A DSP Based On-line UPS

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,eliminates 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.

TYPICAL ON-LINE UPS Block diagram: POWER SOURCE STATIC BY -PASS RECTIFIER INVERTER CRITICAL LOAD BATTERY BANK FILTER INVERTER BATTERY BANK

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:

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.

DSP control of UPS systems. Basic block diagram: surge filter rectifier User interface Software communication battery charger inverter battery o/p filter DSP controller

Internal architecture of DSP controller: 50 Hz sine wave r.m.s Voltage compensator PWM inv.filter A/D Real harmonic detector Imaginary harmonic detector PI compensator PI compensator 5 th harm rms voltage 5 th harm. rms set value

Mathematically, a harmonic function to be eliminated is studied as fallows: for eg; for a 5 th 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,

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 7 th,9 th etc can be eliminated.

Merits of using DSP: Software controllable. Software controllable. Remote monitoring. Remote monitoring. Network management. Network management. High execution speed (30 MIPS). High execution speed (30 MIPS). Algorithm for DSP processors is generally written in any language like C, C++ etc.

Flow chart for voltage control: start if V=S V=output rms voltage S= set value error=0 Non zero error To PWM inverter To PI compensator stop To PWM inverter YesNo

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. eg:multiply+load+modifies 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

Advantages of using DSP in UPSs: High Reliability. High Reliability. Low dimensions. Low dimensions. Precision. Precision. Interactive communication. Interactive communication. Compact and sleek form factor. Compact and sleek form factor.

Closing thoughts: To include more intelligent systems in it’s architecture. To include more intelligent systems in it’s architecture. Cutting the cost by making its use extensive. Cutting the cost by making its use extensive. Increasing the efficiency of electronic components. Increasing the efficiency of electronic components.

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 “Digital Signal Processor based online UPS” manual by “Power electronics Analysis design & applications” by Ned Mohan, Tore M.Undeland,William.P.Robbins 4.“Interfacing DSPs with high performance analog converters” Jim Ryan 5.WEMPEC-25 th anniversary review meeting,R&D innovation center Eaton Corp. 6. “2004 Bores Signal Processing : web pages.. 7.Kenton Wilson, Berekely design technology Inc, Calif..USA.

Questions ???? THANK YOU!!