Bridge-type Fault Current Limiter Research Articles

Multi-modular bridge-type FCL for enhancing FRT capability of VSC-HVDC connected offshore wind plants during AC faults

This paper presents a novel concept Multi-Modular Bridge-Type Fault Current Limiter (MMBFCL) for enhancing the fault ride-through (FRT) capability in Voltage Source Converter (VSC)-based High-Voltage Direct-Current (HVDC) systems. The MMBFCL can be directly connected to HVDC system in ac grid side without series connection of semiconductor switches and series injection transformers. Also, the limiting resistor of each module is determined based on binary arrangements to provide a multi-step insertion resistor BFCL to limit the fault current and enhance the FRT capability under different voltage sag levels. The principle operation and control system of the MMBFCL is described. Then, the performance of the MMBFCL for enhancing the FRT is validated through time domain simulations by PSCAD/EMTDC software in a HVDC integrated wind farm system. Also, the performance of the MMBFCL is compared with the single-modular BFCL (SMBFCL). Simulation results reveal that the MMBFCL compensate the voltage sag for each voltage sag levels without any over voltage at the HVDC terminal. Also, it has superior performance than SMBFCL.

Transient stability enhancement of steam turbine-based power plant by using improved bridge fault current limiter

This paper presents a new bridge Fault Current Limiter (FCL) used for the improvement of the transient stability of steam turbine-based power plants. The proposed FCL is operated by an innovative, accurate adaptive control algorithm with low computational complexity. This algorithm limits the fault currents to the desired values defined by the system’s operator. Additional important advantages of the proposed FCL compared to recently published bridge-type FCLs are the prevention of power losses and harmonic distortion during normal operation and the need for only one current sensor for proper operation.The proposed FCL is compared with a Series Dynamic Breaking Resistor (SDBR) and a conventional bridge FCL with a bypassed resistor. This comparison was conducted by using a power system comprised of a 600MVA steam turbine-driven synchronous generator, a 600MVA step-up transformer, a 200 kW/10kVAR load, and the electric grid. The simulation results show that during the fault operation period the proposed FCL provided the best transient stability of the generator’s stator currents and voltages, the active and reactive powers, and the torque. The FCL operation was also validated with an experimental setup for different values of limit currents and duty cycles.

Power flow management and LVRT enhancement by using multi-functional capacitive bridge-type fault current limiter in DFIG system

This paper proposes a new concept of the fault current limiter (FCL) named multi-functional capacitive bridge-type fault current limiter (MCBFCL). It acts as a variable capacitor to manage active power flow under normal operating condition and enhances the low-voltage ride-through (LVRT) performance of wind farms (WFs) under fault operating conditions. The MCBFCL have been presented based on the capacitive bridge-type fault current limiter (BFCL) and is modified to compensate the transmission line impedance in order to manage power flow, while it is not bypassed under normal operating conditions unlike the conventional FCLs. In this paper, first, the power circuit and principle performance of the MCBFCL are discussed. Then time domain simulations are conducted in PSCAD/EMTDC environment to check the MCBFCL performance under both normal and fault operating conditions. Also, the MCBFCL performance is compared to the resistive and inductive BFCLs in transmission lines with series capacitive compensation. In this work doubly fed induction generator (DFIG)-based wind turbines have been utilized. Simulation results showed that the MCBFCL can manage the power flow under normal operating condition and enhances the LVRT performance of the WF under both symmetrical and asymmetrical fault operating conditions. Also, it has a superior performance in terms of LVRT indices values compared to the resistive and inductive BFCLs.

Design and Implementation of Novel Fault Ride through Circuitry and Control for Grid-Connected PV System

This paper provides a comparison of a designed method of a fault ride through (FRT) circuit, i.e., switch-type fault current limiter (STFCL) and bridge-type fault current limiter (BFCL), to optimize the electrical parameters of grid-connected solar systems (PVSs) under asymmetric single line-to-ground fault and symmetric three-phase fault. The main differences between switch- and bridge-type fault current limiters is the electric component devices such as the bridge rectifier, snubber capacitor, energy absorption bypass and current-limiting inductors. In addition, the designed FRT performance with the inverter control are analyzed in-depth, e.g., a well-adjusted proportional integral (PI) and proposed steepest descent (SD) controller are compared in the fault condition. To compare the proposed method with the conventional method, the AC power and voltage on a common coupling point (PCC) and DC link voltage of the PV system are analyzed with a MATLAB/Simulink model of a 100 kW three-phase grid-connected photovoltaic system. The simulation results of the proposed FRT circuit and SD controller verify the stability improvement and vibration-free and fast and robust responses of electrical parameters on both PV grid sides during asymmetric disturbances.

Enhancing LVRT capability of DFIG using cooperative control of BTFCL and RPC

ABSTRACT To integrate the high penetration of power from wind farms into a grid, one of the key requirements posed by new grid codes is Low Voltage Ride Through (LVRT) capability. This paper studies voltage compensation-based methods to improve fault ride-through capability of the grid-connected Doubly Fed Induction Generator (DFIG). Bridge Type Fault Current Limiter (BTFCL) and Reactive Power Control (RPC), which is acting as an active voltage compensator, are cooperatively controlled in this study to achieve better LVRT capability of DFIG. Additionally, the design considerations to select shunt impedance of BTFCL are described to get optimal performance of the system under consideration. The test system was modelled and simulated in MATLAB/SIMULINK environment. The effectiveness of the proposed method is tested by comparing it with the conventional Crowbar resistance method. Simulation results show that the cooperative control of self-acting BTFCL and an intelligent RPC can effectively reduce the fault current, improves the stator voltage of DFIG for continuous operation and provides reactive power support to the grid during fault conditions.

A Cooperative Approach of Frequency Regulation Through Virtual Inertia Control and Enhancement of Low Voltage Ride-through in DFIG-based Wind Farm

Doubly-fed induction generator (DFIG)-based wind farms (WFs) are interfaced with power electronic converters. Such interfaces are attributed to the low inertia generated in the WFs under high penetration and that becomes prevalent in a fault scenario. Therefore, transient stability enhancement along with frequency stability in DFIG-based WFs is a major concern in the present scenario. In this paper, a cooperative approach consisting of virtual inertia control (VIC) and a modified grid-side converter (GSC) approach for low voltage ride-through (LVRT) is proposed to achieve fault ride-through (FRT) capabilities as per the grid code requirements (GCRs) while providing frequency support to the grid through a synthetic inertia. The proposed approach provides LVRT and reactive power compensation in the system. The participation of the VIC in a rotor-side converter (RSC) provides frequency support to the DFIG-based WFs. The combined approach supports active power compensation and provides sufficient kinetic energy support to the system in a contingency scenario. Simulation studies are carried out in MATLAB/Simulink environment for symmetrical and unsymmetrical faults. The superiority of the proposed scheme is demonstrated through analysis of the performance of the scheme and that of a series resonance bridge-type fault current limiter (SR-BFCL).

Enhancement in fault ride through capabilities with inertia control for DFIG-wind energy conversion system

Doubly fed induction generator (DFIG)–based wind energy conversion system (WECS) has been found very effective in harnessing wind power. Conferring to grid code requirements, DFIG needs to stay connected to the grid under fault conditions. This implicates the requirement of enhancing the transient stability through augmenting the low-voltage ride through (LVRT) capability of DFIG. There are many software and hardware solutions for the improvement of LVRT. Fault current limiter is one of the frequently used hardware solutions for the argumentation of fault ride through requirements. Instead of LVRT, DFIG-based WECS also faces low inertia problems at fault condition. In this article, a combined approach of virtual inertia control with an external retrofit adaptive hysteresis control–based bridge-type fault current limiter (AHC-BFCL) is proposed to improve the LVRT capability as well as the inertia of DFIG-WECS. The results are compared with that of a conventional logic control-BFCL and proportional–integral-BFCL.

A Capacitive Bridge-Type Superconducting Fault Current Limiter to Improve the Transient Performance of DFIG/PV/SG-Based Hybrid Power System

This paper proposes a capacitive bridge-type superconducting fault current limiter (CB-SFCL) to address the most concerning issue with the grid connected hybrid power system by improving the transient performance. The hybrid system incorporates a doubly fed induction generator (DFIG) based wind farm, a solar photovoltaic (PV) system and a synchronous generator (SG) based power system. The CB-SFCL incorporates a high temperature superconductor (HTS) along with a power capacitor to provide adequate reactive power support before and after the fault. The capacitor is kept inactive during normal operation by a control circuit to ensure seamless operation. During fault, the capacitor gets connected in series with the HTS and suppress the fault current. The performance of the CB-SFCL is investigated by proper graphical and mathematical analyses and conclusions are obtained by comparing them with that of the conventional bridge-type superconducting fault current limiter (BSFCL) and the capacitive bridge-type fault current limiter (CBFCL). The analyses support the theoretical superiority of the CB-SFCL over the BSFCL and the CBFCL by a satisfying margin.

Low-Voltage Ride through Capability Augmentation of DFIG-Based Wind Farms Using Series-Parallel Resonance-Type Fault Current Limiter

The introduction of doubly fed induction generators (DFIGs) has facilitated the utilization of wind energy to a great extent and constituted distributed generation (DG) systems in remote places. Therefore, long transmission lines are required to interconnect with the utility grid and, consequently, different short-circuit faults interrupt this transmission. Use of different fault current limiters (FCLs) minimizes the effect of faults and allows normal operation with minimum interruption in power flow. In this study, a series-parallel resonance-type fault current limiter (SPRFCL) is presented for enhancing the low-voltage ride-through (LVRT) capability of DFIG-based wind farms. The SPRFCL preserves the nominal voltage and power quality within the permissible limit during normal operation and during disturbances irrespective of the type of fault. The effectiveness of the proposed SPRFCL is validated by simulating both symmetrical and asymmetrical faults. Alongside the SPRFCL, two state-of-the-art FCLs—the parallel resonance-type fault current limiter (PRFCL) and the capacitive bridge-type fault current limiter (CBFCL)—are considered to investigate and compare the relative performances. Several graphical and numerical studies assure the efficacy of the proposed SPRFCL in wind farm application in multiple aspect. Moreover, the stunning total harmonic distortion (THD) values with the proposed technique signifies the excellency over its competitors. Additionally, the sub-synchronous resonance (SSR) analysis confirms the supremacy of SPRFCL for series compensated lines.

Nonlinear Variable Resistor-Based FCL for Fault Ride-Through Performance Enhancement of DFIG-Based Wind Turbines

Fault ride-through (FRT) requirement is a matter of great concern for doubly fed induction generator (DFIG-) based wind turbines (WTs). This study presents a nonlinear variable resistor- (NVR-) based bridge-type fault current limiter (BFCL) to augment the FRT performance of DFIG-based WTs. First, the BFCL operation and nonlinear control design consideration of the proposed NVR-based BFCL are presented. Then, the NVR-BFCL performance is validated through simulation in PSCAD/EMTDC software. In addition, the NVR-based BFCL performance is compared with the fixed resistor- (FR-) based BFCL for a three-phase symmetrical short circuit fault at the grid side. Simulation results reveal that the NVR-based BFCL provides a smooth and effective FRT scheme and outperforms the FR-based BFCL.

Application of Thyristor Bridge-Type Non-Superconducting FCL with Buck Series Charging to Improve the FRT Capability of the DFIG System

Wind power generation is observing a significant use of doubly-fed induction generator (DFIG) due to its improved efficiency, but the converter used in the configuration is sensitive to the presence of a fault in the grid. This paper presents a fault ride-through (FRT) configuration, which includes a thyristor-based bridge-type non-superconducting fault current limiter (ThyBT-NSFCL) augmented with a buck converter. It has been observed that the proposed topology works fine under a temporary symmetrical fault. The analytical analysis has been carried out to observe the operating principle of the proposed ThyBT-NSFCL under both normal and fault conditions. A comparative study with other topologies such as switched impedance transformer-type non-superconducting fault current limiter (TT-NSFCL), series dynamic breaking resistor (SDBR), and without any current limiter (WCL) have been done to show the effectiveness of the proposed topology. The simulation results show that the proposed ThyBT-NSFCL is a better fault current limiter as compared with other limiters like TT-NSFCL, SDBR, and WCL. The simulation of the proposed ThyBT-NSFCL connected in series with a DFIG system is carried out using PSCAD/EMTDC software. The performance of the proposed topology is quite good, and it can be used as a reliable limiter for future wind energy applications.

Fault current limiter of VSC-HVDC systems using variable resistive bridge controller

This paper proposes a fuzzy logic controller (FLC) based variable resistive bridge type fault current limiter (VR-BFCL) to minimize the impact of faults on voltage source converter high voltage direct current (VSC-HVDC) systems. FLC for VR-BFCL is developed to dynamically insert the appropriate current limiting resistance during contingencies to maintain the fault currents within the acceptable limit. The proposed controller effectively provides variable duties to generate and insert controllable resistance in the system based on fluctuation of direct current (DC) link voltage and point of common coupling (PCC) voltage. The efficacy of the proposed controller is justified through simulations work for balanced and unbalanced faults. The results demonstrate that oscillations in PCC voltage and DC link voltage can be maintained within the acceptable range by controlling fault current through the insertion of the appropriate resistance. It is also found that the proposed controller outperforms the existing method.

SSR Alleviation in SCIG-Based Wind Power Plants Using Resistive Bridge-Type FCL

Series-Compensated Transmission Lines (SCTLs) are widely used for connection of large scale wind power plants (WPPs) to the power system to transmit the active power generated from WPPs. However, it can lead to sub synchronous resonance (SSR) phenomena in WPPs connected with SCTLs. Also, capacitive compensation of transmission lines reduces the line impedance, which leads to increasing short circuit current level in WPPs. This study proposes the resistive bridge-type fault current limiter (RBFCL) for SSR mitigation and limiting short circuit current in WPPs connected with SCTLs. Also, its performance is compared with the static synchronous compensator (STATCOM) and thyristor controlled series capacitor (TCSC) to demonstrate the effectiveness of the RBFCL in terms of SSR mitigation. The WPP used in this paper is modelled based on an aggregated squirrel-cage induction generator (SCIG) derived by an aggregated wind turbine (WT). The PSCAD/EMTDC software and the IEEE first benchmark model are used for this study. Simulation results demonstrate that the RBFCL not only limits the short circuit current contribution of WPPs, but also effectively damps the SSR oscillations due to IGE as well as TI, when the WPP is subjected to a large disturbance.

Multi-resistor BFCL for FRT capability improvement of DFIG-based wind farm

Grid connection of wind farms (WFs) results in increment of short circuit level and decrement of fault ride-through (FRT) capability under fault conditions. Application of bridge-type fault current limiter (BFCL) was recognised as a promising and cost effective solution to cope with these problems. However, full resistor insertion of the conventional BFCL provides high transient overvoltage at the terminal of wind generator under low voltage sag condition, which can lead to failure operation of wind generator in despite of FRT requirement. This study presents a voltage adaptive multi-resistor BFCL (MRBFCL) to solve these problems for wide voltage sag levels. According to the depth of voltage sag level at the grid coupling point voltage, the MRBFCL inserts an appropriate combinational of resistors to compensate voltage sag level at acceptable level. To verify the efficiency of the proposed MRBFCL, time domain simulations were performed in PSCAD/EMTDC software under three different voltage sag levels. Also, the MRBFCL performance is compared with the conventional single-resistor BFCL. Simulation results reveal that the MRBFCL effectively enhance the FRT performance of doubly-fed induction generator (DFIG)-based WFs under wide range of voltage sag level and alleviate over voltage for low voltage sag conditions.

Impact of STATCOM and BFCL on the performance of distance relay and its improvement by adaptive setting for grid‐interactive offshore wind and marine current farm

This study explores the impact of the dynamic impedance of static synchronous compensator (STATCOM) and bridge type fault current limiter (BFCL) on the performance of distance relay and its improvement by adaptive setting for Grid Interactive Offshore Wind and Marine-Current Farm. For assessments, analytical results are presented under different STATCOM settings, low voltage ride through (LVRT) condition, and different types of fault conditions. Moreover, the presence of STATCOM and BFCL significantly changes the apparent impedance characteristic of the studied system. It is also seen that the presence of STATCOM likely to induce an under reach and overreach problem of distance relay. Further, the LVRT capability is significantly affected as STATCOM supplies reactive power to offshore wind generators during a short circuit on the grid side. It is found that the grid integration of OWF and MCF with STATCOM and BFCL is likely to induce mis-coordination and subsequently deteriorate the performance of distance relay, leading to system security problems. Therefore, this study proposed an adaptive setting in order to eliminate the simultaneous influence upon the dynamic impedance due to incorporation of STATCOM and BFCL on the distance relay setting. The simulation results show the efficacy of the proposed adaptive setting.

Improving LVRT capability of microgrid by using bridge-type fault current limiter

A grid-connected microgrid should meet the low voltage ride through (LVRT) requirements. It means that in addition to reactive power injection during low voltage conditions, microgrid has to remain connected to the grid for a predefined time. In this paper, the bridge type fault current limiter (BFCL) is used to improve the low voltage ride through capability of grid-connected microgrids. A new method is proposed to control the BFCL and the voltage-source converters within the microgrid for this purpose. Effectiveness of the proposed method is verified by simulation results and comparison with previous methods.

Transient Performance Improvement of Power Systems Using Fuzzy Logic Controlled Capacitive-Bridge Type Fault Current Limiter

This paper proposes the novel application of a genetic algorithm optimized fuzzy logic controller as a nonlinear controller for capacitive bridge type fault current limiter (CBFCL) to improve the stability performance of the power systems. The proposed controller provides fast convergence for the system and uses data from the system as a feedback in the controller loops. The performance of the proposed genetic algorithm optimized fuzzy logic controlled CBFCL is compared with that of a static nonlinear controller based CBFCL and a static nonlinear controller-based bridge type fault current limiter (BFCL). The detail controller design and stability analysis are carried out on the IEEE 39 bus power system in MATLAB/SIMULINK. To capture a realistic system's response, a wind farm is connected to bus one in the IEEE 39 bus system. From the simulation results and several quantifying parameters, it is shown that the proposed genetic algorithm optimized fuzzy logic controlled CBFCL can effectively improve the stability and the performance of the power system as well as the grid connected wind farm. Further, the proposed controller performs better than the static nonlinear controller based CBFCL and the static nonlinear controller based BFCL.

Sliding Mode Controller-Based BFCL for Fault Ride-Through Performance Enhancement of DFIG-Based Wind Turbines

The fault ride-through (FRT) capability and fault current issues are the main challenges in doubly fed induction generator- (DFIG-) based wind turbines (WTs). Application of the bridge-type fault current limiter (BFCL) was recognized as a promising solution to cope with these challenges. This paper proposes a nonlinear sliding mode controller (SMC) for the BFCL to enhance the FRT performance of the DFIG-based WT. This controller has robust performance in unpredicted voltage sag level and nonlinear features. Theoretical discussions, power circuit, and nonlinear control consideration of the SMC-based BFCL are conducted, and then, its performance is verified through time-domain simulations in the PSCAD/EMTDC environment. To reduce the chattering phenomenon and decrease the reaching time, it used the exponential reaching law (ERL) for designed SMC. Also, the SMC-based BFCL performance is compared with the conventional and PI controller-based BFCL for both symmetrical and asymmetrical short-circuit faults. Simulation results reveal that the SMC-based BFCL provides better performance compared with the conventional and PI controller-based BFCL to enhance the FRT.

Fault Ride Through Capability Improvement of DFIG Based Wind Farm Using Nonlinear Controller Based Bridge-Type Flux Coupling Non-Superconducting Fault Current Limiter

High penetration of Doubly Fed Induction Generator (DFIG) into existing power grid can attribute complex issues as they are very sensitive to the grid faults. In addition, Fault Ride Through (FRT) is one of the main requirements of the grid code for integrating Wind Farms (WFs) into the power grid. In this work, to enhance the FRT capability of the DFIG based WFs, a Bridge-Type Flux Coupling Non-Superconducting Fault Current Limiter (BFC-NSFCL) is proposed. The effectiveness of the proposed BFC-NSFCL is evaluated through performance comparison with that of the Bridge-Type Fault Current Limiter (BFCL) and Series Dynamic Braking Resistor (SDBR). Moreover, a dynamic nonlinear controller is also proposed for controlling the operation of the BFC-NSFCL. Extensive simulations are carried out in the MATLAB/SIMULINK environment for both symmetrical and unsymmetrical temporary as well as permanent faults. Based on the simulation results and different numerical analysis, it is found that the proposed nonlinear controller based BFC-NSFCL is very effective in enhancing the FRT capability of the WF. Also, the BFC-NSFCL outperforms the conventional BFCL and SDBR by maintaining a near-seamless performance during various grid fault situations.

Proactive stabilization of grid faults in DFIG based wind farm using bridge type fault current limiter based on NMPC

ABSTRACT DFIG-based wind turbine has significantly reduced the power rating, cost of the converter and enables subsynchronous and super synchronous operation but it has largely suffered in maintaining the transient stability and power balance between the generator and grid panel when grid faults has occurred. Formerly, the methods such as PID controller, fuzzy controller, PI controller could maintain the stability to the certain extent only since the nature of the wind power plant is unpredictable and also grid faults can occur at any time so this DFIG-based wind turbine is in need of predictive controller for anticipating faults in grid side. To normalize this situation, this work has proposed a (Stochastic dynamic Programming) (SDP) based Non-linear model predictive controller (NMPC) where nonlinear load would be linearized by min-max normalization algorithm and then voltage profile would be analyzed using support vector regression; consequently, based on the analyzing result, dynamic programming based on stochastic would take the action dynamically. By this way, the proposed system has been maintaining the transient stability and power balance between the generator and the grid optimally.