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There are increasingly routine situations where inverter-based generation from wind and solar power resources provides more than 50% of generation capacity during light load conditions in various regions of North America. This leads to concerns for meeting NERC power system reliability and frequency stability requirements. In particular, there have been cases of forced oscillations in recent years that may be made more severe with the presence of inverter-based generation. This paper presents a method for damping inter-area oscillations using the dc power flow capability of utility-scale solar-PV generation. The method incorporates local synchrophasor measurements in conjunction with wide-area SCADA messages to inject controlled power flows to increase system damping. Simulation results for a three-area interconnected power system corresponding to a disturbance event that occurred on June 17, 2016 in the US Eastern Interconnection indicates the proposed method could achieve improving frequency stability and a reduction in the effects of forced oscillations. [ABSTRACT FROM AUTHOR]

In the current energy exchange market it is essential to guarantee continuity and quality of supply both in steady state and during contingencies that might occur in any subsystem of interconnected systems. In this work it is shown how the geographical and topological characteristics of the subnetworks directly affect the quality and reliability in the energy exchange, especially when subsystems are interconnected without asynchronous ties that prevent power, frequency or voltage oscillations. This paper describes the problems faced by the interconnection between Mexico and the countries that define the Interconnected Electric System of the Central American Countries (SIEPAC). Different oscillations that have occurred are analyzed. Discrete control schemes to automatically trigger the 400 KV circuit that interconnects the systems of Mexico and Guatemala are proposed. [ABSTRACT FROM PUBLISHER]

This work explores the contribution of variable-speed wind turbines on two typical problems of multimachine power systems: the frequency regulation and the inter-area oscillations. Towards this end, a multimachine test system is augmented with a variable-speed wind farm. Two additional control loops are included in order to modify the active power delivered by the wind farm in response to frequency deviations and inter-area oscillations. Some guidelines are given to achieve a suitable tuning of the loop gains. In case of the inter-area oscillation compensator, the analysis is carried out for different loading conditions, measurement time delays and input signals. [ABSTRACT FROM PUBLISHER]

Several case studies are presented in this paper to better understand the impact of planned network changes on the dynamic stability of the future Great Britain transmission system. These studies have been conducted on a small network that is reasonably representative of the small signal stability problems present in the UK power system. The effect of wind penetration and HVDC links on the existing low frequency inter-area oscillations is analysed and interpreted for different possible future scenarios by observing the change of damping and frequency of this mode in response to these changes. [ABSTRACT FROM PUBLISHER]

This paper used a twofold method to assess and select suitable control input for PV supplementary wide-area damping controller (WADC) in large-scale interconnected system. The geometric measure of controllability/observability index is used to preselect the input signals for WADC. Then, the Hankel interaction index (HII) is Calculated for each subsystem considering signal transmission delay to determine the optimal signal for WADC. Since the undesired controller interactions are reduced significantly, advanced controller tuning would be achieved with less control effort. A detailed case study is carried out in 16 machine 68 bus test system with WADC at PV by adopting selected signal as the input to the controller. The performance of the controller is verified at different signal transmission delays. [ABSTRACT FROM PUBLISHER]

Inter-area oscillations involve wide areas of the power grid and numerous power system components. Therefore, identifying the components influencing negatively the oscillations damping is extremely challenging. The method proposed in this paper analyzes some variables monitored by phasor measurement units (PMU) in order to have a better understanding of the oscillation behavior. The influence of the following parameters is studied: the topology, the load model, power flows or the presence of fast exciters. The method works by clustering the mode frequency, the voltage angle difference between areas and the mode shapes. All of these variables can be given by PMUs. Starting from a sufficiently damped power system, the proposed clustering determines the main cause of a damping decrease. The weaknesses of the power system can then be emphasized to help the operators to take the appropriate actions to reinforce their system. The method is illustrated on a 4-machine test system. [ABSTRACT FROM PUBLISHER]

With the mature of synchronized phasor measurements technology, developing a phasor measurement units (PMUs) based wide-area damping control system becomes feasible. This paper discusses two practical considerations in the design of a PMU-based wide-area damping control system for power grid inter-area oscillations. The first consideration is the selection of PMU measurements. The second consideration is the selection of PMU data reporting rates. In this work, the synthesis of the damping controller is defined as a problem of mixed H2/H∞ output-feedback control with regional pole placement and solved by the Linear Matrix Inequality (LMI) approach. A two-area four-machine test system is used to illustrate these issues. [ABSTRACT FROM PUBLISHER]

This article presents an implementation of a Nordic grid model in Power System Analysis Toolbox (PSAT) — a free and open-source software. A newly developed hydro turbine and hydro governor (HTG) model is implemented with this grid model and compared with the currently available PSAT turbine and governor models. Small-signal and transient stability analyses of the system using the two models are carried out and compared to demonstrate the difference and necessity of accurate hydro turbine and governor model utilization. The paper ends with a validation of the linearized Nordic grid model generated by PSAT including the newly implemented HTG models. This validation is done through nonlinear time-domain simulation by applying both large and small disturbances. [ABSTRACT FROM PUBLISHER]

In order to reduce the detrimental effects of inter-area oscillations on system stability, it is possible to use Linear Matrix Inequalities (LMIs) to design a multi-objective state feedback control. The LMI optimization comes up with a control law that stabilizes numerous operating conditions simultaneously using a polytopic model of the system. However, the number of cases to be considered is limited by computational complexity and increased chances of infeasibility. In order to circumvent this problem, this paper presents a method for solving multiple polytopic problems having a common base case. The proposed algorithm determines which polytopic control is necessary for a particular contingency and classifies them as belonging to that polytopic domain. The technique was tested on an 8-machine, 13 bus system and provided satisfactory results. [ABSTRACT FROM PUBLISHER]

Selective Modal Analysis (SMA) has been used in the design of WAMS based damping of inter-area oscillations. In conjunction with a Linear Matrix Inequality (LMI) formulation and a polytopic model a single control law can be found to guarantee pole placement for multiple contingencies. The previous attempts have used a model containing all the ε and ω modes, with SMA used to eliminate all other states. In practical applications the resulting system is still too large to use in a polytopic model. This paper presents an algorithm to further reduce the system size to the relevant modes of oscillations. A 16 machine, 68 bus system is used as the test case with PSSs, DC lines and SVCs acting as the control. [ABSTRACT FROM PUBLISHER]

This article analyzes the impact of forced power system oscillations on mode damping estimation. Parametric (Yule-Walker) and non-parametric (Welch) methods for mode estimation are tested in the presence of forced power system oscillations. For mode damping estimation based on non-parametric methods, an application of Half Power Point method is proposed. Performances of the mode estimators are evaluated using both simulated and real synchrophasor data from the Nordic Grid. The presence of forced oscillations poses difficulties to mode damping estimators, these difficulties are identified, illustrated and explained herein. [ABSTRACT FROM PUBLISHER]

The paper presents a novel procedure for real-time detection of inter-area mode using distributed signals obtained by phasor measurement units (PMUs). Wide Area Control System signals could be intrinsically corrupted by noise and moreover characterized by data packets dropout due to transmission errors, buffer overflows and so on. In order to deal with the aforementioned troubles, an architecture which firstly performs a proper reconstruction technique, based upon a linear regression, and a digital filtering is proposed. The signals previously elaborated are fed through several windows of samples to the proposed measurement-based algorithm able to detect in real time electromechanical oscillations. It consists of a preliminary estimation of the electromechanical mode number by using Hankel Singular Value Decomposition (HSVD) and a successive application of the Variable Projection Algorithm (VarPro) to determine the damping and frequencies' mode. Consequently, some control actions have to be implemented if any unstable mode is detected, in order to avoid the power system collapse. A numerical application based on Kundur's 2-area test system confirms the potentiality of the proposed algorithm, comparing moreover its performances with those of other algorithms suitable for this kind of application. [ABSTRACT FROM PUBLISHER]

The application of PMU measurements and collocated control to damp inter-area oscillations with coordinated DC lines and static var compensators (SVCs) is investigated. The closed loop eigenvalues are excluded from a region of the complex plane guaranteeing that low frequency modes must be damped. A 16-machine, 68-bus study system reinforced with four DC lines or two DC lines and two SVCs is considered. The damping performance of the controllers is examined in the frequency and time domains. The simulation results show that the control scheme is able to robustly damp out inter-area oscillations following possible disturbances. [ABSTRACT FROM PUBLISHER]