Method for determining rotor position of EC motor

Abstract

For an EC motor (1), a position of a rotor of the EC motor is determined by injecting a voltage signal (320) and evaluating current fluctuations generated in phases (21, 22, 23) of the EC motor. When the voltage in the phases (21, 22, 23) approaches a maximum value (550), the injection is suspended for each phase (21, 22, 23), respectively.

Description

Technical Field

[0001] The present invention relates to a method for determining the rotor position of an electronically commutated electric motor (EC motor) based on injection. Background Technology

[0002] To control an EC motor, the position of its rotor is required. Various sensors can be used to determine the rotor's position in different ways. One possibility is to feed a voltage signal (also known as an injected voltage signal) into each phase of the EC motor's stator in addition to the voltage required to drive the EC motor, and measure the current generated in each phase. The rotor's position can then be calculated based on the current fluctuations generated by the injected voltage signal. This process is well-known.

[0003] However, it is also known that the maximum available voltage for operating an EC motor is limited to one phase of the EC motor stator, typically via an intermediate circuit voltage limit. This means that if the voltage in a phase is close enough to its maximum value, the injection of a voltage signal into that phase and the subsequent assessment of the resulting current fluctuations may no longer be reliable, as the injected voltage signal will exceed the maximum available voltage. Therefore, EP 2 144 362B1 proposes to supplement the injection of voltage signals and the assessment of current fluctuations at a higher speed using estimates based on machine parameters. This requires the use of additional sensors (e.g., temperature sensors) to determine the machine parameters. An accelerometer is used to check the validity of the speed signal and to weight it differently for this purpose.

[0004] US2017 / 0 264 227A1 describes a method for determining the rotor position of a multiphase EC motor, the method comprising: injecting a voltage signal into at least two phases of the stator; detecting a corresponding current signal in each of the phases; and determining the rotor position based on the detected current signal.

[0005] US11 264 930 B2 also describes injecting a voltage signal into the phase.

[0006] When controlling an EC motor, the voltage or current values ​​of each phase of the stator are transformed into a two-dimensional coordinate system in a known manner. The mutually perpendicular axes of this coordinate system are typically called the d-axis ("direct axis") and the q-axis ("vertical axis"). This coordinate system rotates relative to the stator of the EC motor and is stationary relative to the rotor. The transformation itself is called the Park transformation; the resulting two-dimensional coordinate system is called the Park coordinate system. The Park transformation can occur via the intermediate step of the equally known Clarke transformation, which transforms the voltage or current values ​​of each phase of the stator into a two-dimensional orthogonal coordinate system stationary relative to the stator. The q-component and d-component of the voltage can be controlled via separate controllers. Summary of the Invention

[0007] The purpose of this invention is to provide an injection method for determining the position of the rotor of an EC motor that overcomes the limitations of the prior art.

[0008] This objective is achieved by the method according to claim 1. The dependent claims relate to advantageous embodiments.

[0009] A method for determining the position of the rotor of a multiphase EC motor according to the present invention includes at least the following steps:

[0010] A voltage signal is injected into at least two phases of the stator of the EC motor. This voltage signal is an additional voltage besides the voltage applied to the corresponding phase for the purpose of driving the EC motor. The corresponding voltage signal injected into the phase will generate a current signal in that phase, which is superimposed on the current flowing for the driving purpose. The current signal is detected in each of the at least two phases in which the voltage signal has been injected, so a corresponding current signal exists for each of the at least two phases. The rotor position is determined in a known manner based on the current signal detected in this way. According to the invention, the injection of the voltage signal into the phase is suspended when the voltage of the phase of the EC motor stator drops below a predetermined distance from the maximum voltage of that phase. The predetermined distance is selected to be at least large enough that the maximum voltage of that phase is not exceeded even when the voltage signal is injected into the corresponding phase. It should be noted that the voltage signal to be injected is known in advance. Since the voltage signal is normally injected into at least two phases of the stator of the EC motor, if the injection into one of the phases stops, at least one phase remains from which a current signal can be detected to determine the rotor position of the EC motor. This applies regardless of the rotor speed. At relatively low speeds, the maximum voltage of each phase is always not clearly reached, so the injection of voltage signals and the detection of the generated current signals can be performed without problems. However, in the method according to the invention, the rotor may also rotate at relatively high speeds, and the voltage of the stator phase of the EC motor may reach its maximum. Nevertheless, the rotor position can still be determined using the method according to the invention. No additional sensors, such as temperature sensors or acceleration sensors, are required as in the prior art. The EC motor can still operate at voltages up to the maximum of the phases, which means a further extended performance range for the EC motor.

[0011] In one implementation, the stator of the EC motor has three phases. The rotor position is determined based on the current signal from the voltage signal injected into the uninterrupted phase. At any given time during operation, these are two or three phases; since the voltages on each phase are offset by 120° from each other, the control can be designed such that the injection of the voltage signal is never interrupted simultaneously in two or even all three phases. For this purpose, a predetermined distance must be appropriately selected, and in particular, the predetermined distance cannot be chosen too large. The predetermined distance must be selected such that at any time during the operation of the EC motor, the voltage applied to each phase drops below a predetermined distance from the maximum voltage in at most one phase. Simultaneously, the predetermined distance must be selected such that when a voltage signal is injected into a phase, the voltage generated on that phase does not exceed the maximum voltage. The maximum value of the voltage signal is important here, but these values ​​can be selected to be relatively small relative to the amplitude of the voltage applied to the phase for driving purposes, for example, less than 5% of the amplitude of the voltage for driving purposes.

[0012] In a typical implementation, the EC motor is controlled by adjusting the d-component and q-component of the voltage obtained from the Parker transform of the voltage on the phase. Since the voltage signal does not cause any torque fluctuations in the EC motor, voltage signal injection only occurs in the d-component. To pause voltage signal injection into a specific phase, the d-component is set to a value calculated according to the Parker transform.

[0013] The criteria for suspending the injection of a voltage signal into a specific phase can be checked by evaluating the voltage provided by the controller used for control. If the voltage to be set on the phase is closer to the maximum voltage of that phase than a predetermined distance, the injection of the voltage signal is suspended. However, the conditions for suspending the injection can also be derived based on the determined rotor position. This means that the voltage of each phase can be determined based on the rotor position, which is determined using the method according to the invention. Other options for checking the criteria for suspending the injection are also conceivable. Attached Figure Description

[0014] The invention and its advantages are described in more detail below with reference to the illustrative drawings.

[0015] Figure 1 A diagram illustrating an exemplary embodiment of the method according to the present invention is shown.

[0016] Figure 2 The voltage on the phase without an injected voltage signal is shown.

[0017] Figure 3 The diagram shows the superposition of the voltage on a phase without an injected voltage signal and the voltage including the voltage signal.

[0018] Figure 4 and Figure 3 Correspondingly, it also includes, additionally, a pause in the injection according to the invention.

[0019] Figure 5 It shows Figure 4 The magnified portion. Detailed Implementation

[0020] The accompanying drawings only illustrate exemplary embodiments of the present invention and should not be construed as limiting the present invention to the exemplary embodiments shown.

[0021] Figure 1A diagram illustrating an exemplary embodiment of the method according to the invention is shown. Voltage is supplied to EC motor 1 via three phases 21, 22, and 23. EC motor 1 is controlled via the q and d components (Id, Iq) of the current in the phases and / or the voltages they interact with; these components can be controlled via controllers 3 and 4, respectively. Controllers 3 and 4 can be, for example, proportional-integral controllers. Box 100 shows the conversion of the controlled d / q components into α / β components (Clark coordinates). The α / β components are converted into UVW coordinates (shown by box 200), which reflect the voltage values ​​of each phase and are correspondingly fed to EC motor 1 via phases 21, 22, and 23. Simultaneously, the current at phases 21, 22, and 23 is measured and fed into position determination (box 310). Here, the rotor position of EC motor 1 is determined based on the fluctuations in current intensity generated by the voltage signals injected into each phase. Such an injected voltage signal is represented by block 320; after pause condition 330, the injected voltage signal is superimposed on the controlled d-component and reaches phases 21, 22, and 23 of EC motor 1 via transformations 100 and 200. Pause condition 330 ensures that if injection would cause the maximum voltage of a phase to be exceeded, voltage signal 320 is not injected into that phase. Pause condition 330 can be checked via the voltage to be set by controllers 3 and 4, such that if the voltage to be set in that phase is closer to the maximum voltage than a predetermined distance, the injection of voltage signal 320 into the corresponding phase is omitted. Alternatively, the proximity of the voltage of a phase to the maximum voltage can be determined based on the rotor position, which can be obtained through position determination 310. Other methods are also conceivable.

[0022] Feedback 410 and 420 provide the required d / q components based on the determined rotor position to properly control EC motor 1.

[0023] Figure 2 EC motor 1 is shown (see Figure 1 The voltage U (in volts) of the stator of the EC motor without an injected voltage signal is plotted as a function of time (in seconds). Over time, the voltage value at its local maximum 510 increases, and the duration of the voltage curve decreases. In the case shown, the rotor speed of the EC motor increases. The voltage shown here is the voltage applied to the phase for the purpose of driving the EC motor.

[0024] Figure 3 It was shown again Figure 2 The process of voltage U in the image (dashed line); superimposed on this dashed line (shown as a solid line) is the process of voltage U of the stator of the EC motor with the same injected voltage signal. For example, it can be seen in the region of peak value 511 that the voltage including the injected voltage signal exceeds... Figure 2The local maximum voltage is shown in the figure. This is not a problem as long as it does not exceed the maximum voltage of that phase. However, as the value of the local maximum voltage 510 increases (see...), the problem becomes more serious. Figure 2 This means that as the rotational speed of the EC motor's rotor increases, this may become problematic.

[0025] Figure 4 The effect of the method according to the invention on the voltage curve is shown. For example, in... Figure 3 The figure shows the voltage curve (dashed line) without an injected voltage signal, which is also consistent with... Figure 2 The voltage curve corresponds to the voltage curve in the figure. The voltage including the injected voltage signal is shown as superimposed on the voltage curve without the injected voltage signal (shown as a solid line), but according to the present invention, the injection of the voltage including the injected voltage signal is partially suspended.

[0026] In the region of peak 511, the voltage remains significantly lower than the maximum voltage of that phase, the injection is uninterrupted, and the rotor position of the EC motor can be determined using the current signal generated by the injected voltage signal in that phase throughout the duration 512. As the local maximum voltage increases significantly, according to the invention, a pause in voltage signal injection begins to take effect. For example, no voltage signal is injected into the phase during time interval 513. This prevents the voltage signal from exceeding the maximum voltage of that phase. During time interval 513, the current signal from that phase cannot be used to determine the rotor position. Outside region 513, voltage signal injection into the phase occurs along edge 514 in the voltage curve, and the rotor position can be determined using the current signal generated by that phase along edge 514.

[0027] Figure 5 yes Figure 4 The magnified portion. It shows the voltage curve 520 without an injected voltage signal, which is consistent with... Figure 2 The curves shown correspond to those in the diagram. Voltage curve 521, including the superimposed voltage signal, is superimposed on voltage curve 520. During time intervals 513, 523, and 533, the injection of the voltage signal into the phases indicated by the shown voltage curves 520 and 521 is paused. Here, voltage curve 521 is at a value closer to the maximum voltage 550 than a predetermined distance 555. However, during time intervals 513, 523, and 533, the voltage curves of other phases of the EC motor are far enough from the maximum voltage 550 that voltage signals can be injected into other phases during time intervals 513, 523, and 533. Therefore, during time intervals 513, 523, and 533, the rotor position can be determined using the current signals generated from these other phases. If the voltage of one of the other phases is close to the maximum value 550, causing the injection of the voltage signal into that other phase to be paused, then... Figure 5The voltage curve 521 of the referred phase is far enough from the maximum voltage 550, for example, at one edge of edge 514, therefore from Figure 5 The current signal of the referred phase can be used to determine the position of the rotor of the EC motor.

[0028] List of reference numerals

[0029] 1 EC motor

[0030] 3 Controllers

[0031] 4 Controller

[0032] 21 phases

[0033] 22 phases

[0034] 23 phases

[0035] 100 coordinate transformation

[0036] 200 coordinate transformation

[0037] 310 Location confirmed

[0038] 320 Injected Voltage Signal

[0039] 330 Pause Conditions

[0040] 410 Feedback

[0041] 420 Feedback

[0042] 510 Local Maximum

[0043] 511 peak

[0044] 512 Duration

[0045] 513 time interval

[0046] 514 Edge

[0047] 520 Voltage Curve

[0048] 521 Voltage Curve

[0049] 523 time interval

[0050] 533 time interval

[0051] 550 Maximum value (voltage)

[0052] 555 Pre-determined distance

Claims

1. A method for determining the position of the rotor of a multiphase EC motor (1), the method comprising the steps of: A voltage signal (320) is injected into at least two phases (21, 22, 23) of the stator of the EC motor (1); Detect the corresponding current signal in each of the at least two phases (21, 22, 23) of the stator of the EC motor (1); The position of the rotor is determined based on the detected current signal; Its features are, When the voltage drop at phase (21, 22, 23) is below a predetermined distance (555) from the maximum voltage (550) of that phase, the injection of the voltage signal (320) into that phase is suspended.

2. The method according to claim 1, wherein, The stator of the EC motor (1) has three phases (21, 22, 23), and the position of the rotor is determined according to the current signal of the corresponding phase (21, 22, 23) of which the voltage signal (320) is not interrupted.

3. The method according to claim 2, wherein, The EC motor (1) is controlled by adjusting the d-component and q-component of the voltage obtained from the Parker transformation of the voltage of the phases (21, 22, 23), wherein the voltage signal (320) is injected only into the d-component.

4. The method according to any one of the preceding claims, wherein, The conditions for pausing the injection are determined based on the position of the rotor.

Images