The application of a dynamic voltage restorer (DVR) connected to a wind-turbine-driven doubly fed induction generator (DFIG) is investigated. The setup allows the wind turbine system an uninterruptible fault ride-through of voltage dips. The DVR can compensate the faulty line voltage, while the DFIG wind turbine can continue its nominal operation as demanded in actual grid codes. Simulation results for a 2 MW wind turbine and measurement results on a 22 kW laboratory setup are presented, especially for asymmetrical grid faults. They show the effectiveness of the DVR in comparison to the low-voltage ride-through of the DFIG using a crowbar that does not allow continuous reactive power production.

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Fault Ride-Through of a DFIG Wind Turbine Using a Dynamic Voltage Restorer During Symmetrical and Asymmetrical Grid Faults

A comprehensive review of dynamic voltage restorers

With the deregulation of the electric power energy market, providing quality power has become an important concern of both power suppliers and customers. Efforts have been made to improve the power quality using passive filters, active power filters, hybrid filters and the new concept of custom power. This paper presents a comprehensive review of compensating custom power devices mainly DSTATCOM (distribution static compensator), DVR (dynamic voltage restorer) and UPQC (unified power quality compensator). It is aimed at providing a broad perspective on the status of compensating devices in electric power distribution system to researchers and application engineers dealing with power quality problems. Classified references presented in this paper would serve quick and useful applications.

A Review of Compensating Type Custom Power Devices for Power Quality Improvement

Fault ride through (FRT) capability in wind turbines to maintain the grid stability during faults has become mandatory with the increasing grid penetration of wind energy. Doubly fed induction generator based wind turbine (DFIG-WT) is the most popularly utilized type of generator but highly susceptible to the voltage disturbances in grid. Dynamic voltage restorer (DVR) based external FRT capability improvement is considered. Since DVR is capable of providing fast voltage sag mitigation during faults and can maintain the nominal operating conditions for DFIG-WT. The effectiveness of the DVR using Synchronous reference frame (SRF) control is investigated for FRT capability in DFIG-WT during both balanced and unbalanced fault conditions. The operation of DVR is confirmed using time-domain simulation in MATLAB/Simulink using 1.5 MW DFIG-WT.

Improved fault ride through capability of DFIG based wind turbines using synchronous reference frame control based dynamic voltage restorer.

This paper presents series grid interface topologies for enhancing the fault ride-through (FRT) performance of doubly-fed induction generator (DFIG)-based wind turbines (WTs). Two voltage booster schemes, 1) dynamic voltage restorer (DVR) and 2) resistive type high temperature superconducting fault current limiter (HTS-FCL), are designed and implemented. The test system represents a WT connected to an electric grid with alternatively employing DVR and HTS-FCL. Both schemes provide fast mitigation of voltage dip that maintains the nominal operating conditions for DFIG-WT. To achieve a flexible control solution for balanced and unbalanced fault conditions, the DVR employs positive and negative sequence controllers while the HTS-FCL is designed to perform fast quenching for each phase individually. The potential of the two booster schemes is evaluated and analyzed in positive and negative sequence reference frames. Comprehensive simulation studies are presented to verify the capability of the series grid interface schemes for ensuring the normal operation and smooth wind power evacuation with effective isolation from grid faults. Furthermore, the grid code requirements of reactive current support are evaluated for both schemes at various fault scenarios.

Voltage Booster Schemes for Fault Ride-Through Enhancement of Variable Speed Wind Turbines

The load side voltage disturbances can be effectively mitigated by connecting a series compensating device called dynamic voltage restorer (DVR). Generally, DVR is realized by a voltage source inverter with dc storage device and a series injection transformer. Rating and design issues of an injection transformer are of much concern for the proper operation of the DVR. Voltage underrating of the transformer may lead to its saturation whereas overrating increases the cost and size of the DVR. The voltage applied to the primary winding of the transformer is a combination of several components of different frequencies. In view of above, rating and design issues are presented in this paper. A novel method is proposed to find the voltage rating of the transformer as a function of the fundamental frequency. Furthermore, to reduce the effects of current harmonics in the transformer, A-factor is used. A PSCAD model is used to validate the efficacy of the proposed design method to find the voltage rating, and overall performance of the DVR. The experimental studies confirm the proposed method.

Rating and design issues of DVR injection transformer

The load side voltage disturbances can be effectively mitigated by connecting a dynamic voltage restorer (DVR), a series compensating device. A DVR is realised by a voltage source inverter with DC storage device and a series injection transformer. Rating and design issues of an injection transformer are of prime concern for the proper voltage compensation using DVR. Voltage underrating of the transformer may lead to its saturation, whereas, overrating increases the cost and size of the DVR. The voltage applied to the primary winding of the transformer is a combination of several components of different frequencies. Considering above aspects, rating and design issues are presented in this paper. A novel method is proposed to find the voltage rating of the transformer as a function of the fundamental frequency. Furthermore, the inrush current due to saturation is avoided during transient period. K factor method is used to account for the effects of current harmonics in the transformer. A PSCAD model is used...

V. Jayashankar

Papers

Rating and design issues of DVR injection transformer

Rating and design issues of DVR injection transformer