DE102010019151A1 - Device for transmitting energy in combustion engine drivable motor car, has voltage conversion element whose inductor connects low voltage area and portion between switches over supply path that is different from another supply path - Google Patents

Abstract

The device (1) has a three-phase electrical machine (6) i.e. direct current (DC) machine, operated as a motor or a generator, and a three-phase converter (7) comprising a half bridge with power switches (S1-S6) e.g. MOSFETs. A portion among the power switches is electrically connected with terminals (K1-K3) of the electric machine over a supply path. An inductor (L) of a voltage conversion element electrically connects a low voltage area (2) and the portion between the power switches of the half bridge over another supply path that is different from the former supply path. An independent claim is also included for a method for transmitting energy in a motor car.

Description

The invention relates to a method and a device for transmitting energy in a motor vehicle.

In modern motor vehicles, there is often the need to provide electrical consumers with a supply voltage that can have different voltage levels for different consumers. As a rule, supply voltages of different voltage levels are provided by different energy stores, for example batteries. It is known to provide for conventional low-voltage system low-voltage batteries with an output voltage of 12 V (conventional electrical system batteries). These are used for power supply of, for example, control units in the vehicle, which are designed for a voltage level of 12 V. With the increase of control devices and electrical consumers, especially of high power electrical consumers, in the vehicle, the idea has been developed to integrate a so-called high voltage battery, which has a higher output voltage, for example 42 V, than the low voltage battery in the vehicle. As a result, z. B. at the same power consumption requires a lower current, which can be used smaller cross-sections. In this case, the low-voltage battery and the high-voltage battery are generally formed separately.

In classic, internal combustion engine driven vehicles there is also the problem that for a conversion of electrical energy from the electrical system battery into mechanical energy (motor operation) and for the conversion of mechanical into electrical energy of the electrical system battery (regenerative operation) usually two differently shaped electric motors (eg a starter and an alternator) are needed.

The DE 102 44 229 A1 discloses a generic power supply system equipped with a high voltage system and a low voltage system. The power system includes an AC motor suspended as a load on the high voltage system and driven by the high voltage power source. Further, the power supply system includes an inverter for controlling the supply of the power to the AC motor. Further, the power supply system includes a supply path of the low voltage system for applying a neutral voltage of the AC motor to a load of the low voltage system and a load of the low voltage system for connection to the supply path of the low voltage system, wherein a voltage ratio of the low voltage system to the high voltage system is set to 1: 2 to 1: 4 ,

The DE 198 57 645 A1 discloses an electrical system for an electric vehicle, comprising: a DC input circuit, a voltage inverter connected to the DC input circuit to which an input voltage is applied from the DC input circuit and which generates a variable frequency variable voltage, an AC motor having a plurality of windings each end is connected to an AC output terminal of the inverter while the other ends of the windings are connected to a zero point of the motor windings, a variable-voltage energy storage element connected between the neutral point and a terminal point in the DC input circuit, and a DC power supply connected to the opposite ones Ends of the energy storage element is connected.

It raises the technical problem of providing a method and a device for transmitting energy in a motor vehicle, which on the one hand enable efficient energy transfer and are cost-effective, with an energy transfer from a low voltage range of the electrical system to the electric machine and / or other voltage ranges of the electrical system different voltage levels and energy transfer from the electric machine in the low voltage range, in particular to the electrical system battery, and / or the other voltage ranges is made possible.

The solution of the technical problem results from the objects with the features of claims 1 and 6. Further advantageous embodiments of the invention will become apparent from the dependent claims.

Proposed is a device for transmitting energy in a motor vehicle, wherein the motor vehicle has a vehicle electrical system, wherein the electrical system has at least one low-voltage region with a first voltage level. To the electrical system in this case electrical consumers of the motor vehicle, in particular control devices of the motor vehicle, are connected. The first voltage level may be 12 V, for example. Furthermore, the device comprises at least one electric machine and a converter associated with the electric machine. The electric machine is in a motorized or regenerative mode Operation operable. In a motor operation, the electric machine can serve, for example, as a starter of an internal combustion engine of the motor vehicle. In a generator operation, the electric machine can serve, for example, as an alternator of an internal combustion vehicle. An operating voltage of the electric machine can in this case be variable, in particular higher than 12 V. Preferably, the electric machine is designed as a three-phase electric machine and the inverter as a three-phase inverter. The inverter is used in the motor operation of the electric machine of generating an alternating voltage with a desired frequency and a desired amplitude of a DC voltage. Further, the inverter is used in generator operation of generating a DC voltage having a desired amplitude from an AC voltage generated by the electric machine.

Of course, however, a single-phase design of the electric machine, for example as a DC machine, conceivable.

Furthermore, the device according to the invention comprises at least one intermediate circuit capacitor. In this case, the intermediate circuit capacitor is preferably connected upstream of the converter, so that an operating or input voltage of the converter is equal to the intermediate circuit voltage dropping across the intermediate circuit capacitor. The intermediate circuit voltage can also be variable; in particular, the intermediate circuit voltage can be higher than 12 V.

Furthermore, the device comprises at least one energy store associated with the low-voltage region. This energy storage device may in particular be a battery or so-called onboard power supply battery. Without limitation, the energy storage is referred to below as the onboard power supply battery. The vehicle power supply battery serves to supply energy to electrical consumers connected to the vehicle electrical system, in particular also to a power supply of the electric motor during engine operation. Next, the electrical system battery is an energy storage, in particular a storage of electrical power generated by the electric machine in the generator mode.

Furthermore, the device comprises at least one element for voltage conversion. Via the element for voltage conversion, the converter is electrically coupled to the low-voltage region, in particular to the vehicle electrical system battery. The element for voltage conversion can in this case be operated as a so-called down converter or as a so-called up converter. Preferably, the voltage conversion element is a DC / DC converter.

The converter comprises at least one half bridge with two circuit breakers, wherein a portion of the half bridge between the circuit breakers is electrically connected via a first electrical supply path to a terminal of the electric machine. The power switches are in this case designed, for example, as a MOSFET or IGBT.

According to the invention, the element for voltage conversion also comprises at least two power switches. Furthermore, the element for voltage conversion comprises at least one inductor. In this case, an inductance is an at least partially inductive component, for example a coil. According to the invention, the power switches of the voltage conversion element are the power switches of the at least one half-bridge of the converter. As a result, the element for voltage conversion is at least partially integrated in the inverter.

The at least one inductance of the voltage conversion element is arranged in a second supply path, which electrically connects the low-voltage region and the section of the half-bridge lying between the circuit breakers of the half-bridge.

According to the invention, the second supply path is different from the first supply path. In this way, therefore, the at least one inductance is formed as an individual component, in particular as a component formed separately from an inductance of the electric machine. In contrast to DE 102 44 229 A1 and to DE 198 57 645 A1 an inductance of the element for voltage conversion according to the invention is not formed by an inductance of the electric machine.

This results in an advantageous manner that in generator operation of the electric machine by means of a control unit circuit breaker of the element for voltage conversion are controllable such that electrical energy generated by the electric machine at least partially in the low voltage range, ie to the electrical system battery and / or to the low voltage range connected electrical Consumers, is transferable. Furthermore, in motor operation by means of the control unit, the power switches of the element for voltage conversion can be controlled such that an energy of the low-voltage region, in particular an electrical energy stored in the vehicle electrical system battery, can be transmitted at least partially to the electric machine.

The energy transfer here is independent of voltage differences in the electrical system, so regardless of voltage differences between the low voltage range and a DC link voltage.

In motor operation, an energy supply of the electric machine from the vehicle electrical system battery is thus possible in an advantageous manner. If the electric machine as a starter, z. As used for an internal combustion engine, so no further energy storage must be provided in addition to the electrical system battery in the vehicle in an advantageous manner. In addition, the electric machine in an advantageous manner, the functionality of an alternator, so a generator, take over, with electrical energy can be stored in the electrical system battery. The described operating modes (motor or generator operation) are made possible here by means of the voltage conversion element. For example, high voltages generated by the electric machine during regenerative operation can be converted into a voltage equal to the first voltage level of the converter by means of the voltage conversion element. Likewise, voltages required for a start or a motor operation of the electric machine can be converted from the first voltage level to a desired, in particular higher, voltage level by means of the element for voltage conversion. This results in particular a low-efficiency operation of the electric machine. Since the circuit breakers of the element for voltage conversion are also circuit breakers of at least one half-bridge of the inverter, there is a partially integrated design of the element for voltage conversion. As a result, manufacturing costs and space requirements can be minimized in an advantageous manner.

In particular, in comparison with the doctrine of DE 102 44 229 A1 and the DE 198 57 645 A1 no star point tapping of the electric machine is necessary. This results in an advantageous manner that by means of the device according to the invention electrical machines with different engine circuits, eg. B. delta circuits, can be operated in a motor and generator operation. In a further advantageous manner results in comparison an improved efficiency in the DC converter operation, hereinafter also referred to as converter operation, the inverter, since the at least one inductance of the element can be optimized for voltage conversion to the converter operation.

One possible optimization is z. B. the use of ferrite as a magnetic material. Motor inductances, ie inductances of the electric machine, have to take into account requirements for high forces or torques in their design. In particular, a material of the motor inductances must be designed adapted to high magnetic field strengths, which z. B. leads to the use of more lossy iron than magnetic material. Such requirements are advantageously not in the design or dimensioning of the at least one inductance of the element for voltage conversion.

In a further advantageous manner is made possible by the device according to the invention that a charging or discharging of the electrical system battery does not have to flow in addition to the inductances, such as windings of the electric machine, which z. B. can lead to a lower maximum torque or torque fluctuations.

In an advantageous embodiment of the invention is in the motor operation of the electric machine, a power supply of the electric machine exclusively from the electrical system battery guaranteed. This results in an advantageous manner that a power supply of the electric machine can be done solely from the electrical system battery out. As a result, no further energy storage for the power supply of the electric machine in the vehicle to be arranged.

In a further embodiment, the converter is designed as a three-phase converter, wherein each phase of the converter is associated with a half-bridge, each with two circuit breakers. Analogous to the previous embodiments, a section between the circuit breakers of each half-bridge is electrically connected via first supply paths to terminals of a three-phase electric machine. The voltage conversion element comprises six power switches and three inductors, with the six power switches being the two power switches of the half bridges of the inverter respectively. The inductances of the voltage conversion element are arranged in respective second supply paths, wherein the second supply paths electrically connect the low voltage region and the portion of the respective half bridge lying between the power switches of the respective half bridge and are different from the first supply paths. The design of the voltage conversion element with six circuit breakers and three inductors advantageously increases the degrees of freedom of control in the converter operation of the voltage conversion element. A converter function of the element for voltage conversion is in this case carried out by means of the power switch of all half-bridges, whereby a symmetrical control of the electric machine is advantageously made possible even during an exercised conversion function of the element for voltage conversion. Preferably, the three inductances of the voltage conversion element are the same. In comparison to However, with only one inductance, the respective inductances of the voltage conversion element may be designed for smaller currents.

In a further embodiment, by means of the control unit, a switching of the power switch of the converter and thus also of the element for voltage conversion depending on at least one desired mechanical power of the electric machine and a desired energy transfer in the low voltage range or out of the low voltage system out controllable. In this case, a desired mechanical power of the electric machine comprises a mechanical power in the engine operation, for. B. depending on a desired speed and a desired torque, and a desired mechanical power in the generator mode, for. B. as a function of a desired braking torque of the electric machine. In this case, the control unit essentially has two tasks to fulfill. On the one hand, at least two power switches of the inverter, which are at the same time circuit breakers of the voltage conversion element, must be controlled so as to enable a desired energy transfer from the low voltage range to the electric machine or from the electric machine into the low voltage range. Furthermore, the control unit must control all circuit breakers of the inverter, including the power switch of the element for voltage conversion, so that a desired mechanical power of the electric machine is adjusted. Various methods of control will be explained in more detail below. The inventive device results in an advantageous manner that a desired energy transfer with desired transmission direction and desired amount of energy can be set simultaneously to a desired operation of the electric machine by means of the control unit.

In a further embodiment, the vehicle electrical system has at least one high-voltage region with a second voltage level, wherein the second voltage level is higher than the first voltage level. Preferably, the high voltage region is connected via a supply path to the DC link capacitor. By means of the element for voltage conversion in this case can be converted to a voltage with the second voltage level, a (output) voltage of the electrical system battery, ie a DC voltage with the first voltage level. This makes it possible in an advantageous manner to connect electrical loads to the electrical system, which are designed for a higher operating voltage than an output voltage of the electrical system battery. By means of the element for voltage conversion, it is advantageously possible here for electrical energy to be transferred from the low-voltage region into the high-voltage region and / or to the electric machine. At the same time, electrical energy can be transmitted from the electric machine into the high-voltage region and / or into the low-voltage region during generator operation of the electric machine.

Further proposed is a method for transmitting energy in a motor vehicle, wherein the motor vehicle has a device for energy transmission according to the preceding explanations. In a generator operation of the electric machine, a control unit controls circuit breakers of the element for voltage conversion, which are also circuit breakers of an inverter, such that electrical energy generated by the electric machine is at least partially into the low-voltage area, in particular to the electrical system battery transferred. In this case, a control unit determines switching times of the power switches and controls switching of these power switches according to the calculated switching times. Further, the control unit controls in a motor operation, the power switch of the element for voltage conversion such that an energy of the low voltage region, in particular a stored in the electrical system battery electrical energy is at least partially transmitted to the electric machine. In this case, in the motor operation of the electric machine, a power supply of the electric machine can take place partially or exclusively from the onboard power supply battery. The inventive method advantageously allows an electric machine at the same time as a motor, for. B. as a starter, or as a generator, for. B. as an alternator to use, with a power supply of the electric machine z. B. can be made partially or exclusively from a low-voltage range of the electrical system associated with the vehicle electrical system battery. Furthermore, the electrical energy generated in regenerative operation can also be stored in the vehicle electrical system battery and / or used for supplying electrical power to electrical consumers assigned to the low-voltage region. The method performed by the control unit for the control of the power switch in this case allows two different functions of the inverter can be performed simultaneously. In this case, a first function is a converter function, wherein switching times of circuit breakers of the element for voltage conversion are controlled in dependence on a desired energy transfer into the low-voltage range or out of the low-voltage range. In a second function, the method of controlling the circuit breakers enables operation of the electric machine with desired operating parameters, such as, for example: B. a desired torque and / or a desired speed.

A control or regulation of the circuit breaker can also take place via a so-called control or Regelhierachie with multiple levels. This z. B. a desired current and / or current direction can be specified by the at least one inductance of the element for voltage conversion. The control unit or subunits of the control unit determine from the desired current intensity and / or current direction an intermediate circuit voltage to be set by means of the element for voltage conversion. From this, in turn, switching times of the power switches of the voltage conversion element can be calculated. Likewise, the control unit or a subunit of the control unit from desired operating parameters of the electric machine (torque, speed, direction of rotation) determine a desired terminal differential voltage and / or a desired motor current. Next z. B. from the desired terminal differential voltages switching times of the circuit breaker of the inverter can be calculated.

In a further embodiment, a unit for determining at least one mean phase voltage determines at least one mean phase voltage of the converter at least in dependence on a desired energy transfer into the low-voltage range or out of the low-voltage range. Here, the average phase voltage is a voltage to be set by the voltage conversion element. The average phase voltage is thus the phase voltage of the half-bridge or the half-bridges which simultaneously comprise the power switches of the voltage conversion element.

The half-bridge is between a high voltage supply path and a low voltage supply path, e.g. B. mass arranged. In this case, the phase voltage of a half-bridge denotes that across the half-bridge of the circuit breaker, which is arranged between a section between the circuit breakers of the half-bridge and the supply path with the low voltage.

Furthermore, at least one unit for determining at least one motor voltage of the electric machine determines a motor voltage of the electric machine at least as a function of a desired mechanical power of the electric machine. In this case, the term "motor voltage" refers to a voltage whose properties (eg amplitude, frequency, phase) determine a rotational speed and / or a torque and / or a direction of rotation of the electric machine. If the electric machine z. B. connected in a star connection, the motor voltages denote the strand voltages of the electric machine. If the electric machine is not connected in a star connection, then the motor voltages can be calculated by means of later explained methods. From the motor voltages, the terminal-differential voltages of the electric machine can be derived, which can also determine a mode of operation (torque, speed, direction of rotation) of the electric machine. At least one unit for determining at least one desired phase voltage determines a nominal phase voltage of at least one half-bridge of the converter at least as a function of the average phase voltage and the motor voltage. In particular, by means of the at least one motor voltage or its properties a desired mode of operation (motor or generator operation with a desired speed and a desired torque) can be set. The mean phase voltage determines u. al .; Whether energy is transferred from the electric machine to the low voltage range or from the low voltage range to the electric machine. Since the circuit breakers of the voltage conversion element are at the same time circuit breakers of the converter, problems may arise when a mean phase voltage deviates from a phase voltage determined from a desired motor voltage.

In order to avoid these problems, the unit for determining at least one desired phase voltage determines the final setpoint phase voltage of the converter, in particular also the phase voltage of the at least one half-bridge, which simultaneously comprises power switches of the element for voltage conversion and of the converter, depending on the determined average phase voltage and the at least one motor voltage. This results in different methods for determining the at least one desired phase voltage.

For example, if the electric machine is a three-phase electric machine, the inverter is a three-phase converter and comprises only a first half-bridge associated with a first phase of the electric machine, power switches which are also circuit breakers of the voltage conversion element, the unit may determine at least one setpoint Phase voltage in a first operating mode set the desired phase voltage of the first half-bridge equal to the average phase voltage determined by the at least one unit for determining a mean phase voltage. At the same time, the unit for determining at least one desired phase voltage, the desired phase voltage of the second half-bridge as a sum of the average phase voltage of the first half-bridge (target phase voltage of the first half-bridge) and a desired terminal-difference voltage between the at the Determine the first half-bridge of the inverter connected to the terminal of the electric machine and connected to the second half-bridge terminal of the electric machine. Similarly, the third phase voltage may be determined as a sum of the desired phase voltage of the first half-bridge and a desired terminal-to-differential voltage between the first terminal of the electric machine and the third terminal of the electric machine.

In a second mode of operation, the first desired phase voltage is calculated as a sum of the average phase voltage and a desired first motor voltage. Similarly, a second desired phase voltage is calculated as the sum of the average phase voltage and a desired second motor voltage. Similarly, a third desired phase voltage is calculated as a sum of the average phase voltage and a desired third motor voltage.

The unit for determining at least one average phase voltage, the unit for determining at least one motor voltage and the unit for determining at least one desired phase voltage may in this case be integrated in the control unit or designed as separate control units. Furthermore, the control unit or a subunit of the control unit controls switching of the power switches of the converter in dependence on the determined desired phase voltage. This results in an advantageous manner that a converter operation with desired properties (direction of energy transfer, amount of transmitted energy) and a desired operation of the electric machine (motor or generator operation) with desired properties (eg., Torque, speed, direction of rotation) means of the inverter is enabled.

In a further embodiment, a desired energy transfer into the low-voltage range or out of the low-voltage range and a desired mechanical power of the electric machine are determined by a strategy unit at least as a function of an intermediate circuit voltage and / or at least one vehicle dynamic sensor signal and / or at least one vehicle operation-specific sensor signal.

This results in an advantageous manner that a permissible upper limit of a DC link voltage, the z. B. are predetermined by operating parameters of the DC link capacitor is not exceeded. As a result, in particular a destruction of the DC link capacitor is avoided. The strategy unit forms a top-level control or regulation level of a control or regulation hierarchy. In this case, in particular, the desired energy transfer, which is now to be taken as manipulated variables, is adjusted into the low-voltage region or out of the low-voltage region, and the desired mode of operation of the electric machine is adapted to an intermediate-circuit voltage. Additionally or alternatively, also driving dynamics variables, for example a speed or an acceleration of the vehicle, can be taken into account. Further, additionally or alternatively input variables such. B. accelerator pedal, brake pedal and / or selector lever position are taken into account in the determination of the two control variables. In this case, drive-specific sensor signals designate output signals z. As an accelerator pedal sensor, a brake pedal sensor and / or a selector lever position sensor.

In a further embodiment, the unit for determining at least one desired phase voltage determines the at least one desired phase voltage as a function of a rotational speed of the electric machine. In particular, a control of the switching of the power switches of the inverter according to the previously explained first operating mode and the previously explained second operating mode can be carried out in dependence on a rotational speed. Ideally, the unit for determining at least one desired phase voltage determines the at least one desired phase voltage such that, in particular in the first operating mode, a differential terminal voltage which does not exceed the average phase voltage determined by the average phase voltage determining unit. Further ideally, the unit for determining at least one desired phase voltage determines the at least one desired phase voltage in the second operating mode such that an alternating current component of the current by the at least one inductance of the element for voltage conversion remains sufficiently small, for example, is smaller than a predetermined threshold value.

For reasons of a simpler feasibility, however, a speed-dependent criterion for determining the at least one desired phase voltage can be used instead of these criteria. For this purpose, the device according to the invention may advantageously comprise a sensor for detecting the rotational speed of the electric machine. In the first mode of operation, the current through the at least one inductance of the voltage conversion element is a direct current. However, in the first mode of operation, the magnitude of a differential terminal voltage is, in the best case, limited to one half of the intermediate circuit voltage, whereby operation of the electric machine with a differential terminal voltage above the limit is not possible. In the second operating mode, a differential terminal voltage may assume a level of the intermediate circuit voltage. However, an alternating current component is superimposed on a direct current flowing through the at least one inductance of the at least one element for voltage conversion. By the speed-dependent switching between the two operating modes can be advantageously exploit the advantages of each mode of operation.

In a further embodiment, the unit for determining at least one desired phase voltage determines the at least one desired phase voltage according to a first and a second operating mode, wherein a switchover between the first and the second operating mode depending on a rotational speed of the electric machine, wherein a switching Switching or hysteresis-based switching or fade-based switching is. In the simplest case (hard switching) is switched at a predetermined speed limit "hard" between the first operating mode and the second operating mode. This switching is advantageously easy to implement. However, if the electric machine fluctuates for a long time in a small speed interval by the predetermined speed limit, the case could occur that deviates at unfavorably selected switching times a desired phase voltage, for example, the first phase of a determined for the first phase average phase voltage. This can be avoided in an advantageous manner by means of a hysteresis-based switching. For this purpose, two predetermined speed limits are set, an upper speed limit and a lower speed limit. If the rotational speed of the electric machine exceeds the upper limit, the desired phase voltages are determined according to the second operating mode. If the speed of the electric machine now falls below the lower limit, then a determination of the desired phase voltages according to the first operating mode is performed. Between the lower and the upper limit or between the upper and the lower limit (hysteresis range), the operating mode is kept in which was changed last. A "hard" switching can produce unpleasant acoustic noises in unfavorable cases. This can be avoided in an advantageous manner by a fade-based switching. In this case, again above an upper limit, desired phase voltages are determined according to the second operating mode. Below a lower speed limit, desired phase voltages are determined according to the first operating mode. In the range between the lower and the upper speed limit, for example, the desired phase voltages are linearly interpolated between the desired phase voltages determined according to the first and second operating modes. For this purpose, for example, a cross-fade factor can be used.

Furthermore, the device according to the invention may comprise at least one sensor for sensing a rotor position of the electric machine and / or a sensor for sensing a phase current of the electric machine and / or a sensor for sensing the first voltage level and / or a sensor for sensing the second voltage level and / or a sensor for sensing a charging or discharging current of the onboard power supply battery and / or a sensor for sensing a current flowing through the at least one inductance of the voltage conversion element, the control unit switching the power switches of the converter as a function of at least the rotor position and / or the phase current and / or the first voltage level and / or the second voltage level and / or the charging and / or discharging current and / or the current flowing through the at least one inductor. The different sensor signals can be evaluated at different levels of the control hierarchy.

Next, the DC link capacitor, a thin-film capacitor (Supercap, Boostcap) are connected in parallel. This can absorb or deliver in an advantageous manner in seconds range similar or even greater benefits than the electrical system battery. A power input or output can also be done in an advantageous manner at the same time with a power consumption or delivery of the electrical system battery. As a result, the electric machine can also be operated at least for a short time at higher powers than in operation exclusively via the vehicle electrical system battery.

Next, the control unit switching the power switch in response to energy transfer in a high voltage range of the electrical system in or out of the high voltage range of the electrical system out and / or depending on losses, eg. As of ohmic losses and / or magnetic reversal losses in the electric machine and / or switching losses in the circuit breakers, control. The energy to be transferred into the high-voltage region and / or the losses can be regarded as disturbance variables from a control engineering point of view. Their respective size is determined outside the control and can not be determined by the control unit independently of the energy to be transmitted in the low voltage range and the power generated by the electric machine. To improve the control quality, it may be useful, as known in control engineering, to pre-control these disturbances. For this purpose, z. For example, the major energy consumers responsible for the energy to be transferred into the high voltage range have a measured or estimated value of their current power consumed Report control unit. This can be z. B. via a data bus, such as a CAN bus done. The losses can z. Estimated by calculation or estimation of a simple loss model by the control unit. If a precontrol is carried out by means of the control unit, then the control unit ideally only needs to compensate for a deviation between estimated and real disturbance variables during operation. This results in an advantageous manner that are not total amounts of disturbances to compensate.

The invention will be explained in more detail with reference to second embodiments. The figures show:

1 a schematic circuit diagram of a device for energy transmission (prior art),

2 a schematic circuit diagram of a device according to the invention for energy transmission,

3 a schematic circuit diagram of another device according to the invention for energy transmission and

4 a schematic block diagram of a method for energy transfer.

Hereinafter, like reference numerals designate the same or similar technical characteristics.

1 shows a schematic circuit diagram of a device 1 for transmitting energy in a motor vehicle according to the prior art. The device 1 in this case includes a not fully illustrated electrical system with a low voltage range 2 and a high voltage area 3 , Here, the low voltage range 2 a first voltage level of 12V, which corresponds to a battery voltage U _batt = 12V. The high voltage range shown schematically 3 has a second voltage level of 42V. The low voltage range 2 in this case includes an electrical system battery 4 which has an output voltage U _batt of 12V. Next are to the low voltage area 2 further, schematically illustrated electrical consumers 5 connected. Furthermore, the device comprises 1 an electric machine 6 , The electric machine 6 is as a three-phase electric machine 6 shown. In this case, the electric machine 6 three terminals K1, K2, K3 of the electric machine 6 on. It is further shown that the strands of the electric machine represented by motor inductances ML1, ML2, ML3 6 are connected in a star connection with neutral point S. The motor voltages U _S1 , U _S2 , U _S3 drop across the motor inductances ML1, ML2, ML3. In the in 1 illustrated embodiment, the motor voltages U _S1 , U _S2 , U _{S3 are} equal to the phase voltages of the electric machine 6 , Furthermore, the device comprises 1 a three-phase inverter 7 , The three-phase inverter 7 includes three half-bridges. A first half-bridge comprises a first switch S1 and a second switch S2 of the first half-bridge, wherein diodes D1, D2 are connected in antiparallel to the switches. A second half-bridge of the inverter 7 includes a first switch S3 and a second switch S4 of the second half-bridge. Similarly, diodes D3, D4 are connected in anti-parallel to the first switch S3 and second switch S4 of the second half-bridge. A third half-bridge comprises a first switch S5 and a second switch S6 of the third half-bridge, again diodes D5, D6 being connected in antiparallel to the first and second switches S5, S6 of the third half-bridge. By means of the power switches S1, S2, S3, S4, S5, S6, phase voltages U _P1 , U _P2 , U _{P3 are} set. In this case, the difference between a first phase voltage Um and a second phase voltage U _{P2 forms} a differential terminal voltage U _K1-K2 between the first terminal K1 and the second terminal K2 of the electric machine 6 , Analogously, a second differential terminal voltage U _K1-K3 and a third differential terminal voltage U _{K2-K3 are} determined. By switching the power switches S1, S2, S3, S4, S5, S6, predetermined phase voltages and thus predetermined differential terminal voltages U _K1-K2 , U _K1-K3 , U _{K2-K3 can be} set. Connected in parallel with the half bridges is a DC link capacitor C _ZK . About the intermediate circuit capacitor C _ZK drops an intermediate circuit _voltage U _ZK . Between the low voltage range 2 and the DC _link capacitor C _ZK is an element 8th switched to voltage conversion. The element 8th for voltage conversion comprises an inductance L and two power switches S7, S8, to the circuit breakers in turn diodes D7, D8 are connected in anti-parallel. The element 8th for voltage conversion here is a so-called DC / DC converter.

Below is an overview of an operation of the device 1 written for energy transfer. Initially, all circuit breakers S1, ..., S8 are open. The intermediate circuit capacitor C _ZK is then across the inductance L and the diode D7 in anti-parallel to the power switch S7 of the element 8th for voltage _conversion to about the battery voltage U _batt loaded. If z. B. for starting an internal combustion engine, for which the electric machine 6 acts as a starter, a higher intermediate circuit voltage U _ZK desired, the power switch S8 can be closed. It then builds a current i _L through the inductance L opposite to in 1 illustrated current direction of i _L on. If the power switch S8 is opened again, the inductance L continues to drive the current i _L , which passes through the diode D7 connected in anti-parallel to the power switch S7 in FIG the intermediate circuit capacitor C _ZK flows and thus increases the intermediate circuit _voltage U _ZK . To reduce losses, the circuit breaker S7 can also be closed in this phase. The amount of the current i _L through the inductance L decreases. This becomes the element 8th used for voltage _conversion as an up-converter of the battery voltage U _batt to the intermediate _{circuit voltage} U _ZK .

At z. B. running internal combustion engine, the electric machine 6 as a generator, for. B. as an alternator, work. Here, the three-phase inverter 7 controlled such that the intermediate _{circuit voltage} U _{ZK is} greater than the battery _voltage U _batt . The element 8th for voltage conversion is now used as a _buck converter from the intermediate _circuit voltage U _ZK to the battery _voltage U _batt to electrical loads 5 to supply and / or the electrical system battery 4 to load. In this case, the power switch S7 is closed. It then builds up a current i _L in the 1 illustrated current direction of i _L on. If the power switch S7 is opened again, the inductance L drives the current i _L further through the diode D8, without the intermediate circuit energy is withdrawn. To reduce losses, the circuit breaker S8 can also be closed during this phase. The amount of the current i _L through the inductance L decreases.

2 shows a schematic circuit diagram of a device according to the invention 1 for energy transfer. Analogous to the in 1 illustrated device 1 includes the device according to the invention 1 a low voltage range 2 with a wiring system battery 4 and electrical consumers 5 , Furthermore, the device comprises 1 a three-phase electric machine 6 and a three-phase inverter 7 , In 2 here are no anti-parallel diodes D1, ..., D8 shown, which serves only to simplify the presentation. In 2 It is shown that a section between the circuit breakers S1, S2 of the first half-bridge via a first supply path to a first terminal K1 of the electric machine 6 connected is. In the first supply path, a first phase current i _{P1 flows} . Similarly, sections between the circuit breakers S3, S4 and S5, S6 of the second and third half-bridge with the second and the third terminal K2, K3 of the electric machine 6 connected via first supply paths in which phase currents i _P2 , i _P3 flow. In 2 It is shown that the section between the power switches S1, S2 additionally has a second supply path with the low-voltage region 2 , in particular with the vehicle electrical system battery 4 , connected is. In the second supply path, the inductance L of the element for voltage conversion is arranged. Here, the element for voltage conversion is partially in the inverter 7 integrated. It is shown that the power switches S1, S2 of the first half-bridge on the one hand as a power switch S1, S2 of the inverter 7 and, on the other hand, as power switches S1, S2 of the voltage conversion element shown in FIG 1 are shown as power switches S7, S8 act.

It should be noted that the power switches S1-S6 are preferably designed as MOSFETs, which automatically co-generate the anti-parallel diodes D1-D6 as parasitic components.

In 3 is a circuit diagram of another device according to the invention 1 shown for energy transfer. Here, each section between the circuit breakers S1, S2 and S3, S4 and S5, S6 of the half-bridges of the inverter 7 via second supply paths with the low voltage range 2 , in particular the electrical system battery 4 , connected. Inductances L1, L2, L3 are respectively arranged in the second supply paths. Here, all circuit breakers S1, ..., S6 of the inverter function 7 as circuit breaker of the inverter and the element for voltage conversion.

4 shows a schematic block diagram of a method for energy transfer. In the following, essential aspects of the method for energy transmission, in particular a control or regulation of a switching of z. In 2 shown circuit breaker S1, ..., S6 explained. Hereby be of a current account 0 = P P + _{EM NV} P + _HV + P _DC + P _ET formula 1 went out. Here, P _EM z. B. one of the in 2 illustrated electric machine 6 power converted in motor operation. In motor operation, the electric machine gives 6 the mechanical power P _Mech = M × Ω, where M is a shaft torque and Ω is an angular velocity of a rotor of the electric machine 6 designated. Is simplified assuming that the electric machine 6 lossless, so is the electrical system taken from the electrical system P _EM = P _Mech . Further, the power P _NV denotes one of the low voltage range 2 electrical power transmitted or one in the low voltage range 2 , ie to the electrical system battery 4 and to the electrical consumers 5 , transmitted power. The power P _NV can according to P _NV = U _batt × i _L Formula 2 be calculated. The power P _HV designates that of a high voltage range 3 absorbed or delivered power and is calculated according to P _HV = U _ZK × i _HV Formula 3.

The DC _link capacitor C _ZK takes power in motor operation P _ZK = U _ZK × i _ZK Formula 4 on.

P _Verl refers here flat rate all losses, z. B. ohmic losses and re-magnetization losses in the electric machine 6 and switching losses in the circuit breakers S1, ..., S6.

In the method according to the invention, the powers P _NV and the power P _{EM can be set} by means of a switching of the power switches S1,..., S6.

Following is a motor operation of the electric machine 6 accepted. In a top level of the control hierarchy, one of the low-voltage areas, in particular the vehicle electrical system battery, is used 4 , to be taken power P _NV and an electric power P _{EM of} the electric machine 6 specified.

Here, the from the low voltage range 2 out power P _NV are controlled by means of a change in a current intensity of the current i _L flowing through the inductance L of the voltage conversion element. Assuming a loss of freedom applies U _L = L × di _L / dt Formula 5.

Here, U _L denotes a voltage drop across the inductance L. So is a first phase voltage U _{P1 of} a first half-bridge of in 2 shown inverter 7 greater than the battery _voltage U _batt , the current strength of i _{L increases} . The current intensity of i _L decreases when the first phase _voltage U _{P1 is} less than the battery _voltage U _batt . Here, it is assumed that the battery _voltage U _{batt is} constant and is 12V. The current intensity and a current direction of the current i _L can therefore be changed by setting the first phase voltage U _P1 . In this case, the current intensity and the current direction of the current i _{L can} preferably be detected by means of a sensor, wherein the first phase voltage U _{P1 is} regulated based on a difference between a desired current and a currently detected actual current i _{L, soll} -I _L.

In 4 is shown as one unit 10 For determining a mean first phase _voltage U _P1M, a mean first phase _voltage U _P1M in dependence on a desired current i _{L, soll} and a detected current i _L is calculated by the inductance L. Here it is shown that the setpoint current i _{L, should be} from a strategy unit 11 is determined. The function of the strategy unit 11 will be explained later.

A major limitation of in 2 illustrated device 1 for energy transmission is that a time average of the first phase _voltage U _{P1 must be} equal to an average value of the battery _voltage U _batt , otherwise the onboard power supply battery would be charged or discharged permanently. In addition, it results from operating conditions of conventional rotating electrical machines 6 in that average values of the phase voltages U _P1 , U _P2 , U _P3 must be the same. Under these assumptions, then, the unit 10 to determine the first average phase _voltage U _P1M, the first phase _voltage U _P1 and also the other phase voltages U _P2 , U _P3 must be equal to the battery _voltage U _batt at least as a function of time, independently of the intermediate _{circuit voltage} U _ZK . Preferably, the intermediate circuit voltage U _ZK to twice the battery voltage U _batt is controlled. In this embodiment, therefore, U _ZK preferably corresponds to 24 V. Then, an average value of the phase voltage U _P1 , U _P2 , U _{P3 can be set} to half the intermediate circuit _voltage U _ZK .

The setting of a phase voltage U _P1 , U _P2 , U _P3 can - as known - done by a pulse width modulation. For example, the first phase voltage U _{P1 can be} set by alternately closing or opening the power switches S1, S2 of the first half-bridge. Opening or closing can be done at a constant frequency. Is z. B. within a period of a turn-on time T _{S1 of} the first circuit breaker S1 of the first half-bridge equal to the turn-on time T _{S2 of} the second power switch _S2 of the first half-bridge, the first phase voltage U _{P1 is} on average half the DC link voltage U _{ZK / 2} . If the first power switch S1 is permanently closed, then the first phase voltage U _{P1 is} equal to the intermediate circuit voltage U _ZK . If the second power switch S2 is permanently closed, then the first phase voltage U _{P1 is} equal to zero. By a ratio of the turn-on times T _S1 , T _S2 to the period (sum of the turn-on times T _S1 + T _S2 ), the mean value of the first phase voltage U _{P1 can} therefore be set as desired between zero and the intermediate circuit voltage U _ZK : U _P1 / U _ZK = T _S1 / (T _S1 + T _S2 ) Formula 6.

Next, as previously mentioned, that of the electric machine 6 be set to be generated electric power P _EM . In this case, known methods for controlling electrical machines essentially also for in 2 shown device can be applied. In this case, it can generally be assumed that a setpoint torque M _{soll is} predetermined by a top level of a controller hierarchy, whereby the setpoint torque M _{soll can be determined} by means of known methods and using further ones Inputs of one unit 12 be determined for the determination of motor voltages U _S1 , U _S2 , U _S3 . In 2 is an electric machine 6 represented, which is connected according to a so-called star connection. Here, a first motor voltage U _S1 corresponds to one between a first terminal K1 and a neutral point S of the electric machine 6 adjacent strand tension. Similarly, a second motor voltage U _S2 denotes a between a second terminal K2 of the electric machine 6 and the neutral point S falling strand voltage. Similarly, a third motor voltage U _S3 denotes a between a third terminal K3 and a neutral point S of the electric machine 6 sloping strand tension. It should be noted that the in 2 shown motor voltages U _S1 , U _S2 , U _S3 not for each interconnection of an electric machine 6 can be displayed directly. Is the electric machine 6 For example, interconnected in a delta connection, the motor voltages U _S1 , U _S2 , U _S3 mentioned here are not directly measurable, but only indirectly calculable. Method for calculating the motor voltages U _S1 , U _S2 , U _S3 for any interconnections of electric machines will be explained later. By means of the motor voltages U _S1 , U _S2 , U _S3 , differential terminal voltages U _K1-K2 , U _K1-K3 , U _K2-K3 can be determined. A first differential terminal voltage U _{K1-K2 in} this case describes a voltage difference between a voltage applied to the first terminal K1 voltage and applied to the second terminal K2 voltage. Analogously, a second differential terminal voltage U _K1-K3 and a third differential terminal voltage U _{K2-K3 are} defined. The differential terminal voltages U _K1-K2 , U _K1-K3 , U _K2-K3 correspond to a difference of the phase voltages U _P1 - U _P2 , U _P1 - U _P3 , U _P2 - U _P3 . As a result, it can be seen that desired motor voltages U _S1 , U _S2 , U _{S3 can be set} by means of an adjustment of the phase voltages U _P1 , U _P2 , U _P3 .

As a rule, to determine the motor voltages U _S1 , U _S2 , U _S3 from the setpoint torque M _soll using a rotor position of the electric machine detected by means of a motor position sensor 6 Target phase currents i _{P1, soll} , i _{P2, soll} , i _{P3, shall be} calculated. From this, the motor voltages U _S1 , U _S2 , U _{S3 are} calculated, if appropriate using phase currents i _P1 , i _P2 , i _P3 detected by means of sensors.

Often, but not necessarily, the motor voltages U _S1 , U _S2 , U _{S3 are} cosinusoidal, z. B. U _S1 = U _A × cos (α); U _S2 = U _A × cos (α + 120 °); U _S3 = U _A × cos (α + 240 °) Formula 7.

Here, U _A denotes a maximum voltage amplitude of the motor voltage U _S1 , U _S2 , U _S3 and α is a rotor position of the rotor, not shown, of the electric machine 6 , In general, a frequency of these cosinusoidal voltages and an amplitude of these cosinusoidal voltages increase with increasing speed Ω of the electric machine 6 , Important for the inventive method is that a time average of the motor voltage U _S1 , U _S2 , U _S3 in a rotating electric machine 6 is about zero.

One unity 13 for determining desired phase voltages U _{P1, soll} , U _{P2, soll} , U _{P3, shall be} determined as a function of the first average phase voltage U _P1M and the three motor _voltages U _S1 , U _S2 , U _S3 setpoint values of the phase voltages U _P1 , U, U _{P2, shall} , U _{P3, should} . The determination of the desired phase voltages U _{P1, S} , U _{P2, S} , U _{P3, shall} occur in two different operating modes.

A first operating mode is for a standstill (speed of the electric machine 6 equal to zero) and low speeds of the electric machine 6 used. Here, the first target phase voltage U _P1, equal to that of the unit 10 for determining the first average phase _voltage U _P1M certain first average phase _voltage U _P1M set. The remaining desired phase voltages are determined such that at the terminals K1, K2, K3 of the electric machine 6 Differential terminal voltages U _K1-K2 , U _K1-K3 , U _{K2-K3 are} present, which are specified by the motor voltage U _S1 , U _S2 , U _S3 . The desired phase voltages U _{P1, S} , U _{P2, S} , U _{P3, should be} determined in accordance with U _{P1, soll} = U _P1M ; U _{P2, soll} = U _P1M + (U _S2 - U _S1 ); U _{P3, soll} = U _P1M + (U _S3 - U _S1 ) Formula 8.

The first mode of operation is characterized in that even with stationary and a high torque emitting electric machine 6 the first phase voltage U _P1 and the motor voltages U _S1 , U _S2 , U _S3 can be set independently of each other. Thus, it is possible to obtain a desired power P _NV from the low voltage range 2 to transfer out. At the same time it is possible to use the electric machine 6 in a desired operation, ie with a desired torque and a desired speed to operate.

The disadvantage here is that a terminal differential voltage U _K1-K2 , U _K1-K3 , U _K2-K3 at the terminals K1, K2, K3 of the electric machine 6 may be at most the amount of the mean phase _voltage U _P1M . This can be deduced as shown below. According to a mesh equation: U _P2 = U _P1 + U _S2 - U _S1 Formula 9.

The phase voltages U _P1 , U _P2 , U _P3 , in particular also the second phase voltage U _P2 are, as previously explained, by means of the power switch S3, S4 arbitrarily between 0 and 24 V. adjustable. In the first operating mode, the first phase voltage U _{P1 is} constant and, as previously explained, on average equal to the battery _voltage U _batt = 12 V. Thus, a difference between the second and the first motor voltage U _S2 - U _S1 (differential terminals voltage U _{K1 -K2} ) are only between -12 V to 12 V. This results in a disadvantage that in the first operating mode, the electric machine 6 only with differential terminal voltages U _{P1, soll} , U _{P2, soll} , U _{P3, shall be operated} with a maximum amplitude of -12 V or 12 V, even if the electric machine 6 is designed for higher amplitudes of the differential terminal voltages U _K1-K2 , U _K1-K3 , U _K2-K3 .

The second operating mode is intended for higher speeds. In this case, the setpoint phase voltages U _{P1, soll} , U _{P2, soll} , U _{P3, should be determined} according to U _{P1, soll} = U _P1M + U _S1 ; U _{P2, soll} = U _P1M + U _S2 , U _{P3, soll} = U _P1M + U _S3 Formula 10.

In this case, therefore, the motor voltages U _S1 to U _S3 to that of the unit 10 certain mean phase _voltage U _{P1M is} added to the desired phase _voltages U _{P1, soll} , U _{P2, soll} , U _{P3, soll} to get. It should be noted that in the second operating mode, the requirement to regulate the first phase voltage U _P1 to a constant mean phase _voltage U _{P1M is} not exactly implemented. In this case, the first mean phase _voltage U _P1M becomes that of the unit 12 certain first motor voltage U _S1 superimposed. Preferably, the first motor voltage U _S1 (and also the other motor voltages U _S2 , U _S3 ) is an AC voltage with the mean zero or near zero. Depending on a size of the inductance L of the element for voltage conversion is thus the current i _L an alternating current with the speed-dependent frequency of the first motor voltage U _{S1 are} superimposed. In this case, however, it can be assumed that an average value of the current i _L does not change substantially as a result of the superimposition of an alternating current. A differential terminal voltage U _K1-K2 , U _K1-K3 , U _K2-K3 at the terminals K1, K2, K3 of the electric machine 6 may in the second mode of operation have an amplitude theoretically twice that of the unit 10 determined mean first phase _voltage U _P1M . Is z. B. the battery _voltage U _batt = 12 V and the intermediate _{circuit voltage} U _ZK = 24 V, the electric machine can also with differential terminal voltages U _K1-K2 , U _K1-K3 , U _K2-K3 with amplitudes of -24 V to 24 V are operated. This will be explained in more detail below. Starting from the in the mesh equation of formula 9, the first and the second phase voltage U _P1 , U _P2 in the range between 0 V to 24 V adjustable because the first phase voltage U _{P1 is} no longer a constant phase voltage. It follows that the first differential terminal voltage U _K1-K2 , which corresponds to the difference between the second and the first motor voltage U _S2 - U _S1 , theoretically can assume voltage amplitudes between -24 V and 24 V.

• 1. Im ersten Betriebsmodus sollten die Differenz-Klemmen-Spannungen U_K1-K2, U_K1-K3, U_K2-K3 an den Klemmen K1, K2, K3 die erste mittlere Phasenspannung U_P1M nicht überschreiten.
• 2. Im zweiten Betriebsmodus sollte ein Wechselstromanteil des Stromes i_L durch die Induktivität L des Elements zur Spannungswandlung ausreichend klein bleiben.

Switching between the first and second modes of operation should ideally meet the following requirements:

• 1. In the first operating mode, the differential terminal voltages U _K1-K2 , U _K1-K3 , U _K2-K3 at the terminals K1, K2, K3 _should not exceed the first average phase _voltage U _P1M .
• 2. In the second mode of operation, an AC component of the current i _L should remain sufficiently small through the inductance L of the voltage conversion element.

For reasons of simpler feasibility, these criteria are not directly, but one of the speed Ω of the electric machine 6 dependent criterion used for switching between the first and the second operating mode. In this case, a changeover depending on the rotational speed Ω can be a hard switching, a hysteresis-based or a cross-fade-based switching. Hereinafter, a fade-based switching will be explained. For a blend-based switching, an upper speed limit and a lower speed limit are predetermined. Above the upper speed limit, the desired phase voltages U _{P1, should} , U _{P2, should} , U _{P3, should be determined} according to the second operating mode and below the lower speed limit according to the first operating mode. Between the lower and the upper speed limit, between the desired phase voltages U _{P1, soll} , U _{P2, soll} , U _{P3, should be} linearly interpolated between the operating modes determined in accordance with both operating modes. For this a fading factor u _{fak is} used. If the speed Ω is smaller than the lower speed limit, then the fade factor u _fak = 0. If the speed Ω is greater than the upper speed limit, then the fade factor u _fak = 1. If the speed Ω is between the lower and the upper speed limit, thus, the fade factor u _{fak is determined} according to (Ω - lower speed limit) / (upper speed limit - lower speed limit) Formula 12.

The desired phase voltages U _{P1, soll} , U _{P2, should} , U _{P3, should} then be defined according to U _{P1, soll} = U _P1M + u _fak × U _S1 , U _{P2, soll} = U _P1M + U _S2 - (1 - u _fak ) × U _S1 , U _{P3, soll} = U _P1M + U _S3 - (1 - u _fak ) × U _S1 Formula 13.

In units 14 to determine switching times, the switching times of the power switches S1, ..., S6 depending on the unit 13 determined target phase voltage U _{P1, soll} , U _{P2, should} , U _{P3, should} and determined in dependence on a current intermediate circuit voltage U _ZK and the circuit breakers S1, ..., S6 controlled accordingly.

The in the high voltage range 3 transferred power P _HV and the power loss P _Verl can be considered as disturbance variables from a control point of view. These can be z. B. by means of a pilot control are at least partially compensated, creating a control quality of the regulation of the low voltage range 2 to be transmitted power P _NV and the electric power P _{EM of} the electric machine 6 is improved.

Also, the information transmitted in the intermediate circuit capacitor C _ZK power P _ZK can, analogously to the disturbance variables can not be set independently of the other mentioned in formula 1 services. However, the intermediate circuit _voltage U _ZK depends on i _ZK = P _ZK / U _ZK Formula 14 and dU _ZK / dt = 1 / C _ZK × i _ZK Formula 15 from the power P _ZK . Exceeds z. B. the intermediate circuit voltage U _ZK an allowable upper limit of the intermediate circuit voltage U _ZK , the DC link capacitor C _ZK and / or power switches S1, ..., S6 can be destroyed. If the intermediate circuit _voltage U _{ZK falls below} z. B. a value of 2 × U _batt , the electric machine can only be operated with limited power and / or there may be torque fluctuations. It follows that the intermediate _circuit voltage U _{ZK should} preferably be controlled or regulated. The control or regulation of the intermediate circuit voltage U _ZK can be adjusted indirectly by a suitable choice of the electric power P _EM and the power P _NV . Here, however, there is the problem that only three variables to be controlled (P _EM , P _NV , U _ZK ) with a control unit, which can ultimately set only the power P _NV and the power P _EM , are to be regulated. This problem is due to the strategy unit 11 solved. This can, depending on a particular operating situation, prioritize the controlled variables. This can also be understood as an optimization problem in which a quality function changes depending on the operating situation. This determines the strategy unit 11 a desired setpoint current i _{L, should be represented} by the inductance L and a target torque M _should depending on a current DC link voltage U _ZK , a current battery _voltage U _batt and other input variables, of which an accelerator pedal position FP and a brake pedal position BP are exemplified.

This results in a regulatory hierarchy with a total of four levels. The strategy unit determines in a top level of the rule hierarchy 11 a desired setpoint current i _{L, soll} and a desired setpoint torque M _{soll of} the electric machine 6 , In a second level, the unit determines 10 a first mean phase _voltage U _P1M and the unit 12 Motor voltages U _S1 , U _S2 , U _S3 . In a third level of the regulatory hierarchy, the unit determines 13 Target phase voltages U _{P1, soll} , U _{P2, soll} , U _{P3, soll} . In a fourth and final level of the regulatory hierarchy, units determine 14 Switching times of the circuit breakers S1, ..., S6 of the half-bridges of the inverter 7 ,

The following is an example of some operating situations.

Structure of a DC link voltage U _ZK in a stationary, torque-free electric machine 6 :

Here, the element for voltage conversion, in particular the inductance L and the power switches S1, S2, serves as an up-converter whose function has previously been described in the explanations 2 was presented. The circuit breakers S3, ..., S6 can remain open in this case. Alternatively, the first power switches S3, S5 of the second and third half-bridges can be activated in synchronism with the first power switch S1 of the first half-bridge and the second power switches S4, S6 of the second and third half-bridges in synchronism with the second power switch S2 of the first half-bridge. This changes a state of the stationary and de-energized electric machine 6 not because the differential terminal voltages U _K1-K2 , U _K1-K3 , U _{K2-K3 are} zero. The strategy unit 10 determines a target torque M _soll = 0 and a target intermediate circuit voltage U _{ZK, should be} of z. B. 2 × U _batt . A target current i _{L, should} , in particular a current of the desired current i _{L, should} , then z. B. be set in a simple manner by means of a P-controller. For example, i _{L, should be} according to I _{L, soll} = P _const × (U _{ZK, soll} - U _ZK ) Formula 16 with a gain P _const less than zero at the in 2 illustrated direction of the current i _L in 2 be.

tempering:

This results in two control scenarios. Is a maximum adjustable torque due to the characteristics of the electric machine 6 limited, so the target torque M _{is set} to this maximum possible torque. The strategy unit 10 then determines a desired current i _{L, should} , with which the intermediate circuit voltage U _ZK to a predetermined desired intermediate circuit voltage U _{ZK, is to be} regulated (see formula 16). Is a maximum adjustable torque not by the characteristics of the electric machine 6 but by a maximum, the electrical system battery 4 limited power, the strategy unit determines 10 the setpoint current i _{L, should} be the maximum permissible in terms of amount, with respect to the in 2 shown current direction negative, value i _{L, soll, max} . As a result, the electric machine 6 supplied as much energy as possible. The setpoint torque M _soll can then be set so that the intermediate circuit voltage U _ZK to a predetermined target DC voltage U _{ZK to,} is controlled in the simplest case by means of a P controller in accordance with formula 16 reaches the target torque M _{is intended} here _to a maximum permissible value or if the intermediate circuit voltage U _ZK approaches its maximum permissible value, then the strategy unit can reduce the magnitude of the setpoint current i _{L, soll} . In both scenarios, in addition, the battery _voltage U _{batt can be} detected, wherein when _{falling below} a lower limit of the battery _voltage U _batt the current i _{L, should be} reduced in terms of amount. In this way, an optimum power point of the vehicle electrical system battery can be advantageously achieved 4 to adjust.

recuperation:

Analogous to starting, different control scenarios can also be used in recuperation mode. Is the maximum possible negative moment not by properties of the electric machine 6 limited, so the strategy unit 10 a maximum allowable, in terms of in 2 illustrated current direction of the current i _L positive, target current i _{L, should} spend. In this case, the onboard power supply battery deprives 4 the generator operated electric machine 6 as much electrical energy as possible. The target torque M _soll can be set in this case such that the intermediate circuit voltage U _ZK to a predetermined desired intermediate circuit voltage U _{ZK, should be} regulated, which in turn can be done by means of a simple P-rule according to formula 16. Reaches the setpoint torque M _{is intended} here _to a minimum permissible value or the intermediate circuit voltage approaches U _ZK a minimum permissible value, then, the target current i _{L, to} be reduced by the magnitude strategy unit. In this case too, the battery _voltage U _batt can additionally be detected and, when an upper limit of the battery _voltage U _{batt is exceeded,} the setpoint current i _{L, should be} reduced in terms of amount. If the maximum torque that can be set is determined by properties of the electric machine, the setpoint torque M _{soll should be set} to this maximum torque.

Of course, other operating situations, eg. As a traction, a stall protection, a so-called motor-boost function, a discharge of the DC link capacitor C _ZK in the electrical system battery 4 be realized at the end of travel and a normal generator function without limitation by means of the device according to the invention and the method according to the invention.

In the previous versions, the electrical system battery 4 considered as the sole source of energy by which the electric machine 6 can be supplied with electrical energy during engine operation. In this case, the intermediate circuit capacitor C _ZK can be regarded as a smoothing capacitor, which can absorb or deliver maximum powers at best in the millisecond range. In this case, it makes no sense to design the electric machine to much greater power than the vehicle electrical system battery 4 can temporarily record or deliver. Optionally, a so-called thin-film capacitor can also be connected in parallel with the intermediate circuit capacitor C _ZK . This can then in the range of seconds similar or even greater benefits than the electrical system battery 4 record or submit. Thus, the electric machine 6 on higher performance than the short-term of the electrical system battery 4 deliverable or receivable services. In this case, it may be necessary to design the power switches S1,..., S6 for larger currents.

An energy content of a capacitor depends quadratically on a voltage drop across the capacitor. E = 0.5 × C × U × U Formula 17.

In accordance with the above-explained operating situation of a structure of a DC link voltage U _ZK with stationary, torque-free electric machine can be charged in such an arrangement, the thin-film capacitor to the highest possible energy content. This allows for at least one motor high load case, such. As a cold start of a diesel engine, a short-term electrical power can be made available, the maximum of the electrical system battery 4 exceeds available power. In such a case, the strategy unit would 10 a nominal intermediate _{circuit voltage} U _{ZK, should} specify near a maximum permissible value (eg 4 × U _batt , in this case approx. In addition, the strategy unit could 10 the setpoint current i _{L, should be} limited to a minimum permissible (negative) value.

During a starting operation explained above, a device additionally comprising a thin-film capacitor may be controlled such that the strategy unit 10 a maximum permissible nominal torque M _soll and a minimum permissible nominal current i _{L, should be} requested. The electrical power that exceeds that of the System battery 4 output power is required, the thin-film capacitor can deliver, the intermediate circuit voltage U _ZK decreases. In a case of recuperation, analogous to the recuperation operation explained above, the strategy unit can request a relatively low nominal intermediate _{circuit voltage} U _{ZK, soll} (eg 2 × U _batt ) at the beginning of the recuperation _operation . If the braking is sufficiently strong, the strategy unit would then request a maximum setpoint current i _{L, should} and a minimum, ie absolute maximum regenerative, setpoint moment M _soll . The electrical power that the onboard power supply battery 4 can not absorb, is stored in the thin-film capacitor. To when it reaches the maximum value of the intermediate circuit voltage U _ZK not to abruptly reduce the braking torque, it may make sense that the strategy unit from a predetermined threshold of the intermediate circuit voltage U _ZK, z. B. 90% of a maximum intermediate circuit voltage U _ZK, starts the setpoint torque M _soll magnitude to reduce. After the end of braking, the strategy unit 11 the setpoint current i _{L, should} continue to be left at a high setpoint to prepare the intermediate circuit voltage u _ZK for an optional further recuperation.

There are electrical interconnections of electrical machines conceivable in which the previously described motor voltages U _S1 , U _S2 , U _S3 not explicitly as in the in 2 illustrated device 1 be available. In such interconnected electric machines, a desired mode of operation (speed, torque) of the electric machine and the phase voltages U _P1 , U _P2 , U _P3 or switching times of the power switches S1,..., S6 to be set are determined directly. Also, in addition to the desired torque M _soll and possibly other measured variables usually also the intermediate circuit voltage U _{ZK be} specified. Are not the phase voltages U _P1 , U _P2 , U _P3 , but only duty cycles available, these can be converted according to formula 6 in phase voltages U _P1 , U _P2 , U _P3 . In the following, calculation methods are specified with which calculated phase voltages U _P1 , U _P2 , U _P3 of any electric machine can be converted into the motor voltages U _S1 , U _S2 , U _S3 according to the invention.

In a first case, one subtracts from the predetermined phase voltages U _P1 , U _P2 , U _{P3 in} each case half of the intermediate circuit voltage U _ZK in order to obtain the motor voltages U _S1 to U _S3 . If the time averages of the thus calculated motor voltages U _S1 , U _S2 , U _S3 at an operating at a constant operating point electric machine 6 are equal to or near zero, a correct operation of the electric machine by means of the method according to the invention is possible.

In a second alternative, an average of the phase voltages U _P1 to U _P3 can be determined and subtracted from the respective phase voltages U _P1 , U _P2 , U _P3 to obtain the motor voltages U _S1 , U _S2 , U _S3 .

LIST OF REFERENCE NUMBERS

1

Device for energy transmission

2

Low voltage range

3

High voltage range

4

System battery

5

electrical consumer

6

electric machine

7

inverter

8th

Element for voltage conversion

10

Unit for determining a mean phase voltage

11

strategy unit

12

Unit for determining at least one motor voltage

13

Unit for determining a desired phase voltage

14

Unit for determining switching times

U _batt

battery voltage

U _ZK

Intermediate circuit voltage

U _P1

first phase voltage

U _P2

second phase voltage

U _P3

third phase voltage

U _S1

first motor voltage

U _S2

second motor voltage

U _S3

third motor voltage

L

inductance

U _L

Voltage across the inductance

U _P1M

first mean phase voltage

U _{P1, shall}

first desired phase voltage

U _{P2, shall}

second desired phase voltage

U _{P3, shall}

third desired phase voltage

i _NV

Low voltage range power

i _batt

battery power

i _L

Current through the inductance

_HV

High voltage range power

i _ZK

DC link current

i _P1

first phase current

i _P2

second phase current

i _P3

third phase current

i _{L, shall}

Target current through the inductance

S1

first circuit breaker of the first half-bridge

S2

second circuit breaker of the first half-bridge

S3

first circuit breaker of the second half-bridge

S4

second circuit breaker of the second half-bridge

S5

first circuit breaker of the third half-bridge

S6

second circuit breaker of the third half-bridge

D1

diode

D2

diode

D3

diode

D4

diode

D5

diode

D6

diode

S7

first circuit breaker of the voltage conversion element

S8

second circuit breaker of the voltage conversion element

D7

diode

D8

diode

K1

first terminal of the electric machine

K2

second terminal of the electric machine

K3

third terminal of the electric machine

S

star point

ML1

first motor inductance of the electric machine

ML2

second motor inductance of the electric machine

ML3

third motor inductance of the electric machine

FP

Accelerator sensor signal

BP

Brake pedal sensor signal

M _shall

target torque

α

rotor position

Ω

rotation speed

T _S1

Switching time of the first circuit breaker of the first half-bridge

T _S2

Switching time of the second circuit breaker of the first half-bridge

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10244229 A1 [0004, 0016, 0020]
• DE 19857645 A1 [0005, 0016, 0020]

Claims (10)

Device for transmitting energy in a motor vehicle, wherein the motor vehicle has a vehicle electrical system, wherein the vehicle electrical system at least one low-voltage range ( 2 ) having a first voltage level, the device ( 1 ) at least one electric machine ( 6 ), one of the electric machines ( 6 ) assigned inverter ( 7 ), at least one intermediate circuit capacitor (C _ZK ), at least one low-voltage region associated energy storage, at least one element for voltage conversion and at least one control unit, wherein the electric machine ( 6 ) is operable in a motorized or regenerative mode, wherein the inverter ( 7 ) has at least one half-bridge with two power switches (S1, S2, S3, S4, S5, S6), wherein a section between the power switches (S1, S2, S3, S4, S5, S6) via a first supply path with a terminal (K1 , K2, K3) of the electric machine ( 6 ), wherein the voltage conversion element comprises at least two power switches (S1, S2, S3, S4, S5, S6, S7, S8) and at least one inductance (L), the power switches of the voltage conversion element comprising the power switches (S1 , S2, S3, S4, S5, S6) of the at least one half-bridge of the converter ( 7 ), wherein the at least one inductance (L) of the voltage conversion element in a second supply path, which is the low-voltage region ( 2 ) and that electrically connects the section of the half-bridge lying between the circuit breakers (S1, S2, S3, S4, S5, S6) of the half-bridge, characterized in that the second supply path is different from the first supply path . Apparatus according to claim 1, characterized in that in the motor operation of the electric machine ( 6 ) a power supply of the electric machine ( 6 ) can be ensured only from the energy storage. Device according to one of claims 1 or 2, characterized in that the converter ( 7 ) as a three-phase converter ( 7 ), each phase of the converter ( 7 ) is assigned a half-bridge with two circuit breakers (S1, S2, S3, S4, S5, S6), wherein a portion between the circuit breakers (S1, S2, S3, S4, S5, S6) of each half-bridge over first supply paths each having a Terminal (K1, K2, K3) of a three-phase electric machine ( 6 ), wherein the element for voltage conversion 6 Circuit breaker (S1, S2, S3, S4, S5, S6) and 3 inductors (L1, L2, L3), wherein the 6 circuit breakers (S1, S2, S3, S4, S5, S6), each of the two circuit breakers (S1, S2, S3, S4, S5, S6) of the half-bridges of the converter ( 7 ), wherein in each case one inductances (L1, L2, L3) of the element for voltage conversion are respectively arranged in second supply paths, wherein the second supply paths are the low-voltage region ( 2 ) and electrically connect the portion of the respective half-bridge between the power switches (S1, S2, S3, S4, S5, S6) of the respective half-bridge and are different from the first supply paths. Device according to one of the preceding claims, characterized in that by means of the control unit, a switching of the power switches (S1, S2, S3, S4, S5, S6) of the inverter ( 7 ) in dependence on at least one desired electrical power (P _EM ) of the electric machine and a desired, in the low voltage range ( 2 ) into or out of the low-voltage region ( 2 ) Power to be transmitted (P _NV ) is controllable. Device according to one of the preceding claims, characterized in that the vehicle electrical system additionally comprises at least one high-voltage region ( 3 ) having. Method for transmitting energy in a motor vehicle, wherein the motor vehicle has a vehicle electrical system, wherein the vehicle electrical system has at least one low-voltage range ( 2 ) having a first voltage level, the motor vehicle having at least one electric machine ( 6 ), one of the electric machines ( 6 ) assigned inverter ( 7 ), at least one intermediate circuit capacitor (C _ZK ), at least one low-voltage region associated energy storage, at least one element for voltage conversion and at least one control unit, wherein the electric machine ( 6 ) is operated in a motorized or regenerative mode, wherein the converter ( 7 ) has at least one half-bridge with two power switches (S1, S2, S3, S4, S5, S6), wherein a section between the power switches (S1, S2, S3, S4, S5, S6) via a first supply path with a terminal (K1 , K2, K3) of the electric machine ( 6 ), wherein the voltage conversion element comprises at least two power switches (S1, S2, S3, S4, S5, S6, S7, S8) and at least one inductance (L), the power switches of the voltage conversion element comprising the power switches (S1 , S2, S3, S4, S5, S6) of the at least one half-bridge of the converter ( 7 ), wherein the at least one inductance (L) of the voltage conversion element in a second supply path, which is the low-voltage region ( 2 ) is electrically connected, the second supply path is different from the first supply path, wherein in regenerative operation, the control unit, the power switch (S1, S2, S3, S4, S5, S6) of the voltage conversion element controls such that of the electric machine ( 6 ) generated electrical energy is at least partially transmitted into the low voltage range, wherein in motor operation, the control unit circuit breaker (S1, S2, S3, S4, S5, S6) of the element for voltage conversion controls such that stored in the energy storage electrical energy at least partially to the Electric machine is transmitted. Method according to claim 6, characterized in that a unit ( 10 ) for determining at least one mean phase _voltage (U _P1M ) an average phase _voltage (U _P1M ) of the converter ( 7 ) at least depending on a desired, in the low voltage range ( 2 ) into or out of the low-voltage region ( 2 ) power (P _NV ) to be transmitted, with at least one unit ( 12 ) for determining at least one motor voltage (U _S1 , U _S2 , U _S3 ) of the electric machine ( 6 ) a motor voltage (U _S1 , U _S2 , U _S3 ) of the electric machine ( 6 ) at least as a function of a desired electrical power (P _EM ) of the electric machine ( 6 ), whereby at least one unit ( 13 ) for determining at least one desired phase voltage (U _{P1, soll} , U _{P2, soll} , U _{P3, soll} ) a desired phase voltage (U _{P1, soll} , U _{P2, soll} , U _{P3, soll} ) of the inverter ( 7 ) determined at least as a function of the average phase voltage (U _P1M ) and the motor voltage (U _S1 , U _S2 , U _S3 ), wherein the control unit switching the power switches (S1, S2, S3, S4, S5, S6) of the inverter ( 7 ) in dependence of the desired phase voltage (U _{P1, soll} , U _{P2, soll} , U _{P3, soll} ) controls. A method according to claim 7, characterized in that a desired, in the low-voltage range ( 2 ) into or out of the low-voltage region ( 2 ) power to be transmitted (P _NV ) and a desired electrical power (P _EM ) of the electric machine from a strategy unit ( 10 ) is determined at least as a function of an intermediate circuit voltage (U _ZK ) and / or at least one driving-dynamic sensor signal and / or at least one driving-operation-specific sensor signal (FP, BP). Method according to one of claims 7 or 8, characterized in that the unit ( 13 ) for determining at least one desired phase voltage (U _{P1, soll} , U _{P2, soll} , U _{P3, soll} ) the at least one desired phase voltage (U _{P1, soll} , U _{P2, soll} , U _{P3, soll} ) in dependence on a speed (Ω) of the electric machine ( 6 ) certainly. Method according to claim 9, characterized in that the unit ( 13 ) for determining at least one desired phase voltage (U _{P1, soll} , U _{P2, soll} , U _{P3, soll} ) the at least one desired phase voltage (U _{P1, soll} , U _{P2, soll} , U _{P3, soll} ) according to a first and a second mode of operation, wherein in response to the rotational speed (Ω) is switched between the first and the second operating mode, wherein a switching is a hard switching or a hysteresis-based switching or a fade-based switching.

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