Sensitive Load Voltage Compensation Performed by a Suitable Control Method

 IEEE Transactions on Industry Applications , 2016

ABSTRACT

This work proposes the usage of a repetitive-based control to dynamically restore the voltage applied to sensitive and critical loads of power system. The control intrinsically is able to wipe off harmonic distortion and relies on simple transfer function. As a consequence, there is no need to apply harmonic selective filters. Furthermore, the control system is able to work out on sinusoid references and, thus, avoids the need of employing the dq transform. A recursive least-squares is also included to the control system in order to assure the synchronization of the voltages to be restored. The design of the control parameters along with the system stability is discussed. The experimental results are produced with a setup of a three phase series compensator. The scenarios for emulating faulty voltages are the same for experimental and simulated results. The results corroborate the usage of the proposed method.

KEYWORDS

1.      Bode plot

2.      DVR-Dynamic voltage restorer

3.      Nyquist stability

4.      Repetitive control

5.      Sensitive load

6.      Series compensator

7.      Voltage quality

8.      Voltage sag.

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1 Series compensation system. (a) Electrical grid with compensation

to sensitive load. (b) Single-phase equivalent circuit for the feed of sensitive load.

EXPECTED SIMULATION RESULTS:

Fig. 2. Sagged grid scenario. (a) Sagged and controlled output voltages. (b) Detail of the correction instant.

Fig. 3 Sagged/distorted grid and controlled output voltages.

Fig. 4. Sagged grid and controlled output voltages with RLS algorithm included.

Fig. 5. Sagged/distorted grid scenario. (a) Sagged/distorted and controlled output voltages. (b) Detail of the correction instant.

CONCLUSION

This paper has proposed a repetitive control technique to be applied to a series compensator which protects critical loads against voltage distortions from the power grid. The system stability is assured by a low-pass filter which attenuates the resonant peaks from the repetitive controller above a frequency value. This value should be greater than the expected highest harmonic interference endured by the system. The low-pass filter is cascaded with the repetitive controller. The control system is implemented in the discrete domain, employing the trapezoidal integration. Three scenarios including harmonics and sag interferences have been used to test the proposed control system. The controller has proved to be effective to mitigate them. Furthermore, an experimental setup of the series compensator has been mounted to verify the simulations. The results corroborate the proposed controller.

REFERENCES

[1]         S. Jothibasu and M. Mishra, “An improved direct AC-AC converter for voltage sag mitigation,” IEEE Trans. Ind. Electron., vol. 62, no. 1, pp. 21–29, Jan. 2015.

[2]         M. R. Alam, K. M. Muttaqi, and A. Bouzerdoum, “Characterizing voltage sags and swells using three-phase voltage ellipse parameters,” IEEE Trans. Ind. Appl., vol. 51, no. 4, pp. 2780–2790, Apr. 2015.

[3]         H. Hao and X. Yonghai, “Control strategy of PV inverter under unbalanced grid voltage sag,” in IEEE Energy Conversion Congress and Exposition, ECCE, vol. 1, no. 1, Sept. 2014, pp. 1029–1034.

[4]         Y. W. Li, D. M. Vilathgamuwa, F. Blaabjerg, and P. Loh, “A robust control scheme for medium-voltage-level DVR implementation,” IEEE Trans. Ind. Electron., vol. 54, no. 4, pp. 2249–2261, Aug. 2007.

[5]         S. Jothibasu and M. Mishra, “A control scheme for storageless DVR based on characterization of voltage sags,” IEEE Trans. Power Del., vol. 29, no. 5, pp. 2261–2269, Oct. 2014.

Self-tuned fuzzy-proportional–integral compensated zero/minimum active power algorithm based dynamic voltage restorer

ABSTRACT:

Voltage sag is the most common and severe power quality problem in the recent times due to its detrimental effects on modern sensitive equipment. Generally, direct-on-line starting of the three-phase induction motor (IM) and various kinds of short circuit fault are directly responsible for this event. This study investigates the impacts of starting and stopping of two threephase IMs on the load voltage profile. To be more critical, two three-phase short circuit faults and one unsymmetrical fault are also simulated in the same network at different instants of time. A simple control algorithm of a real power optimised dynamic voltage restorer (DVR) with a reduced power factor strategy is presented to protect the sensitive load from these types of detrimental events. A novel fuzzy-proportional–integral based self-tuned control methodology is implemented in the proposed work to compensate the loss in the DVR circuit as well as to regulate the load voltage and the direct current link voltage. The results show the effectiveness of the adopted control scheme in DVR application to mitigate the voltage sag.

SOFTWARE: MATLAB/SIMULINK

DIAGRAM:

Fig. 1 Investigated distributed test system with DVR

  

EXPECTED SIMULATION RESULTS:

Figure 2. Voltage profile of load and DVR (a) Without DVR, (b) DVR voltage, (c) With DVR, (d) DC voltage

Figure 3 Torque profile of IMs (a) Motor 1without DVR, (b) Motor 2 without DVR, (c) Motor 1 with DVR, (d) Motor 2 with DVR

Figure 4. Pertaining to unsymmetrical fault (a) Load voltage without DVR, (b) DVR voltage, (c) Load voltage with DVR

Figure 5. Active DVR power profile pertaining to (a) In-phase compensation, (b) Present technique

CONCLUSION:

This study divulges a simple yet robust reduced power factor controlled energy optimised algorithm in DVR to offer a common solution to mitigate the severe voltage sag. Minimisation of energy delivered may increase the life of the ESU, therefore limits the expenditure indirectly. The self-tuned fuzzy-PI scheme also plays a significant role to regulate the active power through the DVR as well as to compensate the load voltage and DVR losses. The results obtained in this work shows that the proposed DVR solution provides a good and satisfactory level of compensation. The system voltage has been compensated nearly up to its nominal value. The DC voltage is also very fairly regulated. The application of DVR reduces the level of oscillation in the torque profile of the IM. The proposed method is also compared with other strategies surfaced in the existing literature and it is unfold that the proposed strategy offers better harmonic compensation and it also provides better damping in the load voltage. Thus, it may be concluded that the proposed control technique of DVR, operated by adaptive fuzzy control scheme, may be justified for utilising the same as a common sag mitigating device. Within the context of the present study, the work is ended with simulation only. However, the same may be tested on an experimental bench.

REFERENCES:

[1]      McGranaghan, M.F., Mueller, D.R., Samotyj, M.J.: ‘Voltage sags in industrial systems’, IEEE Trans. Ind. Appl., 1993, 29, (2), pp. 397–403

[2]      Moreno-Munoz, A., De-la-Rosa, J.J.G., Lopez-Rodriguez, M.A., et al.: ‘Improvement of power quality using distributed generation’, Int. J. Electr. Power Energy Syst., 2010, 32, (10), pp. 1069–1076

[3]       Bollen, M.H.J.: ‘Understanding power quality problems’ (Wiley-IEEE Press, Hoboken, NJ, USA, 1999)

[4]      Honrubia-Escribano, A., Gomez-Lazaro, E., Molina-Garcia, A., et al.: ‘Influence of voltage dips on industrial equipment: analysis and assessment’, Int. J. Electr. Power Energy Syst., 2012, 41, pp. 87–95

[5]      Kamble, S., Thorat, C.: ‘Characteristics analysis of voltage sag in distribution system using rms voltage method’, ACEEE Int. J. Electr. Power Eng., 2012,3, (1), pp. 55–61

Investigation on Dynamic Voltage Restorers With Two DC-Links and Series Converters for Three-Phase Four-Wire Systems

 IEEE, 2014

ABSTRACT

This paper proposes three dynamic voltage restorer (DVR) topologies. Such configurations are able to compensate voltage sags/swells in three-phase four-wire (3P4W) systems under balanced and unbalanced conditions. The proposed systems in this work use two independent dc-links. The complete control system, including the PWM technique, is developed and comparisons between the proposed configurations and a conventional one are performed. Simulation and experimental results are provided to validate the theoretical approach.

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1 Typical DVR location in a 3P4W power distribution system

  EXPECTED SIMULATION RESULTS:

Fig. 2. Simulation results. Injected voltages by the DVR considering conventional 3HB topology and proposed configurations with equal dc-link voltages (vCa=vCb ! dc-link ratio 1:1) and different dc-link voltages (vCa 6= vCb ! dc-link ratios 1:2 and 1:3).

Fig. 3 Simulation results. Dynamic system operation under 30% single-phase sag in time domain. (a) Grid voltages. (b) Injected voltages by DVR. (c) Load voltages.

Fig. 4. Simulation results. Dynamic system operation under 30% two-phase sag in time domain. (a) Grid voltages. (b) Injected voltages by DVR. (c) Load voltages.

Fig. 5. Simulation results. Dynamic system operation under 30% three-phase sag in time domain. (a) Grid voltages. (b) Injected voltages by DVR. (c) Load voltages.

CONCLUSION

In this paper three four-wire dynamic voltage restorers (DVRs) have been presented. The studied configurations in this work are based on the concept of open-end winding. Simulated and experimental results presented show that the proposed DVRs are feasible and suitable for power distribution system with YY transformers with neutrals grounded.

REFERENCES

[1]   W. Brumsickle, G. Luckjiff, R. Schneider, D. Divan, and M. Mc- Granaghan, “Dynamic sag correctors: cost effective industrial power line conditioning,” in Industry Applications Conference, 1999. Thirty-Fourth IAS Annual Meeting. Conference Record of the 1999 IEEE, vol. 2, pp. 1339–1344 vol.2, 1999.

[2]   M. McGranaghan, D. Mueller, and M. Samotyj, “Voltage sags in industrial systems,” Industry Applications, IEEE Transactions on, vol. 29, no. 2, pp. 397–403, 1993.

[3]   C.-m. Ho and H.-H. Chung, “Implementation and performance evaluation of a fast dynamic control scheme for capacitor-supported interline DVR,” Power Electronics, IEEE Transactions on, vol. 25, no. 8,pp. 1975–1988, 2010.

[4]   A. Ghosh and G. Ledwich, “Compensation of distribution system voltage using DVR,” Power Delivery, IEEE Transactions on, vol. 17, no. 4, pp. 1030–1036, 2002.

[5]   J. Nielsen, M. Newman, H. Nielsen, and F. Blaabjerg, “Control and testing of a dynamic voltage restorer (DVR) at medium voltage level,” Power Electronics, IEEE Transactions on, vol. 19, no. 3, pp. 806–813,2004.

Predictive Voltage Control of Transformer-less Dynamic Voltage Restorer

IEEE Transactions on Industrial Electronics, 2013

ABSTRACT:

This paper presents a predictive voltage control scheme for effective control of transformer-less dynamic voltage restorer (TDVR). This control scheme utilizes discrete model of voltage source inverter (VSI) and interfacing filter for generation of switching strategy of inverter switches. Predictive voltage control algorithm based TDVR tracks reference voltage effectively and maintains load voltages sinusoidal during various voltage disturbances as well as load conditions. Moreover, this scheme does not require any linear controller or modulation technique. Simulation and experimental results are presented to verify the performance of proposed scheme.

KEYWORDS:

1.      Predictive voltage control

2.      Transformer-less dynamic voltage restorer (TDVR)

3.      Voltage disturbance

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig.1. Single-phase TDVR compensated distribution system.

EXPECTED SIMULATION RESULTS:

Fig.2. Simulation waveforms under voltage sag with 5 mH filter inductance. (a) Source voltage. (b) Load voltage.

Fig.3. Simulation waveforms under voltage sag. (a) Source voltage. (b) Load voltage.

Fig.4. Simulation wave forms under voltage swell. (a) Source voltage. (b) Load voltage.

Fig.5. Simulation waveforms under voltage sag with RC type nonlinear load. (a) Source voltage. (b) Load voltage. (c) Load current.

CONCLUSION:

This paper presents the speed control of BLDC motor using anti wind up PI controller and fuzzy controller for three phase BLDC motor. The simulation results are compared with PI controller results. The conventional PI controller results are slower compared to fuzzy and anti wind up controllers. From the simulation results, it is clear that for the load variation anti wind up PI controller gave better response than conventional PI and fuzzy controller. Hence anti wind up PI controller is found to be more suitable for BLDC motor drive during load variation. It can also be observed from the simulation results that performance of fuzzy controller is better during the case of speed variation.

REFERENCES:

[1]   R. Arulmozhiyal, R. Kandibanv, “Design of Fuzzy PID Controller for Brushless DC Motor”, in Proc. IEEE International Conference on Computer Communication and Informatics, Coimbatore, 2012.

[2]   Anirban Ghoshal and Vinod John, “Anti-windup Schemes for Proportional Integral and Proportional Resonant Controller”, in Proc. National Power electronic conference, Roorkee, 2010.

[3]   M. F. Z. Abidin, D. Ishak and A. Hasni Abu Hassan, “A Comparative Study of PI, Fuzzy and Hybrid PI Fuzzy Controller for Speed Control of Brushless DC Motor Drive”, in Proc. IEEE International conference on Computer applications and and Industrial electronics, Malysia, 2011.

[4]   J. Choi, C. W Park, S. Rhyu and H. Sung, “Development and Control of BLDC Motor using Fuzzy Models”,in Proc. IEEE international Conference on Robotics, Automation and Mechatronics, Chengdu, 2004.

[5]   C. Bohn and D.P. Atherton, “An analysis package comparing PID anti-windup strategies,” IEEE Trans. controls system, Vol.15, No. 2, pp.34-40, 1995.

Evaluation of DVR Capability Enhancement -Zero Active Power Tracking Technique

IEEE, 2016

ABSTRACT:

This paper presents a utilization technique for enhancing the capabilities of dynamic voltage restorers (DVRs). This study aims to enhance the abilities of DVRs to maintain acceptable voltages and last longer during compensation. Both the magnitude and phase displacement angle of the synthesized DVR voltage are precisely adjusted to achieve lower power utilization. The real and reactive powers are calculated in real time in the tracking loop to achieve better conditions. This technique results in less energy being taken out of the DC-link capacitor, resulting in smaller size requirements. The results from both the simulation and experimental tests illustrate that the proposed technique clearly achieved superior performance. The DVR’s active action period was considerably longer, with nearly 5 times the energy left in the DC-link capacitor for further compensation compared to the traditional technique. This technical merit demonstrates that DVRs could cover a wider range of voltage sags; the practicality of this idea for better utilization is better than that of existing installed DVRs.

KEYWORDS:

1.      DVR capability

2.      Energy optimized

3.      Energy source

4.      Series compensator

5.      Voltage stability

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig 1: Single-line diagram of a power system with the DVR connected at PCC.

EXPECTED SIMULATION RESULTS:

Fig.2. D-axis voltages at the system (VSd), DVR (VDVRd), and load (VLd). during in-phase compensation (simulation).

Fig. 3. Q-axis voltages at the system (VSq), DVR (VDVRq), and load (VLq) during in-phase compensation (simulation).

Fig. 4. The overall three-phase voltage signals during in-phase compensation (simulation).

Fig.5 Real power at source (PS), the DVR (PDVR) and load (PL) during in- phase compensation (simulation).

Fig. 6 The DVR DC-side voltage (VDC) during in-phase compensation (simulation).

.Fig. 7. D-axis voltages at the system(VSd), DVR (VDVRd), and load (VLd) during zero-real power tracking compensation (simulation).

Fig. 8.. Q-axis voltages at the system (VSq), DVR (VDVRq), and load (VLq) during zero-real power tracking compensation (simulation).

Fig. 9. The overall three-phase voltage signals during zero-real power tracking compensation (simulation).

Fig. 10. Real power at source (PS), the DVR (PDVR) and load (PL) zero-real power tracking compensation (simulation).

CONCLUSION:

It is clear from both the simulation and experimental results illustrated in this paper that the proposed zero-real power tracking technique applied to DVR-based compensation can result in superior performance compared to the traditional in-phase technique. The experimental test results match those proposed using simulation, although some discrepancies due to the imperfect nature of the test circuit components were seen.

With the traditional in-phase technique, the compensation was performed and depended on the real power injected to the system. Then, more of the energy stored in the DC-link capacitor was utilized quickly, reaching its limitation within a shorter period. The compensation was eventually forced to stop before the entire voltage sag period was finished. When the compensation was conducted using the proposed technique, less energy was used for the converter basic switching process.

The clear advantage in terms of the voltage level at the DC-link capacitor indicates that with the proposed technique, more energy remains in the DVR (67% to 14% in the traditional in-phase technique), which guarantees the correct compensating voltage will be provided for longer periods of compensation. With this technique, none (or less) of the real power will be transferred to the system, which provides more for the DVR to cover a wider range of voltage sags, adding more flexible adaptive control to the solution of sag voltage disturbances.

REFERENCES:

[1]   M. Bollen, Understanding Power Quality Problems, Voltage Sags and Interruptions. New York: IEEE Press, 1999.

[2]   J. Roldán-Pérez, A. García-Cerrada, J. L. Zamora-Macho, P. Roncero-Sánchez, and E. Acha, “Troubleshooting a digital repetitive controller for a versatile dynamic voltage restorer,” Int. J. Elect. Power Energy Syst., vol. 57, pp. 105–115, May 2014.

[3]   P. Kanjiya, B. Singh, A. Chandra, and K. Al-Haddad, “SRF theory revisited to control self-supported dynamic voltage restorer (DVR) for unbalanced and nonlinear loads,” IEEE Trans. Ind. Appl., vol. 49, no. 5, pp. 2330–2340, Sep. 2013.

[4]   S. Naidu, and D. Fernandes, “Dynamic voltage restorer based on a four-leg voltage source converter,” IET Generation, Transmission & Distribution, vol. 3, no. 5, pp. 437–447, May 2009.

[5]   T. Jimichi, H. Fujita, and H. Akagi, “A dynamic voltage restorer equipped with a high-frequency isolated dc-dc converter,” IEEE Trans. Ind. Appl., vol. 47, no. 1, pp. 169–175, Jan. 2011.