In this paper, the design issue of effective damping of electromechanical swings in a medium voltage network with distributed generation by the use of a PSS2A type power system stabiliser is described. This stabiliser was installed in the generating unit with the highest rated power. Time constants of correction blocks, as well as the main gain, were determined by analyzing a single-machine system, generating unit – infinite bus. The time constants were calculated on the basis of the frequency-phase transfer functions both of the electromagnetic moment to the voltage regulator reference voltage and of the generator voltage to the voltage regulator reference voltage, under the assumption of an infinite and real value of the generating unit inertia time constant for various initial generator loads. The main stabiliser gain was calculated by analyzing the position, on the complex plane, of eigenvalues of the state matrix of the single-machine system, linearised around a steady operating point, at the changed value of this gain.
In the paper, the application of multi-criteria optimization of the parameters of PSS3B system stabilizers to damping electromechanical swings in an extended power system (PS) is presented. The calculations of the power system stabilizer (PSS) parameters were divided into two stages. In the first stage, single-machine systems, generating unit - infinite bus, of generating units critical for the angular stability of the PS were analyzed. Time constants and preliminary values of the PSS gains were calculated. In the second stage, the main one, the main gains on which the effectiveness of operation of PSSs depends the most were calculated by multi-criteria optimization of the extended PS. The calculations were carried out in several variants: for two-dimensional objective functions and the six-dimensional objective function. In multi-criteria optimization, the solution is not one set of PSS parameters, but a set of sets of these parameters, i.e. a set of compromises that were determined for each analyzed case. Additionally, for the six-dimensional compromise set, projections of this set on the planes connected with the quantities of individual generating units and the boundary of these projections on these planes were determined. A genetic algorithm adapted to multi-criteria issues was used to minimize the multivariate objective function. Sample calculations were made for the model of the National (Polish) Power System taking into account 57 selected generating units operating in high and extra high voltage networks (220 and 400 kV). The presented calculations show that the applied multi-criteria optimization of the PSS3B stabilizer parameters allows effectively damping electromechanical swings without worsening the voltage waveforms of generating units in the extended PS.
The paper presents a method for determining sets of Pareto optimal solutions (compromise sets) – parameter values of PSS3B system stabilizers working in a multi-machine power system – when optimising different multidimensional criteria. These criteria are determined for concrete disturbances when taking into account transient waveforms of the instantaneous power, angular speed and terminal voltage of generators in one, chosen generating unit or in all units of the system analysed. The application of multi-criteria methods allows taking into account the optimisation process of power system stabilizer (PSS) parameters, many sometimes contradictory requirements (criteria) without losing ability to reach the optimal solution. A choice of the compromise solution can be made by assuming the values of the weighting coefficients associated with particular components of the vector criterion and determining the equivalent, global criterion. A change of the values of those weighting coefficients in the equivalent criterion does not require, in the case of the Pareto optimization, carrying out repeated calculations.
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W artykule zaprezentowano badania układu sterownia grupowego pozwalającego na ograniczenie kołysań mocy małych zespołów wytwórczych pracujących w systemie elektroenergetycznym. Koncepcja układu sterowania opiera się na teorii stabilizatorów systemowych. W procesie optymalizacji wyznaczono parametry stabilizatorów systemowych w zespołach wytwórczych dużej mocy (w pierwszym etapie) oraz optymalne wartości współczynników wagowych regulatora elektrowni wirtualnej (w drugim etapie) z punktu widzenia tłumienia kołysań elektromechanicznych w SEE. W obu etapach do obliczeń wykorzystano algorytm genetyczny.
EN
The paper presents investigations of a group control system enabling the damping of power swings of small generating units operating in the electric power system. The idea of the control system is based on the theory of system stabilizers. There were determined the parameters of system stabilizers used in high-power generating units (at the first stage) and the optimal values of the weighting coefficients of the virtual power plant regulator (at the second stage) from the point of view of damping electromechanical swings in the power system. A genetic algorithm was used for computations at both stages.
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