WIND ENERGY SYSTEM ON THE BASE OF SYNCHRONOUS MACHINE

Transcription

1 The 4th International Conference Computational Mechanics and Virtual Engineering COMEC OCTOBER 2011, Brasov, Romania WIND ENERGY SYSTEM ON THE BASE OF SYNCHRONOUS MACHINE Naima ARAB 1, M.Lokmane BENDAAS 2, SidAli FELLAG 1 1 University of Technology of Tizi Ouzou- Algéria 2 University of Technology of Batna-Algeria Abstract: This paper aims to provide a complete modeling of a wind energy generation system on the base of permanent magnet synchronous machine. Each part of the system is discussed. The MPPT scheme control that allow a maximum power extraction is shown in detail, some commentaries are made compared to earlier published works. 1. INTRODUCTION: The use of wind energy systems is one the potential alternatives that can replace the conventional energy resources like fossil fuels and dangerous nuclear power plant. In Europe only the growth on wind energy is 20% annually and the goal is to reach 180 GW by 2020[6]. This stimulates further students and researchers to continue working on this field of energy. In this paper we will present a complete modeling of a wind power generation system from the modeling of the naturally blowing wind up to an ideal RL power network. A conventional feedback control scheme of maximum power point tracking MPPT which was not shown in many works [1-5&8-11], and wrongly presented in others [6,7] is explicitly shown and discussed. The use of the doubly fed induction machine as a generator machine though present a lot of advantages such as low cost, simplicity in construction, in control and also a good efficiency, it always requires the utilization of gearbox in order to increase the machine speed that make the energy generation possible. The elimination of the gearbox, which is a source of lot problems of maintenances and reliability, can be made by using permanent magnet synchronous machine PMSM, with a big number of pair poles, as generator. So in this study a complete modeling of a permanent magnet synchronous machine is provided and the unity power factor of the injected power into the net is considered and presented in detail. 2. THE GLOBAL WIND ENERGY GENERATION SYSTEM MODELING: The overall scheme of wind energy generation system can be shown in fig1. It is composed from the turbine, generally a three blades one, a gearbox in general case, rigid mechanical shaft that connect the turbine with the machine-generator, then a back-to back static converter to allow the flow of energy in either sides of the machine and the network. This latter is presented as a three line component and will be modeled later, for simplicity raison, as an ideal R-L circuit. Figure 1. The overall scheme of wind power generator system 144

2 In the following sections each part of the overall scheme will be modeled in detail and some commentaries will be made when needed. 3. WIND MODELLING To model the whole system we need first to model the wind. It is known to be randomly blowing. The most accurate method to model it is the empirical one, and by collecting data through experimental means. The collected data can be then injected into programs such as look- up tables available in most simulation packages. Another way that is fair enough for theoretical studying purpose is to get a mathematical approximation of the wind of being as a sum of harmonics and that through a Fourier Distribution as provided in [1-5]: Figure.2 Wind profile On the base of the above expressions the wind profile, that has not been shown in[3], was depicted in figure 2. This form will be set as an input to the turbine model. 4. THE TURBINE MODELING: The mathematical model of the turbine is based on the expression given in [1-5]: 145

3 Figure 3. Power coefficient versus the tip speed ratio at deferent pitch angle. 146

4 147

5 5. THE PMSM SYNCHRONE MODEL The model of PMSM in the dq frame can be given as quoted in [8, 11]: Relying on this model, along with movement equations, was drawn a simulation diagram that will participate in the overall simulation diagram fig.6. An explicit showing of all matlab-function blocks equations will help the reader to swift reproduction. 6. VECTOR CONTROL OF PMSM: The same approach in motoring mode is adopted here for the PMSM generating case. The aim of the vector control is to achieve reactive power elimination in the side of the power network. In the dq frame from the side of the inverter the (d) axes will be responsible for controlling the voltage of the dc link while (q) will control the reactive power, forcing it to be as close as possible to zero. The regulation current loops should be set as in the following bock diagrams: The controllers in the above schemes should be carefully designed as though when forcing the reference reactive power to zero the injected power in the net will have a unity power factor. 148

6 Based on the above models and associating them with PWM back to back converter the complete control scheme of the wind generation system is shown in fig.7. Figure7. Scheme of a complete wind power system control The results of simulation on the matlab-simulink environment of all associated block diagrams (Including Regulation loops) have yielded the following figures. Figure 8(a) shows the active power injected into the net. This one is following the imposed reference power. In figure 8(b) the reactive power also follows its reference (set as zero in our model). That means the unity power factor is successfully obtained. The Result of controlling a dc link is shown in figure 8(c). It is maintaining a constant level avoiding drops in generated power. Figure 8: a) active power, b) reactive power, c) DC link 149

7 7. CONCLUSION The paper has presented an overall simulation of the wind generation system on the matlab-simulink environment, each part of the chain, save the back-to-back converter which is available in matlab packages, has been explained. The MPPT control scheme has been proposed in the correct way that easily allows the controller parameters calculation. The work can suit students and researchers working in this field of renewable energy. Data used in this work: 8. REFERENCES [1] A.Mirecki, «Etude Comparative de chaînes de Conversion d Energie Dédiées à une Eolienne de Petite Puissance». Institut Nationale Polytechnique de Toulouse, [2] R. Melicio V. M. F. Mendes, J. P. S. Catalão, «Computer Simulation of Wind Power Systems: Power Electronics and Transient Stability Analysis», Internationnal Conference on Power System Transients (IPST2009), Kyoto, Japan, Juin 3-6, [3] M. Muyeen, R. Takahashi, T. Murata, J. Tamura, and M.H. Ali, «Transient Stability Analysis of Permanent Magnet Variable Speed Synchronous Wind Generator», Proceeding of international conference on electrical Machines and Systems, oct ,Seoul,Korea. [4] T. Senjyu, Nakasone.N, Yona.A, Saber.A,.Y., Funabashi.T, Sekine.H, «operation strategies for stability of gearless wind power generation systems», IEEE conference, Power and Energy Society General Meeting, Convertion and Delivery of Electrical [5] Ming Yin, Gengyin Li, Ming Zhou, Chengyng Zhao, «Modelling of the wind turbine with a permanent magnet synchronous generator for integration», Power Enginoring Society General Meeting, jun 2007, PP 1-6. Energy in the 21 st Centry, pp.1-7,2008. [6] S.EL-Aimani. «Modélisation de différentes technologies d éoliennes intégrées dans un réseau de moyenne tension», Thèse de Doctorat d Etat en Electronique et Génie Electrique. Ecole Centrale de Lille (ECL), [7] K. Ghedamsi &all, «Control of wind generator associated to a flywheel energy storage system», journal renewable energy, Science direct.elsivier. [8] A. Abedini and A. Nasiri, «PMSG Wind Turbine Performance Analysis During Short Circuit Faults», IEEE Canada Electrical Power Conference, pp.165, jui [9] Yang Yong, «Grid-connected inverter for wind power generation system», J Shanghai Univ (Engl Ed), [10] You Jiang, Meng Fan Rong and Luo Hua, «Variable Speed Constant Frequency Tidal Current Energy Generation and Control Strategy for Maximum Power Point Tracking and Grid Connection», Sustainable Power Generation and Supply, 2009, Supergen 09, Internationnal Conference, PP [11] Monica Chinchilla and all, «Controle of Permanent Magnet Generator Applied to Variable Speed Wind- Energy Systems Connected to the Grid», IEEE Transactions on Energy Conversion, Vol, N, 1, March