Intelligent energy-saving three-phase asynchronous motor for pumping unit

Abstract

The present application relates to a kind of intelligent energy-saving three-phase asynchronous motor for pumping unit, by motor intelligent energy-saving control system, frequency converter, three-phase asynchronous motor is formed, frequency converter is changed by frequency, voltage binding mode change setting, frequency, voltage separation mode, so that frequency and voltage are respectively adjustable, frequency converter accepts single-chip microcomputer instruction, thereby output specified voltage, so that three-phase asynchronous motor runs in optimal efficiency interval;Motor intelligent energy-saving control system acquires the current parameter of frequency converter under periodic load, adjusts voltage to solve the minimum current value corresponding to voltage under load condition using variable step size optimization algorithm, to realize adaptive tracking load change function, so that frequency converter outputs three-phase asynchronous motor optimal operating voltage, realizes motor optimal power dynamic adjustment function, further improves energy-saving effect.

Description

Technical Field

[0001] This invention belongs to the field of electric motor technology, specifically relating to an intelligent energy-saving three-phase asynchronous motor for oil pumping units. Background Technology

[0002] Oil pumping units require a large power input during startup but only a small input power during operation. During normal pumping, the required input power varies for each well due to differences in conditions within the oil field, and the cyclic load of the pumping unit also varies over time. These factors necessitate that the pumping unit motor intelligently determine the load during startup and operation, setting an appropriate motor drive voltage to achieve optimal motor efficiency.

[0003] Invention patent ZL 2013 10018165.7 proposes a frequency and voltage binding mode, using five contactors and two changeover switches to enable the motor to start at high power and operate at low power when running at the mains frequency (50Hz), and to smoothly change the motor speed to achieve energy saving when running at variable frequency (below 50Hz). This invention patent can achieve the goal of high-power starting and low-power operation of oilfield-specific motors. However, it relies solely on speed regulation, and can only set a limited number of speed ranges to adjust the motor power, that is, to achieve the optimal efficiency of the motor within a limited range, thus not maximizing the energy-saving potential. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides an intelligent energy-saving three-phase asynchronous motor for oil pumping units, which can automatically set a reasonable motor drive voltage based on dynamic tracking of load power changes to achieve optimal motor efficiency.

[0005] To achieve the objectives of this invention, a smart energy-saving three-phase asynchronous motor for oil pumping units is provided, comprising a three-phase asynchronous motor, a frequency converter, and characterized in that: the hardware composition of the intelligent energy-saving control system for the motor includes a microcontroller, a memory chip, an LED expansion chip, an interface chip, and a human-machine interaction control unit; the microcontroller serves as the main control unit, employing a 485 interface chip and a 485 communication bus to achieve communication between the microcontroller and the frequency converter, and using an RTU interface to communicate with the oilfield central control system, collecting the current parameters of the frequency converter under periodic loads, and adjusting the voltage using a variable step-size optimization algorithm to solve for the minimum current value corresponding to the voltage under load conditions, thereby... The system enables adaptive tracking of load changes, ensuring the inverter outputs the optimal operating voltage for the three-phase asynchronous motor. A human-machine interface control unit connects to the microcontroller for starting and stopping the motor and setting the stroke rate. An LED expansion chip connects to the microcontroller to drive 6 LEDs. A storage chip connects to the microcontroller to store configuration data from the program. The inverter is changed from a frequency / voltage bound mode to a frequency / voltage separated mode, allowing both frequency and voltage to be adjusted independently. The inverter receives commands from the microcontroller and outputs the specified voltage, ensuring the three-phase asynchronous motor operates within its optimal efficiency range. A USB interface chip is used to send optimized data to the host computer.

[0006] The aforementioned voltage adjustment uses a variable step-size optimization algorithm to solve for the minimum current value corresponding to the voltage under load conditions, thereby achieving adaptive tracking of load changes and ensuring that the inverter outputs the optimal operating voltage for the three-phase asynchronous motor. The specific steps are as follows:

[0007] 1) Add the command request to collect inverter parameters to the queue, and call the callback function when the access is successful;

[0008] 2) Accumulate the current current value. If the current value has not been collected 100 times, return to step 1; otherwise, proceed to step 3.

[0009] 3) Take the average of the accumulated current values. If the current value is greater than the previous current value, the voltage adjustment direction is reversed and the voltage adjustment value is half of the previous adjustment value. Otherwise, continue in the direction of the previous voltage adjustment and the magnitude of the voltage adjustment remains unchanged.

[0010] 4) When the voltage adjustment is less than the manually set threshold, stop the voltage adjustment and the efficiency optimization ends.

[0011] In the aforementioned intelligent energy-saving control system for motors, both the RTU and the microcontroller program need to access the inverter. To prevent inverter access conflicts, the microcontroller software is designed with a queue to queue inverter accesses. Each time, the command and parameters for accessing the inverter are popped from the front of the queue. The access is only considered complete after the inverter returns a response, and then the next access command is popped from the queue.

[0012] Furthermore, the microcontroller is preferably an STM32 processing chip.

[0013] This invention proposes an intelligent energy-saving three-phase asynchronous motor for oil pumping units. The intelligent energy-saving control system of the motor finds the optimal efficiency power point of the motor through optimization algorithms and sets the optimal voltage value of the motor, so that the intelligent energy-saving three-phase asynchronous motor for oil pumping units can dynamically track the load power changes, realize the optimal power dynamic adjustment function of the motor, and further improve the energy-saving effect.

[0014] This invention uses the Vf separation mode of the frequency converter to adjust the motor voltage, which can achieve the following beneficial technical effects: (1) According to the change of load conditions, the microcontroller outputs the optimal operating voltage of the three-phase asynchronous motor, and the frequency converter enables the motor to operate in the optimal efficiency range, thereby realizing intelligent control of the motor. (2) Enables communication between the frequency converter, the microcontroller control system, and the host computer system. Attached Figure Description

[0015] Figure 1 This is a block diagram of the electrical structure of the present invention applied in an oil field;

[0016] Figure 2 This is a hardware structure diagram of the intelligent energy-saving control system for motors of the present invention;

[0017] Figure 3 This is a control flowchart of the intelligent energy-saving control system for motors of the present invention;

[0018] Figure 4 This is a schematic diagram of the human-computer interaction of the present invention. Detailed Implementation

[0019] This invention consists of a three-phase asynchronous motor, a frequency converter, and a smart energy-saving control system for the motor. Its electrical structure for use in oil fields is as follows: Figure 1 As shown, the hardware components of the intelligent energy-saving control system for motors are as follows: Figure 2 As shown, the memory chip stores configuration data from the program. The hardware includes two 485 interface chips: one for communication with the RTU and the other for communication with the frequency converter. The LED expansion chip drives a 6-bit LED, and the USB interface chip sends optimization data to the host computer. The microcontroller acts as the main controller, implementing functions such as human-machine interaction control, efficiency optimization, and communication control.

[0020] The motor control hardware consists of an STM32 processor chip, a memory chip, an LED expansion chip, and an interface chip. It enables the system to perform computation, data storage, and communication functions.

[0021] The control process of the intelligent energy-saving control system for motors is as follows: Figure 3As shown, the software employs a queue to handle inverter access. Each access command and its parameters are popped from the front of the queue. The access process continues until the inverter responds, at which point the next access command is popped from the queue.

[0022] Conditions for efficiency optimization:

[0023] 1) First, during system initialization, read the configuration parameters (set the number of strokes, the actual number of strokes of the pumping unit included in 1 minute). Based on the actual number of strokes of the pumping unit included in 1 minute, determine the time required for one stroke. Divide this time into 100 parts and determine the time for each safety check (i.e., the time required for 0.01 strokes).

[0024] 2) The current value of the current inverter is collected once every 0.01 strokes via the 485 bus. When it reaches 100 strokes, the average current value of the 100 strokes is compared with the average current value of the previous stroke. If it exceeds the manually set threshold, it indicates that the load has changed significantly, and the optimization program is started.

[0025] Efficiency optimization subroutine execution scheme:

[0026] Efficiency optimization is achieved simply by changing the inverter's output voltage. The specific steps are as follows:

[0027] 1) Add the command request to collect inverter parameters to the queue, and call the callback function when the access is successful;

[0028] 2) In the callback function, the current current value is accumulated. If the current value has not been collected 100 times, return to step 1); otherwise, go to step 3.

[0029] 3) Take the average of the accumulated current values. If the current value is greater than the previous current value, the voltage adjustment direction is reversed and the voltage adjustment value is half of the previous adjustment value. Otherwise, continue in the direction of the previous voltage adjustment and the magnitude of the voltage adjustment remains unchanged.

[0030] 4) When the voltage adjustment is less than the manually set threshold (Δv is 1.14V), stop the voltage adjustment and the efficiency optimization ends.

[0031] The callback function described above accumulates the values ​​of 100 stator current samples and calculates the average current accordingly.

[0032] Human-computer interaction process:

[0033] like Figure 4 As shown in the human-computer interaction diagram, the four buttons are defined from left to right as mode selection (K1), plus (K2), minus (K3), and confirmation button (K4);

[0034] 1) Before the motor starts, it should be in standby mode and display the standby symbol;

[0035] 2) To start or stop the motor, press the mode key three times. The leftmost two digital tubes will display F3, indicating a start or stop command. Press the plus or minus key, and the rightmost two digital tubes will display "1" to indicate start and "0" to indicate stop. Press the rightmost button to confirm, and the motor will start or stop.

[0036] 3) After startup, the monitor automatically enters the display state, showing the current stroke (the leftmost two digits) and the preset stroke (the rightmost two digits).

[0037] 4) To change the stroke count, press the mode key twice until the leftmost two digits display F2. Press the plus or minus keys until you get a satisfactory setting, and then press the rightmost confirmation key.

[0038] 5) To modify the actual number of strokes per minute, press the mode key once until the leftmost two digital tubes display F1, press the plus or minus key, and then press the rightmost confirmation key.

[0039] The energy efficiency test results of this invention are as follows:

[0040] 1. Constant load test

[0041] Performance optimization was tested under fixed frequency and variable load conditions. The test conditions were: inverter frequency 50Hz, load power successively 6kW, 5kW, 4kW, 3kW, and 2kW, with a manually set current threshold of e=0.1A. When e>0.1A, the optimization program was started; when the voltage adjustment was less than 1.14V, the voltage adjustment was stopped, and efficiency optimization ended. The optimized power change values ​​were obtained through the motor intelligent energy-saving control system, forming Table 1.

[0042] Table 1 Energy Efficiency at 50Hz

[0043] Load power 6kw 5kw 4kw 3kw 2kw frequency 50Hz 50Hz 50Hz 50Hz 50Hz Initial efficiency 77.3% 76.6% 75.9% 71.2% 65.6% Optimize efficiency 85.2% 83.5% 81.6% 79.1% 75.18%

[0044] Performance optimization was tested under fixed frequency and variable load conditions. The test conditions were: inverter frequency 25Hz, load power 3kW, 2kW, and 1kW respectively. The optimized power change values ​​were obtained through the motor intelligent control system, as shown in Table 2.

[0045] Table 2 Energy Efficiency Table for 25Hz

[0046] Load power 3kw 2kw 1kw frequency 25Hz 25Hz 25Hz Initial efficiency 68.4% 69.5% 65.2% Optimize efficiency 80.0% 76.8% 69.55%

[0047] 2. Variable frequency load test

[0048] Performance optimization was tested under variable frequency and load conditions. The inverter frequency was changed sequentially: 50Hz, 40Hz, 30Hz, and 20Hz; the load power was 3kW, 2kW, and 1kW respectively; the manually set current threshold e=0.1A; and the manually set voltage threshold Δv=1.14V. The optimized power change values ​​were obtained through the intelligent energy-saving control system for the motor, as shown in Table 3.

[0049] Table 3 Energy Efficiency of Variable Frequency

[0050] Load power 5kw 4kw 3kw 2kw frequency 50Hz 40Hz 30Hz 20Hz Initial efficiency 76.1% 75.2% 71.67% 66.43% Optimize efficiency 82.1% 81.5% 78.80% 77.32%

[0051] 3. Cyclic load test

[0052] Performance was optimized under test cycle load conditions, with a manually set current threshold e=0.1A and a manually set voltage threshold Δv=1.14V.

[0053] Experiment 1: The test conditions were as follows: the periodic load was 60s, the loading was 15s, the holding was 15s, the unloading was 15s, and the holding was 15s; the load power was 900w-5.5kw in sequence, and the optimized power change value was obtained through the intelligent energy-saving control system of the motor.

[0054] Experiment 2: The test conditions were as follows: periodic load of 60s, loading for 15s, holding for 15s, unloading for 15s, and holding for 15s; the load power was 750w-9kw in sequence, and the optimized power change value was obtained through the intelligent energy-saving control system of the motor; resulting in Table 4.

[0055] Table 4. Energy Efficiency of Variable Frequency

[0056]

[0057] Based on the above experimental results, it can be seen that the present invention demonstrates a further significant energy-saving effect under various operating conditions.

Claims

1. A kind of intelligent energy-saving three-phase asynchronous motor for pumping unit, including three-phase asynchronous motor, frequency converter, it is characterized in that: The hardware composition of the motor intelligent energy-saving control system includes a single-chip microcomputer, a storage chip, an LED extension chip, an interface chip and a man-machine interactive control unit; the single-chip microcomputer is used as a main control unit, 485 interface chips and a 485 communication bus are adopted to realize communication between the single-chip microcomputer and a frequency converter, an RTU interface is adopted to communicate with an oilfield general control system, current parameters of the frequency converter under a periodic load are collected, a variable step size optimization algorithm is adopted to solve the minimum current value corresponding to the voltage under the load, so as to realize the function of self-adaptive tracking of load changes, and make the frequency converter output the best operating voltage of a three-phase asynchronous motor; the man-machine interactive control unit is connected with the single-chip microcomputer and is used to start and stop the motor and set the stroke frequency; the LED extension chip is connected with the single-chip microcomputer and is used to drive 6 LEDs; the storage chip is connected with the single-chip microcomputer and is used to store configuration data in a program; the frequency converter is changed from a frequency-voltage binding mode to a frequency-voltage separation mode, so that the frequency and the voltage are adjustable respectively, the frequency converter receives instructions from the single-chip microcomputer, so as to output a specified voltage, and make the three-phase asynchronous motor operate in the best efficiency interval; a USB interface chip is used to send optimization data to an upper computer; the software of the motor intelligent energy-saving control system designs a queue, queues the access to the frequency converter, pops out the command and parameters for accessing the frequency converter from the front of the queue each time, and the current access must be ended after the frequency converter returns a response, and then the next access command is popped out from the queue; the conditions for efficiency optimization are as follows: 1) first, read configuration parameters at system initialization, determine the time required for one stroke frequency according to the actual stroke frequency of the pumping unit included in 1 minute, divide the time into 100 parts, and determine the time for each safety check; 2) collect the current current value of the frequency converter through the 485 bus every 0.01 stroke frequency, compare the average current value collected for 100 times with the average current value of the last stroke frequency when 100 times are reached, and if the threshold value set by a person is exceeded, it is indicated that the load has changed obviously, and the optimization program is started; the variable step size optimization algorithm is adopted to solve the minimum current value under the current load, the corresponding voltage is continuously tracked and adjusted, so as to realize the function of self-adaptive tracking of load changes, and make the frequency converter output the best operating voltage of a three-phase asynchronous motor, and the control process is as follows: 1) the command request for collecting the frequency converter parameters is included in the queue, and a callback function is called when the access is successful; 2) in the callback function, the current current value is accumulated, and if the current value is not collected for 100 times, the step 1) is returned, otherwise the step 3) is reached; 3) the average value of the accumulated current value is taken, if the current value is greater than the last current value, the voltage adjustment direction is reversed, and the voltage adjustment value is half of the last adjustment value, otherwise the direction of the last voltage adjustment is continued, and the size of the voltage adjustment is unchanged; 4) when the size of the voltage adjustment is less than the threshold value set by a person, the voltage adjustment is stopped, and the efficiency optimization is ended.

2. The intelligent energy-saving three-phase asynchronous motor for pumping unit according to claim 1, characterized in that: The single-chip microcomputer is an STM32 processing chip.

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