Engee documentation

Start of electric models from the steady-state sinusoidal mode

Introduction

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

  1. Basic — if there is at least one sinusoidal electrical source in the model;

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

Requirements for the model to start from steady-state mode

The model should contain only blocks:

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

    1. 1. Voltage/current sources;

    1. 2. Transformers with linear magnetization branch;

    1. 3. RLC assemblies, including loads;

    1. 4. Power lines;

  2. Switches;

  3. Short circuits.

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 mode, or an error will occur.

Table 1 — Limitations of algorithms_

Blocks or modes in the model

The 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

Blocks described by nonlinear systems of equations (synchronous and asynchronous machines)

Not supported

Not supported

Asymmetric modes

Supported

Not supported

Basic initialization algorithm

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

Advanced initialization algorithm

An advanced option involves finding the initial values of variables by solving a nonlinear system of equations, where the equations of the Load Flow Source blocks for variables are nonlinear , , , . These variables have target values set by the user. Priorities of sinusoidal physical variables are not taken into account (assumed to be equal None).

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

Problem solving

  1. If initialization fails, you can change its settings (in the Initialization group of the Solver Configuration block), for example:

    • Reduce the initialization accuracy by increasing the Tolerance value. Reasonable value - no more 1e-2;

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