# SIMBA 2021.10

Welcome to *SIMBA 2021.10*! This major release brings major changes including **improved solver**, **AC Sweep** and the new **Stop at Steady State** option.

If you haven’t yet, be sure to **download it**.

## Improved Solver

The solver is now about **10x more accurate** with even **faster simulation**.

The maximum relative tolerance of the integration error is now set to 10E-7 instead of 10E-6 previously and this computational overhead is more than compensated by improvements and optimizations of the solver engine.

## AC Sweep

A new test bench is available: **AC Sweep**. It uses the steady-state algorithm to calculate the transfer function of a periodic system at different user-defined frequencies. More information here.

## Stop At Steady-State

When *Stop at Steady-State* is enabled, the *End Time* parameter is not used, and the simulation stops when SIMBA detects the steady state.

This feature is particularly useful during a parametric analysis because each run can have different time constants and the *Stop at Steady-State* feature ensures that each run will stop at its steady state. To determine if the steady state is reached, SIMBA analyzes the RMS value and the highest non-DC harmonics (if any) of all simulated state variables.

## Library Explorer

A new search option is added to the Library tab to quickly search and find your models.

## New PWM Generator and Switch with Threshold models

Two new models are added to the library:

## New Dual Active Bridge Example

This example shows a Dual Active Bridge converter with:

- an input voltage of 95 V,
- an output voltage of 380 V,
- an output power of 1 kW.

### PWM control

Each bridge with a duty cycle of 50%. The phase-shift between the two bridges is set by the discrete controller (PI regulator) in order to regulate the output voltage.

### Power semiconductor switches

Mosfets of this example are set with conduction parameters: a first R{on} resistance for the channel conduction mechanism (forward and reverse conduction when the transistor's gate id driven high) and a second R_{on} resistance and a V_f drop voltage for the body diode.

*Note* : with the command used in this example, mosfets are always used in *synchronous rectification mode* which means that the controlled conduction mechanism (channel) is the major contributor for conducting the reverse current compared to the body diode conduction.

### Transformer ratio

The transformer ratio can be chosen according required values of primary and secondary voltages. Here a secondary voltage of 380V is required and a primary voltage of 95V is considered to be the lowest possible value (worst case), which leads to a transformer ratio of 4.

### Inductor design

The expression below gives the maximum power which can be transferred for a phase-shift angle of \pi / 2 [1]:

with m = \frac{V_2}{V_1}, the transformer ratio.

A maximum power of 2 kW and a margin of 10 % si considered. At a switching frequency of 250 kHz, with V_1 = 95V and V_2 = 380V, this leads to a maximun inductor value of 2.051 \mu H.

This value is compatible with typical values of leakage inductors of high-frequency transformers with these levels of power, voltages and ratio.

[1] M. Blanc, Y. Lembeye, J.P. Ferrieux, Dual Active Bridge (DAB) pour la conversion continu-continu, Techniques de l'ingénieur E3975, 2019.

## Quality of life

In *2021.10*, several bugs are corrected and the general stability of SIMBA is improved. The complete list of changes is available here.

## Roadmap

If you are interested, you can check our roadmap and a public GitHub project is available to share ideas, report bugs, and suggest new features.