Control system for single-phase brushless direct current motor

Abstract

The application provides a control system of a single-phase brushless DC motor, comprising: a power limiting module configured to generate a power limiting signal according to a power limiting condition, an actual power and a limited power; a PWM adjusting module configured to output a PWM modulation duty cycle given quantity to a speed regulator according to an input bus voltage of a control panel, the power limiting signal and a reference speed; wherein when the actual power exceeds the limited power, the power limiting signal causes the PWM adjusting module to reduce the reference speed, so as to reduce the PWM modulation duty cycle given quantity output by the speed regulator, so as to reduce an actual speed; and a lead angle calculation module configured to calculate a lead angle according to the reference speed, the actual speed, the PWM modulation duty cycle given quantity and the actual power.

Description

Technical Field

[0001] This invention relates to the field of intelligent control technology, and in particular to a control system for a single-phase brushless DC motor. Background Technology

[0002] Currently, permanent magnet synchronous single-phase motor drives perform commutation based on Hall effect status (180 degrees per cycle). For example... Figure 1 As shown, when the Hall angle is between 0 and 180 degrees, switch AH performs PWM modulation, switch BL is on, and switches BH and AL are off; when the Hall angle is between 180 and 360 degrees, switch BH performs PWM modulation, switch AL is on, and switches AH and BL are off; this cycle repeats once per electrical cycle to ensure normal motor operation.

[0003] This control method results in a current response with a large rising slope because the decrease in back electromotive force occurs at the beginning and end of each commutation cycle, which leads to uneven current. Summary of the Invention

[0004] The purpose of this invention is to provide a control system for a single-phase brushless DC motor to solve the problem of large commutation current spikes in existing single-phase motors using PWM_ON control technology.

[0005] The present invention also aims to provide a control system for a single-phase brushless DC motor to solve the problem of low efficiency in existing single-phase motors using PWM_ON control technology.

[0006] The present invention also aims to provide a control system for a single-phase brushless DC motor to solve the problem that the speed cannot be maximized in the existing single-phase motor using PWM_ON control technology.

[0007] To solve the above-mentioned technical problems, the present invention provides a control system for a single-phase brushless DC motor, comprising:

[0008] The power limiting module is configured to generate a power limiting signal based on the power limiting conditions, the actual power, and the limited power.

[0009] The PWM adjustment module is configured to output a PWM modulation duty cycle setpoint based on the input bus voltage of the control board, the power limit signal, and the reference speed via a speed regulator. When the actual power exceeds the power limit, the power limit signal causes the PWM adjustment module to reduce the reference speed, thereby reducing the PWM modulation duty cycle setpoint output by the speed regulator and ultimately reducing the actual speed.

[0010] The lead angle calculation module is configured to calculate the lead angle based on the reference speed, actual speed, PWM modulation duty cycle setpoint, and actual power.

[0011] Optionally, in the control system of the single-phase brushless DC motor described above, the PWM adjustment module is configured to perform the following actions:

[0012] Obtain bus voltage and reference speed;

[0013] Calculate the actual rotational speed based on the bus voltage;

[0014] The actual speed and reference speed are provided to the speed regulator to calculate the PWM modulation duty cycle setpoint;

[0015] Based on the given PWM modulation duty cycle, the actual speed is followed, and thus the actual power is followed.

[0016] Optionally, in the control system of the single-phase brushless DC motor described above, the power limiting module is configured to perform the following actions:

[0017] Obtain bus voltage, bus current, reference speed, and power limit;

[0018] The actual power is obtained based on the bus voltage and bus current;

[0019] When the actual power exceeds the limit power, the reference speed is reduced so that the PWM modulation duty cycle setpoint is reduced after passing through the speed regulator, thereby reducing the actual speed and thus reducing the output power.

[0020] Optionally, in the control system of the single-phase brushless DC motor described above, the lead angle calculation module is configured to perform the following actions:

[0021] Obtain the bus voltage, reference speed, actual speed, and PWM modulation duty cycle setpoint;

[0022] The actual power is obtained based on the bus voltage;

[0023] Determine whether the actual power exceeds the power limit and obtain the determination result;

[0024] The lead angle is calculated based on the reference speed, actual speed, PWM modulation duty cycle setpoint, and judgment results.

[0025] Optionally, in the control system of the single-phase brushless DC motor described above, the single-phase brushless DC motor is a permanent magnet synchronous single-phase motor. The first switch is connected between the DC power supply and the first phase of the motor, the second switch is connected between the first phase of the motor and ground, the third switch is connected between the DC power supply and the second phase of the motor, and the fourth switch is connected between the second phase of the motor and ground.

[0026] When the Hall angle of the single-phase brushless DC motor is within the first reference angle range, the Hall sensor outputs the first detection state.

[0027] When the Hall angle of the single-phase brushless DC motor is within the second reference angle range, the Hall sensor outputs the second detection state.

[0028] Optionally, in the control system of the single-phase brushless DC motor described above, the second switch and the fourth switch are turned on;

[0029] When the actual operating angle is equal to the sum of the first reference angle range and the lead angle, the first switch performs PWM modulation and the second switch is turned off.

[0030] When the actual operating angle equals the sum of the second reference angle range and the lead angle, the second switch performs PWM modulation, and the first switch is turned off.

[0031] Optionally, in the control system of the single-phase brushless DC motor described above,

[0032] The dynamic lead angle is generated based on the comparison between the actual speed and the reference speed, and the reference speed and output power are adjusted at any time.

[0033] The dynamic lead angle is limited and filtered.

[0034] By using a limiting factor with a given duty cycle in PWM modulation, the lead angle θ is made... Ahead This is a dynamically adjusted value;

[0035] When the reference speed is greater than the actual speed, and the PWM modulation duty cycle setpoint exceeds the PWM limit value, the error value θ between the actual speed and the reference speed is used. Err The lead angle θ is calculated through PI adjustment of the lead angle calculation module. Ahead :

[0036] θ Err =TargetSpeed ​​- RealSpeed

[0037] θ Ahead =k p θ Err +k i ∫θ Err d t

[0038] in:

[0039] TargetSpeed ​​is the reference speed, RealSpeed ​​is the actual speed, and k is the reference speed. p k is the proportional adjustment constant. i This is the integral adjustment constant.

[0040] Optionally, in the control system of the single-phase brushless DC motor described above, the calculation process of the Hall angle includes:

[0041] After detecting changes in two consecutive Hall position signals, record the time T between the two consecutive Hall position signals and the average electrical angular velocity ω of the motor. n for:

[0042]

[0043] The electrical angle change in each PWM cycle is:

[0044]

[0045] ω n θ is the average electric angular velocity; e The angle changes for each PWM cycle.

[0046] Optionally, in the control system of the single-phase brushless DC motor described above, the actual operating angle is the sum of the lead angle and the Hall angle, and the actual operating angle is:

[0047] θ=θ e +θ Ahead

[0048] θ is the actual rotor angle;

[0049] The commutation is performed every 180 degrees based on the calculated actual rotor angle.

[0050] The inventors of this invention discovered through research that existing control methods suffer from a large current response with a steep rise slope due to the decrease in back electromotive force occurring at the beginning and end of each commutation cycle. This results in uneven current flow. Such peak currents lead to noise and increased component costs, and significantly reduce the overall efficiency of different wind turbines across a wide range of speed control applications. Therefore, technical means should be adopted to control current peaks to improve efficiency and reduce the need for exceeding specified device specifications.

[0051] The inventors of this invention also discovered that, since the motor coil is an inductive load, the current in the coil will have a certain time delay relative to the applied voltage on the coil, thereby affecting the efficiency of the motor and generating noise. The fundamental reason for the low efficiency is that the time delay of the inductive load leads to a large current. Therefore, we introduce the concept of lead angle conduction to counteract the useless work done by the motor caused by the inductive load delay, thereby improving efficiency and reducing the peak current.

[0052] In the control system for a single-phase brushless DC motor provided by this invention, the speed (actual speed and reference speed) and duty cycle (PWM modulation duty cycle setpoint) are determined, and the speed error (error value θ between actual speed and reference speed) is considered. ErrThe lead angle is calculated using a PID control algorithm in the lead angle calculation module, thereby reducing commutation peak current and improving motor speed and efficiency. The lead angle calculation also takes power limitations into account, further enhancing reliability. Attached Figure Description

[0053] Figure 1 This is a schematic diagram of an existing single-phase brushless DC motor circuit;

[0054] Figure 2 This is a schematic diagram of the control system of a single-phase brushless DC motor according to an embodiment of the present invention;

[0055] Figure 3 This is a schematic diagram of the control method of a single-phase brushless DC motor control system according to an embodiment of the present invention;

[0056] Figure 4 This is a schematic diagram of the angle waveform of the control method of the control system of a single-phase brushless DC motor in one embodiment of the present invention;

[0057] Figure 5 This is a schematic diagram of the current waveform of the control method of the control system of a single-phase brushless DC motor in one embodiment of the present invention.

[0058] Figure 6 This is a schematic diagram of the current waveform of the control method of the control system of a single-phase brushless DC motor in one embodiment of the present invention. Detailed Implementation

[0059] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0060] It should be noted that the components in the various figures may be shown exaggeratedly for illustrative purposes and are not necessarily to scale. In each figure, the same reference numerals are used for components that are identical or have the same function.

[0061] In this invention, unless otherwise specified, "arranged on," "arranged above," and "arranged on" do not exclude the possibility of an intermediate element between them. Furthermore, "arranged on or above" merely indicates the relative positional relationship between two components, and in certain cases, such as when the product orientation is reversed, it can also be converted to "arranged below or under," and vice versa.

[0062] In this invention, the various embodiments are merely intended to illustrate the solutions of the invention and should not be construed as limiting.

[0063] In this invention, unless otherwise specified, the quantifiers “a” and “one” do not exclude scenarios involving multiple elements.

[0064] It should also be noted that, in the embodiments of the present invention, only a portion of the components or parts may be shown for clarity and simplicity. However, those skilled in the art will understand that, under the teachings of the present invention, necessary components or parts can be added as needed for specific scenarios. Furthermore, unless otherwise stated, features in different embodiments of the present invention can be combined with each other. For example, a feature in the second embodiment can replace a corresponding or functionally identical or similar feature in the first embodiment, and the resulting embodiment will also fall within the scope of disclosure or description of this application.

[0065] It should also be noted that, within the scope of this invention, the terms "same," "equal," and "equal to" do not imply that the two values ​​are absolutely equal, but rather allow for a certain reasonable margin of error. In other words, the terms also encompass "substantially the same," "substantially equal," and "substantially equal to." Similarly, in this invention, the directional terms "perpendicular to," "parallel to," etc., also encompass the meanings of "substantially perpendicular to" and "substantially parallel to."

[0066] Furthermore, the numbering of the steps in the methods of the present invention does not limit the execution order of the method steps. Unless otherwise specified, the method steps may be executed in different orders.

[0067] The control system for a single-phase brushless DC motor proposed in this invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of this invention will become clearer from the following description and claims. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of this invention.

[0068] The purpose of this invention is to provide a control system for a single-phase brushless DC motor, so as to solve the problems of large commutation current spikes, low efficiency and inability to achieve maximum speed output in existing single-phase motors using PWM_ON control technology.

[0069] To achieve the above objectives, the present invention provides a control system for a single-phase brushless DC motor, comprising: a power limiting module configured to generate a power limiting signal based on a power limiting condition, the actual power, and the limiting power; a PWM adjustment module configured to output a PWM modulation duty cycle setpoint based on the input bus voltage of the control board, the power limiting signal, and a reference speed via a speed regulator; wherein, when the actual power exceeds the limiting power, the power limiting signal causes the PWM adjustment module to reduce the reference speed, thereby reducing the PWM modulation duty cycle setpoint output by the speed regulator, and thus reducing the actual speed; and a lead angle calculation module configured to calculate the lead angle based on the reference speed, the actual speed, the PWM modulation duty cycle setpoint, and the actual power.

[0070] This embodiment provides a control system for a single-phase brushless DC motor, including: a PWM adjustment module configured to output a PWM modulation duty cycle setpoint based on the input bus voltage of the control board and a reference speed via a speed regulator, so that the actual speed follows the response; a power limiting module configured to reduce the reference speed with a power limiting signal when the actual power exceeds the power limit, so that the PWM modulation duty cycle setpoint output by the PWM adjustment module can be reduced after passing through the speed regulator, thereby reducing the actual speed and thus reducing the output power; and a lead angle calculation module configured to calculate the lead angle based on the reference speed, the actual speed, the PWM modulation duty cycle setpoint, and the actual power. In another embodiment, the PWM modulation duty cycle setpoint can also be directly reduced based on the power limiting signal.

[0071] In one embodiment of the present invention, such as Figure 2 As shown, in the control system of the single-phase brushless DC motor, the PWM adjustment module is configured to perform the following actions: acquire the bus voltage and reference speed; calculate the actual speed based on the bus voltage; provide the actual speed and reference speed to the speed regulator to calculate the PWM modulation duty cycle setpoint; and perform a follow-up response on the actual speed based on the PWM modulation duty cycle setpoint, thereby performing a follow-up response on the actual power.

[0072] In one embodiment of the present invention, in the control system of the single-phase brushless DC motor, the power limiting module is configured to perform the following actions: acquire bus voltage, bus current, reference speed and limiting power; acquire actual power based on bus voltage and bus current; determine that when the actual power exceeds the limiting power, reduce the reference speed so that the PWM modulation duty cycle setpoint is reduced after passing through the speed regulator, thereby reducing the actual speed and thus reducing the output power.

[0073] In one embodiment of the present invention, in the control system of the single-phase brushless DC motor, the lead angle calculation module is configured to perform the following actions: obtain the bus voltage, reference speed, actual speed and PWM modulation duty cycle setpoint; obtain the actual power based on the bus voltage; determine whether the actual power exceeds the limit power and obtain the determination result; calculate the lead angle based on the reference speed, actual speed, PWM modulation duty cycle setpoint and determination result.

[0074] In one embodiment of the present invention, in the control system of the single-phase brushless DC motor, the single-phase brushless DC motor is a permanent magnet synchronous single-phase motor. A first switch is connected between the DC power supply and the first phase of the motor, a second switch is connected between the first phase of the motor and ground, a third switch is connected between the DC power supply and the second phase of the motor, and a fourth switch is connected between the second phase of the motor and ground. When the Hall angle of the single-phase brushless DC motor is within a first reference angle range, the Hall sensor outputs a first detection state; when the Hall angle of the single-phase brushless DC motor is within a second reference angle range, the Hall sensor outputs a second detection state.

[0075] In one embodiment of the present invention, in the control system of the single-phase brushless DC motor, the second switch and the fourth switch are turned on; when the actual operating angle is equal to the sum of the first reference angle range and the lead angle, the first switch performs PWM modulation and the second switch is turned off; when the actual operating angle is equal to the sum of the second reference angle range and the lead angle, the second switch performs PWM modulation and the first switch is turned off.

[0076] In one embodiment of the present invention, in the control system of the single-phase brushless DC motor, when the bus voltage is less than the reference voltage and the difference between the two is greater than the voltage threshold, the lead angle that can increase the speed within the power limit range is calculated; when the bus voltage is greater than or equal to the reference voltage, the speed regulator outputs the PWM modulation duty cycle setpoint according to the reference speed and the actual speed, and monitors the relationship between the actual power and the power limit in real time, and adjusts the PWM modulation duty cycle setpoint in real time according to the judgment result, and calculates the lead angle.

[0077] In one embodiment of the present invention, such as Figure 3 As shown, first, a reference speed is set. It is then determined whether the actual speed is less than the reference speed. If so, a PWM limit value is set; otherwise, a PI inverse operation is performed to adjust the lead angle. After setting the PWM limit value, it is further determined whether the PWM modulation duty cycle setpoint is greater than the PWM limit value. If so, it is determined whether the lead angle is less than the limited lead angle; otherwise, a PI inverse operation is performed to adjust the lead angle. When determining whether the lead angle is less than the limited lead angle, if the lead angle is less than the limited lead angle, a PI forward operation is performed to adjust the lead angle; otherwise, the process returns to the step of setting the reference speed. After performing the PI forward (inverse) operation adjustment of the lead angle, the entire process ends.

[0078] In one embodiment of the present invention, in the control system of the single-phase brushless DC motor, a dynamic lead angle is generated based on the comparison between the actual speed and the reference speed, and the reference speed and output power are adjusted in real time; the dynamic lead angle is limited and filtered; and the lead angle θ is controlled by a limiting factor given by the PWM modulation duty cycle. AheadThis is a dynamically adjusted value; when the reference speed is greater than the actual speed, and the PWM modulation duty cycle setpoint exceeds the PWM limit value, the value is adjusted based on the error θ between the actual speed and the reference speed. Err The lead angle θ is calculated through PI adjustment of the lead angle calculation module. Ahead :

[0079] θ Err =TargetSpeed ​​- RealSpeed

[0080] θ Ahead =k p θ Err +k i ∫θ Err d t

[0081] in:

[0082] TargetSpeed ​​is the reference speed, RealSpeed ​​is the actual speed, and k is the reference speed. p k is the proportional adjustment constant. i This is the integral adjustment constant.

[0083] In one embodiment of the present invention, in the control system of the single-phase brushless DC motor, the calculation process of the Hall angle includes: after detecting the change of two adjacent Hall position signals, recording the time T between the two adjacent Hall position signals, and the average electrical angular velocity ω of the motor. n for:

[0084]

[0085] The electrical angle change in each PWM cycle is:

[0086]

[0087] ω n θ is the average electric angular velocity; e The angle changes for each PWM cycle.

[0088] In one embodiment of the present invention, such as Figure 4 As shown, in the control system of the single-phase brushless DC motor, the actual operating angle is the sum of the lead angle and the Hall angle. The actual operating angle is:

[0089] θ=θ e +θ Ahead

[0090] θ is the actual rotor angle;

[0091] The commutation is performed every 180 degrees based on the calculated actual rotor angle. At this time, the commutation is performed every 180 degrees based on the calculated θ, that is, AHBL is turned on from 0 to 180 degrees and BHAL is turned on from 180 to 360 degrees, thereby increasing the motor speed and improving the problems of peak current and low efficiency.

[0092] In the simulation method of this embodiment, a single-phase brushless DC cooling fan system is used. The motor is an IPMSM (10-408Hz), with a power of <300W and a voltage range of DC 36V~76V. When the reference speed is 315Hz, and conventional PWM_ON processing is used, such as... Figure 5 As shown, the motor speed is too low, the noise is high, the power devices overheat severely, and the phase current waveform shows spikes. After introducing lead angle control technology, the motor speed reaches 315Hz and efficiency is improved, as shown below. Figure 6 As shown, the power device heat generation is significantly reduced and the peak current is cut off.

[0093] In the control system for a single-phase brushless DC motor provided by this invention, the speed (actual speed and reference speed) and duty cycle (PWM modulation duty cycle setpoint) are determined, and the speed error (error value θ between actual speed and reference speed) is considered. Err By calculating the lead angle through PID control, the commutation peak current is reduced, thereby improving motor speed and efficiency. The lead angle calculation also takes power limitations into account, further enhancing reliability.

[0094] In summary, the above embodiments have provided detailed descriptions of different configurations of the control system for a single-phase brushless DC motor. Of course, this invention includes, but is not limited to, the configurations listed in the above embodiments. Any modifications made based on the configurations provided in the above embodiments are within the scope of protection of this invention. Those skilled in the art can apply the knowledge gained from the above embodiments to other situations.

[0095] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple; relevant parts can be referred to the method section.

[0096] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the claims.

Claims

1. A control system for a single phase brushless DC motor, characterised in that, The method comprises the following steps: a power limiting module configured to generate a power limiting signal according to an actual power and a limit power; a PWM adjusting module configured to output a PWM modulation duty ratio given amount according to an input actual speed and a reference speed through a speed regulator; wherein when the actual power exceeds the limit power, the power limiting signal causes the PWM adjusting module to reduce the reference speed, so as to reduce the PWM modulation duty ratio given amount output by the speed regulator, and to reduce the actual speed; and a lead angle calculation module configured to calculate a lead angle according to the reference speed, the actual speed and the PWM modulation duty ratio given amount, wherein the single-phase brushless DC motor is a permanent magnet synchronous single-phase motor, the first switch is connected between a DC power supply and a first phase of the motor, the second switch is connected between the first phase of the motor and the ground, the third switch is connected between the DC power supply and a second phase of the motor, and the fourth switch is connected between the second phase of the motor and the ground; when the Hall angle of the single-phase brushless DC motor is in a first reference angle range, the Hall sensor outputs a first detection state; when the Hall angle of the single-phase brushless DC motor is in a second reference angle range, the Hall sensor outputs a second detection state, when the actual running angle is equal to the sum of the first reference angle range and the lead angle, the first switch is PWM modulated and the second switch is turned off; when the actual running angle is equal to the sum of the second reference angle range and the lead angle, the third switch is PWM modulated and the fourth switch is turned off, a dynamic lead angle is generated according to the comparison result of the actual speed and the reference speed, and the reference speed and the output power are adjusted in real time; the dynamic lead angle is limited and filtered; The leading angle is given by PWM modulation of the duty cycle by a given amount of the limiting factor is a dynamic adjustment value; When the reference rotation speed is greater than the actual rotation speed, and the PWM modulation duty cycle is given by a certain amount exceeding the PWM limiting value, the lead angle is calculated by a PI regulator of a lead angle calculation module according to the error value between the actual rotation speed and the reference rotation speed : the lead angle calculated by the PI regulator of the lead angle calculation module : + wherein: Integral adjustment constant, the calculation process of the Hall angle comprises: After detecting the change of the two adjacent Hall position signals, the time T between the two adjacent Hall position signals is recorded, and the average electrical angular velocity of the motor is calculated as follows: is: the electrical angle changes every PWM period are: is the average electrical angular velocity; is the varying angle per PWM cycle, the actual running angle is the sum of the lead angle and the Hall angle, and the actual running angle is: is the actual rotor angle; the commutation is performed every 180 degrees according to the calculated actual rotor angle.

2. The control system of a single-phase brushless DC motor as recited in claim 1, wherein, The PWM adjusting module is configured to perform the following actions: obtain the actual speed and the reference speed; provide the actual speed and the reference speed to the speed regulator to calculate the PWM modulation duty ratio given amount; perform the following actions according to the PWM modulation duty ratio given amount:

3. The control system of a single-phase brushless DC motor as recited in claim 1, wherein, obtain the bus voltage, the bus current, the reference speed and the limit power; obtain the actual power according to the bus voltage and the bus current; when the actual power exceeds the limit power, reduce the reference speed to reduce the PWM modulation duty ratio given amount after the speed regulator, reduce the actual speed, and thus reduce the output power. The lead angle calculation module is configured to perform the following actions:

4. The control system of a single-phase brushless DC motor as recited in claim 1, wherein, obtain the bus voltage, the reference speed, the actual speed and the PWM modulation duty ratio given amount; calculate the lead angle according to the reference speed, the actual speed and the PWM modulation duty ratio given amount. ​

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