Coordination of SMES, SFCL and Distributed Generation Units for Micro-Grid Stability Enhancement via Wireless Communications

ABSTRACT:

To enhance the stability of a micro-grid under fault conditions, this paper proposes the coordination control of a superconducting magnetic energy storage (SMES), an active superconducting fault current limiter (SFCL), and distributed generation units via wireless network communications. This coordination control can smoothly separate the micro-grid from the main network in case of severe or permanent faults, and assist the micro-grid to achieve the fault ride-through (FRT) operation if the fault is minor or temporary. Details on the modeling, control strategy, and network architecture are presented. Moreover, the simulation analysis of a 10 kV class micro-grid including the SMES, SFCL, and photovoltaic generation units is implemented in MATLAB. Concerning the performance evaluation of the coordination control, not only severe and minor faults, but also different communication delays are taken into account. The results confirm the effectiveness of the proposed coordination control.

KEYWORDS:

1.      Coordination control

2.      Distributed generation

3.      Micro-grid

4.      Superconducting fault current limiter (SFCL)

5.      Superconducting magnetic energy storage (SMES)

6.      Wireless communications

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

In order to improve the stability of a micro-grid under short-circuit faults, this paper proposes and investigates the coordination of a SMES unit, an active SFCL, and multiple distributed generation units via the wireless communications. The severe and minor faults are considered, and the impacts of the wireless communication delay on the coordination performance are also studied. The results well demonstrate the effectiveness of the proposed coordination control, and it can maintain the power balance, accelerate the load recovery, suppress the PCC fault current, and mitigate the voltage-frequency fluctuation. Thus, the micro-grid’s transient performance is able to be enhanced considerably, and further the technical advantages of the SMES, active SFCL, distributed generation units and wireless communications can be fully utilized.

In the near future, the improvement of the coordination control will be carried out from multiple aspects, such as the parameter optimizations of the SMES and the SFCL, the robustness advancement of the wireless network, the suitableness enhancement of the coordination control for a large micro-grid/test system including several DG resources and control structures. In addition, the current coordination control does not consider the effects of the load dynamics on the transient performance of the micro-grid, and it means that just two static power loads are used. On the one hand, with regard to the necessity of introducing the load dynamics, it may closely depend on whether the current coordination control of the SMES, active SFCL and distributed generation units is enough to stabilize the micro-grid under the fault conditions. On the other hand, if more electrical devices take part in the coordination control, an intelligent coordination method based on multi-agent system technology can be properly applied. Related research results will be reported in later articles.

 REFERENCES:

 [1] Jae-young Yoon, Seung-ryul Lee, and In-tae Hwang, “A Quantitative Analysis on Future World Marketability of HTS Power Industry,” IEEE Trans. Smart Grid, vol. 4, no. 1, pp. 433–436, Feb. 2013.

[2] Jianwei Li, Qingqing Yang, Francis. Robinson, Fei Liang, Min Zhang, and Weijia Yuan, “Design and test of a new droop control algorithm for a SMES/battery hybrid energy storage system,” Energy, vol. 118, pp. 1110–1122, Jan. 2017.

[3] Meng Song, et al., “100 kJ/50 kW HTS SMES for Micro-Grid,” IEEE Trans. Appl. Superconduct., vol. 25, no. 3, June 2015, Art. ID. 5700506.

[4] Thai-Thanh Nguyen, et al., “Applying Model Predictive Control to SMES System in Microgrids for Eddy Current Losses Reduction,” IEEE Trans. Appl. Superconduct., vol. 26, no. 4, June 2016, Art. ID. 5400405.

[5] Lei Chen, et al., “Comparison of Superconducting Fault Current Limiter and Dynamic Voltage Restorer for LVRT Improvement of High Penetration Micro-Grid,” IEEE Trans. Appl. Superconduct., vol. 27, no. 4, June 2017, Art. ID. 3800607.

 

Control strategy of PMSG based wind energy conversion system under strong wind conditions

 ABSTRACT:

This paper presents a control approach for the Permanent Magnet Synchronous Generator (PMSG) based Wind Energy Conversion Systems (WECS) under a wide range of wind speeds. Generally, most of the wind turbines are turned-off and disconnected from the power grid, in case wind velocity is gone over 25 m/s. It may cause wind power supply shortage from wind farms. This research introduces a pitch angle controller as well as a rotational speed control system so that the PMSG based WECS can generate power if the wind speeds are above 25 m/s. The proposed method reduces the mechanical stress of the wind turbine by preferential reducing of the rotational speed rather than the mechanical torque during strong wind condition. As a result, the chance of turning-off the is reduced compared to the conventional control system because the PMSG based WECS can temporarily tolerate the wind speed up to 35 m/s. A 2 MW WECS with the electrical and mechanical characteristics is modeled in the MATLAB/Sim Power Systems® to verify the proposed research.

KEYWORDS:

1.      WECS

2.      PMSG

3.      Pitch angle control

4.      Strong wind conditions

SOFTWARE: MATLAB/SIMULINK

 CONCLUSION:

This paper describes a control method for the PMSG based WECS under strong wind conditions. Conventional control method is compared with the proposed control method considering same conditions and system parameters. In the MPPT control area, both conventional and proposed systems have shown similar performances. When the wind turbine is controlled at the rated power, the power fluctuation occurs with the conventional method. This is because, it is controlled by only the pitch angle control system with some delays. In the proposed method, both pitch angle and rotational speed control methods are designed for the wide-windrange of wind velocity. As a result, the output power is controlled with high accuracy by using the proposed method. In addition, the proposed method preferentially reduces the rotational speed rather than the mechanical torque in order to reduce the power coefficient and the centrifugal force during the strong wind conditions. For this reason, the allowable condition of power generation can temporarily reach up to the wind speed of 35 m/s. Therefore, it can be said that the PMSG based WECS with the proposed control method can avoid a sudden cut-off from the power grid during strong wind conditions as well as can continue to generate power in the typhoon prone area. However, if the wind speed goes above the 35 m/s the wind turbine needs to be shut down. In doing so it will give some time to bring appropriate load-frequency control action rather than sudden generation curtailment.

REFERENCES:

Aho, J., Buckspan, A., Laks, J., Fleming, P., Jeong, Y., Dunne, F., . . . . . . Johnson, K. (2012). A tutorial of wind turbine control for supporting grid frequency through active power control. 2012 American Control Conference (ACC). (pp. 3120–3131). https:// doi.org/10.1109/ACC.2012.6315180.

Ajami, A., Alizadeh, R., & Elmi, M. (2016). Design and control of a grid tied 6-switch converter for two independent low power wind energy resources based on pmsgs with mppt capability. Renewable Energy, 87(Part 1), 532–543. https://doi.org/10.  1016/j.renene.2015.10.031.

Bonfiglio, A., Delfino, F., Invernizzi, M., & Procopio, R. (2017). Modeling and maximum power point tracking control of wind generating units equipped with permanent magnet synchronous generators in presence of losses. Energies, 10(1), https://doi. org/10.3390/en10010102.

Cader, C., Bertheau, P., Blechinger, P., Huyskens, H., & Breyer, C. (2016). Global cost advantages of autonomous solar-battery-diesel systems compared to diesel-only systems. Energy for Sustainable Development, 31(Supplement C), 14–23. https:// doi.org/10.1016/j.esd.2015.12.007.

Chen, J., & Song, Y. (2016). Dynamic loads of variable-speed wind energy conversion system. IEEE Transactions on Industrial Electronics, 63(1), 178–188. https://doi.org/ 10.1109/TIE.2015.2464181

Control and energy management of a large scale grid-connected PV system for power quality improvement

 ABSTRACT:

Power quality is highlighted as an important parameter in modern power systems. Moreover, grid-connected photovoltaic power plants are increasing significantly in size and capacity. Elsewhere, due to the progressive integration of nonlinear loads in the grid, the principal role of a Solar Energy Conversion System (SECS) is not only to capture the maximum power from solar but, also to ensure some ancillary services and improve the quality of power. This paper presents a novel strategy dedicated to improve the management of active power generation, reactive power compensation and power quality of a SECS, while guaranteeing the possibility of exploiting the full capacity of the Power Conditioning System (PCS) and the PhotoVoltaic System (PVS). The proposed control algorithm is applied to a large scale PVS connected to the grid through a cascade of a DC-DC converter and a PWM inverter. This control strategy manages the SECS function’s priorities, between main active power generation, reactive power compensation and active filtering in such a way to guarantee a smooth and stable DC voltage and ensure a sinusoidal grid current. Top priority is given to the active power production over power quality improvement. Then, priority is given to reactive power compensation over mitigation of current harmonics absorbed by the non-linear load connected to the Point of Common Coupling (PCC). Moreover, the whole system upper limits of active and reactive powers have been determined in the (PQ) power plane on the basis of PVS available power, converters rated power and DC bus voltage smoothness and stability. Finally, a control procedure dedicated to the calculation of the inverter current commands is proposed in order to exploit the full capacity of the SECS and respect the determined power limits. Simulation results confirm the effectiveness and the performance of this control strategy and prove that the SECS can operate at its full power whilst the power quality can be improved by reactive power compensation and active filtering.

KEYWORDS:

1.      Power decoupled control

2.      Harmonic currents

3.      Power quality

4.      Active filtering

5.      Reactive power compensation

6.      SECS full power exploitation

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

In this paper, a novel strategy has been proposed to manage and improve the power quality of a grid connected large scale PVS. More accurately, fuzzy logic controllers have been used to guarantee a decoupled control of active and reactive powers injected into the grid. The PWM inverter is controlled in such a way to manage between active power production and power quality improvement without exceeding the whole system power capacity. The proposed priority control block gives top priority to active power production, then reactive power compensation and finally active filtering. The power capability of the whole system has been delimited in the (PQ) power plane (on the basis of the PVS available power, the power electronics converters rated power and the DC bus voltage smoothness and stability) and fully exploited without over-rating, by the calculation of an appropriate portion of current commands in order to ensure a better active filtering quality and keep the inverter current under its limit value corresponding to the whole system power capacity. Simulation results show the effectiveness and the performance of the proposed approach in terms of power generation, reactive power compensation and active filtering.

REFERENCES:

Ahmad, Z., Singh, S.N., 2018. Improved modulation strategy for single phase grid connected transformerless PV inverter topologies with reactive power generation capability. Sol. Energy 153, 356–375.

Aboudrar, I., El Hani, S., Mediouni, H., Bennis, N., Echchaachouai, A., 2017. Hybrid algorithm and active filtering dedicated to the optimization and the improvement of photovoltaic system connected to grid energy quality. Int. J. Renw. Energy Res. 7 (2), 894–900.

Arul Murugan, S., Anbarasan, A., 2014. Harmonics elimination in grid connected single phase PV inverter. In: Int. Conference on Engineering Technology and Science, Tamilnadu, India, 10–11 February 2014, (3) 1, pp. 1474–1480.

Albarracin, R., Alonso, M., 2013. Photovoltaic reactive power limits. In: 2013 12th IEEE Int. Conference Environ. Electr. Eng. Wroclaw, Poland, 5–8 May 2013, pp. 13–18.

Bhole, N., Shah Dr, P.J., 2017. Enhancement of power quality in grid connected photovoltaic system using predictive current control technique. Int. J. Rece. Innova. Trends in Compu. Communi 5 (7), 549–553.

Constant Power Generation Using Modified MPPT P&O to Overcome Overvoltage on Solar Power Plants

ABSTRACT:

Indonesia is a tropical country that has the privilege of gaining sunshine year-round so that the utilization of solar energy as a solar power plant can be a potential power plant to be developed. One of the problems in the solar power plant system is the power instability generated by the solar panels because it relies heavily on irradiance and relatively low energy conversion efficiency. To solve this problem, the Maximum control of Power Point Tracking (MPPT) is required by the Perturb and Observe (P&O) methods. This P&O MPPT control makes solar PV operate at the MPP point so that the solar PV output power is maximized. However, the MPPT P&O control that works at the MPP point makes the output voltage to the load is also maximum that causes overvoltage. This paper, therefore, discusses the modification of the MPPT Perturb and Observe (P&O) algorithm for Constant Power Generation (CPG) that combines MPPT P&O with the power control settings to the maximum limit of solar PV. This method can set up 2 operating conditions of the solar PV namely MPPT mode and CPG mode. The MPPT mode works when the solar PV output power is smaller than the reference power to maximize solar PV output power. However when the solar PV output power is more than or equal to the reference power then the CPG mode works to limit the solar panel's output power. Based on the simulated results of this MPPT-CPG control shows the load output voltage  response can be kept constant 48 V with less than 5% error that has been verified using a variety of irradiance and reference power.

KEYWORDS:

1.      Constant power generation (CPG)

2.      Maximum power point tracking (MPPT) P&O

3.      Solar PV

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

In this paper, we propose the MPPT P&O-CPG method to be able to control solar panels that work on 2 conditions i.e. in MPPT operations and CPG operations to avoid overvoltage on the load. This MPPT P&O-CPG method has been evaluated through a PSIM simulation. Simulated results indicate that the MPPT mode is identified when the load requirements are greater or equal to the solar power panel (PPV < = Pref) and the voltage on the output side of the < 48V. While CPG mode is identified when the power requirements of the solar panel are greater than the load power (PPV > Pref) and the voltage at > 48V output. The performance of the MPPT P&O-CPG method is proven to avoid excess voltage with a control error limit of ± 5% of the rating voltage on the load although it is still overshot during mode switching due to irradiance fluctuations.

REFERENCES:

[1] M. Hassani, S. Mekhilef, A. Patrick Hu, and N. R. Watson, "A novel MPPT algorithm for load protection based on output sensing control," IEEE Ninth International Conference on Power Electronics and Drive Systems (PEDS), pp. 1120-1124, 2011.

[2] T. Esram, and P. L. Chapman, "Comparison of photovoltaic array maximum power point tracking techniques," IEEE Transactions on Energy Conversion, vol. 22, no. 2, pp. 439-449, June 2007.

[3] D. Beriber, and A. Talha, "MPPT techniques for PV systems," 4^th International Conference on Power Engineering, Energy and Electrical Drives, pp. 1437-1442, 2013.

[4] N. Moubayed, A. El-Ali, and R. Outbib, “Comparison of two MPPT techniques for PV system,” WSEAS Trans Environ Dev, 2009.

[5] E. Prasetyono, D. O. Anggriawan, A. Z. Firmansyah, and N. A. Windarko, "A modified MPPT algorithm using incremental conductance for constant power generation of photovoltaic systems," Engineering  Technology and Applications (IES-ETA) International ElectronicsSymposium on, pp. 1-6, 2017.

Artificial Neural Network for Control and Grid Integration of Residential Solar Photovoltaic Systems

ABSTRACT:  

Residential solar photovoltaic (PV) energy is becoming an increasingly important part of the world's renewable energy. A residential solar PV array is usually connected to the distribution grid through a single-phase inverter. Control of the single-phase PV system should maximize the power output from the PV array while ensuring overall system performance, safety, reliability, and controllability for interface with the electricity grid. This paper has two main objectives. The first objective is to develop an artificial neural network (ANN) vector control strategy for a LCL-filter based single-phase solar inverter. The ANN controller is trained to implement optimal control, based on approximate dynamic programming. The second objective is to evaluate the performance of the ANN-based solar PV system by (a) simulating the PV system behavior for grid integration and maximum power extraction from solar PV array in a realistic residential PV application and (b) building an experimental solar PV system for hardware validation. The results demonstrate that a residential PV system using the ANN control outperforms the PV system using the conventional standard vector control method and proportional resonant control method in both simulation and hardware implementation. This is also true in the presence of noise, disturbance, distortion, and non-ideal conditions.

KEYWORDS:

1.      Artificial neural networks

2.      DC-AC power converters

3.      DC-DC power converters

4.      Dynamic programming

5.      Maximum power point tracker

6.      Optimal control

7.      Solar power generation

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

This paper proposes a single-phase, residential solar PV system based on artificial neural networks and adaptive dynamic programming for MPPT control and grid integration of a solar photovoltaic array through an LCL-filter based inverter. The proposed artificial neural network controller implements the optimal control based on the approximate dynamic programming. Both the simulation and hardware experiment results demonstrate that the solar PV system using the ADP-based artificial neural network controller has more improved performance than that using the proportional resonant or conventional standard vector control techniques, such as no requirement for damping resistance, more reliable and efficient extraction of solar power, more stable DC-link voltage, and more reliable integration with the utility grid. Using the ADP-based neural network control technique, the harmonics are significantly reduced and the system shows much stronger adaptive ability under uncertain conditions, which would greatly benefit the integration of small-scale residential solar photovoltaic systems into the grid.

REFERENCES:

[1] Renewable Energy World Editors. (2014, Nov. 12). Residential Solar Energy Storage Market Could Approach 1 GW by 2018.  Available:http://www.renewableenergyworld.com.

[2] R. A. Mastromauro, M. Liserre and A. D. Aquila, “Control Issues in Single-Stage Photovoltaic Systems: MPPT, Current and Voltage Control”, IEEE Trans. Ind. Informatics, vol. 8, no. 2, pp. 241-254, May 2012.

[3] E. Lorenzo, G. Araujo, A. Cuevas, M. Egido, J. Miñano and R. Zilles, Solar Electricity: Engineering of Photovoltaic Systems, Progensa, Sevilla, Spain, 1994.

[4] J. M. Carrasco, L. G. Franquelo, J. T. Bialasiewicz, E. Galván, R. C. P. Guisado, M. Á. M. Prats, J. I. León, and N. Moreno-Alfonso, “Power- Electronic Systems for the Grid Integration of Renewable Energy Sources: A Survey”, IEEE Trans. Ind. Electron., vol. 53, no. 4, pp. 1002-1016, August 2006.

[5] W. T. Franke, C. Kürtz and F. W. Fuchs, "Analysis of control strategies for a 3 phase 4 wire topology for transformerless solar inverters," inProc. IEEE Int. Symp. Ind. Electron., Bari, pp. 658-663, 2010.

Application of Boost Converter to Increase the Speed Range of Dual-stator Winding Induction Generator in Wind Power Systems

 ABSTRACT:

 In this paper, a topology using a Dual-stator Winding Induction Generator (DWIG) and a boost converter is proposed for the variable speed wind power application. At low rotor speeds, the generator saturation limits the voltage of the DWIG. Using a boost converter, higher DC voltage can be produced while the DWIG operates at Maximum Power Point Tracking (MPPT) even at low speed and low voltage conditions. Semiconductor Excitation Controller (SEC) of the DWIG utilizes Control-Winding Voltage Oriented Control (CWVOC) method to adjust the voltage, considering V/f characteristics. For the proposed topology, the SEC capacity and the excitation capacitor is optimized by analyzing the SEC reactive current considering wind turbine power-speed curve, V/f strategy, and the generator parameters. The method shows that the per-unit capacity of the SEC can be limited to the inverse of DWIG magnetizing reactance per-unit value. The topology is simulated in MATLAB/Simulink platform and experimented with a scaled 1 kW prototype. Both simulation and experimental results demonstrate wide variable speed operation range of the DWIG and verify the optimization.

KEYWORDS:

1.      Boost converter

2.      Control-winding voltage oriented control

3.      Dual-stator winding induction generator (DWIG)

4.      Wind power

5.      Variable speed operation.

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

This paper proposes a topology for variable speed wind power application using dual stator-winding induction generator. A boost converter is utilized for MPPT and wide range variable speed operation, especially at low-speed condition is obtained. At low speeds, DWIG voltage is dropped due to V/f strategy and a boost converter is used to increase the voltage level to meet the higher and constant voltage requirement, such as in voltage source converter DC-link or offshore DC network applications. In the proposed topology, by choosing the optimum excitation capacitor, the capacity of the semiconductor excitation controller is minimized. Finally, to verify the proper operation of the proposed system, simulation and experimental results are presented which validate the wide-speed range operation of the system and the excitation capacitor optimization method.

REFERENCES:

[1] REN21, “Renewables 2016: Global status report,” 2016. [Online]. Available: http://www.ren21.net.

[2] F. Blaabjerg and K. Ma, "Future on Power Electronics for Wind Turbine Systems," IEEE Journal of Emerging and Selected Topics in Power Electronics, vol. 1, no. 3, pp. 139-152, Sept. 2013.

[3] Z. Chen, J. M. Guerrero, and F. Blaabjerg, "A Review of the State of the Art of Power Electronics for Wind Turbines," IEEE Transactions on Power Electronics, vol. 24, no. 8, pp. 1859-1875, Aug. 2009.

[4] V. Yaramasu, B. Wu, P. C. Sen, S. Kouro and M. Narimani, "High-power wind energy conversion systems: State-of-the-art and emerging technologies," Proceedings of the IEEE, vol. 103, no. 5, pp. 740-788, May 2015.

[5] H. Nian and Y. Song, "Direct Power Control of Doubly Fed Induction Generator Under Distorted Grid Voltage," IEEE Transactions on Power Electronics, vol. 29, no. 2, pp. 894-905, Feb. 2014.

 

An Improved Grid Current and DC Capacitor Voltage Balancing Method for Three-Terminal Hybrid AC/DC Microgrid

 ABSTRACT:

 In this paper, a three-terminal AC/DC hybrid microgrid with two DC terminals and one AC terminal is proposed. The proposed system consists of cascaded H-bridge (CHB) converters based AC grid interface and two dual active bridge (DAB) converters based DC subgrid interface that connects two isolated DC buses. In order to reduce the number of power conversion stages and power devices, the DAB converters are directly connected to CHB DC rails according to the system operation requirement. To overcome the imbalanced grid currents and DC rail voltages issues caused by this modified system configuration with only two power conversion stages, an improved method is proposed through the zero-sequence voltage injection in the CHB converters. In addition, to avoid the conflicts between zero-sequence voltage injection and the voltage/current regulation of the system, the impacts of the control parameters to the system stability and dynamic response are investigated. Evaluation results from both three-terminal and five-terminal hybrid AC/DC microgrids show that the generalized effectiveness of the proposed three-phase AC current and DC rail voltage balancing method.

KEYWORDS:

1.      Three-terminal microgrid

2.      Hybrid AC/DC microgrid

3.      Zero-sequence voltage injection

4.      Current balancing control

5.      Voltage balancing control

6.      Grid-voltage sags

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

In this paper, a multi-terminal hybrid AC/DC microgrid structure with two power conversion stages is described in detail and a three-terminal hybrid microgrid with two DC ports is mainly selected for case study. In order to solve the issues of DC capacitor voltages and three-phase grid currents unbalance caused by mismatched DC power between DC ports, an improved control method through the adoption of zero-sequence voltage injection is developed. It has been extensively verified that the grid current and CHB capacitor voltage balancing control can be achieved simultaneously even in the severe case with highly mismatched DC power, grid-voltage sags, or the changes of connection between AC and DC subgrids.

REFERENCES:

[1] P. Ch. Loh, D. Li, Y. K. Chai, and F. Blaabjerg, “Autonomous operation of hybrid microgrid with AC and DC subgrids,” IEEE Trans. Power Electron., vol. 28, no. 5, pp. 2214–2223, May. 2013.

[2] P. Ch. Loh, D. Li, Y. K. Chai, and F. Blaabjerg, “Autonomous control of interlinking converter with energy storage in hybrid AC–DC microgrid,” IEEE Trans. Ind. Appl., vol. 49, no. 3, pp. 1374–1383, May. 2013.

[3] Y. W. Li, D. M. Vilathgamuwa, and P. C. Loh, “Design, analysis and real-time testing of controllers for multi-bus microgrid system,” IEEE Trans. Power Electron., vol. 19, no. 5, pp. 1195–1204, Sep. 2004.

[4] J. M. Guerrero, J. C. Vasquez, J. Matas, L. G. de Vicuna, and M. Castilla, “Hierarchical control of droop-controlled AC and DC microgrids—Ageneral approach toward standardization,” IEEE Trans. Ind. Electron.,vol. 58, no. 1, pp. 158–172, Jan. 2011.

[5] K. T. Tan, X. Y. Peng, P. L. So, Y. C. Chu, and M. Z. Q. Chen, “Centralized control for parallel operation of distributed generation inverters in microgrids,” IEEE Trans. Smart Grid, vol. 3, no. 4, pp. 1977–1987, Dec.2012.