Static power converter configured to measure a value of a filter inductance

Abstract

Static power converter configured to measure a value of a filtering inductance The present description relates to a static power converter (100), comprising at least: - a switching cell (102.1 – 102.3) comprising at least first and second switching switches (104, 106); - a first inductance (113) coupled to an output of the switching cell; - a first measuring switch (122) such that the first inductance is coupled between the first measuring switch and the switching cell; - a control circuit (126) configured to control at least one closing of the first measuring switch during a measurement of a value of the first inductance. Figure for the abstract: Fig. 1

Description

Title of the invention: Static power converter configured to measure a value of a filtering inductance Technical field

[0001] The present description relates generally to the field of electrical power conversion, and in particular that of static power converters. The present description also relates to power systems using static power converters, such as for example that of photovoltaic systems. Prior art

[0002] A power system such as a photovoltaic energy production system comprises at least one photovoltaic energy conversion device. This photovoltaic energy produced in the form of a continuous electrical signal is converted into an alternating electrical signal. This conversion is provided by at least one static DC / AC power converter also called an inverter.

[0003] Failures occurring in a photovoltaic energy production system are often due to the inverter. More specifically, failures in the components forming a filtering circuit at the output of the inverter are often the cause of a significant portion of these failures.

[0004] The filtering circuit of the inverter generally comprises at least one inductance, and corresponds for example to an LCL type filter (inductance - capacitance - inductance) present at the output of each phase of the inverter. In an inductance, the degradation over time of its insulation can cause for example a short circuit of certain turns of the inductance, which can result in saturation of the inductance which can cause failures of other components of the inverter such as IGBTs of the switching cells of the inverter. Summary of the invention

[0005] There is a need to propose a solution making it possible to identify possible failures of the inductance(s) of the filtering circuit(s) within a static power converter, or even to monitor the health of these inductances.

[0006] For this, a static power converter is proposed, comprising at least

[0007] - a switching cell comprising at least first and second switches switching breakers;

[0008] - a first inductor coupled to an output of the switching cell;

[0009] - a first measuring switch such that the first inductance is coupled between the first measuring switch and the switching cell;

[0010] - a control circuit configured to control at least one closing of the first measuring switch when measuring a value of the first inductance.

[0011] According to a particular embodiment, the static power converter further comprises at least:

[0012] - a capacitive element electrically coupled in parallel with the communication cell mutation and on which an input voltage is intended to be applied;

[0013] - a current measuring circuit configured to measure a current intended for cross the first inductance;

[0014] and:

[0015] - the switching cell comprises a central node to which the first and second switching switches are electrically coupled;

[0016] - the first inductor comprises a first electrode coupled to the central node of the switching cell;

[0017] - the first measuring switch is electrically coupled between a second electrode of the first inductance and the capacitive element;

[0018] - the control circuit is configured to control the control switches mutation and the first measuring switch such that during a first part of the measurement of the value of the first inductance, the first measuring switch and the first switching switch are closed.

[0019] According to a particular embodiment, the control circuit is configured to control the switching switches and the first measuring switch such that during a second part of the measurement of the value of the first inductance, the first measuring switch is closed and the first switching switch is open.

[0020] According to a particular embodiment, the static power converter further comprises a circuit for calculating the value of the first inductance from the value of the input voltage and the current measured by the current measuring circuit during the first part of the measurement of the value of the first inductance and / or during the second part of the measurement of the value of the first inductance.

[0021] According to a particular embodiment, the calculation circuit is configured to calculate the value of the first inductance according to the equation:

[0022] L, = V < x^ ^calc v cbus Ai

[0023] with VcbuS corresponding to the input voltage across the capacitive element before measuring the value of the first inductance;

[0024] Ai corresponding to a current variation measured by the measuring circuit of fluent ;

[0025] At corresponding to a duration during which the variation of current Ai is measured.

[0026] According to a particular embodiment, the current measurement circuit is configured to measure the current during the first part of the measurement of the value of the first inductance.

[0027] According to a particular embodiment, the calculation circuit is configured to compare the calculated value of the first inductance to at least one nominal value of the first inductance and / or to at least one previous calculated value of the first inductance.

[0028] According to a particular embodiment, the calculation circuit is configured to calculate, before the measurement of the value of the first inductance, a duration Ton of the first part of the measurement of the value of the first inductance such that:

[0029] T = a Ol!

[0030] with Linitiaie corresponding to the initial value of the first inductance;

[0031] Almax corresponding to the maximum value of the current intended to pass through the first inductance during the first part of the measurement of the value of the first inductance;

[0032] a corresponding to a coefficient greater than 0, and less than or equal to 1.

[0033] According to a particular embodiment, the static power converter further comprises a voltage measurement circuit configured to measure the input voltage intended to be applied to the capacitive element, and the control circuit is configured to start measuring the value of the first inductance when the measured input voltage is greater than a threshold value.

[0034] According to a particular embodiment, the capacitive element comprises at least two capacitors electrically coupled in series at a node, and said node is coupled to a reference electrical potential.

[0035] According to a particular embodiment:

[0036] - the first inductance is part of an LCL type filter further comprising a second inductor of which a first electrode is coupled to the second electrode of the first inductor;

[0037] - the static power converter further comprises a second switch electrically coupled measuring element between a second electrode of the second inductor and the capacitive element;

[0038] - the control circuit is configured to also control the second in measuring switch such as: • during the first and second parts of the measurement of the value of the first inductance, the second measuring switch is open; • during a first part of a measurement of the second inductance, the first measuring switch is open, and the first switching switch and the second measuring switch are closed.

[0039] According to a particular embodiment, the control circuit is configured to control the second measuring switch such that during a second part of the measurement of the second inductance, the first measuring switch and the first switching switch are open, and the second measuring switch is closed.

[0040] According to a particular embodiment, the static power converter comprises:

[0041] - three switching cells each comprising a central node and at least first and second switching switches electrically coupled in series with each other, each being electrically coupled in parallel with the capacitive element;

[0042] - three first inductors each comprising a first electrode coupled to the central node of one of the switching cells;

[0043] - three current measuring circuits each configured to measure a current intended to pass through one of the first three inductances;

[0044] - three first measuring switches each electrically coupled between a second electrode of one of the first inductors and the capacitive element;

[0045] and the driving circuit is configured to measure each of the first inductances and to control the switching switches and the first measuring switches such that during a first portion of a measurement of the value of one of the first inductances, the first measuring switch and the first switching switch coupled to said one of the first inductances are closed, and during a second portion of the measurement of the value of said one of the first inductances, the first measuring switch coupled to said one of the first inductances is closed and the first switching switch coupled to said one of the first inductances is open.

[0046] According to a particular embodiment, the first measuring switches are configured to be controlled by the same control signal.

[0047] According to a particular embodiment, the static power converter is configured to measure the value of the first inductance at regular time intervals, for example daily or at intervals of several days.

[0048] According to a particular embodiment, the static power converter is a multilevel converter, for example of the NPC type or with floating capacitors, and operating as an inverter or voltage and / or current rectifier.

[0049] Also provided is a photovoltaic system comprising at least one photovoltaic panel coupled to a static power converter according to a particular embodiment. Brief description of the drawings

[0050] These characteristics and advantages, as well as others, will be explained in detail in the following description of particular embodiments given without limitation in relation to the attached figures among which:

[0051] [Fig.l] schematically represents a first example of a static power converter according to a particular embodiment;

[0052] [Fig.2] schematically represents electrical test signals obtained on an inductance of the static power converter according to a particular embodiment;

[0053] [Fig.3] schematically represents a second example of a static power converter according to a particular embodiment;

[0054] [Fig.4] schematically represents a third example of a static power converter according to a particular embodiment;

[0055] [Fig.5] schematically represents a fourth example of a static power converter according to a particular embodiment;

[0056] [Fig.6] schematically represents a fifth example of a static power converter according to a particular embodiment;

[0057] [Fig.7] schematically represents a sixth example of a static power converter according to a particular embodiment. Description of the embodiments

[0058] The same elements have been designated by the same references in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same references and may have identical structural, dimensional and material properties.

[0059] For the sake of clarity, only the steps and elements useful for understanding the embodiments described have been shown and are detailed. In particular, the production of the various elements, components and circuits (components of the switching cells, control circuit, current and voltage measurement circuits, calculation circuit, etc.) is not detailed. Those skilled in the art will be able to carry out in detail the various functions described from the functional description given here.

[0060] Unless otherwise specified, when referring to two elements connected to each other, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected (in English "coupled") to each other, this means that these two elements can be connected or be connected by through one or more other elements.

[0061] In the following description, when reference is made to absolute position qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as the terms "above", "below", "upper", "lower", etc., or to orientation qualifiers, such as the terms "horizontal", "vertical", etc., reference is made unless otherwise specified to the orientation of the figures or to a ... in a normal position of use.

[0062] Unless otherwise specified, the expressions "about", "approximately", "substantially", and "of the order of" mean to within 10%, preferably to within 5%.

[0063] The closed state, or passing or saturated state, corresponds to the state in which a switch allows a current to pass, and the open state, or blocked state, corresponds to the state in which the switch does not allow any current to pass.

[0064] [Fig. 1] schematically represents a first example of embodiment of a static power converter 100.

[0065] In the various exemplary embodiments described below, the converter 100 is part of a photovoltaic system 1000 comprising at least one photovoltaic panel 1002 intended to produce a continuous electrical signal (a single photovoltaic panel 1002 is mentioned in the remainder of the description, although the system 1000 may comprise several panels 1002 coupled to the converter 100).

[0066] In the first example described, the converter 100 corresponds to a three-phase inverter.

[0067] In the example of [Fig.l], the converter 100 comprises three switching cells 102.1 - 102.3 each intended for the direct - alternating conversion of the electrical signal produced by the panel 1002 for one of the phases of the three-phase electrical signal delivered at the output of the converter 100.

[0068] Each of the switching cells 102.1 - 102.3 comprises at least one first switching switch 104 and at least one second switching switch 106. In the example described, each of the switching switches 104, 106 comprises at least one power transistor of the IGBT type (including an antiparallel, or "freewheel" diode, visible in [Fig.l]). Alternatively, each of the switching switches 104, 106 may comprise another type of power transistor, for example of the MOSFET or other type. In each switching cell 102.1 - 102.3, the first and second switching switches 104, 106 are electrically coupled to each other in series at a central node 108.

[0069] In this first example, the first switching switches 104 correspond to the so-called “high-side” switches, their common coupling point being the positive terminal of the electrical energy source of the system 1000. second switching switches 106 correspond to the so-called “low-side” switches, their common coupling point being the negative terminal of the electrical energy source of the system 1000.

[0070] In the example of [Fig. 1], each transistor of the first and second switching switches 104, 106 is controlled by a gate driver circuit 110 electrically coupled to the gate of the transistor. In [Fig. 1], the control signals received by the circuits 110 are called S1, ..., S6.

[0071] In the first example described, the converter 100 further comprises a capacitive element electrically coupled in parallel with the switching cells 102.1 - 102.3 and to the terminals of which an input voltage called Vcbus is intended to be applied by the panel 1002. In the example of [Fig.l], this capacitive element comprises two capacitors 112, corresponding for example to capacitors, electrically coupled in series by a first of their electrodes at a node here forming the midpoint of the bus ensuring the connection between the panel 1002 and the input of the converter 100. This node is here coupled to a reference electrical potential of the converter 100, for example ground. As an example, each of the capacitors 112 may have a value equal to 10 mF.

[0072] The DC electrical voltage produced by the panel 1002 is for example measured by a voltage measuring circuit 111 of the converter 100. The voltage measuring circuit 111 corresponding for example to a voltage sensor, electrically coupled in parallel with the panel 1002 and the capacitive element. In addition, the voltage measuring circuit 111 is here configured to measure the input voltage Vcbus obtained at the terminals of the capacitive element.

[0073] The converter 100 according to the first example described further comprises filtering circuits each electrically coupled to the central node 108 of one of the switching cells 102.1 - 102.3. In the example of [Fig.l], the converter 100 comprises three filtering circuits. These filtering circuits are intended to filter the harmonics produced at the output of the switching cells 102.1 - 102.3. Each filtering circuit comprises at least one inductor.

[0074] In the example of [Fig.l], the filtering circuits are of the LCL type, that is to say each comprises a first inductance 113 coupled in series to a second inductance 114, as well as a capacitor 116 of which a first electrode is coupled to the junction node of the two inductances 113, 114. In each of these filtering circuits, the first inductance 113 can be seen as being intended to filter the high-frequency harmonics produced by the switching cell to which the filtering circuit is coupled, while the second inductance 114 can be seen as being intended to filter the low-frequency harmonics produced by this switching cell. According to one example, the first and second inductors 113, 114 may comprise coils, and the capacitors 116 may comprise capacitors.

[0075] In the example of [Fig. 1], a first electrode of the first inductance 113 of each filtering circuit is coupled to the central node 108 of the switching cell 102.1 - 102.3 to which the filtering circuit is coupled. A second electrode of the first inductance 113 of each filtering circuit is coupled to a first electrode of the second inductance 114 and to the first electrode of the capacitor 116 of this filtering circuit. A second electrode of the capacitors 116 of the filtering circuits is coupled to the reference electrical potential of the converter 100.

[0076] In the first example described, the converter 100 further comprises current measurement circuits 118 (three in number in the example of [Fig.l]) configured to measure the currents intended to pass through the first inductances 113. The circuits 118 comprise, for example, current sensors. In the example of [Fig.l], each circuit 118 is interposed between the central node 108 of one of the switching cells 102.1 - 102.3 and one of the filter circuits, the first electrode of the first inductance 113 of each filter circuit being coupled to one of the circuits 118. In [Fig.l], the measurement signals of the currents delivered by the circuits 118 are called Iph a, Iph b, Iph c.

[0077] In the case where the circuits 118 correspond to current sensors, these sensors may be such that their bandwidth is sufficiently high to correctly measure the variation of the current passing through the inductances during the measurement of the value of these inductances. The shorter the duration during which the current is measured, the higher the bandwidth of the current sensor is chosen. For example, the bandwidth of each current sensor may be equal to 100 kHz.

[0078] The network on which the alternating electrical signals are output by the converter 100 is symbolically represented in [Fig.l] by the element designated by the reference 10. In the example of [Fig.l], the converter 100 comprises relays 120 for connection to the network 10 forming an interface between the outputs of the filtering circuits and the network 10. In [Fig.l], the control signals of the relays 120 are called “grid relays”.

[0079] The converter 100 according to the first example further comprises first measuring switches 122 each electrically coupled between the second electrode of one of the first inductors 113 and the capacitive element formed by the capacitors 112. In the example of [Fig.l], the converter 100 comprises three first measuring switches 122. In [Fig.l], the letters “a”, “b” and “c” designate the connection points between a first electrode of the first measuring switches 122 and the filter circuits. In [Fig.l], the control signal of the first measuring switches 122 is called SW1.

[0080] In the example of [Fig.l], the second electrodes of the first measuring switches 122 are electrically coupled to each other and to the second electrode of the capacitor 112 which is also coupled to the second switches 106 of the switching cells 102.1 - 102.3. This configuration makes it possible to transfer a significant amount of energy to the first inductances 113. Alternatively, the second electrodes of the first measuring switches 122 can be electrically coupled to the node forming the midpoint of the bus ensuring the connection between the panel 1002 and the converter 100.

[0081] The first measuring switches 122 are intended to be controlled to carry out a measurement of the value of each of the first inductances 113. In addition, in the example of [Fig.l], the first measuring switches 122 are configured to be controlled by a single control signal SW1. According to a first example, the first measuring switches 122 may correspond to an X-phase contactor (with X corresponding to the number of phases of the converter 100, i.e. three in the example of [Fig.l]) provided with 2X poles and 1 coil. According to a second example, the first measuring switches 122 may be formed by power semiconductor components forming unidirectional current switches, such as for example transistors such as IGBTs, each electrically coupled in series to a diode.

[0082] In the first example described, the converter 100 further comprises second measuring switches 124 each electrically coupled between a second electrode of one of the second inductors 114 and the capacitive element formed by the capacitors 112. In the diagram of [Fig.l], the converter 100 comprises three second measuring switches 124. In [Fig.l], the letters “a'”, “b'” and “c'” designate the connection points between the second measuring switches 124 and the filter circuits. In [Fig.l], the control signal of the second measuring switches 124 is called SW2.

[0083] In the example of [Fig.l], the second electrodes of the second measuring switches 124 are electrically coupled to each other and to the second electrode of the capacitor 112 which is coupled to the second switching switches 106 (configuration allowing a significant transfer of energy to the second inductances 114). Alternatively, the second electrodes of the second measuring switches 124 can be electrically coupled to the node forming the midpoint of the bus ensuring the connection between the panel 1002 and the converter 100.

[0084] The second measuring switches 124 are intended to be controlled to carry out a measurement of the value of each of the second inductances 114. the example of [Fig.l], as for the first measuring switches 122, the second measuring switches 124 are configured to be controlled by a single control signal SW2.

[0085] The converter 100 further comprises a control circuit 126 configured to control the opening and closing of each of the first and second switching switches 104, 106, as well as the opening and closing of each of the first and second measuring switches 122, 124. In the example of [Fig.l], the control circuit 126 is also configured to control the opening and closing of the relays 120.

[0086] The converter 100 described in this example further comprises a circuit 128 for calculating the value of each of the first and second inductances 113, 114 from the value of the input voltage Vcbus measured by the circuit 111 and the values ​​of the currents measured by the circuits 118.

[0087] According to an exemplary embodiment, the control circuit 126 and the calculation circuit 128 may comprise the same microprocessor or FPGA receiving as input the value of the input voltage VcbuS measured by the circuit 111 as well as the values ​​of the currents measured by the circuits 118, and delivering as output the control signals of the switching switches 104, 106, the measuring switches 122, 124 and the relays 120. In [Fig.l], the electrical connections between the circuits 126, 128 and the other elements of the converter 100 are not shown.

[0088] In the example of [Fig.l], the converter 100 is configured to perform a current or voltage conversion with, on one side, a direct voltage intended to be obtained at the terminals of the capacitive element, and on the other, three-phase voltages intended to be obtained at the output of each of the filtering circuits. By way of example, the converter 100 may correspond to a voltage inverter and / or a three-phase current rectifier ensuring the conversion between a direct voltage source, for example a photovoltaic panel, coupled to the capacitive element of the converter 100, and three-phase voltages, for example, intended to be injected and / or received on a network or a rotating machine such as a motor and obtained at the output of the filtering circuits.

[0089] By providing the converter 100 with the measuring switches 122, 124 and by configuring the control circuit 126 and the calculation circuit 128 appropriately, it is possible to monitor the health status of the inductances 113, 114 of the filtering circuits in order to detect a possible failure of these inductances 113, 114. For this, the evolution of the value of these inductances over time will be monitored. An example of steps implemented by the converter 100 to carry out this monitoring is described below.

[0090] At night, in the absence of light, the photovoltaic panel 1002 does not produce of electrical energy and the converter 100 is off. The switching switches 104, 106 of the switching cells 102.1 - 102.3 are in the open state.

[0091] Then, in the presence of light, the photovoltaic panel 1002 produces electrical energy, which results in the appearance of a voltage at the terminals of the panel 1002. The capacitive element formed by the capacitors 112 is electrically charged thanks to this voltage.

[0092] When the capacitive element is sufficiently electrically charged, which can result in having the voltage Vcbus > Vseuii, with Vseuii corresponding to a predefined threshold value, measurements of the values ​​of the inductances 113, 114 are carried out.

[0093] The measurement of the value of one of the first inductances 113 is first carried out. For this, the first measuring switch 122 coupled to this first inductance 122 is closed. In the case of the example shown in [Fig.l], given that all the first measuring switches 122 are controlled by the same control signal SW1, the closing (or opening) of one of the first measuring switches 122 causes the closing (or opening) of the other first measuring switches 122. Furthermore, given that the switching switches 104, 106 of the switching cells 102.1 - 102.3 are open at this stage, this closing of the first measuring switches 122 is carried out at zero current.

[0094] The first switching switch 104 of the switching cell associated with the first inductance 113 whose value is measured is then closed during a first part of the measurement of the value of this first inductance 113 whose duration Ton (in seconds) can be calculated beforehand according to the equation:

[0095] [Math.l] T - nv 1 ™ * Vcbus

[0096] with Linitiaie corresponding to the initial value of the first inductance 113 (in H), that is to say the value of the first inductance 113 before aging, that is to say in the absence of failure;

[0097] Almax corresponding to the maximum value of the current (in A) intended to pass through the first inductance 113 during the first part of the measurement of the value of the first inductance 113;

[0098] VCbuS corresponding to the voltage (in V) across the terminals of the capacitive element formed by the capacitors 112;

[0099] a corresponding to a coefficient greater than 0, and less than or equal to 1.

[0100] According to one example, by choosing first and second inductors 113, 114 each with an initial value (without fault) equal to 200 pH, an Almax value equal to 350 A, a Vcbus voltage equal to 1.4 kV and a coefficient a equal to 1, the duration Ton is equal to 50 ps.

[0101] When the value of the coefficient a is less than 1, this coefficient corresponds to a safety margin applied over the duration Ton to avoid any risk of saturation of the first inductance 113.

[0102] This calculation of the duration Ton is for example carried out by the calculation circuit 128.

[0103] During a part At of this duration Ton, the variation Ai of the current passing through the first inductance 113 is measured by the circuit 118 coupled to this first inductance 113.

[0104] After the duration Ton, the first switching switch 104 of the switching cell associated with the first inductance 113 whose value is measured is open for a second part of the measurement of the value of this first inductance 113. The first inductance 113 discharges in current, the continuity of this current being, in this example, ensured by the antiparallel diode of the second switch 106 of the switching cell associated with the first inductance 113 whose value is measured. A duration Tdischarge of this second part of the measurement of the value of the first inductance 113 can be calculated beforehand, for example by the calculation circuit 128. For example, the duration Tdischarge can be calculated according to the equation:

[0105] [Math.2] T_ / £ \ w 1 discharge ~ \ R )

[0106] with E / R corresponding to the maximum current Imax reached, and “to” corresponds to the ratio L / R, L being the inductance value to be measured and R representing the equivalent resistance (or dynamic resistance taking into account the diode present) of the total mesh of the freewheel passing through the diode of the switch 106. The current I(t) obtained can be expressed by the following equation:

[0107] [Math.3] - ImaxUR

[0108] Curve 20 shown in [Fig.2] corresponds to the current variation obtained in one of the first inductances 113 for a voltage Vcbus designated by the reference 22. In this example, the current charge of this first inductance 113 is carried out for a duration Tonb allowing the current to reach the value Almax. Curve 24 corresponds to the current variation obtained in this same first inductance 113 for a voltage Vcbus designated by the reference 26 and whose value is lower than that designated by the reference 22. In this second case, the duration Ton2 necessary for the current to reach the value Almax is greater than Tonb

[0109] The value, called Lcaic, of the first inductance 113 can be calculated by the calculation circuit 128 according to the equation:

[0110] [Math.4]

[0111] The Lcaic value is for example calculated during the first part of the measurement of the value of the first inductance 113, that is to say during the current charging of this first inductance 113.

[0112] At the end of the first part of the measurement of the value of the first inductance 113, the above steps are repeated for each of the phases of the converter 100 so as to obtain the values ​​of each of the first inductances 113.

[0113] The values ​​of the first inductances 113 obtained can be recorded in a memory of the converter 100 and compared with previously calculated values, for example values ​​of the first inductances 113 calculated the previous day. For each of the first inductances 113, if the difference between the inductance value calculated on day j and that calculated on day j-1 is greater than a threshold value (the value of which is for example a function of the electrical characteristics of the first inductance 113), it is possible to signal to the user the presence of an insulation fault for this first inductance 113 and / or to implement one or more other measures resulting from the identification of this problem.

[0114] The steps described above for measuring the values ​​of the first inductances 113 are then repeated to measure the values ​​of the second inductances 114, this time switching not the first measuring switches 122 but the second measuring switches 124. Furthermore, the value Lcaic2 of each of the second inductances 114 can be calculated by the calculation circuit 128 according to the equation:

[0115] [Math.5] t — V v ^2 r ^calcl ' cbus A Az2 ~^calc

[0116] with Ai2 corresponding to the variation of the current passing through the second inductance 114 during the duration At2. The value Vcbus may be similar or different from that during the measurement of the value of the first inductances 113.

[0117] As for the first inductances 113, the values ​​of the second inductances 114 obtained can be recorded in a memory of the converter 100 and compared with previously calculated values, for example values ​​of the second inductances 114 calculated the previous day. For each of the second inductances 114, if the difference between the inductance value calculated on day j and that calculated on day j-1 is greater than a threshold value (the value of which is for example a function of the electrical characteristics of the second inductance 114), it is possible to signal to the user the presence of an insulation fault for this second inductance 114 and / or to implement one or more other measures resulting from the identification of this problem.

[0118] At the end of the measurements of the values ​​of the first and second inductances 113, 114, the converter 100 can be started in a “classic” operating mode, that is to say carrying out a conversion of the continuous electrical input signal into an alternating electrical output signal. This start-up can in particular comprise the closing of the relays 120 in order to electrically couple the outputs of the filtering circuits of the converter 100 to the network 10.

[0119] The converter 100 therefore makes it possible to measure the value of the inductance(s) present in the filtering circuit(s) before the start of operation of the converter 100, for example with a periodicity of 1 or more days (other periodicities are however possible). To achieve this, the power semiconductor switches of the switching cells and the measuring switches are controlled to apply the voltage of the bus coupled to the input of the converter 100 to the terminals of the inductance whose value is measured. Thus, a so-called "power" current at constant di / dt (characteristic obtained by maintaining the inductance in a non-saturated state) passes through this inductance for a short period of time. The value of the inductance can then be calculated from the slope of the current passing through the inductance.

[0120] The monitoring of the value L of an inductance is directly linked to the number of turns N of the inductance by the following equation:

[0121] [Math.6] L = Reluctance core

[0122] Thus, if inter-turn short circuits occur (with n turns short-circuited), the value of the inductance decreases proportionally according to the factor (Nn)2. For this reason, the converter 100 described above makes it possible to monitor the health status of an inductance via monitoring the value of the inductance.

[0123] The first and second measuring switches 122, 124 can be chosen with a low current rating and without breaking capacity, which makes it possible to choose inexpensive switches. On the other hand, the first and second measuring switches 122, 124 can be chosen with a voltage rating whose value depends on the network and which can be controlled on closing and opening by the control circuit 126 of the converter 100.

[0124] In the exemplary embodiment described above, the converter 100 comprises several output phases. According to a second exemplary embodiment described below in connection with [Fig. 3], the converter 100 may be single-phase.

[0125] Thus, compared to the converter 100 previously described in connection with [Fig.l], the converter 100 shown in [Fig.3] comprises two switching cells 102.1, 102.2, each for example similar to the switching cells of the converter 100 according to the first example.

[0126] The converter 100 according to this second example comprises a single filtering circuit, for example of the LCL type as in the first embodiment described above. This filtering circuit is coupled to the central node 108 of the first switching cell 102.1 through a current measuring circuit 118. The central node 108 of the second switching cell 102.2 is coupled to the second electrode of the capacitor 116 and to the network 10.

[0127] The converter 100 according to this second exemplary embodiment comprises a single first measuring switch 122 used for measuring the first inductance 113 of the filtering circuit and a single second measuring switch 124 used for measuring the second inductance 114 of the filtering circuit. Furthermore, the capacitive element of the converter 100 according to this second exemplary embodiment comprises only a single capacitor 112.

[0128] Although not shown in [Fig.3], the converter 100 also comprises in this example grid control circuits 110, relays 120 for connection to the network 10, a control circuit 126 and a calculation circuit 128.

[0129] The operation of the converter 100 according to this second exemplary embodiment is for example similar to that of the converter 100 according to the first exemplary embodiment. In particular, the steps implemented to measure the values ​​of the first and second inductances 113, 114 may be similar to those previously described for the converter 100 according to the first exemplary embodiment.

[0130] The different possibilities and variant embodiments previously described for the converter 100 according to the first example can also be applied to the converter 100 according to this second example.

[0131] A third example of embodiment of a converter 100, here single-phase, is described below in connection with [Fig.4].

[0132] Compared to the converter 100 previously described in connection with [Fig. 3], a second filtering circuit is present on the branch of the circuit coupled to the central node 108 of the second switching cell 102.2. To carry out the measurements of the inductances 113, 114 of these two filtering circuits, the converter 100 comprises two first measuring switches 122 and two second measuring switches 124. In this third example, the measuring switches 122, 124 can be controlled independently of each other by control signals referenced SW3, SW4, SW5 and SW6 in [Fig. 4] (signals delivered at the output of the control circuit 126 not visible in [Fig. 4]).

[0133] Although not shown in [Fig.4], the converter 100 also comprises in this example grid control circuits 110, relays 120 for connection to the network 10, a control circuit 126 and a calculation circuit 128.

[0134] The operation of the converter 100 according to this third exemplary embodiment is for example similar to that of the converter 100 according to the first exemplary embodiment. In particular, the steps implemented to successively measure the values ​​of the first and second inductances 113, 114 may be similar to those previously described for the converter 100 according to the first exemplary embodiment.

[0135] A fourth example embodiment of a converter 100 is described below in connection with [Fig.5].

[0136] Compared to the converter 100 previously described in connection with [Fig. 1], each of the filtering circuits only comprises a single inductance 113. To carry out the measurements of the first inductances 113, the converter 100 only comprises the first measurement switches 122.

[0137] The operation of the converter 100 according to this fourth exemplary embodiment is for example similar to that of the converter 100 according to the first exemplary embodiment, the steps implemented to successively measure the values ​​of the first inductances 113 may be similar to those previously described for the converter 100 according to the first exemplary embodiment.

[0138] A fifth example embodiment of a converter 100 is described below in connection with [Fig.6].

[0139] As in the example previously described in connection with [Fig.l], the converter 100 according to this fifth embodiment example corresponds to a three-phase inverter comprising three LCL type filtering circuits, three first measuring switches 122 and three second measuring switches 124 making it possible to carry out measurements of the values ​​of the first and second inductances 113, 114 of each of the filtering circuits. In [Fig.6], the circuits 110 are not shown.

[0140] Compared to the converter 100 of [Fig.l], the converter 100 according to this fifth embodiment is a multilevel converter of the NPC type (“Neutral Point Clamped” in English). In this configuration, each switching cell 102.1 - 102.3 comprises two first switching switches 104 coupled to a first diode 130 and two second switching switches 106 coupled to a second diode 132. The control signals of these switching switches are called Si, ..., Si2 and are delivered at the output of the control circuit 126.

[0141] The operation of the converter 100 according to this fifth exemplary embodiment is for example similar to that of the converter 100 according to the first exemplary embodiment, the steps implemented to successively measure the values ​​of the first inductances 113 and the second inductances 114 may be similar to those previously described for the converter 100 according to the first exemplary embodiment.

[0142] A sixth example embodiment of a converter 100 is described below in connection with [Fig.7].

[0143] As in the example previously described in connection with [Fig.l], the converter 100 according to this sixth embodiment example corresponds to a three-phase inverter comprising three LCL type filtering circuits, three first measuring switches 122 and three second measuring switches 124 making it possible to carry out measurements of the values ​​of the first and second inductances 113, 114 of each of the filtering circuits. In [Fig.7], the circuits 110 are not shown.

[0144] Compared to the converter 100 of [Fig.l], the converter 100 according to this sixth embodiment is a multilevel converter of the floating capacitor type (“Flying-Capacitor” in English). In this configuration, each switching cell 102.1 - 102.3 comprises two first switching switches 104 and two second switching switches 106 coupled to a capacitor 134. The control signals of these switching switches are called Si, ..., Si2.

[0145] The operation of the converter 100 according to this sixth exemplary embodiment is for example similar to that of the converter 100 according to the first exemplary embodiment, the steps implemented to successively measure the values ​​of the first inductances 113 and the second inductances 114 may be similar to those previously described for the converter 100 according to the first exemplary embodiment.

[0146] In all the exemplary embodiments, the converter 100 may comprise other components and / or circuits than those previously described.

[0147] In the previously described embodiments, each switching switch comprises at least one IGBT type transistor. Alternatively, each switching switch may comprise at least one MOSFET type transistor. Other examples of switching switches are possible: use of switches other than transistors, use of transistors other than MOSFETs and / or IGBTs, switches comprising different types of transistors, use of N or P type transistor(s), etc.

[0148] In all the embodiments, the switching switches and / or the measuring switches may comprise vertical power components, for example based on wide gap or broadband semiconductors, such as SiC and / or GaN. The use of wide gap semiconductor-based components to form the switches may make it possible to have higher switching speeds of the switches than with other types of components.

[0149] In all the exemplary embodiments, the converter 100 may be of the DC / AC type such as a current switch or inverter (or CSI for “Current Source Inverter” in English, or “Boost Type Inverter”), or AC / AC if the converter 100 comprises a capacitive element as described in the previous embodiments.

[0150] In all the exemplary embodiments, the components of the power switches can operate in switching mode (open or closed state, or saturated or blocked state) with a high switching frequency, for example between a few kHz and a hundred kHz.

[0151] In the various embodiments described above, the calculated inductance values ​​are compared with previously calculated inductance values ​​to monitor the health of the inductances of the filtering circuits. Alternatively, it is possible to calculate one or more values ​​of the inductance(s) of the filtering circuit(s), then to compare this or these values ​​with one or more nominal values ​​corresponding to the fault-free inductance values, for example measured during a factory test before use of the converter 100.

[0152] In the previously described embodiments, the current used to determine the value of one of the inductances is measured during the first part of the phase of measuring the value of the inductance, i.e. during the current charge in the inductance. Alternatively, it is possible to measure this current during the second part of the measurement of the value of the inductance, i.e. during the current discharge of the inductance. In this case, the calculations carried out to obtain the value of the inductance are adapted in order to take into account the non-linearity of this current discharge.

[0153] As a variant of the previously described embodiments, when the converter 100 comprises several first measuring switches 122 and / or several second measuring switches 124, it is possible for these switches 122 and / or 124 to be controlled separately and not by the same control signal.

[0154] As a variant of the previously described embodiments in which the converter 100 comprises filtering circuits comprising one or more first inductances and one or more second inductances whose values ​​are measured, it is possible to measure the value(s) of the first inductance(s) only, or to measure the value(s) of the second inductance(s) only. According to another variant, it is possible to measure the value(s) of the second inductance(s) before measuring the value(s) of the first inductance(s).

[0155] In the previously described embodiments, the converter 100 comprises several switching cells. Alternatively, it is possible for the converter 100 to comprise a single switching cell.

[0156] As a variant of the various embodiments previously described, it is possible for the converter 100 to be part of a power system not cor not corresponding to a photovoltaic system, that is to say a power system in which the input electrical signal is not produced by one or more photovoltaic panels.

[0157] In all the embodiments of the converter 100, the accuracy of the inductance measurement carried out depends directly on the accuracy of the voltage and current measurement circuits used. These circuits can therefore be chosen such that their accuracy is in line with the expected accuracy of the inductance measurement carried out.

[0158] In all the embodiments of the converter 100, all the components except the first measuring switches 122 and / or the second measuring switches 124 may be present in a standard static power converter. In addition to the addition of this or these switches 122, 124, the production of the converter 100 involves carrying out a parameterization of the control circuit 126 and of the calculation circuit 128 making it possible to control this or these switches and to carry out the calculations of the values ​​of the inductances.

[0159] In all the embodiments of the converter 100, the values ​​of the inductances 113, 114 can be measured via measurements of currents passing through these inductances 113, 114, then a calculation of the values ​​of the inductances 113, 114 carried out from the current measurements.

[0160] Various embodiments and variations have been described. Those skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will occur to those skilled in the art.

[0161] Finally, the practical implementation of the embodiments and variants described is within the reach of those skilled in the art from the functional indications given above.

Claims

Claims

1. Static power converter (100), comprising at least: - a switching cell (102.1 - 102.3) comprising at least first and second switching switches (104, 106); - a first inductance (113) coupled to an output of the switching cell (102.1 - 102.3); - a first measuring switch (122) such that the first inductance (113) is coupled between the first measuring switch (122) and the switching cell (102.1 - 102.3); - a control circuit (126) configured to control at least one closing of the first measuring switch (122) during a measurement of a value of the first inductance (113).

2. A static power converter (100) according to claim 1, further comprising at least: - a capacitive element (112) electrically coupled in parallel with the switching cell (102.1 - 102.3) and to which an input voltage is intended to be applied; - a current measuring circuit (118) configured to measure a current intended to flow through the first inductor (113); and wherein: - the switching cell (102.1 - 102.3) comprises a central node (108) to which the first and second switching switches (104, 106) are electrically coupled; - the first inductor (113) comprises a first electrode coupled to the central node (108) of the switching cell (102.1 - 102.3); - the first measuring switch (122) is electrically coupled between a second electrode of the first inductance (113) and the capacitive element (112); - the control circuit (126) is configured to control the switching switches (104, 106) and the first measuring switch (122) such that during a first part of the measurement of the value of the first inductance (113), the first measuring switch (122) and the. first switching switch (104) are closed.

3. A static power converter (100) according to claim 2, wherein the drive circuit (126) is configured to control the switching switches (104, 106) and the first measuring switch (122) such that during a second part of the measurement of the value of the first inductance (113), the first measuring switch (122) is closed and the first switching switch (104) is open.

4. Static power converter (100) according to one of claims 2 or 3, further comprising a circuit (128) for calculating the value of the first inductance (113) from the value of the input voltage and the current measured by the current measuring circuit (118) during the first part of the measurement of the value of the first inductance (113) and / or during the second part of the measurement of the value of the first inductance (113).

5. Static power converter (100) according to claim 4, wherein the calculation circuit (128) is configured to calculate the value of the first inductance (113) according to the equation: J —VX — cale r chus Ai with Vcbus corresponding to the input voltage across the capacitive element (112) before measuring the value of the first inductance (113); Ai corresponding to a current variation measured by the current measurement circuit (118); At corresponding to a duration during which the current variation Ai is measured.

6. A static power converter (100) according to one of claims 4 or 5, wherein the current measuring circuit (118) is configured to measure the current during the first part of the measurement of the value of the first inductance (113).

7. Static power converter (100) according to one of claims 4 to 6, wherein the calculation circuit (128) is configured to compare the calculated value of the first inductance (113) to at least one nominal value of the first inductance (113) and / or to at least one previous calculated value of the first inductance (113).

8. Static power converter (100) according to one of claims 4 to 7, wherein the calculation circuit (128) is configured to calculate, before the measurement of the value of the first inductance (113), a duration Ton of the first part of the measurement of the value of the first inductance (113) such that: T — i On — (ZXW r ebuy with Linitiaie corresponding to the initial value of the first inductance (113); Almax corresponding to the maximum value of the current intended to pass through the first inductance (113) during the first part of the measurement of the value of the first inductance (113); a corresponding to a coefficient greater than 0, and less than or equal to 1.

9. Static power converter (100) according to one of claims 2 to 8, further comprising a voltage measurement circuit (111) configured to measure the input voltage intended to be applied to the capacitive element (112), and in which the control circuit (126) is configured to start measuring the value of the first inductance (113) when the measured input voltage is greater than a threshold value.

10. Static power converter (100) according to one of claims 2 to 9, wherein the capacitive element comprises at least two capacitors (112) electrically coupled in series at a node, and wherein said node is coupled to a reference electrical potential.

11. Static power converter (100) according to one of claims 2 to 10, wherein: - the first inductor (113) is part of an LCL type filter further comprising a second inductor (114) a first electrode of which is coupled to the second electrode of the first inductor (113); - the static power converter (100) further comprises a second measuring switch (124) electrically coupled between a second electrode of the second inductor (114) and the capacitive element (112); - the control circuit (126) is configured to also control the second measuring switch (124) such that: • during the first and second parts of the measurement of the value of the first inductor (113), the second measuring switch (124) is open; • during a first part of a measurement of the second inductance (114), the first measuring switch (122) is open, and the first switching switch (104) and the second measuring switch (124) are closed.

12. The static power converter (100) of claim 11, wherein the drive circuit (126) is configured to control the second measuring switch (124) such that during a second portion of the measurement of the second inductance (114), the first measuring switch (122) and the first switching switch (104) are open, and the second measuring switch (124) is closed.

13. Static power converter (100) according to one of claims 2 to 12, comprising: - three switching cells (102.1 - 102.3) each comprising a central node (108) and at least first and second switching switches (104, 106) electrically coupled in series with each other, each being electrically coupled in parallel with the capacitive element (112); - three first inductors (113) each comprising a first electrode coupled to the central node (108) of one of the switching cells (102.1 - 102.3); - three current measuring circuits (118) each configured to measure a current intended to flow through one of the three first inductances (113); - three first measuring switches (122) each electrically coupled between a second electrode of one of the first inductances (113) and the capacitive element (112); and wherein the driving circuit (126) is configured to measure each of the first inductances (113) and to control the switching switches (104, 106) and the first measuring switches (122) such that during a first part of a measurement of the value of one of the first inductances (113), the first measuring switch (122) and the first switching switch (104) coupled to said one of the first inductances (113) are closed, and during. of a second part of the measurement of the value of said one of the first inductances (113), the first measuring switch (122) coupled to said one of the first inductances (113) is closed and the first switching switch (104) coupled to said one of the first inductances (113) is open.

14. Static power converter (100) according to claim 13, wherein the first measuring switches (122) are configured to be controlled by a same control signal.

15. Static power converter (100) according to one of the preceding claims, configured to carry out a measurement of the value of the first inductance (113) at regular time intervals, for example daily or at intervals of several days.

16. Static power converter (100) according to one of the preceding claims, wherein the static power converter (100) is a multilevel converter, for example of the NPC type or with floating capacitors, and operating as a voltage and / or current inverter or rectifier.

17. Photovoltaic system (1000) comprising at least one photovoltaic panel (1002) coupled to a static power converter (100) according to one of the preceding claims.

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