Engee documentation

The start of electrical models from the steady-state sinusoidal mode

Introduction

Option Start simulation from steady state in the block Solver Configuration allows initialization in such a way that models of electrical networks are started from a steady sinusoidal mode. Depending on the composition of the circuit, one of two initialization algorithms is used.:

  1. Basic — if the model has at least one sinusoidal electrical source;

  2. Advanced — if there is at least one block in the circuit Load Flow Source or one synchronous machine. This option takes into account the target values for power and/or voltage.

Requirements for the model to start from steady state

The model should contain only blocks:

  1. Described by linear systems of equations, for example:

    1. 1. Voltage/current sources;

    1. 2. Linear branch magnetization transformers;

    1. 3. RLC assemblies, including loads;

    1. 4. Power transmission lines;

  2. Switches;

  3. Short circuits;

  4. Synchronous machines:

    1. 1. Synchronous Machine Model 2.1;

    1. 2. Synchronous Machine Round Rotor;

    1. 3. Synchronous Machine Salient Pole;

    1. 4. Simplified Synchronous Machine.

Limitations of algorithms

The limitations for each algorithm are shown in Table 1. If the model is not supported, initialization will be started without trying to find the steady state, or an error will occur.

Table 1 — Limitations of algorithms_

Blocks or modes in the model

Algorithm

Basic

Advanced

Sources of the constant component

Supported

Not supported

Sinusoidal sources of different frequencies

Supported

Not supported

Blocks described by nonlinear characteristics (nonlinear inductors and transformers, semiconductors)

Not supported

Not supported

Synchronous machines

Not supported

Supported (4 blocks)

Asynchronous machines

Not supported

Not supported

Unbalanced modes

Supported

Not supported

Basic initialization algorithm

The basic option involves finding the initial values of variables by solving a linear system of equations. The priorities of sinusoidal physical variables are not taken into account (they are assumed to be equal None).

Advanced initialization algorithm

The advanced version involves finding the initial values of variables by solving a nonlinear system of equations, where the block equations are nonlinear Load Flow Source and synchronous machines for variables , , , . These variables have target values set by the user. The priorities of sinusoidal physical variables are not taken into account (they are assumed to be equal None).

An advanced initialization algorithm is used for calculation of flow distribution in three-phase electric networks.

Problem solving

  1. If initialization does not work, then you can change its settings (in the group Initialization the block Solver Configuration), for example:

    • Reduce the initialization accuracy by increasing the value Tolerance. A reasonable value is no more than 1e−2;

    • Switch to the Newton method by setting the parameter Nonlinear solver, equal to NLSolveJL(method=:newton).

  2. Recommendations for using the block Load Flow Source examples of synchronous machines are given in the section Fixing the problems of flow distribution calculation and initialization.