Control device for three-phase rectifier

Abstract

The invention relates to a control device (12) for a three-phase rectifier (10) connected to each phase (28) of an alternating network (8) and to a neutral (30), the control device being configured so as to, for at least one current switching interval: simultaneously acquire values ​​of the electric current flowing between each phase (28) and the rectifier (10), at a current acquisition time belonging to the current switching interval, the current acquisition time being a function of a reference acquisition time associated with the current switching interval and a current delay depending on electric current values ​​acquired for at least one previous switching interval; and calculate, as a function of the acquired electric current values ​​for the current switching interval, the value of a control signal of the rectifier for at least one switching interval subsequent to the current switching interval.Figure for the abbreviation: Figure 5.

Description

Title of the invention: Control device for three-phase rectifier Technical field

[0001] The present invention relates to a control device for a three-phase rectifier.

[0002] The invention also relates to a charger comprising such a control device, a vehicle comprising such a charger, and a control method implemented by such a control device.

[0003] The invention applies to the field of electric vehicles, and more specifically to chargers equipping such vehicles. State of the art

[0004] It is known to equip an electric vehicle with a charger. Such a charger is intended to be connected to an AC network, such as a three-phase AC network, to recharge a high-voltage battery (typically 400 V) of the vehicle.

[0005] Conventionally, the charger comprises a rectifier associated with a control device for controlling the operation of said rectifier.

[0006] Such a rectifier comprises, for each phase of the AC network, a respective switching branch. Furthermore, the control device is generally configured to control the operation of the rectifier by regulating the electric current injected into each of its switching branches. The purpose of such regulation is to ensure that the electric current flowing in each switching branch follows an expected sinusoidal time profile, in order to give the charger an expected power factor, which is generally optimal (a degraded power factor is sometimes required in order to locally compensate for a network with a capacitive or inductive tendency).

[0007] To this end, it is known to implement a so-called “PWM” (Pulse Width Modulation) regulation, based on a measurement, carried out by means of an electric current sensor associated with each switching branch, of the electric current injected into said switching branch from the corresponding phase of the AC network. More precisely, in such a regulation, the control device generates a control signal intended to control the on or off state of the switching elements of each switching branch over time.

[0008] For each switching branch of the rectifier, such a control signal is a logic signal defined over a plurality of successive switching intervals, each having a duration called "switching period" (generally negligible compared to the network period). For each switching branch, and for each switching interval, the duty cycle of the control signal depends on a desired average value of the electric current injected into said switching branch, from the corresponding phase, during said switching interval.

[0009] An example of the evolution over time of a control signal is illustrated by the upper graph of [Fig. 1]. In this figure, the switching period is noted T c, and the control signal has, depending on the instant considered, a low value equal to 0 or a high value equal to 1.

[0010] Furthermore, an example of the evolution over time of the electric current injected into a switching branch of a rectifier, corresponding to said control signal, is illustrated by the lower graph of [Fig.l]. In this figure, the instantaneous electric current, represented by a solid line, evolves around an average value Im, materialized by a horizontal dashed line.

[0011] Naturally, effective regulation is subject to a reliable determination of the average value of the electric current over a switching interval.

[0012] Now, in theory, for a given switching branch, the average value, over a switching interval, of the electric current injected into said switching branch is the value of said electric current at the midpoint of the high plateau (respectively of the low plateau) of the control signal (simply designated as “central point” hereinafter) during said switching interval. This is visible in [Fig.l], where the curve representing the instantaneous value of the electric current intersects the horizontal line representing the average value Im at the times corresponding to the central points of the high plateaus (points Ab A2) and low plateaus (points Bb B2) of the control signal delivered by the control device.

[0013] A simple way of carrying out the control would therefore consist of measuring the electric current injected into each switching branch at an instant corresponding to the central point of the high plateau (or the low plateau) of the control signal delivered by the control device.

[0014] However, such a method does not give complete satisfaction.

[0015] Indeed, to reduce high-frequency noise resulting, for example, from electromagnetic interference, the measurement signals delivered by the electric current sensors are generally filtered, in particular by means of an RC filter placed between the electric current sensor and the control device.

[0016] In the example of [Fig.l], the time evolution of the filtered measurement signal corresponding to the instantaneous electric current of the lower graph is represented, on this same graph, by a dot-and-dash curve.

[0017] However, conventionally, such an RC filter introduces a delay. It follows that, for a

[0018]

[0019]

[0020]

[0021]

[0022] given switching branch, the value of the measurement signal received by the control device from the electric current sensor, at an instant corresponding to a central point of the control signal, is delayed relative to the value of the electric current actually measured by the electric current sensor for said switching branch at said instant. In particular, the value of the measurement signal at the instant corresponding to the central point of the control signal is different from the average value of the electric current over a switching interval. Therefore, the average value of the electric current over a switching interval is poorly evaluated, which harms the efficiency of the regulation. An aim of the present invention is to remedy at least one of the drawbacks of the state of the art. Another aim of the invention is to propose a control device whose performance is less impacted by the presence of RC filters at the output of the electric current sensors than known control devices. Statement of the invention To this end, the invention relates to a control device of the aforementioned type, in which the three-phase rectifier is intended to be connected, in use, to each phase of a three-phase AC network, the three phases of the AC network defining a neutral among them, the rectifier also being intended to be connected, in use, to the neutral, the control device being configured to generate a signal for controlling the operation of the rectifier, the control signal being defined over a plurality of successive switching intervals, the control device being configured so as to, for at least one current switching interval: • simultaneously acquire values ​​of the electric current flowing between each respective phase of the AC network and the rectifier, at a current acquisition time belonging to the current switching interval, the current acquisition time being a function of a reference acquisition time associated with the current switching interval and of a current delay depending on values ​​of the electric current acquired for at least one previous switching interval; and • calculate, based on the acquired values ​​of the electric current for the current switching interval, the value of the control signal for at least one switching interval subsequent to the current switching interval. Indeed, thanks to such a device, a real-time correction of the control signal is allowed. Such a correction is based on the knowledge of a relationship that the injected currents are supposed to respect in the case of an ideal control.

[0023] Such a control device, on the basis of a determination of a match between the acquired current values ​​of the electric currents and this relationship, is able to calculate a delay intended to compensate for the undesirable effects linked to the time shifts introduced by the electric current acquisition chain.

[0024] As a result, thanks to such a control device, the control signal of the rectifier is effectively calculated on the basis of the average value, over a switching interval, of the electric current injected into each switching branch. The performance of the charger is, consequently, improved.

[0025] Furthermore, such a control device is insensitive to the drift of the filters (and the delays they introduce), such drift being corrected in real time.

[0026] The control device according to the invention can be any type of device such as a server, a computer, a tablet, a calculator, a processor, a computer chip, programmed to implement the method according to the invention, for example by executing the computer program according to the invention.

[0027] Advantageously, the control device according to the invention has one or more of the following characteristics, taken in isolation or in any technically possible combination:

[0028] the current acquisition time associated with the current switching interval is equal to the sum of the corresponding reference acquisition time and the current delay;

[0029] the control signal associated with the current switching interval comprises a high plateau, respectively a low plateau, the reference acquisition instant being the instant corresponding to the midpoint of the high plateau, respectively of the low plateau;

[0030] the control device is configured to implement, for the current switching interval, a calculation of the corresponding current delay comprising: • a determination of an average, over all or part of the switching intervals prior to the current switching interval, of a convergence indicator, the convergence indicator being equal, for each of said switching intervals, to the sum of the three values ​​of the electric current acquired at the respective acquisition time; and • a correction of a previous delay to obtain said current delay, if the calculated average is distinct from a predetermined setpoint (preferably if the calculated average is not zero);

[0031] the control device is configured to implement a new calculation of the current delay when the current switching range corresponds to a zero crossing of the voltage on a predetermined reference phase among the three phases of the alternating network;

[0032] the control device is configured to calculate the average of the convergence indicator over all switching intervals prior to the switching interval current switching, from an immediately preceding zero crossing of the voltage on the predetermined reference phase;

[0033] the correction of the previous delay includes: • a determination of an error equal to a difference between the calculated average of the convergence indicator and a predetermined setpoint; • an amplification of the determined error; • an application of the amplified error to an integral regulator;

[0034] the predetermined instruction is zero.

[0035] The invention also relates to a charger comprising a rectifier and a control device as defined above for controlling the operation of the rectifier.

[0036] The invention also relates to an electric vehicle comprising a charger as defined above, the charger being connected, at output, to a battery of the electric vehicle.

[0037] According to another aspect of the invention, there is provided a method for controlling a three-phase rectifier connected to each phase of a three-phase AC network, the three phases of the AC network defining a neutral among them, the rectifier also being connected, in use, to the neutral, the control method comprising a generation of a signal for controlling the operation of the rectifier, the control signal being defined over a plurality of successive switching intervals, the control method further comprising, for at least one current switching interval, the steps: • simultaneous acquisition of values ​​of the electric current flowing between each respective phase of the AC network and the rectifier, at a current acquisition time belonging to the current switching interval, the current acquisition time being a function of a reference acquisition time associated with the current switching interval and of a current delay depending on values ​​of the electric current acquired for at least one previous switching interval; and • calculation, based on the acquired values ​​of the electric current for the current switching interval, of the value of the control signal for at least one switching interval subsequent to the current switching interval.

[0038] According to another aspect of the invention, there is provided a computer program comprising executable instructions which, when executed by computer, implement the steps of the method as defined above.

[0039] The computer program can be in any computer language, such as for example machine language, C, C++, JAVA, Python, etc. Brief description of the figures

[0040] The invention will be better understood on reading the following description, given solely by way of non-limiting example and made with reference to the appended drawings in which:

[0041] [Fig-1]: [Fig.l] is a graph of the time evolution of a control signal delivered by a control device according to the invention, of an electric current corresponding to the control signal and circulating in a switching branch of a rectifier, and of a measurement signal representative of said electric current;

[0042] [Fig.2]: [Fig.2] is a schematic representation of an electric vehicle according to the invention;

[0043] [Fig.3]: [Fig.3] is a schematic representation of a charger of the vehicle of [Fig.2], in use;

[0044] [Fig.4]: [Fig.4] is a flowchart of a control method implemented by a charger control device of [Fig.3]; and

[0045] [Fig.5]: [Fig.5] is a block diagram illustrating part of the steps of a loop of calculation of the process of [Fig.4].

[0046] It is understood that the embodiments which will be described below are in no way limiting. In particular, it will be possible to imagine variants of the invention comprising only a selection of characteristics described below isolated from the other characteristics described, if this selection of characteristics is sufficient to confer a technical advantage or to differentiate the invention compared to the state of the prior art. This selection comprises at least one preferably functional characteristic without structural details, or with only a part of the structural details if it is this part which is only sufficient to confer a technical advantage or to differentiate the invention compared to the state of the prior art.

[0047] In particular, all the variants and all the embodiments described can be combined with each other if nothing prevents this combination from a technical point of view.

[0048] In the figures and in the remainder of the description, the elements common to several figures retain the same reference. Detailed description

[0049] An electric vehicle 2 according to the invention is illustrated by [Fig.2].

[0050] The electric vehicle 2 comprises a battery 4 and a charger 6, the battery 4 being connected to the output of the charger 6.

[0051] The battery 4 is, in particular, intended to power an electric motor of the electric vehicle 2. Furthermore, the charger 6 is adapted to charge the battery 4 by transferring electrical energy to the battery 4 from an alternating current network 8. Such a network ternative 8 is a three-phase network, for example operating at a network frequency of 50 Hz (hertz) or 60 Hz.

[0052] The charger 6 comprises a three-phase rectifier 10 (also called a “rectifier”) and a control device 12 configured to control the operation of the rectifier 10.

[0053] An example of the architecture of the rectifier 10, called a “six-pulse bridge”, is illustrated by [Fig.3].

[0054] Conventionally, such a rectifier 10 comprises three switching branches 14 connected in parallel between a first branch 16 (or bus 16) and a second branch 18 (or bus 18). Each switching branch 14 comprises two switching elements 20 connected in series between the first branch 16 and the second branch 18, and connected together at an input terminal 22 of the rectifier 10.

[0055] The rectifier 10 further comprises an intermediate terminal 24 connected to each of the first branch 16 and the second branch 18 via a corresponding load 26, such as a capacitor (the two loads 26 not necessarily being identical).

[0056] Each of the first branch 16 and the second branch 18 is electrically connected to a respective terminal of the battery 4, for example via a DC-DC converter ensuring galvanic isolation of the charger 6.

[0057] As shown in the figure, in use, the input terminal 22 of each switching branch 14 is connected to a respective phase 28 of a three-phase AC network 8.

[0058] Furthermore, in use, the intermediate terminal 24 is also connected to a neutral 30 of the alternating network 8, the neutral 30 being defined by the three phases 28, as a common connection point of the three phases 28.

[0059] Furthermore, for each phase 28, the vehicle 2 comprises a respective electric current sensor 32, configured to deliver, to the control device 12, a measurement signal representative of the electric current flowing between said phase 28 and the rectifier 10 (i.e. between the phase 28 and the respective switching branch 14 of the rectifier 10).

[0060] As indicated previously, the control device 12 is configured to control the operation of the rectifier 10. More precisely, the control device 12 is configured to generate a signal for controlling the operation of the rectifier 10.

[0061] Such a control signal is defined over a plurality of successive switching intervals. Conventionally, each switching interval has a duration Tc that is negligible compared to the period of the alternating network 8, for example 14.28 ps (microsecond), corresponding to a frequency of 70 kHz.

[0062] For example, the control device 12 is configured to generate the control signal by implementing pulse width modulation regulation, conventionally known. In particular, for each switching interval, and for each phase 28, the switching signal comprises a high plateau and a low plateau ([Fig.l]).

[0063] To generate the control signal, the control device 12 is configured so as to, for at least one current switching interval, simultaneously acquire values ​​of the electric current flowing between each respective phase 28 of the AC network and the rectifier 10, at a current acquisition time belonging to the current switching interval. Furthermore, the control device 12 is configured to calculate the value of the control signal for at least one switching interval subsequent to the current switching interval, as a function of the three simultaneously acquired values ​​of the electric current during the current switching interval.

[0064] More precisely, the control device 12 is configured so that, for any given current switching interval, the current acquisition time is a function of a reference acquisition time associated with the current switching interval and of a current delay dependent on the value of the electric current acquired for at least one previous switching interval.

[0065] A delay calculation loop 44 (called a “calculation loop”) will now be described with reference to FIGS. 4 and 5.

[0066] Preferably, prior to the implementation of the calculation loop 44, the control device 12 is configured to, during a neutral detection step 40, carry out a detection of the neutral 30. More precisely, the control device 12 is configured to verify, during the detection step 40, that the intermediate terminal 24 is indeed connected to the neutral 30 of the AC network 8.

[0067] In this case, the control device 12 is preferably configured not to implement the calculation loop 44 if the connection of the rectifier 10 to the neutral 30 is not detected.

[0068] Preferably, the control device 12 is also configured to carry out, during a synchronization step 42 subsequent to step 40 and prior to the implementation of the calculation loop 44, a synchronization with the alternating network 8. Such synchronization aims to determine, in real time, the evolution of the voltage of each phase 28. For example, to carry out such synchronization, the control device 12 is configured to implement a phase-locked loop.

[0069] The control device 12 is, furthermore, advantageously configured to implement the calculation loop 44 iteratively, and more precisely at each new switching interval.

[0070] In particular, during an acquisition step 46 of the calculation loop 44, the control device 12 is configured to simultaneously acquire the value of the electric current (from the measurement signal delivered by each electric current sensor 32) flowing between each phase 28 of the AC network and the rectifier 10, at a current acquisition instant belonging to the current switching interval.

[0071] Preferably, for the current switching interval, the current acquisition time is equal to the sum of the corresponding reference acquisition time and a current delay.

[0072] The current delay is, for example, the last delay value stored in a memory of the control device 12.

[0073] Furthermore, the reference acquisition time is preferably the time corresponding to the midpoint of the high plateau, respectively of the low plateau, of the control signal delivered by the control device 12 for the current switching interval.

[0074] Advantageously, the reference acquisition instant is the instant corresponding to the midpoint of the high plateau (respectively of the low plateau) of the control signal delivered by the control device 12 for the current switching interval, to which is added a reference delay corresponding to known characteristics of a filter arranged between the electric current sensors 32 and the control device 12. In this way, the theoretical delays known at the factory outlet are taken into account, which is likely to reduce a convergence time of the delay calculation.

[0075] Furthermore, the control device is configured to calculate, during a calculation step 48, a convergence indicator S ([Fig.5]) equal to the sum of the three values ​​of the electric current acquired at the current acquisition instant.

[0076] Preferably, the control device 12 is, in addition, configured to determine, during an evaluation step 50, whether the current switching range corresponds to a zero crossing of the voltage on a phase of the three-phase network 8 chosen as the reference phase.

[0077] If the outcome of the determination is negative, the control device 12 is preferably configured to keep the value of the delay unchanged.

[0078] If the outcome of the determination is positive, the control device 12 is configured to determine, during an average calculation step 52, an average of the convergence indicator S over all or part of the switching intervals prior to the current switching interval.

[0079] Advantageously, the control device 12 is configured to calculate the average of the convergence indicator S over all of the com intervals mutation preceding the current switching interval since an immediately preceding zero crossing of the voltage on the reference phase of the three-phase network. In other words, the control device 12 is configured to calculate the average of the convergence indicator S over all the switching intervals of the same half-period of the voltage of the reference phase (excluding the current switching interval).

[0080] Since the duty cycle of the control signal changes over a period of the AC network 8, it follows that the ideal delay, which is a function of the instantaneous duty cycle, also changes over a period. Consequently, a calculation of the convergence indicator over a half-period of the voltage is advantageous, insofar as it offers the best compromise on the stability of the regulation.

[0081] Furthermore, the control device 12 is configured to correct the previous delay if the calculated average is different from a predetermined setpoint.

[0082] More precisely, the control device 12 is configured to determine, during an error determination step 54, an error equal to a difference between the calculated average of the convergence indicator S and a predetermined setpoint.

[0083] Advantageously, the predetermined setpoint is equal to 0, as illustrated by [Fig.5]. In fact, the sum of the currents flowing from each phase 28 to the rectifier is, in theory, zero.

[0084] However, the predetermined setpoint is also likely to be non-zero (while remaining small compared to the amplitude of the convergence indicator): in this way, faster convergence and better stability of the regulation are likely to be achieved.

[0085] The control device 12 is further configured to, during an amplification step 56, amplify the determined error. Such amplification corresponds to the multiplication of the error determined at the end of step 54 by a predetermined coefficient. As a result, during the amplification step 56, the determined error, initially homogeneous to an electric current, is converted into an amplified error homogeneous to a duration.

[0086] Advantageously, the control device 12 is also configured to apply the amplified error to the input of an integral regulator, during a regulation step 58.

[0087] This results in a new current delay at the output of the regulator, which is implemented during the next iteration of the calculation loop 44. Functioning

[0088] The operation of the charger 6 will now be described with reference to FIGS. 2 to 5.

[0089] During a preliminary connection step, the rectifier 10 is connected to each phase 28 of the alternating network 8 to charge the battery 4.

[0090] Then, preferably, during the neutral detection step 40, the control device 12 performs a detection of the neutral 30. In this case, the control device 12 does not implement the calculation loop 44 if the connection of the rectifier 10 to the neutral 30 is not detected.

[0091] Then, preferably, during the synchronization step 42, the control device 12 carries out synchronization with the alternating network 8.

[0092] Then, the control device 12 implements the calculation loop 44, advantageously iteratively.

[0093] In particular, during the acquisition step 46 of the calculation loop 44, the control device 12 simultaneously acquires the value of the electric currents flowing between each phase 28 of the AC network and the rectifier 10, at the current acquisition instant associated with the current switching interval.

[0094] Then, during the calculation step 48, the control device calculates the convergence indicator S.

[0095] Then, preferably, during the evaluation step 50, the control device 12 determines whether the current switching range corresponds to a zero crossing of the voltage on the reference phase.

[0096] In this case, if the outcome of the determination is negative, the control device 12 maintains the last value of the delay unchanged. Otherwise, during the averaging step 52, the control device 12 determines the average of the convergence indicator S over all or part of the switching intervals prior to the current switching interval.

[0097] Then, during step 54 of error determination, the control device 12 determines the error equal to the difference between the calculated average of the convergence indicator S and the predetermined setpoint.

[0098] Then, during the amplification step 56, the control device 12 amplifies the determined error.

[0099] Then, advantageously, during the regulation step 58, the control device 12 applies the amplified error to the input of the integral regulator. This results, at the output of the regulator, in the new current delay, which is implemented during the next iteration of the calculation loop 44.

[0100] Of course, the invention is not limited to the examples which have just been described.

Claims

Claims

1. Control device (12) for a three-phase rectifier (10) intended to be connected, in use, to each phase (28) of a three-phase AC network (8), the three phases (28) of the AC network (8) defining a neutral (30) among them, the rectifier (10) also being intended to be connected, in use, to the neutral (30), the control device (12) being configured to generate a signal for controlling the operation of the rectifier (10), the control signal being defined over a plurality of successive switching intervals, the control device (12) being configured so as, for at least one current switching interval: • simultaneously acquire values ​​of the electric current flowing between each respective phase (28) of the AC network (8) and the rectifier (10), at a current acquisition time belonging to the current switching interval,the current acquisition time being a function of a reference acquisition time associated with the current switching interval and of a current delay depending on values ​​of the electric current acquired for at least one previous switching interval; and • calculating, as a function of the values ​​acquired of the electric current for the current switching interval, the value of the control signal for at least one switching interval subsequent to the current switching interval.,

2. A control device (12) according to claim 1, wherein the current acquisition time associated with the current switching interval is equal to the sum of the corresponding reference acquisition time and the current delay.

3. Control device (12) according to claim 1 or 2, wherein the control signal associated with the current switching interval comprises a high plateau, respectively a low plateau, the reference acquisition instant being the instant corresponding to the midpoint of the high plateau, respectively of the low plateau.

4. Control device (12) according to any one of the claims 1 to 3, configured to implement, for the current switching interval, a calculation of the corresponding current delay comprising: • a determination of an average, over all or part of the switching intervals prior to the current switching interval, of a convergence indicator (S), the convergence indicator (S) being equal, for each of said switching intervals, to the sum of the three values ​​of the electric current acquired at the respective acquisition instant; and • a correction of a previous delay to obtain said current delay, if the calculated average is distinct from a predetermined setpoint.

5. Control device (12) according to claim 4, configured to implement a new calculation of the current delay when the current switching range corresponds to a zero crossing of the voltage on a predetermined reference phase among the three phases (28) of the alternating current network (8).

6. A control device (12) according to claim 5, configured to calculate the average of the convergence indicator over all switching intervals prior to the current switching interval, since an immediately prior zero crossing of the voltage on the predetermined reference phase.

7. Control device (12) according to any one of claims 4 to 6, in which the correction of the preceding delay comprises: • a determination of an error equal to a difference between the calculated average of the convergence indicator and the predetermined setpoint; • an amplification of the determined error; • an application of the amplified error to an integral regulator.

8. Control device (12) according to claim 7, in which the predetermined setpoint is zero.

9. Charger (6) comprising a rectifier (10) and a control device (12) according to any one of claims 1 to 8 for controlling the operation of the rectifier (10).

10. Electric vehicle (2) comprising a charger (6) according to claim 9, the charger being connected, at output, to a battery (4) of the electric vehicle (2).

11. A method of controlling a three-phase rectifier (10) connected to each phase (28) of a three-phase AC network (8), the three phases (28) of the AC network (8) defining a neutral (30) among them, the rectifier (10) also being connected, in use, to the neutral (30), the control method comprising generating a signal for controlling the operation of the rectifier (10), the control signal being defined over a plurality of successive switching intervals, the control method further comprising, for at least one current switching interval, the steps: • simultaneous acquisition of values ​​of the electric current flowing between each respective phase (28) of the alternating network (8) and the rectifier (10), at a current acquisition time belonging to the current switching interval, the current acquisition time being a function of a reference acquisition time associated with the current switching interval and of a current delay depending on values ​​of the electric current acquired for at least one previous switching interval; and • calculation, based on the acquired values ​​of the electric current for the current switching interval, of the value of the control signal for at least one switching interval subsequent to the current switching interval.

Images