Simulink Power Library custom block multi switch

Hello,

I'm trying to build a multi switch which connects several terminals. Therefore I'm building a custom block. The model where the switch is to be integrated is build with the Power Library. First I tried to build a simple switch. But this isn't as simple as it sounds... The first big problem is: When I declare the nodes like this:

nodes
      U0 = foundation.electrical.electrical; % +:top
      U1 = foundation.electrical.electrical; % -:bottom
  end

then I cant connect the custom block with components of the Power Library. I havent found anything about the domain of these components. Any suggestions here?

The second problem is, that I have no clue how to make the current go through (in closed position of the switch). First I delcared variable i as a through variable.

    branches
        i : U0.i -> U1.i; % Through variable i from node p to node n
    end

But then it's getting tricky. Because something like

equations        
       U0.i == U1.i;
  end

is not working, I declared a very small resistance and calculated the voltage across the terminals

equations
        v == U0.v-U1.v;
        i == (v)/R; 
end

But this isn't working. Does anyone know how to make a nice switch?

I'm looking forward to your answer

PS: Here is the whole custom block code

component switch1
% switch

      nodes
          U0 = foundation.electrical.electrical; % +:top
          U1 = foundation.electrical.electrical; % -:bottom
      end

      parameters
          R = { 1e-10, 'Ohm' };
      end

      variables
          i = { 0, 'A'   }; % Current
          v = {value = { 0, 'V' }, priority = priority.high}; % Voltage drop

      end

      function setup

      end

      branches
          i : U0.i -> U1.i; % Through variable i from node p to node n
      end

      equations
          v == U0.v-U1.v;
          i == (v)/R;
      end

end

Answer 1

[Joel Van Sickel]

Here is the code which is available from the switch block in simscape foundations:

component controlled_switch
% Switch
% The block represents a switch controlled by an external physical
% signal. If the external physical signal PS is greater than the threshold,
% then the switch is closed, otherwise the switch is open.
%
% The closed resistance is defined by parameter R_closed, and the open
% conductance is defined by parameter G_open. Both parameters must be
% greater than zero.

% Copyright 2005-2018 The MathWorks, Inc.

inputs
    vT = { 0.0, '1' }; % PS:bottom
end

nodes
    p = foundation.electrical.electrical; % :top
    n = foundation.electrical.electrical; % :bottom
end

parameters
    R_closed = { 0.01, 'Ohm' };   % Closed resistance R_closed
    G_open   = { 1e-8, '1/Ohm' }; % Open conductance G_open
    Threshold = { 0.5, '1' };     % Threshold
end

variables
    i = { 0, 'A' }; % Current
    v = { 0, 'V' }; % Voltage
end

branches
    i : p.i -> n.i;
end

equations
    assert(R_closed>0)
    assert(G_open>0)
    v == p.v - n.v;
    if vT > Threshold % Switch is closed
        v == i*R_closed;
    else              % Switch is open
        v == i/G_open;
    end
end

end

Regards,

Joel