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CAPACITOR BANK ARRANGEMENT

IP.com Disclosure Number: IPCOM000257179D
Publication Date: 2019-Jan-18
Document File: 5 page(s) / 316K

Publishing Venue

The IP.com Prior Art Database

Related People

Bishnoi Hemant: AUTHOR [+1]

Abstract

The disclosure is related to a capacitor bank arrangement in a power converter device. The disclosure generally addresses an issue of arranging the capacitors, such as in a dc-link capacitor bank, in order to achieve a low inductance commutation loop. A solution is suggested in which two paralleled sets of power-planes or bus-bars are used to lower an inductance of a commutation loop. Within such arrangements, capacitors may be oriented such that there is a magnetic flux cancellation in between adjacent capacitors.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 45% of the total text.

Page 1 of 5  P180297

© Copyright [2019] ABB. All rights reserved.

CAPACITOR BANK ARRANGEMENT

This disclosure generally relates to a capacitor bank arrangement in a power converter device

such as a wall mounted grid connected converter.

Minimizing the commutation loop inductance in switch mode power converters may be an

important design requirement. Lower inductance in the commutation loop can ensure

faster rise/fall times for the voltages and currents in the switches leading to lower

switching losses and higher efficiency, for instance. In order to achieve low inductance,

the (decoupling) capacitors may be placed close to the switching devices and often power

planes of printed circuit boards (PCB) are used where the terminals of the power modules

are connected directly onto the PCB. The ratio of a distance between the power-ground

plane-pair to the width or length of the power plane is usually small. This ensures that the

magnetic lines of flux cannot wrap around them easily thereby decreasing the volume

available to store magnetic energy. A direct consequence of this is that it reduces the

inductance of the planes. For higher currents, instead of using PCB (which has a

maximum copper thickness owing to manufacturing difficulties) one can replicate the

same effect using planar and often laminated bus-bars, for example. All these techniques

are known and widely using in the industry, however there may be ways to further

decrease this loop inductance.

Fig. 3.1: An example of PEBB assembly comprising decoupling capacitors and power

modules connected by Mersen® laminated bus-bar.

Page 2 of 5  P180297

© Copyright [2019] ABB. All rights reserved.

Normally a single pair of PCB power-planes or laminated bus-bars as shown in the

example of Fig. 3.1 may be used for connecting a capacitor bank. However, according to

an embodiment, a further decrease in inductance may be achieved by using two-pairs of

power-planes or bus-bars. Such PCBs may be able to support power up to a couple of

hundred kWs.

According to an embodiment, the idea is to have two sets of power-planes, with the

number of capacitors, such as radial-can type capacitors or the like, e.g. equally

distributed on the two sets of power planes. These planes can then be short circuit via

vias at one of the PCB. Ideally, the same vias may also be used for connecting the

terminals of the power-module. When large number of the capacitors are required, their

equivalent series inductance (ESLs) typically come in parallel and thus the net

contribution of the capacitor ESL towards the commutation loop inductance is quite small.

What remains is the inductance of the power-planes or bus-bars and any extensions

attached to them in order to the reach the power-modules. By employing two sets of

power planes or bus-bars, for example, this impedance can be further cut down by half.

An example of this kind of scheme is shown in Fig. 3.2.

Fig. 3.2: Capacitors distributed on two sets of power-plane pairs, wh...

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