Method for Checking a Primary or Secondary Unit of an Inductive Charging System

Abstract

A method for checking a test secondary unit of an inductive test charging system for charging an electrical energy store, wherein the test charging system comprises the test secondary unit having a test secondary coil and a reference primary unit having a reference primary coil, includes recording a plurality of actual primary unit impedance values of the test charging system at the reference primary coil for a corresponding plurality of test combinations of values of operating parameters of the test charging system. The method also includes comparing the plurality of actual primary unit impedance values with a reference value range for a primary unit impedance.

Claims

1. A method for checking a test primary unit of an inductive test charging system for charging an electrical energy store, wherein the test charging system comprises the test primary unit having a test primary coil and a reference secondary unit having a reference secondary coil, wherein the method comprises: setting a plurality of different actual secondary unit impedance values of a secondary unit impedance at the reference secondary coil; wherein the plurality of different actual secondary unit impedance values are values from a reference value range for the secondary unit impedance; checking whether an actual charging power of the energy store is able to be regulated to a setpoint charging power for the plurality of different actual secondary unit impedance values.

2. The method according to claim 1, wherein the checking is performed for different setpoint charging powers from a reference power range; and/or is performed for different offset positions between the reference secondary coil and the test primary coil from a reference offset range.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG. 1 shows exemplary components of an inductive charging system.

[0033] FIG. 2 shows exemplary components of a WPT base unit and of a WPT vehicle unit.

[0034] FIG. 3a shows an exemplary inductive coupling system.

[0035] FIG. 3b shows an exemplary model of an inductive coupling system.

[0036] FIG. 3c shows exemplary parameter profiles of the coupling parameters of an inductive coupling system.

[0037] FIG. 3d shows an exemplary reference value range for coupling parameters.

[0038] FIG. 3e shows an exemplary reference value range for the secondary unit impedance.

[0039] FIG. 3f shows an exemplary reference value range for the primary unit impedance.

[0040] FIG. 4a shows an exemplary test bench for checking a test secondary unit.

[0041] FIG. 4b shows an exemplary test bench for checking a test primary unit.

[0042] FIG. 5a shows a flowchart of an exemplary method for checking a test secondary unit.

[0043] FIG. 5b shows a flowchart of an exemplary method for checking a test primary unit.

[0044] FIG. 6 shows an exemplary equivalent circuit diagram for determining losses in an inductive charging system.

DETAILED DESCRIPTION OF THE DRAWINGS

[0045] As set forth at the outset, the present document deals with testing the interoperability between a WPT base unit (or a primary unit) 110 and a WPT vehicle unit (or a secondary unit) 120 in an efficient and reliable manner. It should be taken into account in this case that an inductive charging system consisting of a primary unit 110 and a secondary unit 120 [0046] is able to be operated with different charging powers P from a reference power range (for example between 0 kW and 12 kW); [0047] is able to be operated with different charging voltages from a reference voltage range at the energy store 103 of the vehicle 100 (for example between 300 and 400 V); [0048] is able to be operated with different charging field frequencies from a reference frequency range (for example between 80 kHz and 90 kHz); and/or [0049] is able to be operated with a different spatial offset between the primary coil 111 and the secondary coil 121 (for example with different offset positions from a reference offset range), and therefore with different coupling parameters.

[0050] A particular reference operating range thus results for the inductive charging system, which reference operating range is able to be described by the abovementioned parameters and their reference parameter ranges. An interoperability test is intended to ensure, in an efficient and reliable manner, that a test secondary unit 120 to be tested achieves a predefined minimum efficiency with all of the qualified or permitted (reference) primary units 110 in the defined reference operating range, or that a test primary unit 110 to be tested achieves the predefined minimum efficiency with all of the qualified or permitted (reference) secondary units 120 in the defined reference operating range.

[0051] FIG. 2 shows a circuit diagram of an exemplary WPT base unit 110 (as an example of a primary unit) and of an exemplary WPT vehicle unit 120 (as an example of a secondary unit). The WPT base unit 110 comprises an inverter 213 that is configured so as to generate an AC current at a charging field frequency from a DC current (for example at a DC voltage of around 500 V). The WPT base unit 110 furthermore comprises the primary coil 111 and a primary capacitor 212. FIG. 2 furthermore illustrates, by way of example, a filter 214 of the WPT base unit 110. The WPT base unit 110 thus comprises a series resonant circuit (also referred to as primary resonant circuit here), whose resonant frequency results as f.sub.0=1/2√{square root over (LC)} from the overall capacitance C (in particular the capacitance of the capacitor 212) and the overall inductance L (in particular the inductance of the primary coil 111). The charging field frequency is preferably close to the resonant frequency Jo, in order to generate a primary current that is as high as possible through the primary coil 111 (through a resonance). A high primary current is typically required as the coupling factor k 230 between the primary coil 111 and the secondary coil 121 is relatively small, for example k˜0.1, due to the large air gap 130.

[0052] In the same way, the WPT vehicle unit 120 comprises a resonant circuit (also referred to as secondary resonant circuit here) that is formed from the secondary coil 121 and a secondary capacitor 222. The resonant frequency of this secondary resonant circuit is preferably matched to the resonant frequency of the primary resonant circuit of the WPT base unit 110 in order to achieve an energy transfer that is as good as possible. FIG. 2 furthermore illustrates a filter capacitor 224, a rectifier 101 and an energy store 103 to be charged.

[0053] The effective inductances L.sub.1, L.sub.2 of the primary coil 111 and of the secondary coil 121 depend on the arrangement of the primary coil 111 in relation to the secondary coil 121. In particular, the effective inductance L.sub.1 of the primary coil 111 or the effective inductance L.sub.2 of the secondary coil 121 depend on the magnitude of the underbody clearance 130 and/or on a transverse offset of the primary coil 111 with respect to the secondary coil 121. A changing effective inductance leads to a changing resonant frequency of the primary resonant circuit. The driving of the primary coil 111 should accordingly be adjusted for optimum energy efficiency. In this case, it is in particular possible to adjust the charging field frequency, to adjust a matching network (for example the filter 214) and/or to adjust the voltages.

[0054] The relative positioning, in particular an offset position, between the primary coil 111 and the secondary coil 121 may be described for example by Cartesian coordinates X, Y, Z, as in FIG. 3a. In this case, the Z coordinate indicates the magnitude of the underbody clearance 130. The X and Y coordinates describe the transverse offset of the primary coil 111 with respect to the secondary coil 121.

[0055] The inductive coupling system between the primary coil 111 and the secondary coil 121 may be described or modeled for example by a T equivalent circuit diagram (see FIG. 3b). This model 330 has, as parameters 331, the effective inductance L.sub.1 of the primary coil 111, the effective inductance L.sub.2 of the secondary coil 121 and the coupling factor k (with the mutual inductance M=k.Math. The parameters L.sub.1, L.sub.2, M 331 are in this case functions of the relative position between the primary coil 111 and the secondary coil 121, that is to say functions of x, y, z.

[0056] FIG. 3c shows exemplary profiles/characteristic diagrams 300, 310, 320 for the parameters M, L.sub.1, L.sub.2 331. These profiles/characteristic diagrams 300, 310, 320 may be determined in advance for a particular inductive coupling system. In particular, profiles 300, 310, 320 for the parameters M, L.sub.1, L.sub.2 331 may be measured for a particular combination of reference base unit 110 and reference vehicle unit 120. Reference characteristic diagrams M(x,y,z) 300, L.sub.1(x,y,z) 310 and L.sub.2(x,y,z) 320 may thus be determined for the coupling parameters 331. These reference characteristic diagrams 300, 310, 320 may be determined for one or more combinations consisting in each case of a reference base unit 110 and of in each case a reference vehicle unit 120.

[0057] The reference characteristic diagrams 300, 310, 320 for one or more combinations of reference base units 110/reference vehicle units 120 may be combined into a reference characteristic diagram 351 that indicates possible value tuples of the coupling parameters M, L.sub.1, L.sub.2 331. A value tuple in this case results from the parameter values M(x,y,z), L.sub.1(x,y,z) and L.sub.2(x,y,z) for a particular offset position x,y,z. For a plurality of offset positions and possibly for a plurality of combinations of reference base units 110/reference vehicle units 120, this then results in a plurality of value tuples that are able to be combined so as to form a reference characteristic diagram 351.

[0058] From the reference characteristic diagram 351 for possible combinations of values of the coupling parameters M, L.sub.1, L.sub.2 331, it is then possible to determine a reference value range 352 for the coupling parameters 331 of the inductive coupling system between the primary coil 111 and the secondary coil 121. The reference value range 352 in this case indicates which combinations of values of the coupling parameters M, L.sub.1, L.sub.2 331 are permissible for different offset positions between the primary coil 111 and the secondary coil 121. The reference value range 352 may possibly be increased by a particular tolerance value (for example of 3%, 5% or more) with respect to the reference characteristic diagram 351, in order for example to take into account production tolerances and influences from surrounding vehicle structures.

[0059] FIG. 2 defines different impedances in an inductive charging system. FIG. 2 in particular defines a secondary unit impedance Z.sub.VA 252 that results at the secondary coil 121. FIG. 2 furthermore defines a primary unit impedance Z.sub.GA 251 that results at the primary coil 111. The primary impedance Z.sub.GA 251 may in this case be calculated from the secondary unit impedance Z.sub.VA 252 via the coupling properties of the coils 111, 121. The following coupling formula may in particular be used for this purpose:

[00002]$Z_{\mathrm{GA}}=\frac{j\omega M\left(j\omega L_{{\sigma }_2}+Z_{\mathrm{VA}}\right)}{j\omega M+j\omega L_{{\sigma }_2}+Z_{\mathrm{VA}}}+j\omega L_{{\sigma }_1}$

wherein L.sub.σ1=L1−M and L.sub.σ2=L2−M are the leakage inductances of the coupling system.

[0060] Possible secondary unit impedances Z.sub.VA 252 may be determined for one or more combinations of reference base units 110/reference vehicle units 120 (for different charging powers and/or for different charging voltages) in order to determine a reference characteristic diagram for the secondary unit impedances Z.sub.VA 252. FIG. 3e shows an exemplary reference value range 361 for the secondary unit impedance Z.sub.VA 252 (for a fixed charging power and for different charging voltages).

[0061] The reference value range 361 for the secondary unit impedance Z.sub.VA 252 may then be transferred into a reference characteristic diagram 371 for the primary unit impedance Z.sub.GA 251 (for example by way of the abovementioned formula). In this case, all of the possible value tuples from the reference characteristic diagram 351 for possible combinations of values of the coupling parameters M, L.sub.1, L.sub.2 331 may be taken into account. A reference characteristic diagram 371 for the primary unit impedance Z.sub.GA 251 may thus be determined for different charging voltages, for different charging powers and/or for different offset positions (see FIG. 3f). Furthermore, in the case of using the reference value range 352 (expanded by a tolerance range) for possible combinations of values of the coupling parameters M, L.sub.1, L.sub.2 331, a reference value range 372 for the primary unit impedance Z.sub.GA 251 may be determined in the conversion of the secondary unit impedance values into the primary unit impedance values.

[0062] To check a test vehicle unit 120, the test vehicle unit 120 may be tested in combination with a reference base unit 410 (see FIG. 4a). On the other hand, to check a test base unit 110, the test base unit 110 may be tested in combination with a reference vehicle unit 420 (see FIG. 4b). In this case, different offset positions 402 between the primary coil 411, 111 and the secondary coil 121, 421 may be set for a test. The different offset positions 402 may possibly be set automatically by a setting unit 415.

[0063] To test a test vehicle unit 120 (see FIG. 4a), the energy store 103 of the vehicle 100 may be charged with a particular charging voltage U.sub.DC 403. The charging voltage 403 may be measured using a voltage measurement unit 416. The charging current I.sub.DC may furthermore be measured using a current measurement unit 417. The actual charging power then results from the charging voltage and the charging current. The setpoint charging power 401 may furthermore be predefined at the reference base unit 410. The test vehicle unit 120 and the reference base unit 410 are then able to regulate the actual charging power to the setpoint charging power 401 using a control loop.

[0064] The test combination consisting of the test vehicle unit 120 and the reference base unit 410 (see FIG. 4a) may then be operated with [0065] different charging voltages 403 from the reference voltage range; [0066] different offset positions 402 from the reference offset range; and/or [0067] different setpoint charging powers 401 from the reference power range.

[0068] In this case, a (complex-value) actual primary unit impedance value may be measured at the reference primary coil 411 for a particular operating point (defined by a particular combination of the values of the operating parameters 401, 402, 403) by way of an impedance measurement unit 430. The impedance measurement unit 403 (for example an impedance analyzer) may in this case for example record the magnitude of the voltage U.sub.GA at the reference primary coil 411, the magnitude of the current IGA through the reference primary coil 411 and a phase shift φ.sub.GA between the voltage and the current.

[0069] It is thus possible to determine actual primary unit impedance values for an operating range defined by different charging voltages 403, offset positions 402 and/or setpoint charging powers 401. The actual primary unit impedance values determined in this way may then be compared with the reference value range 372 for the primary unit impedances Z.sub.GA 251. It is in particular able to be checked whether all of the determined actual primary unit impedance values are situated within the reference value range 372. If this is the case, then the test vehicle unit 120 may be activated. If not, it may be necessary to correct the test vehicle unit 120. The interoperability between a test vehicle unit 120 and different base units 110 is thus able to be ensured in an efficient and precise manner.

[0070] To test a test base unit 110, as illustrated in FIG. 4b, it is possible to set different secondary unit impedance values by way of an impedance setting unit 440, which secondary unit impedance values are in turn able to be measured by way of an impedance measurement unit 430. In this case, all of the possible secondary unit impedance values from the reference value range 361 for the secondary unit impedance Z.sub.VA 252 are able to be set by way of the impedance setting unit 440. In the example illustrated in FIG. 4b, the impedance setting unit 440 comprises a settable capacitor and a settable resistor.

[0071] The test base unit 110 may be operated with different setpoint charging powers 401. It is then able to be determined (for different offset positions 402) whether the respective setpoint charging power 401 is able to be provided at the output of the secondary coil 421 of the reference vehicle unit 420. The interoperability of a test base unit 110 is thus able to be checked in an efficient and reliable manner.

[0072] FIG. 4a thus shows a test bench for checking a secondary system, that is to say a test secondary unit 120. The secondary system 120 to be tested is operated with a reference primary coil 411 on the test bench, and in the process a setpoint charging power 401 that is intended to be output on the secondary side, for example to an energy store 103, is set. The setpoint charging power 401 may in this case be subsequently adjusted. The DC charging voltage 403 may be set to a particular value on the secondary side. Furthermore, the relative distance (that is to say the offset position 402) may be varied in a particular reference offset range. It is able to be checked, as interoperability criterion, whether the primary unit impedance values on the reference primary coil 411 are situated within the permitted impedance value range 372 for all of the tested operating points.

[0073] FIG. 4b shows a test bench for checking a primary system, that is to say a test primary unit 110. The primary system 110 is operated with a reference secondary coil 411 on the test bench. At the output of the reference secondary coil 411, the secondary unit impedance 252 is able to be varied in the entire impedance value range 361 via correspondingly settable elements of an impedance setting unit 440 (for example via a settable load resistor and/or via a settable capacitor). In this case, a capacitive load is typically always necessary in the impedance setting unit 440 due to the inductance of the coils. The relative distance, that is to say the offset position 402, may furthermore be varied. It is then able to be checked whether enough power is able to be transferred, for all operating points (that is to say for all secondary unit impedance values, for all offset positions 402 and/or for different setpoint charging powers 401), to regulate the actual charging power to the respective setpoint charging power 401.

[0074] If a design (that is to say a test secondary unit 120 or a test primary unit 110) is intended to interoperate with a plurality of reference designs, then the measurements on the test benches of FIGS. 4a and 4b may accordingly be tested with a plurality of reference counter-coils 411, 421. The respective interoperability conditions should then be met with all reference designs.

[0075] Partial efficiencies of a charging system may also be determined in the context of the measurements. A charging system may be operated, and the input and output voltages of the charging system may be measured, together with the input power of the primary side and the DC output power of the secondary side. The losses within the charging system are able to be determined on the basis of these measured values. The proportional losses in the primary and secondary coil 111, 121 are furthermore able to be determined via the determined currents and voltages with the equivalent circuit from FIG. 6. This measurement may in each case be applied only to one side (primary or secondary) of the charging system.

[0076] By way of example, the current and the voltage may be measured at the input of the primary coil 111, 411 (for example by the impedance measurement unit 430 from FIG. 4a). Furthermore, the current and the voltage may be measured at the output of the secondary coil 121, 421 and/or at the input of the energy store 103 (for example by the voltage measurement unit 416 and the current measurement unit 417 from FIG. 4a). Furthermore, the power drawn from a supply grid by an inductive charging system may be determined. A model of the inductive coupling system (for example the model shown in FIG. 6) may also be taken into account. It is then able to be determined what proportion of losses arises on the primary side of the coupling system and what proportion of losses arises on the secondary side of the coupling system. The power loss of the secondary side of the coupling system is in particular able to be determined for example using the test bench from FIG. 4a.

[0077] FIG. 5a shows a flowchart of an exemplary method 510 for checking a test secondary unit 120 of an inductive test charging system for charging an electrical energy store 103. The test charging system in this case comprises the test secondary unit 120 (for example a vehicle unit) having a test secondary coil 121 and a reference primary unit 410 (for example a base unit) having a reference primary coil 411. The test secondary unit 120 in this case comprises all of the components (for example vehicle parts and bodywork parts) influencing the transfer behavior of the magnetic coupling system. The reference primary unit 410 accordingly also comprises all of the components (for example a coil cover) influencing the transfer behavior of the magnetic coupling system. The method 510 may be performed automatically. In particular, operating parameters 401, 402, 403 of the test charging system, in particular the setpoint charging power 401, the offset position 402 between the test secondary coil 421 and the reference primary coil 111 and/or the charging voltage 403, may be varied automatically in order to test the test secondary unit 120 in a particular predefined reference operating range.

[0078] The method 510 comprises recording 511 a plurality of actual primary unit impedance values of the test charging system at the reference primary coil 411 for a corresponding plurality of test combinations of values of operating parameters 401, 402, 403 of the test charging system. As set forth above, the operating parameters 401, 402, 403 may in this case be at least partly varied automatically. A corresponding actual primary unit impedance value may be measured at the reference primary coil 411 for each test combination of values of the operating parameters 401, 402, 403. In this case, test combinations may be (randomly) considered from the entire reference operating range. The actual primary unit impedance values may be measured using an impedance measurement unit 430.

[0079] The method 510 furthermore comprises comparing 512 the plurality of actual primary unit impedance values with a reference value range 372 for the primary unit impedance 251. The reference value range 372 may in this case have been determined on the basis of one or more reference charging systems. In this case, the reference value range 372 for the primary unit impedance 251 may indicate the actual primary unit impedance values that are present in the one or more reference charging systems at the respective reference primary coil 411. The reference value range 372 for the primary unit impedance 251 may in particular indicate the actual primary unit impedance values of the one or more reference charging systems for the entire reference operating range.

[0080] It is able to be checked whether the plurality of actual primary unit impedance values are all, or in more than X % of the cases (for example X equal to 90 or more), situated within the reference value range 372 for the primary unit impedance 251. If this is the case, it is thus able to be determined that the test secondary unit 120 is interoperable. On the other hand, it may be determined that the test secondary unit 120 is not interoperable.

[0081] FIG. 5b shows a flowchart of an exemplary method 520 for checking a test primary unit 110 of an inductive test charging system for charging an electrical energy store 103. In this case, the test charging system comprises the test primary unit 110 having a test primary coil 111 and a reference secondary unit 420 having a reference secondary coil 421. The test primary unit 110 comprises all of the components (for example a coil cover) influencing the transfer behavior of the magnetic coupling system. The reference secondary unit 420 accordingly comprises all of the components (for example bodywork parts of a vehicle 100) influencing the transfer behavior of the magnetic coupling system.

[0082] The method 520 comprises setting 521 a plurality of different actual secondary unit impedance values of a secondary unit impedance 252 at the reference secondary coil 421. In this case, the actual secondary unit impedance values are situated within a reference value range 361 for the secondary unit impedance 252. The reference value range 361 for the secondary unit impedance 252 may indicate which actual secondary unit impedance values a reference charging system has during operation within the entire reference operating range (that is to say for all of the possible combinations of values of operating parameters 401, 402, 403). The different actual secondary unit impedance values may be set by way of an impedance setting unit 440.

[0083] The method 520 furthermore comprises checking 522 whether an actual charging power of the energy store 103 is able to be regulated to a setpoint charging power 401 for the plurality of different actual secondary unit impedance values. It is in particular able to be checked whether the respectively set setpoint power 401 is able to be transferred to the secondary unit 120 for the different actual secondary unit impedance values.

[0084] The checking 522 may in this case be performed for different setpoint charging powers 401 from a reference power range of the reference operating range. The checking 522 may furthermore be performed for different offset positions 402 between the reference secondary coil 421 and the test primary coil 111 from a reference offset range of the reference operating range. The reference value range 361 for the secondary unit impedance 252 may in this case be different for different setpoint charging powers 401 and/or for different offset positions 402. In other words, the reference value range 361 for the secondary unit impedance 252 may depend on an operating parameter 401, 402, 403 of the test charging system, in particular on the setpoint charging power 401, on the offset position 402 and/or on the charging voltage 403.

[0085] If the result of the checking 522 is that the setpoint charging power 401 in the reference power range is always, or in all cases or at least in X % of the cases (for example X equal to 90 or more), able to be provided as actual charging power, it is thus able to be determined that the test primary unit 110 is interoperable. As an alternative or in addition, a tolerance in relation to the reference power range may be taken into account when determining the interoperability (for example in connection with 100% delivery of the setpoint charging power 401). On the other hand, it may be determined that the test primary unit 110 is not interoperable.

[0086] By way of the measures described in this document, a test primary unit 110 or a test secondary unit 120 are able to be tested in an efficient manner in connection with a reference counter-unit 420, 410. In this case, it is possible to determine properties of the respective test unit 110, 120 (for example efficiency, influence of screening and metal parts, compliance with interoperability criteria). The development of primary units 110 or secondary units 120 is thus able to be simplified, since both partial systems 110, 120 are able to be developed independently of one another. The interoperability of primary units 110 or secondary units 120 is furthermore thus able to be tested in an efficient and reliable manner.

[0087] The present invention is not restricted to the disclosed exemplary embodiments. It should in particular be borne in mind that the description and the figures are intended only to elucidate the principle of the proposed methods, devices and systems.

[0088] The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.