convergence issue

Anonymous
2012-04-25
2013-03-16
  • Anonymous - 2012-04-25

    Hi,

    I can´t fiind why the system doesn´t converge.

    I´m using:

    module residential {
      implicit_enduses LIGHTS|PLUGS;
    };

    …and there are 11 houses: each one with demand around 0.35 kW, with the load curve below:
    schedule plugs_csd1 {
    * 0 * * * 0.721;
    * 1 * * * 0.55325;
    * 2 * * * 0.50125;
    * 3 * * * 0.4709;
    * 4 * * * 0.44435;
    * 5 * * * 0.92685;
    * 6 * * * 0.73115;
    * 7 * * * 0.58645;
    * 8 * * * 0.67225;
    * 9 * * *  0.7386;
    * 10 * * * 0.73295;
    * 11 * * * 1.06715;
    * 12 * * * 0.7792;
    * 13 * * * 0.71825;
    * 14 * * * 0.7095;
    * 15 * * * 0.783;
    * 16 * * * 0.8554;
    * 17 * * * 1.7443;
    * 18 * * * 2.66;
    * 19 * * * 2.23755;
    * 20 * * * 2.1369;
    * 21 * * * 1.73725;
    * 22 * * * 1.4062;
    * 23 * * * 1.05365;
    }

    And there are 9 houses with the curve below:

    schedule plugs_csd0 {
    * 0 * * * 0.66;
    * 1 * * * 0.58;
    * 2 * * * 0.56;
    * 3 * * * 0.55;
    * 4 * * * 0.54;
    * 5 * * * 0.566;
    * 6 * * * 0.697;
    * 7 * * * 0.935;
    * 8 * * * 0.902;
    * 9 * * *  0.893;
    * 10 * * * 0.738;
    * 11 * * * 0.771;
    * 12 * * * 1.006;
    * 13 * * * 0.842;
    * 14 * * * 0.741;
    * 15 * * * 0.947;
    * 16 * * * 1.2556;
    * 17 * * * 1.585;
    * 18 * * * 2.021;
    * 19 * * * 1.902;
    * 20 * * * 1.503;
    * 21 * * * 1.3620;
    * 22 * * * 1.319;
    * 23 * * * 0.950;
    }

    and power around 0.55 kW.

    My transformer configuration are:

    object transformer_configuration:75 {
    connect_type DELTA_GWYE;             
    install_type PADMOUNT;
    power_rating 75;
    primary_voltage 4800;
    secondary_voltage 240;
    resistance 0.04;    
    reactance 0.05; 
    }

    Thank you,

    Douglas

     
  • Jason Fuller

    Jason Fuller - 2012-04-25

    Douglas,

    Is this the only transformer you have?  Attaching a house object to the power system requires a triplex_meter object (the meter is the parent of the house), which then requires a center-tapped or split-phase transformer to connect it to your three-phase backbone.

    Here's a small example:

    object node {
          name n692;     
          phases ABC;     
          nominal_voltage 2401.7771;     
     }
     object transformer_configuration {
                name transf_config;
                connect_type SINGLE_PHASE_CENTER_TAPPED;
                primary_voltage 2401.777;
                secondary_voltage 120;
                powerA_rating 265 kVA;
                impedance 0.00033+0.0022j;
     }
     object transformer {
           name CTTF_A_692;
           phases AS;
           from n692;
           to tn1;
           configuration transf_config;
     }
    object triplex_node {
           name tn1;
           phases CS;
           nominal_voltage 120;
     }
     object triplex_line {
           phases CS;
           from tn1;
           to tm1;
           length 25 ft;
           configuration triplex_line_configuration;
     }
     object triplex_meter {
           name tm1;
           phases CS;
           nominal_voltage 120;
     }
     object house {
         parent tm1;
     }
    
     
  • Jason Fuller

    Jason Fuller - 2012-04-25

    Eh, sorry.  Copy-paste-itis.  Phases in the triplex system should be 'AS', not 'CS' to match the transformer configuration.

    object node {
        name n692;
        phases ABC;
        nominal_voltage 2401.7771;
    }
    object transformer_configuration {
        name transf_config;
        connect_type SINGLE_PHASE_CENTER_TAPPED;
        primary_voltage 2401.777;
        secondary_voltage 120;
        powerA_rating 265 kVA;
        impedance 0.00033+0.0022j;
    }
    object transformer {
        name CTTF_A_692;
        phases AS;
        from n692;
        to tn1;
        configuration transf_config;
    }
    object triplex_node {
        name tn1;
        phases AS;
        nominal_voltage 120;
    }
    object triplex_line {
        phases AS;
        from tn1;
        to tm1;
        length 25 ft;
        configuration triplex_line_configuration;
    }
    object triplex_meter {
        name tm1;
        phases AS;
        nominal_voltage 120;
    }
    object house {
        parent tm1;
    }
    
     
  • Anonymous - 2012-04-25

    Jason,

    1) Actually I´m using the 37 node IEEE system, with triplex meters for each house. I removed the load 728 and intalled the transformer with a secondary grid.
        When I´m trying 16 houses, with loads described above, the simulation converges, but with more than this, it doesn´t.
        If I simply sum these "loads" at the peak period, it doesn´t reach the 75KVA, which is the nominal power of the transformer !

    2) The use of a split-phase transformer is a requirement? I´m asking this because here in Brazil is common to use 3 phase transformers, typically around 75 KVA. -> This provides the 3 phases at the low voltage that I´m using.


    Douglas

     
  • Jason Fuller

    Jason Fuller - 2012-04-25

    Douglas,

    Currently, we only support U.S. systems, which requires a triplex / split-phase secondary.  It's been an issue that we are aware of but haven't been able to address - balanced, three-phase runs down to the home (e.g., Europe or South America) are not supported.

    I imagine this could be fairly easily remedied in the code for the house object (via the "panel" connection which is hard-wired to a 120/240 voltage system), but we haven't had a client call (or honestly enough domain knowledge about non-U.S. systems) to add that function.

    If this isn't the problem, then can you post your connections (from the x-former to the house) and the version of GLD you are using?

     
  • Anonymous - 2012-04-25

    Jason,

    I´m using the 2.0.0 Four Corners , Win32 release.

    There are my connections:



    object overhead_line_conductor:500 { geometric_mean_radius 0.0144; resistance 0.450;} // I assumed these values
    object overhead_line_conductor:501 { geometric_mean_radius 0.00514; resistance 0.700;} // I assumed these values

    object line_spacing:120 {
    distance_AB 0.1;
    distance_BC 0.1;             
    distance_AC 0.1;                                                    
    distance_AN 0.029;
    distance_BN 0.029;                                                       
    distance_CN 0.029;
    }  
    object line_configuration:301 {
    conductor_A overhead_line_conductor:500;
    conductor_B overhead_line_conductor:500;
    conductor_C overhead_line_conductor:500;
    conductor_N overhead_line_conductor:501;
    spacing line_spacing:120;
    }

    object line_spacing {    
          name line_spacing_15;    
          distance_AB 13 ft;   
          distance_BC 13 ft;   
          distance_AC 26 ft;   


    object triplex_line_conductor: { name triplex_4/0 AA; resistance 0.48; geometric_mean_radius 0.0158;  // I copied these values
    }

    object triplex_line_configuration:1 {
         conductor_1 triplex_4/0 AA;
         conductor_2 triplex_4/0 AA;
         conductor_N triplex_4/0 AA;
         insulation_thickness 0.08;
         diameter 0.522;
    }

    object overhead_line{
    phases "ABCN";
    configuration line_configuration:300;
    from m728;
    to 7281;
    length 2000;}

    object meter{
    name 7281;
    phases "ABC";
    nominal_voltage 4800;}

    object transformer{
    name tr1;
    phases "ABC";
    configuration transformer_configuration:75;
    from 7281;
    to no1_tr1;}

    // --------------------------House 1 //
    object triplex_line {
         name triplex_c1;
         phases ABN;
         from no1_tr1;
         to no1_tr1_c1;
         length 30;
         configuration triplex_line_configuration:1;
    }

    object triplex_meter {
         name no1_tr1_c1;
         parent no1_tr1;
         phases ABN;     // <-------- Here are the connections (correct me if I´m wrong!)
         nominal_voltage 240;
    }
    object house {
    parent no1_tr1_c1;
    object plugload {
    shape "type: analog; schedule: plugs_csd0; power: 0.55 kW";   
    };
    }
    // --------------------------House 2 //
    object triplex_line {
         name triplex_c2;
         phases BCN;   
         from no1_tr1;
         to no1_tr1_c2;
         length 15;
         configuration triplex_line_configuration:1;
    }
    object triplex_meter {
         name no1_tr1_c2;
         parent triplex_c2;
         phases BCN;                     
         nominal_voltage 240;
    }
    object house {
    parent no1_tr1_c2;
    object plugload {

    shape "type: analog; schedule: plugs_csd1; power: 0.35 kW";   
    };
    }
    // ------------------- House 3
    .. and goes until House 10 (changing the phases, the load and the lenghts… then:

    // ******************
    // Node 2

    object overhead_line{
            phases "ABCN";
            configuration line_configuration:301;
    from  no1_tr1;
            to no2_tr1;
            length 300;
    }

    // --------------------------House 11 //
    object triplex_line {
         name triplex_c11;
         phases BCN;
         from no2_tr1;
         to no2_tr1_c11;
         length 12;
         configuration triplex_line_configuration:1;
    }
    object triplex_meter {
         name no2_tr1_c11;
         parent triplex_c11;
         phases BCN;
         nominal_voltage 240;
    }
    object house {
    parent no2_tr1_c11;
    object plugload {
    shape "type: analog; schedule: plugs_csd1; power: 0.35 kW";  
    };
    }

    ….
    …and goes until node 16


    Thank you,

    Douglas

     
  • Jason Fuller

    Jason Fuller - 2012-04-26

    Douglas,

    I can immediately see a few things that jump out at me.  Please reference the example I posted above - this is the required format to work with split-phase systems.  But, here are a few things that immediately jump out:

    1) Phases on the secondary side of the transformer in the triplex or split-phase system can only contain two phases, S and {A or B or C}.  This signifies (1) it is a split-phase connection (rather than a 3-phase connection) and (2) which of the three phases it is branching off of.

    2) "transformer_configuration:75", although the configuration/connection type is not shown above, from the transformer object you've posted with phases ABC, I can only guess that this is a WYE-WYE or DELTA-WYE transformer configuration. To connect to the split-phase system, you must have a single phase center tapped configuration (see above) which specifies which phase it is branching from.

    3) You've got some very odd connections going on in the split-phase system above.  For example, in House 11, you've got the triplex line connected from no2_tr1 to no2_tr1_c11, but then no2_tr1_c11 is a child of a completely different node.  In the House 1 connection, you actually have created a small loop where the "from" node (of the triplex line) is also the "to" node due to your parent-child relationship of the triplex meter. 

    From this, I'm guessing you are using the FBS (Forward Back Sweep) method.  In our implementation, FBS is much more robust and will try to solve any system you throw at it.  The NR (Newton Raphson) method, on the other hand, is much more picky about the problem setup due to the need to invert the Jacobian.  When you run into issues of convergence, it can be helpful to switch between the two methods.  To do this:

    module powerflow {
         solver_method NR; // or FBS which is the default
    }
    

    So, I'd recommend fixing your connections to match the posted example.  If you are still having problems, try switching between the two powerflow methods - you should get different error messages if there is a topological problem.

     
  • Douglas Geraldi

    Douglas Geraldi - 2012-04-27

    Hi Jason,

    I´ve changed the circuit, starting again, using the split phase transformer, and NR method. It works, but I´m stiil with doubts about the values that I got.


    _ module powerflow {
    solver_method NR;
    };
    module residential {
    implicit_enduses LIGHTS|PLUGS;
    }
    schedule plugs_csd1 {
    * 0 * * * 0.721;
    * 1 * * * 0.55325;
    * 2 * * * 0.50125;
    * 3 * * * 0.4709;
    * 4 * * * 0.44435;
    * 5 * * * 0.92685;
    * 6 * * * 0.73115;
    * 7 * * * 0.58645;
    * 8 * * * 0.67225;
    * 9 * * *  0.7386;
    * 10 * * * 0.73295;
    * 11 * * * 1.06715;
    * 12 * * * 0.7792;
    * 13 * * * 0.71825;
    * 14 * * * 0.7095;
    * 15 * * * 0.783;
    * 16 * * * 0.8554;
    * 17 * * * 1.7443;
    * 18 * * * 2.66;
    * 19 * * * 2.23755;
    * 20 * * * 2.1369;
    * 21 * * * 1.73725;
    * 22 * * * 1.4062;
    * 23 * * * 1.05365;
    }


    object node {
          name no1;    
          phases ABC;    
    voltage_A 2400.000000-1385.640646j;
    voltage_B -2400.000000-1385.640646j;
    voltage_C 0.000000+2771.281292j;     
          nominal_voltage 4800;    
    }

    object transformer_configuration {
                name transf_config;
                connect_type SINGLE_PHASE_CENTER_TAPPED;
                primary_voltage 2401.777;
                secondary_voltage 120;
                powerA_rating 25 kVA;
                impedance 0.0033+0.022j;
    }

    object transformer {
           name tr1_A;
           phases AS;
           from no1;
           to tn1;
           configuration transf_config;
    }
    object triplex_node {
           name tn1;
           phases AS;
           nominal_voltage 120;
    }

    object triplex_line {
           phases AS;
           from tn1;
           to tm1;
           length 25 ft;
          
           configuration triplex_line_configuration:1;
    }

    object triplex_meter {
           name tm1;
           phases AS;
           nominal_voltage 120;
    }

    object house {
         parent tm1;
         object plugload {
         shape "type: analog; schedule: plugs_csd1; power: 0.55 kW";    
    };
    }
    object recorder{
         name medidor_tr1_c1;
         parent tm1;
         property measured_power, voltage_12, current_1, current_2;
         file medidas_no1_tr1_c1.csv;
         interval 900;
    limit 500; };
    _


    In this circuit, I only get zero current, and the measured_power (when plotted) sometimes goes to a huge value (and it´s not at the peak period…I wonder if this is a random peak).

    Another question is about the  module residential { implicit_enduses LIGHTS|PLUGS;} , I don´t understand why the use of LIGHT|PLUGS, and what is the function of this part.

    My intention is to install a few more houses in this transformer, and measure the voltage changes during a week.

    Thank you,

    Douglas

     
  • Jason Fuller

    Jason Fuller - 2012-04-27

    Douglas,

    By activating the implicit_enduses, you've told the house objects that they should use internal loadshapes for lights and plugs.  These are pre-built loadshapes derived from the ELCAP load study.  If you want to turn them off, use:

    module residential {
         implicit_enduses NONE;
    }
    

    By default, all of the implicit enduses are ON.

    The zero current is an odd "feature" in GLD.  Node _ objects act as current accumulators in the power flow solution methods, but don't actually have a current "measurement".  In other words, this is mathematical tool required for the solution method which gets zeroed out at the end of each iteration.  Another way to think about a current measurement on a node is how do you measure the current "going out" or "going in", especially if the system branches at that node? To measure current, you'll need to access _link objects - triplex lines, transformers, underground lines, etc. - via current_in_A, current_in_B, current_in_C or current_out_A, current_out_B, current_out_C (these equate to phases 1, 2, and N on the triplex system).

    As for the measured power having a large peak, I'm not sure what you mean by a large peak.  The load of a single home does not look like the load of a feeder.  It is a series of pulse trains that are affected by customer usage patterns, external air temperature (HVAC system), or other loads turning on and off.  With the setup you currently have, the only pulse train should be the HVAC system coming on and off at a rate determined by outdoor air temperature, thermostat setpoints, insulation values, etc.  With the default 2500 sq ft setup, these pulses should be on the order of 5-6 kW, superimposed over your analog base load of lights and plugs.

     

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