Abstract: Introduced one kind the reserve -like UPS system which controls based on the MR16 monolithic integrated circuit. Used the numerical control technology to realize the invertor output voltage and the network voltage phase-lock synchronization, could distinguish the electrical network breakdown rapidly and carry on the corresponding hand-off control, cut the process not to affect basically to the load normal work.
Key word: Reserve -like UPS; Inversion; Synchronization
Introduction
Along with the information processing and management technology and the micro electron and so on pinpoint technique’s vigorous development, and the reliable request is also getting higher and higher to the power supply system quality, uses electricity the quality requirement high situation in some, is urgently needed one kind of voltage regulation, to be able the lock following mains frequency, the redundant reliable exchange UPS. UPS is English UninterruptiblePowerSystem abbreviation, Chinese meaning is “the UPS system”. UPS causes power supply system’s reliability and the quality enhances greatly, simultaneously causes the investment and the operating cost reduces, is the information age essential energy system. At many causes the computer obliterated data as a result of the computer system power cut the profession, UPS to play unreplaceable role, like bank, negotiable securities, correspondence, aviation management, production supervisory system and so on.
1 system structure and principle of work
UPS’s type are many, may divide into online -like UPS, online interactive type UPS, reserve -like sine wave UPS, reserve -like square-wave output UPS and Delta according to the different structure and the function transformation UPS. Looked from the performance index that online -like UPS>Delta transformation UPS> the online interactive type UPS> reserve -like sine wave outputs UPS> reserve -like square-wave output UPS. Looked from the price that online -like UPS, Delta transformation UPS and the online interactive type UPS price is high, reserve -like UPS is cheap.
What this system uses is reserve -like sine wave UPS, it is suitable in uses electricity quality Gao You not to request not to be able the power failure load. It by the battery charger, the invertor, the battery unit, the static switch and so on is composed. System principle of work like chart 1 and shown in Figure 2.
When the city electricity power supply is normal as shown in Figure 1, connects invertor’s change-over switch to shut off, connects electrical network’s change-over switch clear, after UPS passes through the original voltage fluctuation very big city electricity one kind of simple exchange manostat slightly constant voltage processing, to user load power supply. Simultaneously passes through the battery charger to the battery unit charge.
When the city electricity power supply is not normal as shown in Figure 2, connects electrical network’s change-over switch to shut off, connects invertor’s change-over switch clear, the invertor, in the battery unit provides under the direct-current energy support, provides 50Hz, the 220V sine wave exchange voltage-stabilized source to the user, simultaneously the battery charger stops the work.
2 control policies
2.1 UPS invertor output voltage and network voltage phase-lock synchronization realization
When city electricity breakdown, is avoids UPS the invertor and the mains supply cut instantaneous has the big current surge to the load, must guarantee that the network voltage and the UPS invertor output voltage frequency, the synchronism and the same peak-to-peak value, this system through the MR16 monolithic integrated circuit to the network voltage sampling and the phase capture, and compares with the establishment network voltage sine form, after logical judgement controls the invertor output voltage the peak-to-peak value and the phase, thus realizes with the network voltage synchronization. As shown in Figure 3, network voltage’s sine wave signal passes through - the 2.5V voltage reference promotion again after the transformer voltage dropping, carries on the comparison with the 2.5V voltage reference, in LM339 out-port after the reverser may obtain in the PTE6 mouth with the sine wave frequency, with the phase square-wave signal, the square-wave rise along for the sine wave zero phase place, drops along for the sine wave 180° the phase place, the square-wave signal delivers monolithic integrated circuit’s I/O mouth, the monolithic integrated circuit through may judge the network voltage to the I/O examination the phase. Through calculates two rises along the time-gap may figure out the electrical network cycle. The UPS invertor sine wave’s production, is through establishes a sine table in MR16 monolithic integrated circuit’s ROM, in the interrupt routine, carries on the pulse width computation by the sine indicator read sine value, thus has the SPWM profile output, the sine indicator for the zero hour correspondence’s sine wave output voltage is also zero, therefore, when examines electrical network zero phase, may consider that through the comparison sine indicator’s value judges whether the phase-lock, the indicator is zero indicates the invertor sine wave output and the network voltage profile phase-lock synchronization, otherwise must realize the phase-lock through the phase shifting track network voltage phase.
Figure 3
2.2 UPS invertors and electrical network hand-off control realization
The hand-off control is (for example thyristor module MTC) realizes through the make-and-break cut electric circuit’s in static state electronic switching. This system selects MTC70 (70A/1200V) the thyristor, as shown in Figure 4, Figure 4 L1 is the electrical network coil, L2 is the invertor coil, N is both’s public grounding, R is a load. In the chart uses the thyristor counter-multiple connection, what because bus bar high is the sine full wave, take SCR1 and SCR2 as the example, forms on the necessity in the sine wave half period SCR2 breakover, SCR1 shuts off, in negative half period SCR1 breakover, SCR2 shuts off, had like this guaranteed winds through the load the electric current is the complete sine wave. The thyristor make-and-break is realizes by the MR16 monolithic integrated circuit auxiliary hand-off control electric circuit. When electrical network breakdown, sends out the cut-off electrical network signal first, then sends out cuts into invertor’s signal; When the electrical network restores, sends out the cut-off invertor signal first, then sends out cuts into electrical network’s signal, this needs the signal transmission electric circuit, simultaneously controls the thyristor to open, to close also needs the gate to trigger the driving circuit extremely. Hand-off control electric circuit as shown in Figure 5, Figure 5 left side PTC0, the PTC6 two groups ports are on-off control signals which the MR16 monolithic integrated circuit transmits, delivers in the basic RS trigger electric circuit which after the light pair isolation is composed of the rejection gate, the RS trigger outputs two groups signals are the interlock, both can only simultaneously for the low level (shutdown signal), not be able simultaneously for the high level (clear signal), thus strengthened system’s security. Self-excited oscillator’s function which is composed of 555 timers is fixed time transmits the trigger pulse, the pulse effective width should not be smaller than the thyristor turn-on time, its output signal and the RS trigger’s output deals with delivers in the gate extremely driving circuit. After Figure 5, level is the thyristor gate extremely pulse driving circuit, may see also isolates the output. Moreover, uses two LED to be effective the power supply way which uses in the demonstration load.
MR16 monolithic integrated circuit through to city electricity breakdown and breakdown whether to restore the judgment shuts off the city electricity or the UPS invertor. After cut-off city electricity or invertor, the load current weakens to zero needs to have a process, then cuts into the invertor or the city electricity again, for guarantee cut operation reliability, this system, in zero electric current cuts into the way in the foundation, has joined in the master routine, if after cut-off city electricity (or invertor) time delay 3ms has not carried on cuts into the operation, no matter whether to examine zero electric current to carry on correspondingly directly cuts into the operation, thus has guaranteed the UPS power supply reliability.
2.3 UPS invertor output voltage mean value reaction control
The UPS inversion system materially is also one kind of control system, regarding this system output voltage, its perturbation quantity is mainly the variation of load and accumulator cell’s voltage change, the accumulator cell voltage may regard as in a short time the definite value, the load change for this system’s host perturbation. According to the reaction control principle, which physical quantity can maintain basically invariable to introduce which physical quantity the negative feedback, therefore, what the closed loop inversion system uses is the voltage closed-loop control. With carries on the comparison through the survey output feedback’s voltage quantity to the quota, after the regulator control computation output, changes the SPWM output pulse width finally, thus causes the output followed to assign the change, the load perturbation is sustains feedback surrounding on the forward channel, therefore, this control structure can resist the load perturbation change. Regarding the regulator, the digitized PI regulator is the present application is most widespread, a maturest technology, already obtained the very good application in the contravariant system. Because in the contravariant system’s load perturbation is the electricity parameter, the dynamic response must be quick, therefore, in the PI control algorithm’s parameter chooses very important, should choose the regulator parameter reasonably in the design process, causes system’s control compatibility, the rapidity to be good, and has the strong robustness.
Figure 5
Contravariant system’s general composition structure as shown in Figure 6.
2.4 UPS invertor output voltage profile compensation
In the contravariant main circuit (as shown in Figure 7), to prevent the identical bridge arm’s two power switching valve to appear goes nonstop to the phenomenon, after often adopts shuts off a power tube, time delay period of time to clear another power tube’s method again, this middle time delay’s time (usually was several μs) has formed the dead area, the dead area existence (, although very small) will create the output voltage profile inevitably the distortion, especially to zero neighbor profile’s influence, this system adopted the optimization to save the sine tabular value method carries on the compensation in MR16 in monolithic integrated circuit ROM to the dead area, realized the smooth sinusoidal voltage profile output.
2.5 UPS invertor’s actuation pattern
In this system, what 4 main power switch component uses is the unipolarity frequency multiplication working, but is not the bipolarity way, because compares with the bipolarity, the unipolarity frequency multiplication way has equivalent “the double” the turn-on frequency merit, the turn-on frequency “the double” manifests in the output voltage profile frequency spectrum. If the choice frequency modulation ratio is an even number, will then most be inferior the overtone to appear in two times on the turn-on frequency sideband.
3 software designs
The system software mainly divides into the master routine and the interrupt servicing subroutine two parts. The master routine by the initialization module, the starting time delay module, the sampling protection module, the regulator module and so on several parts is composed, moreover in the master routine also has to some data carries on the disposal procedure as well as front cuts the overtime cut procedure which the part states, data reduction program including to save the interrupt resources, to interrupts the AD sampling data processing computation and to correspondence receive data processing.
The interrupt routine module’s duty is completes the SPWM profile emanation, completes the voltage, the electric current and the temperature and so on each data AD sampling, and carries on with the city electricity voltage’s phase-lock synchronization cuts the operation the control. Because the interrupt resources limited (each 100μs interrupt one time, interrupt routine execution time cannot surpass 100μs), is impossible to various parameters’ AD sampling each time to interrupt must complete one time, therefore besides the key parameter (output voltage and network voltage), other parameters uses an every two interrupt sampling time method.
4 experimental results
Figure 8 is the city electricity power failure cuts into the UPS invertor instantaneous profile. Figure 9 is cuts into when the invertor by the city electricity the load voltage profile.
5 conclusions
This article introduced entire digitized reserve -like UPS uses MOTOROLA monolithic integrated circuit MC68HC908MR16 to take the master control chip, can achieve the fast phase-lock and the fast cut, does not have the influence basically to the load. The system structure is compact, the reliability is high, moreover the cost is low, the debugging is convenient, has manifested the numerical control superiority fully.
