Experimental study on fault ride-through capability of VSC-based HVDC transmission system (original) (raw)
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Energy Engineering, 2022
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.
On Systematic DC Fault-Ride-Through of Multi-terminal MMC-HVDC Grids
2021 56th International Universities Power Engineering Conference (UPEC), 2021
Development of MMC-HVDC grids, as a new generation of VSC-HVDC systems, has been considerable through the past decade. Emerging of multi-terminal MMC-HVDC networks makes integration of multiple large-scale sustainable sources and asynchronous power grids quite feasible. However, protection and control of the multiterminal HVDC grids under fault situations have always been a vital issue. On the other hand, while modern AC grids get benefits of applied Fault-Ride-Through (FRT) operation and capabilities under AC fault conditions, the multi-terminal HVDC grids lack a systematic DC FRT operation. As the multi-terminal HVDC networks are going to become a backbone grid for the future power systems, it is necessary to define grid code requirements and standardizations considering DC FRT regulations. This paper presents potential DC FRT operations and possible profiles from HVDC grid point of view under DC fault conditions. A systematic DC FRT based on voltage against time profile is proposed. Different characteristics of voltage-based DC FRT are investigated in this study and results can be applicable to DC grid code definitions and requirements.
HVDC over HVAC Transmission System- Fault Conditions Stability Study
Electric Faults can be defined as the flow of a massive current through an alternative path which leads to cause serious equipment's damage, interruption of power, personal injury or death. High Voltage Alternating Current (HVAC) is the most effective and efficient way for energy transmission in modern power systems around the world. But, it's important to use High Voltage Direct Current (HVDC) system to link between different frequency networks and at transmitting energy on very long distance. HVDC operates at one side "converter station", where, the AC is converted to DC, which is then transmitted from sending end converter station, converted back to AC at receiving end to feed the other electrical network. This paper discusses the performance of the electrical grid system at the fault occurrence in HVAC and HVDC system. Also, this paper introduces the mathematical calculation steps at different faults conditions in the transmission line. The simulation of the fault current in this paper has been performed by using MATLAB/Simulink to compare the output fault current in HVAC and HVDC system.
Voltage Source Converter (VSC) based HVDC transmission technology hasbeen selected as the basis for several recent projects due to its controllability,compact modular design, ease of system interface, and low environmentalimpact. This paper investigates the dynamic performance of a 200MW,±100kV VSC-HVDC transmission system under some faulted conditionsusing MATLAB/Simulink. Simulation results confirm the satisfactoryperformance of the proposed system under active and reactive powervariations and fault conditions.
Control Strategies for AC Fault Ride Through in Multiterminal HVDC Grids
IEEE Transactions on Power Delivery, 2000
A fully operational multiterminal dc (MTDC) grid will play a strategic role for mainland ac systems interconnection and to integrate offshore wind farms. The importance of such infrastructure requires its compliance with fault ride through (FRT) capability in case of mainland ac faults. In order to provide FRT capability in MTDC grids, communication-free advanced control functionalities exploiting a set of local control rules at the converter stations and wind turbines are identified. The proposed control functionalities are responsible for mitigating the dc voltage rise effect resulting from the reduction of active power injection into onshore ac systems during grid faults. The proposed strategies envision a fast control of the wind turbine active power output as a function of the dc grid voltage rise and constitute alternative options in order to avoid the use of classical solutions based on the installation of chopper resistors in the MTDC grid. The feasibility and robustness of the proposed strategies are demonstrated and discussed in the paper under different circumstances.
The Journal of Engineering
This paper exploits the impact of different Low Voltage Ridethrough (LVRT) methods and equipment on both the wind energy elements and the grid including wind turbine/farm ability to provide reactive compensation, and maintain controllability during faults. The potential of using SFCL as an alternative LVRT equipment is preliminary studied. The paper also exploits some severe scenarios that could face a multi-terminal HVDC network. The influences of AC faults and control errors are examined. Results show limited deviations between the adopted LVRT methods. The wind turbine has to contribute to the stability of the AC collection grid of the wind farm, but it does not influence the grid, as both are decoupled through the multi-terminal HVDC grid. The implemented test systems and the examined events are developed in Matlab/Simulink and DIgSILENT.
A SURVEY- HVDC SYSTEM OPERATION AND FAULT ANALYSIS
High Voltage Alternating Current (HVAC) is the most easily and famous way for transmission energy in the world. But, it's important to use High Voltage Direct Current (HVDC) system to link between different frequency grids and at transmission energy on high long distance. HVDC operate at one side "converter station", where, the AC is converted to DC, which is then transmitted to a sending end converter station, converted back to AC, and fed into another electrical network. In HVAC transmission system, fault current due to electric faults is too large which affects the overall power system including -Receiving & Sending end bus, Transmission system, Load and even also the Power Generation Unit. HVDC transmission system dramatically reduces these effects, as the fault current due to electric faults is much lower, and only affects the individual faulty section of the overall transmission system. This paper discusses an overview of HVDC technology to use with transmission system. Also, this paper presents a 'fault current' (due to single line to ground faults) analysis and comparisons between HVAC and HVDC system. MATLAB (Simulink) simulation software is used to simulate both HVAC & HVDC system topologies. From the comparison of the simulation output -lower fault current, less fault effect, better performance & higher reliability is demonstrated for HVDC transmission system.
Control of an HVdc Link Connecting a Wind Farm to the Grid for Fault Ride-Through Enhancement
IEEE Transactions on Power Systems, 2000
This paper studies the issue of the fault ride-through capability of a wind farm of induction generators, which is connected to an ac grid through an HVdc link based on voltage sourced converters (VSCs). National grid codes require that wind turbines should stay connected to the power system during and after shortcircuit faults. In the latest literature, when the technology of HVdc based on VSCs is used to connect a wind farm to the power system, the blocking of the VSCs valves for a predefined short time interval is applied, in order to avoid the overcurrents and the tripping of the wind turbines. This paper proposes a control strategy that blocks the converters for a time interval which depends on the severity of the fault and takes special actions in order to alleviate the post-fault disturbances. In this way, the overcurrents are limited, the wind turbines manage to remain connected, and the ac voltage recovers quickly.
Improvement of fault critical time by HVDC transmission
Eighth International Multi-Conference on Systems, Signals & Devices, 2011
This paper investigates the impact of High Voltage Direct Current (HVDC) transmission on the transient stability of a two-machine power system, considering three transmission line configurations: parallel HVAC-HVAC, parallel HVDC-HVDC, and a hybrid HVAC-HVDC operation. The faults are balanced three-phase shortcircuits in AC lines, and single phase faults on DC lines, applied in the mid-point of the interconnection. For each configuration, transient stability of the AC systems is assessed in terms of the fault critical clearing time (CCT), and for different DC power levels. The results indicate the contribution of HVDC transmission in increasing the critical clearing time; and therefore enhancing the systems stability margin and operational security.