Application of Sparse Matrix Converter for Microturbine-Permanent Magnet Synchronous Generator output Voltage Quality Enhancement

Transcription

1 Application of Sparse Matrix Converter for Microturbine-Permanent Magnet Synchronous Generator output Voltage Quality Enhancement N.Vinay Kumar 1, A.Bhaskar 2 1 PG Scholar, Department of Electrical and Electronics Engineering, Narayana Engineering College, Nellore. AP, India. 2 Associate professor, Department of Electrical and Electronics Engineering, Narayana Engineering College. Nellore, AP, India. Abstract The progress of distributed generation set is an important energy option in the present scenario because distribution generation or cogeneration can be used as a backup option to the load for the continuity of the supply or it can be used as peak shaving load. Here Microturbine-Permanent magnet synchronous generator is used as distributed generation set. In which the permanent magnet synchronous generator is having high output frequency. So, there is a necessity to convert High frequency to low frequency (50) Hz, conventional rectifier-inverter or sparse matrix converter can be used as frequency converter. In this paper, simulation results of sparse matrix converter are compared with conventional rectifier-inverter. Keywords---Microturbine-Permanent magnet synchronous generator, sparse matrix converter, filters, Harmonics. I. INTRODUCTION Distributed generation sets have received significant attention as a mean to improve the performance and reliability of electrical power system. They can provide low-cost energy and increase energy efficiency. Moreover, through combined heat and power (CHP) mode of operation and their application can also reduce transmission and distribution (T&D) losses, relieve T&D assets, reduce constraints, and improve overall power quality and reliability. Nowadays, there is a growing interest in deploying Microturbine in distribution generation application, because of their quick start capability and easy controllability useful for efficient peak shaving [1]. In the past few years the uses of Distributed generation sets have increased significantly. MTG s are small, high speed power plants that usually include the turbine, compressor, generator, and power electronics to deliver the power to the load. MTG s [2] have a high- speed gas turbine engine driving an integral electrical generator that produces Kw power while operating at a high speed, generally in the range of 30,000-80,000 rpm. Electric power frequency is produced about 10,000 of Hz and this has to be converted in standard frequency (50) Hz by the application of sparse matrix converter [3]. Microturbine-Generator is having single-shaft and split-shaft. Single shaft is having high speed synchronous machine with the compressor and turbine mounted on the same shaft while the shaft used for power turbine rotating at 3000rpm and a conventional generator connected via a gear box for speed multiplication [3]. In this paper, the Single shaft is usually composed of gas turbine electric power generators. The main advantage of using the single-shaft configuration with Permanent magnet synchronous generator (PMSG) or asynchronous generator is that it is simpler in design. Moreover there is no need for a gear reducer as power electronics sparse matrix converter is used to supply standard frequency to the load. ISSN: Page 169

2 The disadvantages of using high speed Permanent magnet synchronous machine are thermal stress, demagnetization phenomenon centrifugal forces, rotor loses because of fringing effects, high cost etc. The main advantage of coupling a synchronous generator with the split-shaft Microturbine is that it eliminates the use of the rectifier and power converter. These generators are robust and less costly as compared to permanent magnet synchronous generator and all other problem with high speed is eliminated. The use of power electronic interface for power conversion introduces harmonics in the system which reduces the output voltage quality. These harmonics are eliminated if synchronous generator is used with a gearbox. However, the main drawback of a gear box is that it requires maintenance along with its lubricating system. Frequency converter and protection and control system (fig.1) [4]. The interface converter is used to convert permanent magnet synchronous generator output voltage-frequency (High frequency) to power frequency (50/60Hz). In this paper, sparse matrix converter is proposed and this sparse matrix converter is compared with the conventional rectifier-inverter. II. MICROTURBINE-MODELLING In this paper proposed model [5] is considered for Microturbine, and modeling of Microturbine has been done in Matlab/Simulink (fig.2). The model consist of speed controller, accelerator controller, Temperature controller, and fuel (including valve positioned and actuator) The exhaust temperature function is given by: ( ) ( ). (1) The torque function is given by: Where, ( ) ( ). (2) = speed or the turbine W f1, W f2 = fuel flow signals T R = Rated exhaust temperature. Fig.1 Block diagram of a single-shaft Microturbine-Generator III. SPARSE MATRIX CONVERTER The sparse matrix converter is an AC/AC converter which offers a reduced number of components, a low-complexity modulation scheme, and low realization effort. Sparse matrix converters avoid the multistep commutation procedure of the conventional matrix converter improving system reliability and output voltage quality at the load. Characteristics of the sparse matrix converter topology are having 15 IGBT s and 18 Diodes and 7 isolated driver potentials. Compared to the matrix converter, this topology provides identical functionality, but with a reduced numbers of switches and the option of employing an improved zero dc-link current commutation scheme, which provides lower control complexity and higher safety and reliability. Sparse matrix converter is shown in fig. 3 ISSN: Page 170

3 The sparse matrix converter is fed by voltage source and, for this reason; the input terminal should not be short circuited. On the other hand the load has an inductive nature and for this nature, an output phase must never be opened rpm. They can supply customer s baseload requirements or can be used for standby, peak shaving, and cogeneration applications. The block diagram of Microturbine is shown in fig.4 Fig.2 Microturbine model. Fig. 4 Block diagram of Microturbine. V. SIMULATION RESULTS In this section the Microturbine-Generator is simulated in Matlab. The model of permanent magnet synchronous generator is available in Simulink library and is used for generator simulation Fig.3 Sparse matrix converter IV. MICROTURBINE Microturbines are small and simple cycle gas turbines. The output of the Microturbine range typically from around 25 to 300 Kw. Performance improvement technique incorporated in Microturbine include recuperation, low emission technologies, and the use of advanced materials, such as ceramic for the hot section parts. Microturbines are available in single-shaft or splitshaft unit. Single-shaft unit is a high-speed synchronous machine with the compressor and turbine mounted on the same shaft. For these machines, the turbine speed ranges from to In this simulation the focus will on the comparing the sparse matrix converter with conventional rectifier-inverter. The block diagram of the simulated system is shown in fig.5. The reference speed of the Microturbine-Generator is set to 4500 rpm. And at t=14 sec. load is increased from 0.2 Pu to 0.8 Pu. ISSN: Page 171

4 Fig.5 Simulated system International Journal of Engineering Trends and Technology (IJETT) volume 5 number 4 - Nov 2013 Fig.6 Speed of Microturbine-Generator Fig.8 Permanent magnet synchronous generator output voltage at 0.2 Pu and 0.8 Pu Sparse matrix converter and conventional converter operates on these load voltages to construct a 50 Hz. Output wave form of these converters before filtering is shown in fig.9 and fig.10. Fig.7 Mechanical torque of Microturbine-Generator At this speed the frequencies of the output frequency of the permanent magnet synchronous generator is 3000Hz, and must be converted to power system frequency (50 Hz), This can be done by using Sparse matrix converter. In fig.8 shows the permanent magnet synchronous generator output voltage of phase-a ISSN: Page 172

5 Fig.9 Sparse matrix converter output voltage at 0.2 Pu and 0.8 Pu Fig.10. Conventional rectifier-inverter output voltage at 0.2 Pu 0.8Pu These voltages are filtered by using filter to construct the load terminal voltages. The filtered output voltages of the sparse matrix converter and conventional rectifier-inverter are shown in fig. 11 and fig.12. ISSN: Page 173

6 Fig. 11 Load terminal voltage of sparse matrix converter at 0.2 Pu 0.8 Pu Selected FFT signals for the sparse matrix converter and Conventional rectifier-inverter at 0.2 Pu and 0.8 Pu is shown in fig.13 and the total harmonic distortion (THD %) at the load terminal voltage of sparse matrix converter and conventional rectifier-inverter is shown in fig.14 and fig.15. The total harmonic distortion for the load terminal voltage of sparse matrix converter at 0.2 Pu and 0.8 Pu are 5.50% and 4.50% and the Total harmonic distortion for the load terminal voltage of conventional rectifier-inverter are 7.50% and 6.50%. From these values (THD%), we can observe that the total harmonic distortion of load terminal voltage using sparse matrix converter is less than the load terminal voltage of conventional rectifier-inverter and the output voltage of Microturbine-permanent magnet synchronous generator is improved. Fig. 12 Load terminal voltage of conventional rectifier-inverter at 0.2 Pu 0.8 Pu Fig. 13 Selected signals of both sparse matrix converter and conventional rectifier-inverter at the load terminal voltage at 0.2 Pu 0.8 Pu. ISSN: Page 174

7 Fig.15: Total harmonic distortions of the load terminal voltage of conventional rectifier-inverter at 0.2 Pu 0.8 Pu VI. CONCLUSION Fig. 14: Total harmonic distortion of the load terminal voltage of sparse matrix converter at load 0.2 Pu and 0.8 Pu In this paper Microturbine-permanent magnet synchronous generator is used as distributed generation set. Here the application of sparse matrix converter is used as frequency converter for the Microturbine-Generator for improvement of output voltage quality at the load and simulation results of sparse matrix converter is compared with the conventional rectifier-inverter and larger dc-link capacitor which is common in conventional rectifier-inverter is omitted and hence, output voltage quality of the Microturbine- Permanent magnet synchronous generator converter is enhanced. REFERENCES [1] A.K.Saha, S.Chowdhury, S.P.Chowdhary, and P.A.Crossley, Modeling and performance of a Microturbine as a distributed energy resource, IEEE Trans. Energy Conv., vol. 24, no. 2, pp , Jun [2] Stephanie L.Hamilton, Southern California Edison, Project title: Microturbine generator program, Proceedings of the 33 rd Hawaii International conference on system science [3] Johann W.Kolar, Frank schafmeister, Simon D. Round, Hans Ertl, Novel three phase Sparse matrix converter, IEEE Trans. on power electronics, vol. 22, no.5, pp , Sept ISSN: Page 175

8 [4] E.F.Pavinatto, M.B.Peres, P.D. Reis, L.S. Pereira, and F.P.Salles, Use of Microturbine in remote isolated oil and gas facilities in Brazil, IEEE Ind. Appl. Mag., pp.62-68, Nov/Dec [5] R. Norooizian, M.Abedi, G.B.Gharehpetian, and S.H.Ossein, Modeling and simulation of Microturbine-Generator system for ongrid and off-grid operation modes, Int. Conf. on Renewable Energies and Power Quality (ICREPQ 09), Apr About Authors N.Vinay Kumar received B.Tech. Degree from AVS College of Engineering and technology, Venkatachalam affiliated to JNTU ANANTHAPUR, At present he is perceiving M.Tech in Electrical Power Engineering from Narayana Engineering College, Nellore, Andhra Pradesh, India. A.Bhaskar received Master degree in Power Electronic in Industrial Drives (PE & ID) from Sathyabhama University, Chennai. And B.Tech degree from Visvodaya Institute of Technology and science, Kavali. At present he is an Associate Professor in EEE department, Narayana Engineering College, Nellore, Andhra Pradesh, India. ISSN: Page 176