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.

Single- and Two-Stage Inverter-Based Grid Connected Photovoltaic Power Plants With Ride-Through Capability Under Grid Faults

IEEE TRANSACTIONS ON SUSTAINABLE ENERGY, VOL. 6, NO. 3, JULY 2015

 ABSTRACT Grid-connected distributed generation sources interfaced with voltage source inverters (VSIs) need to be disconnected from the grid under: 1) excessive dc-link voltage; 2) excessive ac currents; and 3) loss of grid-voltage synchronization. In this paper, the control of single and two stage grid-connected VSIs in photovoltaic (PV) power plants is developed to address the issue of inverter disconnecting under various grid faults. Inverter control incorporates reactive power support in the case of voltage sags based on the grid codes’ (GCs) requirements to ride-through the faults and support the grid voltages. A case study of a 1-MW system simulated in MATLAB/Simulink software is used to illustrate the proposed control. Problems that may occur during grid faults along with associated remedies are discussed. The results presented illustrate the capability of the system to ride-through different types of grid faults.

 

KEYWORDS:

  1. DC–DC converter
  2. Fault-ride-through
  3. Photovoltaic (PV) systems
  4. Power system faults
  5. Reactive power support
  6. single and two stage inverter

 

SOFTWARE: MATLAB/SIMULINK

 

BLOCK DIAGRAM:

single and two stage inverter

Fig. 1. Diagram of a single-stage GCPPP

 single and two stage inverter

Fig. 2. Diagram of the two-stage conversion-based GCPPP

 

EXPECTED SIMULATION RESULTS:

Fig. 3. Short-circuiting the PV panels: (a) grid voltages; (b) grid currents; and (c) dc-link voltage when applying a 60% SLG voltage sag at MV side of the transformer.

Fig. 4. Short-circuiting the PV panels: (a) overall generated power; (b) injected active power; and (c) reactive power to the grid.

Fig. 5. Turning the dc–dc converter switch ON: (a) grid voltages; (b) grid currents; and (c) dc-link voltage when applying a 60% SLG voltage sag at the MV side.

Fig. 6. Control of the dc–dc converter to produce less power under voltage sag: (a) grid voltages; (b) grid currents; (c) dc-link voltage; (d) input voltage of the dc–dc converter; (e) estimated duty cycle; and (f) actual duty cycle under a 3LG with 45% voltage sag at MV side.

Fig. 7. Control of the dc–dc converter to produce less power under voltage sag: (a) grid voltages under a 3LG with 45% voltage sag at MV side; (b) related grid currents for G = 300 W/m2; and (c) related dc-link voltage; (d) grid voltages under an SLG with 65% voltage sag at theMV side; (e) related grid currents for G = 1000 W/m2; (f) related dc-link voltage; (g) related grid currents under G = 300 W/m2; and (h) related dc-link voltage.”

single and two stage inverter

CONCLUSION

Performance requirements of GCPPPs under fault conditions for single and two stage grid-connected inverters have been addressed in this paper. Some modifications have been proposed for controllers to make the GCPPP ride-through compatible to any type of faults according to the GCs. These modifications include applying current limiters and controlling the dc-link voltage by different methods. It is concluded that for the single-stage configuration, the dc-link voltage is naturally limited and therefore, the GCPPP is self-protected, whereas in the two-stage configuration it is not. Three methods have been proposed for the two-stage configuration to make the GCPPP able to withstand any type of faults according to the GCs without being disconnected. The first two methods are based on not generating any power from the PV arrays during the voltage sags, whereas the third method changes the power point of the PV arrays to inject less power into the grid compared with the prefault condition. The validity of all the proposed methods to ride-through voltage sags has been demonstrated by multiple case studies performed by simulations.

 

REFERENCES

  1. Trilla et al., “Modeling and validation of DFIG 3-MW wind turbine using field test data of balanced and unbalanced voltage sags,” IEEE Trans. Sustain. Energy, vol. 2, no. 4, pp. 509–519, Oct. 2011.
  2. Popat, B. Wu, and N. Zargari, “Fault ride-through capability of cascaded current-source converter-based offshore wind farm,” IEEE Trans. Sustain. Energy, vol. 4, no. 2, pp. 314–323, Apr. 2013.
  3. Marinopoulos et al., “Grid integration aspects of large solar PV installations: LVRT capability and reactive power/voltage support requirements,” in Proc. IEEE Trondheim Power Tech, Jun. 2011, pp. 1–8.
  4. Islam, A. Al-Durra, S. M. Muyeen, and J. Tamura, “Low voltage ride through capability enhancement of grid connected large scale photovoltaic system,” in Proc. 37th Annu. Conf. IEEE Ind. Electron. Soc. (IECON), Nov. 2011, pp. 884–889.

Grid-Connected PV Array with Supercapacitor Energy Storage System for Fault Ride Through

ABSTRACT:

A fault ride through, power management and control strategy for grid integrated photovoltaic (PV) system with supercapacitor energy storage system (SCESS) is presented in this paper. During normal operation the SCESS will be used to minimize the short term fluctuation as it has high power density and during fault at the grid side it will be used to store the generated power from the PV array for later use and for fault ride through. To capture the maximum available solar power, Incremental Conductance (IC) method is used for maximum power point tracking (MPPT). An independent P-Q control is implemented to transfer the generated power to the grid using a Voltage source inverter (VSI). The SCESS is connected to the system using a bi-directional buck boost converter. The system model has been developed that consists of PV module, buck converter for MPPT, buck-boost converter to connect the SCESS to the DC link. Three independent controllers are implemented for each power electronics block. The effectiveness of the proposed controller is examined on Real Time Digital Simulator (RTDS) and the results verify the superiority of the proposed approach.

KEYWORDS:

  1. Active and reactive power control
  2. Fault ride through
  3. MPPT
  4. Photovoltaic system
  5. RTDS Supercapacitor
  6. Energy storage

SOFTWARE: MATLAB/SIMULINK

 BLOCK DIAGRAM:

image001

Fig.1. Grid connected PV system with energy storage

 EXPECTED SIMULATION RESULTS:

 image002

Fig.2. Grid voltage after three phase fault is applied

image003

Fig.3. PV array power PPV with SCESS and with no energy storage

image004

Fig.4. Grid active power Pg for a three phase fault with and without energy storage

image005

Fig.5.SCESS power PSC for the applied fault on the grid side

image006

Fig.6. Grid reactive power Qg during three phase fault

image007

Fig.7. DC link voltage for the applied fault

image008

Fig.8. PV array voltage VPV during three phase fault

image009

Fig.9. MPPT output voltage Vref for the applied fault

CONCLUSION:

This paper presents grid connected PV system with supercapacitor energy storage system (SCESS) for fault ride through and to minimize the power fluctuation. Incremental conductance based MPPT is implemented to track the maximum power from the PV array. The generated DC power is connected to the grid using a buck converter, VSI, buck-boost converter with SCESS. The SCESS which is connected to the DC link controls the DC link voltage by charging and discharging process. A P-Q controller is implemented to transfer the DC link power to the grid. During normal operation the SCESS minimizes the fluctuation caused by change in irradiation and temperature. During a grid fault the power generated from the PV array will be stored in the SCESS. The SCESS supplies both active and reactive power to ride through the fault. RTDS based results have shown the validity of the proposed controller.

REFERENCES:

[1] T. Esram, P.L. Chapman, “Comparison of Photovoltaic Array Maximum Power Point Tracking Techniques,” IEEE Transaction on Energy Conversion, vol.22, no.2, pp.439-449, June 2007

[2] J. M. Enrique, E. Durán, M. Sidrach-de-Cardona, and J. M. Andújar,“Theoretical assessment of the maximum power point tracking efficiency of photovoltaic facilities with different converter topologies,” Sol. Energy, vol. 81, no. 1, pp. 31–38, Jan. 2007.

[3] W. Xiao, N. Ozog, and W. G. Dunford, “Topology study of photovoltaic interface for maximum power point tracking,” IEEE Trans. Ind. Electron., vol. 54, no. 3, pp. 1696–1704, Jun. 2007.

[4] J. L. Agorreta, L. Reinaldos, R. González, M. Borrega, J. Balda, and L. Marroyo, “Fuzzy switching technique applied to PWM boost converter operating in mixed conduction mode for PV systems,” IEEE Trans. Ind. Electron., vol. 56, no. 11, pp. 4363– 4373, Nov. 2009.

[5] A.Schneuwly, “Charge ahead [ultracapacitor technology and applications]”, IET Power Engineering Journal, vol.19, 34-37, 2005.