cet power - enhanced power conversion - white paper

Enhanced Power Conversion :

Integrating AC and DC power with high quality filtering and superior efficiency

Construction Electronique + Communications S.A. (CE+T S.A.) Rue du charbonnage 12 B-4020 Wandre Belgium +32 4 345 67 00 +32 4 345 67 01Email: [email protected] www.cet-power.com VAT : BE-404404480 RPM Liège - N° Enreg. Entrepreneur / Reg. Aannemer Nr. : 404.404.480/09.00.9.3


BackgroundHistorically, AC loads have been a small proportion of the total power requirements in most telecom organizations. That explains why they initially were powered by converting DC into AC via an inverter. With the growth of IT in telecom and other industries however, AC loads such as power routers, servers and other equipment have developed.

As the absolute number and proportion of AC loads in the energy mix has increased, there has been a natural tendency to draw power directly from the grid and rely on UPS for back-up and filtering.

Increasingly, however, organizations are encountering three major problems with this approach.

First of all, while they may entail a lower initial outlay in terms of capital expenditure (CAPEX), UPS require more maintenance and tend to have a shorter lifetime than other solutions. The battery in a UPS typically has a 3 year lifetime whereas batteries in DC infrastructures may have a lifetime of 15 or even 20 years. The internal charging process in a UPS tends to shorten the battery’s lifetime. In short, with a UPS, operating expenditures (OPEX) tend to be higher and thus they have a higher total cost of ownership (TCO) than other solutions.

Secondly, UPS are often seen as a “black box”, the inner workings of which are better understood by the manufacturer than by the power or facilities management departments of most organizations. This leads to higher Operating Expenses due to the

outsourcing of the servicing and maintenance.

This in turn points to a third important issue: maintaining two wholly separate energy regimes in an organization adds complexity and cost. The company must manage

two separate “power chains”: an AC to DC load and an AC to AC load.

Since a chain is only as strong as its weakest link, this added complexity increases the likelihood of failure and may result in a company or organization being unable to meet contractual performance standards as defined in service level agreements (SLAs). Moreover, maintaining two separate energy chains requires two different types of competences and often leads to the setup of two separate departments. All of this just increases cost and complexity.

Leveraging the existing DC infrastructure therefore seems the right way to go!

Diagram 1: the DC and AC energy chains are two different worlds and often two different departments manage each of them.

AbstractMany organizations are encountering problems with the dual power source structure that has arisen with the growth in critical AC loads. It is expensive and complex to maintain two separate “power chains” (AC & DC). Moreover, the UPSs typically used with AC loads have a high total cost of ownership (TCO) and a relatively short lifetime.

Twin Sine Innovation (TSI) is a hybrid solution which integrates the DC and AC power regimes. Within TSI, EPC mode is an innovative, proprietary technology from CE+T Power that provides high quality filtering and a superior efficiency of 96%. In addition to this, it will also lead to a better availability and to more flexibility.

AC LoadUPSGRID

= ~ DC

Load

Battery Backup

GRID

Infrastructure Management

AC Power


DC Power


TSI: a hybrid solutionTwin Sine Innovation (TSI) is a hybrid solution which integrates the DC and AC worlds. With TSI, an AC load safely draws power from the AC grid but can also take advantage of the existing infrastructure of DC batteries. Moreover, TSI converts the grid’s “dirty” energy into “clean” energy with a higher efficiency than a UPS do. TSI converts AC power from the grid at an efficiency of up to 96% and DC power from the battery at an efficiency of up to 92%. With TSI, costly and complex UPS – and dual power chains – are no longer necessary.

Unlike other solutions, however, EPC double converts from the input to output Line, while filtering on both Line and Neutral. This provides above average efficiency compared with other technologies on the market. Most other solutions, which double convert the L and the N, typically offer an efficiency of up to 92% whereas EPC’s combined efficiency goes up to 96%.

EPC mode and TSIAs we just saw, CE+T Power’s TSI converter will help organizations rationalize their power infrastructure. But it will also help them reduce their TCO thanks to its better efficiency and higher availability.

Higher efficiencyA major part of the secret to TSI’s success is the proprietary (patent pending) Enhanced Power Conversion (EPC) technology developed by CE+T Power.

EPC converts AC power from the grid to DC power and then back again to pure AC. More specifically, it works on the L-in / L-out current to provide a safe and stable ACout. Its filtering functions work to contain both differential and common mode disturbances.

AC Load

= ~ DC

Load

Battery Backup

GRID


AC Power


DC Power

Diagram 2: TSI is a hybrid solution which integrates the two energy chains

TSI Module

EPC Line in

Neutral in

Line out

Neutral out IEPC

Diagram 3: EPC’s allows for up to 96% efficiency

~ = ~

Battery Backup

= AC Load

Grid

DC Load

STS

96% 90%99%

Diagram 4: Online Mode

Diagram 4: Standard double conversion will not give more than 92% efficiency. Twice the losses compared to EPC!

Line in

Neutral in

Line out

Neutral out

~ ~

The best of both worlds in a hybrid solutionEPC’s unique architecture and technology offers better efficiency, filtering and stabilizing performances than any other Grid to AC conversion alternatives.

Let’s compare them!

Online Mode

In Online Mode operations, power goes from the grid to a rectifier (which includes a transformer) and then to an inverter where it is converted into AC power. This double conversion gives, when using the latest technologies, an efficiency of about 85.5% : 96% for the rectifier, 90% for the inverter and 99% for the Static Switch.


~ = ~

Battery Backup

= AC Load

Grid

DC Load

STS

99%

Diagram 6: Offline Mode

Battery Backup

AC Load

Grid

DC Load=

~

96%

Diagram 7: TSI Enhanced Power Conversion (EPC)

EPC combines best in class filtering and efficiency!

The table here-below compares the filtering and efficiency of each modes :

Table 1: Comparison Chart

EPC mode

EPC offers the best of both worlds: it offers high quality of differential filtering combined with an efficiency of 96%, far higher than any alternative. EPC stops common mode disturbances too via filtering rather than by relying on the inefficient galvanic insulation of a transformer.

Offline mode

Many organizations choose to place their bet on the quality of the Grid and decide to supply the AC load directly from it.

This offers 99% efficiency but it is also highly vulnerable to grid disturbances and depends on the quality of the AC power feeder.

The rectifier/battery/inverter path is used only as a backup solution.

~ = ~

Battery Backup

= AC Load

Grid

DC Load

STS

90%99%

Diagram 5: Battery Mode

Battery mode

When the grid fails, the Online Mode is automatically switched to the Battery Mode, DC power is drawn from the batteries and converted into AC by the inverter.

Line interactive system

Another mode has appeared lately called, “line interactive”, that uses the DC from the batteries to improve the power coming from the Grid. The problem with this type of solution, however, is that it draws current from the battery in order to correct distortions in the AC wave. The resulting high route mean square (RMS) current in the battery, and more specifically the associated warm-up, tends to wear down the battery faster.

High availabilityEPC also brings higher availability.

With most other systems, when the mains drops out it takes a short time – up to 12 milliseconds – until the Static Switch (single point of failure!) kicks in. While this interval is relatively short, it nonetheless can result in some damages to critical loads and to the reset of the utilities for several minutes.

EPC, on the other hand, provides zero transfer time : Its double converter has an internal energy storage buffer which fills in the brief power gap while the power

Filtering & Stabilizing

Unity Power Factor

LossInput Power for

a 2kW load

Online Mode Yes Yes 13,6% 2,31

Offline No No 1% 2,02

EPC Yes Yes 4% 2,08


source is switched from the grid to the batteries. And with the overload mode, EPC can deliver up to 150% of the normal power for a configurable period of time, if called upon.

Flexibility

Finally, whatever the output power level, the energy can be shared by both input sources (AC & DC) from 0 to 100%.

A very interesting use of this “mixed sources” mode is the ramp up energy applied to an eventual AC source genset when coming back from DC!

ConclusionEPC offers substantial benefits on several levels.

On an organizational level it optimizes the integration of the AC and DC “power chains”, thereby creating a single power regime that is both more reliable and easier and more cost-efficient to manage.

On a performance level, it provides a secured, high quality, filtered ACout at a high efficiency of up to 96%.

This advanced technology – exclusively available from CE+T POWER – helps organizations to reduce costs, simplify operations and to power AC loads with a better efficiency, a higher availability level, and more flexibility.

CE+T Power is the world leader in AC backup technology. The company develops, manufactures and markets Inverters, Modular UPS, Remote Line Powering and Off Grid Powering solutions to the Telecom, Industrial and Datacom/IT markets worldwide.

For more information please visit our website at http://www.cet-power.com

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cet power - enhanced power conversion - white paper

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