Report on Project UDC - Department of Science and Technology

Report on Project UDC
Expert Advisory Committee on Solar Power and Energy Sector
National S&T Entrepreneurship Development Board (NSTEDB)
Department of Science & Technology
March, 2015
Contents
Introduction ............................................................................................................................................ 3
1.
The Technical Review Meeting held on 30th December, 2014 at IIT, Madras.................................... 4
2.
The Cost Review Meeting held on 3rd Feb, 2015 at IIT, Hyderabad ................................................... 7
3.
Conclusion: ...................................................................................................................................... 8
Annexures
Annexure 1: Concept of Brown-out ......................................................................................................... 9
Annexure 2: SLD for UDC ....................................................................................................................... 13
Annexure 3: UDPM Specifications and Functionalities ........................................................................... 14
Annexure 4: Cost Estimation for Substation Implementation ................................................................. 15
Annexure 5: Minutes of First Meeting ................................................................................................... 16
Annexure 6: Minutes of Second Meeting ............................................................................................... 19
Annexure 7: Minutes of Third Meeting .................................................................................................. 22
UDC Report
Introduction
Load shedding is a common phenomenon in India to bridge the gap between power supply and demand.
This results in power-cut (or load-shedding or black-out) in select localities, resulting in the denial of
basic conveniences like lighting, fans and TV during power shortages to a significant portion of our
population. To overcome this, IIT Madras has come up with an innovative technology to provide some
uninterrupted power supply to homes, even when load-shedding is required. The project Uninterrupted
Direct Current (Project UDC) provide homes with uninterrupted, but limited power, sufficient to support
2-3 lights, 1-2 fans or a TV, charge mobile phones/ laptop 24X7, irrespective of power shortages. Instead
of black-outs, this technology offers to perform Brown-outs (BO) by feeding 10% of the normal power to
homes, however in DC forms, which provisions to energize homes even during power shortages. The
details of this technology are given in Annexure 1.
Department of Science and Technology (DST) has set-up an Expert Advisory Committee on “Solar and
Energy Sector,” which was entrusted with the responsibility of evaluating various aspects of the
technology. The committee comprised of Directors of four IITs and eminent area experts from different
IITs. The composition of the committee is as follows:
Prof. Uday B. Desai, Director IIT, Hyderabad - Chairman
Prof. P.P.Chakrabarti, Director IIT Kharagpur - Member
Prof. Bhaskar Ramamurthi, Director IIT Madras -Member
Prof. Timothy Gonsalves, Director, IIT Mandi –Member
Prof. Rajiv Sangal, Director, IIT Varanasi - Member
Prof. Ashok Jhunjhunwala, IIT Madras -Member
Prof. B.G Fernandes, IIT Bombay -Member
Prof. D. Thukaram, Indian Institute of Science, Bangalore-Member
Prof. S.A Kharpade, IIT Bombay -Member
Prof. K. Shanti Swarup, IIT Madras -Member
Prof. G. Bhuvaneswari , BITs , Hyderabad -Member
Prof. Siva Kumar K, IIT Hyderabad -Member
Sh. H.K.Mittal, Sc. G and Head- Innovation and Entrepreneurship(NSTEDB) -Member
Dr. Anita Gupta, Sc. F and Associate Head-Innovation and Entrepreneurship (NSTEDB),
DST -Member Secretary
15. Anand Pandey, Sc. B , DST- Meeting Organizing Committee
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
The terms of reference for the committee included evaluation of UDC / Brown-out technology with
respect to:
Whether the UDC/Brown-out proposal of IIT Madras, involving dropping of voltage at
substation, is technically sound and feasible? What would be the estimated costs per home of
doing it all over the country?
The first advisory committee meeting to evaluate the proposed technology was held on 17th Nov, 2014
at IIT, Delhi (Minutes of meeting are given in Annexure 5). IIT Madras team had presented the concept
of UDC before the committee and shared their experience on the technical and commercial feasibility of
the Brown-Out. The technology and relate requirements were discussed by the committee members.
The committee formed a sub-committee to look into the detailed aspects of the proposal.
The sub-committee for UDC/Brown-Out technology evaluation comprised of the following members:
•
•
•
•
•
•
•
Prof. U B Desai (IIT H)- Convener
Prof K Shanti Swaroop (IITM)
Prof. Ashok Jhunjhunwala (IITM)
Prof. Siva Kumar (IITH)
Prof D. Thukaram, (IISc.)
Venkat Rajaraman –Solarsis (venkat@solarsis.in)
Sridhar Reddy- Esennar Transformers Pvt. Ltd (md@esennar.com)
Two subsequent committee meetings were held, where one of these meetings was focused on analyzing
the technical feasibility of the solution and the other meeting was aimed at evaluating the cost and
production ability of the system. Minutes of these meetings are given in Annexure 6. The technical
review meeting was held on 30th December, 2014 at IIT, Madras. The economic viability aspect of the
UDC was taken up during the third meeting held on 3rd Feb, 2015 at IIT, Hyderabad. The stake holders,
manufacturers and suppliers were invited to present the production and costing of the project. Minutes
of this meeting are given in Annexure 7. The details of the technical and costing aspects discussed during
the meetings are presented in the sections below.
1. The Technical Review Meeting held on 30th December, 2014 at IIT, Madras.
The technical review meeting was held on 30th of Dec 2014 at IIT, Madras. IIT, Madras gave a short
presentation on the proposed solution. The committee members raised and discussed various issues
relating ‘Brown-out’ technology. Selection of proper voltages, changes needed at home and substation
side, load management and costing of the solution were discussed for the implementation of this
solution. Members discussed the rationale behind the brown-out (BO) technology and selection of the
voltages used during brown-out (BO). The details are given below.
Prof. D. Thukaram, Indian Institute of Science, Bangalore and Prof. Shanti Swarup together
shared a presentation raising few clarifications on the implementation feasibility of UDC/BO. They
mentioned that providing 24x7 power supply using UDC was a very good and the idea is worth
investigating as it provides some insights into the realm of DC power distribution along with AC line for
reliable power supply to houses/ rural distribution. In the presentation, Prof Shanti Swarup and Prof.
Thukaram raised concerns on voltage profile, Line losses, voltage drop calculations along the length of
the feeder, reactive power requirements at the substation. A single line diagram (SLD) of the UDC
implementation for better understanding and analysis was asked in his presentation.
The first question was with respect to line-losses, transformer-losses and line-loading and
whether the proposed schemes worsens any of these parameters. Prof Krishna Vasudevan of IIT,
Madras gave a presentation on these issues. The SLD of UDC/Brown-out implementation (given in
Annexure 2) was described. It was explained that UDC/BO is operated at lower voltage levels. As a
result, at lower voltage, flux density levels in the transformer core comes down; this would mean lesser
losses in the core and lesser heating. In the UDC operation, low voltage is accompanied by a lower
power operation as well - this ensures that current in the windings is much lower than rated conditions.
This is quite opposed to normal voltage sag situations where current flowing could be much higher than
normal levels if constant power loads are deployed by the users. On a lower voltage operation, surge
levels will also be correspondingly lower and hence the regular distribution transformer will be stressrelieved to some extent even on surges. It was also discussed among the members that lower voltage
applied to the windings stresses the insulation lesser; this may perhaps have a beneficial impact on life
of insulation, though insulation life depends on a wide variety of factors. Dr. Thukaram, Dr. Shanti
Swarup and the other committee members were satisfied with the answers.
Prof Thukaram IISc, Bangalore, Prof Shanti Swarup, IITM and Dr.Sivakumar, IIT Hyderabad also
raised questions on the Transmission & DC distribution losses during Brown-Out in their presentations.
These queries were discussed in the committee. IITM team, with the help of SLD of UDC
implementation, explained that there is no DC transmission line from the feeder to the homes; instead
the DC distribution is done only inside the homes. To implement Brown-out, no DC feeder is used, the
DC wiring only resides inside the home. The 90 V transmission (10% of the normal power from feeder) in
the line feeds this power to the UDPM, which is capable of receiving AC power either at 230V/90V.
Prof. B. G. Fernandes, IITB, then discussed the loss-reduction in case of brown out condition. In
this case, the supply is at 90 volts, implying a current increase by 2.5 times for the constant power.
However, this is clearly NOT the case, since under brown out the AC supply at each home is cut-off and
at most 10% of the full load is supported on a feeder. For every nine feeders for which power supply was
cut-off during load shedding in the current approach, ten feeders are now affected and goes into brownout situation with a maximum of 10% load. AC supply to each home is cut-off and at only 100 W DC is
allowed to be drawn from the grid, ensuring that the total load on this feeder would be far less than
10% of the normal load. Assuming even 10% of normal power during brown out, the current will go
down by a factor of 4, when voltage goes down by a factor of 2.5. This means loss goes down by 16
times. With power going down to 10% and losses going down by 16 times, even the relative loss (loss
expressed as a fraction of delivered power) goes down by at least 1.6 times. The details are shown in
Appendix 8. The committee members were satisfied that both absolute as well relative losses will go
down during Brown-out.
Some members of the committee then raised a query whether voltage reduction on distribution line
was at all required during Brown-out. Questions were also raised on changes to be carried out at substation. The IITM team discussed the substation changes and the rationale behind voltage-drop
selection:
A reliable and guaranteed instant signaling is, achieved by dropping the voltage level of the 10% power
transmitted during brown-out by say 2.5 times. This is achieved at the sub-station by using a tap on the
33kV/11kV transformer, or adding a 2.5:1 transformer at 11kV output (the block diagram of BO
mechanism is provided in Figure 1 of Annexure 1). This transformer/tap is may also be rated for 10% of
the power that the 11kV line would carry during normal operation. The brown-out operation then
switches the 11kV output to 4.2KV (with 10% power level). This would imply that at homes,
•
•
Switch from 230V AC to 90V AC is used as a signalling method for brown out – no extra
communication systems required. Restoration of 230V AC signals Normal power. The
signalling is used to cut-off / turn-on AC power
Both 230V AC as well 90V AC is converted to 48V DC with maximum power delivered being
limited to 100W.
The committee members discussed use of other communication systems (like GPRS and power-line
communication) to enable signalling. Alternative communication methods had issues like reliability,
delays and jamming. It was concluded that the proposed scheme was the most reliable, instantaneous
and would work in all situations.
The committee then had discussions on the issue of Power stealing with or without UDC. It was noted
that power-stealing could be done during normal load operations also. Even if SMART Meters was to be
used to manage load at homes, keeping the distribution at normal 230V AC, power theft could occur.
The use of UDC makes it more difficult to steal to steal power. As during brown-out, the line voltage is
only 90V, a voltage booster transformer would be required to connect the stolen power to loads.
However, as soon as line changes from Brown-out to NORMAL, the 90V AC would change to 230V AC.
The boost transformer would now increase the load voltage to about 575V, damaging the load. So one
has to have a sophisticated system to steal power as compared to when only 230V is used. Also, even
when appliances are designed to work at lower voltages, the normal range is 130V-240V. 90V would just
cut-off most appliances. The committee concluded that even though UDC scheme was not designed to
stop power-stealing (it is not an anti-theft system), the proposed UDC scheme would help in reducing
power-theft.
The committee members raised clarifications and rationale for use of 48 V DC at the distribution. Prof
B.G. Fernandes made an analysis of distribution losses at homes incurred while using 48 V DC supply, as
compared to using other safe voltages like 24V and 12V DC. The committee concluded that for voltage
lower than 48 V, the wiring losses will be huge. It was noted that safe voltage was below 60 V and
considering the ripple, 48 V will be safe. The use of 48V DC widely used in telecom industry also gives
confidence for its selection as a good candidate. The telecom industry has been using this standard for
over two decades and has come up with sufficiently reliable protection and safety circuits. Also, the
distribution losses at the homes for 48V DC for 100W would be minimal even if existing wiring was used.
The committee concluded that 48V DC is the best choice for in-home low-power distribution.
Having examined all the issues in two meetings, the Committee Conclusion on the TOR on Technical
Feasibility:
Yes, the UDC solution is technologically feasible. Instant signaling is possible with the innovative
signaling solution proposed. Losses are lesser than the normally used 230V AC on the
transmission lines. Protection and required control circuitry are well designed.
The committee concluded that UDC proposal to ensure 24 x 7 power supply at homes was technically a
sound solution.
2.
The Cost Review Meeting held on 3rd Feb, 2015 at IIT, Hyderabad
For discussing the implementation of BO technology and to gain an insight to the market, scale and
production of the technological solutions proposed, the committee invited designers and vendors from
the industry to participate and give recommendations.
The committee discussed on the financial viability of the UDPM module to be installed at home for UDC
implementation. The representatives from companies; Mr. Rathore, Genus, Srinivas Swaminathan from
Power Integrations, Dilip Shetty , consultant appointed by Power Integrations presented the costing of
the module. The costing of these two modules at 100K volume and their sub-parts is as given in Table 1.
The industry representatives mentioned that the pricing was still being worked out. The Current BOM
for 100K volume is close to Rs. 1700, but they were confident that the pricing could be brought down
close to Rs 1500 at 100 K volumes; at 10M volume, and pricing is expected to be Rs 1200.
Some members of the committee examined the sub-modules and Dr. Bhuneswari wondered why the
pricing for the AC-DC convertor was so high. Dileep (consultant to PI) explained that the convertor has a
power-factor correction and is expected to have very low losses all the way from 30W to 125W. The
committee members concluded that the cost target were reasonable and are achievable. In high
volumes (tens of millions) the UDPM installed at home was possible at ₹1200 per home.
The discussions then moved on to the costing of the equipment required at the sub-station. The industry
representatives; A. Sridhar Reddy, MD, ESENNAR Transformers, Mr. Venkat Ramarajan, Solarsis Private
ltd. and Prof. Krishna Vasudevan from IIT, Madras presented the detailed methodology, and costing for
the implementation (given in Appendix 4 ) to be carried out in different kinds (Greenfield and existing)
of sub-station.
Mr. Venkat and Mr. Sridhar Reddy presented the pricing for changes required at Sub-station for UDC
implementation. They presented the scheme for implementing Brown-out (BO) and the field scenario
implementation at Madurantakam, Tamil Nadu. Schematics and additional costing for different options
for implementing BO by stepping down the voltages depending on Greenfield or existing Substation
modification would be in between 283 to 580 per home respectively.
The committee examined different options provided and opined that the implementations were indeed
feasible and that the costing of changes required at the sub-station for UDC implementation was found
to be reasonable. The committee concluded that the substation changes for large scale (tens of millions
of homes) implementation of UDC would cost no more than ₹500 per home.
3. Conclusion:
The committee feels that Project-UDC is a promising solution to help bridge the gap between power
supply and demand. With the detailed discussions and contributions from industry representatives, the
committee members conclude this solution to be technically and economically viable. A study /
implementation over a larger number of substations and feeders (typically few hundreds) would help
establish the scheme and its operational and techno-economical features.
Annexure 1: Concept of Brown-out
Uninterrupted power to homes is achieved using a concept called “brown-outs” (BO) where some
power, say 10%, would continue to be fed on the grid even during power cuts. This would ensure 24X7
powering of basic amenities like lights, fans and TV. During Brown-outs, 90% power in a locality is cut
rather than 100%. This significantly impacts the process of balancing of supply with demand. However
Brown-out poses two problems:
1) Will homes not draw whatever they want during a brown-out, resulting in overloading and line
failure?
2) Is 10% power meaningful and useful to the consumer?
The first problem is overcome by delivering power from the existing single distribution grid line to
homes on two circuits. One is the existing 230V AC unlimited power (subject to fuse ratings, of course)
circuit which is cut off during brown-outs (load-shedding). The second circuit carries a limited amount of
power (10% of maximum power, or say 100W) and is available during normal as well as brown-out
states. As no home can draw more than 10% power during brown-outs, the distribution line is not
overloaded.
The second problem is overcome by providing this limited, but uninterrupted, power in DC form. It can
therefore be used only with DC appliances. This is designed to leverage the fact that a DC-powered LED
tube light consumes 40% of the power, compared to an equivalent lumens AC powered CFL tube light.
Similarly a DC-powered BLDC fan uses only 40% of the power used by an equivalent AC-powered
induction fan. Further, the fact that a TV (LCD/ LED), laptop, tablet, cell-phones or any other electronics
uses only DC power, powering them using DC power-circuit would save 25-50% power loss. It is because
of this that the 100W DC power is not equivalent to a 100W AC power. This DC power can energize 2
fans, 3 lights and a cell phone charger, simultaneously – which would otherwise require about 250W of
AC power. Alternately, one of the fans can be switched off to turn on a 24” LCD/ LED TV, along with its
set-top box, within this 100W.
Substation Requirements
To implement UDC, three things are required:
1. Carry out load shedding by cutting of 90% of power (instead of 100%)
2. Provide power within homes from grid in two circuits
3. Ensure that instant cut-off of the AC line takes place, when load shedding is implemented
This requires that an instant signaling from the sub-station (where the load shedding is carried out) to
each home, reliably, so that AC power is cut off during BO. Similarly, when normal power is restored, the
signal should enable restoration of AC power. A reliable and guaranteed instant signaling is, achieved by
dropping the voltage level of the 10% power transmitted during load shedding by say 2.5 times. This is
achieved at the sub-station by using a tap on the 33kV/11kV transformer, or adding a 2.5:1 transformer
at 11kV output, as shown in the Figure 1. This transformer/ tap is also limited to 10% of the power that
the 11kV line would carry during normal operation. The brown-out then switches the 11kV output to
4.2KV (with 10% power level).
33KV
TRANSFORMER
In the "Brown Out" operation, low voltage is accompanied by a substantially lower power operation as
well - this ensures that current in the windings is much lower than rated conditions. Hence copper losses
11KV
Black-out
•
•
Brown-out
•
Home/shop
11KV/4.2KV
DT
Some 10% of power
TRANSFORMER
(2.5 : 1)
4.2KV
Low
Voltage
cutoff
Instead of complete black-out
feed a lower-voltage small power
to homes
Industries / Large Establishments
Figure 1: Brown-out Mechanism at sub-station
are also lower than rated normal conditions, leading to lower heating levels. This is quite opposed to
normal voltage sag situations where current flowing could be much higher than normal levels if constant
power loads are deployed by users. Also, on a lower voltage operation, surge levels will also be
correspondingly lower and hence the regular distribution transformer will be stress relieved to some
extent even on surges.
The existing AC meter
can be used
AC
Meter
230V/90V
230V/90V AC
DC
Meter
UD
UDPM
Home
Figure 2: Functional Block diagram for UDPM
Since the power is in AC form, it travels on the 11kV distribution line in a normal manner. Losses in the
distribution line does not increase during brown-out even though there is a drop in line voltage, as
power carried is now only 10% of the normal power. The DT steps down the 4.4kV on distribution
voltage to about 90V on each phase before it is fed to homes. Power to industry / large offices is cut-off
during brownout using a Low Voltage Cut Off unit (LVCO). At homes, this line now feeds a unit called an
UDPM (Uninterrupted DC Power Module), which is capable of receiving either 230 V AC or 92 V AC
power. The output from this box would drive 2 circuits (power-lines) as shown in Fig. 2:
-
A 48V DC line on which will be allowed a maximum of 100 W, and services DC devices
A 230 V AC line, fed through existing AC meter, to service all the AC devices.
Figure 3: UDPM a) As finished Product b) PCB
During a brownout, the 230V AC output will be cut off, but the 48V DC line will be on and will continue
to power the DC equipment. The UDPM is also designed to support Bluetooth connectivity and RS 485
connectivity for DC meter readings, other management as well as integration with smart meter. The PCB
of UDPM and finished UDPM product are shown in Figure 3a and Figure 3b.
The POC has shown that UDC is working without any hitches. The trials at Moinabad in Telangana also
re-emphasize this.
…………………………………………………………………………………………..
Annexure 2: SLD for UDC
Annexure 3: UDPM Specifications and Functionalities
UDPM functionality can be divided into two modules:
•
•
AC-DC converter
Communication and Control
The specifications of these modules are given in Table 2.1.
TABLE 2.1: UDPM MODULES AND THEIR SPECIFICATIONS
Modules
M1 : AC
Converter
- DC
Description
Specification
Input Voltage Range
80~265Vac
Output DC Voltage (Programmable)
45-51 V
Output Current
3.125 A
Rated Power Output
150 W
Line Regulation
±1%
Power Factor
@ 80 Vac
0.99
(@ Full Load)
@ 230 Vac
0.97
Efficiency (max.)
@ 130 W
94 to 95 %
M2:
Communication
and Monitoring
Controller for monitoring and protection, Low voltage sensing and DC metering
and DC cut off at 100 W
UDPM Module
Dimension(l*w*h)
160*95*45 mm
Annexure 4: Cost Estimation for Sub-Station Implementation
Annexure 5: Minutes of First Meeting
Department of Science & Technology
National S&T Entrepreneurship Development Board (NSTEDB)
Minutes of the First Meeting of the Expert Advisory Committee
on
Solar Power and Energy Sector held on 17.11.2014 in IIT Delhi.
The list of members who attended the meeting is given at Annexure-I.
1.
Shri H.K Mittal, Head NSTEDB, DST welcomed the members for the first meeting. He
emphasized the specific role of the Committee , whose contribution would result in time
bound and action oriented outcomes paving way for innovative approaches to solve some
of the existing challenges of the power sector in the national interest.
2. Prof. U.B. Desai, Chairman reiterated the broad terms of references of the Committee and
also suggested the composition of subcommittees (as per the Annexure –II ) , each being
entrusted with the responsibility of a specific terms of reference. The subcommittees to be
steered by their conveners would initiate immediate actions so as to come up with a first draft
report within a month’s time.
3. Industry being the key stakeholder in power, it was suggested to involve Industry in the
various sub committees i.e for smart meters, DC Solar, Off-Grid Solar, etc.
4. Prof. Bhaskar Ramamurthi gave the presentation on the Brown out proposal. He along with
Prof. Jhunjhunwala shared their experience on the technical and commercial feasibility of the
brown out involving voltage drop at substation, by providing 48v DC line at home along with
the regular AC supply for ensuring availability of some power for common household usage
in the event of peak load.
5. The Committee felt that 24x 7 reliable electricity supply involves participation of other key
stakeholders including nodal govt. deptt, Electricity Boards, utilities and grid management etc.
The Committee considered the issue very challenging for coming out with an effective
roadmap within 90 days. The members may suggest some innovative approaches on the
matter to make it reliable and effective for implementation.
6. Whitepaper on focused domain of power electronics ( Prof. BG Fernandes and Prof. G.
Bhuvaneswari to contribute and circulate the same within 21 days ) with a road map for India
for taking dominant position in the area, comprehensive short term and long term ( 5-10 yrs)
framework for R&D , formulation of broad topics, emphasizing development of prototypes
and possibly new product development,
cohesive research groups, creating centers of
excellence for undertaking co-ordinated research, industry participation and requirements
of funds etc. It was also suggested to begin with, all the IITs involved in the expert group may
take the lead in this direction.
7. It was decided to hold the next committee meeting in Chennai.
8. There being no other point, the meeting ended with a vote of thanks to the Chair.
List of Participants
1.
Prof. Uday B. Desai, Director IIT, Hyderabad - Chairman
2.
Prof. P.P.Chakrabarti, Director IIT Kharagpur - Member
3.
Prof. Bhaskar Ramamurthi ,Director IIT Madras -Member
4.
Prof. Timothy Gonsalves, IIT Mandi -Member
5.
Prof. Ashok Jhunjhunwala, IIT Madras -Member
6.
Prof. B.G Fernandes, IIT Bombay -Member
7.
Prof. D. Thukaram, Indian Institute of Science, Bangalore-Member
8.
Prof. S.A Kharpade, IIT Bombay -Member
9.
Prof. K. Shanti Swarup, IIT Madras -Member
10. Prof. G. Bhuvaneswari , BITs , Hyderabad -Member
11. Prof. Siva Kumar K, IIT Hyderabad -Member
12. Sh. H.K.Mittal, Sc. G and Head- Innovation and Entrepreneurship(NSTEDB) -Member
13. Dr. Anita Gupta, Sc. F and Associate Head-Innovation and Entrepreneurship (NSTEDB),
DST -Member Secretary
14. Anand Pandey, Sc. B , DST- Meeting Organising Committee
Annexure 6: Minutes of Second Meeting
Minutes of Meeting
of
Second Meeting of Expert Advisory Committee on Solar Power and Energy Sector
National S&T Entrepreneurship Development Board
Department of Science and Technology
At IITM Board Room, IIT Madras on 30th Dec., 2014 from 10am to 4pm
Prof. U.B. Desai, Chairman of the committee, welcomed all members of the committee and briefed on
the minutes of last meeting, held on 17th Nov, 2014.
1. Some of the common questions raised by members were to enquire the impact of Decentralized
Solar on Grid Power when the power is fed back to the Grid from the solutions proposed by IIT
Madras. It was clarified that no power is fed back to the grid through any of the solutions
proposed by IITM. Power generated by solar is directly used to feed the loads.
2. Prof. Bhuvneshwari raised her concern for Battery overcharging when generated power is more
than the power consumed by loads, which would impact the battery life adversely. It was
cleared that, IITM solution is designed such that solar will operate at non MPPT if it goes out of
range and finally cuts off. This means that SPV output will be zero whenever there is no load
connected to it.
3. Prof. Thukaram’s presentation was discussed which was largely focused on issues of Reverse
Metering. Though solutions designed at IITM are not reverse feeding, the committee felt these
issues must be taken up as research issues, which are included in the research areas (page2). His
concern of DC feeder losses being higher than the AC feeder losses was also clarified. To
implement Brown-out, the designed solution does not provision separate DC wiring. No DC
feeder is used, the DC wiring only resides inside the home.
4. Members also raised whether 230V, and not reduced voltage, can also be used during brownout. The complexity of ensuring signalling makes this difficult. The issue of Power stealing with
Brown-out situation was also raised. It was agreed that at 90V, it is much more difficult to steal,
as even if voltage booster transformer is used to operate at 90V, sudden switch to normal
(230V) will give over 500V damaging the device. So one has to have a sophisticated system to
steal power as compared to when only 230V is used. Also, even when appliances are designed
to work at lower voltages, the range acceptable is 130V-240V. 90V would just cut-off the
appliance. Brown-out provides lifeline to consumers and supports 10% of the designed capacity.
5. Prof. P. P. Chakraborthy presented features, challenges and implementation issues for Smart
Meters. During discussions, various issues emerged which need research attention, and are
included in the research areas. The following questions were raised:
a. Whether smart-meters can be used to selectively carry out instantaneous (unscheduled)
black-out in a substation area when required. It was accepted that scheduled black-out
and brown-out is possible. However the unscheduled brown-out (when frequency of
power falls below a certain number and a mandatory instantaneous shut-down or load
reduction is required so that grid does not trip) will be a problem, for every meter would
have to be instantaneously informed of the BO event. It was felt that wireless Internet
(or other forms of Internet) will have some latency; the best would be to cut power
instantaneously, send messages to each smart-meter to go into brown-state, and when
acknowledgement is received from each meter, power is restored. This could be done in
5 seconds to a few minutes, which may be acceptable. It was pointed out that if wireless
Internet was used and a user puts a small jammer close to the meter, the technique
would fail. This can result in power-cuts not being implemented could possibly result
into grid-failure.
b. A question was also asked whether the frequency measurement at each smart-meter
could be used to reduce load at each customer-end. It was pointed out that gridfrequency is not limited to a substation area but will be same for the whole state /
region. So the load-reduction / shedding, cannot be on selective basis, but would have
to be same for all the customers on the grid.
6. Prof. Timothy Gonsalves, presented the standardization efforts for DC wiring and appliances. It
was brought out that it is important to get approvals from CEA, CERC and state regulation
commissions. LVDC, IEC and IEEE standardization efforts should also be followed up.
7. Rationale for use of 48V DC was discussed. It was noted that safe voltage was below 60V and
considering the ripple, 48V will be safe. Fernandes pointed out that for voltage lower than 48V,
the wiring losses will be huge.
Committee members visited the IITM Brown-out demo facility and were also demonstrated the Off Grid
Home (OGH) solution. Committee suggested that homes which are not connected to the grid, should be
connected to OGH solution and that the work can be progressed aggressively.
Next meeting for this committee is planned at IIT Hyderabad on 3rd Feb. with following schedule.
9.30 am– 11:30 am
Sub-Groups meet
11.30 onwards
Main Group Meet
Action Points:
1. Include the common questions asked by members of the meeting as part of FAQ of solutions
proposed by IITM.
2. Economics and Guidelines to be worked out to reach to 30% Off-grid homes.
- Prof. Ashok Jhunjhunwala.
3. To list the indigenous parts in the solutions proposed and link it to “Make in India” program.
– Prof. Bhaskar Ramamurthi
4. For technology and costing of Brown-outs, industry should be involved and be invited in the
next sub-group meeting.
5. Smart meters technology to be reviewed in detail and be discussed – Prof. P. P.
Chakraborthy.
6. Test Beds to be set-up at various places for measuring and validating the DC devices. To
start with, this facility be provided at IIT Madras, IIT Hyderabad, IIT Mandi, IIT Kharagpur and
IIT Bombay. – Prof. Krishna Vasudeva, Prof. B. G. Fernandes, Prof. Bhuvneshwari and Dr. Siva
Kumar.
7. Indian defined Standards to be focussed and followed for DC devices. – Prof. Timothy
Gonsalves.
8. For wide reach, training is important. Training manuals and videos should be prepared.
Research Areas:
1. Impact of Solar Decentralized power on Grid: stability issues, load modelling, PV scalability.
2. Reverse protection at Sub Station in Indian context.
3. Communication with Grid for parameters measurements and control to avoid Grid collapse
and also on amount of reverse feeding by decentralized solar systems.
a. To look out the options for communication mechanism: Power Line carrier
communication, LTE or separate wideband frequency etc.
b. During power shortages, managing scheduled as well as unscheduled black-outs.
4. Reliable solution to handle line tapping.
5. Control and location profiling for smart meters. Defining role of smart meters at homes and
at Sub-stations.
Annexure 7: Minutes of Third Meeting
Minutes of Meeting
of
Third Meeting of Expert Advisory Committee on Solar Power and Energy Sector
National S&T Entrepreneurship Development Board
Department of Science and Technology
At Conference room, IIT Hyderabad on 3rd Feb., 2015 from 9.30 am to 3pm
Prof. U.B. Desai, Chairman of the committee, welcomed all members of the committee and the meeting
started with the introduction
1. Mr. Dileep Shetty, consultant, IIT Madras presented the design, features and costs associated
with UPDM. Various design and costing issues were discussed. It was brought out that major
cost of UDPM is due to magnetically latched relays and high conversion efficiency. At present,
the BOM including the manufacturing cost for 100K volume is close to 1700.
Targeted costs are as follows:
a. For 100K volume, total cost of 1500. With manufacturing and 15% taxes, the price
may be close to 2000.
b. For 10M volume, final pricing expected to be 1200.
The committee noted the pricing and found these to be a reasonable estimate.
Some suggestions made by the committee:
a. Design should take care of efficiencies, power factor correction, ripples and harmonics
b. Specifications may be opened to all manufacturers to come up with lower price quotes.
2. Mr. Venkat Ramarajan, CEO, Cygni, along with Mr. A. Sridhar Reddy, MD, ESENNAR
Transformers, presented the Sub-station side of UDC implementation. He explained the scheme
for implementing Brown-out (BO) and the field scenario implantation at Madurantakam, Tamil
Nadu. Three more places at Andhra Pradesh, Orissa and Kerala have been commissioned.
Schematics and costing for different options for implementing BO by stepping down the
voltages depending on Greenfield or existing Substation modification were discussed.
For implanting BO, the cost is 283 to 580 per home at substation. The committee discussed
the pricing and found it to be reasonable.
Some suggestions by the committee:
a. An auto step down transformer can be used instead of isolated transformer which can
be cost effective. But, protection for auto transformer can be a problem as there is no
isolation. This needs to be checked for a reliable and cost effective solution.
b. Design cost for BO implementation may also be included. End to end cost for consumer
may also be worked out
3. Dr. Shantidev Mohanty presented communication Interface for smart meters. Some important
features and issues with smart meters were briefed. He presented that existing telecom
standards (cellular or otherwise) cannot be used for Smart Meters communication and informed
that the new IEEE standards, IEEE 1701TM and IEEE 1702TM, have stated that existing telecom
standards should not be used for Smart meters communication. Almost all manufacturing
companies are designing end-to-end solution for smart meters. Any MAC and PHY can be
designed for the desired capacities. Japan uses LTE, Italy uses Power Line Communication,
Canada uses Wi-Max for smart Metering. So, communication can be done based on any one or
multiple ways, as long as the spectrum is sufficient to support the requirements.
a. Solution using IEEE802.11ah to be explored for smart metering and connecting to the
central system.
b. Business case for smart meters and criticisms can be prepared and shared.
c. Security issues to be addresses.
d. Serious R & D, Policy recommendation and test beds for Smart Meters.
4. Committee feels a dire need for R&D in Power Electronics. A sub-group should focus on R&D,
education and importance of Power Electronics. A good white paper can come-up. Innovation
labs/centres on Power Electronics systems should be set up.
Some action points and Research areas identified during the discussions of this committee are as below.
It was decided to invite Reji Kumar Pillai, President, India Smart Grid Forum to the next meeting. It was
felt that a session on Electrical Vehicles should also take place in next meeting.
Chairman thanked all members, industry representatives and invitees for attending the meeting. The
meeting concluded with fixing the schedule for next meeting which is planned at IIT Delhi on 23rd March,
2015.
Appendix 8: Understanding losses during Brown-out
Let us assume that a city has 200 feeders (distributed in multiple sub-stations) of 11 kV, each carrying a
peak load of 1 MVA. That implies that the peak demand that the city can have is 200 MVA. Assume that
in a peak hour (when everyone is using peak-load), the total supply to the city available is 164 MVA.
Currently used Approach
In the currently used approach, when 164 MVA of supply is available and the demand is 200MVA, is to
carry out load shedding. 36 of the 200 feeders will therefore be cut-off (load-shedding), resulting into
black-outs for all those fed by those feeders. 164 feeders will be ON and the supply and demand will
both match at 164 MVA. Nearly one fifth of the city will suffer black-out.
The Brown-out Approach to be used by proposed UDC solution
The new approach suggested by IITM, will not do any blackout (or full load shedding). However only 160
feeders (four less than that in currently used approach) will be allowed the full load of 1 MVA each. The
remaining 40 feeders will have brown-out. Each will be eligible for 100 kVA instead due to the power
restriction on the dc outlet. The total load will again be 160 x 1 MVA + 40 x 100 kVA or 164 MVA. Thus
the supply and demand will match. However now 40 feeders will get limited power (of 10% of their
peak) and each home on these feeders will be eligible for limited power in the form of DC.
Let us now compare the two approaches. The full power that was provided to four feeders in the
currently used approach, is now being provided as limited power to 40 feeders.
Loss calculations for the two approaches
Current approach
The four feeders each carry power at 11kV power and supply 1 MVA. The current per phase in each
feeder is therefore 1000/(11√3) or 52.5 A. Assuming R as the line resistance per phase in each feeder,
the total line losses will be 3I2R or 3(52.5)2 x R. For four feeders, the total line-loss L1 is 12 x (52.5)2 x R.
UDC Solution
The computations below assume that there are a total of 200 feeders each having a rated load of 1
MVA. To illustrate the power scarcity conditions, power availability of 164 MVA is considered. Under
normal conditions, supply to 36 feeders would have to be cut to match the supply and demand. 164
feeders would be energised.
Under the proposed structure, it is assumed that the requirements for UDC have been implemented in
all the 200 feeders, so that brown-out could be effected on a rotational basis if required. The
calculations presented assume the feeders are identical in structure and also loading. As the scheme
implementation is spread to various substations, some additional coordination is required among the
substations. The scheme utilization is for limited hours on each feeder when load-shedding takes place,
and during brown out condition some consumers not having dc loads will not be benefitted. Under this
situation, 160 feeders would be supplied with rated power and 40 feeders (36 which would have been
cut and another 4 more), spread across various substations would be operated under brown-out mode.
Thus the power that would have been supplied to 4 feeders is instead used over 40 feeders.
The power from these four feeders is now being provided to 40 feeders; each feeder can supply a
maximum of 100 kVA. However, this is given at 4.4 kV. The current in each feeder is then 100/(4.4√3) or
13.1A. The line losses in each feeder is again 3I2R or 3(13.1)2 x R.
For 40 feeders, the total line-loss L2 is therefore equal to, 120 x (13.1)2 X R.
To compare the two solutions we can now compute the relative line-losses in the two approaches as
L1/L2 = [12 x (52.5)2 x R] / [120 x (13.1)2 x R], which works out to be 1.6.
Thus the relative loss in Brown-out goes down by 1.6.