Nine-level Asymmetrical Single Phase Multilevel Inverter Topology with Low switching frequency and Reduce device counts

ABSTRACT:

This paper presents a new asymmetrical singlephase multilevel inverter topology capable of producing ninelevel output voltage with reduce device counts. In order to obtain the desired output voltage, dc sources are connected in all the combination of addition and subtraction through different switches. Proposed topology results in reduction of dc source, switch counts, losses, cost and size of the inverter. Comparison between the existing topologies shows that the proposed topology yields less component counts. Proposed topology is modeled and simulated using Matlab-Simulink software in order to verify the performance and feasibility of the circuit. A low frequency switching strategy is also proposed in this work. The results show that the proposed topology is capable to produce a nine-level output voltage with less number of component counts and acceptable harmonic distortion content.

KEYWORDS:

1.      Multilevel inverter

2.      Asymmetrical

3.      Total Harmonic Distortion (THD)

4.      Low-frequency switching

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Fig. 1. Proposed nine level inverter topology.

 EXPECTED SIMULATION RESULTS:

Fig. 2. Simulation results for proposed nine level inverter topology; (a)

and (b) are switching pulses, (c) Level generator output voltage.

Fig. 3. Simulation Output results at 50Hz fundamental frequency for R = 150ohm, L= 240, P.F = 0.9

Fig. 4. Simulation Output results at 50Hz fundamental frequency for R =150ohm, L= 240, P.F = 0.9

CONCLUSION:

In this paper a new single-phase multilevel inverter topology is presented. Proposed topology is capable of producing nine-level output voltage with reduce device counts. It can be used in medium and high power application with unequal dc sources. Different modes of operation are discussed in detail. On the bases of device counts, the proposed topology is compared with conventional as well as other asymmetrical nine-level inverter topologies presented in literature. Comparative study shows that, for nine level output, the proposed topology requires lesser component counts then the conventional and other topologies. Proposed circuit is modeled in Matlab/Simulink environment. Results obtained shows that topology works properly. Detailed Simulation analysis is carried out. THD obtained in the output voltage is 8.95% whereas the each harmonic order is < 5%, satisfies harmonic Standard (IEEE-519).

REFERENCES:

[1] J. Rodriguez, L. G. Franquelo, S. Kouro, J. I. Leon, R. C. Portillo, M. A.M. Prats and M. A. Perez, “Multilevel Converters: An Enabling Technology for High-Power Applications”, IEEE Proceeding, Vol 97, No. 11, pp.1786 – 1817, November 2009.

[2] J. R. Espinoza, “Inverter”, Power Electronics Handbook, M. H. Rashid, Ed. New York, NY, USA: Elsevier, 2001,pp. 225 -269.

[3] L. M. Tolbert and T. G. Habetler, “Novel multilevel inverter carrierbased PWM method”, IEEE Transactions on Indsutrial Apllications”, Vol. 35, No. 5, pp. 1098-1107, September 1999.

[4] S. Debnath, J. Qin, B. Bahrani, M. Saeedifard and P. Barbosa, “Operation, Control and Applications of the Modular Multilevel Converter: A Review”, IEEE Transactions on Power Electronics, Vol. 30, No. 1, pp. 37-53, January 2015.

[5] L. G. Franquelo, J. Rodriguez, J. I. Leon, S. Kouro, R. C. Portillo and M. A. M. Prats, “The Age of Multilevel Converters Arrives”, IEEE Industrial Electronics magazine, Vol. 2, No. 2 pp. 28-39, June 2008.

Operation and Control of Smart Transformer for Improving Performance of Medium Voltage Power Distribution System

 ABSTRACT:  

Smart transformer (ST) is a power electronic based transformer equipped with effective control and communication. It is expected to play a significant role in future power distribution system, however, their operational features in the medium voltage (MV) power distribution systems are yet not explored. In this paper, operation and control of ST are presented for improving its performance and operational range in a power distribution system consisting of two radial feeders in a city center. For investigating the performance of ST in above system, one conventional power transformer (CPT) is replaced by the ST whereas other feeder is continued to be supplied through the CPT. In this scheme, the ST is operated such that it makes total MV grid currents of the combined system balanced sinusoidal with unity power factor. Therefore, in addition to providing continuous and reliable operation of ST based loads, the ST can also improve the performance of the loads which are supplied by the CPT in a different feeder. Moreover, the proposed scheme eliminates the need of power quality improvement devices at the other feeder. Therefore, the scheme also makes the application of ST in the distribution system cost effective. Simulation results validate the suitability of ST in improving the performance of multiple feeder medium voltage power distribution system.

KEYWORDS:

1.      Smart transformer (ST)

2.      Medium voltage rectifier

3.      Power distribution system

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. A schematic of conventional power distribution system consisting of

two radial feeders in a city center.

 EXPECTED SIMULATION RESULTS:

Fig. 2. Simulated waveforms when ST is not compensating for feeder II. (a) PCC voltages. (b) Grid currents. (c) MV rectifier currents (d) Feeder II currents.

Fig. 3. Simulated waveforms when ST is compensating for feeder II. (a) PCC voltages. (b) Grid currents. (c) MV rectifier currents (d) Feeder II currents.

Fig. 4. Simulated waveforms during transient conditions when load in feeder II is changed. (a) PCC voltages. (b) Grid currents. (c) MV rectifier currents (d) Feeder II currents.

CONCLUSION:

In this paper, the operation and control of a futuristic power distribution system consisting of two radial feeders with one CPT replaced by an ST is presented. It is shown that the ST can compensate for the loads connected at the feeder supplied by the CPTs, in addition to supplying their own loads. This scheme has potential to eliminate the requirement of power quality improvement devices such as STATCOM, power factor correcting capacitors, etc., connected at the second feeder. This ancillary feature in the medium voltage power distribution systems has potential to make application of ST more attractive and cost effective.

REFERENCES:

[1] S. Bifaretti, P. Zanchetta, A. Watson, L. Tarisciotti, and J. Clare, “Advanced power electronic conversion and control system for universal and flexible power management,” Smart Grid, IEEE Transactions on, vol. 2, no. 2, pp. 231–243, Jun. 2011.

[2] X. She, R. Burgos, G. Wang, F. Wang, and A. Huang, “Review of solid state transformer in the distribution system: From components to field application,” in Energy Conversion Congress and Exposition (ECCE),

2012 IEEE, Sep. 2012, pp. 4077–4084.

[3] S. Alepuz, F. Gonzalez, J. Martin-Arnedo, and J. Martinez, “Solid state transformer with low-voltage ride-through and current unbalance management capabilities,” in Industrial Electronics Society, IECON 2013 - 39th Annual Conference of the IEEE, Nov. 2013, pp. 1278–1283.

[4] S.-H. Hwang, X. Liu, J.-M. Kim, and H. Li, “Distributed digital control of modular-based solid-state transformer using dsp+fpga,” Industrial Electronics, IEEE Transactions on, vol. 60, no. 2, pp. 670–680, Feb. 2013.

A Unity Power Factor Converter with Isolation for Electric Vehicle Battery Charger

ABSTRACT:  

This paper deals with a unity power factor (UPF) Cuk converter EV (Electric Vehicle) battery charger having a high frequency transformer isolation instead of only a single phase front end converter used in vehicle's conventional battery chargers. The operation of the proposed converter is defined in various modes of the converter components i.e. DCM (Discontinuous Conduction Mode) or CCM (Continuous Conduction Mode) along with the optimum design equations. In this way, this isolated PFC converter makes the input current sinusoidal in shape and improves input power factor to unity. Simulation results for the proposed converter are shown for charging a lead acid EV battery in constant current constant voltage (CC-CV) mode. The rated full load and varying input supply conditions have been considered to show the improved power quality indices as compared to conventional battery chargers. These indices follow the international IEC 61000-3-2 standard to give harmonic free input parameters for the proposed  circuit.

KEYWORDS:

1.      UPF Cuk Converter

2.      Battery Charger

3.      Front end converter

4.      CC-CV mode

5.      IEC 61000-3-2 standard

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1 General Schematic of an EV Battery Charger with PFC CUK Converter

 EXPECTED SIMULATION RESULTS:

(a)

(b)

(c)

Fig.2 Simulated performance of the isolated Cuk converter in rated condition (a) rated input side and output side quantities (b-c) harmonic analysis of the current at source end

(a)

(b)

(c)

Fig.3 Simulated performance of the isolated Cuk converter while input is varied to 270V (a) rated input side and output side quantities (b-c) harmonic analysis of the current at source end

(a)

(b)

(c)

Fig.4 Simulated performance of the isolated Cuk converter while input is reduced to 270V (a) rated input side and output side quantities (b-c) harmonic analysis of the current at source end

(a)

(b)

(c)

Fig.5 Simulated performance of the isolated Cuk converter at light load condition (a) rated input side and output side quantities (b-c) harmonic analysis of the current at source end

CONCLUSION:

An isolated Cuk converter based battery charger for EV with remarkably improved PQ indices along with well regulated battery charging voltage and current has been designed and simulated. The converter performance has been found satisfactory and well within standard for rated as well as different varying input rms value of supply voltages. The considerably improved THD in the current at the source end makes the proposed system an attractive solution for efficient charging of EVs at low cost. The proposed UPF converter performance has been tested to show its suitability for improved power quality based charging of an EV battery in CC-CV mode. Moreover, the cascaded dual loop PI controllers are tuned to have the smooth charging characteristics along with maintaining the low THD in mains current. The proposed UPF converter topology have the inherent advantage of low ripples in input and output side due to the added input and output side inductors. Therefore, the life cycle of the battery is increased. MATLAB based simulation shows the performance assessment of the proposed charger for the steady state and dynamics condition which clearly state that the proposed charger can sustain the sudden disturbances in supply for charging the rated EV battery load. Moreover, during whole disturbances in supply voltage, the power quality parameters at the input side, are maintained within the IEC 61000-3-2 standard and THD is also very low.

REFERENCES:

[1] Limits for Harmonics Current Emissions (Equipment current ≤ 16A per Phase), International standards IEC 61000-3-2, 2000.

[2] Muhammad H. Rashid, “Power Electronics Handbook, Devices, Circuits, and Applications”, Butterworth-Heinemann, third edition, 2011.

[3] N. Mohan, T. M. Undeland, and W. P. Robbins, Power Electronics: Converters, Applications and Design. Hoboken, NJ, USA: Wiley, 2009.

[4] B. Singh, S. Singh, A. Chandra and K. Al-Haddad, “Comprehensive Study of Single-Phase AC-DC Power Factor Corrected Converters With High-Frequency Isolation”, IEEE Trans. Industrial Informatics, vol. 7, no. 4, pp. 540-556, Nov. 2011.

[5] A. Abramovitz K. M. Smedley "Analysis and design of a tapped-inductor buck–boost PFC rectifier with low bus voltage" IEEE Trans. Power Electron., vol. 26 no. 9 pp. 2637-2649 Sep. 2011.

The Application of Electric Spring in Grid-Connected Photovoltaic System

ABSTRACT:  

The characteristics of distributed photovoltaic system power generation system is intermittent and instability. Under the weak grid conditions, when the active power of the PV system injected into the grid is fluctuant, the voltage of supply feeder will increase or decrease, thus affecting the normal use of sensitive load. The electric spring can transfer the energy injected into the supply feeder to the wide-voltage load, which is in series with the ES, to ensure the voltage stability of the sensitive load in the system. In this paper, a grid-connected photovoltaic simulation model with electric spring is built in Matlab / simulink. The voltage waveforms on the ES and sensitive load is obtained under the condition of changing the active power injected into the supply feeder by the grid-connected photovoltaic system. Thought the analysis of the waveforms, we can find that the Electric spring is a kind of effective method to solve the voltage fluctuation of the supply feeder in the grid-connected PV system.

KEYWORDS:

1.      Electric spring

2.      Grid-Connected Photovoltaic System

3.      Voltage Regulation

4.      Photovoltaic Consumption

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Figure 1. The photovoltaic system model with Electric spring

 EXPECTED SIMULATION RESULTS:

Figure 2. The effective value of line voltage when the active power of PV system decreases

Figure 3. The line voltage when the active power of PV system increases (with ES)

CONCLUSION:

This paper applies the electric spring to the PV system to solve the problem that the bus voltage fluctuates due to the power fluctuation during the PV power injected into the bus. By building a simulation model in Matlab /Simulink, it is proved that the voltage on the bus can be effectively stabilized after adding the electric spring in the grid-connected photovoltaic system. When the active power of the PV fluctuates, the electric spring can transfer the voltage fluctuation on the bus to the wide-voltage load, in order to ensure that the bus voltage stability in the vicinity of the given value. Therefore, this is an effective method to solve the fluctuation of the bus voltage in PV grid connected system.

REFERENCES:

1. Hui S Y R, Lee C K, Wu F. Electric springs—A new smart grid technology[J]. IEEE Transactions on Smart Grid, 2012, 3(3): 1552-1561.

2. F. Kienzle, P. Ahein, and G. Andersson, “Valuing investments in multi-energy conversion, storage, and demand-Side management systems under uncertainty,” IEEE Trans Sustain. Energy, vol. 2, no. 2, pp. 194–202,Apr. 2011.

3. C. K. Lee and S. Y. R. Hui, “Input voltage control bidirectional power converters,” US patent application, US2013/0322139, May 31, 2013.

4. CHEN Xu, ZHANG Yongjun, HUANG Xiangmin. Review of Reactive Power and Voltage Control Method in the Background of Active Distribution Network[J]. Automation of Electric Power Systems,2016,40(01):143-

5. Lee S C, Kim S J, Kim S H. Demand side management with air conditioner loads based on the queuing system model[J]. IEEE Transactions on Power Systems, 2010, 26 (2): 661-668.