A High Efficiency Non-Isolated Buck-Boost Converter Based on ZETA Converter

ABSTRACT:

  In this paper, a new transformerless buck-boost converter based on ZETA converter is introduced. The proposed converter has the ZETA converter advantages such as, buck-boost capability, input to output DC insulation and continuous output current. The suggested converter voltage gain is higher than the classic ZETA converter. In the presented converter, only one main switch is utilized. The proposed converter offers low voltage stress of the switch; therefore, the low on-state resistance of the main switch can be selected to decrease losses of the switch. The presented converter topology is simple; hence, the control of the converter is simple. The converter has the continuous output current. The mathematical analyses of the presented converter are given. The experimental results confirm the correctness of the analysis.

KEYWORDS:

1.      Transformerless buck-boost converter

2.      Voltage gain

3.      Main switch

4.      Voltage stress

SOFTWARE: MATLAB/SIMULINK

 CONCLUSION:

In this paper, a novel transformerless buck boost converter based on ZETA converter is presented. In this converter, only one main switch is used, which decreases the losses and improves efficiency. The active switch voltage stress is low and switch with low on-state resistance can be utilized. The voltage gain of the converter is higher than that of the classic boost, buck-boost, ZETA, CUK and SEPIC converters. The presented converter structure is simple; hence, the converter control is simple. The buck-boost converters are used in some applications such as fuel-cell, car electronic devices, and LED drivers. Finally, the experimental results are given to verify the proposed converter.

REFERENCES:

 [1] W. Li and X. He, “Review of nonisolated high-step-up DC/DC converters in photovoltaic grid-connected applications,” IEEE Trans. Ind. Electron., vol. 58, no. 4, pp. 1239-1250, Apr. 2011.

[2] H. S. Lee, H. J. Choe, S. H. Ham and B. Kang, “High-efficiency asymmetric forward-flyback converter for wide output power range,” IEEE Trans. Power Electron., vol. 32, no. 1, pp. 433-440, Jan. 2017.

[3] N. Mohan, T. M. Underland, W. P. Robbins, “Power Electronics Converters,Applications and Design” Wiley, New York, USA, 2nd Edition, 1995.

[4] H. Tao, J. L. Duarte, M. A. M. Hendrix, “Line-interactive UPS using a fuel cell as the primary source,” IEEE Trans. Ind. Electron., vol. 55, no. 8, pp. 3012-3021, Aug. 2008.

[5] P. James, A. Forsyth, G. Calderon-Lopez, V. Pickert “DC-DC converter for hybrid and all electric vehicles,” EVS24 Stavanger, Norway, May 13-16, 2009.

 

A frequency response strategy for variable speed wind turbine based on a dynamic inertial response and tip-speed ratio control

 ABSTRACT:

Participation of the wind turbine generators (WTGs) in the frequency regulation service is an appealing issue in order to consider the safe increasing of the wind power generation. The droop and virtual inertia control are the most popular approaches that facilitate the WTGs to provide frequency regulation. However, the intermittent nature of the wind complicates the implementation of these methods and has impacts on the wind turbine stability and may cause violation of the allowed power reserve and minimum turbine rotor speed. Therefore, in this paper, a control approach based on the dynamic de-loading technique is proposed, where the wind turbine operating curve is dynamically adjusted in the response of the frequency deviation throughout controlling the turbine tip-speed ratio which helps the turbine provide steady-state power sharing within the reserved power as well as the transient response within its stability criteria. In addition, the inertial response based on a dynamic gain is suggested. The inertial weighting gain has been formulated where it is continuously regulated in the response of rotor speed and reflects the amount of available kinetic energy in the rotating mass. The effectiveness of the proposed control approaches is verified throughout the comparisons of the results with the fixed inertial gain control and the droop control. The simulation results confirm that the combined control of the proposed tip-speed ratio and dynamic inertia control improve the overall system dynamic behavior in terms of frequency response and turbine stability.

KEYWORDS:

1.      Variable speed wind turbine

2.       Frequency regulation

3.      De-loading

4.      Inertia response

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

This study focused on the frequency regulation capability of VSWTs. A tip-speed ratio control is presented, where the wind turbine operating curve is dynamically adjusted in the response of frequency deviation. Furthermore, inertial response based on a dynamic gain is suggested, where the inertial weighting gain is continuously regulated in the response of the rotor speed and reflects the amount of available kinetic energy. According to the proposed control strategy, the wind turbine can provide frequency regulation effectively up to rated wind speed (over-speed control zone).However, above rated wind speed, the wind turbine will be operated at rated power and cannot provide frequency regulation supports. The proposed control strategy has been analyzed at different load step disturbances at up- and down-frequency events along the over-speed control zone. Also, the proposed control methods are compared with the two different implementations of the droop control and the inertial control. The results proved that the proposed dynamic tip-speed ratio control has the ability to improve frequency nadir and steady state frequency while ensuring stable operation of the wind turbine. Moreover, the proposed control approaches ensure stable operations of the wind turbine even at low wind speed at 7.5 m/s and high step disturbances of 0.15 pu. The proposed control strategy can be extended in the future to be valid for all wind speed ranges and also can be extended to help the WTGs to participate in the load frequency control.

REFERENCES:

1. Dong J, Xue G, Dong M, Xu X (2015) Energy-saving power generation dispatching in China: regulations, pilot projects and policy recommendations-A review. Renew Sustain Energy Rev 43:1285–1300. https://doi.org/10.1016/j.rser.2014.11.037

2. Amano RS (2017) Review of wind turbine research in 21st century. J Energy Resour Technol 139:050801–050801–050801–050808. https://doi.org/10.1115/1.4037757

3. Sawin JL, Seyboth K, Sverrisson F (2016) Renewables 2016: Global Status Report. In: REN21. http://www.ren21.net/wpcontent/ uploads/2016/05/GSR_2016_Full_Report_lowres.pdf

4. Magdy G, Mohamed EA, Shabib G et al (2018) SMES based a new PID controller for frequency stability of a real hybrid power system considering highwind power penetration. IET RenewPowerGener 12:1304–1313. https://doi.org/10.1049/iet-rpg.2018.5096

5. Choi JW, Heo SY, Kim MK (2016) Hybrid operation strategy of wind energy storage system for power grid frequency regulation. IETGenerTransm Distrib 10:736–749. https://doi.org/10.1049/ietgtd. 2015.0149

A Comprehensive Strategy for Power QualityImprovement of Multi-Inverter-Based MicrogridWith Mixed Loads

 

ABSTRACT:

In order to solve the influence of nonlinear and unbalanced mixed loads on output voltage of micro source inverters in microgrid, this paper proposes a comprehensive strategy which can be used to accurate power distribution, harmonic suppression, negative-sequence voltage component suppression, and stability improvement. On one hand, a fundamental control strategy is proposed upon the conventional droop control; the problem of accurate reactive power distribution is solved by introducing virtual impedance to inverters, while considering the aggravating problem of stability because of introducing virtual impedance, a secondary power balance controller is added to improve the stability of voltage and frequency. On the other hand, the fractional frequency harmonic control strategy and negative-sequence voltage control strategy are proposed to solve the influence of mixed loads, which focus on eliminating specific harmonics caused by the nonlinear loads and the negative sequence component of the voltage. The power quality of microgrid can be improved effectively. Finally, small signal analysis is used to analyze the stability of the multi converter parallel system after introducing the whole control strategy. The simulation results show that the strategy proposed in this paper has a great performance on distributing reactive power, regulating and eliminating harmonic components, eliminating negative-sequence components and stabilizing output voltage of inverters and frequency, and improving the power quality of multi inverter-based microgrid.

KEYWORDS:

1.      Microgrid

2.      Mixed loads

3.      Power quality

4.       Harmonic suppression

5.      Negative sequence voltage

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

This paper proposes a comprehensive strategy for accurate power distribution, harmonic suppression, voltage negative sequence component suppression, and stability improvement of multi-inverter-based microgrid, with the combination of virtual impedance droop control and secondary power balance control, the active and reactive can be distributed accurately, meanwhile the stability of voltage and frequency are obviously improved, next a harmonic suppression control strategy is introduced to suppress harmonic components in microgrid. Furthermore, small signal analysis is used to analyze the stability of the proposed multi-converter parallel system after introducing the comprehensive theory. The simulation and experimental of results certify that proposed the strategy has great performance on accurate reactive power distribution, harmonic suppression, voltage negative sequence component suppression, stability improvement.

REFERENCES:

[1] Y. Li, B. Feng, G. Li, J. Qi, D. Zhao, and Y. Mu, ``Optimal distributed generation planning in active distribution networks considering integration of energy storage,'' Appl. Energy, vol. 210, pp. 1073_1081, Jan. 2018.

[2] G. Benysek and M. Pasko, Power Theory and Power Quality Management, 1st ed. Beijing, China: China Machine Press, Oct. 2013.

[3] Z. Jianhua and H. Wei, Microgrid Operation Control and Protection Technology, 1st ed. Beijing, China: China Electric Power Press, Jul. 2010.

[4] Y. Li, Y. Li, G. Li, D. Zhao, and C. Chen, ``Two-stage multi-objective OPF for AC/DC grids with VSC-HVDC: Incorporating decisions analysis into optimization process,'' Energy, vol. 147, pp. 286_296, Mar. 2018.

[5] W. Jibiao, C. Qihong, and L. Li, ``Grid connected inverter control of three phase voltage unbalance compensation in micro grid,'' Autom. Electr. Power Syst., vol. 41, no. 8, pp. 38_44, 2017.

Single Stage Autonomous Solar Water Pumping System Using PMSM Drive

 ABSTRACT:

 This paper presents a single stage standalone solar photovoltaic (SPV) array fed water pumping system using a permanent magnet synchronous motor (PMSM). The vital contribution of this work includes: (i) development of the novel modified vector control (MVC), which improves the torque response of the system, (ii) development of a novel single stage variable step size incremental conductance (VSS-INC) technique, which provides a fast maximum power point tracking (MPPT) and eliminates the need of intermediate stage DC-DC converter and (iii) introduction of SPV power feed-forward term (FFT), which accelerates the overall response of the system under dynamic conditions. This system includes a SPV array, a three-phase voltage source inverter (VSI), a PMSM and a pump. The SPV array converts solar energy into electrical energy. The VSI acts as power processing unit (PPU), which supplies desired currents to drive the PMSM. As the PMSM rotates, the pump coupled to the motor accomplishes the objective of water pumping. This system is modelled and simulated using MATLAB/ Simulink with available simpower system toolbox and the behavior of the system under varying atmospheric conditions are validated experimentally on a developed prototype in the laboratory.

KEYWORDS:

1.      Solar water pumping

2.      Incremental conductance algorithm

3.      Maximum power point tracking

4.      Permanent magnet synchronous motor

5.      Vector control

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

A SPV array fed SWP system using VSS-INC method for MPPT and MVC for speed control of PMSM, is implemented and performance has been analyzed through MATLAB simulation and hardware validation. Simulated and experimental results for starting, steady state and dynamic performances have been found to be quite satisfactory. With the use of VSS-INC technique, neither the steady state nor the transient performance is compromised as in conventional INC. The MVC has improved the torque response. The introduction of feed-forward term has accelerated the overall response of the system. No steady state oscillations are observed and faster response has made the system more effective. Detailed comparative analysis has proven the superiority of this control over existing conventional control. The use of PMSM for driving the pump, has increased the system efficiency and has reduced the system size. The use of single stage topology has eliminated intermediate stage DC-DC converter and reduced the number of components, consequently resulting in reduction of cost, complexity and further increase in the system efficiency and compactness. Simulated and experimental results have found to be quite acceptable and thereby validated the practical feasibility of the system.

REFERENCES:

[1] E. T. Maddalena, C. G. d. S. Moraes, G. Bragança, L. G. Junior, R. B. Godoy and J. O. P. Pinto, “A Battery-Less Photovoltaic Water-Pumping System With Low Decoupling Capacitance,” IEEE Trans. Ind. Appl., vol. 55, no. 3, pp. 2263-2271, May-June 2019.

[2] R. Kumar and B. Singh, “Grid Interactive Solar PV-Based Water Pumping Using BLDC Motor Drive,” IEEE Trans. Ind. Appl., vol. 55, no. 5, pp. 5153- 5165, Sept.-Oct. 2019.

[3] A. Upadhyay, “India rooftop solar power tariff drop to record lows,” Livemint, Aug. 29, 2018. [Online].

Available: https://www.livemint.com/Industry/cYZ78fnbiNFt1ppRtRm3JP/India-rooft op-solar-power-tariff-drop-to-record-lows.html [Accessed Nov. 20, 2019].

[4] M. N. Ibrahim, H. Rezk, M. Al-Dhaifallah and P. Sergeant, “Solar Array Fed Synchronous Reluctance Motor Driven Water Pump: An Improved Performance Under Partial Shading Conditions,” IEEE Access, vol. 7, pp. 77100-77115, 2019.

[5] M. Rezkallah, A. Chandra, M. Tremblay and H. Ibrahim, “Experimental Implementation of an APC With Enhanced MPPT for Standalone Solar Photovoltaic Based Water Pumping Station,” IEEE Trans. Sust. Energy, vol. 10, no. 1, pp. 181-191, Jan. 2019.

 

Standalone Photovoltaic Water Pumping System Using Induction Motor Drive with Reduced Sensors

ABSTRACT:

A simple and efficient solar photovoltaic (PV) water pumping system utilizing an induction motor drive (IMD) is presented in this paper. This solar PV water pumping system comprises of two stages of power conversion. The first stage extracts the maximum power from a solar PV array by controlling the duty ratio of a DC-DC boost converter. The DC bus voltage is maintained by the controlling the motor speed. This regulation helps in reduction of motor losses because of reduction in motor currents at higher voltage for same power injection. To control the duty ratio, an incremental conductance (INC) based maximum power point tracking (MPPT) control technique is utilized. A scalar controlled voltage source inverter (VSI) serves the purpose of operating an IMD. The stator frequency reference of IMD is generated by the proposed control scheme. The proposed system is modeled and its performance is simulated in detail. The scalar control eliminates the requirement of speed sensor/encoder. Precisely, the need of motor current sensor is also eliminated. Moreover, the dynamics are improved by an additional speed feedforward term in the control scheme. The proposed control scheme makes the system inherently immune to the pump’s constant variation. The prototype of PV powered IMD emulating the pump characteristics, is developed in the laboratory to examine the performance under different operating conditions.

KEYWORDS:

1.      Photovoltaic cells

2.      MPPT

3.       Water pumping

4.       Scalar control

5.       Induction motor drives

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

The standalone photovoltaic water pumping system with reduced sensor, has been proposed. It utilizes only three sensors. The reference speed generation for V/f control scheme has been proposed based on the available power the regulating the active power at DC bus. The PWM frequency and pump affinity law have been used to control the speed of an induction motor drive. Its feasibility of operation has been verified through simulation and experimental validation. Various performance conditions such as starting, variation in radiation and steady state have been experimentally verified and found to be satisfactory. The main contribution of the proposed control scheme is that it is inherently, immune to the error in estimation of pump’s constant. The system tracks the MPP with acceptable tolerance even at varying radiation.

REFERENCES:

[1] E. Drury, T. Jenkin, D. Jordan, and R. Margolis, “Photovoltaic investment risk and uncertainty for residential customers,” IEEE J.Photovoltaics, vol. 4, no. 1, pp. 278–284, Jan. 2014.

[2] E. Muljadi, “PV water pumping with a peak-power tracker using a simple six-step square-wave inverter,” IEEE Trans. on Ind. Appl., vol. 33, no. 3, pp. 714-721, May-Jun 1997.

[3] U. Sharma, S. Kumar and B. Singh, “Solar array fed water pumping system using induction motor drive,” 1st IEEE Intern. Conf. on Power Electronics, Intelligent Control and Energy Systems (ICPEICES), Delhi, 2016.

[4] T. Franklin, J. Cerqueira and E. de Santana, “Fuzzy and PI controllers in pumping water system using photovoltaic electric generation,” IEEE Trans. Latin America, vol. 12, no. 6, pp. 1049- 1054, Sept. 2014.

[5] R. Kumar and B. Singh, “BLDC Motor-Driven Solar PV Array-Fed Water Pumping System Employing Zeta Converter,” IEEE Trans. Ind. Appl., vol. 52, no. 3, pp. 2315-2322, May-June 2016.

 

Vehicle-To-Grid Technology in a Micro-grid UsingDC Fast Charging Architecture

 ABSTRACT:

Electric Vehicle (EV) batteries can be utilized as potential energy storage devices in micro-grids. They can help inmicro-grid energy management by storing energy when there is surplus (Grid-To-Vehicle, G2V) and supplying energy back to the  grid (Vehicle-To-Grid, V2G) when there is demand for it. Proper infrastructure and control systems have to be developed in order to realize this concept. Architecture for implementing a V2G-G2V system in a micro-grid using level-3 fast charging of EVs is presented in this paper. A micro-grid test system is modeled which has a dc fast charging station for interfacing the EVs. Simulation studies are carried out to demonstrate V2G-G2V power transfer. Test results show active power regulation in the micro-grid by EV batteries through G2V-V2G modes of operation. The charging station design ensures minimal harmonic distortion of grid injected current and the controller gives good dynamic performance in terms of dc bus voltage stability.

KEYWORDS:

1.      DC fast charging

2.      Electric vehicle

3.      Grid connected inverter

4.      Micro-grid

5.      Off-board charger

6.      Vehicle-to-grid

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

Modeling and design of a V2G system in a micro-grid using dc fast charging architecture is presented in this paper. A dc fast charging station with off-board chargers and a grid connected inverter is designed to interface EVs to the microgrid. The control system designed for this power electronic interface allows bi-directional power transfer between EVs and the grid. The simulation results show a smooth power transfer between the EVs and the grid, and the quality of grid injected current from the EVs adheres to the relevant standards. The designed controller gives good dynamic performance in terms of dc bus voltage stability and in tracking the changed active power reference. Active power regulation aspects of the microgrid are considered in this work, and the proposed V2G system can be utilized for several other services like reactive power control and frequency regulation. Design of a supervisory controller which gives command signals to the individual EV charger controllers is suggested for future research.

REFERENCES:

[1] C. Shumei, L. Xiaofei, T. Dewen, Z. Qianfan, and S. Liwei, “The construction and simulation of V2G system in micro-grid,” in Proceedings of the International Conference on Electrical Machines and Systems, ICEMS 2011, 2011, pp. 1–4.

[2] S. Han, S. Han, and K. Sezaki, “Development of an optimal vehicle-togrid aggregator for frequency regulation,” IEEE Trans. Smart Grid, vol. 1, no. 1, pp. 65–72, 2010.

[3] M. C. Kisacikoglu, M. Kesler, and L. M. Tolbert, “Single-phase on-board bidirectional PEV charger for V2G reactive power operation,” IEEE Trans. Smart Grid, vol. 6, no. 2, pp. 767–775, 2015.

[4] A. Arancibia and K. Strunz, “Modeling of an electric vehicle charging station for fast DC charging,” in Proceedings of the IEEE International Electric Vehicle Conference (IEVC), 2012, pp. 1–6.

[5] K. M. Tan, V. K. Ramachandaramurthy, and J. Y. Yong, “Bidirectional battery charger for electric vehicle,” in 2014 IEEE Innovative Smart Grid Technologies - Asia, ISGT ASIA 2014, 2014, pp. 406–411.

Energy Management and Control Strategy of Photovoltaic/Battery Hybrid Distributed Power Generation Systems With an Integrated Three-Port Power Converter

 ABSTRACT:

Photovoltaic (PV)/battery hybrid power units have attracted vast research interests in recent years. For the conventional distributed power generation systems with PV/battery hybrid power units, two independent power converters, including a unidirectional dc_dc converter and a bidirectional converter, are normally required. This paper proposes an energy management and control strategy for the PV/battery hybrid distributed power generation systems with only one integrated three-port power converter. As the integrated bidirectional converter shares power switches with the full-bridge dc_dc converter, the power density and the reliability of the system is enhanced. The corresponding energy management and control strategy are proposed to realize the power balance among three ports in different operating scenarios, which comprehensively takes both the maximum power point tracking (MPPT) benefit and the battery charging/discharging management into consideration. The simulations are conducted using the Matlab/Simulink software to verify the operation performance of the proposed PV/battery hybrid distributed power generation system with the corresponding control algorithms, where the MPPT control loop, the battery charging/discharging management loop are enabled accordingly in different operating scenarios.

KEYWORDS:

1.      Energy management

2.       Maximum power point tracking

3.      Bidirectional power converter

4.      Photovoltaic/battery hybrid power unit

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

An integrated three-port power converter as the interface for the PV/battery hybrid distributed power generation system is proposed. Compared with the conventional system topology containing an independent DC-DC unidirectional conversion stage and a bidirectional conversion stage, the proposed system has advantages in terms of higher power density and reliability. The phase shift angle of the full bridge and the switch duty cycle are adopted as two control variables to obtain the required DC bus voltage and realize the power balance among three ports. Different operating scenarios of the system under various power conditions are discussed in detail and a comprehensive energy management and control strategy is proposed accordingly. The priority controller can enable one of the control loops in different scenarios to optimize the whole system performance, taking both the MPPT benefit and the battery charging/discharging management requirements into consideration. The simulation results verify the performance of the proposed PV/battery hybrid distributed power generation system and the feasibility of the control algorithm.

REFERENCES:

[1] F. Blaabjerg, Z. Chen, and S. B. Kjaer, ``Power electronics as efficient interface in dispersed power generation systems,'' IEEE Trans. Power Electron., vol. 19, no. 5, pp. 1184_1194, Sep. 2004.

[2] J. M. Carrasco, L. G. Franquelo, J. T. Bialasiewicz, E. Galvan, R. Potillo, M. M. Prats, J. I. Leon, 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, Jun. 2006.

[3] BP Statistical Review of World Energy, British Petroleum, London, U.K., Jun. 2018.

[4] J. P. Barton and D. G. In_eld, ``Energy storage and its use with intermittent renewable energy,'' IEEE Trans. Energy Convers., vol. 19, no. 2, pp. 441_448, Jun. 2004.

[5] M. S. Whittingham, ``History, evolution, and future status of energy storage,'' Proc. IEEE, vol. 100, pp. 1518_1534, May 2012.