Patent Application
20240186801
This patent application claims the benefit and priority of European Patent Application No. 22211809.3 filed on Dec. 6, 2022, the disclosure of which is incorporated by reference herein in its entirety as part of the present application.
The present disclosure relates to a power supply apparatus for electric systems, for example electric power distribution grids, electrical switchboards, electrical panels, and the like.
As is known, an electric system often includes a power supply apparatus to provide an auxiliary power supply to a number of electric or electronic devices operatively associated to the primary equipment. As an example, in an electric system including a MV switchgear, a power supply apparatus is typically arranged to feed the devices included in the control cabinet. A power supply apparatus normally includes an AC/DC converter electrically connected to an AC electric source, for example an electric line. A capacitor bank, which includes a plurality of storage capacitors, is electrically connected between the AC/DC converter and a DC bus feeding a number of electric loads.
In most recent power supply apparatuses, a current limiter may be electrically connected between the AC/DC converter and the capacitor bank in order to limit the charging current provided in output by the AC/DC converter.
Currently available power supply apparatuses show some problematic aspects in relation to their reliability in operation.
Since the storage capacitors are basically connected electrically in parallel, a fault in a storage capacitor may be fed by the remaining non-faulted capacitors as these latter may result short-circuited on the electric fault. Such an occurrence can quickly lead to the failure of the whole capacitor bank with a consequent interruption of the power supply to the electric loads.
As it is easily to understand, the above-mentioned issue results particularly critical in electric systems (e.g., subsea electric installations), for which maintenance interventions are quite difficult and expensive.
Additionally, traditional power supply apparatuses provide relatively poor performances in relation to the diagnostics of possible faults in the storage capacitors, which makes more difficult an effective scheduling of possible maintenance interventions.
Embodiments of the present disclosure provide a power supply apparatus for electric systems, which solves or mitigates the above-mentioned problems.
More particularly, an embodiment of the present disclosure provides a power supply apparatus capable of providing high performances in terms of reliability in operation.
Still another embodiment of the present disclosure provides a power supply apparatus capable of providing advanced diagnostic functionalities of the operation of the capacitor bank.
Yet another embodiment of the present disclosure provides a power supply apparatus having a compact size and easy to install in an electric system.
Another embodiment of the present disclosure provides a power supply apparatus that can be easily manufactured at industrial level, at competitive costs with the power supply apparatuses of the state of the art.
The present disclosure thus provides a power supply apparatus for electric systems, according to the following claim 1 and the related dependent claims.
The power supply apparatus of the invention includes:
The above-mentioned current blocking devices are configured to allow the flow of feeding currents from said storage capacitors to said electric loads and are configured to block currents having opposite directions relative to said feeding currents.
According to an aspect of the disclosure, the power supply apparatus includes a plurality of current limiters. Each current limiter is electrically connected in series between said AC/DC conversion unit and a corresponding storage capacitor. Each current limiter is configured to set a charging current provided by said AC/DC conversion unit to charge the corresponding storage capacitor depending on control signals received in input.
According to an aspect of the disclosure, the power supply apparatus includes a plurality of capacitor dischargers. Each capacitor discharger is electrically connected in parallel to a corresponding storage capacitor. Each capacitor discharger is configured to discharge the corresponding storage capacitor with a discharging current selectable depending on control signals received in input.
According to an aspect of the disclosure, the power supply apparatus includes a control unit including data processing resources. Said control unit may be configured to control the operation of said AC/DC conversion stage, said current limiters and said capacitor dischargers.
According to an aspect of the disclosure, the power supply apparatus includes a plurality of sensor units. Each sensor unit is configured to provide said control unit with detection signals indicative of currents and voltages at the first terminal of a corresponding storage capacitor.
According to an aspect of the disclosure, the aforesaid control unit is configured to carry out diagnostic procedure of said storage capacitors, which includes the following steps:
According to an aspect of the disclosure, the aforesaid diagnostic procedure of said storage capacitors further includes the following steps, if the calculated charging time of each storage capacitor is lower than or equal to said threshold charging time: for each storage capacitor, commanding the corresponding current limiter to set a second charging current corresponding to said predefined charging current; for each storage capacitor, commanding the corresponding current limiter to block the charge of said storage capacitor, when the voltage across said storage capacitor is higher than said second threshold voltage value.
According to an aspect of the disclosure, the aforesaid diagnostic procedure of said storage capacitors further includes the following steps:
In a further aspect, the present disclosure concerns an electric installation, according to the following claim 9 and the related dependent claims.
Further characteristics and advantages will emerge from the description of example, but not exclusive, embodiments of the disclosure, non-limiting examples of which are provided in the attached drawings, wherein:
Referring to the cited figures, the present disclosure relates to a power supply apparatus 1, for example electric power distribution grids, electric switchboards, electric panels, and the like.
The power supply apparatus 1 is particularly adapted for use in medium-voltage electric systems (thereby operating at voltages higher than 1 KV AC and 1.5 kV DC and lower than 72 kV AC and 100 kV DC).
More particularly, the power supply apparatus 1 is adapted for use in subsea electric installations and it will be described in the following with particular reference to these applications, for the sake of simplicity.
The power supply apparatus 1, however, may be employed in electric systems of different type, namely in any electric installation where high levels of reliability in operation are required.
In general terms, the power supply apparatus 1 is configured to harvest electric energy from an AC electric power source 10 and feed one or more electric loads L1, L2, . . . , LM with a DC power supply.
In principle, the AC electric power source 10 and the electric loads L1, L2, . . . , LM may be of any type, according to the needs.
The electric power source 10 may include, for example, a MV electric line or system while a generic electric load may include, for example, a DC/DC converter feeding an electronic module, a protection device electrically connected in series to an electronic module, an electric or electronic device, or the like.
According to the disclosure, the power supply apparatus 1 includes an AC/DC conversion unit 2, which can be electrically connected to the electric power source 10.
The conversion unit 2 is configured to receive an AC input voltage VAC from the electric power source 10 and provide in output a DC charging voltage VCH.
The conversion unit 2 has an input I including a pair of input terminals which, in operation, are electrically connected to the electric power source 10 to receive the input voltage VAC.
The conversion unit 2 has an output O including a pair of output terminals making available the charging voltage VCH. The output O may have an output terminal providing a charging voltage VCH relative to ground and the other output terminal put at a ground voltage.
As it will be more apparent from the following, the conversion unit 2 operates in response to suitable input control signals CS. For example, based on said control signals, it may vary the level of the charging voltage VCH made available at the output O.
In a practical implementation of the disclosure, the conversion unit 2 may include advantageously a suitable AC/DC power switching converter realized at industrial level according to solutions of known type. For example, the conversion unit 2 may include an AC/DC converter of the flyback type or half-bridge type.
According to the disclosure, the power supply apparatus 1 includes a capacitive bank 4 including a plurality of storage capacitors C1, C2, . . . , CN operatively coupled to the conversion unit 2 in such a way to be charged in parallel by this latter.
Each storage capacitor C1, C2, . . . , CN has opposite first and second terminals T1, T2 electrically connected to corresponding internal electric armatures having opposite voltage polarities.
The first terminal T1 (conventionally having a positive voltage polarity) of each storage capacitor C1, C2, . . . , CN is configured to receive a charging current ICH provided by the AC/DC conversion unit.
As mentioned above, in general terms, the storage capacitors C1, C2, . . . , CN are electrically connected in parallel one to another, namely between the output O of the conversion unit 2 and the ground.
The storage capacitors C1, C2, . . . , CN may have their first terminals T1 electrically connected in parallel, in a direct or indirect manner, to the conversion unit 2, more particularly to the output terminal put at a voltage VCH relative to ground.
The storage capacitors C1, C2, . . . , CN may have their second terminals T2 electrically connected in parallel to ground.
According to the embodiments shown in the cited figures, the power supply apparatus 1 includes a plurality of current limiters B1, B2, . . . , BN, each electrically connected in series between the AC/DC conversion unit 2 and a corresponding storage capacitor C1, C2, . . . , CN.
Each current limiter B1, B2, . . . , BN is configured to set a charging current ICH provided by the AC/DC conversion unit 2 to charge a corresponding storage capacitor C1, C2, . . . , CN depending on suitable control signals CS received in input.
Each current limiter B1, B2, . . . , BN may have an input terminal electrically connected to the output O of the conversion unit 2 (namely to the output terminal providing a voltage VCH relative to ground) and an output terminal electrically connected to the first terminal T1 of the corresponding storage capacitor.
In general, the current limiters B1, B2, . . . , BN may be realized at industrial level according to solutions of known type. For example, they may include suitable power circuits configured to provide current foldback functionalities.
According to the embodiments shown in the cited figures, the power supply apparatus 1 further includes a plurality of capacitor dischargers E1, E2, EN, each electrically connected in parallel to a corresponding storage capacitor C1, C2, . . . , CN.
Each capacitor discharger E1, E2, . . . , EN is configured to discharge the corresponding storage capacitor C1, C2, . . . , CN with a discharging current ID that can be set depending on suitable control signals CS received in input.
Each capacitor discharger E1, E2, EN may have an input terminal electrically connected to the first terminal T1 of the corresponding storage capacitor C1, C2, . . . , CN and an output terminal electrically connected to the second terminal T2 of the corresponding storage capacitor.
In general, the capacitor discharger E1, E2, . . . , EN may be realized at industrial level according to solutions of known type. For example, they may include suitable power circuits configured to make available, in a selectable manner, current paths having different equivalent resistances in parallel to the first terminal T1, T2 of the corresponding storage capacitor.
According to the disclosure, the power supply apparatus 1 includes a DC bus 7, which can be electrically connected to the one or more electric loads L1, L2, . . . , LM.
The DC bus 7 is configured to feed the electric loads L1, L2, . . . , LM with a DC feeding voltage VF. In operation, the electric loads L1, L2, . . . , LM are electrically connected in parallel to the DC bus 7 and they absorb an overall feeding current IF.
In general, the DC bus 7 may be realized at industrial level according to solutions of known type. For example, it may be formed by a suitable power conductor having multiple pairs of terminals electrically connectable to the electric loads.
An essential aspect of the disclosure consists in that the power supply apparatus 1 includes a plurality of current blocking devices D1, D2, . . . , DN electrically connected in parallel between the capacitor bank 4 and the DC bus 7.
Each current blocking device D1, D2, . . . , DN has a third terminal T3 electrically connected to the first terminal T1 (the terminal receiving the charging current ICH) of a corresponding storage capacitor C1, C2, . . . , CN and a fourth terminal T4 electrically connected to the DC bus. The current blocking devices D1, D2, . . . , DN are configured to allow corresponding feeding currents IF1, IF2, . . . , IFN to flow from the storage capacitors C1, C2, . . . , CN to the electric loads L1, L2, . . . , LM and are configured to block possible currents flowing according to opposite directions relative to the above-mentioned feeding currents IF1, IF2, . . . , IFN.
Each current blocking device D1, D2, . . . , DN may be configured to switch in a conduction state, at which said current blocking device allows the flow of a current according to a predefined conduction direction, and in an interdiction state, at which said blocking device interrupts the flow of a current passing therethrough.
The switch of a generic blocking device D1, D2, . . . , DN from said conduction state to said interdiction state, and vice versa, basically depends on a voltage difference applied between the third and fourth terminals T3, T4 of said current blocking device.
Each current blocking device D1, D2, . . . , DN may be arranged in such a way to switch in said conduction state, if the third terminal T3 (in practice the first terminal T1 of the corresponding storage capacitor C1, C2, . . . , CN) takes a voltage VC higher than the feeding voltage VF of the DC bus, and switch in said interdiction state, if the third terminal T3 (in practice the first terminal T1 of the corresponding storage capacitor C1, C2, . . . , CN) takes a voltage VC lower than the feeding voltage VF of the DC bus 7.
The arrangement of the current blocking devices D1, D2, . . . , DN provides relevant advantages, particularly when a storage capacitor is subject to fault conditions.
In normal conditions, the blocking devices D1, D2, . . . , DN are in a conduction state, and they allow the storage capacitors C1, C2, . . . , CN to feed the electric loads L1, L2, . . . , LM by providing suitable feeding currents IF1, IF2, . . . , IFN to the DC bus.
When a given storage capacitor C1 is subject to a fault, the corresponding blocking device D1 naturally switches in an interdiction state as the first terminal T1 of the storage capacitor C1 is short-circuited to ground. In this way, the feeding currents IF2, . . . , IFN provided by the remaining storage capacitors C2, . . . , CN cannot flow towards the faulted storage capacitor C1 and continue to flow towards the electric loads L1, L2, . . . , LM.
In practice, the blocking device D1 associated to the faulted storage capacitor C1 prevents that the electric fault is fed by electric energy stored by the remaining storage capacitors C2, . . . , CN. The faulted storage capacitor C1 is thus isolated from the other storage capacitors C2, . . . , CN and the power supply apparatus can still feed the electric loads L1, L2, . . . , LM. The fault of a single storage capacitor C1 thus does not jeopardize the overall operation of the power supply apparatus.
The blocking devices D1, D2, . . . , DN may include suitable power diodes, each having an anode terminal (the third terminal T3) electrically connected to the first terminal T1 of a corresponding storage capacitor C1, C2, . . . , CN and a cathode terminal (the fourth terminal T4) electrically connected to the DC bus.
According to other embodiments of the disclosure (not shown), however, the blocking devices D1, D2, . . . , DN may include suitable power transistors (e.g., IGBTs or equivalent devices) configured to allow the flow of a current along a predefined direction only.
According to example embodiments of the disclosure, the power supply apparatus 1 includes a control unit 3 including suitable data processing resources, for example one or more microprocessors or other data processing devices configured to execute suitable software instructions stored in a memory.
The control unit 3 may be configured to control the operation of the AC/DC conversion stage 2, the current limiters B1, B2, . . . , BN and the capacitor dischargers E1, E2, . . . , EN through suitable control signals CS.
In some cases, the control unit 3 may be integrated in the AC/DC conversion stage 2. According to other embodiments of the disclosure, however, the control unit 3 may be a stand-alone device or integrated in a suitable IED (Intelligent Electronic Device), for example a control & protection relay.
The power supply apparatus 1 may include a plurality of sensor units S1, S2, . . . , SN.
Each sensor unit S1, S2, . . . , SN is configured to provide the control unit 3 with suitable detection signals DS indicative of currents and voltages at the first terminal T3 of a corresponding storage capacitor C1, C2, . . . , CN.
In general, the sensor units S1, S2, . . . , SN may be realized at industrial level according to solutions of known type. For example, they may include suitable capacitive devices amperometric transformers to detect voltages and currents at the first terminal T3, respectively.
According to an aspect of the disclosure, the control unit 7 is configured to carry out a diagnostic procedure 100 of the storage capacitors C1, C2, . . . , CN.
In order to carry out the diagnostic procedure 100, the control unit 3 acquires and process the detection signals DS sent by the above-mentioned sensors units S1, S2, . . . , SN and sends suitable control signals to the AC/DC conversion unit 2, the current limiters B1, B2, . . . , BN and the capacitor dischargers E1, E2, . . . , EN.
Initially, the diagnostic procedure 100 includes a first diagnostic sequence directed to check whether one or more storage capacitors C1, C2, . . . , CN have to be subject to a reforming process before reaching a nominal charging level.
Referring now to
The diagnostic procedure 100 then includes the step 102, in which the control unit 3 commands each current limiter B1, B2, . . . , BN to set a first charging current ICH1 lower than a predefined charging current ICHo (for example a nominal charging current) to charge the corresponding storage capacitor C1, C2, . . . , CN.
In practice, the control unit 3 commands to carry out a light charging process of the storage capacitors C1, C2, . . . , CN, in which each storage capacitor is charged through a charging current ICH1 having a magnitude lower than the nominal charging current ICHo normally charging said storage capacitor.
The diagnostic procedure 100 then includes the step 103, in which the control unit 3 commands each current limiter B1, B2, . . . , BN to block the charge of the corresponding storage capacitor C1, C2, . . . , CN, when the voltage VC across said storage capacitor is higher than a first threshold voltage value VTH1.
In practice, each storage capacitor C1, C2, . . . , CN is charged as described above until the voltage VC across said storage capacitor reaches a predefined charging level corresponding to the first threshold voltage value VTH1. Each current limiter B1, B2, . . . , BN is capable of blocking the charge of the corresponding storage capacitor C1, C2, . . . , CN by setting a null charging current (ICH=0) for said storage capacitor.
At the following step 104 of the diagnostic procedure 100, the control unit 3 calculates, for each storage capacitor C1, C2, . . . , CN, a charging time tCH taken by the voltage VC across of said storage capacitor to reach said first threshold voltage value VTH1. In practice, the control unit 3 calculates the charging time tCH to charge each storage capacitor C1, C2, . . . , CN at the first threshold voltage value VTH1.
The control unit 3 then compares the calculated charging time tCH of each storage capacitor C1, C2, . . . , CN with a predefined threshold charging time tTH.
If the charging time tCH of a given storage capacitor is higher than the threshold charging time tTH, the control unit 3 determines that a reforming process of said storage capacitor is needed.
Advantageously, the control unit 3 is configured to signal to a user or a remote computerized device such a situation, for example in a visual manner, in an audible manner or by transmitting an alarm message.
The reforming process of a generic storage capacitor may be carried out in a known manner, according to the needs.
If the charging time tCH of each storage capacitor C1, C2, . . . , CN is lower than the threshold charging time tTH, the diagnostic procedure 100 includes the step 106, in which the control unit 3 commands each current limiter B1, B2, . . . , BN to set a second charging current ICH2 equal to the above-mentioned predefined charging current ICHo to charge the corresponding storage capacitor C1, C2, . . . , CN.
In practice, the control unit 3 commands to carry out a full charging process of the storage capacitors C1, C2, . . . , CN, in which each storage capacitor is charged through a charging current ICH1 having a magnitude corresponding to the nominal charging current ICHo.
At this stage, the control unit 3 carries out a second diagnostic sequence directed to identify whether one or more C1, C2, . . . , CN are subject to fault conditions.
The diagnostic procedure 100 then includes a step 108, in which the control unit 3 commands each capacitor discharger E1, E2, EN to discharge a corresponding storage capacitor C1, C2, . . . , CN for a predefined discharge time tD and with a discharging current ID corresponding to a predefined feeding current IF corresponding to the overall current absorbed by the electric loads L1, L2, LM electrically connected to the DC bus 7 in normal conditions.
In practice, the control unit 3 commands each capacitor discharger E1, E2, EN to discharge each C1, C2, . . . , CN in a controlled way, according to predefined discharging parameters.
At the step 109 of the diagnostic procedure 100, the control unit 3 commands each capacitor discharger E1, E2, EN to block the discharge of the corresponding storage capacitor C1, C2, . . . , CN, when the above-mentioned predefined discharge time tD has passed.
At the following step 110 of the diagnostic procedure 100, the control unit 3 calculates, for each storage capacitor C1, C2, . . . , CN, a capacitance value CT. This latter may be easily calculated based on the detection signals DS provided by the sensor units C1, C2, . . . , CN operatively coupled to the storage capacitors C1, C2, . . . , CN.
The control unit 3 then compares the calculated capacitance value CT of each storage capacitor C1, C2, . . . , CN with a predefined threshold capacitance value CTH.
If the calculated capacitance value CT of a given storage capacitor C1, C2, . . . , CN is lower than the threshold capacitance value VTH, the control unit 3 determines that a dielectric fault of said storage capacitor is needed.
Advantageously, the control unit 3 is configured to signal to a user or a remote computerized device such a situation, for example in a visual manner, in an audible manner or by transmitting an alarm message.
If the calculated capacitance value CT of a given storage capacitor C1, C2, . . . , CN is higher than or equal to the threshold capacitance value VTH, the control unit 3 determines that said storage capacitor operates correctly.
The control unit 3 can advantageously carry out the diagnostic procedure 100 cyclically, according to the needs. In this way, the operating conditions of the storage capacitors C1, C2, . . . , CN can be periodically checked, according to the needs.
The power supply apparatus of the disclosure has a number of advantages with respect to similar systems of known type.
The power supply apparatus provides improved performances in terms of reliability in operation. By virtue of the arrangement of the blocking devices B1, B2, . . . , BN between the capacitor bank 4 and the DC bus 7, each storage capacitor C1, C2, . . . , CN can be isolated from the remaining storage capacitors in case of fault conditions. The fault in a given storage capacitor cannot therefore be fed by the remaining storage capacitors. As a result, the power supply apparatus can continue to feed the electric loads L1, L2, . . . , LM by exploiting the non-faulted storage capacitors.
The power supply apparatus, according to the disclosure, provides improved performances in terms of diagnostics of the storage capacitors. The operating conditions of the storage capacitors C1, C2, . . . , CN can be periodically checked in an automatic way without the need of arranging a dedicated diagnostics setup but simply exploiting the hardware resources already installed for the normal operation of the storage capacitors.
The power supply apparatus, according to the disclosure has a compact size and a simple overall structure and it relatively easy and cheap to manufacture at industrial level.
| Number | Date | Country | Kind |
|---|---|---|---|
| 22211809.3 | Dec 2022 | EP | regional |
