Vector Control. Application to Induction Motor Control. DSP in Motion Control - Seminar

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David Ellis
6 years ago
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1 Vecto Contol Application to Induction Moto Contol

2 Vecto Contol - Pinciple The Aim of Vecto Contol is to Oient the Flux Poducing Component of the Stato Cuent to some Suitable Flux Vecto unde all Opeating Conditions Diffeent Schemes Possible if Use: Roto Flux Vecto => RFO Stato Flux Vecto => SFO Aigap Flux Vecto => MFO

3 Diect & Indiect Vecto Contol Diffeent Implementations ae Possible Depending on whethe o not thee is Diect Feedback of the Flux Magnitude and Oientation DIRECT VECTOR CONTROL: Uses Sensos o Model to Povide Feedback of the Flux Magnitude and Oientation. INDIRECT VECTOR CONTROL: Uses Assumed Slip Fequency Relationship to Achieve Field Oientation.

4 Roto Flux Oientation - RFO Oientation to the Roto Flux Vecto is the only Scheme that Povides Complete Decoupling of the Toque and Flux Poducing Components in the Induction Moto. => Most Popula Appoach. Both Diect and Indiect Schemes ae Possible. Indiect Schemes ae Favoed due to Poblems of Good Flux Estimation at Low Speeds

5 Pinciple of RFO Contol jsβ jsq i s ψ sd i sd i sq ρ sα

6 Diect RFO Oientation of IM Diect Sensing of Aigap Flux using Hall Sensos Oiginal Method of Blaschke fo Field Oientation Poblems due to Signal Distotions due to Slot Ripple Themal and Mechanical Fagility of Sensos Altenatively Monito Rate of Change of Aigap Flux using Seach Coils Non-Standad Machine Constuction Difficulty of Integating Measued Signals at Low Speeds Most Moden Diect Field Oiented Contolles use a Moto Model to Estimate the Roto Flux Components

7 Voltage Model fo Roto Flux Estimation ψ ( ) L ψ = ψ σ s L L ( ) ψ = ψ + ψ ρ = = v s s s s σ = 1 m L s 2 m L L 2 2 d q tan 1 ψ ψ R q d i dt i s s Total Leakage Facto

8 Cuent Model fo Roto Flux Estimation 1 ψ = ( ( ω ) ψ ) Lmi s 1 j T dt T T ψ = ψ + ψ ρ = = L R 2 2 d q tan 1 ψ ψ q d Roto Time Constant

9 Roto Flux Estimation Voltage Model Difficult at Low Speeds as R s Dominates Stato Voltage Equation Good Estimates at Medium and High Speeds L /L m and σ ae only Modeately Affected by Satuation Cuent Model Allows Low and Zeo Speed Estimation Difficult at High Speeds Due to Coss Coupling Dependency on Roto Time Constant Best Solution is to Combine both Models in a Closed Loop Flux Obseve

10 Closed Loop Flux Obseve v s R s + - Voltage Model σl s i s e j θ Lm 1+ pt e j θ ψ C + - K p + - L L m ψ Cuent Model K2 p

11 Diect Vecto Contol of IM - RFO T e i qs v qs e jρ PWM VSI M ~ ω ψ i ds v ds i ds i qs e -jρ 2 3 ψ T e ρ Flux and Toque Model Measued Moto Signals

12 Indiect Vecto Contol of IM Gained Populaity as Opeation to Zeo Speed is Possible by Adding Roto Position o Speed Tansduce Compute Cuent Components in Synchonous Fame and Slip Fequency to Maintain Field Oientation i i 2 L 3p L qs m ds = T ψ e 1 T d ψ = ψ + L dt m 2 e ω = ω ω = 1 T L i ψ m qs Apply Using Closed-Loop Cuent Contol

13 Indiect Vecto Contol of IM - RFO T e ψ 2 ( L 3p L m ) N D. 1 L m 1 + T d dt i qs i ds Cuent Regulated PWM VSI Encode M ~ 1 T θ e D N. ω 2 θ 2 θ + +

14 Indiect Vecto Contol of IM Contolle is a Feedfowad Stuctue => Paamete Eos Poduce: Incoect Field Oientation Ove- o Unde-Fluxing of Machine Coupled Toque and Flux Responses Excessive Losses and Heating Inefficient Dive Opeation Tansient Toque Oscillations T Eos Most Significant due to Themal and Satuation Changes

15 Slip Gain Tuning of Indiect RFO Use a Model Refeence Adaptive Contolle (MRAC) to tack Vaiations in R o T. Compute some function in two diffeent ways, one of which depends on the paamete to be tacked and one of which does not. Use diffeence to foce paamete to convege to coect value. Suitable Functions: Modified Reactive Powe Electomagnetic Toque Vaious Voltage Tems

16 MRAC fo Slip Gain Tuning Calculation #1 Calculation #2 + - Adaptation Mechanism $T

17 Diect Stato Flux Oiented Contol Recently Diect Stato Flux Oientation (SFO) has emeged as a possible altenative fo IM Contol. Above a few Hz, can Reliably Estimate the Stato Flux using the Voltage Model. Compute Magnitude and Oientation fo Contol fom: ψ = ψ + ψ ξ 2 2 s sd sq = tan 1 ψ ψ sq sd

18 Diect SFO fo IM Main Poblem is that Toque and Flux Axis ae not Decoupled Need to Include a Paamete Dependent Decoupling Netwok Bette Toque/Ampee Pefomance in Field Weakening than RFO Toque and Flux Contol does not equie Speed Feedback Opeation to Low Speeds Difficult due to Inaccuate Flux Estimation Good Altenative fo Medium Pefomance Dives

EE8412 Advanced AC Drive Systems. Topic 6 Field Oriented control (FOC)

EE8412 Advanced AC Drive Systems. Topic 6 Field Oriented control (FOC) Advanced AC Dive Syte Topic 6 Field Oiented contol (FOC) Souce: ABB 1 Advanced AC Dive Syte Field Oiented Contol (FOC) ectue Topi Geneal Block Diaga of FOC Diect Field Oiented Contol Diect FOC with Cuent