Patent Publication Number: US-2021162875-A1

Title: A power transfer system for electric vehicles and a control method thereof

Description:
The present invention relates to the field of power transfer systems for electric vehicles. In particular, the present invention regards an inductive power transfer system capable of exchanging electric power between an electric power system and a battery on board an electric vehicle, in a wireless manner. 
     Wireless inductive power transfer systems for electric vehicles are well known in the state of the art. 
     Typically, these systems are used to charge the electric battery of an electric vehicle. 
     When used as a battery charging systems, wireless inductive power transfer systems employ a transmitter coil, which is placed on or embedded in a ground surface, to inductively transmit electric power to a receiver coil mounted on board an electric vehicle through the air gap between the road surface and the vehicle itself. 
     As in traditional transformers, an AC current flowing in the winding of the transmitter coil produces a magnetic flux making an induced AC current to flow in the winding of the receiver coil. In this way, electric power may be inductively transferred from the transmitter coil to the receiver coil. 
     When used as battery charging systems, wireless power transfer systems for electric vehicles typically include a transmitter-side section, which normally includes the transmitter coil and a power supply system connectable to the mains to feed the transmitter coil, and a receiver-side section, which normally includes, on board the electric vehicle, the receiver coil and a power conversion system to feed the battery with electric power inductively received by the receiver coil. 
     Both the transmitter-side section and the receiver-side section of the power transfer system include a number of controllers to control their operation. Controllers arranged at different sections can mutually communicate through a dedicated communication channel, which is typically a wireless communication channel, e.g. of the Wi-Fi type. 
     In order to ensure a suitable charging process of the battery on board the electric vehicle, electric power transferred to the battery has to be properly controlled according to a charging profile that is typically set-up depending on the characteristics and state-of-charge of the battery and on other additional aspects, such as the reduction of the energy consumption during a charging cycle, the reduction of the time required for the charging process, and the like. 
     In order to follow up said power transfer profile, electric power transmitted between the transmitter coil to the receiver coil needs to be properly controlled. 
     For this reason, controllers of a wireless power transfer system for electric vehicles typically implement a closed-loop control architecture configured to control the operation of the above-mentioned power supplying system as a function of the selected power transfer profile. 
     Control arrangements currently used in power transfer systems of the state of the art often show poor performances in terms of reliability, in particular when safety control functionalities, such the rapid shut-down of the power supplying system in case of faults (e.g. a fault in a component of the transmitter-side section), are requested. 
     The main aim of the present invention is to provide a wireless power transfer system for electric vehicles, which allows overcoming the above-described disadvantages. 
     Within this aim, another object of the present invention is to provide a wireless power transfer system ensuring a suitable transmission of electric power to the battery on board a vehicle, in accordance with a given power transfer profile. 
     Another object of the present invention is to provide a wireless power transfer system ensuring good performances in terms of reliability, even when safety control functionalities are requested for implementation. 
     Another object of the present invention is to provide a wireless power transfer system relatively easy and inexpensive to arrange and produce at industrial level. 
     The above aim and objects, together with other objects that will be more apparent from the subsequent description and from the accompanying drawings, are achieved by a power transfer system for electric vehicles according to the following claim  1  and the related dependent claims. 
     In general definition, the power transfer system, according to the invention, comprises:
         a transmitter-side power sub-system comprising a first rectifying stage electrically coupleable with said electric power system, a DC-bus stage electrically coupled with said first rectifying stage and adapted to provide a first DC power and an inverter stage electrically coupled with said DC-bus stage and adapted to receive said first DC power and provide a first AC power;   a transmitter-side coil sub-system electrically coupled with said inverter stage and adapted to receive said first AC power, said transmitter-side coil sub-system comprising a transmitter coil adapted to receive a first AC current;   one or more transmitter-side controllers adapted to control operation of said transmitter-side power sub-system and transmitter-side coil sub-system;   a receiver-side coil sub-system comprising a receiver coil inductively coupleable with said transmitter coil, said receiver-side coil sub-system being adapted to exchange an AC power with said transmitter-side coil sub-system;   a receiver-side power sub-system comprising a second rectifying stage electrically coupled with said receiver-side coil sub-system and adapted to a second AC power with said receiver-side coil sub-system, said second rectifying stage being electrically coupleable with said battery and adapted to provide a second DC power to said battery;   one or more receiver-side controllers adapted to control operation of said receiver-side coil sub-system and receiver-side power sub-system, said transmitter-side and receiver-side controllers being capable to mutually communicate through a wireless communication channel.       

     According to the invention, said transmitter-side and receiver-side controllers implement a control architecture adapted to control the second DC power received by said battery and adapted to provide fast responsive control functionalities of the first DC power provided by said DC-bus stage by controlling operation of at least one of said rectifying stage and said DC-bus stage. 
     According to an aspect of the invention, said control architecture is adapted to control the first DC power provided by said DC-bus stage. In particular, said control architecture is configured to receive and process a first signal indicative of desired values for said first DC power and a first detection signal indicative of measured values of said first DC power and provide a first control signal to control operation of at least one of said rectifying stage and said DC-bus stage. 
     According to an aspect of the invention, said control architecture is adapted to control the second DC power received by said battery. In particular, said control architecture is configured to receive and process a second signal indicative of desired values for said second DC power and a second detection signal indicative of measured values of said second DC power and provide said first signal. 
     According to an aspect of the invention, said control architecture is adapted to control a first AC current provided by said inverter stage. In particular, said control architecture is configured to receive and process a third signal indicative of desired values for said first AC current and a third detection signal indicative of measured values of said first AC current and calculate a second control signal. Said control architecture is further configured to process said first and second control signals to provide a third control signal to control operation of at least one of said rectifying stage and said first DC-bus stage. 
     In a further aspect, the present invention related to a control method for a power transfer system according to the following claim  11  and the related dependent claims. 
     Said power transfer system comprises:
         a transmitter-side power sub-system comprising a first rectifying stage electrically coupleable with said electric power system, a DC-bus stage electrically coupled with said first rectifying stage and adapted to provide a first DC power and an inverter stage electrically coupled with said DC-bus stage and adapted to receive said first DC power and provide a first AC power;   a transmitter-side coil sub-system electrically coupled with said inverter stage and adapted to receive said first AC power, said transmitter-side coil sub-system comprising a transmitter coil adapted to receive a first AC current;   one or more transmitter-side controllers adapted to control operation of said transmitter-side power sub-system and transmitter-side coil sub-system;   a receiver-side coil sub-system comprising a receiver coil inductively coupleable with said transmitter coil, said receiver-side coil sub-system being adapted to exchange an AC power with said transmitter-side coil sub-system;   a receiver-side power sub-system comprising a second rectifying stage electrically coupled with said receiver-side coil sub-system and adapted to exchange a second AC power with said receiver-side coil sub-system, said second rectifying stage being electrically coupleable with said battery and adapted to provide a second DC power to said battery;   one or more receiver-side controllers adapted to control operation of said receiver-side coil sub-system and receiver-side power sub-system, said transmitter-side and receiver-side controllers being capable to mutually communicate through a wireless communication channel.       

     The method, according to the invention, comprises controlling the second DC power received by said battery and providing fast responsive control functionalities of the first DC power provided by said DC-bus stage by controlling operation of at least one of said rectifying stage and said DC-bus stage. 
     Preferably, the method, according to the invention, comprises controlling the first DC power received by said DC-bus stage by receiving and processing a first signal indicative of desired values for said first DC power and a first detection signal indicative of measured values of said first DC power and by providing a first control signal to control operation of at least one of said rectifying stage and said DC-bus stage. 
     Preferably, the method, according to the invention, comprises controlling the second DC power received by said battery by receiving and processing a second signal indicative of desired values for said second DC power and a second detection signal indicative of measured values of said second DC power and providing said first signal. 
     Preferably, the method, according to the invention, comprises controlling a first AC current provided by said inverter stage by receiving and processing a third signal indicative of desired values for said first AC current and a third detection signal indicative of measured values of said first AC current, calculating a second control signal and processing said first and second control signals to provide a third control signal to control operation of at least one of said rectifying stage and said DC-bus stage. 
    
    
     
       Further characteristics and advantages of the present invention will be more apparent with reference to the description given below and to the accompanying figures, provided purely for explanatory and non-limiting purposes, wherein: 
         FIG. 1  schematically illustrates the power transfer system, according to the present invention; 
         FIGS. 2-5  schematically illustrate some control arrangements employed in the power transfer system, according to the present invention. 
     
    
    
     With reference to  FIG. 1 , the present invention refers to a power transfer system  1  for electric vehicles capable of exchanging electric power between an electric power system  100  (e.g. the mains) and a battery  200  on board an electric vehicle, in a wireless manner. 
     The power transfer system  1  is particularly adapted to be used as a battery charging system capable of transferring electric power harvested from an electric power system  100  to a battery  200  on board an electric vehicle and it will be described with specific reference to this application for the sake of simplicity. 
     However, the power transfer system  1  may be suitable to implement bidirectional power transfer functionalities and therefore it may be employed to transfer electric power from the battery  200  to the electric system  100 . 
     Referring to its application as battery charging system, the power transfer system  1  comprises a transmitter-side section and a receiver-side section, which respectively include a number of power sub-systems and components arranged off-board and on-board the electric vehicle. 
     At the transmitter-side section, the power transfer system  1  comprises a transmitter-side power sub-system  2  electrically coupleable with the electric power system  100 . 
     The transmitter-side power sub-system  2  comprises a first AC/DC rectifying stage  21  electrically coupleable with the electric power system  100  and adapted to receive AC electric power from the power system  100  and to provide DC electric power. 
     Preferably, the first rectifying stage  21  includes a filter and a switching converter (not shown) electrically coupled in cascade to provide a suitable filtering and rectification of the currents and voltages received from the electric power system  100 . 
     Preferably, the first rectifying stage  21  includes power switches controllable by means of a suitable control signal. 
     The transmitter-side power sub-system  2  further comprises a DC-bus stage  22  electrically coupled with the first rectifying stage  21  to be powered by this latter. 
     Conveniently, the DC-bus stage  22  is adapted to transmit DC electric power received from the first rectifying stage  21  and to provide a first DC power P 1   DC , more particularly a first DC current I 1   DC  and a first DC voltage V 1   DC . 
     In some embodiments of the invention, the bus-stage  22  may comprise a capacitive circuit (e.g. a so-called DC-link circuit) to suitably store and make available the electric energy received from the rectifying stage  21 . In this case, the amplitude of the first DC current I 1   DC  and of the first DC voltage V 1   DC  (and therefore the first DC power P 1   DC ) provided by the DC bus-stage  22  may be controlled by suitably tuning the duty-cycle of the power switches of the first rectifying stage  21 . 
     In alternative embodiments, the bus-stage  22  may include a DC-DC switching converter (e.g. a buck switching converter) that conveniently includes power switches controllable by means of a suitable control signal. 
     In this case, the amplitude of the first DC current I 1   DC  and of the first DC voltage V 1   DC  (and therefore the first DC power P 1   DC ) provided by the DC-bus stage  22  may be controlled by suitably tuning the duty-cycle of the power switches of the said DC-DC switching converter and, possibly, of the first rectifying stage  21 . 
     Preferably, the DC-bus stage  22  comprises a first sensing arrangement  220  adapted to detect the first DC current I 1   DC  and the first DC voltage V 1   DC  and provide detection signals indicative of the first DC power P 1   DC . 
     The transmitter-side power sub-system  2  further comprises a DC/AC inverter stage  23  electrically coupled with the first DC-bus stage  22 . 
     The inverter stage  23  is adapted to receive the first DC power P 1   DC , more particularly the first DC current I 1   DC  and the first DC voltage V 1   DC , provided by the DC-bus stage  22 , and to provide a first AC power P 1   AC , more particularly a first AC current I 1   AC  and a first AC voltage V 1   AC . 
     Preferably, the inverter stage  23  comprises a DC/AC switching converter including power switches controllable by means of a suitable control signal. 
     The frequency of the first AC current I 1   AC  and of the first AC voltage V 1   AC  provided by the inverter stage  23  may be controlled by suitably tuning the frequency of the power switches of such an electronic stage. 
     Preferably, the inverter stage  23  comprises a second sensing arrangement  230  adapted to detect the first AC current I 1   AC  and provide detection signals indicative of said current. 
     At the transmitter-side section, the power transfer system  1  comprises a transmitter-side coil sub-system  3  electrically coupled with the inverter stage  23  and adapted to receive a first AC power P 1   AC , more particularly a first AC current I 1   AC  and a first AC voltage V 1   AC , provided by the inverter stage  23 . 
     The transmitter-side coil sub-system  3  comprises a transmitter coil  31  adapted to receive the first AC current I 1   AC  provided by the inverter stage  23 . 
     Preferably, the transmitter-side coil sub-system  3  comprises also a first resonant capacitor  32  electrically coupled (e.g. in series as shown in  FIG. 1 ) with the transmitter coil  31 . 
     Preferably, the transmitter-side coil sub-system  3  comprises auxiliary circuits (not shown) operatively associated with the transmitter coil  31 , e.g. electronic circuits including temperature sensors, and the like. 
     At the transmitter-side section, the power transfer system  1  comprises one or more transmitter-side controllers (collectively indicated by the reference number  6 ) to control the operation of the transmitter-side power sub-system  2  and of the transmitter-side coil sub-system  3 . 
     As an example, the transmitter-side controllers  6  may include a controller to control the operation of the rectifying stage  21 , a controller to control the operation of the bus stage  22  (when including a DC-Dc switching converter), a controller to control the operation of the inverter stage  23  and a controller to control the operation of possible auxiliary circuits included in the transmitter-side coil sub-system  3 . 
     In a practical implementation of the invention, the transmitter-side power sub-system  2  may be arranged in a wall-box device for an electric vehicle charging facility, e.g. for residential purposes. Such a wall-box device may conveniently include the transmitter-side controllers  6  operatively associated with the electronic stages of the transmitter-side power sub-system  2 . 
     The transmitter-side coil sub-system  3  may instead be arranged or embedded in a ground pad device for an electric vehicle charging facility, e.g. for residential purposes. Such a ground pad device may conveniently include possible transmitter-side controllers  6  operatively associated to transmitter-side coil sub-system  3 . 
     At the receiver-side section, the power transfer system  1  comprises a receiver-side coil sub-system  4  comprising a receiver coil  41  inductively coupleable with the transmitter coil  31 . 
     When the transmitter coil  31  and the receiver coil  41  are inductively coupled (obviously with an air gap in therebetween), a first AC current I 1   AC  flowing along the transmitter coil  31  produces a magnetic flux making an induced second AC current I 2   AC  to flow along the receiver coil  41 . In this way, electric power may be inductively exchanged between the transmitter coil  31  and the receiver coil  41 . 
     The receiver-side coil sub-system  4  is thus adapted to exchange an AC power with transmitter-side coil sub-system  3  and provide a second AC current I 2   AC  and a second AC voltage V 2   AC . 
     Due to magnetic coupling losses, electric power is exchanged between the transmitter coil  31  and the receiver coil  41  with efficiency values η&lt;1. 
     A second AC power P 2   AC  at the receiver-side coil sub-system  4  may thus be lower than the first AC power P 1   AC  at the transmitter-side coil sub-system  3 . 
     Preferably, the receiver-side coil sub-system  4  comprises a second resonant capacitor  42  electrically coupled (e.g. in series as shown in  FIG. 1 ) with the receiver coil  41 . 
     Preferably, resonant capacitors  32 ,  42  are conveniently designed to form a resonant RLC circuit together with the inductance of transmitter coils  31 ,  41  and the equivalent impedance seen at the output terminals of the receiver-side coil sub-system  4 . 
     By operating the inverter stage  23  in such a way that the first AC current I 1   AC  flowing along the transmitter coil  31  has a fundamental frequency close or corresponding to the resonant frequency of such a resonant circuit, electric power may be exchanged between the transmitter-side coil sub-system  3  and the receiver-side coil sub-system  4  with high efficiency values despite of the necessarily large air gap between the transmitter coil  31  and the receiver coil  41 . Additionally, the amplitude of the first AC current I 1   AC  flowing along the transmitter coil  31  can be reduced or minimized due to nearly-zero phase shift between said current and the first AC voltage V 1   AC . 
     Preferably, the receiver-side coil sub-system  4  comprises auxiliary circuits (not shown) operatively associated with the receiver coil  41 , e.g. electronic circuits including temperature sensors, and the like. 
     At the receiver-side section, the power transfer system  1  comprises a receiver-side power sub-system  5  comprising a second rectifying stage  51  electrically coupled with the receiver-side coil sub-system  4  and adapted to exchange the second AC power P 2   AC  with the receiver-side coil sub-system  4 . 
     Preferably, the second rectifying stage  51  includes a full-wave diode bridge electrically coupled in cascade with a filter to provide a suitable rectification and filtering of the second AC current I 2   AC  and second AC voltage V 2   AC  received from the receiver-side coil sub-system  4 . 
     As an alternative embodiment, the second rectifying stage  51  may include a switching converter and a filter (not shown) electrically coupled in cascade to provide a suitable rectification and filtering of the currents and voltages received from the receiver-side coil sub-system  4 . In this case, the second rectifying stage  51  may include power switches controllable by means of a suitable control signal. 
     The second rectifying stage  51  is electrically coupleable with the battery  200  and is adapted to provide a second DC power P 2   DC  to said battery, more particularly a second DC current I 2   DC  and a second DC voltage V 2   DC . 
     Preferably, the second rectifying stage  51  comprises a suitable sensing arrangement  510  adapted to detect the second DC current I 2   DC  and the second DC voltage V 2   DC  and to provide detection signals indicative of second DC power P 2   DC  received by the battery  200 . 
     At the receiver-side section, the power transfer system  1  comprises one or more receiver-side controllers (collectively indicated by the reference number  7 ) to control operation of the receiver-side power sub-system  5  and of the receiver-side coil sub-system  4 . 
     As an example, receiver-side controllers  7  may include a controller to control the operation of the rectifying stage  51  and a controller to control the operation of the auxiliary circuits included in the receiver-side coil sub-system  4 . 
     According to the invention, the power transfer system  1  comprises at least a wireless communication channel  8 , through which the transmitter-side and receiver-side controllers  6 ,  7  are capable to mutually communicate. As an example, a communication protocol may be adopted for the communication channel  8 . 
     In a practical implementation of the invention, the receiver-side coil sub-system  4 , the receiver-side power sub-system  5  and the receiver-side controllers  7  are arranged (together with the battery  200 ) on board an electric vehicle. 
     According to the invention, the transmitter-side and receiver-side controllers  6 ,  7  implement a control architecture  10  including control arrangements capable of suitably controlling the transmission of electric power to the battery  200  and, at the same time, providing fast responsive control functionalities, particularly suitable for the implementation of safety functionalities, such as rapid shut-down functionalities and the like. 
     More particularly, the control architecture  10  is adapted to control the second DC power P 2   DC  received by the battery  200  and to provide fast responsive control functionalities of the first DC power P 1   DC  provided by the DC-bus stage  22  by controlling the operation of at least one of the rectifying stage  21  and the DC-bus stage  22 . 
     In a preferred embodiment, the control architecture  10  comprises a first control arrangement  11  adapted to control the first DC power P 1   DC  provided by the DC-bus stage  22 . 
     The first control arrangement  11  is configured to receive and process a first signal P 1   REF  indicative of desired values for the first DC power P 1   DC  and a first detection signal P 1   DCM  indicative of measured values of the first DC power P 1   DC . 
     Preferably, the first signal P 1   REF  is a reference signal indicative of reference values for the first DC power P 1   DC . As an alternative, the first signal P 1   REF  may be a signal indicating to increase or decrease the first DC power P 1   DC  provided by the DC-bus stage  22 . 
     Conveniently, the first detection signal P 1   DCM  is provided by the sensing arrangement  220  included in the DC-bus stage  22  whereas, as it will better emerge from the following, the first signal P 1   REF  is provided by another control arrangement  12  of the control architecture  10 . 
     The first control arrangement  11  is configured to provide a first control signal C 1  to control the operation of at least one between the rectifying stage  21  and the DC-bus stage  22 . 
     More particularly, when the DC-bus stage  22  does not include a DC-DC switching converter, the first control arrangement  11  is configured to provide a first control signal C 1  to control the operation of the rectifying stage  21  whereas, when the DC-bus stage  22  includes a DC-DC switching converter, the first control arrangement  11  is configured to provide a first control signal C 1  to control the operation of one between the rectifying stage  21  and the DC-bus stage  22  or of both these electronic stages. 
     Conveniently, the first control signal C 1  is adapted to control the duty-cycle of the power switches included in at least one of the rectifying stage  21  and the DC-bus stage  22 . 
     Preferably, the control arrangement  11  is configured to form a first closed-loop control arrangement capable of controlling the first DC power P 1   DC  provided by the DC-bus stage  22  by suitably controlling the amplitude of the voltages and currents provided by at least one of the rectifying stage  21  and the DC-bus stage  22 . 
     According to an embodiment of the invention, the first control arrangement  11  comprises a first control module  111  and a second control module  112  logically arranged in cascade. 
     The first control module  111  is configured to receive and process the first signal P 1   REF  and the first detection signal P 1   DCM  and to provide a first error signal P 1   E , which may be indicative of a difference between the first signal P 1   REF  and the first detection signal P 1   DCM . 
     The second control module  112  is configured to receive and process the first error signal P 1   E  and provide the first control signal C 1 . 
     According to an important aspect of the invention, the first control arrangement  11  is implemented at level of the transmitter-side controllers  6 . 
     In this case, the first control arrangement  11  may include control modules suitably implemented by executable sets of software instructions stored by the transmitter-side receivers  6 . 
     The first control arrangement  11  is thus capable of providing fast control functionalities of the first DC power P 1   DC  provided by the DC-bus stage  22 , which are fully compatible with the implementation of safety functionalities, such as the rapid-shut down of the rectifying stage  21  and/or the DC-bus stage  22 . 
     According to the above-mentioned preferred embodiment, the control architecture  10  comprises a second control arrangement  12  adapted to control the second DC power P 2   DC  received by the battery  200 . 
     The second control arrangement  12  is configured to receive and process a second signal P 2   REF  indicative of desired values for the second DC power P 2   DC  and a second detection signal P 2   DCM  indicative of measured values of the second DC power P 2   DC . 
     Preferably, the second signal P 2   REF  is a reference signal indicative of reference values for the first DC power P 1   DC . As an alternative, the second signal P 2   REF  may be a signal indicating to increase or decrease the first DC power P 1   DC  provided by the DC-bus stage  22 . 
     Conveniently, the second detection signal P 2   DCM  is provided by the sensing arrangement  510  included in the second rectifying stage  51  whereas the second signal P 2   REF  is provided by the second one or more controllers  7  in accordance with a power transfer profile selected for the battery  200 . 
     Preferably, the second control arrangement  12  is configured to provide the first signal P 1   REF  for the first control arrangement  11 . In this way, the second control arrangement  12  operates concurrently with the first control arrangement  11  to control the second DC power P 2   DC  received by the battery  200  and it provides the first signal P 1   REF  to be processed by the first control arrangement  11  to control the amplitude of the voltages and currents provided by at least one of the rectifying stage  21  and the DC-bus stage  22 . 
     In the implementation of the second control arrangement  12 , certain signals, such as the second signal P 2   REF  and the second detection signal P 2   DCM  or the first signal P 1   REF , are transmitted by the receiver-side controllers  7  to the transmitter-side controllers  6  through the wireless communication channel  8  to provide the first signal P 1   REF . 
     The second control arrangement  12  is thus capable of responding to a variation of the second DC power P 2   DC  received by the battery  200  with relatively long response times (in the order of tens of ms), which are anyway fully compatible with the implementation of power control functionalities for the battery  200 . 
     Preferably, the second control arrangement  12  is configured to form a second closed-loop control arrangement to control the second DC power P 2   DC  received by the battery  200  by suitably controlling the amplitude of the voltages and currents provided by at least one of the rectifying stage  21  and the DC-bus stage  22 . 
     According to an embodiment of the invention, the second control arrangement  12  comprises a third control module  121  and a fourth control module  122  logically arranged in cascade. 
     The third control module  121  is configured to receive and process the second signal P 2   REF  and the second detection signal P 2   DCM  and provide a second error signal P 2   E , which may be indicative of a difference between the second signal P 2   REF  and the second detection signal P 2   DCM . 
     The fourth processing module  122  is configured to receive and process the second error signal P 2   E  and provide the first signal P 1   REF . 
     According to an alternative embodiment of the invention ( FIG. 2 ), the second control arrangement  12  is implemented at level of the receiver-side controllers  7 . In this case, the second control arrangement  12  may include control modules conveniently implemented by executable sets of software instructions stored by the receiver-side controllers  7 . Additionally, the transmitter-side controllers  6  are adapted to receive the first signal P 1   REF  from the one or more receiver-side controllers  7  through the wireless communication channel  8 . 
     According to an embodiment of the invention ( FIG. 3 ), the second control arrangement  12  is implemented at level of the transmitter-side controllers  6 . In this case, the second control arrangement  12  may include control modules conveniently implemented by executable sets of software instructions stored by the transmitter-side controllers  6 . Additionally, the transmitter-side controllers  6  are adapted to receive the second signal P 2   REF  and the second detection signal P 2   DCM  from the one or more receiver-side controllers  7  through the wireless communication channel  8 . 
     According to some embodiments of the invention ( FIGS. 4-5 ), the control architecture  10  comprises a third control arrangement  13  to control the first AC current I 1   AC  provided by the inverter stage  23 . 
     The third control arrangement  13  is configured to receive and process a third signal I 1   REF  indicative of desired values (e.g. threshold values) for the first AC current I 1   AC  and a third detection signal I 1   ACM  indicative of measured values of the first AC current I 1   AC . 
     The third control arrangement  13  is configured to calculate a second control signal C 2  by suitably processing the third signal I 1   REF  and the third detection signal I 1   ACM    
     Additionally, the third control arrangement  13  is configured to process the first control signal C 1  provided by the first control arrangement  11  and the calculated second control signal C 2  to provide a third control signal C 3  to control the operation of the rectifying stage  23  or the first DC-bus stage  22 . 
     As it is evident from the above, the third control arrangement  13  forms a third closed-loop control arrangement capable of controlling the first AC current I 1   AC  provided by the inverter stage  23  by suitably controlling the amplitude of the voltages and currents provided by at least one of the rectifying stage  21  and the DC-bus stage  22 . 
     Preferably, the third control arrangement  13  intervenes if the first AC current I 1   AC  provided by the inverter stage  23  exceeds the values provided by the current reference signal I 1   RF . In this case, the third control arrangement  13  provides the second control signal C 3  that is conveniently obtained by correcting the control signal C 1  provided by the first control arrangement  11 . 
     Preferably, the third control arrangement  13  does not intervene to correct the control signal C 1 , if the first AC current I 1   AC  provided by the inverter stage  23  does not exceed the values provided by the current reference signal I 1   RF . In this case, the third control arrangement  13  provides a third control signal C 3  that basically coincides with the control signal C 1  provided by the first control arrangement  11 . 
     According to an embodiment of the invention, the third control arrangement  13  comprises a fifth control module  131 , a sixth control module  132  and a seventh control module  133  logically arranged in cascade. 
     The fifth control module  131  is configured to receive and process the third signal I 1   REF  and the third detection signal I 1   ACM  and provide a third error signal I 1   E  indicative of a difference between the second signal P 2   REF  and the second detection signal P 2   DCM . 
     The sixth control module  132  is configured to receive and process the third error signal I 1   E  and provide the second control signal C 2 . 
     The seventh processing module  133  is configured to receive and process the first control signal C 1  and the second control signal C 2  and provide the third control signal C 3 . 
     According to an embodiment of the invention, the third control arrangement  13  is implemented at level of the transmitter-side controllers  6 . In this case, the third control arrangement  13  may include control modules conveniently implemented by executable sets of software instructions stored by the transmitter-side controllers  6 . 
     In a further aspect, the present invention relates to a control method for controlling the operation of a power transfer system  1  as described above. 
     The method, according to the invention, comprises controlling the second DC power P 2   DC  received by the battery  200  and providing fast responsive control functionalities of the first DC power P 1   DC  provided by the DC-bus stage  22  by controlling the operation of at least one of the rectifying stage  21  and the DC-bus stage  22 . 
     According to a preferred embodiment, the method, according to the invention, comprises the following steps:
         controlling the first DC power P 1   DC  received by the DC-bus stage  22  by receiving and processing a first signal P 1   REF  indicative of desired values for the first DC power P 1   DC  and a first detection signal P 1   DCM  indicative of measured values of said first DC power P 1   DC  and by providing a first control signal C 1  to control the operation of at least one of the rectifying stage  21  and the DC-bus stage  22 ;   controlling the second DC power P 2   DC  received by the battery  200  by receiving and processing a second signal P 2   REF  indicative of desired values for the second DC power P 2   DC  and a second detection signal P 2   DCM  indicative of measured values of the second DC power P 2   DC  and by providing the first signal P 1   REF .       

     Preferably, the step of controlling the first DC power P 1   DC  provided by the DC-bus stage  22  comprises:
         receiving and processing the first signal P 1   REF  and the first detection signal P 1   DCM  and providing a first error signal P 1   E .   receiving and processing the first error signal H E  and providing the first control signal C 1 .       

     Preferably, the step of controlling the second DC power P 2   DC  received by the battery  200  comprises:
         receiving and processing the second signal P 2   REF  and the second detection signal P 2   DCM  and providing a second error signal P 2   E  indicative of a difference between the second signal P 2   REF  and the second detection signal P 2   DCM ;   receiving and processing the second error signal P 2   E  and providing the first signal P 1   REF .       

     Preferably, the method, according to the invention, comprises the step of controlling the first AC current I 1   AC  provided by the inverter stage  23  by receiving and processing a third signal I 1   REF  indicative of desired values for the first AC current I 1   AC  and a third detection signal I 1   ACM  indicative of measured values of the first AC current I 1   AC , by calculating a second control signal C 2  and by processing the first and second control signals C 1 , C 2  to provide a third control signal C 3  to control the operation of at least one of the rectifying stage  21  and the DC-bus stage  22 . 
     Preferably, the step of controlling the first AC current I 1   AC  provided by the inverter stage  23  comprises:
         receiving and processing the third signal I 1   REF  and the third detection signal I 1   ACM  and providing a third error signal I 3   E , which may be indicative of a difference between the third signal I 1   REF  and the third detection signal I 1   ACM ;   receiving and processing the third error signal I 1   E  and providing the second control signal C 2 ;   receiving and processing the first and second control signals C 1 , C 2  to provide the third control signal C 3 .       

     The power transfer system, according to the invention, allows achieving the intended aims and objects. 
     The power transfer system, according to the invention, includes a control architecture ensuring a suitable transmission of electric power to the battery on board a vehicle, in accordance with a given power transfer profile, and, at the same time, ensuring fast control functionalities particularly adapted to implement safety control functionalities. 
     In a preferred embodiment, the power transfer system, according to the invention, allows suitable controlling the current flowing in the transmitter coil, thereby ensuring that safety current values are not exceeded. 
     Thanks to its innovative control architecture, the power transfer system, according to the invention, ensures good performances in terms of reliability, even when safety control functionalities are requested to be implemented. 
     The power transfer system, according to the invention, can be easily arranged and produced at industrial level, at competitive costs with respect to similar systems of the state of the art.