ABSTRACT:
In
this paper, analysis and design of a three phase isolated Cuk based power
factor correction (PFC) converter has been proposed. The proposed converter is
operated in discontinuous output inductor current mode (DOICM) to achieve PFC
at ac input. This avoids the inner current control loop which further
eliminates the sensing of current. This makes the system more reliable and
robust. The converter requires only one simple voltage control loop for output
voltage regulation and all the power switches are driven by the same gate
signal which simplifies the gate driver circuit. The detailed operation of the
converter and design calculations are presented. And also a small signal model
of the converter by using CIECE approach is presented to aid the controller
design. The experimental results from a 2-kW laboratory prototype with 208-V
line-to-line input voltage, 400-V output voltage are presented to confirm the
operation of the proposed converter. An input power factor of 0.999, an input
current total harmonic distortion of as low as 4.06% and a high conversion
efficiency of 95.1% are achieved from laboratory prototype.
KEYWORDS:
1. Three phase power factor correction (PFC)
2. Isolation
3. Cuk converter
4. Discontinuous conduction mode (DCM)
5. AC-DC converters
SOFTWARE:
MATLAB/SIMULINK
CIRCUIT DIAGRAM:
Fig.
1. (a) Single phase isolated Cuk PFC converter; (b) Proposed structure of the three
phase isolated Cuk converter.
EXPERIMENTAL RESULTS:
Fig.
2. Experimental waveforms at 1kW output power: (a) input voltages of each phase
(50V/div); (b) input currents of each phase and output voltage (2.0A/div,
200V/div); (c) input voltage (50V/div) and input current (2.0A/div) of each
phase; (d) input current harmonic spectrum.
Fig.3.
Experimental waveforms at 1kW output power: (a) input voltage and voltage
across capacitor 𝑐1𝑎 (100V/div); (b)
output voltage and voltage across capacitor 𝑐2𝑎 (100V/div); (c) one phase transformer primary and
secondary currents (5.0A/div each); (d) output currents of each module
(5.0A/div); (e) transformer primary voltages of each phase (200V/div); (f)
voltage across each switch (200V/div).
Fig.
4. (a) The experimental output voltage (200V/div), output current (2.0A/div)
and input current (5.0A/div) for load power disturbance from 0.8 kW to 1.0 kW;
(b) The experimental output voltage (100V/div), input voltage (100V/div) and
input current (5.0A/div) for phase input voltage disturbance from 100 V to 115
V.
CONCLUSION:
In this paper, a
three phase isolated Cuk converter based power factor correction rectifier
operating in discontinuous output inductor current mode (DOICM) is presented.
Due to the large size input inductor filter, the proposed converter does not
require an additional input filter. The steady state operation of the converter
and each component design have been given in detail. It is shown that by
operating the converter in DOICM, the input currents are sinusoidal and in
phase with input voltages. Subsequently, it does not require inner current
control loop and eliminates the current sensors which reduces the system cost and
increase the reliability. Another advantage is that the converter works with
zero current turn off in the output diode which eliminates the reverse recovery
losses of diodes. To aid the controller design, detailed small signal model of
the converter by using CIECE approach is presented. A simple voltage control
loop with only one output voltage sensor is used to regulate the output
voltage.
An
experimental laboratory prototype of 2 kW is designed and built to confirm the
operation of the proposed converter. The experimental results confirms the
analysis and operation of the converter. A high efficiency of 95.1% and an
input current THD as low as 4.06% are achieved with the developed laboratory
prototype.
REFERENCES:
[1] Limits for Harmonic Current Emissions (Equipment Input Current <16A
Per Phase), IEC/EN61000-3-2, 1995.
[2] IEEE Recommended Practices and Requirements for Harmonics Control
in Electric Power Systems, IEEE Std. 519, 1992.
[3] D. Gauger, T. Froeschle, L. Illingworth and E. Rhyne, "A Three-Phase
Off-Line Switching Power Supply with Unity Power Factor and Low TIF," Telecommunications
Energy Conference, 1986. INTELEC '86. International, Toronto, Canada, 1986,
pp. 115-121.
[4] BREWSTER, R.F., and BARRET, A.H., “Three-phase AC to DC voltage
converter with power line harmonic current reduction,” US Patent 4143414, 6th
March, 1979.
[5] D. Chapman, D.
James and C. J. Tuck, "A high density 48 V 200 A rectifier with power
factor correction-an engineering overview," Proceedings of Intelec 93:
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1, pp. 118-125.
