Three-Level 48-Pulse STATCOM with Pulse Width Modulation

 ABSTRACT:

In this paper, a new control strategy of a three level 48-pulse static synchronous compensator (STATCOM) is proposed with a constant dc link voltage and pulse width modulation at fundamental frequency switching. The proposed STATCOM is realized using eight units of three-level voltage source converters (VSCs) to form a three-level 48-pulse STATCOM. The conduction angle of each three-level VSC is modulated to control the ac converter output voltage, which controls the reactive power of the STATCOM. A fuzzy logic controller is used to control the STATCOM. The dynamic performance of the STATCOM is studied for the control of the reference reactive power, the reference terminal voltage and under the switching of inductive and capacitive loads.

KEYWORDS:

1.      Fuzzy logic control (FLC)

2.      Static synchronous compensator (STATCOM)

3.      Voltage source converter (VSC)

4.      Flexible ac transmission system (FACTS)

5.      Power frequency switching (PFS)

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Fig. 1 System configuration for simulation

 EXPECTED SIMULATION RESULTS:

Fig. 2 a Dynamic performance of STATCOM for varying the reference reactive power. b Zoomed-in waveforms of the STATCOM ac current as well the dc current during a floating, b capacitive and c inductive operations

Fig. 3 Dynamic performance of STATCOM for varying the reference terminal voltage

Fig. 4 Dynamic performance of STATCOM by switching on inductive and capacitive loads

Fig. 5 a ac terminal voltage without STATCOM on switching non-linear load. b Dynamic performance of STATCOM and ac terminal voltage by switching on switching non-linear load

Fig. 6 Dynamic performance of STATCOM by switching on large value of apparent power

Fig. 7 Dynamic performance of STATCOM under short circuit of the upper half of the dc bus capacitance

Fig. 8 Dynamic performance of STATCOM under short circuit of the complete dc bus capacitance

Fig. 9 a Variation of the dc voltage with sudden load change using a PI and an FLC. b Variation of the ac terminal voltage with sudden load change using a PI and an FLC

CONCLUSION:

A new control strategy of a three-level 48-pulse STATCOM has been proposed with a constant dc link voltage and pulse width modulation at fundamental frequency switching. Its performance has been validated using MATLAB/Simulink. Simulation results have validated the satisfactory dynamic and steady performances of the proposed STATCOM operation. The harmonic content of the STATCOM current is found well below 5 % as per IEEE 519 standard [27].

REFERENCES:

1. T. Johns, A. Ter-Gazarian, D.F. Warne, Flexible ac transmission systems (FACTS), IEE Power Energy Series, the Institute of Electrical Engineers, London, UK, 1999

2. N.G. Hingorani, L. Gyugyi, Understanding FACTS: Concepts and Technology of Flexible ac Transmission Systems (IEEE Press, 2000)

3. R.M. Mathur, R.K. Verma, Thyristor-Based FACTS Controllers for Electrical Transmission Systems (Wiley-IEEE Press, 2002)

4. K.R. Padiyar, FACTS Controllers in Power Transmission and Distribution (New Age International (P) Limited Publishers, India, 2007)

5. K.K. Sen, Introduction to FACTS Controllers: Theory, Modeling and Applications (Wiley-IEEE Press, 2009)

Comparative Analysis of 6, 12 and 48 Pulse T-STATCOM

ABSTRACT:

This paper presents the performance and comparative analysis of Static Synchronous Compensator (STATCOM) based on 6, 12 and 48-pulse VSC configuration. STATCOM is implemented for regulation of the voltage at the Point of Common Coupling (PCC) bus which has time-variable loads. The dq decoupled current control strategy is used for implementation of STATCOM, where modulation index M and phase angle ø are varied for achieving voltage regulation at the PCC bus. The 6, 12 and 48-pulse configurations are compared and analyzed on the basis of Total Harmonic Distortion (THD) and time response parameters such as rise time, maximum overshoot and settling time. The simulation of various configurations of STATCOM is carried out using power system block-set in MATLAB/Simulink platform.

KEYWORDS:

1.      FACTS

2.      STATCOM

3.      Decoupled current control system

4.      Voltage Sourced Converter

5.      Total Harmonic Distortion

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig.1:Single line diagram of STATCOM.

EXPECTED SIMULATION RESULTS:

Fig. 2: PCC bus voltage-V_M for 6, 12 and 48 pulse STATCOM respectively.

Fig. 3: q-axis STATCOM current-i_shq for PI controller of 6, 12 and 48 pulse STATCOM respectively.

  

Fig. 4: d-axis STATCOM current-ishd for PI controller of 6, 12 and 48 pulse STATCOM respectively.

                                                                            a: Dc capacitor voltage-V_dc       

                                        


                                                                           b: Active power of loads-P_L

    

c: Reactive power-Q_stat         

                                


d: Active power-P_stat

Fig. 5: V_dc, P_L, Q_stat and P_stat for 48 pulse STATCOM respectively.

CONCLUSION:

In this paper, for voltage regulation and dynamic power flow control a 48-pulse ±100 MVA two-level GTO STATCOM has been modeled and simulated using decoupled current control strategy. By varying the modulation index (M) and phase angle (ɸ) between PCC bus voltage and STATCOM voltage, voltage regulation at the PCC bus is achieved. The THD and various time response parameters of 6, 12 and 48 pulse STATCOM are compared. The results show that THD of output voltage of 48 pulse STATCOM is less than 5%, which satisfies the IEEE 519 standard. Hence, there is no need of active filter. Also, 48 pulse STATCOM has better transient response as compared to 6, 12 pulse STATCOM.

REFERENCES:

[1] K. Padiyar, FACTS controllers in power transmission and distribution. New Age International, 2007.

[2] K. K. Sen and M. L. Sen, Introduction to FACTS controllers: theory, modeling, and applications. John Wiley & Sons, 2009, vol. 54.

[3] A. Edris, “Facts technology development: an update,” IEEE Power engineering review, vol. 20, no. 3, pp. 4–9, 2000.

[4] El-Moursi and A.M. Sharaf, “Novel controllers for the 48-pulse vscstatcom and ssscfor voltage regulation and reactive power compensation,” IEEE Transactions on Powersystems, vol. 20, no. 4, pp. 1985–1997, 2005.

[5] N. G. Hingorani and L. Gyugyi, Understanding FACTS: concepts and technology of flexible AC transmission systems. Wiley-IEEE press, 2000.

Modeling of 18-Pulse STATCOM for Power System Application

ABSTRACT:

A multi-pulse GTO based voltage source converter (VSC) topology together with a fundamental frequency switching mode of gate control is a mature technology being widely used in static synchronous compensators (STATCOMs). The present practice in utility/industry is to employ a high number of pulses in the STATCOM, preferably a 48-pulse along with matching components of magnetics for dynamic reactive power compensation, voltage regulation, etc. in electrical networks. With an increase in the pulse order, need of power electronic devices and inter-facing magnetic apparatus increases multi-fold to achieve a desired operating performance. In this paper, a competitive topology with a fewer number of devices and reduced magnetics is evolved to develop an 18-pulse, 2-level + 100MVAR STATCOM in which a GTO-VSC device is operated at fundamental frequency switching gate control. The inter-facing magnetics topology is conceptualized in two stages and with this harmonics distortion in the network is minimized to permissible IEEE-519 standard limits. This compensator is modeled, designed and simulated by a Sim Power Systems tool box in MATLAB platform and is tested for voltage regulation and power factor correction in power systems. The operating characteristics corresponding to steady state and dynamic operating conditions show an acceptable performance.

KEYWORDS:

1.      Fast Fourier transformation

2.      Gate-turn off thyristor

3.      Magnetic

4.      STATCOM

5.      Total harmonic distortion

6.      Voltage source converter

SOFTWARE: MATLAB/SIMULINK

MATLAB MODEL:

Fig. 1 MATLAB model of ±100MVAR 18-pulse STATCOM

EXPECTED SIMULATION RESULTS:

Fig. 2 Three phase instantaneous voltage(va , vb, vc) and current (ia, ib, ic) with 75MW 0.85pf lagging load when V* sets at 1.0pu, 1.03pu and 0.97pu

Fig. 3 Operating characteristics in voltage regulation mode for 70MW, 0.85pf(lag) load

Fig. 4 Voltage(va) spectrum in capacitive mode

Fig. 5. Voltage spectrum (va) in inductive mode.

Fig. 6. Current (ia) spectrum in capacitive mode.

Fig. 7. Current spectrum (ia) in inductive mode.

Fig. 8 Operating characteristics for unity power factor (upf) Correction in var control mode for 75MW, 0.85pf(lag) load

Fig. 9. Voltage harmonics(va) spectrum for upf correction.

Fig. 10 Current harmonics(ia) spectrum for upf correction

Fig. 11 Operating characteristics following 10% load injection at the instant of 0.24s in voltage regulation mode on 70MW, 0.85pf(lag) load

Fig. 12 Voltage harmonics (va) spectrum after load variation

Fig. 13. Current harmonics (ia) spectrum after load variation.

Fig. 14 Operating characteristics in var control mode for incremental Load variation of 10% at the instant of 0.24s on an initial load of 70MW, 0.85pf(lag)

Fig. 15 Voltage harmonics (va) spectrum after the load injection

Fig. 16. Current harmonics (ia) spectrum after the load injection.

CONCLUSION:

A new 18-pulse, 2-level GTO-VSC based STATCOM with a rating of + 100MVAR, 132kV was modeled by employing three fundamental 6-pulse VSCs operated at fundamental frequency gate switching in MATLAB platform using a Sim Power Systems tool box. The inter-facing magnetics have evolved in two stage sinter- phase transformers (stage-I) and phase shifter (stage-II), and with this topology together with standard PI-controllers, harmonics distortion in the network has been greatly minimized to permissible IEEE-519 standard operating limits [9]. The compensator was employed for voltage regulation, power factor correction and also tested for dynamic load variation in the network. It was observed from the various operating performance characteristics which emerged from the simulation results that the model satisfies the network requirements both during steady state and dynamic operating conditions. The controller has provided necessary damping to settle rapidly steady states for smooth operation of the system within a couple of cycles. The proposed GTO-VSC based 18-pulse STATCOM seems to provide an optimized model of competitive performance in multi-pulse topology.

REFERENCES:

[1] Colin D. Schauder, “Advanced Static VAR Compensator Control System,” U.S. Patent 5 329 221, Jul. 12, 1994.

[2] Derek A. Paice, “Optimized 18-Pulse Type AC/DC, or DC/AC Converter System,” U.S. Patent 5 124 904, Jun. 23, 1992.

[3] Kenneth Lipman, “Harmonic Reduction for Multi-Bridge Converters,” U.S. Patent 4 975 822, Dec. 4, 1990.

[4] K.K. Sen, “Statcom - Static Synchronous Compensator: Theory, Modeling, And Applications,” IEEE PES WM, 1999,Vol. 2, pp. 1177 –1183.

[5] Guk C. Cho, Gu H. Jung, Nam S. Choi, et al. “Analysis and controller design of static VAR compensator using three-level GTO inverter,” IEEE Transactions Power Electronics, Vol.11, No.1, Jan 1996, pp. 57 –65.