3. GPU OVERVIEW
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Ground power unit (GPU) is a 400 Hz
voltage source inverter supplying the
airplanes with external electric power
during stopovers.
Reduce the noise, air pollution.
The standard rating of GPU:
115V RMS, 400-Hz with three phase four
wires
Power rating: 90 kVA (up to 180 kVA in
1s after starting)
Introduction GPU model
Control System
Design
A case study Conclusion
4. 9/5/2022 4
Figure 1: Proposed GPU configuration
Improve system reliability in working with unbalanced loads
Reduce system volume, size and cost
Introduction GPU model
Control System
Design
A case study Conclusion
INVERTER TOPOLOGY
5. GPU TRANSFER FUNCTION
The PWM function is as follows:
𝐺𝑃𝑊𝑀 =
1
1.5𝑇𝑠𝑠+1
(3)
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Introduction GPU model
Control System
Design
A case study Conclusion
The state space equation of LC circuit:
𝑑𝑖𝐿
𝑑𝑡
𝑑𝑣𝑂
𝑑𝑡
=
−𝑟
𝐿
−1
𝐿
1
𝐶
0
𝑖𝐿
𝑣0
+
1
𝐿
0
0
−1
𝐶
𝑣𝐼
𝑖𝑂
(1)
GPU model can be written:
𝑣𝑂 =
𝑣𝐼
𝐿𝐶𝑠2+𝑟𝐶𝑠+1
−
(𝑠𝐿+𝑟)𝑖𝑂
𝐿𝐶𝑠2+𝑟𝐶𝑠+1
(2)
If consider 𝑖𝑂 are disturbance, the GPU transfer function will be:
𝐺 =
1
𝑁(1.5𝑇𝑠𝑠+1)(𝐿𝐶𝑠2+𝑟𝐶𝑠+1)
(4)
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OVERALL CONTROL SYSTEM
Introduction GPU model
Control System
Design
A case study Conclusion
Under the consideration that coupling components is not
significantly, can be ignored. Voltage and current loop control have
no effect each other, can be designed separately.
Figure 2: Overall control system diagram
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DEADBEAT CURRENT LOOP CONTROL DESIGN
Introduction GPU model
Control System
Design
A case study Conclusion
Figure 3: DB current
loop
Then, the DB controller function is:
𝑅𝑖 𝑧 = 𝑟𝐿
1−𝑒
−𝑟𝐿
𝐿
𝑇𝑠
1−𝑒
−𝑟𝐿
𝐿
𝑇𝑠𝑧−1
1−𝑧−2 (7)
The current loop transfer function,
can be derived:
𝐻𝑖 𝑧 =
𝑖𝐿
𝑖𝑟𝑒𝑓
= 𝑧−2
(5)
The current plant model 𝐺𝑖(𝑧) is determined by [8]:
𝐺𝑖 𝑧 =
1−𝑒
−𝑟𝐿
𝐿
𝑇𝑠
𝑟𝐿
𝑧−1
1−𝑒
−𝑟𝐿
𝐿
𝑇𝑠
𝑧−1
(6)
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Figure 4: Discrete parallel resonant voltage controller
[2] F. Rojas, R. Cardenas, J. Clare, M. Diaz, J. Pereda and R. Kennel: A Design Methodology of Multiresonant Controllers for High Performance 400 Hz
Ground Power Units. IEEE Transactions on Industrial Electronics, vol. 66, no. 8, pp. 6549-6559, Aug. 2019.
VOLTAGE RESONANT CONTROL DESIGN
The s domain resonant controller transfer function can be written as [3]:
𝑅𝑛(𝑠) = 𝐾𝑟𝑛
𝑠𝑐𝑜𝑠 𝜃𝑛 −𝜔𝑛𝑠𝑖𝑛 𝜃𝑛
𝑠2−𝜔𝑛
2 (8)
In which, 𝐾𝑟𝑛 is the gain and 𝜃𝑛 is the resonance frequency for the nth
resonant compensator
Introduction GPU model
Control System
Design
A case study Conclusion
9. 9/5/2022 9
[3] Z. Li, Y. Li, P. Wang, H. Zhu, C. Liu and F. Gao: Single-Loop Digital Control of High-Power 400-Hz Ground Power Unit
for Airplanes. IEEE Transactions on Industrial Electronics, vol. 57, no. 2, pp. 532-543, Feb. 2010.
DISCRETE RESONANT CONTROLLER
By Zero Order Hold (ZOH) transform, the model of resonant controller in the
discrete domain can be obtained [3]:
𝑅𝑧(𝑛) =
𝑧−1 𝑠𝑖𝑛 𝜔𝑛𝑇𝑆 𝑐𝑜𝑠 𝜃𝑛 −(𝑧+1) 1−cos(𝜔𝑛𝑇𝑆) 𝑠𝑖𝑛 𝜃𝑛
𝑧2−2 cos 𝜔𝑛𝑇𝑆 𝑧+1 𝜔𝑛
(9)
With 𝑇𝑆 is the system sampling period.
Introduction GPU model
Resonant
controller
A case study Conclusion
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Introduction GPU model
Control System
Design
A case study Conclusion
SYSTEM PARAMETERS
The system parameters are listed in the Table 1.
PARAMETERS VALUE
Induction L = 200 µH
Capacitance C = 25 µF
Inductor resistance 0.02
Switching frequency fc = 18 kHz
Output voltage 115V, 400 Hz
Transformer ration 5/3
Table 1: System parameters
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Introduction Inverter topology
Control system
design
A case study Conclusion
MATLAB SIMULATION
THD = 0.97%
Figure 5: Resistive load R = 1.09 with fundamental controller only
The case of linear load R = 1.09,
only fundamental controller is
required.
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Introduction Inverter topology
Control system
design
A case study Conclusion
MATLAB SIMULATION
Figure 6: Output voltage with a) only fundamental controller b) with 3rd controller is added
THD = 2.26%
THD = 1.9%
The case of nonlinear load, included a diode rectifier, a capacitor of 50µF and a load 1.09 Ω
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Introduction Inverter topology
Control system
design
A case study Conclusion
MATLAB SIMULATION
Figure 7: In the case of a sudden load change a) With DB settling time is 0.035s b) Without DB is 0.08s
Figure 5: Output voltage without DB current controller
THD = 2.39%
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Introduction Inverter topology
Control system
design
A case study Conclusion
EXPERIMENT SYSTEM DESIGN
Figure 8: Experiment system
A 90 kVA GPU prototype based on Texas Instrument TMS320F28379D
microcontroller was built verify the proposed design method
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Introduction Inverter topology
Control system
design
A case study Conclusion
EXPERIMENT RESULTS
Figure 9: Nonlinear load condition with fundamental controller only
The case of nonlinear load, only fundamental controller is implemented:
THD = 3.29%
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Introduction Inverter topology
Control system
design
A case study Conclusion
EXPERIMENT RESULTS
Figure 10: Output voltage under nonlinear load condition with 3rd compensator is added
With 3rd compensator is added
THD = 2.93%
3rd harmonic = 1.9%
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A improvement for GPU configuration is proposed enhance the system
reliability under unbalanced load conditions, also reduce the volume, size and
production cost.
Parallel resonant controller is applied in voltage control loop to control the
fundamental voltage also compensate the harmonics.
Deadbeat control algorithm is implemented for inner current loop to remain
inductor current stable, contributing to the harmonic distortion compensation
at the output voltage
Simulation and experiment results indicate that proposed system can produce a
good quality voltage even under the nonlinear load conditions.
Higher order harmonic compensators (5th, 7th) will be next applied to control
system to improve the system performance.
Introduction Inverter topology
Control system
design
A case study Conclusion
CONCLUSION
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Thank you for attending!
Presenter: Tran Que Son
Email: tranqueson.ktdt@tnut.edu.vn
