WO2019072561A1

WO2019072561A1 - Method for temporally determining switching operations in a device for inductively transmitting power and device for inductively transmitting power

Info

Publication number: WO2019072561A1
Application number: PCT/EP2018/076093
Authority: WO
Inventors: Oliver Blum; Gabriel Krein
Original assignee: Robert Bosch Gmbh
Priority date: 2017-10-10
Filing date: 2018-09-26
Publication date: 2019-04-18
Also published as: DE102017217984A1

Abstract

The invention relates to a method for temporally determining switching operations at electrical switches (T1, …, Tn) in an H-bridge switch on a secondary side (2) of a device for inductively transmitting power (E), the device for inductively transmitting power (E) comprising a transformer having a primary coil (L1) on a primary side (1) and having a secondary coil (L2) on the secondary side (2), and an alternating current being provided by the primary side (1), wherein in a method step S1 a bridge current (i2) and/or a bridge voltage (v2) at an H-bridge (H2) of the H-bridge switch on the secondary side (2) is determined, in a method step S2 an electric current (iL2) at the secondary coil (L2) is determined, the secondary coil (L2) being electrically connected to the H-bridge switch by means of the H-bridge (H2), in a method step S3 a temporal phase difference (P) between a time curve of the current (iL2) at the secondary coil (L2) and a time curve of the bridge current (i2) and/or of the bridge voltage (v2) in a calibration mode of the H-bridge (H2) is determined, and in a method step S4 switch-on and/or switch-off operations at the electrical switches (T1, …, Tn) of the H-bridge switch on the secondary side (2) are carried out, a switching operation occurring at a time point of a zero crossing (0) of the current (iL2) at the secondary coil (L2) temporally shifted by the phase difference (P). (Fig. 1)

Description

Description Title Method for timing switching in a device for inductive transmission of power and device for inductive transmission of power

The present invention relates to a method for timed switching operations in a device for inductive transmission of power and a device for inductive transmission of power.

State of the art

When inductive charging is used, the transmission of energy necessary for charging an energy storage unit takes place via an air gap. The air gap is part of a transformer and in particular the distance between the primary and secondary coil of the

Transformer. When loading electric vehicles, typically a transformer with a large air gap is used. Most of the primary coil is designed in the form of a laid on the floor under the electric vehicle panel or integrated into the street floor. The secondary coil is in

Underbody of the electric vehicle arranged and facing the loading position of the primary coil. An alternating field of the primary coil induces a corresponding current in the secondary coil. The transmittable power scales linearly with the switching frequency. Due to typically used components of the drive electronics of the transformer, losses in

Transmission path and by legal limits for electromagnetic fields, the switching frequency itself is limited, which is typically the

Switching frequency in the frequency range from 10 kHz to 150 kHz.

For inductive charging, a rectifier with an H-bridge switch is usually used on the secondary side. For the necessary for rectification modulation of switching operations at the H-bridge switch is typically synchronized to the bridge current (input current to the H-bridge), however, with distortions of the bridge current compared to an unmodulated Operation of the H-bridge may result. This distortion may make it difficult for such zero crossings of the bridge current to be applied to the

Synchronization of the switching operations of the H-bridge switch to determine which of a temporal fundamental wave of the system of the transformer on the secondary side (distorted by the resonance topology of the components on the

Secondary side). For the correct temporal modulation of the H-bridge switch a suitable reference quantity or time base is necessary. After the distortion of the bridge current, a reconstruction of the fundamental wave is typically possible only with complex procedures.

From DE 102013222227 AI is a device for inductive

Energy transfer and a method for controlling such

Device known. By means of a control, the inductive

Energy transfer between a primary circuit and a secondary circuit are regulated, wherein measuring signals of an inverter and a

Rectifier can be considered. The device for inductive energy transmission can be used in motor vehicles.

Disclosure of the invention

The present invention provides a method for scheduling switching operations according to claim 1 and an apparatus for inductive

Transmission of power according to claim 12. Preferred developments are subject of the dependent claims.

Advantages of the invention

The idea underlying the present invention is to provide an accurate time base for a device for inductive power transmission

Generate basic wave for the modulation of a H-bridge switch on the secondary side of a transformer easily and accurately. Thus, it is possible to correctly synchronize the switching operations in an H-bridge switch even with a distorted bridge current by means of the time base, wherein no time-consuming reconstruction of the time base is necessary. According to the invention, a bridge current and / or a bridge voltage at an H-bridge of the H-bridge switch is determined at a H-bridge switch on the secondary side of a transformer in a device for inductive transmission of power in a method step Sl. Furthermore, in a further method step S2, an electric current is applied to a secondary coil of the

Transformers determined, the secondary coil is electrically connected via the H-bridge with the H-bridge switch. Subsequently, in a method step S3, a temporal phase difference between a time profile of the current at the secondary coil and a time profile of the bridge current and / or the bridge voltage in a calibration mode of the

H-bridge determined. Furthermore, in a method step S4, on and / or off operations are performed on electrical switches of the H-bridge switch on the secondary side, wherein a respective switching operation takes place at a time shifted by the phase difference time of a zero crossing of the current at the secondary coil.

The determination of the phase difference in the calibration mode advantageously results in a temporal phase difference as a constant variable. If the H-bridge switch and thus the electrical switching operations are controlled (modulated) by an external signal, the advantageously always sinusoidal current at the secondary coil

(by an alternating current at the primary coil) as a time reference (timebase) for these switching operations to synchronize them correctly in time with the time base, regardless of unpredictable phase shifts of the bridge current in the modulated mode. The calibration mode corresponds to an operating mode of the H-bridge switch on the secondary side, in which the electrical switches are advantageously not actively modulated and the topology of components on the secondary side oscillates only excited by the secondary coil induced, advantageously sinusoidal, signal. In this case, the phase difference between the current at the secondary coil and the bridge current and / or the bridge voltage advantageously the

Basic oscillation of the resonant topology of the components on the

Secondary side considered (distortion also by component tolerances,

Temperature dependence or age of components). In other words, is used to synchronize the switching operations only the current to the secondary coil, wherein in a modulated operating mode, a switching operation in time by the constant phase difference after a zero crossing of the current at the Secondary coil takes place. In this way, an easily determined and correct time base for the synchronization of the switching operations on the H-bridge switch on the secondary side is advantageously obtained, which is independent of a distorted bridge current and any upsets of

Resonance topology on the secondary side. The time base thus obtained can advantageously also be used for double-sided control or synchronization of the primary side and the secondary side. The aforementioned method steps S1 to S4 are preferably carried out in the order in which S1, S2, S3, S4. The method steps S1, S2 and S3 advantageously take place in the calibration mode and then the method steps S2 and S4 in FIG

modulated mode.

According to a preferred embodiment of the method in step S3, the phase difference between a zero crossing of the time profile of the current at the secondary coil and a zero crossing of the temporal

History of the bridge current determined. The zero crossing can advantageously be detected unambiguously and is advantageously well suited as a time reference point and as an event at which a switching operation can be carried out. By means of a temporal measurement, the phase difference can be determined.

According to a preferred embodiment of the method, the phase difference between a zero crossing of the time profile of the current at the secondary coil and a zero crossing of an edge in the temporal course of the bridge voltage is determined in method step S3. A measurement of the edge, for example a step-like increase or decrease in the bridge voltage, advantageously results in a zero crossing in the calibration mode that corresponds in time to the zero crossing of the bridge current in the calibration mode. According to a preferred embodiment of the method corresponds to

Calibration mode of the H-bridge operation of the H-bridge at the

Secondary side, in which the electrical switches of the H-bridge on the secondary side are not actively modulated. According to a preferred embodiment of the method take place in

Step S4 the on and / or off operations by a

Modulation signal so that the H-bridge switch acts as a rectifier on the secondary side.

According to a preferred embodiment of the method comprises the H-bridge switch on the secondary side, as electrical switches, transistors, which with a pulsed modulation signal in the zero-current or

Zero voltage mode or in the phase shift method (phase shift method) are operated. The transistors can be switched to each other in phase shifted (phase shift method). Vorteillhaft thus operation with relatively low voltages is possible. Alternatively or additionally, the operation may be carried out in the zero-current or zero-voltage mode, wherein a switching operation takes place at a zero crossing of the current or the voltage of the modulation signal. Here are advantageously avoided at high power induction peaks and allows safe switching at high power.

According to a preferred embodiment of the method, the H-bridge switch on the secondary side comprises an LCCL topology. These are advantageously each at least one coil, in particular to the

Secondary coil, a capacitor, a capacitor and a coil, the LCCL topology is advantageously connected via the bridge with the H-bridge switch. As an alternative to the LCCL topology, the H-bridge switch can also be interconnected in other topologies of components.

According to a preferred embodiment of the method, the device for inductive transmission of power for inductive charging a

Energy storage unit used on the secondary side. This is advantageous for batteries for electric vehicles or electronic devices applicable.

According to a preferred embodiment of the method, the primary side comprises an H-bridge switch as an inverter with electrical switches which are operated with a pulsed modulation signal in the zero-current or zero-voltage mode or in the phase shift method. The

Primary side (inverter) and the secondary side (rectifier) can Advantageously be controlled by modulation signals on both sides and in each case

Zero-current (or zero-voltage mode) and / or operated in the phase shift method.

According to a preferred embodiment of the method is in the process step

52 the electric current at the secondary coil over a time interval by means of

measured by a sensor.

According to a preferred embodiment of the method is in the process step

53 determines the phase difference by means of an electronic device, in particular a computer or a control unit.

According to the invention, the device for the inductive transmission of power comprises a transformer having a primary side with a primary coil and a

Secondary side with a secondary coil, wherein the primary side is adapted to provide an alternating current to the primary coil and a H-bridge switch on the secondary side with electrical switches and an H-bridge, wherein the

Secondary coil is electrically connected via the H-bridge with the H-bridge switch, and a control unit which is adapted to perform the method steps Sl to S4.

According to a preferred embodiment, the secondary coil is over a

LCCL topology interconnected with the H-bridge of the H-bridge switch on the secondary side. As an alternative to the LCCL topology, the secondary coil can also be interconnected via other topologies of components.

According to a preferred embodiment, the secondary side comprises a

Energy storage unit, in particular a battery, and the device for inductively transmitting power is as a device for inductive

Charging the energy storage unit set up.

According to a preferred embodiment, the primary side comprises a H-bridge switch as an inverter with electrical switches. Further features and advantages of embodiments of the invention will become apparent from the following description with reference to the attached

Drawings.

Brief description of the drawings

The present invention will be explained in more detail with reference to the embodiment shown in the schematic figures of the drawings. Show it:

Fig. 1 is a schematic diagram of a device for inductive

Transmission of power according to an embodiment of the present invention;

Fig. 2 is a schematic representation of a time course of

Characteristics on the secondary side of a device of Figure 1 in a calibration mode;

Fig. 3 is a schematic representation of a time course of

Characteristics on the secondary side of a device of Figure 1 in a modulated mode; and

4 shows a schematic block diagram of method steps according to an embodiment of the method according to the invention.

In the figures, like reference numerals designate the same or functionally identical elements.

Fig. 1 shows a schematic circuit diagram of a device for inductive power transmission according to an embodiment of the present invention.

The device E has a primary side 1 and a secondary side 2 of a transformer with a primary coil LI and a secondary coil L2. Furthermore, the primary side 1 comprises an arrangement of electrical switches Τ, Τ2 ', T3' and T4 'and the secondary side 2 an arrangement of electrical Switches Tl, T2, T3 and T4, advantageously circuit breakers, which are arranged on the primary side 1 and on the secondary side 2 in each case in a H-bridge switch and which are advantageously transistors, with switched-on diodes, is. On the primary side 1, the primary coil LI is connected via an H-bridge Hl (connection between the points la and lb) to the H-

Bridge switch and on the secondary side 2, the secondary coil L2 is connected via an H-bridge H2 (connection between the points 2a and 2b) with the H-bridge switch. The secondary coil L2 can be part of an LCCL topology, comprising the secondary coil L2, a capacitor C2a, a further capacitor C2b and a coil L2a, wherein additionally further

Coils and capacitors with the H-bridge H2 or the H-bridge switch (about C2c) can be interconnected. Such an LCCL topology can also be present on the primary side 1, wherein the primary coil LI can be connected to the capacitors Cla, Clb and the coil Lla with the H-bridge Hl.

As an alternative to the LCCL topology, both on the primary side and on the

Secondary side also other topologies and interconnections of components applicable. On the primary side 1 is a DC power source lc with the H-bridge switch, which acts as an inverter connected, the

DC power source lc can be connected to a power grid.

The secondary side 2 further has a control unit SE, which according to the method according to the invention from the knowledge of the current iL2 at the secondary coil L2, the bridge current i2 and / or the bridge voltage v2 controls the switching operations on the electrical switches Tl, T2, T3 and T4 ( in Fig. 1 is only a schematic connection with the sensor M and the

Measuring points for the bridge current i2 and the bridge voltage v2 shown, wherein the control unit can pass a processed signal to the switches Tl, T2, T3 and T4). The current iL2 is in this case measured by a sensor M over time and this signal is forwarded to the control unit SE. The sensor detects, for example, the zero crossings of the current iL2. The

Control capability may itself determine bridge current i2 and / or bridge voltage v2 or additional sensors (not shown) may be present. On the secondary side 2, an energy storage unit B, for example a battery, is further shown, which can be charged inductively.

Fig. 2 shows a schematic representation of a time course of Characteristics on the secondary side of the device of FIG. 1 in one

Calibration mode.

Shown is the amplitude (I, U) of the current il_2 at the secondary coil, the bridge current i2 and the bridge voltage v2 as a function of the time t. Since the current il_2 at the secondary coil is always sinusoidal due to an alternating field from the primary coil, the time profile of the bridge current i2 follows the current il_2 such that a zero crossing 0 of the bridge current i2 always follows a constant phase difference P at a zero crossing 0 of the current il_2 , However, due to the resonance topology on the secondary side, the shape of the bridge current i2 is deformed relative to the sinusoidal shape of the current il_2. The profile of the bridge voltage v2 is similar to a pulse modulation with edges F between a maximum positive and maximum negative amplitude. A zero crossing 0 of the bridge voltage v2 on a flank F occurs in

Calibration mode at the same time as a zero crossing of the time

Bridge current i2. Thus, over a time interval T through the course of the current il_2 and the bridge current i2 and / or the bridge voltage v2 knowledge of the phase difference P can be obtained, resulting in a precise knowledge of the zero crossings of the fundamental results.

FIG. 3 shows a schematic representation of a time profile of

Characteristics on the secondary side of a device of FIG. 1 in a modulated mode of the electrical switch. It can be seen here that the bridge current i2 can have a strong distortion with respect to the sinusoidal profile of the current il_2, and that the zero crossings 0 of the current il_2 and of the bridge current i2 are not always shifted by a constant phase difference. Furthermore, the zero crossings of bridge current i2 and bridge voltage v2 do not always coincide in time. However, in order to synchronize switching operations, the current il_2, which is sinusoidal in the modulated mode of FIG. 3, can be referenced via the phase difference (FIG. 2) obtained from the calibration mode. 4 shows a schematic block diagram of method steps S1 to S4 according to an embodiment of the method according to the invention. In the upper part of FIG. 4, the method steps S1 and S2 and S3 are shown in the calibration mode. The bridge current i2 and / or the

Bridge voltage v2 are determined in method step S1, and current il_2 on the secondary coil is determined in method step S2, in particular measured, and in method step S3 the phase difference P is determined. The measured quantities can be determined by sensors and sent to the control unit or a computer for Signal processing internally in the

Device be passed. As shown in the lower part of FIG. 4, in a modulated mode, the electrical switches on the

Secondary side in step S4 the switching on and / or off according to the procedure timed and performed, after in

Step S2 of the time course of the current il_2 was determined (now in the modulated mode). By knowing the phase difference P from the

Calibration mode can now, advantageously by a control unit or by a computer, be referenced in time to the current il_2.

Although the present invention is based on the preferred

Embodiment has been fully described above, it is not limited thereto, but modifiable in a variety of ways.

Claims

claims

1. A method for timing switching operations on electrical switches (Tl, Tn) in a H-bridge switch on a secondary side (2) of a device for inductive transmission of power (E), wherein the device for inductive

Transmission of power (E) comprising a transformer having a primary coil (LI) on a primary side (1) and a secondary coil (L2) on the secondary side (2) and an alternating current provided by the primary side (l), comprising the steps of:

51) determining a bridge current (i2) and / or a bridge voltage (v2) at an H-bridge (H2) of the H-bridge switch on the secondary side (2);

52) determining an electrical current (iL2) at the secondary coil (L2), wherein the secondary coil (L2) is electrically connected to the H-bridge switch via the H-bridge (H2);

53) determining a temporal phase difference (P) between a time profile of the current (iL2) at the secondary coil (L2) and a time profile of the

Bridge current (i2) and / or the bridge voltage (v2) in a calibration mode of the H-bridge (H2); and

54) carrying out on and / or off operations on the electrical switches (Tl, Tn) of the H-bridge switch on the secondary side (2), wherein a respective switching operation at a time by the phase difference (P) shifted time of a zero crossing (0) of the current (iL2) takes place at the secondary coil (L2).

2. The method of claim 1, wherein in step S3, the phase difference (P) between a zero crossing (0) of the time course of the current (iL2) at the secondary coil (L2) and a zero crossing (0) of the time course of

Bridge current (i2) is determined.

3. The method of claim 1, wherein in step S3, the phase difference (P) between a zero crossing (0) of the time course of the current (iL2) at the secondary coil (L2) and a zero crossing (0) of an edge (F) in temporal History of the bridge voltage (v2) is determined.

4. Method according to one of the preceding claims, in which, in method step S3, the calibration mode of the H-bridge (H2) corresponds to an operation of the H-bridge (H2) on the secondary side (2), in which the electrical switches (T1, Tn) the H- Bridge (H2) on the secondary side (2) are not actively modulated.

5. The method according to any one of the preceding claims, wherein in the step S4, the on and / or off operations by a modulation signal carried out so that the H-bridge switch on the secondary side (2) acts as a rectifier.

6. The method of claim 5, wherein the H-bridge switch on the secondary side (2), as electrical switches (Tl, Tn), comprises transistors, which with a pulsed modulation signal in the zero-current or zero-voltage mode or in

Phase shift method can be operated.

7. The method according to any one of the preceding claims, wherein the H-bridge switch on the secondary side (2) comprises an LCCL topology.

8. The method according to any one of the preceding claims, wherein the device for inductive transmission of power (E) for inductive charging a

Energy storage unit (B) on the secondary side (2) is used.

9. The method according to any one of the preceding claims, wherein in step S1, the primary side (1) comprises a H-bridge switch as an inverter with electrical switches (ΤΙ ', ..., Τη'), which with a pulsed modulation signal in zero current or Zero voltage mode or in the phase shift method (phase shift method) are operated.

10. The method according to any one of the preceding claims, wherein in

Process step S2, the electric current (iL2) at the secondary coil (L2) over a time interval (T) by means of a sensor (M) is measured.

11. The method according to any one of the preceding claims, wherein in

Step S3, the phase difference (P) by means of an electronic device, in particular a computer or a control unit (SE), is determined.

12. Device for inductive transmission of power (E) comprising

- A transformer having a primary side (1) with a primary coil (LI) and a secondary side (2) with a secondary coil (L2), wherein the primary side (1) thereto is arranged to provide an alternating current to the primary coil (LI); and

a H bridge switch on the secondary side (2) with electrical switches (T1,

Tn) and an H-bridge (H2), wherein the secondary coil (L2) via the H-bridge (H2) is electrically connected to the H-bridge switch, and

a control unit (SE), which is set up

to determine a bridge current (i2) and / or a bridge voltage (v2) at the H-bridge (H2) of the H-bridge switch on the secondary side (2) and an electrical current (il_2) at the secondary coil (L2),

- A temporal phase difference (P) between a time course of the current (il_2) at the secondary coil (L2) and a time course of the bridge current (i2) and / or the bridge voltage (v2) in a calibration mode of the H-bridge (H2) determine, and

- perform on and / or off operations on the electrical switches (Tl, Tn) of the H-bridge switch on the secondary side (2), wherein a respective switching operation on an electrical switch (Tl, Tn) at a time by the phase difference (P) shifted time of a zero crossing (0) of the current (il_2) takes place at the secondary coil (L2).

13. Device (E) according to claim 12, in which the secondary coil (L2) is connected via an LCCL topology to the H-bridge (H2) of the H-bridge switch on the secondary side (2).

14. Device (E) according to one of claims 12 or 13, wherein the

Secondary side (2) comprises an energy storage unit (B), in particular a battery, and the device (E) as a device for inductive charging of

Energy storage unit (B) is set up.

15. Device (E) according to one of claims 12 to 14, wherein the primary side (1) comprises an H-bridge switch as an inverter with electrical switches (ΤΙ ', ..., Τη').