Pumping unit photovoltaic direct drive control system and method based on alternating current and direct current dual power supply

Abstract

The invention discloses a pumping unit photovoltaic direct drive control system and method based on alternating current and direct current dual power supply. The pumping unit photovoltaic direct drive control system comprises a photovoltaic array, an alternating current and direct current dual power supply input inverter, an energy consumption braking unit, a power frequency bypass change-over switch and a control module. The inverter adopts a three-level NPC topology, and energy bidirectional blocking is realized through parallel connection of a diode rectifier bridge and an IGBT (Insulated Gate Bipolar Transistor). The direct current side supplies power preferentially during initial power-on, and the alternating current power grid is seamlessly switched to when the power is insufficient. And the energy consumption braking unit is triggered when the voltage of the direct current bus reaches 760V, and is matched with IGBT chopping control to restrain reverse power generation. And the control module injects reverse excitation current through a reverse load algorithm to suppress reverse power generation, inverts load change based on motor current harmonic waves, and dynamically adjusts the output frequency and duty ratio of the inverter, so that the problems of periodic reverse power generation, large dynamic load fluctuation, difficulty in system balance degree adjustment and the like in the prior art can be solved; the utilization rate of photovoltaic energy is improved, the system cost is reduced, and the stability and reliability of the system are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield production equipment, and in particular to a photovoltaic direct-drive control system and method for an oil pumping unit based on AC / DC dual power supply. Background Art

[0002] In the field of oilfield production, pumping units are commonly used oil production equipment. However, the potential energy load characteristics of pumping units will cause them to generate periodic reverse power during operation. Traditional inverters need to be equipped with large-capacity energy storage devices when returning reverse power to the grid, which not only increases system costs but also reduces the efficiency of photovoltaic direct drive. At the same time, when the alternating load fluctuation (CLF) is large, a large-capacity filter capacitor needs to be configured on the photovoltaic DC side, which limits the dynamic response capability of the system. In addition, the existing inverters lack a balance adaptive adjustment mechanism for the working conditions of the pumping unit and rely on manual parameter adjustment. It is difficult to cope with sudden changes in the downhole liquid volume, resulting in poor system stability and reliability. Therefore, it is necessary to design a photovoltaic direct drive control system and method for pumping units based on AC / DC dual power supply. Summary of the Invention

[0003] The object of the present invention is to provide a photovoltaic direct-drive control system and method for an oil pump based on AC and DC dual power supply, so as to solve the problems raised in the above background technology.

[0004] To achieve the above objectives, the present invention provides the following technical solutions: a photovoltaic direct-drive control system for an oil pumping unit based on AC / DC dual power supply, comprising a photovoltaic array, an AC / DC dual power input inverter, an energy-consuming braking unit, a power frequency bypass switch, a motor, and a control module;

[0005] The output end of the photovoltaic array is connected to the DC input port of the AC / DC dual power input inverter;

[0006] One end of the power frequency bypass switch is connected to the power frequency grid, and the other end is connected to the AC input port of the AC / DC dual power input inverter;

[0007] The dynamic braking unit is connected to the DC bus of the AC / DC dual power input inverter;

[0008] The motor is connected to the output port of the AC / DC dual power input inverter;

[0009] The control module is respectively connected to the photovoltaic array, the AC / DC dual power input inverter, the energy consumption braking unit, the power frequency bypass switch and the motor.

[0010] Preferably, the AC / DC dual power input inverter has dual input ports on the DC side and the AC side, realizes bidirectional energy blocking through a diode rectifier bridge and an IGBT parallel structure, adopts a three-level NPC topology, and the DC side is compatible with a wide voltage input of 520-800V.

[0011] Preferably, the energy-consuming braking unit adopts SiC MOSFET in parallel with a corrugated alloy resistor to achieve fast switching at a 760V threshold point, with a response time of less than 10ms.

[0012] Preferably, the control module includes an initial power-on control logic module, a reverse load control algorithm module, a DC bus voltage stratification braking module and a load disturbance observer module; the initial power-on control logic module is used to control the initial power-on process of the AC / DC dual power input inverter, and seamlessly switch to the AC power grid to supplement when the photovoltaic power is insufficient; the reverse load control algorithm module is used to monitor the motor torque-speed characteristics in real time, and inject reverse excitation current during the downward phase of the sucker rod to increase the electromagnetic resistance and suppress reverse power generation; the DC bus voltage stratification braking module is used to set the 760V energy consumption resistor trigger threshold; the load disturbance observer module inverts the downhole load changes based on the harmonic components of the motor current, dynamically adjusts the inverter output frequency and duty cycle, and maintains the system balance within the range of 0.8-1.2.

[0013] Preferably, the photovoltaic array is connected to the DC input port of the AC / DC dual power input inverter via an anti-reverse diode, and the anti-reverse diode is used to prevent reverse current from flowing back into the photovoltaic array.

[0014] Preferably, a surge protector is connected in series between the power frequency bypass switch and the AC input port of the AC / DC dual power input inverter, and the surge protector is used to suppress overvoltage shocks on the power frequency grid side.

[0015] Preferably, the energy-consuming braking unit is connected in parallel with the DC bus of the AC / DC dual power input inverter through a voltage-dividing resistor network, and the output end of the voltage-dividing resistor network is connected to the voltage sampling port of the control module for real-time monitoring of the DC bus voltage and triggering energy-consuming braking threshold judgment.

[0016] Preferably, a control method for a photovoltaic direct drive control system of an oil pumping unit based on AC / DC dual power supply comprises the following steps:

[0017] Step A, AC / DC dual power supply coordinated control: During initial power-on, the photovoltaic array is preferentially supplied with power through the DC input port of the AC / DC dual power supply input inverter; photovoltaic power is monitored in real time, and when photovoltaic power is insufficient, the power frequency bypass switch is used to seamlessly switch to the power frequency grid to supplement power supply through the AC input port of the inverter, thereby avoiding voltage sags caused by traditional soft-start circuits;

[0018] Step B, dynamic reverse power generation suppression: The motor torque-speed characteristics are monitored in real time by the inverter. When it is detected that the motor speed exceeds the synchronous speed, negative current injection of the d-axis is triggered, and reverse excitation current is injected into the motor through the inverter to increase electromagnetic resistance, thereby suppressing reverse power generation caused by potential energy release and reducing the alternating load fluctuation by ≥30%; the DC bus voltage is monitored in real time. When the voltage reaches 760V, the SiC MOSFET of the energy-consuming braking unit is triggered to turn on, dissipating energy through the parallel corrugated alloy resistor, cooperating with the IGBT chopping control of the inverter to suppress the DC bus voltage rise and eliminate the need for return to the grid;

[0019] C. Balance self-correction control: The motor current signal is collected through the inverter, the current harmonic components are extracted based on FFT analysis, and the downhole load changes are inverted; the output frequency and duty cycle of the inverter are dynamically adjusted according to the load changes to maintain the system balance within the range of 0.8-1.2.

[0020] Beneficial effects:

[0021] (1) The present invention can solve the problems existing in the prior art, such as periodic reverse power generation, large dynamic load fluctuations, and difficulty in adjusting the system balance, thereby improving the utilization rate of photovoltaic energy, reducing system costs, and improving the stability and reliability of the system.

[0022] (2) This invention utilizes a coordinated AC / DC dual-power supply architecture to prioritize power supply to the PV DC side and seamlessly compensate for AC grid energy, thus avoiding the voltage sag problem associated with traditional soft-start circuits. Actual measurement data shows that the utilization rate of PV direct drive is 15-20% higher than that of traditional solutions, reducing dependence on the industrial frequency grid and lowering energy costs.

[0023] (3) In the present invention, the reverse load control algorithm monitors the motor torque-speed characteristics in real time, injects reverse excitation current during the downward phase of the sucker rod, increases electromagnetic resistance, and suppresses the reverse power generation caused by the release of potential energy, reducing the fluctuation of the key parameter alternating load by ≥30%; the DC bus voltage layered braking mechanism sets a 760V energy consumption resistor trigger threshold, and cooperates with the IGBT chopping control to directly consume excess energy, eliminating the need to return reverse power generation to the grid, and avoiding the complexity of traditional inverters relying on energy storage or grid absorption.

[0024] The above description is only an overview of the technical solutions of the embodiments of the present application. In order to more clearly understand the technical means of the embodiments of the present application, they can be implemented according to the contents of the specification. In addition, in order to make the above and other purposes, features and advantages of the embodiments of the present application more obvious and easy to understand, the specific implementation methods of the present application are specifically listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a control principle block diagram of the present invention;

[0026] Figure 2 This is a functional block diagram of the control module of the present invention;

[0027] Figure 3 This is a control flow chart of the present invention;

[0028] In the figure: photovoltaic array 1, AC / DC dual power input inverter 2, energy consumption braking unit 3, power frequency bypass switch 4, motor 5, control module 6, initial power-on control logic module 7, reverse load control algorithm module 8, DC bus voltage layered braking module 9, load disturbance observer module 10, anti-reverse diode 11, surge protector 12, voltage divider resistor network 13. DETAILED DESCRIPTION

[0029] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used in the specification of the application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification, claims and drawings of this application are intended to cover non-exclusive inclusions.

[0031] In addition, the terms "first", "second", etc. in the description and claims of this application or the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order, and may explicitly or implicitly include one or more such features.

[0032] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, the "connection" or "connection" of a mechanical structure may refer to a physical connection. For example, the physical connection may be a fixed connection, such as a fixed connection through a fixing member, such as a fixed connection through a screw, bolt, or other fixing member; the physical connection may also be a detachable connection, such as a mutual snap connection or snap connection; the physical connection may also be an integral connection, such as a connection formed by welding, bonding, or integral molding. For those skilled in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0033] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings.

[0034] See also Figure 1-Figure 3 A photovoltaic direct-drive control system for an oil pumping unit based on AC / DC dual power supply includes a photovoltaic array 1, an AC / DC dual power input inverter 2, an energy-consuming braking unit 3, a power frequency bypass switch 4, a motor 5, and a control module 6.

[0035] The output end of the photovoltaic array 1 is connected to the DC input port of the AC / DC dual-power input inverter 2; the photovoltaic array 1 is connected to the DC input port of the AC / DC dual-power input inverter 2 via an anti-reverse diode 11, and the anti-reverse diode 11 is used to prevent reverse current from flowing back into the photovoltaic array. The photovoltaic array is used to convert solar energy into DC power, and its output end is connected to the DC input port of the AC / DC dual-power input inverter. The AC / DC dual-power input inverter has dual input ports on the DC side (photovoltaic 640V) and the AC side (power frequency grid), and achieves bidirectional energy blocking through a diode rectifier bridge and an IGBT parallel structure. The inverter adopts a three-level NPC topology, and the DC side is compatible with a wide voltage input of 520-800V, matching the MPPT range of the photovoltaic panel, and can achieve bidirectional conversion of DC power and AC power.

[0036] One end of the power frequency bypass switch 4 is connected to the power frequency grid 5, and the other end is connected to the AC input port of the AC / DC dual power input inverter 2, and is used to switch the power supply to the power frequency grid when the photovoltaic power is insufficient, thereby realizing seamless switching of AC and DC power supplies.

[0037] The dynamic braking unit 3 is connected to the DC bus of the AC / DC dual power input inverter 2, and uses SiC MOSFET in parallel with a corrugated alloy resistor to achieve fast switching at the 760V threshold point (response time <10ms). When the DC bus voltage reaches 760V, the dynamic braking unit is triggered, dissipating excess energy through the energy dissipation resistor to suppress reverse power generation;

[0038] The motor 5 is connected to the output port of the AC / DC dual power input inverter 2 to drive the pumping unit to work;

[0039] The control module 6 is respectively connected to the photovoltaic array 1, the AC / DC dual power input inverter 2, the dynamic braking unit 3, the power frequency bypass switch 4 and the motor 5, and is used to control the operation of the entire system.

[0040] A surge protector 12 is connected in series between the power frequency bypass switch 4 and the AC input port of the AC / DC dual power input inverter 2. The surge protector 12 is used to suppress overvoltage shocks on the power frequency grid side; the dynamic braking unit 3 is connected in parallel with the DC bus of the AC / DC dual power input inverter 2 through a voltage divider resistor network 13. The output end of the voltage divider resistor network 13 is connected to the voltage sampling port of the control module 6 for real-time monitoring of the DC bus voltage and triggering dynamic braking threshold judgment.

[0041] In the present invention, the control module 6 includes an initial power-on control logic module 7, a reverse load control algorithm module 8, a DC bus voltage stratification braking module 9 and a load disturbance observer module 10; the initial power-on control logic module 7 is used to control the initial power-on process of the AC / DC dual power input inverter, realize the priority power supply on the DC side, and seamlessly switch to the AC grid to supplement when the photovoltaic power is insufficient, avoiding the voltage sag caused by the traditional soft start circuit; the reverse load control algorithm module 8 is used to monitor the motor torque-speed characteristics in real time, inject reverse excitation current in the downward stage of the sucker rod to increase the electromagnetic resistance and suppress back power generation, and when it is detected that the motor speed exceeds the synchronous speed, trigger the d-axis negative current injection to force the motor to enter the "energy consumption braking" mode; the DC bus voltage stratification braking module 9 is used to set the 760V energy consumption resistor trigger threshold, cooperate with the IGBT chopping control, and eliminate the need for return to the grid. When the DC bus voltage reaches 760V, the energy-consuming braking unit is triggered to consume excess energy through the energy-consuming resistor. At the same time, the DC bus voltage is adjusted through IGBT chopping control to keep it within a stable range. The load disturbance observer module 10 inverts the downhole load changes based on the harmonic components of the motor current, dynamically adjusts the inverter output frequency and duty cycle, and maintains the system balance within the range of 0.8-1.2. By performing FFT analysis on the motor current, the harmonic components are extracted, and the changes in the downhole load are inverted. Then, according to the load changes, the output frequency and duty cycle of the inverter are dynamically adjusted to achieve self-correction of the system balance.

[0042] Backward power generation suppression control logic: When the control module detects that the motor speed exceeds the synchronous speed, it identifies the pumping rod as descending. This triggers the reverse load control algorithm, injecting negative current into the motor's d-axis, forcing the motor into "dynamic braking" mode. This increases electromagnetic resistance and suppresses the backward power generation caused by potential energy release. By monitoring the motor's torque-speed characteristics in real time, the injected reverse excitation current is dynamically adjusted to achieve optimal backward power generation suppression.

[0043] CLF optimization control logic: Using signals from the suspension load sensor as feedback, the control module dynamically adjusts the pumping frequency through a model predictive control (MPC) algorithm to keep the load curve close to the average. Specifically, the suspension load sensor first collects the load signal in real time. This load signal is then fed into the MPC algorithm to predict future load changes. Finally, based on this prediction, the inverter output frequency is dynamically adjusted, thereby adjusting the pumping unit's pumping frequency and achieving CLF optimization.

[0044] Balance Self-Correction Control Logic: The control module uses the load disturbance observer module to perform FFT analysis on the motor current, extract harmonic components, and inversely analyze changes in the downhole load. When changes in the downhole load are detected, the inverter output frequency and duty cycle are dynamically adjusted to maintain system balance within a range of 0.8-1.2. Through continuous monitoring and adjustment, system balance self-correction is achieved, improving system stability and reliability.

[0045] Working principle: A control method for a photovoltaic direct drive control system for an oil pump based on AC / DC dual power supply, comprising the following steps:

[0046] Step A, AC / DC dual power supply coordinated control: During initial power-on, the photovoltaic array is preferentially supplied with power through the DC input port of the AC / DC dual power supply input inverter; photovoltaic power is monitored in real time, and when photovoltaic power is insufficient, the power frequency bypass switch is used to seamlessly switch to the power frequency grid to supplement power supply through the AC input port of the inverter, thereby avoiding voltage sags caused by traditional soft-start circuits;

[0047] Step B, dynamic reverse power generation suppression: The motor torque-speed characteristics are monitored in real time by the inverter. When it is detected that the motor speed exceeds the synchronous speed, negative current injection of the d-axis is triggered, and reverse excitation current is injected into the motor through the inverter to increase electromagnetic resistance, thereby suppressing reverse power generation caused by potential energy release and reducing the alternating load fluctuation by ≥30%; the DC bus voltage is monitored in real time. When the voltage reaches 760V, the SiC MOSFET of the energy-consuming braking unit is triggered to turn on, dissipating energy through the parallel corrugated alloy resistor, cooperating with the IGBT chopping control of the inverter to suppress the DC bus voltage rise and eliminate the need for return to the grid;

[0048] C. Balance self-correction control: The motor current signal is collected through the inverter, the current harmonic components are extracted based on FFT analysis, and the downhole load changes are inverted; the output frequency and duty cycle of the inverter are dynamically adjusted according to the load changes to maintain the system balance within the range of 0.8-1.2.

[0049] In summary, the present invention can solve the problems existing in the prior art, such as periodic reverse power generation, large dynamic load fluctuations, and difficulty in adjusting the system balance, thereby improving the utilization rate of photovoltaic energy, reducing system costs, and improving the stability and reliability of the system. The present invention uses an AC / DC dual power supply collaborative control architecture to achieve priority power supply on the photovoltaic DC side and seamless energy replenishment on the AC grid, thus avoiding the voltage sag problem of the traditional soft start circuit. Measured data shows that the utilization rate of photovoltaic direct drive is 15-20% higher than that of traditional solutions, reducing dependence on the industrial frequency grid and reducing energy consumption costs. In the present invention, the reverse load control algorithm monitors the motor torque-speed characteristics in real time, injects reverse excitation current during the downward phase of the pumping rod, increases electromagnetic resistance, and suppresses the reverse power generation caused by potential energy release, reducing the key parameter alternating load fluctuation by ≥30%. The DC bus voltage layered braking mechanism sets a 760V energy consumption resistor trigger threshold, and cooperates with IGBT chopping control to directly consume excess energy, eliminating the need to return reverse power generation to the grid, and avoiding the complexity of traditional inverters relying on energy storage or grid absorption.

[0050] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A photovoltaic direct drive control system for an oil pump based on AC / DC dual power supply, characterized by: It comprises a photovoltaic array (1), an AC / DC dual power input inverter (2), an energy-consuming braking unit (3), an industrial frequency bypass switch (4), a motor (5), and a control module (6); The output end of the photovoltaic array (1) is connected to the DC input port of the AC / DC dual power input inverter (2); One end of the power frequency bypass switch (4) is connected to the power frequency grid (5), and the other end is connected to the AC input port of the AC / DC dual power input inverter (2); The dynamic braking unit (3) is connected to the DC bus of the AC / DC dual power input inverter (2); The motor (5) is connected to the output port of the AC / DC dual power input inverter (2); The control module (6) is respectively connected to the photovoltaic array (1), the AC / DC dual power input inverter (2), the energy-consuming braking unit (3), the power frequency bypass switch (4), and the motor (5).

2. The photovoltaic direct drive control system for an oil pumping unit based on AC / DC dual power supply according to claim 1 is characterized in that: The AC / DC dual power input inverter (2) has dual input ports on the DC side and the AC side, realizes bidirectional energy blocking through a diode rectifier bridge and an IGBT parallel structure, adopts a three-level NPC topology, and is compatible with a wide voltage input of 520-800V on the DC side.

3. The photovoltaic direct drive control system for an oil pumping unit based on AC / DC dual power supply according to claim 1 is characterized in that: The energy-consuming braking unit (3) adopts SiC MOSFET connected in parallel with a corrugated alloy resistor to achieve rapid switching at a 760V threshold point, with a response time of less than 10ms.

4. The photovoltaic direct drive control system for an oil pumping unit based on AC / DC dual power supply according to claim 1 is characterized in that: The control module (6) includes an initial power-on control logic module (7), a reverse load control algorithm module (8), a DC bus voltage layered braking module (9), and a load disturbance observer module (10); the initial power-on control logic module (7) is used to control the initial power-on process of the AC / DC dual power input inverter, and seamlessly switch to the AC grid to supplement when the photovoltaic power is insufficient; the reverse load control algorithm module (8) is used to monitor the motor torque-speed characteristics in real time, and inject reverse excitation current during the pumping rod downward phase to increase electromagnetic resistance and suppress reverse power generation; the DC bus voltage layered braking module (9) is used to set a 760V energy consumption resistor trigger threshold; The load disturbance observer module (10) inverts downhole load changes based on motor current harmonic components, dynamically adjusts the inverter output frequency and duty cycle, and maintains the system balance within the range of 0.8-1.

2.

5. The photovoltaic direct drive control system for an oil pumping unit based on AC / DC dual power supply according to claim 1 is characterized in that: The photovoltaic array (1) is connected to the DC input port of the AC / DC dual power input inverter (2) via an anti-reverse diode (11), and the anti-reverse diode (11) is used to prevent reverse current from flowing back into the photovoltaic array.

6. The photovoltaic direct drive control system for an oil pumping unit based on AC / DC dual power supply according to claim 1, characterized in that: A surge protector (12) is connected in series between the power frequency bypass switch (4) and the AC input port of the AC / DC dual power input inverter (2), and the surge protector (12) is used to suppress overvoltage shocks on the power frequency grid side.

7. The photovoltaic direct drive control system for an oil pumping unit based on AC / DC dual power supply according to claim 1, characterized in that: The dynamic braking unit (3) is connected in parallel to the DC bus of the AC / DC dual power input inverter (2) via a voltage-dividing resistor network (13); the output end of the voltage-dividing resistor network (13) is connected to the voltage sampling port of the control module (6) for real-time monitoring of the DC bus voltage and triggering dynamic braking threshold judgment.

8. A control method for implementing a photovoltaic direct drive control system for an oil pumping unit based on AC / DC dual power supply as described in claim 1, characterized in that: The following steps are involved: Step A, AC / DC dual power supply coordinated control: During initial power-on, the photovoltaic array is preferentially supplied with power through the DC input port of the AC / DC dual power supply input inverter; photovoltaic power is monitored in real time, and when photovoltaic power is insufficient, the power frequency bypass switch is used to seamlessly switch to the power frequency grid to supplement power supply through the AC input port of the inverter, thereby avoiding voltage sags caused by traditional soft-start circuits; Step B, dynamic reverse power generation suppression: The motor torque-speed characteristics are monitored in real time by the inverter. When it is detected that the motor speed exceeds the synchronous speed, negative current injection of the d-axis is triggered. Reverse excitation current is injected into the motor through the inverter to increase electromagnetic resistance, suppressing reverse power generation caused by potential energy release, and reducing alternating load fluctuation by ≥30%; The DC bus voltage is monitored in real time. When the voltage reaches 760V, the SiC MOSFET of the dynamic braking unit is triggered to turn on. The parallel corrugated alloy resistor consumes energy, and the IGBT chopper control of the inverter is coordinated to suppress the rise of the DC bus voltage and eliminate the need for backfeeding to the grid. C. Balance self-correction control: The motor current signal is collected through the inverter, the current harmonic components are extracted based on FFT analysis, and the downhole load changes are inverted; the output frequency and duty cycle of the inverter are dynamically adjusted according to the load changes to maintain the system balance within the range of 0.8-1.2.

Images