KR101908731B1 - Converter for an electrical circuit designed to supply electrical propulsion power on board a motor vehicle - Google Patents

Abstract

The present invention relates to an electric circuit (900, 900 ') mounted on a motor vehicle and designed to provide an electric driving force. The electric driving force is derived from the electric power transmitted to the electric circuit 900, 900 'by the battery of the vehicle and converted by at least two cells 901, 903; 901', 903 ' 904 ', 902', and 904 ', respectively. The transistor controls the current flowing in the two inductor elements 902,904; 902 ', 904', and the inductor elements 902,904; 902 ', 904' are coupled to form the magnetic circuit 1400 . The magnetic circuit may be in a differential mode where the apparent inductance of the magnetic circuit 1400 is the sum of the intrinsic inductance of each of the inductor elements or in a differential mode in which the apparent inductance of the magnetic circuit 1400 is the leakage inductance of the coupling between the coupled inductor elements. Can be alternately controlled.

Description

TECHNICAL FIELD [0001] The present invention relates to a converter for an electric circuit mounted on an automobile and designed to supply an electric driving force. BACKGROUND OF THE INVENTION < RTI ID = 0.0 > [0001]

The present invention relates to a converter for an electric circuit mounted on an automobile and designed to provide an electric driving force.

Referring to Figure 1, a vehicle 100, which is driven in whole or in part electrically, is well known and generally comprises a voltage 104 of a battery 104 for powering an electrical machine 106 via an inverter 108, And a power converter 102 for boosting the output voltage of the power converter 102.

The power in this converter 102 is typically 20 to 1000 kW, so it may be desirable to make a multi-cell converter, and the power-supply current provided by the battery 104 is distributed to a number of conversion cells.

The use of such a multi-cell converter faces a cost problem due to the amount of silicon used in the switches 111 and 113 used in the cell, especially the transistors 103 and 105 therein and the power diodes 107 and 109 .

In the case of electric vehicles, particularly hybrid vehicles, the volume and weight of these cells is also a major criterion, but a considerable size of the inductor element - in this example coil 110 - in particular.

Efficiency is another important criterion in the use of the converter since it directly affects the operating range of the vehicle 100.

To increase efficiency, the method of using the inversion cycle of the current flowing in the inductor element 110 of the converter so as to use a zero voltage switching (ZVS) switching method as described below with reference to Figures 2-5 is well known have.

More precisely, Figure 2 shows a situation in which the switch 113 of the converter 102 under substantially 0 V obtained due to the capacitor 204 is opened, which, as will be described below, Is discharged during this opening.

Although the current 302 (FIG. 3) flowing in the collector of the transistor 105 is not zero when the voltage at the terminals of the transistor 105 (collector / emitter voltage) 304 begins to increase, The loss when the switch 105 is opened can be substantially reduced. In the example of FIG. 3, the orders of magnitude of at work is indicated by a key in the drawing.

As a result, by reversing the direction of the current i flowing in the inductor element 110, the capacitor 204 is discharged and the switch can be closed again at 0V.

Referring to FIG. 4, the converter 102 is shown while the direction of the current through the inductor element 110 of the cell is changing, i.e., when the switch 111 is open. As the flow of current through the switches 111 and 113 is blocked, the capacitor 204 is discharged and the diode 109 of the switch 113 becomes conductive when it is fully discharged.

In this case, the voltage 504 at the terminals of the switch 113 (FIG. 5) decreases rapidly during the discharge of the capacitor (step 510) and becomes negative so that the diode 109 (step 512) is turned on.

As a result, the current 502 at the inductor element 110 becomes positive and the cycle repeats again as described above with the opening of the switch 113.

Using this ZVS mode with a fixed switching frequency may be satisfactory if the converter is operating at a high load, but ZVS technology is not as efficient as a small load.

In particular, the current is largely modulated irrespective of the load - the average current approaches zero at low loads (Figure 7) or the average current approaches 50 A at high loads (Figure 6) . In this example, the magnitude of the inversion is a calculated order of 100A from peak to peak, which causes significant iron losses in the inductor.

To mitigate this problem, it is known to use the ZVS method described above in critical conduction mode. In this mode, the inversion of the current is forced for a time sufficient to discharge the capacitor to make the voltage of the switch relatively short, as shown in Fig.

In this case, the current is controlled by a second threshold value having a sign opposite to the first threshold value controlling the average value of the current and discharging the capacitor, the alternation between these two threshold values being dependent on the variable frequency.

This critical conduction mode creates a current inversion in the inductor element, which makes the latter design difficult. In fact, the magnitude of the current reversal can be greater than 100% of the peak current in the high frequency range (between 20kHz and 80kHz), which causes unacceptable power dissipation in the inductor in terms of temperature and efficiency.

Finally, inductor elements are generally based on ferrite or nanocrystalline structure-type materials because of their resistance to ferrite and the fineness of the bands of the nanocrystalline structure that make up the core, and their ability to reduce losses by suppressing the production of eddy currents. .

Unfortunately, ferrite is a substance that is easily saturated by a relatively weak magnetic field compared to other iron-based magnetic materials.

As a result, the magnetic volume required to fabricate the inductor element becomes so large that it can not be employed in hybrid vehicles, or there is a limit to the power storage due to the very large permeability of this material.

In fact, iron or silicon based materials may be more suitable as converters for vehicles in terms of saturation thresholds in excess of 2T in terms of power storage. In addition, these materials are very widely used for power transmission or conversion (transformers, generators, electric motors, etc.) in the form of laminated metal plates.

These materials have the problem of having a very high loss level at high frequencies due to the flux modulation produced by the high frequencies. This is why the frequency used in power transfer varies between a relatively low range, typically between 50 Hz and 1 kHz, and the frequency of the switch does not exceed nearly 10 kHz.

It is an object of the present invention to solve at least one of the above-mentioned problems. It is an object of the present invention to make it possible to use the ZVS method in a critical mode while using high saturation materials such as Fe-Si based materials.

Indeed, the present invention provides a current modulation per cell that is high enough to use the ZVS method in critical conduction mode while minimizing the modulation of flux in magnetic circuits to limit power dissipation and in particular to use high saturation materials such as Fe-Si based materials It is possible to use converters for automobiles in order to obtain them.

The present invention relates to an electric circuit mounted on an automobile and designed to provide an electric driving force. The electric driving force is obtained from the power delivered by at least two cells by the battery of the vehicle, and the electric circuit comprises inductor elements connected to the transistor. The transistor is characterized in that it controls the current flowing in the inductor elements, and the inductor elements are coupled to form a magnetic circuit. The magnetic circuit is characterized by a common mode in which the apparent inductance of the magnetic circuit is of an order of magnitude equal to the sum of the inductances inherent in each of the inductor elements or the leakage inductance of the coupling between the inductor elements with which the apparent inductance of the magnetic circuit is coupled Can be alternately controlled in accordance with the differential mode which is the same as the calculated order.

Because of the present invention, coupling of inductor elements in differential mode greatly reduces flux reversal in the entire magnetic circuit, keeping the current reversal of each cell relatively high according to the common mode, so that the ZVS method operating in the critical mode It is possible to use an electric circuit as an usable multi-cell converter.

Indeed, the present invention uses a coupling of inductors to form the main magnetic circuit used to store power, and a branch circuit that produces a low inductance leakage line to obtain a largely inverted current.

Due to the present invention, it is possible to use materials which could not be used in an unacceptable level of " iron loss ", i. E., Converters that use high frequency and large current inversion without producing loss due to flux inversion or modulation. Thus, the present invention accommodates a larger induction, thereby reducing the volume of magnetic material used in the converter.

In addition to the main configurations described above, the electrical circuit according to the present invention may include one or more of the following additional configurations either singly or in a technically possible combination.

The inductor elements are connected to include a common terminal coupled to the power battery and a terminal coupled to a pair of transistors for controlling charging and discharging of the associated capacitor.

The associated capacitor has a terminal shared by the first pair of transistors of the first cell and a terminal shared by the second pair of transistors of the second cell.

The electrical circuit includes means for using a duty cycle that is distinct from 50% to charge and discharge the capacitor.

- The value of inherent inductance is 500 μH.

- The value of leakage inductance is 50 μH.

The electrical circuit comprises means for controlling the discharge for a sufficient period of time to invert the direction of the current flowing in at least one of the inductor elements 902, 904; 902 ', 904' according to the ZVS method in the critical conduction mode Includes.

At least one of the inductor elements comprises ferrous and silicon based materials, in particular ferrite.

The electric circuit includes a magnetic circuit formed by four half-coils overlapping each other with an air gap of one identical structure to form a coupling of two inductor elements.

The present invention relates to a method of manufacturing an electric circuit mounted on an automobile and designed to provide an electric driving force, the electric driving force being transmitted to the electric circuit by the battery of the vehicle and being driven by at least two cells, for example ZVS Wherein the electric circuit comprises inductor elements connected to the transistor, the transistor being adapted to manage the current flowing in the inductor elements, the inductor elements forming a magnetic circuit of the configuration described above .

Other features and advantages of the invention will become apparent from the following description taken in conjunction with the accompanying drawings, which are intended to be illustrative and not limiting.

The present invention has the effect of enabling the use of the ZVS method in the critical mode while using a high saturation material.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic view of a vehicle transported wholly or partly (hybrid) electrically.
Figures 2 and 4 are electrical circuits used in known electric converters.
Figures 3 and 5 are graphs of electrical and / or voltage changes in a known electrical converter.
Figures 6, 7, and 8 are current transitions in a known electrical converter.
9 is an electric circuit diagram of a converter to which the present invention can be applied.
10 is a state table of switches used in the circuit of Fig.
11 is a view showing the circuit of Fig. 9 according to the Hopkinson model; Fig.
Figures 12 and 13 show the relative change in current and flux in the circuit of Figure 9;
14 is a perspective view of a coil to which the present invention can be applied.
Figure 15 is an electrical representation of the coil of Figure 14;
16 is a variation of the coil illustrated in Fig.
Figure 17 is a variation of the electrical circuit described in Figure 9;
Figures 18 and 19 show a cyclical variation of voltage and current at the terminals of the elements of the converter according to the invention.

Unless otherwise indicated, the same reference numbers are used in the different drawings to designate identical or functionally similar elements.

Figure 9 shows two cells 901 and 903 with a magnetic circuit 900 according to the present invention, namely inductor elements 902 and 904, respectively, indicated as coils. The magnetic circuit

The apparent inductance of the magnetic circuit 900 is relatively high - this high apparent inductance limits the inversion of the magnetic flux as described below to limit the iron hand - for example, the inductor elements 902 and 904, Depending on the common mode corresponding to the sum of the respective inductances L _A and L _B ,

- the apparent inductance of the magnetic circuit is relatively low - this low apparent inductance causes the current to be reversed sufficiently large so that the previously mentioned ZVS method can be used in a particularly critical mode - for example, the coupling of inductor elements Depending on the differential mode corresponding to the leakage inductance

Can be alternately controlled.

In the following description of the invention, the inductance of the coiled inductor elements 902, 904 is LA, LB.

The voltage Vmc of the magnetic circuit in the common mode is the sum of the voltage V _LA or V _LB at the terminals of the inductor elements 902 and 904, hereinafter referred to as the common mode voltage or " Vmc ".

Vmc = (V _LA + V _LB ) / 2

Similarly, the voltage Vmd of the magnetic circuit in the differential mode, hereinafter the differential mode voltage or Vmd, is the difference in the voltage V _LA or V _LB at the terminals of the inductor elements 902 and 904.

Vmd = (V _LA - V _LB ) / 2

This voltage Vmd in the differential mode is not zero when the terminal voltages V _LA or V _LB of the two inductor elements are different. Considering the example shown in FIG. 9 with two cells, this situation can occur when the switch S _LA or S _LB of the cells 901, 903 using the inductor elements is in a different state as shown in the table of FIG. 10 to be.

More specifically, the magnetic circuit 900 can be represented according to the Hopkinson method (FIG. 11). In this case, the inductor element 902 can be represented by the generator ni _A of the reluctance R and current i _A , and the inductor element 904 can be represented by the generator ni _B of the reluctance R and current i _B , The coupling between the two inductor elements 902 and 904 corresponds to the inductor element 906, which is denoted by the reluctance r.

The magnetic fluxes φ _A , φ _B , and φ _C due to each inductor element 902 and 904 and their combination can be determined through the following equation.

_A φ / N L _A = _A i + _B Mi

_B φ / L N = _{B B} i + _A Mi

φ _C = φ _A - φ _B

In the proposed invention, the inductor elements are strongly coupled so that the mutual inductance M is positive and has a magnitude of 450 μH and the inductance L has a magnitude of 500 μH.

In general, the mutual inductance M has a value close to the inherent inductance L _A or L _B of each coil. These intrinsic inductances L _A and L _B are considered equal to L in the following.

The leakage inductance is relatively small as the difference between the inherent inductance and the mutual inductance, and is expressed as a leakage inductance Lf in the following. Therefore, the following can be displayed.

φ _A / N = L (i _A + i _B ) - Lfi _B

_B φ / N L = _(A i + _B i) - _A Lfi

φ _C / N = Lf (i _A - i _B )

By the above equations, the voltage Vmc in the common mode is expressed as follows.

_{Vmc = N [(dφ A /} dt) + (dφ B / dt)] / 2 = (2L-Lf) [(di A / dt) + (di B / dt)] / 2

= (2L-Lf) (di _MC ) / dt

Similarly, the voltage Vmd in the differential mode is expressed as follows.

_{Vmd = N [(dφ A /} dt) - (dφ B / dt)] / 2 = (Lf) [(di A / dt) - (di B / dt)] / 2

= Lf (di _MC ) / dt

As indicated above, the leakage inductance Lf is almost negligible compared to the inductance L of the inductor element. In this case, the voltages in the common mode and the differential mode are expressed as follows.

Vmc = 2L (di _MC ) / dt

Vmd = Lf (di _MC ) / dt

It can be seen that the inductance of the magnetic circuit is equal to the magnitude of the leakage inductance in the differential mode and the inductance of the magnetic circuit in the common mode is the sum of the specific inductances. therefore,

A relatively small leakage inductance in the differential mode allows the current to change very quickly, for example 10 times faster than when using a unique inductance as shown in Figure 12,

In the common mode, a relatively large inherent inductance can provide a relatively low flux inversion. The actual magnetic flux is given by

φ _A / N = L (i _A + i _B ) - Lfi _B = 2Li _MC - Lfi _B

_B φ / N L = _(A i + _B i) - _A Lfi = 2Li _MC - Lfi _A

φ _C / N = Lf (i _A - i _B ) = 2Lfi _MD

Since the leakage inductance is relatively small, the derivative of the above equation is as follows.

Δφ _A / N = - Lf (Δi _B )

Δφ _B / N = _A LfΔi

?? _C / N = 2L? _A

That is, the flux reversal is proportional to a relatively small leakage inductance, resulting in a small inversion as shown in FIG. In this case, these inversions are about 10 times smaller than the inversions obtained when there is no coupling of the induction coils.

More precisely, since it is known that the reversal of the current is substantially equal to the peak current in the critical conduction mode, the inversion rate relative to the peak magnetic field can be measured. In this case, the ratio is as follows.

-LfΔi_B / 2Li_MC = -Lf/LΔφ _A / φ _A = - LfΔi _B / (2Li _MC -Lfi _B )

-Lf? I _B / 2Li _MC = -Lf / L

LfΔi_A / 2Li_MC = Lf/L _{Δφ B / φ B = LfΔi A} / (2Li MC -Lfi A)

Lf? I _A / 2Li _MC = Lf / L

2L/Lf _{Δφ C / φ C = 2LfΔi A} / (2Lfi MD)

2L / Lf

The above equation shows that the inversion speed is substantially the same as the ratio between the leakage inductance and the inductance inherent in the inductor element, and this ratio can be low enough to use Fe-Si based materials.

14, a magnetic circuit 1400 according to the present invention may be constituted by four anti-coils 1402, 1404, 1406 and 1408 wound N times, each of which is connected to an inductance 1405, 1407, 1409 (Fig. 15) and the central leg 1410 so as to adjust the air gap 1403, 1405, 1407, 1409 (Fig.

The central leg 1410 maintains a magnetic flux variation twice that of the outer arm. The center leg should be as short as possible to reduce core losses due to this magnetic flux change proportional to the volume of the center leg.

Moreover, it should be noted that the length of the center leg 1410 has no effect on the operation of the magnetic circuit, and that the inductance depends on the cross-section of the legs and the air gap.

The N-turn coil is wound around the air gap to prevent self-emanation due to the flux lines divided in the air gap, which can be made of Fe-Si ferrite material to store power.

The coil may be constituted by a conductive strip or a single-stranded or multi-stranded wire, and the winding direction of the coils A and B is determined in a direction in which the magnetic driving force (number of amperes) of each coil is added. Fig. 15 showing the magnetic circuit of Fig. 14 shows the direction in which the coil is wound around the air gap.

The present invention can be variously modified. In particular, the problem and the invention have been described primarily through a non-isolated, bi-directional voltage step-down or step-up converter in the form of a buck-boost. However, the present invention can be applied to various types of converters including at least two cells into which the inductor elements can be coupled.

Furthermore, it can be pointed out that the present invention can be applied to fixed or variable frequencies. In particular, the converter can perform the synchronous rectification function. In this case, the frequency and the inductance must be calculated to change the direction of - in the current-maximum current in the inductor so that the ZVS method can be used.

Regarding the use of the magnetic circuit, the structure of the coil, particularly the position of the air gap, the position and the material of the central leg 1410, may be varied in accordance with embodiments of the present invention.

Consequently, in the embodiment shown in Fig. 16 as a field line, the coil 1600 uses a C-shaped core without a center leg.

Fig. 17 shows an electric circuit 900 'optimized to require only one capacitor 2C of capacitors instead of the capacitors of four capacitors C used in Fig.

It is possible to use one capacitor to carry out the ZVS method through selection of the conduction mode. At least one of the two switches of each arm is always in a conductive state so that the current in the inductor is grounded or absorbed by a capacitor connected to the DC bus E when the switch is opened.

If the duty cycle is less than 50% when switch SLA is open (Fig. 18), switch SHB is challenged. The capacitor Czvs is biased under a negative voltage (-E).

When the switch SLA is opened as shown in Fig. 18, the capacitor Czvs is completely discharged and the blocking voltage of the switch SLA becomes E.

Before the switch SLB is closed, the current is negative in the inductor element LB and the switch SHB is opened to charge the capacitor Czvs until the voltage by the inductor element LB reaches the voltage of the DC bus.

Similarly, FIG. 19 shows a case where the duty cycle is greater than 50%.

Claims (10)

An electric circuit (900, 900 ') mounted on an automobile and designed to supply an electric driving force, wherein the electric driving force is transmitted to the electric circuit (900, 900' 903, 901 ', 903 '
902 ', 904', 902 ', 904') coupled to the transistor, wherein the transistor is coupled to the inductor elements (902, 904; 902 ' And controls the currents flowing in the current-
The inductor elements 902, 904 (902 ', 904') are coupled,
According to a common mode in which the apparent inductance of the magnetic circuit 1400 is equal to the sum of the inductances inherent in each inductor element,
- the apparent inductance of the magnetic circuit 1400 depends on the differential mode which is equal to the leakage inductance of the coupling between the coupled inductor elements
To form the magnetic circuit (1400) that can be alternately controlled. The electrical circuit of claim 1, wherein the inductor elements are coupled to have a common terminal coupled to the power battery and a terminal coupled to a pair of transistors that control charging and discharging of the associated capacitor. 900 '). The method of claim 2, wherein the associated capacitor is shared by a terminal shared by the first pair of transistors of the first cell (901, 903) and a second pair of transistors of the second cell (901 ', 903' (900, 900 '), characterized in that the terminals (900, 900' 4. The apparatus of claim 3, wherein the electrical circuit (900, 900 ') comprises means for using a duty cycle that is distinct from 50% to charge and discharge the capacitor (900, 900 '). 5. An electric circuit (900, 900 ') according to any one of claims 1 to 4, characterized in that the intrinsic inductances are 500 μH. 5. An electrical circuit (900, 900 ') according to any one of claims 1 to 4, characterized in that the leakage inductance is 50 μH. 5. A method according to any one of the preceding claims, characterized in that it comprises the steps of: providing a period of time sufficient to invert the current flowing in at least one inductor element (902, 904; 902 ', 904' (900, 900 '), characterized in that it comprises means for controlling the discharge during the discharge. 5. An electric circuit (900, 900 ') according to any one of claims 1 to 4, characterized in that at least one of the inductor elements comprises iron and a silicon based material. 5. The device according to any one of the preceding claims, wherein the electric circuit (900, 900 ') has an air gap of one and the same structure to form a coupling of the two inductor elements An electric circuit (900, 900 ') characterized by comprising a magnetic circuit formed by four half-coils overlapping one another. A method for manufacturing an electric circuit (900, 900 ') mounted on an automobile and designed to supply an electric driving force, the electric driving force being transmitted to the electric circuit (900, 900' Is obtained from the power converted by the cells 901, 903 (901 ', 903'),
902 ', 904', 902 ', 904' coupled to a transistor that manages the current flowing in the inductor elements 902, 904; 902 ', 904'. The inductor elements 902, Characterized in that the inductor elements (902, 904; 902 ', 904') are arranged to engage to form the magnetic circuit (1400) as claimed in any one of the preceding claims. A method for fabricating a circuit (900, 900 ').

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