Method for controlling an electric machine

Abstract

The invention relates to a method (100) for controlling an electric machine comprising two or more phases using a continual switching principle in order to reduce a power loss by switching (112) at least one power stage, each phase having a high-side power stage and a low-side power stage, said method comprising at least the following steps: collecting (102) the necessary data for actuating (108) the electric machine, in particular the power stages: determining (104) the necessary currents or pulse widths of all power stages; determining (106) the power stage with the highest pulse width; actuating (108) a pulse width modulation, wherein a power of the electric machine is adapted; determining (110) the optimum switching time of the one or more power stages; and switching (112) the power stages by means of a control device, the control device generating a switching command in real time in order to control the switching (112) in such a way that the power stage with a highest pulse width is continually switched, or is switched on before the other power stages and switched off after the other power stages, said power stage being switched (112) only when the other power stages are off, a number of further power stages being switched on and off sequentially in combination, it being ensured that a high-side power stage and a low-side power stage are not simultaneously on at any time for the same phase.

Description

[0001] Description

[0002] title

[0003] Method for controlling an electrical machine

[0004] Technical area

[0005] The invention relates to a method for controlling an electrical machine comprising two or more phases using a permanent switching principle to reduce power loss by switching at least one power stage. Furthermore, the invention relates to a use of the method for controlling a three-phase electric motor.

[0006] State of the art

[0007] DE 10 2019 208 524 A1 relates to a method for controlling the operation of an inverter for an electrical machine, in which pulse width modulation values ​​of at least two phases are set in at least two periods by a first setting of the pulse width modulation values ​​of the individual phases in a current measurement period in which a current measurement of at least one current of the electrical machine is carried out, and depending on the

[0008] current measurement period, the pulse width modulation values ​​of the phases are adjusted in at least one further period.

[0009] WO 2019 0158 94 A1 relates to an electrical machine, namely an electric motor and / or a generator. The electrical machine has a stator and a rotor. The rotor is, in particular, permanently magnetic or carries current. The machine is divided into at least two sub-machines. Each sub-machine has the same number of phases. According to the invention, the machine has two power output stages for each sub-machine. The machine further has at least one control unit connected to the power output stages. To control the power output stages, the control unit is designed to generate a pulse-width modulated signal.To control the power output stages, the control unit is designed to generate a pulse-width modulated signal. The control unit is further designed to generate the pulse-width modulated signal for the sub-machines in such a way that a falling or rising edge of a pulse-width modulated pulse for a sub-machine, each representing a switching time, and a pulse center of a pulse-width modulated pulse for another sub-machine of the sub-machines are offset in time from one another.

[0010] Disclosure of the invention

[0011] According to the invention, a method for controlling an electrical machine with two or more phases using a permanent switching principle for reducing power loss by switching at least one power stage is presented. Each phase has a high-side power stage and a low-side power stage. The method has at least the following steps: a. determining necessary data for controlling the electrical machine, b. determining necessary pulse widths of all power stages, c. determining the power stage with a highest pulse width, and d. controlling a pulse width modulation i. determining the optimal switching time of the one or more power stages, and ii.Switching of the power stages by a control unit, wherein the control unit generates a switching command in real time to control the switching in such a way that the power stage with a highest pulse width is permanently switched, wherein the permanent switching corresponds to setting the pulse width to 100%, or is switched on before the other power stages and switched off after the other power stages, wherein the switching of this power stage only occurs when the other power stages are switched off, iii. wherein a number of further power stages are switched on and off sequentially in combination, ensuring that for the same phase a high-side power stage and a low-side power stage are never switched on at the same time.

[0012] An electrical machine, also called a multi-phase electrical machine or three-phase machine, is an electromechanical device that uses a plurality of independent sinusoidal alternating voltages or currents to generate mechanical work or convert electrical energy, and operates with two or more phases. A phase is an electrical state represented by a sinusoidal current or voltage in a system. In a multi-phase electrical machine, the phases are shifted from one another by a certain angle; for example, in a three-phase machine with three phases, by 120 degrees. This phase shift produces a uniform and continuous torque, which leads to efficient rotary motion.

[0013] A high-side power stage and a low-side power stage are components in a power electronic circuit unit that are used to control the current flow through the electrical machine. In both single-phase and multi-phase electrical systems, such as three-phase applications, corresponding power stages are present for each phase. The high-side power stage is the switch located on the positive voltage side. The high-side power stage is used to control the tap between a supply voltage and a load of the electrical machine. The low-side power stage, on the other hand, is the switch located on the negative voltage side. The low-side power stage is used to control the connection between the load and the reference potential.These power levels control both a current flow and a current direction, namely the direction of rotation, and a current intensity to achieve the desired efficiency by specifically activating and deactivating these power levels.

[0014] Pulse width modulation is used to adjust the power delivered to the electric machine. In this process, the pulse width of the pulse-width modulated signal is varied, thereby regulating the average power. Pulse width modulation is controlled by a control unit, such as a microcontroller. The control unit evaluates the analyzed data to specify an optimal switching time for the power stages. Taking into account the required currents in the power stages, the control unit can regulate the pulse width modulation to achieve efficient power control at the electric machine. For example, when controlling pulse width modulation, the currents detected by the sensor and analyzed by the microcontroller are used to determine the optimal switching time.Based on the analysis of the currents and operating requirements, an optimal switching point is determined for all power stages. The switching point is determined in such a way that both maximises efficiency and optimises the load on the electrical machine. This is achieved either by permanently switching the power stage with the highest current, i.e. keeping the power stage with the highest current permanently active until another power stage with a higher current is ready, or by sequentially switching a number of other power stages on and off in combination, ensuring that at no time are a high-side power stage and a low-side power stage for the same phase switched on at the same time.The control unit then adjusts the pulse width modulation accordingly to control the power requirements of the electric motor. After determining the optimal switching point, the control unit switches the power levels accordingly.

[0015] As an alternative to permanently switching the power level with the highest current, this can also be switched outside of the switching operations of the other power levels, so that the other power levels are switched off while this power level is switching.

[0016] In an advantageous development of the method proposed according to the invention, the power stages in an inverter are switched in such a way that they are activated or deactivated depending on the control.

[0017] In a further advantageous development of the method proposed according to the invention, the control comprises an adaptive adjustment of the pulse width modulation based on the current operating conditions of the electrical machine.

[0018] In a further advantageous development of the method proposed according to the invention, a current, a voltage, a torque and a speed are recorded on each phase of the electrical machine, wherein the recording can take place both individually and in combination of the parameters.

[0019] In a further advantageous development of the method proposed according to the invention, the current strengths of the power stages are recorded by sensors in real time.

[0020] In a further advantageous development of the method proposed according to the invention, the current intensities of the power stages are detected by sensors from the group of Hall sensors, current transformer sensors or shunt resistors.

[0021] Furthermore, the invention relates to a use of the method for controlling a three-phase electrical machine.

[0022] Advantages of the invention

[0023] The solution according to the invention advantageously implements a method for controlling an electrical machine with two or more phases using a permanent switching principle to reduce power loss by switching at least one power stage. The optimized switching principle, namely the permanent switching of the power stage with the highest current from the group of power stages of the phases of the electrical machine, increases the operating efficiency of the electrical machine. Furthermore, the permanent switching principle of the power stages reduces energy consumption and thus achieves cost savings.

[0024] Due to the permanent switching principle, the solution according to the invention can improve the service life of the power stages through lower-voltage operation, thus reducing wear and tear and failure. For vehicles or other devices powered by an electric motor, efficient use and reduced power loss result in a longer range. Alternatively, less energy is required to achieve the same range, thus reducing the costs of energy supply and energy storage.

[0025] Furthermore, the permanent switching principle of the power stages enables more efficient operation by controlling and reducing power loss, resulting in lower heat generation within the power stages compared to the state of the art. This reduces the need for complex cooling, saving costs and advantageously reducing system complexity.

[0026] Furthermore, the inventive solution is suitable for integration into existing systems, requiring only reprogramming of the control unit, which includes a microcontroller or PLC. The method according to the present inventive solution is also advantageously applicable to a variety of phase-controlled electrical machines.

[0027] Short description of the drawings

[0028] Embodiments of the invention are explained in more detail with reference to the drawings and the following description.

[0029] They show:

[0030] Figure 1 is a schematic representation of a method for controlling an electrical machine,

[0031] Figure 2 is a schematic representation of phases and power levels of a three-phase electrical machine,

[0032] Figure 3.1 is a graphical representation of a progression of three phases,

[0033] Figure 3.2 is a graphical representation of a permanent switching principle.

[0034] Embodiments of the Invention In the following description of the embodiments of the invention, identical or similar elements are designated by the same reference numerals, whereby a repeated description of these elements is omitted in individual cases. The figures only schematically illustrate the subject matter of the invention.

[0035] Figure 1 shows in schematic form as a block diagram an exemplary method 100 according to the invention for controlling an electrical machine 202 with two or more phases 204, 206, 208 using a permanent switching principle 302 for reducing power loss by switching 112 at least one power stage 204.1, 204.2, 206.1, 206.2, 208.1,

[0036] 208.2. In a first step, the data required for controlling 108 the power stages 204.1, 204.2, 206.1, 206.2, 208.1, 208.2 are recorded 102. For example, the currents of the power stages 204.1, 204.2, 206.1, 206.2, 208.1, 208.2 can be recorded and continuously monitored by Hall sensors, current transformer sensors, or shunt resistors. The sensors continuously monitor the current flow and current and record the data in real time. This data is then forwarded, for example, to a control unit 210, which enables appropriate adjustment to the changing currents.

[0037] In a second step, the required currents are determined104, individually for each power stage 204.1, 204.2, 206.1,

[0038] 206.2, 208.1 , 208.2. Each performance level 204.1 , 204.2, 206.1 , 206.2, 208.1 , 208.2 is analyzed individually. For each performance level 204.1 , 204.2,

[0039] 206.1, 206.2, 208.1, 208.2 determine the necessary current strengths and pulse widths.

[0040] In the third step of the method 100 according to the invention, the control unit 210 determines 106 and compares the necessary pulse widths of the power levels

[0041] 204.1, 204.2, 206.1, 206.2, 208.1, 208.2 and identifies the power level 204.1, 204.2, 206.1, 206.2, 208.1, 208.2 with the highest required pulse width.

[0042] In the fourth step of the method 100 according to the invention, a

[0043] Control 108 of a pulse width modulation 216 with an adjustment of the power of the electric machine 202. The control 108 of the pulse width modulation 216 runs through at least the sub-process steps i. and ii. In sub-process step i., the optimal switching time of one or more power stages 204.1, 204.2 is first determined 110.

[0044] 206.1, 206.2, 208.1, 208.2 based on the analyzed currents. In a further sub-step ii. of the fourth process step d., a switching 112 of the power stages 204.1, 204.2, 206.1, 206.2, 208.1, 208.2 is carried out by a control unit 210. The control unit 210 acts in real time and generates a switching command for controlling a switching unit 200 such that the power stage 204.1, 204.2, 206.1, 206.2, 208.1, 208.2 with the highest current is permanently switched and a number of further power stages

[0045] 204.1, 204.2, 206.1, 206.2, 208.1, 208.2 can be activated and deactivated sequentially 304 in combination 306.

[0046] As an alternative to the permanent switching 302 of the power stage 204.1, 204.2,

[0047] 206.1, 206.2, 208.1, 208.2 with the highest current can also be switched on outside the switching operations of the other power stages 204.1, 204.2, 206.1,

[0048] 206.2, 208.1, 208.2 are switched, so that during the switching 112 of this power stage 204.1, 204.2, 206.1, 206.2, 208.1, 208.2, the other power stages 204.1, 204.2, 206.1, 206.2, 208.1, 208.2 are switched off. The method 100 according to the invention always ensures that at no time are a high-side power stage 212 and a low-side power stage 214 for the same phase 204, 206, 208 switched on simultaneously.

[0049] Figure 2 shows a schematic representation of a circuit unit 200 for a three-phase electrical machine 202 with a control unit 210 with pulse width modulation 216. This circuit unit 200 has a total of six power stages 204.1, 206.1, 208.1, 204.2, 206.2, 208.2, which can be implemented by transistors or comparable semiconductor switches. The power stages 204.1, 206.1, 208.1, 204.2, 206.2, 208.2 are each divided into high-side power stages 212 and low-side power stages 214 to enable optimal power delivery. Figure 2 shows that first, second, and third power stages 204.1, 206.1, 208.1 correspond to first, second, and third high-side power stages 212.1, 212.2, 212.3. The fourth, fifth, and sixth power stages 204.2, 206.2, 208.2 correspond to first, second, and third low-side power stages 214.1, 214.2, 214.3. Each power stage 204.1, 206.1, 208.1, 204.2, 206.2, 208.2 is connected to a corresponding phase 204, 206, 208, which controls a power supply to the electric machine 202.

[0050] By dividing the system into high-side power stages 212 and low-side power stages 214, fine control of the energy flow through the phases 204, 206, and 208 of the electric machine 202 is provided. The high-side power stages 212 switch a positive voltage side and provide efficient control of the current flow through each phase 204, 206, and 208. This enables direct voltage adjustment, which is crucial for precise speed control. In contrast, the low-side power stages 214 switch a negative side of the voltage source. They function in conjunction with the high-side power stages 212 to regulate the current flow through the phases 204, 206, and 208 of the electric machine 202. This division enables more precise control of the phase current, resulting in improvements in both system efficiency and stability.

[0051] The circuit unit 200 shown in Figure 2 includes the control unit 210 with pulse width modulation 216, which ensures precise control of the power stages 204.1, 206.1, 208.1, 204.2, 206.2, 208.2. The control unit 210 modulates the pulse widths of the pulse width modulation signals 216, which are supplied to the power stages 204.1, 206.1, 208.1, 204.2, 206.2, 208.2, in order to control a power supply to the electric machine 202. The pulse width modulation 216 controls the circuit 112 of the power stages 204.1, 206.1, 208.1, 204.2, 206.2, 208.2 in such a way that the power stage 204.1,

[0052] 204.2, 206.1 , 206.2, 208.1 , 208.2 with the highest current is permanently switched and a number of further power stages 204.1 , 204.2, 206.1 ,

[0053] 206.2, 208.1, 208.2 in combination 306 can be activated and deactivated sequentially 304. This enables, for example, precise control of the speed of the electric machine 202 to optimize operation according to the requirements of the respective application. For example, the circuit unit 200 can contain several sensors for monitoring important operating variables such as speed, current, voltage, and temperature.

[0054] This feedback information is used by the controller 210 to adjust the pulse width modulation 216 accordingly to ensure optimal power output while maintaining optimal efficiency and reliability.

[0055] In addition, the control unit 210 monitors and regulates the control 108 of the phases 204, 206, 208 to ensure that the current phases 204, 206, 208 function in perfect accordance with the mains voltage. This ensures stable and efficient operation of the electrical machine 202. The circuit unit 200 can further be equipped with various protective devices, in particular overcurrent protection, overvoltage protection, and temperature monitoring, to protect the electrical machine 202 from damage and to ensure safety.

[0056] Figure 3.1 shows the time course of the three phases 204, 206, and 208. The horizontal axis represents time 308, while the vertical axis represents voltage 310 or, for example, current 312 in the individual phases 204, 206, and 208. To illustrate the time course, each phase 204, 206, and 208 is represented by a separate line. Figure 3.1 shows that phases 204, 206, and 208 are synchronized with each other and exhibit a sinusoidal waveform characteristic of alternating current.

[0057] Figure 3.2 shows a schematic representation of the six power levels 204.1 ,

[0058] 204.2, 206.1, 206.2, 208.1, 208.2 for each of the three phases 204, 206, 208. The phases 204, 206, 208 are each identified by a separate representation of their power levels 204.1, 204.2, 206.1, 206.2, 208.1, 208.2. The horizontal bars represent the power levels 204.1, 204.2, 206.1, 206.2, 208.1, 208.2, while the vertical bars represent the chronological sequence of activation or deactivation of these power levels 204.1, 204.2, 206.1,

[0059] 206.2, 208.1, 208.2. From this Figure 3.2 it can be seen how the power stages 204.1, 204.2, 206.1, 206.2, 208.1, 208.2 are activated permanently and sequentially 304 in each phase 204, 206, 208 in order to control the current flow and ensure the desired power output to the electrical machine 202. In Figure 3.2 it can also be seen that the horizontal bar of each power stage 204.1, 204.2, 206.1, 206.2, 208.1, 208.2 has two areas, the first area being a sequential circuit 304 and the second area being a permanent circuit 302 of the power stages

[0060] 204.1, 204.2, 206.1, 206.2, 208.1, 208.2. In this case, a permanent circuit 302 of the power stages 204.1, 204.2, 206.1, 206.2,

[0061] 208.1 , 208.2 active, which has the highest current of the six power levels 204.1 , 204.2, 206.1 , 206.2, 208.1 , 208.2. Furthermore, it can be seen from Figure 3.2 that in combination 306 with a permanent circuit 302, a power stage 204.1, 204.2, 206.1, 206.2, 208.1, 208.2, two further power stages 204.1, 204.2, 206.1, 206.2, 208.1, 208.2 are sequentially 304 activated and deactivated, but in such a way that at no time are a high-side power stage 212 and a low-side power stage 214 switched on simultaneously for the same phase 204, 206, 208.

[0062] As an alternative to the permanent switching 302 of the power stage 204.1, 204.2,

[0063] 206.1, 206.2, 208.1, 208.2 with the highest pulse width can also be switched on outside the switching operations of the other power stages 204.1, 204.2, 206.1,

[0064] 206.2, 208.1, 208.2 are switched, so that during the switching 112 of this power stage 204.1, 204.2, 206.1, 206.2, 208.1, 208.2, the other power stages 204.1, 204.2, 206.1, 206.2, 208.1, 208.2 are switched off. This process step is not shown in Figure 3.2.

[0065] The invention is not limited to the embodiments described here and the aspects highlighted therein. Rather, numerous modifications are possible within the scope of the claims, which are within the scope of one skilled in the art.

Claims

Claims 1 . Method (100) for controlling an electrical machine (202) comprising two or more phases (204, 206, 208) using a permanent switching principle (302) for reducing power loss by switching (112) at least one power stage (204.1, 204.2, 206.1, 206.2, 208.1, 208.2), wherein each phase (204, 206, 208) has a high-side power stage (212) and a low-side power stage (214), comprising at least the following steps: a. Acquiring (102) the necessary data for controlling (108) the electrical machine (202), in particular the power stages (204.1, 204.2, 206.1, 206.2, 208.1, 208.2), b. Determining (104) the necessary currents or pulse widths of all power stages (204.1, 204.2, 206.1, 206.2, 208.1, 208.2) c. Determining (106) the power stage (204.1, 204.2, 206.1, 206.2, 208.1, 208.2) with a maximum pulse width d. Controlling (108) a pulse width modulation (216), wherein an adjustment of a power of the electric machine (202) takes place, i. Determining (110) the optimal switching time of the one or more power stages (204.1, 204.2, 206.1, 206.2, 208.1 , 208.2) and ii. Switching (112) of the power stages (204.1 , 204.2, 206.1 , 206.2, 208.1, 208.2) by a control unit (210), wherein the control unit (210) generates a switching command in real time to control the switching (112) such that the power level (204.1, 204.2, 206.1, 206.2, 208.1, 208.2) is permanently switched (302) with a highest pulse width, wherein the permanent switching (302) corresponds to setting the pulse width to 100%, or before the other power levels (204.1, 204.2, 206.1, 206.2, 208.1, 208.2) and after the other power levels (204.1, 204.2, 206.1, 206.2, 208.1 , 208.2) is switched off, whereby the switching (112) of this power stage (204.1 , 204.2, 206.1 , 206.2, 208.1 , 208.2) only occurs when the other performance levels (204.1 , 204.2, 206.1, 206.2, 208.1, 208.2) are switched off, iii. wherein a number of further power stages are switched on and off sequentially in combination, ensuring that for the same phase at no time are a high-side power stage (212) and a low-side power stage (214) switched on at the same time.

2. Method (100) according to claim 1, wherein the determining (106) comprises comparing the detected current intensities of the power stages (204.1, 204.2, 206.1 , 206.2, 208.1 , 208.2) among themselves.

3. Method (100) according to claim 1 or 2, wherein the power stages (204.1, 204.2, 206.1, 206.2, 208.1, 208.2) are switched (112) in an inverter such that they are activated or deactivated depending on the control (108).

4. The method (100) according to any one of the preceding claims, wherein the control (108) comprises an adaptive adjustment of the pulse width modulation (216) based on the current operating conditions of the electric machine (202).

5. Method (100) according to one of the preceding claims, wherein the detection (102) of a current, a voltage (310), a torque and a speed takes place on each phase (204, 206, 208) of the electrical machine (202), wherein the detection (102) can take place both individually and in combination of the parameters.

6. Method (100) according to one of the preceding claims, wherein the detection (102) of current intensities of the power stages (204.1, 204.2, 206.1, 206.2, 208.1, 208.2) is carried out by sensors in real time.

7. Method (100) according to one of the preceding claims, wherein the detection (102) of the current intensities of the power stages (204.1, 204.2, 206.1 , 206.2, 208.1 , 208.2) is carried out by sensors from the group of Hall sensors, current transformer sensors or shunt resistors.

8. Use of the method (100) according to one of claims 1 to 7 for controlling an electrical machine (202) having three phases (204, 206, 208).

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