ac motor control and ev applicationsphome.postech.ac.kr/user/cmdlab/acmc(ch1).pdf · four quadrant...
TRANSCRIPT
Operation Sequence
Counter clockwise torque is max.Back emf is max.
Counter clockwise torque is max.Back emf is max.
Commutationtakes place.Disengaging/
Engaging
(b)
S N
(a) (c)
S N S N
Back EMF
As the armature winding rotates in the DC field,the amount of flux passing through the armature winding varies. Hence, the voltage is developed as the rotor rotates.The polarity is opposite to the direction of current flow when motoring.
DC Motor Equivalent Circuit
Note that torque constant and back emf constant are the same.
Prove it.Hint: Derive from the power relationship. (Elec. Power= Mech. Power)
+-
+
-
+-
Four Quadrant Operation
Motoring in the forward direction
Regeneration in the reverse direction
Motoringin the reverse direction
Regenerationin the forward direction
+-
+
-+-
+
-
+-
+
-+-
+
-
+
TL
PI+PI+ +-
--
DC Motor Speed Control Block Diagram
1. Determine current loop PI controller so that there is a slight overshoot to a step input.
2. Replace the current loop by 1. Determine velocity loop PI controller so that it is critically damped.
3. Find a response for step speed command *=1500rpm with load TL = 30 us (t-2).
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Current Controller
++-
-
Speed Control Loop and Bode Plot
Gain
0 dB
-20 dB
PI controller 1st order filter(current controller) Inertial Load
speedSpeed
command
-40 dB
D
E
(a)
(b)
PI and IP Controllers
++-
-
PI controller
speedSpeed
command
++-
-
IP controller
speedSpeed
command+
-+
+
(a)
(b)
00 0.2 0.4 0.6 0.8 1.0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
Time (sec)
PI Controller
IP Controller PI Controller
IP Controller
(a) (b)
Time (sec)
Speed Responses and Current Commands
PI Controller with Reference Model
-
-
Reference Model
Integral control
Proportionalcontrol
+
+
+++
++
+
+
Sensitivity and Complementary Sensitivity Functions
-++
+
Sensitivity andComplementary SensitivityFunctions
Gain Margin and Phase Margin
-180o
PhaseMargin
GainMargin
0
Gain crossover angular frequency
phase crossover angular frequency
Input
Disturbance
Time (sec)
+-
-+ +Output
0 1 1.5 320.5 2.5
Role of the Integral Controller (Disturbance Rejection)
Current Loop Based on a Microcontroller
Hold element(current command)
-Computing cycle(current control)
Controlledsystem
Current detection
PWMexecution
Bode Plots of PI and PI with referencePI
PI with reference
PI
PI with reference
Disturbancerejection
Commandfollowing
PIPI with reference
Sec.