Feasibility of HVDC for Very Weak AC Systems with SCR below 1.5 (original) (raw)
Related papers
On the Indexes to Qualify an HVDC Connected to Very Weak Ac Networks
2007
This paper develops a voltage stability analysis of ac/dc systems using static and modal indexes. The indexes are normalized and compared for different short circuit ratios, SCR, for several known networks at a common voltage base. Two new indexes are proposed to provide more information on reactive power requirements for voltage stability. The first index proposes critical values for several SCR´s, whereas the second allows featuring two types of systems, soft and non-soft, to qualify requirements of reactive power. The approach can assist for considering the reactive compensation or control strategies in HVDC applications.
Stability improvement of a HVDC transmission link between weak AC systems by multi-terminal scheme
2013 Africon, 2013
High Voltage Direct Current (HVDC) schemes are becoming a more attractive solution as they have been used extensively in interconnected weak power AC systems. But, the problem of voltage stability for weak AC systems interconnected by a DC link is critical especially during islanding conditions. The approach to improve more on the stability of such system would be to device a means of injecting locally controlled dc power on the dc-link transmission corridor forming a radial multi-terminal HVDC. However, continuous injection of DC power on the dc line of the VSC HVDC link though will increase the power transfer capability of the system but should have a limit otherwise it will lead to instability of the system. In this paper, a detailed VSC HVDC model and a simple analytical technique using the principle of uniform loading to determine penetration limit is presented. The techniques is applied to our case study and validated with a simulation result. Critical contingencies such as sudden island conditions, threephase to ground fault are simulated with and without DC power penetration. Results show the stability support on the AC side networks by DC power injection on the dc-link.
Multiple Infeed Short Circuit Ratio – Aspects Related to Multiple HVDC into One AC Network
2005 IEEE/PES Transmission & Distribution Conference & Exposition: Asia and Pacific, 2005
The paper suggests an extension of the classical definition of Short Circuit Ratio and Effective Short Circuit Ratio to multiple infeed of HVDC transmission configuration. With such new indexes, which consider the interaction between converter stations, it is possible to predict low frequency resonances, dynamic overvoltages and risk for voltage and power instability at low value of the index, similar to single infeed configuration. In this paper it is also discussed other relevant issues related to integration of multiple HVDC links when the strength of the system is relatively low compared to the amount of power delivered by the HVDC links.
ANALYSIS OF MULTI-TERMINAL HVDC TRANSMISSION SYSTEM FEEDING VERY WEAK AC NETWORKS
This paper presents a line commutated converter (LCC) based multi-terminal HVDC transmission (MTDC) system feeding very weak AC networks with hybrid reactive power compensators (RPC's) at the inverter AC side. The hybrid compensator is accomplished by the equal mixing of any two of the following compensators: synchronous compensator (SC); static var compensator (SVC); static synchronous compensator (STATCOM). The four-terminal HVDC transmission system model is implemented in the Matlab with the firefly algorithm based optimal proportional integral (PI) controller for rectifiers and inverters control. The transient performances of hybrid RPC's (SC+SVC, SVC+STATCOM and SC+STATCOM) are studied under various fault conditions and the results are compared with the performance of the SC, SVC and STATCOM to focus the high quality of the hybrid compensators. The simulation results authorize that the equivalent mixture of SC and STATCOM has a steady and fastest response. The results also reveal the supremacy of the firefly algorithm based optimal PI controller over the conventional PI controller. The harmonic present in the inverter side AC quantities is also calculated under steady state operation to assure the quality of power supply.
IEEE PES Innovative Smart Grid Technologies, Europe, 2014
This paper discusses grid code compliance for pointto-point VSC-HVDC systems used for the grid connection of far and large offshore wind power plants. The study focus on the short circuit current contribution provided by VSC-HVDC system delivery. Sensitivities such as the reactive current boosting gain of the AC voltage controller, the choice of deadband and the method prioritising active versus reactive current during faulted conditions are discussed with focus on power system voltage and rotor angle stability of a multi-machine power system. The paper shows that prioritising the reactive short circuit current versus active current leads to improvement in both voltage response and transient stability of the AC power system. In addition, the removal of the dead-band while increasing the proportional gain of the AC voltage controller is proved to be beneficial for the power system stability.
Review of HVDC control in weak AC grids
Electric Power Systems Research, 2018
Current (HVDC) transmission systems to a weak AC grid has been a challenge in recent years. The main target of this paper is to provide a comprehensive review of the "converter control" approaches for: (1) the Line Commutated Converter (LCC)-based HVDC and (2) the forced commutated converter-based HVDC systems in weak AC grids. The control architecture for each HVDC technology (forced commutated and line commutated) is included. The stability limitations associated with HVDC systems, including LCC-HVDC, Voltage Source Converter (VSC)-based HVDC, and the Current Source Converter (CSC)based HVDC, are elaborated. Moreover, the most recent control approaches for possible integration of LCC-HVDC and VSC-HVDC to very weak AC grids are introduced. Finally, the reliability modeling for each HVDC technology in weak AC grid integration is included for corrective and preventive reliability analysis. The LCC-HVDC technology is the best option associated with high power capacities around 10,000 MW for a bipole configuration [13]. Forced commutated converter-based HVDC is the second type of HVDC transmission which is normally applied for medium power levels up to 1000 MW [13,14]. However, since the advent of Modular Multi-level Converters (MMCs), high power application of VSCs has become a reality [15]. For power transmission lines, the following two different types of converters have been established so far: (1) LCCs, which are Current Source Converters (CSCs) using Thyristor switches, and (2) Voltage Source Converters (VSCs), which use IGBT switches [14]. Other combinations and power electronic switches such as forced commutated converter-based CSCs are possible, but are not common at the
Enhancing Power Transmission Stability with HVDC Systems During Load Contingencies
Journal Européen des Systèmes Automatisés, 2024
The transmission network of a power system is important in connecting interactions between the generation and distribution sides. A significant aspect in the power system profile is voltage improvement. This study intends to examine the impact of inserting High Voltage Direct Current (HVDC) on the system's voltage stability, network power losses and power transfer capacity of transmission network under several cases of load contingency. IEEE 57-Bus test system is used for testing the addition of HVDC transmission based on genetic algorithm. Modeling of point-to-point HVDC transmission and multi-terminal HVDC transmission is carried out using the Power System Simulator for Engineering (PSS/E) version 32 Package Program (A collection of computer programs and organized data files called PSS/E software was developed by Siemens PTI to handle the fundamental tasks of power system performance simulation work). The system's performance was compared with and without the HVDC inserted under different loading scenarios: 5%, 10%, and 20% of the total load. The comparative results can show that active power losses at the normal load case are reduced by 55.714% after inserting point to point HVDC topology, and after inserting multi-terminal HVDC topology reduced by 68.214%. Also, the reactive power losses reduce by 55.714% after inserting point to point HVDC topology and after inserting multi-terminal HVDC topology reduced by 66.830% at the same case. The results shown that inserting HVDC Transmission to the system gives better improvement in bus voltage profile and a significant reduction in total network power losses and increase in power transfer capacity of transmission network. The results also showed that multi-terminal HVDC transmission is better in voltage improvement and total power losses reduction when HVDC Transmission is added to the system.
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.
E3S Web of Conferences, 2019
The Network Code for HVDC systems introduces a requirement for such systems to remain in operation in an AC network during short-circuits. This requirement (among others) is determined by a time curve of a minimum voltage in HVDC connection point. The HVDC system is not allowed to be turned-off while the voltage value exceeds the values of the curve, however the HVDC system in LCC technology does not meet this requirement. The Network Code introduces the possibility of blocking the LCC systems. After the LCC system is blocked it stops transmitting the power, which prevents the LCC system from being turned off during a short-circuit in the network but results in a lack of power exchange between the network and the LCC system. Therefore, the authors developed a proposal to limit the power level being transmitted by the LCC system, thus there is no necessity to block the LCC system operation. The simulation research carried out clearly indicate the validity of this idea. In addition, t...