Conference Agenda

This article presents a non-conventional voltage-transforming system that extracts energy from transmission line (TL) electrical field. The generation system consists in a 20 km collector line built within the right-of-way of a 230 kV transmission line to attend a 100 kW load. A non-conventional substation is conceived to provide adequate voltage regulation. This voltage-transforming system can be replicated at both sides of the TL to feed small remote loads or become an additional supply source for existing rural systems. No intervention on the existent line is necessary. Important results regarding transient, quality and reliability indexes cost evaluation of the system are provided.

This paper proposes an improved method to enhance the dc response of a frequency-dependent transmission line model used in EMT studies. A modification to the rational function approximation of propagation and characteristic admittance matrices of a transmission line is introduced to enforce exact dc values at 0 Hz. Furthermore, weighting factors are applied to improve accuracy at low frequencies. Finally, the order of the propagation function is reduced to decrease the computational effort. The validity of the proposed approach is demonstrated using examples involving underground cables and overhead lines. First, the effect of dc correction is demonstrated by comparing transmission line frequency domain characteristics. In addition, time domain simulations via open and short circuit conditions show a more accurate simulation of HVDC transmission lines with the proposed method.

This paper proposes an inverter control strategy that combines virtual synchronous generator control with harmonic detection based on Fourier linear combiners with adaptive gain. In the proposed strategy, the virtual synchronous generator control calculates the current in the fundamental frequency component, responsible for the control inertial characteristic, and harmonic voltage detector based on Fourier linear combiners selectively detects the harmonic voltages to be damped. The 5th harmonic order adaptive gain is calculated from voltage and current measurements on a bus of interest in the system. Real-time simulation results were developed in a hardware-in-the-loop test-bench to show that the proposed control can simultaneously mitigate the grid voltage and current harmonics and reduce the peaks of frequency oscillations after transients.

This paper presents a co-simulation tool to link multiple instances of an electromagnetic transient (EMT) simulation tool for parallel and fast computations. The tool exploits the propagation delays of transmission lines and cables to create network decoupling into several smaller sub-networks. These sub-networks are solved in parallel without approximations. A multi-rate option is also incorporated, in which the sub-networks can use different numerical integration time-steps. The Functional Mock-up Interface (FMI) is used for creating the co-simulation interface between multiple instances according to a master-slave communication scheme and the data sharing method is implemented using low-level synchronization primitives called semaphores. The interfaces between each subnetwork are automatically initialized for time-domain simulations using load-flow results.

The simulation of electromagnetic transients may suffer from inaccuracies due to a phenomenon known as frequency warping (FW). This paper presents an analysis of the effects of FW on the accuracy of digital simulations, demonstrating that the use of the trapezoidal integration rule (TR), commonly employed in many electromagnetic transients simulators, is the root cause of such inaccuracies. Although FW is considered a major problem in digital signal processing, it is often overlooked when simulating electrical transients. The analysis is carried out in a fourth-order RLC circuit, from which the analytic solution is derived. The circuit is solved using the combined state-space nodal method, considering the TR or recursive convolutions as solution methods for the state-space representation. It was observed that the FW caused a change in the natural oscillation frequency of the system, causing a pulsating behavior of absolute error. The accumulation of errors over time can result in deteriorated solutions when either the time steps are not sufficiently small or the simulation runs for a long enough duration. This paper emphasizes the significance of accounting for the FW phenomenon in digital simulations that rely on integration methods, such as the TR.

Passive component models are necessary to ensure numerical stability in the simulation of electromagnetic transients in power systems. However, it is challenging to represent transmission lines and cables with frequency-dependent wideband models that are accurate, efficient, and passive. This paper proposes a new method for the passivity enforcement of wideband line and cable models. The wideband models rely on pole-residue identification of characteristic admittance and propagation function in rational forms. In case the resulting models are not passive, the proposed method simultaneously applies perturbation to the residue matrices of characteristic admittance and propagation function. The set of equations related to passivity enforcement through the residues of propagation function in phase domain is complex and presented for the first time in this paper. The proposed approach minimizes the overall perturbation for maintaining passivity as opposed to the existing simplified approaches that rely on the perturbation of the residues of either characteristic admittance or diagonal elements of propagation function. The performance of the method is validated with application cases, and it is shown that it outperforms the existing methods that seek simplification in problem formulation.