International Journal of Advanced Research in Electrical, Electronics and Instrumentation Engineering

International Journal of Advanced Research in Electrical, Electronics and Instrumentation Engineering

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Grid Connected DC Voltage Control with MPPT by Buck/Boost Converter

N.M.Jothiswaroopan1, A.R.M.Sasidhar2
  1. Professor, Dept. of EEE, RMK Engineering College, Chennai, Tamilnadu, India
  2. PG Student [PED],Dept. of EEE, RMK Engineering College, Chennai, Tamilnadu, India
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Abstract

The project is about Grid Connected DC voltage Control with MPPT by Buck-Boost Converter. Solar Panel helps to sense both voltage and power ratings and uses MPPT Fuzzy control method for voltage control and regulation by operating both power and current as variables. It calculates temperature i.e., physical signal value. The scheme helps for satisfying the both forward and reverse mode of operation with Buck-Boost process based on the essential DC Voltage Level. Sinusoidal Pulse Width Modulation (SPWM) is used as pulses for inverter work. The switches of Boost Converter are operated in 120* mode of operation to control the short circuit across them. Duty cycle helps to control the current distortion by varying the frequency (in terms of time period) of a generated pulse. It helps to maintain constant voltage in DC Grid. Simulation work is used to verify the outputs. The software used is MATLAB.

Keywords
Solar panel, MPPT Fuzzy control, Buck/Boost Converter

INTRODUCTION
In general, PV Modules produce DC voltage and current. AC voltages and current are necessary for feeding the electricity to the grid. To convert DC to AC, inverters are used. PV array is charged at the Maximum Power Point (MPP) near operating point and had done with MPP Tracking Algorithm. If the operating point is not the MPP, not all the possible power is being fed to the grid.To overcome the high voltage level across DC Grid, the solar panel is available as source for generating DC voltage with two components i.e., power and current. Optimization level (MPPT Fuzzy) has been used for control of the technique. For maintaining voltage as constant across DC Grid, the Buck/Boost operation is done. The maximum and minimum voltage level is varied in the source for the entire function of managing the voltage regulation near grid towards the load and vice–versa.

MAXIMUM POWER POINT TRACKING
To produce the maximum power from a solar array, MPPT algorithms are proposed. The work for MPP development was started over a decade. Difficulty, efficiency range, junction speed, accurate tracking differ with various techniques of MPPT algorithm. There are different methods to implement the system; among those Fuzzy Logic Control is used. Calculation of MPP based on capacity irradiance & temperature using PV module need IMPP and VMPP techniques. Its drawbacks are: to produce the required model of PV array and its necessity, sometimes difficult for more readings. The MPP is perfectly tracked under various atmospheric environments.

FUZZY LOGIC CONTROL
The apply of fuzzy logic control has happened to be trendy over the last decade because it can compact with imprecise inputs, does not need an exact mathematical form and can switch nonlinearity. Microcontrollers also helped in the popularization of fuzzy logic control. The fuzzy logic consists of three stages: fuzzification, inference system and defuzzification. Fuzzification comprises the process of transforming numerical crisp inputs into linguistic variables based on the degree of membership to certain sets. Membership functions, like the ones in Figure 1, are used to associate a grade to each linguistic term. The number of membership functions used depends on the correctness of the controller, but it usually varies between 5 and 7. In Figure, seven fuzzy levels are used: NB (Negative Big), NM (Negative Medium), NS (Negative Small), ZE (Zero), PS (Positive Small), PM (Positive Medium) and PB (Positive Big). The values a, b and c are based on the rangevalues of the numerical variable. In some cases the membership functions are taken less symmetric or even optimized for the application for better accuracy.
image
The inputs of the fuzzy controller are frequently an error, E, and the change in the error, Del E. The error can be selected by the designer, but usually it is chosen as DelP, DelV because it is zero at the MPP. Then E and DelE are provided as follows:
image (1)
image (2)
image

BUCK–BOOST CONVERTER
A single–phase and three phase bidirectional inverter with buck/boost converter, and maximum power point trackers (MPPTs) for dc–distribution applications are provided. In a dc–distribution system, a bidirectional inverter is required to control the power flow between dc bus and ac grid, and to regulate the dc bus to a certain range of voltages, the MPPT topology is formed with buck and boost converters to operate at the dc–bus voltage around 380 V, reducing the voltage stress of its followed inverter.
image

RESULT AND DISCUSSION
Simulations have done in two different phases that is both single and three phase systems. The following are the two outputs for the simulation in both single and three phase system.
image
image

FOR SINGLE PHASE SYSTEM
In this procedure, the temperature changes takes place in between 8 to 40 in terms of voltage. And the voltage across the input source is generated as 23V which is boosted up and maintained the DC grid voltage as 85V as a result. The voltage and current near the load is produced as ±80V and ±8A. The following are the simulation results occurred in Single Phase System.
The following outputs have the axis of Voltage rating and Current as Y–axis and Time period as X–axis.
image
image
image
image

FOR THREE PHASE SIMULATION
The various types of waveforms of voltages across the source, grid and load are designed below. With different input sources, the output generated at the grid remains same.
image
image
image

CONCLUSION
The operation of maintenance of constant voltage across the DC grid is studied. Using MPPT algorithm, the fuzzy control method is properly studied by managing power and current parameters for having equal magnitude in grid voltage. Duty cycle is varied with the help of time period for reducing the short circuit across the switches.

References
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  2. T.–F. Wu, K.–H.Sun, C.–L.Kuo, and C.–H. Chang, "Predictive current controlled 5–kW single–phase bidirectional inverter with wide inductance variation for dc–microgrid applications," IEEE Trans. Power Electron., vol. 25, no. 12, pp. 3076–3084, Dec. 2010.

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  7. H. Kakigano, A. Nishino, and T. Ise, "Distributed voltage control for DC microgrid with fuzzy control and gain–scheduling control," in Proc. IEEEInt. Conf. Power Electron., 2011, pp. 256–263.

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  9. J.–S. Park, J.–K.Choi, B.–G.Gu, I.–S.Jung, E.–C.Lee, and K.–S.Ahn, "Robust DC–Link voltage control scheme for photovoltaic power generation system PCS," in Proc. IEEE Int. Telecommun. Energy Conf., Oct. 2009, pp. 1–4.

  10. D. Salomonsson, L. Soder, and A. Sannino, "An adaptive control system for a DC microgrid for data centers," IEEE Trans. Ind. Appl., vol. 44, no. 6, pp. 1910–1917, Nov./Dec. 2008.

  11. J.–S. Park, J.–K.Choi, B.–G.Gu, I.–S.Jung, E.–C.Lee, and K.–S.Ahn, "A hybrid renewable DC microgrid voltage control," in Proc. IEEE Int.Power Electron. Motion Control Conf., May 2009, pp. 725–729.

  12. Z. Li, T. Wu, X. Yan, K. Sun, and J. M. Gurrero, "Power control of DC microgrid using DC bus signaling," in Proc. IEEE Appl. Power Electron.Conf., Mar. 2011, pp. 1926–1932.

  13. A. Engler, "Applicability of droops in low voltage grids," Int. J. Distrib. Energy Res., vol. 1, no. 1, pp. 1–5, Jan. 2005.

  14. J. A. Restrepo, J. M. Aller, A. Bueno, J. C. Viola, A. Berzoy, R. Harley, and T. G. Habetler, "Direct power control of a dual converter operating as a synchronous rectifier," IEEE Trans. Power Electron., vol. 26, no. 5, pp. 1410–1417, May 2011.

  15. M. G. Molina and P. E. Mercado, "Power flow stabilization and control of microgrid with wind generation by superconducting magnetic energy storage," IEEE Trans. Power Electron., vol. 26, no. 3, pp. 910–922, Mar. 2011.

  16. Y. C. Chang and C. M. Liaw, "Establishment of a switched–reluctance generator–based common DC microgrid system," IEEE Trans. PowerElectron., vol. 26, no. 9, pp. 2512–2527, Sep. 2011.

  17. N. Hur, J. Jung, and K. Nam, "A fast dynamic DC–link power–balance scheme for a PWM converter–inverter system," IEEE Trans. Ind. Electron., vol. 48, no. 4, pp. 794–1803, Aug. 2001.

  18. J. Yao, H. Li, Y. Liao, and Z. Chen, "An improved control strategy of limiting the DC–link voltage fluctuation for a doubly fed induction wind generator," IEEE Trans. Power Electron., vol. 23, no. 3, pp. 1205–1213, May 2008.

  19. T.–F. Wu, L.–C.Lin, C.–H.Chang, Y.–L.Lin, and Y.–C. Chang, "Current improvement for a3 bi–directional inverter with wide inductance variation," in Proc. IEEE ECCE Asia, May/Jun. 2011, pp. 1777–1784.

  20. E. Aeloiza, J.–H. Kim, P. Enjeti, and P. Ruminot, "A real time method to estimate electrolytic capacitor condition in PWM adjustable speed drives and uninterruptible  power supplies," in Proc. IEEE Power Electron. Spec.Conf., Jun. 2005, pp. 2867–2872.
  21. Tsai–Fu Wu, Chih–Hao Chang, Li–Chiun Lin, Gwo–Ruey Yu and Yung–Ruei Chang, "DC–Bus Voltage Control with Three Phase Bi–directional Inverter for DC distribution systems."IEEE Transcations on Power Electronics,Vol.28, No.4, April 2013.

  22. T.–F. Wu, K.–H.Sun, C.–L.Kuo, and C.–H. Chang, "Predictive current controlled 5–kW single–phase bidirectional inverter with wide inductance variation for dc–microgrid applications," IEEE Trans. Power Electron., vol. 25, no. 12, pp. 3076–3084, Dec. 2010.

  23. L. Xu and D. Chen, "Control and design of a DC microgrid with variable generation and energy storage," IEEE Trans. Power Del., vol. 26, no. 4, pp. 2513–2522, Oct. 2011.

  24. Z.–H. Ye, D. Boroyevich, K. Xing, and F.–C. Lee, "Design of parallel sources in DC distributed power systems by using gain–scheduling technique," in Proc. IEEE Power Electron. Spec. Conf., Aug. 1999, pp. 161–165.

  25. Y. Ito, Y. Zhongqing, and H. Akagi, "DC microgrid based distribution power generation system," in Proc. IEEE Int. Power Electron. MotionControl Conf., Aug. 2004, pp. 1740–1745.

  26. J. M. Guerrero, J. C. Vasquez, J. Matas, L. G. D. Vicuna, and M. Castilla, "Hierarchical control of droop–controlled AC and DC microgrid—A general approach toward standardization," IEEE Trans. Ind. Electron., vol. 58, no. 1, pp. 158–172, Jan. 2011.

  27. H. Kakigano, A. Nishino, and T. Ise, "Distributed voltage control for DC microgrid with fuzzy control and gain–scheduling control," in Proc. IEEEInt. Conf. Power Electron., 2011, pp. 256–263.

  28. H.Kakigano,Y. Miura, and T. Ise, "Low–voltage bipolar–type dc microgrid for super high quality distribution," IEEE Trans. Power Electron., vol. 25, no. 12, pp. 3066–3075, Dec. 2010.

  29. J.–S. Park, J.–K.Choi, B.–G.Gu, I.–S.Jung, E.–C.Lee, and K.–S.Ahn, "Robust DC–Link voltage control scheme for photovoltaic power generation system PCS," in Proc. IEEE Int. Telecommun. Energy Conf., Oct. 2009, pp. 1–4.

  30. D. Salomonsson, L. Soder, and A. Sannino, "An adaptive control system for a DC microgrid for data centers," IEEE Trans. Ind. Appl., vol. 44, no. 6, pp. 1910–1917, Nov./Dec. 2008.

  31. J.–S. Park, J.–K.Choi, B.–G.Gu, I.–S.Jung, E.–C.Lee, and K.–S.Ahn, "A hybrid renewable DC microgrid voltage control," in Proc. IEEE Int.Power Electron. Motion Control Conf., May 2009, pp. 725–729.

  32. Z. Li, T. Wu, X. Yan, K. Sun, and J. M. Gurrero, "Power control of DC microgrid using DC bus signaling," in Proc. IEEE Appl. Power Electron.Conf., Mar. 2011, pp. 1926–1932.

  33. A. Engler, "Applicability of droops in low voltage grids," Int. J. Distrib. Energy Res., vol. 1, no. 1, pp. 1–5, Jan. 2005.

  34. J. A. Restrepo, J. M. Aller, A. Bueno, J. C. Viola, A. Berzoy, R. Harley, and T. G. Habetler, "Direct power control of a dual converter operating as a synchronous rectifier," IEEE Trans. Power Electron., vol. 26, no. 5, pp. 1410–1417, May 2011.

  35. M. G. Molina and P. E. Mercado, "Power flow stabilization and control of microgrid with wind generation by superconducting magnetic energy storage," IEEE Trans. Power Electron., vol. 26, no. 3, pp. 910–922, Mar. 2011.

  36. Y. C. Chang and C. M. Liaw, "Establishment of a switched–reluctance generator–based common DC microgrid system," IEEE Trans. PowerElectron., vol. 26, no. 9, pp. 2512–2527, Sep. 2011.

  37. N. Hur, J. Jung, and K. Nam, "A fast dynamic DC–link power–balance scheme for a PWM converter–inverter system," IEEE Trans. Ind. Electron., vol. 48, no. 4, pp. 794–1803, Aug. 2001.

  38. J. Yao, H. Li, Y. Liao, and Z. Chen, "An improved control strategy of limiting the DC–link voltage fluctuation for a doubly fed induction wind generator," IEEE Trans. Power Electron., vol. 23, no. 3, pp. 1205–1213, May 2008.

  39. T.–F. Wu, L.–C.Lin, C.–H.Chang, Y.–L.Lin, and Y.–C. Chang, "Current improvement for a3 bi–directional inverter with wide inductance variation," in Proc. IEEE ECCE Asia, May/Jun. 2011, pp. 1777–1784.

  40. E. Aeloiza, J.–H. Kim, P. Enjeti, and P. Ruminot, "A real time method to estimate electrolytic capacitor condition in PWM adjustable speed drives and uninterruptible  power supplies," in Proc. IEEE Power Electron. Spec.Conf., Jun. 2005, pp. 2867–2872.