TWI597424B - Control method of screw pump and control system using the same - Google Patents

Control method of screw pump and control system using the same Download PDF

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Publication number
TWI597424B
TWI597424B TW104111502A TW104111502A TWI597424B TW I597424 B TWI597424 B TW I597424B TW 104111502 A TW104111502 A TW 104111502A TW 104111502 A TW104111502 A TW 104111502A TW I597424 B TWI597424 B TW I597424B
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TW
Taiwan
Prior art keywords
reverse
electric motor
screw pump
step
torque
Prior art date
Application number
TW104111502A
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Chinese (zh)
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TW201615988A (en
Inventor
鄭隆傑
Original Assignee
台達電子工業股份有限公司
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Priority to US201462067820P priority Critical
Application filed by 台達電子工業股份有限公司 filed Critical 台達電子工業股份有限公司
Priority claimed from US14/706,791 external-priority patent/US9976555B2/en
Publication of TW201615988A publication Critical patent/TW201615988A/en
Application granted granted Critical
Publication of TWI597424B publication Critical patent/TWI597424B/en

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Description

Screw pump control method and its applicable control system

This case relates to a control method, especially a control method of a screw pump and a control system thereof.

Screw pumps or progressive cavity pumps are commonly used in the petrochemical industry to draw oil from oil wells. In general, the operation of the screw pump is controlled by a control system, wherein the control system comprises an electric motor and a motor drive, and the screw pump comprises a pump rod having a rotor and a stator, the pump rod of the screw pump is physically It is located deep in the well to draw oil to the surface, and the geometry formed by the combination of the rotor and the stator constitutes two or more sets of spiral and independent cavities. As the rotor rotates within the stator, the cavity system moves from one end of the stator in a helical manner to the other end to establish a positive displacement (forward rotation) suction action whereby oil is drawn to the surface.

When the screw pump is rotating forward for normal suction operation, the screw pump driven by the electric motor will supply electrical energy to take up the pump rod to draw the oil out to the surface. However, when the instantaneous power interruption causes the pumping action of the screw pump to reverse, many significant problems are encountered. That is, when the power fails, the screw pump will be out of control and stored in the pump due to the oil loaded on the pump rod. The ability of the rod's electrical energy, however, still exists on the pump rod of the screw pump The large storage energy makes the screw pump similar to the coiled coil spring, so the stored energy will be released by the reverse rotation of the pump rod of the screw pump, and the rotor of the screw pump will be turned to the opposite direction, and the screw pump The pump rod will also rotate in the opposite direction until all the oil has fallen into a production tube, and because of gravity, the height of the oil level in the production tube will be equal to the height of the oil level in the well. . The reversal time of the screw pump can last for several hours, depending on the specific application of the screw pump. In the foregoing case, when the power is restored and supplied again, the pumping action of the screw pump cannot be immediately restarted, so the productivity in the process of reversing and waiting for the oil to be sucked back to the surface again loses productivity. Power interruption or loss results in a significant reduction in the productivity of the screw pump.

In addition, when the motor driver is closed by the user, the pumping speed of the screw pump will be slowed down, and then stopped by a braking device according to the predetermined closing schedule, when the motor driver stops supplying the driving voltage to the electric motor and the electric motor When it is turned off, the stored energy will be released by the pump rod of the screw pump at high speed reversal, and since the driving mechanism of the electric motor is usually directly connected to the rotor of the screw pump, the electric motor will also be driven and reversed. Turn, however, the uncontrolled reversal will seriously damage the drive mechanism of the electric motor and other production equipment, such as reversal may cause equipment damage. Furthermore, if this damage occurs at the ground level of the well, it may cause injury to workers and environmental pollution.

Therefore, how to develop a control method for a screw pump that can control the suction action of the screw pump to eliminate the influence of the reversal when the power fails, thereby improving the above-mentioned conventional technology, and the applicable control system are related. There is an urgent need for the technical field to solve the problem.

The purpose of the present invention is to provide a control method of a screw pump and a control system therefor, which can maintain the motor driver and the electric motor by using the generated electric energy converted by the storage potential energy of the screw pump in the event of power failure. Actuated to perform the reversal control of the screw pump, and the brake unit and the brake resistor of the brake device can be used to consume the excess storage position generated when the screw pump is reversed, thereby shortening the brake time of the screw pump. The utility model solves the problem that the driving mechanism or equipment of the electric motor which is caused by the interruption of the electric power in the conventional control system is easily damaged, the safety of the worker is not good, the environmental pollution and the productivity of the screw pump are significantly reduced.

In order to achieve the above object, one of the more broad aspects of the present invention provides a control method, which is an application control system, wherein the control system is used to control the operation of the screw pump, and has an electric motor that rotates synchronously with the screw pump and is used for control. A motor driver for operating an electric motor, the motor driver having a DC/AC converter, the DC/AC converter receiving a DC bus voltage generated by the power supplied by the power source, and converting the DC bus voltage to the electric motor The control method includes the following steps: (a) monitoring the DC bus voltage; (b) detecting whether the DC bus voltage is less than the first threshold, and performing step (c) when the detection result is yes; (c) The storage position energy released by the screw pump due to the reverse operation is converted into power generation and supplied to the motor driver to maintain the motor driver; (d) the motor driver drives the electric motor to control the screw according to the reverse torque limiting strategy The reverse operation of the pump; (e) limiting the DC bus voltage to be greater than the second threshold; (f) detecting whether the power is restored; (g) when step (f) When the measurement result is no, monitor the level of the reverse power generation torque; (h) detect whether the level of the reverse power generation torque is less than the preset torque value; and (i) when the detection result of the step (h) is At this time, the reverse operation of the screw pump is allowed to stop in a natural manner.

In order to achieve the above object, another broad aspect of the present invention provides a control system for controlling the operation of a screw pump, and includes: an electric motor that rotates synchronously with the screw pump; and a motor driver The power source and the electric motor are electrically connected to convert the power provided by the power source to be supplied to the electric motor, wherein the motor driver comprises: a DC/AC converter electrically connected to the electric motor for receiving the power supply. a DC bus voltage generated by the power, and converting the DC bus voltage to the electric motor; and a controller electrically connected to the DC/AC converter to control the operation of the DC/AC converter, and Monitoring the DC bus voltage; wherein when the power provided by the power supply is interrupted and the screw pump is reversed, so that the controller detects that the DC bus voltage is less than the first threshold, the motor driver uses the storage position released by the screw pump The converted generated electric energy can be operated, and the reverse operation of the screw pump is controlled according to the reverse torque limiting strategy

1‧‧‧Control system

11‧‧‧Electric motor

12‧‧‧Motor drive

121‧‧‧AC/DC converter

122‧‧‧DC chain

123‧‧‧DC/AC converter

124‧‧‧ Controller

2‧‧‧ screw pump

3‧‧‧Power supply

V bus ‧‧‧DC bus voltage

1241‧‧‧Speed Estimator

1242‧‧‧Reverse torque limiting unit

1243‧‧‧Speed Control Circuit

1244‧‧‧ Current Control Circuit

1245‧‧‧ pulse width modulation generator

1246‧‧‧ Torque controller

1247‧‧‧Magnetic flux controller

W^ r ‧‧‧ rotational speed estimate

T* e_backspin_limit ‧‧‧ Torque limit

T* e ‧‧‧Torque Command

I* q ‧‧‧Q-axis coordinate current command

I* d ‧‧‧D-axis coordinate current command

u* α ‧‧‧ α current command

u* β ‧‧‧ β current command

Step procedure of S11~S20‧‧‧ control method of this case

S141~S143‧‧‧Step flow of reverse torque limiting strategy

S161~S163‧‧‧ substeps

Figure 1 is a block diagram showing the structure of a control system of the preferred embodiment of the present invention.

Figure 2 is a block diagram of the circuit of the control system shown in Figure 1.

3A and 3B are flowcharts showing the steps of the control method of the preferred embodiment of the present invention.

Fig. 4 is a flow chart showing the steps of the reverse torque limiting strategy in step S14 shown in Fig. 3A.

Figure 5 is a flow chart showing the steps of the sub-steps of step S16 shown in Figure 3B.

Fig. 6 is a waveform timing chart of the AC voltage, the DC bus voltage, the rotational speed of the electric motor, and the reverse state when the control method of the present invention is applied to the control system shown in Fig. 2.

Fig. 7 is a waveform timing chart of the reverse state, the electric torque limit, and the power generation torque limit when the control method of the present invention is applied to the control system shown in Fig. 2.

Some exemplary embodiments embodying the features and advantages of the present invention are described in detail in the following description. It is to be understood that the present invention is capable of various modifications in various aspects, and is not to be construed as a limitation.

Please refer to FIG. 1 and FIG. 2 , wherein FIG. 1 is a schematic structural diagram of a control system according to a preferred embodiment of the present invention, and FIG. 2 is a circuit block diagram of the control system shown in FIG. 1 . As shown in FIG. 1 and FIG. 2, the control system 1 of the present embodiment is configured to control and drive the suction operation of a screw pump 2 to pump oil in the oil well to the surface, wherein the construction of the screw pump 2 It is a well-known technology, so I won't go into details here. The main structure of the control system 1 includes an electric motor 11, a motor driver 12, and a brake device. The electric motor 11 is electrically connected to the rotor of the pump rod of the screw pump 2, and is configured to rotate synchronously with the screw pump 2, thereby driving the rotor of the pump rod of the screw pump 2 to rotate and pumping oil from the oil well to the surface, and the electric motor 11 Preferably, it can be an induction motor. The brake device is composed of a brake unit 5 and a brake resistor 6. The brake unit 5 is electrically connected between the motor driver 12 and the brake resistor 6 for controlling the brake resistor 6 to release or consume the brake resistor 6. .

The motor driver 12 is electrically connected to a power source 3 (for example, a three-phase power source) and an electric motor 11 for controlling the operation of the electric motor 11, and may include an AC/DC converter 121 and a DC link 122 (for example, a DC bus bar). ), the DC/AC converter 123 and a controller 124 are not limited thereto. The AC/DC converter 121 can be, but is not limited to, a three-phase rectifier having a plurality of diodes, and AC/ One of the input terminals of the DC converter 121 is electrically connected to the power source 3, and the AC/DC converter 121 receives power from the power source 3, such as an AC voltage (three-phase AC voltage), and converts the AC voltage into a DC voltage. The DC link 122 can be formed by a capacitor electrically connected to an output end of the AC/DC converter 121 for voltage-stabilizing and filtering the DC voltage outputted by the AC/DC converter 121 to generate a DC bus voltage. V bus. The DC/AC converter 123 can be, but is not limited to, a three-phase inverter having one or a plurality of insulated gate bipolar transistors (IGBTs), and the DC/AC converter 123 is coupled to the DC link 122 and the electric motor. 11 is electrically connected to receive the DC bus voltage Vbus and converted into a driving voltage to drive and control the operation of the electric motor 11. The controller 124 can be, but is not limited to, a signal processor (DSP), and is electrically connected to the DC/AC converter 123 and the DC link 122 for controlling the operation of the insulated gate bipolar transistor of the DC/AC converter 123. The DC bus voltage V bus can be monitored. In other embodiments, the motor driver 12 uses a pulse width modulation (PWM) technique to change the frequency and amplitude of the driving voltage output by the DC/AC converter 123, thereby controlling the rotational speed of the electric motor 11, when driving the voltage. When the frequency is increased, the electric motor 11 is accelerated to rotate, and at the same time, the power of the power source 3 is transmitted to the electric motor 11 through the motor driver 12 to provide the energy required to drive the electric motor 11. The motor driver 12 is preferably a variable frequency drive or a variable speed drive that controls the speed and torque of the electric motor 11 by varying the frequency and amplitude of the drive voltage received by the electric motor 11.

In this embodiment, the controller 124 includes a speed estimator 1241, a reverse torque limiting unit 1242, a speed control circuit (ASR) 1243, a current control circuit (ACR) 1244, and a pulse width modulation. The generator 1245, a torque controller 1246 and a magnetic flux controller 1247, wherein the speed control circuit 1243, the current control circuit 1244, the pulse width modulation generator 1245, the torque controller 1246, and the magnetic flux controller 1247 are configured and actuated The method is a conventional technique, and thus will not be described again. In the present embodiment, the speed estimator 1241 is electrically connected to the electric motor 11 for estimating the rotational speed of the rotor of the electric motor 11 and outputting a rotational speed estimated value W^r. The reverse torque limiting unit 1242 is configured to store a reverse torque limiting strategy and is electrically coupled to the speed estimator 1241 to provide a turn based on the rotational speed estimate W^r from the speed estimator 1241. The moment limits T* e_backspin_limit. The speed control circuit 1243 is electrically connected to the reverse torque limiting unit 1242, and is configured to receive a motor rotational speed command W*r and a torque limit T*e_backspin_limit from the reverse torque limiting unit 124, and according to the motor rotational speed command. W*r and torque limit T* e_backspin_limit provide a torque command T* e. The torque controller 1246 is electrically coupled to the speed control circuit 1243, is configured to receive the torque command T*e, and convert the torque command T*e to a Q-axis coordinate current command I*q. The flux controller 1247 is configured to generate a D-axis coordinate current command I*d. The current control circuit 1244 is electrically connected to the torque controller 1246 and the magnetic flux controller 1247, and is configured according to the Q-axis coordinate current command I* q of the torque controller 1246 and the D-axis coordinate current command I* d of the magnetic flux controller 1247. An α current command u* α and a β current command u* β are respectively generated. The pulse width modulation generator 1245 is electrically connected to the current control circuit 1244 and the AC/DC converter 123, and is configured to generate a pulse according to the α current command u* α and the β current command u* β output by the current control circuit 1244. The width modulation signal, thereby controlling the switching operation of the switching element (for example, the insulating gate bipolar transistor) of the AC/DC converter 123, thereby driving and controlling the operation of the electric motor 11, and eliminating the electric motor 11 The effect of reversing.

In the present embodiment, when the control system 1 controls the electric motor 11 to rotate forward, the screw pump 2 is When the normal rotation is performed for the normal suction operation, the pump rod of the screw pump 2 will be driven by the electric motor 11 to suck the oil from the oil well to the surface, and the screw pump 2 is gradually raised to the petroleum system on the pump rod to The corresponding bit energy (hereinafter referred to as the storage bit energy) is stored on the surface.

Please refer to FIGS. 3A and 3B and cooperate with FIG. 6 and FIG. 7 , wherein FIGS. 3A and 3B are flowcharts of steps of the control method of the preferred embodiment of the present invention, and FIG. 6 is a control method applied to the present application. In the control system shown in Fig. 2, the waveform timing diagram of the AC voltage, the DC bus voltage, the rotational speed of the electric motor, and the reverse state, Fig. 7 is the control method of the present case applied to the control system shown in Fig. 2. Waveform timing diagram for reverse state, electric torque limit, and power generation torque limit. As shown in FIGS. 3A, 3B, 6 and 7, the control method of the present invention can be applied to the controller 124 of the control system 1 shown in FIG. 2, and includes the following steps: First, the motor driver 12 The controller 124 monitors the DC bus voltage V bus (refer to step S11). Next, the controller 124 detects whether the DC bus voltage V bus is less than a first threshold (refer to step S12). When the controller 124 detects that the DC bus voltage V bus is greater than or equal to the first threshold, the pump rod of the screw pump 2 will continue to be driven by the electric motor 11, and the screw pump 2 is in the forward rotation operation and is normally sucked. The oil in the oil well, in this case, will perform step S11 again, and the controller 124 continuously monitors the DC bus voltage V bus . On the contrary, when the controller 124 detects that the DC bus voltage V bus is less than the first threshold in step S12, the controller 124 determines the AC voltage that the power source 3 uses to generate the DC bus voltage V bus from the DC link 122. Since the power interruption (for example, the AC voltage is zero due to the power jump) or the motor driver 12 is turned off in response to the command, the step S13 is executed. In step S13, when the DC bus voltage V bus is less than the first threshold due to power interruption, the pump rod of the screw pump 2 will gradually switch from forward to reverse due to the influence of gravity on the oil on the screw pump 2. The storage position of the oil on the screw pump 2 is released by the reverse action of the pump rod and further converted into electric power for power supply to the motor driver 12 to maintain the operation of the motor driver 12 and the electric motor 11. That is, when the power provided by the power source 3 is lost or when the motor driver 12 is turned off by responding to the command, the control system 1 can maintain the motor driver by regenerating the generated power (ie, the generated power generated by the storage bit energy conversion). 12 and the operation of the electric motor 11 to control the reverse operation of the screw pump 2 until all the oil on the screw pump 2 has been lowered into a production pipe, and the height of the oil level in the production pipe is also the oil of the oil well. The height of the liquid surface is equal.

When step S13 is performed, the motor driver 12 drives the electric motor 11 to control the reverse operation of the screw pump 2 according to a reverse torque limiting strategy (ie, the operation of the screw pump 2 from forward rotation to reverse rotation), For example, the number of revolutions when the screw pump 2 is reversed, etc. (refer to step S14). Referring again to FIG. 4, it is a flow chart of the steps of the reverse torque limiting strategy in step S14 shown in FIG. 3A. As shown in FIG. 4, in the reverse torque limiting strategy of step S14, first, the motor rotational speed command W*r is set to be negative, and when the rotational speed of the electric motor 11 is evaluated as positive by the speed estimator 1241, A forward electric torque limit (Torque limit_motor) is set to zero, thereby not driving the electric motor 11 to rotate in the forward direction, and setting a forward power generation torque limit (Torque limit_generative) to a normal operation value, The normal operation value may be a multiple of a rated torque (for example, 120), whereby the storage position released by the screw pump 2 during the forward rotation of the screw pump 2 (the rotational speed of the forward rotation of the screw pump 2 is gradually decreased) It can be converted into power generation (refer to step S141), in which case the generated electric energy is transmitted to the DC link 122 of the motor driver 12, and the energy (for example, the driving voltage) output by the motor driver 12 is also reduced. When the rotational speed of the electric motor 11 is evaluated by the speed estimator 1241 to be negative and lower than a predetermined value (ie, the electric motor 11 has been The reverse state but the rotational speed has not yet reached the predetermined value), a reverse electric torque limit is set to zero, whereby the electric motor 11 is not forced to rotate in the reverse direction, but the electric motor 11 is subjected to the oil on the screw pump 2 Naturally reversed by the influence of gravity, and a reverse power generation torque limit is set to the normal operation value, which may be a multiple of the rated torque (for example, 120), whereby the screw pump 2 is reversely rotated. During the process (the rotational speed of the reverse rotation of the screw pump 2 is gradually increased), the storage potential energy on the screw pump 2 is converted into electric power generation (refer to step S142). When the rotational speed of the electric motor 11 is evaluated as negative by the speed estimator 1241 and greater than or equal to the predetermined value, a reverse speed control mode is executed, in which case the reverse electric torque limit and the reverse power generation turn The moment limit is set to the normal operation value (for example, 120), thereby controlling the speed of the electric motor 11 in the reverse rotation, for example, maintaining the predetermined value, and also converting the storage position energy on the screw pump 2 into the generated electric energy ( Please refer to step S143).

Please refer to FIG. 3A and FIG. 3B again. After the step S14 is performed, the DC bus voltage V bus is limited to be greater than a second threshold by releasing the excess power generated by the brake unit 5 and the braking resistor 6 (refer to step S15). And wherein the second threshold value may be, but is not limited to, lower than the first threshold value. When the step S15 is performed, the controller 124 detects whether the power supplied from the power source 3 is restored and supplies it again (refer to step S16).

In step S16, when the controller 124 detects that the power supplied by the power source 3 has been restored and is supplied again during the reverse operation of controlling the electric motor 11, the motor driver 12 drives the electric motor 11 to perform the forward rotation and The rotation speed is increased to control the screw pump 2 to immediately draw oil from the oil well (refer to step S17), and then step S11 is performed again. On the other hand, in step S16, when the controller 124 detects that the power supplied by the power source 3 has not recovered and is still interrupted, it monitors a level (refer to step S18). Then, comparing the level with a preset torque value and detecting whether the level is less than the preset torque Value (see step S19). In step S19, when the rank is less than the torque preset value, the reversal of the screw pump 2 is allowed to stop in a natural manner (see step S20). On the other hand, in step S19, when the level of the reverse power generation torque is greater than the preset torque value, step S13 is performed again.

Please refer to FIG. 5, which is a flow chart of the steps of the sub-step of step S16 shown in FIG. 3B. As shown in FIG. 5, in step S16, first, when the controller 124 of the motor driver 12 detects that the time interval elapsed after the electric motor 11 performs the reverse operation is longer than a first preset time, the system controls The forward electric torque limit returns to the normal operating value, which may be a multiple of the rated torque (eg, 120), and sets the motor rotational speed command W* r to a positive value, thereby causing the motor driver 12 to operate at In the normal forward operation mode, the electric motor 11 is driven to change from the reverse rotation to the forward rotation (refer to step S161). However, after the step S161 is performed, if the controller 124 detects that the DC bus voltage V bc is less than the first threshold value, that is, the power source 3 cannot provide power and maintains the DC bus voltage V bc , the controller 124 It is judged that the power supplied from the power source 3 is in an unrecovered state (refer to step S162). When it is determined in step S162 that the power supplied by the power source 3 has not recovered and a second preset time has elapsed, the controller 124 determines that the power system is lost for a long period of time and performs step S18 (please refer to step S163).

In summary, the present invention provides a control method of a screw pump and a control system therefor, which can control the operation of the screw pump to eliminate the influence when the power is reversed and reversed, that is, when the control system of the present case When the motor driver detects a power failure, the control system of the present case can generate electricity by using the storage potential energy of the screw pump (wherein, when the power fails, the pump rod of the screw pump is affected by the gravity of the oil) And the release of the storage capacity, the storage can be tied to all the oil has been reduced to the raw In the production pipe, the height of the oil level of the production pipe is equal to the height of the oil level of the oil well, and the power generation is generated by the conversion of the storage energy to maintain the operation of the motor driver and the electric motor. The reverse operation of the screw pump is controlled, thereby avoiding the relevant driving mechanism or equipment damage of the electric motor and improving the safety of the worker. In addition, when the electric motor and the screw pump are reversed due to the loss of power, the brake unit and the brake resistor of the brake device can dissipate excess storage energy into heat energy, thereby shortening the brake time of the screw pump, thus Once the electric energy is re-supplied, the motor driver of the control system of the present case can drive the electric motor to control the screw pump to immediately perform the positive displacement pumping operation. Therefore, the control method of the screw pump and the applicable control system thereof can improve the screw pump. Productivity.

This case has been modified by people who are familiar with the technology, but it is not intended to be protected by the scope of the patent application.

Step procedure of S11~S20‧‧‧ control method of this case

Claims (12)

  1. A control method is applied to a control system, wherein the control system is used to control the operation of a screw pump, and has an electric motor that rotates synchronously with the screw pump and a motor driver for controlling the operation of the electric motor. The motor driver has a DC/AC converter that receives a DC bus voltage generated by power supplied from a power source and converts the DC bus voltage to the electric motor. The control method includes the following steps: (a) monitoring the DC bus voltage; (b) detecting whether the DC bus voltage is less than a first threshold, and performing step (c) when the detection result is YES; (c) converting a storage position energy released by the screw pump by the reverse operation into a generated electric energy, and supplying the motor drive to the motor drive to maintain the operation; (d) driving the electric motor by the motor drive Controlling the reverse operation of the screw pump according to a reverse torque limiting strategy; (e) limiting the DC bus voltage to be greater than a second threshold; (f) detecting whether the power is restored (g) monitoring the level of a reverse power generation torque when the detection result of the step (f) is negative; (h) detecting whether the level of the reverse power generation torque is less than a predetermined torque value; (i) When the detection result of the step (h) is YES, the reverse operation of the screw pump is allowed to stop in a natural manner.
  2. The control method according to claim 1, wherein the second threshold is lower than the first threshold.
  3. The control method according to claim 1, wherein when the detection result of the step (b) is NO, the step (a) is performed again.
  4. The control method according to claim 1, wherein when the detection result of the step (f) is YES, the step (j) is performed: driving the electric motor to rotate in the forward direction and speeding up the rotation, and performing the step again. (a).
  5. The control method according to claim 1, wherein when the detection result of the step (h) is NO, the step (c) is performed again.
  6. The control method of claim 1, wherein in step (e), the DC bus voltage is limited to be greater than the second threshold by the braking device consuming a portion of the generated electrical energy.
  7. The control method according to claim 1, wherein the reverse torque limiting strategy in the step (d) comprises the following steps: (d1) setting a motor rotational speed command to be negative, and when the electric motor is The rotational speed is evaluated as positive, a forward electric torque limit is set to zero, a forward power generation torque limit is set to a normal operating value; (d2) when the rotational speed of the electric motor is evaluated as negative When the value is lower than a predetermined value, a reverse electric torque limit is set to zero, a reverse power generation torque limit is set to the normal operation value; and (d3) when the rotational speed of the electric motor is evaluated as negative When the predetermined value is greater than or equal to, the reverse speed control mode is executed such that the reverse electric torque limit and the reverse power torque limit are both set to the normal operation value.
  8. The control method of claim 7, wherein the step (f) further comprises the following steps: (f1) when the motor driver detects that the electric motor performs a reverse operation for a time interval longer than one In the first preset time, the forward electric torque limit is controlled to return to the normal operation value, and the motor rotational speed command is set to a positive value, so that the motor driver operates in a normal forward operation mode to drive the electric motor. Change from anyway to positive rotation; (f2) determining that the power is unrecovered when detecting that the DC bus voltage is again less than the first threshold; and (f3) determining that the power is not restored and passing a second preset when the step (f2) is determined At time, step (g) is performed.
  9. A control system for controlling the operation of a screw pump, comprising: an electric motor synchronously rotating with the screw pump; and a motor driver electrically connected to a power source and the electric motor for The power provided by the power source is converted to be supplied to the electric motor, wherein the motor driver includes: a DC/AC converter electrically connected to the electric motor for receiving the power generated by the power source Circulating a voltage and converting the DC bus voltage to the electric motor; and a controller electrically connected to the DC/AC converter for controlling the operation of the DC/AC converter, And monitoring the DC bus voltage; wherein when the power provided by the power supply is interrupted and the screw pump is reversed, so that the controller detects that the DC bus voltage is less than the first threshold, the motor driver is Operating with a generated electrical energy converted by a storage position energy released by the screw pump, and controlling the snail according to a reverse torque limiting strategy The reverse operation of the pump; wherein the controller comprises: a speed estimator electrically connected to the electric motor for estimating a rotational speed of a rotor of the electric motor and outputting a rotational speed estimate; a reverse torque limiting unit electrically connected to the speed estimator for storing the reverse torque limiting strategy and providing a torque limit according to the rotational speed estimation value; a snap control circuit Electrically connecting with the reverse torque limiting unit for providing a torque command according to a motor rotational speed command and the torque limit; a torque controller electrically connected to the speed control circuit for converting the torque command to a Q-axis coordinate current command; a magnetic flux controller for generating a D-axis coordinate current command; and a current control circuit Is electrically connected to the torque controller and the magnetic flux controller for respectively generating an alpha current command and a beta current command according to the Q-axis coordinate current command and the D-axis coordinate current command; and a pulse width modulation The generator is electrically connected to the current control circuit and an AC/DC converter for generating a pulse width modulation signal according to the α current command and the β current command to control at least one of the AC/DC converters The switch performs switching operation of turning on or off.
  10. The control system of claim 9, wherein the motor driver comprises: the AC/DC converter electrically connected to the power source for converting the power provided by the power source to a DC voltage; a DC link is electrically connected to the AC/DC converter for voltage-stabilizing the DC voltage to generate the DC bus voltage, and the DC link is electrically connected to the controller.
  11. The control system of claim 10, wherein the control system further comprises a brake device, and the brake device is composed of a brake unit and a brake resistor, the brake unit is electrically connected to the motor driver and the brake device Between the brake resistors, the brake resistor is used to control the braking resistor to consume energy.
  12. The control system of claim 11, wherein the reverse torque limiting strategy is to set a motor rotational speed command to be negative, and when the rotational speed of the electric motor is evaluated as positive, a positive direction The electric torque limit is set to zero, a forward power generation torque limit is set to a normal operation value, and when the rotational speed of the electric motor is evaluated to be negative and lower than a predetermined value, a reverse electric torque is used. The limit is set to zero, a reverse power generation torque limit is set to the normal operation value, and when the power is When the rotational speed of the motor is evaluated to be negative and greater than or equal to the predetermined value, a reverse speed control mode is executed such that the reverse electric torque limit and the reverse power torque limit are both set to the normal operation value.
TW104111502A 2014-10-23 2015-04-09 Control method of screw pump and control system using the same TWI597424B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US201462067820P true 2014-10-23 2014-10-23

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US14/706,791 US9976555B2 (en) 2014-10-23 2015-05-07 Control method and control system for screw pump

Publications (2)

Publication Number Publication Date
TW201615988A TW201615988A (en) 2016-05-01
TWI597424B true TWI597424B (en) 2017-09-01

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CN2919687Y (en) * 2006-06-12 2007-07-04 大庆油田有限责任公司 Electromagnetic brake device for preventing sucker rod of screw pump well from reversing
JP2008045497A (en) * 2006-08-17 2008-02-28 Heishin Engineering & Equipment Co Ltd Drive method and device of uniaxial eccentric screw pump
TWI411219B (en) * 2008-10-17 2013-10-01 Foxnum Technology Co Ltd Motor driver
CN102400912B (en) * 2010-09-17 2014-12-24 深圳市汇川技术股份有限公司 Shutdown braking system and method for screw pump
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CN203035547U (en) * 2013-02-05 2013-07-03 大庆市沛泽石油科技有限公司 Remote digital control system of direct-drive screw pump

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