Rotating motor drive load system, test equipment, and electrical load and drive train

Abstract

The present invention relates to a drive load system for a rotary electric motor having a controllable power supply connectable to a power supply. The controllable power supply is connected to an intermediate circuit having a capacitor for temporarily storing power, which therefore functions as an energy storage device for stabilizing the intermediate circuit voltage. The drive load system further comprises a motor inverter connected to the intermediate circuit, which converts an intermediate circuit voltage applied to a motor inverter input into a drive current for a rotary electric motor or returns a load current from the electric motor to the intermediate circuit. A closed-loop control circuit of the drive load system has an actual value input of the closed-loop control circuit connected to the motor inverter input, and is configured to control the motor inverter input voltage to a setpoint value U by a controllable power supply. SET According to the present invention, the driving load system is connected to a setpoint input of a closed-loop control circuit, and a current setpoint U SET The set value output device further includes a set value output unit for setting a predetermined set value curve U SET Based on [N(T)], the setpoint U for the closed-loop control circuit is determined according to the motor speed N(T). SET Suitable for determining (T).

Description

[Technical Field]

[0001] The present invention relates to a rotary electric motor drive load system, which can be used in test equipment, in particular for motors, transmissions, brakes or vehicles, for electrical load systems, in particular for generators, or for electrical drive systems, in particular for electric vehicles. [Background technology]

[0002] Modern test rigs in the automotive sector are primarily focused on the areas of motor testing, transmission testing and brake testing. They can be used for any kind of development and functional test rig. The range of applications ranges from simple stationary test rigs to highly dynamic test rigs with Road Load Simulation (RLS), allowing driver or vehicle simulation. Legal emission tests such as ELR, ESC and ETC are other typical applications.

[0003] These test devices use so-called dynamometers, which can drive and load the test object, such as an internal combustion engine or an electric vehicle motor. Furthermore, at least one complete vehicle may be mounted on a running drum that is braked by the dynamometer. Such dynamometers are therefore particularly high-torque drive load machines, consisting of an electric AC motor and a motor inverter. Current is supplied via a DC voltage, and the motor is controlled by a pulse inverter on the machine side. The motor inverter thus supplies the electric motor with a predetermined voltage and time-dependent current, enabling the dynamometer to achieve desired dynamic characteristics in both drive and load modes. These modern pulse inverters are equipped with IGBT (insulated gate bipolar transistor) switching elements, allowing full-current operation in both motor and generator operation. Instead of IGBTs, SIC MOSFETs (metal-oxide semiconductor field-effect transistors) could also be used.

[0004] Pulse inverters equipped with IGBTs or MOSFETs allow highly dynamic control of electric motors, but this flexibility comes at the cost of switching losses in the transistors used in the motor inverter. In this case, the switching losses in the IGBTs of the motor inverter depend on the pulse frequency (high frequencies result in high losses), the current, and the voltage applied to the intermediate circuit or DC bus (high voltages result in high losses). The temperature losses in a three-phase AC motor (induction motor or synchronous motor) connected to a motor inverter depend on the harmonics of the current. These harmonics depend strongly on the pulse frequency (high frequencies result in lower amplitudes, which result in lower losses) and the magnitude of the intermediate circuit voltage (DC bus voltage).

[0005] DE 10 2017 220 682 A1 relates to a control device for a rotary electric AC machine, in which an electric DC machine is controlled in a closed loop based on an intermediate potential, thereby reducing the load on the control central processing unit (CPU).

[0006] DE 10 2019 114 480 A1 discloses a motor control device and a control method in which a motor is controlled by comparing a phase voltage value with a pulse width modulation count value, which reduces errors in the switching process and improves the control accuracy.

[0007] EP 3 809 584 A1 relates to a motor control device in which a motor stop signal is delayed based on the time required for a current detector to convert the leakage current into an analog signal, thereby reducing false detection of leakage current caused by the on-off switching of power conversion elements. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] DE 10 2017 220 682 A1 [Patent Document 2] DE 10 2019 114 480 A1 [Patent Document 3] EP 3 809 584 A1 Summary of the Invention [Problem to be solved by the invention]

[0009] However, all known motor inverter systems suffer from the problem of unnecessary losses in the drive system and alternator when the alternator is rotating at low speeds.

[0010] SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a drive load system for a rotary electric motor, which reduces switching loss in a motor inverter of the drive load system and magnetic loss in the electric motor. [Means for solving the problem]

[0011] The object of the invention is achieved by a drive and load system according to claim 1, a test stand according to claim 13, a load system according to claim 14 and a drive system according to claim 15. Advantageous embodiments and further developments of the invention are set out in the dependent claims.

[0012] According to the present invention, a driving load system for a rotary electric motor is provided, the system comprising a controllable current source connectable to a current supply source. The controllable current source is connected to an intermediate circuit comprising a capacitor for intermediately storing current, the capacitor thus serving as an energy storage device for stabilizing the intermediate circuit voltage. The driving load system further comprises a motor inverter connected to the intermediate circuit, the motor inverter being configured to convert an intermediate circuit voltage applied to an input terminal into a driving current for the rotary electric motor or to return a load current from the electric motor to the intermediate circuit. A closed-loop control circuit of the driving load system has an actual value input connected to an input of the motor inverter and controls the motor inverter input voltage to a setpoint value U via the controllable current source. SETIn accordance with the present invention, the driven load system is connected to a setpoint input of a closed-loop control circuit, and the current setpoint U SET The set value output device is provided to set a predetermined set value curve U SET Based on [N(T)], the setpoint U for the closed-loop control circuit is determined according to the motor rotation speed N(T). SET It is possible to determine (T).

[0013] According to the present invention, a frequency conversion system or motor inverter system for an electric AC machine is provided, preferably controlled by a pulse inverter with switching elements used in the inverter process. Instead of a constant supply voltage being applied to the input of the motor inverter, the input voltage of the motor inverter is set depending on the rotational speed of the AC machine, and particularly at low rotational speeds a lower voltage is applied to the input of the motor inverter. This allows for reduced switching losses in the switching elements of the motor inverter and / or magnetic losses within the AC machine.

[0014] At high voltages, switching losses become larger, but they can be reduced by appropriately reducing the input voltage of the motor inverter. At the same time, the voltage requirements of the electric motor or E-motor increase with increasing speed, so the setpoint curve U SET Advantageously, [N(T)] increases intermittently or continuously with increasing speed N.

[0015] The setpoint curve U is used because the motor inverter and the required supply voltage of the motor reach saturation at a given speed. SET [N(T)] is the saturation speed N SAT to a constant saturation value U MAX It is advantageous to have

[0016] At low speeds, the minimum supply voltage must be applied to the motor inverter input, so the setpoint curve U SET [N(T)] is an additive term with a constant offset value U OFFSETIt is desirable to have

[0017] To ensure that a certain power or supply voltage buffer is available at the motor inverter input when large speed changes occur, the setpoint curve U SET Advantageously, [N(T)] has a positive leading component B*DN / DT as an additive term, and if DN / DT<0, then B*DN / DT=0.

[0018] In order to approximate the setpoint curve as accurately as possible to the actually required supply voltage at the motor inverter input, a certain safety margin or voltage buffer is added to the setpoint curve U SET [N(T)] is divided into N consecutive speed intervals I1 to In, and the corresponding linear gradient A X The gradient A X Regarding A X > A X+1 It is desirable that >0 holds.

[0019] In this case, the setpoint curve U SET In order to adjust or adapt [N(T)] very precisely to the supply voltage required for the speed N, the setpoint curve USET[N(T)] in the X-th speed interval Ix among N consecutive speed intervals I1 to In is expressed by the following relation: U SET_X [N(T)] = A X *N(T) + B X *DN / DT + U OFFSET + U DELTA_X (N X-1 ≦N <N X ) where N0=0, Ax is a gradient coefficient such that A0=0 and Ax>0, DN / DT is the time derivative of the velocity N(T), Bx is a leading coefficient such that Bx=0 if DN / DT<0, U OFFSET is the offset value, U DELTA_X is the continuity value JPEG2025540102000002.jpg18168

[0020] Furthermore, the setpoint curve U SET (N) is the required supply voltage curve U of the motor inverter and the motor. ZK_MIN (N) and the offset value U OFFSET Advantageously, it is constructed as the sum of

[0021] In the case where the required supply voltage curve is measured according to the speed, the required supply voltage curve U ZK_MIN Advantageously, (N) is an interpolated function of data points consisting of the measured required supply voltage and the corresponding speed N.

[0022] In order to be able to take into account the torque M of the motor in addition to the speed N, the setpoint output device is provided with a predetermined setpoint curve U SET Based on [M(T)], the current setpoint U of the closed-loop control circuit is calculated according to the motor torque M(T). SET Advantageously, it is possible to determine (T).

[0023] In order to realize reliable and high-speed switching operations of switching elements involving high currents in a motor inverter, it is preferable that the motor inverter be configured to include a pulse inverter equipped with power semiconductor switching elements, in particular IGBTs or SIC MOSFETs.

[0024] In the high-voltage power supplies of drive load systems and test equipment in general, it is particularly advantageous for the controllable current source for the three-phase high-voltage power supply to have a frequency converter with a controlled rectifier, in particular an active front-end (AFE) converter with PID closed-loop control.

[0025] The present invention also provides a test apparatus, particularly a test apparatus for a motor, transmission, brake, or vehicle. The test apparatus includes an electric drive load system according to the present invention. In this case, the motor or transmission test apparatus has an electric machine, which can be configured as an asynchronous or synchronous machine, connected to a motor inverter and adapted to drive or load a test object configured as an electric motor or an internal combustion engine. The test apparatus further includes a mechanical shaft connection for connecting the shaft of the electric machine to the test object. The motor or transmission test apparatus also includes a torque measurement unit configured to measure the torque M(T) via a torque measurement flange on the shaft connection and transmit it to an evaluation device. The rotational speed N(T) is measured by a rotational speed recording unit in the motor or transmission test apparatus through a pulse generator provided on the shaft connection and transmitted to the evaluation device. The evaluation device is configured to receive the measured torque M(T) and rotational speed N(T) from the torque measurement unit and the rotational speed recording unit and record them for further evaluation of the test procedure.

[0026] The present invention also provides an electric load system, particularly for a generator, that includes the electrically driven load system according to the present invention. In this case, the electric load system has an electric machine configured as a generator and connected to the output of a motor inverter configured to send the generated AC current to a motor inverter and a controllable current source configured as a frequency converter, whereby the frequency-converted current is supplied to a power system. The output voltage applied to the input of the motor inverter is adjusted according to the generator speed, thereby enabling efficient current generation, particularly in power generation systems where the generator rotational speed cannot or does not remain constant. Such a load system is particularly advantageous for use in, for example, gearless wind power generation systems.

[0027] The present invention further provides an electric drivetrain, particularly for electric vehicles, which includes an electric drive load system according to the present invention, and the current source is a mobile current source, particularly a battery module. The electric drivetrain further comprises an electric machine connected to the output of a motor inverter, which converts drive current into rotational power and returns braking power to the motor inverter, and the controllable current source is configured as a DC / DC converter. By adjusting the input voltage of the motor inverter according to the speed of the electric machine, switching losses in the motor inverter and / or magnetic losses in the alternator can be reduced, which significantly reduces the current consumption of the electric vehicle and enables the range of the electric vehicle to be extended. [Brief explanation of the drawings]

[0028] The present invention will now be described in detail with reference to the following drawings. [Figure 1A] 1 is a schematic diagram of a motor or transmission testing device according to an embodiment of the present invention; [Figure 1B] 1 is a schematic block diagram of a motor or transmission testing device according to an embodiment of the present invention; [Figure 2] 1 is a schematic block diagram of an electric drive and load system according to an embodiment of the present invention. [Figure 3] 1 is a schematic block diagram of an electrically driven load system in accordance with an embodiment of the present invention; [Figure 4A] 1 shows a circuit configuration of a frequency converter with a controlled rectifier for controlling an AC machine according to the prior art. [Figure 4B] 1 is a schematic block diagram showing the flow of energy in a drive or load system according to the prior art; [Figure 5A] 1 is a schematic block diagram of an electric drive or load system according to the prior art; [Figure 5B] UN diagram showing the required supply voltage of the motor inverter versus speed, based on the prior art, and the fixed supply voltage applied to the motor inverter input. [Figure 6A] FIG. 1 is a schematic block diagram of a drive-load system according to an embodiment of the present invention. [Figure 6B] 1 is a UN diagram showing the required supply voltage of a motor inverter according to an embodiment of the present invention versus rotational speed, and a setpoint curve versus rotational speed; [Figure 7] 3 is a flowchart of a driving and loading method according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0029] In each figure, corresponding components are designated by the same reference numerals.

[0030] 1A and 1B show schematic diagrams of a motor or transmission testing device 1 according to the present invention. The motor or transmission testing device 1 according to the present invention comprises a drive load system 10 connected to a current source 80.

[0031] 1B, the driven load system 10 according to the invention comprises a controllable current source 100 connectable to a current source 80. The controllable current source 100 is connected to an intermediate circuit ZK, which has a capacitor 200 as an energy storage device for intermediate storage of current and / or for stabilizing the intermediate circuit voltage. Furthermore, the driven load system 10 comprises a motor inverter 300 connected to the intermediate circuit, which generates an intermediate circuit voltage U applied to the motor inverter input. ZK into a drive current for the rotary electric motor 20 or return a load current from the electric motor 20 to the intermediate circuit ZK. The drive load system 10 further comprises a closed-loop control circuit 400, the actual value input of which is connected to the motor inverter input and which converts a set value U SET Motor inverter input voltage U ZK is used as the actual measured value for closed-loop control.

[0032] Additionally, the driven load system 10 is connected to a setpoint input of the closed loop control circuit 400 to provide a current setpoint U SET The set value output device 500 is provided to set a set value curve USET [N(T)] determines the current setpoint U for the closed-loop control circuit 400 based on the speed N(T) of the motor 200. SET (T) is suitable for determining the setpoint curve U against the speed N. SET The determination of is explained in more detail below with reference to Figures 5C and 6B. In this case, the intermediate circuit voltage U at the motor inverter input ZK The main purpose of setting is to reduce the corresponding switching losses in the motor inverter 300 and magnetic losses in the AC machine 20 when controlling the electric motor 20 .

[0033] As further shown in Figures 1A and 1B, the motor or transmission test apparatus 1 includes an electric motor 20 connected to a motor inverter 300, which can be configured as an asynchronous or synchronous machine, and is adapted to drive or load a test specimen 30 configured as an electric motor or an internal combustion engine.

[0034] The asynchronous machine 20 is designed as a squirrel-cage induction machine and is characterized by a wide speed range, high dynamic performance, and high robustness. In the motor or transmission test device 1 according to the present invention, the asynchronous machine 20 constitutes the drive load device for the test specimen 30. The asynchronous machine 20 is capable of high rotational speeds of up to 10,000 RPM and has a low moment of inertia and high overload resistance during high-speed operation. The asynchronous machine 20 is capable of both generator operation and motor operation in two rotation directions and can be coupled to large masses. In combination with the drive load system 10, the machine 20 can perform not only braking but also driving, for example, to simulate downhill driving or gear changes.

[0035] If the test specimen 30 is an electric motor, the electric motor 30 may include an AC machine 32 and a motor inverter 34. In this case, the motor inverter 34 is connected to a DC bus or an intermediate circuit ZK, thereby receiving current from the driven load system 10. Here, a DC / DC converter 600 is optionally connected between the intermediate circuit ZK and the capacitor 200, so that the voltage applied to the intermediate circuit ZK can be appropriately leveled and set to the desired input voltage of the motor inverter 34. However, it is emphasized that the DC / DC converter 600 is an optional component of the electric driven load system 10 according to the present invention.

[0036] The shafts of the asynchronous machine 20 and the test specimen 30 are connected to one another via a mechanical shaft connection 40 to form a torque coupling between the two machines 20 and 30. The electric motor 20 is therefore directly connected to the test specimen 30 via the measurement flange of the torque measuring unit 50 and the shaft connection 40. As the electric motor 20 is designed for a high connectable mass, no intermediate bearing block is required.

[0037] The torque measurement unit 50 is configured to measure the torque M(T) via a torque measurement flange mounted on the shaft connection 40 and transmit the measured torque to the evaluation unit 70. The torque measurement unit 50 is configured as a torque measurement flange with an integrated evaluation unit, enabling dynamically accurate measurements at the interface with the test specimen 30. The shaft torque between the asynchronous machine 20 and the test specimen 30 is recorded via a strain gauge (DMS) measurement bridge mounted on the rotating flange of the torque measurement unit 50 and transmitted contactlessly to the stator side. Signal transmission from the rotor to the stator of the asynchronous machine 20 is performed digitally. The supply voltage is transmitted from the stationary side to the rotating side inductively. Direct measurement on the test specimen 30 ensures dynamically accurate torque measurement. In addition to the torque measurement unit 50, a speed recording unit 60 is also provided. The speed recording unit 60 is configured to measure the speed N(T) via a pulse generator mounted on the shaft connection 40 and transmit the measured torque to the evaluation unit 70. The speed recording unit 60 records the speed using an axially hollow, bearingless, sealed hollow shaft encoder mounted on the opposite side of the test specimen 30. The scanning unit of the speed recording unit 60 is rigidly connected to the shaft 40, i.e., without a coupling. The speed sensor has two scanning systems, one for the drive load system 10 and one for the evaluation unit 70 (see FIG. 1B), allowing redundant speed recording for safe shutdown in the event of a failure of one of the scanning systems. The number of points per revolution is optimally adjusted for each speed range of the asynchronous machine 20.

[0038] The evaluation unit 70 is configured to receive the measured torque M(T) and speed N(T) from the torque measurement unit 50 and the speed recording unit 60, respectively, and record them for further evaluation in the test procedure. In this case, the evaluation unit 70 can be configured as a test rig controller that functionally covers the entire range of modern motor testing.

[0039] As shown in FIG. 1A , in addition to the test rig controller 70, a safety center 72 can be provided to ensure that connected systems / machines are safely shut down when an emergency stop is triggered. The safety center 72 records input information from connected devices and displays the status of these devices. The safety center 72 is a switching device that allows safe and redundant contact duplication of the emergency stop input signal. When the emergency stop command device is activated, the safety contacts of the safety switching device immediately open, thereby stopping hazardous operations and isolating other hazards. In addition to the safety center 72, a power supply module 74 can also be optionally provided, which supplies current to the safety center 72 and the test rig controller 70.

[0040] As shown in FIG. 2, a drive load system 10 according to the present invention can be used in an electric drive and load system 2, 3, in particular an electric load system 2 (eg for a generator) or an electric drive system 3 (eg for an electric vehicle).

[0041] First, a detailed description will be given of the electric load system 2. In the generator load system 2, an electric motor 20 configured as a generator is connected to the motor inverter output of a motor inverter 300, and transmits the generated AC current to the motor inverter 300 and a controllable current source 100, which together function as a frequency converter and supply the frequency-converted current to a power supply system 80. Here, the current supply source 80 is preferably a three-phase high-voltage power supply.

[0042] In the electrical load system 2 for a generator shown in Figure 2, the controllable current source 100 is configured as an AC / DC converter, similar to the motor or transmission test device 1 shown in Figures 1A and 1B, and includes a frequency converter with a controllable power supply rectifier, in particular an active front-end (AFE) converter with PID closed-loop control. Such an AFE converter with PID closed-loop control will be described in more detail below with reference to Figures 4A to 5B.

[0043] An important characteristic of the AFE converter is that such a controllable current source 100 can supply an electric drive current to the motor inverter 300 on the one hand, and on the other hand, supply a DC current generated by the generator 20 and converted by the motor inverter 300 to the power supply system 80 (see FIG. 4B). The driving load system 10 according to the present invention can significantly reduce both the switching loss in the motor inverter 300 and the magnetic loss in the generator 20, so that the electric load system 2 using the driving load system 10 is particularly efficient and enables highly efficient current generation.

[0044] The system shown in Fig. 2 can also be used as an electric drivetrain 3. In this case, the electric drivetrain can be used in any electric mobility device, such as an electric vehicle, an electric aircraft, an electric drone or an electric ship. In this embodiment, a current source 80 is configured as a mobile power source, in particular an accumulator module. A controllable current source 100 configured for this purpose as a DC / DC converter is connected to this accumulator module 80.

[0045] In the electric drivetrain 3 of an electric vehicle, a high-voltage DC / DC converter is preferred, which can ensure a stable traction voltage in the electric drivetrain 3. For this purpose, so-called non-isolated DC / DC converters are used, i.e., those configured as a buck-boost converter that combines a buck converter with a boost converter, allowing for bidirectional energy transfer. This allows for energy transfer from the accumulator module 80 to the electric motor 20, and also allows for current regeneration back into the accumulator module 80. These components of an electric drivetrain for an electric vehicle are well known to those skilled in the art and are part of the course content (see in this regard the course material "POWER ELECTRONICS IN A VEHICLE AND DRIVE TRAIN", Winter semester 2021 / 2022, Professor Martin Maerz, Chair of Power Electronics (LEE), Friedrich-Alexander University Erlangen-Nuremberg).

[0046] During driving, the electric motor 20, connected to the output of the motor inverter, converts the drive current supplied by the controllable current source 100 into rotational power. During braking, the electric motor 20 regenerates braking power to the motor inverter 300, and the controllable current source 100, configured as a DC / DC converter, reduces or converts the high voltage, for example to the operating voltage (14 V) of the traction battery 80, and then supplies the current, which has been converted to direct current by the motor inverter 300 and stored in the capacitor 200 (42 V intermediate circuit capacitor), to the accumulator module 80 again. Use of the drive load system 10 according to the invention makes it possible to reduce switching losses in the motor inverter 300, allowing the electric drivetrain 3 for an electric vehicle to operate particularly efficiently and increasing the driving range of the electric vehicle equipped with this drivetrain 3.

[0047] In the following, the operating mode of the drive load system 10 according to the present invention will be explained based on a comparison with a conventional drive load system.

[0048] FIG. 4A shows an exemplary circuit configuration of a conventional drive load system 10′ for a rotary electric motor 20′. Such a drive load system 10′ is also called a frequency converter with a controlled rectifier. Such a frequency converter includes an active power switch 110′ at its input, configured as a B6 bridge consisting of six power transistors, IGBTs, or power MOSFETs. This requires more control effort, but offers several advantages, such as the ability to regenerate energy back to the power supply, for example, when braking the mass driven by the motor. Furthermore, pulse inverters ensure that the current consumption from the power supply is approximately sinusoidal, significantly reducing low-frequency harmonic content and enabling fast switching between motor and generator operation. On the power supply side, input switching and possible resonant peaks can be sufficiently attenuated by a specialized filter 120′. Active front-end (AFE) frequency converters with PID closed-loop control are described, for example, in the following publication: "DYNAMIC MODEL OF ACTIVE FRONT-END CONVERTERS WITH 2DOF-PI CONTROLLERS FOR DC BUS VOLTAGE CONTROL," ANUP THAPA et al., 2020 IEEE 21ST WORKSHOP ON CONTROL AND MODELING FOR POWER ELECTRONICS (COMPEL), November 9-12, 2020, DOI: 10.1109 / COM-PEL49091.2020.9265801.

[0049] The frequency converter 10′ shown in FIG. 4A consists of a source-side pulse inverter 100′ (the “active front end”) and a machine-side pulse inverter 300′ (the “inverter”). These inverters 100′, 300′ convert the supply voltage from a power supply 80′, which has a constant amplitude and frequency (50 or 60 Hz), into a variable voltage and variable frequency system. Both power elements are equipped with IGBT (insulated gate bipolar transistor) switching elements 110′ or MOSFETs, in particular SIC (silicon carbide) MOSFETs. In general, the present invention encompasses any type of power semiconductor switching element as long as it can reliably and quickly switch high currents. This allows both motor and generator operation at all currents.

[0050] Figure 4B shows the power flow in the system in this case. The field-oriented vector closed-loop control of the machine-side frequency converter 300' (corresponding to the motor inverter 300 of the present invention) achieves excellent closed-loop control dynamics and very good concentricity (smoothness) over the entire rotational speed range. The source-side pulse inverter 100' (corresponding to the controllable current source 100 of the present invention) is operated with a power factor COS Φ = 1. In this setting, no fundamental reactive power is generated. The source current has an approximately sinusoidal waveform. The standard mains filter minimizes pulse frequency harmonics.

[0051] 5A shows a prior art driven load system 10′ for a rotating electric motor 20′, which can be configured as a frequency converter with controlled mains rectifier, or as an AFE converter (Active Front End Converter), as shown in FIG. 4A. The purpose of the driven load system 10′ is to provide a defined supply voltage to the motor inverter 300′ at the power supply input of the motor inverter 300′. In order to ensure that voltage drops are compensated by the intermediate circuit ZK and the capacitor 200′ in the event of high supply currents, the frequency converter 100′ with controlled mains rectifier is provided with a closed-loop control circuit 400′, the actual value input of which is connected to the input of the motor inverter, and which converts the input voltage of the motor inverter 200′ into a setpoint U as the actual value by means of a controllable current source 100′. SET The supply voltage U ZK In the prior art, a voltage is selected at the input of the motor inverter 300' to ensure sufficient power even at maximum load and maximum rotational speed.

[0052] Such a constant voltage supply voltage U ZK is the AC voltage U ZK [VAC] and DC voltage U ZK 5B as [VDC], and is independent of the rotation speed of the electric motor 20. In the example shown in FIG. ZK is set to 500V. However, the supply voltage UKL required by the electric motor 20' or AC motor 20' increases with increasing rotational speed and remains constant after reaching a maximum peak supply voltage. The intermediate circuit voltage or DC bus voltage applied to the input of the motor inverter 300' is, according to the prior art, closed-loop controlled regardless of the rotational speed, thereby providing the required supply voltage to the electric motor 20 over the entire rotational speed range and ensuring a reserve for dynamic behavior, especially in the speed range above the peak supply voltage.

[0053] Such control can result in unnecessarily high intermediate circuit or DC bus voltages in the low speed range, which, as already mentioned at the beginning, leads to associated switching losses. This is particularly true for permanent magnet (PM) machines, which are used in the high speed range and require a relatively low rated voltage at the rated speed operating point. Such an intermediate circuit voltage can be controlled by a constant input voltage U ZK A typical closed-loop control for controlling the supply voltage U provided at low speeds is shown in FIG. 5A. As can be seen from FIG. 5B, ZK is significantly higher than the supply voltage actually required in that speed range. However, in a motor inverter 300' that includes a pulse inverter, this situation will result in unnecessarily high switching losses at low speeds N, especially if the pulse inverter includes power semiconductor switching elements such as IGBTs or MOSFETs, especially SIC MOSFETs.

[0054] 6A shows a driving load system 10 according to an embodiment of the present invention, which can be used for a rotary electric motor 20. The driving load system 10 according to the present invention comprises a controllable current source 100, an intermediate circuit ZK and its capacitor 200, a motor inverter 300, a closed-loop control circuit 400, as well as a setpoint output device 500 connected to a setpoint input of the closed-loop control circuit 400, which setpoint output device outputs a current setpoint U SET (T). Here, the set value output device is configured to output a set value curve U SET Based on [N(T)], the current setpoint U for the closed-loop control circuit is calculated as a function of the motor speed N(T). SET (T) is suitable for determining the setpoint curve U SET The purpose of [N(T)] is to match as closely as possible the required supply voltage profile of AC motor 20, with a certain safety margin, offset, or voltage reserve added. Note that this voltage reserve is proportional to the amount of charge stored in capacitor 200, so it also corresponds to an energy reserve for motor 20.

[0055] Figure 6B shows the setpoint curve U SET (N) is again shown by dashed lines as the AC voltage UZK [VAC] and the corresponding DC voltage UZK [VDC] (corresponding to UZK [VAC] × √2). As shown in FIG. 6B, when the AC motor 20 is rotating at a low speed, the required supply voltage U ZK_MIN , or equivalently, the motor terminal voltage U KL is lower than that at high speed rotation, so according to the present invention, the set value curve U SET It is preferable that (N) has a smaller target voltage value at low speed than at high speed. Therefore, the setpoint curve U SET It is desirable to increase (N) stepwise or continuously as the rotation speed N increases. According to the present invention, the set value curve U SET (N) is the saturation velocity N SATT (In this example, approximately 14,000 RPM) and the steady-state saturation value U MAX (500V in this example). Furthermore, there is a certain voltage reserve for dynamic operation, and the setpoint curve may have a constant offset value U OFFSET as an additive term. This ensures that the target voltage does not fall below the required supply voltage.

[0056] The intermediate circuit voltage in the intermediate circuit ZK, i.e. the DC bus voltage, is therefore calculated on the basis of the rotational speed N and its speed gradient DN / DT. In order to maintain a certain lead voltage as a reserve during the acceleration phase, the setpoint curve U SET [N(T)] may have a positive leading component B*DN / DT as an additive term, which is zero if the speed change is DN / DT<0. Therefore, the intermediate circuit voltage or DC bus voltage U ZK The setpoint value U in the intermediate circuit ZK is calculated based on the current rotational speed N(T) only if the speed gradient, i.e. the time derivative of the rotational speed DN / DT, is less than 0. ZK , i.e. the setpoint of the DC bus voltage, is only added with a positive leading component if the time derivative of the rotational speed is DN / DT>0. In this way, the intermediate circuit voltage U ZKThis is important when the speed gradient DN / DT is large and positive, because in the case of large speed changes or accelerations, the DC bus voltage or intermediate circuit voltage may not be able to follow the machine voltage demand quickly enough to supply the required power to the motor 20.

[0057] Furthermore, as shown in Figure 6B, the set point curve U SET [N(T)] can be divided into N consecutive speed intervals I1 to In. In the embodiment shown in FIG. 6B, the setpoint curve U SET shows a first gradient in a first speed range up to about 4,000 rpm, then switches to a second gradient in a second speed range from 4,000 rpm to 14,000 rpm, and reaches a saturation value U MAX Preferably, the corresponding gradients are switched from high to low, since this configuration best matches the actual progression of the required supply voltage. Therefore, it is preferable that the setpoint curve is divided into N consecutive speed intervals I1 to In, and configured to have a linear gradient Ax in each speed interval Ix, where the gradient is Ax. X > A X+1 > 0 applies.

[0058] Although Figure 6B shows only two speed sections (0 to 4,000 rpm and 4,000 to 14,000 rpm) and two different gradients, the number of speed sections N may be 10 or 100. However, to keep the closed-loop control simple, it is preferable that N be less than 1,000, or less than 500, or less than 200, or less than 100, or less than 90, or less than 80, or less than 70, or less than 60, or less than 50, or less than 40, or less than 30, or less than 20, or less than 10, or less than 9, or less than 8, or less than 7, or less than 6, or less than 5, or less than 4, or less than 3, or 2, or 1.

[0059] In this case, the set value curve U in the X-th speed section Ix of the N consecutive speed sections I1 to In is SET For [N(T)], the following formula preferably applies: U SET_X [N(T)] = A X *N(T) + B X *DN / DT + U OFFSET + U DELTA_X , FOR N X-1 ≦N <N X

[0060] where N0=0, Ax is the gradient coefficient, A0=0 and Ax>0, DN / DT is the time derivative of the velocity N(T), Bx is the leading coefficient, Bx=0 when DN / DT<0, U OFFSET is the offset value, U DELTA_X is the continuity value JPEG2025540102000003.jpg11168

[0061] In addition, the following applies: N(T) > N N = N SAT In the case of U SET_X [N(T)] = U MAX

[0062] Also, the setpoint curve U SET [N(T)] may be fitted as a square root function of the required supply voltage and configured to add an offset value: JPEG2025540102000004.jpg8168

[0063] Additionally, it may contain the preceding component B*DN / DT: JPEG2025540102000005.jpg11168

[0064] Other functions, such as logarithmic functions, can also be considered. The setpoint curve U SET[N(T)] can be used to adjust as precisely as possible, so that the same voltage reserve U OFFSET + B*DN / DT is secured: U SET [N(T)] = E*LOG[F*N(T)^G+1] + B*DN / DT + U OFFSET

[0065] The gradient factor A in this case is preferably in the range: 0.001V / rev / min ~ 1V / rev / min, or 0.005V / rev / min ~ 0.5V / rev / min, or 0.01V / rev / min ~ 1V / rev / min Offset value U OFFSET is preferably in the following range: 1V~1000V, or 5V~500V, or 10V~200V, or 10V~100V The leading factor B is preferably in the following range: 1V·sec / rev / min to 10MV·sec / rev / min, or 10V·sec / rev / min to 1MV·sec / rev / min, or 100V·sec / rev / min ~ 100KV·sec / rev / min The parameter C is preferably in the following range: 0.1V~100V, or 0.5V~50V, or 1V~10V The parameter D is preferably in the following range: 0.1 min / rev ~ 100 min / rev, or 0.5 minutes / revolution to 50 minutes / revolution, or 1 minute / rotation to 10 minutes / rotation The parameter E is preferably in the following range: 0.1V~100V, or 0.5V~50V, or 1V~10V The parameter F is preferably in the following range: 0.1 min / rev ~ 100 min / rev, or 0.5 minutes / revolution to 50 minutes / revolution, or 1 minute / rotation to 10 minutes / rotation The parameter G is preferably in the following range: 0.1 to 100, or 0.5 to 50, or 1 to 10 The voltage values ​​(unit: V) described here are related to the AC voltage values ​​UZK [VAC] shown in FIGS. 5B and 6B.

[0066] If the required supply voltage as a function of speed can be measured or simulated, the setpoint curve U SET (N) is the minimum supply voltage curve U of the motor inverter 300 and the electric machine 20 ZK_MIN (N) and offset value U OFFSET It may be constructed as the sum of

[0067] In this case, the required supply voltage curve U ZK_MIN (N) can be expressed as an interpolated function of data points based on the measured required supply voltage and the corresponding speed N. Such an interpolated function can be any of the functions described above, or can be fitted to the data set. Furthermore, the setpoint curve U ZK_SET (N) is the speed from 0 to N SAT At least one speed section I X and in the speed interval, the setpoint curve may have a stepwise increasing component, a continuous increasing component, a linear increasing component, a square root increasing component, or a logarithmic increasing component. The setpoint curve may be any monotonically increasing function, or any constant monotonically increasing function.

[0068] In addition to controlling the voltage through speed-dependent closed-loop control, the setpoint output device 500 also controls the voltage by generating a predetermined setpoint curve U based on the torque M(T) of the electric machine 20. SET[N(T), M(T)] determines the current setpoint U for the closed-loop control circuit. SET It may also be suitable to determine the intermediate circuit voltage setpoint U(T). It is not possible to control the intermediate circuit voltage in a closed loop using only the torque M(T). However, according to the invention, in addition to evaluating the speed N(T), the torque M(T) can be calculated as a function of the intermediate circuit voltage setpoint U(T). SET It is preferable to use it as a further influencing variable for [N(T), M(T)].

[0069] 7 shows a flowchart of a method for operating the drive and load system 10 for a rotating electric machine 20. The method 1000 includes a first step S1010 of providing a controllable current source 100 connectable to a current supply. The method then includes a step S1020 of providing an intermediate circuit ZK connected to the controllable current source 100, the intermediate circuit ZK comprising a capacitor 200 for intermediate storage of current. The method further includes a step S1030 of providing a motor inverter 300 connected to the intermediate circuit ZK, the motor inverter 300 converting an intermediate circuit voltage applied to a motor inverter input into a drive current for the rotating electric machine 20 or returning a load current from the electric machine 20 to the intermediate circuit ZK. The method further includes a step S1040 of providing a closed-loop control circuit 400, the closed-loop control circuit 400 having an actual value input connected to the motor inverter input and configured to convert the motor inverter input voltage as an actual value to a setpoint value U by the controllable current source 100. SET Further, the step S1050 includes providing a setpoint output device 500, which is connected to the setpoint input of the closed-loop control circuit, and outputs its current setpoint U SET Set (T).

[0070] In step S1060, the current set value U for the closed-loop control circuit 400 is SET (T) is the predetermined set point curve U SET (T) as a function of the speed N(T) of the electric machine.

[0071] Controlling or closed-loop control of the DC bus voltage or intermediate circuit voltage according to the speed and speed gradient has the effect of reducing the switching and magnetic losses occurring in particular in the motor inverter 300 and the electric machine 20. These magnetisation losses occur in the electric machine and in the chokes, if installed (mains side and motor side), and the magnetisation losses in the motor-side chokes can also be reduced.

[0072] This effect is particularly effective for high-speed PM (permanent magnet) synchronous motors. Therefore, during test-bed operation, at low speeds and full loads, only a low supply voltage corresponding to the supply voltage actually required at the operating point is applied to the input of the motor inverter 300, thereby reducing thermal load. According to the present invention, the DC bus voltage of the drive system is closed-loop controlled based on the machine speed and speed gradient to compensate for switching losses by applying a low voltage at low speeds. In this way, magnetic losses in the AC machine and, if necessary, installed motor chokes, as well as switching losses in IGBT switching elements, SIC-MOSFETs, or generally power semiconductor switching elements or power transistors of the drive system, are reduced. As a result, the efficiency of the drive and load system 10 according to the present invention can be improved.

Claims

1. A drive load system (10) for a rotary electric motor (20), comprising: a controllable current source (100) connectable to the current source (80); an intermediate circuit (ZK) connected to the controllable current source (100) and comprising a capacitor (200) for intermediately storing a current; a motor inverter (300) connected to the intermediate circuit (ZK), which converts an intermediate circuit voltage applied to an input terminal of the motor inverter into a drive current for the rotary motor (20) or returns a load current from the rotary motor (20) to the intermediate circuit (ZK); A controllable current source (100) is connected to the motor inverter input, and the motor inverter input voltage is controlled to a set value U ＳＥＴ A closed-loop control circuit (400) for performing closed-loop control as an actual value for A current setpoint U is connected to the setpoint input of the closed loop control circuit (400). ＳＥＴ and a set value output device (500) that sets (T), The setting value output device (500) generates a predetermined setting value curve U ＳＥＴ [N(T)] and is capable of determining a current setting value U ＳＥＴ (T) for the closed-loop control circuit (400) according to the rotational speed N(T) of the electric motor (20). A drive load system (10) characterized by this.

2. The set value curve U ＳＥＴ 2. The driving load system (10) according to claim 1, wherein [N(T)] increases intermittently or continuously as the rotational speed N increases.

3. The set value curve U ＳＥＴ [N(T)] is the saturation speed N ＳＡＴ to a constant saturation value U ＭＡＸ 3. A driving load system (10) according to claim 1 or 2, characterized in that it comprises:

4. The set value curve U ＳＥＴ [N(T)] is added as a constant offset value U ＯＦＦＳＥＴ 3. A driving load system (10) according to claim 1 or 2, characterized in that it comprises:

5. The set value curve U ＳＥＴ 3. The driving load system (10) according to claim 1 or 2, characterized in that [N(T)] has as an additive term a positive leading component B*DN / DT whose value is 0 when the speed change DN / DT<0.

6. The set value curve U ＳＥＴ [N(T)] is the number of consecutive speed intervals I １ 〜In, and varies with a corresponding linear gradient Ax in the X-th speed interval Ix, Ｘ Regarding Ax > Ax ＋１ 3. The driving load system (10) according to claim 1 or 2, characterized in that:

7. N consecutive speed intervals I １ The set value curve USET[N(T)] in the X-th speed section Ix among the speed sections Ix to In is expressed by the following relational expression: U ＳＥＴ＿Ｘ [N(T)] = A Ｘ *N(T) + B Ｘ *DN / DT + U ＯＦＦＳＥＴ + U ＤＥＬＴＡ＿Ｘ (N Ｘ－１ ≦N<N Ｘ ) characterized by following the Here, N ０ = 0, Ax is the gradient coefficient and A ０ = 0 and Ax > 0, DN / DT is the time derivative of the velocity N(T), Bx is a leading coefficient and Bx = 0 when DN / DT < 0, U ＯＦＦＳＥＴ is the offset value, U ＤＥＬＴＡ＿Ｘ is the continuity value 3. A driving load system (10) according to claim 1 or 2, characterized in that:

8. The set value curve U ＳＥＴ (N) is the required supply voltage curve U of the motor inverter (300) and the electric motor (20). ＺＫ＿ＭＩＮ (N) and the offset value U ＯＦＦＳＥＴ 3. The driving load system (10) according to claim 1 or 2, characterized in that it is configured as a sum of

9. The required supply voltage curve U ＺＫ＿ＭＩＮ 9. The driven load system (10) of claim 8, wherein (N) is an interpolated function of data points consisting of measured required supply voltages and corresponding speeds N.

10. The set value output device (500) outputs a predetermined set value curve U ＳＥＴ Based on [N(T), M(T)], a current value U for the closed loop control circuit is calculated in response to the torque M(T) of the electric motor (20). ＳＥＴ 3. A driving load system (10) according to claim 1 or 2, characterized in that it is further possible to determine (T).

11. 3. The drive load system (10) according to claim 1 or 2, characterized in that the motor inverter (300) comprises a pulse inverter with power semiconductor switching elements, in particular IGBTs or MOSFETs.

12. 3. The driven load system (10) according to claim 1 or 2, characterized in that the controllable current source (100) comprises, in the case of a three-phase high-voltage power supply (80), a frequency converter with a controlled rectifier, in particular an active front-end (AFE) converter with PID closed-loop control.

13. A test device (1), in particular a test device for motors, transmissions, brakes or vehicles, comprising: A drive load system (10) according to any one of claims 1 to 12; an electric motor (20) connected to the motor inverter (300) and configured to drive or load a test object (30) designed as an electric motor or an internal combustion engine; a mechanical shaft connection (40) configured to connect the shaft of the electric motor (20) and the test object (30); a torque measuring unit (50) configured to measure the torque M(T) on the shaft connection (40) using a torque measuring flange and to transmit it to an evaluation device (70); a speed recording unit (60) configured to measure the speed N(T) on the shaft connection (40) using a pulse generator and transmit it to the evaluation device (70); an evaluation device (70) configured to receive the measured torque M(T) and the measured speed N(T) from the torque measurement unit (50) and the speed recording unit (60) and to record them for further evaluation of the test procedure.

14. An electrical load system (2), A drive load system (10) according to any one of claims 1 to 11; An electric load system (2), comprising: an electric motor (20) connected to a motor inverter output, configured as a current generator, which transmits a generated AC current to the motor inverter (300) and also to a controllable current source (100) configured as a frequency converter, thereby supplying a frequency-converted current to a power source (80).

15. An electric drivetrain (3), a mobile power source (80), in particular a storage module; A drive load system (10) according to any one of claims 1 to 11; an electric motor (20) connected to the motor inverter output and configured to convert a drive current into a rotational force and return a braking force to the motor inverter (300); An electric drivetrain (3), characterized in that the controllable current source (100) is configured as a DC / DC converter.

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