(ELE 847) Dr. Smr ouro-rener Topc 1.4: DC moor speed conrol Torono, 2009
Moor Speed Conrol (open loop conrol) Consder he followng crcu dgrm n V n V bn T1 T 5 T3 V dc r L AA e r f L FF f o V f V cn T 4 α T 6 T 2 o V α Assume he feld wndng wh consn volge consn curren f (fer rnsen). Wh α he hyrsor recfer cn be conrolled V dc s conrolled. Wh V dc he rmure curren s conrolled. From orque equon:, orque cn be conrolled by. Te TL ωr = Js + D T = consn Speed:, conrolled wh T e! e L f f 2
Moor Speed Conrol (open loop conrol) In summry: we cn conrol speed wh α V α V dc α s he npu vrble of he recfer. V dc s he oupu. We know (opc 1.2), h: V = 2.34V dc, vg n T e cosα ω r V dc, vg 2.34V rms o 90 o 180 α 2.34V rms Cn be lnerzed usng: α = cos 1 V α 1 V 1 α ( 1 cos V ) α 2. VnVα Vdc, vg = 2.34Vn cosα = 2.34Vn cos = 34 V dc, vg = 2. 34V nvα lner 3
< < Moor Speed Conrol (open loop conrol) Wveforms Assume V α =0.5, sep npu. V α V dc,mx ω mx ω ss Δω,mx very hgh, no llowed n prcce Curren rpple frequency f rpple = 6f s (6 pulse recfer). Eg. For 60Hz source f rpple = 360. Rpple mplude Δ, cn be reduced ddng exr nducor n rmure. Mxmum speed overshoo = ( ω mx ω ss ) 100 / ωss 4 s 0 ss.05( ω )
Moor Speed Conrol (open loop conrol) Mn feures of open loop conrol Very smple. No conroller desgn necessry. The speed s djused vryng α. Snce sysem s sble, open loop conrol wll lwys be sble. Mn drwbcks Curren s no mesured no conrolled. Speed s no mesured no conrolled (speed wll chnge f lod orque T L vres. Only sedy se vlue cn be conrolled, dynmc performnce s no conrolled. Sysem vrbles durng rnsens cn no be dmssble (over curren). 5
Closed Loop Conrol wh Curren Feedbck Consder he followng crcu/conrol dgrm 3φ s he rmure curren reference. Conroller/Compensor : necessry o mprove sysem dynmc performnce Typcl lner conrollers: P proporonl I negrl PI proporonl nd negrl (mos populr) PID proporonl negrl nd dfferenl 6
Closed Loop Conrol wh Curren Feedbck Generl feedbck conrol loop dgrm wh PI conroller + τ s P(s) Conroller rnsfer funcon: Y = { x + x = Y P + Y I { τ s Proporonl pr: Y P = x, vrons n x cn be mmedely pssed o he oupu, ffecng sysem dynmc performnce. Inegror pr: Y I = x, o elmne sysem sedy se error (where τ s me consn). τ s 7
Closed Loop Conrol wh Curren Feedbck Smulnk model for PI conroller: PI rnsfer funcon: Y = x + τ s x x Vn Y Vα τ 1 s PI conroller 8
Closed Loop Conrol wh Curren Feedbck Wveforms Sep npu ω 678 α V V 678 Δ Queson: Lner cceleron; why? Answer: consn T e consn n L AF f = s ccurely conrolled. However, no speed feedbck moor speed no conrolled. 9
Conrol wh Curren nd Speed Feedbck Conrol loop/crcu block dgrm: r LAA r f f o V n T1 T3 T 5 V bn V dc e L FF V f V cn T 4 T 6 T 2 o α V α 10
Conrol wh Curren nd Speed Feedbck Funcons of he speed PI conroller: = ω r n sedy se (zero error n sedy se due o he I negrl pr). Conrols he dynmc of he speed (seng me, nd overshoo). The oupu of he speed PI regulor s he reference of. Usully s lmed o 2x,red. In Lb 2, f,red = 16.2A (5hp dc moor),mx = 32.4A. e ω = r ω ω r,lmed τ 1 s Speed PI conroller 11
Conrol wh Curren nd Speed Feedbck Wveforms For, ω s low 0 1 >> 0 speed PI regulor s sured. r 63.9 rd/sec (610 rpm) 50% red speed Hence s lmed o 2,red Speed ncreses: For reduces o. Ths mens h pproches sedy se., ss ω ω ω @ = 1 r r r 2, red. 63.9 32.4 A s lmed Who deermnes he vlue? ω sedy r,ss se, ss 12 1
Conrol wh Curren nd Speed Feedbck Feures: Curren nd speed re ccurely conrolled. No sedy se error n curren or speed ( PI conroller for ech loop). Dynmc response cn be uned (djusble seng me nd overshoo). Curren cn be lmed. How do P nd I ffec he sysem? fs response nd overshoo. τ slow response nd overshoo. or τ unsble sysem. 13
Thnk you for your enon