MATLAB: Does the model created following the documentation not behave correctly in SimPowerSystems 5.3 (R2010b)

Simscape Electrical

I am following the section titled 'Building and Simulating the PWM Motor Drive' in the documentation and creating a model. I made sure all the parameters are specified as shown in the documentation. However the results are unexpected.

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This change has been incorporated into the documentation in Release 2011b (R2011b). For previous releases, read below for any additional information:

This is an error within the documentation for SimPowerSystems 5.3 (R2010b) in the section 'Building and Simulating the PWM Motor Drive'.

While the instructions in the documentation would work in the previous releases (For example R2007b), it will not work in the latest release since the default values have been changed for the 'Asynchronous Machine SI Units' block. If you change the following parameters, it will give the same result as that of what is captured in the documentation:

 Stator resistance and inductance[ Rs(ohm)  Lls(H) ] : [1.115 0.005974]
 Rotor resistance and inductance [ Rr'(ohm)  Llr'(H) ] : [1.083 0.005974]
 Mutual inductance Lm (H) : 0.2037
 Inertia, friction factor, pole pairs : [ J(kg.m^2)  F(N.m.s)   p() ]: [ 0.02 0.005752  2 ]

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MATLAB: What algorithm is used to calculate the Transformation Ratio in the Synchronous machine block in SimPowerSystems

This change has been incorporated into the documentation in Release 2011a (R2011a). For previous releases, read below for any additional information:

The transformation ratio (TR) in the Synchronous machine block can be calculated employing the value of the nominal field current as follow:

        TR = (2/3)*(Inom_field/Ibase_stator) .............................(1)

where,

        'Inom_field' is the nominal field current (in the rotor field) 
        'Ibase_stator' is the stator base current.

The stator base current can be expressed as follows:

         Ibase_stator = sqrt(2/3)*(Pbase/Vbase)

where,

         'Pbase' is the base power
         'Vbase' is the base voltage

Please note that the transformation ratio calculated above is the same as given by the following equation:

          TR = (2/3)*(Nf/Ns).............................(2)

where,

         'Nf' is the number of field winding turns
         'Ns' is the number of stator winding turns

Although the latter expression (2) is more common in literature, the two expressions may be shown to be equal empirically.

MATLAB: Is there an error in the example script in the “Constructing SISO models” entry in the documentation for Control System Toolbox 6.1 (R14SP1)

This bug has been fixed in Release 14 Service Pack 2 (R14SP2). For previous releases, please read below for any possible workarounds:

This has been verified as an error within the documentation for Control System Toolbox 6.1 (R14SP1) within the Constructing SISO Models section. The documentation should read as follows:

 R= 2.0 % Ohms
 L= 0.5 % Henrys
 Km = .015 % torque constant
 Kb = .015 % emf constant
 Kf = 0.2 % Nms
 J= 0.02 % kg.m^2

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Related Solutions

MATLAB: What algorithm is used to calculate the Transformation Ratio in the Synchronous machine block in SimPowerSystems

MATLAB: Is there an error in the example script in the “Constructing SISO models” entry in the documentation for Control System Toolbox 6.1 (R14SP1)

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