Integrated Photovoltaic and Dynamic Voltage Restorer System Configuration

ABSTRACT:  

This paper presents a new system structure for integrating a grid-connected photo voltaic (P V) system together with a self-supported dynamic voltage restorer (DVR). The proposed system termed as a “six-port converter,” consists of nine semiconductor switches in total. The proposed configuration retains all the essential features of normal P V and DVR systems while reducing the overall switch count from twelve to nine. In addition, the dual functionality feature significantly enhances the system robustness against severe symmetrical/asymmetrical grid faults and voltage dips. A detailed study on all the possible operational modes of six-port converter is presented. An appropriate control algorithm is developed and the validity of the proposed configuration is verified through extensive simulation as well as experimental studies under different operating conditions.

KEYWORDS:

  1. Bidirectional power flow
  2. Distributed power generation
  3. Photovoltaic (PV) systems
  4. Power quality
  5. Voltage control

 SOFTWARE: MATLAB/SIMULINK

 CIRCUIT DIAGRAM:

 

 Fig. 1. Proposed integrated PV and DVR system configuration.

 EXPECTED SIMULATION RESULTS:

Fig. 2. Simulation results: operation of proposed system during health grid mode (PV-VSI: active and DVR-VSI: inactive). (a) Vpcc; (b) PQload; (c) PQgrid; (d) PQpv-VSI; and (e) PQdvr-VSI.

Fig. 3. Simulation results: operation of proposed system during fault mode (PV-VSI: inactive and DVR-VSI: active). (a) Vpcc; (b) Vdvr; (c) Vload; (d) PQload; (e) PQgrid; (f) PQpv-VSI; and (g) PQdvr-VSI.

Fig. 4. Simulation results: operation of proposed system during balance three phase sag mode (PV-VSI: active and DVR-VSI: active). (a) Vpcc; (b) Vdvr-VSI; (c) Vload; (d) PQgrid; (e) PQpv-VSI; and (f) PQdvr-VSI.

Fig. 5. Simulation results: operation of proposed system during unbalanced sag mode (PV-VSI: active and DVR-VSI: active). (a) Vpcc; (b) Vdvr-vsi; (c) Vload; (d) PQgrid; (e) PQpv-VSI; and (f) PQdvr-VSI.

Fig. 6. Simulation results: operation of proposed system during inactive PV plantmode (PV-VSI: active and DVR-VSI: active). (a) Vpcc; (b) Vload; (c) Vdc; (d) PQload; (e) PQdvr-VSI; and (f) PQpv-VSI.

 CONCLUSION:

 In this paper, a new system configuration for integrating a conventional grid-connected P V system and self supported DVR is proposed. The proposed configuration not only exhibits all the functionalities of existing P V and DVR system, but also enhances the DVR operating range. It allows DVR to utilize active power of P V plant and thus improves the system robustness against sever grid faults. The proposed configuration can operate in different modes based on the grid condition and P V power generation. The discussed modes are healthy grid mode, fault mode, sag mode, and P V inactive mode. The comprehensive simulation study and experimental validation demonstrate the effectiveness of the proposed configuration and its practical feasibility to perform under different operating conditions. The proposed configuration could be very useful for modern load centers where on-site P V generation and strict voltage regulation are required.

REFERENCES:

[1] R. A. Walling, R. Saint, R. C. Dugan, J. Burke, and L. A. Kojovic, “Summary of distributed resources impact on power delivery systems,” IEEE Trans. Power Del., vol. 23, no. 3, pp. 1636–1644, Jul. 2008.

[2] C. Meza, J. J. Negroni, D. Biel, and F. Guinjoan, “Energy-balance modeling and discrete control for single-phase grid-connected PV central inverters,” IEEE Trans. Ind. Electron., vol. 55, no. 7, pp. 2734–2743, Jul.2008.

[3] T. Shimizu, O. Hashimoto, and G. Kimura, “A novel high-performance utility-interactive photovoltaic inverter system,” IEEE Trans. Power Electron., vol. 18, no. 2, pp. 704–711, Mar. 2003.

[4] S. B. Kjaer, J. K. Pedersen, and F. Blaabjerg, “A review of single-phase grid-connected inverters for photovoltaic modules,” IEEE Trans. Ind.Appl., vol. 41, no. 5, pp. 1292–1306, Sep./Oct. 2005.

[5] T. Esram, J. W. Kimball, P. T. Krein, P. L. Chapman, and P. Midya, m“Dynamic maximum power point tracking of photovoltaic arrays using ripple correlation control,” IEEE Trans. Power Electron., vol. 21, no. 5, pp. 1282–1291, Sep. 2006.

Permanent Magnet Synchronous Generator-Based Standalone Wind Energy Supply System

ABSTRACT

In this paper, a novel calculation, in view of dc interface voltage, is proposed for successful vitality the executives of an independent permanent magnet synchronous generator (PMSG)- based variable speed wind vitality transformation framework comprising of battery, energy unit, and dump stack (i.e., electrolyzer). Additionally, by keeping up the dc connect voltage at its reference esteem, the yield air conditioning voltage of the inverter can be kept consistent regardless of varieties in the breeze speed and load. A compelling control system for the inverter, in view of the beat width adjustment (PWM) conspire, has been created to make the line voltages at the purpose of basic coupling (PCC) adjusted when the heap is uneven. Thus, an appropriate control of battery flow through dc– dc converter has been completed to diminish the electrical torque throb of the PMSG under an uneven load situation. In light of broad reproduction results utilizing MATLAB/SIMULINK, it has been set up that the execution of the controllers both in transient just as in relentless state is very palatable and I can likewise keep up most extreme power point following.

 

 BLOCK DIAGRAM

 

Fig. 1. PMSG-based standalone wind turbine with energy storage and dump load.

 EXPECTED SIMULATION RESULTS

 

Fig. 2. Response of mechanical torque for change in wind velocity.

 Fig. 3. (a) Load current; (b) wind speed.

Fig. 4. DC link voltage.

Fig. 5. RMS output voltage (PCC voltage).

Fig. 6. Instantaneous output voltage at s.

Fig. 7. Instantaneous output line current.

Fig. 8. Powers.

Fig.9. Powers.

Fig. 10. DC link voltage.

Fig. 11. Powers.

Fig. 12. DC link voltage.

 

Fig. 13. Response of controllers.

Fig. 14. Three phase currents for unbalanced load.

Fig. 15. Electrical torque of PMSG with and without dc–dc converter controller.

Fig. 16. Instantaneous line voltages at PCC for unbalanced load.

 

Fig. 17. (a) RMS value of line voltages at PCC after compensation; (b) modulation indexes.

Fig. 18. Instantaneous line voltages at PCC after compensation.

CONCLUSION

Control techniques to direct voltage of an independent variable speed wind turbine with a PMSG, battery, power device, and electrolyzer (goes about as dump stack) are displayed in this paper. By keeping up dc interface voltage at its reference esteem and controlling adjustment records of the PWM inverter, the voltage of inverter yield is kept up consistent at their evaluated qualities. From the reproduction results, it is seen that the controller can keep up the heap voltage great regardless of varieties in wind speed and load.An calculation is created to accomplish clever vitality the executives among the breeze generator, battery, power device, and electrolyzer. The impact of uneven load on the generator is examined and the dc– dc converter control plot is proposed to diminish its impact on the electrical torque of the generator. The dc– dc converter controller not just aides in keeping up the dc voltage steady yet additionally goes about as a dc-side dynamic channel and diminishes the motions in the generator torque which happen because of unequal load. PWM inverter control is consolidated to make the line voltage at PCC adjusted under an uneven load situation. Inverter control additionally helps in decreasing PCC voltage journey emerging because of moderate elements of water elctrolyzer when control goes to it. The complete consonant mutilation (THD) in voltages at PCC is about 5% which portrays the great nature of voltage produced at the client end. The recreation results exhibit that the execution of the controllers is agreeable under unfaltering state just as unique conditions and under adjusted just as lopsided load conditions.

Integrated Photovoltaic and Dynamic Voltage Restorer System Configuration

 

IEEE TRANSACTIONS ON SUSTAINABLE ENERGY, 2015

ABSTRACT:

This paper presents a new system configuration for integrating a grid-connected photovoltaic (PV) system together with a self-supported dynamic voltage restorer (DVR). The proposed system termed as a “six-port converter,” consists of nine semiconductor switches in total. The proposed configuration retains all the essential features of normal PV and DVR systems while reducing the overall switch count from twelve to nine. In addition, the dual functionality feature significantly enhances the system robustness against severe symmetrical/asymmetrical grid faults and voltage dips. A detailed study on all the possible operational modes of six-port converter is presented. An appropriate control algorithm is developed and the validity of the proposed configuration is verified through extensive simulation studies under different operating conditions.

 

KEYWORDS:

  1. Bidirectional power flow
  2. Distributed power generation
  3. Photovoltaic (PV) systems
  4. Power quality
  5. Voltage control

 

SOFTWARE: MATLAB/SIMULINK

 

BLOCK DIAGRAM:

 

Fig. 1. Proposed integrated PV and DVR system configuration.

 

 EXPECTED SIMULATION RESULTS:

 

Fig. 2. Simulation results: operation of proposed system during health grid mode (PV-VSI: active and DVR-VSI: inactive). (a) Vpcc; (b) PQload; (c) PQgrid; (d) PQpv-VSI; and (e) PQdvr-VSI.

Fig. 3. Simulation results: operation of proposed system during fault mode (PV-VSI: inactive and DVR-VSI: active). (a) Vpcc; (b) Vdvr; (c) Vload; (d) PQload; (e) PQgrid; (f) PQpv-VSI; and (g) PQdvr-VSI.

Fig. 4. Simulation results: operation of proposed system during balance three phase sag mode (PV-VSI: active and DVR-VSI: active). (a) Vpcc; (b) Vdvr-VSI; (c) Vload; (d) PQgrid; (e) PQpv-VSI; and (f) PQdvr-VSI.

Fig. 5. Simulation results: operation of proposed system during unbalanced sag mode (PV-VSI: active and DVR-VSI: active). (a) Vpcc; (b) Vdvr-vsi; (c) Vload; (d) PQgrid; (e) PQpv-VSI; and (f) PQdvr-VSI.

  

Fig. 6. Simulation results: operation of proposed system during inactive PV plant mode (PV-VSI: active and DVR-VSI: active). (a) Vpcc; (b) Vload; (c) Vdc; (d) PQload; (e) PQdvr-VSI; and (f) PQpv-VSI.

 

CONCLUSION:

In this paper, a new system configuration for integrating a conventional grid-connected PV system and self supported DVR is proposed. The proposed configuration not only exhibits all the functionalities of existing PV and DVR system, but also enhances the DVR operating range. It allows DVR to utilize active power of PV plant and thus improves the system robustness against sever grid faults. The proposed configuration can operate in different modes based on the grid condition and PV power generation. The discussed modes are healthy grid mode, fault mode, sag mode, and PV inactive mode. The comprehensive simulation study and experimental validation demonstrate the effectiveness of the proposed configuration and its practical feasibility to perform under different operating conditions. The proposed configuration could be very useful for modern load centers where on-site PV generation and strict voltage regulation are required.

 

REFERENCES:

  • A. Walling, R. Saint, R. C. Dugan, J. Burke, and L. A. Kojovic, “Summary of distributed resources impact on power delivery systems,” IEEE Trans. Power Del., vol. 23, no. 3, pp. 1636–1644, Jul. 2008.
  • Meza, J. J. Negroni, D. Biel, and F. Guinjoan, “Energy-balance modeling and discrete control for single-phase grid-connected PV central inverters,” IEEE Trans. Ind. Electron., vol. 55, no. 7, pp. 2734–2743, Jul. 2008.
  • Shimizu, O. Hashimoto, and G. Kimura, “A novel high-performance utility-interactive photovoltaic inverter system,” IEEE Trans. Power Electron., vol. 18, no. 2, pp. 704–711, Mar. 2003.
  • B. Kjaer, J. K. Pedersen, and F. Blaabjerg, “A review of single-phase grid-connected inverters for photovoltaic modules,” IEEE Trans. Ind. Appl., vol. 41, no. 5, pp. 1292–1306, Sep./Oct. 2005.

Design of External Inductor for Improving Performance of Voltage Controlled DSTATCOM

IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS, 2015

ABSTRACT: A distribution static compensator (DSTATCOM) is used for load voltage regulation and its performance mainly depends upon the feeder impedance and its nature (resistive, inductive, stiff, non-stiff). However, a study for analyzing voltage regulation performance of DSTATCOM depending upon network parameters is not well defined. This paper aims to provide a comprehensive study of design, operation, and flexible control of a DSTATCOM operating in voltage control mode. A detailed analysis of the voltage regulation capability of DSTATCOM under various feeder impedances is presented. Then, a benchmark design procedure to compute the value of external inductor is presented. A dynamic reference load voltage generation scheme is also developed which allows DSTATCOM to compensate load reactive power during normal operation, in addition to providing voltage support during disturbances. Simulation and experimental results validate the effectiveness of the proposed scheme.

KEYWORDS:

  1. Distribution static compensator (DSTATCOM)
  2. Current control
  3. Voltage control
  4. Power factor
  5. Power quality

 SOFTWARE: MATLAB/SIMULINK

EQUIVALENT CIRCUIT DIAGRAM:

 

 Fig. 1. Three phase equivalent circuit of DSTATCOM topology in distribution system.

EXPECTED SIMULATION RESULTS:

Fig. 2. Voltage regulation performance of conventional DSTATCOM with resistive feeder. (a) PCC voltages. (b) Load Voltages. (c) Source currents. (d) Filter currents. (e) Load currents.

Fig. 3. Simulation results. (a) During normal operation (i)-(v). (b) During voltage sag (vi)-(x). (c) During voltage swell (xi)-(xv).

CONCLUSION:

This paper has presented design, operation, and control of a DSTATCOM operating in voltage control mode (VCM). After providing a detailed exploration of voltage regulation capability of DSTATCOM under various feeder scenarios, a benchmark design procedure for selecting suitable value of external inductor is proposed. An algorithm is formulated for dynamic reference load voltage magnitude generation. The DSTATCOM has improved voltage regulation capability with a reduced current rating VSI, reduced losses in the VSI and feeder. Also, dynamic reference load voltage generation scheme allows DSTATCOM to set different constant reference voltage during voltage disturbances. Simulation and experimental results validate the effectiveness of the proposed solution. The external inductor is a very simple and cheap solution for improving the voltage regulation, however it remains connected throughout the operation and continuous voltage drop across it occurs. The future work includes operation of this fixed inductor as a controlled reactor so that its effect can be minimized by varying its inductance.

REFERENCES:

[1] M. H. Bollen, Understanding power quality problems. vol. 3, IEEE press New York, 2000.

[2] S. Ostroznik, P. Bajec, and P. Zajec, “A study of a hybrid filter,” IEEE Trans. Ind. Electron., vol. 57, no. 3, pp. 935–942, Mar. 2010.

[3] C. Kumar and M. Mishra, “A voltage-controlled DSTATCOM for power quality improvement,” IEEE Trans. Power Del., vol. 29, no. 3, pp. 1499– 1507, June 2014.

[4] Q. Liu, L. Peng, Y. Kang, S. Tang, D. Wu, and Y. Qi, “A novel design and optimization method of an LCL filter for a shunt active power filter,” IEEE Trans. Ind. Electron., vol. 61, no. 8, pp. 4000–4010, Aug. 2014.

[5] T. Aziz, M. Hossain, T. Saha, and N. Mithulananthan, “VAR planning with tuning of STATCOM in a DG integrated industrial system,” IEEE Trans. Power Del., vol. 28, no. 2, pp. 875–885, Apr. 2013.

A Voltage Regulator for Power Quality Improvement in Low-Voltage Distribution Grids

ABSTRACT:

This paper presents a voltage-controlled DSTATCOM-based voltage regulator for low voltage distribution grids. The voltage regulator is designed to temporarily meet the grid code, postponing unplanned investments while a definitive solution could be planned to solve regulation issues. The power stage is composed of a three-phase four-wire Voltage Source Inverter (VSI) and a second order low-pass filter. The control strategy has three output voltage loops with active damping and two dc bus voltage loops. In addition, two loops are included to the proposed control strategy: the concept of Minimum Power Point Tracking (mPPT) and the frequency loop. The mPPT allows the voltage regulator to operate at the Minimum Power Point (mPP), avoiding the circulation of unnecessary reactive compensation. The frequency loop allows the voltage regulator to be independent of the grid voltage information, especially the grid angle, using only the information available at the Point of Common Coupling (PCC). Experimental results show the regulation capacity, the features of the mPPT algorithm for linear and nonlinear loads and the frequency stability.

KEYWORDS:

  1. DSTATCOM, Frequency Compensation
  2. Minimum Power Point Tracker
  3. Power Quality
  4. Static VAR Compensators
  5. Voltage Control
  6. Voltage Regulation

 SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Low voltage distribution grid under analysis with the voltage regulator

EXPECTED SIMULATION RESULTS:

Fig. 2. Dc bus voltages during the DSTATCOM initialization

Fig. 3. PCC voltages without compensation for linear loads

Fig. 4. PCC voltages with compensation for linear loads

Fig. 5. Voltage regulator currents for linear loads

Fig. 6. Grid, load and voltage regulator currents for linear loads

Fig. 7. PCC voltages without compensation for nonlinear loads

Fig. 8. PCC voltages with compensation for nonlinear loads

Fig. 9. Voltage regulator currents for nonlinear loads

Fig. 10. Grid, load and voltage regulator currents for nonlinear loads

Fig. 11. PCC rms value with linear loads

Fig. 12. Processed apparent power with linear loads

Fig. 13. Voltage regulator currents with mPPT enabled for linear loads

Fig. 14. PCC rms value with nonlinear loads

Fig. 15. Processed apparent power with nonlinear loads

Fig. 16. Voltage regulator currents with mPPT enabled for nonlinear loads

Fig. 17. Total dc bus voltage, PCC voltage, grid voltage and voltage regulator current waveforms of a-phase with mPPT enabled with grid swell

Fig. 18. (a) Total dc bus voltage, PCC voltage, grid voltage and voltage regulator current waveforms of a-phase and (b) detail of total dc bus voltage performance with mPPT enabled with grid sag

CONCLUSION:

This paper presents a three phase DSTATCOM as a voltage regulator and its control strategy, composed of the conventional loops, output voltage and dc bus regulation loops, including the voltage amplitude and the frequency loops. Experimental results demonstrate the voltage regulation capability, supplying three balanced voltages at the PCC, even under nonlinear loads.

The proposed amplitude loop was able to reduce the voltage regulator processed apparent power about 51 % with nonlinear load and even more with linear load (80%). The mPPT algorithm tracked the minimum power point within the allowable voltage range when reactive power compensation is not necessary. With grid voltage sag and swell, the amplitude loop meets the grid code. The mPPT can also be implemented in current-controlled DSTATCOMs, achieving similar results. The frequency loop kept the compensation angle within the analog limits, increasing the autonomy of the voltage regulator, and the dc bus voltage regulated at nominal value, thus minimizing the dc bus voltage steady state error. Simultaneous operation of the mPPT and the frequency loop was verified. The proposed voltage regulator is a shunt connected solution, which is tied to low voltage distribution grids without any power interruption to the loads, without any grid voltage and impedance information, and provides balanced and low-THD voltages to the customers.

REFERENCES:

[1] D. O. Koval and C. Carter, “Power quality characteristics of computer loads,” IEEE Trans. on Industry Applications, vol. 33, no. 3, pp. 613- 621, May/June1997.

[2] Abraham I. Pressman, Keith Billings and Taylor Morey, “Switching Power Supply Design,” 3rd ed., McGraw Hill, New York, 2009.

[3] B. Singh, B.N. Singh, A. Chandra, K. Al-Haddad, A. Pandey and D.P. Kothari, “A review of single-phase improved power quality AC-DC converters” IEEE Trans. on Industrial Electronics, vol.50, no.5, pp.962- 981, Oct. 2003.

[4] K. Mino, H. Matsumoto, Y. Nemoto, S. Fujita, D. Kawasaki, Ryuji Yamada, and N. Tawada, “A front-end converter with high reliability and high efficiency,” in IEEE Conf. on Energy Conversion Congress and Exposition (ECCE),2010, pp. 3216-3223.

[5] Jih-Sheng Lai, D. Hurst and T. Key, Switch-mode supply power factor improvement via harmonic elimination methods,” in 6th Annual IEEE Proc. on Applied Power Electronics Conference and Exposition, APEC’91, 1991, pp. 415-422.

 

 

A Voltage Regulator for Power Quality Improvement in Low-Voltage Distribution Grids

ABSTRACT:

This paper presents a voltage-controlled DSTATCOM-based voltage regulator for low voltage distribution grids. The voltage regulator is designed to temporarily meet the grid code, postponing unplanned investments while a definitive solution could be planned to solve regulation issues. The power stage is composed of a three-phase four-wire Voltage Source Inverter (VSI) and a second order low-pass filter. The control strategy has three output voltage loops with active damping and two dc bus voltage loops. In addition, two loops are included to the proposed control strategy: the concept of Minimum Power Point Tracking (mPPT) and the frequency loop. The mPPT allows the voltage regulator to operate at the Minimum Power Point (mPP), avoiding the circulation of unnecessary reactive compensation. The frequency loop allows the voltage regulator to be independent of the grid voltage information, especially the grid angle, using only the information available at the Point of Common Coupling (PCC). Experimental results show the regulation capacity, the features of the mPPT algorithm for linear and nonlinear loads and the frequency stability.

KEYWORDS:

  1. DSTATCOM
  2. Frequency compensation
  3. Minimum power point tracker
  4. Power quality
  5.  Static VAR compensators
  6. Voltage control
  7. Voltage regulation

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

 Fig. 1. Low voltage distribution grid under analysis with the voltage regulator

 EXPECTED SIMULATION RESULTS:

 

 Fig. 2. Dc bus voltages during the DSTATCOM initialization

 

Fig. 3. PCC voltages without compensation for linear loads

Fig. 4. PCC voltages with compensation for linear loads

Fig. 5. Voltage regulator currents for linear loads

Fig. 6. Grid, load and voltage regulator currents for linear loads

Fig. 7. PCC voltages without compensation for nonlinear loads

Fig. 8. PCC voltages with compensation for nonlinear loads

Fig. 9. Voltage regulator currents for nonlinear loads

Fig. 10. Grid, load and voltage regulator currents for nonlinear loads

Fig. 11. PCC rms value with linear loads

Fig. 12. Processed apparent power with linear loads

Fig. 13. Voltage regulator currents with mPPT enabled for linear loads

Fig. 14. PCC rms value with nonlinear loads

Fig. 15. Processed apparent power with nonlinear loads

Fig. 16. Voltage regulator currents with mPPT enabled for nonlinear loads

Fig. 17. Total dc bus voltage, PCC voltage, grid voltage and voltage regulator current waveforms of a-phase with mPPT enabled with grid swell

Fig. 18. (a) Total dc bus voltage, PCC voltage, grid voltage and voltage regulator current waveforms of a-phase and (b) detail of total dc bus voltage performance with mPPT enabled with grid sag

CONCLUSION:

This paper presents a three phase DSTATCOM as a voltage regulator and its control strategy, composed of the conventional loops, output voltage and dc bus regulation loops, including the voltage amplitude and the frequency loops.

Experimental results demonstrate the voltage regulation capability, supplying three balanced voltages at the PCC, even under nonlinear loads.

The proposed amplitude loop was able to reduce the voltage regulator processed apparent power about 51 % with nonlinear load and even more with linear load (80%). The mPPT algorithm tracked the minimum power point within the allowable voltage range when reactive power compensation is not necessary. With grid voltage sag and swell, the amplitude loop meets the grid code. The mPPT can also be implemented in current-controlled DSTATCOMs, achieving similar results.

The frequency loop kept the compensation angle within the analog limits, increasing the autonomy of the voltage regulator, and the dc bus voltage regulated at nominal value, thus minimizing the dc bus voltage steady state error. Simultaneous operation of the mPPT and the frequency loop was verified.

The proposed voltage regulator is a shunt connected solution, which is tied to low voltage distribution grids without any power interruption to the loads, without any grid voltage and impedance information, and provides balanced and low-THD voltages to the customers.

REFERENCES:

[1] ANEEL National Electric Power Distribution System Procedures – PRODIST, Module 8: Energy Quality. Revision 07, 2014.

[2] M. Mishra, A. Ghosh and A. Joshi, “Operation of a DSTATCOM in voltage control mode,” IEEE Trans. Power Del., vol. 18, no. 1, pp. 258-264, Jan. 2003.

[3] G. Ledwich and A. Ghosh, “A flexible DSTATCOM operating in voltage or current control mode,” IEE Proc.-Gener., Transmiss. Distrib., vol. 149, n. 2, pp. 215-224, Mar. 2002.

[4] T. P. Enderle, G. da Silva, C. Fischer, R. C. Beltrame, L. Schuch, V. F. Montagner and C. Rech, “D-STATCOM applied to single-phase distribution networks: Modeling and control,” in Proc. IEEE Ind. Electron. Soc. Annu. Conf., Oct. 2012, pp. 321 – 326.

[5] C. Kumar and M. Mishra, “Energy conservation and power quality improvement with voltage controlled DSTATCOM,” in Proc. Annu. IEEE India Conf., Dec. 2013 pp. 1-6.

 

Design of External Inductor for Improving Performance of Voltage Controlled DSTATCOM

 

ABSTRACT:

A distribution static compensator (DSTATCOM) is used for load voltage regulation and its performance mainly depends upon the feeder impedance and its nature (resistive, inductive, stiff, non-stiff). However, a study for analyzing voltage regulation performance of DSTATCOM depending upon network parameters is not well defined. This paper aims to provide a comprehensive study of design, operation, and flexible control of a DSTATCOM operating in voltage control mode. A detailed analysis of the voltage regulation capability of DSTATCOM under various feeder impedances is presented. Then, a benchmark design procedure to compute the value of external inductor is presented. A dynamic reference load voltage generation scheme is also developed which allows DSTATCOM to compensate load reactive power during normal operation, in addition to providing voltage support during disturbances. Simulation and experimental results validate the effectiveness of the proposed scheme.

KEYWORDS:

  1. Distribution static compensator (DSTATCOM)
  2. Current control
  3. Voltage control
  4. Power factor
  5. Power quality

 SOFTWARE: MATLAB/SIMULINK

EQUIVALENT CIRCUIT DIAGRAM:

 Fig. 1. Three phase equivalent circuit of DSTATCOM topology in distribution system.

EXPECTED SIMULATION RESULTS:

 Fig. 2. Voltage regulation performance of conventional DSTATCOM with resistive feeder. (a) PCC voltages. (b) Load Voltages. (c) Source currents. (d) Filter currents. (e) Load currents.

Fig. 3. Simulation results. (a) During normal operation (i)-(v). (b) During voltage sag (vi)-(x). (c) During voltage swell (xi)-(xv).

CONCLUSION:

This paper has presented design, operation, and control of a DSTATCOM operating in voltage control mode (VCM). After providing a detailed exploration of voltage regulation capability of DSTATCOM under various feeder scenarios, a benchmark design procedure for selecting suitable value of external inductor is proposed. An algorithm is formulated for dynamic reference load voltage magnitude generation. The DSTATCOM has improved voltage regulation capability with a reduced current rating VSI, reduced losses in the VSI and feeder. Also, dynamic reference load voltage generation scheme allows DSTATCOM to set different constant reference voltage during voltage disturbances. Simulation and experimental results validate the effectiveness of the proposed solution. The external inductor is a very simple and cheap solution for improving the voltage regulation, however it remains connected throughout the operation and continuous voltage drop across it occurs. The future work includes operation of this fixed inductor as a controlled reactor so that its effect can be minimized by varying its inductance.

REFERENCES:

[1] M. H. Bollen, Understanding power quality problems. vol. 3, IEEE press New York, 2000.

[2] S. Ostroznik, P. Bajec, and P. Zajec, “A study of a hybrid filter,” IEEE Trans. Ind. Electron., vol. 57, no. 3, pp. 935–942, Mar. 2010.

[3] C. Kumar and M. Mishra, “A voltage-controlled DSTATCOM for power quality improvement,” IEEE Trans. Power Del., vol. 29, no. 3, pp. 1499– 1507, June 2014.

[4] Q. Liu, L. Peng, Y. Kang, S. Tang, D. Wu, and Y. Qi, “A novel design and optimization method of an LCL filter for a shunt active power filter,” IEEE Trans. Ind. Electron., vol. 61, no. 8, pp. 4000–4010, Aug. 2014.

[5] T. Aziz, M. Hossain, T. Saha, and N. Mithulananthan, “VAR planning with tuning of STATCOM in a DG integrated industrial system,” IEEE Trans. Power Del., vol. 28, no. 2, pp. 875–885, Apr. 2013.

Smooth Shunt Control of a Fuzzy based Distributed Power Flow Controller to Improve Power Quality

 

ABSTRACT

Presently, the quality of power supplied is essential to many customers. Power quality (PQ) is a valued utility service where many customers are prepared to pay and get it. In the future, distribution system operators ought to decide, to provide their customers with distinct PQ ranges at different prices. Here, in this paper, a new control action to improve and maintain and enhance the power quality of an electrical power system is proposed in this paper. Fuzzy based distributed power flow controller (DPFC) is designed and put into action to compensate the voltage imbalances arising in a power system. This customized DPFC is an advanced FACTS device, which has its structure analogous to unified power flow controller (UPFC). DPFC comprises of both series and shunt converters, in which its three phase series converter is distributed over the transmission line as several single phase static converters ensuring high controllability and reliability at a low cost compared to an UPFC. A central controlling circuit is designed to supply reference signals to each of the individual controlling circuits of both series and shunt converters. This customized device is applied to a single machine infinite bus power system having nonlinear loads connected to it and is simulated in MATLAB/Simulink environment by using OPAL-RT 5600 Real-time digital Simulator. The results demonstrate the validation of proposed technique to enhance the power quality.

KEYWORDS

  1. Power quality
  2. Voltage fluctuations
  3. Harmonic analysis
  4. Power harmonic filters
  5. Voltage control
  6. Load flow Voltage Sag and Swell
  7. Fuzzy Logic

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Control network of DPFC

EXPECTED SIMULATION RESULTS

Fig. 2. Voltage waveform during fault condition

Fig. 3. Current waveform during fault condition

Fig. 4. Simulated results for Voltage by employing DPFC controller

Fig. 5. Simulated results for Current by employing DPFC controller

Fig. 6. THD of load voltage without Controller

Fig. 7. FFT Analysis for PI Controller

Fig. 8. FFT Analysis for Fuzzy Controller

CONCLUSION

The work is presented to provide a solution for maintaining Power Quality at the distribution end, compensation of harmonics in grid voltage and in load currents. In order to consummate specified intentions in this paper a new concept for controlling power quality problems was proposed and implemented. By putting the customized device into action, results were analyzed for voltage dips and their mitigations for a three phase source with non-linear loads. The DPFC is modeled by positioning three control circuits designed independently. In this paper we also proposed and implemented the concept of fuzzy logic controller for having better controlling action, which will help in minimization/elimination of harmonics in the system. As compared to all other facts devices the Fuzzy based DPFC converter effectively controls all power quality problems and with this technique we can put THD to 3.04% proving the effectiveness of the proposed controller.

REFERENCES

[1] D. Divan and H. Johal, “Distributed facts-A new concept for realizing grid power flow control,” in IEEE 36th Power Electron. Spec. Conf. (PESC), 2005, pp. 8–14.

[2] K K. Sen, “Sssc-static synchronous series compensator: Theory, modeling, and application”,IEEE Trans. Power Del., vol. 13, no. 1, pp. 241–246, Jan. 1998.

[3] L.Gyugyi, C.D. Schauder, S. L.Williams, T. R. Rietman, D. R. Torgerson, and A. Edris, “The unified power flow controller: A new approach to power transmission control”, IEEE Trans. Power Del., vol. 10, no. 2, pp. 1085– 1097, Apr. 1995.

[4] M. D. Deepak, E. B. William, S. S. Robert, K. Bill, W. G. Randal, T. B. Dale, R. I. Michael, and S. G. Ian, “A distributed static series compensator system for realizing active power flow control on existing power lines”, IEEE Trans. Power Del., vol. 22, no. 1, pp. 642–649, Jan.2007

[5] M. Mohaddes, A. M. Gole, and S. Elez, “Steady state frequency response of statcom”, IEEE Trans. Power Del., vol. 16, no. 1, pp. 18–23, Jan. 2001.

 

A New Control Strategy for a Multi-Bus MV Microgrid Under Unbalanced Conditions

 

ABSTRACT:

This paper proposes a new control strategy for the islanded operation of a multi-bus medium voltage (MV) microgrid. The microgrid consists of several dispatchable electronically-coupled  distributed generation (DG) units. Each DG unit supplies a local load which can be unbalanced due to the inclusion of singlephase  loads. The proposed control strategy of each DG comprises a proportional resonance (PR) controller with an adjustable resonance frequency, a droop control strategy, and a negative-sequence impedance controller (NSIC). The PR and droop controllers are, respectively, used to regulate the load voltage and share the average power components among the DG units. The NSIC is used to effectively compensate the negative-sequence currents of the unbalanced loads and to improve the performance of the overall microgrid system.Moreover, the NSIC minimizes the negative-sequence currents in the MV lines and thus, improving the power quality of the microgrid. The performance of the proposed control strategy is verified by using digital time-domain simulation studies in the PSCAD/EMTDC software environment.

KEYWORDS:

  1. Distributed generation
  2. Medium voltage (MV)
  3. Microgrid
  4. Negative-sequence current
  5. Power sharing
  6. Unbalance load
  7. Voltage control

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

 image001

 Fig. 1. MV multi-bus microgrid consisting of two DG units.

EXPECTED SIMULATION RESULTS:

image002

Fig. 2 Unbalanced load changes in feeder F1 (a) instantaneous real, and (b)

reactive power components.

image003

Fig. 3. Amplitude of (a) positive- and (b) negative-sequence currents of the feeders.

image004

Fig. 4. Instantaneous voltages at DG terminals during unbalanced load changes in feeder F1, (a) DG1and (b) DG2 .

image005

Fig.5. Frequency of islanded microgrid during unbalanced load changes.

image006

Fig. 6. (a) Negative-sequence output impedance of each DG, and (b) amplitude of negative-sequence current of DG units.

image007

Fig. 7. Dynamic response of DG units to unbalanced load changes in feeder F1: (a) real power, and (b) reactive power components of DG units.

image008

Fig. 8. Unbalanced load changes in feeders F3 and F2 (a, b) instantaneous real and reactive power of feeders.

image009

Fig. 9. Amplitude of (a) positive and (b) negative-sequence currents of the feeders.

image010

Fig. 10. (a) Negative-sequence output impedance, and (b) amplitude of negative- sequence current for each DG.

CONCLUSION:

This paper presents a new control strategy for amulti-bus MV microgrid consisting of the dispatchable electronically-coupled DG units and unbalanced loads. The negative-sequence current of a local load is completely compensated by its dedicated DG. However, the negative-sequence current of the nonlocal loads is shared among the adjacent DGs. The proposed control strategy is composed of a PR controller with non-fixed resonance frequency, a droop control, and a negative-sequence impedance controller (NSIC). The PR and droop controllers are, respectively, used to regulate the load voltage and to share the average power among the DG units. The NSIC is used to improve the performance of the microgrid system when the unbalanced loads are present. Moreover, the NSIC minimizes the negative- sequence currents in the MV lines, and thus, improving the power quality of the microgrid. The performance of the proposed control strategy is investigated by using digital time-domain simulation studies in the PSCAD/EMTDC software environment. The simulation results conclude that the proposed strategy:

  • robustly regulates voltage and frequency of the microgrid;
  • is able to share the average power among the DGs;
  • effectively compensates the negative-sequence currents of local loads; and
  • shares the negative-sequence current of the nonlocal loads such that the power quality of the overall microgrid is not degraded.

 REFERENCES:

[1] N. Hatziargyriou, H. Asano, R. Iravani, and C. Marnay, “Microgrids,” IEEE Power Energy Mag., vol. 5, pp. 78–94, Jul.–Aug. 2007.

[2] A. G. Madureira and J. A. P. Lopes, “Coordinated voltage support in distribution networks with distributed generation and microgrids,” IET Renew. Power Gener., vol. 3, pp. 439–454, Sep. 2009.

[3] IEEE Recommended Practice for Monitoring Electric Power Quality, IEEE Std. 1159, 2009.

[4] IEEE Recommended Practice for Electric Power Distribution for Industrial Plants, ANSI/IEEE Std. 141, 1993.

[5] R. Lasseter, “Microgrids,” in Proc. IEEE Power Eng. Soc. Winter Meeting, 2002, pp. 305–308.