Abstract:
A method for balancing a polyphase network for supplying an installation including a plurality of sockets for plugging-in electrical equipment, wherein a phase selector is inserted for each socket, between a system for supplying a polyphase voltage and the socket, and intercepts a command signal for energizing the socket. Once an energizing command has been received from one of the monophase equipments, the least charged phase is selected for powering the equipment, the evaluation of the least charged phase being carried out upstream of the system.

Description:
[0001]    The present patent application claims the priority benefit of French patent application FR13/54796 which is herein incorporated by reference. 
       BACKGROUND 
       [0002]    The present disclosure generally relates to electric installations and, more specifically, to installations receiving a three-phase power supply. An example of application of the present invention relates to electric vehicle charging installations. 
       DISCUSSION OF THE RELATED ART 
       [0003]    Document WO2012/110472 of the applicant discloses a load balancing device on a polyphase network which, to have a load switch from one phase to another, uses a single-phase voltage generated by an inverter. This voltage is first synchronized with the first phase, and then progressively phase-shifted until it is synchronized with the other phase. 
         [0004]    Phase-selection systems which aim at avoiding a loss of power supply of a single-phase load are also known. To achieve this, the selectors monitor the voltage value of the different phases and, if the voltage of the phase used by the single-phase load becomes lower than a threshold, switch to another phase of the polyphase network. Such a phase selector however generally results in increasing the imbalance between phases. 
         [0005]    In installations for charging electric vehicle batteries, a plurality of charging stations are generally powered from a polyphase network (typically, a three-phase network). Electric vehicle chargers are generally single-phase, which poses problems of balancing of the loads connected to the different phases. 
         [0006]    Document EP 0556754 describes an electric distribution system equipped with a phase selector using a circuit for measuring the loading of the phases. 
         [0007]    Documents DE 10 2011 078047 and US 2013 062970 describe a phase selector measuring the loading of the different phases. 
       SUMMARY 
       [0008]    It would be desirable to have a phase selection system in a polyphase network which is compatible with a phase balancing, that is, a balanced load distribution on the different phases of the polyphase network. 
         [0009]    It would further be desirable to have such a selector which is compatible with electric vehicle charging installations. 
         [0010]    An object of an embodiment is to provide a phase selector which overcomes all or part of the disadvantages of usual phase selectors. 
         [0011]    Another object of an embodiment is to provide a solution compatible with single-phase and three-phase equipment. 
         [0012]    To achieve all or part of these and other objects, a method of balancing a polyphase network for powering an installation comprising a plurality of sockets of connection of electric equipment is provided, wherein:
       for each socket, a phase selector is interposed, between a polyphase voltage supply system and said socket, and intercepts a socket energizing control signal; and   once a single-phase equipment energizing control signal has been received, the least loaded phase is selected to power this equipment, the evaluation of the least loaded phase being performed upstream of the system.       
 
         [0015]    According to an embodiment, each phase selector intercepts a control signal for energizing of the socket to which it is associated. 
         [0016]    According to an embodiment, the energizing control signal is transmitted to the socket subsequently to the phase selection. 
         [0017]    According to an embodiment, a control signal for selecting the least loaded phase is sent by said system to said selectors. 
         [0018]    According to an embodiment, the evaluation of the least loaded phase is performed by measuring the current sampled from the different phases upstream of the selector. 
         [0019]    An embodiment also provides a phase selector capable of implementing the phase selection method. 
         [0020]    According to an embodiment, the selector comprises:
       first terminals intended to receive a polyphase power supply;   second terminals intended to be connected to an electric equipment power supply socket;   a set of switches for connecting said first terminals to said second terminals; and   a circuit for controlling said switches.       
 
         [0025]    According to an embodiment, said control circuit interrupts a control connection between the system and a contactor, itself connected to the socket. 
         [0026]    An embodiment also provides a polyphase power supply installation, comprising:
       a system for supplying a polyphase voltage;   a plurality of equipment powering sockets; and   between said system and each socket, a phase selector.       
 
         [0030]    According to an embodiment, an energizing contactor is interposed between each selector and the socket to which it is associated. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0031]    The foregoing and other features and advantages of the present invention will be discussed in detail in the following non-limiting description of specific embodiments in connection with the accompanying drawings, among which: 
           [0032]      FIG. 1  very schematically illustrates an example of electric motor vehicle charging installation of the type to which the embodiments which will be described more specifically apply; 
           [0033]      FIG. 2  shows an example of three-phase sockets in three phase configurations; 
           [0034]      FIG. 3  is a very simplified representation of an embodiment of a phase selector; 
           [0035]      FIG. 4  very schematically shows a phase selector of the type in  FIG. 3  in its environment; 
           [0036]      FIG. 5  is a more detailed block diagram of the phase selector of  FIGS. 3 and 4 ; 
           [0037]      FIGS. 6A and 6B  are timing diagrams illustrating the operation of the phase selector of  FIG. 4 ; 
           [0038]      FIG. 7  schematically shows in the form of blocks an alternative phase selector adapted to a single-phase socket; 
           [0039]      FIG. 8  illustrates an embodiment of a phase balancing system using phase selectors; and 
           [0040]      FIG. 9  illustrates a variation of  FIG. 8 . 
       
    
    
     DETAILED DESCRIPTION 
       [0041]    The same elements have been designated with the same reference numerals in the different drawings. For clarity, only those elements which are useful to the understanding of the embodiments which will be described have been shown and will be detailed. In particular, the elements for supplying the polyphase power supply have not been detailed, the described embodiments being compatible with usual elements. Further, in the application to an electric vehicle charging system comprising multiple stations, the management of the different stations to optimize the sizing and respect the contractual and technical constraints of use of the electric power system which powers the charging installation has not been detailed either, the described embodiments being here again compatible with usual management processes. 
         [0042]      FIG. 1  schematically shows an example of an electric vehicle charging installation. Such an installation equips parking spaces  12  where electric vehicles to be charged are intended to park. Each parking space  12  is equipped with a charging station  2  provided with a socket  4 , most often standardized, intended to receive a plug of an electric vehicle charging cable (not shown in  FIG. 1 ). 
         [0043]    The electric power is distributed to the different stations  2  from system  3 , through connections  31 . System  3  is connected (connection  32 ) to the polyphase electric distribution system (typically three-phase) to sample electric power from the system. System  3  may receive electric power originating from other sources than the polyphase distribution system. It may for example be a photovoltaic installation (for example, photovoltaic panels  14  equipping the roof of a shelter  16  covering spaces  12 ), or a wind-powered or hydroelectric installation. 
         [0044]    In practice, when an electric vehicle desires to charge its batteries, the user plugs the plug of the vehicle charging cable into a socket  4  of a station  2 . The sockets and plugs generally comprise not only power supply conductors, but also connections of communication between the vehicle and system  3  (as a variation, the communication connections may be radio connections). The communication connections are used to verify the proper connection of the electric vehicle to the station and may be used to modulate the vehicle charge power. 
         [0045]    Sockets  4  are most often three-phase sockets (in particular, the power generation from the photovoltaic panels is performed with a three-phase inverter and the photovoltaic installation is most often connected to the three-phase distribution system). However, most electric vehicles have single-phase chargers, so that the plugs which connect them to sockets  4  comprise a single-phase conductor, in addition to a neutral conductor, to a ground conductor, and to one or a plurality of control wires. In the case of a vehicle embarking a single-phase charger, only the conductor connected to terminal B 1  (see  FIG. 2 ) of the socket will be used. 
         [0046]    The phase balancing in the installation is usually statically performed, by connecting terminals B 1  of sockets  4  of charging stations  2  sometimes to phase conductor L 1 , sometimes to phase conductor L 2 , and sometimes to phase conductor L 3 , originating from system  3 . 
         [0047]      FIG. 2  is a simplified representation of an example of standardized sockets  4 . The example taken herein is a socket of type “EV plug alliance type 3” which is both single-phase and three-phase. Three sockets  41 ,  42 , and  43  have been shown in  FIG. 2 . Each socket  4   i  (with i ranging from 1 to 3 in  FIG. 2 ) comprises three terminals B 1 , B 2 , and B 3 , a neutral terminal BN, a ground terminal BT, and one or a plurality (two in the shown example) of communication terminals BC 1  and BC 2 . 
         [0048]    Arbitrarily and as an example, the case where the three phases noted L 1 , L 2 , and L 3  of the network (originating from system  3 ) are respectively connected to terminals B 1 , B 2 , and B 3  for socket  41 , to terminals B 2 , B 3 , and B 1  for terminal  42 , and to terminals B 3 , B 1 , and B 2  for socket  43 . This is generally what is provided in the case of a static balancing. Thus, if three vehicles are respectively plugged by single-phase plugs having their phase pin opposite terminal B 1  and sample the same power at the same time, the phases are balanced. 
         [0049]    This ideal case however does not occur in practice and a charge imbalance between phases can be observed. 
         [0050]    Further, as soon as the number of phases is not a multiple of three (for example, four sockets in the example of  FIG. 1 ), it is no longer possible to balance the phases, even statically. 
         [0051]      FIG. 3  is a simplified representation of an embodiment of a phase selector  5 , intended to be interposed between system  3  and each socket  4   i  for phase balancing purposes. 
         [0052]    Selector  5  comprises an input terminal block  52 , provided with three terminals  521 ,  522 , and  523  intended to be connected to the different phases of a polyphase network (for example, three-phase). For example, these terminals are connected to system  3  of  FIG. 1 . Terminal block  52  also comprises a terminal  524  intended to be connected to the neutral of the three-phase power supply as well as to at least one terminal  526  intended to convey control signals. 
         [0053]    Selector  5  also comprises an output terminal block  54  provided, in this example, with three terminals  541 ,  542 , and  543  intended to supply a socket  4  with the phases of a polyphase power supply, a neutral terminal  544 , and at least one control signal transmission terminal  546 . 
         [0054]    On the output side, terminal block  54  is intended to be connected, directly or via a contactor (not shown in  FIG. 3 ) to a socket  4  of a station  2 . The function of the contactor is, under control of a signal present on terminal  546 , to connect the set of terminals  541  to  544  to socket  4 . As will be seen hereafter, the function of the contactor may be fulfilled by the actual selector  5 . 
         [0055]    In practice, the portions upstream and downstream of selector  5  are connected to ground T, either independently from selector  5  or, as in the shown example, through respective terminals  528  and  548  of input and output terminal blocks. 
         [0056]      FIG. 4  shows an example of a selector  5  in its environment. In this example, terminal block  52  of selector  5  is directly connected to system  3  ( FIG. 1 ). As a variation, control signals C may be conveyed to another circuit. Output terminal block  54  is connected to an intermediate contactor  6  between selector  5  and the socket  4  for which the selector is intended. The case of a vehicle  7  having a single-phase charger  72  for its battery  74  is assumed. Charger  72  is then connected, via a plug  76 , to socket  4 . Plug  76  comprises two pins  766  and  767  intended to connect terminals BC 1  and BC 2  of socket  4 , two pins  761  and  764  intended to respectively connect terminals B 1  and BN of socket  4  and a ground pin  768  intended to connect terminal BT of socket  4 . In the example of a single-phase charger, terminals B 2  and B 3  of socket  4  are not connected to charger  72 . In the case of a two- or three-phase charger, one or two additional pins equip plug  76  to connect terminals B 2  and B 3  of socket  4  in order to connect them to the electric vehicle charger. 
         [0057]    Contactor  6  acts, under control of a signal C′ at the output of terminal block  54 , to control switches  61  to  64  respectively connecting terminals  541  to  544  of output terminal block  54  to terminals B 1 , B 2 , B 3 , and BN of socket  4 . 
         [0058]    In the embodiments which will be described, the function of selector  5  is to branch the three phases from the input terminal block to the output terminal block by selecting the least loaded phase for block  541 , and thus terminal B 1  of socket  4 . 
         [0059]      FIG. 5  is a more detailed simplified representation of an embodiment of selector  5 . In this embodiment, the identification of the least loaded phase is performed by comparison of the effective voltages of each phase. Other methods of identifying the least loaded phase are discussed hereafter. Nine switches  551  to  559  have first (input) terminals connected to terminals  521  to  523  and second (output) terminals connected to terminals  541  to  543  in order to, in operation, branch the three phases present on terminals  521  to  523  towards terminals  541  to  543 . For example, the input terminals of switches  551 ,  554 , and  557  are connected to terminal  521 , the input terminals of switches  552 ,  555 , and  558  are connected to terminal  522 , and the input terminals of switches  553 ,  556 , and  559  are connected to terminal  523 . On the side of terminal block  54 , the output terminals of switches  551  to  553  are connected to terminal  541 , the output terminals of switches  554  to  556  are connected to terminal  542 , and the output terminals of switches  557  to  559  are connected to terminal  543 . Switches  551  to  559  are individually controllable and each receive a signal (signals  562 ) originating from a circuit  56 , preferably included in selector  5 . In the shown example, circuit  56  receives information relative to the voltages present on each of the phases at the selector input. This function has been symbolized in  FIG. 5  by the presence of voltmeters  571 ,  572 , and  573  (V) preferably included in selector  5 , or other voltage measurement circuit, upstream of switches  551  to  559 , providing measurement results (signals  575 ) to circuit  56 . Further, circuit  56  has terminals connected to terminals  526  and  546  to intercept the communications between system  3  and the socket or its contactor, and process the control signals. 
         [0060]    Signal  526  is sent by system  3  to station  2  to trigger the provision of electric power to the vehicle. 
         [0061]    It is provided to select the least loaded phase to charge the vehicle battery. To achieve this, in the example of  FIG. 5 , the phase having the highest voltage, which thus corresponds to the phase from which the loads connected to system  3  (even upstream) draw the less power, is selected. Thus, the phase selection takes part in the phase balancing. 
         [0062]    Advantage is taken from the fact that, when a vehicle is to be charged by the installation, losing a few seconds is of no importance. In other words, a slight delay between the plugging of plug  76  into socket  4 , or its connection control, and the provision of the power supply voltage may be accepted. This delay corresponds to the time required to measure the phases and to select the least loaded phase. More generally, this amounts to intercepting the socket energizing control signal for the time necessary to select the order of the phases presented to the electric equipment connection socket. 
         [0063]      FIGS. 6A and 6B  are timing diagrams illustrating the operation of selector  5 .  FIG. 6A  is a state timing diagram of control signal C provided by system  3  to trigger the provision of a power supply to terminal  4  via contactor  6 .  FIG. 6B  is a sate timing diagram of signal C′ at the output of selector  5  for controlling contactor  6 . In a simple version, signal C, supplied by system  3  to contactor  6 , is a voltage step (digital signal in all or nothing) to control the turning on of switches  61  to  64 . According to this example, the occurrence (time t0) of a rising edge on signal C, corresponding to an instruction for providing the power supply to terminal  4 , triggers the measurement of the voltage levels of phases L 1  to L 3 . As a variation, the voltage measurement is performed periodically and the last measurement is taken into account at time t0. When the measurement is performed (or taken into account) and selector  5  has appropriately switched switches  551  to  559 , circuit  56  switches (time t1) signal C′ to the high state to control contactor  6 . In other words, circuit  56  intercepts the control order originating from system  3  and only transmits it to contactor  6  once the phase to which terminal  541  is connected has been selected. The voltage level measurement may be performed sequentially or in parallel. Similarly, the comparison performed by circuit  56  may be analog or digital. In practice, a microcontroller-type processing unit (μC) will be preferably used. 
         [0064]    The presence of selector  5  and the performed phase selection does not adversely affect the connection of a three-phase plug to socket  4 . Indeed, in the case of a three-phase automobile vehicle charger, socket  4  being powered by the three phases, the operation is maintained. It will just be ascertained to control switches  551  to  559  in adapted fashion to respect the rotation of the phases according to that powering terminal B 1 , that is, the phase rotation illustrated in relation with  FIG. 2 . 
         [0065]    According to an embodiment, selector  5  is interposed between system  3  and the different contactors  6  associated with sockets  4 . In this embodiment, no modification of the rest of the installation is necessary, the phase selection being integrally managed by selector  5 . The intervention of selector  5  is transparent for system  3  and for contactor  6 . 
         [0066]    According to an embodiment, advantage is taken from the fact that switches  551  to  559  of selector  5  may play the role of switches  61  to  63  of connector  6 . In selector  5 , an additional switch (not shown) is provided to interrupt the neutral connection and make it controllable from circuit  56 . This enables to suppress contactor  6 , which is then no longer necessary. 
         [0067]      FIG. 7  illustrates an alternative embodiment of a phase selector  5 ′ adapted to single-phase charging stations. For simplification, the control and ground terminals have not been illustrated in  FIG. 7 . Input terminal block  52 ′ is identical to input terminal block  52  of selector  5  of the previous drawings. However, on the side of output terminal block  54 ′, a single phase terminal  549  is provided and is intended to be connected to a single-phase socket (not shown). The forming of selector  5 ′ is simplified in that only three switches  551  to  553  are necessary. 
         [0068]      FIG. 8  schematically shows an installation according to a preferred embodiment where the general current consumption at the installation level is taken into account. According to this embodiment, instead of measuring the voltages of the phases at the level of selector  5 , information representative of the current drawn from each of the phases by system  3 , that is, by the entire installation, is measured. This operation is illustrated by ammeters  91 ,  92 , and  93  (A) having their measurements sent to an electronic processing circuit  32  (for example, a microcontroller μC) of system  3 . System  3  sends signals relative to the identification of the least loaded phase to respective microcontrollers  56  of the different selectors  5 . In this embodiment, when a selector intercepts a control signal originating from the socket to which it is associated, it transmits the corresponding information to circuit  32  of system  3  to trigger the measurement enabling to estimate the least loaded phase upstream of the installation. As a variation, circuit  32  permanently estimates (periodically) the least loaded phase and transmits the information to the selectors. In this case, each selector has the information when it receives a control signal for from socket and can then provide thereto the phases in the appropriate order. 
         [0069]    An advantage of this embodiment is that it enables to balance the power consumptions downstream of system  3  without taking into account a possible imbalance upstream of system  3 . 
         [0070]      FIG. 9  schematically shows an alternative embodiment according to which the measurement performed by selectors  5  to determine the phase to be connected to stations  2  is a current measurement (ammeter  24 ) performed at the level of sockets  4  on the power supply conductor of terminal B 1  of the concerned sockets. This enables to improve the phase balancing by taking into account the respective power consumptions of the different terminals. To achieve this, circuits  56  of the different selectors should communicate together (connection  58 ). Assuming that each terminal transmits, over a communication but  26  (different from or confounded with the bus conveying signal(s) C′), the result of the current measurement performed by its ammeter, it is possible to determine the least loaded phase by comparing the different measurements. Such an embodiment does not require an intervention at the level of system  3  but however requires having current measurements at the level of terminals  4 . Actually, this embodiment may take advantage of the existence of such current measurement devices present at the level of terminals  4  if the information relative to the performed measurement may be sampled without disturbing the operation. 
         [0071]    An advantage of the embodiments which have been described is that it is now possible to select a phase in a polyphase network, to power a load while taking part in the balancing of the phases of the network. 
         [0072]    Another advantage of the embodiments which have been described is that they are compatible with an automobile vehicle charging station power management system. 
         [0073]    Another advantage, more particularly present in the embodiments of  FIGS. 4 and 5 , is that no modification of existing charging systems is necessary. It is sufficient to interpose a selector  5  between socket  4  and polyphase electric power supply system  3 . In particular, although each socket  4  should preferably be equipped with a phase selector, it is already advantageous to only equip part of them. 
         [0074]    Another advantage of the embodiments which have been described is that they optimize the power sampling from the electric power supply network. 
         [0075]    It should be noted that unlike energized phase switching systems which should preserve an uninterrupted electric power supply, the described embodiments are intended to switch the phases before powering the load. 
         [0076]    Various embodiments have been described. Various alterations and modifications will occur to those skilled in the art. In particular, although the invention has been more specifically described in relation with three-phase network, it more generally applies to any polyphase network. Further, although the invention has been more specifically described in relation with an automobile vehicle charging installation, it more generally applies to a phase selector intended for any charge which may accept a slight delay (typically of a few milliseconds) for its putting into service, for the time necessary to identify the least loaded phase. Further, an installation may be equipped with one or a plurality of systems. Finally, although the above-described embodiments have been described in relation with a preferred example where one selector  5  per socket is provided, it remains possible to connect a plurality of sockets  4  in parallel to the output terminal block of a same selector. The practical implementation of the described embodiments is within the abilities of those skilled in the art based on the functional indications given hereabove by using circuits and tools usual per se.