Re: Calculation of a full Y-matrix
Jose, I am interested in applications of electrical distance idea excluding the loads. I would like to read some papers/reports which compare real life networks using electrical distance with and without the loads. I might be completely wrong, ignoring the load might be useful in some situations. Thanks, Jovan On Tue, Feb 17, 2015 at 2:19 PM, Jose Luis Marin mari...@gridquant.com wrote: OK thanks, I see what you mean now. The way I see it, I was looking at just the *network*, not the network+load system. In this view, you calculate bus A to bus B distances using just the admittances of the transmission network. In other words, the electric circuit we're considering here has all RLC impedances to ground of constant-power injections set to infinity. What you're suggesting is interesting and more accurate, but I'm not sure if it is useful in practice (I'd like to know more). Say for instance that in one of the possible paths from bus A to bus B you have a load at some intermediate bus. If you use this load's RLC value (taken from some particular powerflow solution, of course) in the calculation of the Klein distance, it means you're considering paths going through the *ground node*. Which brings up this interesting question: under normal operation of power networks, can't we safely approximate those RLC values to infinity, since they are much greater than the typical RLC values of transmission lines and transformers? I have a feeling that we can do so, at least in transmission, but I confess I haven't checked the numbers. -- Jose L. Marin Gridquant España SL Grupo AIA On Tue, Feb 17, 2015 at 5:49 PM, Jovan Ilic jovan.i...@gmail.com wrote: Jose, Let me clarify. If you run a power flow you can obtain all the currents and transfer the constant P/Q loads into constant RLC you can rebuild your admittance matrix with this new RLC values. From here, calculating the electrical distance using Z matrix is nothing new. However, as soon as the load changes you have to do it all over again. My point is, you cannot have a single electrical distance matrix for a given system. Paul, I know Paul Hines and I have read a couple of his group's papers on electrical distance. If memory serves, their approach suffered from the same problem of ignoring the load. This was a 3-4 years (or more) ago and they might have made a breakthrough but I'd have to do some reading, Another interesting approach that I ran into was based on the Jacobian but I do not remember the details. I have the paper somewhere and if somebody is really curious how it was done I can look for it. In that approach calculating the equivalent RLC load is not needed but again, the Jacobian changes with the load. I hope I made clear what I meant by my previous e-mail. Jovan On Tue, Feb 17, 2015 at 11:26 AM, Jose Luis Marin mari...@gridquant.com wrote: Jovan, I agree it's not fast and efficient, as it involves inverting the admittance matrix. However, I do not see why not Klein's impedance distance could be used in power networks. I mean, the fact that some (ok, most) injections are expressed as constant power does not invalidate the fact that it's an electric circuit governed by Kirchoff laws. Incidentally, we have sometimes used the path of greatest admittance between two given nodes as an heuristic measure of closeness (actually, the net impedance of such path). It all depends what you want to use these distances for. -- Jose L. Marin Gridquant España SL Grupo AIA On Tue, Feb 17, 2015 at 4:35 PM, Jovan Ilic jovan.i...@gmail.com wrote: Paul, I would not call calculating Zbus fast and efficient. Also, using resistance distance might make sense in standard electric circuits but it does not make sense in power networks with constant powers. As far as I know there is not a very good, theoretically sound, way of calculating electrical distance in power systems. I would love to be corrected on this one. Jovan On Tue, Feb 17, 2015 at 10:20 AM, Paul Cuffe paul.cu...@ucd.ie wrote: Hi Hans, There is indeed a fast and efficient way to calculate this, though you don't encounter it often in the power systems literature. You can use the Klein resistance distance, as defined here: http://link.springer.com/article/10.1007/BF01164627 Once you have inverted your Ybus matrix to get the Zbus, you can calculate the Thevenin impedance between any two nodes, i and j, as follows: Of course, the reciprocal of the Zthev impedance value will give the effective admittance between any two nodes. Hope this helps, Paul On 17/02/2015 15:06, Barrios, Hans wrote: Hello everybody, I was wondering if somebody had already the following issue: I would like to create a “full version” of the Y-matrix, i.e. a matrix where (as long as there is only one synchronous grid) the admittance between each bus is given, even if the bus are not
Re: Calculation of a full Y-matrix
Jose, Let me clarify. If you run a power flow you can obtain all the currents and transfer the constant P/Q loads into constant RLC you can rebuild your admittance matrix with this new RLC values. From here, calculating the electrical distance using Z matrix is nothing new. However, as soon as the load changes you have to do it all over again. My point is, you cannot have a single electrical distance matrix for a given system. Paul, I know Paul Hines and I have read a couple of his group's papers on electrical distance. If memory serves, their approach suffered from the same problem of ignoring the load. This was a 3-4 years (or more) ago and they might have made a breakthrough but I'd have to do some reading, Another interesting approach that I ran into was based on the Jacobian but I do not remember the details. I have the paper somewhere and if somebody is really curious how it was done I can look for it. In that approach calculating the equivalent RLC load is not needed but again, the Jacobian changes with the load. I hope I made clear what I meant by my previous e-mail. Jovan On Tue, Feb 17, 2015 at 11:26 AM, Jose Luis Marin mari...@gridquant.com wrote: Jovan, I agree it's not fast and efficient, as it involves inverting the admittance matrix. However, I do not see why not Klein's impedance distance could be used in power networks. I mean, the fact that some (ok, most) injections are expressed as constant power does not invalidate the fact that it's an electric circuit governed by Kirchoff laws. Incidentally, we have sometimes used the path of greatest admittance between two given nodes as an heuristic measure of closeness (actually, the net impedance of such path). It all depends what you want to use these distances for. -- Jose L. Marin Gridquant España SL Grupo AIA On Tue, Feb 17, 2015 at 4:35 PM, Jovan Ilic jovan.i...@gmail.com wrote: Paul, I would not call calculating Zbus fast and efficient. Also, using resistance distance might make sense in standard electric circuits but it does not make sense in power networks with constant powers. As far as I know there is not a very good, theoretically sound, way of calculating electrical distance in power systems. I would love to be corrected on this one. Jovan On Tue, Feb 17, 2015 at 10:20 AM, Paul Cuffe paul.cu...@ucd.ie wrote: Hi Hans, There is indeed a fast and efficient way to calculate this, though you don't encounter it often in the power systems literature. You can use the Klein resistance distance, as defined here: http://link.springer.com/article/10.1007/BF01164627 Once you have inverted your Ybus matrix to get the Zbus, you can calculate the Thevenin impedance between any two nodes, i and j, as follows: Of course, the reciprocal of the Zthev impedance value will give the effective admittance between any two nodes. Hope this helps, Paul On 17/02/2015 15:06, Barrios, Hans wrote: Hello everybody, I was wondering if somebody had already the following issue: I would like to create a “full version” of the Y-matrix, i.e. a matrix where (as long as there is only one synchronous grid) the admittance between each bus is given, even if the bus are not connected directly by one branch. If I am not missing anything, the Admittance between each bus should be a simple calculation of parallel an series admittances. But I was wondering, if anyone knows a fast and efficient way I can used to calculate this also for big grid structures. Thank you in advance for your contributions! Best regards Hans *Hans Barrios Büchel, M.Sc.* Institut für Hochspannungstechnik / Institute for High Voltage Technology - Nachhaltige Übertragungssysteme / Sustainable Transmission Systems - Wissenschaftlicher Mitarbeiter / Research Assistant RWTH Aachen University Schinkelstraße 2, Raum SG 115.1 52056 Aachen Germany Tel. +49 241 80-94959 Fax. +49 241 80-92135 Mail. barr...@ifht.rwth-aachen.de Web. www.ifht.rwth-aachen.de -- Dr. Paul Cuffe, Senior Researcher, Electricity Research Centre, University College Dublin. Phone: +353-1-716 1743
Re: Calculation of a full Y-matrix
Jovan, I agree it's not fast and efficient, as it involves inverting the admittance matrix. However, I do not see why not Klein's impedance distance could be used in power networks. I mean, the fact that some (ok, most) injections are expressed as constant power does not invalidate the fact that it's an electric circuit governed by Kirchoff laws. Incidentally, we have sometimes used the path of greatest admittance between two given nodes as an heuristic measure of closeness (actually, the net impedance of such path). It all depends what you want to use these distances for. -- Jose L. Marin Gridquant España SL Grupo AIA On Tue, Feb 17, 2015 at 4:35 PM, Jovan Ilic jovan.i...@gmail.com wrote: Paul, I would not call calculating Zbus fast and efficient. Also, using resistance distance might make sense in standard electric circuits but it does not make sense in power networks with constant powers. As far as I know there is not a very good, theoretically sound, way of calculating electrical distance in power systems. I would love to be corrected on this one. Jovan On Tue, Feb 17, 2015 at 10:20 AM, Paul Cuffe paul.cu...@ucd.ie wrote: Hi Hans, There is indeed a fast and efficient way to calculate this, though you don't encounter it often in the power systems literature. You can use the Klein resistance distance, as defined here: http://link.springer.com/article/10.1007/BF01164627 Once you have inverted your Ybus matrix to get the Zbus, you can calculate the Thevenin impedance between any two nodes, i and j, as follows: Of course, the reciprocal of the Zthev impedance value will give the effective admittance between any two nodes. Hope this helps, Paul On 17/02/2015 15:06, Barrios, Hans wrote: Hello everybody, I was wondering if somebody had already the following issue: I would like to create a “full version” of the Y-matrix, i.e. a matrix where (as long as there is only one synchronous grid) the admittance between each bus is given, even if the bus are not connected directly by one branch. If I am not missing anything, the Admittance between each bus should be a simple calculation of parallel an series admittances. But I was wondering, if anyone knows a fast and efficient way I can used to calculate this also for big grid structures. Thank you in advance for your contributions! Best regards Hans *Hans Barrios Büchel, M.Sc.* Institut für Hochspannungstechnik / Institute for High Voltage Technology - Nachhaltige Übertragungssysteme / Sustainable Transmission Systems - Wissenschaftlicher Mitarbeiter / Research Assistant RWTH Aachen University Schinkelstraße 2, Raum SG 115.1 52056 Aachen Germany Tel. +49 241 80-94959 Fax. +49 241 80-92135 Mail. barr...@ifht.rwth-aachen.de Web. www.ifht.rwth-aachen.de -- Dr. Paul Cuffe, Senior Researcher, Electricity Research Centre, University College Dublin. Phone: +353-1-716 1743
Re: Calculation of a full Y-matrix
Hi Jovan, all, Thanks for contributing those points! It's interesting to note that the resistance distance between nodes can also be calculated by simpler eigen/spectral techniques, as in http://repository.ias.ac.in/77807/ and so matrix inversions aren't essential. Anyway, I more meant quick and efficient in the sense of rapidly achieving something with just a few lines of MATLAB script, being the (sometimes) lazy engineer that I am! In my experience, which is, I freely admit, quite limited, the Zthev between two buses is actually a usefully accurate predictor of the incremental phase angle shift that a 1 MW transaction between those buses will require. I know Paul Hines and his group in Vermont have done some interesting work in the area of electrical distance using the Klein formula; that may be of interest. I'm afraid my work in this area is still in review! Thanks, Paul On 17/02/2015 15:35, Jovan Ilic wrote: Paul, I would not call calculating Zbus fast and efficient. Also, using resistance distance might make sense in standard electric circuits but it does not make sense in power networks with constant powers. As far as I know there is not a very good, theoretically sound, way of calculating electrical distance in power systems. I would love to be corrected on this one. Jovan On Tue, Feb 17, 2015 at 10:20 AM, Paul Cuffe paul.cu...@ucd.ie mailto:paul.cu...@ucd.ie wrote: Hi Hans, There is indeed a fast and efficient way to calculate this, though you don't encounter it often in the power systems literature. You can use the Klein resistance distance, as defined here: http://link.springer.com/article/10.1007/BF01164627 Once you have inverted your Ybus matrix to get the Zbus, you can calculate the Thevenin impedance between any two nodes, i and j, as follows: Of course, the reciprocal of the Zthev impedance value will give the effective admittance between any two nodes. Hope this helps, Paul On 17/02/2015 15:06, Barrios, Hans wrote: Hello everybody, I was wondering if somebody had already the following issue: I would like to create a “full version” of the Y-matrix, i.e. a matrix where (as long as there is only one synchronous grid) the admittance between each bus is given, even if the bus are not connected directly by one branch. If I am not missing anything, the Admittance between each bus should be a simple calculation of parallel an series admittances. But I was wondering, if anyone knows a fast and efficient way I can used to calculate this also for big grid structures. Thank you in advance for your contributions! Best regards Hans *Hans Barrios Büchel, M.Sc.* ** Institut für Hochspannungstechnik / Institute for High Voltage Technology - Nachhaltige Übertragungssysteme / Sustainable Transmission Systems - Wissenschaftlicher Mitarbeiter / Research Assistant RWTH Aachen University Schinkelstraße 2, Raum SG 115.1 52056 Aachen Germany Tel. +49 241 80-94959 tel:%2B49%20241%2080-94959 Fax. +49 241 80-92135 tel:%2B49%20241%2080-92135 Mail. barr...@ifht.rwth-aachen.de mailto:barr...@ifht.rwth-aachen.de Web. www.ifht.rwth-aachen.de http://www.ifht.rwth-aachen.de/ -- Dr. Paul Cuffe, Senior Researcher, Electricity Research Centre, University College Dublin. Phone:+353-1-716 1743 tel:%2B353-1-716%201743 -- Dr. Paul Cuffe, Senior Researcher, Electricity Research Centre, University College Dublin. Phone: +353-1-716 1743
Re: Calculation of a full Y-matrix
Paul, I would not call calculating Zbus fast and efficient. Also, using resistance distance might make sense in standard electric circuits but it does not make sense in power networks with constant powers. As far as I know there is not a very good, theoretically sound, way of calculating electrical distance in power systems. I would love to be corrected on this one. Jovan On Tue, Feb 17, 2015 at 10:20 AM, Paul Cuffe paul.cu...@ucd.ie wrote: Hi Hans, There is indeed a fast and efficient way to calculate this, though you don't encounter it often in the power systems literature. You can use the Klein resistance distance, as defined here: http://link.springer.com/article/10.1007/BF01164627 Once you have inverted your Ybus matrix to get the Zbus, you can calculate the Thevenin impedance between any two nodes, i and j, as follows: Of course, the reciprocal of the Zthev impedance value will give the effective admittance between any two nodes. Hope this helps, Paul On 17/02/2015 15:06, Barrios, Hans wrote: Hello everybody, I was wondering if somebody had already the following issue: I would like to create a “full version” of the Y-matrix, i.e. a matrix where (as long as there is only one synchronous grid) the admittance between each bus is given, even if the bus are not connected directly by one branch. If I am not missing anything, the Admittance between each bus should be a simple calculation of parallel an series admittances. But I was wondering, if anyone knows a fast and efficient way I can used to calculate this also for big grid structures. Thank you in advance for your contributions! Best regards Hans *Hans Barrios Büchel, M.Sc.* Institut für Hochspannungstechnik / Institute for High Voltage Technology - Nachhaltige Übertragungssysteme / Sustainable Transmission Systems - Wissenschaftlicher Mitarbeiter / Research Assistant RWTH Aachen University Schinkelstraße 2, Raum SG 115.1 52056 Aachen Germany Tel. +49 241 80-94959 Fax. +49 241 80-92135 Mail. barr...@ifht.rwth-aachen.de Web. www.ifht.rwth-aachen.de -- Dr. Paul Cuffe, Senior Researcher, Electricity Research Centre, University College Dublin. Phone: +353-1-716 1743
Re: Calculation of a full Y-matrix
OK thanks, I see what you mean now. The way I see it, I was looking at just the *network*, not the network+load system. In this view, you calculate bus A to bus B distances using just the admittances of the transmission network. In other words, the electric circuit we're considering here has all RLC impedances to ground of constant-power injections set to infinity. What you're suggesting is interesting and more accurate, but I'm not sure if it is useful in practice (I'd like to know more). Say for instance that in one of the possible paths from bus A to bus B you have a load at some intermediate bus. If you use this load's RLC value (taken from some particular powerflow solution, of course) in the calculation of the Klein distance, it means you're considering paths going through the *ground node*. Which brings up this interesting question: under normal operation of power networks, can't we safely approximate those RLC values to infinity, since they are much greater than the typical RLC values of transmission lines and transformers? I have a feeling that we can do so, at least in transmission, but I confess I haven't checked the numbers. -- Jose L. Marin Gridquant España SL Grupo AIA On Tue, Feb 17, 2015 at 5:49 PM, Jovan Ilic jovan.i...@gmail.com wrote: Jose, Let me clarify. If you run a power flow you can obtain all the currents and transfer the constant P/Q loads into constant RLC you can rebuild your admittance matrix with this new RLC values. From here, calculating the electrical distance using Z matrix is nothing new. However, as soon as the load changes you have to do it all over again. My point is, you cannot have a single electrical distance matrix for a given system. Paul, I know Paul Hines and I have read a couple of his group's papers on electrical distance. If memory serves, their approach suffered from the same problem of ignoring the load. This was a 3-4 years (or more) ago and they might have made a breakthrough but I'd have to do some reading, Another interesting approach that I ran into was based on the Jacobian but I do not remember the details. I have the paper somewhere and if somebody is really curious how it was done I can look for it. In that approach calculating the equivalent RLC load is not needed but again, the Jacobian changes with the load. I hope I made clear what I meant by my previous e-mail. Jovan On Tue, Feb 17, 2015 at 11:26 AM, Jose Luis Marin mari...@gridquant.com wrote: Jovan, I agree it's not fast and efficient, as it involves inverting the admittance matrix. However, I do not see why not Klein's impedance distance could be used in power networks. I mean, the fact that some (ok, most) injections are expressed as constant power does not invalidate the fact that it's an electric circuit governed by Kirchoff laws. Incidentally, we have sometimes used the path of greatest admittance between two given nodes as an heuristic measure of closeness (actually, the net impedance of such path). It all depends what you want to use these distances for. -- Jose L. Marin Gridquant España SL Grupo AIA On Tue, Feb 17, 2015 at 4:35 PM, Jovan Ilic jovan.i...@gmail.com wrote: Paul, I would not call calculating Zbus fast and efficient. Also, using resistance distance might make sense in standard electric circuits but it does not make sense in power networks with constant powers. As far as I know there is not a very good, theoretically sound, way of calculating electrical distance in power systems. I would love to be corrected on this one. Jovan On Tue, Feb 17, 2015 at 10:20 AM, Paul Cuffe paul.cu...@ucd.ie wrote: Hi Hans, There is indeed a fast and efficient way to calculate this, though you don't encounter it often in the power systems literature. You can use the Klein resistance distance, as defined here: http://link.springer.com/article/10.1007/BF01164627 Once you have inverted your Ybus matrix to get the Zbus, you can calculate the Thevenin impedance between any two nodes, i and j, as follows: Of course, the reciprocal of the Zthev impedance value will give the effective admittance between any two nodes. Hope this helps, Paul On 17/02/2015 15:06, Barrios, Hans wrote: Hello everybody, I was wondering if somebody had already the following issue: I would like to create a “full version” of the Y-matrix, i.e. a matrix where (as long as there is only one synchronous grid) the admittance between each bus is given, even if the bus are not connected directly by one branch. If I am not missing anything, the Admittance between each bus should be a simple calculation of parallel an series admittances. But I was wondering, if anyone knows a fast and efficient way I can used to calculate this also for big grid structures. Thank you in advance for your contributions! Best regards Hans *Hans Barrios Büchel, M.Sc.* Institut für
