | | | | |(6. 5–14) |4. 0 |-2. 0 |4. 0 |-2. 0 |0 |-6. 0 | |sec | | | | | | | |(14–20) |0 |-6. 0 |6. 0 |2. 0 |0 |-6. 0 | |sec | | | | | | | 7. Islanding with National Grid To cope with the contingencies, islanding of the simulated Microgrid with National grid is shown in Figs. 20 and 21 respectively. [pic] Fig. 20. Islanding with National Grid pic] Fig. 21. Internal Structure of Fig. 20 It is clear from Fig. 21 that Microgrid is running 6 kW load. At time 0. 3 sec, 1. 5 kW is added with the system, and at 0. 5 sec another 2 kW is connected wit h the system and at 0. 7 sec additional 2. 5 kW load is connected with the system. Now total load connected to Microgrid (interconnected with National grid) is 12 kW, where 6 kW is shared by Microgrid while remaining 6 kW is supported by National Grid. Fig. 21 shows the results measured by scope in which at time interval 1 sec. the breaker of National Grid is open. The purpose behind this is to produce an artificial over current fault when all the 12 kW load is supposed to be shared by Microgrid, resulting in voltage drop at output terminals of Microgrid. During this operation, the over current and under voltage relays will be operated and consequently additional 6 kW load will be disconnected as indicated in Fig. 21(the position of breaker went to ‘0’ at time 1. 0 sec). [pic] Fig. 21. Islanding results The islanding operating is summarized in table IV as: TABLE IV Islanding operation |Time |Load Shared by|Load Shared by |Breaker |Total Load | Interval |Microgrid |National grid |Position | | |(sec) | | | | | |0 – 0. 3 |6. 0 kW |0 kW |ON (1) |6. 0 kW | |At 0. 3 |6. 0 kW |1. 5 kW |ON (1) |7. 5 kW | |At 0. 5 |6. 0 kW |3. 5 kW |ON (1) |9. 5 kW | |At 0. 7 |6. 0 kW |6 kW |ON (1) |12. 0 kW | |At 1. 0 |12. 0 kW |0 |OFF (0) |12. 0 kW | |1. 0 (Relay |6. 0 kW |0 |OFF (0) |6. kW | |operates) | | | | | 8. Conclusions This novel approach comprising of locally available renewable energy resources and integration of these resources for up-gradation to commercial use will really help the National Electric Power Regulatory Authority (NEPRA), Alternative Energy Development Board (AEDB) and Pakistan Electric Power Company (PEPCO) to set their directions while planning about generation of electricity from renewable energy resources to minimize huge gap between demand and supply. Comparing traditional and latest instrumental techniques is really interesting during this research work. Innovative model developed will also help the scientific community at national and international level. For further investigations like the influence of the factors influencing power quality issues is in progress. References [1] Robert H. Lasseter, â€Å"Microgrids and Distributed Generation†, Journal of Energy Engineering, American Society of Civil Engineers, September 2007. [2] Robert H. Lasseter, Final Project Report, â€Å"Control and Design of Microgrid Components†, Power Systems Engineering Research Center, University of Wisconsin-Madison, PSERC Publication 06-03, January 2006, pp. 20-41. [3] Robert H. Lasseter, â€Å"Microgrids,† in Proc. IEEE Power Engineering Society, Winter Meeting, Jan. 27–31, 2002, pp. 305–308. [4] H. Nikkhajoei and R. H. Lasseter, â€Å"Microgrid Protection†, IEEE PES, General Meeting, 24-28 June 2007, Tampa, FL. [5] Sohul A. Qureshi, â€Å"Scope of renewable Energy Resources n Pakistan†, New Horizons, Journal of Electrical and Electronics Engineers, Pakistan, Vol 54, 2007, pp. 151-159. [6] http://www. aedb. org/microhydel_basics. php [7] Hassan Nikkhajoei and Robert H. Lasseter, â€Å"Microgrid Fault Protection Based on Symmetrical and Differential Current Components†, Public Interest Energy Research California Energy Commission, Report coordinated by the Consortium for Electric Reliability Technology Solutions with funding support from the California Energy Commission, Public Interest Energy Research Program, under Contract No. 00-03-024, December 2006, pp. 11-19. [8] Robert H. Lasseter, â€Å"CERTS Microgrid†, Panel on Microgrids Systems, International Conference on System of Systems Engineering, April 16-18, 2007, San Antonio. [9] R. Lasseter, A. Akhil, C. Marnay, J. Stephens, J. Dagle, R. Guttromson, A. S. Meliopoulos, R. Yinger and J. Eto, â€Å"White Paper on Integration of Distributed Energy Resources–The CERTS Microgrid Concept†. LBNL-50829, Office of Power Technologies of the US Department of Energy, Contract DE-AC03-76SF00098, April 2002. [10] Robert H. Lasseter and Paolo Piagi, â€Å"Extended Microgrid Using (DER) Distributed Energy Resources†, IEEE PES GM07, June 24-28, 2007. [11] Paolo Piagi, â€Å"MicroGrid control†, PSERC Tele-Seminar Presentation, Department of Electrical and Computer Engineering, university of Wisconsin-Madison, June 7, 2005, pp. 20-25. [12] Yun Wei Li, D. Mahinda Vilathgamuwa and Poh Chiang Loh, â€Å"Robust Control Scheme for a Microgrid with PFC Capacitor Connected†, IEEE Transactions on Industry Applications, Vol. 43, No. 5, September October 2007. [13] Y. W. Li, D. M. Vilathgamuwa and P. C. Loh, â€Å"A Grid-Interfacing Power Quality Compensator for Three-phase Three-Wire Micro-Grid Applications†, 2004 35lh Annual IEEE Power Electronics Specialists Conference. [14] Yun Wei Li,D. Mahinda Vilathgamuwa and Poh Chiang Loh, â€Å"A Grid-Interfacing Power Quality Compensator for Three-Phase Three-Wire Microgrid Applications†, IEEE Transactions on Power Electronics, Vol. 21, No. 4, JULY 2006. [15] Jiquan Shen, Quanxi Li and Xuyan Tu, â€Å"Study on Cooperative Intelligent Grid†, Proceedings of the 2007 IEEE, International Conference on Integration Technology, March 20 24, 2007, Shenzhen, China.