A single loop repetitive voltage controller for a four

1. Abstract
o Repetitive control approach is proposed to regulate the output voltage of a four-leg Matrix Converter (MC) for an
Aircraft Ground Power Supply (GPU) application.
o The proposed controller reduces the tracking error and increases the stability of the converter.
o Simulations and experimental results from a 7.5KW converter prototype are presented.
Ground power unit based matrix converter:
Ground power units (GPU) are designed to provide a quality three-phase supply, 400Hz to the aircraft.
MC is a direct power converter that can be used to convert AC supply voltages into variable magnitude and frequency output
voltages.
Matrix converters has many advantages over rectifier/inverter systems such as:
 There is no DC link capacitors and this will reduce the weight and the volume.
 A sinusoidal input and output waveforms.
 Controllable power factor.
 Cyclic Venturini modulation technique is used.
A Repetitive controller (RC) based on the Internal Model Principle
is proposed to minimize or eliminate these periodic waveform errors.
Repetitive controller:
The proposed controller consists of second order controller and repetitive controller.
The second order controller is used to achieve the required transient performance and
designed using the Root Locus method with the objective of cancelling the LC filter dominant poles.
The RC is added to the system to improve the steady state system performance.
RC generates a high gain at signal fundamental frequency and its integer multiples.
 The proposed controller is used in the ABC reference frame, where each phase has its own controller.
Q(z) is selected as a low pass filter with Q(z) =0.25Z+0.5+0.25Z-1.
Wesam M. Rohouma1, Liliana de Lillo1, Saúl López2, Pericle Zanchetta1, Patrick W Wheeler1
1 School of Electrical and Electronic Engineering, University of Nottingham, U.K.
2 School of Mechanical and Electrical Engineering, National Polytechnic Institute of Mexico, Mexico.
University of Nottingham, NG7 2RD,Nottingham, UK.
E-mail: eexwr1@nottingham.ac.uk

2. Response to voltage step change
Results and discussion:
A 7.5KVA experimental prototype was successfully built to validate the effectiveness of
the proposed controller.
Conclusions
Steady state operation:
0.02 0.025 0.03 0.035 0.04
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Time
Voltage
0 0.01 0.02 0.03 0.04 0.05 0.06
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2
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6
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Time
Current(Amp)
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0
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Frequency (Hz)
THD= 1.18%
Mag(%ofFundamental)
Unbalanced load test: Output voltage and currents during ±30% load unbalance
0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04
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Time
Votage
0 1000 2000 3000 4000 5000 6000
0
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Frequency (Hz)
THD= 3.14%
Mag(%ofFundamental)
0 0.01 0.02 0.03 0.04 0.05 0.06
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Time
Current(Amp)
Load disconnection and connection:
Wesam M. Rohouma1, Liliana de Lillo1, Saúl López2, Pericle Zanchetta1, Patrick W Wheeler1
1 School of Electrical and Electronic Engineering, University of Nottingham, U.K.
2 School of Mechanical and Electrical Engineering, National Polytechnic Institute of Mexico, Mexico.
University of Nottingham, NG7 2RD,Nottingham, UK.
E-mail: eexwr1@nottingham.ac.uk
 Four-Leg Matrix Converter was presented as GPU for aircraft servicing application.
 A controller consists of plug-in Repetitive controller and second order controller is proposed.
 Single voltage control loop implemented in ABC reference frame.
 Extensive experimental tests showed that the controller was able to offer high tracking accuracy, fast transient response.
 The proposed controller was able to regulate the output voltage during different loading with minimum distortion.
0.04 0.042 0.044 0.046 0.048 0.05 0.052 0.054
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Time
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VRef-A VFB-A
Ia
Ib
Ic
In
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
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Time
Voltage
VRef Vom