DE102022201511B4 - Method for controlling power semiconductors of an inverter, computer program, device for data processing, inverter, electric drive and vehicle - Google Patents

Abstract

What is proposed is a method for controlling power semiconductors of an inverter with at least one phase, each having at least one high-side switch and one low-side switch per phase, characterized in that the resulting voltage is detected during the dead time when switching between two switches of a phase, and If the detected voltage corresponds to a specified target voltage, both switches remain switched off.

Description

The present invention relates to the field of electromobility, in particular to electronic modules for an electric drive.

The use of electronic modules, such as power electronics modules, in motor vehicles has increased significantly in recent decades. This is due on the one hand to the need to improve fuel economy and vehicle performance and on the other hand to advances in semiconductor technology. The main component of such an electronic module is a DC/AC inverter, which is used to power electrical machines such as electric motors or generators with multi-phase alternating current (AC). A direct current generated from a DC energy source, such as a battery, is converted into a multi-phase alternating current. For this purpose, the inverters include a variety of electronic components with which bridge circuits (such as half bridges) are implemented, for example semiconductor power switches, which are also referred to as power semiconductors.

A common method for increasing the performance of inverters is to connect power semiconductors in parallel, e.g. SiC MOSFET, IGBT and parallel-connected freewheeling diode (also known as anti-parallel silicon diode). Before the conductive switch can be changed from the high side to the low side or low side to the high side, a time is required in which both switches are switched off, the so-called dead time. This time is necessary because the semiconductor (the semiconductor component) needs a certain time to switch to the off state and depends on the semiconductor used. Only after the dead time can the opposite switch be switched on again. During this dead time, the current is impressed through the motor winding.

In electrical drive systems, converters, especially pulse inverters, are used to adjust and regulate the power and torque.

Modulation methods such as carrier-based pulse width modulation (with and without imprinting a third harmonic) or space vector modulation methods are used as standard. In this case, the EMC and efficiency properties are primarily determined by the switching frequency of the converter (also called inverter), which is between 8kHz and 10kHz in typical electrical drive systems.

In modern electric drive systems, electromagnetic compatibility (EMC) and efficiency are playing an increasingly important role. For drives powered by converters/inverters, increasingly strict requirements for EMC, acoustics and efficiency must be met.

• - Änderung des Maschinendesigns: Das elektromagnetische Design wird dahingehend optimiert, dass mit weniger Strom gleiches Moment gestellt werden kann.
• - Änderungen der Software/Ansteuerung: Einsatz von Spread Spectrum Methoden. Durch geeignete Anpassung des Modulationsverfahrens werden die spektralen Anteile, die typischerweise bei Vielfachen der Schaltfrequenz maximal sind, reduziert. Durch diese Reduzierung wird das akustische und elektromagnetische Verhalten optimiert.
• - Einsatz von Filtern: Leitungsgebundene Störungen können durch Hardware-Filterkomponenten reduziert werden.
• - Gehäusedesign: Geeignetes Gehäusematerial und Gehäusedesign ermöglicht die Abschirmung von Störstrahlung oder reduziert akustische Auffälligkeiten.

Some measures have already been proposed to help improve the above-mentioned properties. Examples include:

• - Change in the machine design: The electromagnetic design is optimized so that the same torque can be achieved with less current.
• - Changes to the software/control: Use of spread spectrum methods. By appropriately adapting the modulation method, the spectral components, which are typically maximum at multiples of the switching frequency, are reduced. This reduction optimizes the acoustic and electromagnetic behavior.
• - Use of filters: Wired interference can be reduced using hardware filter components.
• - Housing design: Suitable housing material and housing design enables the shielding of interference radiation or reduces acoustic abnormalities.

Methods for controlling power semiconductors are known from the prior art. From the DE 298 15 331 U1 For example, a method for suspending the clocking of switching processes of power semiconductors is known. This is used in particular when idling without torque and is intended to enable a lower operational load on the battery. Furthermore, a limit for the battery voltage in recuperation mode is taken into account.

However, due to the cost-relevant or resource-intensive solution approaches, not all desirable measures can be implemented.

The invention is therefore based on the object of providing a method for controlling power semiconductors of an inverter, which provides a further improvement in terms of electromagnetic compatibility (EMC) and switching losses.

This task is solved by the features of the independent claims. Advantageous refinements are the subject of the dependent claims.

What is proposed is a method for controlling power semiconductors of an inverter with at least one phase, each having at least one high-side switch and one low-side switch per phase, characterized in that the resulting voltage is detected during the dead time when switching between two switches of a phase, and If the detected voltage corresponds to a specified target voltage, both switches remain switched off.

During the dead time, both switches in a phase are closed. If the target voltage is already present during this time, switching-on losses and/or EMC interference signals can be minimized by omitting switching operations between the switches, which output a predetermined target voltage based on the current sign without switching on the other switch.

Furthermore, a computer program is proposed, comprising commands which, when the program is executed by a computer, cause it to carry out the method described.

Furthermore, a device for data processing is proposed, comprising means for carrying out the method described.

Furthermore, an inverter with at least one phase is proposed, each having at least one high-side switch and one low-side switch as well as the device for data processing. In one embodiment, the inverter has three phases.

Furthermore, an electric drive of a vehicle is provided, comprising an electronic module for controlling the electric drive, which has an inverter as described. An electric drive vehicle will also be provided.

Further features and advantages of the invention result from the following description of exemplary embodiments of the invention, based on the figures of the drawing, which show details of the invention, and from the claims. The individual features can be implemented individually or in groups in any combination in a variant of the invention.

• 1 zeigt eine für eine Drehfeldmaschine M benötigten Ansteuerschaltung gemäß dem Stand der Technik.
• 2 zeigt ein Raumzeigerdiagramm mit Spannungsvektor zur Ansteuerung eines elektrischen Antriebs gemäß dem Stand der Technik.
• 3 zeigt einen Umschaltvorgang von einem Lowside- zu einem Highside-Schalter in einer Phase gemäß dem Stand der Technik.

Preferred embodiments of the invention are explained in more detail below with reference to the accompanying drawing.

• 1 shows a control circuit required for an induction machine M according to the prior art.
• 2 shows a space vector diagram with a voltage vector for controlling an electric drive according to the prior art.
• 3 shows a switching process from a lowside to a highside switch in a phase according to the prior art.

In the following descriptions of the figures, the same elements or functions are given the same reference numbers.

As already mentioned at the beginning, one goal of controlling power semiconductors in an inverter in the automotive sector is to comply as closely as possible with the current requirements for EMC, acoustics and efficiency. As already mentioned with reference to the prior art, this can be achieved to a certain extent through various measures such as adapting the hardware and/or software. But there is further potential for optimization.

The invention is described below using an embodiment in which there are three phases, each with a high-side switch 1 and a low-side switch 2, since this is the most common application. However, a different number of phases can also be provided, since the principle of control does not change.

The basic principle of the proposed method is that switching operations between switches 1 and 2 are omitted, which output a predetermined target voltage based on the current sign without switching on the other switch 1 or 2.

The switches 1 and 2 can be formed, for example, as IGBT, although other semiconductor switches can also be used to implement the method.

During the dead time t_tot, which must be maintained between two switching operations of opposite switches (highside 1 and lowside 2), the current is impressed through the motor winding and a voltage is established which corresponds to either the original voltage or the target voltage resulting from the switching should be achieved. If the target voltage is already present, it is no longer necessary to switch to the other switch 1 or 2. Switching could even produce negative effects such as switch-on losses or EMC interference signals.

Therefore, according to the invention, the standard pulse patterns that are generated from one of the above-mentioned modulation methods (e.g. PWM or space vector) are manipulated so that individual Switching operations are omitted. Since only those switching processes are omitted where the target voltage is already present, the control is not negatively influenced by the control. Only information about the current and future switching status and the sign of the current are relevant for the application. The process can also be carried out in the PWM driver. It is advantageously implemented as software for this purpose.

The principle of control is described below using the figures. In 1 A schematic view of a control circuit required for an induction machine M is shown. Three phases are shown here, each of which is controlled by a half bridge, each comprising a highside 1 switch and a lowside 2 switch. U_DC is the supply voltage.

The voltage (vector V) is as in the space vector diagram in 2 shown, in the first sector, the switching pointers shown below are set as standard, whereby the duty cycles (ratio of pulse duration/switch-on time to period duration) are determined by using common modulation methods.

In the standard case, the resulting switching pattern would be as follows: 000 -> 100 -> 110 -> 111 -> 110 -> 100 -> 000, where “000” means that all lowside 2 switches of the three phases are switched on and the associated highside 1 Switches are switched off, and “111” means that all highside 1 switches of the three phases are switched on and the corresponding lowside 2 switches are switched off.

If you now look at the switching behavior in one phase as an example and take the sign of the phase current into account, individual switching pulses can be omitted without negatively influencing the voltage output and regulation.

• - Fall 1: Im Bereich der Totzeit t_tot (beide Schalter 1, 2 aus) liegt die Zielspannung an. Beispiel: 11x entspricht 111
• - Fall 2: Im Bereich der Totzeit t_tot (beide Schalter 1, 2 aus) liegt die Ursprungsspannung an. Beispiel: 11x entspricht 110

3 shows an example of the switchover in a phase, for example the switchover from the switching state 110 to the switching state 111. The dead time t_tot to be maintained during the switchover is also in 2 drawn. There are two cases for the voltage on the relevant phase, which can be determined by the phase current sign:

• - Case 1: The target voltage is present in the dead time range t_tot (both switches 1, 2 off). Example: 11x equals 111
• - Case 2: The original voltage is present in the dead time range t_tot (both switches 1, 2 off). Example: 11x equals 110

• - Einschaltverluste reduziert werden.
• - Die EMV Störaussendung aufgrund einer Reduzierung der Schaltflanken reduziert wird.

The behavior described can now be used to specifically omit those switching states/switching actions that output the target voltage based on the current sign without switching on the respective highside 1 or lowside 2 switch. This omission of individual switching actions results in the effective switching frequency of the system being reduced and thus:

• - Switch-on losses are reduced.
• - The EMC interference emission is reduced due to a reduction in the switching edges.

The measure can be used in the entire control range of the inverter. Due to the fact that the target voltage is set at any time, no change to the controller is necessary. The change can only be implemented in the PWM driver.

The process described above can be combined with further measures to improve the efficiency and EMC properties, which can lead to further improvements overall. Other measures include, for example, varying the switching frequency, randomly shifting the switching edges or hardware measures.

The proposed control method makes it possible to achieve a highly efficient inverter, which is used, for example, as a drive converter or traction converter, in which the switching losses when switching from one active switch to another active switch (high-side to low-side or vice versa) are reduced and EMC properties can be improved. The inverter can be used in an electronic module to control the electric drive of a vehicle equipped with an electric drive. Electrified axles can also be powered by the electric drive.

An electronic module within the scope of this invention is used to operate an electric drive of a vehicle, in particular an electric vehicle and/or a hybrid vehicle, and/or electrified axles. The electronic module includes a DC/AC inverter. It may also include an AC/DC rectifier, a DC/DC converter, a transformer, and/or another electrical converter or part of one include or be a part of such a converter. In particular, the electronic module is used to power an electric machine, for example an electric motor and/or a generator. A DC/AC inverter is preferably used to convert one using a DC voltage Energy source, such as a battery, produces direct current to produce a multi-phase alternating current.

Inverters for electric drives of vehicles, especially cars and commercial vehicles, as well as buses, are designed for the high-voltage range and are designed in particular in a reverse voltage class of approximately 650 volts.

Reference symbol list

1

Highside switch

2

Lowside switch

M

Induction machine

U_DC

Supply voltage

T_dead

dead time

v

vector

Claims (8)

Method for controlling power semiconductors of an inverter with at least one phase, each having at least one high-side (1) switch and one low-side (2) switch per phase, characterized in that in the dead time (t_tot) when switching between the switches (1, 2) The resulting voltage is detected in a phase, and if the detected voltage corresponds to a predetermined target voltage, both switches (1, 2) remain switched off. Computer program, comprising commands which, when the program is executed by a computer, cause it to follow the method Claim 1 to carry out. Device for data processing, comprising means for carrying out the method according to Claim 1 . Device according to Claim 3 , which is designed as a PWM driver. Inverter with at least one phase, each having at least one highside (1) switch and one lowside (2) switch and a device according to Claim 4 . Inverter after Claim 5 , having three phases. Electric drive of a vehicle, comprising an electronic module for controlling the electric drive, which has an inverter Claim 6 having. Vehicle having an electric drive Claim 7 .

Images