This paper develops a systematic procedure of designing a centralized damping control system for power grid interarea oscillations putting emphasis on the signal selection and control system structure assignment. Geometric measures of controllability/observability are used to select the most effective stabilizing signals and control locations. Line power flows and currents are found to be the most effective input signals. The synthesis of the controller is defined as a problem of mixed H 2/H infin output-feedback control with regional pole placement and is resolved by the linear matrix inequality (LMI) approach. A tuning process and nonlinear simulations are then used to modify the controller parameters to ensure the performance and robustness of the controller designed with linear techniques. The design process is tested on the New England 39-bus ten-machine system.

Design of Wide-Area Damping Controllers for Interarea Oscillations

This paper describes an online dynamic security assessment scheme for large-scale interconnected power systems using phasor measurements and decision trees. The scheme builds and periodically updates decision trees offline to decide critical attributes as security indicators. Decision trees provide online security assessment and preventive control guidelines based on real-time measurements of the indicators from phasor measurement units. The scheme uses a new classification method involving each whole path of a decision tree instead of only classification results at terminal nodes to provide more reliable security assessment results for changes in system conditions. The approaches developed are tested on a 2100-bus, 2600-line, 240-generator operational model of the Entergy system. The test results demonstrate that the proposed scheme is able to identify key security indicators and give reliable and accurate online dynamic security predictions.

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An Online Dynamic Security Assessment Scheme Using Phasor Measurements and Decision Trees

Accurate measurement of the rotor angle and speed of synchronous generators is instrumental in developing powerful local or wide-area control and monitoring systems to enhance power grid stability and reliability. Exogenous input signals such as field voltage and mechanical torque are critical information in this context, but obtaining them raises significant logistical challenges, which in turn complicates the estimation of the generator dynamic states from easily available terminal phasor measurement unit (PMU) signals only. To overcome these issues, the authors of this paper employ the extended Kalman filter with unknown inputs, referred to as the EKF-UI technique, for decentralized dynamic state estimation of a synchronous machine states using terminal active and reactive powers, voltage phasor and frequency measurements. The formulation is fully decentralized without single-machine infinite bus (SMIB) or excitation model assumption so that only local information is required. It is demonstrated that using the decentralized EKF-UI scheme, synchronous machine states can be estimated accurately enough to enable wide-area power system stabilizers (WA-PSS) and system integrity protection schemes (SIPS). Simulation results on New-England test system, Hydro-Quebec simplified system, and Kundur network highlight the efficiency of the proposed method under fault conditions with electromagnetic transients and full-order generator models in realistic multi-machine setups.

Local and Wide-Area PMU-Based Decentralized Dynamic State Estimation in Multi-Machine Power Systems

There are both economic and environmental urges for transition from the current outdated power grid to a sensor-embedded smart grid that monitors system stability, integrates distributed energy and schedules energy consumption for household users. Especially with the proliferation of intelligent measurement devices, exponential growth of data empowers this transition and brings new tools for the development of different applications in power system. Under this context, this paper presents a holistically overview on the state-of-the-art of big data technology in smart grid integration. First, the features of smart grid and the multisource of energy data are discussed. Then, this paper comprehensive summarizes the applications leveraged by big data in smart grid, which also contains some brand new applications with the latest big data technologies. Furthermore, some mainstream platforms and knowledge extraction techniques are looked to promote the big data insights. Finally, challenges and opportunities are pointed out in this paper as well.

Big data issues in smart grid – A review

Inter-area oscillations in bulk power systems are typically poorly controllable by means of local decentralized control. Recent research efforts have been aimed at developing wide- area control strategies that involve communication of remote signals. In conventional wide-area control, the control structure is fixed a priori typically based on modal criteria. In contrast, here we employ the recently-introduced paradigm of sparsity- promoting optimal control to simultaneously identify the optimal control structure and optimize the closed-loop performance. To induce a sparse control architecture, we regularize the standard quadratic performance index with an l1-penalty on the feedback matrix. The quadratic objective functions are inspired by the classic slow coherency theory and are aimed at imitating homogeneous networks without inter-area oscillations. We use the New England power grid model to demonstrate that the proposed combination of the sparsity-promoting control design with the slow coherency objectives performs almost as well as the optimal centralized control while only making use of a single wide-area communication link. In addition to this nominal performance, we also demonstrate that our control strategy yields favorable robustness margins and that it can be used to identify a sparse control architecture for control design via alternative means.

Sparsity-Promoting Optimal Wide-Area Control of Power Networks

This paper recalls the 30-year history of wide-area measurements at Hydro-Quebec. At present, a state-of-the art, eight-PMU-based wide-area monitoring system commissioned in 2004 is on line, feeding the EMS with GPS-synchronized angles, frequencies, and harmonic distortion measurements from key 735-kV buses. Specific to Hydro-Quebec is the current use of one such system for frequency regulation reporting and control-room implementation of preventive measures against geomagnetic storm-induced contingencies. Building on this experience, the Hydro-Quebec research institute, together with TransEnergie, is developing advanced applications which, in the long term, will go beyond active monitoring to safely initiate targeted control actions aimed at extending system power transfer limits with respect to both transient and long-term stability. In addition to the major improvement in inter-area mode damping shown previously by the authors, this paper demonstrates that, surprisingly, wide-area control of static VAr compensators (SVC) will also vastly extend the first-swing stability margins. Finally, initial results on a wide-area measurement-based secondary voltage control of the extensive park of dynamic shunt compensators in our grid using a single pilot voltage from the load center are very encouraging.

Wide-area monitoring and control at Hydro-Quebec: past, present and future

This paper applies, to a practical test case, two schemes for determining harmonics in power systems that are not limited to stationary waveforms, but can equally estimate harmonic phasors in waveforms with time-varying amplitudes and changing fundamental frequency. The first scheme relies on the short-time Fourier analysis performed using the fast Fourier transform (FFT) with time-domain windowing and frequency-domain interpolation. Another scheme combines fundamental-frequency tracking with a Kalman filter-based harmonic analyzer, yielding a uniformly sampled, self-synchronizing harmonics tracker. The performance of these advanced measurement schemes for changing harmonics is illustrated convincingly on nonstationary waveforms generated in the EMTP using a realistic series-compensated transmission network.

D. McNabb

Papers

Wide-area monitoring and control at Hydro-Quebec: past, present and future

On-line tracking of changing harmonics in stressed power systems: application to Hydro-Quebec network