IEEE PSS2B versus PSS4B: the limits of performance of modern power system stabilizers

Hydro-Quebec, Varennes, Que., Canada
IEEE Transactions on Power Systems (Impact Factor: 2.92). 06/2005; DOI: 10.1109/TPWRS.2005.846197
Source: IEEE Xplore

ABSTRACT IEEE Std 421.5 as revised by the IEEE excitation system subcommittee will introduce a new type of power system stabilizer model, the multiband power system stabilizers (PSSs). Although it requires two inputs, like the widely used IEEE PSS2B, an integral of accelerating power PSS introduced at the beginning of the nineties as the first practical implementation of a digital PSS, the underlying principle of the new IEEE PSS4B makes it sharply different. The present paper aims at assessing the two families of PSS's from the point of view of their relative performance in tackling a wide range of system problems, using a single set of so-called robust/universal settings. Conclusions are drawn from a large number of small- and large-signal analyzes performed on several test systems and on an actual Hydro-Que´bec system, paying due account to the load models and governor response. Since either of the candidate PSSs can easily be tuned to perform acceptably in a standard local and/or inter-area oscillation scenario, emphasis will be put on comparing them at the inherent limits of the PSS concept, i.e., considering excessive VAR modulation during large generation rejection, fast load pickup on hydro units, and excessive torsional interactions during faults on large turbine-generators.

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    ABSTRACT: The paper deals with developing and testing frequency- adaptive PMU algorithms with wider linearity range than specified in IEEE Std C37.118-1. This goal is achieved by means of three different concepts encompassing robust state-of-the-art design approaches: 1) FIR bandpass filtering, 2) extended Kalman filtering (EKF), and 3) discrete Fourier transform (DFT) demodulation with FIR low-pass smoothing.While FIR-based PMUs are linear phase with no overshoot in either phase or amplitude step responses, the adaptive EKF PMU is more computer-intensive but allows for a reduced group delay and better out-of-band interference rejection at the cost of a phase step response with overshoot. Frequency measurement performances of the various PMUs are assessed in detail. It turned out that FIR PMUs are best for meeting Std C37-118-1 metrics but they are outperformed by EKF under changing harmonics. Test results on three recent commercial PMU models further confirm that PMU algorithms meeting standard C37-118-1 can behave quite differently Under dynamic conditions.
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    ABSTRACT: For the first time, IEEE Std. C37.118.1-2011 now provides metrics for PMU dynamic performance in terms of classes P and M filter designs. This paper attempts to determine whether fulfilling these requirements makes the PMU inherently well suited for stability control applications such as wide-area power system stabilizers (PSSs). In this aim, we considered two different frequency-adaptive approaches for class-P and -M compliance to ensure operation over a wide frequency range. The first is based on a finite-impulse response (FIR) with no overshoot in either the phase or the amplitude step responses, while the second is Kalman filter-based (EKF), which allows for a more refined out-of-band interference rejection at the cost of a phase step response with overshoot. These two approaches are benchmarked against Hydro-Québec`s existing PSS requirements and the conclusion is that the total vector error-based response time is not indicative of the phase lag within the frequency band of interest, nor of the 3-dB bandwidth under sinusoidal amplitude/frequency modulation phenomena, which are key criteria when specifying PSS PMUs. Using simulated and field-recorded network fault responses, we also show that a class-M PMU is unsatisfactory for wide-area stabilizing control, unless its performance is improved during the fault period, which is not covered by Std. C37.118.1-2011.
    IEEE Transactions on Power Systems 05/2013; 28(2). · 2.92 Impact Factor
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    ABSTRACT: The present paper investigates the effective application of phasor measurement units (PMUs) with different technologies and filtering dynamics to the design of wide-area power system stabilizer (WAPSS). Two frequency-adaptive PMU algorithms shown to exceed the C37.118 class-M requirements based on FIR- and Kalman-bandpass filtering are selected for study. Their sharp dynamic differences are characterized using accurate fourth-order transfer functions derived from step responses using system identification techniques. While FIR-based PMUs have no overshoot in their phase and amplitude step responses, the adaptive Kalman filter allows for better out-of-band interference rejection at the cost of a phase step response with overshoot and a higher computational burden. These PMUs are implemented in Simulink and then embedded in electro-magnetic transients (EMT) simulations to experiment the realistic WAPSS behavior with the discrete-time devices in the loop. It is shown that WAPSSs with optimized settings can improve the damping performance of EMT models of a test system and a simplified Hydro-Québec network including PMU filtering dynamics and transmission delays. However, WAPSSs based on EKF-PMUs yielded better performances, thanks to their shorter group delay compared with FIR-PMUs. PMU devices and algorithms meeting standard C37-118 can thus behave quite differently under stressed dynamics.
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Jun 1, 2014