A photovoltaic direct drive control system for pumping unit based on AC-DC dual power supply

Abstract

The utility model discloses a kind of photovoltaic direct-drive control system of pumping unit based on ac-dc dual power supply, including photovoltaic array, ac-dc dual power supply input inverter, energy consumption braking unit, power frequency bypass switch and control module.Inverter adopts three-level NPC topology, and energy two-way block is realized by diode rectifier bridge and IGBT parallel connection.Initial power-on when direct current side priority power supply, seamless switching to ac power grid when power is insufficient.Energy consumption braking unit triggers when direct current bus voltage reaches 760V, cooperates IGBT chopper control and inhibits reverse power generation.Control module injects reverse excitation current by reverse load algorithm and inhibits reverse power generation, based on motor current harmonic inversion load change, dynamically adjusts inverter output frequency and duty cycle, the utility model can solve the problems, such as periodic reverse power generation, dynamic load fluctuation, system balance degree regulation difficulty in prior art, improve the utilization of photovoltaic energy, reduce system cost, improve the stability and reliability of system.

Description

Technical Field

[0001] This utility model relates to the field of oilfield production equipment technology, specifically to a photovoltaic direct-drive control system for oil pumping units based on AC / DC dual power supply. Background Technology

[0002] In oilfield production, pumping units are commonly used equipment. However, the potential energy load characteristics of pumping units cause them to generate periodic backflow power during operation. Traditional inverters require large-capacity energy storage devices to feed this backflow power to the grid, which not only increases system costs but also reduces the efficiency of photovoltaic direct drive. Furthermore, when the alternating load fluctuation (CLF) is large, a large-capacity filter capacitor is required on the photovoltaic DC side, limiting the system's dynamic response capability. In addition, existing inverters lack an adaptive balance adjustment mechanism for pumping unit operating conditions, relying on manual parameter tuning, which makes it difficult to cope with sudden changes in downhole fluid 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. Utility Model Content

[0003] The purpose of this invention is to provide a photovoltaic direct-drive control system for oil pumping units based on AC / DC dual power supply, so as to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, this utility model provides the following technical solution: 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-saving braking unit, a power frequency bypass switching switch, a motor, and a control module;

[0005] The output terminal 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 switching 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 energy-saving 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 connected to the photovoltaic array, the AC / DC dual power input inverter, the energy-saving braking unit, the power frequency bypass switch, and the motor.

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

[0011] Preferably, the energy-saving braking unit uses a SiC MOSFET connected in parallel with a corrugated alloy resistor to achieve rapid switching at the 760V threshold point with a response time of <10ms.

[0012] Preferably, the control module includes an initial power-on control logic module, a reverse load control algorithm module, a DC bus voltage stratified 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, seamlessly switching to the AC 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, injecting reverse excitation current during the downward phase of the sucker rod to increase electromagnetic resistance and suppress reverse power generation. The DC bus voltage stratified braking module is used to set the 760V energy consumption resistor trigger threshold. The load disturbance observer module inverts the downhole load change based on the 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.

[0013] Preferably, the photovoltaic array is connected to the DC input port of the AC / DC dual power input inverter via a reverse protection diode, which 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 switching switch and the AC input port of the AC / DC dual power input inverter. The surge protector is used to suppress overvoltage surges on the power frequency grid side.

[0015] Preferably, the energy-saving braking unit is connected in parallel with the DC bus of the AC / DC dual-power input inverter through a voltage divider resistor network. The output of the voltage divider 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-saving braking threshold judgment.

[0016] Beneficial effects:

[0017] (1) This utility model can solve the problems of periodic reverse power generation, large dynamic load fluctuation and difficulty in adjusting system balance in the existing technology, improve the utilization rate of photovoltaic energy, reduce system cost and improve system stability and reliability.

[0018] (2) This utility model achieves priority power supply to the DC side of the photovoltaic system and seamless power replenishment from the AC grid through a dual AC / DC power supply collaborative control architecture, avoiding the voltage sag problem of traditional soft-start circuits. Actual test data shows that the utilization rate of photovoltaic direct drive is 15%-20% higher than that of traditional solutions, reducing dependence on the power frequency grid and lowering energy consumption costs.

[0019] (3) In this utility model, 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, suppresses the reverse generation generated by potential energy release, and reduces the fluctuation of key parameter alternating load by ≥30%; the DC bus voltage stratification braking mechanism sets a 760V energy consumption resistor trigger threshold, and in conjunction with IGBT chopper control, directly consumes excess energy, eliminates the need for reverse generation to be fed back to the grid, and avoids the complexity of traditional inverters relying on energy storage or grid absorption.

[0020] The above description is merely an overview of the technical solutions of the embodiments of this application. In order to better understand the technical means of the embodiments of this application and to implement them in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the embodiments of this application more apparent and understandable, specific embodiments of this application are described below. Attached Figure Description

[0021] Figure 1 This is a block diagram illustrating the control principle of this utility model;

[0022] Figure 2 This is a block diagram illustrating the principle of the control module of this utility model.

[0023] Figure 3 This is the control flowchart of this utility model;

[0024] In the diagram: 1. Photovoltaic array; 2. AC / DC dual power input inverter; 3. Energy consumption braking unit; 4. Power frequency bypass switch; 5. Motor; 6. Control module; 7. Initial power-on control logic module; 8. Reverse load control algorithm module; 9. DC bus voltage hierarchical braking module; 10. Load disturbance observer module; 11. Anti-reverse diode; 12. Surge protector; 13. Voltage divider resistor network. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims and drawings of this application are intended to cover non-exclusive inclusion.

[0027] Furthermore, the terms "first," "second," etc., in the specification and claims of this application or in the aforementioned drawings are used to distinguish different objects rather than to describe a specific order, and may explicitly or implicitly include one or more of the features.

[0028] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, "connection" or "joining" in mechanical structures can refer to a physical connection, such as a fixed connection, for example, a connection fixed by fasteners, such as a connection fixed by screws, bolts, or other fasteners; a physical connection can also be a detachable connection, such as a snap-fit ​​or interlocking connection; a physical connection can also be an integral connection, such as a connection formed by welding, bonding, or integral molding. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0029] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings.

[0030] Please see 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-saving braking unit 3, a power frequency bypass switching switch 4, a motor 5, and a control module 6.

[0031] The output terminal 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 through a reverse protection diode 11, which 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 terminal 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 (640V photovoltaic) and the AC side (power grid), and achieves bidirectional energy blocking through a diode rectifier bridge and IGBT parallel structure. This inverter adopts a three-level NPC topology, is compatible with a wide voltage input of 520-800V on the DC side, matches the MPPT range of the photovoltaic panel, and can realize bidirectional conversion between DC power and AC power.

[0032] One end of the power frequency bypass switching 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. It is used to switch the power supply to the power frequency grid when the photovoltaic power is insufficient, so as to achieve seamless switching between AC and DC power.

[0033] The energy-saving braking unit 3 is connected to the DC bus of the AC / DC dual-power input inverter 2. It uses SiC MOSFETs and corrugated alloy resistors in parallel to achieve fast switching at the 760V threshold (response time < 10ms). When the DC bus voltage reaches 760V, the energy-saving braking unit is triggered, and excess energy is consumed through the energy-saving resistor to suppress back-generating power.

[0034] The motor 5 is connected to the output port of the AC / DC dual power input inverter 2 and is used to drive the oil pumping unit to work.

[0035] The control module 6 is connected to the photovoltaic array 1, the AC / DC dual power input inverter 2, the energy consumption braking unit 3, the power frequency bypass switch 4, and the motor 5, respectively, and is used to control the operation of the entire system.

[0036] A surge protector 12 is connected in series between the power frequency bypass switching 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 surges on the power frequency grid side. The energy consumption 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 terminal of the voltage divider resistor network 13 is connected to the voltage sampling port of the control module 6, which is used to monitor the DC bus voltage in real time and trigger the energy consumption braking threshold judgment.

[0037] In this 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 tiered braking module 9, and a load disturbance observer module 10. The initial power-on control logic module 7 controls the initial power-on process of the AC / DC dual-power input inverter, prioritizing DC power supply and seamlessly switching to the AC grid to supplement power when photovoltaic power is insufficient, avoiding voltage dips caused by traditional soft-start circuits. The reverse load control algorithm module 8 monitors the motor torque-speed characteristics in real time, injecting reverse excitation current during the downward phase of the sucker rod to increase electromagnetic resistance and suppress back-generating power. When the motor speed exceeds the synchronous speed, it triggers the d-axis negative current injection, forcing the motor into "energy consumption braking" mode. The DC bus voltage tiered braking module 9 sets the 760V energy consumption resistor trigger threshold and, in conjunction with IGBT chopper control, eliminates the need for back-feedback to the grid. When the DC bus voltage reaches 760V, the energy-consuming braking unit is triggered, which consumes excess energy through the energy-consuming resistor. At the same time, the DC bus voltage is regulated by IGBT chopper control to keep it within a stable range. The load disturbance observer module 10 inverts the downhole load change based on the harmonic components of the motor current, dynamically adjusts the inverter output frequency and duty cycle to maintain the system balance within the range of 0.8-1.2. By performing FFT analysis on the motor current, the harmonic components are extracted to invert the downhole load change. Then, according to the load change, the inverter output frequency and duty cycle are dynamically adjusted to achieve real-time self-correction of the system balance.

[0038] Back-generation suppression control logic: When the control module detects that the motor speed exceeds the synchronous speed, it determines that the sucker rod is in the downward phase. At this time, the reverse load control algorithm module is triggered to inject a negative current into the d-axis of the motor, forcing the motor to enter the "energy-consumption braking" mode, increasing electromagnetic resistance, and suppressing back-generation caused by potential energy release. By monitoring the motor torque-speed characteristics in real time, the magnitude of the injected reverse excitation current is dynamically adjusted to achieve the best back-generation suppression effect.

[0039] CLF Optimization Control Logic: Using the suspension load sensor signal as feedback, the control module dynamically adjusts the stroke rate through a model predictive control (MPC) algorithm to make the load curve approximate the average value. Specifically, the load signal is first collected in real time by the suspension load sensor, then the load signal is input into the model predictive control algorithm to predict the load changes over a future period. Finally, the output frequency of the inverter is dynamically adjusted based on the prediction results, thereby adjusting the stroke rate of the pumping unit to achieve CLF optimization.

[0040] The self-correcting balance control logic works as follows: The control module performs FFT analysis on the motor current through the load disturbance observer module, extracts harmonic components, and inversely reflects changes in the downhole load. When a change in the downhole load is detected, the inverter output frequency and duty cycle are dynamically adjusted to maintain the system balance within the range of 0.8 - 1.2. Through continuous monitoring and adjustment, the system balance is self-corrected, improving system stability and reliability.

[0041] Working principle: A control method for a photovoltaic direct-drive control system for an oil pumping unit based on AC / DC dual power supply, comprising the following steps:

[0042] Step A, AC / DC dual power supply coordinated control: During initial power-on, the photovoltaic array is given priority to be powered by the DC input port of the AC / DC dual power supply input inverter; the photovoltaic power is monitored in real time, and when the photovoltaic power is insufficient, the power frequency bypass switching switch seamlessly switches to the power frequency grid to supplement the power supply through the AC input port of the inverter, avoiding the voltage sag caused by the traditional soft start circuit;

[0043] Step B, Dynamic Back-Generation Suppression: The inverter monitors the motor torque-speed characteristics in real time. When the motor speed exceeds the synchronous speed, a negative current injection on the d-axis is triggered. The inverter injects a reverse excitation current into the motor to increase electromagnetic resistance, suppressing back-generation caused by potential energy release, and reducing alternating load fluctuations 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 conduct. Energy is consumed through parallel corrugated alloy resistors. In conjunction with the IGBT chopping control of the inverter, the rise of DC bus voltage is suppressed, eliminating the need for back-to-grid power.

[0044] C. Balance self-correction control: The inverter collects the motor current signal, extracts the current harmonic components based on FFT analysis, and inverses the downhole load change; the output frequency and duty cycle of the inverter are dynamically adjusted according to the load change to maintain the system balance within the range of 0.8-1.2.

[0045] In summary, this invention solves the problems of periodic reverse power generation, large dynamic load fluctuations, and difficulty in adjusting system balance in existing technologies, improving the utilization rate of photovoltaic energy, reducing system costs, and enhancing system stability and reliability. Through an AC / DC dual-power supply collaborative control architecture, this invention achieves priority power supply to the DC side of the photovoltaic system and seamless AC grid replenishment, avoiding the voltage sag problem of traditional soft-start circuits. Actual measurement data shows that the photovoltaic direct-drive utilization rate is increased by 15%-20% compared to traditional solutions, reducing dependence on the power frequency grid and lowering energy consumption costs. In this invention, the reverse load control algorithm monitors the motor torque-speed characteristics in real time and injects reverse excitation current during the downward phase of the sucker rod, increasing electromagnetic resistance and suppressing reverse power generation caused by potential energy release, reducing the key parameter alternating load fluctuation by ≥30%. The DC bus voltage tiered braking mechanism sets a 760V energy consumption resistor trigger threshold, combined with IGBT chopper control, to directly consume excess energy, eliminating the need for reverse power generation to be fed back to the grid and avoiding the complexity of traditional inverters relying on energy storage or grid absorption.

[0046] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A photovoltaic direct-drive control system for an oil pumping unit based on AC / DC dual power supply, characterized in that: It includes a photovoltaic array (1), an AC / DC dual power input inverter (2), an energy-saving braking unit (3), a power frequency bypass switching switch (4), a motor (5), and a control module (6). The output terminal 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 switching switch (4) 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 (2); The energy-saving 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 connected to the photovoltaic array (1), the AC / DC dual power input inverter (2), the energy consumption braking unit (3), the power frequency bypass switching switch (4), and the motor (5), respectively.

2. 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 AC / DC dual power input inverter (2) has dual input ports on the DC side and AC side. It achieves bidirectional energy blocking through a diode rectifier bridge and IGBT parallel structure. It 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, characterized in that: The energy-consuming braking unit (3) uses SiC MOSFET and corrugated alloy resistor in parallel to achieve fast switching at the 760V threshold point with a response time of <10ms.

4. 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 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, 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 downward phase of the sucker rod to increase electromagnetic resistance and suppress reverse power generation. The DC bus voltage stratification braking module (9) is used to set the 760V energy consumption resistor trigger threshold. The load disturbance observer module (10) inverts the downhole load change based on the motor current harmonic component, 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, characterized in that: The photovoltaic array (1) is connected to the DC input port of the AC / DC dual power input inverter (2) through a reverse protection diode (11), which 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 switching 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 surges 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 energy consumption 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) to monitor the DC bus voltage in real time and trigger the energy consumption braking threshold judgment.

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