A method for accelerating the extinction of residual current and a method for controlling the duration of the accelerating extinction of residual current.

Abstract

A method for accelerating the decay of residual current in an open phase when changing electrical position while driving a BLDC motor (10) under high load conditions includes driving the BLDC motor (10) using a unipolar pulse-width modulation pattern ON_PWM, using a voltage observer (40) to monitor the voltage of the open phase to determine whether there is a residual current, and applying a switching pattern to switches (S1-S6) of the BLDC motor (10) while there is a residual current, superimposing the pulse-width modulation pattern used and maximizing the voltage of the open phase to accelerate the decay of the residual current, the switching pattern including opening a switch of a driven phase during a change of electrical position and closing a switch associated with the driven phase during a change of electrical position.

Description

[Technical Field]

[0001] The present invention relates to a refrigerator compressor equipped with a brushless DC three-phase motor (BLDC) having a trapezoidal induced voltage.

[0002] More specifically, the present invention relates to a method for accelerating the elimination of residual current during operation of a BLDC motor under high load conditions, and a method for controlling the duration of the accelerating elimination of residual current. [Background technology]

[0003] A typical drive procedure for a BLDC motor via a three-phase inverter is known as the "six-step" procedure, which is divided into six electrical positions. In this type of drive, only two phases of the motor are commanded to each electrical position, while the third phase remains open and is used to monitor the induced voltage in the motor coils and, consequently, to identify the motor's electrical position.

[0004] Figure 1 of the prior art shows the electronic circuit used to drive a three-phase BLDC motor 10.

[0005] As shown in Figure 1, the circuit includes a power supply 20 that supplies DC / voltage. The power supply 20 may be provided by an input converter stage, such as a DC-DC converter powered by a capacitive filter rectifier or a battery. In addition, the circuit includes a three-phase voltage inverter 30 operably associated with the BLDC motor 10 and the power supply 20, and thus the power supply 20 is powered by a reference voltage V at the bottom of the voltage inverter 30. ref From the definition, a continuous busbar voltage V cc It is configured to supply.

[0006] Furthermore, as shown in Figure 1, the voltage inverter 30 controls the phase F of the BLDC motor 10. a F b and F cIt includes switches S1 - S6 configured to be energized. Further, the voltage inverter includes free - wheel diodes D1 - D6, and each free - wheel diode D1 - D6 is associated in parallel with each switch S1 - S6. The free - wheel diodes D1 - D6 can provide a path for the current of the BLDC motor 10 during the operation of the switches S1 - S6. Thus, switches S1 and S2 are associated with phase F a of the BLDC motor 10, switches S3 and S4 are associated with phase F b of the BLDC motor 10, and switches S5 and S6 are associated with phase F c of the BLDC motor 10.

[0007] According to FIG. 1, the circuit also includes a voltage observer 40 that serves to measure three phase voltages V a , V b and V c related to phases F a , V b and V c of the BLDC motor 10 as well as the bus - bar voltage V cc . Further, the circuit includes a control unit 50 operably associated with the voltage observer 40, which interprets the voltage code, identifies the current electrical position of the BLDC motor 10, and serves to perform correct driving of the voltage inverter.

[0008] Furthermore, according to FIG. 1, ideally, only two phases of the motor are driven at each electrical position, and in this case, the motor current is equal to the current circulating through the bus - bar. Therefore, only one current sensor 60 is used within the bus - bar to control the motor current or to protect against over - current.

[0009] FIG. 2 of the prior art shows the induced voltage waveforms e a -e c , phase voltages V a -V c , and desired currents I a -I c, and the command codes for switches S1-S6 are shown. Furthermore, the induced voltage waveform e a -e c is phase F a F b and F c At the point when each is open, the phase voltage V a , V b and V c To allow for superimposition, the vertical displacement is expressed as Vcc / 2. Furthermore, according to Figure 2, the "6-step" drive is divided into six 60° electrical positions P1-P6, totaling 360° of electrical positions. According to Figure 2, when one of the switches S1-S6 is driven, that switch needs to operate 120° electrically. As mentioned above, such a typical drive can be separated into six electrical positions P1-P6, and in each electrical position, only two phases of the BLDC motor 10 are driven at a time, and a third phase is used to monitor the BEMF induced voltage of the BLDC motor 10, and by monitoring such BEMF induced voltage, the electrical position of the BLDC motor 10 is detected.

[0010] In this sense, one of the challenges associated with driving a BLDC motor under heavy load is the preservation of its electrical position. Typical driving of a BLDC motor without mechanical sensors is based on measuring the induced voltage (BEMF) measured in the open phase, but such a voltage can only be seen when there is no longer any current circulating in that open phase. Therefore, if it takes a long time for the current to dissipate, the induced voltage (BEMF) may be masked by residual current, leading to a malfunction in electrical position detection and potentially driving failure.

[0011] Therefore, the electrical position of the BLDC motor 10 can be estimated in various ways, the more common techniques being detection by zero crossing and detection of induced voltage crossing.

[0012] Figure 3 of the conventional technology illustrates the operation of these two technologies, where the circle represents detection by zero crossing and the trapezoid represents detection of induced voltage crossing.

[0013] Furthermore, it is important to emphasize that in these techniques, monitoring the induced voltage in the open phase is affected by residual current coming from the previous electrical position where the phase was still driven and current was circulating. Such residual current circulates through the freewheeling diode, raising the open phase voltage to V cc Alternatively, force it to zero, and thus mask the induced voltage.

[0014] For example, Figure 4a of the conventional technology shows the busbar voltage V of the voltage inverter 30. cc This shows the open-phase voltage clamp at which the F of the BLDC motor 10 is located at the previous electrical position. b This process occurs when current is discharged and is circulated by the upper freewheeling diode D3 until it completely disappears.

[0015] Figure 4b of the conventional technology shows that when the electrical position changes, the applied current I is related to the phase B of the BLDC motor 10. b , induction voltage e b , and read voltage V b The size indicates how it works.

[0016] For example, Figure 5a of the prior art shows an open-phase voltage clamp with respect to an inverter bridge, such a clamp occurs when current is applied to phase B of the BLDC motor 10 in the previous electrical position, and then begins to circulate through the lower freewheel diode D4 until it completely disappears.

[0017] Figure 5b shows the applied current I related to the phase B of the BLDC motor 10 during the change in electrical position. b , induction voltage e b , and read voltage V b This shows how the size works.

[0018] In addition, the driving technology for BLDC motors without mechanical sensors includes an operating step to filter out the effect of residual current on the reading of the induced voltage BEMF in order to enable proper operation of electrical position sensing.

[0019] For example, Patent Document PI0004062-2, published on April 16, 2002, with the title "ELECTRIC MOTOR CONTROL METHOD, ELECTRIC MOTOR CONTROL SYSTEM and ELECTRIC MOTOR," proposes a minimum protection time after each change in electrical position before initiating the induced voltage BEMF (Beam Emission Midforce) processing based on electrical position detection.

[0020] Patent document US6512341(B2), published on March 14, 2002, with the title "Apparatus and Method of Driving a Brushless Motor," monitors whether the read voltage is clamped to the busbar voltage or to the inverter bridge reference before initiating the processing of the induced voltage BEMF by electrical position detection.

[0021] Nevertheless, none of the aforementioned techniques provide the type of operation necessary to maintain electrical position sensing under high load conditions where the current takes too long to dissipate itself, causing a loss of the ideal moment to shift the drive switch and potentially leading to drive failure of the BLDC motor.

[0022] For example, Figures 6a and 6b of the prior art illustrate zero-crossing losses due to extension until the current disappears. It is important to emphasize that such problems do not limit the techniques for detecting zero-crossings, but rather any technique that relies on monitoring the induced voltage in the open phase. In addition, such figures show that during zero-crossing losses, the F of the BLDC motor 10b Related to the applied current I b , induction voltage e b , and read voltage V b This shows how the size works.

[0023] More specifically, Figure 6a shows the busbar voltage V cc To illustrate an example of clamping the open-phase voltage at zero, Figure 6b shows the clamping of the open-phase voltage at zero, i.e., the reference voltage V of the inverter bridge. ref In this example, we illustrate the case of clamping that causes masking of induced voltage and loss of zero crossing.

[0024] Furthermore, there are several pulse-width modulation patterns for driving BLDC motors, such as the one analyzed in the paper "Assessment of Pulse-Width Modulation Techniques for Brushless DC Motor Drives" by LAI, Y.-S. and LIN, Y.-K, published in the Conference Record of the 2006 IEEE Industry Applications Conference Forty-First IAS Annual Meeting in 2006. The differences between such patterns consist of the possibility of residual current circulation by the DC busbar, the duration of the residual current, and the limitations of the drive circuit of the drive switch.

[0025] Patent document JP2017046513, published on March 2, 2017, with the title of the invention "Motor drive device, drive device of compressor using the same, and freezing device, refrigerator," describes the application of an alternative unipolar switching pattern in which pulse width modulation is alternately applied to the upper and lower switches, always associated with the phase maintained during the previous position change. Such an alternating switching pattern provides faster disposal of current in the open phase and thus improves position detection and operation under high load conditions. The document also refers to the use of such an invention in applications where there is a block valve to prevent system equalization, i.e., applications developed for applications involving non-equalization starting. However, it is important to highlight the alternating switching pattern related to the phase maintained when changing position, as described in the document JP2017046513, which was already used by Becerra, RC et al. in their paper "Four-quadrant sensorless brushless ecm drive" published in the proceedings of the Sixth Annual Applied Power Electronics Conf and Exposition (APEC'91) in 1991.

[0026] Patent document JP2017046512, published on March 2, 2017, with the title of the invention "Motor drive device and compressor drive device using the same, and refrigeration device, refrigerator," describes a switching pattern aimed at returning freewheeling current by a busbar capacitor. This document proposes turning off a switch associated with the phase that has been driven continuously after the motor's position has been changed for a certain period of time, thereby forcing the passage of freewheeling current of the opened phase by the busbar, and thus accelerating the extinction of the freewheeling current, and as a result, preventing position detection from being eliminated under high load conditions. This document further refers to the use of the present invention in applications where a block valve to prevent system equalization is present, i.e., applications developed for applications involving non-equalizing starts.

[0027] The problem with the conventional technology is that the acceleration of the disappearance of residual current does not directly depend on the feedback of such current by the busbar capacitor, but rather on a larger reverse voltage that can be applied in the phase in which the residual current circulates.

[0028] This conceptual difference becomes more apparent when attempting to relate the proposed method for feedback of residual current by a busbar capacitor to typical switching techniques for controlling a BLDC motor, such as the association shown in Figure 2 of Patent JP2017046512 (shown at the top of Figure 8 in this document). As will be shown later, the opening of the two switches in association with the proposed method in Patent JP2017046512 and the unipolar switching applied to the upper switch reduces the effectiveness of accelerating the extinction of residual current despite the residual current carry being fed back by the busbar capacitor.

[0029] To illustrate the problem in patent JP2017046512, it is important to note that the current in each phase of the BLDC motor 10 can be defined from the diagram shown in Figure 1 according to the following equation. TIFF0007897234000001.tif2755

[0030] Here, L represents inductance, R represents resistance, and e a , e b and e b represents the induced voltage, v a , v b and v b V represents the phase voltage at the terminals of the BLDC motor 10, n This represents the voltage that brings about the neutral point, i a i b and i c represents the phase current, and di a / dt, di b / dt represents the derivative of the phase current.

[0031] Furthermore, considering the symmetric motor, i.e., where the resistance R and phase inductance L are all the same, the voltage at the neutral point Vn can be modeled from the above equation as follows: TIFF0007897234000002.tif964

[0032] This allows the dynamic characteristics of the current of the BLDC motor 10, separated into dynamic and controlling action, to be rewritten using the following equation. TIFF0007897234000003.tif27107

[0033] The first part between the parentheses on the right side of the equation represents the dynamic characteristics of the BLDC motor, and the second part between the parentheses represents the control action at each phase according to the voltage applied to each phase of the BLDC motor.

[0034] Therefore, the control action can be defined by the following equation. TIFF0007897234000004.tif3660

[0035] Here, u a u b and u c This represents the control action in each phase, and u nThis represents the control action at the neutral point, and in both cases, it is the voltage v applied to the motor terminals. a , v b , and v c It is a function of .

[0036] This allows the phase current of a BLDC motor to be controlled by controlling the phase voltage.

[0037] For example, current i a To increase the neutral point u n The average voltage of the control action can be increased or decreased. Current i a To reduce the neutral point u n The average voltage of the control action can be reduced or increased over time. Such analysis allows for a better understanding of how to eliminate residual current.

[0038] In this sense, consider the classic 6-step drive of a BLDC motor. Here, the transition to electrical position P1 is analyzed, as shown in Figure 7 of the prior art. To perform the transition to electrical position P1, switch S4 is closed, switch S1 is closed, and switch S5 is opened. When switch S5 is opened, residual current i c The freewheel diode D6 begins to cross.

[0039] According to Figure 7, i a is correct i b Since it is desirable that the phase is negative, a main voltage with phase A and a secondary voltage with phase B are applied, i.e., switches S1 and S4 are driven.

[0040] Furthermore, since there is still residual current in the newly opened phase C, this current circulates through the freewheeling diode D6.

[0041] Therefore, the average score u for such a classical driving pattern n The average voltage of the control action on is given by the following equation. TIFF0007897234000005.tif1196 Here, V cc This is the busbar voltage value.

[0042] Furthermore, the applied voltage for the control action in each phase can be calculated using Set 1 of the following equation. TIFF0007897234000006.tif3676

[0043] Here, i c is correct, i b is negative, and i a ga i c If the purpose is to assume a current of i, then this is i a The rapid rise and current i b Because it is advantageous for maintaining, it is an excellent choice for maintaining torque during changes in electrical position. However, under high load conditions, i c It can sometimes take an extremely long time for it to disappear.

[0044] The solution proposed by patent JP2017046512 consists of returning the freewheeling current by a busbar capacitor. In this sense, as shown in Figure 8, it is proposed to turn off the switch associated with the driven phase for a certain period of time. Thus, in order to perform a transition with respect to the electrical position P1, the switch S4 is opened for a certain period of time, and the current i is returned by the busbar capacitor. c They are forced to return.

[0045] The problem with the prior art is that when associating the pulse width modulation pattern with phase A, as suggested in patent JP 2017046512 and Figure 2 of the same patent, it allows control of the voltage applied to the BLDC motor 10, while forcing the extinction of the current. Such association can lead to the opening of two switches associated with the position, which is bad both for extinction of residual current and for establishing a new drive electrical position.

[0046] While switch S1 is open, current i is affected by the pulse width modulation relationship shown in Figure 8. a The current flows through the freewheeling diode D2, and phase A is connected to the reference of the inverter bridge.

[0047] In this case, the average score u for such a drive pattern n The average voltage of the control action can be expressed by the following formula. TIFF0007897234000007.tif1196

[0048] Furthermore, the voltage applied to each phase can be expressed by set 2 of the following equations. TIFF0007897234000008.tif3677

[0049] Comparing set 1 of the equation with set 2, in reference JP2017046512, the voltage u applied to phase C c It is clear that this becomes equal to the voltage applied in classical driving, that is, it does not accelerate the dissipation of residual current. In addition, current i b and current i a Both are significantly reduced, impairing the BLDC motor torque at the point when the electrical position changes.

[0050] Another problem with conventional technology is that monitoring of residual current duration is not performed to determine how long techniques to reduce freewheel current extinction time should be applied. [Overview of the Initiative]

[0051] The objective of the present invention is to provide a method for accelerating the extinction of residual current, avoiding the drawbacks of the prior art.

[0052] A method for accelerating the extinction of residual current of a phase that is released when the electrical position is changed while driving a BLDC motor (10) under high load conditions (a method for accelerating extinction), The BLDC motor is driven using the unipolar pulse width modulation pattern ON_PWM, By using a voltage observer to monitor the voltage of the open phase, it is determined whether or not there is residual current, This includes superimposing (overlaying) the pulse width modulation pattern used on the BLDC motor switch while residual current exists, and applying a switching pattern that maximizes the voltage of the open phase in order to accelerate the elimination of the residual current, The aforementioned switching pattern is Opening a phase switch that is maintained in the driven state while changing the aforementioned electrical position. This includes closing a switch related to the driven phase while the electrical position is being changed.

[0053] One advantage of the present invention is that it allows for the rapid dissipation of residual current in the open phase under high load conditions, compared to the conventional method.

[0054] Conveniently, the method according to the present invention consists of the fact that, while there is residual current exiting the phase opened by the upper freewheel diode, the voltage read by the voltage observer of the open phase is close to the busbar voltage, and a switching pattern is applied for the accelerated extinction of the residual current.

[0055] The method according to the present invention further comprises the fact that, while there is residual current entering through the phase opened by the lower freewheel diode, the voltage read by the voltage observer of the open phase becomes nearly zero, and a switching pattern is applied for the accelerated extinction of the residual current.

[0056] Furthermore, the method according to the present invention is characterized by the fact that monitoring of residual current must be carried out until such current completely disappears.

[0057] Furthermore, the method according to the present invention consists of the fact that the unipolar pulse width modulation pattern ON_PWM can be replaced with any other unipolar or bipolar pulse width modulation pattern.

[0058] One additional advantage of the method according to the present invention is that it includes maintaining the detection of the location of the effects caused by residual current in the open phase. Another advantage is that the association with pulse width modulation enables the proper operation of the technique for preventing its disturbance.

[0059] The present invention also provides a method for controlling the duration of an accelerated extinction method for residual current. The method is - This includes adjusting the time interval for the accelerated extinction of residual current in order to maintain electrical position detection.

[0060] Conveniently, the method according to the present invention consists of the fact that the required time interval for the accelerated extinction of residual current depends on the window time interval for reading the induced voltage, the minimum window time interval, and the time interval for residual current extinction.

[0061] The method according to the present invention also consists of the fact that the window time interval for reading the induced voltage is the time interval from the time when the residual current disappears until the electrical position of the BLDC motor is detected.

[0062] Furthermore, the method according to the present invention consists of a time interval in which residual current disappears, which is comprised of the time intervals in which the BLDC motor changes its electrical position, and therefore, residual current in the open phase of the BLDC motor is generated until the time when such residual current disappears.

[0063] In addition, the method according to the present invention is based on the fact that the time interval for the accelerated extinction of residual current can be saturated at its minimum value, i.e., zero, and its maximum value, i.e., a value equal to the extinction of residual current.

[0064] Furthermore, the method according to the present invention consists of the fact that a minimum window time interval is defined and is a function of the minimum electrical distance desired for safe operation of electrical position sensing and the electrical speed of the BLDC motor.

[0065] In addition, the method according to the present invention consists of the fact that the increase or decrease in the time interval for the accelerated extinction of residual current is defined by comparing the window time interval for reading the induced voltage with the minimum window time interval.

[0066] The method according to the present invention further comprises the fact that applying a switching pattern to accelerate the dissipation of residual current results in a reduction of current in the phase that remains on during position changes, avoiding the limitation of low-speed overcurrent protection provided by a single current sensor in the busbar, and promoting more effective protection of the BLDC motor against overcurrent.

[0067] Furthermore, the method according to the present invention is such that, when the BLDC motor is started, the time interval for the accelerated extinction of residual current must be equal to the time for residual current extinction. [Brief explanation of the drawing]

[0068] The object and advantages of the present invention will become clearer through the detailed description of the following embodiments and the non-limiting drawings presented at the end of this document.

[0069] [Figure 1] Figure 1 shows the electronic circuit used for the 6-step drive of a conventional BLDC motor.

[0070] [Figure 2] Figure 2 shows the phase voltage and command code, the desired current, and the induced voltage waveform in a conventional BLDC motor.

[0071] [Figure 3] Figure 3 shows a conventional technique for detection by zero crossing or induced voltage crossing.

[0072] [Figure 4a] Figure 4a shows the output of residual current from a conventional upper freewheel diode in phase B.

[0073] [Figure 4b] Figure 4b shows the phase voltage clamping at the busbar voltage of the inverter bridge when residual current is discharged from the motor by the upper freewheeling diode of phase B in the conventional technology.

[0074] [Figure 5a] Figure 5a shows the input of residual current through a conventional phase B lower freewheel diode.

[0075] [Figure 5b] Figure 5b shows the phase voltage clamp at the reference voltage of the inverter bridge when residual current is supplied to the motor by the lower freewheeling diode of phase B in the conventional technology.

[0076] [Figure 6a] Figure 6a illustrates the zero-crossing loss due to the extension of residual current until the conventional technology is obsolete. [Figure 6b] Figure 6b illustrates the zero-crossing loss due to the extension of residual current until the conventional technology is obsolete.

[0077] [Figure 7] Figure 7 shows the transition from the electrical position P1 of the BLDC motor in the conventional drive technology.

[0078] [Figure 8] Figure 8 shows the transition from the electrical position P1 of a BLDC motor in a conventional drive system with residual current feedback via a busbar.

[0079] [Figure 9] Figure 9 shows the transition to electrical position P1 during driving by the method of accelerated extinction of residual current according to the present invention.

[0080] [Figure 10] Figure 10 shows the phase voltage used to monitor the generation of residual current according to the present invention.

[0081] [Figure 11] Figure 11 shows the drive using the method of accelerated extinction of residual current according to the present invention.

[0082] [Figure 12a] Figure 12a shows how the integrity of electrical position sensing of a BLDC motor is monitored according to the present invention. [Figure 12b] Figure 12b shows how monitoring the integrity of electrical position sensing of a BLDC motor is performed according to the present invention.

[0083] [Figure 13a] Figure 13a shows possible practical applications of the method according to the present invention. [Figure 13b] Figure 13b shows possible practical applications of the method according to the present invention. [Modes for carrying out the invention]

[0084] For a BLDC motor 10 driven by a conventional 6-step strategy to operate properly without a mechanical position sensor, residual current circulating in the phase of the BLDC motor 10 that is open (open) to change its electrical position must disappear before a typical event of the next electrical position of the BLDC motor 10 (which may be a zero crossing, a phase voltage crossing, or a voltage that enables phase look-ahead).

[0085] Accordingly, embodiments of the present invention provide a method for accelerating the extinction of residual current, such a method aims to adjust the switching pattern of the BLDC motor 10 to cause the residual current in the open phase to extinct more quickly and to reduce its influence on the currents of the other two phases.

[0086] To enable this, instead of proposing a switching pattern that forces such a current to pass through the busbar, the method according to the invention applies a switching pattern that generates a larger voltage, if possible, in the released phase for the accelerated disappearance of the residual current after changing the position.

[0087] In this sense, according to FIG. 9 showing the transition to the electrical position P1, the option for more quickly extinguishing the residual current i c consists of increasing the voltage resulting from the control action at the average point u c since V n is already at its minimum value.

[0088] Furthermore, since the voltage V a is already at its maximum value connected to the busbar voltage V cc , the best option for increasing u n is constituted by connecting and increasing V b to the busbar voltage V cc as shown in FIG. 9 of the present invention.

[0089] To enable this, in the method according to the invention, while there is a residual current, the pulse-width modulation applied to the switches associated with a certain electrical position is superimposed by a specific switching pattern for the accelerated disappearance of the residual current. According to the present invention, such a switching pattern consists of opening the switches of the phase that continues to be driven while changing the electrical position, and closing the switches associated with the phase that was driven while changing the electrical position. After the residual current has disappeared, the pulse-width modulation selected for voltage control and applied to the BLDC motor 10 is restored.

[0090] As shown in FIG. 9, in the transition to the electrical position P1, a switching pattern is applied, where the switch S4 associated with the phase B in which the driving state is maintained remains open while there is a residual current, and at the same time, the switch S1 associated with the driven phase A is closed during the change to the electrical position P1.

[0091] This results in the average point u for the drive pattern using the method according to the present invention. n The average voltage of the control action in this case can be expressed by the following formula. TIFF0007897234000009.tif11100

[0092] Furthermore, the applied voltage for the control action in each phase of the BLDC motor 10 can be calculated using set 3 of the following equation. TIFF0007897234000010.tif3577

[0093] As can be noted in set 3 of equations, in the method according to the present invention, the newly opened phase C voltage is twice as high as in the classical drive, which helps in the faster dissipation of residual current.

[0094] Another feature of the method according to the present invention is that the switching pattern of the method according to the present invention can be associated with any pulse width modulation pattern for BLDC motors, both unipolar and bipolar types, provided that the switching pattern of the method according to the present invention has priority and superimposes the pulse width modulation pattern while there is residual current. For example, as shown in Figure 11, the method according to the present invention can be associated with applying pulse width modulation only to the upper switches S1, S3 and S5. According to Figure 11, it can be noted that during superposition by the switching pattern for faster dissipation of residual current during changes in electrical position, the switches associated with the driven phase remain open while there is residual current, and at the same time, the switches associated with the driven phase are closed.

[0095] Although it is possible to associate all known modulation patterns, the associated pulse width modulation pattern is preferably of the ON_PWM type and unipolar. In this type of pattern, pulse width modulation is only applied to the switches maintained in the drive state during the change in electrical position. Additionally, such pulse width modulation is only applied to the last 60° electrical part of the switch operation, while in the first 60° part, the switch remains continuously on. This can minimize the losses due to switching and torque fluctuations, and can privilege the detection of the final 30° electrical position of a certain electrical position.

[0096] According to this embodiment, by monitoring the phase voltage of the BLDC motor 10, it is possible to determine the application of a switching pattern for accelerating the disappearance of the residual current in the open phase.

[0097] As shown in FIG. 4a, when the residual current i b exits the BLDC motor 10 through the open phase B, the current circulates through the upper freewheel diode D3 and connects the phase voltage to the busbar. Further, as shown in FIG. 5a, when the residual current i b enters the BLDC motor 10 through the open phase B, the residual current i b circulates through the lower freewheel diode D4 and connects the phase voltage to the reference of the inverter. Thus, by measuring the voltage of the open phase of the BLDC motor 10 measured by the voltage observer 40, the generation of the residual current can be indirectly monitored.

[0098] As shown in FIG. 10, the present invention aims to monitor the generation of the residual current by detecting the phase voltages V a , V b , V c , and the busbar voltage V cc , and apply a switching pattern for accelerating the disappearance of the residual current while such a current exists.

[0099] Therefore, the voltage read by the voltage observer 40 is approximately zero, or the busbar voltage V, in the open phase. cc It must be close (nearby). Therefore, the voltage measured in the open phase should be approximately zero or the busbar voltage V cc While nearby, residual current still exists circulating through the BLDC motor 10.

[0100] It is important to emphasize that such monitoring must be continued until the residual current has completely disappeared.

[0101] A second embodiment of the present invention includes a method for controlling the duration of an accelerated extinction method for residual current to protect electrical position detection. The duration of the accelerated extinction method can be adjusted and even canceled when electrical position detection can operate without risk of failure.

[0102] Naturally, the duration of such methods can vary depending on the type of application in which they are used.

[0103] Such adjustments are made to the window time interval t for reading the induced voltage, as seen in Figures 12a and 12b. j , time interval t of accelerated annihilation of residual current f , and the time interval t for residual current extinction e This can be done by measuring.

[0104] The window time interval for reading the induced voltage consists of the time interval from the point in time when the residual current disappears to the point in time when the electrical position of the BLDC motor is detected.

[0105] In addition, the time interval t of the accelerated annihilation of residual current f This consists of a time interval from the point in time when the BLDC motor 10 changes its electrical position and residual current is generated in the open phase of the BLDC motor 10, to the point in time when accelerated extinction of the residual current is no longer required.

[0106] Furthermore, the time interval t for residual current extinction e This consists of the time interval from the moment the BLDC motor 10 changes its electrical position and a residual current is generated in the open phase of the BLDC motor 10 until the residual current disappears.

[0107] The time interval t for the accelerated annihilation of residual current f It is important to emphasize that this must be saturated at its minimum value, i.e., zero, and at its maximum value, i.e., a value equal to the time te of residual current extinction.

[0108] Furthermore, proper detection of the electrical position of the BLDC motor 10 is achieved by the minimum desired time t relative to the window time interval. jmin This requires a minimum window time t. jmin This can itself be defined as a function of the desired minimum electrical distance and the motor speed, where, That is the case. TIFF0007897234000011.tif2159

[0109] Here, Δθ min ω is the minimum electrical distance desired for the safe operation of electrical position detection. e This is the electrical speed of the BLDC motor 10.

[0110] Therefore, the time interval t of the accelerated annihilation of residual current f The increase or decrease of the desired window minimum time t jmin The window time interval t for reading the induced voltage. j It is defined in comparison to [the other party].

[0111] A conceivable practical application of the present invention is intended to prevent overcurrent protection provided by a single current sensor in a busbar, which is ineffective during changes in electrical position, particularly under low-speed release conditions such as motor startup.

[0112] As shown in the paper "Analysis of torque ripple due to phase commutation in brushless DC machines" by Carlson, R. et al., published in IEEE Transactions on Industry Applications in 1992, control via a hysteresis controller with only one sensor is not very effective during changes in electrical position.

[0113] The problem with using only one current sensor on a DC busbar lies in the limitations of such a configuration when monitoring the current of a phase that remains connected during a change of position. This occurs because the current circulating through the current sensor after a change of position is the current circulating through the connected phase, rather than the current of the phase maintained during the change of position.

[0114] For example, in Figure 4a, the change in position occurs between phase B and phase C, while phase A is maintained. In this case, the current circulating through the DC busbar by the current sensor is the current of phase C, i.e., the phase connected during the change in position. Similarly, in Figure 5b, the current circulating through the DC busbar by the current sensor is the current of phase C, i.e., the phase connected during the change in position.

[0115] Therefore, the current in the phase where the connection is maintained is not monitored immediately after the position change, and its amplitude depends on the rate of change of current in both the incoming and outgoing phases during the position change.

[0116] In certain low-speed operation cases, such as when a motor is starting, the incoming current rises rapidly, while the outgoing current takes longer to dissipate due to the motor's low BEMF induction voltage. As a result, as shown in Figure 13a, while the residual current is dissipating, current leaks from the connected phase, causing a transient overcurrent and compromising the motor's overcurrent protection.

[0117] As previously shown, applying a switching pattern to accelerate the elimination of residual current also reduces the current of the phase maintained during the shift. This eliminates overcurrent during the position change, as shown in Figure 13b, ensuring effective protection of the motor against overcurrent even when there is only one current sensor on the busbar.

[0118] In addition to the embodiments described above, the same inventive concept can be applied to other alternative forms or possibilities of using the present invention, such as in automotive air compressors and starter motors.

[0119] While the present invention has been described in relation to certain preferred embodiments, it should be understood that the invention is not intended to be limited to such specific embodiments. Rather, it is intended to encompass all possible substitutes, modifications, and equivalents within the spirit and scope of the invention, as defined by the appended claims.

Claims

1. A method for accelerating the extinction of residual current in a phase that is opened when the electrical position is changed while driving a BLDC motor (10) under high load conditions, The BLDC motor (10) is driven using the unipolar pulse width modulation pattern ON_PWM, By using a voltage observer (40) to monitor the voltage of the open phase, it is determined whether there is residual current, While residual current is circulating in the open phase, and before the next typical event of the electrical position of the BLDC motor (10), the switch (S) of the BLDC motor (10) is closed. １ -S ６ This includes superimposing a pulse width modulation pattern used on the current and applying a switching pattern that generates a larger voltage possible in the open phase in order to accelerate the extinction of the residual current. The aforementioned switching pattern is Opening a phase switch that continues to be driven while the aforementioned electrical position is changed, This includes closing a switch related to the driven phase while changing the electrical position, A method characterized in that, after the residual current has disappeared, the pulse width modulation pattern used for voltage control applied to the BLDC motor (10) is returned.

2. While there is residual current flowing out from the phase opened by the upper freewheel diode, the voltage read by the voltage observer (40) of the open phase is the busbar voltage (V ｃｃ The method according to claim 1, characterized in that it is near the ) and a switching pattern is applied for the accelerated extinction of the residual current.

3. The method according to claim 1, characterized in that, while there is residual current entering through the phase opened by the lower freewheel diode, the voltage read by the voltage observer (40) of the opened phase becomes nearly zero, and a switching pattern is applied for the accelerated elimination of the residual current.

4. The method according to 1 or 2, characterized in that the monitoring of the residual current must be carried out until the current completely disappears.

5. The method according to claim 1, wherein the unipolar pulse width modulation pattern ON_PWM can be replaced with any other unipolar or bipolar pulse width modulation pattern.

6. A method for controlling the duration of the method for accelerating the extinction of residual current according to any one of claims 1 to 5, In order to maintain the detection of the electrical position, the time interval (t) for the accelerated extinction of residual current is determined. ｆ A method that includes adjusting ).

7. The required time interval (t) for the accelerated dissipation of the residual current ｆ ) is the window time interval (t) for reading the induced voltage. ｊ ), minimum window time interval (t ｊｍｉｎ ), and the time interval (t) between the extinction of residual current ｅ The method according to claim 6, characterized by depending on ).

8. The window time interval (t ｊ ) is composed of the time interval from the point when the residual current disappears to the point when the electrical position of the BLDC motor (10) is detected, The method according to claim 7, characterized in that.

9. The time interval (t) between the disappearance of the residual current ｅ The method according to 7, characterized in that the interval is comprised of the time interval from the moment when the BLDC motor (10) changes its electrical position and a residual current is generated in the open phase of the BLDC motor (10) until such residual current disappears.

10. The time interval (t) for the accelerated disappearance of the residual current ｆ ) is its minimum value, i.e., zero, and its maximum value, i.e., the disappearance of the residual current (t ｅ The method according to 7, characterized in that it can be saturated with a value equal to ).

11. The minimum window time interval (t ｊｍｉｎ ) is defined, and the minimum electrical distance (Δθ) desired for the safe operation of the electrical position detection is defined. ｍｉｎ ) and the electrical speed (ω) of the BLDC motor (10) ｅ The method according to 7, characterized in that it is a function of ).

12. The time interval (t) for the accelerated disappearance of the residual current ｆ An increase or decrease in the minimum window time interval (t) ｊｍｉｎ ) and the window time interval (t) for reading the induced voltage ｊ The method according to any one of claims 6 to 11, characterized in that it is defined by comparing with ).

13. The method according to any one of claims 1 to 12, characterized in that the application of a switching pattern for the accelerated extinction of the residual current results in a reduction of current in the phase that remains on during the change of position, avoiding limiting the protection of low-speed overcurrents provided by a single current sensor in the busbar, and promoting more effective protection of the BLDC motor (10) against overcurrents.

14. When the BLDC motor (10) is started, the time interval (t) for the accelerated disappearance of the residual current occurs. ｆ ) is the time (t) for residual current to disappear. ｅ The method according to any one of claims 1 to 13, characterized in that it must be equal to ).

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