Method of driving a star-connected three-phase motor

Abstract

The invention relates to a method of driving a star-connected three-phase electric machine. The invention discloses a method of driving a three-phase electric machine, the method comprising driving a second phase with a first drive function that is sinusoidal when a first phase is energized. The first phase is switched to a non-energized state and a back electromotive force (BEMF) voltage of the first phase is detected. The driving of the second phase is dependent on an output of a second drive function that is different from the first drive function for at least a portion of the time when the first phase is not energized. The second drive function can be a non-sinusoidal function and can be a cosine function. The second drive function can drive the second phase when the output of the second drive function is a modulation ratio less than 1. The second phase can be driven to a modulation ratio of 1 when the output of the second drive function is a modulation ratio greater than or equal to 1.

Description

Technical Field

[0001] This document covers, in general, methods for controlling three-phase motors. Specifically, it covers methods for controlling a star-connected three-phase sensorless motor. Background Technology

[0002] A three-phase motor uses electricity applied to the motor in three different phases to make the motor rotate. These phases typically involve separate electrical connections and are usually referred to as the U phase, V phase, and W phase. Summary of the Invention

[0003] An implementation of a method for driving a star-connected three-phase motor may include: driving a second phase of the three-phase motor using a first sinusoidal drive function when the first phase of the star-connected three-phase motor is energized; and switching the first phase to a de-energized state. The method may further include detecting a first back electromotive force (BEMF) voltage of the first phase when the first phase is de-energized; and driving the second phase using a second drive function different from the first sinusoidal drive function for at least a portion of the time when the first phase is de-energized.

[0004] Implementations of a method for driving a star-connected three-phase motor may include one, all, or any of the following:

[0005] Three-phase motors can be sensorless brushless DC (BLDC) motors or permanent magnet synchronous motors (PMSM).

[0006] The method may include wherein driving the second phase with a second driving function results in an increase in the voltage applied to the second phase, relative to driving the second phase with a first sinusoidal driving function.

[0007] The method may include the use of a third drive function, different from the second sinusoidal drive function, to drive the third phase of the three-phase motor when the first phase is in a second non-energized state.

[0008] The method may include a situation where driving the third phase with a third driving function results in an increase in the voltage applied to the third phase, relative to driving the third phase with a second sinusoidal driving function.

[0009] The method may include driving the second phase using a second driving function until the first BEMF voltage is detected, and then driving the second phase using a first sinusoidal driving function.

[0010] The method may include driving the second phase using a first sine drive function after driving the second phase for a predetermined amount of time using a second drive function.

[0011] In an implementation of this method, plotting the torque generated by the three-phase motor on the y-axis and the rotor angular position of the three-phase motor rotor on the x-axis can show that the torque generated during at least one 360-degree rotation of the rotor driven by electricity does not change.

[0012] An implementation of a method for driving a star-connected three-phase motor may include: driving a first phase of the star-connected three-phase motor using a first sinusoidal drive function when all three phases are energized; and driving the first phase using a first non-sinusoidal drive function for at least a portion of the time when one phase other than the first phase is not energized and when the first non-sinusoidal drive function produces a modulation ratio less than 1. The method may also include driving the first phase to a modulation ratio of 1 for at least a portion of the time when one phase other than the first phase is not energized and when the first non-sinusoidal drive function produces a modulation ratio greater than or equal to 1.

[0013] Implementations of a method for driving a star-connected three-phase motor may include one, all, or any of the following:

[0014] The modulation ratio can be a low torque ripple modulation ratio.

[0015] The first non-sine driving function can be the first cosine driving function.

[0016] The first cosine driving function can be: Where M is the modulation ratio from 0 to 1, θ is the rotation angle of the three-phase motor, and θ wc A value of 0 degrees is given when θ is less than 30 degrees and greater than or equal to 0 degrees; a value of 60 degrees is given when θ is less than 90 degrees and greater than or equal to 30 degrees; a value of 120 degrees is given when θ is less than 150 degrees and greater than or equal to 90 degrees; a value of 180 degrees is given when θ is less than 210 degrees and greater than or equal to 150 degrees; a value of 240 degrees is given when θ is less than 270 degrees and greater than or equal to 210 degrees; a value of 300 degrees is given when θ is less than 330 degrees and greater than or equal to 270 degrees; and a value of 0 degrees is given when θ is less than 360 degrees and greater than or equal to 330 degrees.

[0017] The first sinusoidal driving function can be: in M is the modulation ratio from 0 to 1, and θ is the rotation angle of the three-phase motor.

[0018] Implementations of the method may include driving the second phase of a three-phase motor using a second sinusoidal drive function when all three phases are energized; driving the second phase using a first non-sinusoidal drive function for at least a portion of the time when one phase other than the second phase is not energized and when the first non-sinusoidal drive function produces a modulation ratio less than 1; and driving the second phase to a modulation ratio of 1 for at least a portion of the time when one phase other than the second phase is not energized and when the first non-sinusoidal drive function produces a modulation ratio greater than or equal to 1.

[0019] The second sinusoidal driving function can be: in M is the modulation ratio from 0 to 1, and θ is the rotation angle of the three-phase motor.

[0020] Implementations of the method may include driving the third phase of a three-phase motor using a third sinusoidal drive function when all three phases are energized; driving the third phase using a first non-sinusoidal drive function for at least a portion of the time when one phase other than the third phase is not energized and the first non-sinusoidal drive function produces a modulation ratio less than 1; and driving the third phase to a modulation ratio of 1 for at least a portion of the time when one phase other than the third phase is not energized and the first non-sinusoidal drive function produces a modulation ratio greater than or equal to 1.

[0021] The third sinusoidal driving function can be: in M is the modulation ratio from 0 to 1, and θ is the rotation angle of the three-phase motor.

[0022] An implementation of a method for driving a three-phase motor may include: driving the U phase of the three-phase motor using a first sinusoidal driving function when all three phases are energized; driving the V phase of the three-phase motor using a second sinusoidal driving function when all three phases are energized; driving the W phase of the three-phase motor using a third sinusoidal driving function when all three phases are energized; and driving the remaining two energized phases of the three phases using a cosine driving function for at least a portion of the time during which one of the three phases is not energized.

[0023] The implementation of a method for driving a three-phase motor may include one, all, or any of the following:

[0024] The modulation ratio can be a low torque ripple modulation ratio.

[0025] In various embodiments of the method, during the period when one of the three phases is not energized and for at least a portion of the time when the cosine drive function produces a modulation ratio less than 1, the remaining two energized phases of the three phases can be driven using the cosine drive function, and during the period when one of the three phases is not energized and for at least a portion of the time when the cosine drive function produces a modulation ratio greater than or equal to 1, the remaining two energized phases of the three phases can be driven to a modulation ratio of 1.

[0026] The cosine driving function can be: Where M is the modulation ratio from 0 to 1, θ is the rotation angle of the three-phase motor, and θ wc A value of 0 degrees is given when θ is less than 30 degrees and greater than or equal to 0 degrees; a value of 60 degrees is given when θ is less than 90 degrees and greater than or equal to 30 degrees; a value of 120 degrees is given when θ is less than 150 degrees and greater than or equal to 90 degrees; a value of 180 degrees is given when θ is less than 210 degrees and greater than or equal to 150 degrees; a value of 240 degrees is given when θ is less than 270 degrees and greater than or equal to 210 degrees; a value of 300 degrees is given when θ is less than 330 degrees and greater than or equal to 270 degrees; and a value of 0 degrees is given when θ is less than 360 degrees and greater than or equal to 330 degrees.

[0027] The first sinusoidal driving function can be:

[0028] The second sinusoidal driving function can be: Furthermore, the third sinusoidal driving function can be: in M is the modulation ratio from 0 to 1, and θ is the rotation angle of the three-phase motor.

[0029] The above and other aspects, features and advantages will become apparent to those skilled in the art from the specific embodiments, the accompanying drawings and the claims. Attached Figure Description

[0030] The embodiments will be described below in conjunction with the accompanying drawings, in which similar reference numerals denote similar elements, and:

[0031] Figure 1 It is a curve of voltage and current amplitude drawn based on the electrical angle position of the rotor for the specific implementation of the method for driving a three-phase motor;

[0032] Figure 2 It is aimed at Figure 1 The method uses the rotor's electrical angle position to plot a torque curve that shows torque fluctuations;

[0033] Figure 3It is a curve of voltage and current amplitude drawn based on the electrical angle position of the rotor for the specific implementation of the method for driving a three-phase motor;

[0034] Figure 4 It is aimed at Figure 3 The method involves plotting a torque curve based on the rotor's electrical angular position.

[0035] Figure 5 It is a torque curve plotted based on the electrical angle position of the rotor for a method of driving a three-phase motor;

[0036] Figure 6 It is aimed at Figure 3 The curve of the Lisajous curve using the method;

[0037] Figure 7 It is aimed at and Figure 3 The method is similar to the Lissajous curve plot, except that a modulation ratio of 0.7 is used;

[0038] Figure 8 This is a schematic diagram illustrating the control of the U-phase in a method of driving a three-phase motor;

[0039] Figure 9 This is a schematic diagram illustrating the control of the U-phase in a method of driving a three-phase motor;

[0040] Figure 10 This is a schematic diagram illustrating the control of the U-phase in a method of driving a three-phase motor;

[0041] Figure 11 This is a schematic diagram illustrating the control of the U-phase in a method of driving a three-phase motor;

[0042] Figure 12 This is a schematic diagram illustrating the control of the U-phase in a method of driving a three-phase motor;

[0043] Figure 13 This is a schematic diagram illustrating the control of the U-phase in a method of driving a three-phase motor;

[0044] Figure 14 This is a schematic diagram illustrating the control of the V phase in a method of driving a three-phase motor;

[0045] Figure 15 This is a schematic diagram illustrating the control of the V phase in a method of driving a three-phase motor;

[0046] Figure 16 This is a schematic diagram illustrating the control of the U-phase in a method of driving a three-phase motor;

[0047] Figure 17 This is a schematic diagram illustrating the control of the V phase in a method of driving a three-phase motor;

[0048] Figure 18 This is a diagram showing the windows representing the BEMF signals of the U-phase, V-phase, and W-phase in a method for detecting the signals of a three-phase motor.

[0049] Figure 19 This is a diagram showing the windows representing the BEMF signals of the U-phase, V-phase, and W-phase in a method for detecting the signals of a three-phase motor.

[0050] Figure 20 This is a diagram showing the windows representing the BEMF signals of the U-phase, V-phase, and W-phase in a method for detecting the signals of a three-phase motor.

[0051] Figure 21 This is a schematic diagram of the current vector in a method for driving a three-phase motor;

[0052] Figure 22 It is a curve of voltage and current amplitude drawn based on the electrical angle position of the rotor for the specific implementation of the method for driving a three-phase motor;

[0053] Figure 23 It is a curve of voltage and current amplitude drawn based on the electrical angle position of the rotor for the specific implementation of the method for driving a three-phase motor;

[0054] Figure 24 It is aimed at Figure 22 The method involves plotting a torque curve based on the rotor's electrical angular position.

[0055] Figure 25 It is aimed at Figure 23 The method plots a torque curve without torque fluctuation based on the rotor's electrical angle position.

[0056] Figure 26 It is aimed at Figure 22 The curve of the Lisajous curve using the method;

[0057] Figure 27 It is aimed at Figure 23 The curve of the Lisajous curve using the method;

[0058] Figure 28 It is a curve of voltage and current amplitude drawn based on the electrical angle position of the rotor for the specific implementation of the method for driving a three-phase motor;

[0059] Figure 29 It is a curve of voltage and current amplitude drawn based on the electrical angle position of the rotor for the specific implementation of the method for driving a three-phase motor;

[0060] Figure 30 It is aimed at Figure 29 The method plots a torque curve without torque fluctuation based on the rotor's electrical angle position.

[0061] Figure 31 It is aimed at Figure 29 The curve of the Lisajous curve using the method;

[0062] Figure 32 This is a circuit diagram that represents the circuitry of a controller used to control a three-phase motor.

[0063] Figure 33 This is a block diagram that represents a controller used to control a three-phase motor;

[0064] Figure 34 This is a timing diagram of a method for controlling a three-phase motor;

[0065] Figure 35 This is a timing diagram of a method for controlling a three-phase motor;

[0066] Figure 36 It is a timing diagram of a method for controlling a three-phase motor; and

[0067] Figure 37 This is a block diagram that representatively illustrates a three-phase motor and the components used to control the three-phase motor and detect the BEMF signal. Detailed Implementation

[0068] This disclosure, its aspects, and embodiments are not limited to the specific components, assembly steps, or method elements disclosed herein. Many additional components, assembly steps, and / or method elements known in the art that conform to the intended drive method for a three-phase motor will be readily apparent and can be used with the specific embodiments of this disclosure. Therefore, for example, although the present invention discloses specific embodiments, such embodiments and implementing components may include any shape, size, style, type, model, version, measure, concentration, material, quantity, method element, step, etc., of such drive methods for three-phase motors known in the art that conform to the intended operation and method.

[0069] During the operation of a three-phase motor, such as at startup and at other times during operation, the motor controller needs to detect the rotor position and rotational speed. Doing so accurately allows for precise motor control by adjusting the timing of the supply voltage applied to the motor windings. In some motors, Hall sensors are used to detect rotor position, but for sensorless motors, the back electromotive force (BEMF) signal can be used to detect the position, such as by comparing the BEMF signal with a voltage to determine when the motor crosses zero.

[0070] During BEMF detection, the phase used to detect the BEMF signal may be temporarily de-energized, causing a change in output torque, known as "torque ripple." Due to torque ripple, the motor's output torque can continuously vary between two or more values. Torque ripple can typically affect motor performance, reduce motor efficiency, increase motor noise, increase wear on motor components, and shorten the lifespan of motor components and the motor itself.

[0071] The methods disclosed herein include a three-phase motor modulation method for improving drive torque ripple. Each phase of the three-phase motor represents one of the windings of the motor stator. In a specific implementation, the method improves drive torque ripple in an N-window drive method. The N-window drive method is a method that includes a window in which a phase is not energized when the phase BEMF voltage of a phase is detected. While different types of three-phase motors can benefit from the methods disclosed herein, one example of a motor that can be driven using the methods disclosed herein is a star-connected three-phase brushless DC (BLDC) motor. Another example is a star-connected three-phase permanent magnet synchronous motor (PMSM or SPMSM). To perfectly compensate for the reduced torque during BEMF sensing, methods such as strict field-oriented control (FOC) (vector control) can be applied. The methods disclosed herein do not use vector control and may be useful for situations where it is desirable to improve (reduce / eliminate) torque ripple but perfect compensation is not required and / or vector control is too expensive or otherwise infeasible. The methods disclosed herein involve using algorithms for driving a three-phase motor, which can be controlled by one or more integrated circuits. In one example, the integrated circuit is a field-programmable gate array (FPGA), but in other implementations, other programmable and non-programmable (i.e., ASIC) circuit types may be used.

[0072] In an N-window drive system where the phase BEMF voltage of one of the three phases is not energized when that phase is detected, the system cannot apply the ideal drive torque vector to the motor due to the unenergized phase, and the motor operation includes torque ripple.

[0073] See now Figure 1The graph representing the control of a three-phase motor includes voltage and current amplitudes plotted according to the electrical angular position of the motor's rotor. The drive voltage amplitudes (U2pm, V2pm, W2pm, where U, V, and W are phases, and 2pm represents two-phase modulation with an unexcited phase) represent the motor terminal voltages and are plotted using lines, dashed lines, and dotted lines, respectively. The phase drive current amplitudes (IU, IV, and IW) represent the phase currents (motor stator currents) and are plotted using squares, triangles, and circles, respectively. For simplicity, the stator inductance and BEMF voltage are omitted to facilitate viewing other details of the graph. The electrical angular position of the rotor is given in radians. As can be seen from the current amplitudes, the current in each phase is approximately sinusoidal, but for each phase, there exists a window where the current is intentionally zero for a period of time. This is the N-window and can also be referred to as the HiZ (high impedance) state of that phase. For example, when phase U is in the zero-phase current window (N-window or HiZ window), the BEMF zero-crossing point can be determined to determine the rotor position of the motor. During this HiZ window, the motor torque decreases, resulting in the torque fluctuations discussed earlier. It should be noted that when the current is approximately sinusoidal, the applied voltage amplitude is also approximately sinusoidal, except during the HiZ window. In this example, a modulation ratio of 0.6 is used.

[0074] Figure 2 Representatively showing relative to Figure 1 The torque of a three-phase motor is plotted based on the electrical angles of its rotor (expressed in degrees). The torque is represented by the q-axis current, converted via the Clark-Parker transformation, which represents the resulting torque. Torque fluctuations are shown in... Figure 2 As can be seen, the torque drops sharply to very low levels at several locations, each of which corresponds to the HiZ window of one of the phases.

[0075] Figure 3 Another example is shown, plotting voltage and current magnitudes based on electrical angle position for the N-window driving method. Aside from the plotted values, the characteristics / details of this plot are similar to those described above for the N-window driving method. Figure 1 The aforementioned features and details. In this example, the phase current is again considered relatively sinusoidal, but with a HiZ period in which the current is intentionally zero for a certain time. Figure 3 The graph includes window 2, which indicates the time period in which the unexcited phase is used to detect the phase BEMF voltage. Figure 3 The driving method uses a modulation ratio of 1.0.

[0076] Figure 4 Representatively showing the targeting Figure 3 The driving method plots the torque based on the rotor's electrical angular position. Aside from the plotted values, the characteristics / details of this graph are similar to those described above for... Figure 2 Those features and details mentioned above. Torque ripple is visible again. Window 4 shown on the graph is aligned with the torque ripple, and also with... Figure 3 By aligning the HiZ window 2, it can be seen that the torque fluctuation corresponds to the HiZ window. Figure 5 It shows the target and Figure 3 The torque diagram is similar to that of the driving method used in this method, except that it uses a modulation ratio of 0.7. Torque fluctuations are still visible in window 6, which corresponds to the HiZ window of the driving method that detects the phase BEMF voltage.

[0077] Figure 6 The diagram shows the effect of using a modulation ratio of 1.0. Figure 3 The driving method uses a Lissajous curve to represent the drive current, converted via a Clarke transform. The I-Alpha axis represents the α-axis current, and the I-Beta axis represents the β-axis current. The Lissajous curve shows the position of the torque when current is applied and the motor is engaged. The locations on the curve where there are no circles indicate where the torque jumps from one value to another—these locations correspond to… Figure 4 and Figure 5 This corresponds to the torque fluctuation. Figure 7 It shows the target and Figure 3 The method is similar to the Lissajous curve of the drive current converted by the Clarke transform, but it uses a modulation ratio of 0.7. In addition to the plotted values, Figure 7 The features / details of the curve are similar to Figure 6 Those features / details.

[0078] When the initial drive modulation ratio used for the drive method is less than 100%, a ratio greater than the initial modulation ratio can be used to modulate two phases (excluding the current HiZ and the non-excited phase) to reduce the torque drop caused by the HiZ window. The motor torque is generated by the q-axis current, and this q-axis current is a vector (the three-phase stator current vector is projected onto the q-axis).

[0079] As described above, the N-window driving method includes a non-excitation time period. In this disclosure, the N-time period or non-excitation time period for any given phase is referred to as a window period, and the excitation time period for any given phase is referred to as an energizing period. For any given phase, the energizing period begins at the end of the window period and ends at the beginning of the window period. When any given phase is in an energizing period, there are two possible scenarios: all phases are in an energizing period (referred to herein as the ALLENG period), or one phase other than the given phase is in the window period (referred to herein as the WNDENG period).

[0080] As a simple example, return Figure 3It can be seen that at an electrical angle of π / 3 (approximately 1.0471976), phase V has a negative current, phase U has a positive current, and phase W has zero current. From the perspective of phase V or phase U, this would be the WNDENG period. At an electrical angle of π / 6 (approximately 0.523599), phase V has a negative phase current, and both phases U and W have positive phase currents. Therefore, this would be the ALLENG period. Therefore, as used in this paper, whether a phase is in a “energized / excited state” or a “non-energized / excited state” is determined by whether the current in that phase is zero (non-energized / excited state) or has a non-zero value (energized / excited state), not by whether the phase drive voltage is zero or non-zero. For example, in... Figure 3 As can be seen, at an electrical angle of π / 6 (approximately 0.523599), phase V has zero drive voltage, while phases U and W both have positive drive voltages. The zero drive voltage of phase V does not mean that phase V is not energized / excited, because as defined herein, if the phase current is non-zero, then the phase is energized / excited. Similarly, at an electrical angle of π / 3 (approximately 1.0471976), even if phase W has a positive / non-zero voltage, it is not energized / excited because it has zero phase current.

[0081] In addition, still refer to Figure 3 And also refer to Figure 32 , Figure 32 The circuit diagram describes a controller that can be used to control a three-phase motor, neglecting the resistance Rs. At an electrical angle of π / 3 (approximately 1.0471976), inverters Q1H and Q1L are switched using pulse width modulation (PWM), Q2H is off and Q2L is on, and Q3H and Q3L are off. Therefore, UOUT outputs a non-zero volt, VOUT outputs a zero volt, and WOUT outputs a HiZ state. Since PWM is performed using synchronous rectification and the motor stator is an inductive load, there are generating and regenerating currents (the zero-volt / zero-drive node can also act as a sink node for another source node). During this angle position, although VOUT outputs zero volt, IV (V-phase current) flows via the U-phase (meaning UOUT is the source node and VOUT is the sink node). Therefore, even though VOUT outputs zero volt during this period, the motor's V-phase is energized via the U-phase. However, during the same time period, even if WOUT has a positive voltage, IW (W-phase current) does not flow because its positive voltage is not based on the drive voltage output by WOUT; therefore, phase W is not energized / excited. The node voltage during the non-energized period indicates the voltage generated (from the impedance of the other two phases) and has the sum of the voltages of the other two phases divided by half. The BEMF voltage overlaps with this period but is not included in the attached figure for simplicity.

[0082] See now Figure 8This diagram illustrates the control of the U-phase in a method of driving a three-phase motor. The graph depicts the voltage drive amplitude of the phase relative to the rotor's electrical angle (in radians). At the top of the graph, a section called the "Window Period of Self-Phase" indicates the window period for the U-phase, or in other words, the period during which the U-phase can be in the HiZ state (with zero phase current) to perform BEMF detection. A "Power-On Period" section is also labeled, indicating the period during which the U-phase has a non-zero phase current (even when the drive voltage is zero), making the U-phase "energized." The energizing period is also shown to alternate between an ALLENG period (where all phases are energized) and a WNDENG period (where one other phase is not energized (e.g., each of the three phases is alternately de-energized)). In this example, there are six windows: two for the U-phase itself (the first and last window periods are half of a single window), two for the W-phase, and two for the V-phase. Therefore, each segment represents a 30-degree rotation of the rotor. Similar graphs can be generated to control the V and W phases. This graph is an example of phase control using a 6-window mode.

[0083] Figure 8 The curve represents the control of phase U without changing the voltage during the WNDENG period, and therefore the torque ripples discussed above will exist. On the other hand, Figure 9 A similar graph for the U-phase in a 6-window mode with a 30-degree window is shown, but where, when a positive voltage is applied to the U-phase and upon reaching the WNDENG window, the voltage applied to the U-phase temporarily switches from a sinusoidal waveform to a different waveform. This different waveform causes an increase in the voltage of the U-phase. In this example, the modulation ratio is 1.0. The HiZ period / window of the U-phase is also shown in this graph. The ALLENG period of the U-phase is controlled based on a first 2-phase modulation waveform, and the WNDENG period of the U-phase is controlled by a second 2-phase modulation waveform. In specific implementations, the second 2-phase modulation waveform may be a processed or modified form of the first waveform, or it may be a completely different waveform not based on the first waveform. In either case, the second waveform (and generally, the different waveforms during the WNDENG period) are referred to herein as low torque ripple (LTR) modulation waveforms because they reduce torque ripple. Although Figure 9 The graph focuses on phase U, but the graphs depicting the control / drive voltages of phases V and W will be similar (but offset from phase U by 120 degrees and 240 degrees, respectively).

[0084] Figure 10 This is a schematic diagram illustrating the control of the U-phase in a method of driving a three-phase motor, and is similar to... Figure 9The difference lies in the use of a modulation ratio of 0.7. Similarly, when a positive voltage is applied to phase U and reaches the WNDENG window, the voltage applied to phase U temporarily switches from a sinusoidal waveform to a different waveform (LTR waveform). It can be seen that the LTR waveform is similar to... Figure 9 The LTR waveform of the 1.0 modulation ratio type differs, but compared to the voltage applied using the original sine wave function, it still typically results in a voltage increase for at least a portion of the WNDENG period. It can be seen that for the WNDENG period where the U phase has zero applied voltage, the applied voltage remains zero. However, at these WNDENG windows, the voltage applied to other phases can be increased to reduce torque ripple. Although Figure 10 The graph focuses on phase U, but the graphs depicting the control / drive voltages of phases V and W will be similar (but offset from phase U by 120 degrees and 240 degrees, respectively).

[0085] The LTR waveform used during the WNDENG window reduces the torque drop at the HiZ window. Therefore, even if one of the three phases of the motor stator is unexcited, the torque reduction is not as large as it would normally be. The alternative LTR waveform is thus defined to reduce torque ripple. In one implementation, when one phase is unexcited, the other two phases are excited and driven by replacing the normal sinusoidal drive value with the LTR drive value. In other implementations, when one phase is unexcited, the other two phases are excited, but only one of them is driven by replacing the normal sinusoidal drive value with the LTR drive value. In the embodiments described and shown herein, the alternative drive value is applied to a star-connected stator. However, in other implementations, the principles and methods disclosed herein are adaptable for use with other types of motors. As shown in the figure, Figure 9 and Figure 10 The curve has 6 WNDENG windows. This is the maximum window size used to replace the normal sinusoidal drive value with the LTR drive value per electrical angle period of the rotor. The segment width is limited to + / - 30 degrees centered on the zero-crossing point of phase BEMF.

[0086] Figure 11 A schematic diagram illustrating the control of the U-phase in a method for driving a three-phase motor in a 3-window mode with a 30-degree window is shown. When a positive voltage is applied to the U-phase and reaches the WNDENG window, the voltage applied to the U-phase temporarily switches from a sinusoidal waveform to an LTR waveform. The LTR waveform causes an increase in the drive voltage for at least a portion of the WNDENG period, relative to the normal sinusoidal drive waveform. When the WNDENG window ends, the voltage applied to the U-phase switches back to the normal sinusoidal waveform. In this example, the modulation ratio is 1.0. The HiZ period / window of the U-phase is also shown in this graph. Although Figure 11The graph focuses on phase U, but the graphs depicting the control / drive voltages of phases V and W will be similar (but offset from phase U by 120 degrees and 240 degrees, respectively).

[0087] Figure 12 This is a schematic diagram illustrating the control of the U-phase in a method of driving a three-phase motor, and is similar to... Figure 11 The difference lies in the use of a modulation ratio of 0.7. Similarly, when a positive voltage is applied to phase U and reaches the WNDENG window, the voltage applied to phase U temporarily switches from a sinusoidal waveform to an LTR waveform. When the WNDENG window ends, the voltage applied to phase U switches back to a normal sinusoidal waveform. It can be seen that the LTR waveform is similar to... Figure 11 The LTR waveform of the 1.0 modulation ratio type differs, but compared to the voltage applied using the original sine wave function, it still typically results in a voltage increase for at least a portion of the WNDENG period. It can be seen that for the WNDENG period where the U phase has zero applied voltage, the applied voltage remains zero. However, at these WNDENG windows, the voltage applied to other phases can be increased to reduce torque ripple. Although Figure 12 The graph focuses on phase U, but the graphs depicting the control / drive voltages of phases V and W will be similar (but offset from phase U by 120 degrees and 240 degrees, respectively).

[0088] Figure 13 A schematic diagram illustrating the control of the U-phase in a method for driving a three-phase motor in a 2-window mode with a 30-degree window is shown. In this case, the WNDENG window does not exist because, in the 2-window mode, the V-phase and W-phase do not have a HiZ window / time period. Therefore, the U-phase is controlled by a normal sine wave without any LTR waveform.

[0089] However, Figure 14 A schematic diagram illustrating the control of phase V in a method for driving a three-phase motor in a two-window mode with a 30-degree window is shown. When a positive voltage is applied to phase V and reaches the WNDENG window (the HiZ window for phase U), the voltage applied to phase V temporarily switches from a sinusoidal waveform to an LTR waveform. The LTR waveform causes an increase in the drive voltage for at least a portion of the WNDENG period, relative to the normal sinusoidal drive waveform. When the WNDENG window ends, the voltage applied to phase V switches back to the normal sinusoidal waveform. In this example, the modulation ratio is 1.0. The graph also shows phase V without a HiZ period / window. Although... Figure 14 The graph focuses on phase V, but the graph depicting the control / drive voltage of phase W will be similar (but offset by 120 degrees from phase V).

[0090] Figure 15This is a schematic diagram illustrating the control of phase V in a method of driving a three-phase motor, and is similar to... Figure 14 The difference lies in the use of a modulation ratio of 0.7. Similarly, when a positive voltage is applied to phase V and reaches the WNDENG window (the HiZ window for phase U), the voltage applied to phase V temporarily switches from a sinusoidal waveform to an LTR waveform. When the WNDENG window ends, the voltage applied to phase V switches back to a normal sinusoidal waveform. It can be seen that the LTR waveform is similar to... Figure 14 The LTR waveform of the 1.0 modulation ratio type differs, but compared to the voltage applied using the original sine wave function, it still typically results in a voltage increase for at least a portion of the WNDENG period. It can be seen that for the WNDENG period with zero applied voltage on the V phase, the applied voltage remains zero. However, at these WNDENG windows, the voltage applied to the W phase can be increased to reduce torque ripple. Although Figure 15 The graph focuses on phase V, but the graph depicting the control / drive voltage of phase W will be similar (but offset by 120 degrees from phase V).

[0091] Figure 16 A schematic diagram illustrating the control of the U-phase in a method for driving a three-phase motor in a 1-window mode with a 30-degree window is shown. In this case, the WNDENG window does not exist because, in 1-window mode, the V-phase and W-phase do not have a HiZ window / time period. Therefore, the U-phase is controlled by a normal sine wave without any LTR waveform.

[0092] Figure 17 A schematic diagram is shown illustrating the control of phase V in a method of driving a three-phase motor in a 1-window mode with a 30-degree window. In this case, a WNDENG window exists, but it does not correspond to the positive voltage applied to phase V, so phase V is not modified from its normal sinusoidal waveform. Figure 17 The modulation ratio is 1.0. No diagram is provided illustrating the control of phase W in a method of driving a three-phase motor in a 1-window mode with a 30-degree window, but phase W will be offset by 120 degrees from phase V, such that the positive voltage applied to phase W will overlap with the WNDENG window of phase U. Therefore, during the WNDENG window, phase W will be driven by an LTR waveform, which will result in an increased applied voltage relative to a normal sinusoidal waveform for at least a portion of the WNDENG period. After the WNDENG period, phase W will return to a normal sinusoidal waveform. Qualitatively, the voltage difference applied to phase W during the WNDENG period between a modulation ratio of 1.0 and 0.7 will be similar to that in... Figure 14 and Figure 15 The voltage difference applied to phase V during the WNDENG period is shown between the 1.0 modulation ratio and the 0.7 modulation ratio.

[0093] There are limitations on the window period for each phase. The limitations on the window period (in degrees) are shown in Table 1 below.

[0094]

[0095] Table 1

[0096] Figure 18 The diagram shows the maximum window duration for the three phases when using a modulation ratio of 1.0 and without an LTR waveform. Different crosshair sections reflect the windows. For example, the W phase is considered to have a first window between 30 and 90 degrees. In radians, this is approximately 0.52 to 1.57 radians. Therefore, in Figure 18 On the curve graph, there exists a first W section, where the letter W is close to the W curve but also within the first crosshair section starting from the left side of the curve graph, which has a line sloping downwards to the right. This W section is shown between approximately 0.52 radians and approximately 1.57 radians, corresponding to 30 degrees and 90 degrees. The next W section (with a similar crosshair) is shown between 210 degrees and 270 degrees (but... Figure 18 (in radians). Figure 19 Similarly, the maximum window time of the three phases is shown when using a modulation ratio of 1.0 and when using an LTR waveform. Figure 20 The maximum window time for the three phases is shown when the modulation ratio is 0.7 and the LTR waveform is used. If a BEMF zero-crossing cannot be detected before the limit shown in Table 1 ends, the HiZ state ends according to the window time limit. In this case, to continue operation, interpolation will be performed by the system's "Rotor Position / Speed ​​Generator" block. Figure 37 (As shown).

[0097] The following is a representative example of the driving functions for the three phases in an implementation using LTR modulation.

[0098]

[0099]

[0100]

[0101] In the above formula, some values ​​are calculated as follows:

[0102]

[0103]

[0104]

[0105] The variables in the above formula are defined as follows:

[0106] U 2pm U-phase 2-phase modulation waveform (fundamental wave of N-window method)

[0107] V 2pm V-phase 2-phase modulation waveform (fundamental wave of N-window method)

[0108] W 2pm W-phase 2-phase modulation waveform (fundamental wave of N-window method)

[0109] U 3pm U-phase 3-phase modulation waveform

[0110] V 3pm V-phase 3-phase modulation waveform

[0111] W 3pm W-phase 3-phase modulation waveform

[0112] U ltrm U-phase modulation waveform during the window period [Low Torque Ripple (LTR) modulation]

[0113] V ltrm V-phase modulation waveform during the window period [Low Torque Ripple (LTR) modulation]

[0114] W ltrm : W-phase modulation waveform during the window period [Low Torque Ripple (LTR) modulation]

[0115] θ: Rotor position in electrical angle

[0116] M: Modulation ratio (0 to 1)

[0117] In this representative example, when one of the three phases is within the window period, the normal sinusoidal waveform will result in a decrease in torque. Therefore, LTR modulation is applied during the window period to reduce torque ripple. In implementation, the transfer function of the motor stator should be considered when operating LTR modulation, but this is omitted in this paper for simplicity and to highlight other aspects of LTR modulation. Table 2 below gives the values ​​of U for different θ values. ltrm V ltrm and W ltrm Modulation ratio allocation.

[0118] θ (degrees) Ultrm Vltrm Wltrm 0≤θ<30 HiZ 0 <![CDATA[M ltr ]]> 30≤θ<90 <![CDATA[M ltr ]]> 0 HiZ 90≤θ<150 <![CDATA[M ltr ]]> HiZ 0 150≤θ<210 HiZ <![CDATA[M ltr ]]> 0 210≤θ<270 0 <![CDATA[M ltr ]]> HiZ 270≤θ<330 0 HiZ <![CDATA[M ltr ]]> 330≤θ<360 HiZ 0 <![CDATA[M ltr ]]>

[0119] Table 2 M in this representative example ltr The value is given by the following formula.

[0120]

[0121] In the above formula, M is the modulation ratio in the range of 0 to 1, and θwc It is the center phase position of the maximum window period, which is given in Table 3 below.

[0122] θ (degrees) <![CDATA[θ wc (degrees)]]> 0≤θ<30 0 30≤θ<90 60 90≤θ<150 120 150≤θ<210 180 210≤θ<270 240 270≤θ<330 300 330≤θ<360 0

[0123] Table 3

[0124] Figure 21 This diagram illustrates the current vector in LTR modulation. In this example, "d" represents the d-axis of the rotor, and "q" represents the q-axis of the rotor. For this graph, it is assumed that the motor stator is configured in a star connection, each phase has a resistance of 1 ohm, and the rotor position is 0 ≤ θ < 30° or 330 ≤ θ < 360°.

[0125] Figure 22 A specific implementation of a method for driving a three-phase motor including LTR modulation is shown, plotting voltage and current amplitudes based on the rotor's electrical angle position. For simplicity, the stator inductance and BEMF voltage are omitted from the plot. The drive phase voltage and drive phase current are shown, and the features / details of this plot are similar to those shown in the diagram, except for the plotted values. Figure 1 The features / details are similar. A modulation ratio of 1.0 is used in this driving method.

[0126] When a positive voltage is applied to a phase and reaches the WNDENG window, the voltage applied to that phase temporarily switches from a sinusoidal waveform to an LTR waveform. The LTR waveform causes an increase in the drive voltage for at least a portion of the WNDENG period, relative to the normal sinusoidal drive waveform. When the WNDENG window ends, the voltage applied to that phase switches back to the normal sinusoidal waveform. The HiZ period / window for each phase is also visible in this graph.

[0127] Figure 23 A specific implementation of a method for driving a three-phase motor including LTR modulation is shown, plotting voltage and current amplitudes based on the rotor's electrical angle position. This plot is similar to... Figure 22 The difference is that a modulation ratio of 0.7 was used. For simplicity, the stator inductance and BEMF voltage are omitted from this graph. The drive phase voltage and drive phase current are shown, and apart from the plotted values, the features / details of this graph are similar to those of the previous one. Figure 1The characteristics / details are similar. When a positive voltage is applied to a phase and reaches the WNDENG window, the voltage applied to that phase temporarily switches from a sinusoidal waveform to an LTR waveform. It can be seen that the LTR waveform with a 0.7 modulation ratio differs from that with a 1.0 modulation ratio, but still results in an increase in the drive voltage for at least a portion of the WNDENG period relative to the normal sinusoidal drive waveform. When the WNDENG window ends, the voltage applied to that phase switches back to the normal sinusoidal waveform. The HiZ periods / windows for each phase are also visible in this graph.

[0128] exist Figures 22 to 23 In the examples, the electrical angle positions and window widths are 0 degrees + / -15 degrees, 60 degrees + / -15 degrees, 120 degrees + / -15 degrees, 180 degrees + / -15 degrees, 240 degrees + / -15 degrees, and 300 degrees + / -15 degrees.

[0129] Figure 24 Representatively showing relative to Figure 22 The torque of a three-phase motor is plotted based on the electrical angles of its rotor (expressed in degrees). The torque is represented by the q-axis current, converted via the Clark-Parker transformation, which represents the resulting torque. Torque fluctuations are shown in... Figure 24 As can be seen, the torque drops sharply to very low levels at several locations, each of these drops corresponding to the HiZ window of one phase. Torque fluctuations are relative to... Figure 4 The torque fluctuations have been improved, but they still exist.

[0130] Figure 25 Representatively showing relative to Figure 23 The torque of a three-phase motor is plotted based on the electrical angle of its rotor (in degrees). The torque is represented by the q-axis current, converted via a Clark-Parker transformation, which represents the generated torque. Torque ripple is no longer observed in this plot. Therefore, this plot is an example of plotting the generated torque of a three-phase motor on the y-axis and the rotor angular position of the three-phase motor's rotor on the x-axis. The plot shows that the torque generated during at least one 360-degree electrically driven rotation of the rotor (the single torque value after the 360-degree electrically driven rotation) remains unchanged. This indicates that, for the LTR modulation equation given above, the torque ripple remains constant when the modulation ratio M is 1, but when the modulation ratio M decreases to 0.7, the ripple is sufficiently reduced to not appear. Figure 25 On the curve. In practical implementation, a modulation ratio higher than 0.7 can also lead to a significant reduction in torque ripple, sufficient to produce a similar effect. Figure 25 The curve is shown. It is also expected that modulation ratios below 0.7 will produce similar results. Figure 25 The graph shows a curve without torque fluctuations.

[0131] Reducing torque ripple can lead to increased motor lifespan, reduced wear on the motor and its components, quieter operation, more efficient operation, and so on. As a non-limiting example, in fan motor applications, a smaller modulation ratio typically means lower motor speed operation, and in this case, it also results in lower torque ripple, thereby reducing fan vibration and noise.

[0132] Figure 26 The diagram shows the effect of using a modulation ratio of 1.0. Figure 22 The driving method uses a Lissajous curve to represent the drive current, converted via a Clarke transform. The I-Alpha axis represents the α-axis current, and the I-Beta axis represents the β-axis current. The Lissajous curve shows the position of the torque when current is applied and the motor is engaged. The absence of circles on the curve indicates where the torque jumps from one value to another—these positions correspond to… Figure 24 This corresponds to the torque fluctuation. Figure 27 The diagram shows the effect of using a modulation ratio of 0.7. Figure 23 The driving method is represented by the Lissajous curve of the driving current converted by the Clarke transformation. In addition to the plotted values, Figure 27 The features / details of the curve are similar to Figure 26 Those features / details. However, despite the existence of positions without circles, torque ripple occurs. Figure 25 The curves are not obvious. These Lisajous curves also show that, in relation to... Figure 6 and Figure 7 When comparing the curves, the drive current value itself varies between TR-modulation and non-TR-modulation modes.

[0133] Lead angle control will now be discussed. Lead angle control adds an offset to the phase position to generate a modified drive voltage waveform. For example, when using LTR modulation as described above and when using a modulation ratio of 0.7, a generated waveform will be given when the lead angle is 0, as shown below. Figure 23 The driving voltage waveform is shown. On the other hand, if the lead angle is changed to 15 degrees, the following waveform is generated: Figure 28 The driving waveform shown. Figure 23 and Figure 28 All are drawn based on the assumption that 0 radians is the point above the zero-crossing point of the BEMF when the U phase rises.

[0134] Therefore, when considering the lead angle, the amount of the lead angle should be taken into account to achieve the above-mentioned U. 2pm V 2pm and W 2pm Formula. But Tables 2 and 3, as well as the above M, are also relevant. ltrThe formula should be implemented by disregarding the θ information of the lead angle. This means that the θ information used to determine the basic two-phase modulation waveform should include the lead angle, but the window period and LTR modulation should be operated using θ information that does not include the lead angle.

[0135] See now Figure 29 This illustrates another example of a specific implementation of a method for driving a three-phase motor (including LTR modulation), showing voltage and current amplitude curves plotted based on the rotor's electrical angle position. This method differs from the methods and formulas disclosed above in that, once BEMF is detected, the LTR modulation phase returns to the normal sinusoidal phase (ALLENG), instead of being driven by LTR modulation across the entire WNDENG window. In practice, this further improves efficiency and reduces torque ripple, thereby reducing noise, extending motor life, and reducing wear, among other things. Figure 29 The example in the example uses a modulation ratio of 0.6 and shows a HiZ window. In addition to the plotted values, Figure 29 Features / details similar to Figure 1 Those features / details. In another representative example, a predetermined time can be selected, and LTR modulation can be used to drive the phase voltage only up to that predetermined time, which is selected to be sufficient to detect BEMF, but still only a fraction of the entire WNDENG window.

[0136] exist Figure 29 In specific implementation, the electrical angle position and width during the window period are 0 degrees +0 / -15 degrees, 60 degrees +0 / -30 degrees, 120 degrees +0 / -15 degrees, 180 degrees +0 / -15 degrees, 240 degrees +0 / -15 degrees and 300 degrees +0 / -15 degrees.

[0137] Figure 30 Representatively showing relative to Figure 29 The torque of a three-phase motor is plotted as the electrical angle (in degrees) of its rotor. The torque is represented by the q-axis current, converted via a Clark-Parker transformation, which represents the generated torque. Again, no torque fluctuation is observed in this plot. Therefore, this plot is another example of plotting the generated torque of a three-phase motor on the y-axis and the rotor angular position of the three-phase motor's rotor on the x-axis, showing that the generated torque remains unchanged during at least one electrically driven 360-degree rotation of the rotor.

[0138] Figure 31 Showing the target Figure 29 The driving method is represented by the Lissajous curve of the driving current converted by the Clarke transformation. In addition to the plotted values, Figure 31 The features / details of the curve are similar to Figure 27Those features / details. However, despite the existence of positions without circles, torque ripple occurs. Figure 30 The curve is not obvious. The Lisajous curve also shows that, in relation to... Figure 7 When comparing the curves, the drive current value varies between TR-modulation and non-TR-modulation types.

[0139] See now Figure 32 This document illustrates an example of a three-phase inverter circuit, which can be used in or with a control module to control a three-phase motor according to the methods disclosed herein. The three-phase inverter circuit uses three half-bridges to drive the motor. As an example of driving only the U phase, PWM is used to pulse-turn on and off the UH phase when a drive voltage is applied to the U phase. When UH is on, UL is off, and vice versa. When the drive voltage of the U phase is zero, UL remains on and UH remains off.

[0140] See now Figure 33 The block diagram representatively illustrates a controller for controlling a three-phase motor using the methods disclosed herein (which may be implemented in an integrated circuit in certain embodiments). Various components are shown, including encoder modules / components, LTR (Low Torque Ripple) modulation modules / components, 2-phase modulation modules / components, etc. A pulse width modulation (PWM) module is not shown, but the electrical connections to be coupled to the PWM module are representatively shown.

[0141] Figure 33 The controller inputs include the following: CLK (operation clock); RSTX (reset – 0 for reset and 1 for activation); RPOS[9:0] (rotor position information - θ) (rotor position information is based on the detected BEMF zero-crossing signal, 0.352 degrees / LSB); LA[7:0] (lead angle / value - θ) la (0.352 degrees / LSB); M[9:0](output modulation ratio – M, full scale is 100%, 0 is 0%); HIZU(U phase unexcited window period status flag, 1: window period, 0: normal); HIZV(V phase unexcited window period status flag, 1: window period, 0: normal); HIZW(W phase unexcited window period status flag, 1: window period, 0: normal); CALCUPD(update event flag used to calculate the next value – when this flag rises, the next value is updated by the input value at that moment).

[0142] Figure 33The controller outputs include the following items: DRVDUTYU[9:0] (drive PWM duty cycle, U phase, full scale is 100%, 0 is 0%); DRVDUTYV[9:0] (drive PWM duty cycle, V phase, full scale is 100%, 0 is 0%); DRVDUTYW[9:0] (drive PWM duty cycle, W phase, full scale is 100%, 0 is 0%);

[0143] It also states that RPOSLA = RPOS + LA. WNDENGU, WNDENGV, and WNDENGW correspond to the WNDENG windows of phases U, V, and W, respectively. HIZU, HIZV, and HIZW are provided by external modules. Figure 33 The PWM module, not shown but coupled to the controller, completes the full N-window drive waveform, including the unexcited phase.

[0144] See now Figures 34 to 36 Several timing diagrams are provided. The calculation of these timing functions must be completed within one drive PWM cycle. Figures 34 to 36 The TCALC shown represents the computation time and should be determined based on the actual design. The period of CALCUPD should match the driving PWM carrier period, but the assertion timing should be optimally designed within the PWM carrier period to minimize system delay relative to RPOS and LA information. This means that TCALC is important for optimizing the design to ensure that timing corresponding to the driving PWM carrier period is established.

[0145] Figure 34 This is an example of a timing diagram for the case where HIZU = 1 and 0 ≤ θ < 30 or 330 ≤ θ < 360. For the case where 150 ≤ θ < 210, the timing is similar to [previous case] as long as the DRVDUTYV output alternates with LTR modulation and the DRVDUTYW output alternates with 2-phase modulation. Figure 34 .

[0146] Figure 35 This is an example of a timing diagram with HIZU = 1 and 90 ≤ θ < 150. With 270 ≤ θ < 330, the timing is similar to [previous example], provided the DRVDUTYW output alternates with LTR modulation and the DRVDUTYU output alternates with 2-phase modulation. Figure 35 .

[0147] Figure 36 This is an example of a timing diagram with HIZW = 1 and 210 ≤ θ < 270°. With 30 ≤ θ < 90°, the timing is similar to [previous example] as long as the DRVDUTYU output alternates with LTR modulation and the DRVDUTYV output alternates with 2-phase modulation. Figure 36 .

[0148] Figure 37 This is a block diagram representatively illustrating a three-phase motor and the components used to control the three-phase motor and detect the BEMF signal. In this representative example, the three-phase inverter and the BEMF detector are separate modules, and all components to the left of these modules are implemented on a single semiconductor device. In this example, the LTR modulation method disclosed herein is implemented using a "2-phase modulation with LTR modulation" block. Figure 37 This configuration is only applicable to three-phase motors with a star configuration.

[0149] In practice, the modulation ratio disclosed herein can be determined by the system capacity, where a modulation ratio of 1.0 is the total system capacity (with applied voltage), and a lower modulation ratio is the corresponding percentage of the total system capacity.

[0150] It should be noted that Table 2 includes values ​​only for 6-window mode. However, U 2pm V 2pm W 2pm The formula takes precedence over Table 2. When using 1-window, 2-window, or 3-window modes, the ALLENG period increases within the 6-window ALLENG period, while the WNDENG period and window period decrease. Therefore, LTR modulation can be defined based on the values ​​in Table 2, even though technically they only represent the 6-window mode.

[0151] It is also noted that the start time of the non-energized section can be determined according to the application, and the end time of the non-energized section can be determined adaptively (or using a predetermined time). When the start time is far from the BEMF zero-crossing point, the robustness of the detection will be improved, but the torque ripple will not be reduced as much.

[0152] In the specific implementation of various methods, three-phase motors may include sensorless brushless DC motors and permanent magnet synchronous motors.

[0153] In various specific implementations of the method, the method may include driving the second phase using a first sine drive function after driving the second phase using a second row function until the first BEMF voltage is detected.

[0154] In various specific implementations of the method, the method may include driving the second phase with a first sine drive function after driving the second phase with a second drive function for a predetermined amount of time.

[0155] In various specific implementations of the method, the method may further include: using a second sinusoidal drive function to drive the second phase of the three-phase motor when all three phases are energized; using the first non-sinusoidal drive function to drive the second phase for at least a portion of the time when one phase other than the second phase is not energized and when the first non-sinusoidal drive function produces a modulation ratio less than 1; and driving the second phase to a modulation ratio of 1 for at least a portion of the time when one phase other than the second phase is not energized and when the first non-sinusoidal drive function produces a modulation ratio greater than or equal to 1.

[0156] In various specific implementations of the method, the method may also include the case where the modulation ratio is a low torque ripple modulation ratio, wherein the second sinusoidal driving function is: in M is the modulation ratio from 0 to 1, and θ is the rotation angle of the three-phase motor.

[0157] In various specific implementations of the method, the method may further include: using a third sinusoidal drive function to drive the third phase of the three-phase motor when all three phases are energized; using the first non-sinusoidal drive function to drive the third phase for at least a portion of the time when one phase other than the third phase is not energized and when the first non-sinusoidal drive function produces a modulation ratio less than 1; and driving the third phase to a modulation ratio of 1 for at least a portion of the time when one phase other than the third phase is not energized and when the first non-sinusoidal drive function produces a modulation ratio greater than or equal to 1.

[0158] In various specific implementations of the method, the method may also include the case where the modulation ratio is a low torque ripple modulation ratio, wherein the third sinusoidal driving function is: in M is the modulation ratio from 0 to 1, and θ is the rotation angle of the three-phase motor.

[0159] In the above description, where specific implementations of the three-phase motor driving method and the implementation components, sub-components, methods and sub-methods are mentioned, it should be readily apparent that various modifications can be made without departing from its essence, and that these specific implementations, implementation components, sub-components, methods and sub-methods can be applied to other three-phase motor driving methods.

Claims

1. A method for driving a star-connected three-phase motor, the method comprising: When the first phase of the star-connected three-phase motor is energized, the second phase of the three-phase motor is driven using the first sinusoidal drive function; Switch the first phase to a non-energized state; When the first phase is in the non-energized state, the first back electromotive force (BEMF) voltage of the first phase is detected. as well as For at least a portion of the time when the first phase is in the non-energized state, the second phase is driven by a second drive function different from the first sinusoidal drive function to generate torque, wherein the torque generated during the 360-degree rotation of the electric drive of the three-phase motor remains unchanged.

2. The method of claim 1, wherein, Compared to driving the second phase using the first sinusoidal driving function, driving the second phase using the second driving function results in an increase in the voltage applied to the second phase.

3. The method of claim 1, further comprising: When the first phase is in a second non-energized state, the third phase of the three-phase motor is driven using a third drive function that is different from the second sinusoidal drive function, and wherein driving the third phase using the third drive function results in an increase in the voltage applied to the third phase compared to driving the third phase using the second sinusoidal drive function.

4. A method of driving a star-connected three-phase motor, wherein, The method includes: When all three phases are energized, the first phase of the star-connected three-phase motor is driven using the first sinusoidal drive function; For at least a portion of the time when one phase other than the first phase is not energized and the first non-sinusoidal drive function produces a modulation ratio less than 1, the first phase is driven using the first non-sinusoidal drive function; and For at least a portion of the time during which one phase other than the first phase is not energized and the first non-sinusoidal drive function produces a modulation ratio greater than or equal to 1, the first phase is driven to a modulation ratio of 1.

5. The method of claim 4, wherein, The first non-sine driving function is the first cosine driving function.

6. The method according to claim 5, wherein: The modulation ratio is a low torque ripple modulation ratio, wherein the first cosine drive function is: Where M is the modulation ratio from 0 to 1, where Let be the rotation angle of the three-phase motor, and wherein when When the temperature is less than 30 degrees Celsius and greater than or equal to 0 degrees Celsius It has a value of 0 degrees; when When the temperature is less than 90 degrees and greater than or equal to 30 degrees, It has a value of 60 degrees; when When the temperature is less than 150 degrees and greater than or equal to 90 degrees, It has a value of 120 degrees; when When the temperature is less than 210 degrees and greater than or equal to 150 degrees, It has a value of 180 degrees; when When the temperature is less than 270 degrees and greater than or equal to 210 degrees, It has a value of 240 degrees; when When the temperature is less than 330 degrees and greater than or equal to 270 degrees... It has a value of 300 degrees; and when When less than 360 degrees and greater than or equal to 330 degrees It has a value of 0 degrees; and The modulation ratio is a low torque ripple modulation ratio, and the first sinusoidal drive function is... ,in Where M is the modulation ratio from 0 to 1, and where The rotation angle of the three-phase motor is given.

7. A method for driving a three-phase motor, the method comprising: When all three phases are energized, the U phase of the three-phase motor is driven using the first sinusoidal drive function; When all three phases are energized, the V phase of the three-phase motor is driven using the second sinusoidal drive function; When all three phases are energized, the W phase of the three-phase motor is driven using the third sinusoidal drive function; as well as During the period when one of the three phases is not energized, for at least a portion of that period, the remaining two energized phases are driven using a cosine drive function. wherein the first sinusoidal drive function is wherein the second sinusoidal drive function is wherein the third sinusoidal drive function is wherein wherein M is a modulation ratio from 0 to 1, and wherein is a rotation angle of the three-phase electric machine.

8. The method of claim 7, further comprising: During the period when one of the three phases is not energized and for at least a portion of the time when the cosine drive function produces a modulation ratio less than 1, the remaining two energized phases of the three phases are driven using the cosine drive function, and during the period when one of the three phases is not energized and for at least a portion of the time when the cosine drive function produces a modulation ratio greater than or equal to 1, the remaining two energized phases of the three phases are driven to a modulation ratio of 1.

9. The method according to claim 8, wherein: The modulation ratio is a low torque ripple modulation ratio, wherein the cosine drive function is: Where M is the modulation ratio from 0 to 1, where Let be the rotation angle of the three-phase motor, and wherein when When the temperature is less than 30 degrees and greater than or equal to 0 degrees, it has a value of 0 degrees. When the degree is less than 90 degrees and greater than or equal to 30 degrees, it has a value of 60 degrees. When the degree is less than 150 degrees and greater than or equal to 90 degrees, it has a value of 120 degrees. When the degree is less than 210 degrees and greater than or equal to 150 degrees, it has a value of 180 degrees. When the value is less than 270 degrees and greater than or equal to 210 degrees, it has a value of 240 degrees. When the temperature is less than 330 degrees and greater than or equal to 270 degrees, it has a value of 300 degrees, and when A value of 0 degrees is given when the angle is less than 360 degrees and greater than or equal to 330 degrees. and The modulation ratio mentioned therein is a low torque ripple modulation ratio.

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