Showing papers on "Fault current limiter published in 2021"

Optimal Allocation of Distributed Generation Units Correlated With Fault Current Limiter Sites in Distribution Systems

Abstract: Integration of distributed generating (DGs) units helps in reducing the extreme loading on the main power grid. DGs are convoyed with high fault currents. High fault currents exceed the ratings of circuit breakers. This article proposes optimal allocation of different types of DGs units correlated with fault current limiters (FCLs) in single stage. The proposed method is assessed with two-stage approach that is carried out based on coyote optimization algorithm (COA) and electrical transient analyzer program (ETAP) at normal and faulty operating conditions, respectively. For this target, a fuzzy-based multiobjective (FBMO) formulation is proposed for enhancing the distribution system performance in both operating conditions. It aims at minimizing the power losses, reducing the fault currents in the network with economizing the installed FCLs sizes. To handle FBMO formulation, the COA has been employed to search for the optimal combination between DGs and FCLs. The proposed methodology is studied on IEEE 33-bus, 69-bus, and the Egyptian East Delta distribution systems. Acceptable power losses and fault level reduction are achieved for normal and faulty operating conditions. Therefore, the effectiveness and capability of the employed single stage for DG units correlated with FCLs allocation are proved compared with bistage approach.

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

Abstract: 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.

Topology Modeling and Design of a Novel Magnetic Coupling Fault Current Limiter for VSC DC Grids

Abstract: In a voltage-source converter dc grid, a dc fault current limiter (FCL) is a key apparatus. When faults occur, it is supposed to effectively and immediately suppress transient short-circuit current to protect other equipment, e.g., converters. Additionally, it is required to bring as little negative effect as possible under normal operation. Although the respective advantages are highlighted in different FCLs, one or two key disadvantages can significantly decrease the overall performance. In this article, a novel magnetic coupling FCL (MCFCL) is proposed and achieves a good balance among its advantages and disadvantages. An MCFCL consists of a mutual inductor and some power electronic switch modules. The mutual inductor metallic primary winding is connected in series to the transmission line and magnetically coupled with the secondary winding. The secondary side impedance is controlled by the power electronic switch modules. The novel 4-segment model is proposed to demonstrate the current-limiting physics, formulate the current-limiting effect, and support the design. One medium voltage (10 kV) case study is carried out based on the numerical simulation. The MCFCL shows a better current-suppressing effect and a lower impedance under normal operation than the benchmark Reactor FCL. Finally, this article is validated on a scaled-down experimental facility.

A Series Stacked IGBT Switch to Be Used as a Fault Current Limiter in HV High-Power Supplies

Abstract: The safe operating condition for the vacuum tubes is very important and critical since they are very expensive and delicate. Providing limited short circuit energy for the vacuum tube and fast transferring from the short circuit to the nominal operation state are absolutely necessary. Extant protection strategies threat the availability of the vacuum tubes. In addition, they cannot completely protect the tube due to the delay of the fault detection system. This article proposes a high voltage (HV) short circuit fault current limiter which can limit the short circuit energy of the system inherently. The proposed structure activates automatically when the current exceeds the predetermined value. Hence, the need for the fault detection unit is minimized. The proposed short circuit fault current limiter is based on the series insulated gate bipolar transistors (IGBTs). Due to the interesting current limiting feature of the IGBTs, the short circuit current is limited for a definite time. During this time interval, the vacuum arc interrupts and the tube can operate instantaneously. In order to provide a safe operating condition of the series-connected IGBTs in the short circuit fault, several external circuits are suggested. The proper operation of the proposed short circuit fault current limiter is evaluated using simulations and experimental prototyping.

Multi-objective optimization for the superconducting bias coil of a saturated iron core fault current limiter using the T-A formulation

Abstract: The short-circuit levels have increased considerably in transmission and distribution systems in the last years. Fault current limiter (FCL) devices are a potential solution to this problem. Among several FCL topologies, this group has good experience in the use of superconducting fault current limiters (SFCL) to reduce the electrical current during short-circuits. The literature also presents studies of the saturated iron core superconducting fault current limiter (SIC-SFCL) topology employing mathematical modeling and prototypes design. Some of them have shown promising results, including the construction of pilot prototypes in medium and high voltage substations. The SIC-SFCL simulation studies presented optimal topologies that reduce the amount of ferromagnetic material used in the core and represent well the behavior of this limiter. The finite element method and the finite element analysis are suitable to model the SIC-SFCL. However, a more detailed study focusing on the optimization of the DC bias superconducting coil of the SIC-SFCL has not been presented in the literature yet. In this context, this work proposes a multi-objective optimization method using the Nelder–Mead algorithm to find an optimal geometry for the superconducting coil. In this optimization, the objectives functions are: to maximize the critical current density in the high-temperature superconductor (HTS), minimize the voltage drop in the copper winding, minimize the current through the DC biased superconducting winding, and minimize the price of the HTS superconducting winding. Before implementing the multi-objective optimization algorithm, we have tested a non-superconducting saturated iron core prototype and used the results to validate the simulation models. After that, we have replaced the DC copper winding with an HTS coil in the simulations and initiate the optimization process. Results show that constructing the DC bias superconducting coil using the minimum possible fill factor might not be the best choice.

Fault Current Limiter Dynamic Voltage Restorer (FCL-DVR) With Reduced Number of Components

Abstract: In this article, a new dual-function fault-current limiter-dynamic voltage restorer (FCL-DVR) topology is proposed. The proposed structure, in addition to performing routine FCL tasks, can be used to improve the voltage quality of point of common coupling. A salient feature of this FCL-DVR is its reduced number of semiconductor switches and gate drive and control circuit components. Perhaps, variety structures of FCL-DVR have been proposed but most distinctive feature of proposed structure is lower power loss. The operation modes and the control strategy of the FCL have been presented and studied. In addition, the proposed structure has been compared with other structures to prove the efficiency of the proposed structure. The simulation results as well as experimental outcomes from a laboratory scaled-down prototype are provided, which prove the efficiency and feasibility of the proposed structure.

A Voltage Balancing Method for Series-Connected IGBTs Operating as a Fault Current Limiter in High-Voltage DC Power Supplies

Abstract: This article proposes a high-voltage fault current limiter (HVFCL) for high-voltage dc power supplies (HVdcPSs) which limits the current of the power supply automatically in the short-circuit fault (SCF). The proposed HVFCL is based on the series-connected insulated gate bipolar transistors (IGBTs). The main achievements of this article are the balanced voltage sharing and a very low value of the short-circuit current near to the load nominal current for the series-connected IGBTs during the SCF. These achievements result in a longer maximum permissible short-circuit time. These achievements are obtained by a control strategy that puts the series-connected IGBTs in a specific operating point in the active region during the SCF. Based on the proposed master–slave control strategy, one of the IGBTs is current controlled and rolls as the master. The other IGBTs are voltage controlled and imitate the master IGBT voltage. Consequently, a balanced voltage sharing is guaranteed for the series-connected IGBTs in the SCF. PSPICE simulations and experimental results are provided to verify the proper performance of the proposed HVFCL.

A New Type of Fast-Response Fault Current Limiter Topology for HVDC Application

Abstract: The inductance of a permanent magnet-biased saturated fault current limiter (PMFCL) increases automatically with the fault current. It can quickly restrain the rising speed of direct current (dc) fault current. However, when the dc circuit breaker (DCCB) opens, the PMFCL will delay the current drop speed and generate overvoltage, which will increase the voltage stress on the DCCB. In this article, a new type of fast-response FCL (NFCL) is proposed. It has the advantage of improving the fault current drop speed. Besides, it can reduce DCCB overvoltage, thus protecting the expensive insulated gate bipolar transistors in the DCCB. In addition, it greatly reduces the energy absorption in the DCCB, thus reducing its manufacturing cost. The NFCL operates automatically without a control device, which means that it responds faster. Moreover, the diode is on the low-voltage side, meaning that insulation manufacturing cost can be reduced. First, the working principle of NFCL cooperation with the DCCB is introduced. Then, the main electromagnetic parameter design requirements of the NFCL are analyzed. Their feasibility is verified by electromagnetic circuit simulation, and a prototype is built and tested. Finally, the experimental and simulation results show that NFCL can improve current drop speed effectively.

Hybrid-Material Based Saturated Core FCL in HVDC System: Modeling, Analyzing and Performance Testing

Abstract: In order to limit the extremely fast rising trend of fault current in a high voltage direct current system, a permanent magnet (PM) biased dc saturated core fault current limiter (DCSFCL) was proposed previously. However, the demagnetization problem of the PM and compromised fault limiting inductance value caused by the inserted PMs are two major issues that need to be solved. In this article, a hybrid-material based fault current limiter (HMFCL) is proposed. First, by means of reconstructing the iron core topology and substituting different soft magnetic materials with their hybrid benefits, the proposed novel HMFCL can present instant change in fault limiting inductance value without threating the safety of the PMs. Then, the Jiles–Atherton hysteresis modeling technique is applied on the HMFCL and its electromagnetic feature is analyzed. The parameters of HMFCL are optimized using genetic algorithm as well. Finally, the effectiveness of the proposed HMFCL is proved by various device and system level simulations as well as a prototype experiment. Results reveal that the proposed HMFCL can limit the fault current by over 80% compared with traditional smoothing reactor.

A Novel Saturated Amorphous Alloy Core Based Fault Current Limiter for Improving the Low Voltage Ride Through Capability of Doubly-Fed Induction Generator Based Wind Turbines

Abstract: This article proposes the use of a novel saturated amorphous alloy core-based fault current limiter (SAACFCL) to improve the low voltage ride through (LVRT) capability of doubly-fed induction generator (DFIG) based wind energy systems, especially during voltage sag events Compared to the traditional cores, which are widely used in fault current limiter (FCL), amorphous alloy core possesses a very narrow B - H loop, which indicates that the SAACFCL requires a smaller dc excitation current, and it will incur low core losses Under normal conditions, this developed SAACFCL accomplishes low impedance and has a negligible impact on the network operation During grid faults, a deep voltage sag causes large fault currents that desaturate the SAACFCL core, increasing its impedance, which limits the fault currents and improves the LVRT capability of DFIG systems The SAACFCL is designed and characterized by ANSYS software To validate the performance of the SAACFCL, a DFIG-based system equipped with the SAACFCL has been modeled in MATLAB/Simulink The simulation results with and without the SAACFCL show that the SAACFCL is capable to achieve the LVRT successfully and can meet the grid code requirement The performance of the SAACFCL has also been compared with that of the saturated iron core FCL (SICFCL) and superconducting FCL (SFCL) The SAACFCL promises better performances than SICFCL and SFCL A small scale SAACFCL has been designed, developed, and tested in the laboratory to check its performance The experimental results show that the proposed SAACFCL can effectively reduce the level of fault current and mitigate voltage sag experienced by the DFIG

Simplified Design of R-SFCL With Shunt Reactor for Protecting HTS Cable in Distribution Network

Abstract: The high temperature superconducting (HTS) cable can be used as a low-voltage tie line between substations for its characteristic of high currentdensity. In this way, the remaining capacity on the low-voltage side of the transformer can be fully utilized. Moreover, The HTS cable can run in parallel with the original tie line, forming an electromagnetic ring network, to ensure the power supply of important loads. However, the short circuit current of the distribution network is large, and the electromagnetic ring network operation results in the quench of HTS cable when the short circuit fault is outside the HTS cable. It is important to ensure the safety of HTS cable under various short circuit faults. To ensure the safe operation of HTS cable in Shenzhen Power Grid, this paper built a distribution network model with HTS cable in Matlab/Simulink. The fault current and thermal process in different fault situation were analyzed. The design of fault current limiter (FCL) which is composed of the resistive superconducting fault current limiter (R-SFCL) and a shunt reactor was completed. The model of R-SFCL using R - Q method is build, and the effectiveness of the R-SFCL design is verified.

Pareto Optimal Allocation of Flexible Fault Current Limiter Based on Multi-Objective Improved Bat Algorithm

Abstract: With the sustainable growth in the integration of distributed generation units in the distribution network, the probability of the fault current level exceeding the rating of existing components increases. Cascaded H bridge fault current limiter is widely used in the power grid due to its advantage in inhibiting surge current flexibly. In order to equilibrate the objective functions of its cost, fault current mitigation effect, and the weighted load reliability index, a novel methodology is proposed to simultaneously optimize the location and size of the limiters in the distribution network. Therein, the sensitivity factor considering the Monte Carlo fault simulation model is introduced to reduce the search space and rank candidate locations referencing the actual conditions. And then, according to the candidate locations and considering different conflicting objective functions, a multi-objective improved bat algorithm is employed to obtain the Pareto optimal solution set. Also, life cycle cost and net present value are introduced to construct an economic model to access the scheme costs and service life. The proposed approach is verified using the modified IEEE 33-bus distribution systems with DGs and IEEE 30-bus Benchmark system. The results demonstrate that the proposed method exhibits higher efficiency in finding optimum solutions and provides a new economic configuration idea for the practical engineering application.

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

Abstract: 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.

A Multi-Port Current-Limiting Hybrid DC Circuit Breaker

Abstract: Recently the hybrid multi-port DC circuit breaker (MP-DCCB) is becoming popular in protecting HVDC grids, thanks to their reduction of power electronics devices. In this paper, an enhanced multi-port current-limiting DCCB (MP-CLCB) for multiple line protection is proposed. The integrated fault current limiter (FCL) inside the MP-CLCB can clear the fault faster with slightly increased costs. To reduce the energy dissipation requirement for the surge arresters caused by the newly added current-limiting path, an energy transfer path which provides a loop with the inductors during the current decay stage is designed. The theoretical analysis of the pre-charging, current-limiting, fault interruption and energy dissipation of the MP-CLCB is carried out. Moreover, the design principles of the energy dissipation and the key parameters of the MP-CLCB are provided. The proposed approaches are verified through simulations in PSCAD/EMTDC. The results show that the MP-CLCB can replace multiple DCCBs, accelerate the fault current interruption and reduce the energy dissipation requirement for the surge arresters.

A Nonlinear Backstepping Control Scheme for Rapid Earth Fault Current Limiters in Resonant Grounded Power Distribution Systems: Applications for Mitigating Powerline Bushfires

Abstract: This work presents a nonlinear backstepping control scheme for rapid earth fault current limiters (REFCLs) in resonant grounded power distribution systems to mitigate the severity of powerline bushfires. The main feature of the proposed control scheme is that it quickly eliminates both active and reactive components of the fault current to make it zero for reducing the chance of igniting bushfires. The nonlinear backstepping control scheme is employed on the dynamical model of a REFCL equipped with a T-type inverter. The desired tracking of the fault current is ensured with the proposed scheme by appropriately injecting the current to the neutral point. The performance of the controller is evaluated in terms of the fault current and faulty phase-to-ground voltage under different fault conditions while following the standard criteria for the practical operation. The fault current compensation capability of the proposed scheme is evaluated for both low and high impedance faults. Simulation results in software and processor-in-loop platforms clearly demonstrate the fault current is limited to a value much lower than its desired value of 0.5~A in less than 1~s which means that the chance of igniting bushfires will be reduced with the proposed controller.

A Mathematical Approach to Simultaneously Plan Generation and Transmission Expansion Based on Fault Current Limiters and Reliability Constraints

Abstract: Today, generation and transmission expansion planning (G&TEP) to meet potential load growth is restricted by reliability constraints and the presence of uncertainties. This study proposes the reliability constrained planning method for integrated renewable energy sources and transmission expansion considering fault current limiter (FCL) placement and sizing and N-1 security. Moreover, an approach for dealing with uncertain events is adopted. The proposed planning model translates into a mixed-integer non-linear programming model, which is complex and not easy to solve. The problem was formulated as a tri-level problem, and a hybridization framework between meta-heuristic and mathematical optimization algorithms was introduced to avoid linearization errors and simplify the solution. For this reason, three meta-heuristic techniques were tested. The proposed methodology was conducted on the Egyptian West Delta system. The numerical results demonstrated the efficiency of integrating G&TEP and FCL allocation issues in improving power system reliability. Furthermore, the effectiveness of the hybridization algorithm in solving the suggested problem was validated by comparison with other optimization algorithms.

Design of Capacitive Bridge Fault Current Limiter for Low-Voltage Ride-Through Capacity Enrichment of Doubly Fed Induction Generator-Based Wind Farm

Abstract: The increase in penetration of wind farms operating with doubly fed induction generators (DFIG) results in stability issues such as voltage dips and high short circuit currents in the case of faults. To overcome these issues, and to achieve reliable and sustainable power from an uncertain wind source, fault current limiters (FCL) are incorporated. This work focuses on limiting the short circuit current level and fulfilling the reactive power compensation of a DFIG wind farm using a capacitive bridge fault current limiter (CBFCL). To deliver sustainable wind power to the grid, a fuzzy-based CBFCL is designed for generating optimal reactive power to suppress the instantaneous voltage drop during the fault and in the recovery state. The performance of the proposed fuzzy-based CBFCL is presented under a fault condition to account for real-time conditions. The results show that the proposed fuzzy-based CBFCL offers a more effective solution for overcoming the low voltage ride through (LVRT) problem than a traditional controller.

Optimal Shunt-Resonance Fault Current Limiter for Transient Stability Enhancement of a Grid-Connected Hybrid PV/Wind Power System

Abstract: This paper proposes an optimal design of Shunt-Resonance Fault Current Limiter (SRFCL) to enhance the Fault Ride-Through (FRT) capability and improve the transient stability of a grid-connected hybrid PV/wind power system. The design parameters of the SRFCL are optimized by using Particle Swarm Optimization (PSO) technique. The proposed SRFCL topology is designed in such a way that it can provide superior protection capability for limiting the fault current and supporting the grid voltage than the conventional Bridge Fault Current Limiter (BFCL). The effectiveness of the SRFCL in supporting the dynamic performance and improving the transient stability of the hybrid energy system is validated during both symmetrical and unsymmetrical faults in the electrical utility. Moreover, its credibility is evaluated compared with that of the BFCL and the FRT control schemes. Simulations have been performed using the MATLAB/SIMULINK software. The results illustrate that the proposed SRFCL augments significantly the dynamic behavior and the transient stability of the hybrid power system during the fault events. Also, when the optimal SRFCL is employed, the injected active power by the hybrid system and the grid voltage profile are improved considerably under the grid disturbances. Furthermore, the comparison confirms the superiority of the SRFCL performance to both the BFCL topology and the FRT control scheme in every aspect.

Protection Coordination of Bidirectional Overcurrent Relays Using Developed Particle Swarm Optimization Approach Considering Distribution Generation Penetration and Fault Current Limiter Placement

Abstract: This article is treated with the protection coordination of bidirectional overcurrent relays (OCRs) in distribution power systems to obtain the best performance at a minimum total time dial setting (TDS). High penetration of distribution generation (DG) into distribution systems may significantly affect the protective system; since they increase the short-circuit level by injecting an extra share of fault current, it results in changes in the power/current flow direction. Accordingly, the fault current limiter (FCL) devices should be utilized to mitigate the short-circuit current. FCLs and DGs both will disturb the protection settings of protective equipment. The characteristics and the set point of inverse time relays depend on the fault clearing time (FCT) and the pick-up current. Therefore, an optimization approach is required to minimize the FCTs and TDSs of main relays and backup ones to protect all equipment. Moreover, this strategy selects the optimal placement of the FCL cooperatively according to the cost minimization. The optimization approach is implemented based on the particle swarm optimization (PSO) method within an extra parameter to improve the convergence speed and find the global solution, especially at initial iterations. The proposed optimization approach named developed PSO (DPSO) is tested on the IEEE 14-bus system and compared with some existing methods. Finally, the analysis and evaluations present the effectiveness of the best current transformer (CT) settings with

A Novel Modularization Design Method of PM Biased SCFCL Considering Leakage Flux Effect and Permeance Matrix Modeling

Abstract: A DC system saturated core fault current limiter (DCSFCL) was proposed to limit the fast rising trend of fault current in HVDC system. However, traditional method to calculate and design the DCSFCL tend to neglect leakage flux around the permanent magnet (PM), leading to large calculation error and inappropriate design procedure. The novel contribution of this paper is that it proposed a modularization method to analyze the permeance of both PM and adjacent air. Hence, the leakage flux effect is considered properly and a more accurate permeance matrix can be derived in a pure mathematical way. In this case, DCSFCL can be calculated much faster than the FEA simulation program with a promising accuracy regarding fault limiting performance. More importantly, design flow of the DCSFCL and related PM biased devices was given as well. Calculation result shows that inductance value calculated by the proposed method has less than 1% error compared with fine meshed FEA simulation result and about 20% increase in accuracy compared with traditional method that neglects PM leakage flux effect. Prototype of the DCSFCL was also built and experimental tests were carried out to verify the correctness of the proposed method.

Study of Fault Current Limiter—A Survey

Abstract: The requirement of electric energy is gaining pace in day-to-day life. Due to which, distributed energy source (DES) has been introduced in power sector. But while connecting DES with the distribution network this will increase the fault current level of the system [1]. Many protective devices like high impedance transformer, series reactor, switchgear, etc., are being used to limit the fault current which make the system costlier, cause low dependability and reduced operational flexibility [2]. As these devices are expensive, it is necessary to protect them from fault. A fault current limiter (FCL) is an alternative and flexible means of standard protective device, and it overcomes the problems occur due to increased fault current levels. This paper focuses on different types of FCL and its application in power system which are still in research.

An Integrated Control and Protection Scheme for Microgrids

Abstract: The increasing trend in integrating intermittent distributed energy resources (DERs) into AC microgrids presents operational challenges in stability and protection. In islanded microgrids with power electronic interfaces, protection poses a major challenge due to the level of short circuit currents resulting from inverter output capabilities. However, traditional protection schemes that are utilized in distribution systems are no longer appropriate to protect the microgrid in the presence of different levels of fault currents This paper develops an integrated control and protection framework based on state observer and fault current limiter (FCL) devices. A single state observer has been developed to detect and identify the faults that occur within multiple protection zones. In addition, controlled switches, consisting of FCLs have been utilized to limit the fault currents and provide rapid switching during the faults. An adaptive integration proposed in this paper has been applied to islanded microgrid configuration and is demonstrated to be an effective means to protect the system and maintain the voltage and frequency within acceptable range with the capability of power continuity during both transient and persistent faults.

Centralized Locating Strategy of Fault Current Limiters in MMC-based Multi-terminal HVDC Grid

Abstract: In this paper, a centralized locating strategy of fault current limiter (FCL) in high voltage direct current (HVDC) grid is proposed and analyzed. By employing FCLs at the output sides of MMCs, the proposed centralized locating strategy could reduce the number of FCLs in multi-terminal high voltage direct current (MTDC) grid. A typical application scenario based on Zhangbei-Beijing 4-terminal HVDC grid is introduced in this paper. Mathematical model of the proposed strategy is built and numerical solutions are calculated. Then, the simulation model is built in PSCAD/EMTDC and different locating strategies of FCL are studied. Simulation results verify the rationality of theoretical analysis. Also, calculation and simulation results demonstrate that the proposed centralized strategy has similar current limiting performance with the conventional distributed FCL locating strategy. When the proposed strategy is applied, the MMCs could be protected from over currents. What’s more, the reliability and reconnection of partial system after faults is ensured. The healthy part of MTDC grid could maintain continuous operation and transmit active power as normal. When applying different FCL locating strategies, the total investment of FCLs are calculated and compared. Calculation results prove that the proposed centralized locating strategy can effectively reduce the investment of FCLs compared with the conventional distributed strategy and is more suitable for MTDC grid.