Fortification of Voltage Recompense by Scheming of CMHBI

(1)

International Journal of Recent Advances in Engineering & Technology (IJRAET)

________________________________________________________________________________________________

ISSN (Online): 2347 - 2812, Volume-3, Issue -9, 2015 90

Fortification of Voltage Recompense by Scheming of CMHBI - DSTATCOM

1T Rakesh, ²V Madhusudhan, ³M Sushama

1Research Scholar JNTUH, Hyderabad, ²Principal & Dean KORMCE, Kadapa, ³Professor EEE Department, JNTUCEH, Hyderabad

Abstract: This article proposes a Distribution Static Compensator based on cascaded H-Bridge multilevel inverter. The deliberate controller aims at achieving voltage reparation during load circumstances. The voltage slump and voltage engorge causes dent for the intact system. The planned system consists of five levels cascaded H-Bridge multilevel inverter which uses a battery as a DC sources. If the voltage slump or voltage engorge is present in the circuit, then the cascaded H-Bridge multilevel inverter compensates the voltage. Usually, the DSTATCOM is connected to the power networks at a Point of Common Coupling through a transformer where the voltage eminence predicament is an apprehension.

Keywords—Distribution Static Synchronous Compensator (DSTATCOM), Cascaded H-Bridge Multilevel inverter, Flexible AC Transmission System (FACTS), Voltage slump, Voltage engorge.

I. INTRODUCTION

Multilevel inverters have become more and more popular in high power transmission, distribution systems and industry applications. The main advantages of multilevel inverters are elevated effectiveness, power factor is secure to unity, no electromagnetic obstruction exists etc. So multilevel is used extensively compared to further type of inverters. The three types of multilevel inverters are diode clamped, flying capacitor and cascaded multilevel inverter. Compared with diode clamped and flying inverter, the cascaded H-Bridge multilevel inverter saves a hefty sum of clamped diodes and flying capacitors. A cascaded H-Bridge multilevel inverter with one and the same DC voltage has been generally used for static compensator relevance because of simple formation, natural modular and high excellence output continuum. The problem of voltage reparation can be minimized or trounce by using apt FACTS devices such as SVC, UPFC, DSTATCOM, etc.

DSTATCOM is an admired FACTS controller for the power system to shore up the voltage, amplify the transmission competence, enhance the voltage stability and recover the transient stability by injecting/engrossing the reactive power to/starting the power system. DSTATCOM is a STATCOM used in the distribution system which is a shunt associated FACTS device. It is connected to reimburse bus voltages. Squat

imprecise AC voltage waveform is achieved by moreover increasing switching incidence or increasing the cascaded number of modules, which bring high power trouncing or high cost to the DSTATCOM system.

Voltage sags are the short extent voltage reduction and voltage engorge are the short interval overvoltage in the system. Both causes dimple to the part or full system. It is caused by fault in adjacent systems, sudden increase of loads, capacitor banks, power electronics loads, motor starting etc. DSTATCOM is a device consists of a coupling transformer and the voltage synchronous controller. Compared to Static VAR compensator, DSTATCOM provides quicker control and improved control range. Power electronics role is used to control the output of the power using the semiconductor switches. The semiconductor switches are worked only with the help of triggering pulses. Microcontroller is used to generate the triggering gate pulses for the semiconductor switches which are used in the inverter circuit.

II.PRINIPLE OF DSTATCOM

Figure 1 shows the schematic diagram of DSTATCOM.

DSTATCOM is connected in shunt at PCC is one of the effectual elucidation for system in front of such problems. DSTATCOM is a popular FACTS controller for the power system to sustain the voltage, increase the transmission competence, boost the voltage strength and improve the transient stability by injecting/engrossing the reactive power headed for commencing the power system.

Fig 1. Basic Structure of DSTATCOM

(2)

________________________________________________________________________________________________

Figure 2 shows the operating modes of DSTATCOM. In the system voltage, the circumstances real power and reactive power is equal to zero. Consequently, DSTATCOM are operated as a purposeful comparable of a SVC. But it provides quicker control than SVC and also DSTATCOM had an enhanced control range. AC voltage source by voltage source converter (VSC) associated to a DC capacitor (energy storage contrivance).the DSTATCOM is allied to the PS at the PCC, using transformer seepage reactance which gives active and reactive power barter between PS and the DSTATCOM. Ideally the output voltage of the VSC is in phase with source voltage.

Fig 2. Operating modes of DSTATCOM The AC terminals of the VSC are connected to the Point of Common Coupling (PCC) through an inductance, which could be a filter inductance or the leakage inductance of the coupling transformer The DC side of the converter is coupled to a DC capacitor. If the output voltage of the VSC is equal to the AC terminal voltage, no reactive power is delivered to the system. If the output voltage is greater than the AC terminal voltage, the DSTATCOM is in the capacitive mode of operation.

III.BLOCK DIAGRAM

Microcontroller is worn to engender the triggering pulses and then the pulse is given to the driver circuit.

The driver circuit is used to augment to the gate voltage obligatory by switches. There are three promising modes of maneuver in DSTATCOM.

If the output voltage of the VSC is equal to the AC terminal voltage, no reactive power is delivered to the system. If the output voltage is greater than the AC terminal voltage, the DSTATCOM is in the capacitive mode of operation. Then the surfeit power flows in the course of the load to battery. If the output voltage of the voltage synchronous controller is less than the AC terminal voltage, the DSTATCOM is in the inductive mode of operation. Then the power flows from battery to load.

By using the following formula, the number of switching devices used in multilevel inverter can be calculated,

N= 2(m-1)

Where N= number of switching devices and m= number of levels

In this paper, five levels of multilevel output are required. So 2(5-1) = 8 devices.

Fig 3. Block diagram of DSTATCOM

The active and reactive powers exchanged between the system and the converter to compensate the voltage. It also leads to advance the power quality and increase the efficiency of the system.

The active and reactive powers exchanged between the system and the converters are,

Where δ=Phase angle between Vs and V_i, and X is the total reactance of the reactor and transformer.

IV. SIMULATION MODEL

Fig 4. Simulation diagram of DSTATCOM

(3)

________________________________________________________________________________________________

The model publicized above is three phase of 415 volt, 50Hz is connected to a non linear load. By injecting the reparation voltage the voltage is reparation are done.

Fig 5. Result of 5 level inverter output

Fig. 6. Simulation result of load voltage without compensation where the load is connected at 0.2 sec by

the breaker gives the voltage sag

Fig 7. Simulation result of RMS load voltage without compensation

Fig 8. Simulation result of RMS load current without compensation where the load is connected at 0.2 sec by

the breaker gives the voltage sag

Fig 9. Simulation result of load voltage with compensation

Fig 10. Simulation result of RMS load voltage with compensation

Fig 11. Simulation result of RMS current with compensation

Fig 12. Simulation result of output voltage and current The operation of system with and without DSTATCOM is shown in the above graphs. DSTATCOM is disconnected by the breaker up to 0.2 sec and connected at 0.2 sec for ensures the operation DSTATCOM. It also saves the damage against the system.

V. CONCLUSION

This manuscript describes a cascaded multilevel H- Bridge inverter based DSTATCOM used for voltage reparation. Thus the voltage compensation were verified lucratively in the course of computer simulation and the archetype is to be done with the 100 volt laboratory downscaled model have confirmed the effect of voltage compensating during voltage sag and voltage swell under various conditions.

REFERENCE

[1] W. Song and A. Q. Huang, ―Fault-tolerant design and control strategy for cascaded H-bridge multilevel converter-based STATCOM,‖ IEEE Trans. Ind. Appl., vol. 57, no. 8, pp. 2700–2708, Aug. 2010.

[2] S. Mekhilef and M. N. Abdul Kadir, ―Voltage control of three-stage hybrid multilevel inverter using vector transformation,‖ IEEE Trans.

(4)

________________________________________________________________________________________________

Power Electron., vol. 25, no. 10, pp. 2599–2606, Oct. 2010.

[3] C. Han, A. Q. Huang, M. E. Baran, S.

Bhattacharya, W. Litzenberger,L. Anderson, A.

L. Johnson, and A.-A. Edris, ―STATCOM Impact study on the integration of a large wind farm into a weak loop power system,‖ IEEE Trans. Energy Convers., vol. 23, no. 1, pp. 226–233, Mar. 2008.

[4] N. Hatano and T. Ise, ―Control scheme of cascaded h-bridge STATCOM using zero- sequence voltage and negative-sequence current,‖

IEEE Trans. Power Del., vol. 25, no. 2, pp. 543–

550, Apr. 2010.

[5] K. Sivakumar, A. Das, R. Ramchand, C. Patel, and K. Gopakumar, ―A hybrid multilevel inverter topology for an open-end winding inductionmotor drive using two-level inverters in series with a capacitor-fed Hbridge cell,‖ IEEE Trans. Ind. Electron., vol. 57, no. 11, pp. 3703–

3714, Nov. 2010.

[6] R. Sternberger and D. Jovcic, ―Analytical modeling of a square-wavecontrolled cascaded multilevel STATCOM,‖ IEEE Trans. Power Del., vol. 24, no. 4, pp. 2261–2269, Oct. 2009.

[7] Y. He, D. Si-xing, and L. Jin-Jun, ―A study on the DC link voltage balancing for power conditioners based on cascaded H-bridges,‖ in Proc. IEEE 8th Int. Conf. Power Electron., May/Jun. 2011, pp. 1821–1827.

[8] A. J.Watson, P.W. Wheeler, and J. C. Clare, ―A complete harmonic elimination approach to DC link voltage balancing for a cascaded multilevel rectifier,‖ IEEE Trans. Ind. Electron., vol. 54, no.

6, pp. 2946–2953, Dec.2007.

[9] F. Z. Peng, J.-S. Lai, J.W. McKeever, and J.

VanCoevering, ―A multilevel voltage-source inverter with separateDCsources for static var generation,‖ IEEE Trans. Ind. Appl., vol. 32, no.

5, pp. 1130–1138, Sep./Oct. 1996.

[10] Y. S. Lai and F. S. Shyu, ―Topology for hybrid multilevel inverter,‖ Proc. Inst. Elect. Eng.—

Elect. Power Appl., vol. 149, no. 6, pp. 449–458, Nov. 2002.

[11] M. Manjrekar and T. Lipo, ―A hybrid multilevel inverter topology for drive applications,‖ in Proc.

IEEE Appl. Power Electron. Conf., Feb. 1998, vol. 2, pp. 523–529.

[12] C. Silva, ―A novel modulation technique for a multilevel hybrid converter with floating capacitors,‖ in Proc. 36th IEEE Ind. Electron.

Soc. Annu. Meet., Nov. 2010, pp. 296–302.

[13] D. U. Zhong, B. Ozpineci, L. M. Tolbert, and J.

N. Chiasson, ―DCAC cascaded H-bridge multilevel boost inverter with no inductors for electric/hybrid electric vehicle applications,‖

IEEE Trans. Ind. Appl., vol. 45, no. 3, pp. 963–

970, May/Jun. 2009

