Method for controlling a converter for converting a first electrical voltage into a second electrical voltage

Abstract

The invention relates to a method, implemented by a control system of an electrical converter, for controlling the converter, which method comprises the following steps: - a step (40) of determining the peak-to-peak amplitude of the current in a low-frequency switching branch of the converter; - a step (42) of comparing the peak-to-peak amplitude with a threshold current value; - if the peak-to-peak amplitude is greater than or equal to the threshold current value, a step (44) of deactivating the switching branch; - otherwise, a step (46) of determining whether a mathematical relationship is satisfied; - if the relationship is not satisfied, which corresponds to a discontinuous conduction mode of diodes, a step (48) consisting in keeping the switching branch active; - otherwise, a step (50) consisting in keeping active or in deactivating the switching branch according to a predefined criterion.

Description

[0001] DESCRIPTION

[0002] METHOD FOR CONTROLLING A CONVERTER FROM A FIRST ELECTRICAL VOLTAGE TO A SECOND ELECTRICAL VOLTAGE

[0003]

[0001] The invention relates to a method, implemented by a system for controlling a converter from a first electrical voltage to a second electrical voltage, for controlling the converter. The converter is connected to an alternating electrical voltage source. Preferably, the first electrical voltage is thus an alternating electrical voltage (preferably sinusoidal) from a single-phase, two-phase or three-phase electrical supply network, and the second electrical voltage is a direct electrical voltage. The invention further relates to an assembly comprising a converter from a first electrical voltage to a second electrical voltage, and a system for controlling the converter configured to implement the steps of such a method.The invention also relates to an electric charger for an electric or hybrid vehicle, comprising such an assembly, as well as to an electric or hybrid vehicle, in particular an automobile, comprising such an electric charger.

[0004]

[0002] Known in the state of the art are electric chargers for electric or hybrid vehicles, on board such a vehicle and intended to be connected to a terminal or to an electric charging station, itself connected to a sinusoidal electric voltage source (such as a single-phase, two-phase or three-phase electric power supply network) for the electric power supply of the vehicle. Such an electric charger conventionally comprises a converter of a first alternating electric voltage into a second direct electric voltage, as well as a direct current to direct current converter configured to convert at high frequency the second direct electric voltage into a third direct electric voltage (this third direct electric voltage being used for example for an electric storage battery of the vehicle).The high-frequency direct current to direct current converter (typically a chopper) is connected to the output of the first converter.

[0003] The converter of a first alternating electrical voltage into a second direct electrical voltage typically comprises an electromagnetic disturbance filtering stage and an active power factor correction stage connected to the output of the electromagnetic disturbance filtering stage via at least one main inductor.

[0005]

[0004] The electromagnetic disturbance filtering stage is connected to the sinusoidal electrical voltage source, and makes it possible to filter harmonics generating electromagnetic disturbances. As known per se in a topology of the “bidirectional synchronous rectifier with mid-point cascode assembly” type (also called totem-pole topology), the active power factor correction stage comprises a low-frequency switching electronic branch and at least one high-frequency switching electronic branch. The low frequency corresponds in practice to the frequency of the voltage supplied by the single-phase, two-phase or three-phase electrical power supply network. The active power factor correction stage makes it possible to absorb a current from the electrical power supply network that is as sinusoidal as possible with a minimal phase shift (preferably zero) between the fundamental of the absorbed current and the mains voltage.This allows, among other things, to substantially reduce low-frequency disturbances in the vehicle's supply current, and therefore to reduce the harmonic rate in this current. The function of this stage is thus to take a "quasi-sinusoidal" electric current using a current control loop (implemented in particular via the main inductor). The principle of sinusoidal sampling then consists of "forcing" the current flowing in the main inductor(s) to follow a sinusoidal reference (not rectified), by controlling the closing and opening of the power switches controlled in the electronic switching branches. The active power factor correction stage thus delivers power to a capacitive load as well as to the vehicle's battery, and makes it possible to actively correct the current absorbed by this load and this battery (using the current control loop).

[0006]

[0005] When the sinusoidal electrical voltage source comprises a neutral conductor line, the electromagnetic disturbance filtering stage is provided with a line connected on the one hand to this neutral conductor line and on the other hand to an intermediate terminal located in the middle of the low-frequency switching electronic branch of the active power factor correction stage. When the active power factor correction stage implements a topology of the “mid-point cascode bidirectional synchronous rectifier” type, this low-frequency switching electronic branch makes it possible to process regular alternations in the input electrical voltage signal (positive and negative alternations), as well as to allow rectification of the voltage.The low-frequency switching electronic branch may comprise controllable electronic switches (typically transistors), in which case the low-frequency switching electronic branch has a switching frequency substantially equal to that of the input power supply network (for example 50 Hz). Alternatively, the low-frequency switching electronic branch may comprise diodes. The use of diodes allows for an economic gain (due to the lower manufacturing cost of diodes compared to transistors).The disadvantage of using diodes is that the conduction losses in diodes are higher than the conduction losses in transistors, and diodes do not allow bidirectional power transfer (i.e. from the vehicle battery to the capacitive load, and vice versa), i.e., the electric current can only flow in one direction in the low-frequency switching electronic branch, for a given sign of the grid voltage. Therefore, not only is the converter discharge mode (power transfer from the vehicle battery to the capacitive load) not possible using diodes, but reactive power control (phase shift of the grid current relative to the grid voltage) is not possible either. Such reactive power control consists of applying a phase shift to the grid current setpoint.This phase shift between the network voltage and the network current then generates reactive power, power which can for example be used by a "smart" electrical network to balance the overall reactive power.

[0006] The high-frequency switching electronic branch provides high-frequency switching of the input electrical current, which makes it possible to generate an input sinusoidal wave in phase with the voltage of the input electrical supply network, as well as high-frequency ripples intended to be filtered by the electromagnetic disturbance filtering stage. The shape of the switched current is regulated by a high-frequency pulse width modulation control which induces a ripple on the current, depending on the main inductance, the switching frequency and the value of the DC voltage in the output bus of the converter.When the current is sufficiently low, the ripple on the current flowing in the low-frequency switching electronic branch can be higher than the average current, which, when this branch includes diodes, introduces a discontinuous conduction mode within the diodes.

[0007]

[0007] In the converter charging mode (transfer of power from the capacitive load to the vehicle battery), the diodes of the low-frequency switching electronic branch thus introduce a discontinuous conduction mode, which makes the digital control implemented in the converter control system more complex (additional computational load and increase in algorithmic complexity), and degrades the performance of the system as a whole. Indeed, the discontinuous conduction mode of the diodes requires that the digital control implement functions for predicting the discontinuous conduction modes, correcting the measurement of the average current and correcting the high-frequency control command.Because digital control in the discontinuous conduction mode of diodes is based on prediction, and because the transition between continuous and discontinuous conduction modes generates harmonic distortion, the final performance and efficiency are never as good as when the low-frequency switching electronic branch only comprises transistors, which themselves operate only in a continuous conduction mode.

[0008]

[0008] Therefore, despite the cost reduction it brings, the use of diodes in load mode in the low-frequency switching electronic branch has the following disadvantages, compared to the use of transistors:

[0009] - the efficiency of the active power factor correction stage is lower;

[0010] - conduction losses are higher;

[0011] - digital control is more complex and more demanding in computing resources, to manage the discontinuous conduction mode of the diodes;

[0012] - it is not possible to implement reactive power control (current phase shift).

[0013]

[0009] The aim of the invention is to overcome the drawbacks of the prior art by proposing a method, implemented by a system for controlling a converter from a first electrical voltage to a second electrical voltage, for controlling said rectifier, which makes it possible to implement reactive power control and bidirectional power transfer within the converter (charging and discharging modes), while offering in the charging mode flexibility in control, reasonable computational complexity and / or consumption of memory resources and by implementing a converter with reduced manufacturing costs.

[0014]

[0010] To do this, the invention thus relates, in its broadest acceptance, to a method, implemented by a system for controlling a converter from a first electrical voltage to a second electrical voltage, for controlling said converter, the converter being connected to an alternating electrical voltage source comprising a neutral conductive line and at least one phase conductive line, the alternating electrical voltage source providing the first electrical voltage, the converter comprising an active power factor correction stage, the active power factor correction stage comprising two low-frequency electronic switching branches connected in parallel, and at least one high-frequency electronic switching branch, each low-frequency electronic switching branch comprising two low-frequency half-switching branches connected in series at a first intermediate terminal,at least one switching half-branch of a first low-frequency switching branch comprising at least one switching member provided with a controllable electronic switch, at least one switching half-branch of a second low-frequency switching branch comprising at least one diode, each first intermediate terminal being connected to the neutral conducting line, said at least one high-frequency electronic switching branch comprising two high-frequency switching half-branches connected in series at a second intermediate terminal, at least one high-frequency switching half-branch comprising at least one switching member, said at least one second intermediate terminal being connected to said at least one phase conducting line via an inductance,each of the diodes being configured to allow in its on state a maximum current value for passage through the diode greater than the maximum current value for passage authorized by each controllable electronic switch in its on state, and greater than the critical conduction current value of the diode, the method comprising a charging phase during which the electric current flows in a first direction in the first low-frequency switching branch or in the second low-frequency switching branch, and a discharging phase during which the electric current flows in a second direction, opposite to the first direction of circulation, in the first low-frequency switching branch, the control system being configured to apply, during the charging phase of the method, an instantaneous current setpoint l, spto the current flowing in the or each inductance, the control system comprising means for measuring the first and second electrical voltages and means for determining, from the first and second electrical voltages measured, the peak-to-peak amplitude l ci of the intensity of the current capable of flowing in the first low-frequency switching branch, the first low-frequency switching branch being initially activated at the start of the charging phase of the process, the process comprising, during its charging phase, the steps of:

[0015] - a step of measuring the first and second electrical voltages;

[0016] - a step of determining, from the first and second measured electrical voltages, the peak-to-peak amplitude l ci of the intensity of the current flowing in the first low-frequency switching branch;

[0017] - a peak-to-peak amplitude comparison step l ci at a threshold current value l seU ii predefined, the value l seU ii being such that: Or

[0018] Imax is the maximum amplitude of the current intensity capable of flowing in the first low-frequency switching branch;

[0019] - if the peak-to-peak amplitude l ci is greater than or equal to the predefined threshold current value Iseuii, a step of deactivation of the first low-frequency switching branch;

[0020] - if the peak-to-peak amplitude Id is strictly lower than the predefined threshold current value Iseuii, a step of determining whether the following mathematical relationship (1) is verified, making it possible to detect whether the electrical conduction mode of the diodes is a continuous or discontinuous conduction mode: sgn(u) provides the sign of the function u(t) and is therefore equal to -1 or 1 when u(t) is non-zero;

[0021] - if, at the end of the verification, the mathematical relation (1) is false, a step consisting of keeping the first low-frequency switching branch active;

[0022] - if, at the end of the verification, the mathematical relation (1) is true, a step consisting of keeping active or deactivating the first low-frequency switching branch depending on the verification of a predefined criterion.

[0023]

[0011] By controlling the converter in this way during the latter's charging mode (activation of the first low-frequency switching branch when the current is sufficiently low, and deactivation of the latter when the current is greater than the limit conduction current of the controllable electronic switches, the current then passing through the second low-frequency switching branch), the method according to the invention makes it possible to eliminate the discontinuous conduction modes of the diodes likely to appear in the second low-frequency switching branch (it is then the first switching branch which is conductive), while benefiting from the advantages linked to this second switching branch (low cost in particular) outside the discontinuous conduction zones.This allows to optimize the system performance, especially in terms of harmonic distortion and power transfer efficiency (the power transfer being bidirectional). It also allows to introduce flexibility in the control (in the converter charging phase), to significantly simplify the digital control algorithm during this charging phase (which reduces the computational load and the consumption of memory resources), as well as to reduce costs. It is worth noting that the activation conditions of the first low-frequency switching branch are based on theoretical predictions including safety margins, which guarantees that no overcurrent or discontinuous conduction mode can occur.Indeed, the diodes are designed to support a maximum electrical power during the charging phase of the converter, while the controllable electronic switches (typically transistors) support a lower electrical power (in particular during the discharge phase), but allow, during the charging phase and for low electrical currents, to avoid discontinuous conduction modes linked to the diodes. In addition, the determination of whether the mathematical relation (1) is verified or not makes it possible to know whether or not there is at least one operating zone for which the electrical conduction mode of the diodes is a discontinuous conduction mode (if the mathematical relation (1) is not verified, then such an operating zone exists).

[0024]

[0012] Preferably, if, at the end of the verification, the mathematical relationship (1) is true, the verification of the predefined criterion in the step of keeping the first low-frequency switching branch active or not consists of comparing the conduction losses in the diodes with the conduction losses in the controllable electronic switches, the first low-frequency switching branch being kept active if the conduction losses in the diodes are greater than the conduction losses in the controllable electronic switches, the first low-frequency switching branch being deactivated in the opposite case. This makes it possible to optimize the efficiency of the converter, in particular from the point of view of conduction losses.

[0025]

[0013] The invention also relates to an assembly comprising a converter of a first electrical voltage into a second electrical voltage and a system for controlling said converter, the converter being capable of being connected to an alternating electrical voltage source comprising a neutral conductive line and at least one phase conductive line, the converter comprising an active power factor correction stage, the active power factor correction stage comprising two low-frequency electronic switching branches connected in parallel, and at least one high-frequency electronic switching branch, each low-frequency electronic switching branch comprising two low-frequency half-switching branches connected in series at a first intermediate terminal,at least one switching half-branch of a first low-frequency switching branch comprising at least one switching member provided with a controllable electronic switch, at least one switching half-branch of a second low-frequency switching branch comprising at least one diode, each first intermediate terminal being capable of being connected to the neutral conductive line, said at least one high-frequency electronic switching branch comprising two high-frequency switching half-branches connected in series at a second intermediate terminal, at least one high-frequency switching half-branch comprising at least one switching member, said at least one second intermediate terminal being capable of being connected to said at least one phase conductive line via an inductance,each of the diodes being configured to allow in its on state a maximum current value for passage through the diode greater than the maximum current value allowed by each controllable electronic switch in its on state, and greater than the critical conduction current value of the diode, the control system comprising means for measuring the first and second electrical voltages and means for determining, from the first and second electrical voltages measured, the peak-to-peak amplitude Id of the intensity of the current capable of flowing in the first low-frequency switching branch, the control system of the converter being configured to implement the steps of a control method as described above, the control system being configured to apply, during the charging phase of the method, an instantaneous current setpoint l, spto the current flowing in the or each inductance.

[0026]

[0014] The invention also relates to an electric charger for an electric or hybrid vehicle intended to be connected to a terminal or to an electric charging station connected to an alternating electric voltage source, for the electrical supply of said electric or hybrid vehicle, the electric charger comprising an assembly as described above.

[0027]

[0015] The invention also relates to an electric or hybrid vehicle, in particular an automobile, comprising an electric charger as described above.

[0028]

[0016] Embodiments of the present invention will be described below, by way of non-limiting examples, with reference to the appended figures in which:

[0029] - [Fig.1] is a schematic representation of an assembly comprising a converter of a first electrical voltage into a second electrical voltage and a system for controlling the converter, the control system being configured to implement the steps of a control method according to the present invention; and

[0030] - [Fig.2] is a flowchart representing a control method according to an embodiment of the present invention, implemented by the control system of FIG. 1.

[0031]

[0017] With reference to Figure 1, an assembly 2 is illustrated comprising a converter 4 of a first electrical voltage LU into a second electrical voltage U2, and a system 6 for controlling the converter 4, according to an embodiment of the invention. The converter 4 is connected on the one hand to an alternating electrical voltage source (such as for example a single-phase, two-phase or three-phase electrical power supply network - such a source not being shown in the figure for reasons of clarity) providing the first electrical voltage LU, and on the other hand to a load 3 delivering between its terminals the second electrical voltage U2.The alternating electrical voltage source (preferably sinusoidal) conventionally comprises a neutral conductive line N1 and at least one phase conductive line (in this case a single phase conductive line P1 in the particular embodiment illustrated in FIG. 1 for which the electrical supply network is a single-phase network).

[0032]

[0018] The assembly 2 is typically installed within an electric or hybrid motor vehicle, more precisely within an electric charger intended to be connected to an electric charging terminal or station, itself connected to the source of alternating electric voltage, for the electric power supply of the vehicle (neither the vehicle, nor the charging terminal or station, nor the charger as a whole being shown in the figure for reasons of clarity). Preferably, the first electric voltage LU is an alternating electric voltage from the single-phase electric power supply network, and the second electric voltage U2 is a direct electric voltage making it possible to supply an electric storage battery of the vehicle, after transformation by one or more other stage(s) of the electric charger (such as for example a step-down chopper).The converter 4 thus supplies the second direct electrical voltage U2 on an output bus 5 to which the load 3 is connected (here for example a bank of capacitors), the value of this second direct electrical voltage U2 being for example of the order of 400 Vdc or 800 Vdc. The second electrical voltage U2 is thus stabilized by the bank of capacitors 3.

[0033]

[0019] The converter 4 conventionally comprises an electromagnetic disturbance filtering stage (not shown in FIG. 1 for reasons of clarity) and an active power factor correction stage 7 connected to the output of the electromagnetic disturbance filtering stage via at least one main inductor 8. In the particular embodiment of FIG. 1, the active power factor correction stage 7 is connected to the output of the electromagnetic disturbance filtering stage via two main inductors 8, which for example each have the same inductance value.

[0034]

[0020] The active power factor correction stage 7 comprises two low-frequency switching electronic branches 16A, 16B connected in parallel, and at least one high-frequency switching electronic branch 18A, 18B. In the particular embodiment of FIG. 1, the active power factor correction stage 7 is a bidirectional synchronous rectifier with a midpoint cascode assembly and comprises two high-frequency switching electronic branches 18A, 18B connected in parallel. The number of high-frequency switching electronic branches 18A, 18B is thus equal to the number of main inductors 8. In a variant not shown, the active power factor correction stage 7 could comprise a single high-frequency switching electronic branch 18A, 18B.Each high-frequency switching electronic branch 18A, 18B provides high-frequency switching of the input electric current, which makes it possible to generate an input sine wave in phase with the voltage of the input power supply network, as well as high-frequency ripples intended to be filtered by the electromagnetic disturbance filtering stage.

[0035]

[0021] Each low-frequency electronic switching branch 16A, 16B comprises two low-frequency switching half-branches 16A1, 16A2, respectively 16B1, 16B2, connected in series at an intermediate terminal 20A, 20B. Each intermediate terminal 20A, 20B is connected to the neutral conductor line N1. Each half-branch 16A1, 16A2 of a first low-frequency switching branch 16A comprises a switching member 24. The first low-frequency electronic switching branch 16A has a switching frequency substantially equal to that of the input electrical power supply network (for example 50 Hz). Each half-branch 16B1, 16B2 of a second low-frequency switching branch 16B comprises a diode 30. Each high-frequency switching electronic branch 18A, 18B comprises two high-frequency switching half-branches 18A1, 18A2, respectively 18B1, 18B2 connected in series at an intermediate terminal 22A, 22B.Each intermediate terminal 22A, 22B is connected to one of the main inductors 8 (each main inductor 8 being connected to the phase conductive line P1 via the electromagnetic disturbance filtering stage). Each high-frequency switching half-branch 18A1, 18A2, 18B1, 18B2 comprises a switching member 25. In a variant not shown, each half-branch 16A1, 16A2, 16B, 18A1, 18A2, 18B1, 18B2 comprises a number N2 of switching members 24, 25, N2 being an integer greater than or equal to two. The switching of the switching members 24, 25 is controlled by a control unit 29 of the control system 6.

[0022] As known per se, each switching member 24, 25 is bidirectional in current and unidirectional in voltage.Each switching member 24, 25 comprises a controllable electronic switch 26 and a diode 28 (which is a so-called “parasitic” diode) connected in antiparallel, thus ensuring bidirectional current flow paths. Each switch 26 is, for example, formed from an insulated gate bipolar transistor, also called an IGBT transistor (from the English “Insulated Gate Bipolar Transistor”). All the IGBT transistors 26 are, for example, identical. The gate of each IGBT transistor 26 is connected to the aforementioned control means to receive a corresponding control signal.Alternatively, the IGBT transistor 26 is replaced by any semiconductor electronic component comprising a control electrode and two conduction electrodes, such as a bipolar transistor, a field effect transistor, a thyristor, a gate-turn-off thyristor, an IGCT thyristor (from the English "Insulated Gate Commutated Thysistor"), or an MCT thyristor (from the English "MOS Controlled Thyristor") for example. The controllable electronic switches 26 of the switching members 24 of the first low-frequency switching electronic branch 16A are different from the controllable electronic switches 26 of the switching members 25 of the high-frequency switching electronic branches 18A, 18B.

[0036]

[0023] The control system 6 of the converter 4 is configured to control the switching of the switching members 24, 25 (at a different switching frequency depending on whether they are the switching members 24 of the first low-frequency switching electronic branch 16A or the switching members 25 of the high-frequency switching electronic branches 18A, 18B). The control system 6 is configured to control two control loops at the level of the high-frequency switching electronic branches 18A, 18B and the main inductors 8: a first control loop where the electric current is controlled via a current setpoint (the current setpoint being able to be phase-shifted relative to the voltage of the input electrical supply network if reactive power is to be generated), and a second control loop where the electric voltage is controlled via a voltage setpoint.More precisely, the control system 6 is configured to apply an instantaneous current setpoint l. sp to the current flowing in each inductance 8, during a charging phase of the converter 4 (during which the electric current flows in a first direction in the first low-frequency switching branch 16A or in the second low-frequency switching branch 16B, and the power transfer takes place from the input power supply network to the capacitive load 3). The converter 4 can also operate in a discharging phase during which the electric current flows in a second direction, opposite to the first direction of circulation, in the first low-frequency switching branch 16A, and the power transfer takes place from the capacitive load 3 to the input power supply network or to an external load connected to the vehicle.

[0037]

[0024] In addition to the control unit 29, the control system 6 comprises means 31 for measuring the first and second electrical voltages LU, U2 and means 32 for determining, from the first and second measured electrical voltages LU, U2, the peak-to-peak amplitude l ci of the intensity of the current capable of flowing in the first low-frequency switching branch 16A. In particular, the expression of the peak-to-peak amplitude l ci the intensity of the current capable of circulating in the first low-frequency switching branch 16A is given by the following relation (2):

[0038] L is the minimum inductance value of each main inductor 8 (taking into account the inductance variation linked to component dispersions and operating conditions); and

[0039] F s is the switching frequency of each high-frequency switching branch 18A, 18B.

[0040]

[0025] The control system 6 also comprises means (not shown in the figures) for measuring, over a switching period of each high-frequency switching branch 18A, 18B, the average current flowing through each main inductance 8. The peak-to-peak amplitude l ci the intensity of the current capable of flowing in the first low-frequency switching branch 16A then corresponds to the variation in current passing through each main inductance 8 during the switching period of each high-frequency switching branch 18A, 18B.

[0041]

[0026] Each diode 30 is chosen so as to allow in its on state a maximum current value for passage through the diode 30 greater than the maximum current value for passage allowed by each controllable electronic switch 26 of the first low-frequency electronic switching branch 16A (in its on state), and greater than the critical conduction current value of the diode 30. In other words, each diode 30 is chosen in such a way that there is at least one operating zone for which, when the electric current passes through the diode 30, the electric conduction mode is a continuous conduction mode. Each diode 30 is dimensioned so as to support the maximum electric power in the charging phase of the converter 4.The controllable electronic switch 26 of each switching member 24 of the first low-frequency electronic switching branch 16A is sized so that the maximum passing current value authorized by the controllable electronic switch 26 covers the discontinuous conduction zones of the diodes 30.

[0042]

[0027] The method for controlling the converter 4, implemented by the control system 6, will now be described with reference to FIG. 2. Initially, the method is in the charging phase of the converter 4. The first low-frequency switching branch 16A is activated by the control system 6 at the start of the charging phase (in other words, at any time during this activation phase, only one of the two switching members 24 of the first branch 16A is in a closed state; the one of the two switching members 24 which is in the closed state being a function of the sign of the voltage LU of the supply network). The instantaneous current setpoint l sp(sinusoidal) intended to be applied to the current flowing in each inductance 8 is calculated by the control system 6. The control system 6 then calculates, from the measurement of the average current flowing through each main inductance 8 over a switching period of each high-frequency switching branch 18A, 18B, the control signals to be applied to the switching members 25 of the high-frequency switching branches 18A, 18B, to enable monitoring of the instantaneous setpoint l sp .

[0028] During the charging phase of the converter 4, the method comprises an initial step 39 of measuring, by the measuring means 31 of the control system 6, the first and second electrical voltages U1, U2.

[0043]

[0029] The method comprises a following step 40 during which the control system 6 determines (via its means 32), from the first and second measured electrical voltages LU, U2, the peak-to-peak amplitude lci of the intensity of the current flowing in the first low-frequency switching branch 16A. The peak-to-peak amplitude Id is determined using the mathematical relationship (2) previously described.

[0044]

[0030] The method comprises a following step 42 during which the control system 6 compares the peak-to-peak amplitude l ci at a threshold current value l seU ii predefined. The value uii is such that:

[0045] Imax is the maximum amplitude of the current intensity capable of flowing in the first low-frequency switching branch 16A.

[0046]

[0031] If the peak-to-peak amplitude l ciis greater than or equal to the predefined threshold current value Iseuii, the method comprises a following step 44 during which the control system 6 deactivates the first low-frequency switching branch 16A (in other words, at any time during this deactivation phase, the two switching members 24 of the first branch 16A are at the same time in their open state). The electric current, which flows in the converter 4 in the first direction of circulation (charging phase), then flows in the second low-frequency switching branch 16B provided with the diodes 30. At the end of step 44, the method loops back to the initial measurement step 39.

[0047]

[0032] Otherwise, the method comprises a following step 46 during which the control system 6 determines whether the following mathematical relationship (1) is verified: sgn(u) provides the sign of the function u(t) and is therefore equal to -1 or 1 when u(t) is non-zero.

[0033] Determining whether the mathematical relation (1) is verified or not makes it possible to know whether or not there exists at least one operating zone for which the electrical conduction mode of the diodes 30 is a discontinuous conduction mode (if the mathematical relation (1) is not verified, then such an operating zone exists).

[0048]

[0034] At the end of the determination step 46, if the control system 6 determines that the mathematical relationship (1) is not verified (this alternative being materialized by the arrow “A” in FIG. 2 and corresponding to a discontinuous conduction mode of the diodes 30), the method comprises a following step 48 during which the control system 6 keeps the first low-frequency switching branch 16A active. The method then loops back to the initial measurement step 39.

[0049]

[0035] If the control system 6 determines that the mathematical relationship (1) is verified (this alternative being materialized by the arrow “B” in FIG. 2 and corresponding to a continuous conduction mode of the diodes 30), the method comprises a following step 50 during which the control system 6 determines whether a predefined criterion is verified, and maintains active or on the contrary deactivates the first low-frequency switching branch 16A depending on the verification of the criterion. Preferably, according to a particular embodiment of the invention, the verification of the predefined criterion consists of comparing on the one hand the conduction losses in the diodes 30 of the second low-frequency switching branch 16B, with the conduction losses in the controllable electronic switches 26 of the first low-frequency switching branch 16A on the other hand.During step 50, the control system 6 keeps the first low-frequency switching branch 16A active (during a sub-step 50A) if the conduction losses in the diodes 30 are greater than the conduction losses in the controllable electronic switches 26. The control system 6 deactivates the first low-frequency switching branch 16A (during a sub-step 50B) otherwise. At the end of step 50, the method loops back to the initial measurement step 39.

[0050]

[0036] The method for controlling a converter according to the invention makes it possible to implement reactive power control and bidirectional power transfer within the converter (charging and discharging modes), while offering in the charging mode flexibility in control, reasonable computational complexity and / or consumption of memory resources and by implementing a converter with reduced manufacturing costs.

Claims

CLAIMS 1. Method, implemented by a system (6) for controlling a converter (4) from a first electrical voltage (U1) to a second electrical voltage (U2), for controlling said converter (4), the converter (4) being connected to an alternating electrical voltage source comprising a neutral conductive line (N1) and at least one phase conductive line (P1), the alternating electrical voltage source providing the first electrical voltage (U1), the converter (4) comprising an active power factor correction stage (7), the active power factor correction stage (7) comprising two low-frequency switching electronic branches (16A, 16B) connected in parallel, and at least one high-frequency switching electronic branch (18A, 18B), each low-frequency switching electronic branch (16A, 16B) comprising two low-frequency switching half-branches (16A1, 16A2, 16B1,16B2) connected in series at a first intermediate terminal (20A, 20B), at least one switching half-branch (16A1, 16A2) of a first low-frequency switching branch (16A) comprising at least one switching member (24) provided with a controllable electronic switch (26), at least one switching half-branch (16B1, 16B2) of a second low-frequency switching branch (16B) comprising at least one diode (30), each first intermediate terminal (20A, 20B) being connected to the neutral conductor line (N1), said at least one high-frequency switching electronic branch (18A, 18B) comprising two high-frequency switching half-branches (18A1, 18A2, 18B1, 18B2) connected in series at a second intermediate terminal (22A, 22B), at least one high-frequency switching half-branch (18A1, 18A2, 18B1, 18B2) comprising at least one switching member (25), said at least one second intermediate terminal (22A,22B) being connected to said at least one phase conductive line (P1) via an inductance (8), each of the diodes (30) being configured to authorize in its on-state a maximum current value for passage through the diode (30) greater than the maximum current value for passage authorized by each controllable electronic switch (26) in its on-state, and greater than the value, of critical conduction current of the diode (30), the method comprising a charging phase during which the electric current flows in a first direction in the first low-frequency switching branch (16A) or in the second low-frequency switching branch (16B), and a discharging phase during which the electric current flows in a second direction, opposite to the first direction of circulation, in the first low-frequency switching branch (16A), the control system (6) being configured to apply, during the charging phase of the method, an instantaneous current setpoint l sp to the current flowing in the or each inductance (8), the control system (6) comprising means (31) for measuring the first and second electrical voltages (U1, U2) and means (32) for determining, from the first and second measured electrical voltages (U1, U2), the peak-to-peak amplitude l ciof the intensity of the current capable of flowing in the first low-frequency switching branch (16A), the first low-frequency switching branch (16A) being initially activated at the start of the charging phase of the method, characterized in that the method comprises, during its charging phase, the steps of: - a step (39) of measuring the first and second electrical voltages (U1, U2); - a step (40) of determining, from the first and second measured electrical voltages (U1, U2), the peak-to-peak amplitude Id of the intensity of the current flowing in the first low-frequency switching branch (16A); - a step (42) of comparing the peak-to-peak amplitude l ci at a threshold current value l seU ii predefined, the value l seU ii being such that: OR Imax is the maximum amplitude of the current intensity capable of flowing in the first low-frequency switching branch (16A); - if the peak-to-peak amplitude l ci is greater than or equal to the predefined threshold current value Iseuii, a step (44) of deactivating the first low-frequency switching branch (16A); - if the peak-to-peak amplitude l ci is strictly less than the value of predefined threshold current Iseuii, a step (46) of determining whether the following mathematical relationship (1) is verified, making it possible to detect whether the electrical conduction mode of the diodes (30) is a continuous or discontinuous conduction mode: sgn(u) provides the sign of the function u(t) and is therefore equal to -1 or 1 when u(t) is non-zero; - if, at the end of the verification (46), the mathematical relationship (1) is false, a step (48) consisting of keeping the first low-frequency switching branch (16A) active; - if, at the end of the verification (46), the mathematical relationship (1) is true, a step (50, 50A, 50B) consisting of maintaining active or deactivating the first low-frequency switching branch (16A) depending on the verification of a predefined criterion.

2. Method according to claim 1, characterized in that, if, at the end of the verification (46), the mathematical relationship (1) is true, the verification of the predefined criterion in the step (50, 50A, 50B) consisting of keeping the first low-frequency switching branch (16A) active or not consists of comparing the conduction losses in the diodes (30) with the conduction losses in the controllable electronic switches (26), the first low-frequency switching branch (16A) being kept active if the conduction losses in the diodes (30) are greater than the conduction losses in the controllable electronic switches (26), the first low-frequency switching branch (16A) being deactivated in the opposite case.

3. Assembly (2) comprising a converter (4) of a first electrical voltage (U1) into a second electrical voltage (U2) and a system (6) for controlling said converter (4), the converter (4) being capable of being connected to an alternating electrical voltage source comprising a neutral conductive line (N1) and at least one phase conductive line (P1), the converter (4) comprising an active power factor correction stage (7), the active power factor correction stage (7) comprising two low-frequency electronic switching branches (16A, 16B) connected in parallel, and at least one high-frequency electronic switching branch (18A, 18B), each low-frequency electronic switching branch (16A, 16B) comprising two low-frequency half-switching branches (16A1, 16A2, 16B1, 16B2) connected in series at a first intermediate terminal (20A, 20B), at least one half-switching branch (16A1, 16A2) of a first low-frequency switching branch (16A) comprising at least one switching member (24) provided with a controllable electronic switch (26), at least one half-switching branch (16B1, 16B2) of a second low-frequency switching branch (16B) comprising at least one diode (30), each first intermediate terminal (20A, 20B) being capable of being connected to the conductive line neutral (N1), said at least one high-frequency electronic switching branch (18A,18B) comprising two high-frequency switching half-branches (18A1, 18A2, 18B1, 18B2) connected in series at a second intermediate terminal (22A, 22B), at least one high-frequency switching half-branch (18A1, 18A2, 18B1, 18B2) comprising at least one switching member (25), said at least one second intermediate terminal (22A, 22B) being capable of being connected to said at least one phase conductive line (P1) via an inductance (8), each of the diodes (30) being configured to allow in its on-state a maximum current value for passage through the diode (30) greater than the maximum current value for passage authorized by each controllable electronic switch (26) in its on-state, and greater than the critical conduction current value of the diode (30), the control system (6) comprising means (31 ) for measuring the first and second electrical voltages (U1, U2) and means (32) for determining,from the first and second measured electrical voltages (U1, U2), of the peak-to-peak amplitude Id of the intensity of the current capable of flowing in the first low-frequency switching branch (16A), characterized in that the system (6) for controlling the converter (4) is configured to implement the steps of a control method according to claim 1 or 2, the control system (6) being configured to apply, during the charging phase of the method, an instantaneous current setpoint l, sp to the current flowing in the or each inductance (8).

4. Electric charger for an electric or hybrid vehicle intended to be connected to a terminal or an electric charging station connected to an alternating electric voltage source, for the electrical supply of said electric or hybrid vehicle, characterized in that it comprises an assembly (2) according to claim 3.

5. Electric or hybrid vehicle, in particular an automobile, characterized in that it comprises an electric charger according to claim 4.

Images