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As a significant part of electrical load, air conditioners draw attentions for their sometimes-unfriendly load characteristics, especially their dynamic responses during grid voltage disturbances. In this paper, a novel under-voltage control strategy for variable-speed air conditioners is introduced, which can keep air conditioners load characteristic as constant impedances when unexpected voltage...
This paper presents a utilization technique for enhancing the capabilities of dynamic voltage restorers (DVRs). This paper aims to enhance the abilities of DVRs to maintain acceptable voltages and last longer during compensation. Both the magnitude and phase displacement angle of the synthesized DVR voltage are precisely adjusted to achieve lower power utilization. The real and reactive powers are...
Contingency analysis plays a key role in evaluating the performance of a system under stressed conditions. This paper proposes Trajectory Violation Integral (TVI) index as a measure to quantify the effect of contingency. Contingency clustering enables partitioning of the system into coherent and independent Voltage Control Areas. The data that is worked on during contingency clustering is of high...
In this paper, a new approach based on dynamic relative gain is proposed for partitioning voltage control areas in bulk power systems. The critical nodes of voltage stability are determined using voltage stability index, “L index”. The cross relative gain between the critical nodes and other nodes are calculated based on the concept of dynamic transfer function (DTF) and dynamic cross relative gain...
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...
The integration of renewable energy sources in power systems has steadily increased in the recent years in the vision of significantly decreasing the carbon emissions produced by the conventional power plants. Although the incorporation of the renewable energy sources in the power system network is environmentally beneficial, at the same time it poses some challenges regarding their smooth operation...
This paper presents a placement method of fuzzy logic based unified power flow controller (UPFC) in power system network by analyzing dynamic voltage stability. Voltage stability indices namely LQP and voltage collapse point indicators (VCPI) indices are used to determine the weakest line for UPFC by dynamic load variation. The controllers of the shunt and series converters of the UPFC are developed...
Conventional load shedding control strategy adjusts undervoltage load shedding and underfrequency load shedding respectively, and undervoltage load shedding only focuses on local voltages without consideration on characters of transient voltage responses. This paper analyses the relationship between the disturbance scale and transient voltage drops, thus proposing a novel index for the disturbance...
The paper presents a comprehensive methodology for voltage stability assessment of power systems using modern analytical tools. The paper also highlights the importance of proper power system component modeling, especially dynamic loads, for achieving higher accuracy. A case study for a practical system is presented and simulation results are discussed.
It is hard to determine critical point of voltage stability exactly for some online voltage stability algorithm and its decision-making time is required to be very small, which hinders its practical application on power system. A novel control strategy of voltage stability based on generator dynamic reactive power releasing is presented to deal with the problem. When voltage collapse happens, stator...
This paper presents an on-line equivalent algorithm for power system based on phasor measurement unit. The method considers the changes of the system parameters and load level, which overcome parameters rift problem and the shortage of traditional two points power flow method that supposing the parameters are fixed after a small disturbance. On this basis, voltage stability and Alert margin are proposed,...
Insufficient reactive power in DC converter stations may deteriorate the whole system operating conditions. In this paper, the ratio between reactive power consumption and active power transmission as a HVDC system provides Emergency DC Power Support (EDCPS) is analyzed and derived. Then multicircuit HVDC system EDCPS Strategies with reactive power controls, such as emergency reactive power compensation,...
This paper covers the modelling of the standard IEEE 14 bus system using the MATLAB package. The basic system is tested under large and small disturbances to study the dynamic behaviour of the system and the stability margins associated with the different configurations of the system. As a suggested solution to increase stability margins of the system, Sen transformer is added, modelled and tested...
Under voltage load shedding (UVLS) plays a vital part in power system control when the system is subjected to large disturbances. Load shedding has been employed for long time as the last remedy to preclude major power system failure which is activated by under frequency or under voltage relays. This paper proposes an advanced method for under voltage load shedding incorporating the bus participation...
The paper investigates the possibility of ranking synchronous generators in a power system according to their contribution to system angular and voltage stability. The aim of this research is to establish fast semi-analytical methodology, i.e., avoiding transient simulations, to determine which synchronous generators can be safely disconnected from the network or replaced by other types of generators,...
This paper presents model predictive control method for load shedding based on trajectory sensitivities. According to the basic principle of model predictive control, aiming at minimizing the quadric performance index which comprehensively considers both the control cost and the deviation between bus voltage predictive trajectories and their reference values, the receding optimization model is described...
Trajectory sensitivity analysis can provide valuable insights into the security of an electric power system. There is a strong correlation relating the system stability and the corresponding trajectory sensitivity. In this paper it is analyzed the influence of load shedding in the voltage stability of an electric power system using trajectory sensitivity analysis. It is recognized that voltage instability...
Voltage stability is one of the aspects of the power system stability. Since regulating transformers are more and more used in modern power system, tap change has often been considered as a principal mechanism that may lead to voltage collapse, but tap change can also rescue a would-be collapse system by extending the power transfer limit. Using time domain medium-and-long term voltage stability simulation...
In this paper a voltage stability analysis is described, which is coupled with an online dynamic security and protection assessment system (DSA). The focus will lie on the calculated indices and their algorithms using time domain simulations. Because the online DSA collects information from four different modules, the voltage stability module, small signal stability module, the transient stability...
This paper deals with bifurcations and loadability issues in power systems. A single machine system with dynamic state space represented by a set of differential algebraic equations is considered. It is emphasized that this small system can give a first step in understanding the issues discussed in this paper. Using system loading as a bifurcation parameter and considering two methodologies for calculating...
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