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Design of 3-phase static modular double-conversion lithium-ion-based UPS system
Author(s)
Ngongo, Prosper Kabasele
Date Issued
2022
Type
Thesis
Publisher
Cape Peninsula University of Technology
Abstract
A challenge for industries nowadays is to optimize the functionality of their critical processes.
Whether they be manufacturing, production, healthcare, banking, data, research, or shopping centres,
they are becoming large and complex with several critical loads and processes whose availability is
crucial to their overall effectiveness and market competitiveness. Based on their design specifications
and accuracies expected, these processes often tend to have a low tolerance and are susceptible to
power failures, spikes, brown-out, dip, or surges. They require a high integrity power supply to
guarantee their correct functioning, increase their robustness against the damaging effect of power
disturbances and operational availability. Eskom’s network instability, lower energy availability, and
poor power quality, unfortunately, cannot guarantee the integrity of supply to these critical loads. An
increase in load shedding in the past few years highlights this low energy availability factor. Based on
these reasons, the facility opted to install 4 x 1100kVA online lead-acid-based rotary uninterruptible
power supplies (UPSs) to sustain a sturdy power supply through periods of power disturbances. The
sustainability of power will also allow orderly processes shutdown in case of prolonged power
interruption and avoid any outage-related financial setbacks. Commissioned back in 1995, they have
attained their end-of-life and suffer regular costly maintenances, higher losses, and higher spares cost
due to unavailability. Although these are considered legitimate running costs, they occur on a capital
scale after few years. Given the system’s age, running cost, and inefficiency, the facility would be
efficiently and cost-effectively served by newer high-performance UPS systems. The process of
choosing the right UPS system and energy storage solution for critical infrastructure has now become
more challenging than ever. Today’s UPS technologies and their corresponding backup storage
solution must maintain or even increase the availability and manageability of power on their respective
facilities. In the effort to reduce the total cost of ownership, it is imperative to extend lifetime,
decrease footprint, streamline maintenance, and lower cooling costs and other operating expenses, in
addition to reducing the upfront capital investment. Lithium-ion-based static UPS systems are poised
to enhance energy storage for secure power applications. They provide benefits in reducing the
installation and maintenance costs and have low waste energy resources making them have high
operational efficiency and weigh less than the rotary UPS system. The energy storage system used in
these systems has since transformed from medium-lifetime, sprawling, and heavy lead-acid batteries to
a long-life, compact, lightweight solution with predictable performance, simplified maintenance, and
robust life cycle management. It is not just the UPS system that develops through the adoption of
lithium-ion technology; critical power is also going through a period of rapid changes calling for UPS
systems to increase their availability and manageability of power. Facilities are, therefore, required to
revisit their complete concept of critical power and develop new supply methodologies. There is now a
strong need to bring up innovative ways that dispatch the battery stored energy differently. Facilities
must continually evaluate their time of energy use in relation to their tariff structures for better energy
management and costs control. Time-of-use tariffs are structured to reward consumer who lowers their consumption during peak periods. The intervention strategy will present a comprehensive assessment
that offers a site-specific solution. It will also provide a financial and performance analysis of the
current rotary UPS system versus the new static UPS system with the desire to improve the facility’s
power protection, secure its long-term availability, strengthen its energy efficiency capacity, and
reduce maintenance costs and carbon footprint. It will evaluate the financial impact that tariff
structures and various modelled energy dispatch have on the facility energy budget.
Whether they be manufacturing, production, healthcare, banking, data, research, or shopping centres,
they are becoming large and complex with several critical loads and processes whose availability is
crucial to their overall effectiveness and market competitiveness. Based on their design specifications
and accuracies expected, these processes often tend to have a low tolerance and are susceptible to
power failures, spikes, brown-out, dip, or surges. They require a high integrity power supply to
guarantee their correct functioning, increase their robustness against the damaging effect of power
disturbances and operational availability. Eskom’s network instability, lower energy availability, and
poor power quality, unfortunately, cannot guarantee the integrity of supply to these critical loads. An
increase in load shedding in the past few years highlights this low energy availability factor. Based on
these reasons, the facility opted to install 4 x 1100kVA online lead-acid-based rotary uninterruptible
power supplies (UPSs) to sustain a sturdy power supply through periods of power disturbances. The
sustainability of power will also allow orderly processes shutdown in case of prolonged power
interruption and avoid any outage-related financial setbacks. Commissioned back in 1995, they have
attained their end-of-life and suffer regular costly maintenances, higher losses, and higher spares cost
due to unavailability. Although these are considered legitimate running costs, they occur on a capital
scale after few years. Given the system’s age, running cost, and inefficiency, the facility would be
efficiently and cost-effectively served by newer high-performance UPS systems. The process of
choosing the right UPS system and energy storage solution for critical infrastructure has now become
more challenging than ever. Today’s UPS technologies and their corresponding backup storage
solution must maintain or even increase the availability and manageability of power on their respective
facilities. In the effort to reduce the total cost of ownership, it is imperative to extend lifetime,
decrease footprint, streamline maintenance, and lower cooling costs and other operating expenses, in
addition to reducing the upfront capital investment. Lithium-ion-based static UPS systems are poised
to enhance energy storage for secure power applications. They provide benefits in reducing the
installation and maintenance costs and have low waste energy resources making them have high
operational efficiency and weigh less than the rotary UPS system. The energy storage system used in
these systems has since transformed from medium-lifetime, sprawling, and heavy lead-acid batteries to
a long-life, compact, lightweight solution with predictable performance, simplified maintenance, and
robust life cycle management. It is not just the UPS system that develops through the adoption of
lithium-ion technology; critical power is also going through a period of rapid changes calling for UPS
systems to increase their availability and manageability of power. Facilities are, therefore, required to
revisit their complete concept of critical power and develop new supply methodologies. There is now a
strong need to bring up innovative ways that dispatch the battery stored energy differently. Facilities
must continually evaluate their time of energy use in relation to their tariff structures for better energy
management and costs control. Time-of-use tariffs are structured to reward consumer who lowers their consumption during peak periods. The intervention strategy will present a comprehensive assessment
that offers a site-specific solution. It will also provide a financial and performance analysis of the
current rotary UPS system versus the new static UPS system with the desire to improve the facility’s
power protection, secure its long-term availability, strengthen its energy efficiency capacity, and
reduce maintenance costs and carbon footprint. It will evaluate the financial impact that tariff
structures and various modelled energy dispatch have on the facility energy budget.
Additional information
Thesis (MEng (Electrical Engineering))--Cape Peninsula University of Technology, 2022
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