DSPs for intelligent UPS management
Now there is a need for systems' availability
and reliability 24X7 in every business, and consequently
a need for better power conditioning technologies. DSPs
might be a solution to your UPS problems.
Today's factory and office control systems run more mission-critical
applications than ever before. Uptime demands are increasing, which means there
is a need for systems' availability and reliability 24X7. Hence the need for
better power conditioning technologies.
Put it in perspective
First came UPS systems with bipolar transistors. At the time of its release
these transistors allowed frequencies of switching much higher than any of their
predecessors. This became the founding block for Pulse-Width Modulation (PWM).
The PWM was followed by UPS systems with PWM chopping. Here the electronically
controlled transistors opened and closed faster to produce finer chopping required
for a sinusoidal output voltage. That led to substantial regulation of output
voltage under both steady and transient situations.
Then came the UPS systems that assured free frequency regulation, which is the
key to adapting to non-linear loads and better discrimination. Thus, they would
supply more current if a fault raised the requirement. Parallel-connected UPSs
with Application Specific Integrated Circuits (ASIC), and without centralized
load sharing were next to take the UPS market. The use of ASIC components made
it possible to integrate a number of digital and logical functions in a single
component, instead of requiring cards.
Furthermore, its Insulated Gate Bipolar Transistors (IGBTs) considerably reduced
the power required, for control, from what bipolar transistors used. It also
made higher switching frequencies possible. These components started the trend
for simplified circuits and better reliability. The microprocessors, from this
point, were used for more than just the display. They constituted the heart
of the UPS control electronics. The new in-built intelligence was used to communicate
with connected equipment. The result: easier operation and enhanced reliability.
Slowly but surely the UPS became an integral part of the computer environment.
Now, computer users count on the devices designed specifically for them.
The latest trend is the use of Digital Signal Processors (DSPs) for Sine Wave
generation for optimized real-time processing. The Sine Wave range can be expanded
from 20 to 480 A. This new application contributes to Total Harmonic Management.
The Power of DSP technology
A DSP controller provides an improved and cost-effective solution for UPS design,
with high performance. It replaces of bulky transformers, relays, and mechanical
bypass switches with smaller, more intelligent functional equivalents. It gives
increased power efficiency, and power density. Plus it is compact and light.
The DSP has integrated functions selected for sophisticated embedded controls,
in UPS applications. Except for signal conditioning and actuators that provide
the interface between the DSP and the power circuitry, with DSP all the control
implementations are digital.
DSP implementation has fewer parts, increased reliability and a greater immunity
to noise. The DSP feedback and control loops are implemented digitally so there
is no need for compensation for component tolerance. In short, DSP technology
provides a cost-effective alternative to control multiple power converters,
and meets the demands of advanced power topologies.
The three power stages
DSP technology enables the practical implementation of non-traditional topologies
that were previously very expensive. One such topology utilizes three solid-state
electronic power stages to regulate and condition power. The power management
and voltage to the critical load is controlled with DSP by operating these three
The first stage includes a front-end filter and surge protection section with
a rectifier to remove spikes and surges. The DSP-controlled rectifier acts as
an electronic power-factor-correcting AC-to-DC boost circuit. It provides dynamic
output voltage regulation.
The second stage functions as a DC-to-AC inverter during battery operation.
It acts as a balancing circuit for the DC voltage into the inverter during normal
operation, and also supplies energy for recharging the batteries.
The third stage comprises the inverter that acts as an electronic DC-to-AC converter
circuit that regulates the output voltage delivered to the load. This converter
generates a maximum AC output voltage that is lower than the DC voltage input
to the inverter. The DSP controls the rectifier, balancer, and inverter and
provides a superior output voltage regulation without having to use battery
power at all.
The DSP facilitates and maintains the battery charge using advanced battery
charging and monitoring algorithms. Thereby increasing battery life. The DSP-controller
integrated electronic bypass provides power to the load with out any expensive
DSP technology enables practical implementation of sophisticated UPS topologies
and controls. It can simultaneously control multiple power converters to optimize
system efficiency, advanced battery management, improved output voltage regulation,
better bypass capability and communications with other equipment. The result:
smaller, lighter, well designed UPS's with higher performance.