Single Phase Dynamic Voltage Restorer Topology Based on Five-level Ground point Shifting Inverter

ABSTRACT

A Single Phase Dynamic Voltage Restorer (DVR) based on five-level ground point shifting multilevel inverter topology has been proposed in this paper. The proposed inverter has a floating ground point. Therefore, by shifting the ground point, it is observed that the inverter circuit gives five output voltage levels from single DC voltage source. This configuration uses less number of switches compared to the existing multilevel inverter topologies. A fast sag swell identification technique using d-q reference frame is also discussed in this paper. This proposed topology of the DVR can compensate voltage sag, swell, flicker and maintain the required voltage at the load bus. The detailed simulation study is carried out using MATLAB/Simulink to validate the result.

 KEYWORDS

  1. Voltage sag
  2. Swell
  3. Ground Point Shifting Multilevel Inverter (GPSMI)
  4. Topology
  5. DVR

 SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM


Fig. 1. General structure of the proposed DVR.

EXPECTED SIMULATION RESULTS

Fig. 2. (a) Grid terminal voltage (vt) and (b) load voltage (vl) during sag

mitigation.

Fig. 3. direct axis value of the d-q reference frame which is used to detect

sag in the system.

Fig. 4. During voltage sag (a) grid terminal voltage (vt), (b) series injected

voltage (vinj) and (c) inverter terminal voltage (vinv).

Fig. 5. FFT analysis of the series injected voltage (vinj).

Fig. 6. (a) Grid terminal voltage and (b) load voltage during Voltage flicker

 CONCLUSION

This paper proposes dynamic voltage restorer based on the ground point shifting multilevel Inverter topology (GPSMI). And explained  the operation of the multilevel inverter and the power circuit diagram. The inverter topology requires less number of switches than conventional multi-level inverter. In this inverter topology, only two switches are active at any instant of time that reduce switch conduction loss. Using this multi-level inverter, reduced the passive filter requirement in the DVR topology. Proper PWM for this proposed inverter has been explained. Instantaneous sag identification technique using d-q reference frame has also been explained. This proposed DVR can mitigate the power quality problem like sag/swell and voltage flicker.

REFERENCES

 [1] IEEE Guide for Voltage Sag Indices,” in IEEE Std 1564-2014 , vol., no., pp.1-59, June 20 2014

[2] IEEE Guide for Identifying and Improving Voltage Quality in Power Systems,” in IEEE Std 1250-2011 (Revision of IEEE Std 1250-1995) , vol., no., pp.1-70, March 31 2011

[3] A. G ho sh and G. Led w i ch, ”Structures and control of a dynamic voltage regulator (DVR),” Power Engineering Society Winter Meeting, 2001. IEEE, Columbus, OH, 2001, pp. 1027-1032 vol.3. do i: 10.1109/PE  S W.2001.917209

[4] Hui wen Li u, Bowen Z hen g and X  ion  g Z h an, ”A comparison of two types of storage less DVR with a passive shunt converter,” 2016 IEEE 8th International Power Electronics and Motion Control Conference (I P EM C-EC CE Asia), He f e i, 2016, pp. 1280-1284.

[5] P. C. Lo h, D. M. Vi lath g  a m  u  w  a , S. K. tang, H. L. Long, ”Multilevel dynamic voltage restorer”, IEEE Power Electronic Letters, vol. 2, no. 4, pp. 125-130, Dec. 2004.

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.