ABSTRACT:
The
power electronic transformer (PET) is an emerging technology that is quickly
becoming a key component of the next-to-come power distribution networks
(PDNs), due to its versatility on energy management, as well as, the
improvement on the quality of the energy. PDNs are characterized by their
unbalanced conditions, causing that PETs driven by conventional dq0 controls
introduce current distortions on the primary winding of the transformer. Such
distortion is evidenced in the 2! oscillations of Vd and Vq acting as harmonic
sources. In this sense, this paper proposes a novel control approach for PETs.
The key idea behind of this proposal consists of operating each phase
independently, which is achieved through the enclosed rectification and the
mitigation of the 2! Oscillations in a Dual Active Bridge (DAB) topology. The attained
advantages by this control scheme are: (a) balancing of the primary winding currents;
(b) unitary power factor; (c) negligible harmonic distortion; and (d) 2!
oscillation mitigation on the DC bus.
KEYWORDS:
1. AC-DC-AC
2. Power
conversion
3. Power
electronic transformer
4. Dual
active bridge
5. VSC
6. Unbalanced
control
7. Voltage sags
8. Unbalanced
input voltages.
SOFTWARE: MATLAB/SIMULINK
CIRCUIT DIAGRAM:
Fig. 1. Three-phase VSC rectifier with an unbalanced control
EXPECTED SIMULATION RESULTS:
Fig.
2. Simulation for an unbalanced voltage sag during V a g = 1\0_; V b g = 0:5\ 120_; V c g = 0:5\120__
.
Fig.
3. Simulation for an unbalanced voltage sag during V a g = 1\0_; V b g = 1\ 120_; V c g = 0:1\120__
.
Fig.4.
Simulation for an unbalanced voltage sag during V a g = 0:8\0_; V b
g =
0:6\ 133:9_; V c g =
0:6\133:9__
.
Fig.
5. Simulation for an unbalanced voltage sag with dq0 control during V a g =
1\0_; V b g = 1\ 120_; V c g =
0:1\120__
.
CONCLUSION:
The main contribution of this work consists in a new control structure, which employ a phasorial approach with a single PI control, for PETs working on distribution systems where the operation with unbalanced input voltages is frequently. The capacity of this control of independently generate the modulation variables mabc i with different magnitudes and angles, reach a better performance than other control structures; dq0, for example, to mitigate the problems caused by unbalanced input voltages conditions. Under these input conditions in a PET, the advantages achieve by the proposed control are: (i) balanced AC input currents, (ii) sinusoidal AC input current, and (iii) PF = 1. Furthermore, the control structure is an easy-to-implement and requires no additional components. Finally, in this work, all the advantages mentioned above were validated by using simulation and a lab prototype.
REFERENCES:
[1]
H. Chen and D. Divan, “Soft-switching solid-state transformer (s4t),” IEEE
Trans. Power Electr., vol. 33, no. 4, pp. 2933–2947, 2018.
[2]
H. Chen, A. Prasai, and D. Divan, “Dyna-c: A minimal topology for bidirectional
solid-state transformers,” IEEE Trans. Power Electr., vol. 32, no. 2, pp.
995–1005, 2017.
[3]
G. Brando, A. Dannier, and A. Del Pizzo, “A simple predictive control technique
of power electronic transformers with high dynamic features,” in 5th IET
Intern. Conf. on Power Electr., Mach. and Drives, 2010, pp. 1–6.
[4]
K. K. Mohapatra and N. Mohan, “Matrix converter fed open-ended power electronic
transformer for power system application,” in IEEE PES GM - Conversion and
Delivery of Electrical Energy in the 21st Century, 2008, pp. 1–6.
[5]
D. Wang, C. Mao, J. Lu, S. Fan, and F. Peng, “Theory and application of
distribution electronic power transformer,” Electric Power Syst. Research, vol.
77, no. 3, pp. 219–226, 2007.
