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Content available remote Control of over currents and over voltages of the shunt capacitor banks
EN
The transition state, which, happened at the commutation of simple and multiple condensers batteries provokes the generation of dynamic disturbances (over currents and over voltages). For successful compensation these perturbations must be kept within accepted limits. The present work describes and establishes a relationship of the transients and the complex interaction between shunt capacitor banks, source and the load. In order to keep transients under control, the overvoltage factor (km) must be kept nearer to one and must be not superior to unity.
PL
Stan przejściowy, który nastąpił przy komutacji baterii prostych i wielokrotnych kondensatorów, powoduje powstawanie zaburzeń dynamicznych (przetężenia i przepięcia). Dla skutecznej kompensacji te perturbacje muszą być utrzymywane w akceptowanych granicach. W niniejszej pracy opisano i ustalono związek stanów nieustalonych oraz złożoną interakcję między bateriami kondensatorów bocznikowych, źródłem i obciążeniem. Aby utrzymać stany nieustalone pod kontrolą, współczynnik przepięcia (km) musi być bliższy jedności i nie może być wyższy od jedności.
EN
A phase-locked loop (PLL) is a closed-loop feedback control device that synchronizes its output signal with an input signal in both frequency and time. This paper presents a robust method for tracking against adverse conditions of the fundamental sequence component of utility voltage. The proposed phase-locked loop (PLL) is a hybrid configuration of the phase- locked loop type-3 (SRF type-3) synchronous reference frame coupled with a feed-forward frequency estimator using a selective harmonic filtering technique. A SRF type -2 based PLL has a secondary closed path. Under the ramp frequency transition, it has a steady-state step and a frequency error. In the proposed PLL, the constant gain loop filter is used to eliminate the phase and frequency error. Feed-forward operation with selective harmonic pre-filtering enables fast-tracking with a low tracking error of the reference signal. From the results it is evident that the proposed PLL achieves a high bandwidth and quick dynamic response without endangering the stability and filtering capability. The proposed system has been tested through MATLAB Simulink platform under abnormal conditions.
EN
Groundings are necessary parts included in lightning and shock protection. In the case of a surge current, high current phenomena are observed inside the grounding. They are result of the electrical discharges around the electrode when the critical field is exceeded in a soil. An available mathematical model of grounding was used to conduct computer simulations and to evaluate the influence of current peak value on horizontal grounding parameters in two cases. In the first simulations, electrode placed in two different soils were considered. The second case was a test of the influence of current peak value on grounding electrodes of various lengths. Simulation results show that as soil resistivity increases in value, the surge impedance to static resistance ratio decreases. In the case of grounding electrodes lengths, it was confirmed that there is a need to use an operating parameter named effective grounding electrode length, because when it is exceeded, the characteristics of grounding is not significantly improved during conductance of lightning surges. The mathematical model used in the paper was verified in a comparison with laboratory tests conducted by K.S. Stiefanow and with mathematical model described by L. Grcev.
EN
A new method to construct a discrete-time variable-structure repetitive controller for a class of linear systems perturbed by multiple-period exogenous signals is presented. The proposed control scheme combines the features of the discrete-time multiple-period repetitive control (MP-RC) and variable-structure control (VSC) techniques. The MP-RC part is assigned to simultaneously track and reject periodic signals consisting of multiple uncorrelated fundamental frequencies. The VSC part is then integrated to provide a fast transient response and robustness against plant parameter variations. Stability and robustness analyses are also elaborated to ensure that the resulting closed-loop system satisfies the desired control objectives. Moreover, it is shown through an example that the repetitive control system constructed using the proposed control method can effectively track a sinusoidal reference signal despite the presence of a multiple-period disturbance.
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