Digital UPS/EPS Control System Key Technologies And Its Applications Study

The development of power transistor, DSP microcontroller and cyberneticspromotedinverterpowertohighperformance.Nowadays,theresearchanddevelopmentof digital control technique for inverter power supplyhas become apopular topic in theelectric power field. Uninterrupted power supply (UPS) systems are importantequipments which have been widelyapplied to modern information system. Emergencypower supply (EPS) is a key facility for the security and fire protection system of tallbuildings, hotels etc. To meet the development and products promotion of UPS/EPScontrol techniques, this paper presents the research of UPS/EPS system digital controlkey technology, and provides theory foundation and realization means for the digitalinverterpowersupplydesignanddevelopment.(1) Based on the project research purposes, contents and requirements, the projectimplementation and technique realization scheme have been put forward. According tothe project tasks undertaken by author, the theory and technique foundation have beenresearched. The research emphases and the conquered difficulty of this project havebeen pointed out. Based on the digital UPS/EPS inverter control, waveform control andsystem control argument, this paper summarized the domestic and foreign researchsituationanddevelopmenttrend.(2) Based on the analysis of inverter power structure, the mathematical andsimulation model of the digital UPS/EPS control system were found. Unlike the formermodeling way, the UPS/EPS system was separated into inverter model and output filtermodel, and its mathematical model was built independently. It made the systemstructure clear and convenient for the system control algorithm design. And the inverterPWM control technique has been used for the inverter. The waveform control strategyhas been employed for the output filter. The method of three-phase filter decoupling totwo single-phase filters through DQO coordinate transformation was introduced. Itsimplifiedthesystem analysis and controllerdesign,and it's easyforthree-phasepowermodelintroducingsingle-phasepowerstudymethod.(3) According to the UPS/EPS inverter, digital inverter control technology wasstudied on two categories of carrier modulation and space vector modulation. In thecategory of carrier PWM technology, a pulse multiplied digital SPWM technique wasput forward. And its waveform spectrum proved that the technique can obtain twice the harmonics frequency than the common SPWM technique can, under the same carrierfrequency. In the category of space vector PWM technology, the theory of thethree-phase SVPWM technology was studied and its DSP realization method was putforward. Through the analysis of single-phase inverter voltage vector space andintroductionofaplanecoordinaterotationtransform,asingle-phaseSVPWMtechniquewas put forward.TheapplicationoftheSVPWM technologytosingle-phaseis not onlyconvenient for the algorithm realization by using DSP, but also the various optimizedPWM technology obtained in the three-phase SVPWM technology can be applied tosingle-phase inverter power supply. This paper also further studied and compared thetwo PWM inverter control algorithms, and proved that they are equivalence in nature.The results proved that space vector PWM is a special kind of carrier PWM, the zerosequencesignalistheconnectionwithspacevectorPWMandcarrierPWM.(4) To solve the problem of the performance and load adaptability of UPS/EPSorigin system being not satisfying, this paper researched several practical digitalwaveform control strategies. Through the controller arithmetic deducing and analysis,thecontroller realizationmethodwas put forward. Andthroughthe simulationresearch,its own characteristic was analyzed. In addition, the paper put forward digital servocontrol theory based on inverter waveform control arithmetic. The algorithm basic ideaistotreattheinvertpowersupplyasaservosystem,anditcouldeffectivelyenhancethesystemdynamicorstaticperformanceandsystemloadadaptability.(5) For the UPS/EPS system control and function realization: Firstly, a DSPbased(frequency-variable) asynchronous modulation algorithm was put forward. Thisalgorithm resolved digital sinusoidal signal generation problems for PWM invertercontroltechnology.Second,aCcallableDSPprogrammemoryaccessingtechniquewasgiven. This technologysolved the problem of TI C2000 series DSPchip RAM shortageproblem in arithmetic implementation and the DSP program space accessing problemduring in C language operating. Third, an asynchronous varying-Frequency modulationalgorithm based on the inverter digital phase lock technique was put forward. Thisarithmetic effectively solved the impact problem of the system and loads in the UPSbypass/inverteroutput switching,and also solvedtheEPS quickstart andfast-switchingproblemunderthecitypowerfailure.(6) The Digital UPS/EPS system design innovation includes system hardwaremodularization design, embeddedμC/OS system control software application,applying novel control arithmetic, remote network monitor, and system failure selfdiagnosis. UPS realized product promotion and its performance were enhanced. EPS replacedthedieseldynamoandrealizedtheemergencepowersupplyingmodechange.SPS replaced the varying-frequency dynamo and improved power conversionefficiency.AndDPSprovidedpowerfailureprotectofindustrydriveequipment.The research and development of digital UPS/EPS system control key technologyperfected and enriched the control theory system for the inverter power supply,effectively solved problems in inverter power design and industrialization process.Invertercontrol arithmeticsolvedinverterpowercontrolproblem,simplifiedthecontrolarithmetic and improved inverter efficiency. Waveform control strategies enhancedsystemdynamicandstaticrespondingcharacteristic,inverterwaveformqualityandloadadaptability. System control technique solved the inverter system control and thefunction realization problems, the asynchronous frequency-variable modulationalgorithm solved the sine reference signal generation problem in inverter PWM controlarithmetic. The asynchronous frequency-variable modulation phase lock algorithmsolved the UPS bypass/inverter output switching impact problem and ESP quick startandfast-switchingproblem.