A Two-Level, 48-Pulse Voltage Source Converter for HVDC Systems

ABSTRACT

This paper deals with an analysis, modeling and control of a two level 48-pulse voltage source converter for High Voltage DC (HVDC) system. A set of two-level 6-pulse voltage source converters (VSCs) is used to form a 48-pulse converter operated at fundamental frequency switching (FFS). The performance of the VSC system is improved in terms of reduced harmonics level at FFS and THD (Total Harmonic Distribution) of voltage and current is achieved within the IEEE 519 standard. The performance of the VSC is studied in terms of required reactive power compensation, improved power factor and reduced harmonics distortion. Simulation results are presented for the designed two level multipulse converter to demonstrate its capability. The control algorithm is disused in detail for operating the converter at fundamental frequency switching.

KEYWORDS

Two-Level Voltage Source Converter, HVDC Systems, Multipulse, Fundamental Frequency Switching, Harmonics.

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Fig. 1 A 48-Pulse voltage source converter based HVDC system configuration

EXPECTED SIMULATION RESULTS:

Fig. 2 Steady state performance of proposed 48-pulse voltage source converter

Fig. 3 Dynamic performance of proposed 48-pulse voltage source converter

Fig. 4 Waveforms and harmonic spectra of 48-pulse covnerter (a) supply voltage (b) supply current (c) converter voltage

CONCLUSION

A 48-pulse two-level voltage source converter has been designed, modeled and controlled for back-to-back HVDC system. The transformer connections with appropriate phase shift have been used to realize a 48-pulse converter along with a control scheme using a set of two level six pulse converters. The operation of the designed converter configuration has been simulated and tested in steady sate and transient conditions which have demonstrated the quite satisfactory converter operation. The characteristic harmonics of the system has also improved by the proposed converter configuration.

REFERENCES

[1] J. Arrillaga, Y. H. Liu and N. R. Waston, “Flexible Power Transmission, The HVDC Options,” John Wiley & Sons, Ltd, Chichester, UK, 2007.

[2] Gunnar Asplund Kjell Eriksson and kjell Svensson, “DC Transmission based on Voltage Source Converter,” in Proc. of CIGRE SC14 Colloquium in South Africa 1997, pp.1-8.

[3] Y. H. Liu R. H. Zhang, J. Arrillaga and N. R. Watson, “An Overview of Self-Commutating Converters and their Application in Transmission and Distribution,” in Conf. IEEE/PES Trans. and Distr.Conf. & Exhibition, Asia and Pacific Dalian, China 2005.

[4] B. R. Anderson, L. Xu, P. Horton and P. Cartwright, “Topology for VSC Transmission,” IEE Power Engineering Journal, vol.16, no.3, pp142- 150, June 2002.

[5] G. D. Breuer and R. L. Hauth, “HVDC’s Increasing Poppularity”, IEEE Potentials, pp.18-21, May 1988.

A Two-Level 24-Pulse Voltage Source Converter with Fundamental Frequency Switching for HVDC System

ABSTRACT

This paper deals with the performance analysis of a two-level, 24-pulse Voltage Source Converters (VSCs) for High Voltage DC (HVDC) system for power quality improvement. A two level VSC is used to realize a 24-pulse converter with minimum switching loss by operating it at

fundamental frequency switching (FFS). The performance of this converter is studied on various issues such as steady state operation, dynamic behavior, reactive power compensation, power factor correction, and harmonics distortion. Simulation results are presented for a two level 24-pulse converter to demonstrate its capability.

KEYWORDS

1.      Two-Level Voltage Source Converter

2.       HVDC

3.      Multipulse

4.      Fundamental Frequency Switching

5.       Harmonics

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1 A 24-Pulse voltage source converter based HVDC system

Configuration

 EXPECTED SIMULATION RESULTS

Fig. 2 Synthesis of Stepped AC voltage waveform of 24-pulse VSC.

Fig. 3 Steady state performance of proposed 24-pulse voltage source

Converter

Fig. 4 Dynamic performance of proposed 24-pulse voltage source converter

Fig. 5 Waveforms and harmonic spectra of 24-pulse covnerter i) supply

voltage ii) supply current (iii) converter voltage

CONCLUSION

A two level, 24-pulse voltage source converter has been designed and its performance has been validated for HVDC system to improve the power quality with fundamental frequency switching. Four identical transformers have been used for phase shift and to realize a 24-pulse converter along with control scheme using a two level voltage source converter topology. The steady state and dynamic performance of the designed converter configuration has been demonstrated the quite satisfactory operation and found suitable for HVDC system. The characteristic harmonics of the converter system has also improved by the proposed converter configuration with minimum switching losses without using extra filtering requirements compared to the conventional 12-pulse thyristor converter.

REFERENCES

[1] J. Arrillaga, “High Voltage Direct Current Transmission,” 2nd Edition, IEE Power and Energy Series29, London, UK-1998.

[2] J. Arrilaga and M. Villablanca, “24-pulse HVDC conversion,” IEE Proceedings Part-C, vol. 138, no. 1, pp. 57–64, Jan. 1991..

[3] Lars Weimers, “HVDC Light: a New Technology for a better Environment,” IEEE Power Engineering Review, vol.18, no. 8, pp. 1920-1926, 1989.

[4] Vijay K. Sood, “HVDC and FACTS Controller, Applications of Static Converters in Power Systems”, Kluwar Academic Publishers, The Netherlands, 2004.

[5] Gunnar Asplund Kjell Eriksson and kjell Svensson, “DC Transmission based on Voltage Source Converters, in Proc. of CIGRE SC14 Colloquium in South Africa 1997.

A New Control Strategy for Active and Reactive Power Control of Three-Level VSC Based HVDC System

ABSTRACT

This paper presents a new control strategy for real and reactive power control of three-level multipulse voltage source converter based High Voltage DC (HVDC) transmission system operating at Fundamental Frequency Switching (FFS). A three-level voltage source converter replaces the conventional two-level VSC and it is designed for the real and reactive power control is all four quadrants operation. A new control method is developed for achieving the reactive power control by varying the pulse width and by keeping the dc link voltage constant. The steady state and dynamic performances of HVDC system interconnecting two different frequencies network are demonstrated for active and reactive powers control. Total numbers of transformers used in the system are reduced in comparison to two level VSCs. The performance of the HVDC system is also improved in terms of reduced harmonics level even at fundamental frequency switching.

KEYWORDS

1.      HVDC

2.      Voltage Source Converter

3.      Multilevel

4.      Multipulse

5.      Dead Angle (β)

SOFTWARE:  MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1 A three-level 24-Pulse voltage source converter based HVDC system

CONTROL SCHEME

Fig. 2 Control scheme of three-level VSC based HVDC system using dynamic dead angle (β) Control

EXPECTED SIMULATION RESULTS

                        

Fig. 3 Performance of rectifier station during simultaneous real and reactive power control of three-level 24-pulse VSC based HVDC system

Fig. 4 Performance of inverter station during simultaneous real and reactive power control of three-level 24-pulse VSC based HVDC system

Fig. 5 Variation of angles (δ) and (β) values of three-level 24-pulse VSC based HVDC system during simultaneous real and reactive power control

CONCLUSION

A new control method for three-level 24-pulse voltage source converter configuration has been designed for HVDC system. The performance of this 24-pulse VSC based HVDC system using the control method has been demonstrated in active power control in bidirectional, independent control of the reactive power and power quality improvement. A new dynamic dead angle (β) control has been introduced for three-level voltage source converter operating at fundamental frequency switching. In this control the HVDC system operation is successfully demonstrated and also an analysis of (β) value for various reactive power requirement and harmonic performance has been carried out in detail. Therefore, the selection of converter operation region is more flexible according to the requirement of the reactive power and power quality.

REFERENCES

[1] Gunnar Asplund, Kjell Eriksson and kjell Svensson, “DC Transmission based on Voltage Source Converters,” in Proc. Of CIGRE SC14 Colloquium in South Africa 1997, pp.1-7.

[2] “HVDC Light DC Transmission based on Voltage Source Converter,” ABB Review Manual 1998, pp. 4-9.

[3] Xiao Wang and Boon-Tech Ooi, “High Voltage Direct Current Transmission System Based on Voltage Source Converter,” in IEEEPESC’ 90 Record, vol.1, pp.325-332.

[4] Michael P. Bahrman, Jan G. Johansson and Bo A. Nilsson, “Voltage Source Converter Transmission Technologies-The Right Fit for the Applications,” in Proc. of IEEE-PES General Meeting, Toronto, Canada, July-2003, pp.1840-1847.

[5] Y. H. Liu R. H. Zhang, J. Arrillaga and N. R. Watson, “An Overview of Self-Commutating Converters and their Application in Transmission and Distribution,” in Conf. Proc of IEEE/PES T & DConf. & Exhibition, Asia and Pacific Dalian, China 2005, pp.1-7.

Analysis and Design of Three-Level, 24-Pulse Double Bridge Voltage Source Converter Based HVDC System for Active and Reactive Power Control

ABSTRACT

This paper deals with the analysis, design and control of a three-level 24-pulse Voltage Source Converter (VSC) based High Voltage Direct Current (HVDC) system. A three level VSC operating at fundamental frequency switching (FFS) is proposed with 24-pulse VSC structure to improve the power quality and reduce the converter switching losses for high power applications. The design of three-level VSC converter and system parameters such as ac inductor and dc capacitor is presented for the proposed VSC based HVDC system. It consists of two converter stations fed from two different ac systems. The active power is transferred between the stations either way. The reactive power is independently controlled in each converter station. The three-level VSC is operated at optimized dead angle (β). A coordinated control algorithm for both the rectifier and an inverter stations for bidirectional active power flow is developed based on FFS and local reactive power generation. This results in a substantial reduction in switching losses and avoiding the reactive power plant. Simulation is carried to verify the performance of the proposed control algorithm of the VSC based HVDC system for bidirectional active power flow and their independent reactive power control.

KEYWORDS

Voltage Source Converter (VSC), Three-level VSC, Fundamental Frequency Switching (FFS), HVDC System, Power Flow Control, Reactive Power Control, Power Quality, Total Harmonic Distortion (THD), Dead Angle (β).

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1 Three-level 24-pulse double bridge VSC based HVDC system

EXPECTED SIMULATION RESULTS:

Fig. 2a Performance of rectifier station during reactive power control of three level 24-pulse VSC HVDC system

Fig. 2b Performance of Inverter station during reactive power control at rectifier station of three-level 24 pulse VSC HVDC system

Fig. 2c Variation of (δ) and (α) values for rectifier and inverter Stations for reactive power variation of a three-level 24-pulse VSC HVDC system

Fig. 3a Rectifier station during active power reversal of three-level 24-pulse VSC HVDC system

Fig. 3b Inverter station during active power reversal of three-level 24-pulse VSC HVDC system

Fig. 3c Variation of (δ) and (α) values during active power reversal of three level 24-pulse VSC HVDC system.

CONCLUSION

A new three-level, 24-pulse voltage source converter based HVDC system operating at fundamental frequency switching has been designed and its model has been developed and it is successfully tested for the independent control of active and reactive powers and acceptable level harmonic requirements. The reactive power has been controlled independent of the active power at both conditions. The converter has been successfully operated in all four quadrants of active and reactive powers with the proposed control. The reversal of the active power flow has been implemented by reversing the direction of dc current without changing the polarity of dc voltage which is very difficult in conventional HVDC systems. The power quality of the HVDC system has also improved with three-level 24-pulse converter operation. The harmonic performance of this three-level, 24-pulse VSC has been observed to an equivalent to two-level 48-pulse voltage source converter.

REFERENCES

 [1] “It’s time to connect,” Technical description of HVDC Light Technology, ABB HVDC Library.

[2] J. Arrillaga, “High Voltage Direct Current Transmission,” 2nd Edition, IEE Power and Energy Series 29, London, 1998.

[3] Vijay K. Sood, “HVDC and FACTS Controllers - Applications of Static Converters in Power Systems,” Kluwer Academic Publishers, Masachusetts, 2004.

[4] J. Arrillaga, Y. H. Liu and N. R. Waston, “Flexible Power Transmission- The HVDC Options,” John Wiley & Sons, Ltd, Chichester, UK, 2007.

[5] J. Arrillaga and M. E. Villablanca, “A modified parallel HVDC convertor for 24 pulse operation,” IEEE Trans. on Power Delivery, vol. 6, no. 1, pp. 231-237, Jan 1991.

A Novel Control Method for Transformerless H-Bridge Cascaded STATCOM with Star Configuration

ABSTRACT

This paper presents a transformerless static synchronous compensator (STATCOM) system based on multilevel H-bridge converter with star configuration. This proposed control methods devote themselves not only to the current loop control but also to the dc capacitor voltage control. With regards to the current loop control, a nonlinear controller based on the passivity-based control (PBC) theory is used in this cascaded structure STATCOM for the first time. As to the dc capacitor voltage control, overall voltage control is realized by adopting a proportional resonant controller. Clustered balancing control is obtained by using an active disturbances rejection controller. Individual balancing control is achieved by shifting the modulation wave vertically which can be easily implemented in a field-programmable gate array. Two actual H-bridge cascaded STATCOMs rated at 10 kV 2 MVA are constructed and a series of verification tests are executed. The experimental results prove that H-bridge cascaded STATCOM with the proposed control methods has excellent dynamic performance and strong robustness. The dc capacitor voltage can be maintained at the given value effectively.

KEYWORDS:

Active disturbances rejection controller (ADRC), H-bridge cascaded, passivity-based control (PBC), proportional resonant (PR) controller, shifting modulation wave, static synchronous compensator (STATCOM).

SOFTWARE: MATLAB/SIMULINK

CONTROL BLOCK DIAGRAM:

Fig. 1. Control block diagram for the 10 kV 2 MVA H-bridge cascaded STATCOM.

Fig. 2. Block diagram of PBC.

EXPERIMENTAL RESULTS:

Fig. 3. Experimental results verify the effect of PBC in steady-state process. (a) Ch1: reactive current; Ch2: compensating current; Ch3: residual current of grid. (b) Ch1: reactive current; Ch2: compensating current; Ch3: residual current of grid.

Fig. 4. Experimental results show the dynamic performance of STATCOM in the dynamic process. Ch1: reactive current; Ch2: compensating current; Ch3: residual current of grid.

Fig. 5. Experimental results in the startup process and stopping process. (a) Ch1: reactive current; Ch2: compensating current; Ch3: residual current of grid. (b) Ch1: reactive current; Ch2: compensating current; Ch3: residual current of grid.

CONCLUSION

This paper has analyzed the fundamentals of STATCOM based on multilevel H-bridge converter with star configuration. And then, the actual H-bridge cascaded STATCOM rated at 10 kV 2 MVA is constructed and the novel control methods are also proposed in detail. The proposed method has the following characteristics.

1) A PBC theory-based nonlinear controller is first used in STATCOM with this cascaded structure for the current loop control, and the viability is verified by the experimental results.

2) The PR controller is designed for overall voltage control and the experimental result proves that it has better performance in terms of response time and damping profile compared with the PI controller.

3) The ADRC is first used in H-bridge cascaded STATCOM for clustered balancing control and the experimental results verify that it can realize excellent dynamic compensation for the outside disturbance.

4) The individual balancing control method which is realized by shifting the modulation wave vertically can be easily implemented in the FPGA.

The experimental results have confirmed that the proposed methods are feasible and effective. In addition, the findings of this study can be extended to the control of any multilevel voltage source converter, especially those with H-bridge cascaded structure.

REFERENCES

[1] B. Gultekin and M. Ermis, “Cascaded multilevel converter-based transmission STATCOM: System design methodology and development of a 12 kV ±12 MVAr power stage,” IEEE Trans. Power Electron., vol. 28, no. 11, pp. 4930–4950, Nov. 2013.

[2] B. Gultekin, C. O. Gerc¸ek, T. Atalik, M. Deniz, N. Bic¸er, M. Ermis, K. Kose, C. Ermis, E. Koc¸, I. C¸ adirci, A. Ac¸ik, Y. Akkaya, H. Toygar, and S. Bideci, “Design and implementation of a 154-kV±50-Mvar transmission STATCOM based on 21-level cascaded multilevel converter,” IEEE Trans. Ind. Appl., vol. 48, no. 3, pp. 1030–1045, May/Jun. 2012.

[3] S. Kouro, M. Malinowski, K. Gopakumar, L. G. Franquelo, J. Pou, J. Rodriguez, B.Wu,M. A. Perez, and J. I. Leon, “Recent advances and industrial applications of multilevel converters,” IEEE Trans. Ind. Electron., vol. 57, no. 8, pp. 2553–2580, Aug. 2010.

[4] 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.

[5] 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.