Device for the inductive transmission of electrical energy

Abstract

Device for the inductive transmission of electrical energy from a stationary unit with a power supply unit (11) and a primary inductor (10) connected thereto to a vehicle located adjacent to the stationary unit with a secondary inductor (1), characterized in that the vehicle has a secondary regulator (2) for adjusting the secondary power drawn from the secondary inductor (1), which includes a switching device (6; 7; 8;9) includes, by means of which the extracted secondary power can be changed in stages, that the stationary unit has a primary controller (12) for adjusting the primary power that can be fed into the primary inductance (10), which includes a first measuring device by means of which an electrical operating parameter of the power supply device (11) influenced by the secondary power can be measured, and that the primary controller (12) adjusts the primary power that can be fed in as a function of changes in the operating parameter measured by the first measuring device, and that a battery (3) is arranged in the vehicle, which in the operation of the device with a current (I; S ) the charging current (I) generated by the secondary inductance (1) B ) is charged, that the secondary controller (2) contains a second measuring device by means of which the charging current (I) B) is measurable, and that the secondary controller (2) contains a computing device which, in the event of a deviation of the value of the charging current (I) measured by the second measuring device B ) from a setpoint, one of the ratios between the setpoint and the measured value of the charging current (I) B ) dependent timing of switching operations, which is carried out by the switching device (6; 7; 8; 9).

Description

[0001] The invention relates to a device for the inductive transmission of electrical energy according to the preamble of claim 1.

[0002] When charging an electric vehicle battery, the charging current must be constantly adjusted to an appropriate value, depending on the battery's specifications and its current state of charge. The necessary charging electronics can be located either on board the vehicle or in the charging station. With inductive power transfer from the charging station to the vehicle, if all charging electronics are located in the vehicle, the charging station must continuously provide the maximum possible charging power, which must then be reduced in the vehicle to the currently required level. This results in relatively high power losses on both the primary and secondary sides and necessitates a correspondingly robust and therefore complex design for the secondary-side charging electronics.

[0003] To avoid this, the power supplied on the primary side can be regulated according to the power demand on the secondary side. However, this requires corresponding communication between the secondary and primary sides. This communication can either be handled via a completely separate communication channel, such as a radio link, or a data signal can be modulated onto the transmission path intended for inductive energy transfer. Both solutions, however, require specialized communication hardware on both the primary and secondary sides, which entails corresponding costs.

[0004] DE 696 02 739 T2 discloses devices and methods for creating a fast recharging of the batteries of an electric vehicle.

[0005] DE 101 58 794 B4 discloses an inductive contactless power transmitter.

[0006] The invention is therefore based on the objective of providing a simple and cost-effective solution for controlling the charging process for the inductive charging of an electric vehicle at a charging station.

[0007] This problem is solved according to the invention by a device having the features of claim 1. Advantageous embodiments of the invention are specified in the dependent claims.

[0008] According to the invention, in a generic device for the inductive transmission of electrical energy, the vehicle has a secondary controller for adjusting the secondary power drawn from the secondary inductor, which includes a switching device by means of which the drawn secondary power can be changed in steps. The stationary unit has a primary controller for adjusting the primary power that can be fed into the primary inductor, which includes a first measuring device by means of which an electrical operating parameter of the power supply device influenced by the secondary power can be measured, and the primary controller adjusts the feed-in primary power as a function of changes in the operating parameter measured by the first measuring device.In this context, primary and secondary power always refer to active power, and the attribute "feedable" means that the primary power is not specified but offered, and the power actually flowing into the primary coil also depends on the power drawn from the secondary coil.

[0009] This opens up the possibility of regulating the primary power supplied from the secondary side as needed, without requiring a separate communication channel and corresponding hardware. On the secondary side, only a switching device for stepwise adjustment of the secondary power, preferably for switching it on and off, is required. Such a switching device must be present anyway to terminate the energy transfer on the secondary side if necessary, particularly when a vehicle battery is fully charged or if a fault of any kind occurs. Therefore, the solution according to the invention does not incur any additional hardware costs on the secondary side. The same applies analogously to the primary side, since the energy transfer there must be monitored by measurement equipment anyway, and a device for adjusting the feed-in primary power is generally already present.The existing inductive transmission link is used to transmit information about the secondary-side power requirements, without frequency division multiplexing, i.e., without the need for modulation and demodulation.

[0010] The preferred application of the invention is the charging of a vehicle battery. In this case, a measurement of the charging current is provided on the secondary side, and if the measured value of the charging current deviates from its target value, the switching device executes a sequence of switching operations that depends on the ratio between the target value and the measured value. Depending on this switching pattern, which acts back on the primary side and can be detected there using an electrical operating parameter, the feed-in power of the primary is then adjusted.

[0011] A preferred embodiment of the invention provides for a periodic switching of the secondary power between two stages at a predetermined time interval when the measured charging current exceeds the setpoint. The duty cycle of this switching corresponds to the ratio between the setpoint and the measured charging current. The primary controller thus receives immediate information about the necessary reduction in primary power and can adjust it accordingly. If one of the two secondary power stages corresponds to a shutdown, the average value of the secondary power input is reduced to the necessary extent in advance, before the primary controller reacts and reduces the primary power accordingly.

[0012] Another preferred embodiment of the invention provides that, if the measured value of the charging current exceeds the setpoint, the system switches to the lower of two stages, preferably to a shutdown, which continues until an electrical operating parameter of the secondary side, dependent on the primary power in the lower stage, reaches a value at which switching to the higher stage results in the charging current matching its setpoint. In this case, the primary controller reduces the primary power value at a predetermined rate until it detects on the primary side that the secondary side has switched back to the higher stage. In this way, the absorption of excessive secondary power is prevented even before the primary controller reacts.It may take a little longer here until the correct value of the primary power is reached, because the primary controller does not receive any information about the extent of the secondary-side deviation between the actual value and the target value of the target variable, i.e. the charging current, due to the secondary-side switching.

[0013] The invention is not limited to power control in one direction, i.e., a reduction of the primary power, but also includes increasing the primary power when needed. This is achieved by encoding the direction of the deviation between the actual value and the setpoint of a secondary-side target variable in the temporal pattern of the switching operations occurring on the secondary side and detected on the primary side. Upon receiving a corresponding code, the primary power can also be increased by a predetermined step or at a predetermined rate.

[0014] Further details and advantages of the invention are disclosed in the following description of an exemplary embodiment with reference to the drawings. These show Fig. 1 a block diagram of the secondary side of a device according to the invention and Fig. 2 a block diagram of the primary side of a device according to the invention.

[0015] How the block diagram of Fig. Figure 1 shows that the secondary side of an inductive energy transfer device according to the invention, arranged on board an electrically powered vehicle (not shown), comprises, among other things, a secondary coil 1, a charge controller 2 as a secondary regulator, and a battery 3. The battery 3 is charged with a direct current I during operation of the device. B charged, which is from an alternating current I induced in the secondary coil 1 Sis converted by a converter 4. The converter 4 contains a rectifier and can additionally contain a voltage converter if the output voltage of the rectifier requires further reduction to charge the battery 3. Since the entire arrangement together with the following is further illustrated by Fig. To ensure that the primary side of the circuit, as explained in section 1, is operated in resonance, a tuning network 5 is connected between the secondary coil 1 and the converter 4. This tuning network 5 ensures that the resonance condition is met at the desired operating frequency.

[0016] The charge controller 2 contains a measuring device by means of which it can measure the battery voltage U B battery 3 and the charging current I B can be measured. From these values, the current state of charge of battery 3 can be determined. From this, the charging current I can be derived. BA setpoint value I0, which changes during a charging process, in particular decreases. Furthermore, the charge controller 2 is also configured to regulate the secondary current I flowing in the secondary coil 1. S to measure. To influence the charging current I B The charge controller 2 provides a switch 6, controllable by the charge controller 2, in parallel to the secondary coil 1, by which the secondary coil 1 can be short-circuited.

[0017] Alternative to measuring the secondary current I S It could also be possible to measure the output current I1 or I2 of the balancing network 5 or the converter 4, respectively. Alternatively to switch 6, a switch 7 or 8 could be provided to short-circuit the input or output of converter 4, respectively. Measuring the output current I2 of converter 4 is only meaningful in combination with a switch 8 at the output of converter 4, since otherwise the current I2 would always be the same as the charging current I. Bis identical. Furthermore, as an alternative to switch 6, a switch 9 could also be provided for short-circuiting or disconnecting a circuit branch within the balancing network 5. It is obvious that each of the switches 6 to 9 influences, i.e., effectively disconnects, the charging current I. B This is possible. The effect of switch 9 is based on the fact that its activation cancels the function of the balancing network 5, causing the normally resonant system to become out of resonance, which leads to a significant drop in the charging current I. B leads.

[0018] The primary side of a device according to the invention comprises, as shown in the block diagram of Fig. 2 emerges, a primary coil 10, which is supplied by a power supply device 11 with a primary current I P is supplied, and a primary controller 12. This contains a measuring device by means of which it measures the primary current IP The power supply device 11 comprises a rectifier 13, the input of which is connected to a power supply network, an intermediate circuit 14 connected to the output of the rectifier 13, which generates a DC voltage of predetermined magnitude from the output voltage of the rectifier, and a converter 15, which generates an AC voltage of predetermined frequency and amplitude from the DC voltage of the intermediate circuit 14 with which it is supplied, which is supplied to the primary coil 10.

[0019] Since the entire arrangement, together with that of the preceding one, is based on Fig. To ensure that the primary side described in section 1 is operated in resonance, a tuning network 16 is connected between the converter 15 and the primary coil 10. This tuning network 16 ensures that the resonance condition is met at the desired operating frequency. As described in section 1, the primary side is to be operated in resonance. Fig. 2 analogous to Fig. The line shown as a dashed line 1 could be used as an alternative to measuring the primary current I on the primary side. P also a measurement of the output current I3 or the input current I4 or the input voltage U4 of the inverter 15 or the input current I N of rectifier 13 from the power supply network.

[0020] The invention enables the control of the primary-side power input, i.e., the primary power that can be supplied to the primary coil 10 at maximum secondary-side power output, depending on the secondary-side power requirement, which is derived from the setpoint of the charging current I. BThis results in the operation of the device without the need for a separate communication channel between the secondary and primary sides. It is understood that the actual power flowing into the primary coil 10 always depends on the configuration of the secondary coil 1. Whenever the primary power is referred to here, this always means the maximum available primary power. The operation of the device according to the invention is explained below.

[0021] After the device is commissioned, which occurs after a vehicle is parked at a charging station and the secondary coil 1 is correctly aligned with the primary coil 10, by means of an initiation signal (not relevant here), the primary controller 12 sets the inverter 15 to maximum power. This power may depend on the rated power data of the secondary side, which must be known to the primary controller 12 in this case. This results in a corresponding maximum value for the primary current I.P and corresponding maximum values ​​of the secondary current I S and the charging current I B battery 3.

[0022] If the value of the charging current I B If the current state of charge of battery 3 is too high, the charge controller 2 short-circuits the secondary coil 1 by closing switch 6, so that the secondary side no longer draws any power apart from losses in the secondary coil 1 itself. This secondary-side short circuit affects the primary side and causes a sudden change in the primary power drawn by the primary coil 10 from the power supply unit 11. This is regulated by the primary controller 12 based on the primary current I. P and the primary voltage U P detects and signals to it a secondary need for a reduction in the primary service offered.

[0023] According to a first embodiment of the invention, a computing device contained in the charge controller 2 determines the measured value of the charging current I from the B and whose current setpoint I0 determines the extent of the necessary reduction of the charging current I B , which is determined by the ratio I0 / I B The charge controller periodically closes and opens the short-circuit switch 6 with a duty cycle of opening time T0 to total period T. P , which corresponds to the ratio I0 / I B This corresponds to the same duty cycle T0 / T. P The time course of the primary power measured by the primary controller 12 also shows this, as it also alternates periodically between two values ​​as a result of the actuation of the switch 6.

[0024] From the duty cycle T0 / T P A computing device contained in the primary controller 12 calculates the change in the amplitude of the primary current I. P, which are used to adjust the charging current I B The inverter 15 adjusts its setting accordingly via a control line to achieve its setpoint I0. For this purpose, the inverter 15 contains, for example, an H-bridge circuit. Its switching angle is changed to a value that determines the primary current I. P with the required value. In the simplest case, the amplitude of the primary current I can be P reduced by a factor that is determined by multiplying the ratio T0 / T P It is calculated using a correction factor. However, a more complex relationship may also exist and be taken into account mathematically.

[0025] In the manner described above, the primary-side power can only be reduced, which is also the normal case when charging a battery, since the required charging current I BThe charging current decreases as battery 3 charges. However, it can also happen that the charging current I B The inductive load must be increased during a charging process, for example, if the vehicle's weight decreases during charging due to passengers exiting the vehicle or unloading items from the trunk or cargo area. The suspension's extension then increases the air gap between the secondary coil 1 mounted on the underside of the vehicle and the primary coil 10 located on the ground at the charging station, causing a drop in the inductively transferred power.

[0026] To signal a need for an increase in the primary power supplied from the secondary side, the charge controller 2 performs one or more switching operations with the short-circuit switch 6, the timing of which deviates significantly from the pattern defined for signaling a reduction need. For example, the switch may be closed for a period T P a significantly exceeding time interval or a periodic closing and opening with a period of T that differs from the period P a different, significantly shorter period and a characteristic duty cycle are provided. Such a signal pattern is interpreted by the primary controller as a request for a power increase and leads to a corresponding control of the inverter 15.

[0027] The required increase in primary power can be signaled by the charge controller 2, analogous to the required decrease, by the duty cycle of a periodic actuation of switch 6. Alternatively, the primary power can be increased by a predetermined step or continuously at a predetermined rate without prior knowledge of the required increase. If an increase of one step proves insufficient, the charge controller 2 can request further increases in the same manner until the charging current I B The target value I0 is reached or exceeded. If this value is exceeded, a reduction or a cessation of the continuous increase can be requested in the manner described above. In any case, it is advisable for the charge controller 2 to request a change in primary power only when the deviation of the charging current I exceeds a certain threshold. Bexceeds a tolerance threshold from its target value I0 in order to avoid constant pulsing around the target value I0.

[0028] According to a second, simpler embodiment of the invention, it is dispensed with to signal the necessary extent of the power reduction by a periodic switching of the secondary power to the primary side, but rather the secondary-side short-circuit switch 6 is activated when the setpoint value I0 of the charging current I is exceeded. B The charging controller 2 closes the circuit, and the primary controller 12 determines this based on the primary power and subsequently reduces the primary power supplied, i.e., the value of the primary current I. P in stages or continuously at a predetermined time rate.

[0029] Since after closing the short-circuit switch 6 the charging current I BWhen the voltage drops to zero, it is no longer available as a measured value, so a different criterion is needed on the secondary side to achieve the correct operating point of the system. In this case, the secondary current I is used as the criterion. S The value used is also different from zero in the event of a short circuit of the secondary coil 1 by the switch 6. However, for this to be relevant, the relationship between the secondary current I must be considered. S in case of short circuit and the charging current I B This relationship can be known when switch 6 is open. It can be determined experimentally beforehand and stored in a memory of the charge controller 2. The relationship between I S and I B It can be approximated by a constant factor, but it could also be a non-linear characteristic curve that can be stored as a formula or table.

[0030] The relationship between I can be approximated as follows: S and IB can also be determined and stored during operation when the primary controller 12 controls the primary current I P At the beginning of the charging process, the current increases at a predetermined rate over time. In this case, however, switch 6 is open, meaning the current I measured at that time is... S is not the short-circuit current of secondary coil 1, so that the change in secondary current I S by opening switch 6, i.e., the difference between normal operation and short circuit of secondary coil 2 is then not taken into account.

[0031] In the simplest case, the ratio between the secondary current I can be used to determine S immediately after the closing of switch 6, i.e. before a reaction of the primary regulator 12 and the charging current I B Immediately before closing switch 6, a proportionality factor is determined and a target value for the secondary current I is set. SIn the event of a short circuit, the charging current can be calculated by multiplying the target value I0 of the charging current by this proportionality factor.

[0032] In the second embodiment, the charge controller 2 therefore measures the secondary current I after the switch 6 is closed. S , while the primary controller 12 controls the primary-side power supplied, i.e., the primary current I P reduced at a constant rate, and compares the measured secondary current I S with a target value I S0 , which he derives from the current target value I0 of the charging current I B and the stored relationship between I S and I B has determined. If the secondary current I S its target value I S0Once the required voltage is reached, the charge controller 2 reopens the switch 6. This switching action affects the primary side and is detected by the measuring device of the primary controller 12 based on the primary power, whereupon the primary controller 12 reduces the primary current I. P It ended at the currently reached value.

[0033] In the second embodiment, a need to increase the primary power can be signaled by actuating switch 6 according to a predetermined time pattern, for example, by one or more very short pulses. In this case, the primary power can be increased by the primary controller 12 at a predetermined rate, and the resulting increase in the charging current I B are directly measured by the measuring device of the charge controller 2. If the charging current I BOnce its target value is reached, the charge controller 2 can signal this to the primary controller 12 by reactivating the switch 6 according to a predetermined time pattern. For example, the same pattern could be used here as for signaling an increased power demand, since the primary controller 12 is then already in the power increase operating mode and the repeated reception of the same signal can then be interpreted differently.

[0034] While the first embodiment has the advantage that it does not require calibration of a relationship between the charging current I B and the secondary current I S The second embodiment has the advantage that it involves significantly fewer switching operations with a relatively large switched power, which can be a potential source of electromagnetic interference and may require appropriate countermeasures.

[0035] As in Fig. As shown in Figure 1 with switches 7 and 8 at the input and output of the converter 4 respectively, and switch 9 at the adjustment network 5, the charging current I must be switched off. B and thus the secondary power does not have to be supplied directly at the secondary coil 1, but can alternatively also be supplied at another point on the secondary side. Accordingly, in the second embodiment, the current I carried by the secondary coil does not necessarily have to be S not only can the current be measured, but when using a switch 7 or 8 at the output of the adjustment network 5 or the converter 4, the current I1 or I2 at that location could also be measured, as shown in Fig. 1 is indicated by dashed lines. In this case, a prior calibration of the relationship between the current I1 and I2 measured with switch 7 and 8 closed, respectively, and the charging current I would be necessary. BThis occurs when switch 7 or 8 is open. If the charging current I is switched off... B By means of switch 9 on the balancing network 5, the secondary current I must be adjusted, just as when using switch 6. S be measured.

[0036] As in Fig. As shown in Figure 2, the primary-side detection of a power shutdown on the secondary side via one of the switches 6 to 9 does not necessarily have to be based on the power flowing directly into the primary coil 10, but can alternatively also be based on another primary-side electrical quantity such as, in particular, the output current I3 or the input current I4 of the converter 15 or the current I drawn from the power supply network by the power supply unit 11. N to be done, as it is in Fig.2 is indicated by dashed lines. All these quantities are affected by a secondary-side power shutdown and are therefore fundamentally suitable as measured variables for detecting such a power shutdown.

[0037] From the preceding description of exemplary embodiments, a person skilled in the art will discover possible variations for implementing the invention. For example, it is not essential that the charging current I BThe secondary side is not completely switched off; rather, it only needs to be ensured that its change due to a secondary-side switching operation is pronounced enough to be readily detectable based on a primary-side operating parameter. Furthermore, the secondary-side switching could, in principle, also occur between more than two stages, although switching between only two stages is particularly easy to implement and therefore preferred. Regarding the primary-side setting, instead of the switching angle of the inverter 15, the switching frequency, and thus the frequency of the primary current I, could also be used. P These modifications can be varied, as the transmitted power also changes due to the design of the transmission system for resonant operation. Such and similar modifications are at the discretion of the person skilled in the art and are intended to be covered by the protection of the claims.

Claims

[1] Device for inductive transmission of electrical energy from a stationary unit with a power supply unit (11) and a primary inductor (10) connected thereto to a vehicle standing adjacent to the stationary unit with a secondary inductor (1), characterized by, that the vehicle has a secondary regulator (2) for adjusting the secondary power drawn from the secondary inductor (1), which includes a switching device (6; 7; 8; 9) by means of which the drawn secondary power can be changed in steps, that the stationary unit has a primary regulator (12) for adjusting the primary power that can be fed into the primary inductor (10), which includes a first measuring device by means of which an electrical operating parameter of the power supply device (11) influenced by the secondary power can be measured, and that the primary regulator (12) adjusts the feed-in primary power as a function of changes in the operating parameter measured by the first measuring device, and that a battery (3) is arranged in the vehicle, which, in the operation of the device with a current (I) S ) the charging current (I) generated by the secondary inductance (1) B) is charged, that the secondary controller (2) contains a second measuring device by means of which the charging current (I) B ) is measurable, and that the secondary controller (2) contains a computing device which, in the event of a deviation of the value of the charging current (I) measured by the second measuring device B ) from a setpoint, one of the ratios between the setpoint and the measured value of the charging current (I) B ) dependent timing of switching operations, which is carried out by the switching device (6; 7; 8; 9). [2] Device according to claim 1, characterized by , that the secondary power can be switched between two stages by the switching device (6; 7; 8; 9) and that the secondary power in one of the stages has at least approximately the value zero. [3] Device according to claim 1 or 2, characterized by, that the timing of the switching operations contains a code that indicates whether the deviation of the measured value of the charging current (I) B ) is positive or negative from its target value. [4] Device according to any one of claims 1 to 3, characterized by , that the primary controller (12) changes the value of the feed-in primary power depending on the time course of the changes of the operating parameter when abrupt changes occur in the operating parameter measured by the first measuring device. [5] Device according to any one of claims 1 to 4, characterized by , that the secondary power can be switched between two stages by the switching device (6; 7; 8; 9), and that if the target value of the charging current (I) is exceeded B) a periodic switching between the stages occurs at a predetermined time interval based on the measured value, whereby the duty cycle of the switching between the stages corresponds to the ratio between the setpoint and the measured value of the charging current (I B ) corresponds, and that the primary controller (12) changes the value of the feed-in primary power depending on the duty cycle of the changes in the operating parameter when abrupt changes occur in the operating parameter measured by the first measuring device. [6] Device according to any one of claims 1 to 4, characterized by , that the secondary power can be switched between two stages by the switching device (6; 7; 8; 9), and that it is activated when the target value of the charging current (I) is exceeded B) by means of the value measured by the second measuring device, switching from the higher to the lower stage until an electrical operating parameter of the secondary inductance (1) or of a circuit (4, 5) connecting it to the battery (3), which in the lower stage depends on the primary power input and can be measured by the second measuring device, reaches a value at which switching to the higher stage results in a match of the charging current (I B ) with its setpoint, and that the primary controller (12) reduces the value of the feed-in primary power at a predetermined rate of time when a sudden change in the operating parameter measured by the first measuring device occurs, until another sudden change in the operating parameter measured by the first measuring device occurs. [7] Device according to claim 6, characterized by, that the operating parameter measurable by the second measuring device is the current (I) carried by the secondary inductor (1). S ) or the output current (I1) of a balancing network (5) connected downstream of the secondary inductor (1) or the output current (I2) of a converter (4) connected upstream of the battery (3). [8] Device according to any one of claims 3 to 7, characterized by , that in the presence of a below-target value of the charging current (I B ) the primary power input is increased by the primary controller (12) by a predetermined step or at a predetermined time rate through the codes displaying the measured value. [9] Device according to any one of claims 1 to 8, characterized by , that the operating parameter of the power supply device (11) measured by the first measuring device is the voltage (U) applied to the primary coil (10). P) or the output current (I3) or the input current (I4) of a converter (15) contained in the power supply unit or the current (I) drawn from the power supply network by the power supply unit (11) N ) is. [10] Device according to any one of claims 1 to 9, characterized by , that the switching device (6; 7; 8; 9) is a two-pole switch connected in parallel to the secondary inductance (1) or to the output of a balancing network (5) connected downstream of the secondary inductance (1) or to the output (I2) of a converter (4) connected upstream of the battery (3). [11] Device according to any one of claims 1 to 9, characterized by , that the switching device (6; 7; 8; 9) is a two-pole switch connected in parallel or in series to at least one element of a balancing network (5) connected downstream of the secondary inductance (1), so that the function of the balancing network (5) depends on the switch position.

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