Modeling, Implementation and Performance Analysis of a Grid-Connected Photovoltaic/Wind Hybrid Power System

ABSTRACT:

This paper investigates dynamic modeling, design and control strategy of a grid-connected photovoltaic (PV)/wind hybrid power system. The hybrid power system consists of PV station and wind farm that are integrated through main AC-bus to enhance the system performance. The Maximum Power Point Tracking (MPPT) technique is applied to both PV station and wind farm to extract the maximum power from hybrid power system during variation of the environmental conditions. The modeling and simulation of hybrid power system have been implemented using Matlab/Simulink software. The effectiveness of the MPPT technique and control strategy for the hybrid power system is evaluated during different environmental conditions such as the variations of solar irradiance and wind speed. The simulation results prove the effectiveness of the MPPT technique in extraction the maximum power from hybrid power system during variation of the environmental conditions. Moreover, the hybrid power system operates at unity power factor since the injected current to the electrical grid is in phase with the grid voltage. In addition, the control strategy successfully maintains the grid voltage constant irrespective of the variations of environmental conditions and the injected power from the hybrid power system.

KEYWORDS:

  1. PV
  2. Wind
  3. Hybrid system
  4. Wind turbine
  5. DFIG
  6. MPPT control

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1. The system configuration of PV/wind hybrid power system.

 EXPECTED SIMULATION RESULTS:

(a) Solar Irradiance.

(b) PV array voltage.

(c) PV array current.

(d) A derivative of power with respect to voltage (dPpv/dVpv).

Fig. 2. Performance of PV array during the variation of solar irradiance.

(a) PV DC-link Voltage.

(b) d-q axis components of injected current from PV station.

(c) Injected active and reactive power from PV station.

(d) Grid voltage and injected current from PV station.

(e) The power factor of the inverter.

(f) Injected current from PV station.

Fig. 3. Performance of PV station during variation of the solar irradiance.

(a) Wind speed profile.

(b) The mechanical torque of wind turbine.

(c) The DC-bus voltage of DFIG.

(d) Injected active and reactive power from the wind farm.

(e) The power factor of the wind farm.

(f) Injected current from the wind farm.

Fig. 4. Performance of wind farm during variation of the wind speed.

(a) Power flow between PV station, wind farm, and hybrid power system.

(b) Injected active and reactive power from the hybrid system.

(c) PCC-bus voltage.

Fig. 5. Performance of hybrid power system at PCC-bus.

 CONCLUSION:

In this paper, a detailed dynamic modeling, design and control strategy of a grid-connected PV/wind hybrid power system has been successfully investigated. The hybrid power system consists of PV station of 1MW rating and a wind farm of 9 MW rating that are integrated through main AC-bus to inject the generated power and enhance the system performance. The incremental conductance MPPT technique is applied for the PV station to extract the maximum power during variation of the solar irradiance. On the other hand, modified MPPT technique based on mechanical power measurement is implemented to capture the maximum power from wind farm during variation of the wind speed. The effectiveness of the MPPT techniques and control strategy for the hybrid power system is evaluated during different environmental conditions such as the variations of solar irradiance and wind speed. The simulation results have proven the validity of the MPPT techniques in extraction the maximum power from hybrid power system during variation of the environmental conditions. Moreover, the hybrid power system successfully operates at unity power factor since the injected reactive power from hybrid power system is equal to zero. Furthermore, the control strategy successfully maintains the grid voltage constant regardless of the variations of environmental conditions and the injected power from the hybrid power system.

REFERENCES:

[1] H. Laabidi and A. Mami, “Grid connected Wind-Photovoltaic hybrid system,” in 2015 5th International Youth Conference on Energy (IYCE), pp. 1-8,2015.

[2] A. B. Oskouei, M. R. Banaei, and M. Sabahi, “Hybrid PV/wind system with quinary asymmetric inverter without increasing DC-link number,” Ain Shams Engineering Journal, vol. 7, pp. 579-592, 2016.

[3] R. Benadli and A. Sellami, “Sliding mode control of a photovoltaic-wind hybrid system,” in 2014 International Conference on Electrical Sciences and Technologies in Maghreb (CISTEM), pp. 1-8, 2014.

[4] A. Parida and D. Chatterjee, “Cogeneration topology for wind energy conversion system using doubly-fed induction generator,” IET Power Electronics, vol. 9, pp. 1406-1415, 2016.

[5] B. Singh, S. K. Aggarwal, and T. C. Kandpal, “Performance of wind energy conversion system using a doubly fed induction generator for maximum power point tracking,” in Industry Applications Society Annual Meeting (IAS), 2010 IEEE, 2010, pp. 1-7.

 

Improved Fault Ride Through Capability in DFIG Based Wind Turbines Using Dynamic Voltage Restorer With Combined Feed-Forward and Feed-Back Control

IEEE ACCESS, volume 5, date of current version October 25, 2017.

ABSTRACT: This paper investigates the fault ride through (FRT) capability improvement of a doubly fed induction generator (DFIG)-based wind turbine using a dynamic voltage restorer (DVR). Series compensation of terminal voltage during fault conditions using DVR is carried out by injecting voltage at the point of common coupling to the grid voltage to maintain constant DFIG stator voltage. However, the control of the DVR is crucial in order to improve the Fault Ride Through capability in the DFIG-based wind turbines. The combined feed-forward and feedback (CFFFB)-based voltage control of the DVR verifies good transient and steadystate responses. The improvement in performance of the DVR using CFFFB control compared with the conventional feed-forward control is observed in terms of voltage sag mitigation capability, active and reactive power support without tripping, dc-link voltage balancing, and fault current control. The advantage of utilizing this combined control is verified through MATLAB/Simulink-based simulation results using a 1.5-MW grid connected DFIG-based wind turbine. The results showgood transient and steady-state response and good reactive power support during both balanced and unbalanced fault conditions.

 

 KEYWORDS:

  1. Doubly-fed induction generator (DFIG)
  2. Dynamic voltage restorer (DVR)
  3. Fault Ride-Through (FRT)
  4. Low Voltage Ride Through (LVRT)
  5. Combined feed forward feedback control
  6. MPPT

 

SOFTWARE: MATLAB/SIMULINK

 

BLOCK DIAGRAM:

fault ride through

Fig. 1. Schematic Diagram of DVR with DFIG.

 

 EXPECTED SIMULATION RESULTS:

 DVR using CFFFB control

Fig 2. DVR using CFFFB control: (a) supply voltage with 35 % balanced sag in pu, (b) load voltage in pu, and (c) DVR injection voltage in Volts.

Fig. 3. (a) Active Power of DFIG with CFFFB control DVR with 35 % balanced sag in pu. (b) Reactive Power of DFIG with CFFFB control DVR with 35 % balanced sag in pu. (c) Rotor speed control of DFIG with CFFFB controlled DVR with 35 % balanced sag in pu. (d) DC-link voltage with CFFFB controlled DVR with 35 % balanced sag in pu. (e) Stator current (GSC current) of DFIG with CFFFB controlled DVR with 35 % balanced sag in pu. (f) Rotor current (RSC current) of DFIG with CFFFB controlled DVR with 35 % balanced sag in pu.

DVR using CFFFB control

Fig. 4 DVR using CFFFB control: (a) supply voltage with 35 % unbalanced sag of Phase A (in red) in pu, (b) load voltage in pu, and (c) DVR injection voltage in Volts.

Fig. 5. (a) Active Power of DFIG with CFFFB control DVR with 35 % unbalanced sag in pu. (b) Reactive Power of DFIG with CFFFB control DVR with 35 % unbalanced sag in pu. (c) Rotor speed control of DFIG with CFFFB controlled DVR with 35 % unbalanced sag in pu. (d) DC-link voltage with CFFFB controlled DVR with 35 % unbalanced sag in pu. (e) Stator current (GSC current) of DFIG with CFFFB controlled DVR with 35 % unbalanced sag in pu. (f) Rotor current (RSC current) of DFIG with CFFFB controlled DVR with 35 % unbalanced sag in pu.

 DVR using CFFFB control

Fig. 6. DVR using CFFFB control: (a) supply voltage with short circuit three phase to ground fault in pu, (b) load voltage in pu, and (c) DVR injection voltage in Volts.

 DVR using CFFFB control

Fig. 7 (a) Active Power of DFIG with CFFFB control DVR with short circuit three phase to ground fault in pu. (b) Reactive Power of DFIG with CFFFB control DVR with short circuit three phase to ground fault in pu (c) Rotor speed control of DFIG with CFFFB controlled DVR with short circuit three phase to ground fault in pu. (d) DC-link voltage with CFFFB controlled DVR with short circuit three phase to ground fault in pu. (e) Stator current (GSC current) of DFIG with CFFFB controlled DVR with short circuit three phase to ground fault in pu. (f) Rotor current (RSC current) of DFIG with CFFFB controlled DVR with short circuit three phase to ground fault in pu.

Fig. 8 Harmonic spectrum of DVR Load voltage with Feed Forward control shows THDD5.24 %.

Fig. 9 Harmonic spectrum of DVR Load voltage with CFFFB control shows THDD4.47 %.

  

CONCLUSION:

This paper investigates the performance of DVR with combined Feed-Forward and Feed-Back control for the FRT capability improvement in DFIG based wind turbines. Series compensation scheme using DVR proves to be very effective with good reactive power compensation scheme, voltage control and power flow control. The performance comparison suggests that the operation of DVR is a good suit for improving FRT capability in DFIG based variable speed wind turbines as per grid code standards. The investigated combined Feed Forward and Feed Back (CFFFB) control has many advantages like simplicity with limited controller complexity. The controller is used to investigate the improvement in performance of Fault Ride Through capability operation in DFIG wind turbine while modifying the voltage control of a DVR. The DVR proves to deliver very good transient voltage control, fault current control and reactive power support. The controller contributes in better harmonic compensation compared to conventional control as per IEEE 519 standards. The simulation results performed using a 1.5 MW DFIG based wind turbine connected to electrical grid show better performance of DVR with the combined Feed-Forward and Feed-Back control for improving the Fault Ride Through capability of DFIG based wind turbines.

 

REFERENCES:

  • A. J. Amalorpavaraj, K. Palanisamy, S. Umashankar, and A. D. Thirumoorthy, “Power quality improvement of grid connected wind farms through voltage restoration using dynamic voltage restorer,” Int. J. Renew. Energy Res., vol. 6, no. 1, pp. 53_60, Mar. 2016.
  • A. J. Amalorpavaraj, P. Kaliannan, and U. Subramaniam, “Improved fault ride through capability of DFIG based wind turbines using synchronous reference frame control based dynamic voltage restorer,” ISA Trans., vol. 70, no. 1, pp. 465_474, Jul. 2017.
  • Morren and S. W. H. D. Haan, “Ridethrough of wind turbines with doubly-fed induction generator during a voltage dip,” IEEE Trans. Energy Convers., vol. 20, no. 2, pp. 435_441, Jun. 2005.
  • Holdsworth, X. G. Wu, J. B. Ekanayake, and N. Jenkins, “Comparison of _xed speed and doubly-fed induction wind turbines during power system disturbances,” IEE Proc.-Gen. Transmiss. Distrib., vol. 150, no. 3, pp. 343_352, May 2003.
  • D. Hansen and G. Michalke, “Fault ride-through capability of DFIG wind turbines,” Renew. Energy, vol. 32, no. 9, pp. 1594_1610, Jul. 2007.

Modeling and Control of Multi-Terminal HVDC with Offshore Wind Farm Integration and DC Chopper Based Protection Strategies

2013, IEEE

ABSTRACT: Multi-Terminal HVDC based on three-level neutral-clamped voltage source converters (VSC) is an ideal approach for the integration of DFIG wind farms to the power grid. However, dc-link faults and ac faults are major concerns for the safety and consistency of VSC-HVDC system. This paper demonstrates methods employing both full bridge and half bridge DC-DC converters for the fast clearance and protection of dc and ac ground faults respectively. In addition, control strategies incorporating decoupling control and feed-forward compensation on both grid side and wind farm side VSCs are also presented. Normal operations are observed to examine the performance of the MT-HVDC system, and also dc-link fault and three-phase ground fault at inverter side are simulated to verify the effectiveness of the approach employing DC-DC converters to suppress dc current overshoot in case of dc-link fault and mitigate dc voltage overshoot during three-phase ac ground fault. This proposed MT-HVDC transmission system and the fault-ride through capabilities provided by the dc choppers is validated by the simulation studies using detailed Matlab/Simulink model for normal operation, dc and ac ground faults.

KEYWORDS:

  1. VSC-HVDC
  2. DFIG
  3. DC chopper
  4. Faults

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

 Fig. 1 Topology of the proposed multi-terminal VSC-HVDC system.

 EXPECTED SIMULATION RESULTS:

 

 Fig. 2 Simulation results of MT-HVDC during normal operation: (a) active power of wind farm, (b) dc voltage, and (c) ac rms current.

Fig. 3 Simulation results of 6 DFIG units during normal operation: (a) active power, (b) reactive power, (c) ac rms voltage, and (d) back-to-back dc-link voltage of DFIG unit.

Fig. 4 Simulation results of MT-HVDC during dc pole-to-pole fault with and without full bridge dc chopper protection: (a) dc voltage, and (b) dc current.

Fig. 5 Simulation results of MT-HVDC during three-phase ac ground fault at inverter side with and without half bridge dc chopper protection: (a) ac rms voltage at inverter side, (b) dc voltage overshoot without protection measures, and (c) dc voltage with protection measures.

CONCLUSION:

This paper investigates a multi-terminal VSC-HVDC system, which integrates two DFIG wind farms to the ac grid. The control strategies of both WFVSC and GSVSC stations are discussed in detail, and two approaches employing both full bridge and half bridge dc choppers are extended and displayed. Simulation studies are carried out in normal, dc pole-to-pole and ac ground fault operations, and the result verifies the effectiveness of the proposed MT-HVDC system in both the performance of wind power delivery and the protection measures for various fault conditions. Specifically, the dc voltage drop and dc current overshoot are eliminated during dc fault with full bridge dc choppers, while only a 8% voltage overshoot is observed with the implementation of half bridge dc choppers in case of three-phase ac ground fault.

REFERENCES:

[1] S. G. Hernandez, E. M. Goytia and O. A. Lara, “Analysis of wide area integration of dispersed wind farms using multiple VSC-HVDC links,” in Proc. of EPE, Sevilla, pp. 17-26, 2008.

[2] S. Towito, M. Berman, G. Yehuda and R. Rabinvici, “Distribution generation case study: electric wind farm doubly fed induction generators”, in Proc. Convention of Electrical and Electronics Engineering(CEEE), Israel, pp. 393-397, Nov. 2006.

[3] N. Flourentzou, V. G. Agelidis, and G. D. Demetriades, “VSC-based HVDC power transmission systems: an overview,” IEEE Trans. Power Electron., vol. 24, no. 3, pp. 592-602, Mar. 2009.

[4] L. Xu, L. Yao, and C. Sasse, “Grid integration of large DFIG-based wind farms ssing VSC transmission,” IEEE Trans. Power Syst., vol. 22, no. 3, pp.976-984, Aug. 2007.

 

Modeling and Control of Multi-Terminal HVDC with Offshore Wind Farm Integration and DC Chopper Based Protection Strategies

 

ABSTRACT:

Multi-Terminal HVDC based on three-level neutral-clamped voltage source converters (VSC) is an ideal approach for the integration of DFIG wind farms to the power grid. However, dc-link faults and ac faults are major concerns for the safety and consistency of VSC-HVDC system. This paper demonstrates methods employing both full bridge and half bridge DC-DC converters for the fast clearance and protection of dc and ac ground faults respectively. In addition, control strategies incorporating decoupling control and feed-forward compensation on both grid side and wind farm side VSCs are also presented. Normal operations are observed to examine the performance of the MT-HVDC system, and also dc-link fault and three-phase ground fault at inverter side are simulated to verify the effectiveness of the approach employing DC-DC converters to suppress dc current overshoot in case of dc-link fault and mitigate dc voltage overshoot during three-phase ac ground fault. This proposed MT-HVDC transmission system and the fault-ride through capabilities provided by the dc choppers is validated by the simulation studies using detailed Matlab/Simulink model for normal operation, dc and ac ground faults.

KEYWORDS:

  1. VSC-HVDC
  2. DFIG
  3. DC chopper
  4. Faults

 SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

Fig. 1 Topology of the proposed multi-terminal VSC-HVDC system.

EXPECTED SIMULATION RESULTS:

 

Fig. 2 Simulation results of MT-HVDC during normal operation: (a) active power of wind farm, (b) dc voltage, and (c) ac rms current.

Fig. 3 Simulation results of 6 DFIG units during normal operation: (a) active power, (b) reactive power, (c) ac rms voltage, and (d) back-to-back dc-link voltage of DFIG unit.

Fig. 4 Simulation results of MT-HVDC during dc pole-to-pole fault with and without full bridge dc chopper protection: (a) dc voltage, and (b) dc current.

Fig. 5 Simulation results of MT-HVDC during three-phase ac ground fault at inverter side with and without half bridge dc chopper protection: (a) ac rms voltage at inverter side, (b) dc voltage overshoot without protection measures, and (c) dc voltage with protection measures.

CONCLUSION:

This paper investigates a multi-terminal VSC-HVDC system, which integrates two DFIG wind farms to the ac grid. The control strategies of both WFVSC and GSVSC stations are discussed in detail, and two approaches employing both full bridge and half bridge dc choppers are extended and displayed. Simulation studies are carried out in normal, dc pole-to-pole and ac ground fault operations, and the result verifies the effectiveness of the proposed MT-HVDC system in both the performance of wind power delivery and the protection measures for various fault conditions. Specifically, the dc voltage drop and dc current overshoot are eliminated during dc fault with full bridge dc choppers, while only a 8% voltage overshoot is observed with the implementation of half bridge dc choppers in case of three-phase ac ground fault.

REFERENCES:

[1] S. G. Hernandez, E. M. Goytia and O. A. Lara, “Analysis of wide area integration of dispersed wind farms using multiple VSC-HVDC links,” in Proc. of EPE, Sevilla, pp. 17-26, 2008.

[2] S. Towito, M. Berman, G. Yehuda and R. Rabinvici, “Distribution generation case study: electric wind farm doubly fed induction generators”, in Proc. Convention of Electrical and Electronics Engineering(CEEE), Israel, pp. 393-397, Nov. 2006.

[3] N. Flourentzou, V. G. Agelidis, and G. D. Demetriades, “VSC-based HVDC power transmission systems: an overview,” IEEE Trans. Power Electron., vol. 24, no. 3, pp. 592-602, Mar. 2009.

[4] L. Xu, L. Yao, and C. Sasse, “Grid integration of large DFIG-based wind farms ssing VSC transmission,” IEEE Trans. Power Syst., vol. 22, no. 3, pp.976-984, Aug. 2007.

[5] L. Weimers, “HVDC Light: A new technology for a better environment”, IEEE Power Eng. Review, vol. 18, no. 8, pp.19-20, Aug. 1998.

Dynamic Behavior of DFIG Wind Turbine Under Grid Fault Conditions

 

ABSTRACT:

The use of doubly fed induction generators (DFIGs) in wind turbines has become quite common over the last few years. These machines provide variable speed and are driven with a power converter which is sized for a small percentage of the turbine-rated power. This paper presents a detailed model of induction generator coupled to wind turbine system. Modeling and simulation of induction machine using vector control computing technique is done. DFIG wind turbine is an integrated part of distributed generation system. Therefore, any abnormalities associates with grid are going to affect the system performance considerably. Taking this into account, the performance of DFIG variable speed wind turbine under network fault is studied using simulation developed in MATLAB/SIMULINK.

KEYWORDS

  1. DFIG
  2. DQ Model
  3. Vector Control

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Fig. 1 Simulink model of DFIG system

EXPECTED SIMULATION RESULTS:

 Time (sec)

 Fig. 2 Stator currents during balance condition

Time (sec)

Fig. 3 Rotor currents during balance condition

   Time (sec)

Fig. 4 Speed and torque during balance condition.

Time (sec)

Fig. 5 Acive and reactive power during balance condition

CONCLUSION:

This paper presents a study of the dynamic performance of variable speed DFIG coupled with wind turbine. The dynamic behavior of DFIG under power system disturbance was simulated using MATLAB/SIMULINK.Accurate transient simulations are required to investigate the influence of the wind power on the power system stability. The DFIG considered in this analysis is a wound rotor induction generator with slip rings. The stator is directly connected to the grid and the rotor is interface via a back to back power converter. Power converter are usually controlled utilizing vector control techniques which allow the decoupled control of both active and reactive power flow to the grid. In the present investigation, the dynamic DFIG performance is presented for both normal and abnormal grid conditions. The control performance of DFIG is satisfactory in normal grid conditions and it is found that, both active and reactive power maintains a study pattern in spite of fluctuating wind speed and net electrical power supplied to grid is maintained constant.

REFERENCES:

[1] T. Brekken, and N. Mohan, “A novel doubly-fed induction wind generator control scheme for reactive power control and torque pulsation compensation under unbalanced grid voltage conditions”, IEEE PESC Conf Proc., Vol 2, pp. 760-764, 2003.

[2] L. Xu and Y. Wang, “Dynamic modeling and control of DFIG-based wind turbines under unbalanced network conditions”, IEEE Trans. On Power System, Vol 22, Issues 1, pp. 314-323, 2007.

[3] F.M. Hughes, O. Anaya-Lara, N. Jenkins, and G. Strbac, “Control of DFIG based wind generation for power network support”, IEEE Trans. On Power Systems, Vol 20, pp. 1958-1966, 2005.

[4] S. Seman, J. Niiranen, S. Kanerva, A. Arkkio, and J. Saitz, “Performance study of a doubly fed wind-power induction generator Under Network Disturbances”, IEEE Trans. on Energy Conversion, Vol 21, pp. 883-890, 2006.

[5] T. Thiringer, A. Petersson, and T. Petru, “Grid disturbance response of wind turbines equipped with induction generator and doubly-fed induction generator”, in Proc. IEEE Power Engineering Society General Meeting, Vol 3, pp. 13-17, 2003.