Bidirectional electric converter device with dual active bridge converter in series with dc / ac bridge converter

Abstract

The invention relates to a bidirectional n-phase electric converter device (1) having the following features: - input terminals (18) for connecting a DC voltage source, - a DC / DC converter (10; 110; 210) which is connected to the input terminals (18) and which comprises first switch elements (31; 134), - p intermediate circuits (90; 190; 290) which are connected to the DC / DC converter (10; 110; 210) on the output side, - a DC / AC converter (40; 140; 240) comprising second switch elements, wherein - the DC / AC converter (40; 140; 240) is connected downstream of the p intermediate circuits (90; 190; 290), and - the DC / AC converter (40; 140; 240) has output terminals for connecting an electric machine (60; 160; 260) or an electric AC network (270), and - a control device (80; 280) for actuating the second switch elements (32; 135) of the DC / AC converter (40; 140; 240) such that a step-shaped n-phase output voltage (410) can be provided. The DC / AC converter (40; 140; 240) is designed as a base frequency-clocking rotor-controlled n-phase voltage system.

Description

[0001] EMX0211Bidirectional electrical converter device The invention relates to a bidirectional electrical converter device according to the features of the preamble of claim 1. Bidirectional electrical converters are well known in practice and are offered in a wide variety of embodiments. For example, EP 3 713 066 A1 discloses a DC-DC converter with a secondary resonant circuit capacitor. The DC-DC converter has a transformer, with a rectifier circuit and a resonant circuit arranged on the primary side and a further rectifier circuit and an energy storage device arranged on the secondary side. Furthermore, CH 714 079 A2 discloses a converter for potential-free electrical energy transmission, which discloses an isolated two-stage pulse rectifier. A dual active bridge converter is provided in the first stage.The Dual Active Bridge has a full bridge on both the primary and secondary sides, which are connected to each other via a transformer. The Dual Active Bridge is a DC / DC converter, meaning a DC signal is present on the input and output sides of the Dual Active Bridge. The second stage of the two-stage pulse rectifier has a three-phase bridge circuit that controls a three-phase machine. The problem with these electrical converters, particularly when operating electrical machines, is that when using PWM control, as is typically used in three-phase bridge circuits, both large dU / dt EMX0212 occur on the supply line to an electrical machine and high-frequency current ripples on a sinusoidal current.Both the high dU / dt and di / dt lead to intensive interference emissions from the drive system via the machine's control line, as well as to high-frequency leakage currents within the machine, which, in addition to EMC emissions, impair the properties of the ball bearings through micropitting. Due to the high dU / dt of the voltage signal, the demands on the machine's insulation system increase, and the overall service life of the machine is reduced. To mitigate these effects, active and passive filters are generally used; however, these significantly increase the installation space and the cost of the overall system. The present invention is based on the problem of remedying this. This problem is solved by the electrical converter with the features of patent claim 1. Advantageous embodiments and further developments of the invention are specified in the dependent claims.Here and in the following, unless otherwise stated, the bidirectional converter device is referred to as an electrical converter device. According to the invention, an electrical converter device is provided which has input terminals for connecting a DC voltage source and a DC / DC converter connected to the input terminals and having first switching elements, where n is an integer number greater than or equal to one. The converter device has p intermediate circuits connected to the DC / DC converter on the output side, where p is an integer number greater than or equal to one. In addition, the electrical converter device has a DC / AC converter with second switching elements, where the DC / AC converter is connected downstream of the p intermediate circuits. The DC / AC converter has n output terminals for connecting the electrical machine.In addition, a control device is provided for controlling the second switching elements so that a stepped and rotor-position-dependent n-phase voltage signal can be provided, and the DC / AC converter is designed as a fundamental frequency-clocked, rotor-controlled n-phase three-phase voltage system. The electrical converter device is configured such that power can flow from the input side to the output side and vice versa. A bidirectional power flow is particularly advantageous when the electrical converter device is used to operate electrical machines, since during braking torques the kinetic energy can be fed back into an energy storage device connected to the input side. In addition, in generator mode, the electrical machine can feed the energy storage device or a grid or other consumer via the electrical converter device.Advantageously, the electrical converter device is designed to operate an n = 3-phase electrical machine. Compared to single-phase machines, three-phase machines have a number of advantages. Firstly, they generally have higher power, higher efficiency, require less space, and offer better load distribution. In a favorable embodiment of the invention, the control device controls the first switching elements such that the output voltage of the DC / DC converter is adjusted such that an at least approximately sinusoidal voltage signal can be provided at the n output terminals.Advantageously, the output voltage of the DC / DC converter is tracked within a limited amplitude range, wherein the limited amplitude range lies between 0 and 50 percent of an intermediate circuit voltage, and wherein the limited amplitude range preferably lies between 0 and one-sixth of the intermediate circuit voltage. Advantageously, the second switching elements of the control device can be controlled using an MSK method. The MSK method is described in the dissertation "A mechanical commutation method for operating permanent-magnet synchronous machines from a DC voltage source" from 2012 by Tobias Theopold (née Rösmann). In a further advantageous embodiment of the invention, the MSK control method has 12 switching states, wherein the switching states are rotor-position-dependent.The advantage of MSK control is that the second switching elements are only switched once per electrical revolution. Advantageously, the control of the current and its torque depends on a rotor angle Δε, whereby a rotor angle Δε is stored in one or more look-up tables for different speed-torque combinations. The MSK method has - as already mentioned - a switching sequence that is dependent on the rotor position. Rotor-controlled three-phase voltage systems require a DC voltage as input variables, which is usually designed as an intermediate circuit voltage, and a predetermined phase offset Δε, whereby the phase offset EMX0215 can also be referred to as the rotor angle. The rotor angle is the phase difference between the rotor voltage and a rotor-controlled three-phase voltage system. The torque is a function of the rotor angle.The torque and thus the power at a given speed is directly proportional to the argument of the rotor angle of a cosine function. The rotor angle lies in a range between zero and 90 degrees electrically, whereby a rotor angle of zero degrees causes no torque to be generated and a rotor angle of 90 degrees causes maximum torque to be generated. The rotor angle of 90 degrees represents a borderline case and is referred to as the tipping point. If the rotor angle exceeds 90 degrees, the electrical machine loses synchronization and tips over. The machine operates in an unstable operating range. The electrical rotor position is determined by the mechanical rotor position and the number of pole pairs. Rotor position-based control methods are mostly used for permanent magnet synchronous machines. The control takes place, among other things, in the so-called dq coordinate system.The dq coordinate system is usually aligned with the excitation flux, whereby in permanent-magnet synchronous machines the amplitude of the excitation flux lies in the d-direction. To detect the d-direction, the rotor position is determined. The q-direction is perpendicular to the d-direction. The dq coordinate system rotates with the position of the rotor during operation. In addition to the dq coordinate system, a stator-related coordinate system, also known as the αβ coordinate system, is used in control processes. The α-direction of the αβ coordinate system is usually aligned with the first winding axis. The β-direction is perpendicular to the α-direction. EMX0216The electrical converter device is primarily controlled by a digital control device. The control of the electrical converter device is significantly influenced by the switching behavior of the switching elements.The control of the first switching elements and second switching elements is dependent on current, voltage, rotor position and time. The control of the first switching elements and the second switching elements is coordinated by a control device. A voltage measurement is carried out at the input terminals of the three-phase bridge circuit arranged on the input side of the DC / DC converter. The measured voltage is passed on to the control device. In addition, a voltage measurement is carried out at the one or more intermediate circuits. The intermediate circuit voltage measured across the intermediate circuit capacitors is also passed on to the control device. The current of the electrical phases of the electrical machine is measured by means of a current measurement and passed on to the control device. The rotor position is detected by means of a rotor bearing detection and passed on to the control device.The control device preferably controls the second switching elements of the DC / AC converter using the MSK method. The generated output voltage of the DC / AC converter is actively controlled by the high-performance DC / DC converter as an actuator. This enables control of the amplitude of the stator current by controlling the stator voltage, and thus also controls / regulates the torque. Torque and phase current are interdependent. A larger phase current leads to a larger torque and vice versa. If a permanent-magnet synchronous machine is used, as envisaged in the present exemplary embodiment, an angle is established between the rotor voltage and the rotor-controlled three-phase voltage system, depending on the operating situation. This angle is referred to as the rotor angle and is load-independent.The rotor voltage is defined as the voltage that represents the voltage induced in the stator winding by the excited rotor. Using an appropriate look-up table, both the speed and torque behavior can be actively influenced over a wide operating range. The electrical machine can also be controlled using the so-called block clock method. A specific current control system injects a rectangular current into the machine's windings, whereby in a three-phase machine only two phases carry current at a time. The control of the phases depends on the rotor position. The rotor moves through an electrical angle, with electrical commutation of the current to the next phase taking place every sixty degrees. With this control method, the amplitude of the output voltage and thus the level of the amplitude of the output current is predetermined by the level of the intermediate circuit voltage.An undesirable common-mode voltage arises with this control method, which must be dissipated. The block-clock method has a relatively simple control structure. It is, for example, a cascade control system with an inner and outer control loop. An inner current control loop is subdivided into the outer speed control loop. The current controller outputs a voltage setpoint, which the power switches of an inverter circuit adjust. Phase current values ​​and rotor position are determined and, if necessary, transferred to the corresponding control loops as actual values ​​using differentiation or integration. The control structures of both control loops are designed with negative feedback. The actual values ​​are subtracted from the setpoints, which then determines the corresponding controlled variable. Another control method for controlling the electrical machine is pulse width modulation.Here, the semiconductors are switched on and off repeatedly over an electrical period, resulting in an almost sinusoidal output signal on average. The advantage of the PWM method is that the output current can be regulated directly, which makes the electrical converter device highly efficient. It can be advantageous if a combination of MSK and PWM methods is used to control the electrical converter unit. The PWM method is used when starting up or at low speeds, and the MSK method as speeds increase. With a number of pole pairs of one and a maximum speed of 30,000 rpm, a combination of both control methods would mean, for example, that the PWM method is used up to approximately ten percent of the maximum speed, i.e. approximately 300 rpm, and the MSK method is used for speeds above this.According to an advantageous development of the invention, the electrical machine has a mechanical commutation device. The mechanical commutation device can be implemented using brushes or slip rings. Mechanical commutation devices are characterized by a robust and cost-effective design. The control does not require complex electronics, thus increasing reliability. In another embodiment of the invention, the p intermediate circuits are designed as capacitive intermediate circuits. Capacitive intermediate circuits are less susceptible to interference than inductive intermediate circuits. This reduces electromagnetic interference. In addition, capacitive intermediate circuits have a fast response time, allowing them to react quickly to changes in the load. Capacitive intermediate circuits are used in applications where fast control is required.Capacitive DC links generally have lower losses, require less space, and are lower in cost than inductive DC links. The DC link capacitor(s) are charged when the electrical converter device is commissioned. The capacitive DC link is advantageously implemented using one or more capacitors. It is recommended to connect capacitors with different ESRs in parallel. For example, it is recommended to connect a capacitor with a high ESR in parallel with a capacitor with a low ESR. Electrolytic capacitors, ceramic capacitors, and film capacitors are usually connected in parallel in electrical converter devices. Electrolytic capacitors generally have a higher ESR than film capacitors or ceramic capacitors.In contrast to electrolytic capacitors, which use a liquid dielectric, ceramic capacitors have a ceramic dielectric, while film capacitors have layered metal foils. The liquid in electrolytic capacitors has a higher resistance and thus a higher ESR. While electrolytic capacitors are mostly used as energy buffers, ceramic capacitors and film capacitors are used to filter out the high-frequency component of the current. In addition, the intermediate circuit can be formed from an arrangement of capacitive and inductive impedances. The impedances are EMX021. 10connected in a CLC arrangement, whereby the CLC arrangement forms a first capacitance connected in parallel with the rectifier. An inductance connects the first and a second capacitance, also connected in parallel with the rectifier. The special arrangement of the impedances will be referred to here and in the following as a decoupling filter. The decoupling filter has better common-mode rejection than a single intermediate circuit capacitor. With a simple intermediate circuit capacitor, the neutral conductor jumps back and forth between different potentials, which can lead to increased common-mode interference. Another way to make the intermediate circuit less sensitive to common-mode interference is to connect two intermediate circuit capacitors in series. The neutral conductor is connected between the two series-connected intermediate circuit capacitors.The intermediate circuit voltage is clamped to a specific voltage value. In a particularly preferred embodiment of the invention, the switching frequency of the first switching elements is in the range from approximately 500 kHz to approximately 1 MHz. According to another advantageous development of the invention, the DC / DC resonant converter has a three-phase high-frequency transformer. The advantage of high-frequency transformers is that, for the same power, a significantly smaller installation space is required than is the case with low-frequency transformers. In addition, high-frequency transformers are generally more efficient. High-frequency transformers have lower stray magnetic fields. This is particularly advantageous in sensitive applications. The high-frequency transformer is preferably designed as a planar transformer. Planar transformers generally have a smaller installation space than EMX021. 11conventional transformers, since the windings are arranged flat on a single plane. Planar transformers also have lower leakage inductance. This leads to better efficiency and reduces electromagnetic interference. Cooling the high-frequency transformer is easier due to the flat design, as the planar transformer is attached to one or more heat sinks. Advantageously, the high-frequency transformer is designed as a delta-star transformer, with the primary side of the high-frequency transformer connected in a delta and the secondary side of the high-frequency transformer connected in a star. In another embodiment of the invention, the DC / DC resonant converter is designed as a CLLC topology, with the CLLC topology having two capacitors and two inductors of the high-frequency transformer.The impedances of the CLLC topology are designed to enable zero voltage switching (ZVS) or zero current switching (ZCS) over the largest possible frequency range and the widest possible voltage range on the input and output sides in order to reduce switching losses. With ZVS, the semiconductors are switched at zero voltage crossing, which ideally means no power loss occurs. With ZCS, the semiconductors are switched at zero current crossing. Here, too, no power loss occurs under idealized conditions. In a further embodiment of the invention, the impedance arrangement of the CLLC topology initially has a capacitance, followed by two inductors and a further capacitance connected downstream. DC / DC CLLC converters are generally characterized by a high efficiency of up to 99 percent. EMX021. 12Advantageously, the control device is designed to control the first and second switching elements as a function of current, voltage, rotor position, and time. According to an advantageous development of the invention, the DC / DC converter in the three-phase system has a three-phase bridge circuit on the input side. The three-phase bridge circuit, which is also called a B6C bridge, is characterized by its simple design and has proven itself in practice as a reliable inverter circuit. In the single-phase system, the DC / DC converter has a full bridge on the input and output sides. In addition to two-level converter topologies, three-level converter topologies such as the neutral point clamped inverter or the flying capacitor inverter as well as multi-level converter topologies can be used.In a further preferred embodiment of the invention, the three-phase bridge circuit of the DC / DC converter has three half-bridges on both the input and output sides of the DC / DC converter, with each half-bridge having two switching elements. In a single-phase system, both the input-side inverter circuit of the DC / DC converter and the output-side rectifier circuit of the DC / DC converter have two half-bridges. According to an advantageous development of the invention, the first switching elements are designed as silicon carbide (SIC) or gallium nitride (GaN) power switches, for example as MOSFETs. Semiconductors made of silicon carbide are characterized by their high dielectric strength. In addition, higher switching frequencies are possible than with conventional silicon semiconductors. In general, silicon carbide semiconductors have lower losses, higher temperature resistance, and a lower RDSon than conventional silicon semiconductors.Gallium nitride semiconductor EMX021. 13are used primarily in applications with high switching frequencies. The switching losses for GaN semiconductors are significantly lower than for conventional silicon semiconductors. In a further advantageous embodiment of the invention, the second switching elements are designed as IGBTs or MOSFETs. For lower switching frequencies, it is recommended to use conventional silicon-based MOSFETs or IGBTs, as these have significant cost advantages over SIC or GaN semiconductors. The DC / DC converter and the DC / AC converter are advantageously arranged in a common electrically conductive housing. The housing is preferably made of a metal. A metallic housing improves the electromagnetic compatibility of the overall system. Metal housings can shield against electromagnetic interference that emanates from or affects the components contained therein.The metal housing also offers protection against external influences such as moisture and dirt. In addition, metal housings are more robust and resistant to external influences than plastic housings. According to the invention, a method for operating an electrical converter device is described, wherein the electrical converter device controls at least one DC / DC converter via first switching elements and at least one DC / AC converter via second switching elements by means of a control device, wherein the second switching elements of the DC / AC converter are controlled in such a way that the at least one output voltage of the DC / AC converter is pulse-shaped, wherein the at least one output voltage of the DC / DC converter is adjusted between the pulses of the output voltage of the DC / AC converter in such a way that a quasi-sinusoidal phase current is established at the output of the electrical converter device. EMX021. 14In a further advantageous method for operating an electrical converter device, the second switching elements of the DC / AC converter are controlled according to the MSK method, wherein the MSK method forms a twelve-pulse output voltage at the output of the electrical converter device. In a further advantageous method for operating an electrical converter device, the DC / DC converter is the actuator of the rotor-controlled three-phase voltage system, whereby the amplitude of the rotor current is regulated by the DC / DC converter. In a further advantageous method for operating an electrical converter device, the torque is regulated by the phase shift between the rotor voltage and the rotor-controlled three-phase voltage system. The electrical converter device is advantageously used to operate electrical machines.Advantageously, the electrical converter device is used to supply an electrical AC network.

[0002] EMX021 15Three exemplary embodiments of the invention are explained below with reference to figures. In the first exemplary embodiment, a three-phase electrical machine is controlled via a DC / AC converter which is fed via p = 3 intermediate circuits. In the second exemplary embodiment, a three-phase electrical machine is controlled via a DC / AC converter which is fed via p = 1 intermediate circuit. In the third exemplary embodiment of the invention, the electrical machine is operated in generator mode and feeds a three-phase electrical network. Fig. 1 shows a circuit equivalent circuit diagram of the electrical converter device, which has a three-phase DC / DC converter, three intermediate circuits, a three-phase DC / AC converter, a control device and an electrical machine, Fig.Figure 2 shows a circuit equivalent circuit diagram of the electrical converter device, which has a single-phase DC / DC converter, an intermediate circuit, a three-phase DC / AC converter, a control device, and an electrical machine. Figure 3 shows a circuit equivalent circuit diagram of the electrical converter device, which has a single-phase DC / DC converter, an intermediate circuit, a three-phase DC / AC converter, and a control device. Figure 4 shows the block diagram of the control device of the electrical converter unit, which has three sub-areas, namely a drive control, a motor control, and power electronics, EMX021. 16Fig. 5 shows the switching table of the MSK control, Fig. 6 shows an output voltage signal of a phase which has 12 switching states as an example. In addition, the time profile of a tracked output voltage of a phase of the DC / DC converter is shown, Fig. 7 shows a time profile of a phase current in an electrical machine. In the following figures, the same reference numerals designate the same parts with the same meaning. The first embodiment of the invention is explained in more detail with reference to Fig. 1. The electrical converter device 1 of the first embodiment has a three-phase DC / DC converter 10, three intermediate circuits 90, a three-phase DC / AC converter 40, a control device 80 and an electrical machine 60. The DC / DC converter 10 has a DC voltage input side 11 and a DC voltage output side 12.The DC voltage input side 11 of the DC / DC converter 10 is fed by an energy storage device or an AC supply network or a DC supply network (all three not shown) at the input terminals 22 of the DC / DC converter 10. The DC / DC converter 10 is designed as a three-phase, highly efficient DC / DC resonant converter 17. The DC / DC converter 10 has a DC / AC converter 14 on the input side, wherein the DC / AC converter 14 is preferably designed as a three-phase bridge circuit 15. On the output side, the DC / DC converter 10 has an AC / DC converter 13, which EMX021. 17converts an alternating signal into a direct signal. A three-phase, high-performance high-frequency transformer 20 is formed between the three-phase bridge circuit 20 arranged on the input side and the AC / DC converter 13, with capacitors 21 and inductors 22 connected upstream or downstream on the input and output sides. In addition, a fuse 100 is connected upstream of the DC / DC converter 10, which fuse triggers in the event of a fault and switches off the electrical converter device 1. Alternatively, the electrical converter device 1 can be safely switched off by appropriately controlling the switching elements 30, wherein the electrical converter device has first switching elements 31 and second switching elements 32. The DC / DC converter 10 has first switching elements 31 and the DC / AC converter 40 has second switching elements 32.The three-phase bridge circuit 15 of the DC / DC converter 10, arranged on the input side, forms three half-bridges 36, each having two first switching elements 31. The two first switching elements 31 of a half-bridge 36 are connected in series with one another, wherein the first switching element 31 of a half-bridge 36, which is connected to plus 2, is referred to as the upper switching element 33 and the first switching element 31, which is connected to minus 3, is referred to as the lower switching element 34. The first switching elements 31 are preferably designed as MOSFETs. The semiconductor material of the first switching elements 31 is preferably made of silicon carbide or gallium nitride. Due to their topology, MOSFETs consist of a switch 37 and a body diode 35 arranged anti-parallel to the switch 37. Are the properties of the body diode 35 for the possible application EMX021. 18is not sufficient, it is recommended to arrange another diode in anti-parallel to the switch 37 so that the required properties for the switching element 30 are met. MOSFETs have a drain, source and gate connection. By applying an external voltage to the gate connection of the MOSFET, the voltage between gate and source changes and the resistance between drain and source decreases. The switching element 30 opens. If the external voltage previously applied to the gate connection is removed, there is no voltage between gate and source and the resistance between drain and source increases. The switching element 30 closes. Due to the intended high switching frequencies, it is recommended to use initial switching elements 31 which have a small RDSon in order to keep switching losses as low as possible. The RDSon denotes the minimum on-state or on-state resistance of a MOSFET.The first switching elements 31 of the three-phase bridge circuit 15 arranged on the input side of the DC / DC converter 10 convert a DC signal at the input terminals 19 of the DC / DC converter 10 into a high-frequency AC signal. The high-frequency AC signal is transmitted via a high-frequency transformer 20. The high-frequency transformer 20 has a transformation ratio of one, but can also have a transformation ratio other than one, e.g., 7 / 4. The high-frequency transformer 20 has a primary side 24 and a secondary side 25. Due to its topology, the high-frequency transformer 20 has a galvanic isolation 27 between the primary side 24 and the secondary side 25. The DC voltage input side 11 is thus galvanically isolated from the EMX021 electrical machine. 1960, whereby the reference voltage of both subsystems differs and interference signals are reduced. The high-frequency transformer 20 is preferably operated in a frequency range between 500 kHz and 1 MHz. The high-frequency transformer 20 can also be operated in a smaller or larger frequency range. The higher the frequency at which the high-frequency transformer 20 is operated, the smaller the installation space of the high-frequency transformer 20 for the same power transmission. The high-frequency transformer 20 is designed as a three-phase transformer 26. Compared to three single-phase transformers that are connected to one another, three-phase transformers 26 are smaller, cheaper, and lighter because the copper and iron core are used more effectively. The high-frequency transformer 20 is particularly preferably designed as a three-phase planar transformer 28.Planar transformers 28 are designed either as individual components or integrated on an overall circuit board. The high-frequency transformer 20 is preferably designed as a delta-star transformer. The primary side 24 of the high-frequency transformer 20 is connected in a delta, whereas the secondary side 25 of the high-frequency transformer 20 is connected in a star. The DC / DC converter 10 is preferably designed as a DC / DC resonant converter 17. The DC / DC resonant converter 17 has a CLLC topology. In the embodiment shown in Fig. 1, the CLLC topology is designed such that a capacitance 21, followed by an inductance 22, is connected to the primary side 24 of the high-frequency transformer 20. The secondary side 25 of the high-frequency transformer 20 has a further EMX021, based on the topology-dependent galvanic isolation. 20Inductance 22 with a series-connected capacitance 21. The two inductances 22 of the CLLC topology can be the leakage inductances 23 of the high-frequency transformer 20, or in addition to the topology-dependent leakage inductances 23 of the high-frequency transformer 20, additional inductances 22 are connected in series with the leakage inductance 23 of the high-frequency transformer 20. The inductances 22 and capacitances 23 of the CLLC topology form a series resonance. If the resonant frequency of the series resonance is greater than the switching frequency of the first switching elements, the first switching elements 31 can be switched on and off with almost no loss. Preferably, the first switching elements 31 switch on and off with no loss. For this purpose, the first switching elements 31 are controlled such that they use the zero-voltage switching or zero-current switching methods, or both methods simultaneously.In zero current switching, a switching element 30 is switched on or off at zero current crossing. In zero voltage switching, a switching element 30 is switched on or off at zero voltage crossing. If both zero voltage switching and zero current switching are used in a switching process, a switching element 30 is switched on or off at both zero current crossing and zero voltage crossing. The power loss of a switching process results from the product of current and voltage present during the switching process. If either current or voltage or current and voltage is zero at the switching time, the power loss of the switching process is also zero. An AC / DC converter 13 is connected downstream of the secondary side 25 of the high-frequency transformer 20. The AC / DC converter 13 is EMX021. 21preferably designed as a three-phase bridge circuit 16. Each output-side phase 29 of the high-frequency transformer 20 is connected to a half-bridge 36 of the output-side three-phase bridge circuit 16 of the DC / DC converter 10. The output-side phases 29 of the high-frequency transformer 20 are connected between the upper switching elements 33 and lower switching elements 34 of first switching elements 31 of a half-bridge 36. An intermediate circuit capacitor 91 is connected downstream of each half-bridge 36. The first switching elements 31 of the output-side three-phase bridge circuit 16 of the DC / DC converter 10 are controlled in such a way that the currents cancel each other out. The intermediate circuit capacitor 91 maintains the intermediate circuit voltage at a predefined voltage value. In the first embodiment, the electrical converter unit 1 has three intermediate circuit capacitors 91 and thus three intermediate circuits 90.For very high operating voltages, it is advisable to connect several intermediate circuit capacitors 91 in series to achieve the required dielectric strength. By connecting the intermediate circuit capacitors 91 in series, the total capacitance of the intermediate circuit capacitors 91 connected in series is reduced by a factor of 1 / z, where z is the number of intermediate circuit capacitors 91 connected in series. The intermediate circuit 90 preferably has an electrolytic capacitor and a ceramic capacitor and / or film capacitor, with the electrolytic capacitor arranged in parallel with the ceramic capacitor and / or film capacitor. The electrolytic capacitor serves as an energy buffer, with the ceramic capacitor and / or film capacitor compensating for the high-frequency current ripple and thus keeping the intermediate circuit voltage at an approximately constant value. The intermediate circuit capacitors 91 are connected to each other on the negative side. EMX021. 22A half-bridge 36 is connected downstream of each intermediate circuit capacitor 91. The half-bridge 36 connected downstream of the intermediate circuit capacitor 91 has second switching elements 32. The three half-bridges 36 connected downstream of the intermediate circuit capacitor 91 are components of the DC / AC converter 40. Each half-bridge 36 connected downstream of an intermediate circuit capacitor 91 is connected to a phase 62 of the electrical machine 60. The second switching elements 32 are preferably designed as IGBTs or MOSFETs. The second switching elements 32 switch much more slowly than the first switching elements 31. The half-bridges 36 connected downstream of the intermediate circuit capacitor 91 control the individual phases 62 of the electrical machine 60. If IGBTs are used as switching elements 30, then unlike with MOSFETs, a diode must necessarily be arranged anti-parallel to the switch 37, since the topology-dependent body diode 35 of a MOSFET is not present in IGBTs.The electric machine 60 is particularly preferably designed as a permanent-magnet synchronous machine 63. Permanent-magnet synchronous machines 63 have permanent magnets in the rotor. As a result, the rotor is always magnetized and does not need to be magnetized via the stator, as is the case with asynchronous machines or reluctance machines. In particular, magnetizing the rotor across a large air gap leads to considerable losses. Therefore, permanent-magnet synchronous machines 63 are characterized by higher efficiency and higher power density compared to asynchronous machines and reluctance machines. Permanent-magnet synchronous machines 63 can have magnets buried in the rotor (IPM) or surface-mounted magnets. The EMX021. 23Different designs of the permanent-magnet synchronous machine result in different magnetic conductances developing in the d-direction and q-direction, whereby the d-direction and q-direction develop different inductances Ld and Lq. For permanent-magnet synchronous machines 63, Ld is not equal to Lq, where Ld is smaller than Lq and for a rotationally symmetrical rotor with surface magnets, Ld = Lq applies. The general torque consists of a reluctance torque, which develops due to the different inductances in the d-direction and q-direction in interaction with the phase currents, and a synchronous torque, which develops due to the permanent excitation in interaction with the phase currents. The three phase currents are converted into the dq coordinate system for simplified control handling.In permanent-magnet synchronous machines where Ld = Lq, no reluctance torque is generated, so it is recommended to use only the iq current in base speed operation, with the id current being regulated to zero. In the field-weakening range, a negative id current is impressed, which weakens the field, reduces the induced voltage in the winding phases, and thus enables higher speeds at the same voltage. The lower torque yield is a disadvantage. In permanent-magnet synchronous machines where Ld is less than Lq, MMPA optimization is used in the base speed range, for example, whereas MMPV optimization is used in the field-weakening range, for example. In another embodiment of the invention, the electrical machine is designed as a separately excited synchronous machine. The EMX021. 24A separately excited synchronous machine has an excitation winding in the rotor. The excitation winding makes the separately excited synchronous machine easy to control, as the rotor magnetization can be easily controlled via the current supplied to the excitation winding. The control of the separately excited synchronous machine is similar to that of a permanently excited synchronous machine, although the current control is not based on the excitation flux but on the main flux. The position of the main flux is calculated using a current-voltage model. In another embodiment of the invention, the electrical machine is designed as a reluctance machine. In reluctance machines, a general distinction is made between the synchronous reluctance machine and the switched reluctance machine. For both topologies, the reluctance machine is characterized by an extremely robust design and low manufacturing costs.Furthermore, the reluctance machine is usually operated at very high speeds, which means that the power density is usually higher than that of an asynchronous machine. The three electrical phases 62 of the electrical machine 60 are interconnected in a star connection 61. However, the phases 62 can also be connected in a delta connection. In a star connection 61, the switching elements 30 of the electrical converter device 1 must be controlled such that the currents in the neutral conductor balance each other out. The electrical converter device 1 measures current and voltage values ​​at relevant areas. A current and voltage measurement 81 is carried out on the DC voltage input side 11 and passed on to a control device 80. In addition, an EMX021. 25A voltage measurement 82 is carried out on the three intermediate circuits 90 and also transferred to the same control device 80. A current measurement 83 is carried out on the phases 62 of the electrical machine 60. The current determined by the current measurement 83 and the rotor position, which is determined by a rotor position detection 84, are transferred to a control device 80. Fig. 2 shows an electrical converter device 1, a single-phase DC / DC converter 110, an intermediate circuit 190, a three-phase DC / AC converter 140, a control device 180 and an electrical machine 160. The DC / DC converter 110 is connected on the input side to an energy source. The energy source can be a battery or an AC / DC supply or a DC / DC supply. A fuse 200 is connected between the power source and the DC / DC converter 110, which safely disconnects the electrical converter device 1 from the power source in the event of a fault. The DC / DC converter 110 is designed as a single-phase device.The DC / DC converter 110 has a full bridge 111 on the input side and a full bridge 112 on the output side with first switching elements 134. A transformer 120 is formed between the two full bridges 111-112. The transformer 120 is preferably designed as a high-frequency transformer 121. A full bridge 111-112 has four switching elements 130. The switching elements 130 are arranged in half bridges 136. A half bridge 136 consists of two switching elements 130 that are connected in series. Each switching element 130 has a switch 132 and a diode 133 arranged antiparallel to the switch 132. A full bridge 111-112 has two half bridges 131 connected in parallel. The first switching elements 134 of the input EMX021. 26The output-side full bridge 111 converts a DC signal into a high-frequency AC signal, whereas the output-side full bridge 112 converts the high-frequency AC signal into a DC signal. The advantage of high-frequency AC signals is that the high-frequency transformer 121 has a higher efficiency and a smaller installation space for the same power than is the case with low-frequency AC signals. The first switching elements 134 are preferably designed as MOSFETs and use gallium nitride or silicon carbide as semiconductor materials. The switching frequency of the first switching elements 134 of the two full bridges 111-112 of the DC / DC converter 110 is preferably between 500 kHz and 1 MHz. However, the switching frequency of the first switching elements 134 can also be in a smaller or larger frequency range. A high-frequency transformer 121 is connected between the two full bridges 111-112 of the DC / DC converter 110.The high-frequency transformer 121 has impedances on the input and output sides. The impedances are a capacitance 122 and an inductance 123 on the input and output sides, respectively, where the inductance 123 can be the leakage inductance 124 of the high-frequency transformer 121. Thus, the DC / DC converter 110 is preferably designed as a DC / DC resonant converter 113 in CLLC topology. The high-frequency transformer 121 is connected on the supply line 125 between two first switching elements 134 of a half-bridge 131 of a full bridge 111-112. The output line 126 of the high-frequency transformer is connected between two first switching elements 134 of the other half-bridge 131 of a full bridge 111-112. EMX021. 27On the output side, the DC / DC converter 110 is connected to a capacitive intermediate circuit 190. The capacitive intermediate circuit 190 is implemented using an intermediate circuit capacitor 191. The intermediate circuit capacitor 191 can be implemented from several intermediate circuit capacitors 191 arranged in series or parallel to one another. Electrolytic capacitors, film capacitors, and ceramic capacitors are preferably used. The intermediate circuit 190 serves as an energy buffer and filters out the high-frequency current component. A DC / AC converter 140 is connected downstream of the intermediate circuit capacitor 191, wherein the DC / AC converter 140 is designed as a three-phase bridge circuit 141. The three-phase bridge circuit 141 has three half-bridges 131, each with two second switching elements 135. The second switching elements 135 are designed as IGBTs or MOSFETs.The switching frequency of the second switching elements 135 is significantly lower than that of the first switching elements 134 and is approximately in the three-digit frequency range. However, the switching frequency can also be in a larger or smaller frequency range. The three-phase bridge circuit 141 controls the individual phases 161 of the electrical machine 160. The MSK method, block clocking, the PWM method, or a combination of the aforementioned can be used as the control method. The control of the first switching elements 134 and second switching elements 135 is handled by the control device 180. For this purpose, voltage values, current values, and the rotor position are recorded and fed to a control device 180. The control device 180 controls the second switching elements 135 of the three-phase bridge circuit 141 such that a twelve-pulse EMX021. 28A voltage signal is generated. In addition, the control device 180 controls the first switching elements 134 of the DC / DC converter 110 such that the output voltage of the DC / DC converter 110 is adjusted such that the output voltage of the DC / DC converter 110 with the output voltages of the three-phase bridge circuit 141 causes a quasi-sinusoidal current waveform in the phases 162 of the electrical machine 160. Fig. 3 shows the third exemplary embodiment of the electrical converter device 1, which has a single-phase DC / DC converter 210, two intermediate circuits 290, a three-phase DC / AC converter 240 and a control device 280. The three-phase DC / AC converter 240 is designed as a three-phase bridge circuit 241, wherein the three-phase bridge circuit 241 is connected to a three-phase AC network 270. However, the AC network 270 can also be single-phase, whereby the DC / AC converter 240 is preferably designed as a full bridge.An intermediate circuit 250 is formed between the three-phase bridge circuit 221, which is connected to the electrical machine, and the DC / DC converter 210. The other intermediate circuit 290 is formed between the three-phase bridge circuit 241, which is connected to the AC network 270, and the DC / DC converter 210. In this exemplary embodiment, the electrical converter device 1 is similar to the electrical converter device 1 from exemplary embodiment two, but can also correspond to the electrical converter device 1 from exemplary embodiment one. In exemplary embodiment three, in contrast to the previously shown exemplary embodiments, an electrical machine 260 is preferably additionally connected via a DC / AC converter 220 to the DC voltage input side 211 of the DC / DC converter 210. An intermediate circuit capacitor 251 is preferably EMX021. 29between DC / DC converter 210 and DC / AC converter 220, which is connected to the electrical machine 260. Preferably, a three-phase electrical machine 260 is used, so that the DC / AC converter 220 is preferably designed as a three-phase bridge circuit 220. The switching elements 230 of the three-phase bridge circuit 220 have a maximum switching frequency of a few hundred Hz. The switching elements 230 are preferably designed as IGBTs or MOSFETs and consist of a switch 231 and a diode 232 arranged anti-parallel to the switch 231. A single-phase electrical machine 260 can also be used, which is connected to an intermediate circuit 250 via a full bridge 222. In Fig. 4, the control is via a control device 80; 280 of the electrical converter device 1 is shown using a block diagram. The control is similar for the three previously listed application examples.The control device 80; 280 can be divided into three sub-areas. These sub-areas are a drive control 310, a motor control 330, and power electronics 350 and measurement data acquisition 390. The power electronics 350 controls the electric machine. The measurement data acquisition 390 measures voltages, currents, and the rotor position and transmits the values ​​to a control unit. The drive control 310 is a cascade control system with three control loops. A distinction is made between the outer control loop 316 of the position control 315, the middle control loop 321 of the speed control 320, and the inner control loop 326 of the current control 325. EMX021. 30 The outer control loop 316, which performs the position control 315, is the position setpoint ^^ ref and the actual position value ^^ ist The actual position value ^^ istcan be determined by means of a rotor position sensor (84). The actual position value ^^ ist and the position setpoint ^^ ref are subtracted from each other. Since experience has shown that no disturbances affect this control loop, it is recommended to implement the position controller 315 as a P controller. The output variable of the position controller 315 is the speed setpoint ^^ ref of the speed controller 320. The speed controller 320 forms the middle control loop 321. The speed controller 320 is supplied with the speed setpoint ^^ ref of the position controller 315. The actual speed ^^ istis determined from the change in the motor position angle and is also transferred to the speed controller 320. The middle control loop 321, like all three control loops, has negative feedback. This means that the actual value is subtracted from the setpoint. It is recommended to implement the speed controller 320 as a PI controller. The I component is required to compensate for the load torque disturbance. The output of the speed controller 320 is the torque setpoint. ref of the current controller 325. The current controller 325 forms the inner control loop 326. On the input side, the target torque ^^ refand the actual currents are transferred. It is recommended to convert the actual currents into the dq coordinate system before transferring them to the inner control loop 326. For this purpose, the current is determined for each or at least two phases of the electrical machine, for example, using a Rogowski coil. Subsequently, the three phase currents 62; 161 are transferred into the dq coordinate system using the Park transformation. It is recommended to control the id and iq currents independently of each other. For this purpose, EMX021 31 The two control loops of the d-component and the q-component are decoupled by means of a feedforward control of the coupling terms. The current control 325 has the voltages ^^ as output variables. sd_ref and ^^ sq_ref The output voltages ^^ sd_ref and ^^ sq_ref of the current regulator 325 are transferred to a Cartesian-polar converter 340. The Cartesian-polar converter 340 converts the voltages ^^ sd_ref and ^^ sq_ref, which are present in the Cartesian coordinate system, into polar coordinates. In the polar coordinate system, a voltage space vector with an amplitude and an angle is given. The Cartesian-to-polar converter 340 has the pole wheel angle Δε and the voltage amplitude ^^ as output variables. abs_ref The rotor angle Δε is the phase shift between the rotor voltage and the rotor-controlled three-phase voltage system. The current intermediate circuit voltage ^^ dc_actThe rotor angle Δε and the current rotor position ε are transferred to the MSK modulator 360, which provides the DC / AC output voltage 420. The MSK modulator 360 controls the corresponding switching elements 30; 130; 230, as the name suggests, using the MSK method. The power required at each operating point depends on the speed and torque. At a given speed, the current and thus the torque are controlled via the rotor angle Δε. Different rotor angles Δε are set for different speed-torque combinations. The respective rotor angles Δε can be stored in one or more look-up tables. By varying the rotor angle Δε accordingly, both the speed and the torque behavior can be actively influenced over a wide operating range. The pre-calculated rotor angles Δε can significantly reduce real-time computing power. EMX021 32 The tension ^^ abs_refis transferred to the DC / DC regulator 370, as well as the current voltages of the DC / DC converter 10; 110; 210 and the output voltages 420 of the DC / AC converter at the terminals of the electric machine, which the MSK modulator 360 sets via the second switching elements 32; 135 of the DC / AC converter 10; 110; 210. The DC / DC regulator 370 transfers the voltage setpoints of the DC / DC converter to the CLLC modulator 380. dcdc_act. The first switching elements 31; 134 are then switched in such a way that the voltages at the output of the DC / DC converter 10; 110; 210 are tracked in such a way that, by superposition with the output voltage 410 of the DC / AC converter 40; 140; 240, a quasi-sinusoidal current waveform is established in the phases of the electrical machine 60; 160; 260 or of the electrical AC network 270. The tracked voltage at the output 420 of the DC / DC converter 10; 110; 210, which represents the intermediate circuit voltage, is tracked within a limited amplitude range. The limited amplitude range lies in the range between zero and fifty percent of the intermediate circuit voltage, wherein the limited amplitude range is preferably in a range between zero and one-sixth of the intermediate circuit voltage. The regulator of the DC / DC converter 370 also has a cascade structure. An outer voltage control loop is superimposed on the inner current control loop.Both the current regulator and the voltage regulator are preferably designed as PI controllers. The DC / DC converter 10; 110; 210 serves as an actuator for the rotor-controlled three-phase voltage system. The control of the DC / DC converter 10; 110; 210 regulates and limits the current in the electrical converter unit 1 and thus also in the electrical machine 60; 160; 260. In exemplary embodiment three, almost the same control topology is used as in exemplary embodiments one and two. EMX021. 33The control of the DC / AC converter 40; 140; 240, which is directly connected to the AC grid 270, ensures that exactly as much active power is fed into the AC grid 270 as the electrical machine 60; 160; 260 feeds in on the input side. Otherwise, the intermediate circuit voltage at the intermediate circuit capacitor 91; 191 changes, which is undesirable. The second switching elements 32; 135 are to be switched by the control device 80; 280 such that the intermediate circuit voltage remains almost constant at a predefined setpoint. The current flowing from the DC / AC converter 40; 140; 240 into the intermediate circuit capacitor 91; 191 is referred to here and below as direct current. At a constant mains voltage and constant intermediate circuit voltage, the direct current is proportional to the active current on the mains side. Instead of direct current, it is advisable to control the active current on the mains side by using the phase voltages as the actuator.The reactive current results from the active current. In the control engineering equivalent circuit diagram, the active current corresponds to the current id and the reactive current to the current iq. In steady-state operation, the reactive current is regulated to zero, resulting in a power factor of one. Fig. 5 shows the switching table 401 of the MSK control method. Each switch changes its switching state only once per electrical revolution. The switching table 401 has eleven columns. The first column indicates the designation of the respective switching state. A distinction is made here, among other things, between F state and I state. The switching states with the prefix F correspond to the switching states of the fundamental frequency clocking in direct self-regulation, and the switching states with the prefix I correspond to the switching states in which one of the phases is not carrying any current.A combination of the switching states with the prefix F and the switching states with the prefix I contains all switching states of the MSK method. The second column gives EMX021. 34at which electrical rotor angle the switching state changes. In this example switching sequence, the switching sequence begins at F1 and ends at I6. The switching state changes electrically every 30 degrees. Columns three to five indicate the state of the phase voltage. Columns six to twelve indicate the switching states of the second switching elements. A one means that the switch is closed, a zero that the switch is open. Fig. 6 shows the output voltage 410 of the DC / AC converter 40; 140; 240 for an electrical phase 62; 161 of the electrical machine 60; 160; 260. The output voltage 410 has a twelve-pulse switching pattern. The twelve-pulse nature arises from the fact that three additional possible voltage states can be set. These are plus, minus, and zero.Plus means that the phase is supplied with a positive voltage, minus with the negative voltage, and zero that there is no voltage across phase 62; 161 and therefore no current flows through the respective phase 62; 161. It can be seen that when switching with a zero phase, the length of the voltage vector is shortened, so that one can only speak of a quasi-twelve-pulse three-phase voltage system. The zero state across a phase is preferably established directly. During the switching sequence, it can happen that the anti-parallel diodes 35; 133; 232 of the second switching elements 32; 135 clamp the phase voltage to plus or minus. The inductive behavior of the phase phases means that the current initially continues to be driven despite switching on or off, and the corresponding diodes conduct. Once the current has been reduced, the diodes block, and the actual voltage state is reached.Switching at zero current can at least partially prevent or shorten such unwanted clamping of the phase voltage. EMX021. 35In addition, in Fig. 6, the same diagram shows the tracked voltage 420 at the output of the DC / DC converter 10; 110; 210 for an electrical phase 62; 161 of the electrical machine 60; 160; 260. By superposing the output voltage 410 of the DC / AC converter 40; 140; 240 with the tracked voltage 420 at the output of the DC / DC converter 10; 110; 210, a quasi-sinusoidal curve of the phase current 430 of the electrical machine 60; 160; 260 results. The dynamically tracked voltage 420 of the high-performance DC / DC converter 10; 110; 210 lies within a limited amplitude range. The limited amplitude range of the tracking voltage 420 is preferably in a range from zero to fifty percent, with the tracking voltage 420 particularly having an amplitude range from zero to one-sixth of the intermediate circuit voltage. In Fig.Figure 7 shows a quasi-sinusoidal waveform of the phase current 430 in the electrical machine. The quasi-sinusoidal waveform of the phase current 430 in the electrical machine is created by the superposition of the output voltage 410 of the DC / AC converter and the tracking voltage 420 of the DC / DC converter. The approximately sinusoidal waveform of the phase voltage leads to an approximately sinusoidal waveform of the phase current 430 in the electrical machine. EMX021. 36List of reference symbols 1 Electrical converter unit 2 Plus 3 Minus 10 DC / DC converter 11 DC input side 12 DC output side 13 AC / DC converter 14 DC / AC converter 15 Three-phase bridge circuit (primary) 16 Three-phase bridge circuit (secondary) 17 DC / DC resonant converter 18 Input terminals 20 High-frequency transformer 21 Capacitance 22 Inductance 23 Leakage inductance 24 Primary side 25 Secondary side 26 Three-phase transformer 27 Galvanic isolation 28 Planar transformer 29 Phase 30 Switching element 31 First switching element 32 Second switching element 33 Upper switching element 34 Lower switching element 35 Body diode 36 Half bridge 37 Switch 40 DC / AC converter EMX021 3760 Electrical Machine 61 Star Connection 62 Electrical Phase 63 Permanent Magnet Synchronous Machine 81 DC Current and Voltage Measurement 82 DC Link Voltage Measurement 83 Motor Current Measurement 84 Rotor Position Detection 90 DC Link 91 DC Link Capacitor 100 Fuse 110 DC / DC Converter 111 Input Full Bridge 112 Output Full Bridge 113 DC / DC Resonant Converter 120 Transformer 121 High Frequency Transformer 122 Capacitance 123 Inductance 124 Leakage Inductance 125 Supply Line 126 Derivative 130 Switching Element 131 Half Bridge 132 Switch 133 Diode 134 First Switching Element 135 Second Switching Element 140 DC / AC Converter 141 Three Phase Bridge Circuit 160 Electrical Machine EMX021 38161 Phase of electrical machine 190 Intermediate circuit 191 Intermediate circuit capacitor 200 Fuse 210 DC / DC converter 211 DC voltage input side 220 DC / AC converter 221 Three-phase bridge circuit 222 Full bridge 230 Switching elements 231 Switch 232 Diode 240 DC / AC converter 241 Three-phase bridge circuit 250 Intermediate circuit motor 251 Intermediate circuit capacitor AC / DC 260 Electrical machine 270 AC mains 280 Control device 290 Intermediate circuit mains 310 Drive control 315 Position control 316 Outer control loop 320 Speed ​​control 321 Middle control loop 325 Current control 326 Inner control loop 330 Motor control 340 Cartesian-polar converter 350 Power electronics EMX021 39 360 MSK Modulator 370 DC / DC Converter Control 380 CLLC Modulator 390 Data Acquisition 401 Switching Table 410 Output Voltage DC / AC 420 Tracking Voltage 430 Phase Current

Claims

EMX021 40Patent claims 1. Bidirectional n-phase electrical converter device (1) with the following features: ^ input terminals (18) for connecting a DC voltage source, ^ a DC / DC converter (10; 110; 210) connected to the input terminals (18) with first switching elements (31; 134), ^ p intermediate circuits (90; 190; 290) connected on the output side to the DC / DC converter (10; 110; 210), ^ a DC / AC converter (40; 140; 240) with second switching elements (32; 135), wherein the DC / AC converter (40; 140; 240) is connected downstream of the p intermediate circuits (90; 190; 290), ^ the DC / AC converter (40; 140; 240) has output terminals for connecting an electrical machine (60; 160; 260) or an electrical AC network (270), ^ a control device (80; 280) for controlling the second switching elements (32; 135) of the DC / AC converter (40; 140; 240) such that a stepped n-phase output voltage (410) can be provided, and ^ the DC / AC converter (40; 140;240) is designed as a fundamental frequency clocked, rotor-controlled n-phase three-phase voltage system.

2. Electrical converter device (1) according to claim 1, characterized in that the electrical converter device (1) is designed with n = 3 phases.

3. Electrical converter device (1) according to claim 1, characterized in that the control device (80; 280) controls the first switching elements (31; 134) such that the; EMX021 41The output voltage of the DC / DC converter (10; 110; 210) is tracked such that an at least approximately sinusoidal voltage signal can be provided at the n output terminals.

4. Electrical converter device (1) according to claim 3, characterized in that the output voltage (420) of the DC / DC converter (10; 110; 210) is tracked within a limited amplitude range, wherein the limited amplitude range lies within zero to fifty percent of an intermediate circuit voltage, and wherein the limited amplitude range is preferably from zero to one-sixth of the intermediate circuit voltage.

5. Electrical converter device (1) according to one of claims 1 to 4, characterized in that the control of the second switching elements (32; 135) of the DC / AC converter (40; 140; 240) takes place according to an MSK method.Electrical converter device (1) according to claim 5, characterized in that the MSK control method has twelve switching states, wherein the switching states are rotor position-dependent.

7. Electrical converter device (1) according to one of the preceding claims, characterized in that the control of the current and its torque is dependent on a magnet wheel angle Δε, wherein a magnet wheel angle Δε is stored in one or more look-up tables for different speed-torque combinations.

8. Electrical converter device (1) according to one of the preceding claims, characterized in that the electrical. EMX021 42Machine (60; 160; 260) has a mechanical commutation device.

9. Electrical converter device (1) according to one of the preceding claims, characterized in that the p intermediate circuits (90; 190; 290) are designed as capacitive intermediate circuits (90; 190; 290).

10. Electrical converter device (1) according to claim 9, characterized in that the capacitive intermediate circuit (90; 190; 290) is realized by an intermediate circuit capacitor (91; 191).

11. Electrical converter device (1) according to one of the preceding claims, characterized in that a switching frequency of the first switching elements (31; 134) is in the range from approximately 500 kHz to approximately 1 MHz.

12. Electrical converter device (1) according to one of the preceding claims, characterized in that the DC / DC converter (10; 110; 210) has a three-phase high-frequency transformer (20; 120). 13.Electrical converter device (1) according to claim 12, characterized in that the high-frequency transformer (20; 120) is designed as a delta-star transformer, wherein a primary side of the high-frequency transformer (20; 120) is connected in a delta and a secondary side of the high-frequency transformer (20; 120) is connected in a star. EMX021 4314. Electrical converter device (1) according to one of the preceding claims, characterized in that the DC / DC converter (10; 110; 210) is designed as a DC / DC resonant converter (17; 113).

15. Electrical converter device (1) according to claim 14, characterized in that the DC / DC converter (10; 110; 210) is designed as a CLLC topology, wherein a CLLC topology has two capacitors (21; 122) and two inductors (22; 123) of the high-frequency transformer (20; 120).

16. Electrical converter device (1) according to one of claims 14 to 15, characterized in that the arrangement of impedances of the CLLC topology initially comprises a capacitance (21; 122), followed by two inductances (22; 123) and a further capacitance (21; 122) connected downstream.Electrical converter device (1) according to claim 15 or 16, characterized in that the inductances (22; 123) of the CLLC topology are the leakage inductances (123; 124) of the high-frequency transformer (20; 120).

18. Electrical converter device (1) according to one of the preceding claims, characterized in that the control device (80; 280) is designed to control the first switching elements (31; 134) and the second switching elements (32; 135) as a function of current, voltage, rotor position, and time.

19. Electrical converter device (1) according to one of the preceding claims, characterized in that the DC / DC converter (10; 110; 210) has a three-phase bridge circuit (15; 141) on the input side and on the output side. EMX021 4420. Electrical converter device (1) according to claim 19, characterized in that the three-phase bridge circuit (15; 141) has n half-bridges (36; 131), each half-bridge (36; 131) having two switching elements (32; 135).

21. Electrical converter device (1) according to one of the preceding claims, characterized in that the first switching elements (31; 134) are designed as silicon carbide (SIC) or gallium nitride (GaN) MOSFETs.

22. Electrical converter device (1) according to one of the preceding claims, characterized in that the second switching elements (32; 135) are designed as IGBTs or MOSFETs.

23. Electrical converter device (1) according to one of the preceding claims, characterized in that the DC / DC converter (10; 110; 210) and the DC / AC converter (40; 140; 240) are arranged in a metallic housing. 24.Method for operating an electrical converter device (1), wherein the electrical converter device (1) controls at least one DC / DC converter (10; 110; 210) via first switching elements (31; 134) and at least one DC / AC converter (40; 140; 240) via second switching elements (32; 135) by means of a control device (80; 280), wherein the second switching elements (32; 135) of the DC / AC converter (40; 140; 240) are controlled in such a way that the at least one output voltage (410) of the DC / AC converter (40; 140; 240) is pulse-shaped, wherein the at least one output. EMX021 45input voltage (420) of the DC / DC converter (10; 110; 210) is tracked between pulses of the output voltage (410) of the DC / AC converter (40; 140; 240) such that a quasi-sinusoidal phase current (430) is formed at the output of the electrical converter device (1).

25. Method for operating an electrical converter device (1) according to claim 25, characterized in that the second switching elements (32; 135) of the DC / AC converter (40; 140; 240) are controlled according to the MSK method, wherein the MSK method forms a twelve-pulse output voltage (410) at the output of the electrical converter device (1).

26. A method for operating an electrical converter device (1) according to one of claims 25 to 26, characterized in that the DC / DC converter (10; 110; 210) is the actuator of the rotor-controlled three-phase voltage system, whereby the amplitude of the phase current (430) is controlled by the DC / DC converter (10; 110; 210).Method for operating an electrical converter device (1) according to one of claims 25 to 27, characterized in that the torque control is effected by the phase shift between the rotor voltage and the rotor-controlled three-phase voltage system.

28. Electrical converter device (1) according to one of the preceding claims, characterized in that the electrical converter device (1) is used to operate an electrical machine (60; 160; 260) or to supply an n-phase AC electrical network (270).

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