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Study of Vector Control Algorithm and Inverter design for BLDC Motor, V/f control Algorithm


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Study of Vector Control Algorithm and Inverter design for BLDC Motor, V/f control Algorithm

  1. 1. Study of Vector Control Algorithm and Inverter design for BLDC Motor, V/f control Algorithm Project by: Amol Mahurkar, Ayush Modani, Ghanshyam Mali, Heena Karir, Manoj Autade, Vivek Kumar
  2. 2. Objectives 2  Working of BLDC Motor  Different Control Algorithms for BLDC Motor  Vector Control Algorithm (Sensorless)  Inverter Design for BLDC Motor  Parametric Discussion on Inverter Design  Working of Induction Motor  Voltage versus Frequency Control Algorithm
  3. 3. Vector Control Algorithm for BLDC Motors Sinhgad College of Engineering, Pune
  4. 4. Contents 4  Classification of motors  Motor Basics  BLDC motor and its construction  BLDC Control methods – Sensored Control  Clarke/Park Transformation  Sensorless control  Vector Control
  5. 5. Actuators  Industrial fans  Blowers and pumps  Machine tools  Household appliances  Power tools  Disk drives. Actuators Rotational Linear Applications 5
  6. 6. Classification of motors DC Voltage Supply AC Voltage Supply DC Motors Universal Motors Solenoids Synchronous Motors EC Motors Stepper Motors Brushed Brushless Brushless Driver Electronics 6
  7. 7. Understanding the motor basics 7
  8. 8. Simple model of DC motor 8
  9. 9. BLDC Motor Merits Demerits  Less Maintenance  Longer Life  Flat SpeedVs.Torque Characteristics  High Efficiency  High Output Power/ Frame Size  Low Rotor Inertia  Higher Speed Range  Low Electric Noise Generation  Higher Cost of Building  Complex & Expensive Control 9
  10. 10. Brushless DC motor  Rotor is Permanent Magnet.  Stator is Electromagnet.  Windings is on the stator.  Three phase supply is given to windings of stator  Torque is produced due to interaction between magnetic field of rotor and magnetic field produced by current in the stator. 10
  11. 11. Space vector rotation sequence 11
  12. 12. Control Methods BLDC Control methods Vector Control Sensored Sensorless Sinusoidal Drive Control Trapezoidal Drive Control Sensored Sensorless 12
  13. 13. Vector control vs 1200 control Performance→ Variable Speed Low Noise, High Efficiency Large Torque High Response COST  120°Drive System Vector Control. Typically for Industry Use Due to cost for Appliances  1200control vs.Vector Control  Low performance low cost vs. high performance high cost 13
  14. 14. 3-phase Inverter Q0, Q1, Q2, Q3, Q4, Q5: Can be either of Power MOSFET or IGBT 14
  15. 15. 15
  16. 16. Sensor versus drive timing 16
  17. 17. Sensored Control 17
  18. 18. Sensored Control 18
  19. 19. How do you Control Torque on a DC motor? PI Controller PWM1 PWM2 ADC + - Desired Current Error Signal Measured Current 19
  20. 20. Principle of FOC 20
  21. 21. Maximum Torque per Amp 21
  22. 22. Measure current already flowing in the motor Measure ia and ib. Calculate ic, from Kirchoff’s Law. A, B, and C axes are “fixed” with respect to the motor housing.This reference frame is also called the “stationary frame” or “stator frame”. 22
  23. 23. Compare the measured current(vector) with the desired current(vector), and generate error signals. isis Error We must regulate the current vector magnitude and angle by regulating ia, ib, and ic. Commanded Rotor axis flux 23
  24. 24. Measure the rotor angle to determine if the net current vector is oriented at 900 with respect to the rotor flux Θd Usually accomplished with a resolver or encoder. 24
  25. 25. Commanded Convert the three phase current vectors into two orthogonal vectors that will result In the same net current vector. In other words, convert 3-phase motor to 2-phase motor. Then we have only two current values to regulate instead of three! This is often referred to as the FORWARD CLARKE TRANFORMATION i α i β 25
  26. 26. Jump up on the rotating reference frame, whose x-axis is rotor flux axis. This is often referred to as the FORWARD PARK TRANFORMATION Commanded i q i d Θd Total 4 trig calculations 7 multiplications 3 additions 26
  27. 27. + - id (commanded) error(t) id (measured) + - iq (commanded) error(t) iq (measured) id and iq are handled independently. Since the comparison is performed in the rotating frame, AC frequency is not seen. Thus, they are DC quantities! Under normal conditions, we have all the d-axis flux we need supplied by the permanent magnets in the rotor. So commanded id is set to zero. This is how much torque we want! id can however be used to weaken the field of the machine. iq controls the amount of torque generated by the motor. 27
  28. 28. + - error(t) + - iq (commanded) error(t) iq (measured) id (commanded) id (measured) P ʃ I + + vd P ʃ I + + vq The PI regulator is a good choice for current regulation Amplify the error signals to generate correction voltages 28
  29. 29. Modulate the correction voltages onto the motor terminals Commanded i q i d Θd We now need to “jump off” of the rotating reference frame Transfer the voltage vectors back on to the stationary rectangular coordinate system. Reverse ParkTransformation 29
  30. 30. Commanded Next, we transform the voltage vectors from the rectangular coordinate system to three phase vectors. Reverse ClarkeTransformation 30
  31. 31. Over time, under steady-state conditions, the correction voltages va, vb, and vc will be sine waves phase shifted by 1200 va vb vc 31
  32. 32. Overview of Clarke – Park Transformation 32
  33. 33. Rotor with surface-mount magnets Non-salient design (magnetically round) Assuming no saliency, stationary frame equations are: Back –EMF component Sensorless Sinusoidal Control 33
  34. 34. 34
  35. 35. Basic Model 35
  36. 36. Complete Model 36
  37. 37. Thankyou 37
  38. 38. Inverters
  39. 39. Contents  Power switching  MOSFET  IGBT  MOSFET vs IGBT  Freewheeling Diode  Back EMF
  40. 40. POWER SWITCHING  BJT :Ability to handle high currents and high voltages, Current controlled device.  Both the MOSFET and IGBT devices are voltage controlled devices.  Control of the MOSFET and IGBT devices much easier.
  41. 41. MOSFET  Voltage controlled device  Fast switching  No thermal runaway  Small on state resistance  Asymmetric blocking capacity  High power dissipation  PLOSS = Irms 2 * RDS-ON Where: RDS-ON = drain-to-source on-state resistance Irms = drain-to-source rms current
  42. 42. IGBT  Voltage controlled device  Advantages of both Power MOSFET and BJT  Slower switching device  Asymmetric blocking capacity  Conductivity Modulation  PLOSS = Iave *VCE-SAT Where: VCE-SAT = Collector-to-emitter saturation voltage Iave = collector-to-emitter average current
  43. 43. MOSFET vs IGBT  IGBTs are slower than MOSFETs.  IGBT has a very low on-state voltage drop due to conductivity modulation and has superior on-state current density.
  44. 44. Comparison
  45. 45. Freewheeling Diode  A Freewheeling diode is a diode used to eliminate the sudden voltage spike seen across an inductive load when its supply voltage is suddenly reduced or removed.
  46. 46. Operation with Freewheeling Diode
  47. 47. Back EMF  When a BLDC motor rotates, each winding generates a voltage known as back EMF, which opposes the main voltage supplied to the windings according to Lenz’s Law.  It depends on, Angular velocity of the rotor Magnetic field generated by rotor magnets The number of turns in the stator windings  Equation is as, Back EMF = (E) ∝ NlrBω
  48. 48. Continued…..  Back-EMF refers to conclude the speed of the motor's rotation.  Steps: i. Provide current to the Motor windings (as a constant voltage or a PWM motor input to vary the speed). ii. Remove the current from the windings and "float" them.  The time required for the motor to flip from a motor to a generator depends on the stored charge in the induction of the motor windings.
  49. 49. Continued…..
  50. 50. THANKYOU
  52. 52. CONTENTS  Introduction the induction motor.  Stator and Rotor construction.  RMF Generation.  Induced EMF and its direction.  Motor speed and Slip.  Torque vs speed and torque vs slip.  Need of V/F.  Block diagram of V/F control.  Comparison of V/F and Vector control.
  53. 53. INDUCTION MOTOR •Motors operate on principle of Induction and hence the name “Induction Motors” is used •Motors also known as AC motors because Alternating Current (AC) is required •All AC motors are “brushless” –No mechanical contacts to wear –Requires AC source –If used, inverter creates desired freq and magnitude of AC •AC induction motors for lower cost applications –Single speed applications: fan, blower, pump, compressor –No control, just start the AC power source –Relays are used for ON/OFF
  54. 54. STATOR CONSTROCTION •Stator has windings with lamination to–Create strong magnetic field–Maintain continuous flux •Three phase motor windings are sinusoidal around the stator to produce a roughly sinusoidal distribution in flux •When three phase AC voltages are applied to the stator windings, a rotating magnetic field is produced–The rotating magnetic field of the stator drags the rotor around. MORE
  55. 55. ROTOR CONSTRUCTION Squirrel cage construction –Behaves like shorted 3- phase windings –Rotor bars are often skewed to prevent cogging –No magnets or windings
  57. 57. INDUCED EMF  Voltage is induced by following the Lenz Law. So rotor will rotate in same direction as that of RMF, to minimize the relative flux cutting. STATOR ROTOR
  58. 58. INDUCTION MOTOR SPEED  So, the IM will always run at a speed lower than the synchronous speed  The difference between the motor speed and the synchronous speed is called the Slip Where nslip= slip speed nsync= speed of the magnetic field nm = mechanical shaft speed of the motor slip sync mn n n= −
  59. 59. THE SLIP sync m sync n n s n − = Where s is the slip Notice that : if the rotor runs at synchronous speed s = 0 if the rotor is stationary s = 1 Slip may be expressed as a percentage by multiplying the above eq. by 100, notice that the slip is a ratio and doesn’t have units
  60. 60. SLIP CAUSES….. 1) Fr = s*F 2) E2r = s*E2  Where  Fr: Frequency of Induced Voltage  F: Applied Frequency  E2r: Induced EMF in Rotor  E2: Max. induced EMF in Secondary.
  61. 61. TORQUE VS SLIP  T α sR(E2) 2 R 2 + (sx)2  For LowSlip: T α s.  For HighSlip: T α 1/s.  Operated in stable region ie. Region where(T<Tm) SLIP(s) Unstable Stabl e torque Tm Tfl S= 0 S=Sm S=1 Tm
  62. 62. CONSTANT SUPPLY FREQUENCY Torque ,speed ,slip char.
  64. 64. Induced Torque is zero at synchronous speed. ‡ The graph is nearly linear between no load and full load (at near synchronous speeds). ‡ Max torque is known as pull out torque or breakdown torque ‡ Starting torque is very large. ‡ Torque for a given slip value would change to the square of the applied voltage. ‡ If the rotor were driven faster than synchronous speed, the motor would then become a generator. ‡ If we reverse the direction of the stator magnetic field, it would act as a braking action to the rotor
  65. 65. WHY V/F Ns = (120*F)/P  Constant Torque Applications. T α sR(E2)2 R2 + (sx)2  Avoid core saturation Φg α (V/f).  Vector control gives high torque at low RPM  Long distance controlling is easier with V/f  In V/f single drive can drive more than 1 motor.
  68. 68. THANKYOU
  69. 69. Q & A ??