Analysis of Discrete & Space Vector PWM Controlled Hybrid Active Filters For Power Quality Enhancement

ABSTRACT:

It is known from the fact that Harmonic Distortion is one of the main power quality problems frequently encountered by the utilities. The harmonic problems in the power supply are caused by the non-linear characteristic based loads. The presence of harmonics leads to transformer heating, electromagnetic interference and solid state device mal-functioning. Hence keeping in view of the above concern, research has been carried out to mitigate harmonics. This paper presents an analysis and control methods for hybrid active power filter using Discrete Pulse Width Modulation and Space Vector Pulse Width Modulation (SVPWM) for Power Conditioning in distribution systems. The Discrete PWM has the function of voltage stability, and harmonic suppression. The reference current can be calculated by‘d-q’ transformation. In SVPWM technique, the Active Power Filter (APF) reference voltage vector is generated instead of the reference current, and the desired APF output voltage is generated by SVPWM. The THD will be decreased significantly by SVPWM technique than the Discrete PWM technique based Hybrid filters. Simulations are carried out for the two approaches by using MATLAB, it is observed that the %THD has been improved from 1.79 to 1.61 by the SVPWM technique.

KEYWORDS:

  1. Discrete PWM Technique
  2. Hybrid Active Power Filter
  3. Reference Voltage Vector
  4. Space Vector Pulse Width Modulation (SVPWM)
  5. Total Harmonic Distortion (THD)
  6. Voltage Source Inverter (VSI)

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Figure 1. Configuration of an APF using SVPWM

EXPECTED SIMULATION RESULTS:

Figure 2. Source current waveform with hybrid filter

Figure 3. FFT analysis of source current with hybrid filter

Figure 4. Simulation results of balanced linear load

(a) The phase-A supply voltage and load current waveforms

(b) The phase-A supply voltage and supply current waveforms

Figure 5. Simulation results of unbalanced linear load

(a) Three-phase load current waveforms

(b) Three-phase supply current waveforms

Figure 6. Simulation results of non-linear load

(a) The three-phase source voltage waveforms

(b) The three-phase load current waveforms

(c) The three-phase source current waveforms

Figure 7. Harmonic spectrum of non-linear load

(a) The phase-A load current harmonic spectrum

(b) The phase-A source current harmonic spectrum

 CONCLUSION:

In this paper, a control methodology for the APF using Discrete PWM and SVPWM is proposed.These methods require a few sensors, simple in algorithm and are able to compensate harmonics and unbalanced loads. The performance of APF with these methods is done in MATLAB/Simulink. The algorithm will be able to reduce the complexity of the control circuitry. The harmonic spectrum under non-linear load conditions shows that reduction of harmonics is better. Under unbalanced linear load, the magnitude of three-phase source currents are made equal and also with balanced linear load the voltage and current are made in phase with each other. The simulation study of two level inverter is carried out using SVPWM because of its better utilization of DC bus voltage more efficiently and generates less harmonic distortion in three-phase voltage source inverter. This SVPWM control methodology can be used with series APF to compensate power quality distortions. From the simulated results of the filtering techniques, it is observed that Total Harmonic Distortion is reduced to an extent by the SVPWM Hybrid filter when compared to the Discrete PWM filtering technique i.e. from 1.78% to 1.61%.

REFERENCES:

[1] EI-Habrouk. M, Darwish. M. K, Mehta. P, “Active Power Filters-A Rreview,” Proc.IEE-Elec. Power Applicat., Vol. 147, no. 5, Sept. 2000, pp. 403-413.

[2] Akagi, H., “New Trends in Active Filters for Power Conditioning,” IEEE Trans. on Industry applications,Vol. 32, No. 6, Nov-Dec, 1996, pp. 1312-1322.

[3] Singh.B, Al-Haddad.K, Chandra.A, “Review of Active Filters for Power Quality Improvement,” IEEE Trans. Ind. Electron., Vol. 46, No. 5, Oct, 1999, pp. 960-971.

[4] Ozdemir.E, Murat Kale, Sule Ozdemir, “Active Power Filters for Power Compensation Under Non-Ideal Mains Voltages,” IEEE Trans. on Industry applications, Vol.12, 20-24 Aug, 2003, pp.112-118.

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

 

ABSTRACT:

This paper presents a new asymmetrical single phase multilevel inverter topology capable of producing nine level 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

CIRCUIT DIAGRAM:

Fig. 1. Proposed nine level inverter topology.

EXPECTED SIMULATION RESULTS:

 

  • (a) Output voltage waveform
  • (b) Voltage Output Harmonic spectrum
  • (c) Load current waveform
  • (d) Load Current Harmonic spectrum
  • Fig. 2. Simulation Output results at 50Hz fundamental frequency for R =150ohm, L= 240, P.F = 0.9

(a) Output voltage waveform

  • (b) Voltage Output Harmonic spectrum

  • (c) Load current waveform
  • (d) Load Current Harmonic spectrum
  • Fig. 3. 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 carrier based 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.

Three-Phase Shunt Active Power Filter for Power Improvement Quality using Sliding Mode Controller

ABSTRACT:

In this paper, experimental study of Sliding Mode Controller (SMC) DC bus voltage of three phase shunt active power filter (APF), to improve power quality by compensating harmonics and reactive power required by nonlinear load is proposed. The algorithm used to identify the reference currents is based on the Self Tuning Filter (STF). For generation of the pulse switching of the IGBTs inverter the hysteresis current controller is used, implemented into an analogue card. Finally, various experimental results are presented under steady state and transient conditions.

KEYWORDS:

  1. Shunt Active Power Filter (APF)
  2. Total Harmonic Distortion (THD)
  3. Sliding Mode Controller (SMC)
  4. Self Tuning Filter (STF)

 SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

 

Fig. 1: The basic compensation principle of the shunt APF.

 EXPECTED SIMULATION RESULTS:

 

 

Fig. 2. Experimental APF results: load current iL (A), filter current iF (A)

and source current iS (A). Ch1 to Ch4 scale: 5 A/div. Time scale: 20 ms/div.

 

Fig. 3. Experimental APF results: load current iL (A), filter current iF (A),

source current iS (A) and source voltage Vs (V). Ch1 and Ch3 scale: 5 A/div;

Ch2 scale: 100 V/div;Ch4 scale: 80 V/div; Time scale: 10 ms/div.

Figure 4. Experimental APF results : load current iL(A), filter current iF(A) ,

source current iS(A) and DC voltage Vdc(V). Ch1,Ch3 and Ch4 scale: 10

A/div. Ch2 scale: 100 V/div. Time scale: 20 ms/div.

Figure 5. Experimental APF results: DC voltage Vdc (V) and DC reference

voltage V*dc (V). Ch1 and Ch2 scale: 100 V/div. Time scale: 1s/div

CONCLUSION:

The control of the shunt Active Power Filter was divided in three parts, the first one realized by the dSPACE system to generate the reference currents, the second one achieved by an analogue card for the switching pattern generation, implementing a hysteresis current controller and the third party use a sliding mode controller SMC. A SMC controlled shunt active power filter has been studied to improve the power quality by compensating both harmonics and reactive power requirement of the nonlinear load. The performance of the SMC controller has been developed in real time process and successfully tested in the laboratory The results of experiment study of APF control technique presented in this paper are found quite satisfactory to eliminate harmonics and reactive power components from utility current. The shunt APF presented in this paper for the compensation of harmonic current components in non-linear load was effective for harmonic isolation and keeping the utility supply line current sinusoidal. The validity of this technique was proved on the basis of experiment results. The APF is found effective to meet IEEE- 519-1992 standard recommendations on harmonics levels.

REFERENCES:

[1] Chaoui; J.P.Gaubert; F.Krim; G.Champenois, “PI Controlled Threephase Shunt Active Power Filter for Power Quality Improvement” A. “Electric Power Components and Systems, 1532-5016, Volume 35, Issue 12, 2007, Pages 1331 – 1344.

[2] D. Benatous, R. Abdessemed, “Digital voltage control of AC/DC PWM Converter with improved power factor and supply current ”, Journal of electric machines and power systems, Taylor and francis, 2000.

[3] G. A. Capolino, A. Golea, H. Henao, “Système de réduction des perturbations réseau pour commande vectorielle ”, Proc. Colloque SEE Perturbations Réciproques des Convertisseurs et des Réseaux, Nantes, 6 juillet 1992.

[4] M. Abdusalam, P. Poure and S. Saadate,’’ A New control scheme of hybrid active filter using Self-Tuning Filter,’’ POWERENG, International Conference on Power Engineering , Energy and Electrical Drives, Setubal Portugal,12-14 April (2007).

[5] M. Abdusalam, P. Poure and S. Saadate, « Study and experimental +6validation of harmonic isolation based on Self-Tuning-Filter for threephase active filter ». ISIE, IEEE International Symposium on Industrial Electronics, Cambridge, UK, (2008).

 

A Control Technique for Integration of DG Units to the Electrical Networks

ABSTRACT:

This paper deals with a multi objective control technique for integration of distributed generation (DG) resources to the electrical power network. The proposed strategy provides compensation for active, reactive, and harmonic load current components during connection of DG link to the grid. The dynamic model of the proposed system is first elaborated in the stationary reference frame and then transformed into the synchronous orthogonal reference frame. The transformed variables are used in control of the voltage source converter as the heart of the interfacing system between DG resources and utility grid. By setting an appropriate compensation current references from the sensed load currents in control circuit loop of DG, the active, reactive, and harmonic load current components will be compensated with fast dynamic response, thereby achieving sinusoidal grid currents in phase with load voltages, while required power of the load is more than the maximum injected power of the DG to the grid. In addition, the proposed control method of this paper does not need a phase-locked loop in control circuit and has fast dynamic response in providing active and reactive power components of the grid-connected loads. The effectiveness of the proposed control technique in DG application is demonstrated with injection of maximum available power from the DG to the grid, increased power factor of the utility grid, and reduced total harmonic distortion of grid current through simulation and experimental results under steady-state and dynamic operating conditions.

KEYWORDS:

  1. Digital signal processor
  2. Distributed generation (DG)
  3. Renewable energy sources
  4. Total harmonic distortion (THD)
  5. voltage source converter (VSC)

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

image001

Fig. 1. General schematic diagram of the proposed control strategy for DG system.

 EXPECTED SIMULATION RESULTS:

image002

Fig. 2. Load voltage, load, grid, and DG currents before and after connection of DG and before and after connection and disconnection of additional load into the grid.

image003

Fig. 3. Grid, load, DG currents, and load voltage (a) before and after connection of additional load and (b) before and after disconnection of additional load.

image004

Fig. 4. Phase-to-neutral voltage and grid current for phase (a).

image005

Fig. 5. Reference currents track the load current (a) after interconnection of DG resources and (b) after additional load increment.

image006

Fig. 6. Load voltage, load, grid, and DG currents during connection of DG link to the unbalanced grid voltage.

CONCLUSION:

A multi objective control algorithm for the grid-connected converter-based DG interface has been proposed and presented in this paper. Flexibility of the proposed DG in both steady-state and transient operations has been verified through simulation and experimental results.

Due to sensitivity of phase-locked loop to noises and distortion, its elimination can bring benefits for robust control against distortions in DG applications. Also, the problems due to synchronization between DG and grid do not exist, and DG link can be connected to the power grid without any current overshoot. One other advantage of proposed control method is its fast dynamic response in tracking reactive power variations; the control loops of active and reactive power are considered independent. By the use of the proposed control method, DG system is introduced as a new alternative for distributed static compensator in distribution network. The results illustrate that, in all conditions, the load voltage and source current are in phase and so, by improvement of power factor at PCC, DG systems can act as power factor corrector devices. The results indicate that proposed DG system can provide required harmonic load currents in all situations. Thus, by reducing THD of source current, it can act as an active filter. The proposed control technique can be used for different types of DG resources as power quality improvement devices in a customer power distribution network.

REFERENCES:

[1] T. Zhou and B. François, “Energy management and power control of a hybrid active wind generator for distributed power generation and grid integration,” IEEE Trans. Ind. Electron., vol. 58, no. 1, pp. 95–104, Jan. 2011.

[2] M. Singh, V. Khadkikar, A. Chandra, and R. K. Varma, “Grid interconnection of renewable energy sources at the distribution level with power quality improvement features,” IEEE Trans. Power Del., vol. 26, no. 1, pp. 307–315, Jan. 2011.

[3] M. F. Akorede, H. Hizam, and E. Pouresmaeil, “Distributed energy resources and benefits to the environment,” Renewable Sustainable Energy Rev., vol. 14, no. 2, pp. 724–734, Feb. 2010.

[4] C. Mozina, “Impact of green power distributed generation,” IEEE Ind. Appl. Mag., vol. 16, no. 4, pp. 55–62, Jun. 2010.

[5] B. Ramachandran, S. K. Srivastava, C. S. Edrington, and D. A. Cartes, “An intelligent auction scheme for smart grid market using a hybrid immune algorithm,” IEEE Trans. Ind. Electron., vol. 58, no. 10, pp. 4603–4611, Oct. 2011.

 

Analysis and Design of Three-Level, 24-Pulse Double Bridge Voltage Source Converter Based HVDC System for Active and Reactive Power Control

ABSTRACT

This paper deals with the analysis, design and control of a three-level 24-pulse Voltage Source Converter (VSC) based High Voltage Direct Current (HVDC) system. A three level VSC operating at fundamental frequency switching (FFS) is proposed with 24-pulse VSC structure to improve the power quality and reduce the converter switching losses for high power applications. The design of three-level VSC converter and system parameters such as ac inductor and dc capacitor is presented for the proposed VSC based HVDC system. It consists of two converter stations fed from two different ac systems. The active power is transferred between the stations either way. The reactive power is independently controlled in each converter station. The three-level VSC is operated at optimized dead angle (β). A coordinated control algorithm for both the rectifier and an inverter stations for bidirectional active power flow is developed based on FFS and local reactive power generation. This results in a substantial reduction in switching losses and avoiding the reactive power plant. Simulation is carried to verify the performance of the proposed control algorithm of the VSC based HVDC system for bidirectional active power flow and their independent reactive power control.

 

KEYWORDS

Voltage Source Converter (VSC), Three-level VSC, Fundamental Frequency Switching (FFS), HVDC System, Power Flow Control, Reactive Power Control, Power Quality, Total Harmonic Distortion (THD), Dead Angle (β).

 

SOFTWARE: MATLAB/SIMULINK

 

BLOCK DIAGRAM:

image001

Fig. 1 Three-level 24-pulse double bridge VSC based HVDC system

 

EXPECTED SIMULATION RESULTS:

image002

Fig. 2a Performance of rectifier station during reactive power control of three level 24-pulse VSC HVDC system

image003

Fig. 2b Performance of Inverter station during reactive power control at rectifier station of three-level 24 pulse VSC HVDC system

image004

Fig. 2c Variation of (δ) and (α) values for rectifier and inverter Stations for reactive power variation of a three-level 24-pulse VSC HVDC system

image005

Fig. 3a Rectifier station during active power reversal of three-level 24-pulse VSC HVDC system

image006

Fig. 3b Inverter station during active power reversal of three-level 24-pulse VSC HVDC system

image007

Fig. 3c Variation of (δ) and (α) values during active power reversal of three level 24-pulse VSC HVDC system.

 

CONCLUSION

A new three-level, 24-pulse voltage source converter based HVDC system operating at fundamental frequency switching has been designed and its model has been developed and it is successfully tested for the independent control of active and reactive powers and acceptable level harmonic requirements. The reactive power has been controlled independent of the active power at both conditions. The converter has been successfully operated in all four quadrants of active and reactive powers with the proposed control. The reversal of the active power flow has been implemented by reversing the direction of dc current without changing the polarity of dc voltage which is very difficult in conventional HVDC systems. The power quality of the HVDC system has also improved with three-level 24-pulse converter operation. The harmonic performance of this three-level, 24-pulse VSC has been observed to an equivalent to two-level 48-pulse voltage source converter.

 

REFERENCES

[1] “It’s time to connect,” Technical description of HVDC Light Technology, ABB HVDC Library.

[2] J. Arrillaga, “High Voltage Direct Current Transmission,” 2nd Edition, IEE Power and Energy Series 29, London, 1998.

[3] Vijay K. Sood, “HVDC and FACTS Controllers – Applications of Static Converters in Power Systems,” Kluwer Academic Publishers, Masachusetts, 2004.

[4] J. Arrillaga, Y. H. Liu and N. R. Waston, “Flexible Power Transmission- The HVDC Options,” John Wiley & Sons, Ltd, Chichester, UK, 2007.

[5] J. Arrillaga and M. E. Villablanca, “A modified parallel HVDC convertor for 24 pulse operation,” IEEE Trans. on Power Delivery, vol. 6, no. 1, pp. 231-237, Jan 1991.