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IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 35, NO. 4, JULY/AUGUST 1999
Assessment of Ride-Through Alternatives
for Adjustable-Speed Drives
Annette von Jouanne, Member, IEEE, Prasad N. Enjeti, Senior Member, IEEE, and Basudeb Banerjee, Member, IEEE
Abstract— Adjustable-speed drive (ASD) ride-through issues
have caused increased concerns due to the susceptibility of ASD’s
to power disturbances, and the costly results of process disruptions. These losses can be avoided for critical production
processes by using ASD’s with ride-through capabilities. This paper assesses industrial ride-through requirements through power
quality surveys and the results of an ASD ride-through questionnaire conducted by the authors. ASD ride-through alternatives
are evaluated based on design, implementation, and cost considerations, in order to determine the most suitable solutions for
various kilovoltampere ratings and time duration requirements.
Index Terms— Adjustable-speed drive, drives, energy storage,
process disruptions, ride-through, tripping.
I. INTRODUCTION
T
HE application of adjustable-speed drives (ASD’s) in
commercial and industrial facilities is increasing due
to improved efficiency, energy savings, and process control.
However, ASD’s are often susceptible to voltage disturbances,
such as sags, swells, transients (e.g., due to capacitor switching), and momentary interruptions (outages). According to
survey reports, voltage sags of 10%–30% below nominal for
3–30-cycle durations account for the majority of power system
disturbances, and are the major cause of industry process
disruptions [1].
Depending on the application, and the characteristics of the
disturbance, the ASD-controlled process may be momentarily
interrupted or permanently tripped out. This can result in a
significant loss in revenue and costly downtime. For example, in continuous process systems, such as metal casters,
paper machines, winders, extruders, etc., any interruptions
to that process can halt the entire manufacturing flow, with
extremely costly implications. The cumulative cost estimates
of power disturbances in the U.S. range from $20 000 000 000
Paper IPCSD 99–01, presented at the 1998 Industry Applications Society
Annual Meeting, St. Louis, MO, October 12–16, and approved for publication
in the IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS by the Industrial Power
Converter Committee of the IEEE Industry Applications Society. This work
was supported by the Electric Power Research Institute (EPRI). Portions of
this paper were published in EPRI Final Report TR-109903, December 1997.
Manuscript released for publication January 13, 1999.
A. von Jouanne is with the Power Electronics Laboratory, Department of
Electrical and Computer Engineering, Oregon State University, Corvallis, OR
97331-3211 USA (e-mail: avj@ece.orst.edu).
P. N. Enjeti is with the Power Quality Laboratory, Department of Electrical
Engineering, Texas A&M University, College Station, TX 77843-3128 USA
(e-mail: enjeti@eesun1.tama.edu).
B. Banerjee is with Power Electronics, Energy Delivery, Electric Power
Research Institute, Palo Alto, CA 94304 USA (e-mail: bbanerje@epri.com).
Publisher Item Identifier S 0093-9994(99)04391-1.
to $100 000 000 000 per year, where industries have reported
losses ranging from $10 000 to $1 000 000 per disrupting event
[1]. These losses can be significantly reduced for critical
production processes by using ASD’s with ride-through capabilities, such as the one shown in Fig. 1.
II. INDUSTRIAL POWER ENVIRONMENT
A piece of critical information necessary to determine the
most cost-effective ride-through solution is the environment
in which the critical ASD-controlled process is expected to
operate. Once this is defined, design objectives and mitigation
devices can be specified. Recent advances in power-line monitoring technologies enable detailed analysis of the electrical
environment. Thus, using statistics of average annual events,
industry customers can predict downtime costs and make
comparisons with the cost of additional ASD ride-through.
A number of power quality surveys aimed at defining
the electrical environment have been conducted in North
America including: Sabin et al. (conducted by EPRI) [2],
Dorr [conducted by the National Power Laboratory (NPL)] [3],
Hughes et al. [conducted by the Canadian Electrical Association (CEA)] [4], Allen and Segal [5], Key [6], and Goldstein
and Speranza [7], in addition to several European surveys [8].
From these power quality surveys and an ASD ride-through
questionnaire conducted by the authors, it was determined that
the most beneficial full-power ride-through duration is 0.5–5 s,
and should withstand a 50% sag. In addition, industrial ASD’s
are primarily process critical, requiring full speed and torque
operation during a disturbance. The majority of the drives
employed by industries and experiencing ASD ride-through
problems are in the fractional to 300-kVA range [1].
III. MODIFICATIONS TO EXISTING ASD TOPOLOGIES
Existing drive topologies can be modified to achieve a
higher level of immunity to line disturbances. These include
adding more capacitors to the dc bus, ride-through using load
inertia, operating ASD’s at reduced speed and/or load, and
using lower voltage motors. An important distinction between
each of the possible ride-through approaches is their ability to
provide full-power (full speed and torque) ride-through, which
is required by many applications.
A. Additional Capacitors
By adding capacitors to the dc bus, additional energy
needed for full-power ride-through during a voltage sag can
0093–9994/99$10.00  1999 IEEE
VON JOUANNE et al.: ASSESSMENT OF RIDE-THROUGH ALTERNATIVES FOR ASD’S
909
Fig. 1. Use of energy storage as an add-on module for ASD ride-through.
be provided to the motor. A typical 460-V 60-Hz 10-hp ac
motor drive can be assumed to have a dc-link capacitance of
F. The dc-link voltage
(assuming continuous
conduction) is given by
V
for
V
(1)
A typical ASD is set to trip if the dc-link voltage drops 0.9
V. Also, the
times the nominal value, which is
for a 10-hp
load is
average dc-link current
A
(2)
Now, under short-term power interruption, the filter capacitors
must provide the power to the ASD motor. The ride-through
can be computed as follows:
duration
ms.
(3)
A of 25.8 ms translates into 1.55 cycles at 60-Hz frequency.
Thus, 5000 F on the dc link can only provide a full-power
ride-through of 10 hp for 1.55 cycles. If the outage were to last
cycles) the capacitance required to
for 0.5 s (i.e.,
provide the ride-through can be calculated as
F
(4)
From (4), it is clear that an additional 20 5000- F capacitors
would have to be added to the dc bus. Therefore, if the user
were to use 2500- F caps rated at 400 V connected in series,
they would then need 160 capacitors, connected in 80 groups.
Assuming the cost of each capacitor to be $40, the total cost
amounts to $6400 for a 10-hp drive. The cost of enclosures,
fuses, a precharge circuit, and bus bars are additional.
Advantages
• It is a simple and rugged approach, which can provide
limited ride-through for minor disturbances.
Disadvantages
• The cost is relatively high.
• It involves a large cabinet space, additional precharge
circuits, and safety considerations.
Approximate Cost: $600/kW, as demonstrated above.
B. Use of Load Inertia
The inverter control software can be modified such that
when a power disturbance causes the dc-bus voltage to fall
below a specified value (i.e., below 560 V, on a 460-V lineto-line (L–L) system supporting a 620-V dc bus) the inverter
will adjust to operate at a frequency slightly below the motor
frequency, causing the motor to act like a generator [9]. The
drive will absorb a small amount of energy from the rotating
load to maintain the dc bus at a specified level (i.e., 560
V). Commercial drives are available on the market with this
feature, and will maintain the specified dc bus for 2 s during
a dip that does not exceed 20%.
Advantages
• No additional hardware is required, only a software
modification in the inverter.
• Commercial drives are available on the market with this
feature with 2 s of ride-through for sags to 80% nominal
voltage.
• Since the drive and motor have been actively transferring
energy during the power disturbance, no loss of phasing
has occurred between the drive and the motor, and the
motor’s magnetic field has not deenergized. Thus, there
are no delays to start accelerating the motor as soon as
the ac power line returns to normal, assuming the load
can handle it [9].
Disadvantages
• The motor speed is reduced and the torque is reversed,
which is acceptable for fan/pump-type loads, but may not
be acceptable for certain load types.
• The sustainable ride-through duration will be dependent
on the load inertia.
Approximate Cost: Negligible, minor software modification [9].
C. Operate ASD’s at Reduced Speed/Load
Since the dc-bus current varies with the frequency of the
drive for variable-torque loads, such as fans and pumps, a
reduction in the motor speed will result in a reduction in the
dc-bus current. Therefore, a fan and pump system running at
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IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 35, NO. 4, JULY/AUGUST 1999
Fig. 2. ASD with boost converter ride-through device as an add-on module.
40 Hz will draw less current than a system running at 60
Hz and will, therefore, be able to operate for a longer period
during a voltage sag situation [9]. The effect would be the
same as increasing the capacitance, or energy stored, on the
dc bus. Similarly, if the motor load were reduced, the dcbus current would be reduced and, thus, a longer ride-through
duration could be achieved.
Advantages
• No additional hardware is required.
• At 50% speed and load, it would provide four times the
ride-through of a normal drive system.
Disadvantages
• Application may not tolerate reduced speed/load operation.
• It is only useful for variable-torque (fans and pumps)
loads.
Approximate Cost: None [9].
D. Use of Lower Voltage Motors
If a 230-V ac motor were used with a 460-V ac drive, the
dc-bus voltage (nominally 620 V) could drop to as low as
45% (to 280 V) and still provide 230-V ac to the motor. Note
output to the motor
[9].
that the maximum
Then, as the voltage drops, the inverter changes its duty cycle
to maintain a constant 230-V ac to the motor.
Advantages
• No additional hardware is required.
• An increase of approximately 2.8 times the ride-through
time of a normal drive system is realized [9].
Disadvantages
• The ASD rating is twice the horsepower rating of the
230-V motor.
• A 230-V motor with the same horsepower rating as a
460-V motor will require twice the current at full load
and, thus, will have to be larger.
• The motor insulation must be capable of handling the
higher voltages provided by a 460-V ASD.
Approximate Cost: Cost of drive in dollars per kilowatt for
derating.
IV. MORE ADVANCED HARDWARE MODIFICATIONS
A. Boost Converter Ride-Through
A boost converter can be used to maintain the dc-bus
voltage during a voltage sag, and can either be integrated into
new drives between the rectifier and the dc-link capacitors or
retrofitted as an add-on module, as in Fig. 2 [10]. The addon module is used to retrofit existing drives with ride-through
capabilities, or for multiple drives with a common dc bus,
such as synthetic fiber drives. During a voltage sag, the boost
converter will sense a drop in the dc-bus voltage and begin to
regulate the dc bus to the minimum voltage required by the
inverter (i.e., 585 V, which is user adjustable). In the case of
a retrofit where a boost module is added to an existing ASD,
proper coordination of fault protection logic is necessary.
Advantages
• It can provide ride-through for sags up to 50%.
• The dc-bus voltage can be regulated as required by the
inverter, and is user adjustable.
Disadvantages
• Additional hardware is required, which will have to be
suitably rated due to the additional current drawn during
a voltage sag.
• In the case of an outage, the boost converter will not be
able to provide ride-through, and the drive will trip.
Approximate Cost: $100–$200/kW [10].
B. Active Rectifier ASD Front End
Fig. 3 shows an ASD with an active pulsewidth modulation
(PWM) rectifier. Such a system is available from many ASD
manufacturers up to 500 kW. Replacing the diode rectifier
with an active PWM rectifier has the following advantages:
1) regulated dc bus which offers immunity to voltage sags
and transients; 2) low input current harmonics and compliance
to IEEE 519 harmonic limits; and 3) power flow in both
directions, enabling regenerative braking. The range of ridethrough that this approach can provide is limited only by the
current rating of the rectifier. By this method, ride-through for
sags of up to 10% can be provided at full load. By derating
the rectifier by a factor of 1.5, the ride-through capability can
be extended to sags of up to 40% at full load [11].
VON JOUANNE et al.: ASSESSMENT OF RIDE-THROUGH ALTERNATIVES FOR ASD’S
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Fig. 3. ASD with PWM rectifier.
COMPARISON
OF
TABLE I
ENERGY STORAGE CHARACTERISTICS
Advantages
• Clean input power in steady state, unity power factor, and
compliance to IEEE 519 distortion limits are provided.
• The active rectifier provides a regulated dc-bus voltage,
hence, it is self correcting under voltage sags. A suitable
rectifier derating is necessary to provide full-power ridethrough under a sag.
• Power flow in both directions enables regenerative braking. This feature could add to improved efficiency in some
applications.
Disadvantages
• An ASD with an active PWM rectifier is nearly equivalent
to two diode rectifier ASD’s in cost.
• The ASD package is larger in size, since, in addition to
the active rectifier hardware, three input filter inductors
become necessary.
• The active rectifier operates the ASD with higher dc-link
at
voltage; this results in higher differential mode
the motor terminals. Also, due to two PWM insulated gate
bipolar transistor (IGBT) inverter stages, the commonand EMI are higher.
mode
Approximate Cost: Twice the cost of a regular ASD.1
V. ASD RIDE-THROUGH USING ENERGY
STORAGE TECHNOLOGIES
A variety of energy storage technologies are candidates for
providing the needed full-power ASD ride-through, including
1 Available
HTTP: http://www.baldor.com
Fig. 4. Energy storage system as a standby system for ac line power.
battery backup systems, super capacitors, motor–generator
(M-G) sets, flywheel energy storage systems, superconducting
magnetic energy storage (SMES), and fuel cells. Table I
gives a comparison of the energy storage characteristics
[12]–[14].2, 3 Energy storage can be used as a standby system
for the ac line power to supply a number of ASD’s along with
other loads, as shown in Fig. 4. A voltage sag mitigation approach termed as dynamic voltage restoration (DVR) has been
developed by Westinghouse as part of EPRI’s custom power
program for advanced distribution [15]. The DVR (Fig. 4)
is a solid-state dc-to-ac switching converter that injects three
single-phase ac output voltages in series with the distribution
2 Available
3 Available
HTTP:http://www.piller.com
HTTP:http://www.amsuper.com
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IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 35, NO. 4, JULY/AUGUST 1999
feeder and in synchronism with the voltages of the distribution
system. The DVR is, therefore, capable of injecting missing
voltage during a sag and can provide ride-through to sensitive
loads and ASD’s. A portable 2-MVA DVR with 1-MJ storage
has been demonstrated by Westinghouse [16].
In addition, independent modules can be used to maintain
the dc bus of a single ASD (Fig. 1), or for multiple drives
connected to a common dc bus. The charging devices in
Figs. 1 and 4 are needed to power the energy storage system
to normal levels during startup and after discharges. In Fig. 1,
a boost converter is used as an interface with the dc bus for
when a modest step-up is required. For ASD ride-through,
power density, energy density, and efficiency characteristics
are critical.
to the choice and preparation of the electrode materials and
increases in the effective capacitive plate surface area [1]. An
ASD can be designed with integrated supercapacitors, or an
add-on module, as shown in Fig. 1.
A 100-kW commercially available configuration [13] uses
8 56-V modules in series, resulting in 448 V, which is then
boosted to the necessary voltage using a boost converter. Each
module has a combined capacitance of 96.4 F and, thus, has
capability of
an energy storage
kJ
for a 100-kW ride-through
The total energy storage
system is then
kJ
A. Battery Backup Systems
Battery backup systems operate similarly to adding capacitive energy storage, with the advantage that their energy per
volume ratio is much higher than standard capacitors [12].
An ASD can be retrofitted with battery backup as an addon module on the dc bus, as shown in Fig. 1. In order to
12-V
maintain a dc bus of 575 V during an outage, 48
series-connected batteries can be used. The required battery
current will be dependent on the load. For example, for a 10-hp
motor, batteries capable of handling 15 A would be sufficient.
Because batteries store energy in electrochemical form in
“cells,” their operation is subject to several limits. One such
limit is the cycle life, which is the number of charge/discharge
cycles possible for a given cell (see Table I). Another limit is
the depth of discharge, which is the fraction of stored energy
that can be withdrawn. This will be dependent on the rate
of discharge, and will affect the cycle life. In addition, the
ambient temperature and the proper charging current must be
monitored and kept within limits. The average footprint will be
large (the floor area covered by the device) and, since some
depleted materials are considered hazardous waste, disposal
costs can be high. Batteries are suitable for 5 kW–10 MW
loads and can provide full-power ride-through for up to 1 h.
Advantages
• They can provide ride-through for deep sags and full
outages.
• Batteries are easily obtained.
• Transfer time is almost instantaneous.
Disadvantages
• Additional hardware and space are required, although not
as much as with standard capacitors.
• There is a relatively low cycle life.
• More maintenance is required to ensure peak performance.
• The electrolyte is corrosive and may be hazardous to the
application, and will need to be properly disposed of when
depleted.
Approximate Cost: $100–$200/kW [12].
B. Supercapacitors
Supercapacitors (or ultracapacitors) offer substantial increases in energy density over conventional capacitors due
(5)
MJ
(6)
Equation (6) shows the total energy stored in the supercapacitors. Further, the stored energy is a direct function of the
capacitor voltage. Therefore, a drop in 30% of the capacitor
voltage from to 0.7 V amounts to the release of 50% of its
stored energy. Using this as a design criteria, the ride-through
for a 100-kW ASD load (under short-term power
duration
interruption) can be computed as follows:
V
For
and
(7)
V,
s
(8)
Thus, a maximum of 6 s ride-through can be obtained with
this approach.
Advantages
• They can provide ride-through for deep sags and full
outages.
• They offer long cycle life and fast recharge rates.
• There is an easily monitored state of charge.
• There are minimal maintenance needs.
Disadvantages
• Additional hardware and space are required, although not
as much as with standard capacitors.
• It is an emerging technology.
Approximate Cost: $300–$400/kW [12], [13].
C. M-G Sets Using Written-Pole Technology
M-G sets use their rotating mass to supply energy during
a voltage sag or outage. Written-pole technology is able to
provide 15 s of ride-through for complete interruptions at full
load [17]. This M-G set uses an electric-motor-driven synchronous generator that can output a constant 60-Hz frequency,
regardless of the speed of the machine, and, thus, could be
used in the configuration shown in Fig. 4. Typical units are
available in 15 and 35 kVA ratings. The generator can supply
a constant output by continuously changing the polarity of the
rotor’s field poles. During a sag or outage, the generator rotor
can continue to output 60 Hz for 15 s under full load due to
the mass and inertia of the rotor. For longer time periods, a
diesel engine can be used to supply energy to the generator.
VON JOUANNE et al.: ASSESSMENT OF RIDE-THROUGH ALTERNATIVES FOR ASD’S
913
Fig. 5. M-G set with a flywheel, providing power directly to the ASD dc bus.
An M-G set can also supply power directly to the dc bus of
the ASD through an ac-motor-driven dc generator. In order to
reduce the necessary size of the M-G set and the rotor mass,
a flywheel can be used for the storage of kinetic energy, as
shown in Fig. 5, which will be discussed in the next section
[9].
Advantages
• They can provide ride-through for deep sags and full
outages.
• They are very reliable and can provide 15 s of ridethrough.
Disadvantages
• Additional hardware and space are required.
• Maintenance is required for the rotating components.
Approximate Cost: $200–$300/kW [9], [14].
D. Flywheels
Flywheels, which store kinetic energy in a rotating mass, are
also showing promise for ASD ride-through. A modification
to the typical M-G set described in the previous section is
shown in Fig. 5, where an ac motor drives a dc generator,
with a flywheel, providing power directly to the dc bus of
the ac drive [9]. Advancements in high-strength composite
materials have been important in the development of flywheels.
In addition, high-temperature superconducting (HTS) bearings
that are magnetically levitated to reduce bearing friction and
drag losses have recently become available [18]. Flywheels
are suitable for 1 kW–10 MW applications, and can provide
full-power ride-through for up to 1 h.
Advantages
• They can provide ride-through for deep sags and full
outages.
• They significantly reduce the size and necessary mass of
M-G sets.
Disadvantages
• Additional hardware and space are required.
• Maintenance is required for the rotating components.
Approximate Cost: $200–$300/kW [12].
E. SMES
In a SMES system, a large amount of current is kept
circulating in a superconducting coil or magnet, to be supplied
to the system when needed. Since there are only negligible
losses in the superconducting coil, the transfer of energy in
and out of storage is highly efficient and rapid. However, to
remain superconducting, the coil must be cooled to cryogenic
temperatures, which requires a fairly sophisticated refrigeration subsystem [12]. A SMES system can be interfaced with
a power distribution system, as shown in Fig. 4, now taking
into account that the SMES is a dc current source rather than
a voltage source. A SMES unit can also be applied as shown
in Fig. 6, and directly connected to the dc bus of an ASD or
to a number of ASD’s which share a common dc bus. The
auxiliary power supply shown in Fig. 6 is needed to supply
power to the part of the circuit that is outside the liquid helium
chamber. When there is a sag or an outage, the switch in
the outer circuit will open, forcing the circulating current into
the filter capacitors of the drive to maintain the dc bus [9].
Safety concerns have been addressed through the design of
protection systems that dissipate the stored energy resistively,
either internally or externally [12].
Advantages
• It is reliable, with little maintenance.
• A SMES can handle rapid repeated discharging and
charging without affecting its performance or life.
Disadvantages
• Additional hardware and space are required.
• A sophisticated cooling system is required to maintain
cryogenic temperatures and the associated power loss.
• There are high cost and safety concerns.
Approximate Cost: $600–$800/kW [14].
F. Fuel Cells
Fuel cells provide continuous power through the consumption of hydrocarbon fuel, typically, natural gas. Thus, the
operation is more similar to a battery, in that electrochemical
rather than electromechanical conversion occurs. A fuel cell
could be interfaced with the ac line of a power distribution
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Fig. 6. SMES unit providing ride-through power directly to the dc bus of the ASD.
system, as shown in Fig. 4, similar to applying an M-G set.
However, it would be more appropriate to operate the fuel cell
at all times, because the expense is much greater than an MG set and it cannot be quick started from cold standby [12].
Thus, they would not be as appropriate for backup power for
an individual ASD dc bus.
Advantages
• They are reliable and efficient, with little maintenance and
few mechanically moving parts.
Disadvantages
• They cannot respond rapidly to load changes.
• Additional hardware and high cost are involved.
Approximate Cost: $1500/kW [14].
VI. TECHNIQUES FOR MEDIUM-VOLTAGE RIDE-THROUGH
A majority of ASD’s for medium-voltage (2300/4160 V)
drives address fan/pump-type loads for energy savings and
fall into two categories, current-source inverters (CSI’s) and
voltage-source inverters (VSI’s). The CSI approach employs
SCR/gate-turn-off thyristor (GTO) devices and ride-through
options can be implemented by employing flywheels and
SMES systems, as discussed in Sections V-D and V-E.
The VSI’s for medium-voltage motor drives are based on
multilevel inverter technology. These can be further classified
into two types [1], cascaded inverter-type multilevel VSI’s (CIML-VSI’s), as shown in Fig. 7 [19],4, 5 and three-level neutralpoint-clamped (NPC) inverters. The CI-ML-VSI consists of
several power cells connected in series (Fig. 7). Each power
cell is a single-phase IGBT-based VSI. A complicated input
transformer becomes necessary to supply dc power to each
power cell. The NPC inverter, on the other hand, is constructed
with integrated gate commutated thyristor (IGCT) devices.6, 7
In CI-ML-VSI’s (Fig. 7),
power cells are often used
for redundancy and to enhance fault-tolerant capability. The
power cells also enhances the ride-through
use of
capability for this inverter during a voltage sag disturbance.
4 Available
HTTP:http://www.robicon.com
HTTP:http://www.ticind.com
6 Available HTTP:http://www.ge.com/gemis/ds0.html
7 Available HTTP:http://www.abb.fi/vsd/mediumac. html
5 Available
Fig. 7. CI-ML-VSI for medium-voltage ASD’s.
Due to the presence of many series-connected power cells,
ride-through via load inertia is complicated to implement. To
achieve ride-through during a power interruption (for example,
5 s), the DVR approach discussed in Section V seems to be
appropriate.
In NPC-type medium-voltage inverters, a single dc-link
voltage powers the inverter. Therefore, all of the techniques
discussed earlier to provide ride-through apply to this inverter
as well. The best-suited options would be load inertia ridethrough, the boost converter approach, and energy storage
options, such as flywheels and SMES, with costs as given
in Table II.
Advantages
• Redundancy for ride-through is easy to implement.
VON JOUANNE et al.: ASSESSMENT OF RIDE-THROUGH ALTERNATIVES FOR ASD’S
SUMMARY
OF
915
TABLE II
ASD RIDE-THROUGH ALTERNATIVES
* provides full-power ride-through
** can provide full-power ride-through for single-phase sags
<50%
Fig. 8. Summary of ride-through time versus relative cost.
Fig. 10. For critical loads not requiring full power ride-through.
Disadvantages
• Ride-through for CSI-type systems is expensive to implement.
Approximate Cost: $300–$600/kW for CSI [12], [14].
VII. JUSTIFYING ASD RIDE-THROUGH COSTS
Fig. 9. For critical loads requiring full-power ride-through.
In order to determine whether or not applying ASD ridethrough technologies will be cost effective, interruption costs
can be estimated. With recent advances in power-line monitoring technologies, detailed analyses of the electrical environment have been conducted and can be obtained by
industrial customers. Thus, using statistics of average annual
events, industry customers can predict downtime costs and
make comparisons with the cost of additional ASD ridethrough. Table II and Fig. 8 summarize ASD ride-through
characteristics and costs. Interruption costs can be estimated
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IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL. 35, NO. 4, JULY/AUGUST 1999
through the following general formula [20]:
interruption cost
value of lost production
outage-related costs
outage-related savings.
VIII. CONCLUSIONS AND RECOMMENDATIONS
FOR ASD RIDE-THROUGH
The purpose of this paper is to address ASD ride-through
requirements of industrial customers and match those ridethrough needs with appropriate solutions. After analysis of
the implementation and cost studies, the most cost-effective
and practical ASD ride-through solutions were matched with
the most appropriate ASD ratings and ride-through durations
and summarized for low-voltage applications in Figs. 9 and
10. Fig. 9 suggests the most appropriate ASD ride-through
techniques for critical loads requiring full-power (full speed
and torque) ride-through. Therefore, only the approaches indicated with an asterisk in Table II were possibilities. Fig. 10
suggests the most appropriate ASD ride-through solutions for
loads that do not require full-power ride-through. Note that the
boost converter and active rectifier techniques are included in
Fig. 10, since they can only provide full-power ride-through
for single-phase sags 50%, as indicated in Table II.
REFERENCES
[1] A. von Jouanne and P. Enjeti, “ASD ride-through technology alternatives and development,” Electric Power Research Institute, Palo Alto,
CA, EPRI Final Rep. TR-109903, Dec. 1997.
[2] D. D. Sabin, “An assessment of distribution system power quality,”
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Annette von Jouanne (S’94–M’95) received the
B.S. and M.S. degrees in electrical engineering
with an emphasis in power systems from Southern
Illinois University, Carbondale, in 1990 and 1992,
respectively, and the Ph.D. in electrical engineering/power electronics from Texas A&M University,
College Station, in 1995.
While working towards the Ph.D. degree, she also
worked with the Toshiba International Industrial
Division on joint university/industry research. In
1995, she joined the Department of Electrical and
Computer Engineering, Oregon State University, Corvallis, where she is in
the Energy Systems Group, working primarily on power electronic converters,
power quality, adjustable-speed drive (ASD) ride-through, and investigating
and mitigating the adverse effects of applying ASD’s to ac motors. She is also
the Associate to the Motor Systems Resource Facility (MSRF), an EPRI/BPA
Center at Oregon State University for motors and drives research and testing.
Dr. von Jouanne was the recipient of the IEEE Industry Applications
Magazine Prize Paper Award for 1996. She has also served as an Associate
Editor for the IEEE TRANSACTIONS ON INDUSTRIAL ELECTRONICS since 1997
and is a Registered Professional Engineer in the State of Washington.
Prasad N. Enjeti (S’86–M’88–SM’95), for a photograph and biography, see
p. 637 of the May/June 1999 issue of this TRANSACTIONS.
Basudeb (Ben) Banerjee (M’72) was born in Calcutta, India. He received the B.S.E.E. degree from
the University of Calcutta, Calcutta, India, in 1966
and the M.S.E.E. degree from the University of
South Carolina, Columbia, in 1975.
He is the Power Conditioning and Advanced
Motor-Drive Manager of the Energy Delivery and
Utilization Division, Electric Power Research Institute (EPRI), Palo Alto, CA. He joined EPRI in 1985
as Senior Project Manager in the Industrial Program.
In 1989, he was transferred to the Power Electronics
and Controls Program and is currently responsible for the development of
power electronics technology and advanced motor and drive systems for enduse sectors, power quality mitigation hardware, advanced components and
systems for electric vehicles, and advanced energy storage technology for
power quality solutions. Prior to joining EPRI, he was Engineering Manager
for Square D Company, Columbia, SC. In this position, he was responsible
for design and application of products such as adjustable-speed drives,
medium-voltage motor controllers, motor controllers for material handling,
and submersible pump applications. His research interests include the design,
development, and application of power electronics and controls systems,
power quality, power system engineering, power conditioning systems, and
electric vehicle technology. He has worked in all aspects of manufacturing
power electrical and electronics equipment from research and development
to product management, liabilities, applications, standardization/costing, and
safety. He has participated in NEMA standards subcommittees and has organized the EPRI-sponsored National Motors and Drives Steering Committee.
Mr. Banerjee has been a member of IEEE standards subcommittees.