Fault Ride-Through(FRT)Behavior in VSC-HVDC as Key Enabler of Transmission Systems Using SCADA Viewer Software

The world’s energy consumption and power generation demand will continue to rise.Furthermore,the bulk of the energy resources needed to satisfy the rising demand is far from the load centers.The aforementioned requires long-distance transmission systems and one way to accomplish this is to use high voltage direct current(HVDC)transmission systems.The main technical issues for HVDC transmission systems are loss of synchronism,variation of quadrature currents,amplitude,the inability of station 1(rectifier),and station 2(inverter)to either inject,or absorb active,or reactive power in the network in any circumstances(before a fault occurs,during having a fault in network and after a fault cleared),and the variations of power transfer capabilities.Additionally,faults impact power quality such as voltage dips and power line outage time.This paper presents a method of overcoming the aforementioned technical issues using voltage-source converter(VSC)based HVDC transmission systems with SCADA VIEWER software and dynamic grid simulator.The benefits include having a higher capacity transmission system and proposed best method for control of active and reactive power transfer capabilities.Simulation results obtained using MATLAB validated the experimental results from SCADA Viewer software.The results indicate that the station’s rectifier or inverter can either inject or absorb either active power or reactive power in any circumstance.Also,the reverse power flow under different modes of operation can ride through faults.At a 100.0%power transfer rate,the rectifier injected 775.0 W into the network.At a 0.0%power transfer rate,the rectifier injected 164.0 W into the network.At a-100.0%rated power,the rectifier injected 1264.0 W into the network and direction was also changed.

Fault Diagnosis and Phase Disposition Reconfiguration of a 5-Level Double-Boost Power Factor Corrector with Fault-Tolerant Capability

A 5-level PFC （power factor correction） topology with fault-diagnostic and fault-tolerant capability is proposed and compared to known structures. It is derived from a 3-level non differential double-boost PFC including fly-cap cells. The series-connection of the two low-voltage switching-cells is decoupled by a single flying capacitor that provides a direct fault-tolerant capability and a post-failure operation increasing the availability of converter. The monitoring of the voltages across flying capacitors allows a rapid detection and localization either for open circuit failure or short-circuits failure. A PWM （pulse width modulation） phase-disposition type reconfiguration is also used and presented in order to optimize both normal operation and post-fault continuation. The design and the most important features are highlighted thanks to a digital control frame and a mock-up rated to： AC voltage network 115 V-load 400 V-nominal power 4 kW-switching frequency 62 kHz.

DC faults ride-through capability analysis of Full-Bridge MMC-MTDC System

Full-Bridge Modular Multilevel Converter(FBMMC) has strong ability to ride through serious DC faults,thus it is very suitable for multi-terminal flexible HVDC applications.However,no references have reported the locating and isolating of DC faults and corresponding DC faults ride-through capability evaluation index.This paper introduces the topology mechanism of FBMMC and its loss reduction operation mode,theoretically certifies that the universal decoupled control strategy of Voltage Source Converter(VSC) and the similar modulation strategies of Half-Bridge MMC(HBMMC) can be applied to FBMMC for constructing complete closed-loop control system.On the basis of the existing DC faults locating and isolating schemes of 2-level VSC based Multi-Terminal HVDC(VSC-MTDC) system and the particularity of FBMMC,this paper proposes the DC faults wire selection "handshaking" method of the FBMMC-MTDC system,and proposes the DC Fault Ride-Through Capability Index(DFRTI) for evaluating the DC faults suppressing capability of the VSC-MTDC systems,including FBMMC-MTDC.Simulations of FBMMC-MTDC in PSCAD/EMTDC validate the correctness and effectiveness of the proposed control strategy and evaluation index.

Neutral-point-clamped hybrid multilevel converter with DC fault blocking capability for medium-voltage DC transmission

This paper proposes a novel hybrid multilevel converter with DC fault-blocking capability, i.e., the neutral-point clamped hybrid multilevel converter(NHMC).By employing two types of unipolar full-bridge submodules along with director switches, which are composed of seriesconnected insulated-gate bipolar transistors, the NHMC combines the features and advantages of the neutral-point clamped converter and the modular multilevel converter.The basic topology, operating principles, modulation scheme, and energy-balancing scheme of the NHMC are presented. The DC fault-blocking capability of the NHMC is investigated. The number of power electronic devices used by the NHMC is calculated and compared with other multilevel converters, showing that the proposed NHMC can be an economical and feasible option for medium-voltage DC transmission with overhead lines. Simulation results demonstrate the features and operating scheme of the proposed NHMC.

Application of MMC with Embedded Energy Storage for Overvoltage Suppression and Fault Ride-through Improvement in Series LCCMMC Hybrid HVDC System

The series line-commutated converter(LCC)and modular multilevel converter(MMC)hybrid high-voltage direct current(HVDC)system provides a more economical and flexible alternative for ultra-HVDC(UHVDC)transmission,which is the so-called Baihetan-Jiangsu HVDC(BJ-HVDC)project of China.In one LCC and two MMCs(1+2)operation mode,the sub-module(SM)capacitors suffer the most rigorous overvoltage induced by three-phase-to-ground fault at grid-side MMC and valve-side single-phase-to-ground fault in internal MMC.In order to suppress such huge overvoltage,this paper demonstrates a novel alternative by employing the MMC-based embedded battery energy storage system(MMC-BESS).Firstly,the inducements of SM overvoltage are analyzed.Then,coordinated with MMC-BESS,new fault ride-through(FRT)strategies are proposed to suppress the overvoltage and improve the FRT capability.Finally,several simulation scenarios are carried out on PSCAD/EMTDC.The overvoltage suppression is verified against auxiliary device used in the BJ-HVDC project in a monopolar BJ-HVDC system.Further,the proposed FRT strategies are validated in the southern Jiangsu power grid of China based on the planning data in the summer of 2025.Simulation results show that the MMC-BESS and proposed FRT strategies could effectively suppress the overvoltage and improve the FRT capability.

A Continuous Fault Ride-through Scheme for DFIGs Under Commutation Failures in LCC-HVDC Transmission Systems

Experimental and theoretical studies have confirmed that,relative to a one-shot voltage fault,a doubly-fed induction generator(DFIG)will suffer a greater transient impact during continuous voltage faults.This paper presents the design and application of an effective scheme for DFIGs when a commutation failure(CF)occurs in a line-commutated converter based high-voltage direct current(LCC-HVDC)transmission system.First,transient demagnetization control without filters is proposed to offset the electromotive force(EMF)induced by the natural flux and other low-frequency flux components.Then,a rotor-side integrated impedance circuit is designed to limit the rotor overcurrent to ensure that the rotor-side converter(RSC)is controllable.Furthermore,coordinated control of the demagnetization and segmented reactive currents is implemented in the RSC.Comparative studies have shown that the proposed scheme can limit rotor fault currents and effectively improve the continuous fault ride-through capability of DFIGs.

A DC Chopper Topology to Mitigate Commutation Failure of Line Commutated Converter Based High Voltage Direct Current Transmission

To reduce the probability of commutation failure(CF)of a line commutated converter based high-voltage direct current(LCC-HVDC)transmission,a DC chopper topology composed of power consumption sub-modules based on thyristor full-bridge module(TFB-PCSM)is proposed.Firstly,the mechanism of the proposed topology to mitigate CF is analyzed,and the working modes of TFB-PCSM in different operation states are introduced.Secondly,the coordinated control strategy between the proposed DC chopper and LCC-HVDC is designed,and the voltage-current stresses of the TFB-PCSMs are investigated.Finally,the ability to mitigate the CF issues and the fault recovery performance of LCC-HVDC system are studied in PSCAD/EMTDC.The results show that the probability of CF of LCC-HVDC is significantly reduced,and the performances of fault recovery are effectively improved by the proposed DC chopper.

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).