Tom De Rybel

LS-SVM-based on-load tap changer control for distribution networks with rooftop PV's

This paper discusses voltage regulation using on-load tap changers (OLTC) with line drop compensation (LDC) on low-voltage distribution networks with a high penetration of photovoltaic generation (PV). Load flow simulations show that PV generators affect the performance of classical LDC in a negative way. However, when a database exists where voltages measured by smart-meters are stored, Least-Squares support vector machines (LS-SVM) can be used to estimate the maximum and minimum voltage in the system, without needing a grid model, nor real-time communication. Control of the OLTC can then be executed to widen the gap between the system voltage and the acceptable limits, based on the maximum and minimum system voltage estimates.

Voltage regulation strategies for flemish LV distribution grids utilizing single-phase PV inverters

Both the electric power consumption and the presence of small-scale embedded generators (SSEGs) are gradually increasing in Flemish LV distribution grids. The changes brought about by these trends are certain to have a significant impact on system performance and efficiency and to necessitate advances in the planning and operation of LV grids. In this paper, three voltage regulation strategies that utilize active and reactive power management are proposed and their performance is evaluated in four Flemish LV distribution grids. From the assessment, it was concluded that single-phase SSEGs can fully eliminate the over-voltages of the domestic customers, in contrast with the remaining violations of under-voltage statutory limits. The results clearly highlight the increase of curtailed active power, when utilizing the equal curtailment method, compared with the hierarchical mechanism.

Implementation of a digital directional Fault Passage Indicator

Fault Passage Indicators (FPIs) are a cost effective solution to increase grid reliability. The connection of Distributed Generation units can lead them to misoperate and undermine the reliability improvements. Directional FPIs is a solution to overcome this problem. In this paper, the fault detection methods and direction-polarization principles for an isolated grid are described. As well, the implementation is done in Matlab-Simulink, from the signal processing techniques till the logic scheme for fault confirmation and automated reset. Some simulations are conducted to evaluate the performance of such FPI.

Optimal placement and sizing of active in-line voltage regulators in flemish LV distribution grids

Over the past few years, both the integration of small-scale embedded generators and the electric power consumption have been increased rapidly in the low-voltage (LV) distribution networks. These two trends are likely to result in a number of power quality issues such as voltage rise/drop and voltage unbalance. Regarding the mitigation of the voltage rise/drop effects, several utilities have already implemented the application of on-load tap changer (OLTC) in secondary distribution transformers. However, the voltage control via OLTC transformers might be infeasible in the case of radial feeders with both large number of branches and long distribution lines. This paper evaluates the performance of active in-line voltage regulators (IVRs) in LV grids. The study also investigates the optimal placement and sizing of active IVRs in Flemish LV networks. Concerning the OLTC control of the IVRs, an algorithm from a previous work is used. Finally, the influence on various power quality metrics is tested, when IVRs are incorporated into the system.

Optimal Placement and Sizing of Active In-Line Voltage Regulators in Flemish LV Distribution Grids

Over the past few years, both the integration of small-scale embedded generators and the electric power consumption have been increased rapidly in the low-voltage (LV) distribution networks. These two trends are likely to result in a number of power quality issues such as voltage rise/drop and voltage unbalance. Regarding the mitigation of the voltage rise/drop effects, several utilities have already implemented the application of on-load tap changer (OLTC) in secondary distribution transformers. However, the voltage control via OLTC transformers might be infeasible in the case of radial feeders with both large number of branches and long distribution lines. This paper evaluates the performance of active in-line voltage regulators (IVRs) in LV grids. The study also investigates the optimal placement and sizing of active IVRs in Flemish LV networks. Concerning the OLTC control of the IVRs, an algorithm from a previous work is used. Finally, the influence on various power quality metrics is tested, when IVRs are incorporated into the system.

Dynamic Thermal Modeling of Voltage Divider Capacitive Coupling

This paper deals with the thermal model and compensation of the thermal drift in a capacitive voltage sensor installed on top of the semiconducting layer of cross-linked polyethylene (XLPE) cable. The analysis of the thermal phenomena underlying the system shows a high dependency on the relative permittivity of the XLPE material. The first compensation method consists of installing an external capacitor with the same temperature coefficient as the cable capacitance. This method is limited because of the nonlinear thermal behavior of the cable capacitance. The second method consists of measuring the conductor current and the outer XLPE temperature, and estimating the temperatures and properties of the cable by means of an offline-derived, built-in model. The simulations and tests show the obtained improvements of the different methods in the operational temperature range.