Offshore Wind Farm Power Control Using HVdc Link Control de puissance d’un parc éolien en mer utilisant la liaison CCHT

ABSTRACT:

In this paper, a method is presented to control offshore wind farm output power. This method is able to fix the wind farm output power even during wind speed variations. In the proposed method, the offshore wind farm is connected to the onshore grid through the high-voltage dc (HVdc) cable. Moreover, the power control of the wind turbines is achieved by controlling the HVdc convertors. In the proposed system, the generator side convertors have to control the active power absorbed from the wind, and the grid side ones are obtained to control the HVdc link voltage. The control system is based on applying the appropriate modulation index to the voltage source converters. Two control strategies are proposed and analyzed to control wind farm output power. The simulation results illustrate that the proposed method is able to smooth the output power of the offshore wind farms appropriately. The proposed wind farm configuration and the control system are validated by simulations in the MATLAB/Simulink environment.

KEYWORDS:

  1. Current source inverter (CSI)
  2. Offshore wind farm
  3. Permanent magnet synchronous generator (PMSG)
  4. PQ-bus
  5. Voltage source converter (VSC)

 SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Fig. 1. Proposed configuration of wind turbines connection.

 EXPECTED SIMULATION RESULTS:

 

 Fig. 2. (a) Wind speed variations (m/s). (b) Turbine rotational speed (rad/s).

(c) Turbine efficiency.

Fig. 3. HVdc link voltage.

Fig. 4. Wind farm output power.

CONCLUSION:

In this paper, the configuration and control methods have been proposed for the offshore wind turbines, connected to the onshore grid. This method is capable to control and smooth the wind farm output power, injected to the onshore grid. The proposed system can mitigate the fluctuations of wind farm output power, even during wind speed variations. In other words, the wind farm can operate such as a PQ-bus. Moreover, two strategies (fixed power and MPPT) have been analyzed and compared with each other. Finally, the proposed method is compared with other similar works to smooth the output power of the wind farm. The main result is that the proposed method can smooth the output power better than the TSR, PAC, and OTC methods. But it is a bit weaker than the KEC method in power smoothing issue. Moreover, using this method, the wind farm is able to cooperate in frequency control of the onshore grid by controlling the desired active power, to improve the power system operation, which is the future work of the authors.

REFERENCES:

[1] J. O. Dabiri, “Potential order-of-magnitude enhancement of wind farm power density via counter-rotating vertical-axis wind turbine arrays,” J. Renew. Sustain. Energy, vol. 3, no. 4, p. 043104, 2011.

[2] J. Hua, “A floating platform of concrete for offshore wind turbine,” J. Renew. Sustain. Energy, vol. 3, no. 6, p. 063103, 2011.

[3] A. Urtasun, P. Sanchis, I. S. Martín, J. López, and L. Marroyo, “Modeling of small wind turbines based on PMSG with diode bridge for sensorless maximum power tracking,” Renew. Energy, vol. 55, pp. 138–149, Jul. 2012.

[4] (2007). Global Wind and Energy Council, Market Forecast 2010- 2014. [Online]. Available: http://www.gwec.net/fileadmin/documents/ Publications/GlobalWind2007report/market/forecast%2020102014

[5] M. Kesraoui, N. Korichi, and A. Belkadi, “Maximum power point tracker of wind energy conversion system,” Renew. Energy, vol. 4, no. 10, pp. 2655–2662, 2011.

Multiconverter Unified Power-Quality Conditioning System: MC-UPQC

 

ABSTRACT:

This paper presents a new unified power-quality conditioning system (MC-UPQC), capable of simultaneous compensation for voltage and current in multibus/multifeeder systems. In this configuration, one shunt voltage-source converter (shunt VSC) and two or more series VSCs exist. The system can be applied to adjacent feeders to compensate for supply-voltage and load current imperfections on the main feeder and full compensation of supply voltage imperfections on the other feeders. In the proposed configuration, all converters are connected back to back on the dc side and share a common dc-link capacitor. Therefore, power can be transferred from one feeder to adjacent feeders to compensate for sag/swell and interruption. The performance of the MC-UPQC as well as the adopted control algorithm is illustrated by simulation. The results obtained in PSCAD/EMTDC on a two-bus/two-feeder system show the effectiveness of the proposed configuration.

KEYWORDS:

  1. Power quality (PQ)
  2. PSCAD/EMTDC
  3. Unified power-quality conditioner (UPQC)
  4. Voltage-source converter (VSC)

 SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Fig. 1. Typical MC-UPQC used in a distribution system.

Fig. 2. Control block diagram of the shunt VSC.

Fig. 3. Control block diagram of the series VSC.

EXPECTED SIMULATION RESULTS:

Fig. 4. BUS2 voltage, series compensating voltage, and load voltage in Feeder2.

Fig. 5. Nonlinear load current, compensating current, Feeder1 current, and capacitor voltage.

Fig. 6. Simulation results for an upstream fault on Feeder2: BUS2 voltage, compensating voltage, and loads L1 and L2 voltages.

Fig. 7. Simulation results for load change: nonlinear load current, Feeder1 current, load L1 voltage, load L2 voltage, and dc-link capacitor voltage.

Fig. 8. BUS1 voltage, series compensating voltage, and load voltage in Feeder1 under unbalanced source voltage.

 CONCLUSION:

In this paper, a new configuration for simultaneous compensation of voltage and current in adjacent feeders has been proposed. The new configuration is named multi converter unified power-quality conditioner (MC-UPQC). Compared to a conventional UPQC, the proposed topology is capable of fully protecting critical and sensitive loads against distortions, sags/swell, and interruption in two-feeder systems. The idea can be theoretically extended to multibus/multifeeder systems by adding more series VSCs. The performance of the MC-UPQC is evaluated under various disturbance conditions and it is shown that the proposed MC-UPQC offers the following advantages:

1)  power transfer between two adjacent feeders for sag/swell and interruption compensation;

2) compensation for interruptions without the need for a battery storage system and, consequently, without storage capacity limitation;

3) sharing power compensation capabilities between two adjacent feeders which are not connected.

REFERENCES:

[1] D. D. Sabin and A. Sundaram, “Quality enhances reliability,” IEEE Spectr., vol. 33, no. 2, pp. 34–41, Feb. 1996.

[2] M. Rastogi, R. Naik, and N. Mohan, “A comparative evaluation of harmonic reduction techniques in three-phase utility interface of power electronic loads,” IEEE Trans. Ind. Appl., vol. 30, no. 5, pp. 1149–1155, Sep./Oct. 1994.

[3] F. Z. Peng, “Application issues of active power filters,” IEEE Ind. Appl. Mag., vol. 4, no. 5, pp. 21–30, Sep../Oct. 1998.

[4] H. Akagi, “New trends in active filters for power conditioning,” IEEE Trans. Ind. Appl., vol. 32, no. 6, pp. 1312–1322, Nov./Dec. 1996.

[5] L. Gyugyi, C. D. Schauder, S. L. Williams, T. R. Rietman, D. R. Torjerson, 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.

Implementation of Adaptive Filter in Distribution Static Compensator

 

ABSTRACT:

This paper presents an implementation of an adaptive filter in a three-phase distribution static compensator (DSTATCOM) used for compensation of linear/nonlinear loads in a three-phase distorted voltage ac mains. The proposed filter, which is based on adaptive synchronous extraction, is used for extraction of fundamental active- and reactive-power components of load currents in estimating the reference supply currents. This control algorithm is implemented on a developed DSTATCOM for reactive-power compensation, harmonics elimination, load balancing, and voltage regulation under linear and nonlinear loads. The performance of DSTATCOM is observed satisfactory under unbalanced time-varying loads.

KEYWORDS

  1. Adaptive filter (AF)
  2. distribution static compensator (DSTATCOM)
  3. harmonics
  4. load balancing
  5. sinusoidal tracking algorithm
  6. voltage-source converter (VSC)

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Fig.1. Schematic of three-leg DSTATCOM.

EXPECTED SIMULATION RESULTS:

(a)

(b)

                                                             (c)

Fig. 2. (a), (b), and (c) Various intermediate signals of the control algorithm at load injection. (a) Ch. 1 and 2: 200 V/div; Ch. 3 and 4: 20 A/div; Time axis: 50 ms/div. (b) Ch. 1, 2, 3, and 4: 20 A/div; Time axis: 20 ms/div. (c) Ch. 1, 2,3, and 4: 20 A/div; Time axis: 20 ms/div.

 Fig. 3. Steady-state performance of DSTATCOM at linear lagging PF load in PFC mode. (a) Ps. (b) PL. (c) Pc. (d) vab, isa. (e) vbc, isb. (f) vca, isc.

Fig. 4. Steady-state performance of DSTATCOM at nonlinear loads in PFC mode. (a) vab, isa. (b) vbc, isb. (c) vca, isc. (d) Harmonic spectrum of isa. (e) vab, iLa. (f) Harmonic spectrum of iLa.

Fig. 5. Dynamic performance of DSTATCOM at unbalanced linear loads. (a) vab, isa, isb, isc. (b) vab, iLa, iLb, iLc. (c) vdc, isa, iCa, iLa.

Fig. 6. Dynamic performance of DSTATCOM at unbalanced nonlinear loads. (a) vab, isa, isb, isc. (b) vab, iLa, iLb, iLc. (c) vdc, isa, iCa, iLa

Fig. 7. Steady-state performance of DSTATCOM at linear lagging PF load in ZVR mode. (a) Ps. (b) PL. (c) Pc. (d) vab, isa. (e) vbc, isb. (f) vca, isc.

Fig. 8. Steady-state performance of DSTATCOM at nonlinear load in ZVR mode. (a) vab, isa. (b) vbc, isb. (c) vca, isc. (d) Harmonic spectrum of isa. (e) Harmonic spectrum of iLa. (f) iCa. (g) Ps. (h) PL.

Fig. 9. Variation of Vt, isa, and iLa with vdc under unbalanced linear loads.

 CONCLUSION:

 A DSTATCOM has been implemented for a three-phase distribution system. An AF has been used for control of DSTATCOM. This AF has been found simple and easy to implement, and its performance has been observed satisfactory with nonsinusoidal and distorted voltages of ac mains under load variation. The performance of DSTATCOM with its AF has been demonstrated for harmonics elimination, reactivepower compensation, and load balancing with self-supporting dc link in PFC and ZVR modes. The dc-link voltage of the DSTATCOM has been also regulated to a desired value under time-varying load conditions.

 REFERENCES:

 [1] E. F. Fuchs and M. A. S. Mausoum, Power Quality in Power Systems and Electrical Machines. London, U.K.: Elsevier, 2008.

[2] H. Akagi, E. H. Watanabe, and M. Aredes, Instantaneous Power Theory and Applications to Power Conditioning. Hoboken, NJ, USA: Wiley, 2007.

[3] A. Emadi, A. Nasiri, and S. B. Bekiarov, Uninterruptible Power Supplies and Active Filters. Boca Raton, FL, USA: CRC Press, 2005.

[4] J. Jacobs, D. Detjen, C. U. Karipidis, and R. W. De Doncker, “Rapid prototyping tools for power electronic systems: Demonstration with shunt active power filters,” IEEE Trans. Power Electron., vol. 19, no. 2, pp. 500– 507, Mar. 2004.

[5] A. Ghosh and G. Ledwich, Power Quality Enhancement Using Custom Power Devices. New Delhi, India: Springer Int. Edition, 2009.

Dynamic Modeling of Microgrid for Grid Connected and Intentional Islanding Operation

 

 ABSTRACT:

 Microgrid is defined as the cluster of multiple distributed generators (DGs) such as renewable energy sources that supply electrical energy. The connection of microgrid is in parallel with the main grid. When microgrid is isolated from remainder of the utility system, it is said to be in intentional islanding mode. In this mode, DG inverter system operates in voltage control mode to provide constant voltage to the local load. During grid connected mode, the Microgrid operates  in constant current control mode to supply preset power to the main grid. The main contribution of this paper is summarized as

  • Design of a network based control scheme for inverter based sources, which provides proper current control during grid connected mode and voltage control during islanding
  • Development of an algorithm for intentional islanding detection and synchronization controller required during grid
  • Dynamic modeling and simulation are conducted to show system behavior under proposed method using

From the simulation results using Simulink dynamic models, it can be shown that these controllers provide the microgrid with a deterministic and reliable connection to the grid.

 KEYWORDS:

  1. Distributed generation (DG)
  2. grid connected operation
  3. intentional islanding operation and islanding detection
  4. Microgrid

SOFTWARE: MATALAB/SIMULINK

BLOCK DIAGRAM:

Fig.1. Dynamic model of microgrid with controller.

EXPECTED SIMULATION RESULTS:

Fig. 2. Line Current without current controller

Fig.3. Line Voltage without Voltage controller

Fig. 4. Line Voltage with voltage controller

Fig. 5. Phase voltage waveform (a) without re-closure controller (b) with re-closure controller

Fig. 6. Synchronization for grid reconnection (a) without re-closure algorithm (b) with re-closure algorithm

CONCLUSION:

Current and voltage Control techniques have been developed for grid connected and intentional islanding modes of operation using PI controllers. An intentional islanding detection algorithm responsible for switching between current control and voltage control is developed using logical operations and proved to be effective. The reconnection algorithm coupled with the synchronization controller enabled the DG to synchronize itself with the grid during grid reconnection. The performance of the microgrid with the proposed controllers and algorithms  has been analyzed by conducting simulation on dynamic model using SIMULINK. The simulation results presented here confirms the effectiveness of the control scheme.

REFERENCES:

[1] L. Shi, M.Y. Lin Chew. “A review on sustainable design of renewable energy systems,” science direct journal present in Renewable and Sustainable Energy Reviews, Vol. 16, Issue 1, 2012, pp. 192–207.

[2] Q. Lei, Fang Zheng Peng, Shuitao Yang. “Multi loop control method for high performance microgrid inverter through load voltage and current decoupling with only output voltage feedback,” IEEE Trans. power. Electron, vol. 26, no. 3, 2011, pp. 953–960.

[3] J. Selvaraj and N. A. Rahim, “Multilevel inverter for grid-connected PV system employing digital PI controller,” IEEE Trans. Ind. Electron., vol. 56, no. 1, 2009, pp. 149–158.

[4] I. J. Balaguer, Fang Zheng Peng, Shuitao Yang, Uthane Supatti Qin Lei. “Control for grid connected and intentional islanding modes of operations of distributed power generation,” IEEE Trans. Ind. Electron., vol. 56, no. 3, 2009, pp. 726–736.

[5] R. J. Azevedo, G.I. Candela, R. Teodorescu, P.Rodriguez , I.E-Otadui “Microgrid connection management based on an intelligent connection agent,” 36th annual conference on IEEE industrial electronics society, 2010, pp. 3028–3033.

A Control Technique for Integration of DG Units to the Electrical Networks

ABSTRACT:

This paper deals with a multi objective control technique for integration of distributed generation (DG) resources to the electrical power network. The proposed strategy provides compensation for active, reactive, and harmonic load current components during connection of DG link to the grid. The dynamic model of the proposed system is first elaborated in the stationary reference frame and then transformed into the synchronous orthogonal reference frame. The transformed variables are used in control of the voltage source converter as the heart of the interfacing system between DG resources and utility grid. By setting an appropriate compensation current references from the sensed load currents in control circuit loop of DG, the active, reactive, and harmonic load current components will be compensated with fast dynamic response, thereby achieving sinusoidal grid currents in phase with load voltages, while required power of the load is more than the maximum injected power of the DG to the grid. In addition, the proposed control method of this paper does not need a phase-locked loop in control circuit and has fast dynamic response in providing active and reactive power components of the grid-connected loads. The effectiveness of the proposed control technique in DG application is demonstrated with injection of maximum available power from the DG to the grid, increased power factor of the utility grid, and reduced total harmonic distortion of grid current through simulation and experimental results under steady-state and dynamic operating conditions.

KEYWORDS:

  1. Digital signal processor
  2. Distributed generation (DG)
  3. Renewable energy sources
  4. Total harmonic distortion (THD)
  5. voltage source converter (VSC)

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

image001

Fig. 1. General schematic diagram of the proposed control strategy for DG system.

 EXPECTED SIMULATION RESULTS:

image002

Fig. 2. Load voltage, load, grid, and DG currents before and after connection of DG and before and after connection and disconnection of additional load into the grid.

image003

Fig. 3. Grid, load, DG currents, and load voltage (a) before and after connection of additional load and (b) before and after disconnection of additional load.

image004

Fig. 4. Phase-to-neutral voltage and grid current for phase (a).

image005

Fig. 5. Reference currents track the load current (a) after interconnection of DG resources and (b) after additional load increment.

image006

Fig. 6. Load voltage, load, grid, and DG currents during connection of DG link to the unbalanced grid voltage.

CONCLUSION:

A multi objective control algorithm for the grid-connected converter-based DG interface has been proposed and presented in this paper. Flexibility of the proposed DG in both steady-state and transient operations has been verified through simulation and experimental results.

Due to sensitivity of phase-locked loop to noises and distortion, its elimination can bring benefits for robust control against distortions in DG applications. Also, the problems due to synchronization between DG and grid do not exist, and DG link can be connected to the power grid without any current overshoot. One other advantage of proposed control method is its fast dynamic response in tracking reactive power variations; the control loops of active and reactive power are considered independent. By the use of the proposed control method, DG system is introduced as a new alternative for distributed static compensator in distribution network. The results illustrate that, in all conditions, the load voltage and source current are in phase and so, by improvement of power factor at PCC, DG systems can act as power factor corrector devices. The results indicate that proposed DG system can provide required harmonic load currents in all situations. Thus, by reducing THD of source current, it can act as an active filter. The proposed control technique can be used for different types of DG resources as power quality improvement devices in a customer power distribution network.

REFERENCES:

[1] T. Zhou and B. François, “Energy management and power control of a hybrid active wind generator for distributed power generation and grid integration,” IEEE Trans. Ind. Electron., vol. 58, no. 1, pp. 95–104, Jan. 2011.

[2] M. Singh, V. Khadkikar, A. Chandra, and R. K. Varma, “Grid interconnection of renewable energy sources at the distribution level with power quality improvement features,” IEEE Trans. Power Del., vol. 26, no. 1, pp. 307–315, Jan. 2011.

[3] M. F. Akorede, H. Hizam, and E. Pouresmaeil, “Distributed energy resources and benefits to the environment,” Renewable Sustainable Energy Rev., vol. 14, no. 2, pp. 724–734, Feb. 2010.

[4] C. Mozina, “Impact of green power distributed generation,” IEEE Ind. Appl. Mag., vol. 16, no. 4, pp. 55–62, Jun. 2010.

[5] B. Ramachandran, S. K. Srivastava, C. S. Edrington, and D. A. Cartes, “An intelligent auction scheme for smart grid market using a hybrid immune algorithm,” IEEE Trans. Ind. Electron., vol. 58, no. 10, pp. 4603–4611, Oct. 2011.

 

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: 1

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

 

CONTROL SCHEME

2

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

EXPECTED SIMULATION RESULTS

3

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

4

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

5

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:

image001

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

 

EXPECTED SIMULATION RESULTS:

image002

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

image003

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

image004

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

image005

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

image006

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

image007

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.