METHOD FOR INDUCTIVE ENERGY TRANSFER

Description

[0001] The present invention relates to a method for inductive energy transmission between a primary part and a secondary part, wherein the primary part and the secondary part are parts of a transport system, preferably a linear motor system, a planar motor system or a magnetic levitation train, wherein the primary part corresponds to a fixed part of the transport system and the secondary part to a part of the transport system that is movable relative to this part, wherein the secondary part is moved relative to the primary part, wherein an electrical primary current is introduced from a supply unit into a transmitting coil arranged on the primary part to build up a first alternating magnetic field for energy transmission, whereby an electrical alternating voltage is induced in a receiving coil arranged on the secondary part,which causes an electrical secondary current at the secondary part and thus a power flow comprising an uncompensated active power to at least one consumer connected to the receiving coil.

[0002] Contactless energy transfer processes play an important role in a large number of technical applications. Charging systems for electric cars and transport systems in the form of linear or planar motor systems, in which moving components must be supplied with electrical energy, are just a few examples. Their advantages over conductive energy transfer systems include, in particular, a more compact design, often made possible by the elimination of cables and connectors, a resulting greater robustness, and often a longer service life due to a reduction in wearing parts. Although contactless energy transfer systems have been known for a long time, the constant demands for greater efficiency and lower losses are continually leading to new technological challenges.

[0003] A key challenge in this context, particularly important for transport systems, is the implementation of efficient and low-loss contactless energy transmission while taking feed-in and transmission limitations into account. Feed-in and transmission limitations often arise from the physical limitations of power electronic devices, particularly when these are located in supply units for the electrical supply of energy transmission systems. Examples of physical limitations in this regard include limited DC link voltages and thus limited supply voltages, limited electrical currents due to often limited thermal load capacity, and electromagnetic effects such as the skin or proximity effect.A direct consequence of a limited supply voltage in combination with a limited permissible current is a limitation of the available electrical (supply) power, which can severely impair the delivery of electrical energy from a supply unit to a power supply system.

[0004] To solve this problem, the state of the art often relies on the concept of "resonant coupling." In the case of inductive energy transfer, capacitive energy storage devices in the form of capacitors are connected to the commonly provided transmitting and receiving coils. Connecting the transmitting and receiving coils with capacitors creates resonant circuits, while the combination of the resonant circuits results in a resonant electrical circuit. The usual goal of resonant coupling at this point is to select the frequency of the supply voltage applied to the transmitting coil, often referred to as the excitation frequency, as close as possible to a resonant frequency of the resonant electrical circuit. This primarily increases the magnetic coupling between the transmitting and receiving coils, which can often result in efficient and low-loss energy transfer.

[0005] In the case of the aforementioned transport systems, for example in the form of a linear motor system, a planar motor system, or a magnetic levitation train, the implementation of resonant coupling is often significantly complicated, particularly due to the fact that relative movements between the components involved in energy transfer during operation are not only possible, but are usually the norm. Such relative movements often significantly influence the resonance frequencies of an energy transfer system. Due to the fact that resonant coupling typically requires precise and highly accurate matching between the excitation frequency and the resonance frequency, shifts in resonance frequencies can in many cases have a very negative impact on the amount of energy ultimately transferred.

[0006] In this context, stationary components of a transport system are often referred to as "primary parts," whereas components of a transport system that are movable relative to a primary part are commonly referred to as "secondary parts." Particularly in linear motor technology, electrical and / or electronic components are increasingly arranged on the movable secondary parts, for which an appropriate electrical power supply must be provided. Since, on the one hand, batteries on and in the secondary parts are often undesirable, and on the other hand, conductive energy transmission for supply is frequently not feasible, the question of contactless energy transmission, which should be low-loss and efficient, is of great importance, especially in linear and planar motor systems, despite the difficult conditions caused by possible relative movements between the primary and secondary parts. This circumstance is also reflected in the known state of the art.

[0007] For example, US 7958830 B2 describes an inductive energy transfer for a linear motor from a stationary primary part to a relatively movable secondary part. It mentions that the circuit for receiving energy on the secondary part is set to couple maximum energy, but it does not explain what this setting means specifically, for example, with regard to a possible tuning of an excitation frequency with a resonant frequency.

[0008] EP 2793356 B1 and EP 2903407 A1, on the other hand, also disclose a capacitive energy transfer for linear motors from a static primary part to a relatively movable secondary part. For this purpose, both the primary and secondary parts are equipped with electrode plates. In both publications, the electrode plates serve to create an electric field between the primary and secondary parts, through which the desired energy transfer takes place. Similar to US 7958830 B2, EP 2793356 B1 describes a tuning of the electrical components involved in the energy transfer to achieve a minimum impedance of the electrical circuit formed by the electrical components involved. However, here, too, no details are provided on how this adjustment is carried out.The document US 2012 / 217111 A1 also describes a system for supplying power to electric vehicles on the road, in which several modules arranged in or beneath a roadway are provided to provide inductive power to electric vehicles. However, the components of US 2012 / 217111 A1 must be stationary.

[0009] The concepts disclosed in the cited publications have several disadvantages in practical implementation. In the case of capacitive energy transfer, the necessary installation of additional electrode plates is particularly critical. The associated additional hardware expenditure cannot be implemented in a justifiable manner in many cases. In addition, electromagnetic interference is often an undesirable side effect of capacitive energy transfer systems, which often complicates and sometimes even prevents their use. Not least for these reasons, the present invention is directed toward inductive energy transfer systems.

[0010] A further disadvantage of known methods for both capacitive and inductive energy transfer in transport systems, as mentioned above, arises from the fact that relative movements typically occur between a supplying primary part and a supplied secondary part. This can change the transmission and coupling relationships between the components of an energy transfer system, which can result, among other things, in a shift in the electrical resonance frequencies of the energy transfer system. If contactless energy transfer in this context is based on resonant coupling, the excitation frequency must, for obvious reasons, be adapted to any changing resonance frequencies. Such an adaptation is not disclosed in the prior art.In addition to relative movements between the primary and secondary parts, heating, aging, wear and non-linear properties of electrical components can also cause changes in the transmission ratios, which further increases the need for a suitable adaptation mechanism.

[0011] Another significant problem in this context, which is not addressed in the prior art, concerns the type of energy or power transmitted. For obvious reasons, only transmitted active power makes a lasting contribution to the supply of a load located on a secondary part of a transport system. In contrast, reactive power, which is always transmitted during inductive energy transmission, is known to oscillate exclusively between the energy storage devices present in the energy transmission system and therefore does not contribute to a usable supply of a load. The focus of efficient inductive energy transmission must therefore primarily be on the transmitted active power, which is often not done sufficiently in the prior art.

[0012] In linear and planar motors, the problems mentioned are often exacerbated in practice by the requirement to avoid, as far as possible, the additional component complexity and costs associated with installing separate transmitting coils for inductive energy transfer. For this reason, existing drive coils are often also used as transmitting coils for inductive energy transfer to generate a propulsive force between a primary and a secondary part. Typically, however, these coils have a high stray inductance, which is caused in particular by an air gap that is large compared to other applications of inductive energy transfer. In this context, stray inductances refer to those parts of the transmitting and receiving coils that generate a magnetic flux that does not pass through the other coil and therefore only has a self-induction effect.As is well known, a so-called main inductance represents the portion of both coils that generates a magnetic flux passing through both coils, thus possessing both self- and mutual induction effects and thus establishing the coupling of the primary and secondary sections necessary for inductive energy transfer. With regard to the actual energy transfer, large stray inductances are disadvantageous for several reasons. In particular, they increase the reactive power generated, which directly reduces the transferable active power, especially when the supply voltage or power is limited.

[0013] If a transmitting coil is to simultaneously transmit energy and generate propulsive force, this is usually achieved by superimposing low-frequency currents, which are introduced into the drive coils to generate propulsive force and are therefore also referred to as drive currents, with higher-frequency currents, which in turn bring about the desired energy transfer. If, in such a case, the available supply voltage is limited and a large portion of this limited supply voltage is already used to generate currents for force generation, it is clear that the remaining voltage reserve must be optimally utilized to transmit active power.

[0014] It is therefore an object of the present invention to improve the contactless and, above all, inductive energy transfer between a primary and a relatively movable secondary part of a transport system. This should result in minimal additional hardware expenditure, enable robust and reliable adaptation to changing transmission conditions during operation, and, in particular, optimize the transmitted active power.

[0015] This object is achieved according to the invention by the features of the independent claims.This is based on a system for inductive energy transmission between a primary and a secondary part, wherein the primary part and the secondary part are parts of a transport system, preferably a linear motor system, a planar motor system or a magnetic levitation train, wherein the primary part corresponds to a fixed part of the transport system and the secondary part to a part of the transport system that is movable relative to this, wherein the secondary part is moved relative to the primary part, in which an electrical primary current is introduced into a transmitting coil arranged on the primary part by means of a supply unit, which electrical primary current brings about a first alternating magnetic field for energy transmission, which induces an electrical alternating voltage in a receiving coil arranged on the secondary part and thereby brings about a current and thus a first power flow to at least one consumer connected to the receiving coil.With regard to the first power flow, it applies that this would also occur without the application of the inventive method described below, but would only transport a so-called nominal active power. Such nominal active power is also referred to below as "uncompensated" active power.

[0016] Essentially, the present invention for such a system provides for the introduction of a secondary-side compensation current into the secondary-side receiving coil or into a possibly additional coil arranged on the secondary part by means of a compensation unit arranged on the secondary part, which is moved relative to the primary part. The purpose of the secondary-side introduction of compensation current is to generate a second alternating magnetic field, which induces a compensation voltage in the transmitting coil on the primary part. This compensation voltage changes the phase shift between the total voltage drop across the transmitting coil and the current flowing through the transmitting coil. According to the invention, this phase shift is changed in such a way that the effective power transferred from the primary to the secondary part during the energy transfer is increased.This approach takes into account the fact that the active power transmitted to a consumer on the secondary side is particularly important for supplying it.

[0017] According to the invention, no primary-side compensation current, which changes the phase shift between the electrical primary voltage drop across the transmitting coil and the primary current flowing through the transmitting coil, is introduced into the transmitting coil arranged on the primary part. This compensation current is provided by an electrical storage element connected in series with the transmitting coil and between the supply unit and the transmitting coil. Capacitors are preferably used as electrical storage elements for providing a compensation current. However, a capacitor connected in series with the transmitting coil would prevent the introduction of a direct current into the transmitting coil. For this reason, the omission of storage elements connected in series with the transmitting coil also allows DC electrical quantities, such as a direct electrical current, to be set in the transmitting coil.

[0018] In a particularly advantageous manner, the phase shift between the primary voltage drop across the transmitting coil and the primary current flowing through the transmitting coil is changed only, i.e., exclusively, by the primary-side compensation voltage caused by the secondary-side compensation current and induced in the transmitting coil. In this case, electrical storage elements for providing a compensation current are completely dispensed with on the primary side, which includes the elimination of storage elements connected both in series and in parallel with the transmitting coil.

[0019] The ability to supply a transmitting coil with direct current via the supply unit is particularly crucial when using the energy transmission system in transport systems, such as a linear motor system, a planar motor system, or a magnetic levitation train. In these cases, transmitting coils are often also used to generate a driving force, which in many cases also requires direct currents to be introduced into the transmitting coils.

[0020] Advantageously, additional storage elements provided on the primary part for providing a primary-side compensation current are completely dispensed with. In this case, no storage elements connected in series or parallel to the transmitting coil, such as capacitors or other storage elements, are provided. Although storage elements connected in parallel to the transmitting coil would not fundamentally preclude the use of the energy transmission system in question in one of the aforementioned transport systems, in many cases the use of storage elements connected in parallel to transmitting coils is associated with considerable effort, particularly since linear motor systems have a large number of transmitting coils, meaning that in such a case a large number of storage elements would have to be provided overall.

[0021] Reactive power transmitted during inductive energy transmission is known to oscillate back and forth between electrical storage elements and therefore makes no lasting contribution to supplying secondary-side loads. The present invention takes this circumstance into account and therefore focuses, as described, on the transmitted active power. It has been shown that, to increase the transmitted active power, the phase relationship between the voltage drop across the transmitting coil and the current flowing through the transmitting coil is particularly important. Maximum transmitted active power is achieved when this phase relationship is either zero or plus / minus 180 degrees. By introducing a secondary-side compensation current, this phase relationship is modified such that the transmitted active power is increased compared to operation without the introduction of compensation current.In this case, the (paradoxical) case may even occur that the total apparent power transmitted is lower compared to the operation of an inductive energy transmission system without the inventive compensation current input. Resonant coupling is not explicitly sought and, in particular, is not a necessary prerequisite for the use of the inventive method.

[0022] In other words, the secondary side supports the primary side with an additional voltage induced in the main inductance of the power transmission system during the recharging of the main inductance. This frees up a voltage reserve in the supply unit, which is used to increase the transmitted active power. Since this freed-up voltage reserve, used to increase the transmitted active power, is subsequently in phase with the current already flowing, the phase difference between the total voltage drop across the transmitting coil and the current flowing through the transmitting coil changes in the manner described above.

[0023] In this context, it should be noted that the power introduced with the secondary-side compensation current itself represents a mostly capacitive reactive power. For the present invention, it is crucial that this mostly capacitive reactive power is deliberately transferred from the secondary side to the primary side. In addition to the inventive change in the aforementioned phase relationship, this often results in the reactive power occurring in the main inductance and often also in the primary-side stray inductances no longer having to be provided exclusively by the supply unit. The advantageous side effect of at least partial secondary-side compensation of primary-side reactive power can often contribute to a further improvement in energy transfer.

[0024] Advantageously, at least 50% of the reactive power of the main inductance is provided on the secondary side, i.e., by the secondary part. Preferably, however, at least 75% of the reactive power of the main inductance can also be provided by the secondary part, or at least 90% of the reactive power of the main inductance can be provided by the secondary part. Most preferably, the entire reactive power of the main inductance is provided by the secondary part.

[0025] Advantageously, less than 20% of the reactive power of the primary-side stray inductances is always provided on the secondary side, i.e., by the secondary part. However, less than 15% of the reactive power of the primary-side stray inductances can also be provided by the secondary part, or less than 10% of the reactive power of the primary-side stray inductances can be provided by the secondary part. Thus, within the scope of the invention, a significantly larger portion of the reactive power of the main inductance is typically compensated than by the reactive power of the primary-side stray inductances.

[0026] Within the scope of the present invention, it is thus possible to dispense with primary-side reactive power compensation. Of course, primary-side reactive power compensation can also be dispensed with if the secondary part does not fully compensate the reactive power of the main inductance, e.g., if complete compensation of the reactive power of the main inductance is not desired. Advantageously, this eliminates the need for components for reactive power compensation on the primary part, such as capacitors connected in parallel or series with the primary-side transmitting coil.

[0027] To implement the steps described above, a secondary-side compensation unit is used, as mentioned above, which supplies a secondary-side compensation current to a receiving coil provided on the secondary part or receives it from it. Such a compensation unit can be implemented in various ways, for example, in the form of a controllable alternating current source, which itself is supplied with previously inductively transmitted energy, or by capacitors with at least partially variable capacitance. In this context, combinations of different approaches for introducing a secondary-side compensation current are also conceivable, particularly to combine the advantages of several different technologies.At this point, it is noteworthy that although the compensation unit according to the invention is only provided on the secondary part, a precise modification, in particular of the phase relationships between primary-side variables, is still possible.

[0028] The use of a compensation unit located solely on the secondary part represents a significant advantage, particularly in the implementation of efficient energy transfer in long-stator linear motors. Such drive systems are typically characterized by a large number of drive coils located on the primary part. In practice, these drive coils are often used simultaneously as transmitting coils for inductive energy transfer to generate a propulsive force. This is usually achieved by superimposing electrical currents to generate a propulsive force with higher-frequency currents for energy transfer.If only a single compensation unit is required on the secondary side in such a system and a compensation unit does not have to be connected to each of the many drive coils on the primary side, as would be necessary in the form of capacitors in the context of the aforementioned resonant inductive coupling, immense hardware, cost and design effort can often be avoided.

[0029] A further advantage of the inventive concept is its improved adaptability to changing transmission ratios compared to many conventional concepts, for example, due to relative movements between the primary and secondary sections. This advantage arises, on the one hand, from the fact that only the secondary-side compensation current needs to be adjusted for adaptation, for example, by varying the frequency and / or phase position and / or amplitude of the compensation current delivered by the compensation unit. Particularly in linear motor systems, the need to optimize components on a large and extended primary section can lead to difficulties in practical implementation.On the other hand, practical use has shown that the modification of a phase shift between two electrical quantities of a primary part can be carried out much more robustly than a highly sensitive tuning of an excitation frequency to a possibly rapidly changing resonance frequency.

[0030] The present invention is described below with reference to the Figuren 1 bis 6 which show exemplary, schematic and non-limiting advantageous embodiments of the invention. Fig. 1 an inductive energy transfer system Fig. 2 possible designs of the compensation unit Fig. 3 a possible design of a secondary consumer Fig. 4 a simplified abstraction of the considered inductive energy transfer system Fig. 5 a long stator linear motor system Fig. 6 the implementation of the inductive energy transmission system according to the invention in a long stator linear motor system.

[0031] Fig. 1 shows the basic structure of an inductive energy transmission system 1. From a supply unit S, an electrical alternating voltage is supplied to the part of the energy transmission system 1 located on the primary part I u S The most important fact is that the alternating voltage u S is typically limited in magnitude, particularly in accordance with the initial statements regarding the physical limits of power electronics used for supply, and therefore cannot be increased arbitrarily during energy transmission. The frequency of the supply voltage u S is also referred to as "excitation frequency" below.

[0032] The supply voltage u S subsequently causes a primary current i S in the form of an alternating electrical current through the primary-side ohmic resistance R 1 , which represents all ohmic resistances concentrated on the primary part I, and the primary-side transmitting coil L 1 . The ohmic resistance R 1 is in the Fig.1 shown embodiment between the transmitting coil L 1 and the supply unit S are switched so that the ohmic resistance R 1 and the transmitting coil L 1 form a series circuit.

[0033] The excitation frequency of the supply voltage u S sets the frequency of the primary current i S The frequency of the primary current i S corresponds to the frequency of the supply voltage u S , which corresponds to the excitation frequency.

[0034] In the Fig.1 In the embodiment of the invention shown, the primary-side ohmic resistance is between the supply unit S and the transmitting coil L 1 R 1. The primary-side ohmic resistance R 1 is arranged in series with the transmitting coil L 1. Otherwise, on the primary part I between the transmitting coil L 1 and the supply unit S no further electrical storage elements, such as capacitors etc., are provided, and thus in particular no further electrical storage elements such as the ohmic resistance R 1 in series with the transmitter coil L 1. Since only the ohmic resistance R 1 is connected between the supply unit S and the transmitting coil L 1, it is possible to also feed direct currents into the transmitting coil L 1, which is particularly important for applications in transport systems.

[0035] Subsequently, the primary voltage drops at the primary coil u L 1. In order to improve the magnetic coupling between primary I and secondary II and / or to reduce the air gap between them, the transmitting coil L 1 optional iron core E 1. Possible embodiments of an iron core E 1 can be provided by ferrites, powder cores, or even laminated structures, although the term "magnetic core" is also commonly used instead of the term iron core. The same can be applied to the receiving coil. L 2 on the secondary part II through the iron core E 2 should be provided.

[0036] The primary current i S In the next step, the first alternating magnetic field is formed for energy transfer. This first alternating magnetic field contributes to the formation of a time-varying magnetic flux Φ which the transmitting coil L 1 and the receiving coil L 2. The two coils L 1 and L 2 are separated by the air gap Δ L According to the law of induction, the receiving coil L 2 an electrical voltage u i = − N 2 ⋅ d dt Φ which in turn induces a secondary current i V on the part of the energy transfer system 1 located on the secondary part II. N 2 represents the number of turns of the receiving coil L 2. The current i V flows further over the resistor R 2 , which, like the resistance R 1 cumulatively represents the ohmic resistances of the secondary part, to at least one consumer V, at which the voltage u V drops. The at least one consumer V can represent a variety of electronic devices, for example a communication, measuring or control unit, or even an accumulator or energy storage device that is charged with the transmitted energy.

[0037] The inventive introduction of a secondary-side compensation current i K In the case shown, this is done by the compensation unit K. The secondary compensation current i K This subsequently causes a second alternating magnetic field for effective power optimization, which is superimposed on the first alternating magnetic field for energy transfer, thus creating a resulting total alternating magnetic field. The second alternating magnetic field for effective power optimization creates a L 1 an additional alternating voltage, subsequently referred to as "primary compensation voltage" u K The magnetic field in the transmitting coil L 1 induced primary side compensation voltage u K represents a further component of the entire transmitting coil L 1 falling primary voltage u L 1 and thus influences the phase shift between the signal at the transmitting coil L 1 falling primary voltage u L 1 and the transmitting coil L 1 flowing primary current i S According to the invention, this phase shift is modified so that the resulting transmitted active power is increased.

[0038] In order to define the concept of increasing the transmitted active power more concretely, the concept of nominal or uncompensated active power is first defined. P N introduced. The uncompensated active power P N describes the active power which, in a conventional operation of an inductive energy transmission system known from the prior art, without introducing the compensation current according to the invention i K would be achieved. Nominal or uncompensated active power P N For this reason, it is also referred to as active power without compensation or active power without changed phase shift. If the method according to the invention is applied and a secondary-side compensation current is i K into the receiving coil L 2, the transmitted active power is converted into a resulting output active power P R According to the invention, the resulting output active power P R an increase in the originally transmitted, uncompensated active power P N by at least 10% to 100%, preferably by 100% to 500% and particularly preferably by 500% to 5000% or more.

[0039] Since the compensation unit K in a preferred embodiment represents an active component which itself must be supplied with electrical energy, Fig. 1 A connecting line Y from the consumer V to the compensation unit K is shown in dashed form, which, if necessary, enables an electrical supply to the compensation unit K. However, it is also possible for the compensation unit K to simultaneously extract the transmitted energy and function as a rectifier G. In such cases, the consumers V can also be connected directly to the compensation unit K. This can occur, for example, if the compensation unit K contains a controllable alternating current source that can also function as the rectifier G.

[0040] For the concrete implementation of the compensation unit K, several concepts known from electronics can be used. The decisive criterion for the realization of the compensation unit K is that a compensation current with the appropriate phase, amplitude and frequency i K to the secondary part of the circuit of the energy transmission system 1. More complex implementation variants can be provided by controllable alternating current sources. Less complex implementations, on the other hand, are possible, for example, by L 2 parallel-connected, capacitive storage elements are possible, whose capacity is adjusted during operation in order to always provide a desired secondary-side compensation current i K to pick up or drop off.

[0041] Two implementation variants are described in Fig. 2 shown, where Fig. 2a a connection of three capacitors C by means of two switches T 1 and T 2 shows. Depending on the switch position, different capacitive resistances result. Furthermore, a number of other possible approaches exist for the implementation of variable capacitances. Mechanically variable capacitors, such as trimming or variable capacitors, which can be based on a variety of materials for dielectrics and electrode plates, and electrically variable capacitors, such as capacitance diodes, are only a few examples. A preferred embodiment of a variable capacitance is provided by conventional capacitors, such as electrostatic fixed capacitors, in which an additive capacitive current is fed in, thus varying their capacitance. This implementation variant is described in Fig. 2b illustrated by a variable current source connected in parallel with the capacitor C. In addition to capacitive storage elements, variable inductive storage elements are also conceivable for implementing a compensation unit K. Examples of these include coils in which the positioning of an iron core is changed, or in which, analogous to the introduction of an additive capacitive current in capacitors, an additive voltage is applied to change the inductance.

[0042] In certain cases, it may prove particularly advantageous to connect capacitors and coils in parallel or in series in a compensation unit K. Possible implementations of a compensation unit K further include, in particular, microprocessor-based hardware, microcontrollers, and integrated circuits (ASIC, FPGA, etc.), especially to determine and ultimately correctly introduce a suitable compensation current. i K to enable, for example, by controlling a controllable AC power source. In the present case, analog circuits, for example based on analog operational amplifier circuits, are also to be mentioned as components of the compensation unit K. At this point, it should be mentioned that the introduction of the compensation current i K directly into the receiving coil L 2 represents a preferred embodiment of the present invention, but it is also possible to use the compensation current i K into another coil provided specifically for this purpose on the secondary part II and to generate the second alternating magnetic field according to the invention using this additional coil.

[0043] A possible concrete design of a consumer V is shown in Fig. 3 In this case, the rectifier G rectifies the transmitted alternating quantities u V and i V to equal quantities u G and i G which ultimately one or more electrical loads provided on the secondary part II R L In many cases, a voltage regulator is also connected upstream of a consumer V.

[0044] In order to describe the basic principle of the present invention in more detail, Fig. 4 For clarification, a further abstraction step was taken and the Fig. 1 The structure shown is shown in a highly simplified manner. The supply unit S and the compensation unit K are shown as current sources, although voltage sources could also be used for both elements. For the following steps, it is particularly important that the current impressed by the supply unit i S does not change or changes only slightly. For the sake of a simple explanation, we have omitted to consider influences that commonly occur in reality, such as parasitic elements, leakage currents, non-sinusoidal input voltages, etc. The following explanations can, however, easily be expanded to include such influences and are therefore not to be understood as restrictive. Furthermore, it is assumed that the transmitting coil L 1 and the receiving coil L 2 have the same number of turns, meaning that no transformation ratio needs to be considered. A generalization of the following statements to a transformation ratio is trivial for the expert. In order to minimize the influence of the compensation current introduced on the secondary side, i K To emphasize clearly, the voltage induced by this on the primary side I u K with its own voltage source in series with the transmitting coil L1. The transmitter coil L 1 falling primary voltage is again u L 1, where the primary voltage that would occur without applying the method according to the invention is ũ L 1. If we first assume operation without secondary compensation current i K and purely sinusoidal quantities with a frequency f in Hz, can be used for the primary current i S and the primary voltage u L 1 without restriction of generality i S t = I ^ ⋅ sin 2 πf ⋅ t + π 180 φ i and u L 1 t = u ˜ L 1 t = U ^ L ⋅ sin 2 πf ⋅ t + π 180 φ u be written, where Î and Û L represent the amplitudes of the two quantities, the angles φ i and φ u whose phase positions are described in degrees and the expression Δφ = φ u - φ i describes their phase shift relative to each other. As is well known, the transmitting coil L 1 on the receiving coil L2 pure reactive power is transmitted when Δφ = ±90 degrees. However, if Δφ = 0 or Δφ = 180 degrees, the latter being identical to Δφ = -180 degrees, the transmitted power becomes pure active power. If one further considers that for the secondary compensation current i K induced primary-side compensation voltage u K the expression u K = L 12 d dt i K applies, where L 12 the coupled mutual inductance of the transmitter coil L 1 and receiving coil L 2, in the case of a compensation current i K i K t = I ^ K ⋅ sin 2 πf ⋅ t + π 180 φ K with the same frequency f also for the compensation voltage u K a sinusoidal description can be given, in particular as u K t = U ^ K ⋅ sin 2 πf ⋅ t + π 180 φ uK .

[0045] The amplitude Û K and the phase shift φ u K depend here according to the relationship between u K and i K from the amplitude Î K and the phase shift φ K This means that the total voltage drop across the transmitter coil is now u L 1 t = u ˜ L 1 t + u K t = U ^ L ⋅ sin 2 πf ⋅ t + π 180 φ u + U ^ K ⋅ sin 2 πf ⋅ t + π 180 φ uK applies, which is also known as u L 1 t = U ^ LK ⋅ sin 2 πf ⋅ t + π 180 φ uLK with the amplitude U ^ LK = U ^ L ⋅ cos π 180 φ u + U ^ K ⋅ cos π 180 φ uK 2 + U ^ L ⋅ sin π 180 φ u + U ^ K ⋅ sin π 180 φ uK 2 and the phase position φ uLK = arctan U ^ L ⋅ sin π 180 φ u + U ^ K ⋅ sin π 180 φ uK U ^ L ⋅ cos π 180 φ u + U ^ K ⋅ cos π 180 φ uK The expressions for the amplitude Û LK and phase position φ uLK depend directly on the amplitude Û K and the phase shift φ uK and thus also from the compensation current i K This shows that the compensation current i K on the one hand the phase position φ uLK the resulting primary voltage u L 1 and on the other hand the phase relationship Δφ between i S and the primary voltage u L 1 can be modified. This can ultimately directly influence how much active and how much reactive power is transferred. It should be noted again at this point that the Fig. 4 The situation shown is a highly simplified representation to illustrate the basic principle of the method according to the invention.

[0046] The core of the control task to be solved by the compensation unit K can therefore be formulated as the determination of the secondary-side compensation current i K , which maximizes the transmitted active power. To solve this core task, since the frequency is determined by the primary voltage u S or the primary current i S is usually already specified, preferably the amplitude and phase position of the secondary compensation current i K adjusted.

[0047] To make a suitable choice for the amplitude and phase position of the secondary compensation current i K To determine the optimal power level, various adaptation algorithms can be used, for example, a so-called "Maximum Power Point Tracker" or other controllers and / or (autonomous) learning mechanisms designed specifically for this purpose. To check whether a specific selection or change in the amplitude or phase position of the secondary compensation current i K a desired change in the phase relationship Δφ between primary current i S and primary voltage u L 1 has actually been achieved, can be seen, for example, from measurement data of primary current i S and primary voltage u L 1 whose phase relationship is calculated.

[0048] To obtain the required secondary compensation current i K in the compensation unit K, the compensation unit K can be supplied with measurement data of relevant electrical quantities, in particular primary-side quantities uL 1 and / or i S , but also from secondary variables such as u i , u V or i V , For this purpose, suitable measuring sensors can be provided, preferably on the secondary side II, but also on the primary side I, which transmit their measured values ​​to the compensation unit K. In a preferred embodiment of the method according to the invention, the primary-side voltage u S and the primary current i S measured and transmitted wirelessly, for example by means of a radio connection, to the compensation unit K in order to avoid cabling between the primary part I and the secondary part II, in particular when implementing the method according to the invention in a transport system 2.

[0049] A particularly advantageous implementation of the method according to the invention also results from an indirect determination of primary-side voltage u S and primary current i S , for example, from measurement data recorded on the secondary side II of induced voltage u i and secondary current i V using an observer or a filter on the primary voltage u S and the primary current i S is expected, meaning that neither a radio connection nor cabling between primary I and secondary part II is necessary to implement the method according to the invention.

[0050] In a further advantageous embodiment, primary-side electrical quantities such as voltage u S and electricity i S Instead, a direct current can be used u G , which, as in Fig. 3 shown, preferably generated by a rectifier G arranged on the secondary side II, can be used as a measure of the quality of the primary-side phase shift. This approach is based on the finding that in the case of an increased output active power transmitted to the load V and thus to the rectifier G P R from the rectifier G in many cases a higher DC voltage u g A higher DC voltage u g can therefore be a measure of increased active power transmission. Here, too, the voltage u g does not necessarily have to be measured directly, but can also be determined indirectly by means of filtering or observation.

[0051] Furthermore, it is of course not excluded that, despite the adaptation of a secondary compensation current on the secondary part II i K or a compensation unit K, in addition also the excitation frequency of the input voltage u S This allows the excitation frequency to be adapted to an emerging electrical resonance frequency of the energy transmission system 1. However, with this approach, care must be taken that the resulting changes in the primary-side electrical variables do not impair the actual objective of the present invention, namely the adaptation of the phase shift between the primary-side variables primary voltage u L 1 and primary current i S , is negatively affected.

[0052] Within the scope of the present invention, however, it may also be advantageous to adjust the excitation frequency, i.e. the frequency of the primary electrical current i S and / or the frequency of the supply voltage u S , different from an electrical resonance frequency of the energy transfer system 1. The frequency of the primary electrical current i S can be at least 1% of the value of the frequency of the electrical primary current i S or by at least 5% of the value of the frequency of the primary electric current i S or by at least 10% of the value of the frequency of the primary electric current i S or by at least 50% of the value of the frequency of the primary electric current i S deviate from an electrical resonance frequency of the energy transfer system 1.

[0053] Generally speaking, it may be advantageous within the scope of the present invention to operate the energy transmission system 1 at a frequency outside the electrical resonance frequencies of the energy transmission system 1.

[0054] In several applications of the present invention, it has been found that a maximum of active power transferred from the primary side I to the secondary side II is achieved when the excitation frequency and thus the frequency of the electrical primary current i S by more than 1%, or by more than 3%, or by more than 5% of the value of the frequency of the primary electrical current i S deviates from the lowest non-zero resonance frequency of the energy transfer system 1. In these cases, the energy transfer system 1 is deliberately operated outside its resonance frequencies and thus outside its resonance points.

[0055] Advantageously, the energy transmission system 1 is operated at a frequency that is higher, e.g., by 1% or by 3% or by 5%, than the lowest electrical resonance frequency of the energy transmission system 1.

[0056] As mentioned at the beginning, electromagnetic transport systems 2 such as linear or planar motor systems are a preferred application area of ​​the inventive method for inductive energy transmission. To further address the specific features of the implementation of the invention, Fig. 5 First, a general description of a possible design of a transport system 2. The transport system 2 consists of a number of transport segments TSk (k is an index that stands for all existing transport segments TS1, TS2, TS3, ...), of which, for reasons of clarity, only the transport segments TS1 ... TS7 are shown as examples. The transport segments TSk form various route sections, for example, a straight line, curves with different angles and radii, switches, etc., and can be combined very flexibly to form the transport route of the transport system 2. Together, the transport segments TSk thus form a transport route along which the transport units Tn (n is an index that stands for all existing transport units T1, T2, T3, T4, ...) can be moved. This modular structure enables a very flexible design of the transport system 2.The transport segments TSk are usually attached to a stationary support structure 6 (in . Fig. 5 not shown).

[0057] In the present case, the transport system 2 is designed as a long stator linear motor, wherein the stator segments TSk each form a part of a long stator of a long stator linear motor in a manner known per se. Therefore, a plurality of stationary electrical drive coils 7, 8 forming the stator are arranged in the longitudinal direction in a known manner along the long stator of the transport segments TSk (in Fig. 5 for reasons of clarity only indicated for the transport segments TS1, TS2, TS4, TS5, TS6, TS7), through which a drive current flows and which is connected to the drive magnets 4, 5 on the transport units T1 ... Tn (in Fig. 5 (for reasons of clarity, only indicated for the transport unit T6) can interact to generate a propulsive force FV in a known manner to move the transport unit Tn. Typically, the electric drive current also includes a DC component, i.e., a direct current.

[0058] In addition to transport systems 2 designed as long stator linear motors, transport systems implemented as planar motors represent another important application of the method according to the invention. A planar motor essentially has a stator that forms a transport plane in which one or more transport units can be moved at least two-dimensionally. With regard to the travel according to the invention, the transport units function as secondary parts II. The stator is generally constructed from one or more transport segments that take on the role of the primary parts I. In order to move the transport units in the transport plane, a driving force acting on the transport unit is generated by the interaction of a magnetic field of the stator (of the transport segment(s)) and a magnetic field of the transport unit.To cause the transport unit to move in a specific direction, at least one of the magnetic fields, i.e., that of the stator and / or that of the transport unit, must be temporally variable to follow the movement of the transport unit. However, usually only one magnetic field, usually that of the stator, is temporally variable, while the other magnetic field (that of the transport unit) is usually constant, i.e., does not vary over time.

[0059] How the method for inductive energy transmission of the present invention can be implemented in a transport system 2 is described in Fig. 6 shown in detail. Fig. 6 shows a detailed view of two adjacent straight transport segments TSk, TSk+1. The transport segments TSk, TSk+1 are arranged on a stationary support structure 6 to form a transport path or themselves form part of the stationary support structure 6. A magnetically conductive and elastic material 3 can preferably be attached between the transport segments TSk, TSk+1. The drive coils 7 of the long stator linear motor are arranged on the transport segments TSk and TSk+1, respectively. The drive magnets 4 are arranged on the transport unit Tn. A drive magnet 4 can be designed as an electromagnet (excitation coils) and / or as a permanent magnet. The drive coils 7 are preferably arranged on teeth 12 of a ferromagnetic core 13 (for example, an iron laminated core). The drive coils 7 can, of course, also be designed without a core.Of course, guide elements such as rollers, wheels, sliding surfaces, guide magnets, etc. (not shown here for reasons of clarity) can also be provided on the transport unit Tn in order to guide and hold the transport unit Tn along the transport path 20, in particular even when stationary. In order to generate a magnetic flux that is as uniform as possible in the longitudinal direction x of the transport path 20, i.e. in the direction of movement of the transport unit Tn, and consequently a uniform propulsion force Fv, the drive coils 7 are usually arranged on the transport segments TSk, TSk+1 at a regular distance from one another in the longitudinal direction (or direction of movement) x, usually referred to as the slot pitch τ n.

[0060] How Fig. 6 shows, the transport units Tn take on the role of the secondary parts II with regard to the inventive method for inductive energy transmission, which are analogous to the Fig. 1 The function of the primary part I is taken over by the extended long stator, where, as mentioned, the drive coils 7 can also be used for energy transmission by superimposing a higher-frequency current for energy transmission on a low-frequency drive current to generate a propulsive force Fv. In order not to unnecessarily energize drive coils 7 that are far away from a transport unit Tn and therefore cannot contribute to energy transmission, usually only drive coils in the immediate vicinity of a transport unit Tn are energized. It should be noted that for energy transmission, several adjacent drive coils 7 can also be used as transmitting coils. L 1 can work together.

[0061] Several special features associated with the transport system 2 further emphasize some of the previously mentioned advantages of the method according to the invention. Thus, when designing and constructing transport systems 2, it is often desirable to select the slot pitch τ n as small as possible in order to be able to realize the most precise positioning of a transport unit Tn. When reducing the slot pitch τ n, the drive coils 7 move closer together, which leads in particular to an increase in primary-side stray inductances, which entail an increased reactive power requirement, with all the aforementioned negative consequences with regard to inductive energy transmission. Since in transport systems 2 the supply voltage u S limited and stray inductances are comparatively large, in such cases almost the entire available voltage u S However, the method according to the invention also makes it possible in such cases, despite sometimes considerable primary-side reactive power and other restrictions, such as limited supply voltages u S or limited primary currents i S to also transmit active power to an extent that still makes it possible to supply one or more secondary consumers with sufficient electrical energy.

[0062] Another point that becomes particularly apparent in the case of transport systems 2 is the frequent need for adaptation to changes in the transmission ratios, which in this context result from the inherent relative movements between the primary part I and the secondary part II. If a single secondary-side compensation unit K is sufficient to realize efficient energy transmission as described, adaptation can be carried out comparatively easily, since in concrete terms only the compensation unit K or the compensation current provided by it i K must be adapted to changing transmission ratios. Furthermore, this avoids the immense hardware complexity that would be associated with installing a compensation unit K on the primary side for each drive coil 7.

[0063] The aforementioned extension of the method according to the invention to simultaneously adapt the excitation frequency to a resulting electrical resonance frequency of the energy transmission system 1 can represent a valuable extension option in the case of long-stator linear motors and planar-type motors. Since the transmission ratios can continuously change due to movements between the primary part I and the secondary part II, a further improvement in energy transmission can be achieved by additionally adjusting the excitation frequency and a resonance frequency of the energy transmission system 1.

Claims

1. A method for inductive energy transmission between a primary part (I) and a secondary part (II), the primary part (I) and the secondary part (II) being parts of a transport system (2), preferably of a linear motor system, a planar motor system or a magnetic levitation railroad system, the primary part (I) corresponding to a stationary part of the transport system (2) and the secondary part (II) corresponding to a part of the transport system (2) that is movable relative thereto, the secondary part (II) being moved relative to the primary part (I), a primary electrical current (iS) being fed from a supply unit (S) into a transmitting coil (L1) arranged on the primary part (I) in order to create a first alternating magnetic field for energy transmission, whereby an electrical AC voltage (ui) is induced in a receiving coil (L2) arranged on the secondary part (II), which AC voltage (ui) causes an electrical secondary current (iV) on the secondary part (II) and thus a power flow comprising an uncompensated active power (PN) to at least one load (V) connected to the receiving coil (L2), characterized in that a secondary-side compensation current (iK) is fed into a secondary-side coil (Lk) by a compensation unit (K) arranged on the secondary part (II) which is moved relative to the primary part (I), in that a second alternating magnetic field is generated by the secondary-side compensation current (iK) in the secondary-side compensation current (Lk), which second alternating magnetic field is superimposed on the first alternating magnetic field for energy transmission and induces a primary-side compensation voltage (uK) in the transmitting coil (L1), in that a phase shift between the electrical primary voltage (uL1) dropping across the transmitting coil (L1) and the primary current (iS) flowing through the transmitting coil (L1) is changed by the primary-side compensation voltage (uK) induced in the transmitting coil (L1) in such a way that a resulting output active power (PR), which is transmitted by the primary part (I) after the change of the phase shift on the at least on load (V) connected to the receiving coil (L2) is increased compared to the uncompensated active power (PN) without a changed phase shift and in that no primary-side compensation current, which changes the phase shift between the electrical primary voltage (uL1) dropping across the transmitting coil (L1) and the primary current (iS) flowing through the transmitting coil (L1) and which is provided by an electrical storage element connected in series to the transmitting coil (L1) and between the transmitting coil (L1) and the supply unit (S), is fed into the transmitting coil (L1) arranged on the primary part (I).

2. The method according to claim 1, characterized in that the phase shift between the electrical primary voltage (uL1) dropping across the transmitting coil (L1) and the primary current (iS) flowing through the transmitting coil (L1) is changed only by the primary-side compensation voltage (uK) caused by the secondary-side compensation current (iK) and induced in the transmitting coil (L1).

3. The method according to claim 1 or claim 2, characterized in that an electrical drive current is introduced into the transmitting coil (L1) in addition to the primary current (iS) in order to create a first alternating magnetic field by means of which the drive force (Fv) acting on the secondary part (II) is generated.

4. The method according to claim 3, characterized in that a direct current is introduced into the transmitting coil (L1) with the electrical drive current.

5. The method according to any of the preceding claims, characterized in that the electrical primary voltage (uL1) dropping across the transmitting coil (L1) and the primary current (iS) flowing through the transmitting coil (L1) are determined and transmitted to the compensation unit (K), in that from the transmitted data of primary voltage (uL1) and primary current (iS), the phase shift between primary voltage (uL1) and primary current (iS) is determined, and in that on the basis of the phase shift between primary voltage (uL1) and primary current (iS), the secondary-side compensation current (iK) is changed in order to bring the phase shift between primary voltage (uL1) and primary current (iS) closer to zero or closer to 180 degrees.

6. The method according to any of the preceding claims, characterized in that the secondary-side compensation current (iK) fed by the compensation unit (K) into the receiving coil (L2) is adapted to changes in the transmission conditions between the transmitting coil (L1) and the receiving coil (L2) which are caused in particular by aging, temperature influence or wear of the transmitting coil (L1) and receiving coil (L2), the supply unit (S) or the at least one load (V) and / or by changes in the relative position between primary part (I) and secondary part (II).

7. The method according to any of the preceding claims, characterized in that the frequency of the primary current (iS), which is fed from the supply unit (S) into the transmitting coil (L1) arranged on the primary part (I) is adjusted to conform to an arising resonance frequency of a resonant electrical circuit, which is formed by at least the transmitting coil (L1), the receiving coil (L2), the compensation unit (K) and the at least one load (V).

8. A device for inductive energy transmission, comprising a primary part (I) and a secondary part (II), the primary part (I) and the secondary part (II) being parts of a transport system (2), preferably a linear motor system, a planar motor system, or a magnetic levitation railroad system, and the primary part (I) corresponding to a stationary part of the transport system (2) and the secondary part (II) corresponding to a part of the transport system (2) that is movable relative thereto, a supply unit (S) being provided on the primary part (I) in order to feed an electrical primary current (iS) into a transmitting coil (L1) arranged on the primary part (I) in order to create a first alternating magnetic field for energy transmission, a receiving coil (L2) and at least one load (V) which can be connected electrically to the receiving coil (L2) being arranged on the secondary part (II), an electrical AC voltage (ui) being induced in the receiving coil (L2) by the first alternating magnetic field for energy transmission, which AC voltage (ui) causes an AC current (iV) on the secondary part (II) and thus a power flow comprising an uncompensated active power (PN) to the at least one load (V) which can be connected to the receiving coil (L2), characterized in that at least one compensation unit (K) is arranged on the secondary part (II), which compensation unit is designed to feed a secondary-side compensation current (iK) into a secondary-side coil (Lk) and thereby generate a second alternating magnetic field which is superimposed on the first alternating magnetic alternating field for energy transmission and which induces a primary-side compensation voltage in the transmitting coil (L1), a phase shift between the primary voltage (uL1) dropping across the transmitting coil (L1) and the primary current (iS) flowing through the transmitting coil (L1) being changed by the primary-side compensation voltage (uK) induced in the transmitting coil (L1) such that the resulting output active power (PR), which is transmitted from the primary part (I), after the change of the phase shift between the primary voltage (uL1) dropping across the transmitting coil (L1) and the primary current (iS) flowing through the transmitting coil (L1) to the at least one load (V) which can be connected to the receiving coil (L2), is increased compared to the uncompensated active power (PN) without a changed phase shift, and in that no electrical storage elements connected in series with the transmitting coil (L1) are provided on the primary part (I) between the transmitting coil (L1) and the supply unit (S) in order to feed a primary-side compensation current for changing the phase shift between the electrical primary voltage (uL1) dropping across the transmitting coil (L1) and the primary current (iS) flowing through the transmitting coil (L1) into the transmitting coil (L1).

9. The device according to claim 8, characterized in that the at least one compensation unit (K) comprises at least one electrically variable capacitor, and / or at least one electrically variable coil, and / or an interconnection of at least one electrically variable capacitor and one electrically variable coil.