Dynamic Voltage Restorer Using Switching Cell Structured Multilevel AC-AC Converter

IEEE Transactions on Power Electronics, 2016

ABSTRACT:

Dynamic voltage restorer (DVR) technology has become a mature power quality product. In high-power applications, DVR using a multilevel converter is commonly used. However, DVR using a multilevel direct pulse width modulation (PWM) ac-ac converter has not been well studied. This paper presents a new DVR topology using a cascaded multilevel direct PWM ac-ac converter. In the proposed scheme, the unit cell of the multilevel converter consists of a single-phase PWM ac-ac converter using switching cell (SC) structure with coupled inductors. Therefore, the multilevel converter can be short- and open-circuited without damaging the switching devices. Neither lossy RC snubber nor a dedicated soft commutation strategy is required in the proposed DVR. This improves the reliability of the DVR system. The output voltage levels of the multilevel converter increase with the number of cascaded unit cells, and a high ac output voltage is obtained by using low-voltage-rating switching devices. Furthermore, a phase-shifted PWM technique is applied to significantly reduce the size of the output filter inductor. A 1-kW prototype of single-phase DVR is developed, and its performance is experimentally verified. Finally, the simulation results are shown for a three-phase DVR system.

 

KEYWORDS:

  1. Commutation problem
  2. coupled inductor
  3. direct PWM AC-AC converter
  4. dynamic voltage restorer (DVR)
  5. multilevel converter
  6. pulse width modulation (PWM)
  7. switching cell (SC)

 

SOFTWARE: MATLAB/SIMULINK

 

CIRCUIT DIAGRAM:

Fig. 1. Three-phase DVR systems using VSI [2]. (a) DVR with energy storage. (b) DVR with no energy storage.

 

EXPECTED SIMULATION RESULTS:

 

Fig. 2. Simulated waveforms of the three-phase DVR ( voa=vob=voc=220 Vrms,Po=3kW, )

 

CONCLUSION:

In this paper, a new DVR system, employing the proposed cascaded multilevel direct PWM ac-ac converter, was presented. Compared with the conventional DVR topologies using the VSI, the proposed scheme has the advantages of fewer power stages, higher efficiency, and the elimination of bulky dc-link capacitor. In addition, unlike the existing DVR with the direct PWM ac-ac converter, the proposed DVR ensures stable operation because the proposed cascaded multilevel ac-ac converter has the following unique advantages over the conventional ac-ac converters.

  • It is immune to EMI noise because the switching devices are not damaged by the EMI noise’s misgating on- or off.
  • The commutation problem found in the conventional ac-ac converters can be effectively eliminated without using either dedicated soft commutation strategy or lossy RC snubber circuits.
  • It operates properly even with highly distorted input voltage, which is impossible with the conventional approach using soft commutation strategy.

Furthermore, the proposed multilevel ac-ac converter can obtain high ac output voltage with low-voltage-rating switching devices by cascading unit cells. The equivalent output frequency of the multilevel converter is increased by using a phase-shifted PWM technique, which reduces the size of the output LC filter. The performance of the proposed DVR is successfully verified by using a 1-kW prototype. Finally, a three-phase DVR system using the proposed scheme is verified through simulation.

 

REFERENCES:

  • -H. Kwon, G. Y. Jeong, S.-H. Han, and D. H. Lee, “Novel line conditioner with voltage up/down capability,” IEEE Trans. Ind. Electron., vol. 49, no. 5, pp. 1110–1119, Oct. 2002.
  • Nielsen and F. Blaabjerg, “A detailed comparison of system topologies for dynamic voltage restorers,” IEEE Trans. Ind. Appl., vol. 41, no. 5, pp. 1272–1280, Sep./Oct. 2005.
  • C. Aeoliza, N. P. Enjeti, L. A. Moran, O. C. Montero-Hernandez, and S. Kim, “Analysis and design of a novel voltage sag compensator for critical loads in electrical power distribution systems,” IEEE Trans. Ind. Appl., vol. 39, no. 4, pp. 1143–1150, Jul./Aug. 2003.
  • E. Brumsickle, R. S. Schneider, G. A. Luckjiff, D. M. Divan, and M. F. McGranaghan, “Dynamic sag correctors: Cost-effective industrial power line conditioning,” IEEE Trans. Ind. Appl., vol. 37, no. 1, pp. 212– 217, Jan./Feb. 2001.

Design and Simulation of Single Phase Shunt Active Power Filter using MATLAB

ABSTRACT:

Power Quality issues are becoming a major concern of today’s power system engineers. Harmonics play significant roll in deteriorating power quality, called harmonic distortion. Harmonic distortion in electric distribution system is increasingly growing due to the widespread use of nonlinear loads. Large considerations of these loads have the potential to raise harmonic voltage and currents in an electrical distribution system to unacceptable high levels that can adversely affect the system. IEEE standards have defined limits for harmonic voltages and harmonic currents. Active power filters have been considered a potential candidate to bring these harmonic distortions within the IEEE limits. This paper deals with an active power filter (APF) based on simple control. A voltage source inverter with pulse width modulation (PWM) is employed to form the APF. A diode rectifier feeding capacitive-resistive load is considered as nonlinear load on ac mains for the elimination of harmonics by the proposed APF. MATLAB model of the scheme is simulated and obtained results are studied.

KEYWORDS:

  1. Power Quality
  2. THD
  3. Non-linear Load
  4. PWM

 SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Figure 1 Principle of Shunt connected SPAPF

EXPECTED SIMULATION RESULTS:

Figure 2. Load Current without SPAPF

Figure 3. Load Current Harmonic Spectrum without SPAPF

Figure 4. Load Voltage without SPAPF

Figure 5. Load Current Harmonic Spectrum without SPAPF

Figure 6. Load Current with SPAPF

Figure 7. Load Current Harmonic Spectrum with SPAPF

Figure 8. Load Voltage without SPAPF

Figure 9. Load Voltage Harmonic Spectrum with SPAPF

 CONCLUSION:

A simple control scheme of the single phase active power filter is proposed which requires sensing of one current and two voltages only. The APF results in sinusoidal unity power factor supply current. It is concluded that the reduced value of dc bus capacitor is able to give quite satisfactory operation of the APF system. The voltage controller gives fast response. The proposed APF is able to reduce THD of supply current and supply voltage below prescribed permitted limits specified by IEEE 519.

REFERENCES:

[1] D. C. Bhonsle, Dr. R. B. Kelkar and N. K. Zaveri, “Power Quality Issues-In Distribution System”, IE(I) 23rd National Convention of Electrical Engineers, Pune, November 2007 Proceedings, pp. 108-111.

[2] K. C. Umeh, A. Mohamed, R. Mohmed, “ Comparing The Harmonic Characteristics of Typical Single Phase Nonlinear Loads”, National Power Energy Conference (PECon) 2003 Proceedings, Bangi, Malaysia, pp. 383-387.

[3] Mohamed S. A. Dahidah, N. Mariun, S. Mahmod and N. Khan, “Single Phase Active Power Filter for Harmonic Mitigation in Distribution Power Lines”, National Power and Energy Conference (PECon) 2003 Proceedings, Bangi, Malaysia, pp. 359-362.

[4] Dalila Mat Said Ahmed, Abdullah asuhaimi, Mohd Zin, “Power Supply Quality Improvement: Harmonic Measurement and Simulation,” National Power and Energy Conference (PECon), 2003 Proceedings, Bangi, Malaysia, pp. 352-358.

[5] C. Gopalkrishnan, K Udaykumar, T. A. Raghvendiran, “Survey of Harmonic Distortion for Power Quality Measurement and Application of Standard including Simulation,” 2001, Anna University, India.

 

A Fast Space-Vector Modulation Algorithm for Multilevel Three-Phase Converters

 

ABSTRACT:

This paper introduces a general space-vector modulation algorithm for -level three-phase converters. The algorithm is computationally extremely efficient and is independent of the number of converter levels. At the same time, it provides good insight into the operation of multilevel converters.

 KEYWORDS:

  1. Digital control
  2. Pulse width modulation
  3. Space vectors

 SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Fig.1.Types of multilevel converters.

Fig .2.Classification of multilevel modulations.

 EXPECTED SIMULATION RESULTS:

 Fig.3.Normalized line-to-line PWM voltage waveforms for three, four and five-level converters.

CONCLUSION:

This paper has presented a fast new SVM algorithm for multilevel three-phase converters. The algorithm is general and applicable to converters with any number of levels. In addition, the number of steps required to select the nearest three vectors and compute their duty cycles remains the same regardless of the number of converter levels or the location of the reference vector. In addition, the computational efficiency of this algorithm makes it a useful simulation tool for further study of the properties of multilevel converters.

REFERENCES:

[1] L. M. Tolbert and F. Z. Peng, ―Multilevel converters for large electric drives,‖ in Proc. IEEE APEC’98, vol. 2, 1998, pp. 530–536.

[2] Y. Chen, B. Mwinyiwiwa, Z. Wolanski, and B.-T. Ooi, ―Regulating and equalizing dc capacitance voltages in multilevel statcom,‖ IEEE Trans. Power Delivery, vol. 12, pp. 901–907, Apr. 1997.

[3] J.-S. Lai and F. Z. Peng, ―Multilevel converters—A new breed of power converters,‖ IEEE Trans. Ind. Applicat., vol. 32, pp. 509–517, May/June 1996.

[4] P. M. Bhagwat and V. R. Stefanovic, ―Generalized structure of a multilevel PWM inverter,‖ IEEE Trans. Ind. Applicat., vol. IA-19, pp. 1057–1069, Nov./Dec. 1983.

[5] G. Sinha and T. A. Lipo, ―A four level rectifier-inverter system for drive applications,‖ IEEE Trans. Ind. Applicat., vol. 30, pp. 938–944, July/Aug. 1994.

Simulation of a Space Vector PWM Controller for a Three-Level Voltage-Fed Inverter Motor Drive

ABSTRACT

Multilevel voltage-fed inverters with space vector pulse width modulation strategy are gained importance in high power high performance industrial drive applications. This paper proposes a new simplified space vector PWM method for a three-level inverter fed induction motor drive. The three- level inverter has a large number of switching states compared to a two-level inverter. In the proposed scheme, three-level space vector PWM inverter is easily implemented as conventional two-level space vector PWM inverter. Therefore, the proposed method can also be applied to multilevel inverters. In this work, a three-level inverter using space vector modulation strategy has been modeled and simulated. Simulation results are presented for various operation conditions using R-L load and motor load to verify the system model.

 

KEYWORDS

  1. Space vector PWM
  2. Three-level inverters
  3. Multilevel inverters

 

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

image001

Fig.1 Three level multilevel inverter using cascaded inverters with separated DC sources

 

EXPECTED SIMULATION RESULTS

image002

Fig.2 The line output voltage waveform for fo=10Hz and m=0.65

image003

Fig.3 Three-phase line output current waveforms for fo=10Hz and m=0.65

image004

Fig.4 The line output voltage waveform and its spectrum for fo=10Hz and m=0.65.

image005

Fig.5 The line output voltage waveform for fo=50Hz and m=0.7

CONCLUSION

The space vector PWM algorithm for a three level voltage-fed inverter using cascaded H-bridges inverter has been modeled and simulated using Simulink/MATLAB package program. Simulation results have been given for both R-L and induction motor loads using 1 kHz switching frequency with various output frequencies. The proposed control algorithm used in the three-level inverter can be easily applied to multilevel inverters with more than three levels. It has been shown that high quality waveforms at the output of the multilevel inverter can be obtained even with 1 kHz of low switching frequency.

 

REFERENCES

  1. M. Bhagwat and V.R. Stefanovic, “Generalized Structure of A Multilevel Inverter”, IEEE Trans. On I.A., Vol. IA-19, n.6, 1983, pp. 1057-1069.
  2. K. Mondal, J.O.P Pinto, B.K. Bose, “A Neural- Network-Based Space Vector PWM Controller for a Three-Level Voltage-Fed Inverter Induction Motor Drive”, IEEE Trans. on I.A., Vol. 38, no. 3, May/June 2002, pp.660-669.
  3. K. Mondal, B.K. Bose, V. Oleschuk and J.O.P Pinto, “Space Vector Pulse Width Modulation of Three-Level Inverter Extending Operation Into Overmodulation Region”, IEEE Trans. on Power Electronics, Vol. 18, no. 2, March 2003, pp.604-611.
  4. Manjrekar and G. Venkataramanan, “Advanced Topologies and Modulation Strategies for Multilevel Inverters”, Power Electronics Specialists Conference, Vol. 2, 23-27 June 1996, pp. 1013-1018.
  5. Nabae, I. Takahashi and H. Akagi, “A New Neutral-Point-Clamped PWM Inverter”, IEEE Trans. on I.A., Vol. 17, No.5, September/October 1981, pp.518-523.

Modeling and Analysis of 3-Phase VSI using SPWM Technique for Grid Connected Solar PV System

ABSTRACT:

Solar energy is one of the most promising Renewable Energy Sources (RES) that can be used to produce electric energy through Photovoltaic (PV) process. The Solar Photovoltaic (SPV) systems which directly supply power to the grid are becoming more popular. A power electronic converter which converts DC power from the PV array to AC power at required voltage and frequency levels is known as Inverter. Generally different Pulse Width Modulation (PWM) techniques have been implemented for grid connected 3-phase Voltage Source Inverter (VSI) system. This paper describes few types of PWM techniques and mathematical model of LC filter circuit is given using state space analysis. Sine-PWM technique is proposed for 3-phase VSI and implemented using the state space model of the LC filter circuit. The simulation is performed in MATLAB/Simulink platform. Simulation results are presented for the inverter and load side to demonstrate the satisfactory performance of the sine-PWM technique.

 KEYWORDS:

 Pulse width modulation

Solar photovoltaic

Voltage source inverter

 SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

image001

Fig. 1. General Block Diagram of Grid Connected SPV system

 EXPECTED SIMULATION RESULTS:
image002

Fig. 2. Carrier wave (Vtri) and Modulating wave (Vsin)

image003

Fig. 3. Inverter Output line to line Voltages (ViAB,ViBC,ViCA)

image004

Fig. 4. Inverter Output Currents (iiA,iiB,iiC)

image005

Fig. 5. Load line to line voltages (VLAB, VLBC, VLCA)

image006

Fig. 6. Load Phase Currents (iLA,iLB,iLC)

image007

Fig. 7. Inverter output line voltage, Inverter output current, Load line

voltage, Load phase currents

CONCLUSION:

Increasing demand on energy efficiency and power quality issues, grid connected solar PV systems is taking a good place. In this paper SPWM and SVPWM techniques have been discussed for 3-phase grid connected VSI. The LC filter circuit is used in the proposed system. This filter circuit is mathematically modeled by using state space analysis and complete state space equation is obtained. The SPWM technique is implemented and simulated on 3 phases VSI using state space model of the LC filter circuit for grid connected solar PV system. Various simulation results are analyzed and presented on the inverter and load side of the proposed system in order to demonstrate the satisfactory performance of sine-PWM technique for grid connected solar PV system.

 REFERENCES:

[1] J.Y. Lee, and Y.Y. Sun, “A New SPWM Inverter with Minimum Filter Requirement,” International Journal of Electronics, Vol. 64, No. 5, pp. 815-826, 1988.

[2] K. Zhou and D. Wang, “Relationship Between Space-Vector Modulation and Three- Phase Carrier-Based PWM: A Comprehensive Analysis,” IEEE Transactions on Industrial Electronics, Vol. 49, No. 1, pp. 186- 196, February 2002.

[3] A.W. Leedy, and R.M. Nelms, “Harmonic Analysis of a Space Vector PWM Inverter using the Method of Multiple Pulses,” IEEE Transactions on Industrial Electronics, Vol. 4, pp. 1182-1187, July 2006.

[4] A.M. Khambadkone, and J. Holtz, “Current Control in Over-modulation Range for Space Vector Modulation based Vector Controlled Induction Motor Drives,” IEEE Industrial Electronics Society, Vol.2, pp. 1134- 1339, 2000.

[5] E. Hendawi, F. Khater, and A. Shaltout, “Analysis, Simulation and Implementation of Space Vector Pulse Width Modulation Inverter,” International Conference on Application of Electrical Engineering, pp. 124-131, 2010.

High-Efficiency MOSFET Transformerless Inverter for Non-isolated Microinverter Applications

ABSTRACT

State-of-the-art low-power-level metal–oxide–semiconductor field-effect transistor (MOSFET)-based transformerless photovoltaic (PV) inverters can achieve high efficiency by using latest super junction MOSFETs. However, these MOSFET-based inverter topologies suffer from one or more of these drawbacks: MOSFET failure risk from body diode reverse recovery, increased conduction losses due to more devices, or low magnetics utilization. By splitting the conventional MOSFET based phase leg with an optimized inductor, this paper proposes a novel MOSFET-based phase leg configuration to minimize these drawbacks. Based on the proposed phase leg configuration, a high efficiency single-phase MOSFET transformerless inverter is presented for the PV microinverter applications. The pulsewidth modulation (PWM) modulation and circuit operation principle are then described. The common-mode and differential-mode voltage model is then presented and analyzed for circuit design. Experimental results of a 250Whardware prototype are shown to demonstrate the merits of the proposed transformerless inverter on non-isolated two-stage PV microinverter application.

 KEYWORDS: Microinverter, MOSFET inverters, photovoltaic (PV) inverter, transformerless inverter.

 SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

image001

Fig. 1. Two-stage nonisolated PV microinverter.

CIRCUIT DIAGRAM:

image002

Fig. 2. Proposed transformerless inverter topology with (a) separated magnetic and (b) integrated magnetics.

 EXPERIMENTAL RESULTS:

image003

Fig. 3. Output voltage and current waveforms.

image004

Fig. 4. PWM gate signals waveforms.

image005

Fig. 5. Inverter splitting inductor current waveform.

image006

Fig. 6. Waveforms of voltage between grid ground and DC ground (VEG ).

CONCLUSION

This paper proposes a MOSFET transformerless inverter with a novel MOSFET-based phase leg, which achieves:

1) high efficiency by using super junction MOSFETs and SiC diodes;

2) minimized risks from the MOSFET phase leg by splitting the MOSFET phase leg with optimized inductor and minimizing the di/dt from MOSFET body diode reverse recovery;

3) high magnetics utilization compared with previous high efficiency MOSFET transformerless inverters in [21], [22], [25], which only have 50% magnetics utilization.

The proposed transformerless inverter has no dead-time requirement, simple PWM modulation for implementation, and minimized high-frequency CMissue. A 250Whardware prototype has been designed, fabricated, and tested in two-stage nonisolated microinverter application. Experimental results demonstrate that the proposed MOSFET transformerless inverter achieves 99.01% peak efficiency at full load condition and 98.8% CEC efficiency and also achieves around 98% magnetic utilization. Due to the advantages of high efficiency, low CM voltage, and improved magnetic utilization, the proposed topology is attractive for two-stage nonisolated PV microinverter applications and transformerless string inverter applications.

 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] S. B. Kjaer, J. K. Pedersen, and F. Blaabjerg, “A review of singlephase grid-connected inverters for photovoltaic modules,” IEEE Trans. Ind. Appl., vol. 41, no. 5, p. 1292, Sep. 2005.

[3] Q. Li and P. Wolfs, “A review of the single phase photovoltaic module integrated converter topologies with three different dc link configurations,” IEEE Trans. Power Electron., vol. 23, no. 3, pp. 1320–1333, May 2008.

[4] Y. Xue, L. Chang, S. B. Kjaer, J. Bordonau, and T. Shimizu, “Topologies of single-phase inverters for small distributed power generators: An overview,” IEEE Trans. Power Electron., vol. 19, no. 5, pp. 1305–1314, 2004.

[5] W. Yu, J. S. Lai, H. Qian, and C. Hutchens, “High-efficiency MOSFET inverter with H6-type configuration for photovoltaic non-isolated AC-module applications,” IEEE Trans. Power Electron., vol. 56, no. 4, pp. 1253–1260, Apr. 2011.

A High Step-Up DC to DC Converter Under Alternating Phase Shift Control for Fuel Cell Power System

ABSTRACT

This paper investigates a novel pulse width modulation (PWM) scheme for two-phase interleaved boost converter with voltage multiplier for fuel cell power system by combining alternating phase shift (APS) control and traditional interleaving PWM control. The APS control is used to reduce the voltage stress on switches in light load while the traditional interleaving control is used to keep better performance in heavy load. The boundary condition for swapping between APS and traditional interleaving PWM control is derived. Based on the aforementioned analysis, a full power range control combining APS and traditional interleaving control is proposed. Loss breakdown analysis is also given to explore the efficiency of the converter. Finally, it is verified by experimental results.

 KEYWORDS: Boost converter, Fuel cell, Interleaved, Loss breakdown, Voltage multiplier.

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

image001

Fig. 1. Grid-connected power system based on fuel cell.

image002

Fig. 2. Main theoretical waveforms at boundary condition.

EXPERIMENTAL RESULTS:

 image003image004 image005 image006Fig.3 Experimental results at boundary condition with traditional interleaving control (L = 1158 μH, R = 2023 Ω, and D = 0.448). (a) CH1-S1 Driver Voltage, CH2 L1 Current, CH3-S1 Voltage Stress, CH4-Output Voltage, (b) CH1-S1 Driver Voltage, CH2 C1 Current, CH3-S1 Voltage Stress, CH4-OutputVoltage, (c) CH1-S1 DriverVoltage,CH2 D1 Current,CH3-S1 Voltage Stress, CH4-Output Voltage, (d) CH1-S1 Driver Voltage, CH2 DM1 Current, CH3-S1 Voltage Stress, CH4-Output Voltage.

image007

Fig. 4. Traditional interleaving control at nominal load (L = 1158 μH and R = 478 Ω).]

image008

Fig. 5. Traditional interleaving control in Zone A (L = 1158 μH and R = 1658 Ω).

CONCLUSION

The boundary condition is derived after stage analysis in this paper. The boundary condition classifies the operating states into two zones, i.e., Zone A and Zone B. The traditional interleaving control is used in Zone A while APS control is used in Zone B. And the swapping function is achieved by a logic unit. With the proposed control scheme, the converter can achieve low voltage stress on switches in all power range of the load, which is verified by experimental results.

 REFERENCES

[1] N. Sammes, Fuel Cell Technology: Reaching Towards Commercialization. London, U.K.: Springer-Verlag, 2006.

[2] G. Fontes, C. Turpin, S. Astier, and T. A. Meynard, “Interactions between fuel cells and power converters: Influence of current harmonics on a fuel cell stack,” IEEE Trans. Power Electron., vol. 22, no. 2, pp. 670–678, Mar. 2007.

[3] P. Thounthong, B. Davat, S. Rael, and P. Sethakul, “Fuel starvation,” IEEE Ind. Appl. Mag., vol. 15, no. 4, pp. 52–59, Jul./Aug. 2009.

[4] S.Wang,Y.Kenarangui, and B. Fahimi, “Impact of boost converter switching frequency on optimal operation of fuel cell systems,” in Proc. IEEE Vehicle Power Propulsion Conf., 2006, pp. 1–5.

[5] S. K. Mazumder, R. K. Burra, and K. Acharya, “A ripple-mitigating and energy-efficient fuel cell power-conditioning system,” IEEE Trans. Power Electron., vol. 22, no. 4, pp. 1437–1452, Jul. 2007.