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This work studies the modeling and control of a six-phase generator and rectifier unit in MVDC systems. The design approach for the generator's automatic voltage regulator (AVR) is developed based on the generator's linearized models. The dc terminal impedance of the generator-rectifier unit is derived based on system analysis and numerical approximation. Further, the dc terminal impedance of the...
This paper presents a study of the impact of severe generation imbalance on reactive power margins. In particular, the focus of the study is the analysis of characteristics of the reactive power margins under two common strategies A) generation redispatch and B) load shedding when a significant loss of generation occurs in a power system. Simulation results show that, at some buses, Strategy A may...
Results from two practical and fast methods to estimate systems' Maximum Loading Point (MLP) using Phasor Measurement Units (PMUs) are used in this paper as initial values for a robust and very efficient method that takes advantage of the geometric characteristics of the maximum loading hyperplane and uses the load flow with step size optimization (LFSSO) technique to estimate the system's proximity...
This paper describes an approach for determining generation-shedding for dynamic Remedial Action Scheme (RAS) based on minimum cost. A generation-shedding cost function is developed based on generator fuel cost, startup/shut down cost, and bid price. The proposed method updates RAS control actions online based on the system operating conditions and cost functions. The Single Machine Equivalent (SIME)...
A hybrid simulation/measurement-based framework for online dynamic security assessment (DSA) is proposed in this work. It combines the strengths and features of simulation-based and measurement-based approaches to develop a tool that integrates the results and provides real-time situational awareness on available operating margins against major stability problems. High performance computing capability...
This paper demonstrates the effectiveness of post-fault corrective control action through the planned Western HVDC link in the Great Britain (GB) transmission network. It is shown that both transient as well as oscillatory stability problems could be tackled using such a corrective control strategy which allows higher pre-fault loading of the AC network without compromising security. The corrective...
With the advent of smart-grid technology, the wide application of FACTS (Flexible AC Transmission Systems)- based damping controllers exerts influences on both small signal stability and transient stability. Traditional Modal Analysis (MA) method can hardly meet the requirements of online applications. According to the inter-area oscillation mode to be studied, the multi-machine system can be equivalent...
Monitoring the long term voltage stability of the power grid is necessary to ensure its secure operation. In this paper, a voltage stability index that is linear with the power demand, called the M-index, based only on angles is proposed. The linearity of the M-index can be utilized to estimate the load margin directly. The linearity of the M-index is proved for the two-bus system and a method to...
System splitting is an efficient way to prevent widespread blackout. Finding proper splitting schemes for on-line application is becoming increasingly difficult due to the combinatorial explosion nature of the problem. This paper considers a new problem formulation of system splitting with priority service areas and proposes an efficient three-stage method for designing on-line system splitting. These...
Voltage instability may be predicted by the Thevenin equivalent based approach using only local measurements taken at the monitored buses. This paper focuses on reliable estimation of Thevenin parameters from measurements, which are crucial in judging voltage stability. Two parameter estimation methods (least squares and Kalman filter) and a proposed new hybrid method are tested on the NPCC 140-bus...
Short-term voltage stability problem (STVSP) is a serious threat to receiving-end power systems which are short of reactive power reserves. This paper discusses how to plan the size of shunt capacitor banks (SCB) in a receiving-end power system to achieve a maximum voltage stability margin. The local generators and SCB are two important reactive power resources in receiving-end power systems. The...
Transient stability constrained optimal power flow (TSCOPF) is a challenging problem of power system. In this paper, TSCOPF is decomposed into three sub-problems, namely transient stability assessment (TSA), the stability constraint constructing and simple TSCOPF. They are solved iteratively to achieve the optimal operation point. In the TSA sub-problem, each contingency is simulated and the stability...
Stability-constrained optimal power flow (SOPF) is an effective and economic tool to enhance stability performance by adjusting initial steady-state operating conditions, with the consideration of rotor angle and short-term voltage performance criteria. SOPF belongs to the category of dynamic optimization problems which are computationally expensive. In order to reduce its computational complexity,...
Power flow solvable boundary plays an important role in contingency analysis, security assessment, and planning processes. However, to construct the real solvable boundary in multidimensional parameter space is burdensome and time consuming. In this paper, we develop a new technique to approximate the solvable boundary of distribution systems based on Banach fixed point theorem. Not only the new technique...
This paper presents MatLVDC, i.e. an open source Matlab toolbox to analyse dynamic phenomena in DC distribution networks, that are gaining importance because of reported energy savings and the increasing number of DC loads and distributed energy resources (DER). The toolbox aims at facilitating the design processes and research on DC distribution networks including a high share of renewable energy...
The integration of large-scale wind generation has brought great challenges to the small-signal stability analysis of power systems, due to the output uncertainty of wind farms. To solve this problem, this paper extends the conventional concept of small-signal stability region (SSSR) to a concept of robust small-signal stability region (R-SSSR), which is capable of dealing with the effects of uncertain...
This paper discusses experiences in the use of online stability analysis tools in Electric Reliability Council of Texas (ERCOT) interconnection, USA. In order to prevent certain unstable system conditions, the online stability analysis tool - DSATools - has been implemented in the ERCOT control room. Using real-time information from the Energy Management System (EMS), DSATools calculates the system...
Most of the ongoing smart grid projects are focused on power distribution system automation and upgrades. Although there is no electricity market in the distribution system yet, this will be a natural step with increasing penetration of distributed energy resources (DER). This work extends transmission locational marginal price (LMP) concept to distribution level. A new Optimal Power Flow (OPF) methodology...
Continuation power flow is an important tool for assessing power system voltage stability. A continuation power flow method for distribution networks is proposed in view of unbalanced three-phase lines and loads in distribution networks with distributed generations (DG). The proposed method consists of tangent predictor and Newton corrector. A local geometric parameterization technique is utilized...
Voltage instability caused by integrating large-scale wind generation into a weak system is a well-known challenge. The ERCOT 2012 Long Term System Assessment report indicated that a voltage stability limit will constrain wind power delivery to the rest of the ERCOT system if the northwestern-most portion of the ERCOT Panhandle CREZ system becomes over-subscribed. To identify the system upgrades necessary...
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