ABSTRACT:
The diode-front-end (DFE) CHB inverters have
prevailed in the non-regenerative industry drive domain for high-power
medium-voltage applications. The regenerative version of the CHB drives is made
possible by adding the extra active-front-end (AFE) rectifier in each power
cell, such as a three-phase PWM rectifier. However, due to the instantaneous power
unbalance, the dc-link capacitors of the regenerative power cell need to be
overdesigned to maintain a stable low ripple dc-link voltage. To reduce the
dc-link capacitance, this paper proposes a novel closed-loop voltage ripple
controller for the regenerative CHB drive without adding extra sensors. In the
proposed method, dc-link voltage ripple amplitude and phase angle are
accurately detected with a high-performance adaptive filter. Moreover, a latent
instability issue is discussed and is avoided in the proposed controller. The
performance of the proposed control strategy is validated experimentally on a
seven-level regenerative CHB drive.
KEYWORDS:
1. Multilevel Drives
2. DC-Link Capacitor Reduction
3. Regenerative
4. Adaptive filtering
5. Stability
SOFTWARE: MATLAB/SIMULINK
SCHEMATIC DIAGRAM:
Fig. 1 Proposed Capacitor Reduction Control Scheme based on
Adaptive Filter
EXPECTED SIMULATION RESULTS:
Fig.
2 Simulation Result with Frequency Varitaion
CONCLUSION:
Due
to the unbalanced instantaneous power flow, an oversized dc-link capacitor is
required to be designed in each power cell to achieve a low voltage ripple
dc-bus in regenerative CHB drives. To reduce the dc-link capacitance while
maintaining a low dc-link voltage ripple, this paper proposes a novel
closed-loop voltage ripple controller for the regenerative CHB drive without
extra sensors. The dc-link voltage ripple amplitude and phase angle are
accurately detected with a high-performance adaptive filter under the output
frequency variation. Moreover, a latent instability issue is discussed in
detail. This issue is then avoided in the proposed voltage ripple controller by
setting a suboptimal operation point and a mechanism to retract away from the
unstable region. The proposed capacitance reduction strategy is validated on a
seven-level regenerative CHB drive showing good stability and performance. It
was verified that the dc capacitance can be reduced to 25% of its original
design while a 5% dc voltage ripple is allowed. Therefore, the size and cost of
the regenerative CHB system can be greatly reduced, while the lifetime and
reliability of the motor drive are improved.
REFERENCES:
[1] B. Wu and M. Narimani, High-power converters and AC drives. IEEE-Wiley Press, 2017.
[2] J. Rodriguez, P. W. Hammond, J. Pontt, R. Musalem, P. Lezana and M. J. Escobar, "Operation of a medium-voltage drive under faulty conditions," in IEEE Transactions on Industrial Electronics, vol. 52, no. 4, pp. 1080-1085, Aug. 2005.
[3] P. W. Hammond, "A new approach to enhance power quality for medium voltage drives," in IEEE Transaction on Industry Applications, vol. 33, no. 1, pp. 202–208, Feb. 1997.
[4] J. Rodriguez, J. Pontt, N. Becker, and A. Weinstein, “Regenerative drives in the megawatt range for high-performance downhill belt conveyors,” IEEE Transactions on Industry Applications, vol. 38, no. 1, pp. 203–210, 2002.
[5] J. Rodriguez, L. Moran, J. Pontt, J. Espinoza, R. Diaz, and E. Silva, “Operating Experience of Shovel Drives for Mining Applications,” IEEE Transactions on Industry Applications, vol. 40, no. 2, pp. 664–671, 2004.
