HARMONICS REDUCTION AND POWER QUALITY IMPROVEMENT BY USING DPFC

ABSTRACT

The DPFC is derived from the unified power-flow controller (UPFC). The DPFC can be considered as a UPFC with an eliminated common dc link. The active power exchange between the shunt and series converters which is through the common dc link in the UPFC is now through the transmission lines at the third-harmonic frequency. The DPFC employs the distributed concept, in which the common dc-link between the shunt and series converters are eliminated and three-phase series converter is divided to several single-phase series distributed converters through the line. According to the growth of electricity demand and the increased number of non-linear loads in power grids harmonics, voltage sag and swell are the major power quality problems. DPFC is used to mitigate the voltage deviation and improve power quality. Simulations are carried out in MATLAB/Simulink environment. The presented simulation results validate the DPFC ability to improve the power quality.

KEYWORDS:

1.      Load flow control

2.      FACTS

3.       Power Quality

4.      Harmonics

5.      Sag and Swell Mitigation

6.      Distributed Power Flow Controller

7.      Y– transformer

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. Flowchart from UPFC to DPFC.

Fig. 2. DPFC configuration.

EXPECTED SIMULATION RESULTS:

Fig 3. three phase voltage sag waveform without DPFC

Fig. 4. Three phase voltage sag waveform with DPFC

Fig.5. 3- load current swell waveform without DPFC

Fig.6 Mitigation of 3- load current swell with DPFC

Fig.7.  Total harmonic distortion of load voltage without DPFC

Fig.8. Total harmonic distortion of load voltage with DPFC

CONCLUSION

This paper has presented a new concept called DPFC. The DPFC emerges from the UPFC and inherits the control capability of the UPFC, which is the simultaneous adjustment of the line impedance, the transmission angle, and the bus voltage magnitude. The common dc link between the shunt and series converters, which is used for exchanging active power in the UPFC, is eliminated. This power is now transmitted through the transmission line at the third-harmonic frequency. The series converter of the DPFC employs the DFACTS concept, which uses multiple small single-phase converters instead of one large-size converter. The reliability of the DPFC is greatly increased because of the redundancy of the series converters. The total cost of the DPFC is also much lower than the UPFC, because no high-voltage isolation is required at the series-converter part and the rating of the components of is low. To improve power quality in the power

transmission system, the harmonics due to nonlinear loads, voltage sag and swell are mitigated. To simulate the dynamic performance, a three-phase fault is considered near the load. It is shown that the DPFC gives an acceptable performance in power quality improvement and power flow control.

REFERENCES

[1]   S.Masoud Barakati Arash Khoshkbar sadigh and Mokhtarpour.Voltage Sag and Swell Compensation with DVR Based on Asymmetrical Cascade Multicell Converter North American Power Symposium (NAPS),pp.1-7,2011.

[2]    Zhihui Yuan, Sjoerd W.H de Haan, Braham Frreira and Dalibor Cevoric “A FACTS Device: Distributed Power Flow Controller (DPFC)” IEEE Transaction on Power Electronics, vol.25, no.10, October 2010.

[3]    Zhihui Yuan, Sjoerd W.H de Haan and Braham Frreira “DPFC control during shunt converter failure” IEEE Transaction on Power Electronics 2009.

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

Modeling and Control of Flywheel Energy Storage system for Uninterruptible Power Supply

ABSTRACT

Flywheel Energy Storage has attracted new research attention recently in applications like power quality, regenerative braking and uninterruptible power supply (UPS). As a sustainable energy storage method, Flywheel Energy Storage has become a direct substitute for batteries in UPS applications. Inner design of the flywheel unit is shown to illustrate the economical way to construct the system. A comprehensive model of Flywheel energy storage system (FESS) that bridges the gap caused by power outage for critical loads in commercial and industrial areas is presented. The basic circuit consists of bidirectional power converter and flywheel unit coupled with interior permanent magnet synchronous motor (IPMSM). Maximum torque per ampere (MTPA) and flux weakening are used in the control scheme on IPMSM. Detailed block diagrams of the control scheme are given. The FESS for UPS application is modeled, simulated, and analyzed in MATLAB/SIMULINK environment.

KEYWORDS:

1.      Control systems

2.      DC-AC power conversion

3.      Energy storage

4.      Flywheels

5.      Load flow control

6.      Pulse width modulated power converters

7.      Permanent magnet motors

SOFTWARE: MATLAB/SIMULINK

CIRCUIT DIAGRAM:

Fig. 1. Basic circuit diagram of the FESS in UPS.

EXPECTED SIMULATION RESULTS:

Fig. 2. Flywheel speed in charging mode.

Fig. 3. Electromagnetic torque of IPMSM.

Fig. 4. Power grid voltage sag and outage

Fig. 5. Power failure detection signal.

Fig. 6. Flywheel speed in discharging mode.

Fig. 7. DC bus voltage

Fig. 8. 3-phase voltage of critical load (phase to ground) without FESS.

Fig. 9. 3-phase voltage of critical load (phase to ground) with FESS

CONCLUSION

This paper presents a modeling and control method of FESS in UPS system. A cost effective and reliable flywheel design is brought forward to prove the possible mass utilization of FESS in industrial applications. The control algorithm of FESS is described with detailed block diagram, including the torque control of IPMSM that driving the flywheel, voltage sags and outage detection and DC bus regulation. Simulation results are presented to validate the control strategy. Future tasks will include control strategy on mitigating unbalanced voltage sags, parameter variation of IPMSM and experiment verification of the control methods.

REFERENCES

[1]   R. BROWN Daryl and D. CHVALA William, "Flywheel Energy Storage An alternative to batteries for uninterruptible power supply systems," Pacific Northwest National Laboratory, ETATS-UNIS, Richland, Washington, US, 2004.

[2]   Ralph H Jansen. Timothy P Dever, "G2 Flywheel Module Design," University of Toledo 2801 W. Bancroft St. Toledo, Ohio, US, Tech Rep. NASA/CR-2006-213862, 2006.

[3]   Active Power Corp. (2008), "Quantitative Reliability Assessment of Ball Bearings versus Active Magnetic Bearings for Flywheel Energy Storage Systems," [Online] Available: http://www.activepower.com/fileadmin/documents/white_papers/WP_111_Bearing_Assessment.pdf.

[4]   S. Morimoto, M. Sanada, and Y. Takeda, "Wide-speed operation of interior permanent magnet synchronous motors with high-performance current regulator," Industry Applications, IEEE Transactions on, vol. 30, pp. 920-926, 1994.

[5]   Barbara H Kenny and Peter E Kascak, "DC Bus Regulation with a Flywheel Energy Storage System," NASA, John H. Glenn Research Center, Lewis Field Cleveland, Ohio, US, Tech Rep. NASA TM-2002-211897-REV102PSC–61, 2003.

COMPENSATION OF VOLTAGE DISTRIBUNCES IN SMIB SYSTEM USING ANN BASED DPFC CONTROLLER

ABSTRACT

Since last decade, due to advancement in technology and increasing in the electrical loads and

also due to complexity of the devices the quality of power distribution is decreases. A Power quality issue is nothing but distortions in current, voltage and frequency that affect the end user equipment or disoperation; these are main problems of power quality so compensation for these problems by DPFC is presented in this paper. The control circuits for DPFC are designed by using line currents, series reference voltages and these are controlled by conventional ANN controllers. The results are observed by MATLAB/SIMULINK model.

KEYWORDS:

1.      Power Quality

2.      Voltage Sag

3.      DPFC

4.      Voltage Swell.

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Figure 1: Schematic Diagram for DPFC

EXPECTED SIMULATION RESULTS:

Figure 2: Output Voltage during fault condition

Figure 3: Output Current during Fault Condition

Figure 4: Output voltage compensated by DPFC controller

Figure 5: Compensated Output Current by DPFC controller

Figure 6: Active and Reactive Power

Figure 7: THD value of system output voltage without DPFC

Figure 8: THD value of DPFC (pi controller) load voltage

Figure 9: THD for output voltage under ANN controller

CONCLUSION

In this paper we implemented a concept to controlling the power quality issues i.e. DPFC. The proposed theory of this device is mathematical formulation and analysis of voltage dips and their mitigations for a three phase source with linear load. In this paper we also proposed a concept of Ann controller for better controlling action. As compared to all other facts devices the DPFC based ANN has effectively control all power quality problems and with this technique we get the THD as 3.65% and finally the simulation results are shown above.

REFERENCES

[1]   Ahmad Jamshidi, S.Masoud Barakati, and M.Moradi Ghahderijani presented a paper on “Impact of Distributed Power Flow Controller to Improve Power Quality Based on Synchronous Reference Frame Method” at IACSIT International Journal of Engineering and Technology, Vol. 4, No. 5, October 2012.

[2]   Ahmad Jamshidi, S.Masoud Barakati, and Mohammad Moradi Ghahderijani posted a paper “Power Quality Improvement and Mitigation Case Study Using Distributed Power Flow Controller” on 978-1-4673-0158-9/12/$31.00 ©2012 IEEE.

[3]   Srinivasarao, Budi, G. Sreenivasan, and Swathi Sharma. "Comparison of Facts Controller for Power Quality Problems in Power System", Indian Journal of Science and Technology, 2015.

ENERGY STORAGE AND TOPOLOGIES

Energy can neither be created nor destroyed. But it can be transformed from one form to another. Electrical energy is the form of energy that can be transmitted efficiently and easily transformed to other forms of energy. The main disadvantages with electrical energy involve storing it economically and efficiently. Electrical energy can be converted and stored in different forms:

• Electrochemical Energy

• Electrostatic Energy

• Electromagnetic Energy

• Electromechanical Energy

1. ELECTROCHEMICAL ENERGY STORAGE

In this type of storage, electrical energy is converted and stored in the form of chemical energy. There are two main categories: batteries and fuel cells. Batteries use internal chemical components for energy conversion and storage whereas fuel cells use synthetic fuel (for example Hydrogen, methanol or hydrazine) supplied and stored externally. Both use two electrodes, an anode and a cathode, that exchange ions through an electrolyte internally and exchange electrons through an electric circuit externally. The Lead-acid battery, discovered by Plante in 1859, is the most widely used battery. The battery consists of pairs of lead electrode plates immersed in a dilute sulphuric acid that acts as an electrolyte. Every alternate lead plate is coated with lead dioxide. Discharging results in the conversion of both of the electrodes to lead sulphate. Charging restores the plates to lead and lead dioxide. The physical changes in electrodes during charging and discharging deteriorates the electrodes and hence reducing their life. The main advantages are they have a well-established technology.

The main drawbacks with batteries are:

• Slow response during energy release

• Limited number of charge discharge cycles

• Relatively short life time

• High internal resistance

• Low energy density

• Maintenance requirements for some types

• Environmental hazards

W. R. Grove demonstrated the first hydrogen-oxygen fuel cell in 1839. The byproduct of a Hydrogen fuel cell is water. By electrochemical decomposition of water into hydrogen and oxygen and holding them apart, hydrogen fuel cells store electrical energy. During discharge, the hydrogen is combined with oxygen, converting the chemical energy to electrical energy. The main advantages are environment friendly. The main drawbacks with fuel cells as energy storage elements are:

• Slow response during energy release

• Temperature dependence

• Corrosion problems

• Hydrogen storage

• Inefficient transfer of electrical energy to chemical energy

2. ELECTROSTATIC ENERGY STORAGE

Electric energy can be converted and stored in the form of electrostatic field between the parallel plates of a charged capacitor. The amount of energy stored is proportional to square of the voltage across the parallel plates and to its capacitance. For a fixed voltage, the volume energy density for a parallel plate capacitor is proportional to capacitance, which is proportional to the permittivity of the insulator between the parallel plates. Most of the insulators have relative permittivity in the range of 1 to 10. Due to the small capacitance, ordinary capacitors can store very limited amount of energy. Ultra capacitors use electrochemical material for improving permittivity and hence energy density. They require less maintenance and have much longer lifetimes compared to batteries. They have high energy density and does not having moving parts. The main drawbacks with capacitors are:

• Cost

• Temperature dependence

• Not rugged

3. ELECTROMAGNETIC ENERGY STORAGE

Electric energy can be converted and stored in the form of an electromagnetic field. A Superconducting magnetic energy storage (SMES) coil consists of a superconducting coil carrying large DC currents. The amount of energy stored is proportional to the square of the DC current flowing through the coil and to its inductance. The volume energy density is proportional to the permeability of the material used for the coil. In order to keep the temperature of the superconductor below its critical temperature, a cryogenic cooling system is required. Increasing the DC current increases the amount of energy stored. Once the current in the coil reaches its maximum value, the voltage across it is zero and the SMES is fully charged. This storage scheme has very low losses due to negligible resistance in the coil. Also SMES coils can be built for larger energy and power. The main drawbacks with SMES are:

• Cost

• Reliability in maintaining cryogenic cooling

• Compensation of external stray fields

• Electromagnetic forces on the conductors

• Bulk/volume

4. ELECTROMECHANICAL ENERGY STORAGE

Electrical energy can be converted and stored in the form of kinetic energy in a flywheel. Motor/generator sets, DC machines and induction machines are used for energy conversion. The amount of energy stored in a flywheel is proportional to the square of angular velocity and to its inertia for a given design stress. The energy storage technologies discussed above have their own advantages and disadvantages but the following advantages make flywheels a viable alternative to other energy storage systems:

• Low cost

• High power density

• Ruggedness

• Greater number of charge discharge cycles

• Longer life

• Less maintenance

• Environmental friendly

• Fast response during energy release

Flywheels can be designed for low speed or high-speed operation. A low speed flywheel has advantages of lower cost and the use of proven technologies when compared to a high-speed flywheel system. The main disadvantages are:

• less energy stored per volume

• higher losses

• increased volume and mass