Effect of static load models on hopf bifurcation point and critical modes of power systems

This paper presents the effect of different static load models on Hopf bifurcation point and critical eigenvalues of power systems. Three most commonly used static load models are investigated thoroughly under various operating conditions and with different power system controllers. Some interesting new observations hase emerged in the damping ratio of the critical mode, especially when power system controllers are introduced for control, in the system to control Hopfbifurcations. These observations would be useful in controller design for Hopf bifurcation or oscillation control

Influence of induction motor in stability of power system with high penetration of large-scale PV

Inverter-Based Energy Resources (IBERs) have become an ordinary portion of the generation mix in power systems. Furthermore, converter-based technology has come to dominate modern motor loads on the consumption side. This transition in components towards accommodating power electronic devices alters the dynamic response of the power system. This paper investigates the impact of these elements on the dynamic stability of the power system. Firstly, this study successes to optimize a suitable model for converter-based motor loads. Secondly, indices of transient and voltage stabilities are used to quantify the strength of the power system at different circumstances incorporating the induction motor loads. Finally, this analysis provides an insight into the mutual interactions between transient and voltage stabilities. It is concluded that converter-based motor loads improve the voltage recovery when compared with direct-connected induction motors. However, the system is vulnerable to transient stability with the proliferation of inverter-based motor loads when IBERs dominant in the generation mix. © 2020 IEEE

Impact of PV plant and load models on system strength and voltage recovery of power systems

In recent years, non-conventional inverter-based sources, namely, wind, PV, and others have emerged as excellent alternatives to the traditional synchronous machine for power generation. It has also been reported that the so-called system strength may be reduced with high penetration of non-conventional generations (NCGs). A number of methods have been used to assess system strength which may not reflect the interdependency or reciprocal influence of various factors affecting it. This paper presents a thorough assessment to quantify the implications of and the interaction of various factors affecting system strength, with the voltage recovery index being used as a quantification tool. © 2020 IEEE

A new global index for short term voltage stability assessment

The utility scale of non-conventional generators (NCGs), such as wind and photovoltaic (PV) plants, are competitive alternatives to synchronous machines (SMs) for power generation. Higher penetration of NCGs has been respondent of causing several recent incidents leading up to voltage collapse in power systems due to the distinct characteristics of NCGs under different operating conditions. Consequently, the so-called system strength has been reduced with higher NCGs penetration. A number of indices have been developed to quantify system strength from the short-term voltage stability (STVS) perspective. None of the indices capture the overall performances of power systems on dynamic voltage recovery. In this paper, an improvement in one of the STVS indices namely, the Voltage Recovery Index (VRI), is proposed to overcome shortcomings in the original index. Moreover, the improved index is globalized to establish a new index defined as system voltage recovery index (VRIsys) to quantify STVS at the system level. The amended VRI and developed VRIsys are used in systematic simulations to quantify the impact and interaction of various factors that could affect system strength. The assessment was conducted using time-domain simulation with direct connected induction motors (DCIMs) and a proliferation of converter-based technologies on both the generation and load sides, namely, NCGs and Variable Speed Drives (VSDs), respectively. © 2013 IEEE

Dynamic voltage signature of large scale PV enriched streesed power system

Renewable power generations including flexible demand and energy storage systems leverage significant changes in network operation. Thereby, power systems with high renewable penetration manifest deteriorated resilience to disturbances. Hence, the stable operation of the system could be affected. With a paradigm shift, dynamic voltage stability becomes one of the major concerns for the transmission system operators (TSOs). Predicting the dynamic voltage signature for the transmission system with high penetration of renewables is essential to assist in selecting appropriate corrective control. This paper utilized a comprehensive assessment framework to identify the dynamic voltage signature of the power system with PV and various loads. The voltage recovery index has been chosen as the quantifiable index to extricate the dynamic voltage signature. The applicability of the proposed framework is discussed using simulation studies on the IEEE-39 bus test system. © 2020 IEEE

Influence of Renewable Energy based Microgrid on Low Frequency Oscillation of Power Systems

Increase proliferation of microgrid (MG) technologies with extended use of renewable energy sources (RES) can affect the system stability performance since dynamic characteristics of this kind of MG are different from conventional generation. Sharing certain portion of or entire generated power from synchronous generator with MG results in decrease of total system inertia. On the other hand, connecting RES based MG near a central load eventually enhance system performance due to improvement in reliability, reduction of power loss and congestion on transmission line. This paper investigates the impact of RES based MG on local and inter-area oscillatory modes of power systems. This study focuses on low oscillatory eigenvalues in the frequency range of 0.1-2 Hz. Eigenvalues analysis is performed to observe damping ratios and stability margins of the system due to MG integration. Furthermore, time domain simulation is then carried out to validate the result from eigenvalues analysis

Influence of large-scale PV on voltage stability of sub-transmission system

Voltage instability is considered as one of the main threats to secure operation of power systems around the world. Grid connected renewable energy-based generation are deploying in recent years for many economic and environmental reasons. This type of generation could have significant impact on power system voltage stability given the nature of the primary source for generation and the technology used for energy conversion. This paper presents the results of an investigation of static voltage stability in heavily stressed IEEE-14 bus test system with large-scale PV integration. The study focused on the impact of large-scale PV penetrations and dynamic VAr placements on voltage stability of the sub-transmission system. For this study, the test system loads are modeled as the summer peak load of a realistic system. The comparison of STATCOM and SVC performance with large-scale PV is also discussed

Dynamic Droop Control in Microgrid for Stability Enhancement Considering RES Variation

Abstract—In this paper, small signal stability analysis of a hybrid Microgrid (MG) considering RES variations is addressed. As wind speed or solar irradiance fluctuates, active power output from DGs might vary significantly. Hence, the power sharing scheme would change considerably. Dynamic droop-gain control is proposed to deal with the RES change and maintain the stability of MG. The proposed control method provides adjustable power sharing strategies to manage RES fluctuation and ensure frequency and voltage regulation of each DGs. Eigenvalues analysis and time domain simulation suggest that at high wind speed and solar irradiance the damping ratio of critical modes and dynamic performance of DG units defer significantly. As the dynamic droop controller implemented, the damping performance and stability margin of the hybrid MG were improved in different operating condition, ensuring stable MG operation in most of RES conditions. Keywords—Microgrid, RES variations, variable droop, power sharing, small signal stability

Forced oscillation detection amid communication uncertainties

This article proposes a novel technique for the detection of forced oscillation (FO) in a power system with the uncertainty in the measured signals. The impacts of communication uncertainties on measured signals are theoretically investigated based on the mathematical models developed in this article. A data recovery method is proposed and applied to reconstruct the signal under the effects of communication losses. The proposed FO detection with communication uncertainties is evaluated in the modified 14-machine Southeast Australian power system. A rigorous comparative analysis is made to validate the effectiveness of the proposed data recovery and FO detection methods

Microgrid Impact on Low Frequency Oscillation and Resonance in Power System

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