Dear Wang, As I used the PID control many times, I am sure that there is no problem with the code…I suggest you to check the following two points: 1) Concentration unit: it happened to me to make trivial errors because of the _expression_ of concentration: check if the output of your model is not expressed in percent or per mille instead of ppm; 2) Input 11 (Fraction of ySet for proportional effect) should be set to zero and parameter 1 (mode) to zero. In addition, you should plot the output 2 and 4 in order to understand where the problem is. Output 2 should be equal to set-point concentration minus actual concentration, output 4 to output 2 multiplied by kp. Good luck! Best regards, Marcello De : wanghongyang1767@gmail.com [mailto:wanghongyang1767@gmail.com] De la part de wangyang Dear marcello.caciolo, Many thanks for your quick reply! I know and understand all what you explained. Since my profession for Bachelor and Master is Automation control. That is also the reason why I suspect the function of PID controller in TRNSYS. As you said, I tried many time the gain Kp and integral time Ki and small time step 1 min or smaller in order to avoid oscillations, a large difference between the set point 1000 ppm and actual CO2 concentration etc. I mentioned already as my first email about PID controller: I set the set point CO2 concentration 1000 ppm as PID controller's set point; its control signal links to Opening Factor (OF) of windows; indoor CO2 concentration links to PID's controlled variable. However, when indoor CO2 concentration is less than set point 1000 ppm, PID begins to activate OF i.e. windows are open. Based on PID principle, control signal should be set to zero. BUT it is not like this. As we know, if CO2 concentration is not getting to set point 1000 ppm, at this time windows are open will result in the ERROR (between the set point and actual indoor CO2 concentration) increasing. So I'm puzzled! So I suspect the function of PID controller in TRNSYS. Now, I only would like a solution for this problem as I said in recent emails and the adequate explanations for this OF_CO2 concentration_PID control issue in TRNSYS . Many thanks in advance! br wang 2011/11/16 <marcello.caciolo@aximaseitha-gdfsuez.com> Dear Wang, I find that your problem description is not very clear, but I try anyway to guess what you want to do. In my understanding, if you want CO2 concentration to be less than 1000 ppm, you should use a PID control with a positive gain and an output signal between 0 and 1, directly connected to the OF. In this way, if the CO2 concentration is less than 1000 ppm, the error (and integral and derivative part of the signal, if present) of the PID control will be negative, so that control signal is set to zero. On the other hand, when CO2 concentration is above 1000 ppm, the error is positive and the output signal will be more than 0, so opening the window. Take care to the choice of the gain of the PID: a too high value could generate oscillations, while a value too low will lead to a large difference between actual and setpoint CO2 concentration. Also note that, without an integral part, the PID control is purely proportional and will always lead to a CO2 concentration higher than 1000 ppm. However, the integral time should be high enough to prevent oscillations. The time period should be also short enough in order to avoid instabilities in control. Guessing a good value of the gain and the integral time of a PID needs to wall understand the main principles of a proportional and integral controller. I suggest you to have a look to some textbooks about HVAC control in order to understand these principles. I hope that these explanation will help you. Best regards, Marcello CACIOLO Direction Commerciale
P Pensez à l'environnement avant d'imprimer ce message De : trnsys-users-bounces@cae.wisc.edu [mailto:trnsys-users-bounces@cae.wisc.edu] De la part de wangyang Dear David, As I said yesterday, I linked PID's output Control Signal to a minus 1 then to OF. The results are still very WEIRD. OF becomes minus value which is not reasonable very much i.e. the window is open towards abnormal direction; CO2 concentration is not decreasing as we hoped, however, it is becoming much more bigger e.g. 4000 ppm. Now, I only would like a solution for this problem as I said in last email and the adequate explanations for this OF_CO2 concentration_PID control issue. Many thanks in advance! br wang 2011/11/15 王洋 <wanghongyang1767@gmail.com> Dear David, Many thanks for your reply! I already saw both of them as you mentioned, however, they are not helpful for my simulation results i.e. they don't explain the things I wanted. Your heating/cooling example is very vivid. Do you mean I need add an equation after the PID i.e. link PID's output Control Signal to a minus 1 then to OF? Now, I only would like a solution for this problem as I said in last email and the adequate explanations for this OF_CO2 concentration_PID control issue. Many thanks in advance! br wang
2011/11/14 David BRADLEY <d.bradley@tess-inc.com> Wang,
Dear all, I have a question about PID controller in TRNSYS for its developer. Which expert knows PID controller in TRNSYS developer? Or Which expert could pass me the source code of PID controller or its internal algorithm etc.? I guess PID controller in TRNSYS is based on empirical equation or iterative algorithm. Since there is very weird simulation results i.e. I set the set point CO2 concentration 1000 ppm as PID controller's set point; its control signal links to Opening Factor (OF) of windows; indoor CO2 concentration links to PID's controlled variable. However, when indoor CO2 concentration is less than set point 1000 ppm, PID begins to activate OF i.e. windows are open. But based on PID principle, as we know, if CO2 concentration is not getting to set point 1000 ppm, at this time windows are open will result in the ERROR (between the set point and actual indoor CO2 concentration) increasing. So I'm puzzled! Please PID controller in TRNSYS developer or other experts explain this weird phenomenon! Many thanks in advance! br wang 2011/11/12 <trnsys-users-request@cae.wisc.edu> Send TRNSYS-users mailing list submissions to Erik, Dear TRNSYS users, I have a simple question regarding weather reading and interpolating direct normal radiation (DNI) values for time steps less than an hour. As long as I have been using TRNSYS (using TRNSYS 16.1) I have understood this can be done in a few ways as follows, including the consequence for an example TM2 file (see attached screen shot for clarification): 1.) Do not interpolate, using Type 15 with output DNR (not interpolated): you end up with a "steppy" profile 2.) Using Type 15, but with 2-axis tracking and the output "Beam radiation for surface": you get a discontinuous "spikey" profile, but the integration of energy across the hour is respected 3.) Same as 2, but using Type109-TMY2: You get a smooth profile, but often there appear inexplicable spikes at the beginning or end of the day. The one in the plot obviously is an extreme case. For reference: I just used the Daggett profile "US-CA-Daggett-23161.tm2" which came with TRNSYS, but the behavior is not specific to this file. Generally, I have been using 2, but it can cause problems if there is, for example, some triggering function based on DNI and the DNI hovers around the threshold. Is there another option for getting a smoother profile or is it best just to not interpolate? Any opinions? Feel free to point me to an earlier post on this topic in case I missed it. Thanks, Erik Boschek _______________________________________________ TRNSYS-users mailing list TRNSYS-users@cae.wisc.edu https://mailman.cae.wisc.edu/listinfo/trnsys-users -- *************************** David BRADLEY Principal Thermal Energy Systems Specialists, LLC 22 North Carroll Street - suite 370 Madison, WI 53703 USA P:+1.608.274.2577 F:+1.608.278.1475 d.bradley@tess-inc.com http://www.tess-inc.com http://www.trnsys.com
Graham,
Nidal, I drew a house using Trnsys3d that consists of: 3 bed rooms, living room, guest room and bath . The house was divided into 6 zones. Wall_zone5, for example, is adjacent two walls for two different zones. I am wondering how to identify a wall (using Object Info) that is adjacent two or more walls of diff. zones. Best Regards Nidal Abdalla _______________________________________________ TRNSYS-users mailing list TRNSYS-users@cae.wisc.edu https://mailman.cae.wisc.edu/listinfo/trnsys-users -- *************************** David BRADLEY Principal Thermal Energy Systems Specialists, LLC 22 North Carroll Street - suite 370 Madison, WI 53703 USA P:+1.608.274.2577 F:+1.608.278.1475 d.bradley@tess-inc.com http://www.tess-inc.com http://www.trnsys.com
Dear TRNSys Users, I have a problem with external file of type 51a (cooling tower with an external performance File): That the simulation with this type causes error and this can't read this external file (.txt) Would you please help me how to correct the file joined or send me a truth format of this .txt file Many thanks in advance Mkacher Walif
_______________________________________________ TRNSYS-users mailing list TRNSYS-users@cae.wisc.edu https://mailman.cae.wisc.edu/listinfo/trnsys-users -- *************************** David BRADLEY Principal Thermal Energy Systems Specialists, LLC 22 North Carroll Street - suite 370 Madison, WI 53703 USA P:+1.608.274.2577 F:+1.608.278.1475 d.bradley@tess-inc.com http://www.tess-inc.com http://www.trnsys.com
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