Enhancement of Power Quality in Distribution System using D-Statcom

ABSTRACT:

STATCOM (static synchronous compensator) as a shunt-link flexible AC transmission system(FACTS) controller has shown extensive feasibility in terms of cost-effectiveness in a wide range of problem solving abilities from transmission to distribution levels. Advances in power electronic technologies such as Voltage Source Converter (VSC) improves the reliability and functionality of power electronic based controllers hence resulting in increased applications of STATCOM. In this paper, design and implementation of a Distribution type, Voltage Source Converter (VSC) based static synchronous compensator (DSTATCOM) has been carried out. It presents the enhancement of power quality problems, such as voltage sag and swell using Distribution Static Compensator (D-STATCOM) in distribution system. The model is based on Sinusoidal Pulse Width Modulation (SPWM) technique. The control of the Voltage Source Converter (VSC) is done with the help of SPWM.

The main focus of this paper is to compensate voltage sag and swell in a distribution system. To solve this problem custom power devices are used such as Fixed Compensators (FC, FR), Synchronous Condenser, SVC, SSSC, STATCOM etc. Among these devices Distribution STATCOM (DSTATCOM) is the most efficient and effective modern custom power device used in power distribution networks. DSTATCOM injects a current into the system to mitigate the voltage sag and swell. The work had been carried out in MATLAB environment using Simulink and SIM power system tool boxes. The proposed D-STATCOM model is very effective to enhance the power quality of an isolated distribution system feeding power to crucial equipment in remote areas. The simulations were performed and results were found to be satisfactory using MATLAB/SIMULINK

KEYWORDS:

1.      Statcom

2.      Facts Controllers

3.      D-Statcom

4.      Voltage Source Converter

5.      Total Harmonic Distortions

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig.1 Schematic diagram of D-STATCOM

EXPECTED SIMULATION RESULTS:

Fig.2 Three Phase to Ground -Voltage at Load Point is 0.6600 p.u

Fig.3 Double Line to Ground- Voltage at Load Point is 0.7070 p.u

Fig.4 Line to Line- Voltage at Load Point is 0.7585

Fig.5 Single Line to Ground- Voltage at Load Point is 0.8257

Fig.6 The waveforms shows THD (41.31%) results of fixed load and variable inductive load.

Fig.7 The wave forms shows THD (21.28%) results of fixed load and variable capacitive load

Fig.8 Three Phase to Ground-Voltage at Load Point is 0.9367 p.u

Fig.9 Double Line to Ground- Voltage at Load Point is0.9800 p.u

Fig.10 Line to Line- Voltage at Load Point is 1.068

Fig.11 Single Line to Ground - Voltage at Load Point is 0.9837

Fig.12 The waveform for pure inductive,capacitive loads with statcom

Fig.13 The waveform for without filter THD results 41.31%

Fig.14 The above waveform for with filter THD results 1.11%

CONCLUSION:

The simulation results show that the voltage sags can be mitigate by inserting D-STATCOM to the distribution system. By adding LCL Passive filter to D-STATCOM, the THD reduced. The power factors also increase close to unity. Thus, it can be concluded that by adding DSTATCOM with LCL filter the power quality is improved.

REFERENCES:

[1] A.E. Hammad, Comparing the Voltage source capability of Present and future Var Compensation Techniques in Transmission System, IEEE Trans, on Power Delivery. Volume 1. No.1 Jan 1995.

[2] G.Yalienkaya, M.H.J Bollen, P.A. Crossley, “Characterization of Voltage Sags in Industrial Distribution System”, IEEE transactions on industry applications, volume 34, No. 4, July/August, PP.682-688, 1999

[3] Haque, M.H., “Compensation of Distribution Systems Voltage sags by DVR and D STATCOM”, Power Tech Proceedings, 2001 IEEE Porto, Volume 1, PP.10-13, September 2001.

[4] Anaya-Lara O, Acha E., “Modeling and Analysis Of Custom Power Systems by PSCAD/EMTDC”, IEEE Transactions on Power Delivery, Volume 17, Issue: 2002, Pages: 266 272.

[5] Bollen, M.H.J.,”Voltage sags in Three Phase Systems”, Power Engineering Review, IEEE, Volume 21, Issue: 9, September 2001, PP: 11-

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.

A Power Quality Improved Bridgeless Converter-Based Computer Power Supply

ABSTRACT:

Poor power quality, slow dynamic response, high device stress, harmonic rich, periodically dense, peaky, distorted input current are the major problems that are frequently encountered in conventional switched mode power supplies (SMPSs) used in computers. To mitigate these problems, it is proposed here to use a nonisolated bridgeless buck-boost single-ended primary inductance converter (SEPIC) in discontinuous conduction mode at the front end of an SMPS. The bridgeless SEPIC at the front end provides stiffly regulated output dc voltage even under frequent input voltage and load variations. The output of the front end converter is connected to a half-bridge dc–dc converter for isolation and also for obtaining different dc voltage levels at the load end that are needed in a personal computer. Controlling a single output voltage is able to regulate all the other dc output voltages as well. The design and simulation of the proposed power supply are carried out for obtaining an improved power quality that is verified through the experimental results.

KEYWORDS:

1.      Bridgeless converter

2.      Computer power supply

3.      Input current

4.      Power factor correction (PFC)

5.      Power quality

SOFTWARE: MATLAB/SIMULINK

SCHEMATIC  DIAGRAM:

Fig. 1. Schematic diagram of the PFC converter based SMPS.

EXPECTED SIMULATION RESULTS:

Fig. 2. (a) Performance of the computer power supply at rated condition. (b) Input current and its harmonic spectrum at full load condition. (c)Waveform across various components of the bridgeless converter.

Fig. 3. (a) Performance of the computer power supply at light load condition.

(b) Input current and its harmonic spectrum at light load condition.

CONCLUSION:

A bridgeless nonisolated SEPIC based power supply has been proposed here to mitigate the power quality problems prevalent in any conventional computer power supply. The proposed power supply is able to operate satisfactorily under wide variations in input voltages and loads. The design and simulation of the proposed power supply are initially carried to demonstrate its improved performance. Further, a laboratory prototype is built and experiments are conducted on this prototype. Test results obtained are found to be in line with the simulated performance. They corroborate the fact that the power quality problems at the front end are mitigated and hence, the proposed circuit can be a recommended solution for computers and other similar appliances.

REFERENCES:

[1] D. O. Koval and C. Carter, “Power quality characteristics of computer loads,” IEEE Trans. Ind. Appl., vol. 33, no. 3, pp. 613–621, May/Jun. 1997.

[2] A. I. Pressman,K.Billings, and T. Morey, Switching Power SupplyDesign, 3rd ed. New York, NY, USA: McGraw Hill, 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. Ind. Electron., vol. 50, no. 5, pp. 962–981, Oct. 2003.

[4] K. Mino, H. Matsumoto, Y. Nemoto, S. Fujita, D. Kawasaki, R. Yamada, and N. Tawada, “A front-end converter with high reliability and high efficiency,” in Proc. IEEE Conf. Energy Convers. Congr. Expo., 2010, pp. 3216–3223.

[5] J.-S. Lai, D. Hurst, and T. Key, “Switch-mode supply power factor improvement via harmonic elimination methods,” in Proc. IEEE 6th Annu. Appl. Power Electron. Conf. Expo., 1991, pp. 415–422.

An Intelligent Speed Controller for Indirect Vector Controlled Induction Motor Drive

ABSTRACT:

This paper presents the speed control scheme of indirect vector controlled induction motor (IM) drive. PWM controlling scheme is based on Voltage source inverter type space vector pulse width modulation (SVPWM) and the Conventional-PI controller or Fuzzy-PI controller is employed in closed loop speed control. Decoupling of the stator current into torque and flux producing (d-q) current components model of an induction motor is involved in the indirect vector control. The torque component Iq current of an IM is developed by an intelligent based Fuzzy PI controller. Based on settling time and dynamic response the performance of Fuzzy Logic Controller is compared with that of the PI Controller to sudden load changes. It’s provides better control of motor torque with high dynamic performance. The simulated design is tested using various tool boxes in MATLAB. Simulation results of both the controllers are presented for comparison.

KEYWORDS:

1.      Indirect Vector Control (IVC)

2.      Space Vector Pulse Width Modulation (SVPWM)

3.      PI Controller

4.      Fuzzy Logic Controller (FLC)

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig.1 Block diagram of a proposed scheme

EXPECTED SIMULATION RESULTS:

Fig.2 Starting response

Fig.3 Step response

Fig.4 Speed response for with and without load impact

Fig.5 Torque response for with and without load impact

CONCLUSION:

In this paper the concept of fuzzy logic has been presented and the SVM based indirect vector controlled induction motor drive is simulated using both PI and Fuzzy PI controller. The results of both controllers under the dynamics conditions are compared and analyzed. The simulation result support that the FLC settles quickly and has better performance than when PI controller.

REFERENCES:

[1] Bimal K.Bose, “Modern Power Electronics and AC Drives”, Pearson education.

[2] Leonhand.W, ‘Control of Electrical Drives’, Springer Verlag 1990.

[3] Yang Li Yinghong, Chen Yaai and Li Zhengxi “A Novel Fuzzy Logic Controller for Indirect Vector Control Induction Motor

[4] Drive” Proceeding of the 7th World Congress on Intelligent and Automation Jun 25 – 27, 2008, Chongqing,China, pp. 24-28

[5] R.A. Gupta, Rajesh Kumar, S.V.Bhangale “Indirect Vector Controlled Induction Motor Drive with Fuzzy Logic based Intelligent Controller”, ICTES,UK,December 2007,pp.368-373.