Transition from alternating current to direct current low voltage distribution networks

Abstract

Maximising the capacity of the existing alternating current (AC) distribution network infrastructure by conversion to direct current (DC) may hold significant advantages. In particular it may provide a greater flow of electrical energy within urban areas, allowing a lower investment cost for adoption of electrical vehicles and domestic heating. Integration with Smart Grid applications will require maintained levels of reliability, and improved efficiency and flexibility. The transition of the cable infrastructure from the legacy low voltage AC system to low voltage DC is considered in this study. In particular this study investigates the limitations of DC supplied through the existing distribution network without major reconstruction , and proposes optimal configurations that could be adopted in a smart-DC distribution network. The implications for power flow in the network are considered with regards to existing cable limitations. It is concluded that a better understanding of cable and joint reliability is required before such changes are made to existing LV networks.

High-Efficiency mosfet-Based MMC Design for LVDC Distribution Systems

“…The symbols used in the analysis are defined as follows: Level-shifted SPWM modulation, specifically phase opposition disposition (POD), is exploited to generate a sinusoidal output waveform. The cumulative upper and lower arm voltages, V au and V al , can be expressed as (5) and (6) respectively, in which mu and ml describe the switching actions in the upper and lower arms respectively.…”

“…In particular, the number of high-capacity power electronic interfaces, such as electric vehicle chargers and embedded PV generation, have increased significantly [3][4][5]. LVDC networks are able to provide increased capacity without the need to upgrade existing cables [6,7].…”

Overview of power electronics technology and applications in power generation transmission and distribution

“…Furthermore, if the amount of energy produced by the in situ generation and storage is sufficient to meet the local demand plus the associated power losses, then the DC feeders may act as an independent micro-grid, isolated from the HV utility supply, with the AC connection points Overview of power electronics technology and applications in power generation transmission and… 511 taking the character of back up supply points [82]. During this transition, an interesting issue worth researching, particularly in urban areas, is how to use the current AC infrastructures to host DC ones in order to reduce the cost as much as possible [83].…”

High-gain-high-power (HGHP) DC-DC converter for DC microgrid applications: Design and testing

“…Though designing a complete safety system for DC is difficult, other safety mechanisms like residual current detector and insulation resistance monitoring device guarantee the necessary safety and monitoring functions. The growth of DC distribution is constrained due to lack of higher current interrupting capacity of DC circuit breaker, protection schemes, and operational experience. However, expert research on fault detection and protection of DC distribution system has resulted in advanced protection schemes, which are capable of investigating different faults and prove to be effective for DC distribution system with distributed energy sources When DC distribution is carried out through underground cables in urban areas, corrosion is likely to be more compared with AC …”

“…However, expert research on fault detection and protection of DC distribution system has resulted in advanced protection schemes, which are capable of investigating different faults and prove to be effective for DC distribution system with distributed energy sources. [63][64][65][66] (iii) When DC distribution is carried out through underground cables in urban areas, corrosion is likely to be more compared with AC. 67 (iv) Though there are different arguments towards the voltage levels and standards, to reach a breakthrough, standardisation of voltage levels is an important step.…”