# Patent

## Title
Power supply system with heterogeneous multiple input

## Abstract

The invention relates to a power supply system that is adapted be connected in input to N distinct power supply grids (R1, . . . , RN) delivering a direct or alternating input voltage (V1, VN) and to deliver a direct distribution voltage (VBUS), N being an integer greater than or equal to 2, of the type comprising a distribution bus operating under the distribution voltage (VBUS), N unidirectional converters (C1, . . . , CN) that can respectively be connected in input to a given power grid (R1, . . . , RN), and control means capable of controlling the unidirectional converters (C1, . . . CN). The power supply system also includes an energy storage device connected to the distribution bus and having a quantity of energy (E), and the control means are adapted to control the unidirectional converters (C1, . . . CN) simultaneously to regulate the electrical power (P1, . . . PN) delivered by each of said unidirectional converters (C1, . . . , CN) as a function of the quantity of energy (E).

## Background
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a power supply system with heterogeneous multiple inputs, i.e. connected in input to a plurality of electrical power grids delivering direct or alternating current.
More particularly, the invention relates to a power supply system adapted to be connected in input to N distinct power grids delivering a direct or alternating input voltage and to deliver a direct distribution voltage, N being an integer greater than or equal to 2, comprising:

    
    
        a distribution bus operating under the distribution voltage,
        N unidirectional converters that can respectively be connected in input to a given power grid and able to deliver an electrical power to the distribution bus, and
        control means capable of controlling the unidirectional converters.
    
    


This type of power supply is particularly used in aeronautics, and is designed to provide regulated voltage to the onboard electronic circuits of an aircraft.
These power supplies are thus subject to a number of specific constraints.
For example, they must be able to switch from a priority power supply grid to a redundant power supply grid in a secured manner—i.e. while avoiding any exchange of energy between said grids—, with well-controlled transitional phases without oscillations in the context of increasing the dynamics and impedance of those power supply grids. The withdrawal of power from grids other than the priority grid must also be minimized.
Furthermore, they must make it possible to withdraw a normal-operation voltage on each of the redundant power supply grids to power auxiliary electronic equipment.
These power supply systems must also make it possible to withstand power line disturbances occurring on the selected power supply grid and allow filtering of inrush currents coming from the downstream electronic equipment.
Lastly, they must be able to operate from power supply grids delivering electrical power supplies having very different formats, for example whereof the supplied current is direct for some and alternating for others, whereof the voltage and/or frequency is different, and which are not connected to a same ground potential.
2. Description of the Related Art
FR 2 815 789 describes a power supply system of the aforementioned type capable of selecting a power supply grid from among a plurality of power supply grids. The switching logic between the power supply grids is rigid and implemented by a dedicated control member capable of ordering opening or closing of the contacts of a diode switch as a function of the voltage delivered by each of the converters.
US 2005/134239 also describes a power supply system of the aforementioned type. In that document, various topologies are considered, in which direct or alternating voltages delivered by distinct power supply grids are combined in order to supply a load situated downstream of the power supply system.
However, these solutions are not fully satisfactory.
In fact, in the current context of increasing dynamics of the power supply grids, the rigidity of the switching logic of the power supply system described in the first document involves frequent and abrupt switches between the power supply grids, as well as low-voltage operating phases of the unidirectional converters. These converters are then strongly biased and the redundant power supply grids are called on more than is strictly necessary. This in particular results in disruptions of the distribution voltage delivered to the electronic equipment situated downstream.
In the second cited document, the power supply system cannot make a prioritized selection of the power supply grids. Furthermore, it is not adapted to filter the inrush currents coming from the equipment situated downstream.
SUMMARY OF THE INVENTION
One aim of the invention is to resolve these problems.
To that end, the invention relates to a power supply system adapted to be connected in input to N distinct power supply grids delivering a direct or alternating input voltage and to deliver a direct distribution voltage, N being an integer greater than or equal to 2, of the type comprising:

    
    
        a distribution bus operating under the distribution voltage,
        N unidirectional converters that can respectively be connected in input to a given power grid and able to deliver electrical power to the distribution bus,
        control means capable of controlling the unidirectional converters,

characterized in that the power supply system also includes an energy storage device connected to the distribution bus and having a quantity of energy, and in that the control means are adapted to control the unidirectional converters simultaneously to regulate the electrical power delivered by each of said unidirectional converters as a function of the quantity of energy.

    
    


According to other aspects of the invention, the invention comprises one or more of the following features, considered alone or according to all technically possible combinations, and in which:

    
    
        the energy storage device is a capacitive storage device operating under a storage voltage representative of the quantity of energy, the control means being adapted to control the unidirectional converters simultaneously to regulate the electrical power delivered by each of said unidirectional converters as a function of the storage voltage;
        the energy storage device is an inductive storage device passed through by a storage current, the control means being able to control the unidirectional converters simultaneously to regulate the electrical power delivered by each of said unidirectional converters as a function of the storage current;
        decreasing storage voltage thresholds are associated with the power supply grids and define a priority order between said power supply grids such that a first power supply grid, whereof the storage voltage threshold is higher than the storage voltage threshold of a second power supply grid, is given a higher priority relative to said second power supply grid;
        the control means comprise N storage regulating loops respectively associated with a unidirectional converter and capable of regulating the electrical power delivered by said unidirectional converter to the distribution bus, each storage regulating loop comprising a progressive reduction control characteristic beyond a voltage threshold associated with the corresponding power supply grid, the slope of said progressive reduction corresponding to the static gain of said storage regulating loop;
        the progressive reductions of the control characteristics of the N storage regulating loops are done over value ranges of the storage voltage that are disjoint from one another;
        the maximum value of the control characteristic of a storage regulating loop is also the maximum value of the control characteristics of the N−1 other storage regulating loops;
        the respective static gains of the N storage regulating loops have decreasing values, the static gain of a storage regulating loop whereof the unidirectional converter is associated with a first power supply grid being smaller than the static gain of the storage regulating loop whereof the unidirectional converter is associated with a power supply grid with a higher priority relative to said first power supply grid;
        the static gain of a storage regulating loop whereof the unidirectional converter is associated with a first power supply grid is determined by the equation Gi=Gi−1*VSTi/VSTi−1, where Gi is the static gain of said storage regulating loop, VSTi is the storage voltage threshold associated with said first power supply grid, V STi−1 is the smallest of the storage voltage thresholds higher than the storage voltage threshold VSTi, and Gi−1 is the static gain of the storage regulating loop whereof the unidirectional converter is associated with the power supply grid whereof the storage voltage threshold is VSTi−1;
        the control means have N distribution regulating loops respectively associated with a given unidirectional converter and capable of regulating the electrical power delivered by said unidirectional converter to the distribution bus as a function of the distribution voltage to limit the distribution voltage or to limit a distribution current supplied to the distribution bus;
        each unidirectional converter associated with a given power supply grid has:
        an intermediate grid,
        a unidirectional primary converter capable of preventing electrical power transfers between the power supply grid with which said unidirectional converter is associated and the other power supply grids, said unidirectional primary converter being connected in input to the corresponding power supply grid and capable of delivering to the intermediate grid a regulated intermediate voltage from the input voltage of said power supply grid, and
        a bidirectional insulator capable of galvanically insulating the power supply grid with which said unidirectional converter is associated from the other power supply grids, said bidirectional insulator being connected in input to the intermediate grid and at its output to the distribution bus, and being capable of being controlled by the control means to regulate the electrical power delivered by the unidirectional converter to the distribution bus and to regulate electrical power coming from the distribution bus and delivered by said bidirectional insulator to the corresponding intermediate bus;
        the primary converters include rectifier means for the voltage, filtering means for the voltage in common mode and differential mode, protection means against overvoltages, and protection means against lightning;
        the control means have N positive reaction loops respectively associated with a given bidirectional insulator and capable of regulating, as a function of the intermediate voltage of the corresponding intermediate grid, the electrical power delivered by said bidirectional insulator to the distribution bus, and therefore by the corresponding unidirectional converter to the distribution bus, on the one hand, and the electrical power delivered by said bidirectional insulator to the corresponding intermediate bus on the other hand;
        for each unidirectional converter, the associated storage regulating loop is capable of regulating the electrical power delivered by said unidirectional converter as a function of the storage voltage via a first control variable, the associated distribution regulating loop is capable of regulating the electrical power delivered by said unidirectional converter as a function of the distribution voltage via a second control variable, and the associated positive reaction loop is capable of regulating the electrical power delivered by said unidirectional converter via a third control variable, the power delivered by said unidirectional converter to the distribution bus being proportional to the difference between the minimum of the first and second control variables on the one hand, and the third control variable on the other hand;
        the energy storage device is connected to the distribution bus via a two-way loader capable of transferring electric energy between the distribution bus and the energy storage device; and
        the energy storage device comprises a loader regulating loop capable of controlling the two-way loader to regulate the energy transfer between the two-way loader and the distribution bus to slave the distribution voltage to a reference distribution voltage.
    
    





BRIEF DESCRIPTION OF THE DRAWINGS
So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
The invention will be better understood upon reading the following description, provided solely as an example, and done in reference to the appended drawings, in which:
FIG. 1 is a diagrammatic illustration of a power supply system according to a first embodiment of the invention;
FIG. 2 is a view similar to that of FIG. 1 of a power supply system according to a second embodiment of the invention;
FIG. 3 is a view similar to that of FIG. 3 of a power supply system according to a third embodiment of the invention;
FIG. 4 is a diagram illustrating control characteristics of storage regulating loops of the invention; and
FIG. 5 is a diagrammatic illustration of voltage and power variations during the operation of a power supply system according to the third embodiment.



DETAILED DESCRIPTION
In reference to FIG. 1, which illustrates a first embodiment of the invention, the power supply system 10 with heterogeneous multiple inputs, hereafter “power supply system 10” or “system 10,” is adapted to be connected in input to N power supply grids Ri, N being an integer greater than or equal to 2 and where i is an integer comprised between 1 to N, preventing electric energy transfers between the power supply grids Ri and delivering a direct and regulated distribution voltage VBUS to electronic equipment situated downstream from the input voltages V1, . . . VN delivered by the power supply grids Ri.
To provide the distribution voltage VBUS, the system 10 is capable of drawing electrical energy from the power supply grids Ri according to a priority order between those grids. This priority order is described in more detail below. The drawing of electrical energy is done in a secured manner, without any energy exchange between the power supply grids Ri, and so as to minimize the electrical energy withdrawn from the power supply grids Ri other than the priority power supply grid.
Furthermore, the system 10 is adapted to withstand power disruptions or disappearances of the input voltage Vi of the power supply grid Ri currently selected, and to filter the inrush currents coming from the electronic equipment situated downstream.
To that end, the system 10 has N unidirectional converters C1, . . . , CN, a distribution bus 16, and an energy storage device 18. The power supply system 10 also has control means 20 for controlling the N unidirectional converters Ci.
The power supply grids Ri deliver electricity in various formats. For example, certain currents delivered by the power supply grids Ri are direct and the corresponding input voltage Vi is 28 V or 270 V, and the current coming from other power supply grids Ri is alternating and the input voltage Vi is for example 115 V or 230 V, and its frequency is comprised in the range 46 Hz-800 Hz.
In the example of FIG. 1, the system 10 is connected to N power supply grids R1, . . . , RN, some of which are powered by alternators and others of which are powered by batteries. The input voltages V1, . . . , VN then have significant dynamics, the impedances of the grids Ri also being significant. This imposes a voltage profile on the inputs of the converters Ci that is very dynamic and not very controlled.
The unidirectional converters Ci are adapted to prevent any transfer of electrical energy between the power supply grids Ri and to respectively deliver a regulated electrical power P1, . . . , PN to the distribution bus 16 from an input voltage V1, . . . , VN.
To that end, each unidirectional converter Ci is adapted to be connected in input to a given power supply grid Ri and is connected at its output to the distribution bus 16.
Each unidirectional converter is also adapted to be controlled by the control means 20 to regulate the electrical power P1, . . . , PN that it delivers to the distribution bus 16, as will be seen hereafter.
Furthermore, each unidirectional converter Ci connected to a power supply grid Ri supplying an alternating current is capable of rectifying the current so as to deliver a direct current to the distribution bus 16.
Alternatively, each unidirectional converter Ci is also capable of galvanically insulating the power supply grid Ri to which it is connected from the other power supply grids R1, . . . , RN.
In a known manner, such converters 14 are for example made by converters of the “Flyback” type known by those skilled in the art.
The distribution bus 16 is adapted to ensure the transfer of energy between the power supply grids Ri and the electronic equipment situated downstream of the power supply system.
To that end, as previously indicated, the outputs of the unidirectional converters Ci are all connected to the distribution bus 16, which operates under a distribution voltage VBUS. The downstream electronic equipment is then connected to the distribution bus 16 directly, or is connected thereto via a secured switch (not shown) and/or one or more power converters.
The distribution voltage VBUS is adapted to be slaved to a reference distribution voltage V*BUS and to be kept below a maximum value VBUS_MAX via the control of the unidirectional converters, as will be seen hereafter.
In the example of FIG. 1, the reference distribution voltage V*BUS is for example equal to 12 V.
The energy storage device 18 is capable of storing electrical energy coming from the distribution bus 16 and returning the stored electrical energy to the distribution bus 16, as well as allowing the power supply system 10 to withstand power disruptions or disappearances of the input voltages V1, . . . , VN.
Furthermore, it is adapted to filter load pulsations resulting from electrical power inrushes done by the downstream electronic equipment. In fact, the frequencies of the load pulsations are generally of a much higher order of magnitude than that of the frequency of the charge-discharge cycles of the energy storage device 18, which is the decisive one for controlling the unidirectional converters Ci. The load pulsations are then attenuated for the power supply grids Ri, as will be seen hereafter.
The energy storage device 18 is connected to the distribution bus 16 and operates under a storage voltage VST.
In the embodiment of FIG. 1, the energy storage device 18 is a capacitive device, the storage voltage VST being representative of a quantity of electrical energy E that it contains. The storage voltage VST is regulated at a stipulated storage voltage V*ST. For example, the value of the stipulated storage voltage V*ST is equal to 90 V.
The control means 20 are adapted to simultaneously control the unidirectional converters Ci to regulate the electrical powers P1, . . . , PN delivered by those converters to the distribution bus 16 as a function of the quantity of electrical energy E.
In the example of FIG. 1, the control means 20 are capable of controlling the unidirectional converters Ci to regulate the electrical powers P1, . . . , PN delivered by those converters to the distribution bus 16 as a function of the storage voltage VST.
The control of these unidirectional converters Ci by the control means 20 implements a regulating algorithm of the electrical powers P1, . . . , PN delivered as a function of the storage voltage VST, as will be seen hereafter.
The control means 20 comprise N storage regulating loops X1, . . . , XN. Each storage regulating loop Xi is respectively associated with a given unidirectional converter Ci.
Each storage regulating loop Xi is adapted to command the corresponding unidirectional converter Ci from the measurement of the storage voltage VST.
N storage voltage thresholds VST1, . . , VSTN are respectively associated with the N power supply grids R1, . . . , RN.
These storage voltage thresholds VST1, . . . , VSTN are decreasing and define a priority order between the power supply grids Ri such that the reference storage voltage threshold VSTi power supply grid Ri has priority relative to the power supply grids RSTi+k whereof the reference storage voltages VSTi+k are smaller, k being an integer comprised between 1 and N−i.
The control means 20 are then adapted to command the corresponding unidirectional converter Ci as a function of the storage voltage VST so that the electrical power transferred to the distribution bus 16 by the power supply grids Ri, . . . , RN among which said power supply grid Ri has priority preferably comes from the power supply grid Ri, as will be seen later.
The control of the unidirectional converters Ci is done by each storage regulating loop Xi via a first control variable φSSi that is a function of the storage voltage VST.
In reference to FIG. 4, which illustrates the control characteristics 23 of the storage regulating loops Xi in the case where N is equal to 3, the control characteristics 23, i.e. the functions determining the first control variable φSS1, . . . , φSSN of the corresponding regulating loops X1, . . . , XN as a function of the storage voltage VST, each have a progressive reduction 24 of transferred power, the progressive reductions 24 of the various control characteristics 23 being done on ranges of values of the storage voltage VST that are disjoint from one another.
The slopes of the progressive reductions 24 respectively correspond to the static gain Gi of the corresponding storage regulating loop Xi.
The control characteristic 23 of a given storage regulating loop Xi has a storage cut-off voltage equivalent to the storage voltage threshold V STi associated with the corresponding power supply grid Xi.
The control characteristics 23 have a common maximum φS_MAX that corresponds to the command of a maximal electrical power transfer Pi between the considered power supply grid Ri and the distribution bus 16.
It should be noted that when the first control variable φSSi is equal to φS_MAX, the unidirectional converter Ci is commanded for a maximal transfer of electrical power Pi, but the electrical power transferred to the distribution bus can be zero. This is for example the case when the corresponding input voltage Vi is zero.
Each power supply grid Ri has an associated reference storage voltage V*STi of the power supply grid Ri defined by:
V*STi=VSTi+φS_MAX/Gi, where Gi is the static gain of the storage regulating loop Xi, φS_MAX is the maximum of the control characteristics 23 of the distribution regulating loops Xi, and VSTi is the storage voltage threshold of the power supply grid Ri.
The reference storage voltage V*STi of the power supply grid Ri is then the value of the storage voltage at which the storage voltage VST is stipulated when the storage voltage VST is over the value range of the progressive reduction 24 of the control characteristic 23 of the distribution regulating loop Xi.
The reference storage voltage V*STi corresponds to the minimum of the values of the storage voltage VST at which the first control variable φSSi is equal to 0, i.e. at which the unidirectional converter Ci is commanded by the control means 20 to transfer zero electrical power Pi to the distribution bus 16.
The closed-loop control of the storage voltage VST to that value V*STi thus makes it possible to minimize the withdrawal of electrical energy on the corresponding power supply grid Ri.
The value range on which the progressive reduction 24 of the control characteristic 23 of the regulation loop Xi is done is thus [VSTi; V*STi], with V*ST1 equal to V*ST. This value range thus defines an operating region of the system 10 associated with the reference power supply grid Ri.
The progressive reductions 24 of the control characteristics 23 are separated from one another by transparency ranges 25. The transparency ranges 25 are respectively associated with a given power supply grid Ri and correspond to a quantity of energy that the energy storage device 18 can supply to the distribution bus 16 to supply the downstream electronic equipment upon disappearance of the input voltage Vi of the corresponding power supply grid Ri, as will be seen hereafter.
The static gain Gi of the storage regulating loop Xi is determined by the equation: Gi=Gi−1*VSTi/VST−1, where Gi is the static gain of the storage regulating loop Xi, VSTi is the storage voltage threshold associated with the power supply grid Ri, VSTi−1 is the smallest of the storage voltage thresholds above the storage voltage threshold VSTi, and Gi−1 is the gain of the storage regulating loop whereof the unidirectional converter is associated with the power supply grid whereof the storage voltage threshold is VSTi1.
The static gains Gi of the N storage regulating loops Xi have decreasing values, the static gain Gi of a storage regulating loop Xi whereof the unidirectional converter Ci is associated with a first power supply grid Ri being smaller than the static gain Gk of the storage regulating loops Xi whereof the unidirectional converter Ck is associated with a power supply grid Rk with a higher priority relative to said first power supply grid Ri.
The higher the static gain Gi, the closer the storage voltage VST is kept to the reference storage voltage V*STi of the power supply grid Ri.
However, the higher the static gain Gi, the less the energy storage device 18 can filter the load pulsations. In fact, a high static gain Gi translates to a compensation of the slightest variation of the storage voltage VST through the modification of the electrical power Pi delivered by its unidirectional converter Ci. In other words, the higher the static gain Gi, the more the load pulsations are visible for the corresponding power supply grid Ri.
Furthermore, when the storage voltage VST decreases, the electricity contained in the storage means 18 available for filtering of the load pulsations decreases.
This translates to an increase in the current passing through the energy storage device 18 and significant variations of the storage voltage VST.
This voltage variation can be expressed in the following form for a sinusoidal load pulsation ILOAD:




  
    Δ
    ⁢
    
      
    
    ⁢
    
      V
      ST
    
  
  =
  
    
      
        V
        BUS
      
      
        V
        ST
      
    
    ⁢
    
      
        I
        LOAD
      
      
        Y
        Cst
      
    
  




Where YCst is the storage capacity of the energy storage device.
A better filtering of the load pulsations is then obtained by increasing the maximum storage capacity YCst, or by relaxing the closed-loop control of the storage voltage VST to the reference storage voltage V′STi of the power supply grid Ri, i.e. by decreasing the static gain Gi of the corresponding regulating loop Xi.
The operation of the power supply system 10 according to the invention will now be described in reference to FIG. 4.
FIG. 4 illustrates the algorithm for regulating the electrical powers P1, . . . , PN 20 as a function of the storage voltage VST, the algorithm being carried out by the control means 20. The values of the storage voltage VST are divided into regions (1 to 7).
The region 1 is a transient condition caused by the response time of the regulating loops, as will be seen hereafter.
In this region 1, the energy storage device 18 then transfers its electrical enegy to the distribution bus 16 to power the downstream electronic equipment, the unidirectional converters Ci being driven by the storage regulating loops Xi so as not to transfer electrical power Pi to the distribution bus 16.
The quantity of energy E then decreases, and the storage voltage VST drops as far as a region 2, which is an operating region of the power supply system 10 associated with the priority power supply grid R1.
In this region 2 delimited by the storage voltage values VST1 and V*ST, the storage regulating loop X1 commands the unidirectional converter C1 such that the storage voltage VST is kept close to the reference storage voltage V*ST. If the storage voltage VST drops below the reference storage voltage V*ST, the storage regulating loop X1 commands the increase in the electrical power P1 such that the storage voltage VST increases.
Conversely, if the storage voltage VST exceeds V*ST and penetrates the region 1, the storage regulating loop X1 commands the unidirectional converter such that the electrical power P1 delivered is zero.
In steady state, the electrical powers P1, . . . , PN delivered by the unidirectional converters C1, . . . , CN to the distribution bus 16 correspond to the electrical load power PLOAD delivered as output to the electronic equipment via the distribution voltage VBUS. The distribution voltage is then kept at the value of the reference distribution voltage V*BUS.
When the input voltage V1 decreases, for example during a breakdown occurring on the power supply grid R1, the electrical power delivered by the unidirectional converter C1 to the distribution bus 16 decreases, which tends to cause the storage voltage VST to drop. The regulating loop X1 commands the unidirectional converter C1 to increase the electrical power transfer P1 between the power supply grid R1 and the distribution bus 16, potentially up to saturation of the storage regulating loop X1.
The saturation of the storage relating loop Xi corresponds to the command by said loop to the corresponding unidirectional converter Ci of the maximum electrical power Pi transfer between the power supply grid Ri and the distribution bus 16 (the electrical power Pi actually transferred possibly being zero).
If the input voltage V1 disappears, the electrical power P1 delivered by the unidirectional converter C1 to the distribution bus is insufficient to load the energy storage device 18, and the energy storage device 18 discharges while powering the electronic equipment. The storage voltage VST then decreases as far as a region 3.
This region 3 corresponds to the transparency range 25 of the power supply grid R1 in which the storage regulating loop X1 is saturated, and the other storage regulating loops X2, . . . , XN command their respective unidirectional converter Ci to transfer zero power P2, . . . , PN between the corresponding power supply grid Ri and the distribution bus 16.
As long as the input voltage V1 of the priority power supply grid R1 remains insufficient, the energy storage device 18 discharges and the storage voltage VST decreases until it moves into a region 4.
In this region 4, delimited by the storage voltage values VST2 and V*ST2 and which corresponds to an operating region associated with the power supply grid R2, the storage regulating loop X2 of the priority power supply grid R2 after the priority power supply grid R1 commands the corresponding unidirectional converter C2 to perform a transfer of electrical power P2 toward the distribution bus 16 so that the storage voltage VST remains close to the value V*ST2, i.e. so as to balance the power consumed on the power supply grid R2 and the power supplied to the bus 16.
The storage regulating loop X1 of the priority power supply grid R1 then remains saturated.
The static gain G2 of the storage regulating loop X2 is then defined via the static gain G1 according to the equation G2=G1*VST2/VST1.
As before, if the storage voltage VST decreases, for example due to the disappearance of the input voltage V2, the storage regulating loop X2 commands the unidirectional converter C2 to increase the power transfer P2 between the power supply grid R2 and the distribution bus 16 so as to provide a surplus of electrical energy to reload the energy storage device 18.
If the storage voltage VST continues to drop despite the saturation of the storage regulating loop X2, the storage voltage VST decreases toward a second transparency range 25 that corresponds to the transparency of the power supply grid R2.
If the input voltages V1 or V2 do not reappear, the storage voltage VST then decreases as far as a region 6 delimited by the storage voltage values VST3 and V*ST3. In this region 6, the storage regulating loop X3 commands the unidirectional converter C3 to perform a transfer of electrical power P3 so that the storage voltage VST is kept close to the value V*ST3, i.e. so as to balance the power consumed on the power supply grid R3 and the power supplied to the distribution bus 16.
The storage regulating loops X1 and X2 are still saturated.
However, in the region 4, if the priority power supply grid reappears, i.e. the power supply grid R1, the electrical power P1 transferred to the distribution bus 16 by the unidirectional converters C1 increases gradually from 0.
The storage regulating loop X1 of this grid being saturated, the electrical power simultaneously transferred by the two unidirectional converters C1 and C2 to the distribution bus 16 corresponds to a surplus of electrical energy relative to what the power supply system 10 delivers to the electronic equipment, which results in recharging the energy storage device 18 and increasing the storage voltage VST.
The storage voltage VST then increases until it climbs out of region 4, i.e. the command by the storage regulating loop X2 to the unidirectional converter C2 to transfer zero electrical power P2 from the power supply grid R2 to the distribution bus 16.
The transfer of electrical power P1 between the priority grid R1 and the distribution bus 16 being maximal, the storage voltage VST continues to increase until it enters the region 2, which corresponds to the nominal operation of the power supply system 10.
In practice, the power supply system 10 is initially in the region 7, the storage voltage VST being zero and all of the storage regulating loops Xi being saturated. When less than one power supply grid is available, the saturation of these loops causes the increase in said storage voltage VST until it enters the operating region associated with the priority power supply grid Ri, as described above.
The control logic of the control means 20 is thus done as a function of the quantity of energy E of the energy storage device 18 and simultaneously regulates the electrical power Pi delivered by each unidirectional converter Ci to the distribution bus 16.
This control logic does not rely on the evaluation of the availability of the power supply grids Ri and any switching which, at a given moment, limits the number of power supply grids Ri capable of supplying electricity to the distribution bus 16 to one.
In fact, when the storage voltage VST is below several storage voltage thresholds VSTi, the storage regulating loops Xi associated with the power supply grids Ri of storage voltage thresholds VSTi higher than the storage voltage VST are saturated. These power supply grids Ri are thus ready to transfer their electrical power Pi to the distribution bus 16 without delay or switching.
This in particular makes it possible to minimize the amplitude of the transient phases in case of the appearance of one of the power supply grids.
Furthermore, the electrical power Pi supplied by a power supply grid Ri to the distribution bus 16 increases and decreases gradually and continuously, which minimizes disruptions on the power supply grids Ri.
FIG. 2 illustrates a second embodiment of the invention.
In this second embodiment, the power supply system 10 comprises the same elements as above. These will therefore not be described again.
Furthermore, the power supply system 10 includes a two-way loader 26.
The control means 20 include N distribution regulating loops designated by references Y1, . . . , YN and a loader regulating loop BE capable of driving the loader 26 to subjugate the distribution voltage VBUS to the reference distribution voltage V*BUS.
Furthermore, the control means 20 include N control blocks L1, . . . , LN respectively connected as input to a storage regulating loop Xi and a distribution regulating loop Yi, and as output to the corresponding unidirectional converter Ci.
The loader 26 is connected on the one hand to the distribution bus 16 and on the other hand to the energy storage device 18. It is capable of withdrawing electrical power on the distribution bus 16 and delivering it to the energy storage device 18, and vice versa.
The loader 26 is for example made up of a step-down converter controlled synchronously or a common inductance voltage step-down/step-up converter.
The N distribution regulating loops Yi are adapted to control the electrical power Pi delivered by the unidirectional converters Ci to the distribution bus 16 as a function of the distribution voltage VBUS. This control is done by each distribution regulating loop Yi via a second control variable φFS1, . . . , φFSN.
More particularly, the distribution regulating loops Yi are adapted to control the unidirectional converters Ci to limit the distribution voltage VBUS.
To that end, each distribution regulating loop Yi is associated with a local distribution voltage V*BUSi such that if the distribution voltage VBUS exceeds the local distribution voltage V*BUSi, the corresponding distribution regulating loop Yi commands the limitation of the electrical power Pi supplied by the corresponding converter, which in return tends to limit the distribution voltage VBUS.
The local distribution voltages V*BUS1, . . . , V*BUSN are strictly decreasing and greater than the reference distribution voltage V*BUS of the loader regulating loop BE.
When the distribution voltage VBUS is greater than V*BUS, which occurs in particular when several unidirectional converters Ci transfer a non-zero electrical power to the distribution bus 16, the electrical power Pi coming from the priority power supply grid Ri among those power supply grids is thus transferred as a priority to the distribution bus 16.
Each control block Li is adapted to limit the electrical power Pi delivered by the corresponding unidirectional converter Ci through the selection of the minimum between the first control variable φSSi of the storage relating loop Xi and the second control variable φFSi of the distribution regulating loop Yi.
Alternatively, the distribution regulating loops Yi can control the unidirectional converters Ci to limit a distribution current IBUS that they supply to the distribution bus 16.
The operation of the power supply system 10 according to the second embodiment follows from the operation of the invention according to the first embodiment and will now be described, still in reference to FIG. 4.
In this embodiment, aside from the aspects of the operation of the power supply system 10 previously described, the loader 26 withdraws electrical power on the distribution bus 16 when the distribution voltage VBUS exceeds the reference distribution voltage V*BUS and transfers that electrical power to the energy storage device 18, i.e. it loads the energy storage device 18.
Conversely, when the distribution voltage VBUS drops below its reference value V*BUS, the loader 26 compensates by discharging the energy storage device 18 so as to introduce a surplus of electrical energy onto the distribution bus 16, which tends to increase the distribution voltage VBUS.
In reference to FIG. 4, in a region associated with a power supply grid Ri, when a priority power supply grid Rj reappears (j is an integer smaller than i), the saturation of the storage regulation loop Xj translates to a rapid increase in the distribution voltage VBUS. In order to prevent these excursions of the distribution voltage VBUS on the distribution bus 16 that may harm the downstream electronic equipment, the control block Lj of the unidirectional converter Ci limits the electrical power Pi that it delivers by proceeding as described above.
The control blocks Li thereby guarantee that the distribution voltage VBUS remains under maximum distribution voltage VBUS_MAX.
It should be noted that the speeds of the distribution regulating loops Yi are higher than the speeds of the corresponding storage regulating loops Xi.
This embodiment is therefore advantageously used to limit the distribution voltage VBUS.
FIG. 3 illustrates a third embodiment of the invention, in which the power supply system 10 has the same members as in the second embodiment; these members therefore will not be described again.
In this third embodiment, each unidirectional converter C1, . . . , CN associated with a given power supply grid has:

    
    
        an intermediate grid T1, . . . , TN,
        a unidirectional primary converter F1, . . . , FN and
        a two-way insulator I1, . . . , IN.
    
    


Furthermore, the control means 20 have N positive reaction loops Z1, . . . , ZN. Each positive reaction loop Zi is respectively associated with a given two-way insulator Ii.
The primary unidirectional converters Fi, hereafter primary converters Fi, can prevent transfers of electrical energy between the power supply grid Ri with which they are respectively associated and the other power supply grids.
Each primary converter Fi is connected in input to the corresponding power supply grid Ri and can deliver, to the corresponding intermediate grid Ti, an intermediate voltage VPi regulated at a stipulated intermediate voltage V*Pi, from the input voltage Vi of said power supply grid. Each primary converter Fi is then driven by a primary regulating loop FECi to that end.
The primary converters Fi have current rectifying means, means for filtering the input voltage Vi in common mode and in differential mode, as well as protection means against overvoltages and protection means against lightning.
The primary converters Fi are for example of the common inductance voltage step-down/step-up type when the current supplied by the corresponding power supply grid is direct and the input voltage Vi is equal to 28 V or 270 V, and are for example of the Boost PFC type when the supplied current is alternating and the input voltage Vi is equal to 115 V or 230 V.
The two-way insulators Ii, hereafter insulators Ii, can allow the two-way transfer of electrical energy between the associated intermediate grid Ti and the distribution bus 16. Moreover, the insulators Ii can galvanically insulate the power supply grid Ri with which the unidirectional converter Ci to which they belong is associated from the other power supply grids Ri and power the primary auxiliary equipment (not shown).
Each insulator Ii is connected in input to an intermediate grid Ti and at its output to the distribution bus 16. Via an output 28, the intermediate grid Ti makes it possible to power auxiliary equipment (not shown) and auxiliary circuits (not shown) to which they deliver a polarization current for their operation.
Each positive reaction loop Zi is associated with a given insulator Ii and can control said insulator Ii to regulate the electrical power Pi that this insulator delivers as a function of the intermediate voltage VPi. This command is done via a third control variable φP1, . . . , φPN.
Moreover, each positive reaction loop Zi can control the insulator Ii to regulate an electrical power P′i transferred by the insulator Ii to the associated intermediate bus Ti from the distribution bus 16.
The electrical power P′i is used to power electronic equipment via its connection to an intermediate bus Ti whereof the insulator Ii is currently commanded not to transfer electrical power Pi to the distribution bus 16.
In the example of FIG. 3, this for example thus makes it possible to power electronic equipment from an intermediate bus T2 of the unidirectional converter C2, which is also controlled by the storage regulation loop X2 to deliver zero electrical power P2 to the distribution bus 16 during the nominal operation of the power supply system 10.
The insulators Ii are for example made by converters of the Dual Active Bridge type or from Load-Resonant Converters (LRC). They are for example provided with Active Secondary Rectifier devices.
As illustrated in FIG. 3, the regulation of the electrical power Pi delivered by each unidirectional converter Ci to the distribution bus 16 is done via the control of the insulators I1, . . . , IN. The control of each insulator Ii is done:

    
    
        by the associated storage regulation loop Xi as a function of the storage voltage VST,
        by the associated distribution regulating loop Yi as a function of the distribution voltage VBUS, and
        by the associated positive reaction loop Zi as a function of the intermediate voltage VPi of the corresponding intermediate bus Ti.
    
    


In this third embodiment, the control block Li and the positive reaction loop Zi associated with a given unidirectional converter Ci are then connected at their output to a subtracter CPi capable of controlling the insulator Ii for a transfer of electrical power Pi as a function of three control variables φSSi, φFSi and φPi.
The electrical power Pi delivered by each unidirectional converter Ci to the distribution bus 16 is proportional to the difference between the minimum of the first control variable φSSi and the second control variable φFSi on the one hand, and the third control variable φPi on the other hand, i.e.:

Pi∝min(φSSi; φFSi)−φPi.

It should be noted that the storage regulation loop Xi of each unidirectional converter Ci is the only regulation loop capable of controlling the electrical power Pi delivered by said insulator Ii upward, the distribution regulating loop Yi and the positive reaction loop Zi being adapted to limit that electrical power Pi.
The operation of the power supply system 10 according to the third embodiment of the invention follows from the operation of the system 10 according to the second embodiment and will now be described in reference to FIGS. 3, 4 and 5.
Aside from the aspects of the operation of the system 10 according to the second embodiment previously described, during the operation of the power supply system 10 in a region associated with a given power supply grid Ri, it happens that the input voltage Vi delivered by the corresponding power supply grid Ri decreases temporarily. Such a phenomenon is called a brown-out.
This voltage drop translates to a decrease in the corresponding intermediate voltage VPi.
Without information pertaining to this input voltage drop Vi, the storage Xi and distribution Yi regulating loops control the corresponding insulator Ii to transfer the same electrical power Pi from the intermediate grid Ti to the distribution bus 16, which can cause the intermediate voltage VPi to disappear.
The positive reaction loop Zi of the considered power supply grid Ri then controls the insulator Ii through the increase in the third control variable φPi so that the electrical power Pi supplied to the distribution bus 16 decreases.
The electronic equipment is then powered via both the power supply grid Ri, the operation of which is degraded, and the energy storage device 18, as long as the storage voltage remains in the voltage range [VSTi, V*STi].
When the storage voltage is situated in a value range [VSTi, V*Sti], corresponding to a power supply grid Ri, the intermediate voltage VPk seen by each primary converter Fk associated with a power supply grid Rk of lower priority than the power supply grid Ri is higher than the stipulated intermediate voltage V*Pk, due to the two-way nature of the insulators Ik, with k an integer greater than i.
In fact, the distribution voltage VBUS is seen by the primary converter Fk subject to a transform coefficient and the action of the corresponding positive reaction loop Zk, such that the intermediate voltage VPk is kept above the stipulated intermediate voltage V*Pk.
The associated primary converters Fi are commanded by their primary regulating loop FECk to transfer zero electrical power from the power supply grid Rk to the corresponding intermediate grid Tk.
FIG. 5 is an illustration of the variations of the storage voltage VST, the distribution voltage VBUS, and the electrical powers P1 and P2 as a function of time when a power supply system 10 according to the third embodiment of the invention is started up in the event it is connected as input to power supply grids R1, R2 (N=2). In the example of FIG. 5, the appearance of the power supply grids Ri is simultaneous.
Until moment {circle around (1)}, the storage regulating loops Xi are saturated. The unidirectional converter C1 supplies its maximum power, while the converter C2 supplies a power limited by the distribution regulating loop Y2. The distribution voltage VBUS is therefore regulated to the local distribution voltage VBUS2*.
Until moment {circle around (2)}, the power transferred to the distribution bus 16 by the two converters C1 and C2 is limited by the capacity of the loader 26 to absorb electricity. The power supplied by the converter C2 is used to load the storage device 18 more quickly, and is significantly smaller than the nominal power of the unidirectional converter C2.
After moment {circle around (2)}, the storage regulating loop X2 begins to desaturate. The power supplied by the converter C2 gradually decreases. The distribution voltage VBUS rapidly converges toward the reference VBUS* defined by the loop BE.
At moment {circle around (3)}, the converter C2 is commanded for zero transferred power P2. The converter C1 continues to supply its maximum power, supplying both the downstream load and increasing the storage voltage VST.
At moment {circle around (4)}, the storage voltage VST is equal to VST1 and the storage regulation loop X1 begins to desaturate. The electrical power P1 supplied by the converter C1 converges toward the load power PLOAD consumed by the load.
At moment {circle around (5)}, the system is balanced and the converter C1 supplies an electrical power P1 equal to the load power PLOAD consumed by the load.
Alternatively, the energy storage device 18 is an inductive storage device passed through by a storage current IST representative of a quantity of electricity E that it contains.
In this alternative, the control means 20 can simultaneously control the unidirectional converters Ci to regulate the electrical power Pi delivered by each of said unidirectional converters 14 as a function of the storage current IST.
While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

## Claims

1. A power supply system adapted to be connected in input to N distinct power supply grids (R1, . . . , RN) delivering a direct or alternating input voltage (V1, . . . , VN), and to deliver a direct distribution voltage (VBUS), N being an integer greater than or equal to 2, of the type comprising:
a distribution bus operating under the distribution voltage (VBUS),
N unidirectional converters (C1, . . . , CN) adapted to be respectively connected in input to a given power grid (R1, . . . , RN) and adapted to deliver an electrical power (P1, . . . , PN) to the distribution bus, and
control means adapted to control the unidirectional converters (C1, . . . , CN),
characterized in that the power supply system also includes an energy storage device connected to the distribution bus and having a quantity of energy (E), and in that the control means are adapted to control the unidirectional converters (C1, . . . , CN) simultaneously to regulate the electrical power (P1, . . . , PN) delivered by each of said unidirectional converters (C1, . . . , CN), according to a priority order between the power supply grids determined as a function of the quantity of energy (E).

2. The power supply system according to claim 1, characterized in that the energy storage device is a capacitive storage device operating under a storage voltage (VST) representative of the quantity of energy (E), the control means being adapted to control the unidirectional converters (C1, . . . , CN) simultaneously to regulate the electrical power (P1, . . . , PN) delivered by each of said unidirectional converters (C1, . . . , CN) as a function of the storage voltage (VST).

3. The power supply system according to claim 1, characterized in that the energy storage device is an inductive storage device passed through by a storage current (IST), the control means being adapted to control the unidirectional converters (C1, . . . , CN) simultaneously to regulate the electrical power (P1, . . . , PN) delivered by each of said unidirectional converters (C1, . . . , CN) as a function of the storage current (IST).

4. The power supply system according to claim 2, characterized in that decreasing storage voltage thresholds (V ST1, . . . , VSTN) are associated with the power supply grids (R1, . . . , RN) and define a priority order between said power supply grids (R1, . . . , RN) such that a first power supply grid (R1, . . . , RN) whereof the storage voltage threshold (V ST1, . . . , V STN) is higher than the storage voltage threshold (V ST1 , VSTN) of a second power supply grid (R1, . . . , RN), is given a higher priority relative to said second power supply grid (R1, . . . , RN).

5. The power supply system according to claim 4, characterized in that the control means comprise N storage regulating loops (X1, . . . , XN) respectively associated with a unidirectional converter (C1, . . . , CN) and capable of regulating the electrical power (P1, . . . ,PN) delivered by said unidirectional converter (C1, . . . ,CN) to the distribution bus, each storage regulating loop (X1, . . . , XN) comprising a progressive reduction control characteristic beyond a voltage threshold (VST1, . . . , VSTN) associated with the corresponding power supply grid (R1, . . . , RN), the slope of said progressive reduction corresponding to the static gain (Gi) of said storage regulating loop (X1, . . . , XN).

6. The power supply system according to claim 5, characterized in that the progressive reductions of the control characteristics of the N storage regulating loops (X1, . . . ,XN) are done over value ranges of the storage voltage (VST) that are disjoint from one another.

7. The power supply system according to claim 5, characterized in that the maximum value (φS—MAX) of the control characteristic of a storage regulating loop (X1, . . . ,XN) is also the maximum value of the control characteristics of the N-1 other storage regulating loops (X1, . . . ,XN).

8. The power supply system according to claim 5, characterized in that the respective static gains (Gi) of the N storage regulating loops (X1, . . . , XN) have decreasing values, the static gain (G1, . . . ,GN) of a storage regulating loop (X1, . . . XN) whereof the unidirectional converter (C1, . . . ,C N) is associated with a first power supply grid (R1, RN) being smaller than the static gain (G1, . . . ,GN) of the storage regulating loop (X1, . . . , XN) whereof the unidirectional converter (R1, . . . ,RN) is associated with a power supply grid (R1, . . . , RN) with a higher priority relative to said first power supply grid (R1, . . . , RN).

9. The power supply system according to claim 8, characterized in that the static gain (G1 ,. . . , GN) of a storage regulating loop (X1, . . . , XN) whereof the unidirectional converter (C1, . . . , CN) is associated with a first power supply grid (R1, . . . , RN) is determined by the equation Gi=Gi-1*VSTi |VSTi-1where Gi is the static gain (G1, . . . GN) of said storage regulating loop (X1, . . . , X N), VSTi is the storage voltage threshold associated with said first power supply grid (R1, . . . , RN), VSTi-1 is the smallest of the storage voltage thresholds higher than the storage voltage threshold VSTi, and Gi-1 is the static gain (G1 GN) of the storage regulating loop (X1, . . . , XN) whereof the unidirectional converter (C1, . . . , CN) is associated with the power supply grid (R1, . . . , RN) whereof the storage voltage threshold is VSTi-1.

10. The power supply system according claim 1, characterized in that the control means have N distribution regulating loops (Y1, . . . , YN) respectively associated with a given unidirectional converter (C1, . . . , CN) and capable of regulating the electrical power (P1, . . . ,PN) delivered by said unidirectional (C1, . . . ,CN) converter to the distribution bus (16) as a function of the distribution voltage (V BUS) to limit the distribution voltage (VBUS) or to limit a distribution current (I BUS)supplied to the distribution bus.

11. The power supply system according to claim 1, characterized in that each unidirectional converter (C1, . . . CN) associated with a given power supply grid (R1, . . . , RN) includes:
an intermediate grid (T1, . . . , TN),
a unidirectional primary converter (F1, . . . , FN) capable of preventing electrical power transfers between the power supply grid (R1, . . . , RN) with which said unidirectional converter (C1, . . . , CN) is associated and the other power supply grids (R1, . . . , RN), said unidirectional primary converter (C1, . . . , CN) being connected in input to the corresponding power supply grid (R1, . . . , RN) and capable of delivering to the intermediate grid (T1, . . . , T N) a regulated intermediate voltage (V P1, . ., VPN) from the input voltage (V1, . . . , VN) of said power supply grid, and
a bidirectional insulator (I1, . . . , IN) capable of galvanically insulating the power supply grid (R1, . . . , RN) with which said unidirectional converter (C1, . . . CN) is associated from the other power supply grids (R1, . . . , RN), said bidirectional insulator (I1, . . . , IN) being connected in input to the intermediate grid (T1, . . . , TN) and at its output to the distribution bus (16), and being capable of being controlled by the control means (20) to regulate the electrical power (P1, . . . ,PN) delivered by the unidirectional converter (C1, . . . , CN) to the distribution bus and to regulate electrical power (P′1, P′ N) coming from the distribution bus and delivered by said bidirectional insulator (I1, . . . , IN) to the corresponding intermediate bus (T1, . . . , TN).

12. The power supply system according to claim 11, characterized in that the primary converters (F1, . . . , FN) include rectifier means for the voltage, filtering means for the voltage in common mode and differential mode, protection means against overvoltages, and protection means against lightning.

13. The power supply system according to claim 11, characterized in that the control means have N positive reaction loops (Z1, . . . , ZN) respectively associated with a given bidirectional insulator (I1, . . . , IN) and capable of regulating, as a function of the intermediate voltage (VP1, . . . , VPN) of the corresponding intermediate grid (T1, . . . , TN), the electrical power (P1, . . . ,PN) delivered by said bidirectional insulator to the distribution bus, and therefore by the corresponding unidirectional converter (C, . . . CN) to the distribution bus, on the one hand, and the electrical power (P′1, . . . ,P′ N) delivered by said bidirectional insulator (I1, . . . , IN) to the corresponding intermediate bus (N1, . . . , N N) on the other hand.

14. The power supply system according to claim 5, characterized in that for each unidirectional converter (C1, . . . ,CN), the associated storage regulating loop (X1, . . . , XN) is capable of regulating the electrical power (P1, . . . , PN) delivered by said unidirectional converter (C1, . . . , CN) as a function of the storage voltage (VST) via a first control variable φSS1, . . . , φSSN) the associated distribution regulating loop (Y1, . . . , YN) is capable of regulating the electrical power (P1, . . . , PN) delivered by said unidirectional converter (C1, . . . , CN) as a function of the distribution voltage (VBUS) via a second control variable (φFS1, . . . , φFSN) and the associated positive reaction loop (Z1, . . . , ZN) is capable of regulating the power delivered by said unidirectional converter via a third control variable (φP1 ,. . ., φPN), the power delivered by said unidirectional converter (P1, . . . , PN) to the distribution bus being proportional to the difference between the minimum of the first (φSS1, . . . , φSSN) and second (φFS1, . . . , φFSN) control variables on the one hand, and the third control variable on the other hand (φP1 , . . . , φPN).

15. The power supply system according to claim 1, characterized in that the energy storage device is connected to the distribution bus via a two-way loader capable of transferring electric energy between the distribution bus and the energy storage device.

16. The power supply system according to claim 15, characterized in that the energy storage device comprises a loader regulating loop (BE) capable of controlling the two-way loader to regulate the transfer of electrical energy between the two-way loader and the distribution bus to slave the distribution voltage (V BUS) to a reference distribution voltage (V* BUS).