Determination of ametryn in river water, river sediment and bivalve mussels by liquid chromatography-tandem mass spectrometry

Analytical methods employing liquid chromatography-mass spectrometry (LC-MS-MS) for ametryn determination in river water, river sediment and in freshwater bivalve mussel Corbicula fluminea are described. Liquid-liquid extraction was used for sample preparation. The analyses of ametryn in samples were performed on a reversed-phase RP-18 column with MS detection in positive electrospray and multi reaction monitoring modes. The quantitation limit of ametryn was 20 ng L-1, 0.1 ng g-1 and 0.5 ng g-1, for water, sediment and bivalve samples, respectively. Linearity, precision, accuracy and recovery were also reported. The results obtained for method validation are within the international limits and in accordance with literature, suggesting that the developed methods are suitable for the quantitation of ametryn in river water, river sediment and in bivalve Corbicula fluminea. These methods were applied for the analysis of samples from Mogi-Guaçu River and Pardo River, São Paulo State. Results indicated that the highest level of ametryn was 1.44 ng g-1 in bivalve samples from Mogi-Guaçu River.Foram descritos métodos analíticos empregando cromatografia líquida acoplada a espectrometria de massas (LC-MS-MS) para a determinação de ametrina em água superficial, sedimento de rio e no molusco bivalve Corbicula fluminea. A técnica de extração líquido-líquido foi utilizada para a preparação das amostras. As análises das amostras foram feitas em coluna RP-18 de fase reversa com detecção no modo electrospray positivo e Multi Reaction Monitoring (MRM). O limite de quantificação de ametrina foi 20 ng L-1, 0,1 ng g-1 e 0,5 ng g-1 para amostras de água, sedimento e bivalves, respectivamente. Na etapa de validação dos métodos foram avaliadas também a linearidade, a precisão, a exatidão e a recuperação. Os resultados obtidos na validação do método estão de acordo com os limites internacionais e com a literatura, sugerindo que o método desenvolvido é adequado para a quantificação de ametrina em amostras de água superficial, sedimento de rio e nos bivalves Corbicula fluminea. Estes métodos foram aplicados na análise de amostras coletadas no Rio Mogi-Guaçu e Rio Pardo, São Paulo, Brasil. O nível mais elevado de ametrina foi 1,44 ng g-1, encontrado nas amostras de bivalves do Rio Mogi-Guaçu.FAPESPCoordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)CNP

Transmission electron microscopy for characterization of acrosomal damage after Percoll gradient centrifugation of cryopreserved bovine spermatozoa

The objective of this study was to characterize acrosomal ultrastructure following discontinuous Percoll gradient centrifugation of cryopreserved bovine sperm. Semen was collected from six bulls of different breeds and three ejaculates per bull were evaluated. Frozen semen samples were thawed and the acrosomal region of sperm cells was evaluated by transmission electron microscopy (TEM) before (n = 18) and after (n = 18) Percoll centrifugation. The evaluation of 20 sperm heads from each of the 36 samples analyzed ensured that a large number of cells were investigated. The data were subjected to analysis of variance at a level of significance of 5%. Percoll centrifugation reduced the percentage of sperm exhibiting normal acrosomes (from 61.77 to 30.24%), reduced the percentage of sperm presenting atypical acrosome reactions (from 28.38 to 4.84%) and increased the percentage of sperm exhibiting damage in the acrosome (from 6.14 to 64.26%). The percentage of sperm with typical acrosome reactions was not significantly different before (3.70%) and after (0.67%) centrifugation. TEM distinguished four different types of acrosomal status and enabled ultrastructural characterization of acrosomal injuries. The percentage of sperm exhibiting normal acrosomes decreased and damage in the acrosome was the most frequent acrosomal injury with the Percoll gradient centrifugation protocol utilized

Direct Power Control Of A Doubly Fed Induction Generator By Using A Neuro-fuzzy Controller

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)In this article, a direct power control strategy for a doubly fed induction generation is presented. The control variables - d-axis and q-axis rotor voltages - are determined through a control system that consists of a neuro-fuzzy inference system and a Takagi-Sugeno fuzzy logic controller of first order. The input variables of the control system are the rotor speed, active and reactive power references, and their respective errors. Constant converter switching frequency is achieved, what eases the design of ac harmonic filter and power loss reduction of power converter. Another features are the rotor current-sensorless operation, lower cost implementation and the gain of reliability. To validate the strategy simulation and experimental results are presented for abrupt and linear variations of active and reactive power. © 2011 IEEE.3237 CAPES,Cons. Nac. Desenvolv. Cient. Tecnol. (CNPq),CREDSUPER/UNICRED - Filiada ao Sistema,IEEE Power Electronics Society (PELS),FAPERNConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Leonhard, W., (1985) Control of Electric Drives, , Springer-VerlagBlaabjerg, F., Lov, F., Wind power - A power soucer now enabled by power electronics (2007) 9th Brasilian Power Electronics ConferenceDatta, R., Rangathan, V.T., Variable-speed wind power generation using doubly fed wound rotor induction machine - A comparison with alternative schemes (2002) IEEE Trans. on Energy Conversion, 17 (3), pp. 414-421. , SepVas, P., (1998) Sensorless Vector and Direct Torque ControlKawabata, Y., Ejiogu, E., Kawabata, T., Vector-controlled double-inverter-fed wound-rotor induction motor suitable for high-power drives (1999) IEEE Transactions on Industry Applications, 35, pp. 1058-1066Datta, R., Ranganathan, V.T., Direct power control of grid-connected wound rotor induction machine without rotor position sensors (2001) IEEE Trans. Power Electron, 16 (3), pp. 390-399. , MayXu, L., Cartwright, P., Direct active and reactive power control of DFIGfor wind energy generation (2006) IEEE Trans. on Energy Conversion, 21 (3), pp. 750-758. , SeptZhi, D., Xu, L., Direct power control od DFIG with constant switching frequency and improved transient performance (2007) IEEE Trans. Energy Conversion, 22 (1), pp. 110-118. , MarJacomini, R.V., Fran, A., Bim, E., Simulation and experimental studies on double-fed induction generator power control operating at subsynchronous operation speed (2009) The Eighth International Conference on Power Electronics and Drive Systems, , November 2-5 Taipei. Taiwan. R.O.CPetersson, A., Harnefors, L., Thiringer, T., Evaluation of current control methods for wind turbines using doubly-fed induction machines (2005) IEEE Trans. Power Electron, 20 (1), pp. 2270-2281. , JanTakahashi, I., Noguchi, T., A new quick-response and high-efficiency control strategy of an induction motor (1986) IEEE Trans. Industry Applications, 22 (5), pp. 820-827Grabowski, Z.P., Kazmierkowski, M.P., Bose, B.K., Blaabjerg, F., A simple direct-torque neuro-fuzzy control of PWM-inverter-fed induction motor drive (2000) IEEE Trans. on Industrial Eletronics, 47 (4), pp. 863-870. , AugLai, Y.S., Lin, J.C., New hybrid fuzzy controller for direct torque control induction motor drive (2003) IEEE Trans. on Power Eletronics, 18 (5), pp. 1211-1219. , SeptToufouti, R., Meziane, S., Benalla, H., Direct torque control for induction motor using intelligent techniques⋯ (2007) Journal of Theoretical and Applied Information Technology, pp. 35-44Liu, S.X., Wang, M.Y., Chen, Y.G., Li, S., A novel fuzzy direct torque control system for three-level inverter-fed induction machine (2010) International Journal of Automation and Computing, pp. 78-85. , FebruaryBim, E., (2009) Maquinas ELetricas e Acionamento, , Elsevier PublicationsJang, J.-S.R., ANFIS: Adaptative-network-based fuzzy inference system (1993) IEEE Trans. Syst. Man. Cyber, 23 (3), pp. 665-684. , May/JuneTakagi, T., Sugeno, M., Fuzzy identification of systems and its applications to modeling and control (1985) IEEE Transactions on Systems. Man and Cybernetic

Implementation Of The Direct Power Control Of A Doubly Fed Induction Generator By Using A Takagi-sugeno Neuro-fuzzy Inference System

A Takagi-Sugeno neuro-fuzzy inference system for direct power control of a doubly fed induction generator is presented in this paper. The control variables - d-axis and q-axis rotor voltages - are determined by a control system that consists of a neuro-fuzzy inference system and a first order Takagi-Sugeno fuzzy logic controller. To validate the proposed strategy, experimental tests are made for the DFIG operating speed is slightly less than the synchronous speed. The operation of the generator with abrupt and linear changes in stator power and under variable or constant speeds are tested. © 2013 IEEE.852857The Institute of Electrical and Electronics Engineers (IEEE),IEEE Industrial Electronics Society (IES),Austrian Institute of Technology (AIT),Vienna University of Technology (TU Vienna)Leonhard, W., (1985)Liu, C.-H., Hsu, Y.-Y., Effect of rotor excitation voltage on steadyState stability And maximum output power of A doubly fed induction generator (2011) IEEE Trans. Ind. Electron, 58 (4), pp. 1096-1109. , AprKoutroulis, E., Kalaitzakis, K., Design of A maximum power tracking system for wind-energy-conversion Applications (2006) IEEE Trans. Ind. Electron, 53 (2), pp. 486-494. , AprBjaabjerg, F., Teodorescu, R., Liserre, M., Timbus, A.Y., Overview of control And grid synchronization for distributed power generation systems (2006) IEEE Trans. Ind. Electron, 53 (5), pp. 1398-1409. , OctCarrasco, J.M., Franquelo, L.G., Bialasiewicz, J.T., Galvan, E., Guisado, R.C.P., Leon, J., Alfonso, N., Power-Electronic systems for the grid integration of renewable energy sources: A survey (2006) IEEE Trans. Ind. Electron, 53 (4), pp. 1002-1016. , AugBonnet, F., Vidal, P.E., Pietrzak-David, M., Dual direct torque control of doubly fed induction machine (2007) IEEE Trans. Ind. Electron, 54 (5), pp. 2482-2490. , SepVas, P., (1998) Sensorless Vector and Direct Torque ControlKawabata, Y., Ejiogu, E., Kawabata, T., Vector-controlled doubleinverter-fed wound-rotor induction motor suitable for high-power drives (1999) IEEE Transactions on Industry Applications, 35, pp. 1058-1066Datta, R., Ranganathan, Y.T., Direct power control of grid-Connected wound rotor induction machine without rotor position sensors (2001) IEEE Trans. Power Electron, 16 (3), pp. 390-399. , MayXu, L., Cartwright, P., Direct Active And reactive power control of dFIG for wind energy generation (2006) IEEE Trans. on Energy Conversion, 21 (3), pp. 750-758. , SeptJacomini, R.Y., Frana, A., Bim, E., Simulation And experimental studies on doublejed induction generator power control operating At subsynchronous operation speed (2009) The Eighth International Conference on Power Electronics and Drive Systems, , November 2-5, Taipei, Taiwan, R.O.cPetersson, A., Harnefors, L., Thiringer, T., Evaluation o.f current control methods for wind turbines using doubly-Fed induction machines (2005) IEEE Trans. Power Electron, 20 (1), pp. 2270-2281. , JanTakahashi, L., Noguchi, T., A new quick-Response And highEfficiency control strategy of An induction motor (1986) IEEE Trans. Industry Applications, 22 (5), pp. 820-827Habertler, T.G., Profumo, F., Pastorelli, M., Tolbert, L.M., Direct torque control od induction machines using space vector modulation (1992) IEEE Trans. Industry Applications, 28, pp. 1045-1053. , Sept./OctKenny, B.H., Lorenz, R.D., Stator And rotor flux based deadbeat direct torque control of induction machines (2001) Cont'. Rec. IEEE-lAS Annu. Meeting, 1, pp. 133-139Lascu, C., Boldea, L., Bjaabjerg, F., A modifiel direct torque control for induction motor sensorless drive (2000) IEEE Trans. Industry Applications, 36, pp. 122-130. , Jan./FebZhi, D., Xu, L., Direct power control o.f dFIG with constant switching frequency And improved transient performance (2007) IEEE Trans. Energy Conversion, 22 (1), pp. 110-118. , MarJou, S., Lee, S., Park, Y., Lee, K., Direct power control of A dFIG in wind turbines to improve dynamic responses (2009) Journal of Power Electronics, 9 (4). , SeptemberGrabowski, Z.P., Kazmierkowski, M.P., Bose, B.K., Bjaabjerg, F., A simple direct-Torque neuro-Fuzzy control of pWM-Inverter-Fed induction motor drive (2000) IEEE Trans. on Industrial Eletronics, 47 (4), pp. 863-870. , AugLai, Y.S., Lin, J.C., New hybrid fuzzy controller for direct torque control induction motor drive (2003) IEEE Trans. on Power Eletronics, 18 (5), pp. 1211-1219. , SeptToufouti, R., Meziane, S., Benalla, H., Direct torque control for induction motor using intelligent techniques (2007) Journal of Theoretical and Applied Information Technology, pp. 35-44Liu, S.X., Wang, M.Y., Chen, Y.G., Li, S., A novel fuzzy direct torque control system for t hree-Level inverter-Fed induction machine (2010) International Journal of Automation and Computing, pp. 78-85. , FebruaryBim, E., (2009) Mdquinas Eletricas e Acionamento, , Elsevier PublicationsJang, J.-S.R., ANFlS: Adaptative-network-based fuzzy inference system (1993) IEEE Trans. Syst., Man, Cyber, 23 (3), pp. 665-684. , May/JuneJang, J.-S.R., Sun, C.-T., Neuro-fuzzy modeling And control (1995) Proc. IEEE, 83, pp. 378-406. , MarTakagi, T., Sugeno, M., Fuzzy identification of systems And its Applications to modeling And control (1985) IEEE Transactions on Systems, Man and CyberneticsVasudevan, M., Arumagam, R., High-Performance Adaptive intelligent direct torque control schemes for induction motor drivers (1985) IEEE Transactions on Systems, Man and CyberneticsVas, P., (1992) Application O.f Fuzzy, Neural, Fuzzy-Neural, and GeneticAlgorithm-Based Techniques, , Oxford Science Publication

Experimental Results Of Sliding-mode Power Control For Doubly-fed Induction Generator

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)This paper proposes a decoupled control of active and reactive power for doubly-fed induction generators (DFIG) through the rotor currents using sliding mode control (SMC). In order to decouple the active and reactive power generated, stator-flux-oriented vector control is applied. The sliding mode control strategy proposes is based on two sliding modes plus PI controllers whose main advantage is the easy implementation. Simulation and experimental results are presented to validate the proposed control scheme for a 2 kW DFIG during stator active and reactive power steps and speed variation. During transient operation it is checked good dynamic response. © 2013 IEEE.686691CAPES,CNPq,et al.,FAPERGS,Rio Grande do Sul - Governo do Estado,Secretaria de Ciencia, Inovacao e Desenvolvimento Tecnol.Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Abad, G., Lpez, J., Rodrguez, M., Marroyo, L., Rodrguez, M., Iwanski, G., (2011) Doubly Fed Induction Machine: Modeling and Control for Wind Energy Generation Applications, , John Wiley & SonsBaroudi, J.A., Dinavahi, V., Knight, A.M., A review of power converter topologies for wind generators (2007) Renewable Energy, 32, pp. 2369-2385Netto, A.J., Barros, P.R., Jacobina, C.B., Lima, A.M.N., Da Silva, E.R.C.V., Indirect field-oriented control of an induction motor by using closed-loop identification (2005) Industry Applications Conference. Fourtieth IAS Annual MeetingTapia, A., Tapia, G., Ostolaza, J.X., Saenz, J.R., Modeling and control of a wind turbine driven doubly fed induction generator (2003) IEEE Transactions on Energy Conversion, 18 (2), pp. 194-204. , JunShen, B., Ooi, B.-T., Novel sensorless decoupled p-q control of doubly-fed induction generator(dfig) based on phase locking to gamma-delta frame (2005) Power Electronics Specialists ConferenceJacomini, R.V., França, A., Bim, E., Simulation and experimental studies on double-fed induction generator power control operating at subsynchronous operation speed (2009) Power Electronics and Drive SystemsLima, F.K.A., Luna, A., Rodriguez, P., Watanabe, E.H., Blaabjerg, F., Rotor voltage dynamics in the doubly fed induction generator during grid faults (2010) IEEE Trans. on Power Electronics, 1 (1), pp. 118-130. , JanMendes, V.F., De Sousa, C.V., Silva, S.R., Rabelo, B.C., Hofmann, W., Modeling and ride-through control of doubly fed induction generators during symmetrical voltage sags (2011) IEEE Transactions on Energy Conversion, 26 (4), pp. 1161-1171. , DecSguarezi Filho, A.J., De Filho Oliveira, M.E., Ruppert, E., A predictive power control for wind energy (2011) IEEE Transactions on Sustainable Energy, 2 (2), pp. 97-105Edwards, C., Spurgeon, S.K., (1998) Sliding Mode Control: Theory and Applications, , Taylor & Francis systems and control book seriesNaouar, W., Monmasson, E., Naassani, A., Slama-Belkhodja, I., Fpga-based dynamic reconfiguration of sliding mode current controllers for synchronous machines (2012) IEEE Transactions on Industrial Informatics, 99, pp. 18-25Rashid, M., (2004) Power Electronics Circuits, Devices and Applications, , Pretince HallLascu, C., Boldea, I., Blaabjerg, F., Direct torque control of sensorless induction motor drives: A slidingmode approach (2004) IEEE Transactions on Industry Applications, 25 (2), pp. 582-590. , march-aprilChen, S.Z., Cheung, N.C., Wong, K.C., Wu, J., Integral variable structure direct torque control of doubly fed induction generator (2011) Renewable Power Generation, IET, 5 (1), pp. 18-25. , JanHu, J., Nian, H., Hu, B., He, Y., Zhu, Z.Q., Direct active and reactive power regulation of dfig using sliding-mode control approach (2010) IEEE Transactions on Energy Conversion, 25 (4), pp. 1028-1039. , DecJeong, H.G., Kim, W.S., Lee, K.B., Jeong, B.C., Song, S.H., A sliding-mode approach to control the active and reactive powers for a dfig in wind turbines (2008) Power Electronics Specialists ConferenceZheng, X., Li, W., Wang, W., High-order sliding mode controller for no-load cutting-in control in dfig wind power system (2010) Systems and Control in Aeronautics and Astronautics (ISSCAA), 2010 3rd International Symposium onDa Costa, J.P., Pinheiro, H., Degner, T., Arnold, G., Robust controller for dfigs of grid-connected wind turbines (2011) IEEE Transactions on Industrial Eletronics, 58 (9), pp. 4023-4038. , SepLazarini, M.V., Ruppert Filho, E., Induction motor control didactic set-up using sensorless and sliding mode dtc strategy (2008) Eletrnica de Potncia, 13 (4), pp. 291-299Shiau, L.-G., Lin, J.-L., Stability of sliding-mode current control for high performance induction motor position drives (2001) Electric Power Applications, IEE Proceedings, 148 (1), pp. 69-75Sguarezi Filho, A.J., Ruppert Filho, E., The complex controller for three-phase induction motor direct torque control (2009) Sba Controle e Automao., 20 (2), pp. 256-26

Microarthropod communities as a tool to assess soil quality and biodiversity: a new approach in Italy

AGRICULTURE, ECOSYSTEMS & ENVIRONMEN

Decoupled Power Control For Doubly-fed Induction Generator Using Sliding-mode Control [rozsprze{ogonek}żone Sterowanie Moca{ogonek} W Generatorze Dfig Przy Wykorzystaniu Metody ślizgowej]

This paper proposes a decoupled control of active and reactive power for doubly-fed induction generators (DFIG) through the rotor currents using sliding mode control (SMC). In order to decouple the active and reactive power generated, stator-flux-oriented vector control is applied. The sliding mode control strategy proposes is based on two sliding modes plus PI controllers whose main advantage is the easy implementation. Simulation and experimental results are presented to validate the proposed control scheme for a 2 kW DFIG during stator active and reactive power steps and speed variation. During transient operation it is checked good dynamic response.898100105Abad, G., López, J., Rodríguez, M., Marroyo, L., Rodríguez, M., Iwanski, G., (2011) Doubly Fed Induction Machine: Modeling and Control for Wind Energy Generation Applications, pp. 414-421. , John Wiley & SonsBaroudi, J.A., Dinavahi, V., Knight, A.M., (2007) A review of power converter topologies for wind generators, 32, pp. 2369-2385. , Renewable EnergyNetto, A.J., Barros, P.R., Jacobina, C.B., Lima, A.M.N., da Silva, E.R.C., Indirect field-oriented control of an induction motor by using closed-loop identification (2005) Industry Applications Conference, 2, pp. 1357-1362. , 2005. Fourtieth IAS Annual Meeting. OctTapia, A., Tapia, G., Ostolaza, J.X., Saenz, J.R., Modeling and control of a wind turbine driven doubly fed induction generator (2003) IEEE Transactions on Energy Conversion, 18, pp. 194-204. , N0. 2, JunShen, B., Ooi, B.-T., Novel Sensorless Decoupled P-Q Control of Doubly-Fed Induction Generator(DFIG) Based on Phase Locking to Gamma-Delta Frame (2005) Power Electronics Specialists Conference, pp. 2670-2675. , 2005. PESC '05. IEEE 36th, JunChowdhury, B.H., Chellapilla, S., Double-fed induction generation control for variable speed wind power generation (2006) Electric Power System Research, (76), pp. 786-800Jacomini, R.V., França, A., Bim, E., Simulation and Experimental Studies on Double-fed Induction Generator Power Control Operating at Subsynchronous Operation Speed (2009) The Eighth International Conference on Power Electronics and Drive Systems, (2-5). , Taipei, Taiwan, R.O. CLima, F.K.A., Luna, A., Rodriguez, P., Watanabe, E.H., Blaabjerg, F., Rotor Voltage Dynamics in the Doubly Fed Induction Generator During Grid Faults (2010) IEEE Trans. on Power Electronics, 25 (1), pp. 118-130Flores Mendes, V., de Sousa, C.V., Silva Rocha, S., Cezar Rabelo, B., Hofmann, W., Modeling and Ride-Through Control of Doubly Fed Induction Generators During Symmetrical Voltage Sags (2011) IEEE Transactions on Energy Conversion, 26 (4), pp. 1161-1171Edwards, C., Spurgeon, S.K., Sliding Mode Control: Theory And Applications (1998) Taylor & Francis systems and control book seriesNaouar, W., Monmasson, E., Naassani, A., Slama-Belkhodja, I., FPGA-Based Dynamic Reconfiguration of Sliding Mode Current Controllers for Synchronous Machines (2012) IEEE Transactions on Industrial Informatics, (99)Rashid, M., (2004) Power electronics circuits, devices and aplications, , Pretince HallChen, S.Z., Cheung, N.C., Wong, K.C., Wu, J., Integral variable structure direct torque control of doubly fed induction generator (2011) Renewable Power Generation, 5, pp. 18-25. , IET, N0. 1, JanLascu, C., Boldea, I., Blaabjerg, F., Direct torque control of sensorless induction motor drives: A sliding-mode approach (2004) IEEE Transactions on Industry Applications, 40 (2), pp. 582-590. , march-aprilHu, J., Nian, H., Hu, B., He, Y., Zhu, Z.Q., Direct Active and Reactive Power Regulation of DFIG Using Sliding-Mode Control Approach (2010) IEEE Transactions on Energy Conversion, 25, pp. 1028-1039. , N0. 4, DecJeong, H.G., Kim, W.S., Lee, K.B., Jeong, B.C., Song, S.H., A sliding-mode approach to control the active and reactive powers for A DFIG in wind turbines (2008) IPower Electronics Specialists Conference, pp. 120-125. , 2008. PESC 2008. IEEE, juneZheng, X., Li, W., Wang, W., High-order sliding mode controller for no-load cutting-in control in DFIG wind power system (2010) Systems and Control in Aeronautics and Astronautics (ISSCAA), 2010 3rd International Symposium, pp. 1304-1308. , on, juneda Costa, J.P., Pinheiro, H., Degner, T., Arnold, G., Robust Controller for DFIGs of Grid-Connected Wind Turbines (2011) IEEE Transactions on Industrial Eletronics, 58 (9), pp. 4023-4038Sguarezi Filho, A.J., de oliveira Filho, M.E., Ruppert, E., A predictive power control for wind energy (2011) IEEE Transactions on Sustainable Energy, 2, pp. 97-105Lazarini, M.V., Ruppert Filho, E., Induction motor control didactic set-up using sensorless and sliding mode dtc strategy (2008) Eletrônica de Potência, 13 (4), pp. 291-299Leonhard, W., (1985) Control of Electrical Drives, , Springer-Verlag Berlin Heidelberg New York Toky