Power Flow Control of Interconnected AC-DC Microgrids in Grid-Connected Hybrid Microgrids Using Modified UIPC

ABSTRACT:

  This paper introduces a new approach for power flow control of interconnected AC-DC microgrids in grid-connected hybrid microgrids based on implementing a modified unified interphase power controller (UIPC). A typical grid-connected hybrid microgrid including one AC microgrid and one DC microgrid is considered as studied system. Instead of using the parallel-connected power converters, these microgrids are interconnected using a modified UIPC. As the first contribution of this paper, the conventional structure of UIPC, which uses three power converters in each phase, is modified so that a reduced number of power converters is implemented for power exchange control between AC-DC microgrids. The modified structure includes one power converter in each phase, named as line power converter (LPC), and a power converter which regulates the DC bus voltage, named as bus power converter (BPC) here. The AC microgrid is connected to the main grid through the LPCs which their DC buses are linked and can operate in capacitance mode (CM) or inductance mode (IM). A fuzzy logic controller is used in the control structure of the LPCs. The fuzzy inference system is optimized based on H∞ filtering method to reduce the errors in membership functions design. Through the BPC, the DC voltage of LPCs is supplied by the DC microgrid. However, since the DC microgrid voltage is provided here by a PV system, the DC link voltage of the LPCs is fluctuating. Thus, as the second contribution, to stabilize the DC link fluctuations, a new nonlinear disturbance observer based robust multiple-surface sliding mode control (NDO-MS-SMC) strategy is presented for DC side control of the BPC. The simulation results confirm the effectiveness of the proposed power flow control strategy of the improved UIPC for hybrid microgrids.

KEYWORDS:

 

1.      Hybrid microgrid

2.      UIPC

3.      Power control

4.      Disturbance observer

5.      Multi-surface SMC

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

The hybrid microgrid structure is the most probable option in the future smart grids to gather together the renewable resources as well as AC/DC loads. This is due to the fact that this structure has the merits of both AC and DC microgrids simultaneously. One conventional problem with this structure is the power exchange control between interconnected AC and DC microgrids. In this study, a UIPC based solution has been proposed as a superior alternative to the parallel-connected power converters which have brought many problems. A modified structure of the UIPC has firstly been proposed and then effective control strategies have been introduced for the modified UIPC. The simulation results validated the modified model as well as the power exchange control performance between AC and DC microgrids.

REFERENCES:

[1] Runfan Zhang, Branislav Hredzak, "Distributed Finite-Time Multi-Agent Control for DC Microgrids with Time Delays”, IEEE Transactions on Smart Grid, Early Access, 2018.

[2] Kumar Utkarsh, et al, "Distributed Model-predictive Real-time Optimal Operation of a Network of Smart Microgrids", IEEE Transactions on Smart Grid, Early Access, 2018.

[3] Haifeng Qiu, et al, " Bi-level Two-stage Robust Optimal Scheduling for AC/DC Hybrid Multi-microgrids", IEEE Transactions on Smart Grid, Early Access, 2018.

[4] Pengfeng Lin, et al, "A Distributed Control Architecture for Global System Economic Operation in Autonomous Hybrid AC/DC Microgrids", IEEE Transactions on Smart Grid, Early Access, 2018.

[5] Daniel E. Olivares, et al, "Trends in Microgrid Control", IEEE Transactions on Smart Grid Volume: 5, Issue: 4, pp. 1905 – 1919, 2014.  

Power Flow Control of Hybrid Micro-Grids Using Modified UIPC

ABSTRACT:

This work introduces a replacement advent for power flow control of interconnected AC-DC micro-grids in hybrid micro-grids connected to grids. It also supports implementing an Adaptive Neuro Fuzzy Inference System (ANFIS) controlled modified Unified Inter-Phase Power Controller (UIPC). For study, a classic hybrid micro-grid connected to grid comprising of a AC micro-grid and a DC micro-grid is taken into account. These micro-grids are interconnected employing a modified UIPC, rather than using the power converters connected in parallel. As the first input of this paper is the standard structure of UIPC, which used three power converters in every phase. It was then modified such as number of power converters is used less and implemented for the control of the exchange of power between AC-DC microgrids. In every phase there is one power electronic converter in the improved structure. It is called as Line Power Converter (LPC). Also there is Bus Power Converter (BPC) to regulate the voltage of the DC bus. The Line Power Converters links the AC micro-grid to the main grid. The DC buses are also linked with them. It can be operated in Inductance Mode (IM) as well as Capacitance Mode (CM). The control structure of LPCs has an Adaptive Fuzzy Logic Controller in it. For hybrid micro-grids, the capability of the suggested power flow control strategy is confirmed by the MATLAB simulation results.

KEYWORDS:

1.      Ac micro-grid

2.      Dc micro-grid

3.      Grid control

4.      Hybrid micro-grid

5.      UIPC

6.      UPFC

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

The hybrid micro-grid structure is the favorable option in the future smart grids to gather together the renewable resources for AC/DC loads. This is because of the fact that this structure holds the merits of AC as well as DC micro-grids simultaneously. There is one conventional problem with this structure. That is to efficiently control the exchange of power within interconnected micro-grids comprising of AC and DC system. In this particular work, an ANFIS controlled UIPC solution is suggested as a superior alternative to the power electronic converters connected in parallel which have brought many problems. An improved design of the UIPC was initially suggested and then effective strategies for control are presented for the modified UIPC. The results of simulation are used to validate the modified model along with performance of the control of power exchange between micro-grids having AC and DC system.

REFERENCES:

[1] H.a. Pan M. Ding R. Bi L. Sun Research on Cooperative Planning of Distributed Generation Access to AC/DC Distribution (Micro) Grids Based on Analytical Target Cascading Energies 12 10 2019 1847. (https://doi.org/10.3390/ en12101847)

[2] Du Yi, Jiang Daozhuo, Yin Rui, Pengfei Hu, Wang Yufen, ‘‘Modeling and simulation of DC distribution network based on distributed energy” 2013 2^nd International Symposium on Instrumentation & Measurement, Sensor Network and Automation (IMSNA)

[3] J.M. Guerrero J.C. Vasquez J. Matas L.G. de Vicuna M. Castilla Hierarchical Control of Droop-Controlled AC and DC Microgrids—A General Approach Toward Standardization IEEE Trans. Ind. Electron. 58 1 2011 158 172 10.1109/ TIE.2010.2066534 http://ieeexplore.ieee.org/document/5546958/

[4] JiaLihu, ‘‘Architecture Design for New AC-DC Hybrid Micro-grid”, DC Microgrids (ICDCM), IEEE First International Conference on, 2015.

[5] D. Riana Aryani and Hwachang Song, ‘‘Coordination Control Strategy for AC/DC Hybrid Microgrids in Stand-Alone Mode‘‘ Energies 9 6 2016 469. (https://doi.  org/10.3390/en9060469) 

Multifunctional Grid-Tied PV System Using Modified KLMS Control

 ABSTRACT:

This paper deals with the modified kernel least mean square (KLMS) control strategy in double-stage, solar photovoltaic (PV) grid tied system to enhance the power quality at common coupling point (CCP). This proposed control algorithm has less oscillations, fast convergence, fast dynamic response and good steady state performance. A control strategy is used to extract the fundamental active current component of load and generates reference grid current for a DC-AC converter. The proposed modified KLMS control mitigates multiple power quality concerns such as harmonics reduction, unity power factor and load balancing. The dynamic performance of proposed system is confirmed into the MATLAB\Simulink environment. Test results on hardware implementation are presented at varying solar irradiation levels and load unbalancing. Test results are found satisfactory and total harmonic distortion (THD) of the grid currents are observed well within the IEEE-519 standard.

KEYWORDS:

1.      Solar PV Generation

2.      Voltage Source Converter (VSC)

3.      Distributed Network

4.      Power Quality

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

The proposed modified KLMS based control scheme for double stage solar PV system, has been simulated in MATLAB\Simulink environment and simulated results are validated through the experimental prototype. The MPPT has extricated the peak power point successfully (nearly 100%) from the solar PV array under varying insolation levels. The proposed control effectively provides harmonics compensation, grid currents balancing and unity power factor in the grid tied system. This proposed modified KLMS control scheme has extracted the fundamental current component efficiently. Under the load unbalancing condition, the fundamental current component has shown faster convergence and less oscillations than LMS and LMF controls. Moreover, it has good steady state and dynamic performances than LMS and LMF controls. Moreover, the THD of grid currents, is meeting the IEEE-519 standard[12].

REFERENCES:

[1] International Energy Agency, “Medium term renewable energy market report 2016,” [Online].Available http://www.iea.org

[2] P. Shukl and B. Singh, “Delta-Bar-Delta Neural Network (NN) Based Control Approach for Power Quality Improvement of Solar PV Interfaced Distribution System,” IEEE Trans. on Ind. Info.., early access 2019.

[3] S. M. Fatemi, M. S. Shadlu and A. Talebkhah, “Comparison of Three-Point P&O and Hill Climbing Methods for Maximum Power Point Tracking in PV Systems,” 10th Int. Power Elec., Drive Sys.and Tech. Conf.(PEDSTC), Shiraz, Iran, 2019, pp. 764-768.

[4] E. H. M. Ndiaye, A. Ndiaye, M. A. Tankari and G. Lefebvre, “Adaptive Neuro-Fuzzy Inference System Application for The Identification of a Photovoltaic System and The Forecasting of Its Maximum Power Point,” 7th Int. Conf. on Renew. Ene. Rese.and App.(ICRERA), Paris, 2018, pp. 1061-1067.

[5] N. Arab, B. Kedjar, A. Javadi and K. Al-Haddad, “A Multifunctional Single-Phase Grid-Integrated Residential Solar PV Systems Based on LQR Control,” IEEE Trans. on Ind. Appl., vol. 55, no. 2, pp. 2099-2109, March-April 2019.

 

Multifunctional Grid Connected Inverter Interfaced by Wind Energy Conversion System

ABSTRACT:

This study deals with a three-phase multifunctional grid-connected inverter interfaced with a wind energy conversion system (WECS) is described. The studied system consists of a permanent magnet synchronous generator (PMSG) based wind turbine, a rectifier and a three-phase voltage source inverter connected to the utility at the point of common coupling. To ensure the multifunctional feature, we propose a direct power control (DPC) which is applied to eliminate line current harmonics, compensate reactive power and feeding wind power into the utility. Simulation results are provided to demonstrate the effectiveness of the proposed system. The results show that the control algorithm of system is effective for eliminating harmonic currents, reactive power compensation and inject the active power available from the PMSG wind turbine into the load and/or grid, which allowed us to confirm the robustness of the proposed strategy.

KEYWORDS:

1.      Inverter

2.      Wind energy conversion system

3.      Permanent magnet synchronous generator

4.      Rectifier

5.      DPC

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

This paper focused on applying direct power control to a three-phase multifunctional grid-connected inverter interfaced with a wind energy conversion system. The proposed control scheme is used in order to achieve harmonics elimination, reactive power compensation, and simultaneously inject the active power available from the PMSG wind turbine into the load and/or grid. The analysis of the simulation results obtained has attested the robustness, the effectiveness and the good performance of proposed system. The DPC method has very good performance in injection of active power produced by PMSG wind turbine to the distribution networks and simultaneously compensating harmonics and reactive power.

REFERENCES:

[1] H.G. Kim, D.C. Lee, J.K. Seok and G.M. Lee, “Stand-alone wind power generation system using vector-controlled cage-type induction generators,” in Proc. of Inter. Conference on Electrical Machines and systems, vol.1, pp.289-292, Nov.2003.

[2] B. Singh and G.K. Kasal, “Voltage and Frequency Controller for a threephase four wire autonomous wind energy conversion systems,” IEEE Trans. Energy Conversion, vol. 23, no.2, pp.509–518, June 2008.

[3] A.Krama, L.Zellouma and B. Rabhi “Improved Control of Shunt Active Power Filter Connected to a Photovoltaic System Using Technique of Direct Power Control,” 8th International Conference on Modelling, Identification and Control (ICMIC-2016).

[4] M.R. Bengourina, M. Rahli, S. Saadi,, L.Hassaine, “Optimization of direct power control of three-phase shunt active power filter by using PSO algorithm”, Leonardo Electronic Journal of Practices and Technologies, vol. 16, no.31, pp. 218-234, Dec 2017.

[5] A.Chaoui., J. Gaubert, F. Karim,, “Power quality improvement using DPC controlled three-phase shunt active filter”, Electric Power Systems Research, vol. 80, pp. 657–666, 2010.

 

Modelling and voltage control of the solar-wind hybrid micro-grid with optimized STATCOM using GA and BFA

ABSTRACT:

Electricity generation from the wind and solar photovoltaic (PV) systems are highly dependent  upon weather conditions. Their intermittent nature leads to fluctuations in their output. Therefore, the need for rapid compensation for energy transmission and distribution systems is increasingly important. Static Synchronous Compensator (STATCOM) can be adopted for reactive power compensation and for decreasing the voltage fluctuation caused by the system and renewable energy sources. This study presents modelling of a Solar PV-Wind Hybrid Micro-grid and the increase of the stable operating limit of the system in case of the incorporation of STATCOM is examined. The major contribution of this paper is the optimization of gain parameters of four PI controllers in STATCOM control circuit based on genetic algorithms (GA) and Bacteria Foraging Algorithm (BFA) and therefore obtaining better responses and voltage stability in terms of nonlinear nature of solar-wind hybrid micro-grid. The Simulink models of the system architecture include a wind turbine model, a solar PV power system model and a STATCOM. It is certified that the voltage fluctuation at the end of the bus bar is reduced by 8% using conventional PI controller, by 10% for GA-based PI controller, and by 15% for BFA based PI controller under variable load. The results obtained by GA and BFA-based optimization of PI controllers are compared with that of the conventional controller and better results attained.

KEYWORDS:

1.      Voltage control

2.      Bacteria foraging algorithm

3.      PV-wind hybrid system

4.      Static synchronous compensator

5.      Genetic algorithm

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

In this study, the impacts of a 2MWwind power induction generator based wind generation system and a 0.4MW solar power generation system on the grid were investigated. For this hybrid system, it has been pointed out that STATCOM provides reactive power compensation. A solar PV-wind power system with a hybrid structure was designed and the voltage profiles at the output were examined. STATCOM was incorporated to study the voltage profiles in the system according to capacitive and reactive operating states. On this basis, this work pointed out that power instability in large transmission systems can be minimized, and the fluctuations caused by the adoption of renewable energy sources to the system can be diminished. The comparisons of the results showed that the effectiveness of the STATCOM tuned with GA and BFA was improved. By acquiring the best values for PI controller gains, voltage swell occurred due to the change in reactive power has been overcome and a better dynamic response was reached. In future studies, different optimization techniques and different FACTS devices can be used to compare and determine a more effective one.

REFERENCES:

[1] F.H. Gandoman, A. Ahmadi, A.M. Sharaf, P. Siano, J. Pou, B. Hredzak, V.G. Agelidis, Review of FACTS technologies and applications for power quality in smart grids with renewable energy systems, Renew. Sustain. Energy Rev. 8 (2018) 502–514, https://doi.org/10.1016/j.rser.2017.09.062.

[2] A. Mohanty, M. Viswavandya, D.K. Mishra, P.K. Ray, S. Pragyan, Modelling & simulation of a PV based micro grid for enhanced stability, Energy Proc. (2017) 94–101, https://doi.org/10.1016/j.egypro.2017.03.060.

[3] H. Liao, S. Abdelrahman, J.V. Milanovic´ , Zonal mitigation of power quality using FACTS devices for provision of differentiated quality of electricity supply in networks with renewable generation, IEEE Trans. Power Deliv. 23 (2017) 1975–1985, https://doi.org/10.1109/TPWRD.2016.2585882.

[4] A. Saraswathi, P. Sanjeevikumar, S. Shanmugham, F. Blaabjerg, A.H. Ertas, V. Fedák, Analysis of enhancement in available power transfer capacity by STATCOM integrated SMES by numerical simulation studies, Eng. Sci. Technol., Int. J. 19 (2) (2016) 671–675, https://doi.org/10.1016/j.jestch.2015.10.002.

[5] D. Menniti, A. Pinnarelli, N. Sorrentino, An hybrid PV-Wind supply system with D-Statcom interface for a water-lift station, International Symposium on Power Electronics, Electrical Drives, Automation and Motion, 2010. DOI: 10.1109/SPEEDAM.2010.5545070.

Modelling and Voltage Control of the Solar- Wind Hybrid Micro-Grid with Optimized STATCOM

 ABSTRACT:

Electricity generation from the wind and solar photovoltaic (PV) systems are highly dependent upon weather conditions. Their intermittent nature leads to fluctuations in their output. Therefore, the need for rapid compensation for energy transmission and distribution systems is increasingly important. Static Synchronous Compensator (STATCOM) can be adopted for reactive power compensation and for decreasing the voltage fluctuation caused by the system and renewable energy sources. This study presents modelling of a Solar PV-Wind Hybrid Micro-grid and the increase of the stable operating limit of the system in case of the incorporation of STATCOM is examined. The major contribution of this paper is the optimization of gain parameters of four PI controllers in STATCOM based on genetic algorithms (GA) and therefore obtaining better responses and voltage stability in terms of nonlinear nature of solar-wind hybrid micro-grid. The Simulink models of the system architecture include a 2 MW wind turbine model based on a doubly fed induction generator (DFIG), 0.4 MW solar PV power system model and a STATCOM rated at 3 MVAR. It is certified that the voltage fluctuation at the end of the bus bar is reduced by 8 % using conventional PI controller. The results obtained by GA-based optimization of PI controllers are compared with that of the conventional controller and better results attained.

KEYWORDS:

1.      Flexible AC transmission systems

2.      Genetic Algorithm

3.      PV-Wind hybrid system

4.       Static synchronous compensator

5.      Voltage control

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

In this study, the impacts of a 2 MW wind power induction generator based wind generation system and a 0.4 MW solar power generation system on the grid was investigated. For this hybrid system, it has been pointed out that STATCOM provides reactive power compensation. A solar PV-wind power system with a hybrid structure was designed and the voltage profiles at the output were examined. STATCOM was incorporated to study the voltage profiles in the system according to capacitive and reactive operating states. On this basis, this work pointed out that power instability in large transmission systems can be minimized, and the fluctuations caused by the adoption of renewable energy sources to the system can be diminished. The comparisons of the results showed that the effectiveness of the STATCOM tuned with GA was improved. By acquiring the best values for PI controller gains, voltage swell occurred due to the change in reactive power has been overcome and a better dynamic response was reached. In future studies, different other optimization techniques will be used to determine a more effective one.

REFERENCES:

[1] F. H. Gandoman, A. Ahmadi, A. M. Sharaf, P. Siano, J. Pou, B. Hredzak, V. G. Agelidis, “Review of FACTS technologies and applications for power quality in smart grids with renewable energy systems”, Renewable and Sustainable Energy Reviews, vol. 82,pp. 502–514, 2018. DOI: 10.1016/j.rser.2017.09.062.

[2] A. Mohanty, M. Viswavandya, D. K. Mishra, P. K. Ray, S. Pragyan, “Modelling & simulation of a PV based micro grid for enhanced stability”, Energy Procedia, vol. 109, pp. 94–101, 2017. DOI: 10.1016/j.egypro.2017.03.060.

[3] H. Liao, S. Abdelrahman, J. V. Milanovic, “Zonal mitigation of power quality using FACTS devices for provision of differentiated quality of electricity supply in networks with renewable generation”, IEEE Trans. Power Deliv., vol. 23, pp. 1975–85, 2017. DOI: 10.1109/TPWRD.2016.2585882.

[4] V. Kumar, A. S. Pandey, S. K. Sinha, “Grid integration and power quality issues of wind and solar energy system: A review”, Int. Conf. Emerging Trends in Electrical Electronics & Sustainable Energy Systems (ICETEESES 2016), Sultanpur, India, 2016, pp. 71–80. DOI: 10.1109/ICETEESES.2016.7581355.

[5] D. Menniti, A. Pinnarelli, N. Sorrentino, “An hybrid PV-Wind supply system with D-Statcom interface for a water-lift station”, IEEE Int. Symposium on Power Electronics, Electrical Drives, Automation and Motion, Pisa, Italy, 2010. DOI: 10.1109/SPEEDAM.2010.5545070. 

LMMN Based Adaptive Control for Power Quality Improvement of Grid Intertie Wind-PV System

ABSTRACT:

  A new topology comprising of wind turbine driven synchronous generator (SG) and solar photovoltaic (PV) array for renewable energy harvesting, is proposed in this work. The stochastic inputs for proposed system, are agitated by the nonlinear time dependent parameters such as variable wind speed and changing solar insolation. The speed variations are absorbed using back to back interfaced power electronic converters (PECs) namely synchronous generator side converter (SGC) and utility grid side converter (UGC) with a common DC link where solar PV array is tied directly. The power injection into the utility grid, is levelled by the optimal utilization of PECs. The SGC uses vector control (VC) for speed control of SG and maintains unity power factor (UPF) at stator terminals. UGC acquires its switching pulses with proper application of least mean mixed norm (LMMN) control technique. The new application of LMMN control scheme is used for harmonics compensation and fundamental load component extraction. The DC link voltage is regulated using proportional integral (PI) controller. A prototype is developed and tested under different conditions of sudden changes in load, wind velocity variations as well as under varying solar PV insolation. The power sharing scheme proves to be effective. The power quality (PQ) issues are also addressed and mitigated effectively. The performance is exhibited for the validation of the proposed system and its control.

KEYWORDS:

1.      Utility Grid

2.      Wind

3.      SG

4.      Solar PV Array

5.      SGC

6.      UGC

7.      LMMN Control

8.      Load Compensation

9.      Power Quality

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

A three-phase grid intertie wind-PV system with effective load compensation capability, is proposed and its suitability is justified through hardware validation on a developed prototype in the laboratory under various operating conditions such as changing wind velocity, variations in solar insolation and perturbation in nonlinear load. The parallel operation of solar PV array and wind driven SG, allows a possibility of load sharing. The fundamental extraction from the load currents, is successfully done with the application of LMMN adaptive filtering control. The load current fundamental component is extracted, moreover, the disturbances and harmonic content in grid currents are removed in order to improve the power quality at CPI. The aim of improving the voltage profile and reducing the harmonic content at the CPI, is attained successfully by implementing the LMMN adaptive control. The LMMN adaptive control schemes, leads to fast response and less misadjustments. The maximum power is extracted effectively from solar PV array and wind turbine using P&O algorithm. Sensorless VC for speed control of SG, has resulted in low system cost and increased system reliability. Test results obtained under steady state and dynamic conditions, show the acceptability of control techniques. Moreover, the grid currents under the enforced conditions, have their THD below 5% confirming to the IEEE-519 standard.

REFERENCES:

[1] O. A. Lara, N. Jenkins, J. Ekanayake, P. Cartwright and M. Hughes, “Wind energy Generation Modelling and control”, Wiley-IEEE Press, 2009.

[2] V. A. Suryad, S. Doolla and M. Chandorkar, “Microgrids in India: Possibilities and Challenges,” IEEE Electrif. Magazine, vol. 5, no. 2, pp. 47-55, June 2017.

[3] M. Faisal, M. A. Hannan, P. J. Ker, A. Hussain, M. Mansur and F. Blaabjerg, “Review of energy storage system technologies in microgrid applications: Issues and challenges,” IEEE Access, 2018.

[4] M. G. Molina, “Energy storage and power electronics technologies: a strong combination to empower the transformation to the smart grid,” Proc. IEEE, vol. 105, no. 11, pp. 2191-2219, Nov. 2017.

[5] R. Vijayapriya, P. Raja and M. P. Selvan, “A modified active power control scheme for enhanced operation of PMSG based WGS,” IEEE Trans. Sustain. Ener., Early Access.