Power Quality Improvement and Low Voltage Ride through Capability in Hybrid Wind-PV Farms Grid-Connected Using Dynamic Voltage Restorer

ABSTRACT:

 

The paper proposes the application of a Dynamic Voltage Restorer (DVR) to enhance the power quality and improve the low voltage ride through (LVRT) capability of a three-phase medium-voltage network connected to a hybrid distribution generation (DG) system. In this system, the photovoltaic (PV) plant and the wind turbine generator (WTG) are connected to the same point of common coupling (PCC) with a sensitive load. The WTG consists of a DFIG generator connected to the network via a step-up transformer. The PV system is connected to the PCC via a two-stage energy conversion (DC-DC converter and DC-AC inverter). This topology allows, first, the extraction of maximum power based on the incremental inductance technique. Second, it allows the connection of the PV system to the public grid through a step-up transformer. In addition, the DVR based on Fuzzy Logic Controller (FLC) is connected to the same PCC. Different fault condition scenarios are tested for improving the efficiency and the quality of the power supply and compliance with the requirements of the LVRT grid code. The results of the LVRT capability, voltage stability, active power, reactive power, injected current, and DC link voltage, speed of turbine and power factor at the PCC are presented with and without the contribution of the DVR system.

KEYWORDS:

1.      Active power

2.      DC-link voltage DFIG

3.      Dynamic Voltage Restorer

4.      LVRT

5.      Power Factor

6.      Photovoltaic

7.      Voltage Stability

8.      Reactive Power

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

 

FIGURE 1: PV-WTG hybrid system with DVR and a load connected to grid.

 

EXPECTED SIMULATION RESULTS:

 

FIGURE 2: Voltage phase magnitude at PCC during faults with typical LVRT and HVRT characteristics requirements of Distributed Generation Code of Germany as an example.

FIGURE 3: Voltage phase magnitude at PCC during sag fault.

 

FIGURE 4: Voltage phase magnitude at PCC during short circuit fault.

 

 FIGURE 5: Phase voltage at PCC during sag fault.

 

FIGURE 6: DVR voltage contribution at PCC during sag fault.

FIGURE 7: Phase voltage at PCC during short circuit fault.

  

FIGURE 8: Total active power of hybrid system at PCC injected to grid.

 

 

FIGURE 9: PV active power at PCC injected to grid.

 

FIGURE 10: Wind active power at PCC injected to grid.

 

FIGURE 11: Total reactive power of hybrid system at PCC injected to grid.

 

FIGURE 12: PV reactive power at PCC injected to grid.

 

 FIGURE 13: Wind reactive power at PCC injected to grid.

 FIGURE 14: Total PV-WT current injected to grid at PCC.

FIGURE 15: PV current injected at PCC.

FIGURE 16: WT current injected at PCC to grid.

 

FIGURE 17: Power factor at PCC.

 

FIGURE 18: Turbine rotor speed.

 

FIGURE 19: Vdc link at WTG inverter.

 

 FIGURE 20: Vdc link voltage at PV inverter.

 

CONCLUSION:

The simulation study was carried out using MATLAB to demonstrate the effectiveness of the proposed DVR control system to improve the power quality and LVRT capability of the hybrid PV-WT power system. The system has been tested under different fault condition scenarios. The results have shown that the DVR connected to the PV-Wind hybrid system at the medium voltage grid is very effective and is able to mitigate voltage outages and short circuit failure with improved voltage regulation capabilities and flexibility in the correction of the power factor.

The results of the simulation also prove that the system designed is secure since the required voltage ranges are respected correctly and the DG generators operate reliably. The main advantage of the proposed design is the rapid recovery of voltage; the power oscillations overshoot reduction, control of rotor speed and preventing the system from having a DC link overvoltage and thus increasing the stability of the power system in accordance with LVRT requirements.

REFERENCES:

[1] J. Hossain, H. Roy Pota, “Robust Control for Grid Voltage Stability High Penetration of Renewable Energy,” Springer ,1st ed., pp.1–11, 2014.

[2] S. Talari et al.,"Stochastic modelling of renewable energy sources from operators' point-of-view: A survey," Renewable and Sustainable Energy Reviews, Vol.81, no.2, , pp.1953-1965,Jan.2018.

[3] R. Teodorescu ,M. Liserre, P. Rodríguez, “Grid Converters For Photovoltaic And Wind Power Systems, “John Wiley & Sons Ltd.,1st ed.,2011.

[4] G. Romero Rey, L. M.Muneta, “Electrical Generation and Distribution Systems and Power Quality Disturbances,” InTech, 1st ed., 2011.

[5] L.Ruiqi, G.Hua, Y.Geng, “Fault ride-through of renewable energy conversion systems during voltage recovery,” J. Mod. Power Syst. Clean Energy,vol. 4,no.1,pp:28-39, 2016.

Modeling, Control, and Performance Evaluation of Grid-Tied Hybrid PV/Wind Power Generation System: Case Study of Gabel El-Zeit Region, Egypt

 ABSTRACT:

 

The potential for utilizing clean energy technologies in Egypt is excellent given the abundant solar irradiation and wind resources. This paper provides detailed design, control strategy, and performance evaluation of a grid-connected large-scale PV/wind hybrid power system in Gabel El-Zeit region located along the coast of the Red Sea, Egypt. The proposed hybrid power system consists of 50 MW PV station and 200 MW wind farm and interconnected with the electrical grid through the main Point of Common Coupling (PCC) busbar to enhance the system performance. The hybrid power system is controlled to operate at the unity power factor and also the Maximum Power Point Tracking (MPPT) technique is applied to extract the maximum power during the climatic conditions changes. Modeling and simulation of the hybrid power system have been performed using MATLAB/SIMULINK environment. Moreover, the paper presented a comprehensive case study about the realistic monthly variations of solar irradiance and wind speed in the study region to validate the effectiveness of the proposed MPPT techniques and the used control strategy. The simulation results illustrate that the total annual electricity generation from the hybrid power system is 1509.85 GWh/year, where 118.15 GWh/year (7.83 %) generates from the PV station and 1391.7 GWh/year (92.17%) comes from the wind farm. Furthermore, the hybrid power system successfully operates at the unity power factor since the injected reactive power is kept at zero.

KEYWORDS:

1.      PV

2.      wind

3.      hybrid system

4.      Gamesa G80

5.      Gabel El-Zeit

6.      Egypt

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

 

FIGURE 1. Configuration of the proposed PV/wind hybrid system.

 EXPECTED SIMULATION RESULTS:

  

FIGURE 2. PV array side results.

FIGURE 3. Dynamic action of the VSI controller.

FIGURE 4. Dynamic performance of the PV station at the B1-bus.

FIGURE 5. Gamesa wind turbine results

FIGURE 6. Dynamic performance of the wind speed at the B2-bus.

FIGURE 7. Performance of the hybrid system at the PCC bus.

 CONCLUSION:

This paper presented the detailed design, control strategy, and performance analysis of 250 MW grid-connected PV/wind hybrid power system in Gabel El-Zeit region, Egypt. This area is characterized by a good level of solar irradiation with an annual average value of 199.75 kWh/m2 and powerful wind speed with an average value of 14.08 m/s at 60 m hub height. The proposed hybrid power system consists of 50MW PV station based Sanyo HIP-200B PV module and 200 MW wind farm based Gamesa G80 wind turbine and it is inte- grated with the grid through the main PCC bus to support the system performance. The hybrid power system is adjusted to work at the unity power factor and also the MPPT algorithms are applied to capture the optimum power from the hybrid system under the changes of climatic conditions. Adaptive InCond MPPT technique based variable step-size is applied to the boost converter to extract the maximum power from the PV station during the solar irradiance variation. On the other hand, a modi_ed P&O MPPT strategy is implemented on the RSC of DFIG to obtain the maximum power from the wind farm during the change of wind speed.

Moreover, this paper analyzed the actual monthly changes of solar irradiance and wind speed in the study area to evaluate the dynamic performance of the hybrid system and validate the ef_ciency of the proposed MPPT techniques and the control systems. The simulation results have illustrated that the proposed InCond MPPT algorithm tracks accurately the MPPs, where the PV station power increases signi_cantly from 8.9MWin January to its maximum value (17.9 MW) in June, then it falls drastically to the minimum value of 8.2MW in December. Also, the DC-link voltage controller of the VSI adjusts successfully the DC-link voltage at its reference value (500 V) regardless of the solar irradiance variation.

Furthermore, the proposed P&O MPPT strategy sustains the optimal value of the wind turbine performance coef_cient, Cp D 0:48, to extract the maximum power from the wind farm during the change of wind speed. Therefore, the active power rises dramatically from 127.6 MW in January to the rated value (200 MW) in June, then it decreases gradually until reaching the minimum value of 112.4MWin November. Besides, the GSC controller has successfully stabilized the DC-bus voltage to the desired value (1150 V) regardless of the wind speed change.

Additionally, the simulation results have shown that the total annual electricity generation from the hybrid power system is 1509.85 GWh/year, where 118.15 GWh/year (7.83 %) generates from the PV station and 1391.7 GWh/year (92.17%) comes from the wind farm. Moreover, the control system always maintains the hybrid power system at the unity power factor as the injected reactive power is kept at zero. Also, the PCC bus voltage is sustained perfectly constant irrespective of the changes in climatic conditions and the magnitude of generated active power.

REFERENCES:

[1] K. D. Patlitzianas, ``Solar energy in Egypt: Signi_cant business opportunities,'' Renew. Energy, vol. 36, no. 9, pp. 2305_2311, Sep. 2011.

[2] H. M. Sultan, O. N. Kuznetsov, and A. A. Z. Diab, ``Site selection of large-scale grid-connected solar PV system in egypt,'' in Proc. IEEE Conf. Russian Young Researchers Electr. Electron. Eng. (EIConRus), Jan. 2018, pp. 813_818.

[3] Ministry of Electricity and Renewable Energy. (2018). New and Renewable Energy Authority (NREA) Annual Report for the Egypt. [Online]. Available: http://www.nrea.gov.eg/Content/reports/Englishv 2AnnualReport.pdf

[4] M. EL-Shimy, ``Viability analysis of PV power plants in Egypt,'' Renew. Energy, vol. 34, no. 10, pp. 2187_2196, Oct. 2009.

[5] M. G. M. A. Y. Hatata and M. Rana Elmahdy, ``Analysis of wind data and assessing wind energy potentiality for selected locations in Egypt,'' Int. J. Sci. Eng. Res., vol. 6, p. 6, Mar. 2015.

Power Quality Improvement in Solar Fed Cascaded Multilevel Inverter With Output Voltage Regulation Techniques

ABSTRACT:

 

The presence of harmonics in solar Photo Voltaic (PV) energy conversion system results in deterioration of power quality. To address such issue, this paper aims to investigate the elimination of harmonics in a solar fed cascaded _fteen level inverter with aid of Proportional Integral (PI), Arti_cial Neural Network (ANN) and Fuzzy Logic (FL) based controllers. Unlike other techniques, the proposed FLC based approach helps in obtaining reduced harmonic distortions that intend to an enhancement in power quality. In addition to the power quality improvement, this paper also proposed to provide output voltage regulation in terms of maintaining voltage and frequency at the inverter output end in compatible with the grid connection requirements. The simulations are performed in theMATLAB / Simulink environment for solar fed cascaded 15 level inverter incorporating PI, ANN and FL based controllers. To exhibit the proposed technique, a 3 kWp photovoltaic plant coupled to multilevel inverter is designed and hardware is demonstrated. All the three techniques are experimentally investigated with the measurement of power quality metrics along with establishing output voltage regulation.

KEYWORDS:

1.      Harmonics

2.      intelligent control

3.      multilevel inverter

4.      photo voltaic's

5.      power quality

6.      voltage regulation.

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

 

FIGURE 1. Fuzzy logic control structure.

 EXPECTED SIMULATION RESULTS:

 

FIGURE 2. Variation of output voltage with respect of irradiance.

FIGURE 3. Fifteen level output voltage with variable irradiance.

FIGURE 4. Regulated fifteen level output voltage with PI controller.

FIGURE 5. FFT analysis for PI based voltage regulation.

FIGURE 6. Regulated fifteen level output with ANN based controller.

FIGURE 7. FFT analysis for ANN based voltage regulation.

FIGURE 8. Regulated fifteen level output voltage with FLC.

FIGURE 9. FFT analysis for FLC based voltage regulation.

CONCLUSION:

The voltage regulation topology along with power quality improvement is considered and implemented both in simulation and experimental setup for a solar fed 15 level inverter. While considering the results, it is found that FLC presents better results for VR while considering the variations at the input solar PV. Despite this, FLC is considered for the nine-level by [23], but the implementation is carried out with the DC power supplies without utilizing the solar panels. All the other methods are implemented for low power and lesser levels of MLI topology. Commercial utilization of MLI by providing the constant output voltage is investigated, and the experimental results prove the effectiveness of the proposed system. The method is applicable for the users require grid interaction along with the power quality improvement.

 REFERENCES:

[1] S. Karekezi and T. Ranja, Renewable technologies in Africa. London, U.K.: Zed Books, 1997.

[2] S. Karekezi and W. Kithyoma, ``Renewable energy strategies for rural africa: Is a PV-led renewable energy strategy the right approach for providing modern energy to the rural poor of sub-saharan africa?'' Energy Policy, vol. 30, nos. 11_12, pp. 1071_1086, Sep. 2002.

[3] S. Karekezi andW. Kithyoma, ``Renewable energy in Africa: Prospects and limits in Renewable energy development,'' Workshop Afr. Energy Experts Operationalizing NEPAD Energy Initiative, vol. 1, pp. 1_30, 2-4 Jun. 2003. Jun. 2017. [Online]. Available: https://sustainabledevelopment.un. org/content/documents/nepadkarekezi.pdf

[4] D.-R. Thiam, ``Renewable decentralized in developing countries: Appraisal from microgrids project in senegal,'' Renew. Energy, vol. 35, no. 8, pp. 1615_1623, Aug. 2010.

[5] F. Christoph, World Energy Scenarios: Composing energy futures to 2050. London, U.K.: World Energy Council, 2013.