A DSP Based On-line UPS

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A DSP Based On-line UPS
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Role of UPS in daily life

• As an auxiliary power source in case of line
  outage, particularly useful to sensitive loads.
• Maintains quality of the power supply,i.e,eliminat
  es harmonics.
• Supplies power according to the load demand.

Among various UPS topologies, on-line UPS
provides maximum protection to the loads against
any utility power problem.
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TYPICAL ON-LINE UPS

• Block diagram

STATIC BY -PASS
POWER SOURCE
INVERTER
INVERTER
RECTIFIER
CRITICAL LOAD
FILTER
BATTERY BANK
BATTERY BANK
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PULSE WIDTH MODULATION

• Need for PWM
• To control inverter switching.
• To realize desired output waveform.
• To minimize the harmonic content in the output
  wave.

Mechanism of PWM
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Different PWM techniques

• Analog PWM circuits.
• Using Micro-processors.
• With Digital Signal Processor chips.

• Significance of using DSPs
• Sophisticated switching algorithm.
• Flexibility in configuration.
• No analog circuitry.
• Chance for up gradation.

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DSP control of UPS systems.

• Basic block diagram

battery charger
battery
inverter
o/p filter
rectifier
surge filter
DSP controller
User interface
Software communication
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• Internal architecture of DSP controller

rms set value
50 Hz sine wave
r.m.s Voltage compensator
PWM inv.
filter
A/D
5th harm
Real harmonic detector
PI compensator
Imaginary harmonic detector
PI compensator
5th harm.
rms voltage
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Mathematically, a harmonic function to be
eliminated is studied as fallows for eg for a
5th harmonic, the signal correlation function for
harmonic distortion waveform is written as,
Therefore considering the 3 phases a,b,c and
calculating the average value of the distortion
wave for real and imaginary parts seperately,we
get,
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and these amplitude components are
applied to a PI compensator to generate a
distortion correction signal, necessary to cancel
out harmonics from o/p voltage.

• In the same way, any harmonic 7th,9th etc
• can be eliminated.

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Merits of using DSP

• Software controllable.
• Remote monitoring.
• Network management.
• High execution speed (30 MIPS).

• Algorithm for DSP processors is generally
  written in any language like C, C etc.

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Flow chart for voltage control
start
Voutput rms voltage S set value
if VS
Yes
No
Non zero error
error0
To PWM inverter
To PI compensator
To PWM inverter
stop
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DSPs vs. Microprocessors
1.Per cycle access 1-8 instructions
1-4 instructions 2.Software
compatibility Can be linked with MATLAB Can
be linked with GUI 3.Performance
Compound instructions RISC instructions
perform perform multiple
single operation. Operations.
egmultiplyloadmodifies eg
add ,load or store. the address register.
4.SIMD Limited SIMD features. No SIMD
support. 5.Real time DSP chips used
5.Microprocessors used are are TMC62X, Blackfin
etc P4,powerpc etc
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Advantages of using DSP in UPSs

• High Reliability.
• Low dimensions.
• Precision.
• Interactive communication.
• Compact and sleek form factor.

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Closing thoughts

• To include more intelligent systems in its
  architecture.
• Cutting the cost by making its use extensive.
• Increasing the efficiency of electronic
  components.

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REFERENCES
1.DSP control of high-power feeding non-linear
loads by
Annette Von Jouanne Prasad N.Enjeti ,from IEEE
transactions on IE,vol 43,no.1,Feb
1996. 2.Digital Signal Processor based online
UPS manual by www.cranessoftware.com 3.Power
electronics Analysis design applications by
Ned Mohan, Tore M.Undeland,William.P.Robbins 4.In
terfacing DSPs with high performance analog
converters Jim Ryan 5.WEMPEC-25th anniversary
review meeting ,RD innovation center Eaton
Corp. 6. 2004 Bores Signal Processing  web
pages.. 7.Kenton Wilson, Berekely design
technology Inc, Calif..USA.
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Questions????
THANK YOU!!