CN105545732A - Screw pump operation control method and its control system - Google Patents

Abstract

The invention provides a screw pump operation control method, which is applied to a control system with an electric motor and a motor driver which synchronously rotate with a screw pump, and comprises the following steps: monitoring the DC bus voltage; if the detected direct current bus voltage is smaller than a first threshold value, the stored potential energy on the screw pump is converted into electricity generation energy to be provided for a motor driver; controlling the reverse rotation operation of the screw pump; limiting the voltage of the direct current bus to be larger than a second threshold value; detecting whether the power is recovered or not, and monitoring the level of the reverse power generation torque if the power is not recovered; detecting whether the grade of the reverse power generation torque is smaller than a preset torque value; if so, the reverse operation of the screw pump is allowed to stop in a natural manner. The invention also provides a screw pump operation control system. The operation control method and the control system of the screw pump provided by the invention can solve the problems that equipment is easy to damage, the safety of workers is poor, the environment is polluted, the productivity of the screw pump is obviously reduced and the like caused by the interruption of electric energy.

Description

Screw pump operation control method and its control system

technical field

The invention relates to the field of screw pump operation control, in particular to a screw pump operation control method and a control system thereof.

Background technique

Screw pumps or progressive cavity pumps are commonly used in the petrochemical industry to pump oil from oil wells. Generally speaking, the operation of the screw pump is controlled by a control system, wherein the control system includes an electric motor and a motor driver, while the screw pump includes a pump rod with a rotor and a stator. The pump rod of the screw pump is physically It is located deep in the oil well to pump oil to the surface, and the geometric shape 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 chamber is moved in a helical fashion from one end of the stator to the other to create a positive displacement (forward rotation) suction action, thereby sucking the oil out to the surface.

When the screw pump is rotating forward and performing normal suction operation, the screw pump driven by the electric motor will provide electrical energy to wind the pump rod to suck the oil to the surface. However, when the momentary power interruption causes the suction action of the screw pump to reverse, many obvious problems will be encountered, that is, when the power fails, the screw pump will lose control due to the oil loaded on the pump rod and store it in the pump rod. The electric energy capacity of the pump rod, however, there is still a huge stored energy on the pump rod of the screw pump, making the screw pump similar to a wound 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 is changed to turn in the opposite direction, and the pump rod of the screw pump will also rotate in the opposite direction, until all the oil has descended into the production tube, and because of gravity, the oil level in the production tube will eventually The height of will be equal to the height of the oil level in the well. The reverse time of the screw pump can last for several hours, depending on the specific application of the screw pump. In the aforementioned cases, when the power is restored and supplied again, the pumping action of the screw pump cannot be restarted immediately, so the productivity is lost during the reversal process and the time spent waiting for the oil to be pumped to the surface again. Therefore, power interruption or loss will cause a significant reduction in the productivity of the screw pump.

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

Therefore, how to develop a control method and an applicable control system for the screw pump that can control the suction action of the screw pump to eliminate the impact of the reverse rotation when the power fails, and then improve the lack of the above-mentioned known technology is really a problem. It is a problem urgently needed to be solved by those in the relevant technical fields.

Contents of the invention

The purpose of the present invention is to provide a method for controlling the operation of a screw pump and its control system, which can maintain the actuation of the motor driver and the electric motor by using the generated electric energy converted from the stored potential energy on the screw pump when the power fails , to carry out the reverse control of the screw pump, and use the brake unit and brake resistor of the brake device to consume the excess storage potential energy generated by the screw pump during reverse rotation, thereby shortening the braking time of the screw pump and solving the problem of traditional When the control system is interrupted by electric energy and the screw pump is reversed, the driving mechanism or equipment of the electric motor is easily damaged, the safety of the staff is not good, the environment is polluted, and the productivity of the screw pump is significantly reduced.

In order to achieve the above purpose, a broad implementation of the present invention is to provide a screw pump operation control method, which is to use a screw pump operation control system, wherein the screw pump operation control system is used to control the operation of the screw pump, and has the same function as The electric motor of the screw pump synchronously rotates and the motor driver used to control the operation of the electric motor. The motor driver has a DC/AC converter. The DC/AC converter receives the DC bus voltage generated by the power provided by the power supply and converts the DC bus voltage To perform conversion to provide 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 value, and performing step (c) when the detection result is yes; (c) Convert the stored potential energy released by the screw pump due to reverse operation into electrical energy for power generation, and provide it to the motor driver to keep the motor driver in motion; (d) The motor driver drives the electric motor according to the reverse torque limit strategy (i.e. method) to control the reverse operation of the screw pump; (e) limit the DC bus voltage greater than the second threshold; (f) detect whether the power is restored; (g) when the detection result of step (f) is no, Monitoring the level of reverse power generation torque; (h) detecting whether the level of reverse power generation torque is less than a preset torque value; and (i) when the detection result of step (h) is yes, allowing the reverse rotation of the screw pump The run stops in a natural way.

In an embodiment of the invention, the second threshold is lower than the first threshold.

In an embodiment of the present invention, when the detection result of step (b) is negative, step (a) is executed again.

In one embodiment of the present invention, when the detection result of step (f) is yes, execute step (j): drive the electric motor to rotate forward and increase the rotation speed, and execute step (a) again.

In an embodiment of the present invention, when the detection result of step (h) is negative, step (c) is performed again.

In an embodiment of the present invention, in step (e), a braking device of the control system consumes part of the generated electric energy to limit the DC bus voltage to be greater than the second threshold.

In one embodiment of the present invention, the reverse torque limiting strategy in step (d) includes the following steps:

(d1) Set the motor rotation speed command to be negative, and when the rotation speed of the electric motor is evaluated to be positive, set the positive electric torque limit to zero, and set the positive power generation torque limit to a normal operation value;

(d2) setting the reverse motoring torque limit to zero and the reverse generating torque limit to the normal operating value when the rotational speed of the electric motor is evaluated to be negative and below a predetermined value; and

(d3) When the rotation speed of the electric motor is evaluated to be negative and greater than or equal to the predetermined value, execute the reverse speed control mode, so that the reverse electric torque limit and the reverse power generation torque limit are both set to the normal operating value.

In one embodiment of the present invention, step (f) also includes sub-steps as follows:

(f1) When the motor driver detects that the electric motor performs reverse running for a time interval longer than a first preset time, control the forward electric torque limit to return to the normal operating value, and set the motor rotation speed The command is a positive value, so that the motor driver operates in the normal forward operation mode and drives the electric motor from reverse rotation to forward rotation;

(f2) When it is detected that the DC bus voltage is lower than the first threshold value again, it is judged that the electric power is in an unrecovered state; and

(f3) When it is determined in step (f2) that the power has not been restored and the second preset time has elapsed, perform step (g).

To achieve the above purpose, another broad implementation aspect of the present invention is to provide a screw pump operation control system for controlling the operation of the screw pump, the screw pump operation control system includes: an electric motor, the electric motor and the screw pump The pump rotates synchronously; and the motor driver is electrically connected to the power supply and the electric motor to convert the power provided by the power supply to the electric motor, wherein the motor driver includes: a DC/AC converter and is electrically connected to the electric motor , for receiving a DC bus voltage generated by power supplied by the power source, and converting the DC bus voltage for supplying to the electric motor; and a controller, electrically connected with the DC/AC converter, for controlling the DC/AC conversion The operation of the drive, and monitor the DC bus voltage; wherein when the power provided by the power supply is interrupted and the screw pump runs in reverse, so that the controller detects that the DC bus voltage is less than the first threshold value, the motor driver is released by the screw pump. The generated electrical energy converted by the potential energy is stored for operation, and the reverse operation of the screw pump is controlled according to the reverse torque limiting strategy.

In one embodiment of the present invention, the motor driver includes:

an AC/DC converter, electrically connected to the power source, for converting the power provided by the power source into a DC voltage; and

A DC link; electrically connected to the AC/DC converter for stabilizing and filtering the DC voltage to generate the DC bus voltage, and the DC link is electrically connected to the controller.

In one embodiment of the invention, the controller includes:

a speed estimator, electrically connected to the electric motor, for estimating the rotational speed of a rotor of the electric motor and outputting an estimated rotational speed;

a reverse torque limiting unit, electrically connected to the speed estimator, for storing the reverse torque limiting strategy, and providing torque limit according to the rotational speed estimate;

A snap-action control circuit, electrically connected to the reverse torque limiting unit, for providing a torque command according to a motor rotation speed command and the torque limit;

A torque controller, electrically connected to the speed control circuit, for converting the torque command into a Q-axis coordinate current command;

A magnetic flux controller, used to generate a D-axis coordinate current command;

a current control circuit, electrically connected to the torque controller and the magnetic flux controller, for generating an α current command and a β current command respectively according to the Q-axis coordinate current command and the D-axis coordinate current command; and

A pulse width modulation generator, electrically connected with the current control circuit and the AC/DC converter, for generating a pulse width modulation signal according to the α current command and the β current command to control the AC/DC converter At least one switch is switched on or off.

In one embodiment of the present invention, the control system also has a braking device, and the braking device is composed of a braking unit and a braking resistor, the braking unit is electrically connected between the motor driver and the braking resistor, for The operation of the braking resistor is controlled so that the braking resistor consumes energy.

In one embodiment of the present invention, the reverse torque limit strategy is to set a motor rotation speed command to be negative, and set a positive electric torque limit when the rotation speed of the electric motor is evaluated as positive is zero, sets a positive generating torque limit to a normal operating value, and sets a reverse electric motoring torque limit to zero, a reverse generating torque limit is set as the normal operating value, and when the rotation speed of the electric motor is evaluated to be negative and greater than or equal to the predetermined value, a reverse speed control mode is executed to make the reverse Both the motoring torque limit and the reverse generating torque limit are set to the normal operating value.

In an embodiment of the present invention, the control system is used to implement the operation control method of the screw pump described in any one of the above items.

Description of drawings

Fig. 1 is the structural representation of the screw pump operation control system of preferred embodiment of the present invention;

Fig. 2 is a schematic diagram of the circuit structure of the screw pump operation control system shown in Fig. 1;

Fig. 3 is a flow chart of the steps of the screw pump operation control method in a preferred embodiment of the present invention;

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

Fig. 5 is the step flowchart of the sub-step of step S16 shown in Fig. 3;

Fig. 6 is a waveform sequence diagram of AC voltage, DC bus voltage, electric motor speed and reverse state when the control method of the present invention is applied to the screw pump operation control system shown in Fig. 2;

FIG. 7 is a time sequence diagram of waveforms in the reverse state, electric torque limit and power generation torque limit when the control method of the present invention is applied to the screw pump operation control system shown in FIG. 2 .

Wherein, the reference signs are explained as follows:

1: Control system

11: Electric motor

12: Motor driver

121: AC/DC Converter

122: DC link

123: DC/AC converter

124: Controller

2: Progressive cavity pump

3: Power

Vbus: 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: Flux controller

W^r: Estimated rotational speed

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

S11～S20: the flow of steps of the control method of the present invention

S141～S143: Step flow of reverse torque limit strategy

S161～S163: sub-steps

detailed description

Some typical embodiments embodying the features and advantages of the present invention will be described in detail in the description in the following paragraphs. It should be understood that the present invention can have various changes in different aspects without departing from the scope of the present invention, and that the description and illustrations therein are illustrative in nature and not restrictive this invention.

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 schematic circuit block diagram of the control system shown in FIG. 1 . As shown in Figures 1 and 2, the control system 1 of this embodiment is based on controlling and driving the suction action of a screw pump 2, so as to suck the oil in the oil well to the surface, wherein the structure of the screw pump 2 is 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 braking device. The electric motor 11 is electrically connected to the rotor of the pump rod of the screw pump 2, and is structured to rotate synchronously with the screw pump 2, and then drives the rotor of the pump rod of the screw pump 2 to rotate to pump oil from the oil well to the surface, and the electric motor 11 is relatively Best for induction motors. The braking device is composed of a braking unit 5 and a braking resistor 6, wherein the braking unit 5 is electrically connected between the motor driver 12 and the braking resistor 6 to control the action of the braking resistor 6 so that the braking resistor 6 is released or consumed energy.

The motor driver 12 is electrically connected with a power source 3 (such as a three-phase power supply) and the electric motor 11, and is used to control the operation of the electric motor 11, and may include an AC/DC converter 121, a DC link 122 (such as a DC bus), A DC/AC converter 123 and a controller 124, but not limited thereto. The AC/DC converter 121 can be but not limited to be composed of a three-phase rectifier with a plurality of diodes, and an input end of the AC/DC converter 121 is electrically connected to the power source 3, and the AC/DC converter 121 is connected to the power source 3 Receives electric power, such as AC voltage (three-phase AC voltage), and converts the AC voltage to DC voltage. The DC link 122 can be formed by a capacitor, which is electrically connected to an output terminal of the AC/DC converter 121, and is used for stabilizing and filtering the DC voltage output by the AC/DC converter 121 to generate a DC bus voltage Vbus . The DC/AC converter 123 may be, but not limited to, constituted by a three-phase inverter having one or more insulated gate bipolar transistors (IGBTs), and the DC/AC converter 123 is connected to the DC link 122 and the electric motor 11 The electrical connection is used to receive the DC bus voltage Vbus and convert it into a driving voltage to drive and control the operation of the electric motor 11 . The controller 124 may be, but not limited to, a signal processor (DSP), and is electrically connected to the DC/AC converter 123 and the DC link 122 to control the action of the IGBT of the DC/AC converter 123 , and can monitor the DC bus voltage Vbus. In other embodiments, the motor driver 12 uses pulse width modulation (PWM) technology to change the frequency and amplitude of the driving voltage output by the DC/AC converter 123, thereby controlling the rotation speed of the electric motor 11. When the frequency of the driving voltage increases , the electric motor 11 accelerates to rotate, and at the same time, the electric power of the power source 3 will be 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 driver or a variable speed driver, which controls the speed and torque of the electric motor 11 by changing the frequency and amplitude of the driving 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, a pulse width modulation generator 1245, a torque controller 1246 and a magnetic flux controller 1247, wherein the structure and action mode of 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 Known technology, so no more details here. In this embodiment, the speed estimator 1241 is electrically connected to the electric motor 11 and is used for estimating the rotation speed of the rotor of the electric motor 11 to output an estimated rotation speed value W^r. The reverse torque limiting unit 1242 is configured to store a reverse torque limiting strategy, and is electrically connected to the speed estimator 1241, so as to provide a rotational speed according to the rotational speed estimation value W^r from the speed estimator 1241. Moment limit 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 rotation speed command W*r and the torque limit T*e_backspin_limit from the reverse torque limiting unit 124, and according to the motor rotation speed command W *r and the torque limit T*e_backspin_limit to provide a torque command T*e. The torque controller 1246 is electrically connected to the speed control circuit 1243 and configured to receive the torque command T*e and convert the torque command T*e into a Q-axis coordinate current command I*q. The magnetic flux controller 1247 is structured 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 structured based on 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 width modulation signal according to the α current command u*α and the β current command u*β output by the current control circuit 1244 , so as to control the switching action of the switching element (such as the insulating gate bipolar transistor) of the AC/DC converter 123 on or off, thereby driving and controlling the operation of the electric motor 11, and eliminating the negative reaction of the electric motor 11. The impact of turning time.

In this embodiment, when the control system 1 controls the electric motor 11 to rotate forward to make the screw pump 2 rotate forward to perform normal suction, the pump rod of the screw pump 2 will be driven by the electric motor 11 to pump the oil. Pumping from the oil well to the surface, at this time the screw pump 2 stores the corresponding potential energy (hereinafter referred to as storage potential energy) because the oil on the pump rod gradually rises to the surface.

Please refer to Fig. 3 and cooperate with Fig. 6 and Fig. 7, wherein Fig. 3 is the flow chart of the steps of the control method of the preferred embodiment of the present invention, Fig. 6 is when the control method of the present invention is applied to the control system shown in Fig. 2, AC Voltage, DC bus voltage, the speed of the electric motor and the waveform sequence diagram of the reverse state, Fig. 7 is when the control method of the present invention is applied to the control system shown in Fig. 2, the reverse state, electric torque limit and power generation torque Restricted waveform timing diagram. As shown in Fig. 3, Fig. 6 and Fig. 7, the control method of the present invention can be applied in the controller 124 of the control system 1 shown in Fig. 2, and includes the following steps: first, the controller 124 of the motor driver 12 monitors the DC Bus voltage Vbus (see step S11). Next, the controller 124 detects whether the DC bus voltage Vbus is smaller than the first threshold (please refer to step S12). When the controller 124 detects that the DC bus voltage Vbus is greater than or equal to the first threshold value, 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 forward rotation operation to normally pump oil in the oil well , in this case, step S11 will be executed again, and the controller 124 will continuously monitor the DC bus voltage Vbus. Conversely, when the controller 124 detects that the DC bus voltage Vbus is less than the first threshold in step S12, the controller 124 determines that the AC voltage provided by the power supply 3 to make the DC link 122 generate the DC bus voltage Vbus is due to power interruption. (For example, the AC voltage is zero due to power failure) or is decreasing because the motor driver 12 is turned off in response to the command, at this time, step S13 is executed. In step S13, when the DC bus voltage Vbus is less than the first threshold value due to power interruption, the pump rod of the screw pump 2 will gradually switch from forward rotation to reverse rotation due to the oil on the screw pump 2 being affected by gravity, while the screw pump The stored potential energy of the oil on 2 is released by the reverse action of the pump rod and further converted into electrical energy for power generation to supply the motor driver 12 to maintain the actuation of the motor driver 12 and the electric motor 11, that is, when the power supply 3. When the provided power is lost or when the motor driver 12 is shut down due to the response to the command, the control system 1 can maintain the motor driver 12 and the electric motor through the regenerated power generation (that is, the power generation generated by the conversion of the stored potential energy). 11, and then control the reverse operation of the screw pump 2 until all the oil on the screw pump 2 has dropped into the production pipe, and the height of the oil liquid level in the production pipe is also equal to that of the oil well.

After step S13 is executed, the motor driver 12 drives the electric motor 11 to control the reverse running of the screw pump 2 according to a reverse torque limiting strategy (that is, the running process of the screw pump 2 gradually changing from forward rotation to reverse rotation), For example, the rotation speed of the screw pump 2 when it reverses (refer to step S14). Please refer to FIG. 4 again, which is a flow chart of the reverse torque limiting strategy in step S14 shown in FIG. 3 . As shown in FIG. 4 , in the reverse rotation torque limiting strategy in step S14, the motor rotational speed command W*r is first set to be negative, and when the rotational speed of the electric motor 11 is evaluated as positive by the speed estimator 1241, A positive electric torque limit (Torquelimit_motor) is set to zero, thereby not driving the electric motor 11 to rotate forward, and a positive power generation torque limit (Torquelimit_generative) is set to a normal operating value, the The normal operating value can be a multiple of a rated torque (for example, 120), so that the storage position released by the screw pump 2 can be reduced while the screw pump 2 is still rotating in the forward direction (the speed of the screw pump 2 in forward rotation gradually decreases). can be converted into generated electric energy (refer to step S141), in this case, the generated electric energy is transmitted to the DC link 122 of the motor driver 12, and the output energy (eg driving voltage) of the motor driver 12 is also reduced. When the rotation speed of the electric motor 11 is evaluated by the speed estimator 1241 as being negative and lower than a predetermined value (that is, it means that the electric motor 11 is in the reverse state but the rotation speed has not yet reached the predetermined value), a reverse electric torque is limited It is set to zero, so that the electric motor 11 is not forced to rotate in the reverse direction, but the electric motor 11 is naturally reversed due to the oil on the screw pump 2 being affected by gravity, and a reverse power generation torque limit is set. As the normal operating value, the normal operating value can be a multiple of the rated torque (for example, 120), so that the screw pump 2 is reversely rotated (the speed of the screw pump 2 reversely rotates is gradually increased). The stored potential energy on the pump 2 is converted into electric power generation (see step S142). When the rotation speed of the electric motor 11 is evaluated as negative by the speed estimator 1241 and is greater than or equal to the predetermined value, a reverse speed control mode is executed. Torque limits are all set to the normal operating value (for example, 120), thereby controlling the speed of the electric motor 11 during reverse rotation, for example, maintaining at a predetermined value, and also converting the stored potential energy on the screw pump 2 into electrical energy for power generation (see step S143).

Please refer to FIG. 3 again. After step S14 is executed, the excess generated electric energy is released through the braking unit 5 and the braking resistor 6 to limit the DC bus voltage Vbus to be greater than the second threshold value (see step S15), wherein the second threshold value can be is but not limited to being lower than the first threshold. After step S15 is executed, the controller 124 detects whether the power provided by the power supply 3 is recovered and supplied again (please refer to step S16).

In step S16, when the controller 124 detects that the power provided by the power supply 3 has recovered and is supplied again during the reverse operation of the electric motor 11, the motor driver 12 will drive the electric motor 11 to perform forward rotation and speed up. Rotate the speed to control the screw pump 2 to immediately suck oil from the oil well (see step S17), and then execute step S11 again. On the contrary, in step S16, when the controller 124 detects that the power provided by the power source 3 is not restored but still interrupted, it monitors the level of the reverse generating torque (refer to step S18). Next, compare the level of the reverse generating torque with a preset torque value to detect whether the level is smaller than the preset torque value (please refer to step S19). In step S19, when the level is smaller than the preset torque value, the reverse rotation of the screw pump 2 is allowed to stop naturally (see step S20). On the contrary, in step S19, when the level of the reverse generating torque is greater than the preset torque value, step S13 is executed again.

Please refer to FIG. 5 , which is a flow chart of the sub-steps of step S16 shown in FIG. 3 . As shown in FIG. 5, in step S16, firstly, when the controller 124 of the motor driver 12 detects that the time interval elapsed by the electric motor 11 to perform the reverse operation is longer than the first preset time, control the forward electric torque limit Return to the normal operating value, which may be a multiple of the rated torque (for example, 120), and set the motor rotational speed command W*r to a positive value, thereby making the motor driver 12 operate in the normal forward running mode Drive the electric motor 11 from reverse rotation to forward rotation (please refer to step S161). However, after step S161 is executed, if the controller 124 detects that the DC bus voltage Vbc is lower than the first threshold value again, it means that the power supply 3 cannot provide power to maintain the DC bus voltage Vbc, and the controller 124 judges that the DC bus voltage Vbc provided by the power supply 3 The electric power of is not restored (refer to step S162). And when step S162 determines that the power provided by the power supply 3 has not recovered and the second preset time has elapsed, the controller 124 determines that the power has been lost for a long time and executes step S18 (please refer to step S163).

To sum up, the present invention provides a control method of a screw pump and its applicable control system, which can control the operation of the screw pump to eliminate the influence when the power is lost and reversed, that is, when the control of the present invention When the motor driver of the system detects a power failure, the control system of the present invention can use the generated electric energy converted by the stored potential energy on the screw pump (wherein when the power fails, the pump rod of the screw pump will be affected by gravity due to oil). And release the storage potential energy, the storage potential energy will be zero when all the oil has dropped into the production pipe, and the oil liquid level height of the production pipe is also equal to the oil liquid level height of the oil well, and the generated electric energy is converted and stored Potential energy) to maintain the actuation of the motor driver and the electric motor, so as to control the reverse operation of the screw pump, thereby avoiding damage to the driving mechanism or equipment related to the electric motor, and at the same time improving the safety of the staff. In addition, when the electric motor and screw pump are reversed due to power loss, the brake unit and brake resistor of the brake device can convert the excess stored potential energy into heat energy and consume it, so the braking time of the screw pump can be shortened. Once the electric energy is supplied again, the motor driver of the control system of the present invention can drive the electric motor to control the screw pump to immediately perform positive displacement suction action, so the control method of the screw pump of the present invention and its applicable control system can be Improve the productivity of screw pumps.

The various modifications of the present invention through Ren Shijiang's thinking by those of ordinary skill in the art all belong to the protection scope of the claims of the present invention.

Claims (14)

1. a screw pump progress control method, apply a control system, this control system is in order to control the operation of a screw pump, and there is the motor driver controlling this electric motor with an electric motor of this screw pump synchronous axial system and being used for and run, this motor driver has stream/a-c transducer always, the DC bus voltage that the electric power that this AC/DC converter receives to be provided by a power supply produces, and this DC bus voltage is changed, to be supplied to this electric motor, it is as follows that this screw pump progress control method comprises step:

A () monitors this DC bus voltage;

B () is detected this DC bus voltage and whether is less than the first threshold values, and perform step (c) when testing result is for being;

C this screw pump is run because carrying out reversing the storage potential energy discharged and is converted to generating electric energy by (), and be supplied to this motor driver, makes this motor driver maintain start;

(d) by this motor driver drive this electric motor according to reversion torque restriction strategy and control this screw pump reversion run;

E () limits this DC bus voltage and is greater than the second threshold values;

F whether () is detected electric power and is recovered;

G (), when the testing result of step (f) is no, monitors the grade of reverse power generation torque;

Whether h grade that () detects this reverse power generation torque is less than preset torque value; And

I (), when the testing result of step (h) is for being, allows the reversion of this screw pump to run and stopping in a natural manner.

2. screw pump progress control method as claimed in claim 1, it is characterized in that, this second threshold values is lower than this first threshold values.

3. screw pump progress control method as claimed in claim 1, is characterized in that, when the testing result of step (b) is no, again perform step (a).

4. screw pump progress control method as claimed in claim 1, it is characterized in that, when the testing result of step (f) is for being, perform step (j): drive this electric motor rotate forward and accelerate rotational speed, and again perform step (a).

5. screw pump progress control method as claimed in claim 1, is characterized in that, when the testing result of step (h) is no, again perform step (c).

6. screw pump progress control method as claimed in claim 1, is characterized in that, in step (e), limit this DC bus voltage be greater than this second threshold values by this generating electric energy of brake apparatus consumption part of this control system.

7. screw pump progress control method as claimed in claim 1, it is characterized in that, it is as follows that this reversion torque restriction strategy in step (d) comprises step:

(d1) set revolution speed command as negative, and when the rotational velocity of this electric motor is assessed as timing, be zero by electronic for forward torque limit setting, the torque limit setting that generated electricity by forward is a values for normal operation;

(d2) when the rotational velocity of this electric motor be assessed as negative and lower than a predetermined value time, being zero by reverse electronic torque limit setting, is this values for normal operation by reverse power generation torque limit setting; And

(d3) when the rotational velocity of this electric motor be assessed as negative and be more than or equal to this predetermined value time, perform speed reversal control mode, make this reverse electronic torque restriction and this reverse power generation torque restriction all be set as this values for normal operation.

8. screw pump progress control method as claimed in claim 7, it is characterized in that, it is as follows that step (f) also comprises sub-step:

(f1) when this motor driver detects that the first Preset Time is longer than in this electric motor execution reversion operation institute's elapsed time interval, control the electronic torque restriction of this forward and return this values for normal operation, and set this revolution speed command as on the occasion of, make this motor driver operate in normal forward operating mode and drive this electric motor to change into rotating forward by anyway rotating;

(f2) when detecting that this DC bus voltage is less than this first threshold values again, judge that electric power is not as returning to form; And

(f3) when step (f2) judges that electric power does not recover and through the second Preset Time, performs step (g).

9. a screw pump operation control system, for controlling the operation of a screw pump, comprises:

One electric motor, carries out synchronous axial system with this screw pump; And

One motor driver, is electrically connected with a power supply and this electric motor, changes in order to the electric power provided by this power supply, and to be supplied to this electric motor, wherein this motor driver comprises:

One AC/DC converter, is electrically connected with this electric motor, the DC bus voltage that the electric power provided by this power supply in order to reception produces, and is changed by this DC bus voltage, to be supplied to this electric motor; And

One controller, is electrically connected with this AC/DC converter, in order to control the operation of this AC/DC converter, and monitors this DC bus voltage;

The blackout wherein provided when this power supply and this screw pump carry out reversion and run, when this controller detects that this DC bus voltage is less than this first threshold values, the generating electric energy of the bit of storage the subject of knowledge and the object of knowledge conversion this motor driver being used discharged by this screw pump runs, and the reversion controlling this screw pump according to reversion torque restriction strategy runs.

10. screw pump operation control system as claimed in claim 9, it is characterized in that, this motor driver comprises:

One AC/DC converter, is connected with this power electric, is converted to VDC in order to the electric power provided by this power supply; And

One direct-current chain, is electrically connected with this AC/DC converter, and in order to by this VDC voltage regulation filtering, to produce this DC bus voltage, and this direct-current chain is electrically connected with this controller.

11. screw pump operation control systems as claimed in claim 10, it is characterized in that, this controller comprises:

One velocity estimator, is electrically connected with this electric motor, exports a rotational velocity estimated value in order to estimate the rotational velocity of a rotor of this electric motor;

One reversion torque limiter, is electrically connected with this velocity estimator, in order to store this reversion torque restriction strategy, and provides torque to limit according to this rotational velocity estimated value;

One quick-action control circuit, is electrically connected with this reversion torque limiter, in order to provide a torque instruction according to a revolution speed command and this torque restriction;

One torque controller, is electrically connected with this speed control circuit, in order to change this torque instruction into a Q axial coordinate current-order;

One magnetic flux controller, in order to produce a D axial coordinate current-order;

One current control circuit, is electrically connected with this torque controller and this magnetic flux controller, in order to produce a α current-order and a β current-order respectively according to this Q axial coordinate current-order and this D axial coordinate current-order; And

One PWM generator, be electrically connected with this current control circuit and this AC/DC converter, in order to produce a pulse width modulating signal according to this α current-order and this β current-order, carry out the switchover operation of conducting or cut-off with at least one switch controlling this AC/DC converter.

12. screw pump operation control systems as claimed in claim 11, it is characterized in that, this control system also has a brake apparatus, and this brake apparatus is made up of a brake unit and a brake resistance, this brake unit is electrically connected between this motor driver and this brake resistance, in order to control the start of this brake resistance, make this brake resistance consumption energy.

13. screw pump operation control systems as claimed in claim 12, it is characterized in that, this reversion torque restriction strategy is set a revolution speed command as negative, and when the rotational velocity of this electric motor is assessed as timing, be zero by the electronic torque limit setting of a forward, the torque limit setting that generated electricity by one forward is a values for normal operation, and when the rotational velocity of this electric motor be assessed as negative and lower than a predetermined value time, be zero by a reverse electronic torque limit setting, be this values for normal operation by a reverse power generation torque limit setting, again when the rotational velocity of this electric motor be assessed as negative and be more than or equal to this predetermined value time, perform a speed reversal control mode, this reverse electronic torque restriction and this reverse power generation torque restriction is made all to be set as this values for normal operation.

14. as the screw pump operation control system of claim 12, and it is characterized in that, this screw pump operation control system is for performing the screw pump progress control method as described in any one of claim 1-8.