Distributed voltage control with electric spring smart loads

Abstract

The installation of renewable energy sources (RES) has increased drastically throughout the last years, with RES ranging from solar, wind, hydroelectricity and various more. This increase leads to tougher challenges when handling the distribution of electricity, due to power quality issues introduced like over voltage, under voltage, frequency fluctuations and the injection of harmonics into the grid. This project will mainly tackle the voltage and frequency fluctuation issue thus keeping the grid voltage stable. In order obtain control on these fluctuations real and reactive compensation is required. Critical loads are loads that cannot withstand variations on their supply voltage thus a constant 230V rms (single phase) is required in order to ensure that no damage is incurred. On the other hand non critical loads can withstand tolerances in their supply voltages without affecting the operation or performance of the equipment. In order to control these aforementioned power quality issues one can find various compensators, mainly statcoms, static var compensators and energy storage system. Statcoms and static var compensators can only control reactive power while on the other hand control of both real and reactive powers can be achieved by means of an energy storage system although these tend to be quite bulky and expensive. A new concept is introduced in order to compensate for these issues, this is the smart load with electric spring system in this case a back to back converter topology is being used in order to compensate for both real and reactive power compensation. These electric spring systems (ES) are divided into three types. The first type consists of a DC link capacitor as a storage system while the second type of ES uses a battery instead of the capacitor on the other hand the last type which is used throughout this project replaces the battery with a back to back converter. A more in depth explanation is provided in the literature section. This project serves as proof of concept of an ES system operating with a back to back converter in various voltage scenarios. The ES was modelled, designed and simulated by means of Simulink and Plecs.