Method for heating a motor vehicle

Abstract

The invention relates to a method for heating a motor vehicle with an electric motor (150) as a traction motor, which is controlled by means of deadbeat direct torque control and flux control, so-called deadbeat direct torque and flux control (DB DTFC). The invention is characterized in that the torque (T) and the magnetic flux (ψ) are controlled decoupledly and losses are generated with the AC currents to produce heat.

Description

[0001] The invention relates to a method for heating a motor vehicle with an electric motor as a traction motor, which is controlled using deadbeat direct torque and flux control (DB DTFC). The traction motor can be designed, for example, as a permanent magnet synchronous motor or synchronous reluctance motor, whereby the concept of the invention is applicable to all types of electric motors that employ such a control system.

[0002] Electric motors can, of course, also operate in generator mode, i.e., converting mechanical energy into electrical energy, so they are generally referred to as electrical machines. In the following, the term "motor" is therefore not limited to this mode of operation, but should be understood as a synonym for an electrical machine.

[0003] Motor vehicles equipped with an internal combustion engine generate sufficient waste heat when the engine is running to heat the passenger compartment and / or the vehicle battery. This is not possible with motor vehicles that use an electric motor as a traction motor. However, it is also possible for vehicles with an electric motor to use waste heat generated when powering the electric motor to heat the vehicle and / or the vehicle battery. Heating electrically powered vehicles using waste heat is known from numerous publications. For example, DE 10 2021 107 091, DE 10 2014 211 447, DE 10 2017 222 684, DE 10 2009 000 204 and DE 10 2019 133 634 show examples of the prior art of controlling electrical machines for heating a vehicle or at least for heating part of it.However, these types of heat generation are very inefficient and loss-making in the current state of technology.

[0004] DE 10 2021 107 091 describes a method for heating a motor vehicle with a three-phase electric motor as a traction motor. A pulse-controlled inverter is provided to supply power to the electric motor, as well as a coolant circuit for cooling the coolant of the electric motor and the pulse-controlled inverter, which transfers heat via the coolant to a heat exchanger for heating the passenger compartment and / or to the vehicle battery. When the electric motor is stopped, a positive d-current and a negative d-current are controlled in the d-axis, generating heat loss that is transferred into the coolant and thus into the vehicle.

[0005] DE 10 2014 211 447 discloses a method and a device for controlling the temperature of an interior of a motor vehicle with an electric drive by means of a heat pump arrangement, wherein the operating point of the electric drive is varied such that the generation of waste heat in at least one electrical component of the electric drive is controlled.

[0006] DE 2017 222 684 A1 relates to a method for controlling heat loss in an electric drive motor of a motor vehicle, wherein the predetermined heat loss is provided by a three-phase machine which is designed as a drive motor.

[0007] DE 10 2019 133 634 relates to a method for operating an electrical machine in a motor vehicle, wherein the machine can be operated in a loss- and power-optimized efficient operating mode or a loss- and power-increasing inefficient operating mode.

[0008] From DE 10 2009 000 204 an electric drive for a vehicle, in particular a motor vehicle, has become known, wherein the operating heat generated by the electric motor when generating the rotary movement is dissipated and conducted into the passenger compartment of the vehicle.

[0009] The object of the invention is to avoid the disadvantages of the prior art and to provide heating energy in the car in an efficient manner.

[0010] According to the invention, this is achieved by controlling the torque and the magnetic flux in a decoupled manner and by using the AC currents to generate losses to produce heat.

[0011] In a first embodiment of the invention, the control is implemented in such a way that the vehicle's torque incurs losses independently of the generated AC currents. It is particularly preferred if the control is implemented in such a way that no undesirable high-frequency torques (NVH) arise. Because the torque and the magnetic flux in the electric motor are controlled decoupled, freely selectable flux trajectories can preferably be commanded and controlled at a constant torque. It is particularly preferred if the flux trajectories are commanded with a sinusoidal or triangular shape with a specific amplitude and frequency.

[0012] It is particularly advantageous if the driver's torque can be controlled independently of the AC currents generated to generate losses.

[0013] The invention achieves a higher heat input by decoupling the torque and magnetic flux in the electric motor. With a simple, low-computational-intensive, and established solution, the vehicle's torque can be controlled independently of the currents used to generate losses.

[0014] The invention will be described below with reference to the figures without limitation thereto.

[0015] Showing: Fig. 1 a current control according to the state of the art with uniform currents -Id and Iq as setpoint specification Fig. 2 an alternative embodiment of a current control according to the state of the art with currents in the form of impressed harmonics in the d- and q-direction (Id, Iq) Fig. 3 an inventive embodiment of a control of an electrical machine with deadbeat controller

[0016] In Fig. Figure 1 shows a current control system for the drive of a motor vehicle with an electric motor as the traction motor. The drive 1 comprises a so-called Central Vehicle Controller (CVC) 3, which represents the control center in an electrically powered, software-defined vehicle. In principle, the Central Vehicle Controller 3 is a computer that regulates communication between all vehicle components. The Central Vehicle Controller 3 is a type of intermediary that translates the digital world of software into the analog world of sensors and actuators. With the help of this intermediary in the form of a Central Vehicle Controller 3, software can be used that controls the vehicle but communicates all instructions via a control center. This translation is carried out by the vehicle control unit, which is also referred to as the Central Vehicle Controller 3.The Central Vehicle Controller 3 handles all communication within the vehicle and is connected to all devices. In particular, it eliminates the need for different data protocols for control. The signal applied to the Central Vehicle Controller 3 takes the form of a setpoint specification, e.g., a constant current in I. q - and I d - Direction as in Fig. 1, is transmitted via a so-called SVM coding 130 to an electrical machine, which in the present example is designed as a synchronous reluctance motor (SynRM) 150.

[0017] In an alternative embodiment, the electrical machine can also be designed as a permanently excited synchronous motor, whereby the idea of ​​the invention is possible for all types of electric motors and thus the type of electrical machine shown is to be understood only as an embodiment without limitation of the idea.

[0018] A synchronous reluctance motor is a reluctance motor in the form of a three-phase synchronous machine with a rotor (rotor) that has salient poles (also in the form of a so-called flux-barrier section). The stator (stator) of the synchronous reluctance motor, like other three-phase machines, has three coils, each spatially offset by 120°, which are fed by three-phase alternating voltage. Due to the rotating field generated by the stator, the rotor has certain preferred directions due to the varying magnetic conductivity along its circumference. In reluctance motors, the torque is generated by the reluctance force through the preferred directions, and not, as in other electrical machines, by the Lorentz force. As with all synchronous motors, the rotor rotates synchronously with the rotating field of the supply voltage network. The speed is linked to the frequency of the alternating voltage via the number of pole pairs.

[0019] In practice, synchronous reluctance motors are usually designed with four poles. The stator of a synchronous reluctance motor typically has the same structure as a standard asynchronous motor with distributed windings. The rotor is made of electrical steel to prevent eddy currents. When supplied with three-phase current, the windings distributed in the stator slots generate a rotating field circulating in the motor's air gap. When supplied via a frequency converter, the speed can be increased from zero to the operating speed and adjusted during operation. Suitable rotor position control in the frequency converter ensures that the rotor does not fail, especially during load changes. In the preferred magnetic direction (d-direction), there is low magnetic resistance, and the magnetic flux is well guided in the iron. At a 45° angle to this (q-direction), the air barriers impede the magnetic flux.When current is applied to the stator winding, poles and gaps are created in the rotor. If the rotor follows the stator field synchronously, its poles are connected to the poles of the rotating field via a spring, so to speak. When loaded, the rotor lags slightly, creating a rotor angle that disappears again when the load is removed. The d and q directions of the rotor correspond to the respective axes of the coordinate system defined by the D / q transformation. In general, the better the flux guidance along the d axis and the more the flux is impeded along the q axis, the greater the motor torque. The operation of synchronous reluctance motors is described, for example, in Peter F. Brosch's "Zeitschrift Elektrotechnik", June 2011 issue, pages 36 ff.

[0020] In Fig. Figure 1 shows a current control with a current 10 in the d-direction and a current 12 in the q-direction. The applied currents I d and I qlead to the resulting flux ψ and torque T in the drive shown in graphs 20 and 22.

[0021] Alternatively to the Fig. 1 shown current control is in Fig. 2 shows a current control system, where the setpoint value of the current in the d- and q-direction is applied as harmonics. The same components as in Fig. 1 are assigned the same reference numerals. The impressed harmonics according to Fig. 2 in the d- and q-directions essentially generate a torque of the synchronous reluctance motor 150. To avoid such a torque, the applied current must be selected, which requires considerable computational effort, so that no torque is generated. This is complex and also leads to losses in the resulting flux ψ and torque T in the drive.

[0022] According to the invention, the synchronous reluctance machine 150 is therefore provided with a sinusoidal flux control and a deadbeat controller 100. The deadbeat controller 100 is characterized in that the time for the control process is specified via the sampling time. The deadbeat controller 100 regulates in a fixed number of steps, where the settling time is t n and n is the degree of the path. The manipulated variable amplitude adapts to the sampling time.

[0023] The deadbeat controller 100 according to the invention is as shown in Fig. 3, precedes the SVM coding 130. The synchronous reluctance motor 150 is connected downstream of the controller and the SVM coding 130. In the inventive embodiment of the invention and controlled system, the target voltage is calculated using a differential torque equation so that the desired torque is regulated. In addition to the components imposed on the deadbeat controller 100, the resulting flux ψ and the torque T in the drive are also specified. The resulting flux ψ is as in the Fig. 1 and Fig. 2 is designated by 20, the torque in the drive by 22. The structure of the control system for the synchronous reluctance motor 150 as in Fig. 3 results in the torque T and the magnetic flux ψ in the synchronous reluctance motor 150 being controlled in a decoupled manner. For this purpose, a unit designated 110 is provided for estimating the flux and torque; the resulting values ​​are assigned the index e. With the design and implementation of a deadbeat controller 100, the vehicle's torque can be controlled independently of the AC currents generated for loss generation, while simultaneously generating losses with AC currents.

[0024] With such a solution, on the one hand, no undesirable torque and no high-frequency torque are generated, as for example in the embodiment of the invention according to Fig.2. Compared to the state-of-the-art controls with d- and q-currents, the torque T and the magnetic flux ψ in the synchronous reluctance motor 150 can be controlled decoupled. This makes it possible to command and control freely selectable flux trajectories while simultaneously maintaining a constant required torque. For this purpose, flux trajectories with a sinusoidal or triangular shape with a specific amplitude frequency can be selected and commanded depending on the drive in question. In particular, it is possible to control the vehicle's torque independently of the AC current generated to generate losses and simultaneously generate losses with AC currents using a simple, low-computational-intensive solution that is also established in vehicle construction. Undesired torque and high-frequency torque are avoided by the new control strategy. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This 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

[0000] DE 10 2021 107 091 [0003, 0004] DE 10 2014 211 447 [0003, 0005] DE 10 2017 222 684

[0003] DE 10 2009 000 204 [0003, 0008] DE 10 2019 133 634 [0003, 0007] DE 2017 222 684 A1

[0006] Cited non-patent literature

[0000] Peter F. Brosch “Magazine Electrical Engineering”, June 2011 issue, p. 36 ff

[0019]

Claims

[1] Method for heating a motor vehicle with an electric motor (150) as a traction motor, which is controlled by means of deadbeat direct torque control / control and flux control, so-called Deadbeat Direct Torque and Flux Control (DB DTFC) (100), characterized by that the torque and the magnetic flux are controlled in a decoupled manner and that losses are generated with the AC currents to produce heat. [2] Method according to claim 1, characterized by that the control is such that the driver's torque generates losses independently of the AC currents generated. [3] Method according to claim 2, characterized by that the control is carried out in such a way that no unwanted high-frequency moments (NVH) arise. [4] Method according to one of claims 1 to 3, characterized by that the moment and the flow are controlled with freely selectable flow trajectories, preferably to a constant moment. [5] Method according to one of claims 1 to 4, characterized by that the flow trajectories are commanded with sinusoidal or triangular shape with a specific amplitude and frequency. [6] Method according to one of claims 1 to 5, characterized by that the driver torque is controlled independently of the AC currents generated to generate losses. [7] Method according to one of claims 1 to 6, characterized by that the electric motor is designed as a traction motor as a permanent magnet synchronous motor. [8] Method according to one of claims 1 to 6, characterized by that the electric motor is designed as a traction motor as a synchronous reluctance motor (150)

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