12. Glossary

voltage source

A voltage source designates a dipole with zero internal impedance, i.e. an ideal voltage source.

Therefore, it imposes the voltage across its terminals independently of the current flowing through it. The voltage which it imposes may be continuous or alternating, it may even be square and present discontinuities. What matters is that the voltage across its terminals is independent of the external circuit and of the current it flows.

The impedance of a capacitor tends to zero when the frequency tends to infinity. It is then said, by extension, that a capacitor is a source of instantaneous voltage, which means that the voltage at its terminals cannot vary instantaneously.

current source

A current source is a dipole which has an infinite impedance, which is also the basis of the symbol “ideal current source” (DIN):

Consequently, it imposes the current circulating through it independently of the voltage applied across it. The current it imposes may be continuous or alternating, it may be so square and present discontinuities. What is important is that the current is independent of the external circuit or the voltage applied across its terminals.

The impedance of an inductance tends to infinity when the frequency tends to infinity. It is then said, by extension, that an inductor is a source of instantaneous current, which means that the current through it cannot vary instantaneously.

switch

A switch is an electric dipole which ideally has:

• a conducting state (ON) in which the dipole can be assimilated to a short circuit (V = 0),

• a blocked state (OFF) in which the dipole can be assimilated to an open circuit (I = 0),

• the ability to switch instantly from one state to the other.

In power electronics, the switches are often realized by associating several power semiconductor devices.

switching frequency

The switching frequency is the number of “on-off” cycles per second of a switch. In circuits with several switching cells, the chopping signals may be a combination of the chopping of several cells but in this documentation, the switching frequency is always defined with respect to a switch. In general, all switches in a given circuit switch at the same frequency, so we will often use ‘switching frequency’ without referring to a particular ‘switch’.

semiconductor

In this document, semiconductor implicitly denotes a ‘power semiconductor’, ie a semiconductor device such as it behaves as close as possible to an ideal switch. In our design environment, the term ‘semiconductor’ designates a device sold as one reference: it may be a discrete component (generally a single chip in a case), or a power module (generally a combination of several chips in a single case). It is marketed with a datasheet and is identified as an elementary component in our database.

switching cell

An elementary switching cell is made up of a pair of switches arranged to chop a DC voltage into a pulse train comprising 2 voltage levels: zero and the DC voltage. For more information, see Switching cell.

flying capacitor cell

A flying capacitor cell is a series association of elementary switching cells using flying capacitors. For more information, see Macro switching cell.

macrocell

A macrocell (short for ‘macro switching cell’) is a series / parallel association of elementary switching cells able to chop a DC voltage into a waveform with different voltage levels. It forms the basis of a multilevel converter. For more information, see Macro switching cell.

apparent frequency

Frequency of the square signal obtained by the sum of individual square signals of frequency f. If these individual square signals are correctly shifted (\(\dfrac{2 \cdot \pi}{N}\), N=number of signals). The apparent frequency will be 2f.

target and effective

The “target” fields are user-specified inputs (via the multi-parameter sweep) used to initialize the design. The “effective” fields represent the values adjusted by the solver as necessary. Some examples can be found in the following table:

Target	Effective
For 3-phase DC/AC conversion stages with electrical machine, the target speed is imposed by the user.	The resulting AC frequency \(f_{0}\) is rounded due to solver requirements. The effective speed is the real operating speed of the machine and can be slightly different to the target speed.