Direct Torque Control of DFIG Driven by Wind Turbine System Connected to the Grid

ABSTRACT:

This paper described a Direct Torque Control (DTC) applied to a Doubly Fed Induction Generator (DFIG) driven by a Wind Turbine (WT) connected to the grid. This control strategy based on the regulation of the flux and the torque, the currents and voltages are used to estimate the torque and the flux and compare those magnitudes to the reference values, the obtained results will be converted to digital form by hysteresis comparators. The commutation table will use those values and the sector number to choose the voltage vector. The aim of this study is to treat three modes that can drive WT-DFIG system utilizing Maximum Power Point Tracking (MPPT) technique. Computer simulation has carried out under MATALB/Simulink environment and the obtained results demonstrate the effectiveness of the proposed control.

 KEYWORDS:

1.      Direct Torque Control

2.      Doubly Fed Induction Generator

3.      Wind Turbine

4.      Wind Energy

5.      Maximum Power Point Tracking

 SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Fig.1. DTC Control applied to DFIG connected to the grid.

EXPECTED SIMULATION RESULTS:

Fig.2. Wind speed.

Fig.3. Cp (λ) Characteristic.

Fig.4. Mechanical speed (generator speed).

Fig.5. Waveform of Slip.

Fig.6. Electromagnetic Torque.

Fig.7. Rotor and Reference flux.

Fig.8. The rotor flux.

Fig.9. Wave form of Rotor flux φ_rα and φ_rβ.

Fig.10. Rotor Current Ir(abc)

Fig.11. Rotor Reactive Power

Fig.12. Stator Current Is(abc)

Fig.13. Stator Power

 

Fig.14. Rotor Power

Fig.15. The FFT analysis of phase (a) stator current (Synchronous mode).

CONCLUSION:

A study of Direct Torque Control strategy applied to Doubly Fed Induction Generator used for Wind Turbine Conversation system has been presented in this paper. As known, the wind has a random movement imposing indiscriminate speed for the turbine, therefore driving DFIG in different modes (sub-synchronous, synchronous and super synchronous modes), those modes have been treated in this work. The obtained results show clearly satisfactory performances, they showed a good dynamic of the torque and the flux, low THD in synchronous mode and constant stator frequency, while keeping a better precision of control, as well as the efficiency of the control strategy leading to better performances.

REFERENCES:

 

[1] C. J. Nobles, E. F. Schisterman, Sandie Ha, Keewan Kim, and all, “Ambient air pollution and semen quality,” Environmental Research. 163, 2018, pp. 228-236.

[2] B. Sawetsakulanond, V. Kinnares, “Design, analysis, and construction of a small scale self-excited induction generator for wind energy application,” Energy Journal. 2010, pp. 4975–4985.

[3] A. Tapia, G. Tapia, J.X. Ostolaza, J.R. Saenz, “Modeling and control of a wind turbine driven doubly fed induction generator,” IEEE Trans. Energy Convers. 2003, pp. 194–204.

[4] “GWEC’s Global Wind Report - Annual Market Update,” the Global Wind Energy Council, 2017. Available: http://www.gwec.net.

[5] “Renewables 2017 global status report 2017,” Ren21, 2017.

DTC of DFIG included in a Wind Turbine Connected to the Grid

ABSTRACT:

This article presents a contribution of the application of direct torque control, for the control of the powers of a double power induction generator (DFIG), used in a constant speed wind energy conversion system. This type of control based on two hysteresis band controllers of torque and flux. The simulation results showed that it is possible to control the rotor powers with this method.

 KEYWORDS:

1.      DFIG

2.      DTC

3.      WIND TURBINE

4.      GRID

 SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Fig.1. Block diagram of DTC.

 EXPECTED SIMULATION RESULTS:

Fig.2. The rotor flux sector location.

Fig.3. evolution of rotor flux estimated components.

Fig.4. Waveform of the alpha/beta rotor flux (Wb).

Fig.5. The rotor flux  (Wb).

Fig.6. Waveform of the alpha/beta rotor currents

Fig.7. Waveform of the rotor currents and voltages.

CONCLUSION:

This paper presents the simulation of the direct torque control for a doubly fed induction generator connected to the grid. The results obtained confirm the theoretical studies of this commande, and show the effectiveness of the proposed control strategy.

REFERENCES:

[1] A. Kadri , H. Marzougui , K. Omrani , F. Bacha, “DTC of Doubly Fed Induction Generator for Wind Power System based on Rotor Flux Estimation,” International Confernece on Control Engineering Information Technology. Tunisia, vol. 34, pp. 33-38, December 2017.

[2] Y. Sahri, S.Tamalouzt, S. L. Belaid, “Direct Torque Control of DFIG Driven by Wind Turbine System Connected to the Grid,” International Conference on Wind Energy and Applications in Algeria. Algeria, pp. 88-93, November 2018.

[3] N. El Ouanjli1 , A. Derouich , A. El Ghzizal , M. Taoussi , Y. El Mourabit, “Direct torque control of doubly fed induction motor using three-level NPC inverter,” Protection and Control of Modern Power Systems 4. October 2019

[4] G.Naveen, P.K.S.Sarvesh, B.Rama Krishna, “DTC Control Strategy for Doubly Fed Induction Machine,” International Journal of Engineering and Advanced Technology. India, vol. 3, pp. 92-95, October 2013.

[5] A. Bakouri, H. Mahmoudi, A. Abbou, “Intelligent Control for Doubly Fed Induction Generator Connected to the Electrical Network,” International Journal of Power Electronics and Drive System. Indonesia, vol. 7, pp. 688-700, September 2016.

Seven-Level Packed U-Cell (PUC) Converter with Natural Balancing of Capacitor Voltages

 ABSTRACT:

A seven-level Packed U-Cell inverter is presented in this paper. The converter uses a single dc source and two floating capacitors, whose voltages are balanced in open loop, to produce multilevel output voltage. Peak magnitude of the output phase voltage is equal to the magnitude of dc source. Voltages across floating capacitors add intermediate voltage-levels by establishing an asymmetric ratio (with respect to the available dc voltage in the circuit). The average energy exchange (when the network is in steady state) of the capacitors with the rest of the inverter-circuit will be zero. This helps the capacitors to maintain desired voltages and thus create intermediate levels of steady dc voltages. Performance of the converter is validated in simulation by MATLAB/Simulink and testing of the converter is done for resistive as well as inductive loads. Experimental verification of the converter is carried out on a laboratory prototype and the obtained results match well with the simulation.

KEYWORDS:

1.      PUC converter

2.      Natural balancing

3.      Open-loop control

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

 

A seven-level Packed U-Cell converter is presented. The converter contains only one dc source and two floating capacitors. Voltages of floating capacitors along with the available dc voltage source establish a ratio of 3:2:1. Floating capacitors work by the principle of current-sec balance and therefore have natural balancing capability. Concept of natural balancing works regardless of the modulation index and load power factor. Time-domain expressions for the capacitor voltages are derived considering a specific switching operation of the converter. This helped in analytically validating the concept of natural balancing. Capacitor requirement in terms of kJ/MVA is discussed which forms an important aspect of the converter. Losses and efficiency of the converter are presented in comparison with few basic topologies including a standard two-level inverter. Performance of the inverter is validated through extensive simulations in MATLAB/Simulink. Experimental verification is done by developing a laboratory prototype to confirm the usefulness of the proposed concept.

REFERENCES:

[1] K. Boora and J. Kumar, “A Novel Cascaded Asymmetrical Multilevel Inverter With Reduced Number of Switches,” in IEEE Transactions on Industry Applications, vol. 55, no. 6, pp. 7389-7399, Nov.-Dec. 2019.

[2] C. W. Flairty, “A 50-kva adjustable-frequency 24-phase controlled rectifier inverter,” IRE Transactions on Industrial Electronics, vol. IE-9, no. 1, pp. 56–60, May 1962.

[3] K. K. Gupta, A. Ranjan, P. Bhatnagar, L. K. Sahu, and S. Jain, “Multilevel inverter topologies with reduced device count: A review,” IEEE Transactions on Power Electronics, vol. 31, no. 1, pp. 135–151, Jan 2016

[4] F. Sebaaly, H. Vahedi, H. Y. Kanaan and K. Al-Haddad, “Experimental Design of Fixed Switching Frequency Model Predictive Control for Sensorless Five-Level Packed U-Cell Inverter,” in IEEE Transactions on Industrial Electronics, vol. 66, no. 5, pp. 3427-3434, May 2019.

[5] A. Routray, R. Singh and R. Mahanty, “Harmonic Reduction in Hybrid Cascaded Multilevel Inverter Using Modified Grey Wolf Optimization,” in IEEE Transactions on Industry Applications.

Robust ANN-Based Control of Modified PUC-5 Inverter for Solar PV Applications

 ABSTRACT:

Conventional PI controllers are vulnerable to changes in parameters and are difficult to tune. In this work, an artificial neural network (ANN) based controller is developed for the robust operation of a single-phase modified packed U-cell five-level inverter (MPUC-5) for solar PV application under variable insolation conditions. An MPUC-5 is a converter with a main and an auxiliary dc link of equal magnitude; although five-level operation is also still feasible with different voltages also. The maximum power point (MPP) of a PV array changes with the variation in the solar insolation. This results in a variable voltage at the output of the boost converter while maintaining the load line at the MPP. Consequently, the fundamental value of the output of the MPUC-5 also tends to change. Thus, it is required to produce angles that commit to an ac output voltage with a constant fundamental value and constrained to a minimum total harmonic distortion along with a third-order harmonic mitigation as per the grid codes, irrespective of the change in the dc-link voltages. A genetic algorithm is employed for this purpose. A large dataset is prepared for two-angle and four-angle operation of MPUC-5 under various dc-link voltages and constraints with which an ANN-based controller is trained. A neural network with a hidden layer is trained with the back propagation technique; and once a correlation is developed, the network can be operated for a wide range of operating conditions. The robustness of the controller is verified through simulation in MATLAB/Simulink environment and validated by experimental emulation in an hardware in loop environment.

KEYWORDS:

1.      Artificial neural network (ANN)

2.      Genetic algorithm (GA)

3.      Modified packed U-cell (MPUC) Inverter

4.      multilevel inverter (MLI)

5.      selective harmonic elimination (SHE)

6.      total harmonic distortion (THD)

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

 In this work, a five-level modified PUC inverter with a dc link ratio of 1:1 is considered whose switching is controlled by an ANN-based controller. Furthermore, the controller is implemented in a solar PV system where it provides a robust performance by keeping the fundamental value of the voltage across the load constant despite a change in the voltages of the dc links of the converter. GA is employed to furnish the angles that provided such result under constraints of low values of the THD and mitigation of the low-order harmonics, especially the third-order harmonics. A total of 10 201 combinations of such angles were found for two-angle and four-angle operation of the converter separately and were graphically presented. An ANN controller which was based on MLP was then trained on these angles based on the back propagation technique. The robustness of the controller was then verified in Simulink with variations in dc-link voltages. Then, it was also verified for Solar PV application. The output of the converter was of constant fundamental with the THDs and third-order harmonics within the prescribed limits of IEEE. The real-time hardware emulation for the MPUC-5 with the ANN-based controller was successfully performed on Typhoon HIL-402.

 

REFERENCES:

[1] B. Wu and M. Narimani, “High-power converters and AC drives,” in High-Power Converters and AC Drives. Hoboken, NJ, USA:Wiley, 2017, pp. 119–140.

[2] A. Nabae, I. Takahashi, and H. Akagi, “A new neutral-point-clamped PWM inverter,” IEEE Trans. Ind. Appl., vol. IA- 17, no. 5, pp. 518–523, Sep. 1981. [Online]. Available: http://ieeexplore.ieee.org/xpls/abs_all. jsp?arnumber=645616

[3] T. Meynard and H. Foch, “Multi-level conversion: High voltage choppers and voltage-source inverters,” in Proc. Conf. Rec. 23rd Annu. Power Electronics Specialists, Toledo, Spain, 1992, pp. 397–403.

[4] F. Z. Peng, J.-S. Lai, J.W. McKeever, and J. VanCoevering, “A multilevel voltage-source inverter with separate DC sources for staticVar generation,” IEEE Trans. Ind. Appl., vol. 32, no. 5, pp. 1130–1138, Sep./Oct. 1996.

[5] J.-S. Lai and F. Z. Peng, “Multilevel converters—A new breedof power converters,” IEEE Trans. Ind. Appl., vol. 32, no. 3, pp. 2348–2356, May/Jun. 1996.

Modified Seven-Level Pack U-Cell Inverter for Photovoltaic Applications

 ABSTRACT:

This paper proposes a modified configuration of single-phase Pack U-Cell (PUC) multilevel inverter in which the output voltage has higher amplitude than the maximum DC link value used in the topology as a boost operation. The introduced inverter generates seven-level AC voltage at the output using two DC links and six semiconductor switches. Comparing to cascaded H-bridge and neutral point clamp multilevel inverters, the introduced multilevel inverter produces more voltage levels using less components. The proposed inverter is used in PV system where the green power comes from two separate PV panels connected to the DC links through DC-DC converters to draw the maximum power. Due to boost operation of this inverter, two different PV panels can combine and send their powers to the grid. Simulations and experimental tests are conducted to investigate the good dynamic performance of the inverter in grid-connected PV system.

KEYWORDS:

1.      PV Inverter

2.      Pack U-Cell

3.      Modified Pack U-Cell

4.      PUC5

5.      MPUC5

6.      Power Quality

7.      Renewable Energy Conversion

 SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

  In this paper a modified multilevel inverter topology has been presented. The proposed MPUC inverter can generate 7-level voltage waveform at the output with low harmonic contents. Unlike the reported PUC topology, the 7-level MPUC inverter is capable to produce voltage levels more than the DC sources used in the structure. It can sum up the DC buses amplitudes to deliver more power to the output. The associated switching algorithm has been designed and implemented on the introduced MPUC topology with reduced switching frequency aspect. Moreover, photovoltaic application has been targeted for this inverter to deliver power from PV panels with different voltage/current rating to grid. In this regard, results have been shown to validate the acceptable voltage regulation and current controlling of the grid-connected inverter as well as the implemented P&O MPPT algorithm.

REFERENCES:

 [1] B. Singh, A. Chandra, and K. Al-Haddad, Power Quality: Problems and Mitigation Techniques: John Wiley & Sons, 2014.

[2] I. Gowaid, G. Adam, A. Massoud, S. Ahmed, and B. Williams, "Hybrid and Modular Multilevel Converter Designs for Isolated HVDC-DC Converters," IEEE Journal Emerg. and Select. Topics in Power Electron., vol. PP, no. 99, p. 1, 2017.

[3] H. Vahedi, K. Al-Haddad, Y. Ounejjar, and K. Addoweesh, "Crossover Switches Cell (CSC): A New Multilevel Inverter Topology with Maximum Voltage Levels and Minimum DC Sources," in IECON 2013-39th Annual Conference on IEEE Industrial Electronics Society, Austria, 2013, pp. 54-59.

[4] P. W. Hammond, "A new approach to enhance power quality for medium voltage drives," in Petroleum and Chemical Industry Conference, 1995. Record of Conference Papers., Industry Applications Society 42nd Annual, 1995, pp. 231-235.

[5] A. Nabae, I. Takahashi, and H. Akagi, "A new neutral-point-clamped PWM inverter," IEEE Trans. Ind. Applications, no. 5, pp. 518-523, 1981.

Novel Cascaded Switched-Diode Multilevel Inverter for Renewable Energy Integration

 ABSTRACT:

In this paper, a new topology of two-stage cascaded switched-diode (CSD) multilevel inverter is proposed for medium voltage renewable energy integration. First, it aims to reduce the number of switches along with its gate drivers. Thus, the installation space and cost of a multilevel inverter are reduced. The spike removal switch added in the first stage of the inverter provides a flowing path for the reverse load current, and as a result, high voltage spikes occurring at the base of the stepped output voltage based upon conventional CSD multilevel inverter topologies are removed. Moreover, to resolve the problems related to dc source fluctuations of multilevel inverter used for renewable energy integration, the clock phase-shifting (CPS) one-cycle control (OCC) is developed to control the two-stage CSD multilevel inverter. By shifting the clock pulse phase of every cascaded unit, the staircase-like output voltage waveforms are obtained and a strong suppression ability against fluctuations in dc sources is achieved. Simulation and experimental results are discussed to verify the feasibility and performances of the two-stage CSD multilevel inverter controlled by the CPS OCC method.

KEYWORDS:

1.      Novel cascaded multilevel inverter

2.      Two-stage

3.      One-cycle control

 SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

 A new topology of two-stage CSD multilevel inverter has been proposed in this paper. n cascaded basic units and one spike removal switch form the first stage. Then by adding a full-bridge inverter as the second-stage converter, both of the positive and negative output voltage levels are generated. Since the one full-bridge converter in the output side leads to the restriction on high-voltage applications, the proposed topology is suitable for medium-voltage renewable energy integration. The comparisons with the CHB and cascaded half-bridge topologies show that the CSD topology requires less switches and related gate drivers for realizing Nlevel output voltage. As a result, the installation space and cost of the multilevel inverter are reduced. Meanwhile, the spike removal switch added in the first stage provides a flowing path for the reverse load current under R-L loads, thus, the high voltage spikes, due to the collapsing magnetic field in a very short time interval, are removed. The CPS OCC method, which is composed by n similar but dependent OCC controllers, has been designed and implemented to control the CSD multilevel inverter. Simulation and experimental results demonstrate that, by shifting the clock pulse phase of each cascaded unit, the staircase-like voltage waveforms are obtained. Moreover, to evaluate the performance of CPS OCC, in both the simulation and experiment, the DC sources mixed with low frequency ripples are implemented to simulate the DC supply from renewable energy generations, and the comparative results between CPS OCC and CPS SPWM reveal that CPS OCC possesses a superior ability in suppressing the unbalance or low frequency ripples in DC sources. These results demonstrate that the CPS OCC method can be a substitute for conventional controllers to control multilevel inverters for renewable energy integration with improved control performances.

REFERENCES:

[1] M. S. B. Ranjiana, P. S. Wankhade, and N. D. Gondhalekar, “A modified cascaded H-bridge multilevel inverter for solar applications,” in Proc. 2014 Int. Conf. Green Comput. Commun. Elect. Eng., 2014, pp. 1–7.

[2] F. S. Kang, S. J. Park, S. E. Cho, C. U. Kim, and T. Ise, “Mutilevel PWM inverters suitable for the use of stand-alone photovoltaic power systems,” IEEE Trans. Energy Convers., vol. 20, no. 4, pp. 906–915, Dec. 2005.

[3] L. V. Nguyen, H.-D. Tran, and T. T. Johnson, “Virtual prototyping for distributed control of a fault-tolerant modular multilevel inverter for photovoltaics,” IEEE Trans. Energy Convers., vol. 29, no. 4, pp. 841–850, Dec. 2014.

[4] J. Rodriguez, J. S. Lai, and F. Z. Peng, “Mutilevel inverters: A survey of topologies, controls, and application,” IEEE Trans. Ind. Electron., vol. 49, no. 4, pp. 724–738, Aug. 2002.

[5] F. Z. Peng and J. S. Lai, “Mutilevel converters—A new breed of power converters,” IEEE Trans. Ind. Appl., vol. 32, no. 3, pp. 509–517, May/Jun. 1996.

Comparative Analysis between Five Level Conventional and Modified Cascaded H-Bridge Five Level Inverter Using Multicarrier Pulse width Modulation Techniques

 ABSTRACT:

Multilevel Inverters are getting popular and have become more attractive to researchers in the recent times for high power applications due to their better power quality and higher efficiency as compared to two level inverters. This research work presents a detailed comparative analysis of various multicarrier sinusoidal PWM schemes such as In Phase Disposition, Phase Opposition Disposition and Alternate Phase Opposite Disposition implemented on five level conventional and modified cascaded h-bridge inverters in MATLAB/SIMULINK software. Conventional five level topology uses eight switches and suffers from increased switching complexity while modified five level topology uses only five switches and is recommended to reduce switching complexity and switching losses. It also ensures less number of components, reduced size and overall cost of the system. The effect of modulation index (Ma) on the output harmonic contents in various PWM techniques is also analyzed.

KEYWORDS:

1.      Pulse Width Modulation

2.      Total Harmonic Distortion

3.      Cascaded H-Bridge Multilevel Inverter

4.      Modified Multilevel Inverter

5.      Level Shifted Modulation

6.      Phase Shifted Modulation         

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

 It is observed that POD PWM technique has slightly less %THD than IPD and APOD in conventional as well modified MLI. Also, it is concluded that increasing Modulation Index (Ma) reduces %THD. Conventional and Modified MLI has almost same total harmonic distortions but Modified MLI uses only 5 switches whereas Conventional MLI uses 8 switches, hence switching complexity, switching losses and cost of the system is reduced and Modified MLI is recommended to be better choice.

REFERENCES:

[1] B.L Nayak, G. Venkataratnam “ THD and Switching losses Analysis of Multi-Level Inverter Fed 3- Φ Induction Motor Drive”, International Journal of Scientific and Engineering Research, Vol. 5, issue 1,pp 2067-2074”

 [2] E. Beser, B. Arifoglu, S. Camur and E.K Beser “Design and Application of a Single Phase Multilevel Inverter Suitable for using as Voltage Harmonic Source”, Journal of Power Electronics, Vol. 10, No. 2, March 2010.

[3] Y.M Park, H.S Ryu, H.Y Lee, M.G Jung and S.H Lee “Design of Cascaded H-Bridge Multilevel Inverter based on Power Electronics building blocks and control for High Performance”, Journal of Power Electronics, Vol. 10, No. 3, May 2010.

 [4] S. Kouro, K. Gopakumar, J. Pou “Recent Advances and Industrial Applications of Multilevel Converters”, IEEE transaction on Industrial Electronics, Vol. 57, No. 8, August 2010.

[5] P.V Kumar, C.S Kumar and K.R Reddy “ Single Phase Cascaded Multilevel Inverter using Multicarrier PWM Technique”, ARPN Journal of Engineering and Applied Sciences, Vol. 8, No. 10, October 2013.