A Transient Component Based Approach for Islanding Detection in Distributed Generation

ABSTRACT:

 In this paper, transient response of the microgrid caused due to unintended switching events and faults have been investigated in distributed generation (DG) system. The proposed technique is based on two new criteria; i) transient index value (TIV) and ii) positive sequence superimposed current angle at PCC. The proposed method utilizes three phase voltage signals at DG end to compute the TIV. The performance of the proposed integrated approach has been evaluated on a sample test system and a practical distribution network consisting of combined heat and power plant, wind turbine generators, and photovoltaic system. The simulation results demonstrate that the proposed technique exhibits high reliability and leads to faster detection of islanding condition as compared to the existing passive islanding detection methods not only for zero active and reactive power mismatch conditions, but also for transient events caused due to nonlinear loads.

 KEYWORDS:

1.      Distributed generation

2.      Islanding condition

3.      Least square approach

4.      Power mismatch

5.      Voltage signal

 SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

In this paper, two criterion-based approach using TIV derived from three phase voltages and sign of PSSC angle was proposed for islanding detection. For the detection of islanding event in microgrid system, the voltage from DG end and current signal injected to PCC are accessed. The detection methodology has been tested for different critical conditions such as low active and reactive power mismatch and results obtained were accurate and reliable. Also, the method is not prone to false detection even during severe non-islanding conditions such as capacitor switching, fault conditions, switching of large block of load and opening of DG end breakers. The presence of nonlinear load has no effect on the detection using proposed algorithm. With the proposed approach, the non-detection zone had reduced and hence the reliability of the operation was assured. Because of faster detection capacity (less than one cycle) and simple computational procedure, more reliable and secured way to detect islanding phenomenon is possible in the digital platform using the proposed integrated technique.

REFERENCES:

[1] IEEE Standard 929-2000: ‘IEEE standard for Interconnecting Distributed Resources with Electric Power Systems’, 2003.

[2] M. A. Redfern, O. Usta, and G. Fielding, “Protection against loss of utility grid supply for a dispersed storage and generation unit”, IEEE Trans Power Del., vol. 8, no. 3, pp. 948-954, Jul. 1993.

[3] W. Wang, J. Kliber, G. Zhang, W. Xu, B. Howell, and T. Palladino, “A power line signaling based scheme for anti-islanding protection of distributed generators-part II: field test results”, IEEE Trans. Power Del. ,vol. 22, no. 3, pp. 1767-1772, Jul. 2007.

[4] W. Xu, G. Zhang, C. Li, W. Wang, G. Wang, and J. Kliber, “A power line signaling based technique for anti-islanding protection of distributed generators-part 1: scheme and analysis,” IEEE Trans. Power Del., vol. 22, no. 3, pp. 1758-1766, Jul. 2007.

[5] P. Gupta, R. S. Bhatia, and D. K. Jain, “Active ROCOF relay for islanding detection,” IEEE Trans. Power Del., vol. 32, no. 1, pp. 420-429, Feb.2017.

 

A simplified phase-shift PWM-based feedforward distributed MPPT method for grid-connected cascaded PV inverters

ABSTRACT:

The modularity and decreased filter size properties have made cascaded multilevel inverters (MLIs) more applicable than conventional two-level inverters, especially in high and medium power photovoltaic (PV) applications. However, partial shading of PV modules will affect negatively the output power of the unshaded modules. There are several existing solutions in the literature to address this challenge, however almost all of them suffer from complex implementations, low efficiency, and high cost. This paper presents a new simplified feedforward distributed maximum power point tracking (MPPT) method for three-phase grid-connected cascaded MLIs. The cascaded MLI provides a modular, and highly efficient single stage power conversion for PV systems. The proposed distributed MPPT method is depending on the phase-shift pulse width modulation (PSPWM) method with a simplified implementation. The proposed method is developing a feedforward signal that is proportional to the maximum power of the individual module. Then, the current controller, and the modulating signal are multiplied with the proportionality factor of the module maximum power. Furthermore, a modified modulation compensation method without using proportional-integral (PI) controllers is introduced to solve the problem of the unbalanced three-phase PV output currents that results from PV power mismatches and shading. A case study is implemented for 15 kW PV system to investigate the performance of the proposed method. In addition, comprehensive comparisons with the previous attempts in the literature are provided to verify the superior performance of the new proposed control method.

KEYWORDS:

1.      Distributed maximum power point tracking (MPPT)

2.      Cascaded multilevel inverter

3.      Phase-shift PWM (PS-PWM)

4.      Photovoltaic (PV)

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

This paper presents a distributed MPPT method for grid-tied PV systems with cascaded H-bridge inverters. The proposed method is based on employing a feedforward control method for extracting the MPPT of individual modules through adapting the percentage sharing of each module. The proposed method is superior solution for PV system grid integration due to its simple implementation, signal stage power conversion, no added complexity with increasing the number of connected modules, and it eliminates the need for individual control loop for each module. The proposed distributed MPPT method is validated through various operating scenarios of the selected case study. The results show the ability of the proposed distributed MPPT to extract MPPT of each PV module at normal and partial shading conditions. Moreover, the proposed modulation compensation method shows the injection of balanced output currents, even if at partial shading condition. The relative performance of the proposed distributed MPPT method is also compared with the most notable methods in the literature according to various performance criteria, including ability to extract individual MPPT, implementation complexity, system cost, THD content and balance output currents, and system efficiency. The comparisons show the validity and superiority of the presented distributed MPPT method over the notable candidates in the literature.

REFERENCES:

Abdalla, I., Corda, J., Zhang, L., 2013. Multilevel DC-link inverter and control algorithm to overcome the PV partial shading. IEEE Trans. Power Electron. 28 (1), 14–18.

Abdalla, I., Corda, J., Zhang, L., 2016. Optimal control of a multilevel DC-link converter photovoltaic system for maximum power generation. Renew. Energy 92 (Jul.), 1–11.

Al-Dhaifallah, M., Nassef, A.M., Rezk, H., Nisar, K.S., 2018. Optimal parameter design of fractional order control based INC-MPPT for PV system. Sol. Energy 159 (Jan.), 650–664.

Ando, Y., Oku, T., Yasuda, M., Shirahata, Y., Ushijima, K., Murozono, M., 2017. A compact SiC photovoltaic inverter with maximum power point tracking function. Sol. Energy 141, 228–235.

Azizi, A., et al., 2018. Impact of the aging of a photovoltaic module on the performance of a grid-connected system. Sol. Energy 174, 445–454.

A Novel High-Gain DC-DC Converter Applied in Fuel Cell Vehicles

 ABSTRACT:

The DC-DC converter for fuel cell vehicles should be characterized by high-gain, low voltage stress, small size and high-efficiency. However, conventional two-level, three-level and cascaded boost converters cannot meet the requirements. A new non-isolated DC-DC converter with switched-capacitor and switched-inductor is proposed in this paper, which can obtain high-gain, wide input voltage range, low voltage stresses across components and common ground structure. In this paper, the operating principle, component parameters design, and comparisons with other high-gain converters are analyzed. Moreover, the state-space averaging method and small-signal modeling method are adopted to obtain the dynamic model of converter. Finally, simulation and experimental results verify the effectiveness of the proposed topology. The input voltage of the experimental prototype ranges from 25V to 80V. The rated output voltage is 200V and rated power is 100W. The maximum efficiency is 93.1% under rated state. The proposed converter is suitable for fuel cell vehicles.

KEYWORDS:

1.      Fuel cell vehicles

2.      DC-DC converter

3.      Switched-capacitor and switched- inductor

4.      High-gain

5.      Low voltage stress

SOFTWARE: MATLAB/SIMULINK

 CONCLUSION:

This paper presents a non-isolated DC-DC converter topology for fuel cell vehicles. The proposed converter can obtain high-gain and wide input voltage range. The voltage gain can reach 2(1−d)/(1−2d) and duty cycle d<0.5 while achieving high-gain. The voltage stresses across components are less than half of the output voltage, which is beneficial to reduce the size and cost of the converter. In addition, the circuit topology is a common ground structure, which can avoid EMI and safety problems. The converter can always maintain the stability of the output voltage by closed-loop control. There are not the voltage overshoot and impulse current during soft-start process by adopting the soft-start program. Under the rated state, the measured maximum efficiency of the prototype is 93.1%. The proposed converter is suitable for fuel cell vehicles.

REFERENCES:

[1] G. Du, W. Cao S. Hu Z. Lin and T. Yuan “Design and Assessment of an Electric Vehicle Powertrain Model Based on Real-World Driving and Charging Cycles ” IEEE Trans. Veh. Technol., vol. 68, no. 2, pp. 1178-1187, Feb. 2019.

[2] Z. Geng, Q. Chen, Q. Xia D. S. Kirschen and C. Kang “Environmental Generation Scheduling Considering Air Pollution Control Technologies and Weather Effects ” IEEE Trans. Power Syst., vol. 32, no. 1, pp. 127-136, Jan. 2017.

[3] H. Bi P. Wang and Y. Che “A Capacitor Clamped H-Type Boost DC-DC Converter With Wide Voltage-Gain Range for Fuel Cell Vehicles ” IEEE Trans. Veh. Technol., vol. 68, no. 1, pp. 276-290, Jan. 2019.

[4] L. Li, S. Coskun, F. Zhang R. Langari and J. Xi “Energy Management of Hybrid Electric Vehicle Using Vehicle Lateral Dynamic in Velocity Prediction ” IEEE Trans. Veh. Technol., vol. 68, no. 4, pp. 3279-3293, Apr.2019.

[5] N. Elsayad, H. Moradisizkoohi, and O. A. Mohammed “A Single-Switch Transformerless DC-DC Converter With Universal Input Voltage for Fuel Cell Vehicles: Analysis and Design ” IEEE Trans. Veh. Technol., vol. 68, no. 5, pp. 4537-4549, Mar. 2019.

 

A New Step-Up Switched-Capacitor Voltage Balancing Converter for NPC Multilevel Inverter-Based Solar PV System

 ABSTRACT:

This paper proposed a grid connected solar Photovoltaic (PV) Systems with a new voltage balancing converter suitable for Neutral-Point-Clamped (NPC) Multilevel Inverter (MLI). The switched capacitors used in the proposed converter is able to balance the DC link capacitor voltage effectively by using proper switching states. The proposed balancing converter can be extended to any higher levels and it can boost the DC input voltage to a higher voltage levels without using any magnetic components. This feature allows the converter to operate with the boosting capability of the input voltage to the desired output voltage while ensuring the self-balancing. In this paper the proposed converter is used for a grid connected solar PV system with NPC multilevel inverter, which is controlled using vector control scheme. The proposed grid connected solar PV system with associated controllers and maximum power point tracking (MPPT) is implemented in Matlab/SimPowerSystem and experimentally validated using dSPACE system and designed converters. The simulation and experimental results show that the proposed topology can effectively balance the DC link voltage, extract maximum power from PV module and inject power to the grid under varying solar irradiances with very good steady state and dynamic performances.

KEYWORDS:

1.      Solar photovoltaics

2.      NPC multilevel inverter

3.      Balancing circuit

4.      Dc-link voltage balancing

5.      Grid connected PV system

 

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

A new step-up voltage balancing converter for solar photovoltaic system which is suitable for NPC-MLI has been proposed in this paper. The proposed converter not only can boost the input PV voltage at the desired output level, but also can remove the magnetic elements which reduces the weight and cost of the system. It also requires only one DC source or PV array output to produce multi-level output, which reduces the number of input voltage sources required in such systems. Capacitance calculation, voltage ripple of the capacitors, output power and normalized energy according to the number of output levels are also analyzed. A deep comparison with other DC-DC topologies has been done and showed the cost effectiveness of the proposed converter. The proposed converter is implemented for a grid connected solar PV system with a NPC multilevel inverter, which is controlled using vector control scheme. The proposed system with associated controllers is implemented in Matlab/SimPowerSystem and experimentally validated using dSPACE DSP (digital signal processor) system and designed converters. The simulation and experimental results confirms that the proposed topology can effectively balance the DC link voltage, extract maximum power from PV module and inject power to the grid under varying solar irradiances with very good steady state and dynamic performances.

REFERENCES:

[1] P. R. Bana, K. P. Panda, R. T. Naayagi, P. Siano, and G. Panda, ``Recently developed reduced switch multilevel inverter for renewable energy integration and drives application: Topologies, comprehensive analysis and comparative evaluation,'' IEEE Access, vol. 7, pp. 54888_54909, 2019.

[2] S. Shuvo, E. Hossain, T. Islam, A. Akib, S. Padmanaban, and M. Z. R. Khan, ``Design and hardware implementation considerations of modified multilevel cascaded H-Bridge inverter for photovoltaic system,'' IEEE Access, vol. 7, pp. 16504_16524, 2019.

[3] F. Z. Peng, ``A generalized multilevel inverter topology with self voltage balancing,'' IEEE Trans. Ind. Appl., vol. 37, no. 2, pp. 611_618, Mar./Apr. 2001.

[4] A. Taghvaie, J. Adabi, and M. Rezanejad, ``A self-balanced step-up multilevel inverter based on switched-capacitor structure,'' IEEE Trans. Power Electron., vol. 33, no. 1, pp. 199_209, Jan. 2018.

[5] V. Dargahi, A. K. Sadigh, M. Abarzadeh, S. Eskandari, and K. A. Corzine, ``A new family of modular multilevel converter based on modified flying-capacitor multicell converters,'' IEEE Trans. Power Electron., vol. 30, no. 1, pp. 138_147, Jan. 2015.

A Microgrid Based on Wind Driven DFIG, DG andSolar PV Array for Optimal Fuel Consumption

ABSTRACT:

This paper presents a green energy solution to a microgrid for a location dependent on a diesel generator (DG) to meet its electricity requirement. The proposed microgrid is powered by two renewable energy sources such as wind energy conversion system (WECS) using doubly fed induction generator (DFIG) and solar photovoltaic (PV) system. The solar PV array is directly connected to common DC bus of back-back voltage source converters (VSCs), which are connected in the rotor side of DFIG. Moreover, a battery energy storage (BES) is connected at the same DC bus through a buck-boost DC-DC converter to provide path for excess stator power of DFIG. The extraction of maximum power both from wind and solar is achieved through rotor side converter (RSC) control and buck-boost DC-DC converter control, respectively. A modified perturb and observe (P&O) algorithm is presented to extract maximum power from the solar PV array. Moreover, the control of load side converter (LSC), is designed to optimize the fuel consumption of DG. A novel generalized concept is proposed to compute the reference DG power output for optimal fuel consumption. The microgrid is modelled and simulated using SimPowerSystems tool box of MATLAB, for various scenarios such as varying wind speeds, varying insolation, effect of load variation on bidirectional converter and unbalanced nonlinear load connected at point of common coupling (PCC). The DFIG stator currents and DG currents, are found balanced and sinusoidal. Finally, an experimental prototype is developed in the laboratory to validate the proposed scheme.

KEYWORDS:

1.      Wind Turbine

2.      Doubly fed induction generator (DFIG)

3.      Diesel generator

4.      Solar photovoltaic array

5.      Bidirectional buck boost converter

6.      Battery energy storage

7.      Power quality

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

The proposed microgrid based on wind turbine driven DFIG, DG and solar PV array with BES, has been presented. The solar PV array is directly connected to DC link of back-back connected VSCs, whereas BES is connected through buck-boost converter. The system has been simulated for various scenarios such as variable wind speeds, variable insolation and unbalanced nonlinear load connected at PCC. Moreover, the performance of buckboost converter at change in load has been investigated. The simulated results have shown the satisfactory performance to achieve optimal fuel consumption. The DFIG stator voltages, currents and DG currents, are found balanced and sinusoidal, as per the IEEE 519 standard. A prototype has been developed in the laboratory to validate the performance of the microgrid. Test results have shown quite good performance under variable wind speeds, variable insolation and change in load.

REFERENCES:

 [1] J. Knudsen, J. D. Bendtsen, P. Andersen, K. K. Madsen, and C. H. Sterregaard, “Supervisory control implementation on diesel-driven generator sets,” IEEE Trans. Ind. Electron., vol. 65, no. 12, pp. 9698- 9705, Dec. 2018.

[2] J. Jo, H. An, and H. Cha, “Stability improvement of current control by voltage feedforward considering a large synchronous inductance of a diesel generator,” IEEE Trans. Ind. Applicat., vol. 54, no. 5, pp. 5134- 5142, Sept.-Oct. 2018.

[3] Y. Zhang, A. Melin, S. M. Djouadi, M. Olama, and K. Tomsovic, “Provision for guaranteed inertial response in diesel-wind systems via model reference control,” IEEE Trans. Power Systems, Early Access.

[4] N. Nguyen-Hong, H. Nguyen-Duc, and Y. Nakanishi, “Optimal sizing of energy storage devices in isolated wind-diesel systems considering load growth uncertainty,” IEEE Trans. Ind. Applicat., vol. 54, no. 3, pp. 1983-1991, May-June 2018.

[5] W. Li, P. Chao, X. Liang, J. Ma, D. Xu, and X. Jin, “A practical equivalent method for DFIG wind farms,” IEEE Trans. Sustain. Energy, vol. 9, no. 2, pp. 610-620, April 2018.

A Management of power flow for DC Microgrid with Solar and Wind Energy Sources

 ABSTRACT:

Today there is a rapid proliferation of DC loads into the market and DC micro grid with renewable energy sources is emerging as a possible solution to meet growing energy demand. As different energy sources like solar, wind, fuel cell, and diesel generators can be integrated into the DC grid, Management of power flow among the sources is essential. In this paper, a control strategy for Management of power flow in DC micro grid with solar and wind energy sources is presented. As the regulation of voltage profile is important in a standalone system, a dedicated converter is to be employed for maintaining the DC link voltage. DC link voltage is regulated by the battery circuit while maximum power is extracted from Solar and Wind to feed the loads connected at the DC bus. A power flow algorithm is developed to control among three sources in the DC Microgrid. The algorithm is tested for various load conditions and for fluctuations in solar and wind power in MATLAB/SIMULINK environment.

KEYWORDS:

1.      DC microgrid

2.      Power flow administration

3.      Photovoltaics

4.      Wind conversion systems

SOFTWARE: MATLAB/SIMULINK

 CONCLUSION:

A Management of power flow and control algorithm for DC microgrid with solar and wind energy sources is presented. As the system involves different intermitted energy sources and load whose demand can vary, it is necessary to develop a Management of power flow and control algorithm for the DC Microgrid. To provide ceaseless power supply to the loads and balance the power flow among the different sources at any time, a Management of power flow algorithm is developed. The feasibility of the algorithm has been tested for various load conditions and for changes in solar and wind power.

REFERENCES:

 

 [1] F. Katiraei, M. R. Iravani, A. L. Dimeas, and N. D. Hatziargyriou, "Microgrids management: control and operation aspects of microgrids," IEEE Power Energy Mag., vol. 6, no. 3, pp. 54-65, May/Jun. 2008.

[2] W. Jiang and B. Fahimi, “Active current sharing and source management in fuel cell-battery hybrid power system,” IEEE Trans. Ind. Electron., vol. 57, no. 2, pp. 752–761, Jan. 2010.

[3] L. Xu and D. Chen, "Control and operation of a DC microgrid with variable generation and energy storage," IEEE Trans. Power Del., vol. 26, no. 4, pp. 25 I 3-2522, Oct. 2011.

[4] Jin C, Wang P, Xiao J, "Implementation of hierarchical control in DC microgrids,"IEEE Transaction of Industrial Electronics, vol.61(8), pp.4032-4042,2014.

[5] L. Xiaonan, J. M. Guerrero, S. Kai, and J. C. Vasquez, "An Improved Droop Control Method for DC Microgrids Based on Low Bandwidth Communication With DC Bus Voltage Restoration and Enhanced Current Sharing Accuracy," Power Electronics, IEEE Transactionson,vol.29,pp.1800-1812,2014.

A low-voltage ride-through strategy using mixed potential function for three-phase grid-connected PV systems

 ABSTRACT:

This paper presents a new control strategy for low-voltage ride-through for 3-phase grid-connected photovoltaic systems. The proposed fault ride through control algorithm, which is designed based on mixed potential function, can protect the inverter from over current failure under both symmetric and asymmetric faults, reduce the double frequency oscillation and provides reactive power support by applying a voltage compensation unit. With the proposed method, the inverter can also inject sinusoidal current during asymmetric faults. The method does not require a hard switch to switch from the Maximum Power Point Tracking (MPPT) to a non-MPPT algorithm, which ensures a smooth transition.

KEYWORDS:

1.      Current control

2.      Fault-ride-through

3.      Photovoltaic

4.      Micro-grids

5.      Large-signal analysis

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

This paper proposes a LVRT control strategy for low voltage distribution networks with PV system directly connected to the grid. The method is based on the classic cascaded voltage and current loops in dqframe, while the positive and negative sequence components are used to modify the reference DC-link voltage to limit the inverter current during the grid faults. The mixed-potential function is used to regulate the compensation term of the DC-link voltage. Through applying this regulation, the double grid frequency oscillation, which is appeared in inverter active power and DC-link voltage following an asymmetric fault, can be reduced. The method also generates sinusoidal inverter current during faults. The reactive power injection is used to supply the required reactive power to restore the voltage. In choosing the DC-link capacitor this should be taken into account that the proposed method increases the DC-link voltage during faults. However, since the protection systems must operate within a fracture of a second, this should not be a huge burden on an appropriate power capacitor. The proposed method is validated in MATLAB/SIMULINK. Simulation results show the proposed LVRT control strategy can be used for both symmetric and asymmetric faults. The simulation results also demonstrate that the proposed voltage compensation unit, derived from the mixed potential function, reduces the double grid frequency oscillation. The presented results show that for a severe voltage sag (3-phase fault), the proposed method could reduce the fault current to 1.5 pu to protect the inverter from overcurrent failure. For asymmetric voltage sags, the proposed method could limit the fault current to almost rated value. In addition, this method does not require a hard switch to switch from the MPPT to a non-MPPT algorithm, which ensures a smooth transition. It is noted that the proposed method does not affect the

REFERENCES:

[1] D.E. Olivares, A. Mehrizi-Sani, A.H. Etemadi, C.A. Canizares, R. Iravani, M. Kazerani, A.H. Hajimiragha, O. Gomis-Bellmunt, M. Saeedifard, R. Palma- Behnke, G.A. Jimenez-Estevez, N.D. Hatziargyriou, Trends in microgrid control, IEEE Trans. Smart Grid 5 (4) (2014) 1905–1919, https://doi.org/10.1109/TSG. 2013.2295514.

[2] B. Lasseter, Microgrids, Proc. IEEE Power Eng. Soc. Winter Meeting 1 (2002) 146–149.

[3] R. Meyer, A. Zlotnik, A. Mertens, Fault Ride Through Control of Medium-voltage Converters With LCL Filter in Distributed Generation Systems, (2013), pp. 1954–1961, https://doi.org/10.1109/ECCE.2013.6646947 edn..

[4] J. Hu, Y. He, L. Xu, B.W. Williams, Improved control of DFIG systems during network unbalance using PIR current regulators, IEEE Trans. Ind. Electron. 56 (2) (2009) 439–451, https://doi.org/10.1109/TIE.2008.2006952.

[5] A. Camacho, M. Castilla, J. Miret, J.C. Vasquez, E. Alarcon-Gallo, Flexible voltage support control for three-phase distributed generation inverters under grid fault, IEEE Trans. Ind. Electron. 60 (4) (2013) 1429–1441, https://doi.org/10.1109/TIE. 2012.2185016.