WO2021052949A2 - Procédé de détection d'un court-circuit d'une charge cc et redresseur doté d'un tel procédé - Google Patents

Procédé de détection d'un court-circuit d'une charge cc et redresseur doté d'un tel procédé Download PDF

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Publication number
WO2021052949A2
WO2021052949A2 PCT/EP2020/075748 EP2020075748W WO2021052949A2 WO 2021052949 A2 WO2021052949 A2 WO 2021052949A2 EP 2020075748 W EP2020075748 W EP 2020075748W WO 2021052949 A2 WO2021052949 A2 WO 2021052949A2
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WO
WIPO (PCT)
Prior art keywords
rectifier
load
voltage
output capacitance
network
Prior art date
Application number
PCT/EP2020/075748
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German (de)
English (en)
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WO2021052949A3 (fr
Inventor
Marcel Kratochvil
Alexander UNRU
Original Assignee
Sma Solar Technology Ag
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Publication of WO2021052949A2 publication Critical patent/WO2021052949A2/fr
Publication of WO2021052949A3 publication Critical patent/WO2021052949A3/fr

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H11/00—Emergency protective circuit arrangements for preventing the switching-on in case an undesired electric working condition might result
    • H02H11/005—Emergency protective circuit arrangements for preventing the switching-on in case an undesired electric working condition might result in case of too low isolation resistance, too high load, short-circuit; earth fault
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/165—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
    • G01R19/16566—Circuits and arrangements for comparing voltage or current with one or several thresholds and for indicating the result not covered by subgroups G01R19/16504, G01R19/16528, G01R19/16533
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/165—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
    • G01R19/16566—Circuits and arrangements for comparing voltage or current with one or several thresholds and for indicating the result not covered by subgroups G01R19/16504, G01R19/16528, G01R19/16533
    • G01R19/16571—Circuits and arrangements for comparing voltage or current with one or several thresholds and for indicating the result not covered by subgroups G01R19/16504, G01R19/16528, G01R19/16533 comparing AC or DC current with one threshold, e.g. load current, over-current, surge current or fault current
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
    • G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
    • G01R31/52—Testing for short-circuits, leakage current or ground faults
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/10—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers
    • H02H7/12—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers
    • H02H7/125—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers for rectifiers
    • H02H7/1257—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for converters; for rectifiers for static converters or rectifiers for rectifiers responsive to short circuit or wrong polarity in output circuit

Definitions

  • the invention relates to a method for detecting a short circuit in a DC load which is connected to an alternating voltage (AC) network via a rectifier.
  • the invention additionally relates to a rectifier which is designed and set up to carry out the method according to the invention.
  • the DC load can be, for example, an electrolyzer or a rechargeable battery.
  • a gaseous energy carrier for example hydrogen.
  • an electrolyser is connected to an alternating voltage (AC) network via a rectifier.
  • AC alternating voltage
  • the electrolysis of water into hydrogen and oxygen takes place via a power flow from the AC network.
  • a reaction speed of the electrolysis is controlled via the power flow through the rectifier.
  • the hydrogen can be processed into another gaseous energy carrier (e.g. methane) or stored directly.
  • the stored hydrogen can be used to generate energy, for example in a fuel cell, or as a starting product in the chemical industry.
  • precharge resistors must at least briefly can tolerate a relatively high power flow. For this reason, too, such precharge resistors are relatively expensive. In normal operation of the electrolyzer, however, they are not required, but rather are bridged with low impedance. It is therefore desirable to dispense with such precharge resistors as far as possible.
  • Document US 6339526 B1 discloses a battery backup system which is connected to a load via a low-voltage isolating circuit.
  • the low-voltage isolating circuit comprises a low-voltage monitor connected between an input and an output of the low-voltage isolating circuit, as well as an isolating switch controlled by the low-voltage monitor, which is designed to connect the input to the output.
  • the low-voltage isolating circuit furthermore comprises a short-circuit protection circuit which is designed to determine a short circuit in the load and, together with the low-voltage monitor, to prevent the isolating switch from closing as a function of a specific short circuit.
  • the invention is based on the object of specifying a method for detecting a short circuit at an input of a DC load which can be connected to an AC network via a rectifier, in particular an actively controllable rectifier. Damage to components of the DC load and / or the rectifier, in particular in the event of an actual short circuit in the DC load, should be excluded as far as possible.
  • the method should be able to be carried out as inexpensively as possible. It is also an object of the invention to provide a rectifier suitable for the method. Specifically, the rectifier required for the method should also be as inexpensive as possible and, in particular, be designed with as few precharge resistors as possible.
  • the object of providing a method for detecting a short circuit at the input of a DC load that can be connected to an AC network via a rectifier is achieved according to the invention with a method having the features of independent claim 1.
  • Advantageous embodiments of the method are shown in Claims 2 to 11 reproduced.
  • the object of indicating a rectifier suitable for carrying out the method is achieved according to the invention with the features of independent claim 12.
  • Advantageous embodiments of the rectifier are given in claims 13 to 16.
  • a method according to the invention is used to detect a short circuit in a DC load that can be connected to an AC network via a rectifier.
  • the rectifier comprises at least one AC / DC converter and an output capacitor as an energy store.
  • the procedure consists of the following steps:
  • the output capacitance is a capacitance of the rectifier that is connected to a DC output of the rectifier, or is connected in a switchable manner via a switch, so that - if necessary when the switch is switched through - a voltage drop across the output capacitance is also at the DC output of the rectifier is applied.
  • the at least one AC / DC converter can also comprise several AC / DC converters, which are connected in parallel to one another to the DC output of the rectifier.
  • the method uses the effect that when and during the connection of the output capacitance to the input of the DC load, a direct (in the sense of continuously occurring) _ WO 2021/052949 _ l _ PCT / EP2020 / 075748 _
  • Power flow from the AC grid via the rectifier into the DC load is suppressed. Rather, the removal of a power flow from the AC network into the rectifier, on the one hand, and the output of a power flow from the rectifier into the DC load, on the other hand, do not take place at the same time, but rather offset in time to one another.
  • the rectifier is connected to the AC grid via an AC disconnection unit. The connection results in a power flow from the AC network into the rectifier, but a simultaneous output of a power flow from the rectifier into the DC load is suppressed. Instead, the energy taken from the AC network is initially temporarily stored in the rectifier and only passed on with a time delay, in particular later on to the DC load.
  • a single-stage rectifier With a single-stage rectifier, the output of the power flow to the DC load can be suppressed by an open DC disconnector.
  • a DC disconnector via which the output capacitance of the rectifier can be connected to or disconnected from the DC load, is usually arranged at the DC output of the corresponding rectifier and is therefore not an additional component a power flow to the DC load can also be suppressed by deactivating a DC / DC converter which is arranged between the AC / DC converter and the DC output of the two-stage rectifier. Only after the power flow has been taken from the AC network and its energy has been temporarily stored in the rectifier, for example in its output capacitance and / or an intermediate circuit capacitance of the rectifier, the rectifier delivers power to the DC load.
  • the output capacitance of the rectifier which contains at least part of the energy previously drawn from the AC network, is electrically connected to the DC load, for example by closing the DC isolating switch.
  • a further flow of power from the AC network into the rectifier, in particular into the output capacitance of the rectifier connected to the DC load is suppressed.
  • the suppression can take place in that the previously closed AC disconnection unit is opened again and the AC / DC converter of the rectifier is galvanically isolated from the AC network.
  • the power flow from the AC network into the output capacitance of the rectifier can also be suppressed via a deactivated DC / DC converter of the rectifier.
  • the setting of the source voltage at the output capacitance of the rectifier via the power flow taken from the AC network can, but does not necessarily have to take place at the same time as the power flow is drawn from the AC network.
  • the setting of the source voltage at the output capacitance and the associated charging of the output capacitance take place with a time delay to the removal of the power flow from the AC network.
  • a power flow can be drawn from the AC network, which is initially stored in an intermediate circuit capacitance upstream of the output capacitance.
  • the output capacitance can then be set to the source voltage at a later point in time via charge transport from the intermediate circuit capacitance to the output capacitance.
  • any short circuit in the DC load that may be present is detected only by means of a limited amount of energy that was previously taken from the AC network and temporarily stored in the rectifier.
  • a suitable choice of the limited amount of energy can prevent damage to components of the rectifier and / or the DC load.
  • a value of the source voltage at the output capacitance of the rectifier can be selected in such a way that components of the DC load and / or the rectifier are damaged when an amount of energy assigned to the source voltage is transferred to the DC load, in particular in the case of a DC load. Load present short circuit, is excluded.
  • the detection of the voltage U present at the input of the DC load and of the current I flowing via the input of the DC load can also include a detection of a time profile of the respective variables. Detection can be carried out directly on the DC load using a separate measuring unit. Alternatively, however, the detection can also take place via a measuring unit of the rectifier which is anyway arranged at the DC output of the rectifier. An evaluation of the detected voltage U and / or the detected current I can also be carried out by a constitution existing control unit of the rectifier take place. In this way, the method can be carried out as inexpensively as possible, since no additional components of the rectifier are required to carry out the method.
  • the DC load can in particular comprise an electrolyzer.
  • At least one of the following criteria can be checked to signal a short circuit in the DC load: an amount of a change over time in the voltage dU / dt applied to the input of the DC load exceeds a first threshold value assigned to the source voltage (dü / dt) TM, and / or the current I flowing through the DC input of the DC load exceeds a second threshold value ITH, and / or a quotient of the voltage applied to the input of the DC load and the voltage applied to the input of the DC The current I flowing in the load falls below a third threshold value RTH.
  • the method can signal a short circuit in the DC load if at least one of the criteria is met during the check.
  • the values of voltage U and current I can be provided with time stamps which identify the point in time of their detection. This is particularly useful when the time curves of the voltage U or the current I are detected and evaluated. In this case, values of voltage U and current I detected at the same time or at least promptly can be assigned to one another. For signaling a short circuit in the DC load, it is sufficient if the at least one criterion is met only during a limited time span within the detected time profile and not in the entire detected time profile.
  • the AC / DC converter can usually be designed as an actively controllable AC / DC converter and actively controllable semiconductor switches, for example transistors exhibit.
  • a freewheeling diode can be connected in anti-parallel to each of the actively controllable semiconductor switches.
  • the AC / DC converter is free of actively controllable semiconductor switches and only contains diodes for rectifying the AC voltage.
  • both the free-wheeling diodes of an actively controllable AC / DC converter and the diodes of a non-actively controllable AC / DC converter are not able to suppress a power flow from the AC network, provided that AC voltage is still present at an AC input of the AC / DC converter.
  • the rectifier is designed as a single-stage rectifier.
  • the output capacitance of the single-stage rectifier can be charged via the freewheeling diodes or the diodes of the AC / DC converter to a source voltage that corresponds to the amplitude of the alternating voltage of the AC network.
  • the output capacity is charged when the AC disconnection unit is closed.
  • the output capacitance When connecting the output capacitance to the DC load, on the other hand, the output capacitance can be galvanically isolated from the AC network via an opened AC isolating unit of the rectifier, whereby a further power flow from the AC network into the output capacitance of the single-stage rectifier can be effectively suppressed .
  • the output capacitance of the single-stage rectifier it may be necessary for the output capacitance of the single-stage rectifier to be set to a source voltage whose value is below an amplitude of the alternating voltage of the AC network.
  • the setting of the output capacitance to the source voltage can include that a voltage of the output capacitance which is initially above the source voltage is reduced to the desired value of the source voltage by dissipating the energy stored in the output capacitance.
  • the energy stored in the output capacitance can be dissipated by pulsing semiconductor switches in the AC / DC converter. Alternatively or cumulatively, however, the dissipation can also be brought about by operating at least one small consumer connected to the output capacitance, for example a fan of the rectifier. So that when the energy is dissipated, another power flow from the AC network into the output capacitance and thus a renewed charging of the output capacitance is suppressed, the output capacitance can be separated from the AC network during the dissipation of the energy stored in it.
  • the rectifier can be designed as a multi-stage rectifier and comprise a DC / DC converter connected downstream of the AC / DC converter and an intermediate circuit capacitance arranged between them.
  • a power flow from the AC network into the output capacitance can be suppressed via an at least temporary deactivation of the DC / DC converter, for example via an open semiconductor switch of the DC / DC converter.
  • the output capacitance can be set to a source voltage via the DC / DC converter connected upstream of the output capacitance, the value of which is below the amplitude of the alternating voltage of the AC network.
  • a limited amount of charge can be taken from the upstream intermediate circuit capacitance by the DC / DC converter and fed to the output capacitance.
  • the limited amount of charge can include all or only part of the amount of charge present in the intermediate circuit capacitance.
  • the power flow for setting the source voltage at the output capacitance can be taken from the AC network via a precharge resistor arranged at the AC input of the rectifier.
  • a current in the initially uncharged output capacitance or intermediate circuit capacitance of the rectifier can be effectively limited via the precharge resistor.
  • a rectifier according to the invention is designed to convert an alternating voltage into a direct voltage.
  • the rectifier has an AC input to connect the rectifier to an AC network and a DC output to connect the rectifier to a DC load.
  • the rectifier further comprises an AC / DC converter, an output capacitance connected to the DC output of the rectifier, _ WO 2021/052949 _ zl _ PCT / EP2020 / 075748 _ an AC disconnection unit connected to the AC input and a DC disconnector connected to the DC output.
  • the rectifier comprises a control unit for controlling the rectifier, which is designed and set up to carry out the method according to the invention and its embodiments.
  • the AC disconnection unit comprises a precharge resistor.
  • the AC disconnection unit is designed to provide a connection between the AC / DC converter of the rectifier and the AC network, on the one hand via the precharge resistor and, on the other hand, in a direct manner, i.e. without interposing the precharge resistor.
  • an intermediate connection of the precharge resistor is required in particular when a previously uncharged energy store of the rectifier is charged with a power flow from the AC network.
  • the power flow into the uncharged energy store is limited to a value at which damage to
  • the energy store can be, for example, the output capacitance of a single-stage rectifier.
  • the rectifier can be designed in multiple stages and one between the AC / DC converter and the
  • the precharge resistor can also reduce the power flow to a previously uncharged
  • the rectifier in particular its AC / DC converter, possibly also its DC / DC converter, can be designed for bidirectional operation with respect to one direction of the power flow and be set up.
  • a bidirectionally operating rectifier is designed in a first operating mode to convert an alternating voltage into a direct voltage.
  • it is designed in a second operating mode to operate as an inverter and convert a direct voltage into an alternating voltage. This is particularly advantageous when the _ WO 2021/052949 _ 10 _ PCT / EP2020 / 075748 _
  • a DC power generation system for example a photovoltaic (PV) system or a fuel cell.
  • PV photovoltaic
  • a bidirectional rectifier is also useful if the rectifier is connected to a battery on the DC side.
  • a separate measuring unit can be used to detect the voltage U present at the input of the DC load, as well as the current I flowing through the input of the DC load.
  • the separate measuring unit can be connected to the rectifier for control purposes in such a way that the measured values of voltage U and / or current I are forwarded to the rectifier's control unit.
  • the detection takes place outside the rectifier, but the evaluation of the detected values of voltage U and / or current I takes place inside the rectifier, namely in particular by the control unit of the rectifier.
  • the rectifier itself comprises a measuring unit for detecting a voltage applied to the DC load and / or a current flowing via the input of the DC load.
  • the measuring unit can be a measuring unit which is already present in the rectifier and is designed to detect a current I flowing via the DC output of the rectifier and / or a voltage U present at the DC output of the rectifier.
  • the voltage U present at the input of the DC load corresponds to the voltage U present at the DC output of the rectifier Case (the usual interconnection of the rectifier with the DC load) the current I flowing through the input of the DC load also the current flowing through the DC output of the rectifier.
  • the usual interconnection of rectifier and DC load for the voltage applied to the output capacitance as well as for the current flowing from the output capacitance in the direction of the DC output.
  • control unit of the rectifier it is possible for the control unit of the rectifier to be designed to control future operation of the rectifier as a function of whether a short circuit or no short circuit was detected on the DC load. Specifically, if the method did not detect a short circuit on the DC load, the Control unit enable normal operation of the rectifier to supply the DC load from the AC network.
  • the control unit can be designed and set up to establish a low-impedance connection of the rectifier to the AC network on the one hand by closing the AC disconnection unit and, on the one hand, to establish a low-impedance connection of the rectifier to the DC load by closing the DC disconnector.
  • the control unit can control the rectifier in response to the detected short circuit in the DC load in such a way that a permanent power flow from the AC network via the rectifier into the DC Load and thus normal operation of the rectifier for supplying the DC load is prevented.
  • the control unit can be designed and set up to prevent the AC disconnection unit from closing in response to a detected short circuit in the DC load, provided it is still open. If it is a two-stage rectifier, the control unit can optionally also prevent the semiconductor switches of the DC / DC converter from pulsing and thus deactivate the DC / DC converter.
  • the control unit can open the AC disconnection unit and thus disconnect the rectifier from the AC Create a network. If the rectifier is already connected to the DC load with low impedance via a closed DC isolating switch, the control unit can open the DC isolating switch in response to a detected short circuit in the DC load, in order to permanently isolate the rectifier from the DC load to separate.
  • FIG. 1 shows a rectifier according to the invention for connecting an AC network and a DC load in a first embodiment
  • FIG. 2 shows a rectifier according to the invention for connecting an AC network and a DC load in a second embodiment
  • 3 shows a flow chart of a method according to the invention in a first variant
  • FIG. 4 shows a flow chart of a method according to the invention in a second variant.
  • a rectifier 1 according to the invention is shown in a first embodiment.
  • the rectifier 1 is designed to convert an alternating voltage into a direct voltage and for this purpose is connected to an alternating voltage (AC) network 20 at its AC input 2 and to an input 32 of a DC load 30 at its DC output 3.
  • the AC network 20 is illustrated by way of example as a three-phase AC network and the rectifier 1 as a three-phase rectifier with three phase connections at its AC input 2.
  • the AC network 20 can have a different number of phase conductors, for example two phase conductors or just one phase conductor.
  • the rectifier 1 can also have a different number of phase connections at its AC output 2.
  • the DC load 30 is shown by way of example in FIG. 1 as an electrolyzer 31. In the context of the invention, however, the DC load 30 can also be designed as a DC load different from an electrolyzer.
  • the DC load 30 does not necessarily have to be designed exclusively for power consumption, but can, in particular in the case of a bidirectional rectifier 1, also have a power-generating operating mode in addition to the power-consuming operating mode. This is the case, for example, with a DC load 30 designed as a battery.
  • the rectifier 1 is designed as a single-stage rectifier and contains (when viewed from the AC network 20) an AC isolating unit 5, a sine filter 9, an AC / DC converter 10, one between the AC / DC converter 10 and the DC output 3 of the rectifier 1 arranged output capacitance 4, a DC disconnector 14 and a control unit 15 for controlling the components of the rectifier 1.
  • the connections for control and / or communication are shown in Fig. 1 by dashed lines Arrows symbolizes.
  • the AC disconnection unit 5 includes a precharge resistor 7, a first AC disconnection switch 6 and a second AC disconnection switch 8.
  • the first AC disconnection switch 6 is in series with the _ WO 2021/052949 _ 13 _ PCT / EP2020 / 075748 _
  • Pre-charging resistor 7 connected.
  • the second AC disconnector 8 is connected in parallel to the series circuit comprising the precharge resistor 7 and the first AC disconnector 6.
  • the AC disconnection unit 5 is designed, the AC / DC converter 10 and the output capacitance 4 connected to it in a first operating mode via the precharge resistor 7 and in a second operating mode directly or low-impedance and without the interposition of the precharge resistor 7 with the AC grid 20 to connect.
  • the sine filter 9 is designed to attenuate high-frequency interference signals, which are generated due to the timing of semiconductor switches of the AC / DC converter 10, in their propagation in the direction of the AC network 20.
  • the sine filter 9 is designed to dampen interference signals already present in the AC network 20 in their propagation in the direction of the DC output 3 of the rectifier 1.
  • the DC disconnector 14 can be single-pole as well as multi-pole. It can be designed to disconnect the DC load 30 while a current is flowing and therefore have means for arc extinction and / or arc suppression.
  • the DC isolating switch 14 is designed to connect the output capacitance 4 to the DC load 30 with low impedance in the closed state and to disconnect it from the DC load 30 in the open state.
  • the DC disconnector 14 is in particular free of a precharge resistor.
  • the rectifier 1 also has a measuring unit 13 which is designed and set up to measure a voltage U present at the output capacitance 4 and / or a current I flowing from the output capacitance 4 in the direction of the DC output 3, in particular its time profiles.
  • the measuring unit 13 is designed to transfer the measured values of voltage U and current I to the control unit 15 for evaluation.
  • the control unit 15 is at the same time able to evaluate the detected values of voltage U and / or current I in accordance with the method according to the invention for detecting a short circuit 33 of the DC load 30.
  • the control unit 15 can be designed and set up to control the rectifier 1 as a function of a result of the evaluation.
  • control unit 15 can be set up to open both the DC disconnector 14 and the AC disconnector 6, 8 of the AC disconnector 5 when a short circuit 33 is detected at the input 32 of the DC load 30, provided that the respective disconnector 6, 8, 14 are not already open.
  • the control unit 15 can be set up to open both the DC disconnector 14 and the AC disconnector 6, 8 of the AC disconnector 5 when a short circuit 33 is detected at the input 32 of the DC load 30, provided that the respective disconnector 6, 8, 14 are not already open.
  • WO 2021/052949 14 PCT / EP2020 / 075748 In this way, both a power flow from the AC network 20 into the rectifier 1 and a power flow from the rectifier 1 into the DC load 30 can be reliably suppressed.
  • FIG. 2 shows a second embodiment of the rectifier 1 according to the invention for supplying a DC load 30 from an AC network 20.
  • the rectifier 1 corresponds in many features to the rectifier 1 already described in FIG. 1, which is why reference is made to the description under FIG. 1 with regard to the matching features. Therefore, only the differences from FIG. 1 are explained in more detail below.
  • the rectifier 1 in FIG. 2 is designed as a multi-stage rectifier 1.
  • it also contains a DC / DC converter 12 which is connected on the input side to the AC / DC converter 10 via an intermediate circuit capacitance 11 and on the output side via the output capacitance 4 to the DC output 3 of the rectifier 1.
  • the intermediate circuit capacitance 11 is decoupled from the output capacitance 4 via the DC / DC converter 12, so that different voltage values can be set at the intermediate circuit capacitance 11 and the output capacitance 4.
  • the rectifier 1 can also be designed to prevent a power flow from the AC network 20 into the output capacitance 4 - as well as via the DC output 3 - even when the AC disconnection unit 5 is closed.
  • semiconductor switches of the DC / DC converter 12 can be opened.
  • the DC / DC converter 12 can also be designed to carry out a charge transport from the intermediate circuit capacitance 11 into the output capacitance 4, so that the output capacitance 4 is set to the desired value of the source voltage by the charge transport.
  • the DC / DC converter 12 can be designed as a step-up converter, step-down converter or as a combined step-up / step-down converter.
  • the DC / DC converter 12 can, depending on the type of the rectifier 1, be a unidirectional as well as a bidirectional DC / DC converter 12.
  • FIG. 3 a flow chart of the method according to the invention is shown in a first variant, as carried out in the rectifier 1 shown in FIG. 1 _ WO 2021/052949 _ 15 _ PCT / EP2020 / 075748 _ can be.
  • the reference symbols also shown in FIG. 1 are used in the following description.
  • the method for detecting a short circuit 33 begins in a state in which the rectifier 1 is disconnected from the AC network 20 due to an opened AC disconnection unit 5 and from the DC load 30 due to an opened DC disconnector 14.
  • a first step S1 the first AC disconnector 6 is closed, so that the output capacitance 4 is connected to the AC network 20 via the precharge resistor 7.
  • the DC isolating switch 14 initially remains open.
  • the output capacitance 4 is charged by a power flow taken from the AC network 20 and by freewheeling diodes assigned to the semiconductor switches of the AC / DC converter 10.
  • the power flow taken from the AC network 20 and flowing into the initially uncharged output capacitance 4 is limited by the precharge resistor 7 in such a way that damage to components of the rectifier 1 is excluded.
  • a time curve of the voltage U across the output capacitance 4 can be followed by the measuring unit 13.
  • the DC isolating switch 14 is open, so that a flow of power from the rectifier 1 into the DC load 30 is prevented.
  • the AC disconnection unit 5, in particular its first AC disconnection switch 6, is opened by the control unit 15, as a result of which further charging of the output capacitance 4 from the AC network 20 is prevented.
  • the first AC disconnector 6 can be opened when a value of the source voltage is reached which corresponds to the amplitude of the alternating voltage in the AC network 20 and in which further charging would not take place even with the AC disconnection unit 5 closed.
  • the AC disconnection unit 5 can, however, also be opened beforehand and the charging of the output capacitance 4 can be actively stopped if a lower value of the source voltage is desired. If the voltage of the output capacitance 4 is above a desired value of the source voltage when the AC disconnection unit 5 is opened, an optional fourth step S4 can follow, in which the higher voltage value on the output capacitance 4 is reduced to the desired value of the source voltage by dissipation.
  • the dissipation can be achieved by activating small consumers connected to the output capacitance 4, for example a fan of the rectifier 1 (not shown in FIG. 1), or by a _ WO 2021/052949 _ '16' _ PCT / EP2020 / 075748 _ suitable operation of semiconductor switches of the AC / DC converter 10 can be brought about.
  • the fourth step S4 which is only to be carried out optionally, is shown in dashed lines in FIG. 3.
  • the output capacitance 4 set to the source voltage is connected to the DC load 30 by closing the DC isolating switch 14. While the output capacitance 4 is connected to the DC load 30 via the closed DC disconnector 14, the AC disconnection unit 5 is operated in an open state.
  • a seventh step S7 the detected values of voltage U and / or current I or their time profiles are evaluated by the control unit 15. It is checked whether the detected voltage U, the detected current I, and / or a combination of the detected values Voltage U and the detected current I meet at least one predetermined criterion.
  • the criteria in FIG. 3 are checked as to whether a change in voltage dU / dt over time exceeds a first threshold value (dü / dt) TM, whether the detected current I exceeds a second threshold value ITH and / or whether the quotient of voltage and Current U / l falls below a third threshold value RTH. If the detected values of voltage U and / or current I do not meet any of the criteria during the check, the control unit concludes that the DC load 30 does not have a short circuit 33.
  • the AC / DC converter 10 is connected to the AC network 20 with low impedance.
  • the DC isolating switch 14 is already closed and the rectifier 1, controlled by the control unit 15, starts its normal operation for supplying the DC load 30. If, on the other hand, the detected values of voltage U and / or current I meet at least one of the criteria mentioned, the control unit 15 closes the checking of the detected values of voltage U and current I for a short circuit 33 present at the DC load 30.
  • the method consequently branches into a tenth step S10, in which the control unit 15 signals a short circuit 33 present at the DC load 30 and, in an eleventh step S11, all AC disconnectors 6, 8 of the AC disconnection unit 5 and the DC are opened -Isolation switch 14, provided that the corresponding disconnectors are not already open, brings about.
  • the rectifier 1 is thus galvanically isolated both from the AC network 20 and from the DC load 30. Any power flow through the rectifier 1, both from the AC network 20 into the rectifier and from the rectifier 1 into the DC load 30, is thus reliably suppressed.
  • the short circuit at the DC load 30 can be eliminated safely.
  • FIG. 4 shows a flow chart of the method according to the invention in a second variant.
  • the second variant of the method can be carried out with the rectifier 1 shown in FIG. 2.
  • the method is similar in many steps to the method shown in FIG. 3. In the following, therefore, only the differences from the method variant shown in FIG. 3 are described.
  • the method starts in a state in which all AC disconnectors 6, 8 of the AC disconnection unit 5 and the DC disconnector 14 are open.
  • the first AC disconnection switch 6 of the AC disconnection unit is closed. As also described in FIG. 3, this connects the AC / DC converter 10 to the AC network 20 via the precharge resistor 7.
  • the power flow that occurs from the AC network 20 is initially used in a step S21 _ WO 2021/052949 _ 18 _ PCT / EP2020 / 075748 _ the intermediate circuit capacitance 11 is charged to a voltage which corresponds to the amplitude of the alternating voltage in the AC network 20.
  • a source voltage is set at the output capacitance 4.
  • the DC / DC converter 12 For this purpose, through suitable operation of the DC / DC converter 12, an amount of charge is transported from the intermediate circuit capacitance 11 into the output capacitance 4 until the desired value of the source voltage at the output capacitance 4 is reached.
  • the voltage U currently present at the output capacitance 4 can be observed via the measuring unit 13.
  • the DC / DC converter 12 is deactivated in a step S23, so that further charge transport from the intermediate circuit capacitance 11 into the output capacitance 4 is prevented.
  • the AC disconnection unit 5, in particular the first AC disconnection switch 6 of the AC disconnection unit 5, can be opened.
  • step S24 is only optional and not absolutely necessary, since a flow of power from the AC network 20 into the output capacitance 4 is already prevented by the deactivated DC / DC converter 12. In FIG. 4, the optional step S24 is therefore shown in dashed lines.
  • step S25 the output capacitance 4 previously charged to the source voltage is finally connected to the DC load 30 with low impedance by closing the DC isolating switch 14.
  • Control unit 20 AC grid

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Rectifiers (AREA)

Abstract

La demande concerne un procédé de détection d'un court-circuit (33) d'une charge CC (30) qui peut être raccordée à un réseau CA (20) par un redresseur (1) comportant un convertisseur CA/CC (10). Le procédé comprend les étapes suivantes : - Réglage d'une tension de source sur une capacité de sortie (4) du redresseur (1) par l'intermédiaire d'un flux de puissance redressé prélevé dans le réseau CA (20) ; - Raccordement de la capacité de sortie (4), préalablement réglée à la tension de source, du redresseur (1) à l'entrée (32) de la charge CC (30), ce qui entraîne la suppression d'un autre flux de puissance circulant du réseau CA (20) au redresseur (1) et d'une recharge correspondante de la capacité de sortie (4) ; - Détection d'une tension U appliquée à une entrée (32) de la charge CC (30) et/ou d'une intensité I circulant par l'entrée (32) de la charge CC (30) ; - Signalement d'un court-circuit (33) lorsque la tension U détectée, un décalage en temps de la tension U détectée, l'intensité I détectée, un décalage en temps de l'intensité I détectée, une association de la tension U détectée et de l'intensité I détectée et/ou une association des décalages en temps de la tension U détectée et de l'intensité I détectée remplissent au moins un critère prédéfini. La demande concerne également un redresseur (1) conçu pour la mise en oeuvre du procédé.
PCT/EP2020/075748 2019-09-19 2020-09-15 Procédé de détection d'un court-circuit d'une charge cc et redresseur doté d'un tel procédé WO2021052949A2 (fr)

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DE102019125296.2 2019-09-19
DE102019125296.2A DE102019125296B4 (de) 2019-09-19 2019-09-19 Verfahren zum detektieren eines kurzschlusses einer dc-last und gleichrichter mit einem derartigen verfahren

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DE102021113205A1 (de) 2021-05-20 2022-11-24 Bayerische Motoren Werke Aktiengesellschaft Verfahren zum betrieb eines kurzschlussgesicherten versorgungssystems und kurzschlussgesichertes versorgungssystem

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US6339526B1 (en) 1998-07-01 2002-01-15 Lucent Technologies Inc. Low voltage cutoff circuit with short circuit detection capability and method of operation thereof

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EP0563695B1 (fr) * 1992-03-31 1999-05-26 Siemens Aktiengesellschaft Procédé et dispositif pour déterminer des court-circuits dans des branches de réseaux électriques
JP2903863B2 (ja) * 1992-05-29 1999-06-14 三菱電機株式会社 インバータ装置
CN104283441B (zh) * 2013-07-12 2017-08-11 尼得科控制技术有限公司 一种直流电源及提供直流电源的方法
JP6765325B2 (ja) * 2017-03-07 2020-10-07 株式会社日立産機システム 電力変換装置および地絡箇所判定方法
JP6517862B2 (ja) * 2017-03-27 2019-05-22 ファナック株式会社 短絡故障検出機能を備えたコンバータ装置及びコンバータ装置の短絡故障検出方法

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6339526B1 (en) 1998-07-01 2002-01-15 Lucent Technologies Inc. Low voltage cutoff circuit with short circuit detection capability and method of operation thereof

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