Three-phase High Power Factor Rectifier Control Strategy And Realization,

Since the rectifiers for electrolysis are used widely in the fieldof metallurgy and chemical industry, it must supply powerful andcontinuous current. So the rectifier must have high coefficient ofperformance. The conventional thyristor or diode rectifiers haveinherent drawback have low power factor and the harmonics of the linecurrent relatively high. It not only induces harmonics pollution butalso decrease the coefficient of performance.Pointing to these problems, the paper presents respectivestrategies of the tow kinds of topologies (three-phase six-switch Boostrectifier and three-phase single-switch Boost rectifier) on the baseof debating about the power factor correction and harmonics inhibitiontechnologies and investigating the operating principle of three-phasePFC rectifier.The conventional control methods of three-phase six-switch Boostrectifier can be divided to indirect current (PAC) mode and directcurrent mode. The direct current mode includes hysteresis currentcontrol (HCC), triangular wave comparing control (TWCC), dpo conversioncontrol (dpoCC). Basing on steady condition, the phase and amplitudecontrol (PAC) has a low dynamic response and dc current offset that isaffected by the parameters. The hysteresis current control has a fastdynamic response, good accuracy. However, it switching frequency varieswith the dc load current, which makes the filter devising difficult.The triangular wave comparing control has a fixed frequency but has alow dynamic performance. The dpo conversion control can track currentwithout any error in steady state, but it need complex computation. Itis obvious that these control method have shortcomings in differentextent and difficult to digitalized. So the paper presents a strategyin chapter 3, which use the space vector PWM control inner loop switchand multimode control (PI/adaptive fuzzy control) adjust the outer loop.The multimode control (PI/adaptive fuzzy control) has robustperformance with load occurring nonlinear changes. The simplified spacevector PWM control is easy to carried out by microcontroller. By thelIlimp1ement of MATLAB5. 2, a simu1ation model for three--phase AC to DCrectifier is set up. Comparing the nove1 method with several traditioncontrol ari thmet ic, the result of s imulat ion show that it has favorableperformance -Three--phase sing1e--switch Boost rectifiers are common1y used forthree--phase high--power--factor (HPF) app1 ication since their inputcurrent wave--shape automat ical 1 y fo11 ows the input vo1 tage wave shape.However, if the three--phase sing1e--swi tch Boost rect ifier is imp1ementwi th the convent ional constant--frequency out--vo1 tage feedback contro1,the rect ifier input current exhibit re1ative1y 1arge harmonics. As aresu1t, at power levers above 5kW, the harmonics imposes severe design,performance and cost trade--offs. The out--vo1tage feedback cannot reducethe harmonics effective1y, moreover it 1ead to high transientdeviations of the output voltage with respect to steady state va1ue.Due to an out--voltage 'overshoot during a step--up transition,'power--stage semi conductor components wi th a higher vo1tage rat ing areusua1ly required to maintain the necessary design margin between themaximum vo1tage stress of the components and their vo1tage rating.Pointing to these prob1ems, the paper introduces a newharmonic--inject ion technique wi th the feedforward contro1 in chapter4. By this technique a 1ow harmonics can be achieved with an exce11enttransient performance. A simu1ation of this strategy by the using ofPspice7. 1, the resu1t show that it has obvious power factor correctioneffect and has an advantage of harmonics inhibition.The genera1--purpose contro1ler and a few of periphera1 devices canimp1ement the strategies in chapter 5. The contro11er part isaccomp1 ished by the Inte1 80C196KC, inc1uding the double--chip CPUsstructure with keyboard and disp1ay functio...