Matrix Converter Used for Battery Charging Application

7/24/2019 Matrix Converter Used for Battery Charging Application

1/4

Matrix Converter Used For UPS Application

Critical loads such as data storage and computer systems, life support

equipment, process equipment controllers, telecommunications equipment and

emergency systems require continuous operation when there is a power failure.

Associated problems such as poor overall power factor, heating eects, device

malfunction and destruction of other equipment caused by nonlinear loads have

been recorded. This trend reects in the increase use of uninterruptible power

supply (!"# to provide uninterrupted and reliable power supply with the

provision of unity supply power factor. !" systems have progressed from rotary

to hybrid and static type. $otating type uses motor%generator sets that are often

used in high sinusoidal output applications. &ybrid type combines the use of

motor%generator sets and static type. 'n this system the static !" are used to

bridge the gap between the loss of the primary source and availability of a

secondary source such as a manually started diesel generator.

enerally static !" system are as shown in )ig.* comprising three basicelements+ a rectier-charger unit that converts input AC power into C power, an

inverter unit that converts C power of a battery to AC power and a static bypass

switch that transfers the critical load to the bac/%up supply and isolating from the

mains. A manual bypass switch is also normally added to cater for maintenance

or repair purposes of the !" unit. The rectier or charger normally uses a

bridge%diode in implementation without aording any control function. A

transformer is used to step%down voltage during rectication operation, whilst

during mains%failure the transformer performs as a step%up transformer. &owever

due to the presence of bloc/ing switch operation there will be some distortions in

the voltage and current. 'n order to minimise this distortion we now use mati0converter instead of rectier and inverter.

The single phase matri0 converter ("!1C# requires 2 bi%directional switches

as shown in )ig. 3+ each capable of conducting current in both directions,

bloc/ing forward and reverse voltages. 't requires the use of bidirectional

switches capable of bloc/ing voltage and conducting current in both directions.

The '4T were used due to its popularity amongst researchers that could lead to

high%power applications with reasonably fast switching frequency for ne control.

The "!1C topology has been presented to operate as an ninterruptible !ower

"upply Circuit (!"# incorporating nity !ower )actor Control. A single circuit isdeveloped that performs both the rectier and inverter operation may also

*


2/4

incorporate active power lter operation. The inverter transforms a C input into

an AC output using the well%/nown "inusoidal !ulse 5idth 1odulation ("!51#

technique, while it6s oering a reverse power ow through controlled rectier

operation.

A systematic switching sequence is required that allows for the energyowing in the '4Ts to decay in order to minimise the stress on the switches. 'n

conventional converters, free%wheeling diodes are used for this purpose. 'n "!1C

these free%wheeling diodes do not e0ist, hence switching sequence needs to be

developed to allow forced controlled free%wheeling. This is to protect the

converter from being damaged as a result of voltage and current spi/es.

Proposed UPS Using SPMC7

sing "!1C the proposed system comparable to typical static !" system is

as illustrated in g.2. 'n comparison only a single%circuit are required to perform

both the inverter and rectier operation. "ince "!1C is characterised by purecontrollable switching function, the need for the bloc/ing switch is eliminated

and maybe replaced by sophisticated control algorithm that could be developed

in the future. 8bserve also the use of "!1C reduces the need of having two

separate circuits. 'n the proposed !", typical static !" system shown in )ig.2 is

used.

'n comparison only a single circuit is required to perform both the rectier

and inverter operations during normal and bac/%up modes respectively.

Inverter Operation:

3


3/4

uring power failure the "!1C operates as a inverter. The battery of "!1C

topology will supply for the load. 4y this approach during positive half cycle, "*

and "2 will be on and "3 and "9 will be o. uring negative half cycle at "3 and

"9 will be on, and "* and "2 will be o.

Rectifer Operation7

5hen there is no power failure, the main will supply for the load. The battey

'n )ig.*3 %*9 the upper switch of the rst leg which is closer to the

capacitor is used to charge up the battery while the lower switches of both the

rst and second leg ensure close trac/ing of the supply current to a sinusoidal

reference current. 'n this, the switches of the rst leg operate in alternate

sequence. This boost%charging strategy involves fast switching action of the

switching devices which are piloted by !ulse 5idth 1odulation (!51# technique.

All of these switching actions are carried out in the current control loop (CC:#.

"ince instantaneous switching actions is required of the "!1C to ma/e thesupply current follows the sinusoidal reference current closely, the current

control loop time response has to be fast. 'n the simulation wor/s an operating

switching frequency of 3; C:#. 'n this

control loop the voltage of the battery is compared with a set reference in order

to provide for the appropriate action of the switch. The switch is turned on upondetection of equality of both voltage levels. 8n the other hand, if the voltage

9


4/4

level of the battery is lower than the set reference the switch is turned o and

the boost energy is directed bac/ to the battery. Therefore, this control loop is

vital in ensuring the battery life is sustained.

2

Documents

Matrix Converter Used for Battery Charging Application