Working with Equation System

1. Click the Calculation Order button order on the Calculation ribbon tab. The Calculation Order dialog box opens.

2. Click the Add button.

3. Select the Equation System item in the menu that opens. An empty system is added after the selected element.

4. Drag the required equations to the system.

The selected equations will be combined to an equation system.

NOTE. When changing type of equations included into the system, take into account the features described in the Change Equation Type section.

1. Click the Calculation Order button order on the Calculation ribbon tab. The Calculation Order dialog box opens.

2. Drag all equations out of the system.

3. Select the equation system.

4. Click the Delete button.

The equation system is deleted from the model.

1. Click the Calculation Order button order on the Calculation ribbon tab. The Calculation Order dialog box opens.

2. Select the equation system.

3. Click the Equation System Parameters button.

Select the method of solving equation system:

• Hybrid Method. The source system is solved by using modification of the hybrid algorithm implemented in the MINPACK-1 library of mathematical methods.

• Minimum of Errors. It finds minimum of a function having N variables.

• Newton Method. The source system is solved by using iterations with finding of partial derivatives. It is required to set additional parameters of the method.

If the Newton method is selected to solve the equation system, set parameters of the method:

• Increment of Argument. Specify percent of argument increment on calculating partial derivatives. Default value is 0.00100%. Minimum valid value: 0.00001%.

• Method of Calculating Approximations. Specify the method of calculating the following approximation to solve a linearized equation system. This system must be calculated when the system of non-linear equations is solved using the Newton method. The available methods:

• Inverse of Matrix. The following approximation is calculated using an inverse of matrix. The obtained solution is more reliable.

• Gauss Method. The following approximation is calculated by the Gaussian elimination that gradually reduces the system order and excludes unknowns. The solution is found quicker.

• Calculate Jacobian after each N Iterations. It determines the frequency of Jacobian calculation on solving a system of non-linear equations. The default value is one, that is, Jacobian is calculated at each iteration. The greater is the value of this property, the more rarely Jacobian is calculated, and the faster the equation system is solved.

Set initial values of output variables. The Initial Values group contains radio buttons that determine the mode of setting initial values and the table that shows initial values.

Available modes:

• Find Automatically. Default. Initial values are determined automatically. The last point of sample period is taken as the initial value of the output variable.

• Specify Manually. Initial values are determined by entering values in the table.

In the Accuracy of Solution box specify accuracy of solution of the equation system. Default value: 0.000001.

In the Maximum Number of Iterations box specify maximum number of iterations to solve the equation system. The default value: 1000.