Voltage regulation considerations for the design of hybrid distribution transformers

Abstract

Abstract-The future substation depends on finding a way to mitigate the effects of the drawbacks of the conventional legacy by employing the efficiency of the solid state switches [1]. This paper discusses the considerations of designing a distribution transformer that provides additional functions in regulating the voltage and controlling the reactive power that is injected in the distribution network, using a fractional rated converter attached partially with the windings of the transformer. This approach aims mainly to enhance the unit with more flexibility in controlling the voltage at the last mile of the network, in order to decrease the losses and meet the future expectations for low voltage networks modifications, and that by using a power electronic (PE) approach has less losses and more functionality (depending on the reliability of transformer and intelligence of PE). The design of a hybrid distribution transformer is detailed and its functionality in regulating the voltage is discussed as a combination between the features of one of the most reliable network devices, the transformer, and the effect of PE existence with less losses in both switching and conduction losses. Reduced ratings PE are used in this approach, whereby the solid state switches are controlled according to the immediate need for voltage control in low voltage (LV) networks.

Control Configurations for Reactive Power Compensation at the Secondary Side of the Low Voltage Substation by Using Hybrid Transformer

“…As can be seen from Figure 7, the output voltage of the converter V con is controlled to add or decrease the voltage to the overall output voltage of the phase (VA output, VB output, and VC output). In addition, in order to obtain a sinusoidal wave output, an LC filter is included [21]. As introduced above, the DC link of the back-to-back converter is controlled by using a dq transformation [32].…”

“…Nevertheless, using full rated converters, usually located after or before the DT as a standalone device, yields high losses for switching and conduction as well as requiring high maintenance. In order to bridge this research gap, several works have been published in the literature proposing to perform VAr compensation [18][19][20], voltage regulation [21,22], or even both [23,24] using reduced ratings for the SSS. In particular, the so-called hybrid distribution transformer (HT) [25][26][27], which consists of using an embedded fractional rated converter partially attached to the windings of the DT, has been widely used [19,20,23,24,28].…”

Voltage Control in LV Distribution Grid Using AC Voltage Compensator with Bipolar AC/AC Matrix Choppers

“…Various HT topologies with different regulatory capabilities have been proposed in the scientific literature. A few review articles have been published to explain the concept of how they work [5][6][7][8][9][10]. The most frequently considered HT systems are topologies with a back-to-back converter [11][12][13][14][15][16][17], matrix converter [18][19][20][21] or various types of AC/AC choppers [22][23][24].…”