Ultracapacitor UPS (U-UPS) for voltage dips and micro-interruptions

Power interruptions are the most frequent power supply problems with wide-ranging consequences for industry. The causes of these interruptions include short-circuits in the distribution grid, lightning strikes, the connection and disconnection of power plants as well as volatile energy producers such as wind and solar. Because technologies and production processes are becoming increasingly complex, the electronic components and control units of the production systems respond very sensitively to such voltage dips and micro-interruptions. The consequences range from faults to complete system failures.

UPS systems for smooth operations

Uninterruptible power supplies (UPS) are technical systems that protect companies from such disruptions. Typical solutions make use of batteries, rotating flywheels or ultracapacitors for temporary storage of energy. The technologies can differ greatly in terms of the areas of application as well as the procurement and operating costs.

Battery-based UPS systems are often used in distributed fashion for the protection of individual production components. They are inexpensive and store the energy by means of chemical reactions. However, they are subject to aging which results in decreasing reliability. For this reason, the batteries must be replaced after just a few years.

Flywheel-based UPS systems offer larger power capacities and long lifespans, making them suitable as central protection for entire systems. The investment costs are very high, however. Additional costs arise from the required annual maintenance as well as the regular replacement of wearing parts.

The UPS system based on ultracapacitors from the German manufacturer FREQCON –

“Ultracapacitor Uninterruptible Power Supply” (U-UPS) – is specially designed for bridging short voltage dips up to 10 seconds and represents an especially economical solution for such applications. Compared with the other UPS solutions, the procurement, energy and operational costs are significantly lower while offering high efficiency and low losses.

Functioning principle of U-UPS

The U-UPS solution from FREQCON responds to voltage dips or micro-interruptions and automatically takes over the load in less than 10 milliseconds. The integrated FREQCON Fast Disconnector (FFD) disconnects the power supply from the public grid and creates its own isolated network with the energy stored in the ultracapacitors. This island grid operates with the same nominal voltage, phase angle and frequency as the public grid. When the distribution grid returns to the required voltage, the system automatically synchronizes with the public grid within a few milliseconds and re-establishes the connection. In normal operation, the ultracapacitors of the

U-UPS solution are only charged by the public grid. This functioning principle applies to applications in the low- to medium-voltage range. If the voltage dip lasts longer and the energy stored in the ultracapacitors is no longer sufficient to supply the load of the production system, the U-UPS automatically connects to the public power grid without synchronization.

Many applications and advantages

The U-UPS is particularly suited for industrial applications, which are especially sensitive to disruptions due to time-critical workflows and networked production systems. The U-UPS system is designed for 20 years of sustained operation in such industrial environments with minimal maintenance requirements. Thanks to the powerful and robust multi-source converter technology (MSC), line disturbances can be smoothly bridged for durations from seconds to several minutes. Additional battery storage systems or generators can be integrated to compensate for disruptions lasting multiple hours.

Due to their electrochemical structure, the ultracapacitors offer very fast charging and discharging times as well as a very long lifespan of up to 1 million cycles.

The power capacities of the U-UPS system can be scaled from 170 kilowatts to 5 megawatts, depending on the specific project. The systems can be designed for indoor installation and as a turnkey, transportable container solution.

U-UPS as turnkey container solution

Source: FREQCON GmbH

View into the container for the Italian packaging manufacturer – complete system with MSC, ultracapacitor storage system and cooling system

Source: FREQCON GmbH

Space-saving setup of the U-UPS system for the Italian packaging manufacturer

Cabinet setup from left to right

Cabinet 1: Control systems

Cabinet 2: Powerstacks / IGBTs

Cabinet 3: Choke coils

Cabinet 4: DC switch, AC filter, circuit breaker

Cabinet 5: EMC filter

Cabinet 6: Ultracapacitors

Source: FREQCON GmbH

System setup of U-UPS for low-voltage applications

Source: FREQCON GmbH

System setup of U-UPS for medium-voltage applications

Source: FREQCON GmbH

 

Contributed by:

Henning Stoppel, Technical Sales, FREQCON GmbH

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