Download PNIMNiPE_nr56 - Instytut Maszyn, Napędów i Pomiarów

Nr 64
Prace Naukowe Instytutu Maszyn, Napędów i Pomiarów Elektrycznych
Politechniki Wrocławskiej
Nr 64
Studia i Materiały
Nr 30
2010
PWM rectifier, integrated power module,
hardware design, TMX320R2812, auto-code generation
Michał KNAPCZYK*, Krzysztof PIEŃKOWSKI**
THREE-PHASE PWM RECTIFIER BASED ON INTEGRATED
POWER MODULE AND FIXED-POINT DIGITAL SIGNAL
PROCESSOR FOR RAPID PROTOTYPING ISSUES
The paper presents a laboratory test-bench with a three-phase two-level PWM rectifier. The setup
is based on a 3.3kW integrated power module and a 32-bit fixed-point digital signal processor with a
Simulink auto coder for rapid prototyping of control strategies. The setup has been diversified into
separate modules for different tasks: grid voltage and grid current measurement modules, hardware
dead-time block with IGBT gate signal inverted logic driver, analogue signal processing block for
sensor-to-processor interface, auxiliary control electronics and power circuits with overvoltage and
overload protections. These modules assembled in unit provide entire functionality of the laboratory
setup with the PWM rectifier for flexible and fast implementation of control strategies either for their
further development or for the purpose of didactics. In order to demonstrate the operation of the proposed test-bench Sliding-Mode Voltage Oriented Control with -PWM has been implemented to control the PWM rectifier. Numerous experimental results have been presented and discussed.
1. INTRODUCTION
Modern power electronics devices for commercial use are controlled by numerous
types of microcontrollers. A code of newly developed and thoroughly tested control
algorithms is next optimized to be run within a possibly lowest time-consuming microprocessor routine. However research and development phase of design of new control
schemes for power electronics equipment requires versatile and flexible control units
usually based on fast fix-point or even floating-point digital signal processors. These are
usually mounted on evaluation boards equipped with dedicated peripherals like PWM
__________
*
3cap Technologies GmbH, 85764 Oberschleißheim, Germany, [email protected]
Politechnika Wrocławska, Instytut Maszyn, Napedów i Pomiarów Elektrycznych, ul. Smoluchowskiego
19, 50-370 Wrocław, Poland, [email protected].
**
2
modules for control of power electronics devices, ADC converters, general purpose
inputs and outputs, as well as RAM or EEPROM for flashing the software and recording
diagnostics alerts. They provide communication with PC usually via a standard serial or
USB port. In field of high quality energy conversion integrated power modules have
recently revolutionized the design of modern power converters. For high power conversion the semiconductor structures are designed as integrated modules containing SCR or
GTO legs. In range up to medium power ratings complete IGBT- or MOSFET-based
three-phase two-level and multi-level converters are available. Further improvements in
design of power modules have led to integration of protective electronics with the semiconductor structure inside its package or outside it in case of its tiny dimensions [1,2,3].
Such intelligent power modules are protected against overloading, over/under-voltage
and over-heating [6,7,8,11]. This paper describes a design of a laboratory test-bench
with the three-phase two-level PWM rectifier based on 3.3 kW IGBT power module
FS10R06VL4 with EiceDRIVER 6ED003E06-F and evaluation board eZdsp R2812
with TMX320R2812 digital signal processor. The presented design process providing
increased quality of system performance has been significantly improved in comparison
with the previous hardware setup presented by authors in [4].
2. DESIGN OF LABORATORY SETUP WITH PWM RECTIFIER
The PWM voltage-source rectifier requires for its proper operation the exact information about grid voltages, grid currents and the output DC voltage (Fig.1).
Fig.1. Diagram of proposed experimental setup of PWM rectifier
3
2.1. INTEGRATED POWER MODULE
The power unit of the proposed prototype of the PWM rectifier is based on the 3.3
kW IGBT power module by EUPEC/INFINEON with the electronic interface
EiceDRIVER™ 6ED003E06-F [11]. The reason of the widespread use of the IGBT
transistors is their voltage-based control because practically no power is taken during the
switching process unlike in case of SCRs or GTOs. The crucial problem in realization of
the driver system for the transistor-based two-level bridge is a floating reference voltage
for gate signals of the upper-side transistors. The problem has been overcome by the
application of a dedicated IGBT driver IR2136S of International Rectifier using the
boot-strap technique. Fig.2 presents the three-phase IGBT power module mounted on a
heat-sink with additional protective electronics.
Fig.2. EiceDRIVER 6ED003E06-F: overview (left); block diagram [11] (right)
The FS10R06VL4 power module presented in Fig.3 provides the maximal DC-link
voltage Udcmax=300V and the maximal DC-link current Idcmax=10A. The minimum deadtime for the IGBT transistors in each leg of the converter is Tdead=1.8s.
Fig.3. EUPEC module FS10R06VL4 consisting of six IGBTs integrated in gel-filled package
4
Fig.4 presents the detailed functional diagram of the proposed laboratory setup of the
PWM rectifier with the FS10R06VL4 integrated power module containing six IGBT
transistors with respective shunt diodes, the IR2136S IGBT driver and the LM393M
voltage comparators. The on-board electronics is supplied with 15VDC. This electronic
interface provides short-circuit, under/over-voltage and over-current protection by a
shunt resistor, the IR driver and comparators. In case of power modules which are
equipped with NTC temperature sensor in their internal structure EiceDRIVER can also
provide an over-temperature protection [11].
P1/CON9 - CONTROL
1 2 3 4 5 6 7 8 9
BYG20J
NC
BYG20J
BYG20J
1
VCC
VB1
HO1
2
3
4
5
6
7
8
100k
MCL4148
VS1
27
82
10u
26
82
FS10R06VL4
VB2
HO2
FLT
28
VS2
24
23
10u
9
82
22
MCL4148
11
ITRIP
VB3
EN
HO3
RCIN
VS3
20
19
10n
0.1u
10u
15k
18
EU
10n
VSS
LO1
LO2
0.1u
13
COM
LO3
G1
16
+
-
270
G2
G3
EV
G4
G5
EW
G6
15
82
14
15k
IR2136S
0.1u
120
15k
15k
N
(-)
LM393M
68k
15k
10n
12
SUPPLY
15V
15k
82
0.1u
47u
MCL4148
U
V
W
82
2
1
P
(+)
560k
10
P2/CON2
HIN1
HIN2
HIN3
LIN1
LIN2
LIN3
33m
2.2k
NTC
LM393M
(optional)
8.2k
33k
33k
+
-
0.1u
2.2k
15k
0.1u
0.1u
100k
0.1u
560k
10n
Fig.4. Detailed diagram of EiceDRIVER 6ED003E06-F with FS10R06VL4 6-pack module [11]
Table 1 presents selected electrical characteristics of the proposed FS10R06VL4
power module with its driver circuit 6ED003E06-F.
Table 1. Selected parameters of EiceDRIVER 6ED003E06-F with FS10R06VL4 6-pack module
DC-link voltage Udc:
DC-link current Idc (@TC=25°C)
Collector-emitter voltage UCE
Maximal switching frequency fswitch
Minimal PWM ratio
Total power dissipation Ptot (@TC=25°C)
Minimal dead-time for IGBTs in one leg Tdead
Driver supply voltage Uin
360V
10A
600V
15kHz
0.1
78W
1.8s
15V
5
2.2. VOLTAGE AND CURRENT SENSORS
In the proposed laboratory setup with the PWM rectifier voltage and current transducers offered by LEM have been applied. The operation of these sensors is based on
Hall-effect to provide galvanic separation between the microprocessor and the power
module, as well as to provide high linearity and accuracy of voltage and current sensing
[9]. Fig.5 presents prototype boards with LV25-P sensors for grid and DC-link voltage
measurement and grid current transducers LA50-P. The voltage measuring range in case
of LV25-P is set up using carefully selected shunt power resistors. The current measuring range for LA50-P can be easily adjusted by setting an appropriate number of turns of
a current cable round a transducer’s core.
Fig.5. Prototype boards with transducer for AC-DC voltages (left) and ac currents sensing (right)
Fig.6 shows a coupling and scaling interface for the transducers and the DSP. Since
the analog-to-digital converter (ADC) of the DSP requires positive input signals in range
from 0 to 3V the offset signals have been added to the scaled output signals of the proposed transducers. The matching circuit is based on inverting operational amplifiers
TL074 and RC low-pass filters for the anti-aliasing purpose. For the maximum protection of the DSP the inputs of the ADC channels have been equipped with the 1N5711
Schottky barrier diodes operating as voltage limiters.
Fig.6. Scaling interface between voltage and transducers and analog-to-digital converter of DSP
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2.3. OPTOCOUPLERS, DEAD TIME AND POSITIVE-TO-NEGATIVE LOGIC CONVERTER
For galvanic separation between the power module with its interface electronics and
the microprocessor-based control system fast logic gate opto-couplers HCPL-2211 have
been applied. The hardware dead-time module has been designed using SN7414
Schmitt-trigger inverters, SN5406 buffers with open-collector outputs and the RC
branches. Besides providing blinking time the proposed circuit inverses control signal to
negative logic routine. Despite its sensitiveness to changes of ambient temperature the
circuit shown in Fig.7 provides satisfactorily stable functionality at typical laboratory
conditions. There are six independent circuits for each of six IGBTs.
+15V
7805
+5V
TMX320R2812
HCPL-2211
GPIO
(PWM)
ACTIVE HIGH
SN7414D
C1
SN7406D
B1
SN7414D
A1
to IGBT
ACTIVE LOW
Fig.7. Opto-coupler, dead time and positive-to-negative logic converter (left); signal routine (right)
Fig.8 (left) presents the prototype board with the complete set of circuits presented
in Fig.7 for one IGBT. The parameters of the RC branch have been tuned in order to
make signals reach a Schmitt-trigger’s threshold in 2s as shown in Fig.8 (right).
C1
C2
Fig.8. Evaluation board with optocouplers and hardware dead-time (left);
measured control signals for one leg of IGBT module (right)
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2.4. FAULT PROTECTION SYSTEM AND LINE POWER ADAPTER
The proposed prototype of the PWM rectifier has been equipped with software and
hardware protection systems against hazardous effects of any possible faults or power
overshoots. As it is shown in Fig.9, in case of short-circuit or overvoltage the power
module should be cut off from the supply line throughout respectively varistors, fuses
and a relay. Moreover a brief unexpected collapse of the low DC voltage supplying the
DSP and control electronics causes the cut-off of the power module and safe discharge
of the DC-link capacitor thru a discharging resistor.
Fig.9. Overview of protective equipment of proposed setup of PWM rectifier
In order to provide a low DC input voltage for auxiliary electronics and sensors a
power adapter has been designed. Fig.10 presents its application with a wiring diagram.
For safety reasons the power module supply voltage of 15VDC is provided separately.
Fig.10. Power adapter for DC low voltage: front view (left); schematic diagram (right)
8
2.5. TMX320R2812 DIGITAL SIGNAL PROCESSOR
For the realization of the control tasks in the experimental setup of the PWM rectifier
an evaluation board eZdsp™ R2812 by Spectrum Digital® based on TMX320R2812
Digital Signal Processor by Texas Instruments has been chosen. Fig.11 presents the
front view of the DSP applied in the proposed setup of the PWM rectifier. The block
diagram beside shows the DSP’s internal functionality.
Fig.11. eZdsp board based on TMX320R2812 DSP by Texas Instruments [10]
The TMX320R2812 is the fixed-point, 32-bit data word microprocessor with two
overlapping data and program address spaces, 18K words on-chip RAM, 128K words
on-chip FLASH, 64K words off-chip SRAM, 30MHz clock (maximal rate up to
150MHz), 56 multiplexed digital inputs/outputs, 12-bit 16-channel analog-to-digital
converter (80ns), 45 interrupts divided into 8 levels of priority, 5V supply voltage and
two Event Managers including a hardware 2-level/3-level PWM modulator.
The DSP is embedded on an evaluation board presented in Fig.12 with the interface
electronics for the transducers and two external 8-bit digital-to-analog converters (DAC)
for monitoring of inner control variables direct on an oscilloscope.
Fig.12. DSP socket with interface electronics (Fig.6) (left); pin layout for PWM and DACs (right)
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2.6. OVERVIEW OF PWM RECTIFIER PROTOTYPE
The complete laboratory setup of the PWM rectifier consists of the six component
boards presented in the previous sections assembled one on another and connected as
shown in Fig.13 to provide the functionality depicted in Fig.1.
Fig.13. Overview of assembled prototype of PWM rectifier on test-bench
3. SIMULINK MODEL FOR AUTO-CODE GENERATION
The idea of Sliding-Mode Voltage Oriented Control (SM-VOC) for the PWM rectifier described in details in [5] is the decomposition of the grid current vector ig based on
the Park transformation into the two rectangular components igd and igq
-q)
coordinate frame oriented with the grid voltage vector as depicted in Fig.14 (left). Fig.14
(right) presents a block diagram of the proposed control method.
Fig.14. Sliding-Mode Voltage Oriented Control: vector decomposition (left); block diagram (right)
10
Fig.15 demonstrates the Simulink model of Sliding-Mode Voltage Oriented Control
presented in Fig.14 (right) realized with help of Target for TI C2000™ toolbox including C28x IQmath Library for fast fixed-point arithmetic.
SM-VOC
R2812 eZdsp
voltage
C281 x A 5
ADC
A5
egAB
A4
A4
egBC
A0
A0
igA
A1
A1
igB
A3
A3
udc
analog -to
-digital
converter
egAB
current
angle
egBC
angle
egd
igA
egq
igB
igd
Input1
left
igq
Input2
right
scaling
DACleft
DACright
Out to SCOPE
reference currents
id *, iq *
computation
signal offset
cancelation
egd
id*
egq
id*
sd
id
phi*(rad)
0
phi *
u0*
switching fcn
for d -axis
iq*
PI
d
a
s1*
q
b
s2*
angle
c
s3*
iq*
sq
820
switching fcn
for q -axis
udc *
C281 x
to IGBTs
iq
i_load
GPIO DO
u0
Digital Output
To switches
Fig.15. Target for TI C2000 model of Sliding-Mode Voltage Oriented Control for auto-coding
Fig.16 presents one of applications of the fixed-point IQmath arithmetic model of selected parts of Sliding-Mode Voltage Oriented Control for real-time auto-coding.
reference currents
id *, iq *
computation
4
u0*
egd
egq
id*
i_load
A IQmath
Y
B IQNdiv
IQN / IQN 1
1
id *
1
egd
phi*(rad)
u0*
5
i_load
A IQmath
Y
BIQNmpy
IQN x IQN
iq*
2
egq
3
phi *(rad )
A IQmath
Y
BIQNmpy
IQN x IQN 1
A IQmath
Y
BIQNmpy
IQN x IQN 2
A IQmath
Y
B IQNdiv
IQN / IQN
2
iq *
Fig.16. Target for TI C2000 model of Sliding-Mode Voltage Oriented Control for auto-coding
Texas Instruments IQmath Library is set of highly optimized and high precision
mathematical function library to port the floating-point algorithm into fixed-point code
on TMS320C28x devices. These routines are typically used in computationally intensive
real-time applications where optimal execution speed and high accuracy is critical. The
TI IQmath library shortens significantly the time of DSP application development [10].
11
4. SELECTED EXPERIMENTAL RESULTS
The experiments have been carried out using the parameters presented in Table 2.
Due to the properties of the power module of the PWM rectifier presented in Table 1 the
experimental verification has been performed at a reduced grid voltage.
Table 2. Parameters of experimental setup with PWM rectifier
Grid phase voltage eg:
Grid voltage frequency fg:
Grid resistance Rg:
Choke inductance Lg:
DC-link capacitance Cd:
DC-link nominal voltage Udc:
Load resistance Rload:
SM-VOC sampling rate:
38V
50Hz
100m
11.3mH
1000F
100V
35
35s
Fig.17 (left) presents a measured phase grid voltage and three-phase sinusoidal grid
currents at step change of a converter load (Rload=35) and at unity power factor
condition (UPF). Fig.17 (right) shows the grid currents in the (d-q) coordinate frame at
step change of converter load derived with help of DACs.
igC
igB
igA
egA
Fig.17. Experimental results of Sliding-Mode Voltage Oriented Control for proposed PWM rectifier:
phase grid voltage and three-phase grid currents at step load change and unity power factor (left);
grid currents in (d-q) coordinate frame at step change of converter load (right)
The transient of the DC-link voltage at step change of converter load is shown in
Fig.18 (left). Since the measured phase grid voltage is corrupted with low-order harmonics (mainly the third), this grid voltage distortion is also penetrating into the DC-link
12
voltage making it oscillate. However there is no fourth wire in the system and the influence of the third harmonic is thus cancelled and the grid currents remain sinusoidal.
Fig.18 (right) presents the rectifier input line-to-line PWM voltage produced with help
of the delta-modulation (-PWM) for SM-VOC. Since the grid voltage is reduced the
presence of voltage drops over IGBTs is thus distinct.
Fig.18. Experimental results of Sliding-Mode Voltage Oriented Control for proposed PWM rectifier:
transient of DC-link voltage (left); rectifier input PWM voltage under delta-modulation (right)
5. CONCLUSIONS
The paper presents a thorough design of the experimental setup of the PWM rectifier
based on a DSP control unit. For the proper operation the PWM rectifier requires feedback information about all state variables. Hence the voltage and current sensors with its
auxiliary electronic have been constructed and examined. The real-time application of
the Sliding-Mode Voltage Oriented Control (SM-VOC) for the PWM rectifier requires a
faster and more efficient digital signal processor than in case of its linear counterpart
(VOC) to achieve the comparable quality of the control process. This is due to the fact
that Sliding-Mode Control of the PWM rectifiers uses the delta-modulation that is realized on-line at each calculation step of the control algorithm. In contrary, SV-PWM is
realized in a separate hardware module (Event Manager) at a definable rate regardless of
a control algorithm rate. However as it was shown in this paper it is possible to implement the proposed sliding-mode-control technique in TMX320R2812 DPS which is
dedicated for power electronics applications. The proper selection of values of the choke
inductance and the DC-link capacitor, as well as neglecting a sensorless control in the
algorithm provide the satisfactory performance of the sliding-mode-based control techniques using the proposed digital controller.
13
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