Search

Due to the wide frequency range of sub-synchronous oscillations (SSOs) in converter-tied grids, existing SSO parameter estimators generally use a long window to pre-identify the SSO frequency, and thus generally have slow responses in SSO parameter estimation. To deal with this problem, this paper proposes an online SSO stability analysis-based SSO parameter estimator. The operating condition of the grid is updated online by measuring the fundamental voltage/current phasor. Then the impedance of the converter is updated based on the identified operating condition, and the SSO stability is analyzed online. If an unstable SSO mode is detected, the identified SSO frequency is used to build the imaginary exponential function-based signal model, and the SSO parameters are estimated based on the least square method. Case studies show that the proposed method has a much faster response than the methods recently published in the literature, and can obtain accurate SSO parameter estimates. • A new SSO estimator is shown • SSO analysis results are used • It is fast and accurate [ABSTRACT FROM AUTHOR]

Highlights • A wide-area monitoring and early-warning system of SSO is proposed. • The system incorporates locally deployed S-PMUs and a centralized DC&SDA. • A global view of SSO is established with the subsynchronous state estimation. • The subsynchronous power & current flow is formed to locate oscillation source/path. • Two stability criteria are used for the real-time evaluation of SSO stability. Abstract With the increasing penetration of renewable power generation (RPG) in modern power systems, subsynchronous oscillation (SSO) induced by the interaction between RPG and the grid is posing a great threat to the system stability and equipment safety. To address this issue, this paper proposes a wide-area monitoring and early-warning system of SSO. It incorporates the locally deployed subsynchronous phasor measurement units (S-PMUs) and a centralized data center & subsynchronous dynamics analyzer (DC&SDA). Several key functions have been developed, including: (1) the subsynchronous state estimation (SSE) to form global view or observability of SSO dynamics, (2) the establishment of subsynchronous power & current flow to locate oscillation source/path, and (3) the real-time evaluation of subsynchronous stability using two complementary criteria, one based on the identification of oscillation damping and the other based on the frequency characteristics of the impedance models. The practicality and performance of the proposed system have been demonstrated with electromagnetic transient (EMT) simulations on a practical system that suffered SSO incidents. [ABSTRACT FROM AUTHOR]

Due to the interactions between the generators/power electronic devices and the grids, wideband oscillation events have occurred frequently in renewable power systems with frequencies from several Hz to several kHz. Wideband oscillation monitoring techniques have been emerging in recent years to identify and analyze these events. Unlike existing review papers that concentrate on fundamental synchrophasor technology, this paper reviews the wideband monitoring technology. Specifically, the synchronized wideband phasor measurement techniques and the synchronized waveform measurement techniques are first reviewed. Next, the measurements' applications on wideband oscillation identification, early warning, and mitigation, and other applications in power system operation are carefully introduced. Also, the challenges in wideband phasor estimation and waveform data compression are discussed, and possible solutions are highlighted. Finally, future research opportunities on new applications in wideband oscillation and power quality are highlighted. [Display omitted] • This review focuses on wideband phasor and waveform measurements and applications. • This is the first paper that concentrates on the wideband oscillation monitoring. • The challenges on wideband measurements are discussed. • Future researches on new applications of wideband measurements are highlighted. [ABSTRACT FROM AUTHOR]

• A multi-modal damping control (MADC) is proposed to damp multiple oscillation modes independently. • A general design framework for damping multiple oscillation modes is given. • MADC is validated to damp sub-synchronous and super-synchronous oscillations in Type-4 wind farms. Type-4 wind farms connected to weak AC grids have the risk of sub-synchronous oscillation/interaction (SSO/SSI) with multiple oscillation modes, which can lead to unplanned outages and system destabilization. This paper first presents the magnitude and frequency characteristics of the oscillations followed by the control design requirements. Then, it gives a general design of grid-side multi-modal adaptive damping control (MADC) to stabilize multiple oscillation modes. The MADC utilizes an FFT-based inter-harmonic phasor measurement algorithm, which can detect and track multiple oscillation modes simultaneously. The MADC uses bus voltages and line currents as inputs to extract and control each oscillation mode without considering the coupling of the modes due to the frequency coupling effect. The unstable modes are stabilized by injecting phase-shifted currents with multiple frequencies such that the impedance response of the whole system around the concerned frequencies is reshaped. Notable features of the proposed damping control include automatic and independent detection, tracking and suppression of multiple oscillation modes. The proposed MADC's damping performance is validated through extensive electromagnetic transient (EMT) simulations of type-4 wind farms connected to a weak ac grid causing super-/sub-synchronous oscillations. The system model and the proposed damping control are designed and tested in commercial EMT software. [ABSTRACT FROM AUTHOR]

Highlights: [•] The new approach is based on the supplementary-excitation-signal-injection test. [•] It can identify frequencies and mechanic damping of all torsional modes concerned. [•] A solid theoretical foundation is established upon the dynamic shaft model. [•] A systematic test and identification procedure is developed. [•] The approach is applied in practical systems and validated through field test. [ABSTRACT FROM AUTHOR]

Abstract: This paper proposes systematic procedures to design wide-area damping controls (WADCs) in large interconnected power systems. An efficient model reduction method is first introduced, based on the pseudo-random binary signal (PRBS) probing technique and the prediction error identification algorithm (PEM). Then, the comprehensive controllability concept, as well as its calculating method, is proposed for properly locating the supplementary damping controllers. Further, an improved modal performance index is adopted as the measure of the stabilizing effect. With various constraints taken into account to meet practical engineering requirements, finally, the optimized and coordinated tuning of WADC parameters under various operation scenarios is achieved by a constrained nonlinear programming algorithm. The proposed approach has been tested on a practical 437-machine, 2791-node interconnected power system and the simulation results have demonstrated its high effectiveness in damping inter-area oscillations and enhancing across-region transfer capabilities. [Copyright &y& Elsevier]

Abstract: The phasor measurement units (PMU) and wide-area measurement systems (WAMS) have been widely established in modern power systems to improve the monitoring of the system behavior as well as the system control. In this paper, an integrated scheme for the monitoring and detection of low-frequency oscillations has been developed, based on our extensive experience in using Prony algorithm for oscillation analysis in practical WAMS projects. By analyzing the real-time synchro-phasors, the proposed scheme is competent to identify the characteristics of the low-frequency oscillations in real-time and alert the operators once the oscillation is under-damped or divergent. To ensure accurate monitoring of system dynamics and reliable detection of dangerous oscillations with noise-polluted WAMS measurements, several key signal-processing techniques are implemented, including delicate designing of prefilters, Prony analysis result correction, and comprehensive indices for stability evaluation. In the end, the developed scheme is tested with simulated signals and measurements from practical power systems. Its applications to large-scale power grids for detection and early-warning of low-frequency oscillations are also presented. The results have convincingly demonstrated the validity and practicability of the developed scheme. [Copyright &y& Elsevier]