Electric converter comprising a controllable inductance

Abstract

The invention relates to an electric converter (1) comprising a first pair of terminals (3) having a first voltage (V1) and a second pair of terminals (5) having a second voltage (V2), the first voltage (V1) being higher or having a maximum value higher than the second voltage (V2), the electric converter (1) comprising: a voltage conversion module (7); an inductance (11) connected between the pair of intermediate terminals (9) and the first pair of terminals (3), the inductance (11) being configured to have an impedance in a step-down operating mode (15) that is higher than in a step-up operating mode (17).

Description

[0001] DESCRIPTION

[0002] TITLE: Electrical converter including a controllable inductor

[0003] Scope of the invention

[0004] The present invention relates to an electrical converter, in particular bidirectional DC-DC or DC-AC, comprising a controllable impedance in order to maintain network stability.

[0005] Previous art

[0006] A voltage converter can only be used in one direction, either stepping down or stepping up. However, for certain applications, the voltage converter can be used in two operating modes: one mode with current flowing in one direction and a second mode with current flowing in the opposite direction.

[0007] Current topologies do not allow for technical compliance in both operating modes of a reversible converter. Indeed, the constraints for maintaining network stability differ between the two operating modes.

[0008] The first mode is, for example, a buck converter: a high voltage converted to a low voltage. The EMC constraint (on the high-voltage side) is to have a low-level high-frequency spectrum for a differential current and, above all, to adhere to a very restrictive template.

[0009] To meet these constraints, one solution is to add a differential inductance which will "smooth the current" and thus avoid current harmonics.

[0010] This same converter can operate in reverse mode, that is, in boost mode. A low voltage is converted to a high voltage. In this mode, the standard requires very low voltage ripple.

[0011] One solution is to place one or more capacitors upstream of the inductor to absorb the voltage ripple caused by the input inductance. This solution works, but the size of the capacitors can be significant.

[0012] Therefore, there is a need to reduce the voltage ripple across the differential inductance in boost mode while keeping the converter to a limited size. The present invention aims to resolve all or part of the aforementioned drawbacks.

[0013] Description of the invention

[0014] To this end, the present invention relates to an electrical converter comprising a first pair of terminals presenting a first voltage and a second pair of terminals presenting a second voltage, the first voltage being higher or having a higher maximum value than the second voltage, the electrical converter comprising:

[0015] a voltage conversion module arranged between a pair of intermediate terminals and a second pair of terminals so as to deliver a modified voltage between the pair of intermediate terminals and the second pair of terminals,

[0016] an inductance connected between the intermediate terminal pair and the first terminal pair, the inductance being configured to present a higher impedance in a buck operating mode than in a boost operating mode.

[0017] The power converter operates in buck mode when the input voltage (the first voltage) is higher than the output voltage (the second voltage). In this case, energy is transferred from the first pair of terminals to the second pair of terminals; this is typically the source-to-load direction.

[0018] The power converter operates in boost mode when the input voltage (the second voltage) is lower than the output voltage (the first voltage). In this case, energy is transferred from the second terminal pair to the first terminal pair; this is typically a way of storing energy in the source for later release.

[0019] Thus, talking about a lowering mode and a raising mode allows us to deduce the direction of energy flow.

[0020] Depending on the operating mode between the first voltage and the second lower voltage, the impedance of the inductance is adjusted, which allows the same electrical converter to be used in both step-down and step-up operating modes.

[0021] According to one aspect of the invention, the inductance is connected in series between one terminal of the intermediate terminal pair and one terminal of the first terminal pair, the electrical converter further comprising a control and command device configured to, in step-down operating mode, allow current to pass through the inductance and configured to, in step-up operating mode, limit current to pass through only a part of the inductance.

[0022] In other words, the control device allows the inductance value to decrease, thus enabling the second operating mode. This reduction in inductance value lowers the input impedance of the electrical converter.

[0023] By "only a part" of the inductance, it is understood that the inductance has a particular arrangement which forces the current to flow on only a part of the winding, the other part of the winding not being conducting in this boost mode of operation.

[0024] The power converter thus exhibits a high input impedance in buck mode and a low input impedance in boost mode. This arrangement reduces the weight and size of the reversible power converter.

[0025] The voltage converter thus has an identical structure that can be adapted to meet the functional requirements of both operating modes. The control and command device allows the inductance value to be adjusted according to the selected operating mode.

[0026] Preferably, the inductor is a differential inductor. The voltage converter thus has a unique topology without the need for large components such as a power capacitor.

[0027] A small capacitor can, however, be added between the first pair of terminals.

[0028] According to one aspect of the invention, the control and command device is configured to measure a current between said terminal of the first pair of terminals and a corresponding terminal of the second pair of terminals, the control and command device being configured to allow current to pass through the inductance when the measured current is positive and configured to limit current to pass through the inductance when the measured current is negative.

[0029] Measuring the direction of the current allows the control and command device to determine the operating mode based on the operating state of an electrical installation in which the electrical voltage converter is located.

[0030] The voltage converter is therefore autonomous and adaptive. For example, in an electrical installation including a battery that can either be used as a power source or recharged, current measurement allows the voltage converter to automatically switch its operating mode.

[0031] Preferably, the control and command device includes a current sensor suitable for measuring a current flowing in the electrical voltage converter between said terminal of the first pair of terminals and said terminal of the second pair of terminals.

[0032] According to one aspect of the invention, the control and command device includes a bypass element mounted on the inductance, the bypass element being arranged to leave the conducting inductance in step-down mode and to leave only a part of the conducting inductance in step-up mode.

[0033] In other words, the current flows through the entire inductor in buck mode, while in boost mode the bypass element allows current to flow through only a portion of the inductor. This bypasses the complementary portion, which is not conducting in boost mode.

[0034] According to one aspect of the invention, the bypass element comprises a switch with one terminal connected to one end of the inductance and another terminal connected to an intermediate location of the inductance so as to allow current to flow through the switch when the switch is in a closed position.

[0035] Thus, the switch is arranged in a closed position in lift mode and is arranged in an open position in step-down mode.

[0036] According to one aspect of the invention, the control and command device includes a switch manager adapted to open or close the switch according to a signal from the current sensor.

[0037] For a bidirectional electrical converter, for example DC-DC, AC-AC, AC-DC or DC-AC, depending on the operating mode chosen, step-down or step-up, the inductance is either inserted or short-circuited by the switch.

[0038] In buck mode, a high impedance is required, so the control and command device opens the switch via the switch manager.

[0039] In boost mode, a low impedance is required, so the control and command device closes the switch via the switch manager.

[0040] According to one possibility, the switch may include an NMOS and a series low-pass filter. The low-pass filter is composed, for example, of a magnetic core that is operational in buck mode and saturates in boost mode. According to one aspect of the invention, the inductor comprises a single winding, and the intermediate location corresponds to a location on a turn of the winding that is not an end turn.

[0041] The advantage of short-circuiting one or more of the first turns is to have a small leakage inductance needed for high-frequency filtering (part of the inductance not short-circuited).

[0042] According to one aspect of the invention, the control and command device further comprises a shielding element surrounding the loop(s) bypassed by the bypassing element in boost mode, the shielding element being connected to said end of the inductance.

[0043] Furthermore, it is possible to add shielding connected to the switch. Preferably, the shielding element is a sheath surrounding the twisted coil(s). Specifically, the wiring element is also connected at the intermediate location of the inductor.

[0044] According to one aspect of the invention, the control and command device further comprises an additional winding connecting said end and the intermediate location of the inductance.

[0045] Preferably, the additional winding is wound around a magnetic core of the inductor.

[0046] According to one aspect of the invention, the inductance comprises several independent windings arranged on parallel circuit branches, at least one winding being configured to be non-conducting in boost mode.

[0047] This alternative allows the same function to be performed as the previous setups.

[0048] Preferably, at least one winding is mounted between a terminal of the first pair of terminals and a corresponding terminal of the intermediate pair of terminals. At least one other winding is mounted between another terminal of the first pair of terminals and another corresponding terminal of the intermediate pair of terminals.

[0049] Here, the inductance comprises several entities distributed over the two branches connecting the first pair of terminals and the intermediate pair of terminals.

[0050] According to one aspect of the invention, at least one winding configured to be non-conducting in boost mode is in differential mode.

[0051] According to one example, a group of two windings are mounted on two parallel circuit branches, one being in differential mode and arranged to be conducting in step-down mode and the other being in common mode and arranged to be conducting in step-up mode.

[0052] Furthermore, a third winding in differential mode is mounted on a circuit branch in parallel with said group of two windings.

[0053] The first winding and the third winding can be made of hand-wound wires in the same direction and the second winding can be of hand-wound wires in the opposite direction.

[0054] Thus, in step-down mode, we obtain a differential mode inductance and in step-up mode we obtain at least partially a common mode inductance.

[0055] According to one aspect of the invention, at least one winding configured to be non-conducting in boost mode is mounted in series with a diode.

[0056] The diode is designed to determine the conducting or non-conducting state depending on the direction of the current. In this example, the first winding, operating in differential mode, is configured to conduct in step-down mode thanks to the corresponding diode.

[0057] Similarly, the second common-mode winding arranged to conduct in boost mode is connected in series with a corresponding diode.

[0058] Each diode is also connected in parallel with a corresponding switch. However, this configuration functions even if the switches are not activated in the event of a switch failure. The switches serve to increase efficiency by reducing conduction losses in the diodes.

[0059] The present invention also relates to a machine equipped with an electrical converter as described above. The machine may be a turbomachine, for example a turbojet engine.

[0060] The present invention further relates to a method for controlling and commanding an electrical converter as described above, comprising the following steps:

[0061] measure the current between said terminal of the first pair of terminals and a corresponding terminal of the second pair of terminals,

[0062] allow current to flow through the inductor when the measured current is positive, and

[0063] limit the current flow through the inductor when the measured current is negative.

[0064] This arrangement allows the choice of the step-down or step-up operating mode following the current measurement. According to one aspect of the invention, the current is measured at regular intervals so as to adapt the operation of the control and command device in case of change in the installation in which the control and command device is used.

[0065] Depending on the inductance configuration, a single-winding inductance is used and the switch is closed in boost mode, which limits the current flow through the inductance.

[0066] In the case of a multi-winding inductor, the use or limitation of current flow can be achieved using corresponding switches and / or diodes. In practice, and as an example, each diode is connected in parallel with a switch.

[0067] This arrangement allows for correct operation even if the switches cannot be controlled due to the current flow being permitted or blocked through the diodes. The switches serve to increase efficiency by reducing conduction losses in the diodes.

[0068] In particular, the first winding is switching in step-down mode, the corresponding switch being then closed by the control and command device, the switch of the second winding being open.

[0069] The second winding is in boost mode and in this case the corresponding switch is closed, the switch of the first winding being open.

[0070] The control process thus consists of determining the direction of the current and adapting the path of the current to bypass or not certain windings.

[0071] The various aspects defined above, which are not incompatible, can be combined.

[0072] Brief description of the figures

[0073] The invention will be better understood with the aid of the detailed description set forth below in relation to the accompanying drawings.

[0074] [Fig. 1] is a diagram of a bidirectional electrical converter.

[0075] [Fig. 2] is a diagram of a detail of the electrical converter.

[0076] [Fig. 3] is a diagram of an inductor and a control and command device for the inductor.

[0077] [Fig. 4] is a diagram of one variant of the inductor and the inductor control and command device. [Fig. 5] is a diagram of a second variant of the inductor and the inductor control and command device.

[0078] [Fig. 6a] is a diagram of a third variant of the inductance and the control and command device of the inductance in buck operating mode.

[0079] [Fig. 6b] is a diagram of the third variant of the inductance and the inductance control and command device in boost operating mode.

[0080] [fig. 7] is a diagram representing the steps of a control and command process for the electrical converter.

[0081] Description with reference to the figures

[0082] In the detailed description that will follow of the figures defined above, the same elements or elements fulfilling identical functions may retain the same references in order to simplify the understanding of the invention.

[0083] As illustrated in Figure 1, an electrical converter 1 comprises a first pair of terminals 3 presenting a first voltage VI and a second pair of terminals 5 presenting a second voltage V2.

[0084] The first voltage VI is higher or has a higher maximum value than the second voltage V2, whether it is a direct or alternating voltage.

[0085] The electrical converter 1 includes a voltage conversion module 7 arranged between a pair of intermediate terminals 9 and the second pair of terminals 5 so as to deliver a modified voltage between the pair of intermediate terminals 9 and the second pair of terminals 5.

[0086] The electrical converter 1 includes an inductance 11 connected in series between a terminal 9a of the intermediate terminal pair 9 and a terminal 3a of the first terminal pair 3.

[0087] The electrical converter 1 includes a control and command device 13 configured to, in a step-down operating mode 15, permit current to pass through the inductance 11 and configured to, in a step-up operating mode 17, limit current to pass through only a part of the inductance 11.

[0088] In other words, the control device 13 reduces the value of the inductance 11 to achieve the second operating mode. This reduction in the value of the inductance 11 reduces the input impedance of the electrical converter 1.

[0089] The converter thus presents a high input impedance of the electrical converter 1 in step-down mode 15 and a low input impedance in step-up mode 17. This arrangement makes it possible to reduce the weight and volume of the reversible electrical converter 1.

[0090] The voltage converter 1 thus has an identical structure that can be adapted to meet the functional requirements of both operating modes. The control device 13 allows the value of the inductance 11 to be adjusted according to the selected operating mode.

[0091] Inductance 11 is a differential inductance. The voltage converter 1 thus has a unique topology without the addition of large components such as a power capacitor.

[0092] A smaller capacitor 19 can however be added between the first pair of terminals 3.

[0093] The control and command device 13 is configured to measure a current between a terminal 3a of the first pair of terminals 3 and a corresponding terminal 5a of the second pair of terminals 5.

[0094] The control and command device 13 is configured to allow current to pass through the inductance 11 when the measured current is positive and configured to limit current to pass through the inductance 11 when the measured current is negative.

[0095] Measuring the direction of the current allows the control and command device 13 to determine the operating mode according to the operating state of an electrical installation in which the electrical voltage converter 1 is located.

[0096] The voltage converter 1 is therefore autonomous and adaptive. For example, in an electrical installation including a battery that can either be used as a power source or recharged, current measurement allows the voltage converter 1 to automatically switch its operating mode.

[0097] The control and command device 13 includes a current sensor 21 adapted to measure a current flowing in the electrical voltage converter 1 between said terminal 3a of the first pair of terminals 3 and said terminal 5a of the second pair of terminals 5. As illustrated in figures 2 to 5, the control and command device 13 includes a bypass element 23 mounted on the inductance 11, the bypass element 23 being arranged to leave the inductance 11 conducting in step-down mode 15 and to leave only part of the inductance 11 conducting in step-up mode 17.

[0098] In other words, the current flows through the entire inductance 11 in step-down mode 15, while in step-up mode 17 the bypassing element 23 makes the current flow through only a part of the inductance 11. There is thus a bypass of the complementary part which is not conducting in step-up mode 17.

[0099] The bypass element 23 includes a switch 25 with one terminal connected to one end of the inductance 11 and another terminal connected to an intermediate location of the inductance 11 so as to allow current to flow through the switch 25 when the switch 25 is in a closed position.

[0100] Thus, the switch 25 is arranged in a closed position in lift mode 17 and is arranged in an open position in step-down mode 15.

[0101] The control and command device 13 includes a switch manager Tl 25 adapted to open or close the switch 25 according to a signal from the current sensor 21.

[0102] For a bidirectional electrical converter 1, for example DC-DC, AC-AC, AC-DC or DC-AC, depending on the operating mode chosen, step-down 15 or step-up 17, the inductance 11 is either inserted or short-circuited by the switch 25.

[0103] In step-down mode 15, a high impedance is required, so the control and command device 13 opens the switch 25 via the switch 25 manager 27.

[0104] In boost mode 17, a low impedance is required, so the control and command device 13 closes the switch 25 via the switch 25 manager 27.

[0105] According to one possibility shown in Figures 3 to 5, the switch 25 can include an NMOS and a low-pass filter in series. The low-pass filter is composed, for example, of a magnetic core that is operational in buck mode 15 and saturates in boost mode 17.

[0106] The inductance 11 comprises a single winding and the intermediate location corresponds to a location on a turn of the winding that is not an end turn. The advantage of short-circuiting one or more of the first turns is to have a small leakage inductance 11 necessary for high-frequency filtering (part of the inductance 11 not short-circuited).

[0107] As illustrated in Figure 4, the control and command device 13 may further include a shielding element 29 surrounding the loop(s) bypassed by the bypassing element 23 in boost mode 17, the shielding element 29 being connected to said end of the inductance 11.

[0108] Furthermore, it is possible to add a shield that connects to the switch 25. Preferably, the shielding element 29 is a sheath surrounding the twisted coil(s). In particular, the wiring element is also connected to the intermediate location of the inductor 11.

[0109] As illustrated in Figure 5, the control and command device 13 may, according to an alternative to Figure 4, include an additional winding 31 connecting said end and the intermediate location of the inductance 11.

[0110] Preferably, the additional winding 31 is wound around a magnetic core of the inductance 11.

[0111] According to another alternative shown in Figure 6a and Figure 6b, the inductance 11 comprises several independent windings arranged on parallel circuit branches, one winding being configured to be non-conducting in boost mode 17.

[0112] This alternative allows the same function to be performed as the previous configurations. The winding configured to be non-conducting in boost mode 17 is in differential mode.

[0113] A group of two windings are mounted in parallel between another terminal 3b of the first pair of terminals 3 and another terminal 9b of the intermediate pair of terminals 9, a first winding 33 being in differential mode and arranged to be conducting in step-down mode 15 and a second winding 35 being in common mode and arranged to be conducting in step-up mode 17.

[0114] Furthermore, a third winding 37 in differential mode is mounted on a circuit branch in parallel with said group of two windings, that is to say between terminals 3a and terminal 9a.

[0115] The first winding 33 and third winding 37 can be made of wires in the same direction and the second winding 35 can be made of wires in the opposite direction. Thus, in step-down mode 15, we obtain a differential mode inductance 11 and in step-up mode 17 we obtain at least in part a common mode inductance 11.

[0116] The winding configured to be non-conducting in boost mode 17 is mounted in series with a diode 39.

[0117] Diode 39 is adapted to define the conducting or non-conducting state according to the direction of the current. In the example, the first winding in differential mode is arranged to be conducting in step-down mode 15 thanks to the corresponding diode 39.

[0118] Similarly, the second common-mode winding arranged to be conducting in boost mode 17 is connected in series with a corresponding diode 39.

[0119] Each diode 39 is also connected in parallel with a corresponding switch 25. However, this configuration functions even if the switches 25 are not activated in the event of a control fault in the switches 25. The switches 25 serve to increase efficiency by reducing conduction losses in the diodes 39.

[0120] The present invention also relates to a machine equipped with an electrical converter 1 as described above. The machine may be a turbomachine, for example a turbojet engine.

[0121] As illustrated in Figure 7, a method for controlling and commanding an electrical converter 4, as described above, comprises the following steps:

[0122] To measure the current between terminal 3a of the first pair of terminals 3 and the corresponding terminal 5a of the second pair of terminals 5,

[0123] E2 allows current to flow through inductor 11 when the measured current is positive, and

[0124] E3 limit the current flow through inductance 11 when the measured current is negative.

[0125] This arrangement allows the choice of the step-down operating mode 15 or the step-up operating mode 17 following the current measurement.

[0126] The current is measured at regular intervals so as to adapt the operation of the control and command device 13 in case of change in the installation in which the control and command device 13 is used.

[0127] According to the configuration of the inductor 11 shown in Figures 1 to 5, a single-winding inductor 11 is used and the switch 25 is closed in boost mode 17, which limits the current flow through the inductor 11. In the case of a multi-winding inductor 11 as shown in Figures 6a and 6b, the use or limitation of current flow can be achieved by corresponding switches 25 and / or diodes 39. In practice, and as shown in Figures 6a and 6b, each diode 39 is connected in parallel with a switch 25.

[0128] This arrangement allows correct operation even if the switches 25 cannot be controlled due to the permitting or blocking of current flow through the diodes 39. The switches 25 serve to increase efficiency by reducing conduction losses in the diodes 39.

[0129] In particular, the first winding 33 is non-conducting in step-down mode l5 (Figure 6a), the corresponding switch 25a being then open by the control device 13, while the switch 25b of the second winding 35 is closed. In this case, current flows through the coils wound in opposite directions, i.e., the second winding 35 and the third winding 37. The inductances are in differential mode and the magnetic fluxes add up: There is a high inductance.

[0130] The second winding 35 is non-conducting in boost mode 17 (Figure 6b), and in this case, the corresponding switch 25b is open, while the switch 25a of the first winding 33 is closed. In this case, current flows through the coils wound in the same direction, that is, through the first winding 33 and the third winding 37. The magnetic fluxes cancel each other out: there is a low inductance.

[0131] The control process thus consists of determining the direction of the current and adapting the path of the current to bypass or not certain windings.

[0132] As can be understood, the invention is not limited to the single form of execution described above by way of example, but rather encompasses all variants of its realization.

Claims

DEMANDS 1. Electrical converter (1) comprising a first pair of terminals (3) having a first voltage (VI) and a second pair of terminals (5) having a second voltage (V2), the first voltage (VI) being higher or having a higher maximum value than the second voltage (V2), the electrical converter (1) comprising: a voltage conversion module (7) disposed between a pair of intermediate terminals (9) and the second pair of terminals (5) so as to deliver a modified voltage between the pair of intermediate terminals (9) and the second pair of terminals (5), an inductance (11) connected between the intermediate terminal pair (9) and the first terminal pair (3), the inductance (11) being configured to present an impedance in a step-down operating mode (15) higher than in a step-up operating mode (17).

2. Electrical converter (1) according to claim 1, in which the inductance (11) is connected in series between a terminal (9a) of the intermediate terminal pair (9) and a terminal (3a) of the first terminal pair (3), the electrical converter (1) further comprising a control and command device (13) configured to, in step-down operating mode (15), permit the passage of current through the inductance (11) and configured to, in step-up operating mode (17) limit the passage of current in only a part of the inductance (11).

3. Electrical converter (1) according to claim 2, wherein the control and command device (13) is configured to measure a current between said terminal (3a) of the first pair of terminals (3) and a corresponding terminal (5a) of the second pair of terminals (5), the control and command device (13) being configured to allow current to flow through the inductance (11) when the measured current is positive and configured to limit current to flow through the inductance (11) when the measured current is negative.

4. Electrical converter (1) according to any one of claims 2 or 3, wherein the control and command device (13) comprises a bypass element (23) mounted on the inductance (11), the bypass element (23) being arranged to leave the inductance (11) conducting in step-down mode (15) and to leave only part of the inductance (11) conducting in step-up mode (17).

5. Electrical converter (1) according to claim 4, wherein the bypassing element (23) comprises a switch (25) with one terminal connected to one end of the inductor (11) and another terminal connected to an intermediate location of the inductor (11) so as to permit current to flow through the switch (25) when the switch (25) is in a closed position.

6. Electrical converter (1) according to claim 5, wherein the inductance (11) comprises a single winding and the intermediate location corresponds to a location on a turn of the winding that is not an end turn.

7. Electrical converter (1) according to any one of claims 2 to 6, wherein the control and command device (13) further comprises a shielding element (29) surrounding the turn or turns bypassed by the bypassing element (23) in boost mode (17), the shielding element (29) being connected to said end of the inductance (11).

8. Electrical converter (1) according to claim 1, wherein the inductance (11) comprises several independent windings arranged on parallel circuit branches, at least one winding being configured to be non-conducting in boost mode (17).

9. Electrical converter (1) according to claim 8, wherein at least one winding configured to be non-conducting in boost mode (17) is in differential mode.

10. A method for controlling and commanding an electrical converter according to any one of claims 1 to 9 in combination with claim 2, comprising the following steps: (El) measure a current between said terminal (3a) of the first pair of terminals (3) and a corresponding terminal (5a) of the second pair of terminals (5), (E2) allow current to flow through inductance (11) when the measured current is positive, and (E3) limit current to flow through inductance (11) when the measured current is negative.

Images