Download Control of High Speed Permanent Magnet Synchronous Motors

Control of High Speed Permanent
Magnet Synchronous Motors
Dong Le and Liping Zheng
Calnetix Technologies, Inc.
California, USA
Motor & Drive System 2013
February 7-8, 2013
Orlando, Florida
1
Introduction
Permanent Magnet Synchronous Motors are
becoming more and more popular due to
high performance.
High performance PMSM controllers are still
challenging when considering
 High Speed
 High efficiency
 High acceleration/deceleration
 Sensorless
 Robust to parameter changes
 Longer cables
2
Transformation
 Clarke’s Transformation
[ f  0 ]  [T 0 ][ f abc ]
T 0
1  12
2
 0  23
3 1
1
 2
2
 12 
3 
2 
1

2 
Park’s Transformation
[ f dq ]  [Tdq ( d )][ f  ]
 cos sin 
Tdq ( )  


sin

cos





3
PWM Active Rectifier
ADVANTAGES:
 Bi-directional flow
 Nearly sinusoidal current
 Regulation of power factor to unity
 Low harmonic distortion of current
 Controlled DC link voltage regardless of grid
voltage (360-520 Vac)
 The motor may operate at full speed without field
weakening by maintaining the DC link voltage
above the voltage peak
4
Sensorless Flux Vector Control
 Virtual Flux Estimator:
 The voltage imposed by the line power in combination with the
AC side inductors are assumed to be quantities related to a
virtual motor
 Thus, R and L represent the stator resistance and stator
leakage inductance of the virtual motor and the phase to
phase line voltage Uab, Ubc, Uca would be induced by the
virtual air gap flux. In other words, the integration of the
voltages leads to a virtual line flux vector in stationary αβ
coordinates
L
5
Sensorless Flux Vector Control–
Cont.
 ADVANTAGES
 Sensorless:
•Simpler
•Isolation between power and control circuits
•Higher reliability and more cost effective
 Flux vector control:
•Better noise immunity (use of integrator instead of
differentiator).
•Near sinusoidal current waveform
•Better harmonic reduction (low pass filter in the integrator
reduces nth harmonics by a factor of 1/k, and strongly reduce
the high frequency ripple in the system)
•Angle of virtual flux is less sensitive than angle of voltage
vector to disturbances in line voltage
•Simple algorithms
•Good dynamic response
•PLL is able to track the flux smoothly event through zero speed
6
Sensorless Flux Vector Control–
Cont.
 Volt/Hz drive:
 Volt/Hz control of a machine is based on the principle of maintaining a
constant magnetic flux in the motor
 The terminal voltage must increase roughly proportional to the applied
frequency
 V/Hz drives typically add a low frequency voltage boost to increase
starting torque capability
 V/Hz drives typically add a steady state slip compensation which
increases with frequency based on current measurement to give better
steady state speed regulation
 V/Hz drives may also add stability compensators to overcome mid
frequency instabilities evident in highly efficient machines
 Volt/Hz works well on applications that the load is predictable, and does
not change quickly such as fan loads
 For better torque control, flux vector control was developed. This
technique controls not only the magnitude, but also the orientation of
the AC excitation, thus the vector name. This is based on field
orientation principles which state that: “If the current vector is
controlled relative to the rotor flux vector, then the magnitude of the
flux vector and the motor torque can be independently controlled. 7
Sensorless Flux Vector Control–
Cont.
Based on the DC link voltage Udc and the inverter switch state Sa, Sb,
Sc of the rectifier input voltage
2
1

Us

Udc
(
Sa

( Sb  Sc )
are estimated as follows
2
3
Us  
1
2
Udc ( Sb  Sc )
Then the virtual Flux ψL
components are calculated in the
stationary coordinates system:
diL 
) dt
dt
diL 
 L    (Us   L
) dt
dt
And torque:
 L    (Us   L
3 n
T  * ( Iqs  ds  Ids  qs )
2 2
8
Sensorless Flux Vector Control–
Cont.
 Sensor-less flux vector drives use direct field orientation to
provide higher performance
 Instead of implying the orientation of the flux vector by
satisfying the equations, the flux vector is directly
measured from terminal electrical quantities of voltage and
current
 The drive continuously integrates and solves the previous
equations to obtain instantaneous measurements of the
rotor flux vector and motor torque
 The inputs to the drive are the stator voltage and current
vector
 The current vector is best directly measured,
 But the voltage can be deduced from a DC link voltage
measurement and the PWM switching pattern
9
Sensorless Flux Vector Control–
Cont.
TOPOLOGY OF INNER LOOP FOR SENSORLESS FLUX VECTOR CONTROL
10
Sensorless Motor Control Block
11
Active Rectifier Control Block
12
Detection & Protection
Ground fault detection
Over/Under voltage, Over current
 Programmable
DESAT
As required for protecting power devices
Line start lock-out
Unit shall not motor/generator or put power back to
GRID
until commanded
Over Temperature
Provide caution signal for heat sink temperature to
allow for controlled shutdown or fold back
13
Packaging Design
 Packaging design take into account
Thermal performance
Grounding scheme for noise immunity,
EMI/EMC
Accessibility/maintainability of the system
 Enclosure Design Features
 User friendly
 Provide Faraday cages for control logic to block
electric field and electromagnetic radiation (RF)
 Meet customer design specification
14
IGBT Module SelectionLosses
15
IGBT Temperature Distribution
Bi-Direction Power Electronics
17
Function Block Diagram
18
Function Block Diagram - Details
19
Active Rectifier Control Block
ACTIVE RECTIFIER CONTROL BLOCK
ic
Vc
ib
Vb
Udc
load
ia
Va
Sa
Sc
Sb
UL
Current measurement
&
Line voltage estimation
IL
UL
PWM
IL
+
Udc_ref
k,
Us
Us
V_reg
d, q
Usq
d, q
Usd
Id_reg
Iq_reg
+
-
+
Iq_ref
Id_ref=0
20
Sensorless Motor Controller Block
21
Motor Control Simulation
Simulink Simulation Model
22
Simulation Results
Current Waveforms
Current vs. time
200
Ia
Ib
Ic
150
Current (A)
100
50
0
-50
-100
-150
-200
0.425
0.43
0.435
Time(seconds)
0.44
0.445
23
Catch Spin
Also caught flying catch - Synchronize the
drive with the spinning motor
24
Test
Double Pulse Test
25
Test Setup- Back to Back
 Operate system from 10 kW
to 252 kW from/into grid
480VRMS
P
E
MOTOR
GEN
P
E
Coupling
26
255kW Back To Back Testing Picture
27
Ground Systems
 Single Point
A. Series (Common or Daisy Chain)
B. Parallel(Separate)
 Multipoint
 Hybrid
NOTE: Series or daisy chain should be avoid whenever
possible to prevent common currents from developing voltage
drops across their common reference. The concept of typing all
the various subassemblies together to a central point via
INDIVIDUAL WIRE is no longer acceptable. Such connection
while working in very low frequency but tend to enhance cross
talk between subassemblies for high frequency circuits.
1
BAD
2
3
1
PREFERED
2
3
28
How to Connect Circuit to Single
Point Reference
Rule is to Reduce Ground Loop Area
Bad Example:
Good Example:
29
Connect Equipment to Single
Point Reference
30
Minimize Ground Loop Area
BAD
(LARGE GROUND LOOP AREA)
vcc
vcc
gnd
gnd
GOOD
(SMALL GROUND LOOP AREA)
31
Analog and Digital Ground
analog section
digital section
32
Conclusion
 Use PWM active rectifier instead of passive rectifier:




Bi-directional power flow
Nearly sinusoidal current
Regulation of power factor to unity
Controlled and regulated bus voltage regardless of grid voltage (360-520Vac)
 Use of virtual flux estimator instead of voltage estimator with Phase Lock Loop
provides:
 Better noise immunity (use of integrator instead of differentiator)
 Better harmonic reduction
 Angle of virtual flux is far less sensitive than angle of voltage vector to
disturbances in the line voltage.
 Simple algorithm
 Excellent dynamic responses
 Phase lock loop is able to track the flux smoothly event through zero
speed
 Catchspin feature can synchronize the spinning motor.
 Proper grounding is very critical to have high performance motor control
33