This study presents the impact of wind power plant components modelling on harmonics propagation and harmonic small-signal stability studies. Different types of cable and transformer modelling techniques are taken into consideration, e.g. state-of-the-art standard models and latest academic developments. The models are compared based on system-level studies in a real-life large offshore wind power plant. It is shown that the use of detailed cable and transformer models increases the overall damping estimation in the system, and therefore improves the resonance characteristics and small-signal stability margins of the investigated wind power plant.
This paper presents a new approach to wide-band modeling of tower footing grounding impedances. Appropriate representation of transmission tower footing impedances is essential in electromagnetic transient simulations for proper evaluation of overvoltages and flashovers in the system during fast-front transient conditions such as lightning strikes. In this paper, a field solver is used to precisely model the most popular types of tower footing grounding systems, i.e. rods, counterpoises and ring electrodes, for a variety of dimensions and soil parameters. Results are stored in a lookup table and used for generating frequency-dependent models that are exported to electromagnetic (EM) transient simulators. The table and model generation tool can be used by utility companies to model tower footings while taking into account local variations along the right-of-way, such as local variations in soil resistivity. The presented examples show close agreement of results of lightning studies using developed electrode models included in EM tools: PSCAD, EMTP-RV and ATP-EMTP.A sensitivity study shows that the maximum voltage at the tower top during a direct lightning strike can be up to 19% higher when using the adopted modeling procedure, compared to a standard approach of using a fixed resistor equal to the power frequency resistance.
Long HVDC cables are difficult to emulate in laboratory settings due their complex behaviour and fast transient response. This paper presents the methodology for the design and the laboratory implementation of a HVDC cable emulator with a Power Hardware in the Loop approach. The cable representation in the real time simulation is based on the Universal Line Model present in state of the art software for electromagnetic transients analysis. The proposed cable emulation reproduces the cable dynamics up to the kHz range with present commercially available hardware. Moreover, this approach offers a higher flexibility in adapting the cable characteristics and length compared to other existing alternatives.
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