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NEW DESIGN FOR DC-DC CONVERTER AND BATTERIES SETUP IN A DC-GRID APPLICATION

IP.com Disclosure Number: IPCOM000249812D
Publication Date: 2017-Apr-10
Document File: 3 page(s) / 229K

Publishing Venue

The IP.com Prior Art Database

Related People

Mahmoud Amr: AUTHOR

Abstract

The novel solution is a DC grid modification in which the DC-DC converter is utilized as a charger for the batteries through the shore connection directly, without a use of extra converters for shore connection. The batteries are further connected directly to the DC-link during the peak power demand, whereby the batteries are internally connected in series, and after the peak power demand the batteries are again connected internally in parallel and via the DC-DC converter, which boosts the voltage again.

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© Copyright [2017] ABB. All rights reserved.

NEW DESIGN FOR DC-DC CONVERTER AND BATTERIES SETUP IN A DC-GRID

APPLICATION

In prior art marine DC grid applications provided with batteries, a normal solution is to

connect the batteries via a DC-DC converter to the DC link. The DC-DC converter is

thus dimensioned according to the power of the loads connected to the DC grid, e.g. the

thruster motor plus the propulsion motor. The thruster motor, however, works only for a

short time e.g. 3 or 4 minutes, which means that there might be, according to the case,

from one to four extra DC-DC converter unit modules to cover the demand of the

thruster motor, plus the DC-DC converter unit modules needed for the propulsion motor.

The shore connection of the vessel is normally provided with one or more separate

dedicated converters in order to convert the AC electric power to DC electric power.

The batteries are normally connected in parallel with a voltage of 450 V to the DC-DC

converter, whereby the DC-DC converter choke will boost the voltage up to 1000 V. In

cases the batteries need to be connected directly to the DC-link, the configuration of

batteries is still parallel, but the voltage increases to a level of 1100 V or 1000 V.

First of all the batteries can, during the peak demand of power, be connected directly to

the DC-link, but the configuration of the connection should be a series connection. A

series connection of 450 V plus 450 V results in a total voltage of 900 V. This voltage

will be enough to run the DC-link without any under voltage problems. The energy

saving of this step during the peak demand of power is about 2% as there is no need for

a DC-DC converter conversion.

When the peak demand of power is over and the only load is the propulsion motor, then

the batteries can be connected in a parallel connection with a voltage of 450 V to the

DC-DC converter, whereby the DC-DC converter choke will boost the voltage up to

1000 V. The DC-DC converter may, however, now be dimensioned according to the

steady need of power. The saving are due to the fact that it is possible to reduce the

amount of DC-DC converter modules used to cover the power need of the thruster

motors, which means 1 to 4 DC-DC converter modules depending on the case. The

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© Copyright [2017] ABB. All rights reserved.

solution saves money, space, energy and the DC-DC converter becomes...