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.

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.

A Grid Connected Single Phase TransformerlessBuck-Boost Based Inverter Which Can Control TwoSolar PV Arrays Simultaneously

 ABSTRACT:

A new buck-boost based single phase transformerless grid connected photo voltaic (PV) inverter which is having the capability to operate two serially connected subarrays at their respective maximum power point is proposed in this paper. The series connection of the two subarrays and the buck-boost nature of the inverter reduces the number of serially connected modules in a subarray. Further, independent operation of the two subarrays enhances the overall power extraction from the subarrays while they are experiencing significant mismatch at their operating conditions, e.g. insolation level and/or operating temperature. The topological structure of the inverter and its control technique ensures negligible amount of high frequency components in its common mode voltage. As a consequence the overall leakage current associated with the subarrays are restricted well within the permissible limit specified in the standard, VDE 0126-1-1. The operating principle of the proposed scheme along with its rigorous analysis has been presented. The reference current generation for the buck-boost inductor and the controller configuration of the proposed inverter have been elaborated in detail. Detailed simulation study with a 1.3 kW PV system has been carried out to show the viability of the proposed scheme.

KEYWORDS:

1.      Buck-boost inverter

2.      Maximum power point

3.      Single phase

4.      Transformerless

5.      Grid connected inverter

6.       Difference in operating condition

7.      Series connection

8.       Sub-arrays

SOFTWARE: MATLAB/SIMULINK

CONCLUSION:

A new buck-boost based transformerless grid connected solar PV inverter which is capable of operating two serially connected subarrays at their respective maximum power points while significant amount of difference is present in their operating conditions, was proposed in this paper. The buckboost nature of the inverter along with its ability to operate two serially connected subarrays at their respective maximum power point enhances the overall power extraction from the subarrays while they are experiencing wide difference at their operating conditions. A simple inductor current control technique which is independent of modes of operation (CCM or DCM) was adopted to control ig. The topological structure of the inverter and its control technique restrict the overall leakage current associated with the subarrays within the permissible limit. The operating principle of the proposed inverter was mentioned. The reference current generation for the buck-boost inductor and the controller configuration of the proposed inverter was elaborated in detail. A 1.3 kW PV system with the proposed inverter was simulated, and the simulation results were presented to confirm the viability of the proposed inverter.

REFERENCES:

[1] M. Islam and S. Mekhilef, “Efficient Transformerless MOSFET Inverter for a Grid-Tied Photovoltaic System,” IEEE Transactions on Power Electronics, vol. 31, no. 9, pp. 6305-6316, 2016.

[2] H. Xiao and S. Xie, “Transformerless split-inductor neutral point clamped three-level PV grid-connected inverter,” IEEE Transactions on Power Electronics, vol. 27, no. 4, pp. 1799-1808, 2012.

[3] P. Sharma, and V. Agarwal, “Maximum power extraction from a partially shaded PV array using shunt-series compensation,” IEEE Journal of Photovoltics, vol. 4, no. 4, pp. 1128-1137, 2014.

[4] C. Olalla, C. Deline, D. Clement, Y. Levron, M. Rodriguez, and D. Maksimovic, “Performance of power-limited differential power processing architectures in mismatched PV systems,” IEEE Transactions on PowerElectronics, vol. 30, no. 2, pp. 618-630, 2015.

[5] V. Samavatian, and A. Radan, “A High Efficiency Input/Output Magnetically Coupled Interleaved BuckBoost Converter With Low Internal Oscillation for Fuel-Cell Applications: CCM Steady-State Analysis,” IEEE Transactions on Industrial Electronics, vol. 62, no. 9, pp. 5560- 5568, 2015.