Abstract:
A solar energy based mobile EV fast charger (SE-MEVFC) system comprising a mobile EV fast charger system installed in the service track for providing EV charging service and a stationary solar energy generation system located in the charging station as power source for recharging mobile on-board storage battery, offers EV charging servicers for EVs where they stranded on the road or in remote area. The SE-MEVFC system has following unique features: (1) since it has universal battery interface, it can charge any EV battery; (2) since its energy source comes from solar energy based EV charging station, it provides 100% pollution free EV charging service; (3) since it is high power battery charger system, EV battery can be fully charged in minutes rather than hours, unlike those of prior art that use gasoline based generators to generate AC power and relies on low power EV on-board charger (OBC) to charge EV battery, namely, for over 2 hours charging time getting about 10 miles driving range. Therefore, a solar energy based mobile EV fast charger (SE-MEVFC) system can ease drivers&#39; anxiety for not being able to find charging station effectively, and at same times it makes EV operation completely pollution free and hence increases MPGe of EVs.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application 62/350,982 and hereby incorporates the application by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to non-stationary high power EV fast charger operating with a storage battery system that is replenished by solar energy, capable of providing EV fast charging services to EVs where they are stranded, such as but not limited to solar energy based mobile Electric Vehicle (EV) fast charger system. 
       BACKGROUND 
       [0003]    At the starting of the 21st century, the awareness for electric and other alternative fuel vehicles has increased due to growing concern over the problems that associate with hydrocarbon-fueled vehicles harming to the environment caused by their emissions and the sustainability of the current hydrocarbon-based transportation infrastructure. However the shortcoming of electrical vehicles (EV) is the limitation of driving range on their fully charged batteries and charging time. The range is usually between 60 to 300 miles per charge and charging time is between 8 hours to 10 hours or more, resulting in that EVs can be stranded on the road if their batteries are depleted or there is no EV charging station nearby. Therefore, high power mobile EV fast charger system is much needed to ease those emergency situations. 
         [0004]    The techniques disclosed in Pat. Application WO 2012178010 A1, U.S. Pat. No. 6,979,913 B2 and U.S. Pat. No. 7,057,303 B2 represent the prior art of mobile EV chargers. However these prior art systems use regular fossil fuel power generator as power source. They suffer two major drawbacks: (1) since they use gasoline powered generator to produce AC power, they emit CO 2  harming the environment and causing significant reduction of Mile Per Gallon Equivalent (MPGe) of EV, which severely cut the benefit of EV itself and even defeat the purpose of using EV; (2) they merely produce AC power and relie on EV on board charger (OBC) to charge EV battery which would take hours due to its small charger. Therefore, it is ideal to provide solar energy based high power mobile EV fast charger to eliminate pollution, increase the MPGe of EV and decrease charging time effectively. 
         [0005]    The object of this invention is to provide a pollution free, high efficient and high power solar energy based mobile EV fast charger (SE-MEVFC) system that offers EV fast charging service in minutes rather than hours to EVs where they are stranded on the road or in remote area. 
       SUMMARY 
       [0006]    One non-limiting aspect of the present invention contemplates a high power solar energy based mobile EV fast charger (SE-MEVFC) comprising three sections: 1. A high power mobile EV fast charger with a multi-function power conversion system (MFPCS), an universal battery interface system, an on-board battery system, an alternator power interface, and an alternator power source all mounted on a service truck; 2. a stationary solar power system with a solar power source, an AC power source, a MFPCS, LCL filter plus an isolation transformer, and multiple DC inductors interfaced with on-board battery system in mobile EV fast charger; 3. numerous system operation modes: EV fast charger with on-board battery mode (Mode 1), EV battery charger with truck alternator mode (Mode 2), on-board battery charger with truck alternator mode (Mode 3), on-board battery charger with solar power generation mode (Mode 4), an interleaved multi-phase on-board battery charger mode (Mode 5), on-board battery charger with AC grid power mode (Mode 6). 
         [0007]    One non-limiting aspect of the present invention contemplates a MFPCS to provide DC/DC, DC/AC, AC/DC power conversion hardware functions comprising a three phase IGBT module mounted on a liquid cooled heatsink, connected to a DC-link capacitor, and controlled by a IGBT gate drive circuit card, a DSP interface circuit card, a Texas Instrument (TI) DSP control Card; a DC current sensor, three primary current sensors. 
         [0008]    One non-limiting aspect of the present invention contemplates TI DSP control card to provide power conversion and battery charger software functions comprising Mode 1 control library comprising isolated EV fast charger control algorithms, Mode 2 control library comprising isolated EV fast charger control and DC/DC boost converter control algorithms, Mode 3 control library comprising DC/DC boost EV fast charger control algorithms, Mode 4 control library comprising three phase grid-tied inverter control plus direct on-board battery charger control algorithms, Mode 5 control library comprising interleaved multi-phase battery charger control algorithms, Mode 6 control library comprising PWM rectifier battery charger control algorithms. 
         [0009]    One non-limiting aspect of the present invention contemplates high frequency (HF) isolated EV fast charger control algorithms to charge EV battery with on-board battery system comprising EV battery data base of voltage, current, temperature, state of charge (SOC), age, chemistry, charging requirements for all EV battery system, battery voltage and current control means, DC current control means, full bridge PWM means. 
         [0010]    One non-limiting aspect of the present invention contemplates DC/DC boost converter control algorithms to regulate the DC-link voltage of mobile EV battery charger with truck alternator power comprising a DC voltage control means, a boost current control means, a boost PWM means. 
         [0011]    One non-limiting aspect of the present invention contemplates DC/DC boost EV fast charger control algorithms to charge on-board battery with truck alternator power comprising battery voltage and current control means, a boost current control means, a boost PWM means. 
         [0012]    One non-limiting aspect of the present invention contemplates three phase grid-tied inverter control plus direct on-board battery charger control algorithms to produce AC grid power and charge on-board battery with solar power directly at station when solar power is greater than battery voltage (V MP &gt;V B ) comprising maximum power point tracking (MPPT) means, DC voltage control means, battery charging power calculation means, AC current reference generation means, AC current control means, and Space Vector Modulation (SVM) means. 
         [0013]    One non-limiting aspect of the present invention contemplates interleaved multiphase battery charger control algorithms to charge on-board battery with solar energy at station when solar power is less than battery voltage (V MP &lt;V B ) comprising an optimal solar energy tracking means, an battery voltage control means, a multiphase DC current control means, and interleaved multi-phase PWM means. 
         [0014]    One non-limiting aspect of the present invention contemplates PWM rectifier battery charger control algorithms to convert AC grid power to DC charging on-board battery at station comprising battery voltage and current control means, AC current generation means, AC current control means and SVM means. 
         [0015]    One non-limiting aspect of the present invention contemplates a mobile EV fast charger with on-board battery mode (Mode 1) comprising a configuration of HF isolated EV battery charger (when MFPCS connecting to on-board battery and universal battery interface which connecting to EV battery) and Mode 1 control library. 
         [0016]    One non-limiting aspect of the present invention contemplates a mobile EV battery charger with truck alternator mode (Mode 2) comprising a configuration of a single phase boost converter (when one phase leg of MFPCS connecting to alternator power through a boost inductor), a HF isolated EV fast battery charger (when the other two phase legs of MFPCS connecting to universal battery interface which further connecting to EV battery) and Mode 2 control library. 
         [0017]    One non-limiting aspect of the present invention contemplates an on-board battery charger with truck alternator mode (Mode 3) comprising a single phase boost battery charger configuration (when one phase leg of MFPCS connecting to alternator power through a boost inductor and to on-board battery) and Mode 3 control library. 
         [0018]    One non-limiting aspect of the present invention contemplates an on-board battery charger with solar power generation mode (Mode 4) comprising a three phase grid tied inverter and direct on-board battery charger configuration (when solar power voltage is greater than battery voltage (V MP &gt;V B ) and with MFPCS connecting to stationary solar panels and on-board battery and to stationary LCL filter and isolation transformer which further connecting to AC grid power) and Mode 4 control library. 
         [0019]    One non-limiting aspect of the present invention contemplates an interleaved multi-phase battery charger mode (Mode 5) comprising a three phase interleaved battery charger configuration (when solar power voltage is less than battery voltage (V MP &lt;V B ) and with MFPCS connecting to solar energy source through intermedium of multiple DC inductors and to on-board battery) and Mode 5 control library. 
         [0020]    One non-limiting aspect of the present invention contemplates an on-board battery charger with AC grid power mode (Mode 6) comprising a PWM rectifier battery charger configuration (when MFPCS connecting to on-board battery and to LCL filter plus an isolation transformer which connecting to AC grid power source) and Mode 6 control library. 
         [0021]    One non-limiting aspect of the present invention contemplates a universal battery interface system operable to charge any type of EV batteries comprising re-configurable high frequency (HF) transformer means, transformer re-configuration switch means, diode rectifier means, and output L-C filter means. 
         [0022]    One non-limiting aspect of the present invention contemplates re-configuration HF transformers to provide galvanic isolation and universal battery voltage arrangement comprising one primary winding and two secondary windings with a turns ratio of n; primary winding connected in parallel while secondary windings placed in combination of series and/or parallel connections resulting in rescaling turns ratio to matching any EV voltage range. 
         [0023]    One non-limiting aspect of the present invention contemplates transformer re-configuration switch means comprising transformer re-configuration control table which determines the relationship between effective transformer turns ratio and EV battery voltage ranges. 
         [0024]    One non-limiting aspect of the present invention contemplates a mobile EV fast charger comprising an user interface allowing user to select EV model from EV battery data base or a communication interface allowing direct communication between mobile EV fast charger and EV when EV is in charging service, so as to setting right hardware configuration and launching corresponding battery charger control algorithms before battery charging process begins. 
         [0025]    One non-limiting aspect of the present invention contemplates a solar energy based mobile EV fast charger (SE-MEVFC) system capable of charging EV battery in minutes and quickly re-loading solar energy to its on-board storage battery through a stationary solar energy system and its unique system configuration comprising: SE-MEVFC operating as EV fast charger with on-board battery in mode  1 ; SE-MEVFC operating as EV battery charger with truck alternator in mode  2 ; SE-MEVFC operating as on-board battery charger with truck alternator in mode  3 ; SE-MEVFC operating as on-board battery charger with solar power generation in mode  4 ; SE-MEVFC operating as interleaved multi-phase battery charger in mode  5 ; and SE-MEVFC operating as on-board battery charger with AC grid power in mode  6 . 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]    The present invention is pointed out with particularity in the appended claims. However, other features of the present invention will become more apparent and the present invention will be best understood by referencing to the following detailed description in conjunction with the accompany drawings in which: 
           [0027]      FIG. 1  illustrates the functional block diagram of a solar energy based high power mobile EV fast charger system as contemplated by one non-limiting aspect of the present invention. 
           [0028]      FIG. 2  schematically illustrates a MFPCS as contemplated by one non-limiting aspect of the present invention. 
           [0029]      FIG. 3  schematically illustrates a universal battery interface system as contemplated by one non-limiting aspect of the present invention. 
           [0030]      FIG. 4  illustrates a transformer re-configuration switches control table as contemplated by one non-limiting aspect of the present invention. 
           [0031]      FIG. 5  schematically illustrates a mobile EV fast charger system having a MFPCS, a mobile on-board battery system, an universal battery interface system, a truck alternator power source and an alternator power interface, as contemplated by one non-limiting aspect of the present invention. 
           [0032]      FIG. 6  schematically illustrates a mobile EV fast charger system operated as an on-board battery charger either by solar energy or AC grid power as contemplated by one non-limiting aspect of the present invention. 
           [0033]      FIG. 7 a    illustrates the functional block diagram of universal EV fast charger control algorithms with a user interface function as contemplated by one non-limiting aspect of the present invention. 
           [0034]      FIG. 7 b    illustrates the functional block diagram of universal EV fast charger control algorithms with a direct communication function as contemplated by one non-limiting aspect of the present invention. 
           [0035]      FIG. 8  illustrates the functional block diagram of PWM rectifier battery charger control algorithms for recharging mobile on-board battery system as contemplated by one non-limiting aspect of the present invention. 
           [0036]      FIG. 9  illustrates the functional block diagram of a DC/DC boost converter control as contemplated by one non-limiting aspect of the present invention. 
           [0037]      FIG. 10  illustrates the functional block diagram of a DC/DC boost converter battery charger control algorithms as contemplated by one non-limiting aspect of the present invention. 
           [0038]      FIG. 11  illustrates the functional block diagram of three phase grid tied inverter plus on-board battery charger control algorithms as contemplated by one non-limiting aspect of the present invention. 
           [0039]      FIG. 12  illustrates the interleaved multi-phase on-board battery charger control algorithms as contemplated by one non-limiting aspect of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0040]    As required, detailed embodiments of the present invention are disclosed herein; However, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. 
         [0041]      FIG. 1  illustrates a solar energy based high power mobile EV fast charger system  10  comprising a mobile EV fast charger  12  and a stationary solar power system  24 . The mobile EV fast charger  12  comprising a MFPCS  14 , a mobile on-board battery system  16 , a universal battery interface system  18 , a truck alternator power source  20 , an alternator power interface system  22 , three DC inductors, may charge a EV battery system  30  on the road using on-board batteries  16  or truck alternator power source  20 , or charge on-board battery  16 . The stationary solar power system  24  comprising a MFPCS  186 , LCL filters plus isolation transformer  26 , an AC power grid  28 , solar energy  154 , and mobile on-board battery recharging interfaces  188 ,  190 , may re-charge the on-board battery  16  with either solar energy  154  or AC grid power  28  if needed or otherwise convert solar energy to AC grid power for supplying building loads. The mobile on-board batteries  16  may also be recharged by truck alternator power  20  when truck is moving. 
         [0042]      FIG. 2  schematically illustrates a MFPCS  14  having a IGBT module  32  mounted on a liquid cooled heatsink  34  and connected to a DC capacitor  36  as contemplated by one non-limiting aspect of the present invention. The MFPCS  14  is shown for exemplary and non-limiting purpose being as a power converter to facilitate DC/DC or AC/DC power converting functions utilized in either a EV fast charger with on-board battery mode (Mode 1), or a EV battery charger with truck alternator mode (Mode 2), or an on-board battery charger with truck alternator mode (Mode 3), or an on-board battery charger with solar power generation mode (Mode 4), or a interleaved multi-phase on-board battery charger with solar power mode (Mode 5), or an on-board battery charger with AC grid power mode (Mode 6). 
         [0043]    A primary current sensing system  38  and a DC current sensing  40  may be included to facilitate sensing currents provided to primary winding of HF transformer in universal EV fast charger  12  or to LCL filter plus isolation transformer  26  in a three-phase single stage battery charger  24  and to DC input. The DSP interface card  44  may condition and filter feedback from current sensor  38 ,  40  and other sensing devices within the system, and provide the feedback signals to TI control card  46  for further processes. The TI control card  46  with Mode 1 control library  48 , Mode 2 control library  50 , Mode 3 control library  52 , Mode 4 control library  54 , Mode 5 control library  178 , and Mode 6 control library  192  may cooperate with DSP interface card  44  and IGBT gate drive  42  to control IGBT module  32  such that the opening and closing switches  56 ,  58 ,  60 ,  62 ,  64 ,  66  can be coordinated to produce the desired voltage/current waveform patterns for DC/DC, DC/AC and AC/DC power conversions. 
         [0044]    Universal battery interface system  18  illustrated in  FIG. 3  comprising two identical HF transformers  70  with each transformer having one primary winding and two separated secondary windings, a set of On-Off transformer reconfiguration switches  72  connecting those secondary windings to output circuits, a diode rectifier circuit  74  converting an AC voltage pulse trains to DC ones, a output L-C filter  76  eliminating HF switching harmonic components, may be reconfigured automatically such that it interfaces with EV batteries with any voltage range. 
         [0045]    The output voltage amplitude of a MFPCS based universal EV fast charger  12  (In  FIG. 1 ) is determined by transformer turns ratio n, the connection of primary windings, the connection of secondary windings, and the PWM control of the power converter. Two HF transformers with turns ratio n are configured in such way that primary windings are connected in parallel while the secondary windings are operated in combination of series and/or parallel connections with the opening and closing of switches  78 ,  80 ,  82 ,  84 ,  86 ,  88 ,  90 ,  92 ,  94  under DSP control to achieve a voltage level matching that of EV battery system  30  (In  FIG. 1 ). 
         [0046]      FIG. 4  illustrates a transformer re-configuration control table  96  used by a controller to match the EV fast charger voltage range with any EV batteries when on-board battery voltage range is 300v-420v and transformer turns ratio is 1.5. For example, when CT 1 =0, CT 2 =1, CT 3 =1, CT 4 =0, CT 5 =1, CT 6 =1, CT 7 =0, CT 8 =1, CT 9 =1, the mobile EV fast charger operates in battery voltage range of 150v-210v; when CT 1 =1, CT 2 =0, CT 3 =0, CT 4 =0, CT 5 =1, CT 6 =1, CT 7 =1, CT 8 =0, CT 9 =0, the mobile EV fast charger operates in battery voltage range of 300v-420v; when CT 1 =1, CT 2 =0, CT 3 =0, CT 4 =1, CT 5 =0, CT 6 =0, CT 7 =1, CT 8 =0, CT 9 =0, the mobile EV super charger operates in battery voltage range of 600v-840v. 
         [0047]      FIG. 5  schematically illustrates an exemplary mobile EV fast charger  12  operated in either Mode 1 or Mode 2 configurations to charge EV battery system  30  having a 600-800V voltage range, or Mode 3 configuration to charge mobile on-board battery  16  with truck alternator power. In Mode 1 operation MFPCS  14  with its DC-link capacitor connected to mobile on-board battery system  16 , and with two phase legs connected to universal battery interface system  18  with transformer re-configurable switches operated as CT 1 =1, CT 2 =0, CT 3 =0, CT 4 =1, CT 5 =0, CT 6 =0, CT 7 =1, CT 8 =0, CT 9 =0, is operated as a HF transformer isolated Full-Bridge (FB) DC/DC converter to charge EV battery system  30  with on-board battery system  16 . In Mode 2 operation MFPCS  14  with one phase leg connected to a alternator network comprising truck alternator power  20  and alternator power interface  22 , and with two other phase legs connected to universal battery interface system  18 , is operated as a HF transformer isolated Full-Bridge (FB) DC/DC converter to charge EV battery system  30  with truck alternator power  20  if on-board battery  16  is depleted. In Mode 3 operation MFPCS  14  with its DC-link capacitor connected to mobile on-board battery system  16 , and with one phase leg connected to a alternator network comprising truck alternator power  20  and alternator power interface  22 , is operated as a single phase boost battery charger to charge on-board battery system  16  when truck is moving. 
         [0048]      FIG. 6  schematically illustrates an mobile EV fast charger  10  operated in either Mode 4 or Mode 5 or Mode 6 configurations to re-charge mobile on-board battery system  16  at charging station. In Mode 4 operation where solar power voltage is greater than battery voltage (V MP &gt;V B ) MFPCS  14  with its DC-link capacitor connected to mobile on-board battery  16  and stationary solar energy  154 , and with three phase legs connected to stationary LCL filters plus isolation transformer  26  which connecting to AC power grid  28 , is operated as three phase grid tied inverter and direct on-board battery charger to produce AC grid power  28  and charge on-board battery  16  with solar energy  154  directly. In Mode 5 operation where solar power voltage is less than battery voltage (V MP &lt;V B ) MFPCS connected to solar energy  154  through multiple DC inductors  210  and to on-board battery  16 , is operated as three-phase interleaved battery charger to charge on-board battery  16  using solar energy  154 . In Mode 6 operation where solar energy  154  is not present MFPCS  14  is operated as a PWM rectifier battery charger to charge on-board battery  16  with AC grid power  28 . 
         [0049]      FIGS. 7 a , 7 b    illustrate universal EV fast charger with user interface control algorithms  98  and universal EV fast charger with communication interface control algorithms  118 . In both control algorithms  98  and  118 , they incorporate a EV battery data base  100  providing battery voltage reference and battery current reference to battery voltage control  102  and battery current control  104  based on the battery information including but not limited to EV manufacturer and model number, chemistry, voltage and current ranges, Stage of Charge (SOC), temperatures and charging requirements. While the battery voltage is regulated by battery voltage control  102  in constant voltage mode, the battery current is regulated by battery current control  104  in constant current mode. Using the output of either voltage control  102  or current control  104 , a DC current control  106  regulates DC current by commanding full-bridge PWM  108  to generate PWM signals controlling IGBT  110  to produce AC voltage pulse trains for universal battery interface  112  which provides optimal charging voltage and current for an EV battery system  30 . 
         [0050]    In control algorithms  98 , an user interface  114  may be included allowing the operator of a mobile EV super charger to select the EV model from EV battery data base  100  so that the corresponding hardware configuration and battery charging control algorithms are selected before the battery charging process begin. In control algorithms  118 , a communication interface  116  which establishes an instant communication between a mobile EV fast charger and a EV when they are connected, may automatically reconfigured the hardware and select battery charging control algorithms before the battery charging process begin. 
         [0051]    In the functional block diagram of PWM rectifier charger control algorithms  120  as illustrated in  FIG. 8 , While the battery voltage is regulated by battery voltage control  102  in constant voltage mode, the battery current is regulated by battery current control  104  in constant current mode. Using the output of either voltage control  102  or current control  104 , an AC current reference generation  126  produces current references for AC current control  128  which regulates AC current by commanding SVM  130  to generate PWM signals controlling IGBT  132  to charge mobile on-board batteries  16  with AC grid power. 
         [0052]    In the functional block diagram of DC/DC boost converter control algorithms  134  as illustrated in  FIG. 9 , the DC voltage control  136  regulates the DC voltage by generating a reference for DC current control  106 . The current control  106  regulates DC current by commanding boost PWM  140  to generate PWM signals controlling IGBT  142  to boost lower voltage of truck alternator to 420V at DC Link Capacitor  36  inside MFPCS  14  (in  FIG. 2 ). This 420V voltage at DC Link Capacitor  36  is used by HF transformer isolated Full-Bridge (FB) DC/DC converter to charge EV battery system  30  (in  FIG. 5 ). 
         [0053]    In the functional block diagram of DC/DC boost battery charger control algorithms  144  as illustrated in  FIG. 10 , while the battery voltage is regulated by battery voltage control  102  in constant voltage mode, the battery current is regulated by battery current control  104  in constant current mode. Using the output of either voltage control  102  or current control  104  as DC current reference, the DC current control  106  regulates DC current by commanding boost PWM  140  to generate PWM signals controlling IGBT  142  to recharge mobile on-board batteries  16  with truck alternator power. 
         [0054]    In the functional block diagram of three phase grid-tied inverter plus direct on-board battery charger control algorithms  156  as illustrated in  FIG. 11 , Maximum Power Point Tracking (MPPT)  160  extract the maximum solar power by producing dynamic voltage reference to DC voltage control  148 . DC voltage control  148  regulates DC voltage by generating solar power command  164 . It is then subtracted from required on-board battery charging power  166  calculated by block  158  based on on-board battery charging current reference I BR    184  and EV battery voltage V B    182  to get inverter power command  168 . Inverter power command  168  is fed to AC current reference generation  126  to create current reference for AC current control  128  which regulates AC current by commanding SVM  130  to generate PWM signals controlling IGBT  176  to provide on-board battery charging power with part of solar energy  154  ( FIG. 6 ) and convert the rest to AC grid power. 
         [0055]      FIG. 12  illustrates the functional block diagram  196  of interleaved multi-phase on-board battery charger control algorithms. In diagram  196  where battery voltage is regulated by battery voltage control  198 , battery current is regulated by optimal solar power tracking  200 . The output I MPR    202  of either  198  or  200  is fed into multi-phase current control  204  to regulate DC current of each DC inductor by commanding interleaved multi-phase PWM  206  to generate signals controlling IGBT  208  to charge on-board battery  16  (in  FIG. 6 ). 
         [0056]    While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the invention, rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without depart from the sprit and scope of the invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the invention.