Low-rotation-speed operation control method of pump and operation control method of water pump

Abstract

The invention provides a low-rotating-speed operation control method of a pump and an operation control method of a water pump, and the low-rotating-speed operation control method of the pump comprises the steps that S1, when the current rotating speed of a motor of the water pump is lower than a rotating speed threshold value, a voltage signal Ud1 based on a preset frequency and a preset amplitude is applied to an initial set direct axis d1 of the motor; s2, calculating a current signal Id1 on an initially set direct axis d1 and a current signal Iq1 on an initially set quadrature axis q1; s3, multiplying the current signal Iq1 after band-pass filtering based on a preset frequency by a shaping factor to obtain a current signal Iq2, and performing first low-pass filtering processing on the current signal Iq2 to obtain a current signal Iq3; s4, the current signal Iq3 is input into a PI controller, the PI controller adjusts the included angle theta between the initial set direct axis d1 and the actual direct axis d, and the PI controller outputs the included angle theta as a first target angle and a second target angle; s5, performing second low-pass filtering on the current signal Id1 to obtain a current signal Id2; and according to the current signal Id2, obtaining the position of the actual direct axis d.

Description

Technical Field

[0001] The invention belongs to the technical field of canned pump control, and in particular relates to a low-speed operation control method of a pump and an operation control method of a water pump. Background Art

[0002] The existing water pump motor starting control uses a position sensorless control. The calculation of the position sensorless control relies on the back electromotive force generated by the rotor rotation estimated by the software. However, the magnitude of the back electromotive force is proportional to the motor speed. At low speeds, the back electromotive force is very small, and the signal-to-noise ratio of the control method based on the back electromotive force observer is very poor. It is impossible to estimate the position of the motor rotor based on the back electromotive force. Therefore, the motor start-up generally adopts a three-stage control method, which includes positioning, open-loop acceleration and closed-loop operation. The low speed range is skipped through open-loop acceleration, thereby achieving stable operation of the motor. The above signal-to-noise ratio refers to the ratio of the voltage of the amplifier's output signal to the noise voltage output at the same time. The higher the signal-to-noise ratio of the device, the less noise is generated.

[0003] like Figure 1 As shown in the flow-head performance curve of the water pump, the water pump can only work within the range of zone 1 in the figure, where curve I is the working curve of the flow and head of the water pump under the condition of maximum speed. Curve II is the flow and head curve of the water pump when the water pump is installed in the circulation system, the pipeline resistance of the circulation system where the water pump is located is constant, and the water pump is under different speed conditions. Curve III is the flow and head curve of the water pump under the condition of minimum speed.

[0004] The area 1 surrounded by the above curves I, II and III is the working area of ​​the water pump. The area outside the above curves II and I is area 2. The water pump works in area 2 and is limited by the rated power of the selected water pump. The area between the above curve II and the X-axis with a head of 0 is area 3. The water pump works in area 3 and is limited by the pipe resistance in the circulation system where the water pump is installed. The area between the above curves II and III and the Y-axis with a flow rate of 0 is area 4. The water pump works in area 4 and is limited by the minimum speed of the water pump. The water pump cannot work in area 4 when it is started.

[0005] The specific reasons why the water pump cannot work in zone 4 when it is started are:

[0006] The existing control method for detecting the motor rotor position using a position-free observer is generally used in the open-loop driving stage of the motor. Specifically, the control method for detecting the motor rotor position using a position-free observer is that the operation of the motor relies on the electromagnetic field generated by the stator coil being energized to drive the magnetic field of the permanent magnet rotor to generate torque. Therefore, the position of the stator coil can be determined only when the rotor position is known in real time.

[0007] The above-mentioned open-loop dragging stage refers to applying current to the stator coil to generate a magnetic field and dragging the rotor to rotate when the rotor position of the motor is uncertain. In this open-loop dragging stage, since the position of the rotor is unknown, in order to start the motor, a larger current is usually applied to the stator coil to generate a larger torque. If the current applied to the stator coil is too large during this stage, the starting torque of the motor will be large. In order to protect the motor and hardware, the current of the stator coil needs to be limited. When it is detected that the current exceeds the predetermined value, the overcurrent protection will be triggered, which will cause the motor to fail to start. If the current applied to the stator coil is too small, the torque generated is small, resulting in the rotor coil being unable to rotate synchronously with the stator magnetic field, thereby causing the motor to lose step.

[0008] Therefore, when the motor is working at a low speed, the back EMF is very small and the position cannot be found through the back EMF. The control method based on the back EMF observer estimates the motor rotor position, which limits the minimum stable operating speed of the water pump and makes it impossible to find the position through the back EMF. Figure 1 The low flow and small head area shown, that is Figure 1 Work within Zone 4. Summary of the invention

[0009] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a low-speed operation control method for a pump, so that when the current operating speed of the water pump is lower than the speed threshold, the true position of the rotor of the water pump's motor can be obtained, and when the water pump is started, it can directly perform closed-loop operation at zero speed, and the water pump can operate within 4 zones of the pump's flow-head curve.

[0010] This embodiment also provides an operation control method for a water pump, which can enable the current operating speed of the water pump to operate stably within the hysteresis range.

[0011] To achieve this object, the present invention adopts the following technical solutions:

[0012] A method for controlling low-speed operation of a pump, comprising:

[0013] S1. When the current speed of the water pump motor is lower than the speed threshold, a voltage signal U based on a preset frequency and a preset amplitude is applied to the initial set direct axis d1 of the motor. d1 , the preset frequency is greater than the rotational speed frequency of the motor and is in a first preset ratio; the preset amplitude is less than the rated DC voltage of the motor and is in a second preset ratio;

[0014] S2, detect the three-phase current signal of the motor, and calculate the current signal I on the initial set direct axis d1 d1 , and the initial setting of the current signal I on the quadrature axis q1q1 ;

[0015] S3, the current signal I after bandpass filtering based on the preset frequency q1 The current signal I is obtained by multiplying the shaping factor q2 , and the current signal I q2 Perform the first low-pass filtering to obtain the current signal I q3 , the cut-off frequency of the first low-pass filter is less than the preset frequency; wherein the shaping factor is set to make the current signal I q2 It is related to the angle θ between the initial straight axis d1 and the actual straight axis d;

[0016] S4, the current signal I q3 The PI controller is used to adjust the angle θ until the current signal I q3 When a preset value is reached, the PI controller outputs the angle θ as a first target angle and a second target angle, the first target angle is smaller than the second target angle, and the difference between the second target angle and the first target angle is a first predetermined angle;

[0017] S5, current signal I d1 Perform a second low-pass filter to obtain the current signal I d2 , the cut-off frequency of the second low-pass filter is not less than a preset frequency;

[0018] According to the current signal I d2 The angle θ is determined to be a first target angle or a second target angle to obtain the position of the actual direct axis d-axis.

[0019] Preferably, in step S1, applying a voltage signal based on a preset frequency and a preset amplitude to an initially set direct axis d1 of the motor includes:

[0020] The voltage signal is U d1 =U hfi cos(ωt), the preset amplitude is U hfi , U hfi is 1 / 20-1 / 10 of the stable voltage value of the DC voltage loaded on the motor; the preset frequency is the voltage signal frequency ω, and the voltage signal frequency ω is 10-20 times the speed frequency of the motor of the water pump; U q1 =0.

[0021] Preferably, in step S1, the voltage signal U d1 After inverse Park transformation and inverse Clark transformation, it is converted into a three-phase voltage signal and loaded on the initially set direct axis D1 axis.

[0022] Preferably, step S2 detects the three-phase current signal of the motor, and calculates the current signal I on the initial set direct axis d1 through Clark transformation and Park transformation. d1 The current signal I on the initial setting quadrature axis q1 q1 .

[0023] Preferably, in step S2, the current signal I of the initially set quadrature axis q1 is calculated. q1 for:

[0024]

[0025] Among them, L d is the direct-axis inductance, L q is the quadrature-axis inductance.

[0026] Preferably, the shaping factor in step S3 is sin(ωt).

[0027] Preferably, in step S4, the current signal I q3 =0, the first target angle output by the PI controller is 0°, and the second target angle is π.

[0028] Preferably, in step S5, according to the current signal I d2 Determining the angle θ as a first target angle or a second target angle includes:

[0029] For the current signal I d2 The absolute value of the peak value is compared with the absolute value of the valley value;

[0030] If the current signal I d2 If the absolute value of the peak value is greater than the absolute value of the valley value, it is determined that the angle output by the PI controller is the first target angle;

[0031] If I d2 If the absolute value of the peak value is smaller than the absolute value of the valley value, it is judged that the angle output by the PI controller is the second target angle.

[0032] A method for controlling the operation of a water pump, comprising:

[0033] Determining the current operating speed of the motor of the water pump;

[0034] When the current operating speed of the motor is lower than the first preset speed S1, the motor operates in the mode of the low speed operation control method of the pump according to any one of claims 1 to 8;

[0035] When the current operating speed of the motor is higher than a second preset speed S2, the second preset speed S2 is greater than the first preset speed S1, and the motor operates in the mode of the control method based on the back-EMF observer;

[0036] When the current operating speed of the motor is between the first preset speed S1 and the second preset speed S2, the motor operates in one of the low speed operation control method mode of the pump and the back-EMF observer-based control method mode.

[0037] Preferably, in the speed-up phase of the motor in the time period t1-t3, the speed of the motor at time t1 is a first preset speed S1, the speed of the motor at time t2 is the moment when the angle of the stator of the motor is detected, and the speed of the motor at time t3 is a second preset speed S2;

[0038] In the time period t1-t2, the motor operates in one of the low speed operation control method mode of the pump and the control method mode based on the back electromotive force observer;

[0039] After time t2, the motor operates in the mode of the control method based on the back-EMF observer, and the low-speed operation control method mode of the pump is turned off;

[0040] And / or, the motor is in a deceleration phase in a time period of t4-t6, the speed of the motor at time t4 is the second preset speed S2, the motor is at a time when the angle of the stator of the motor is detected at time t5, the speed of the motor at time t6 is the first preset speed S1, and the speed of the motor at time t7 is 0;

[0041] During the time period t4-t5, one of the low speed operation control method of the motor selection pump and the control method based on the back electromotive force observer is operated;

[0042] The motor is operated using the low speed operation control method of the pump during the time period t5-t6, and the mode of the back-EMF observer-based control method is turned off.

[0043] Compared with the prior art, the present invention has the following beneficial effects: the low-speed operation control method of the pump in the present invention can obtain the true position of the rotor when the rotor is in a stationary state, and when the water pump is started, it can directly enter closed-loop operation at zero speed.

[0044] Moreover, the control method enables the water pump to operate stably under different working conditions, thus filling the gap of the water pump operating stably in the 4 zones of the flow-head performance curve of the water pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1is the flow-lift performance curve of the water pump in the prior art;

[0046] Figure 2 It is a flow chart of the low speed operation control method of the pump in the present invention;

[0047] Figure 3 is the voltage signal U applied on the initial setting direct axis d1 in the present invention. d1 Schematic diagram of

[0048] Figure 4 This is a working principle diagram of the low speed operation control method of the pump in the present invention;

[0049] Figure 5 It is a working principle diagram of the operation control method of the water pump in the present invention;

[0050] Figure 6 The current signal I of the initial setting quadrature axis q1 axis in the present invention is q1 and the angle θ;

[0051] Figure 7 The current signal I of the initial setting quadrature axis q1 axis in the present invention is q1 Multiply by sin(ωt) to get the current signal I q2 and the angle θ;

[0052] Figure 8 is the current signal I in the present invention q2 A relationship diagram between the current signal Id3 obtained after the second low-pass filtering and the angle θ;

[0053] Fig. 9 It is a schematic diagram of the working mode of the water pump operation control method in the present invention under the time and speed of the speed increase stage;

[0054] Fig.10 It is a schematic diagram of the working mode of the water pump operation control method in the present invention under the time and speed of the deceleration stage;

[0055] Fig.11 This is a phase current waveform diagram actually tested when the motor in the present invention is working. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0057] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0058] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0059] In the description of the present invention, it should be noted that the terms "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or are the positions or positional relationships in which the inventive product is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0060] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "disposed" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0061] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0062] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0063] like Figure 2-Figure 8 As shown, this embodiment provides a low speed operation control method for a pump, including S1, when the current speed of the motor of the water pump is lower than the speed threshold, applying a voltage signal U based on a preset frequency and a preset amplitude to the initial set direct axis d1 of the motor d1 The preset frequency is greater than the motor speed frequency and is in a first preset ratio; the preset amplitude is less than the rated DC voltage of the motor and is in a second preset ratio.

[0064] In this embodiment, the actual direct axis of the motor of the water pump is the d axis, and the quadrature axis of the motor is the q axis. It is assumed that the direct axis of the motor at the initial position is the initially set direct axis d1 axis, and the quadrature axis of the motor at the initial position is the initially set quadrature axis q1 value. The angle between the initially set direct axis d1 axis of the motor and the actual direct axis d axis is θ.

[0065] In step S1, a voltage signal based on a preset frequency and a preset amplitude is applied to the initial set direct axis d1 of the motor, including:

[0066] The voltage signal U d1 =U hfi cos(ωt), the preset amplitude is U hfi , U hfi The preset frequency is the voltage signal frequency ω, which is 10-20 times the speed frequency of the motor of the water pump. The voltage signal U applied to the initial setting of the quadrature axis q1 value is q1 =0.

[0067] The power supply of the motor of the water pump is direct current, and the direct current voltage refers to the voltage value of the direct current power supply when the motor of the water pump is working stably.

[0068] The power supply of the motor of the water pump is AC power, which is converted into DC power to supply power to the motor. The DC voltage is the corresponding voltage value after the AC power is converted into DC power when the motor of the water pump is working stably.

[0069] In this embodiment, the three-phase PWM signal applied to the motor is a periodic signal, and the value of t is the frequency of the PWM signal applied to the motor.

[0070] Specifically, in step S1, the voltage signal U d1After the inverse Park transformation and the inverse Clark transformation, the voltage signal U is converted into a three-phase voltage signal and loaded on the initial set direct axis d1. d1 After inverse park transformation, it is converted into a voltage signal V α And the voltage signal V β , and converted into three-phase voltage signals through inverse Clark transformation, which are V a , V b , V c .

[0071] S2, detect the three-phase current signal of the motor and calculate the current signal I on the initial direct axis d1 d1 , and the initial setting of the current signal I on the quadrature axis q1 q1 .

[0072] In this embodiment, in step S2, the three-phase current signal of the motor is detected, and the current signal I on the initial set direct axis d1 is calculated through Clark transformation and Park transformation. d1 The current signal I on the initial setting quadrature axis q1 q1 Specifically, the three-phase current signal I a , I b , I c , after Clark transformation, we get I α , I β , and then the current signal I on the initial set direct axis d1 is obtained after Park transformation calculation d1 The current signal I on the initial setting quadrature axis q1 q1 .

[0073] In this step, the current signal I of the initial setting quadrature axis q1 is calculated. q1 for:

[0074]

[0075] Among them, L d is the direct-axis inductance, L q is the quadrature-axis inductance.

[0076] S3, the current signal I after bandpass filtering based on the preset frequency q1 The current signal I is obtained by multiplying the shaping factor q2 , and the current signal I q2 Perform the first low-pass filtering to obtain the current signal I q3 , the cut-off frequency of the first low-pass filter is less than the preset frequency. Wherein, the shaping factor is set to make the current signal I q2 It is related to the angle θ between the initial straight axis d1 and the actual straight axis d. Specifically, the shaping factor is set to make I q2It is related to the change of the term of the angle θ.

[0077] In this embodiment, the current signal I q1 Bandpass filtering is performed, and the passband center frequency of the bandpass filtering is ω. The I q1 The low-frequency signal in the current signal I is filtered out by the bandpass filter in this embodiment, that is, the frequency signal related to the rotation speed is filtered out, and the current signal I is retained. q1 The high-frequency signal in , where the voltage signal frequency is ω.

[0078] The shaping factor in step S3 is sin(ωt). Therefore, after bandpass filtering, I q1 The product of the current signal I is obtained by multiplying it by sin(ωt) q2 , so that the current signal I q2 It is only related to the change of the angle θ and has an effect on the current signal I q2 After the first low-pass filtering, the current signal I is obtained. q3 , the cut-off frequency of the first low-pass filter is less than the voltage signal frequency.

[0079] The current signal I can be filtered out by the first low-pass filter q2 The high frequency signal in I q2 The low-frequency signal, that is, the current signal I q2 After the first low-pass filter, the signal related to the rotation speed is filtered out.

[0080] I q1 The current signal I obtained by multiplying it with sin(ωt) q2 The term in ωt always remains positive, so that the current signal I q2 It is only related to the terms of the angle θ.

[0081] S4, the current signal I q3 The PI controller is used to adjust the angle θ between the initial direct axis d1 and the actual direct axis d until the current signal I q3 When the preset value is reached, the PI controller outputs an angle θ of the first target angle and a second target angle, the first target angle is smaller than the second target angle, and the difference between the second target angle and the first target angle is a first predetermined angle.

[0082] In this embodiment, the current signal I q3 Input to the PI controller, the PI controller has a preset current signal I of the q1 axis set inside. q_ref , the PI controller is based on the preset current signal I of the q1 axis q_ref For the current signal I q3 The PI controller adjusts the angle θ until I q3=0, the first target angle output by the PI controller is 0°, and the second target angle is π.

[0083] S5, current signal I d1 Perform a second low-pass filter to obtain the current signal I d2 , the cut-off frequency of the second low-pass filter is not less than the preset frequency;

[0084] According to the current signal I d2 The included angle θ is determined to be the first target angle or the second target angle to obtain the position of the actual direct axis d-axis.

[0085] Specifically, in this embodiment, in step S5, the PI controller is internally set with a preset current signal I of the d1 axis d_ref , the PI controller is based on the preset current signal I of the d1 axis d_ref For the current signal I d1 Processing of the current signal I d1 Perform a second low-pass filter to obtain the current signal I d2 The cut-off frequency of the second low-pass filter is not less than the voltage signal frequency, ensuring that the current signal I d2 Specifically, in step S5, according to the current signal I d2 The angle between the initial setting direct axis d1 and the actual direct axis d is determined to be 0°, that is, the initial setting direct axis d1 and the actual direct axis d coincide with each other, and the angle at which the actual direct axis d is located is the position of the initial setting direct axis d1. Since the position of the initial setting direct axis d1 is determined, the position of the actual direct axis d is determined. Assuming that the angle at which the initial setting direct axis d1 is located is θ1, the angle at which the actual direct axis d is located is θ1. Alternatively, according to the current signal I d2 Determine that the angle between the initial straight axis d1 and the actual straight axis d is π. Since the position of the initial straight axis d1 can be determined, assuming that the angle of the initial straight axis d1 is θ1, the angle of the actual straight axis d is θ1+π.

[0086] In this embodiment, when the current speed of the water pump motor is lower than the speed threshold, a voltage signal based on a preset frequency and a preset amplitude is applied to the initial setting direct axis d1 of the motor. By detecting the three-phase current signal of the motor, the current signal I of the initial setting direct axis d1 is calculated. d1 , and the initial setting of the current signal I on the quadrature axis q1 q1 .

[0087] Current signal I q1 Perform bandpass filtering, the passband center frequency of the bandpass filter is the preset frequency, and the current signal I is filtered out by bandpass filtering q1The low-frequency signal with a medium frequency lower than the preset frequency, that is, in this embodiment, the frequency signal related to the rotation speed is filtered out by bandpass filtering, and the current signal I is retained. q1 The high-frequency signal in, where the voltage signal frequency ω.

[0088] After the bandpass filter, I q1 Multiplying it with the shaping factor, we get the current signal I q2 , so that the current signal I q2 It is only related to the angle θ and the current signal I q2 After the first low-pass filtering, the current signal I is obtained. q3 , the current signal I can be filtered out after the first low-pass filter q2 The high frequency signal in I q2 The low-frequency signal, that is, the current signal I q2 After the first low-pass filter, the signal related to the rotation speed is filtered out.

[0089] The current signal I q3 Input PI controller, PI controller adjusts the angle θ between the initial setting direct axis d1 and the actual direct axis d until the current signal I q3 When the preset value is reached, the PI controller outputs the angle θ as the first target angle and the second target angle.

[0090] By the current signal I d1 Perform a second low-pass filter to obtain the current signal I d2 , according to the current signal I d2 The angle θ is determined to be the first target angle or the second target angle. The position of the actual direct axis d1 is obtained by simply calculating the known initial position of the direct axis d1 and the angle θ.

[0091] In this embodiment, the low-speed operation control method of the pump can obtain the real position of the rotor when the rotor is in a stationary state. When the water pump is started, it can directly enter a closed-loop operation at zero speed.

[0092] Moreover, the control method enables the water pump to operate stably under different working conditions, thus filling the gap of the water pump operating stably in the 4 zones of the flow-head performance curve of the water pump.

[0093] like Figure 6-Figure 8 As shown, Figure 6 The current signal I of the initial setting quadrature axis q1 is q1 and the angle θ, Figure 7 The current signal I is obtained by multiplying the current signal Iq1 of the quadrature axis q1 by sin(ωt) q2 and angle θ. q1After multiplying by sin(ωt), it is only related to θ. Figure 8 is the current signal I q2 A relationship diagram between the current signal Id3 obtained after the second low-pass filtering and the angle θ.

[0094] The current signal I q3 As the input signal of the PI controller. The PI controller is a linear controller that forms a control deviation based on the given value and the actual output value, and forms the control quantity by linearly combining the proportion and integral of the deviation to control the controlled object.

[0095] Preferably, in step S5, according to the current signal I d2 Determining the angle θ as the first target angle or the second target angle includes:

[0096] For the current signal I d2 The absolute value of the peak is compared with the absolute value of the valley;

[0097] If the current signal I d2 If the absolute value of the peak value is greater than the absolute value of the valley value, it is determined that the angle output by the PI controller is the first target angle;

[0098] If I d2 If the absolute value of the peak value is smaller than the absolute value of the valley value, it is judged that the angle output by the PI controller is the second target angle.

[0099] According to the calculation of the PI controller above, the PI controller adjusts θ until I q3 =0, the output angle after calculation by the PI controller converges to 0° or π, because the initial setting position of the direct axis d1 is known, the actual position of the direct axis d is obtained, that is, the position of the rotor at the initial position of the motor, and the control of the water pump is controlled according to the calculated rotor position.

[0100] For example, assuming that the angle between the initial setting direct axis d1 and the actual direct axis d is θ, the PI controller continuously adjusts the value of θ during the calculation process until I q3 =0, that is, I q2 =0,I q1 = 0, the output angle of the PI controller is 0° or π. At this point, it is still impossible to determine whether the angle between the actual direct axis d and the initial set direct axis d1 is 0° or π. Therefore, it is necessary to use I d2 The absolute value of the peak value and the absolute value of the valley value determine the angle of the PI controller output.

[0101] If I d2If the absolute value of the peak value is greater than the absolute value of the valley value, it is judged that the current PI controller converges to 0°. At this time, it means that the preset initial setting direct axis d1 axis and the actual direct axis d axis coincide with each other. At this time, θ is the angle corresponding to the PI controller convergence to 0°.

[0102] If I d2 If the absolute value of the peak value is smaller than the absolute value of the valley value, it is judged that the PI controller converges to π, that is, the angle between the initial setting direct axis d1 and the actual direct axis d is π, and the angle of the actual direct axis d is the position of the initial setting direct axis d1 plus π.

[0103] In this embodiment, in step S5, when I q3 =0, which is I q1 =0, θ=N1*(π / 2), N1 is an integer of π / 2, and the output angle of the PI controller is 0° or π.

[0104] like Fig. 9 and Fig.10 As shown, this embodiment also provides a water pump operation control method, including:

[0105] Determine the current operating speed of the water pump motor;

[0106] When the current operating speed of the motor is lower than the first preset speed S1, the motor works in the mode of the low speed operation control method of the pump;

[0107] When the current operating speed of the motor is higher than the second preset speed S2, the second preset speed S2 is greater than the first preset speed S1, and the second preset speed S2 is greater than the first preset speed S1, the motor operates in a mode of a control method based on a back-EMF observer;

[0108] When the current operating speed of the motor is between the first preset speed S1 and the second preset speed S2, the motor selects one of the low speed operation control method mode of the pump and the back electromotive force observer-based control method mode to operate.

[0109] In this embodiment, when the water pump is started and the speed of the water pump is less than the first preset speed S1, the motor works in the mode of the low speed operation control method of the pump, that is, Fig. 9 The Hfi mode in is enabled. When the motor is not started, the position of the stator can be determined by using the low speed operation control method of the pump. At the same time, the motor can also work in zone 4 of the flow-head curve by using the low speed operation control method of the pump.

[0110] When it is detected that the current operating speed of the motor is within the range of the first preset speed S1 and the second preset speed S2, it belongs to the hysteresis interval of the motor operation. The mode of the low speed operation control method of the pump and the mode of the control method based on the back electromotive force observer are both enabled. In the hysteresis interval, the motor selects one of the modes to work, and can be flexibly switched according to needs.

[0111] The control method based on the back-EMF observer in this embodiment is a conventional technical means in the prior art and will not be described in detail here.

[0112] The control method based on the back-EMF observer is suitable for working in the high-speed area, and the low-speed operation control method of the pump is suitable for working in the low-speed area of ​​the motor. However, in the intersection area of ​​high speed and low speed, both control methods need to be able to work, that is, the motor can work in any of the above two modes.

[0113] like Fig. 9 and Fig.10 As shown, preferably, when the current operating speed of the motor is between the first preset speed S1 and the second preset speed S2, the speed-up phase and the speed-down phase of the motor need to be considered.

[0114] Specifically, Fig. 9 As shown, the motor is in the motor acceleration stage during the time period t1-t3, the motor speed at time t1 is the first preset speed S1, the motor speed at time t2 is the moment when the angle of the motor stator is detected, and the motor speed at time t3 is the second preset speed S2.

[0115] During the time period t1-t2, the motor selects the pump to operate in one of the low speed operation control method mode and the back electromotive force observer-based control method mode.

[0116] After time t2, the motor operates in the mode of the control method based on the back electromotive force observer, and the low speed operation control method mode of the pump is turned off. More specifically, at time t2, the Hfi mode is turned off and the Obs mode is turned on.

[0117] and / or, if Fig.10 As shown, the motor is in the deceleration stage during the time period t4-t6, the motor speed at time t4 is the second preset speed S2, the motor speed at time t5 is the moment when the angle of the motor stator is detected, and the motor speed at time t6 is the first preset speed S1.

[0118] During the time period t4-t5, one of the low speed operation control method of the motor selection pump and the control method based on the back electromotive force observer is operated.

[0119] The motor operates using the low speed operation control method of the pump during the time period t5-t7, and the control method based on the back electromotive force observer is turned off. Fig.10 As shown, at time t1, the Hfi mode is turned on and the Obs mode is turned off.

[0120] Preferably, in this embodiment, the first preset speed S1 is 500 r / min, and the second preset speed S2 is 1000 r / min.

[0121] In this embodiment, the water pump is allowed to operate stably under different working conditions, thus filling the gap in the flow-head curve of the water pump in the low flow and low head range. Fig.11 The figure shows the actual phase current waveform when the motor is working. Fig.11 It can be seen that the startup from 0 speed to rated speed is stable, and the Hfi mode is switched to the Obs mode, that is, the low-speed operation control method mode of the pump is switched to the control method mode based on the back-EMF observer. There is no fluctuation in the phase current during switching, indicating that the motor is stable.

[0122] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for controlling low speed operation of a pump, characterized in that: include: S1. When the current speed of the water pump motor is lower than the speed threshold, a voltage signal U based on a preset frequency and a preset amplitude is applied to the initial set direct axis d1 of the motor. d1 , the preset frequency is greater than the rotational speed frequency of the motor and is in a first preset ratio; The preset amplitude is smaller than the rated DC voltage of the motor and is in a second preset ratio; S2, detect the three-phase current signal of the motor, and calculate the current signal I on the initial set direct axis d1 d1 , and the initial setting of the current signal I on the quadrature axis q1 q1 ; S3, the current signal I after bandpass filtering based on the preset frequency q1 The current signal I is obtained by multiplying the shaping factor q2 , and the current signal I q2 Perform the first low-pass filtering to obtain the current signal I q3 , the cut-off frequency of the first low-pass filter is less than the preset frequency; wherein the shaping factor is set to make the current signal I q2 It is related to the angle θ between the initial straight axis d1 and the actual straight axis d; S4, the current signal I q3 The PI controller is used to adjust the angle θ until the current signal I q3 When a preset value is reached, the PI controller outputs the angle θ as a first target angle and a second target angle, the first target angle is smaller than the second target angle, and the difference between the second target angle and the first target angle is a first predetermined angle; S5, current signal I d1 Perform a second low-pass filter to obtain the current signal I d2 , the cut-off frequency of the second low-pass filter is not less than a preset frequency; According to the current signal I d2 The angle θ is determined to be a first target angle or a second target angle to obtain the position of the actual direct axis d-axis.

2. The low speed operation control method of a pump according to claim 1, characterized in that: In step S1, a voltage signal based on a preset frequency and a preset amplitude is applied to the initial set direct axis d1 of the motor, including: The voltage signal is U d1 =U hfi cos(ωt), the preset amplitude is U hfi , U hfi is 1 / 20-1 / 10 of the stable voltage value of the DC voltage loaded on the motor; the preset frequency is the voltage signal frequency ω, and the voltage signal frequency ω is 10-20 times the speed frequency of the motor of the water pump; U q1 =0.

3. The low speed operation control method of a pump according to claim 1 or 2, characterized in that: In step S1, the voltage signal U d1 After inverse Park transformation and inverse Clark transformation, it is converted into a three-phase voltage signal and loaded on the initially set direct axis D1 axis.

4. The low speed operation control method of a pump according to claim 1 or 2, characterized in that: Step S2 detects the three-phase current signal of the motor, and calculates the current signal I on the initial set direct axis d1 through Clark transformation and Park transformation. d1 The current signal I on the initial setting quadrature axis q1 q1 .

5. The low speed operation control method of a pump according to claim 2, characterized in that: In step S2, the current signal I of the initially set quadrature axis q1 is calculated. q1 for: Among them, L d is the direct-axis inductance, L q is the quadrature-axis inductance.

6. The low speed operation control method of a pump according to claim 5, characterized in that: The shaping factor in step S3 is sin(ωt).

7. The low speed operation control method of a pump according to claim 1 or 2, characterized in that: In step S4, the current signal I q3 =0, the first target angle output by the PI controller is 0°, and the second target angle is π.

8. The method for controlling low speed operation of a pump according to claim 7, characterized in that: In step S5, according to the current signal I d2 Determining that the angle θ is a first target angle or a second target angle includes: For the current signal I d2 The absolute value of the peak is compared with the absolute value of the valley; If the current signal I d2 If the absolute value of the peak value is greater than the absolute value of the valley value, it is determined that the angle output by the PI controller is the first target angle; If I d2 If the absolute value of the peak value is smaller than the absolute value of the valley value, it is judged that the angle output by the PI controller is the second target angle.

9. A method for controlling the operation of a water pump, characterized in that: include: Determining the current operating speed of the motor of the water pump; When the current operating speed of the motor is lower than the first preset speed S1, the motor operates in the mode of the low speed operation control method of the pump according to any one of claims 1 to 8; When the current operating speed of the motor is higher than the second preset speed S2, the second preset speed S2 is greater than the first preset speed S1, and the motor operates in a mode of a control method based on a back-EMF observer; When the current operating speed of the motor is between the first preset speed S1 and the second preset speed S2, the motor operates in one of the low speed operation control method mode of the pump and the back-EMF observer-based control method mode.

10. The water pump operation control method according to claim 9, characterized in that: The motor is in the speed-up stage in the time period t1-t3, the speed of the motor at time t1 is the first preset speed S1, the motor is at the moment when the angle of the stator of the motor is detected at time t2, and the speed of the motor at time t3 is the second preset speed S2; In the time period t1-t2, the motor operates in one of the low speed operation control method mode of the pump and the control method mode based on the back electromotive force observer; After time t2, the motor operates in the mode of the control method based on the back-EMF observer, and the low-speed operation control method mode of the pump is turned off; And / or, the motor is in a deceleration stage during a time period from t4 to t6, the speed of the motor at time t4 is the second preset speed S2, the motor is at a time when the angle of the stator of the motor is detected at time t5, the speed of the motor at time t6 is the first preset speed S1, and the speed of the motor at time t7 is 0; During the time period t4-t5, one of the low speed operation control method of the motor selection pump and the control method based on the back electromotive force observer is operated; The motor is operated using the low speed operation control method of the pump during the time period t5-t6, and the mode of the back-EMF observer-based control method is turned off.

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