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Saturday 3 November 2018

Dual-function PV-ECS integrated to 3P4W distribution grid using 3M-PLL control for active power transfer and power quality improvement



 ABSTRACT:
This study proposes a single-stage solar photovoltaic energy conversion system (PV-ECS) integrated to a three phase four-wire (3P4W) distribution grid with dual-function capabilities, i.e. active power transfer and power quality (PQ) enhancement at the point of interaction (PoI). The PV-ECS system comprises of a solar photovoltaic array and a voltage source inverter (VSI), supplying active power (during daytime) to the distribution grid and connected single-phase and three-phase loads. Apart from transfer of power, the system also improves the PQ at the PoI by compensating reactive power and neutral current, attenuating harmonics, correcting power factor and balancing grid currents. During night, the VSI acts as a shunt active power filter mitigating PQ issues, thereby increasing the device utilisation factor. A three-phase magnitude-phase locked loop (3M-PLL) method is utilised to extract and estimate fundamental term of load currents and an incremental conductance algorithm is applied for maximum power point tracking. To demonstrate its effectiveness, the system is modelled and its performance is simulated on MATLAB and experiments are performed on a developed prototype in the laboratory.

SOFTWARE: MATLAB/SIMULINK

 CIRCUIT DIAGRAM:


Fig. 1 System configuration and control scheme
(a) Structure diagram of 3P4W grid-connected PV-ECS

EXPECTED SIMULATION RESULTS



Fig. 2 Dynamic behaviour of system at
(a), (b) Unbalanced load, (c) Step increase in irradiance from 700 to 1000 W/m2


CONCLUSION:  
A dual-function single-stage PV-ECS integrated to the 3P4 distribution grid has been proposed here. Two modes of operation of PV-ECS are to supply and transfer active power to the grid and tied loads as well as to improve quality of power at PoI. An In  Cbased approach is utilised here for tracking MPP of solar PV array and a 3M-PLL-based control scheme is utilised for extracting  fundamental components of load current. Simulated and test results have demonstrated the performance of the system under various conditions such as non-linear loading, unbalanced loading and varying irradiance levels. Test results have shown that the system has improved the power quality at the PoI by compensating neutral current and reactive power, correcting power factor and balancing loads on the grid side. The harmonics are reduced to below 5% on grid side, which is within the limits of an IEEE-519 standard. Moreover, test results have indicated that the system has operated suitably during night-time (sunlight unavailability) thereby increasing the utilisation factor of the VSI by two-fold. The single stage structure has decreased the losses in the system and increased the total efficacy of the system.
REFERENCES:
[1] Muro, M., Saha, D.: ‘Why rooftop solar – and full retail feed in tariffs – benefits all consumers’, 30 May 2016. Available at http:// reneweconomy.com.au/2016/rooftop-solar-net-metering-is-a-netbenefit- 28170
[2] Meza, E.: ‘India implements new 40 GW rooftop, small PV plant program’, 20 May 2016. Available at http://www.pv-magazine.com/news/details/beitrag/ india-implements-new-40-gw-rooftop--small-pv-plant-program-_100024678/ #axzz4ADc3MIV6
[3] Deo, S., Jain, C., Singh, B.: ‘A PLL-less scheme for single-phase grid interfaced load compensating solar PV generation system’, IEEE Trans. Ind. Inf., 2015, 11, (3), pp. 692–699
[4] Yang, Y., Blaabjerg, F., Wang, H., et al.: ‘Power control flexibilities for grid connected multi-functional photovoltaic inverters’, IET Renew. Power Gener., 2016, 10, (4), pp. 504–513
[5] Agarwal, R., Hussain, I., Singh, B.: ‘LMF based control algorithm for single stage three-phase grid integrated solar PV system’, IEEE Trans. Sust. Energy, 2016, 7, (4), pp. 1379–1387


Development of a Bidirectional DC/DC Converter with Dual-Battery Energy Storage for Hybrid Electric Vehicle System



ABSTRACT:
This study develops a newly designed, patented, bidirectional dc/dc converter (BDC) that interfaces a main energy storage (ES1), an auxiliary energy storage (ES2), and dc-bus of different voltage levels, for application in hybrid electric vehicle systems. The proposed converter can operate in a step-up mode (i.e., low-voltage dual-source-powering mode) and a step-down (i.e., high-voltage dc-link energy-regenerating mode), both with bidirectional power flow control. In addition, the model can independently control power flow between any two low-voltage sources (i.e., low-voltage dual-source buck/boost mode). Herein, the circuit configuration, operation, steady-state analysis, and closed-loop control of the proposed BDC are discussed according to its three modes of power transfer. Moreover, the simulation and experimental results for a 1 kW prototype system are provided to validate the proposed converter.
KEYWORDS:

1.      Bidirectional dc/dc converter (BDC)
2.      Dual battery storage
3.      Hybrid electric vehicle

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:



Fig. 1. Typical functional diagram for a FCV/HEV power system.

 EXPECTED SIMULATION RESULTS



Fig.2. Measured waveforms for low-voltage dual-source-powering mode: (a) gate signals; (b) output voltage and inductor currents.





Fig.3. Measured waveforms for high-voltage dc-bus energy-regenerating mode: (a) gate signals; (b) output voltage and inductor currents.



Fig. 4. Measured waveforms of gate signals, output voltage and inductor currents for the low-voltage dual-source buck/boost mode: (a) buck mode; (b) boost mode.




Fig. 5. Waveforms of controlled current step change in the low-voltage dual-source-powering mode: (a) by simulation; and (b) by measurement. (iH is changed from 0 to 0.85 A; iL1 is changed from 0 to 2.5 A; Time/Div=20 ms/Div


Fig. 6. Waveforms of controlled current step change in the low-voltage dual-source boost mode: (a) by simulation; and (b) by measurement. (iES1 is changed from 0 to -6 A; iL2 is changed from 0 to 12 A; Time/Div=20 ms/Div)




Fig. 7. Waveforms of controlled current step change in the low-voltage dual- source buck mode: (a) by simulation; and (b) by measurement. (iES1 is changed from 0 to 6 A; iL2 is changed from 0 to 12 A; Time/Div=20 ms/Div)

CONCLUSION:
A new BDC topology was presented to interface dual battery energy sources and high-voltage dc bus of different voltage levels. The circuit configuration, operation principles, analyses, and static voltage gains of the proposed BDC were discussed on the basis of different modes of power transfer. Simulation and experimental waveforms for a 1 kW prototype system highlighted the performance and feasibility of this proposed BDC topology. The highest conversion efficiencies were 97.25%, 95.32%, 95.76%, and 92.67% for the high-voltage dc-bus energy-regenerative buck mode, low-voltage dual-source-powering mode, low-voltage dual-source boost mode (ES2 to ES1), and low-voltage dual-source buck mode (ES1 to ES2), respectively. The results demonstrate that the proposed BDC can be successfully applied in FC/HEV systems to produce hybrid power architecture (has been patented [37]).
REFERENCES:
[1] M. Ehsani, K. M. Rahman, and H. A. Toliyat, "Propulsion system design of electric and hybrid vehicles," IEEE Transactions on industrial electronics, vol. 44, no. 1, pp. 19-27, 1997.
[2] A. Emadi, K. Rajashekara, S. S. Williamson, and S. M. Lukic, "Topological overview of hybrid electric and fuel cell vehicular power system architectures and configurations," IEEE Transactions on Vehicular Technology, vol. 54, no. 3, pp. 763-770, 2005.
[3] A. Emadi, S. S. Williamson, and A. Khaligh, "Power electronics intensive solutions for advanced electric, hybrid electric, and fuel cell vehicular power systems," IEEE Transactions on Power Electronics, vol. 21, no. 3, pp. 567-577, 2006.
[4] E. Schaltz, A. Khaligh, and P. O. Rasmussen, "Influence of battery/ultracapacitor energy-storage sizing on battery lifetime in a fuel cell hybrid electric vehicle," IEEE Transactions on Vehicular Technology, vol. 58, no. 8, pp. 3882-3891, 2009.
[5] P. Thounthong, V. Chunkag, P. Sethakul, B. Davat, and M. Hinaje, "Comparative study of fuel-cell vehicle hybridization with battery or supercapacitor storage device," IEEE transactions on vehicular technology, vol. 58, no. 8, pp. 3892-3904, 2009




Combination Analysis and Switching Method of a Cascaded H-Bridge Multilevel Inverter Based on Transformers With the Different Turns Ratio for Increasing the Voltage Level



 ABSTRACT:
This paper analyzes the combination in a cascaded H-bridge multilevel inverter (CHBI) based on transformers with the different turn ratios for increasing the voltage level and proposes the switching method for achieving the output voltage distribution among H-bridge cells (HBCs). The transformers used in this paper are connected to the output of the respective HBCs, and the secondary sides of all the transformers are connected in series for generating the final output voltage. Only one of the transformers, in particular, has a different turn ratio for increasing the output voltage level. In this paper, the possible turn ratio of the special transformer with a different turn ratio is discussed in detail, and a switching method based on the level-shifted switching method for the topology used in this paper is proposed. To verify the effectiveness of the proposed method, a three-phase 21-level CHBI is experimentally tested.
KEYWORDS:
1.      Cascaded H-bridge inverter (CHBI)
2.      Cascaded multilevel
3.      Level-shifted switching method
4.      Multilevel inverter

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:


Fig. 1. Transformer-based CHBI topology used in this paper.


EXPECTED SIMULATION RESULTS




Fig. 2. Simulation results of the proposed switching method with the
balanced voltage distribution at Mi = 1.


Fig. 3. Simulation results of the proposed switching method atMi =1. (a) With and (b) without the balanced voltage and power distributions.





CONCLUSION:
Transformer-based CHBI topology was introduced in this paper. The comparison analysis between topologies was shown in Table XI. The theoretical analysis regarding the selection of the turns ratio of the subtransformer was presented. In addition, a switching method based on the level-shifted switching method with the balanced voltage and power distributions was proposed for the transformer-based CHBI topology. Several requirements related to the decision of switching devices and the design of transformer were suggested.A21-level CHBIwas used to determine the feasibility and effectiveness of the proposed switching method.
When using the proposed switching method, two issues are to be noted: 1) to use the proposed switching method, the configuration of transformer-based CHBI topology should follow that of Table II. It guarantees that the minimum variation (dVx ) of the voltage level is always the same. 2) If the system operates in the wide voltage range (wideMi ), Table VII should be changed as that explained in this paper to guarantee a balanced voltage distribution for Mi range required. Table VI guarantees a balanced voltage distribution for 0.8<Mi < 1. Consequently, this configuration can be applied for the main power supply system generating the ac voltage in grid.
REFERENCES:
[1] J. Rodr´ıguez, S. Bernet, B. Wu, J. O. Pontt, and S. Kouro, “Multilevel voltage-source-converter topologies for industrial medium-voltage drives,” IEEE Trans. Ind. Electron., vol. 54, no. 6, pp. 2930–2945, Dec. 2007.
[2] J. S. Lee and K. B. Lee, “New modulation techniques for a leakage current reduction and a neutral-point voltage balance in transformerless photovoltaic systems using a three-level inverter,” IEEE Trans. Power Electron., vol. 29, no. 4, pp. 1720–1732, Apr. 2014.
[3] C. H. Ng, M. A. Parker, L. Ran, P. J. Tavner, J. R. Bumby, and E. Spooner, “A multilevel modular converter for a large, light weight wind turbine generator,” IEEE Trans. Power Electron., vol. 23, no. 3, pp. 1062–1074, May 2008.
[4] V.Yaramasu and B.Wu, “Predictive control of a three-level boost converter and an NPC inverter for high-power PMSG-based medium voltage wind energy conversion systems,” IEEE Trans. Power Electron., vol. 29, no. 10, pp. 5308–5322, Oct. 2014.
[5] J. Mei, B. Xiao, K. Shen, L. M. Tolbert, and J. Y. Zheng, “Modular multilevel inverter with new modulation method and its application to photovoltaic grid-connected generator,” IEEE Trans. Power Electron., vol. 28, no. 11, pp. 5063–5073, Nov. 2013.



Autonomous Power Management for Interlinked AC-DC Microgrids



ABSTRACT:
The existing power management schemes for interlinked AC-DC microgrids have several operational drawbacks. Some of the existing control schemes are designed with the main objective of sharing power among the interlinked microgrids based on their loading conditions, while other schemes regulate the voltage of the interlinked microgrids without considering the specific loading conditions. However, the existing schemes cannot achieve both objectives efficiently. To address these issues, an autonomous power management scheme is proposed, which explicitly considers the specific loading condition of the DC microgrid before importing power from the interlinked AC microgrid. This strategy enables voltage regulation in the DC microgrid, and also reduces the number of converters in operation. The proposed scheme is fully autonomous while it retains the plug-nplay features for generators and tie-converters. The performance of the proposed control scheme has been validated under different operating scenarios. The results demonstrate the effectiveness of the proposed scheme in managing the power deficit in the DC microgrid efficiently and autonomously while maintaining the better voltage regulation in the DC microgrid.
KEYWORDS:
1.      Autonomous control
2.      Distributed control
3.      Droop control
4.      Hybrid microgrids
5.      Interlinked microgrids
6.      Power management
SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Interlinked AC-DC microgrids and their control strategy.

EXPECTED SIMULATION RESULTS


Fig. 2 Scenario 1: Results showing (a) generators and tie-converter power, (b) DC microgrid voltage and (c) tie-converter control signals for four different load operating conditions.



Fig. 3. Scenario 2: Results showing (a) DC microgrid load demand, (b) generators and tie-converter power, (c) DC microgrid voltage and (d) tie-converter control signals at varying solar PV and load operating conditions.

CONCLUSION:
An autonomous power management scheme has been presented for interlinked AC-DC microgrids having different configurations. The proposed scheme manages the power deficit in the DC microgrid efficiently and autonomously. The number of tie-converters in operation has been reduced with the proposed prioritization to avoid unnecessary operational losses. The scheme has demonstrated better voltage regulation in the DC microgrid. The performance and robustness of the proposed scheme have been validated for two different scenarios of the DC microgrid at variable load conditions.
REFERENCES:
[1] J. Rocabert, A. Luna, F. Blaabjerg, and P. Rodr´ıguez, “Control of power converters in AC microgrids,” IEEE Transactions on Power Electronics, vol. 27, no. 11, pp. 4734–4749, Nov. 2012.
[2] M. Liserre, T. Sauter, and J. Y. Hung, “Future energy systems: integrating renewable energy sources into the smart power grid through industrial electronics,” IEEE Industrial Electronics Magazine, vol.4. no. 1, pp. 18–37, Mar. 2010.
[3] M. Tsili and S. Papathanassiou, “A review of grid code technical requirements for wind farms,” IET Renewable Power Generation, vol. 3, no. 3, pp. 308–332, Sep. 2009.
[4] T. Strasser, F. Andr´en, J. Kathan, C. Cecati, C. Buccella, P. Siano, P. Leit˜ao, G. Zhabelova, V. Vyatkin, P. Vrba, and V. Maˇr´ık, “A review of architectures and concepts for intelligence in future electric energy systems,” IEEE Transactions on Industrial Electronics, vol. 62, no. 4,pp. 2424–2438, Apr. 2015.
[5] A. Kwasinski, “Quantitative evaluation of dc microgrids availability: Effects of system architecture and converter topology design choices,” IEEE Transactions on Power Electronics, vol. 26, no. 3, pp. 835–851, Mar. 2011.

Friday 2 November 2018

Autonomous Power Control and Management Between Standalone DC Microgrids



ABSTRACT:
Renewable integrated DC Microgrids (DCMGs) are gaining popularity by feeding remote locations in qualitative and quantitative manner. Reliability of autonomous DC microgrids (ADCMG) depend on battery capacity and size due to stochastic behavior of renewables. Over charging and discharging scenarios compel the microgrid into insecure zone. Increasing the storage capacity is not an economical solution because of additional maintenance and capital cost. Thus interconnecting neighbor microgrids increases virtual storing and discharging capacity when excess power and deficit scenario arises respectively in any of the DCMG. Control strategy plays vital role in regulating the power within and between microgrids. Power control and management technique is developed based on bus signaling method to govern sources, storages and loads to achieve effective coordination and energy management between microgrids. Proposed scheme is simple and reliable since bus voltages are utilized in shifting the modes without having dedicated communication lines. Proposed scheme is validated through real time simulation of two autonomous DC grids in real time digital simulator (RTDS) and its results are validated by hardware experimentation.
KEYWORDS:
1.      Autonomous DC Microgrid
2.      Bus signaling method
3.      Power control and management scheme
4.      Renewable sources
5.      Real time simulation
SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:


Fig. 1. System architecture for interconnection of two ADCMGs.



EXPECTED SIMULATION RESULTS




Fig. 2. Operating zones of ADCMG1: (a) Bus voltage, (b) Irradiation, (c) PV
output power, (d) Battery terminal voltage, (e) Battery output power, and (f) Load power.


Fig. 3. Operating zones of ADCMG2: (a) Bus voltage, (b) Irradiation, (c) PV
output power, (d) Battery terminal voltage, (e) Battery output power, and (f)
Load power.




Fig. 4. Operation of BDC using PCMS: (a) ADCMG1 voltage, (b) ADCMG2
voltage, (c) Power exported from ADCMG1, (d) Power exported from
ADCMG2, (e) Powers within ADCMG1, and (f) Powers within ADCMG2.

CONCLUSION:
A PCMS is developed based on bus signaling technique for inter DC grid power flow in case of ADCMGs to increase the system reliability and efficient utilization of resources. Two practical DC grid voltages (380V, 48V) are considered for evaluating the performance of developed scheme in simulation. PCMS is explored under normal and extreme scenarios including the over and under loading conditions of ADCMGs, further more with over charging and discharging of battery. It can be observed from above analysis that proposed PCMS is stable, efficient and effective in realizing communication independent control even under dynamic power variations during the power exchange. This statement is also justified with experimental results obtained through prototype model developed in the laboratory with reduced voltage of ADCMG1. Proposed system provides isolation and also enhances system reliability. Application potential of system suits low and medium voltage customers like domestic consumers, data centers, telecommunication systems, etc. in isolated locations where utility connection is not present or feasible.
REFERENCES:
[1] T. Dragicevi, X. Lu, J. C. Vasquez, and J. M.Guerrero, “DC Microgrids – Part II: A Review of Power Architectures, Applications and Standardization Issues,” IEEE Trans. Power Electron., vol. 31, no. 5, pp. 3528–3549, May. 2016.
[2] Q. Yang, L. Jiang, H. Zhao, and H. Zeng, “Autonomous Voltage Regulation and Current Sharing in Islanded Multi-inverter DC Microgrid,” IEEE Trans. Smart Grid, vol. PP, no. 99, pp. 1–1, 2017.
[3] J. Torreglosa, P. Garcia, L. Fernandez, and F. Jurado, “Predictive Control for the Energy Management of a Fuel Cell-Battery-Supercapacitor Tramway,” IEEE Trans. Ind. Informat., vol. 10, no. 1, pp. 276-285, Feb. 2013.
[4] L. Herrera, W. Zhang, and J. Wang, “Stability Analysis and Controller Design of DC Microgrids with Constant Power Loads,” IEEE Trans. Smart Grid, vol. 8, no. 2, pp. 881–888, March. 2017.
[5] D. E. Olivares, A. Mehrizi-sani, A. H. Etemadi, C. A. Cañizares, R. Iravani, M. Kazerani, A. H. Hajimiragha, O. Gomis-bellmunt, M. Saeedifard, R. Palma-behnke, G. A. Jiménez-estévez, and N. D. Hatziargyriou, “Trends in Microgrid Control,” IEEE Trans. Smart Grid, vol. 5, no. 4, pp. 1905–1919, July. 2014.