IEEE Transactions on Applied Superconductivity, 2017
ABSTRACT
This paper presents the design and evaluation of a mini-size
GdBCO magnet for hybrid energy storage (HES) application in a kW-class dynamic
voltage restorer (DVR). The HES-based DVR concept integrates with one
fast-response high power superconducting magnetic energy storage (SMES) unit and
one low-cost high-capacity battery energy storage (BES) unit. Structural
design, fabrication process and finite-element modeling (FEM) simulation of a
3.25 mH/240 A SMES magnet wound by state-of-the-art GdBCO tapes in SuNAM are presented.
To avoid the internal soldering junctions and enhance the critical current of
the magnet simultaneously, an improved continuous disk winding (CDW) method is
proposed by introducing different gaps between adjacent single-pancake coil layers
inside the magnet. About 4.41% increment in critical current and about 3.42%
increment in energy storage capacity are demonstrated compared to a
conventional CDW method. By integrating a 40 V/100 Ah valve-regulated lead-acid
(VRLA) battery, the SMES magnet is applied to form a laboratory HES device for
designing the kW-class DVR. For protecting a 380 V/5 kW sensitive load from 50%
voltage sag, the SMES unit in the HES based scheme is demonstrated to avoid an
initial discharge time delay of about 2.5 ms and a rushing discharging current
of about 149.15 A in the sole BES based scheme, and the BES unit is more
economically feasible than the sole SMES based scheme for extending the compensation
time duration.
KEYWORDS:
1. Superconducting
magnetic energy storage (SMES)
2. SMES
magnet design
3. Hybrid
energy storage (HES),
4. Battery
energy storage (BES)
5. Continuous
disk winding (CDW)
6. Dynamic
voltage restorer (DVR)
7. Voltage
sag compensation.
SOFTWARE:
MATLAB/SIMULINK
CIRCUIT
DIAGRAM:
Fig. 1.
Circuit topology of the HES-based DVR.
EXPECTED SIMULATION RESULTS:
Fig 2. Transient voltage curves: (a) Load voltage
before compensation; (b) Compensation voltage from the DVR; (c) Load voltage
after compensation.
Fig.
3. Transient current and power curves: (a)
SMES coil current; (b) Output power from the SMES coil; (c) Output power from
the whole DVR.
Fig.
4. Transient voltage curves: (a) Load voltage
before compensation; (b) Compensation voltage from the DVR; (c) Load voltage
after compensation.
Fig.
5. Transient current and power curves of the
SMES and BES systems: (a) Operating current; (b) Output power.
CONCLUSION
The structural design, fabrication process
and FEM simulation of a 3.25 mH/240 A SMES magnet wound by state-of-the-art
GdBCO tapes have been presented in this paper. The FEM simulation results have
proved the performance enhancements in both the critical current and energy
storage capacity by using the improved CDW scheme. Such a mini-size SMES magnet
having relatively high power and low energy storage capacity is further applied
to combine with a 40 V/100 Ah VRLA battery for developing a laboratory HES
device in a kW-class DVR. In a 5 Kw sensitive load applications case, voltage
sag compensation characteristics of three different DVR schemes by using a sole
SMES system, a sole BES system and a SMES-BES-based HES device have been
discussed and compared. With the fast-response high-power SMES, the maximum
output current from the BES system is reduced from about 149.15 A in the BES-based
DVR to 62.5 A in the HES-based DVR, and the drawback from the initial discharge
time delay caused by the inevitable energy conversion process is offset by
integrating the SMES system. With the low-cost high-capacity BES, practical
compensation time duration is extended from about 32 ms in the SMES-based DVR
to a longer duration determined by the BES capacity. Therefore, the proposed HES
concept integrated with fast-response high-power SMES unit and low-cost
high-capacity BES unit can be well expected to apply in practical large-scale
DVR developments and other similar SMES applications.
REFERENCES
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