Abstract

With the recent developments in power electronics technologies, increased deployment of distributed energy resources (DER) with DC output type at distribution voltage levels and significant increase in the number of sensitive AC and DC loads integrated in distribution network have enforced the traditional power network in the continuous renovation process. In this paper, the load flow solution of hybrid AC/DC distribution networks with the multi-terminal configuration is studied. The impact of voltage source converter (VSC) losses and AC and DC line losses in the presence of DER in the distribution system are assessed. The motivation of this analysis is to consider an increase in the number of converter stations which might result in non-negligible converter losses and the presence of various DER within the network imposing different network scenarios. The proposed schemes are simulated on two modified IEEE 33 bus hybrid AC/DC distribution network test system equipped with VSC-MTDC and the results are presented. Obtained results show that by considering the network losses and the converter losses with large number of converters within the network could lead to very different load flow solution and power transfer between networks, especially considering the AC or DC bus dominated network.

Highlights

  • The main challenges of current power systems are to meet the ever growing requirements for higher quality and reliability of electricity in a sustainable, secure and competitive manner in distribution systems [1]

  • Recent significant advancements in power electronic technologies, renewable based distributed energy resources (DER), flexible AC transmission systems (FACTS), energy storage systems (ESSs), and advanced control strategies based on information and communication technologies (ICTs) have motivated redesigning the power system with integrated AC

  • AC/DC distribution network interconnected with multi-terminal HVDC (MTDC) networks

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Summary

Introduction

The main challenges of current power systems are to meet the ever growing requirements for higher quality and reliability of electricity in a sustainable, secure and competitive manner in distribution systems [1]. The hybrid AC and DC microgrids should be smart enough to integrate, control and manage the growing rate of deploying DC output type distributed generations (DGs), energy storage systems, and increasing number of DC electronic loads [4,5,6]. A mathematical model for VSC is explored for proper modeling of converter losses, which are computed as a polynomial function that depends on the phase current of the converter, taking into account the difference in losses type when the converter acts as a rectifier or an inverter In this assessment, the impact of converter losses on the load flow solution along with the losses in AC and DC distribution networks facilitated with DGs connection at appropriate locations is studied in term of effectively reducing the network losses. The sequential load flow algorithm is implemented in an open source Matlab toolbox, MATPOWER [40]

VSC Station Model and Operation Modes
Types of VSC
VSC-MTDC Power Injection Modeling and Operation
Modeling Converter Losses
Converter Control Modes
Load Flow Results for Topology 1
Load Flow Results for Topology 2
Conclusions
Full Text
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