DSTATCOM employing hybrid neural network control technique for power quality improvement

ABSTRACT

A new hybrid control technique called gradient descent back propagation (GDBP)-based i cos ϕ for a three phase two level distribution static compensator (DSTATCOM) to perform the functions such as harmonic mitigation, power factor correction under reactive loads, which further reduces the DC link voltage across the self-supported capacitor of voltage source converter (VSC). The weighted value of fundamental active and reactive components of load currents are extracted using the proposed control technique to generate the reference source currents. Furthermore, these currents are used to trigger the VSC of the DSTATCOM. The effectiveness of this control technique is demonstrated through simulation using MATLAB/SIMULINK and sim power system tool boxes. The real-time implementation of DSTATCOM is also realised by real-time digital simulator. These results reveal the robustness of the proposed DSTATCOM as it is showing outstanding harmonic compensation capabilities under the various loading conditions and keeping the total harmonics distortion of the source current well <5%, the limit imposed by IEEE-519 standard.

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1 Complete layout of the proposed DSTATCOM with control algorithm

(i) Schematic diagram of the power distribution system including proposed DSTATCOM

EXPECTED SIMULATION RESULTS:

Fig. 2 MATLAB results for (i) System performance using i cos ϕ control technique-based DSTATCOM, (ii) Harmonic spectra of source current, (iii) Harmonic spectra of load current and, (iv) Waveform of a-phase source voltage and source current

Fig. 3 MATLAB results for (i)System performance using i cos ϕ control technique-based DSTATCOM under unbalanced condition, (ii) Harmonic spectra of source current, (iii) Harmonic spectra of load current and, (iv) Waveform of a-phase source voltage and source current

Fig. 4 MATLAB results for (i) System performance by GDBP controlled i cos ϕ-based DSTATCOM, (ii) Harmonic spectra of source current, (iii) Harmonic spectra of load current and (iv) Waveform of a-phase source voltage and source current

Fig. 5 MATLAB results for (i) System performance by GDBP controlled i cos ϕ-based DSTATCOM under unbalanced loading condition, (ii) Harmonic spectra of source current, (iii) Harmonic spectra of load current and, (iv) Waveform of a-phase source voltage and source current

Fig. 6 MATLAB results for (i) Comparison of vdc under balanced condition and, (ii) Comparison of vdc under unbalanced condition

CONCLUSION

The DSTATCOM using GDBP-based i cos ϕ control technique is regarded as one of the suitable challenging solution for the improvement of power quality. It has performed better for the source current harmonic reduction, power factor improvement, voltage regulation and load balancing than traditional method. Also less amount of voltage is required to store the energy across the self-supported capacitor causing decrease in rating of DSTATCOM. This proposed technique assures the corrective actions under any source voltage and load conditions. The simulation results obtained from MATLAB/ SIMULINK .

REFERENCES

[1]   Angelo, B.: ‘Handbook on power quality’ (John Wiley & Sons, NJ, USA, 2008)

[2]   Dugan, R.C., Mc Granaghan, M.F., Beaty, H.W.: ‘Electric power systems quality’ (McGraw-Hill, New York, NY, USA, 2006, 2nd edn.)

[3]   Bollen, M.H.J.: ‘Understanding power quality problems’ (IEEE press, Wiley India Edition, 2011)

[4]   Ghosh, A., Ledwich, G.: ‘Power quality enhancement using custom power devices’ (Springer International Edition, 2009)

[5]    Padiyar, K.R.: ‘FACTS controllers in power transmission and distribution’ (New Age International, New Delhi, India, 2008)

A Superconducting Magnetic Energy Storage- Emulator/Battery Supported Dynamic Voltage Restorer

ABSTRACT:

                This study examines the use of superconducting magnetic and battery hybrid energy storage to compensate grid voltage fluctuations. The superconducting magnetic energy storage system (SMES) has been emulated by a high current inductor to investigate a system employing both SMES and battery energy storage experimentally. The design of the laboratory prototype is described in detail, which consists of a series-connected three phase voltage source inverter used to regulate AC voltage, and two bidirectional DC/DC converters used to control energy storage system charge and discharge. ‘DC bus level signaling’ and ‘voltage droop control’ have been used to automatically control power from the magnetic energy storage system during short-duration, high power voltage sags, while the battery is used to provide power during longer-term, low power under-voltages.

Energy storage system hybridisation is shown to be advantageous by reducing battery peak power demand compared with a battery-only system, and by improving long term voltage support capability compared with a SMES-only system. Consequently, the SMES/battery hybrid DVR can support both short term high-power voltage sags and long term undervoltages with significantly reduced superconducting material cost compared with a SMES-based system.

KEYWORDS:

1.      Dynamic Voltage Restorer (DVR)

2.       Energy Storage Integration

3.       Sag

4.       Superconducting Magnetic Energy Storage

5.       Battery

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Figure 1. Hybrid energy storage DVR system configuration.

EXPECTED SIMULATION RESULTS:

Figure 2. Simulated PLL Algorithm results: (a) Simulated voltage sag with phase jump (b) Phase jump angle (c) Blue trace: supply phase angle. Red trace: PLL output: ‘Pre-sag compensation’ with controller gains: k_p = 0.5, k_i = 5, (d) Blue trace: supply phase angle. Red trace: PLL output: ‘In phase compensation’ with controller gains k_p = 200, k_i = 50.

Figure 3. Hybrid System Experimental results: 0.1s Three phase sag to 35% of nominal voltage. (a) Supply voltages (b) Load voltages (c) DC Link Voltage (d) Battery Current (e) SMES-inductor current.

Figure 4. Battery System Experimental results: 0.1s Three phase sag to 35% of nominal voltage. (a) Supply voltages (b) Load voltages (c) DC Link Voltage (d) Battery Current.

Figure 5. Hybrid System Experimental results: Long-term three phase under voltage (a) RMS supply phase-voltage. (b) RMS load phase-voltage (c) DC Bus Voltage (d) Battery Current (e) SMES-inductor current.

.

CONCLUSION:

The performance a novel hybrid DVR system topology has been assessed experimentally and shown to effectively provide voltage compensation for short-term sags and long-term under-voltages. A prototype system has been developed which demonstrates an effective method of interfacing SMES and battery energy storage systems to support a three phase load. The system has been shown to autonomously prioritise the use of the short-term energy storage system to support the load during deep, short-term voltage sags and a battery for lower depth, long-term under-voltages. This can have benefits in terms of improved voltage support capability and reduced costs compared with a SMES-based system. Additional benefits include reduced battery power rating requirement and an expected improvement in battery life compared with a battery-only system due to reduced battery power cycling and peak discharge power.

REFERENCES:

[1] P.K. Ray, S.R. Mohanty, N. Kishor, and J.P.S. Catalao, "Optimal Feature and Decision Tree-Based Classification of Power Quality Disturbances in Distributed Generation Systems," Sustainable Energy, IEEE Trans., vol. 5, Sept. 2014, pp. 200-208.

[2] D. Novosel, G. Bartok, G. Henneberg, P. Mysore, D. Tziouvaras, and S. Ward, "IEEE PSRC Report on Performance of Relaying During Wide-Area Stressed Conditions," Power Delivery, IEEE Trans., vol. 25, Jan. 2010, pp. 3-16.

[3] "IEEE Recommended Practice for Monitoring Electric Power Quality," in IEEE Std 1159-1995, ed. New York, NY: IEEE Standards Board, 1995, p. i.

[4] S. Jothibasu and M.K. Mishra, "A Control Scheme for Storageless DVR Based on Characterization of Voltage Sags," Power Delivery, IEEE Trans., vol. 29, July 2014, pp. 2261-2269.

[5] B. Otomega and T. Van Cutsem, "Undervoltage Load Shedding Using Distributed Controllers," Power Systems, IEEE Trans., vol. 22, Nov. 2007, pp. 1898-1907.

A Filterless Single-Phase AC-AC Converter Based on Coupled Inductors with Safe-Commutation Strategy and Continuous Input Current

ABSTRACT:

A novel single phase ac-ac converter with no LC input/output filters is presented in this paper. The proposed converter has all the advantages of the previous single phase impedance source ac-ac converters; it can operate in buck/boost and in-phase/out-of phase with the input voltage, that makes it appropriate for voltage sags/swells compensator without any dc storage. A coupled transformer based on T-structure is utilized to give an opportunity to access desired output voltage with various duty cycles. In this topology snubber circuit is not required, because a safe commutation strategy enables to eliminate voltage and current spikes produced by short-circuit path. In addition, the converter performs in continuous current mode, so there is no inrush current. Also, the characteristic which the output voltage reverses or maintains phase angle with the input voltage is supported well, because the input and output share the same ground. Eventually, circuit analysis, operating principles and simulation results in MATLAB/SIMULINK are presented to verify the performance of the converter.

KEYWORDS:

1.      Continuous input current

2.       T-source

3.       Safe commutaion strategy

4.      Ground sharing

5.      Dynamic voltage restorer (DVR)

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Fig. 1. Filterless single-phase T-source ac-ac converter

EXPECTED SIMULATION RESULTS:

Fig. 2. Simulation results of the proposed converter in boost in-phase mode at

D = 0.9, R=10 Ω and n = 2, input/output voltage, c2 voltage, output current,

input current.

Fig. 3. Simulation result of the proposed converter in boost in-phase mode at

D = 0.9, R=20 Ω and n = 2, output current waveform.

Fig. 4. Simulation results of the proposed converter in boost in-phase mode at

D = 0.9, R=10 Ω and n = 3, input/output voltage, output current, input current.

Fig. 5. Simulation results of the proposed converter in buck out-of-phase mode

at D = 0.2, R=10 Ω and n = 2, input/output voltage, output current

CONCLUSION:

In this study, a single phase T-source ac-ac converter has been introduced. The novel topology operates in continuous current mode and low THD, with no filters in input and output. With consider of this point, some privileges rise up such as declining in size and reducing in cost of the converter. Also, output voltage enables to reverse or sustain the phase angle relevant to input voltage greatly, because of the common ground. In addition, a safe commutation strategy is used to prevent appearance of voltage spikes and current spikes, so it leads to the converter could be designed without any snubber circuits in bidirectional switches. The presence of a coupled transformer based on T- structure in the topology gives this permission to converter that operates in a wider range of duty cycles control. Furthermore, by using of T-source in this topology, desirable voltage gain has been obtained in small conducting duration, which leads to increase efficiency and decrease losses considerably. Moreover, this converter can be applied for DVR devices with utilizing buck-boost feature to compensate various voltage sags and voltage swells. Eventually, accuracy performance and theoretical results of the converter have been verified with consequences of the simulation.

REFERENCES:

[1] X. Liu, P.Wang, P. C. Loh, and F. Blaabjerg, “A three-phase dual-input matrix converter for grid integration of two AC type energy resources,” IEEE Trans. Ind. Electron., vol. 60, no. 1, pp. 20–30, Jan. 2013.

[2] Y. W. Li, F. Blaabjerg, D. M. Vilathgamuwa, and P. C. Loh, “Design and comparison of high performance stationary-frame controllers for DVR implementation,” IEEE Trans. Power Electron., vol. 22, no.2, pp.602-612, March 2007.

[3] T. Friedli, J.W. Kolar, J. Rodriguez, and P.W. Wheeler, “Comparative Evaluation of Three-Phase AC–AC Matrix Converter and Voltage DC-Link Back-to-Back Converter Systems,” IEEE Trans. Ind. Electron., vol. 59, no.12, pp. 4487 – 4510, Dec. 2012.

[4] L. Empringham, J.W. Kolar, J. Rodriguez, and P.W. Wheeler, “Technological Issues and Industrial Application of Matrix Converters: A Review, ” IEEE Trans. Ind. Electron., vol. 60, no. 10, pp. 4260-4271, May 2013.

[5] O. Ellabban, H. Abu-Rub, and Ge Baoming, “Field oriented control of an induction motor fed by a quasi-Z-source direct matrix converter, ” in Proc. IEEE 39th Ann. Conf. Ind. Electron. Society, pp. 4850-4855, Vienna, 2013.

Analysis and Control of  DSTATCOM for a Line Voltage Regulation

ABSTRACT

This paper describes a modeling and AC voltage direct control techniques of distribution static synchronous compensator (DSTATCOM) using EMTDC/PSCAD package. Moreover it is presented to make model of three-phase four-wire real distribution system and applied to model of DSTATCOM using EMTDC. Using AC voltage direct control, low harmonics and offset in the voltage as well as fast dynamic responses are achieved. The derived simulations are tried to verify the result of this paper.

KEYWORDS:

1.      Distribution System

2.      Power Quality

3.      Custom Power Device

4.      Shunt Compensation Device

5.      Distribution Static Compensator (DSTATCOM)

6.       Voltage Sag, Harmonics

7.       Zero sequence

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Fig.1. Schematic of distribution system

EXPECTED SIMULATION RESULTS:

Fig.2. Load voltages at the sensitive load terminal [kV](EMTDC/PSCAD simulation )

Fig.3. Harmonics components at the sensitive load terminal

Fig.4. Bode-plot to demonstrate the stability of control of DSTATCOM

Fig.5. Voltage waveform of each phase using proposed DSTATCOM Control scheme

Figure 6. Harmonics of the load terminal using proposed control scheme

CONCLUSION

In this paper, typical distribution system was modeled using EMTDC/PSCAD simulation package. And the single-phase-to-ground fault in distribution system was simulated and analyzed. In the simulation, the component of harmonics in distribution system was analyzed. Also, in this paper, the AC voltage direct control scheme to eliminate sag-voltage and harmonics was proposed and simulated of DSTATCOM. Further work will improve of control scheme of DSTATCOM and application of real distribution system to examine their effective and robustness.

REFERENCES

[1]   John S. Hsu, "Instantaneous Phasor Method for Obtaining Instantaneous Balanced Fundamental Components for Power Quality Control and Continuous Diagnostics," IEEE Transactions on Power Delivery, Vol.13, No.4, October 1998, pp.1494-1500

[2]    Johan H.R. and Enslin, "Unified Approach to Power Quality Mitigation," Industrial Electronics, Proceedings. ISIE '98. IEEE International Symposium on Volume: 1, pp.820

[3]   Gregory F. Reed, Masatoshi Takeda, "Improved power quality solutions using advanced solid-state switching and static compensation technologies," Power Engineering Society 1999 Winter Meeting, IEEE

[4]    Boon Teck Ooi, Joos, G, Xiaogang Huang, "Operating Principles of Shunt STATCOM Based On 3-Level Diode-clamped Converters," Power Engineering Society 1999 Winter Meeting, IEEE

[5]    Seung-gun Song, "The Technology for Distribution System Protection ," Korea Electric Power Company, 1995, pp.233 -335