# Electrical Engineering

11
Have you used the MATCASC software for MATLAB? Where can I find it?
We're working on vulnerability studies of electric power systems and we found in some papers that the MATCASC software can be used in those studies. But we can't find where to download it.

Hi again Lu Xiao, sorry if I did not respond before. The MATCASC tool is a library that you need to add to your MATLAB folder program and set the path to it. Please check the notes added to the mail by the Dr. Yakup Koç. I hope that the tool be useful for you. Regards.

3
How does the transmission line parameters vary with cable length?

Hello,

While modelling a transmission line, I have considered L',R',C',G' are the inductance per unit length, resistance per unit length, capacitance per unit length and conductance per unit length respectively.

However, I don't know how does these parameters vary if the length of the transmission line is increased (say doubled).

Kindly clarify.

Thank you.

Hi,

THis doesnot clarify my doubt. Let me put my question in this way. Suppose, I have my R, L, C, G for a 50m cable as 44 ohms, 1.5uH, 12nF and 50uS. Then what would be the effect on the values if I try to model a cable of length 100m.

I know that the resistance would for sure increase. What would be the effect on other values as I increase the cable length.

Would the L,C,G values increase or decrease_

Thank you.

2
How can I get MVA Ratings of the Generators connected in IEEE 24 Bus test system ?

Basically, according to IEEE 24 RTS data available i have MWs rating available for the Generators connected in that system. But, as i am working in PSAT Tool in Matlab , i need to enter the values of MVA & kV ratings of Generators connected at several buses. Check the attachment figure.

2
How do I make a map of energy infrastructure?

I am trying to make an infrastructure map of Pakistan for my thesis like this one
http://www.ppib.gov.pk/Energy%20Map%202011.pdf

Can anyone tell me most suitable and easiest way to do it?

I have tried QGIS but I dont seem to understand how to do it

Thanks

I think spatial interface and presentation can be effectively managed provided data architecture and modeling are efficient. It would be beneficial if these are shared.

34
Which indexing service does present better evaluation? ISI or Scopus?
Or other indexing service?

I used Scopus in a recent Bibliometric study on Portuguese research in e-government because it offers a broader coverage of publicarmos no the subject.

HTTPS:://www.researchgate.net/publication/268212619_Bibliometric_Analysis_of_Portuguese_Research_in_e-government

• Source
##### Article: Bibliometric Analysis of Portuguese Research in e-government
[Hide abstract]
ABSTRACT: In this article we present a bibliometric analysis of journal articles, conference papers and book chapters published internationally by researchers affiliated to Portuguese institutions in the subject of e-government in the past ten years. The Scopus® database was used as source. The identified articles were analyzed concerning year of publication, citations, topics addressed, scope, methods used, and authors and their affiliation institutions. A benchmark exercise was also performed by comparing Portuguese bibliometrics with all the other countries in the European Union. We conclude that e-government research in Portugal still has a substantial room for improvement. This is apparent from the small number of researchers and institutions involved in e-government research, the limited number of topics addressed, and the results of the international benchmark. By establishing the evolution and current standing of e-government research in Portugal our conclusions are useful to researchers in the area of e-government, and to research managers and research policy makers.
12/2014; 16:279-287. DOI:10.1016/j.protcy.2014.10.093
9
How can I analyze stability for solar array, DC DC converter, and battery system?

Say we got a solar array which supply power to battery through a DCDC converter. We want to design two control loops for the converter.

One is the inner(fast) loop which regulates the converter output voltage or current. This loop can be analysis by the traditional converter small signal model.

Another one is outter(slow) loop which is regulate the converter input voltage or current  (solar array output voltage or current). How can we analysis the stability for this loop? Do we need to include the small signal module of solar array? If the voltage or current is regulated by some algorithms, how to model the algorithm?

Any tips would be very helpful, thank you

Hi Somesh,

Thanks for your answer. The difficulty part is we want to know the TF before we building the hardware.

10
Can anybody tell me how to set the common mode in single to differential output amplifier?

differential amplifier: Can anybody tell me how to set the common mode voltage in single to differential output amplifier?

To get a common mode voltage of about 5v and a differential voltage of 100mV, proceed as follows: V1 is applied to one input and V2 to another input. Output is (V2-V1)*DMG + common mode effects. CM is actually 5.05V, while DM is [100*50/51]mV. The DM and Cm signals are at same frequency!

Set one input as 5V and another as 5.1V. One method of doing this is to have a 5.1V from function generator and get 5V from this through a divider of say 1k and 50k.

In general Cm is 50 hz while DM may be 1kHz. One can get this  as follows. Connect V1 through 1k to 5V, 50 Hz and through 50k to 5V 1khz. Connect V2 to same 5V 50 hz through 1k, but return it to ground through 50k.. one can simulate all these if necessary using circuit maker or p Spice. You can make small changes as necessary to get exactly Cm and DM voltages. .

You can get any other combination of Cm and DM voltages using this method of resistive summing. If you change 1k above to 100 ohms, DM signal will be about 10mV. you can raise or lower the CM voltage by setting the output of 50 hz generator.

Does this help?

35
Is it possible to have light without electrical power?

In general, light is produced for household purpose with bulb, CFL, tube, LED etc from electrical power. There is a big portion of world that lives in dark after sun sets. These people do not want electrical power, they want light first.

Is it possible to create a pollution free light without electric power and without burning something. Light that is sufficient to illuminate a 12 x 12 feet hut without an electricity connection. Light that is very very cheap (not more than \$1 per week and 8 hours per day)….Don’t tell solar or known things….suggest something wild…some new idea….innovative…no power only light….Just for the sake of discussion….

Hi Vasile, the picture is very nice. It's worth seeing. In return, look at a triode about of the year 1917th. Beautiful, is not it? This, however, shone with electricity. :-)

Josef

PS

It is product S&H.

5
Can mutual information measure the relationship between two vectors that are multidimensional both?

If I want to build a time series model, of which the output and the input are both multivariate, I need to do a feature/variable selection work. How can I measure the input vector and the output vector? Does the mutual information work?

The multivariate mutual information can be positive or negative, I think it is not easy to compare that, right? Plz share your opinions.

https://en.wikipedia.org/wiki/Multivariate_mutual_information

Okay. I think i made a mistake about the problem. The real point i want to get is to measure two group variables, not multivariate, like MI((X,Y);Z) not MI(X,Y,Z). I hope everyone here clear. Thanks.

4
How does an algorithm (PSO,ACO,GA etc) decide the optimal location of capacitor for voltage profile improvement?

I am working on optimal placement of capacitor for voltage improvement.

Hi,

The  multiple objective function must to include, nominal voltage and current, cos fi, deformation of the electric signal as a result of the presence of non linear elements, and other, by each subcircuit component and for the complete circuit. There are a group fo optimizatization algorithms that could be used, most of them could be included under the concept of the Integration of Variables Method that I mentioned in the previous mesage.

Best wishes,

Jose Arzola

2
What method would you suggest to try for Defect Oriented Testing of analog circuits in order to achieve better fault coverage?

Although many analog fault simulation papers have been published in the last 20 years, no general-purpose analog fault simulator is presently available commercially. The two dominant reasons for this are that there is no industry-accepted parametric fault model, and the time to simulate all possible defects in an industry analog circuit is prohibitive (years!).

Lets have this discussion with the hope of having some good outcomes from it!

Yes, the testing of analog circuits is a very interesting issue. Guaranteed parameters by manufacturers should suffice for conventional electronics. It is assumed, of course - design, functional sample, prototype series, etc. Testing method ("sensitive sites") must already be part of the design - is elected "by nature" of the circuit! And in modern (smart) structures it may be some tests repeated "in operation" - and thus continuously evaluate the situation.

6
How can I write mfile for a new statcom model for power flow using N.R.method?

Power flow in IEEE 30 nodes. Two statcom connect to 10,24 bus.

Agree with Tapan Prakash

6
What will be the mathematical model and dynamics of a pmdc motor coupled with a link system?

i have a pmdc motor coupled with a load where load is nothing but a link which is rotating clockwise and anticlockwise by 180 degree what will be the mathematical model and dynamics of this motor load configuration?

thanx all for ur response....but still i didnt get the answer. i just want the free body diagram of the previous figure i attached so that i can find centre of mass and other such dynamics to find state space equations.

4
How do I evaluate the performance of a self-fabricated small scale V-blender machine?

We have developed a new 90 degree V-Blender with angular velocity variation from 15 to 90 rpm. I would like to know on how to check for the reliability of this machine. Thanks in advance

Thank you for the idea. Really useful for my project studies.

16
Sometimes we use an integral action to avoid static errors. What does it means?

Sometimes we use an integral action to avoid static errors. What does it means? A+.

Hi

I advice you to see these documents. You will find what you need.

I hope that I helped you, let us know if you have another questions or you need more details.

Best regards

14
Can a remote power generation plant be directly connected to transmission lines instead of installing new lines to feed the S/S?

Can a power generation  plant be directly connected to transmission lines instead of installing new lines to feed the S/S?

Economics is a good point. I am always interested in that. But Haseeb did not ask whether these options are economics or not. He may have lots of money to connect DG in anyway he likes.... (joking...).

Not sure, it is a practical question or theoretical question.

51
What is the best software for simulation of Power electronic projects?

Hi

What is the best software for simulation of  Power electronic projects such as DC/DC converters with high Input-Output Voltage or Current? I think that MATLAB(Simulink) some times is not good for them.

Best Regards.

I will suggest OpenModelica. It is open source free software. It caters to simulation of all types of electrical/electronic/control circuits along with many other domains like mechanical/hydraulic/thermal/flow/physiology and what not.

For electrical circuit simulation, one can use traditional Spice3 library if one is used to it, or one may use new semiconductor libraries which are simpler from computation point of view. OpenModelica can very well do everything you do in MATLAB/SIMULINK or PSIM.

There are a lot of examples and learning curve is steep. Use and experience its beauty.

4
Can anyone suggest, what are the factors considered for optimal DG placement in literature till date?
Like some considered bus sensitivity, voltage sensitivity, power stability index, voltage stability index anyone know other than these factors?

http://www.sciencedirect.com/science/article/pii/S0142061514006504

6
What is the correlation in the values of PD in terms of PC and dB?

I am dealing with partial discharge in Ultra High Voltage systems and equipment. What is the correlation in the values of PD in terms of PC and dB?

Hi,

from my experience High Voltage is an issue of Electrotechnics (ELT).

In ELT are used Volts, kVolts and also Mega Volts to characterize HV pulses.

dB are a possible measuring unit of Tension V (dBuV) and Power (dBm) in of some instruments used more in Electronics or Telecommunications

So, if you have such an instrument, please check the conversion between

Volt and dB microVolt (dBuV)

http://www.eeweb.com/toolbox/rf-unit-converter

in example, in a 50 Ohm measuring system

120 dBmicroVolt = 1 V (rms)

All the Best, Alberto

16
Does the reflection problems exist for DC transmission lines?

Reflection problems are usually defined for AC transmission lines. I would like to know whether DC lines can have this problem. And I also would like to know whether the length of the transmission lines have an influence on the reflection problems either for AC or DC lines.

Is the DC an electromagnetic wave?

Thank you very much,

Antonio Faggio

In DC problems, we merely deal with reflection issues during switching. As you remember form 'Signals and Systems' course, the switched signals are not considered as purely DC, where their spectrum contains infinite frequencies (rather than the DC one in which there exist only f=0). When a switch is closed to transfer energy from a DC source through some line to a load, the energy is propagated to the load with the velocity of waves in that line (The line may be disperssive so the velocity is a function of frequency). After the signal reaches the load impedance, some portion of energy is reflected back to the generator if the load is not matched. The reflected wave is again facing the impedance of generator on the other side, and this transient event goes on until the amplitude of the reflected waves is diminished. But if you want to calculate the reflection, you must compute the reflection coefficient for the continues spectrum of the unit-step function (Obviously the load impedance is frequency dependant as well as the charactristic impedance of line). For further disscussion you can refer to Dr. Cheng's book about fields and waves.

5
What is the effect of the flange of a surge arrester used in higher voltage rating lines?

What is the effect of the flange of a surge arrester used in higher voltage rating lines?

Thanks for the answer Mr.Pieter Swanevelder. :-)

1
Can I use MPC algorithm using forecast data without specific model for prediction in distribution system?

Hi everyone,

I am trying to apply MPC for voltage or reactive power control. i have distribution system which is not dynamical so i dont have dynamic system for MPC prediction. the system is static. if I have forecast data (load forecast or forecast data of PV or Wind), can i apply MPC with forecast data and how?

Thanks

You can read this paper "Model Predictive Control of Voltages in Active Distribution Networks" on IEEE Transactions on Smart Grid in 2013 . Here is the link, https://www.researchgate.net/post/Can_I_use_MPC_algorithm_using_forecast_data_without_specific_model_for_prediction_in_distribution_system.

3
Any advice on why the gate driver is having trouble turning on N-channel power MOSFET?

My half-bridge gate driver seems to be having trouble turning on the MOSFET on the high-side of my buck converter. I am thinking the MOSFET's gate capacitance may be too high, but I'm not quite sure, I'm trying to look through the data gate driver's datasheet to find any information that could help me determine this, but I'm not sure what rating to look for exactly. If anyone could help me with this I would greatly appreciate it.

I've attached the datasheets for the driver and MOSFET that I'm using. By the way I am using bootstrap circuitry to drive both high and low-side MOSFETs, with a boot capacitor of 0.1uF, ceramic.

The high side driver works by virtue of a charge pump made with C4,  low side MOSFET, and a diode D4. The value of C4 is poorly explained in datasheets, and it must obey some switching frequency relationship. If C4 is not charging properly, there's no high side action at all.

6
How to rewind a Bldc motor from a Distributed stator winding to a Concentrated Stator winding with the same Slot-Pole pair combination?

Can anyone tell me how to rewind a Bldc motor from a Distributed Stator winding to a Concentrated Stator winding with the same Slot-Pole pair combination?

Thank you Ron and Pinaki for answering.

4
Is there a possibility to calculate the actual power of a speed-controlled pump by knowing the output frequency of the inverter?

A pump is driven by an asynchronous motor which in turn is connected to the grid via an inverter. When the rated power of the motor for 50Hz is known, can I apply a linear relationship between power and frequency to calculated the actual power for various frequencies?

Hello,  Sebastian! Indeed, there is no linear relationship between power of pump and output frequency of converter.

But, as a rule of thumb, there is the next assumption in terms of centrifugal fans and pumps. If we control pump/fan by means of electric drive (or any drive) then water/air speed and flow changes proportional to speed of motor. Water/air pressure change depends on square of speed of motor. The load torque depends on square of speed too. The input power of pump/fan, finally, depends on motor speed^3. It means that if we provide the permanent ratio between the stator current frequency, that is the output frequency of inverter, and the motor speed (or, at least, we can take that the slip caused by torque could be negligibly small) then we could define the change of input power of pump/fan (that is output power of the electric motor) as a function proportional to the change of stator current frequency^3 (P1/P2=(f1/f2)^3)

For example, if f=50 Hz and speed=1500rev/min, pump/fan power = 12 kW, then under f=25 Hz and speed~750rev/min, power ~ 2 kW.

For sure, this approach is very rough and inaccurate, it could not be recommended for accurate calculations, but if we have to sketch the range of inverter frequency change due to change of  power (speed) of pump/fan then this technique is useful.

This approach is not feasible for any calculation of stator or rotor current and, consequently, not feasible for calculation power losses because the value of current strongly depends on parameters of equivalent circuit and control system.

Regards.

39
What do coupling capacitors really do in AC amplifiers? Are they rechargable "batteries" conveying voltage variations or diverting biasing currents?

We have already discussed how the AC current "passes" through a capacitor
https://www.researchgate.net/post/Does_the_current_flow_through_a_capacitor_and_if_so_why?,

and we have realized the biasing is usually a series summation
https://www.researchgate.net/post/What_does_biasing_mean_and_how_is_it_implemented_in_electronic_circuits?

Now it is interesting to discuss what coupling capacitors really do in AC amplifiers (the most widely known application of these techniques). The usual viewpoint at the capacitive coupling is that the capacitors prevent affecting the DC biasing current from the previous stage; thus the name "DC blocking capacitors". For example, Wikipedia says:

"In analog circuits, a coupling capacitor is used to connect two circuits such that only the AC signal from the first circuit can pass through to the next while DC is blocked. This technique helps to isolate the DC bias settings of the two coupled circuits."

This explanation is true and it does good work for conventional "teachers" that do not like their student to "trouble" them with confusing questions-:) But it is a formal and sketchy "explanation" since it actually does not explain how the AC signal passes through the coupling networks and what they really do. The frequency-domain explanation where the CR coupling hetwork is presented as a high-pass filter is even more formal...

Here, I would like to suggest to your attention more four fresh and not so usual time-domain explanations of the legendary capacitive coupling technique; I have been using them at the lectures with my students through years.

The key points of understanding and explaining the capacitive coupling are first to see that the capacitor is "hanged", as a kind of bridge, between two sources: from the left side - by the perfect input voltage source that has to ensure a galvanic path to ground; from the right side - by the (more) imperfect voltage source built by the biasing voltage divider and the power supply. Then, assuming the input voltage is zero, it is easy to see that the capacitor charges to the bias voltage of the right source (the left is absent) and the amplifier is correctly biased. Finally, wiggling the input voltage fast enough (so that the average voltage across the capacitor to stay almost constant), we can use one of the (and why not the all?) viewpoints below to explore the circuit operation in an attractive manner.

PERFECT VOLTAGE SOURCE IN PARALLEL TO IMPERFECT ONE. First, we can see that two voltage sources are connected in parallel to the amplifier input. The left of them is composed of two perfect voltage sources in series (the input source and the charged capacitor); the right is the biasing one. So, In this arrangement, the perfect left source (Vin + Vbias) dominates over the imperfect biasing source and imposes its full voltage on the amp input.

CURRENT STEERING. The BJT emitter-grounded amplifier is a special case of this arrangement since its input (the base-emitter junction) behaves as a constant-voltage nonlinear element (a voltage stabilizer). Now we have two (almost) perfect voltage sources connected in parallel and this combination is supplied by the biasing current source (the base resistor and the power supply in the attached picture below). So, when the input voltage varies, the biasing current vigorously diverts (is steered) between the input source and the amp input.

SERIES VOLTAGE SUMMER. Of course, we can see the series voltage summer (according to the Kirchhoff's voltage law) needed for the biasing - it sums the input voltage Vin and the biasing voltage Vbias across the charged capacitor so their sum Vin + Vbias is applied to the amp input.

VOLTAGE SHIFTING. And finally, we can imagine the capacitor is a kind of an electrical "shock-absorber" shifting (translating, moving, displacing...) the input voltage variations. The Flash movies below will help you to imagine it (do not pay attention to the weird Cyrillic characters):
http://www.circuit-fantasia.com/ResearchGate/Shock_absorber.swf
http://www.circuit-fantasia.com/ResearchGate/Input_blocking_capacitor.swf

We have already considered the charged capacitor as a voltage source:
https://www.researchgate.net/post/Is_a_charged_capacitor_a_voltage_source_Is_a_charged_inductor_a_current_source_Is_there_any_difference_between_them_and_true_electrical_sources?

I hope you, creative teachers considering students as human beings with imagination and intuition, will appreciate and even add more viewpoints at the legendary capacitive coupling technique...

Regards, Cyril

Well, today's "semiconductor youngsters" usually do not know what is it the proper voltage and soothing glow cathodes. Don't touch of anode! :-))

17
What is the difference between a microgrid and a smartgrid?
Can anybody help me to know what the difference is between a microgrid and a smartgrid?

I would rather saying, there is no difference between Micro grid and smart grid in  respect to load, source of generation, AC or DC except smart control system for efficiency and reliability in the system. Smart Grid Consumer Collaborative (SGCC) and others find that the average consumer knows little about how electricity is generated, distributed and consumed, the impact of using it, or how to maximize efficiency and cost savings.

10
What is qd0 transformation?

I am modelling induction generator via simulink. If the unbalance supply is given to induction generator, should I use symmetrical components to get currents or qd0 transformations? I am confused, as in built-in "asynchronous machine block" there is qd0 transformation is used. Can I use that block if induction generator is fed with unbalanced supply, or do I need to use a symmetrica component?

Hi, the hybrid model has been also used in analyzing an induction generator connected to the grid through a forced-commutated ac voltage controller:

1-        M. A. Abdel-halim, “Solid-state control of a grid connected induction generator,” Electric Power Components and Systems Journal, Vol. 29, No. 2, 2001, pp. 163-178.

7
Interference from the multi-path signal.

As we all know, by adding cyclic prefix, OFDM signals can be able to tackle with both ISI and ICI. But how does the reflected signal affect the demodulation (FFT/DFT) on the same sub-carrier? In MATLAB simulation (without adding any noise, and only one reflected signal was introduced), the demodulated constellations are clustered around the target points as the figure below shows. Can this effect be explained or is there any equalisation method to reverse this distortion?

Hi

This Constellation show a 4-QAM constellation-Coherent Interference. for more information you can refer to the "Digital communication book".
Good Luck

23
Technical papers versus scientific papers, what is your opinion?
The engineer involved in design and prototypes manufacturing for research purposes is searching for valuable ideas in research papers, application notes, technical papers, patents and other articles. Are the technical papers less or more important than research papers for the experimental researcher ?

For exemplification:
http://www.power-eetimes.com/en/the-top-10-most-popular-power-management-technical-articles-of-2013.html?cmp_id=7&news_id=222907367

thank you,
Vasile Surducan

Dear @Vasile, let me bring good article related to your issue. At first sight, it may be not obvious.

Fundamental Science and Useful Applications!

"These basic ideas arose from scientists trying to understand the fundamental laws of nature. This doesn’t mean that technological applications automatically followed, or could follow, since the most significant applications are often the least predictable. The key problem is how to invest so as to maximize the potential for innovation. Most advances in technology are incremental and based on existing knowledge—suitable material for private investors who need short-term returns. But the big advances come from the big ideas, which come most often to those who are searching for them, rather than waiting for them to drop as fruits from a tree. Here the investment is long term, the benefits incalculable and the damage immeasurable unless governments support the diversity of basic research that has produced so much in the past, but will continue to do so only if properly nurtured in the future..."